API 579 Fitness-For-Service Engineering Assessment Procedure

American Petroleum Institute Date: To: Re:

1220 L Street, Northwest Washington, D.C.200054070 202-682-8000

March 2000 Purchasers of API Recommended Practice 579, Fitness for Service, First Edition Errata

This package contains an Errata to API Recommended Practice 579, Fitnessfor Sevice, First Edition. This package consists of the pages that have changed since the January 2000 printing. To update your copy of API Recommended Practice 579, replace the following pages as indicated: Part of Book Changed

Old Pages to be Replaced

New Panes

Section 1

l-l to l-2 l-5 to l-6 2-5 to 2-10

l-l to l-2 l-5 to l-6 2-5 to 2-10

Section 4

4-9 to 4-10 4-19 to 4-20 4-35 to 4-36 4-45 to 4-46

4-9 to 4-10 4-19 to 4-20 4-35 to 4-36 4-45 to 4-46

Section 5

5-33 to 5-40 6-27 to 6-28

5-33 to 5-40 6-27 to 6-28

7-3 to 7-4 7-13 to 7-20

7-3 to 7-4 7-13 to 7-20

Section 8

8-15-8-16 8-25 to 8-26 8-37 to 8-38 8-51 to 8-56

8-15-8-16 8-25 to 8-26 8-37 to 8-38 8-51 to 8-56

Section 9

9-13 to 9-14 9-41 to 9-42 9-53 to 9-54 9-65 to 9-66 B-9 to B-10 B-29 to B-30

9-13 to 9-14 9-41 to 9-42 9-53 to 9-54 9-65 to 9-66 B-9 to B-10 B-29 to B-30 F-5 to F-6 F-9 to F-14 F-21 to F-26 F-63 to F-64 F-73 to F-74 F-89 to F-90 G-l to G-4

Section 2

Section 6 Section 7

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Appendix B Appendix F

F-5 to F-6 F-9 to F-14 F-21 to F-26 F-63 to F-64 F-73 to F-74 F-89 to F-90

Appendix G

G-l to G-4

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API Recommended Practice 579 Fitness For Service Jan, 2000

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API ENVIRONMENTAL, HEALTH AND SAFETY MISSION AND GUIDING PRINCIPLES The members of the American Petroleum Institute are dedicated to continuous efforts to improve the compatibility of our operations with the environment while economically developing energy resources and supplying high quality products and services to consumers. We recognize our responsibility to work with the public, the government, and others to develop and to use natural resources in an environmentally sound manner while protecting the health and safety of our employees and the public. To meet these responsibilities, API members pledge to manage our businesses according to the following principles using sound science to prioritize risks and to implement cost-effective management practices: To recognize and to respond to community concerns about our raw materials, products and operations.

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To operate our plants and facilities, and to handle our raw materials and products in a manner that protects the environment, and the safety and health of our employees and the public.

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To make safety, health and environmental considerations a priority in our planning, and our development of new products and processes.

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To advise promptly, appropriate ofÞcials, employees, customers and the public of information on signiÞcant industry-related safety, health and environmental hazards, and to recommend protective measures.

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To counsel customers, transporters and others in the safe use, transportation and disposal of our raw materials, products and waste materials.

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To work with others to resolve problems created by handling and disposal of hazardous substances from our operations.

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To participate with government and others in creating responsible laws, regulations and standards to safeguard the community, workplace and environment.

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To promote these principles and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materials, petroleum products and wastes.

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Fitness-for-Service

Downstream Segment API RECOMMENDED PRACTICE 579 FIRST EDITION, JANUARY 2000

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SPECIAL NOTES

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed. API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train and equip their employees, and others exposed, concerning health and safety risks and precautions, nor undertaking their obligations under local, state, or federal laws. Information concerning safety and health risks and proper precautions with respect to particular materials and conditions should be obtained from the employer, the manufacturer or supplier of that material, or the material safety data sheet. Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letter patent. Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. Sometimes a one-time extension of up to two years will be added to this review cycle. This publication will no longer be in effect five years after its publication date as an operative API standard or, where an extension has been granted, upon republication. Status of the publication can be ascertained from the API Authoring Department (telephone 202-682-8000). A catalog of API publications and materials is published annually and updated quarterly by API, 1220 L Street, N.W., Washington, D.C. 20005. This document was produced under API standardization procedures that ensure appropriate notification and participation in the development process and is designated as an API standard. Questions concerning the interpretation of the content of this standard or comments and questions concerning the procedures under which this standard was developed should be directed in writing to the general manager of the Authoring Department (shown on the title page of this document), American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the general manager. API standards are published to facilitate the broad availability of proven, sound engineering and operating practices. These standards are not intended to obviate the need for applying sound engineering judgment regarding when and where these standards should be utilized. The formulation and publication of API standards is not intended in any way to inhibit anyone from using any other practices. Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

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ii Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS

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(Jan, 2000)

FOREWORD (Jan, 2000) --``````-`-`,,`,,`,`,,`---

This publication is a result of a need for standardization of fitness-for-service assessment techniques for pressurized equipment in the refinery and chemical industry. In this context, fitness-for-service is defined as the ability to demonstrate the structural integrity of an in-service component containing a flaw or damage. This publication is intended to supplement and augment the requirements in API 510, API 570 and API 653: (i) to ensure safety of plant personnel and the public while older equipment continues to operate; (ii) to provide technically sound fitness-for-service assessment procedures to ensure that different service providers furnish consistent life predictions; and (iii) to help optimize maintenance and operation of existing facilities, maintain availability of older plants, and enhance long-term economic viability. This document reflects the best practices known in the industry, but it is not a mandatory standard or code. In this regard, the terms shall and must are only used to state mandatory requirements with respect to the assessment procedures which will not be correct unless followed explicitly. The term should is used to state that which is considered good practice and is recommended but is not absolutely mandatory. The term may is used to state that which is considered optional. This publication was prepared by a committee that included representatives of the American Petroleum Institute and the Chemical Manufacturers Association, as well as individuals associated with related industries. Much of the technical background for this publication is from a base resource document developed by a Joint Industry Program on Fitness-For-Service administered by The Materials Properties Council. The research efforts undertaken by this research consortium and the technical information contained within the base resource document were invaluable in the preparation of this publication. The voluntary efforts of the member companies who comprised the Task Group are duly noted. It is the intent of the American Petroleum Institute to periodically revise this publication. All owners and operators of pressure vessels, piping and tankage are invited to report their experiences in utilizing the fitness-for-service assessment procedures in this publication whenever such experiences suggest a need for revision or expansion of the practices set forth herein. API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the information contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict. Suggested revisions, reports, comments, and request for interpretations are invited and should be submitted to the Manager of the Downstream Segment, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005. See Appendix J for further information regarding inquiries about API 579.


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TABLE OF CONTENTS (Jan, 2000) SECTION 1 1.1 1.2 1.3 1.4

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1.5 1.6 1.7 1.8

– Introduction

Introduction..................................................................................................................................1-1 Scope ............................................................................................................................................1-1 Organization and Use..................................................................................................................1-2 Responsibilities ...........................................................................................................................1-3 1.4.1 Owner-User.....................................................................................................................1-3 1.4.2 Inspector.........................................................................................................................1-3 1.4.3 Engineer..........................................................................................................................1-3 Qualifications ...............................................................................................................................1-4 Definition Of Terms .....................................................................................................................1-4 References....................................................................................................................................1-4 Tables ...........................................................................................................................................1-4

SECTION 2 – Fitness-For-Service 2.1 2.2 2.3

2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11

Engineering Assessment Procedure

General..........................................................................................................................................2-1 Applicability And Limitations Of The FFS Assessment Procedures ......................................2-2 Data Requirements ......................................................................................................................2-2 2.3.1 Original Equipment Design Data..................................................................................2-2 2.3.2 Maintenance And Operational History.........................................................................2-4 2.3.3 Required Data/Measurements For A FFS Assessment ..............................................2-5 2.3.4 Recommendations For Inspection Techniques And Sizing Requirements .............2-5 Assessment Techniques And Acceptance Criteria ..................................................................2-5 Remaining Life Evaluation..........................................................................................................2-9 Remediation .................................................................................................................................2-9 In-Service Monitoring ..................................................................................................................2-10 Documentation.............................................................................................................................2-10 References....................................................................................................................................2-10 Tables And Figures......................................................................................................................2-11 Example Problems.......................................................................................................................2-16

SECTION 3 – Assessment Of Equipment For Brittle Fracture 3.1 General..........................................................................................................................................3-1 3.2 Applicability And Limitations Of The Procedure ......................................................................3-2 3.3 Data Requirements ......................................................................................................................3-3 3.3.1 Original Equipment Design Data..................................................................................3-3 3.3.2 Maintenance And Operational History.........................................................................3-3 3.3.3 Required Data/Measurements For A FFS Assessment ..............................................3-3 3.3.4 Recommendations For Inspection Techniques And Sizing Requirements .............3-4 3.4 Assessment Techniques And Acceptance Criteria ..................................................................3-4 3.4.1 Overview .........................................................................................................................3-4 3.4.2 Level 1 Assessment.......................................................................................................3-4 3.4.3 Level 2 Assessment.......................................................................................................3-6 3.4.4 Level 3 Assessment.......................................................................................................3-9 3.5 Remaining Life Assessment – Acceptability For Continued Service .....................................3-10 3.6 Remediation .................................................................................................................................3-10 3.7 In-Service Monitoring ..................................................................................................................3-11 3.8 Documentation.............................................................................................................................3-11 3.9 References....................................................................................................................................3-12 3.10 Tables And Figures......................................................................................................................3-12 3.11 Example Problems.......................................................................................................................3-32

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SECTION 5 – Assessment Of Local Metal Loss 5.1 General..........................................................................................................................................5-1 5.2 Applicability And Limitations Of The Procedure ......................................................................5-1 5.3 Data Requirements ......................................................................................................................5-3 5.3.1 Original Equipment Design Data..................................................................................5-3 5.3.2 Maintenance And Operational History.........................................................................5-3 5.3.3 Required Data/Measurements For A FFS Assessment ..............................................5-3 5.3.4 Recommendation For Inspection Techniques And Sizing Requirements ...............5-4 5.4 Assessment Techniques And Acceptance Criteria ..................................................................5-5 5.4.1 Overview .........................................................................................................................5-5 5.4.2 Level 1 Assessment.......................................................................................................5-5 5.4.3 Level 2 Assessment.......................................................................................................5-7 5.4.4 Level 3 Assessment.......................................................................................................5-17 5.5 Remaining Life Assessment .......................................................................................................5-17 5.5.1 Thickness Approach......................................................................................................5-17 5.5.2 MAWP Approach ............................................................................................................5-18 5.6 Remediation .................................................................................................................................5-18 5.7 In-Service Monitoring ..................................................................................................................5-18 5.8 Documentation.............................................................................................................................5-18 5.9 References....................................................................................................................................5-19 5.10 Tables And Figures......................................................................................................................5-20 5.11 Example Problems.......................................................................................................................5-32 SECTION 6 – Assessment Of Pitting Corrosion 6.1 General..........................................................................................................................................6-1 6.2 Applicability And Limitations Of The Procedure ......................................................................6-1 6.3 Data Requirements ......................................................................................................................6-1 6.3.1 Equipment Original Design Data..................................................................................6-1 6.3.2 Maintenance And Operational History.........................................................................6-2 6.3.3 Required Data/Measurements For A FFS Assessment ..............................................6-2 6.3.4 Recommendation For Inspection Techniques And Sizing Requirements ...............6-3


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SECTION 4 – Assessment Of General Metal Loss 4.1 General..........................................................................................................................................4-1 4.2 Applicability And Limitations Of The Procedure ......................................................................4-1 4.3 Data Requirements ......................................................................................................................4-3 4.3.1 Original Equipment Design Data..................................................................................4-3 4.3.2 Maintenance And Operational History.........................................................................4-3 4.3.3 Required Data/Measurements For A FFS Assessment ..............................................4-3 4.3.4 Recommendations For Inspection Techniques And Sizing Requirements .............4-6 4.4 Assessment Techniques And Acceptance Criteria ..................................................................4-6 4.4.1 Overview .........................................................................................................................4-6 4.4.2 Level 1 Assessment.......................................................................................................4-7 4.4.3 Level 2 Assessment.......................................................................................................4-10 4.4.4 Level 3 Assessment.......................................................................................................4-12 4.5 Remaining Life Assessment .......................................................................................................4-13 4.5.1 Thickness Approach......................................................................................................4-13 4.5.2 MAWP Approach ............................................................................................................4-13 4.6 Remediation .................................................................................................................................4-14 4.7 In-Service Monitoring ..................................................................................................................4-16 4.8 Documentation.............................................................................................................................4-16 4.9 References....................................................................................................................................4-17 4.10 Tables And Figures......................................................................................................................4-17 4.11 Example Problems.......................................................................................................................4-34

6.5 6.6 6.7 6.8 6.9 6.10 6.11

Assessment Techniques And Acceptance Criteria ..................................................................6-3 6.4.1 Overview .........................................................................................................................6-3 6.4.2 Level 1 Assessment.......................................................................................................6-4 6.4.3 Level 2 Assessment.......................................................................................................6-7 6.4.4 Level 3 Assessment.......................................................................................................6-13 Remaining Life Assessment .......................................................................................................6-13 Remediation .................................................................................................................................6-14 In-Service Monitoring ..................................................................................................................6-14 Documentation.............................................................................................................................6-14 References....................................................................................................................................6-15 Tables And Figures......................................................................................................................6-15 Example Problems.......................................................................................................................6-24

SECTION 7 – Assessment Of Blisters And Laminations 7.1 General..........................................................................................................................................7-1 7.2 Applicability And Limitations Of The Procedure ......................................................................7-1 7.3 Data Requirements ......................................................................................................................7-2 7.3.1 Equipment Original Design Data..................................................................................7-2 7.3.2 Maintenance And Operational History.........................................................................7-2 7.3.3 Required Data/Measurements For A FFS Assessment ..............................................7-2 7.3.4 Recommendation For Inspection Techniques And Sizing Requirements ...............7-3 7.4 Assessment Techniques And Acceptance Criteria ..................................................................7-4 7.4.1 Overview .........................................................................................................................7-4 7.4.2 Level 1 Assessment.......................................................................................................7-4 7.4.3 Level 2 Assessment.......................................................................................................7-5 7.4.4 Level 3 Assessment.......................................................................................................7-7 7.5 Remaining Life Assessment .......................................................................................................7-7 7.6 Remediation .................................................................................................................................7-8 7.7 In-Service Monitoring ..................................................................................................................7-8 7.8 Documentation.............................................................................................................................7-9 7.9 References....................................................................................................................................7-9 7.10 Tables And Figures......................................................................................................................7-9 7.11 Example Problems.......................................................................................................................7-20 SECTION 8 – Assessment Of Weld Misalignment And Shell Distortions 8.1 General..........................................................................................................................................8-1 8.2 Applicability And Limitations Of The Procedure ......................................................................8-1 8.3 Data Requirements ......................................................................................................................8-3 8.3.1 Original Equipment Design Data..................................................................................8-3 8.3.2 Maintenance And Operational History.........................................................................8-3 8.3.3 Required Data/Measurements For A FFS Assessment ..............................................8-3 8.3.4 Recommendation For Inspection Techniques And Sizing Requirements ...............8-3 8.4 Assessment Techniques And Acceptance Criteria ..................................................................8-6 8.4.1 Overview .........................................................................................................................8-6 8.4.2 Level 1 Assessment.......................................................................................................8-6 8.4.3 Level 2 Assessment.......................................................................................................8-6 8.4.4 Level 3 Assessment.......................................................................................................8-18 8.5 Remaining Life Assessment .......................................................................................................8-19 8.6 Remediation .................................................................................................................................8-20 8.7 In-Service Monitoring ..................................................................................................................8-20 8.8 Documentation.............................................................................................................................8-20 8.9 References....................................................................................................................................8-20 8.10 Tables And Figures......................................................................................................................8-22 8.11 Example Problems.......................................................................................................................8-52

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6.4

SECTION 9 – Assessment Of Crack-Like Flaws

9.4

9.5

9.6 9.7 9.8 9.9 9.10 9.11

General..........................................................................................................................................9-1 Applicability And Limitations Of The Procedure ......................................................................9-2 Data Requirements ......................................................................................................................9-3 9.3.1 General............................................................................................................................9-3 9.3.2 Original Equipment Design Data..................................................................................9-4 9.3.3 Maintenance And Operating History............................................................................9-4 9.3.4 Required Data/Measurements For A FFS Assessment – Loads And Stresses .......9-4 9.3.5 Required Data/Measurements For A FFS Assessment – Material Properties .........9-5 9.3.6 Required Data/Measurements For A FFS Assessment – Flaw Characterization.....9-6 9.3.7 Recommendations For Inspection Techniques And Sizing Requirements .............9-11 Assessment Techniques And Acceptance Criteria ..................................................................9-11 9.4.1 Overview .........................................................................................................................9-11 9.4.2 Level 1 Assessment.......................................................................................................9-12 9.4.3 Level 2 Assessment.......................................................................................................9-13 9.4.4 Level 3 Assessment.......................................................................................................9-19 Remaining Life Assessment .......................................................................................................9-21 9.5.1 Subcritical Crack Growth ..............................................................................................9-21 9.5.2 Leak Before Break Analysis..........................................................................................9-23 Remediation .................................................................................................................................9-27 In-Service Monitoring ..................................................................................................................9-28 Documentation.............................................................................................................................9-29 References....................................................................................................................................9-30 Tables And Figures......................................................................................................................9-32 Example Problems.......................................................................................................................9-66

SECTION 10 – Assessment Of Components Operating In the Creep Regime 10.1 General..........................................................................................................................................10-1 10.2 Applicability And Limitations Of The Procedure ......................................................................10-1 10.3 Data Requirements ......................................................................................................................10-1 10.3.1 Original Equipment Design Data..................................................................................10-1 10.3.2 Maintenance And Operational History.........................................................................10-1 10.3.3 Required Data/Measurements For A FFS Assessment ..............................................10-1 10.3.4 Recommendations For Inspection Techniques And Sizing Requirements .............10-1 10.4 Assessment Techniques And Acceptance Criteria ..................................................................10-1 10.4.1 Overview .........................................................................................................................10-1 10.4.2 Level 1 Assessment.......................................................................................................10-1 10.4.3 Level 2 Assessment.......................................................................................................10-1 10.4.4 Level 3 Assessment.......................................................................................................10-1 10.5 Remaining Life Assessment .......................................................................................................10-1 10.5.1 Creep Rupture Life.........................................................................................................10-1 10.5.2 Creep Fatigue Interaction .............................................................................................10-1 10.5.3 Creep Crack Growth ......................................................................................................10-1 10.6 Remediation .................................................................................................................................10-1 10.7 In-Service Monitoring ..................................................................................................................10-1 10.8 Documentation.............................................................................................................................10-1 10.9 References....................................................................................................................................10-1 10.10 Tables And Figures......................................................................................................................10-1 10.11 Example Problems.......................................................................................................................10-1 SECTION 11 – Assessment Of Fire Damage 11.1 General..........................................................................................................................................11-1 11.2 Applicability And Limitations Of The Procedure ......................................................................11-1 11.3 Data Requirements ......................................................................................................................11-2


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9.1 9.2 9.3

11.4

11.5 11.6 11.7 11.8 11.9 11.10 11.11

11.3.1 Original Equipment Design Data..................................................................................11-2 11.3.2 Maintenance And Operational History.........................................................................11-2 11.3.3 Required Data/Measurements For A FFS Assessment ..............................................11-2 11.3.4 Recommendations For Inspection Techniques And Sizing Requirements .............11-6 Assessment Techniques And Acceptance Criteria ..................................................................11-7 11.4.1 Overview .........................................................................................................................11-7 11.4.2 Level 1 Assessment.......................................................................................................11-7 11.4.3 Level 2 Assessment.......................................................................................................11-8 11.4.4 Level 3 Assessment.......................................................................................................11-10 Remaining Life Assessment .......................................................................................................11-11 Remediation .................................................................................................................................11-11 In-Service Monitoring ..................................................................................................................11-11 Documentation.............................................................................................................................11-11 References....................................................................................................................................11-11 Tables And Figures......................................................................................................................11-12 Example Problems.......................................................................................................................11-52

A. A.1 A.2 A.3 A.4 A.5 A.6 A.7 A.8 A.9 A.10

Thickness, MAWP And Membrane Stress Equations For A FFS Assessment General..........................................................................................................................................A-1 Calculation of Minimum Wall Thickness, MAWP (MFH), And Membrane Stress ..................A-1 Pressure Vessels – Internal Pressure........................................................................................A-4 Pressure Vessels – External Pressure.......................................................................................A-21 Piping Components.....................................................................................................................A-29 API-650 Storage Tanks ................................................................................................................A-34 Thickness Equations For Supplemental Loads........................................................................A-34 Stress Calculation Equations for Ring Stiffeners ....................................................................A-36 References....................................................................................................................................A-37 Tables and Figures ......................................................................................................................A-37

B. B.1 B.2 B.3 B.4 B.5 B.6 B.7 B.8

Stress Analysis Overview For A FFS Assessment Stress Analysis Methods for a Fitness-For-Service Assessment...........................................B-1 Linear Elastic Stress Analysis Methods And Acceptance Criteria .........................................B-2 Nonlinear Elastic Plastic Stress Analysis Methods And Acceptance Criteria.......................B-5 Assessment for Structural Stability ...........................................................................................B-8 Methods For Fatigue Evaluation ................................................................................................B-19 Fitness-For-Service Assessments Using Finite Element Analysis.........................................B-29 References....................................................................................................................................B-35 Tables and Figures ......................................................................................................................B-36

C. C.1 C.2 C.3 C.4 C.5 C.6 C.7 C.8 C.9

Compendium of Stress Intensity Factor Solutions General..........................................................................................................................................C-1 Stress Analysis ............................................................................................................................C-2 Stress Intensity Factor Solutions for Plates .............................................................................C-4 Stress Intensity Factor Solutions for Plates with Holes ..........................................................C-17 Stress Intensity Factor Solutions for Cylinders .......................................................................C-24 Stress Intensity Factor Solutions for Spheres..........................................................................C-36 Stress Intensity Factor Solutions for Elbows And Pipe Bends...............................................C-40 Stress Intensity Factor Solutions for Nozzles and Piping Tees..............................................C-40 Stress Intensity Factor Solutions for Ring-Stiffened Cylinders..............................................C-42


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Appendices

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C.10 C.11 C.12 C.13 C.14 C.15 C.16

Stress Intensity Factor Solutions for Sleeve Reinforced Cylinders .......................................C-44 Stress Intensity Factor Solutions for Round Bars and Bolts..................................................C-44 Stress Intensity Factor For Cracks At Fillet Welds ..................................................................C-46 Stress Intensity Factor For Cracks In Clad Or Weld Overlayed Plates And Shells...............C-49 The Weight Function Method For Surface Cracks ...................................................................C-50 References....................................................................................................................................C-54 Tables and Figures ......................................................................................................................C-56

D. D.1 D.2 D.3 D.4 D.5 D.6 D.7 D.8 D.9 D.10 D.11 D.12 D.13 D.14 D.15

Compendium of Reference Stress Solutions General..........................................................................................................................................D-1 Stress Analysis ............................................................................................................................D-2 Reference Stress for Plates ........................................................................................................D-9 Reference Stress Solutions for Plates with Holes ...................................................................D-12 Reference Stress Solutions for Cylinders.................................................................................D-13 Reference Stress Solutions for Spheres ...................................................................................D-22 Reference Stress Solutions for Elbows And Pipe Bends ........................................................D-24 Reference Stress Solutions for Nozzles and Piping Tees .......................................................D-24 Reference Stress Solutions for Ring-Stiffened Cylinders .......................................................D-25 Reference Stress Solutions for Sleeve Reinforced Cylinders.................................................D-26 Reference Stress Solutions for Round Bars and Bolts ...........................................................D-26 Reference Stress Solutions For Cracks At Fillet Welds ..........................................................D-28 Reference Stress Solutions For Cracks In Clad Or Weld Overlayed Plates And Shells.......D-28 References....................................................................................................................................D-28 Tables and Figures ......................................................................................................................D-29

E. E.1 E.2 E.3 E.4 E.5 E.6 E.7 E.8 E.9 E.10 E.11

Residual Stresses in a Fitness-For-Service Evaluation General..........................................................................................................................................E-1 Applicability and Limitations ......................................................................................................E-1 Data Requirements and Definition of Variables........................................................................E-2 Full Penetration Welds in Piping and Pressure Vessel Cylindrical Shells.............................E-3 Full Penetration Welds in Spheres and Pressure Vessel Heads.............................................E-7 Full Penetration Welds in Storage Tanks ..................................................................................E-11 Full Penetration Welds at Corner Joints (Nozzles or Piping Branch Connections) .............E-13 Full Penetration and Fillet Welds at a Tee Joint .......................................................................E-14 Repair Welds ................................................................................................................................E-15 References....................................................................................................................................E-17 Tables and Figures ......................................................................................................................E-19

F. F.1 F.2

Material Properties For A FFS Assessment General..........................................................................................................................................F-1 Strength Parameters ...................................................................................................................F-1 F.2.1 Yield and Tensile Strength............................................................................................F-1 F.2.2 Flow Stress.....................................................................................................................F-2 F.2.3 Ramberg-Osgood Stress-Strain Relationship ............................................................F-3 Physical Properties......................................................................................................................F-4 F.3.1 Elastic Modulus .............................................................................................................F-4 F.3.2 Poisson’s Ratio ..............................................................................................................F-4 F.3.3 Coefficient of Thermal Expansion................................................................................F-4 F.3.4 Thermal Conductivity ....................................................................................................F-4 F.3.5 Thermal Diffusivity ........................................................................................................F-4 F.3.6 Density ............................................................................................................................F-4 Fracture Toughness ....................................................................................................................F-5 F.4.1 General............................................................................................................................F-5 F.4.2 Fracture Toughness Parameters..................................................................................F-5 F.4.3 Fracture Toughness Testing ........................................................................................F-6 F.4.4 Lower Bound Fracture Toughness ..............................................................................F-10

F.3

F.4

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F.5

F.6

F.7

F.8

F.9 G. G.1 G.2 G.3

Assessing Fracture Toughness From Charpy V-Notch Data ....................................F-12 Fracture Toughness for Materials Subject to In-Service Degradation .....................F-14 Temper Embrittlement and Other Aging Effects On The Fracture Toughness Of Cr-Mo Steels ..............................................................................................................................F-16 F.4.8 Fracture Toughness of Austenitic Stainless Steels ...................................................F-17 F.4.9 Probabilistic Fracture Toughness Distribution ..........................................................F-17 F.4.10 Effect of Loading Rate on Toughness .........................................................................F-20 F.4.11 Sources of Fracture Toughness Data..........................................................................F-22 Material Data for Crack Growth Calculations ...........................................................................F-22 F.5.1 Categories of Crack Growth .........................................................................................F-22 F.5.2 Fatigue Crack Growth Equations .................................................................................F-23 F.5.2.1 Overview .........................................................................................................................F-23 F.5.2.2 Paris Equation................................................................................................................F-23 F.5.2.3 Walker Equation.............................................................................................................F-24 F.5.2.4 Bilinear Equation ...........................................................................................................F-25 F.5.2.5 Modified Forman Equation ...........................................................................................F-25 F.5.2.6 NASGRO Equation.........................................................................................................F-26 F.5.2.7 Collipriest Equation .......................................................................................................F-27 F.5.2.8 ASME Section XI Ferritic Steel Air and Water Equation.............................................F-27 F.5.2.9 ASME Section XI Austenitic Steel Equations for in Air & Water Environments ......F-28 F.5.3 Fatigue Crack Growth Data...........................................................................................F-28 F.5.4 Stress Corrosion Crack Growth Equations.................................................................F-31 F.5.5 Stress Corrosion Crack Growth Data ..........................................................................F-32 Fatigue Curves.............................................................................................................................F-33 F.6.1 General............................................................................................................................F-33 F.6.2 Fatigue Curves Based on Smooth Bar Test Specimens............................................F-33 F.6.3 Fatigue Curves Based on Welded Test Specimens ...................................................F-34 Material Data for Creep Analysis................................................................................................F-37 F.7.1 Creep Rupture Data .......................................................................................................F-37 F.7.2 Creep Strain-Rate Data..................................................................................................F-37 F.7.3 MPC Project Omega Data..............................................................................................F-38 F.7.4 Isochronous Stress-Strain Curves...............................................................................F-40 F.7.5 Creep Regime Fatigue Data (Crack Initiation).............................................................F-40 F.7.6 Creep Crack Growth Data .............................................................................................F-40 References....................................................................................................................................F-42 F.8.1 Technical References ....................................................................................................F-42 F.8.2 Yield Strength, Tensile Strength, Creep Rupture Strength and Creep Strain Rate Data .........................................................................................................................................F-44 F.8.3 Physical Properties........................................................................................................F-46 F.8.4 Fracture Toughness Data .............................................................................................F-46 F.8.5 Fatigue and Stress Corrosion Crack Growth Data .....................................................F-46 F.8.6 Creep Crack Growth Data .............................................................................................F-47 F.8.7 Fatigue Curves (Crack Initiation) for Components Operating in the Creep Regime F-48 Tables and Figures ......................................................................................................................F-48 Deterioration And Failure Modes Deterioration and Failure Modes................................................................................................G-1 Pre-Service Deficiencies .............................................................................................................G-1 In-Service Deterioration and Damage........................................................................................G-1 G.3.1 Overview .........................................................................................................................G-1 G.3.2 General Metal Loss Due to Corrosion and/or Erosion...............................................G-2 G.3.3 Localized Metal Loss Due to Corrosion and/or Erosion............................................G-2 G.3.4 Surface Connected Cracking........................................................................................G-3 G.3.5 Subsurface Cracking and Microfissuring/Microvoid Formation...............................G-4 G.3.6 Metallurgical Changes...................................................................................................G-5


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F.4.5 F.4.6 F.4.7

References....................................................................................................................................G-6 Tables and Figures ......................................................................................................................G-6

H. H.1 H.2 H.3 H.4 H.5

Validation Overview.......................................................................................................................................H-1 Non-Crack-Like Flaws .................................................................................................................H-1 Crack-Like Flaws .........................................................................................................................H-1 References....................................................................................................................................H-1 Tables and Figures ......................................................................................................................H-1

I.

Glossary Of Terms And Definitions

J. J.1 J.2

Technical Inquiries Introduction..................................................................................................................................J-1 Inquiry Format..............................................................................................................................J-1

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SECTION

I-

INTRODUCTION (Jan, 2000)

1.1

introduction The ASME and API design codes and standards for pressurized equipment provide rules for the design, fabrication, inspection and testing of new pressure vessels, piping systems, and storage tanks. These codes do not address the fact that equipment degrades while in-service and that deficiencies due to degradation or from original fabrication may be found during subsequent inspections. Fitness-For-Service (FKS) assessments are quantitative engineering evaluations which are performed to demonstrate the structural integrity of an in-service component containing a flaw or damage. This Recommended Practice provides guidance for conducting I;Fs assessments using methodologies specifically prepared for equipment in the refining and petrochemical industry. The guidelines provided in this recommended practice can be used to make run-repair-replace decisions to help ensure that pressurized equipment containing flaws which have been identified by inspection can continue to operate safely. Scope

1.2.1

The methods and procedures in this recommended practice are intended to supplement augment the requirements in API 510, API 570 and API 653.

1.2.2

The assessment procedures in this recommended practice can be used for fitness-for-service assessments and/or rerating of components designed and constructed to the following codes: .

ASME B&PV Code, Section VIII, Division

.

ASME B&PV Code, Section VIII, Division 2

.

ASME B&PV Code, Section 1

.

ASME B31.3 Piping Code

.

ASME 831 .I Piping Code

.

API 650

.

API 620

and

1

1.2.3

The assessment procedures in this recommended practice may also be applied to pressure containing equipment constructed to other recognized codes and standards, including international and internal corporate standards. This recommended practice has broad application since the assessment procedures are based on allowable stress methods and plastic collapse loads for noncrack-like flaws, and FAD-based strategies for crack-like flaws (see Section 2, paragraph 2.4.2).

1.2.3.1

The user is advised to first review the validation discussion of Appendix H when the procedures of this recommended practice are applied to pressure containing equipment not constructed to the codes listed in paragraph 1.2.2. The information in Appendix H, along with a knowledge of the of differences in design codes, should enable the user to factor, scale, or adjust the acceptance limits of this recommended practice such that equivalent I?Z-% in-service margins can be attained for equipment not constructed to these codes. When evaluating other codes and standards the following attributes of the ASME and API design codes should be considered: . Material specifications .

Upper and/or lower temperature

.

Material strength

.

Material fracture toughness

.

Design rules for shell sections


properties

limits for specific materials

and the design allowable

stress

basis

requirements

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1.2

API RECOMMENDED PRACTICE 579

1-2

.

Design rules for shell discontinuities such as nozzles and conical transitions

.

Design requirements for cyclic loads

.

Design requirements for operation in the creep range

.

Weld joint efficiency or quality factors

.

Fabrication details and quality of workmanship

.

Inspection requirements, particularly for welded joints

Jan, 2000

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1.2.3.2

As an alternative, users may elect to correlate the pressure-containing component’s material specification to an equivalent ASME or API listed material specification to determine an associated allowable stress. This approach provides an entry point into the ASME or API codes (refer also to Appendix A) wherein the pressure-containing component is reconciled or generally made equivalent to the design bases assumed for this recommended practice. Hence general equivalence is estab!ished and the user may then app!y the acceptance limits of these fitness for service procedures unaltered. Equivalent ASME and ASTM material specifications provide a satisfactory means for initiating a reconciliation between the ASME and API design codes and other codes and standards. However, the user is cautioned to also consider the effects of fabrication and inspection requirements on the design basis (e.g., joint efficiency with respect to minimum thickness sizing).

1.2.4

The Fitness-For-Service assessment procedures in this recommended practice cover both the present integrity of the component given a current state of damage and the projected remaining life. Assessment techniques are included to evaluate flaws including: general and localized corrosion, widespread and localized pitting, blisters and laminations, weld misalignment and shell distortions, and crack-like flaws including environmental cracking. In addition, evaluation techniques are provided for condition assessment of equipment including resistance to brittle fracture, long-term creep damage, and fire damage.

1.2.5

Analytical procedures, material properties including environmental effects, NDE guidelines and documentation requirements are included in the fitness-for-service assessment procedures in this document. In addition, both qualitative and quantitative guidance for establishing remaining life and in-service margins for continued operation of equipment are provided in regards to future operating conditions and environmental compatibility.

1.2.6

The Fitness-For-Service assessment procedures in this recommended practice cover situations involving flaws commonly encountered in the refining and petrochemical industry in pressure vessels, piping and tankage. The procedures are not intended to provide a definitive guideline for every possible situation that may be encountered. However, flexibility is provided to the user in the form of an advanced assessment level to handle uncommon situations that may require a more detailed analysis.

1.2.7

The methods and procedures in this recommended practice can also be used in conjunction with the National Board Inspection Code (NBIC) to the extent currently permitted by that document and local regulations.

1.3

Organization

And Use

The organization, applicability and limitations, required information, analysis techniques and documentation requirements are described in Section 2.0 of this document. In addition, an overview of the acceptance criteria utilized throughout the document to qualify a component with a flaw is provided. First time users of the Fitness-For-Service assessment technology in this document are urged to carefully review Section 2.0 prior to starting an analysis.

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Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE 1-3 _________________________________________________________________________________________________

1.4

Responsibilities

1.4.1

Owner-User The owner-user of pressurized equipment shall have overall responsibility for fitness-for-service assessments completed using the procedures in this recommended practice.

1.4.2

Inspector

1.4.2.1

The Inspector shall be responsible to the owner-user for determining that the requirements of API 510, API 570 and API 653 for inspection and testing are met. In addition, the Inspector shall provide all necessary inspection data required for a fitness-for-service assessment in accordance with the appropriate section of this document.

1.4.2.2

The Inspector shall ensure that the results of the assessment are documented and filed with the appropriate permanent equipment records.

1.4.2.3

In some instances, the Inspector may also be responsible for the fitness-for-service assessment if a screening (Level 1, see Section 2, paragraph 2.4 for definition) type of analysis is performed.

1.4.3

Engineer

1.4.3.1

The Engineer is responsible to the owner-user for most types of fitness-for-service assessments, documentation, and resulting recommendations. The exception is that screening analyses (Level 1 analyses, see Section 2, paragraph 2.4 for definition) may be performed by an Inspector; however, even in this case the Engineer should review the analysis.

1.4.3.2

In the context of this document, the term Engineer applies to the combination of the following disciplines unless a specific discipline is cited directly. In many cases, a fitness-for-service assessment will require several engineering disciplines and some will require input from all of those described below.

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a.

Materials or Metallurgical Engineer – Responsibilities include identification of the material damage mechanisms, establishment of corrosion/erosion rates, determination of material properties including strength parameters and crack-like flaw growth parameters, development of suitable remediation methods and monitoring programs, and documentation.

b.

Mechanical or Structural Engineer – Responsibilities include computations of the minimum required thickness and/or MAWP (MFH) for a component, and any required thermal and stress analysis. The mechanical engineer should be knowledgeable in the design of pressure containing equipment including pressure vessels, piping, and tankage.

c.

Inspection Engineer – Responsibilities include those stated for either the mechanical or materials engineer as well as those stated for the Inspector.

d.

Fracture Mechanics Engineer – Responsibilities include assessment of crack-like flaws using the principles of fracture mechanics. The Materials or Mechanical Engineer may also perform this function.

e.

Non-Destructive Examination (NDE) Engineer – Responsibilities include development of methods to detect, characterize, and size or quantify the amount of damage. In addition, the NDE Engineer shall recommend and ensure the accuracy of the NDE technique used for flaw sizing. The Inspection, Materials or Mechanical Engineer may also perform this function.

f.

Process Engineer – Responsibilities include documentation of past and future operating conditions, including normal and upset conditions, and identification of the contained fluid and

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1-4 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

1.5

Qualifications

1.5.1

Qualifications for the Inspector (see paragraph 1.4.2) shall be per API 510, API 570, and API 653, as applicable.

1.5.2

Engineers (see paragraph 1.4.3) involved in Fitness-For-Service assessments shall have a degree in engineering and a minimum of two years experience in the inspection and failure analysis, or the design, construction, repair, and operation of pressure vessels, piping and tankage in the refining and/or petrochemical industry.

1.5.3

Qualifications for the Inspector (see paragraph 1.4.2) and the Engineer (see paragraph 1.4.3) shall also meet any special owner/user qualifications and local jurisdictional requirements.

1.6

Definition Of Terms Definitions of common technical terms used throughout this document may be found in Appendix I.

1.7

References

1.7.1

Throughout this document, references are made to various international codes, standards, recommended practices, and technical reports which cover: ·

Design, fabrication, inspection and testing of pressure vessels, piping, and tankage

·

In-service inspection of pressure vessels, piping, and tankage

·

Fitness-for-service standards applicable to welded components

·

Materials selection and behavior in refining and chemical plant processing environments

Rules for the use of these codes, standards, recommended practices and technical reports are stated in the each section and appendix of this document. The referenced codes, standards, and recommended practices in this recommended practice, with the year of the acceptable edition, are listed in Table 1.1.

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1.7.2

References to other publications which provide background and other pertinent information to the assessment procedures used in this recommended practice are included in each section and appendix, as applicable.

1.8

Tables


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its contaminant levels. The process engineer should have a chemical engineering background.

Table 1.1 And Recommended

Standards,

Title Calculation Refineries

of Heater-Tube

Recognition

of Conditions

Inspection

Identification

Thickness

Causing

in Petroleum

Deterioration

of Piping, Tubing, Valves,

of Pressure

Relieving

of Atmospheric

Practice

for Inspection

Recommended

Practice

for Positive Materials

Recommended

Practice for Risk-Based

of Welding Identification

Inspection

Inspection

of Pressure

Inspection

of Fired Boilers and Fired Heaters

Pressure Rerating,

Vessel Inspection Code: Maintenance Repair and Alteration

Vessels

Design and Construction Storage Tanks Steel Tanks

Tank Inspection,

of Large, Welded,

Inspection,

Low-Pressure

for Oil Storage

Repair, Alteration,

Manual for Determining Corroded Pipelines National

and Reconstruction

the Remaining

Board Inspection

Strength

of

Document

- Risk Based Inspection

Steels for Hydrogen Service at Elevated Temperatures Pressures in Petroleum Refineries and Petrochemical Plants Avoiding

Environmental


Cracking

RP 530

Fourth Edition,1996

ANSI/API

RP 571

In Progress

ANSI/API

RP 574

(See Note 2)

ANSI/API

RP 575

(See Note 2)

ANSI/API

RP 576

(See Note 2)

ANSI/API

RP 577

In Progress

ANSI/API

RP 578

In Progress

ANSI/API

RP 580

In Progress

ANSI/API

RP 572

(See Note 2)

ANSI/API

RP 573

(See Note 2)

510

Eight Edition, June, 1997

ANSI/API

Std 620

Ninth Edition, 1996

ANSI/API

Std 650

Ninth Edition, 1993 (Including Addenda 1,2&3)

ANSI/API

Std 653

Second Edition, 1995

ANSI/API

831 G

ANSI/NB-23 and

and

in Amine Units

Year (1)

ANSI/API

ANSI/ASME

Code

Piping Inspection Code: Inspection, Repair, Alteration, Rerating of In-Service Piping Systems Base Resource

and

Devices

Recommended

Welded

or Failure

and Fittings

Recommended Practice for Inspection Low Pressure Storage Tanks Inspection

Practices

1991

1995

API 570

First Edition, June 1993

API Pub1581

(See Note 2)

API RP 941

Fifth Edition, January, 1997

API RP 945

(See Note 2)

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Codes,

PRACTICE FOR FITNESS-FOR-SERVICE

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RECOMMENDED

Jan, 2000

API RECOMMENDEDPRACTICE 579

1-6

Table 1.1 Codes, Standards, And Recommended Title

Jan, 2000

Practices Year (1)

Minimum Design Loads for Buildings and Other Structures

ASCE 7

(See Note 2)

Alternative Method to Area Replacement Rules for Openings Under internal Pressure, Section VIII, Division 1

ASME B&PV Code Case 2168

1995

Alternative Method of Calculating Maximum Allowable Stresses Based on a Factor of 3.5 on Tensile Strength, Section I! and Section V!!!, Division ?


1998

Alternative Rules for Determining Allowable Compressive Stresses For Cylinders, Cones, Spheres and Formed Heads Section VIII, Divisions 1 and 2


1998

Alternative Maximum Allowable Stresses Based on a Factor of 3.5 on Tensile Strength, Section II and Section VIII, Division 1


1998

Rules For Construction of Power Boilers

ASME B&PV Code Section I

1999

Boiler and Pressure Vessel Code, Section II, Part D Properties

ASME B&PV Code Section II, Part D

1999

ASME B&PV Code Section Ill, Division 1

1997

Boiler and Pressure Vessel Code, Section VIII, Pressure Vessels Division 1

ASME B&PV Code Section VIII, Division 1

1999

Boiler and Pressure Vessel Code, Section VIII, Pressure Vessels Division 2, Alternative Rules

ASME B&PV Code Section VIII, Division 2

1999

ASME B&PV Code Section Xl

1999

Factory-Made Wrought Steel Buttwelding Fittings

ASME B16.5

1995

Process Piping

ASME 831.3

1996

ASTM A20

(See Note 2)

Electric-Fusion-Welded Austenitic Chromium-Nickel Alloy Steel Pipe for High Temperature Service

ASTM A358

(See Note 2)

Standard Test Methods and Definitions for Mechanical Testing of Steel Products

ASTM A370

1990

General Requirements for Specialized Carbon and Alloy Steel Pipe

ASTM A530

(See Note 2)

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Identification

Subsection NH - Class 1 Components in Elevated Temperature Service

Rules For Inservice Inspection Of Nuclear Power Plant Components

Specification for General Requirements for Steel Plates for Pressure Vessels.

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Title

Identification

Year (1)

Electric-Fusion Welded Steel Pipe for Atmospheric and Lower Temperatures

ASTM A671

(See Note 2)

Electric-Fusion Welded Steel Pipe for High-Pressure Service at Moderate Temperatures

ASTM A672

(See Note 2)

Carbon and Alloy Steel Pipe, Electric-Fusion Welded for High-Pressure Service at High Temperatures

ASTM A691

(See Note 2)

Standard Practices for Cycle Counting in Fatigue Analysis

ASTM E1049

1990

Standard Test Method for Measurement of Fracture Toughness

ASTM E1820

1996

Test Method For The Determination of Reference Temperature, T0, For Ferritic Steels In The Transition Range

ASTM E1921

1998

Standard Test Method for Measurement of Fatigue Crack Growth Rates

ASTM E647

1988

ASTM E8

(See Note 2)

Standard Guide for Examination and Evaluation of Pitting Corrosion

ASTM G46

(See Note 2)

Specification for Unfired Fusion Welded Pressure Vessels

BS 5500

(See Note 2)

Method for Determination of KIC, Critical CTOD and Critical J Values of Welds in Metallic Materials

BS 7448: Part 2

1997

Code of Practice for Fatigue Design and Assessment of Steel Structures

BS 7608

(See Note 2)

Guide on Methods For Assessing the Acceptability of Flaws in Structures

BS 7910

1999

Guidance on Methods for Assessing the Acceptability of Flaws in Fusion Welded Structures

BS PD 6493

1991

Methods for the Assessment of the Influence of Crack Growth on the Significance of Defects in Components Operating at High Temperatures

BS PD 6539

1994

Design of Steel Pressure Pipes

DIN 2413 Part 1

(See Note 2)

Design of Steel Bends Used in Pressure Pipelines

DIN 2413 Part 2

(See Note 2)

ISO/TR 7468-1981(E)

(See Note 2)

Test Methods of Tension Testing of Metallic Materials

Summary of the Average Stress Rupture Properties of Wrought Steels for Boilers and Pressure Vessels

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Table 1.1 Codes, Standards, And Recommended Practices


Title //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Identification

Year (1)

Guidance On Assessment of the Fitness For Purpose of Welded Structures, Draft For Development

IIW/IIS – SST 1157

1990

Guidelines for Detection, Repair, and Mitigation of Cracking of Existing Petroleum Refinery Pressure Vessels in Wet H2S Environments

NACE Std RP0296

1996

Assessment Procedure For High Temperature Response Of Structures

Nuclear Electric R-5

1998

Assessment Of The Integrity of Structures Containing Defects

Nuclear Electric R-6

1998

Evaluation Of Design Margins For ASME Code Section VIII

PVRC

March, 1996

Evaluation Of Design Margins For ASME Code Section VIII, Division 1 And 2 – Phase 2 Studies

PVRC

June, 1997

SAQ/FoU-Report 96/08

1997

WES 2805

1997

A Procedure for Safety Assessment of Components with Cracks – Handbook Method of Assessment for Flaws in Fusion Welded Joints with Respect to Brittle Fracture and Fatigue Crack Growth

Notes: 1. The specific editions of the standards where a date is provided contain provisions relevant to this edition of API 579. 2. Updates to API 579 will not consider changes in this document. Generally, the latest edition of this document may be used in performing an assessment, as long as the equipment component being assessed meets any stipulated limitations therein. However, in some assessments the edition of the document in force at the time of the equipment's construction should be used if dictated by either jurisdictional requirements or the judgment of the Engineer (see paragraph 1.4.3) performing the assessment.


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Table 1.1 Codes, Standards, And Recommended Practices

SECTION 2 – Fitness-For-Service Engineering Assessment Procedure (Jan, 2000) 2.1

General

2.1.1

This document contains Fitness-For-Service (FFS) assessment procedures that can be used to evaluate pressurized components containing flaws or damage. If the results of a fitness-for-service assessment indicate that the equipment is suitable for the current operating conditions, the equipment can continue to be operated at these conditions provided suitable monitoring/inspection programs are established. If the results of the fitness-for-service assessment indicate that the equipment is not suitable for the current operating conditions, calculation methods are provided to rerate the component. For pressurized components (e.g. pressure vessels and piping) these calculation methods can be used to find a reduced Maximum Allowable Working Pressure (MAWP) and/or coincident temperature. For tank components (shell courses) the calculation methods can be used to determine a reduced Maximum Fill Height (MFH).

2.1.2

The Fitness-For-Service assessment procedures in this document are organized by flaw type and/or damage mechanism. A list of flaw types and damage mechanisms and the corresponding section which provides the FFS assessment methodology is shown in Table 2.1. In some cases, it may be necessary to use the assessment procedures from multiple sections if the primary type of damage is not evident. For example, the metal loss in a component may be associated with general corrosion, local corrosion and pitting. If multiple damage mechanisms are present, a degradation class, e.g., corrosion/erosion, can be identified to assist in the evaluation. An overview of degradation classes in this document is shown in Figure 2.1. As indicated in this figure, several flaw types and damage mechanisms may need to be evaluated to determine the Fitness-For-Service of a component. Each section referenced within a degradation class includes guidance on how to perform an assessment when multiple damage mechanisms are present.

2.1.3

The general Fitness-For-Service assessment procedure used in this Recommended Practice (RP) for all flaw types is provided in this section. An overview of the procedure is provided in the following eight steps. The remaining sections in this RP utilize this assessment methodology for a specific flaw type or damage mechanism and provide specific details covering Steps 2 through 8 of this procedure.

2.1.3.1

Step 1 – Flaw and Damage Mechanism Identification: The first step in a Fitness-For-Service assessment is to identify the flaw type and cause of damage (see paragraph 2.1.2). The original design and fabrication practices, the material of construction, and the service history and environmental conditions can be used to ascertain the likely cause of the damage. An overview of damage mechanisms which can assist in identifying likely causes of damage is provided in Appendix G. Once the flaw type is identified, the appropriate section of this document can be selected for the assessment (see Table 2.1 and Figure 2.1).

2.1.3.2

Step 2 – Applicability and Limitations of the FFS Assessment Procedures: The applicability and limitations of the assessment procedure are described in each section, and a decision on whether to proceed with an assessment can be made.

2.1.3.3

Step 3 – Data Requirements: The data required for a FFS assessment depend on the flaw type or damage mechanism being evaluated. Data requirements may include: original equipment design data, information pertaining to maintenance and operational history, expected future service, and data specific to the FFS assessment such as flaw size, state of stress in the component at the location of the flaw, and material properties. Data requirements common to all FFS assessment procedures are covered in this section. Data requirements specific to a damage mechanism or flaw type are covered in the section containing the corresponding assessment procedures.

--``````-`-`,,`,,`,`,,`---


2-1

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.1.3.4

Step 4 – Assessment Techniques and Acceptance Criteria: Assessment techniques and acceptance criteria are provided in each section. If multiple damage mechanisms are present, more than one section may have to be used for the evaluation.

2.1.3.5

Step 5 – Remaining Life Evaluation: An estimate of the remaining life or limiting flaw size should be made for the purpose of establishing an inspection interval. The remaining life is established using the FFS assessment procedures with an estimate of future damage. The remaining life can be used in conjunction with an inspection code to establish an inspection interval.

2.1.3.6

Step 6 – Remediation: Remediation methods are provided in each section based on the damage mechanism or flaw type. In some cases, remediation techniques may be used to control future damage associated with flaw growth and/or material degradation.

2.1.3.7

Step 7 – In-Service Monitoring: Methods for in-service monitoring are provided in each section based on the damage mechanism or flaw type. In-service monitoring may be used for those cases where a remaining life and inspection interval cannot adequately be established because of the complexities associated with the service environment.

2.1.3.8

Step 8 – Documentation: Documentation should include a record of all information and decisions made in each of the previous steps to qualify the component for continued operation. Documentation requirements common to all FFS assessment procedures are covered in this section. Documentation requirements specific to a damage mechanism or flaw type are covered in the section containing the corresponding assessment procedures.

2.2

Applicability And Limitations Of The FFS Assessment Procedures

2.2.1

The FFS assessment procedures in this document were developed to assess components with a flaw resulting from single or multiple damage mechanisms. In the context of this document, a component is defined as any pressurized part that is designed using a nationally recognized code or standard (see paragraph 2.2.2). Equipment is defined to be an assemblage of components. Therefore, the pressurized equipment covered in this document includes all pressure boundary components of pressure vessels, piping, and tank shell courses of storage tanks. Fitness-for-service procedures for fixed and floating roof structures, and bottom plates of tanks are covered in Section 2 of API 653.

2.2.2

The FFS assessment procedures in this document were developed assuming that the component was designed and fabricated to a recognized code or standard (see Section 1, paragraphs 1.2.2 and 1.2.3).

2.2.3

For equipment components that are discovered to not have been designed, or constructed to the original design criteria, the principles in this document may be used to evaluate the in-service damage and as-built condition relative to the intended design. FFS assessments of this type shall be performed by an Engineer (see Section 1, paragraph 1.4.3) knowledgeable and experienced in the design requirements of the applicable code.

2.2.4

Each section in this document where FFS Assessment procedures are described include a segment which states the applicability and limitations of the procedures. The limitations and applicability of an analysis procedure are stated relative to the Level of Assessment (see paragraph 2.4).

2.3

Data Requirements

2.3.1

Original Equipment Design Data

2.3.1.1

The following original equipment design data should be assembled to perform a FFS assessment. The extent of the data required depends on the damage mechanism and assessment level. A data sheet is included in Table 2.2 to record the required information that is common to all FFS


Not for Resale


assessments. In addition, a separate data sheet is included with each section of this document to record information specific to the flaw type, damage mechanism, and assessment procedure. a.

Data for pressure vessels may include some or all of the following: An ASME Manufacturer's Data Report or, if the vessel is not Code stamped, other equivalent documentation or specifications.

2.

Vessel fabrication drawings showing sufficient details to permit calculation of the MAWP of the component containing the flaw. If a rerate to a different condition of pressure and/or temperature is desired (i.e. increase or decrease in conditions), this information should be available for all affected components. Detailed sketches with data necessary to perform MAWP calculations may be used if the original fabrication drawings are not available.

3.

The original or updated design calculations for the load cases in Table A.1 of Appendix A, as applicable, and anchor bolt calculations.

4.

The inspection records for the component at the time of fabrication.

5.

User Design Specification if the vessel is designed to the ASME Code, Section VIII, Division 2.

6.

Material test reports.

7.

Pressure-relieving device information including pressure relief valve and/or rupture disk setting and capacity information.

8.

A record of the original hydrotest including the test pressure and metal temperature at the time of the test or, if unavailable, the water or ambient temperature.

--``````-`-`,,`,,`,`,,`---

1.

b.

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c.

Data for piping components may include some or all of the following: 1.

Piping Line Lists or other documentation showing process design conditions, and a description of the piping class including material specification, pipe wall thickness and pressure-temperature rating.

2.

Piping isometric drawings to the extent necessary to perform a FFS assessment. The piping isometric drawings should include sufficient details to permit a piping flexibility calculation if this analysis is deemed necessary by the Engineer in order to determine the MAWP (maximum safe or maximum allowable operating pressure) of all piping components. Detailed sketches with data necessary to perform MAWP calculations may be used if the original piping isometric drawings are not available.

3.

The original or updated design calculations for the load cases in Table A.1 of Appendix A, as applicable.

4.


5.


6.

A record of the original hydrotest including the test pressure and metal temperature at the time of the test, or if unavailable, the water or ambient temperature.

Data for tanks may include some or all of the following: 1.


The original API data sheet.

Not for Resale


--``````-`-`,,`,,`,`,,`---

2.

Fabrication drawings showing sufficient details to permit calculation of the maximum fill height (MFH) for atmospheric storage tanks and the MAWP for low pressure storage tanks. Detailed data with sketches where necessary may be used if the original fabrication drawings are not available.

3.

The original or updated design calculations for the load cases in Table A.1 of Appendix A, as applicable, and anchor bolt calculations.

4.


5.


6.

A record of the last hydrotest performed including the test pressure and metal temperature at the time of the test or, if unavailable, the water or ambient temperature.

2.3.1.2

If some of these data are not available, physical measurements or field inspection of the component should be made to provide the information necessary to perform the assessment.

2.3.2

Maintenance And Operational History

2.3.2.1

A progressive record including, but not limited to, the following should be available for the equipment being evaluated. The extent of the data required depends on the damage mechanism and assessment level. a.

The actual operating envelope consisting of pressure and temperature, including upset conditions should be obtained. If the actual operating conditions envelope is not available, an approximation of one should be developed based upon available operational data and consultation with operating personnel. An operating histogram may be required consisting of pressure and temperature data recorded simultaneously for some types of FFS assessments (e.g., Section 10.0 for components operating in the creep regime).

b.

Documentation of any significant changes in service conditions including pressure, temperature, fluid content and corrosion rate. Both past and future service conditions should be reviewed and documented.

c.

The date of installation and a summary of all alterations and repairs including required calculations, material changes, drawings and repair procedures. The calculations should include the required wall thicknesses and MAWP (MFH for atmospheric storage tanks) including definition and allowances for supplemental loads such as static liquid head, wind, and earthquake loads.

d.

Records of all hydrotests performed as part of the repair including the test pressure and metal temperature at the time of the tests or, if unavailable, the water or ambient temperature at the time of the test if known.

e.

Results of prior in-service examinations including wall thickness measurements and other NDE results that may assist in determining the structural integrity of the component and in establishing a corrosion rate.

f.

Records of all internal repairs, weld build-up and overlay, and modifications of internals.

g.

Records of "out-of-plumb" readings for vertical vessels.

h.

Foundation settlement records if the corrosion being evaluated is located in the bottom shell course of the tank.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

RECOMMENDED

PRACTICE

FOR FITNESS-FOR-SERVICE

2.3.2.2

If some of these data are not available, physical measurements should be made to provide the information necessary to perform the assessment.

2.3.3

Required Data/Measurements

2-5

For A FFS Assessment

--``````-`-`,,`,,`,`,,`---

2.3.3.1

Each section in this document which contains FFs assessment procedures includes specific requirements for data measurements and flaw characterization based on the damage mechanism being evaluated. Examples of flaw characterization include thickness profiles for local corrosion/erosion, pitting depth, and dimensions of crack-like flaws. The extent of information and data required for a FFS assessment is dependent on the assessment level and damage mechanism being evaluated.

2.3.3.2

The Future Corrosion Allowance (FCA) should be established for the intended future operating period. The FCA should be based on past inspection information or corrosion rate data relative to the component material in a similar environment. Corrosion rate data may be obtained from API Publication 581 or other sources (see paragraph A.2.7 of Appendix A). The FcA is calculated by multiplying the anticipated corrosion rate by the future service period considering inspection interval requirements of the applicable inspection code. The F?% assessment procedures in this document include provisions to ensure that the F&I is available for the future intended operating period.

2.3.4

Recommendations

For Inspection Technique And Sizing Requirements

Recommendations for Non Destructive Examination (NDE) procedures with regard to detection and sizing of a particular damage mechanism and/or flaw type are provided in each section. 2.4

Assessment Techniques And Acceptance

2.4.1

Three Levels of assessment are provided in each Section of this document which cover FK!? assessment procedures. A logic diagram is included in each Section to illustrate how these assessment levels are interrelated. In general, each assessment level provides a balance between conservatism, the amount of information required for the evaluation, the skill of the personnel performing the assessment, and the complexity of analysis being performed. Level 1 is the most conservative, but is easiest to use. Practitioners usually proceed sequentially from a Level 1 to a Level 3 analysis (unless otherwise directed by the assessment techniques) if the current assessment level does not provide an acceptable result, or a clear course of action cannot be determined. A general overview of each assessment level and its intended use are described below.

2.4.1.1

Level 7 - The assessment procedures included in this level are intended to provide conservative screening criteria that can be utilized with a minimum amount of inspection or component information. Level 1 assessments may be performed by either plant inspection or engineering personnel (see Section 1, paragraphs 1.4.2 and 1.4.3).

2.4.1.2

Level 2 -The assessment procedures included in this level are intended to provide a more detailed evaluation that produces results that are more precise than those from a Level 1 assessment. In a Level 2 Assessment, inspection information similar to that required for a Level 1 assessment are needed; however, more detailed calculations are used in the evaluation. Level 2 assessments would typically be conducted by plant engineers, or engineering specialists experienced and knowledgeable in performing FFs assessments.

2.4.1.3

Level 3 -The assessment procedures included in this level are intended to provide the most detailed evaluation which produces results that are more precise than those from a Level 2 assessment. In a Level 3 Assessment the most detailed inspection and component information is typically required, and the recommended analysis is based on numerical techniques such as the finite element method.


Criteria

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PRACTICE 579

A Level 3 analysis is primarily intended for use by engineering knowledgeable in performing FFs assessments. methodologies

presented

Jan, 2000 specialists

in this document

experienced

and

2.4.2

Each of the FFS assessment following acceptance criteria:

utilize one or more of the

2.4.2.1

Allowable Stress

2.4.2.2

Remaining Strength factor- Structural evaluation procedures using linear elastic stress analysis with stress classification and allowable stress acceptance criteria provide only a rough approximation of the loads which a component can withstand without failure. A better estimate of the safe load carrying capacity of a component can be provided by using nonlinear stress analysis to: develop limit and plastic collapse loads, evaluate the deformation characteristics of the component (e.g. deformation or strain limits associated with component operability), and assess fatigue and/or creep damage including ratcheting.

- This acceptance criteria is based upon calculation of stresses resulting from different loading conditions, classification and superposition of stress results, and comparison of the calculated stresses in an assigned category or class to an allowable stress value. An overview and aspects of these acceptance criteria are included in Appendix B. The allowable stress value is typically established as a fraction of yield, tensile or rupture stress at room and the service temperature, and this fraction can be associated with a design margin. This acceptance criteria method is currently utilized in most new construction design codes. In F??.? applications, this method has proven to have limited applicability because of the difficulty in establishing suitable stress classifications for components containing flaws. As an alternative, assessment methods based on elastic-plastic analysis can be used (see Appendix B, paragraph 8.6.4). Elastic-plastic analysis methods were used to develop the Remaining Strength Factor (see paragraph 2.4.2.2).

a.

In this document, the concept of a remaining strength factor is utilized to define the acceptability of a component for continued service. The Remaining Strength Factor (RSfl defined as:

is

--``````-`-`,,`,,`,`,,`---

where

b.

LDC

=

J5Yc

=

Limit or plastic collapse flaws), and Limit or plastic collapse

load of the damaged load of the undamaged

component

(component

with

component.

With this definition of the RSF, acceptance criteria can be established using traditional code formulas, elastic stress analysis, limit load theory, or elastic-plastic analysis. For example, to evaluate local thin areas (see Section 5) the FFS assessment procedures provide a means to compute a RSF. If the calculated RSF is greater than the allowable RSF (see below) the damaged component can be placed back into service. If the calculated RSF is less than the allowable value, the component can be repaired, rerated or some form of remediation can be applied to reduce the severity of the operating environment. The rerated pressure can be calculated from the RSF as follows:

MAWe=MAWP AUWP, = UAWP

for for

RSF < RSY$

RSF>RSF,

where


Not for Resale

(2.2)

(2.3)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

API RECOMMENDED

2-6

RECOMMENDED

Jan, 2000

MA WPr = MA WI-’ =

C.

RSF

=

RSF,

=

For tankage, the

PRACTICE

RSF acceptance criteria is:

MFHr = MFH

d.

2.4.2.3

for

RSF c RSF,

(2.4)

RSF 2 RSF,

(2.5)

RSF and RSF, are defined in paragraph 2.4.2.2.b and, MFHr

=

MFH

=

Reduced permissible maximum fill height of the damaged tank course, and Maximum fill height of the undamaged component (see paragraph A.2.1 of Appendix A).

The recommended value for the allowable Remaining Strength Factor, RSF,, is 0.90 for equipment in process services. This value has been shown to be conservative (see Appendix H). This value may be reduced based upon the type of loading (e.g. normal operating loads, occasional loads, short-time upset conditions) and/or the consequence of failure. For example, a lower factor could be utilized for low pressure piping containing a flaw which conveys cooling water, or for a shell section containing a flaw subject to normal operating pressure and design wind loads.

Failure Assessment Diagram - The Failure Assessment Diagram crack-like flaws in components. a.

2-7

Reduced permissible maximum allowable working pressure of the damaged component, Maximum allowable working pressure of the undamaged component (see paragraph A.2.1 of Appendix A), Remaining strength factor computed based on the flaw and damage mechanism in the component, and Allowable remaining strength factor (see paragraph 2.4.2.2.d).

for

where


(FAD) is used for the evaluation of

The FAD approach was adopted because it provides a convenient, technically based method to provide a measure for the acceptability of a component with a crack-like flaw when the failure mechanism is measured by two distinct criteria: unstable fracture and limit load. Unstable fracture usually controls failure for small flaws in components fabricated from a brittle material and plastic collapse typically controls failure for large flaws if the component is fabricated from a material with high toughness. In a FFS analysis of crack-like flaws, the results from a stress analysis, stress intensity factor and limit load solutions, the material strength, and fracture toughness are combined to calculate a toughness ratio, K, , and load

L, . These two quantities represent the coordinates of a point which is plotted on a twodimensional FD to determine acceptability. If the assessment point is on or below this curve, then an acceptable margin below the postulated failure curve on the FAD (the failure ratio,

curve represents the upper bound on component acceptability), the component is suitable for continued operation. A schematic which illustrates the procedure for evaluating a crack-like flaw using the Failure Assessment Diagram is shown in Figure 2.2. b.

In the assessment of crack-like flaws, partial safety factors are utilized along with the FAD acceptance criteria to account for variability of the input parameters in a deterministic fashion. Three separate partial safety factors are utilized: a factor for applied loading; a factor for material toughness; and a factor for flaw dimensions. The partial safety factors are applied to the stresses resulting from a stipulated loading condition, the fracture toughness and the flaw size parameters prior to the FAD analysis. The partial safety factors recommended for use --``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

API RECOMMENDED

2-8

PRACTICE 579

Jan, 2000

with Section 9 of this document (see Table 9.2) were developed based upon the results of a series of probabilistic analyses of components with crack-like flaws. Other values for these factors may be used based on a risk assessment where the potential failure modes and type of loading (e.g., normal operating loads, occasional loads, short-time upset conditions) are considered. The in-service margin for a component with a crack-like flaw provides a measure of how close the component is to the limiting condition in the FAD. The in-service margin is defined by how far the assessment point, which represents a single operating condition, is within the failure envelope of the FAD. This point is determined based on the results from stress and fracture mechanics analyses after applying the three partial safety factors discussed above. The in-service margin is defined to be greater than or equal to one when the point resides underneath or on the F”D failure curve. The recommended minimum allowable value for the in-service margin is set at 1 .O.

2.4.3

The FFS assessment procedures provided in this document are deterministic in that all information required for an analysis (independent variables) are assumed to be known. However, in many instances all of the important independent variables are not known with a high degree of accuracy. In such cases, conservative estimates of the independent variables are made to ensure an acceptable safety margin, and this approach can lead to overly conservative results. The following types of analyses can be used to provide insight into the dependency of the analysis results with variations in the input parameters. The deterministic FFS assessment procedures in this Practice can be used with any of these analyses.

2.4.3.1

Sensitivity Analysis - The purpose of such an analysis is to determine if a change in any of the independent (input) variables has a strong influence on the computed safety factors. The sensitivity analysis should consider the effects of different assumptions with regard to loading conditions, material properties and flaw sizes. For example, there may be uncertainties in the service loading conditions; the extrapolation of materials data to service conditions; and the type, size, and shape of the flaw. Confidence is gained in an assessment when it is possible to demonstrate that small changes in input parameters do not dramatically change the assessment results; and when realistic variations in the input parameters, on an individual or combined basis, still lead to the demonstration of an acceptable safety margin. If a strong dependence on an input variable is found, it may be possible to improve the degree of accuracy used to establish the value of that variable.

2.4.3.2

Probabilistic Analysis - The dependence of the safety margin on the uncertainty of the independent variables can be evaluated using this type of analysis. All or a limited number of the independent variables are characterized as random variables with a distribution of values. Using Monte Carlo simulation, first order reliability methods or other analytical techniques, the failure probability is estimated. These methods can be used to combine a deterministic FE!? assessment model with the distributions prescribed for the independent variable to calculate failure probabilities. Once a probability of failure has been determined, an acceptable level must be established based on multiple factors such as jurisdictional regulations and the consequence of failure.

2.4.3.3

Partial Safety Factors - Individual safety factors that are applied to the independent variables in the assessment procedure. The partial safety factors are probabilistically calibrated to reflect the effect that each of the independent variables has on the probability of failure. Partial safety factors are developed using probabilistic analysis techniques considering a deterministic model, distributions of the main independent variables of the model, and a target reliability or probability of failure. The advantage of this approach is that uncertainty can be introduced in an assessment by separately combining the partial safety factors with the independent variables in a deterministic analysis model; the format of the analysis is similar to that used by many design codes. Partial safety factors are only utilized in the assessment of crack-like flaws (see Section 9 and paragraph 2.4.2.3.b).


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

C.

RECOMMENDED

PRACTICE


2-9

2.5

Remaining Life Assessment

2.51

Once it has been established that the component containing the flaw is acceptable at the current time, the user should determine a remaining life for the component. The remaining life in this document is used to establish appropriate inspection interval and/or in-service monitoring plan, or the need for remediation. The remaining life is not intended to provide a precise estimate of the actual time to failure. Therefore, the remaining life can be estimated based on the quality of available information, assessment level, and appropriate assumptions to provide an adequate safety factor for operation until the next scheduled inspection.

2.5.2

Each FFs assessment section in this document provides guidance on calculating a remaining life. In general, the remaining life can be calculated using the assessment procedures in each section with the introduction of a parameter that represents a measure of the time dependency of the damage taking place. The remaining life is then established by solving for the time to reach a specified operating condition such as the iK4WP (MFH) or a reduced operating condition (see paragraph 2.4.2.2.b).

2.5.3

Remaining life estimates will fall into one of the following three general categories.

2.5.3.1

The Remaining Life Can be Calculated With Reasonable Certainty- An example is general uniform corrosion, where a future corrosion allowance can be calculated and the remaining life is the future corrosion allowance divided by the assumed corrosion rate from previous thickness data, corrosion design curves, or experience in similar services. Another example may be long term creep damage, where a future damage rate can be estimated. An appropriate inspection interval can be established at a certain fraction of the remaining life. The estimate of remaining life should be conservative to account for uncertainties in material properties, stress assumptions, and variability in future damage rate.

2.5.3.2

The Remaining Life Cannot be Established with Reasonable Certainty - Examples may be a stress corrosion cracking mechanism where there is no reliable crack growth rate data available or hydrogen blistering where a future damage rate can not be estimated. In this case remediation methods should be employed, such as application of a lining or coating to isolate the environment, drilling of blisters, or monitoring. inspection would then be limited to assuring remediation method acceptability, such as lining or coating integrity.

253.3

There is Little or No Remaining Life - In this case remediation, such as repair of the damaged component, application of a lining or coating to isolate the environment, and/or frequent monitoring is necessary for future operation.

2.6

Remediation

2.6.1

As mentioned in the previous paragraph, under some circumstances remediation is called for. Examples include: where a flaw is not acceptable in its current condition; the estimated remaining life is minimal or difficult to estimate; or the state-of-the-art analysis/knowledge is insufficient to provide an adequate assessment. Appropriate remediation methods are covered within each FFS assessment section.

2.6.2

Only general guidelines are provided in this document; each situation will require a customized approach to remediation. Periodic checks should be made to ensure that the remediation steps have prevented additional damage from occurring, and are in a condition that they can be expected to continue to provide protection in the future. The user may need to refer to other documents for detailed remediation procedures; for example, weld repair guidelines can be found in applicable repair codes, such as API 510, API 570, API 653 and NBIC 23.



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

MA WP, ( MFHr)

--``````-`-`,,`,,`,`,,`---

Jan, 2000

API RECOMMENDED

2-10

579

Jan, 2000

In-Service Monitoring Under some circumstances, the future damage rate/progression cannot be estimated easily or the estimated remaining life is short. In-service monitoring is one method whereby future damage or conditions leading to future damage can be assessed, or confidence in the remaining life estimate can be increased. Monitoring methods typically utilized include: corrosion probes to determine a corrosion rate; hydrogen probes to assess hydrogen activity; various ultrasonic examination methods and acoustic emission testing to measure metal loss or cracking activity; and measurement of key process variables and contaminants. Appropriate in-service monitoring methods are covered within each FFs assessment section.

2.8

Documentation

2.8.1

A Fitness-For-Service analysis should be sufficiently documented such that the analysis can be repeated at a later date. Documentation requirements specific to a particular assessment are described in the corresponding section covering the I?Fs assessment procedure. The following items should be included in the documentation.

2.8.1.1

The equipment design data, and maintenance and past operational history to the extent available should be documented for all equipment subject to a F’s assessment.

2.8.1.2

Inspection data including all readings utilized in the FK!? assessment.

2.8.1.3

Assumptions and analysis results including:

--``````-`-`,,`,,`,`,,`---

.

Section, edition, and analysis level of this document and any other supporting documents used to analyze the flaw or damage.

.

Future operating and design conditions including pressure, temperature and abnormal operating conditions.

.

Calculations for the minimum required thickness and/or AL??!?$?P.

.

Calculations for remaining life and the time for the next inspection.

.

Any mitigation/monitoring recommendations that are a condition for continued service.

2.8.2

All calculations and documentation used to determine the fitness-for-service of a pressurized component should be kept with the inspection records for the component or piece of equipment in the owner-user inspection department. This documentation will be a part of the records required for mechanical integrity compliance.

2.9

References

2.9.1

Ainsworth, R.A., Ruggles, M.B., and Takahashi, Y., “Flaw Assessment Procedure for HighTemperature Reactor Components,” Journal of Pressure Vessel Technology, Vol. 114, American Society of Mechanical Engineers, New York, May, 1992, pp. 166-170.

2.9.2

API, Base Resource Document on Risk-Based Inspection, API Publication 581, American Petroleum Institute, Washington D.C., 1996.

2.9.3

Buchheim, G.M., Osage, D.A., Prager, M., Warke, W.R., “Fitness-For-Service and Inspection for the Petrochemical industry,” ASME PVP-Vol. 261, American Society of Mechanical Engineers, New York, 1993, pp. 245-256.

2.9.4

Buchheim, G.M., Osage, D.A., Warke, W.R., Prager, M., “Update for Fitness-For-Service and Inspection for the Petrochemical Industry,” ASME PVP-Vol. 288, American Society of Mechanical Engineers, New York, 1994, pp. 253-260.

March 2000


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.7

PRACTICE


Kim, D.S., Reynolds, J.T., "Fitness-For-Service Analysis in Turnaround Decision Making," ASME PVP-Vol. 261, American Society of Mechanical Engineers, New York, 1993, pp. 283-294.

2.9.6

Osage, D.A. and Prager, M., "Status and Unresolved Technical Issues of Fitness-For-Service Assessment Procedures for the Petroleum Industry," ASME PVP-Vol. 359, American Society of Mechanical Engineers, New York, 1997, pp. 117-128.

2.9.7

Yin, H., Bagnoli, D.L., "Case Histories Using Fitness-For-Service Methods," ASME PVP-Vol. 288, American Society of Mechanical Engineers, New York, 1994, pp. 315-328.

2.10

Tables And Figures

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.9.5


Not for Resale


Table 2.1 Overview of Flaw and Damage Assessment Procedures Section

Overview

Brittle Fracture

3

Assessment procedures are provided for evaluating the resistance to brittle fracture of existing carbon and low alloy steel pressure vessels, piping, and storage tanks. Criteria are provided to evaluate normal operating, start-up, upset, and shut-down conditions.

General Metal Loss

4

Assessment procedures are provided to evaluate general corrosion. Thickness data used for the assessment can be either point thickness readings or detailed thickness profiles. A methodology is provided to utilize the assessment procedures of Section 5 when the thickness data indicates that the metal loss can be treated as localized.

Local Metal Loss

5

Assessment techniques are provided to evaluate single and networks of Local Thin Areas and groove-like flaws in pressurized components. Detailed thickness profiles are required for the assessment. The assessment procedures can also be utilized to evaluate blisters as provided for in Section 7.

Pitting Corrosion

6

Assessment procedures are provided to evaluate widely scattered pitting, localized pitting, pitting which occurs within a region of local metal loss, and a region of localized metal loss located within a region of widely scattered pitting. The assessment procedures can also be utilized to evaluate a network of closely spaced blisters as provided for in Section 7.

Blisters and Laminations

7

Assessment procedures are provided to evaluate isolated and networks of blisters and laminations. The assessment guidelines include provisions for blisters located at weld joints and structural discontinuities such as shell transitions, stiffening rings, and nozzles.

Weld Misalignment and Shell Distortions

8

Assessment procedures are provided to evaluate stresses resulting from geometric discontinuities in shell type structures including weld misalignment and shell distortions (e.g. out-of-roundness, bulges, and dents).

Crack-Like Flaws

9

Assessment procedures are provided to evaluate crack-like flaws. Solutions for stress intensity factors and reference stress (limit load) are included in Appendices C and D, respectively. Methods to evaluate residual stress as required by the assessment procedure are described in Appendix E. Material properties required for the assessment are provided in Appendix F. Recommendations for evaluating crack growth including environmental concerns are also covered.

High Temperature Operation and Creep

10

Assessment procedures are provided to determine the remaining life of a component operating in the creep regime. Material properties required for the assessment are provided in Appendix F. Recommendations for evaluating crack growth including environmental concerns are also covered.

Fire Damage

11

Assessment procedures are provided to evaluate equipment subject to fire damage. A methodology is provided to rank and screen components for evaluation based on the heat exposure experienced during the fire. The assessment procedures of the other sections of this publication are utilized to evaluate component damage.

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Flaw or Damage Mechanism


Table 2.2 Overview of Data Required for Flaw and Damage Assessment The following data are required for most types of Fitness-For-Service assessments and it is recommended that this completed table accompany the data table completed for the specific damage type which are located in the respective section. Equipment Identification: Equipment Type: _____ Pressure Vessel _____ Storage Tank _____ Piping Component Component Type & Location: Design Code: _____ ASME Section VIII Div. 1 _____ ASME Section VIII Div. 2 _____ ASME B31.3 _____ API 650 _____ API 620 _____ other: Material of Construction (e.g. ASTM Specification): MAWP: MFH: Minimum Required Wall Thickness: Temperature: Cyclic Operation:

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Type of Damage Metal Loss – General: Metal Loss – Local: Metal Loss – Pitting: Blisters: Misalignment: Dent: Bulge: Crack-Like Flaw: Creep Damage: Fire Damage: Location of Damage (provide a sketch) Internal/External: Near weld: Orientation: Environment Internal: External: Repair and Inspection History

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Operations History

Future Anticipated Operations


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Figure 2.1 FFS Assessment Procedures For Various Degradation Classes

Degradation Classes

Section 9 Assessment of Crack-Like Flaws - Below the Creep Regime

Section 4 Assessment of General Metal Loss

Crack-Like Flaws

Section 9 Assessment of Crack-Like Flaws

Fire Damage

Section 11 Assessment of Fire Damage

Section 4 Assessment of General Metal Loss

Section 5 Assessment of Localized Metal Loss


Section 6 Assessment of Pitting Damage

Creep Damage

Section 10 Assessment of Creep Damage

Mechanical Damage


Section 8 Assessment of Misalignment and Shell Distortions

Not for Resale

Section 3 Brittle Fracture Assessment

Corrosion/Erosion


Section 8 Assessment of Weld Misalignment and Shell Distortions

Section 7 Assessment of Blisters


Section 10 Assessment of Creep Damage

2-14


Brittle Fracture

Jan, 2000 Recommended Practice For Fitness-For-Service 2-15 _________________________________________________________________________________________________

Figure 2.2 Overview Of An FFS Analysis For Crack-Like Flaws Using The Failure Assessment Diagram

Flaw Dimensions

Stress Analysis

Stress Intensity Factor Solution, KI

Material Toughness, KMAT

Kr =

KI KMAT

Failure Assessment Diagram Envelope Brittle Fracture

TOUGHNESS RATIO

Unacceptable Region Mixed Mode - Brittle Fracture And Plastic Collapse

Assessment Point

Acceptable Region Plastic Collapse LOAD RATIO

Lr =

Iref Iys

Reference Stress Solution, Iref

Flaw Dimensions

Material Yield Stress, Iys

Stress Analysis

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2-16 API Recommended Practice 579 Jan, 2000 _________________________________________________________________________________________________ 2.11 Example Problems Example problems are included for each Section of this document which contains FFS assessment procedures. The example problems are provided to illustrate the application of the rules and evaluation procedures for a Level 1 and/or Level 2 Assessment. Example problems are provided in both metric and English units.

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SECTION 3 – Assessment Of Existing Equipment For Brittle Fracture

3.1

General

3.1.1

This section provides guidelines for evaluating the resistance to brittle fracture of existing carbon and low alloy steel pressure vessels, piping, and storage tanks. Assessment of other materials that could be susceptible to brittle fracture such as ferritic, martensitic and duplex stainless steels are not addressed explicitly; however, the same principles in this section can be used to evaluate these materials. The purpose of this assessment is to avoid a catastrophic brittle fracture failure consistent with ASME Code, Section VIII design philosophy. It is intended to prevent the initiation of brittle fracture; however, it does not ensure against service-induced cracks resulting in leakage or arrest of a running brittle fracture. Unlike other sections in this Recommended Practice, this section is used to screen for the propensity for brittle fracture. If a crack-like flaw is found, Section 9 can be used for the assessment.

3.1.2

A brittle fracture assessment may be required as part of the assessment procedure of another section in this Recommended Practice. In addition, the following circumstances that could necessitate a brittle fracture assessment: ·

A change in process operating conditions that increases the possibility of low metal temperatures.

·

A process hazards review indicates that process temperatures lower than anticipated in the original design are possible.

·

The equipment item is rerated using a lower design margin.

·

The equipment can experience significant internal pressure (i.e. design pressure) at or near ambient temperature because of start-up or shut-down conditions.

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The owner/user may identify other circumstances where a brittle fracture assessment of equipment items may be warranted based on operating conditions and/or the condition of the component. 3.1.3

The Critical Exposure Temperature (CET) as used in this section is defined as the lowest metal temperature derived from either the operating or atmospheric conditions. The CET may be a single temperature at an operating pressure or an envelope of temperatures and pressures (see paragraph 3.3.3). The CET is determined for different types of equipment as follows.

3.1.3.1

Pressure Vessels – The CET is defined as the lowest metal temperature at which a component will be subjected to a general primary membrane tensile stress greater than 55.2 MPa (8 ksi). The CET may also be defined as follows: ·

The minimum metal temperature at which a component could be subjected to a pressure greater than 40% of the MAWP for vessels constructed to the ASME Code, Section VIII, Division 1, Editions prior to 1999.

·

The minimum metal temperature at which a component could be subjected to a pressure greater than 35% of the MAWP for vessels constructed to the ASME Code, Section VIII, Division 1, 1999 Edition and later.

·

The minimum metal temperature at which a component could be subjected to a pressure greater than 30% of the MAWP for vessels constructed to the ASME Code, Section VIII, Division 2.

·

For pressure vessels designed to higher allowable stresses than those permitted in these codes, the CET may be taken as the lowest metal temperature at which the vessel will be subjected to a pressure which causes a membrane stress of 55.2 MPa (8 ksi).


3-1 Not for Resale

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(Jan, 2000)


Piping – The CET for piping systems constructed to the ASME B31.3 Piping Code is defined as the lowest metal temperature at which a component will be subject to either 30% of the MAWP or a combined total longitudinal stress equal to 55.2 MPa (8 ksi) due to pressure, weight effects, and displacement strains. The CET for piping is determined from the anticipated process and atmospheric conditions (see paragraph 3.3.3).

3.1.3.3

Atmospheric And Low Pressure Storage Tanks – The CET for atmospheric storage tanks constructed to API 650 is defined as the lower of either the lowest one-day mean atmospheric temperature plus 8°C (15°F), or the hydrostatic test temperature. The CET for low pressure storage tanks constructed to API 620 can be established using the methodology for pressure vessels (see paragraph 3.1.3.1).

3.1.4

The Minimum Allowable Temperature (MAT) is the permissible lower metal temperature limit for a given material at a thickness based on its resistance to brittle fracture. It may be a single temperature, or an envelope of allowable operating temperatures as a function of pressure. The MAT is derived from mechanical design information, materials specifications, and/or materials data.

3.2

Applicability And Limitations Of The Procedure

3.2.1

This section provides guidelines to assess the risk of brittle fracture of components in the following equipment: ·

Pressure vessels constructed in accordance with any edition of ASME Boiler and Pressure Vessel Code, Section VIII, Divisions 1 and 2; however, the same guidelines may be used for pressure vessels constructed to other recognized codes and standards (see Section 2, paragraphs 2.2.2 and 2.2.3).

·

Pressure vessels constructed in accordance with any edition of the former API or API/ASME Code for Unfired Pressure Vessels for Petroleum Liquids and Gases.

·

Piping systems constructed in accordance with the ASME B31.3 or ASME B31.1; however, the same guidelines may be used for piping systems constructed to other recognized codes and standards (see Section 2, paragraphs 2.2.2 and 2.2.3).

·

Atmospheric or low-pressure above ground storage tanks that are either welded or riveted, nonrefrigerated, or operating at atmospheric or low pressure, and constructed in accordance with any edition of API 650 or API 620.

3.2.2

The Level 1 and 2 Assessment procedures in this section can be applied to components subject to general corrosion, local metal loss and pitting damage provided the assessment criteria in Sections 4, 5, and 6, respectively, are satisfied. A Level 3 Assessment is required for the evaluation of a component with a crack-like flaw.

3.2.3

The guidelines in this section were developed assuming that the equipment being assessed for brittle fracture will continue to be included in the normal plant inspection and maintenance program consistent with API 510, API 570 and API 653, as applicable. If environmental cracking or a service condition which may result in a loss in the material toughness is possible, the Level 3 procedures of this section may have to be utilized in the assessment. For example, low alloy steels such as 2 ¼ Cr – 1 Mo may lose ductility at ambient temperature if exposed to high temperatures (above 400°C (750°F)) for long periods of time because of thermal aging degradation mechanisms. Components made from these types of materials require special precautions if a hydrotest or other low temperature pressurization is required.


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3.1.3.2

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The CET for pressure vessels is determined from the anticipated process and atmospheric conditions (see paragraph 3.3.3).


3.3

Data Requirements

3.3.1

Original Equipment Design Data In order to carry out a brittle fracture assessment, mechanical design information and materials of construction of all components should be obtained. These data are required for pressure containing components in order to identify the component that governs its brittle fracture limitations. Specific materials properties test data, such as Charpy V-notch and tensile data, if available, will be used for higher levels of assessment. An overview of the original equipment data that may be required for an assessment are provided in Section 2, paragraphs 2.3.1. A summary of the original equipment design data typically used for an assessment is shown in Table 3.1.

3.3.2

Maintenance And Operational History In addition to original equipment design data, information pertaining to repair history, and past and future operating conditions should be gathered. These data should include a summary of repairs and alterations, and include the current design pressure and temperature as well as the current wall thickness. Previous or proposed operating pressures and temperatures should be included as well as start-up, shut-down, transient and/or upset operating conditions, and extreme environmental conditions. These data are used to establish the most severe operating and exposure conditions encountered during the life of the equipment. Information related to environmental exposure will also be needed to determine whether there is a risk of environmental cracking. An overview of the maintenance and operational history information required for an assessment are provided in Section 2, paragraphs 2.3.2. A summary of the maintenance and operational history data typically used for an analysis is shown in Table 3.1.

3.3.3

Required Data/Measurements For A FFS Assessment The CET pressure-temperature envelope should be determined after consideration of all potential operating conditions (including start-up, shut-down and upset conditions) using review procedures encompassing hazard analysis or other comparable assessment methodologies. Of special concern with existing equipment is any change in the operation that has occurred after the equipment was originally placed into service which could cause a lower CET than it was originally designed for. In determining the CET, the current process design and safety philosophies should be employed. The CET pressure-temperature envelope should consider the following process conditions and ambient factors:

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a.

The lowest one-day mean atmospheric temperature, unless a higher temperature is specified (e.g., specifying a minimum required startup temperature and coincident pressure). If a higher temperature is specified, it must be confirmed that the system has control capabilities and/or operating procedures are in place to maintain the higher temperature.

b.

The lowest metal temperature under normal operating conditions.

c.

The lowest metal temperature associated with startup, shutdown, upset conditions, standby, pressure tightness testing, and hydrotest. The following items should be considered:

d.

·

Failure of warning and/or shut-down systems (e.g. a pump stops, control valve shuts, etc.).

·

A colder than expected warming stream.

·

Reboiler failure or stall (e.g., flow loss of reboiling medium, failure of a control valve, etc.).

·

The possibility of future field hydrotest.

Potential for autorefrigeration due to depressurization, either during operations or due to equipment failure (e.g., a safety relief valve sticks open). In some services where autorefrigeration can occur, equipment can be chilled to a temperature below the CET at an

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applied pressure less than that defined in paragraph 3.1.3.1. When this occurs the possibility of any repressurization of equipment before the material has had sufficient time to warm up to the CET must be considered. The effect of autorefrigeration on the equipment depends upon the state of the process fluid, for example whether the vessel contents are all liquid, all gas, or a mixture and how the vessel may be vented. Autorefrigeration, caused by depressurization, may also occur in a flowing system with a flashing liquid. As the pressure decreases, the temperature will follow the vapor pressure curve. For a pure gas, the effect of pressure on temperature is small and governed by Joule-Thompson cooling. However, when a vessel is depressurized through a long line, the gas flowing through the line may be cold because it was autorefrigerated in the vessel. e.

3.3.4

Shock chilling (see Appendix I); the CET should not be higher than the temperature of the liquid causing the shock chilling.

Recommendations For Inspection Technique And Sizing Requirements The current component wall thickness is required for all assessments. Methods for establishing this thickness are provided in Section 4, paragraph 4.3.4.

3.4

Assessment Techniques And Acceptance Criteria

3.4.1

Overview

3.4.1.1

An overview of the assessments levels for pressure vessels and piping is shown in Figure 3.1. A separate assessment procedure is provided for tankage which is shown in Figure 3.2. A summary of the three assessment levels is described below.

3.4.1.2

The Level 1 assessment procedures are intended to be used for equipment that meets toughness requirements in a recognized code or standard. This can be determined from impact test results, the use of industry accepted impact test exemption curves, or comparison of the equipment to the original design code or standard toughness requirements.

3.4.1.3

The Level 2 Assessment procedures for pressure vessels and piping are divided into three methods (see Figure 3.1). In the first method (Method A), equipment may be exempt from further assessment if it can be shown that the operating pressure and temperature is within a safe envelope with respect to component design stress and minimum acceptable temperature. In the second method (Method B) equipment may be qualified for continued service based on a hydrotest. In the third method (Method C) equipment may be qualified for continued service based on materials of construction, operating conditions, service environment and past operating experience. A separate assessment procedure is provided for tankage (see Figure 3.2) which is based on a combination of these three methods.

3.4.1.4

A Level 3 Assessment may be used for equipment which does not meet the acceptance criteria for Levels 1 and 2. This equipment must be evaluated on an individual basis with the help of process, materials, mechanical, inspection, safety, and other specialists as appropriate. A Level 3 Assessment will normally involve a more detailed evaluation, using a fracture mechanics methodology (see Section 9). The factors that control the susceptibility to brittle fracture include stress, flaw size and material toughness all of which are systematically evaluated in a Level 3 Assessment.

3.4.2

Level 1 Assessment

3.4.2.1

Pressure Vessels

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Assessment Level 1 is appropriate for equipment that meets toughness requirements in recognized codes and standards. This can be determined from impact test results, or from the use of industry accepted impact test exemption curves. A Level 1 assessment typically requires only a review of existing equipment records.

b.

Pressure vessels which have a CET equal to or greater than the MAT, as demonstrated by conformance to recognized toughness standards described below, are exempt from further brittle fracture assessment provided conditions do not change in the future. If a change in the operating conditions is made which effects the CET, a reassessment is recommended. These vessels require no special treatment other than to continue their inclusion in a normal plant inspection and maintenance program encompassing generally accepted engineering practices such as contained in API 510 or other recognized inspection code.

c.

A general procedure for determining the MAT for a pressure vessel fabricated from materials which have not been impact tested is provided in Table 3.2. The MAT can be established for a component using a governing thickness and the exemption curves in Figure 3.3. These curves are limited to components designed to the ASME Code, Section VIII, Division 1 or 2, and other recognized pressure vessel codes provided the design allowable stress is less than or equal to 172.5 MPa (25 ksi). Alternatively, exemption curves from other recognized codes and standards may be utilized. If impact test results are available for all of the components being evaluated, the MAT can be set at the impact test temperature required by the ASME Code, Section VIII, Division 1 or 2, as applicable, or other international codes and standards.

d.

When determining the MAT, parts such as shells, heads, nozzles, manways, reinforcing pads, flanges, tubesheets, flat cover plates, and attachments which are essential to the structural integrity of the vessel shall be treated as separate components. Each component shall be evaluated based on its individual material classification (see Table 3.3, Table 3.4, and Figure 3.3) and governing thickness (see Figure 3.4). The MAT for the vessel is the highest MAT determined for all of the components. Rules for establishing the governing thickness are provided below.

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a.

1.

e.

The governing thickness ( t g ) of a welded part, excluding castings, is as follows: ·

for butt joints except those in flat heads and tubesheets, the nominal thickness of the weld joint (see Figure 3.4A)),

·

for corner, fillet, or lap welded joints, including attachments as defined above, the thinner of the two parts joined (see Figure 3.4(B),(F) and (G)),

·

for flanges, flat heads, or tubesheets, the thinner of two parts joined or the flat component thickness divided by 4, whichever is larger (see Figure 3.4(C),(D) and (E)), and

·

for welded assemblies comprised of more than two components (e.g., nozzle-toshell joint with reinforcing pad), the governing thickness and permissible MAT of each of the individual welded joints of the assembly shall be determined, and the warmest of the MAT values so calculated shall be used as the permissible Minimum Allowable Temperature of the welded assembly (see Figure 3.4(B)).

2.

The governing thickness of a casting is its largest nominal thickness.

3.

The governing thickness of flat non-welded parts, such as bolted flanges, tubesheets, and flat heads, is the component thickness divided by four (see Figure 3.4(C)).

When using the exemption curves in Figure 3.3, the MAT for P1 Group 1 and 2 materials in the ASME Code can be lowered by 17°C (30°F) if the equipment was subject to PWHT and the reference thickness is less than or equal to 38 mm (1.5 inches); however, this adjusted temperature cannot be below -48°C (-55°F) as described in Table 3.5, Note 6.


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Vessels constructed to the ASME Code, Section VIII, Division 1 which meet the following requirements satisfy the Level 1 assessment; the MAT does not need to be computed on a component basis to complete the assessment. 1.

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3.4.2.2

3.4.2.3

The material is limited to P-No. 1, Gr. No. 1 or 2 as defined in ASME Code Section IX, and the thickness, as defined in paragraph 3.4.2.1.c, does not exceed the following: ·

12.7 mm (1/2 inch) for materials listed in Curve A of Figure 3.3, and

·

25.4 mm (1 inch) for materials listed in Curve B, C, or D of Figure 3.3.

2.

The completed vessel has been hydrostatically tested per the ASME Code, Section VIII, Division 1, provided the test pressure is at least 1.5 times the design pressure for vessel constructed prior to the 1999 Addendum, or 1.3 times the design pressure of vessels constructed to or after the 1999 Addendum.

3.

The design temperature is less than or equal to 343°C (650°F) and greater than or equal to -29°C (-20°F). Occasional operating temperatures less than -29°C (-20°F) are acceptable when due to lower seasonal atmospheric temperature.

4.

Thermal or mechanical shock loadings are not a controlling design requirement.

5.

Cyclic loading is not a controlling design requirement.

Piping Systems a.

Assessment Level 1 is appropriate for equipment that meets toughness requirements in recognized codes and standards. This can be determined from impact test results, or from the use of industry accepted impact test exemption curves. A Level 1 assessment typically requires only a review of existing equipment records.

b.

Piping systems should meet the toughness requirements contained in ASME B31.3 at the time the piping system was designed (or an equivalent piping design code if that code contains material toughness requirements). Piping systems should be evaluated on a component basis; the MAT for a piping system is the highest MAT obtained for all of the components in the system.

Atmospheric and Low Pressure Storage Tanks a.

Atmospheric storage tanks constructed to API 650 shall meet the Level 1 Assessment criteria contained in Figure 3.2, as applicable, and the accompanying notes. The Level 1 Assessment criteria requires that these tanks meet the toughness requirements contained in API 650 or an equivalent construction code.

b.

Low pressure storage tanks constructed to API 620 shall be evaluated as a pressure vessel using the assessment procedures of paragraph 3.4.2.1.

c.

Atmospheric or low pressure storage tanks which contain a refrigerated product shall be evaluated using a Level 3 Assessment.

3.4.2.4

If the component does not meet the Level 1 Assessment requirements, then a Level 2 or Level 3 Assessment can be performed.

3.4.3

Level 2 Assessment

3.4.3.1

Pressure Vessels – Method A


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f.


3.4.3.2

a.

Pressure vessels may be exempt from further assessment at this level if it can be demonstrated that the operating pressure/temperature is within a safe envelope with respect to component design stress and the MAT.

b.

The MAT may be adjusted from the value determined in the Level 1 assessment by considering temperature reduction allowances which may apply to pressure vessels with actual operating stresses at the low temperature pressurization condition that are below the allowable value from the original construction code at the design condition. This includes vessels designed for elevated temperatures with an allowable stress lower than the allowable stress permitted for ambient temperature service. The temperature reductions permitted for pressure vessels can be determined using the procedure in Table 3.2. The temperature reductions in this procedure are provided in terms of a thickness or stress ratio (see Figure 3.5). For allowable stress values above 172.5 MPa (25 ksi), a Level 3 Assessment is required.

c.

When evaluating components with a metal thickness below the minimum required thickness ( t min ) as permitted in Sections 4, 5 and 6, the required thickness as defined in Figure 3.5 ( t r ) shall be based on the minimum required thickness of the undamaged component at the design conditions.

Pressure Vessels – Method B a.

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b. 3.4.3.3

A vessel may be qualified for continued service based on a hydrotest. A minimum acceptable temperature for operating pressures below the hydrotest pressure can be determined using Figure 3.6. This allowance is limited to hydrotest pressures of 125%, 130% and 150% of the design pressure (based on the original design code) and to materials with an allowable design stress equal to or less than 172.5 MPa (25 ksi). 1.

The test pressure should be corrected for the difference in allowable stresses between the design and hydrotest temperatures, but should not result in a general primary membrane stress higher than 90% of the specified minimum yield strength for the steel used in the construction of the vessel. This can provide an additional advantage for vessels designed for elevated temperatures that have a design stress value lower than the allowable stress at ambient temperature.

2.

The metal temperature during hydrotest, rather than water temperature, is the relevant parameter in a brittle fracture assessment. Therefore, it is preferable to measure and use this value directly. Records of the measured metal temperature used in the assessment should be kept.

3.

If the hydrotest is performed at a temperature lower than the MAT as determined by a Level 1 assessment, it should be noted that there may be a significant risk of brittle fracture during the hydrotest.

4.

The MAT shall not be less than -104°C (-155°F) after adjustments using this procedure.

If the vessel is subject to multiple operating conditions, an MAT curve can be established using Figure 3.6 by plotting the pressure versus the permissible temperature.

Pressure Vessels – Method C a.

This assessment method is used when material impact test or toughness data are not available. Service experience in regard to brittle fracture has been excellent with pressure vessels which have been built to the ASME Code, Section VIII, Division 1 and other recognized standards. For this reason, pressure vessels with a governing thickness less than or equal to 12.7 mm (0.5 in.), or which meet all of the criteria listed below, may be considered to be acceptable for continued service without further assessment. Vessels which satisfy these

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b.

c.

3.4.3.4

1.

Pressure vessels fabricated from P-1 and P-3 steels (as defined in ASME Code, Section IX,) where the design temperature is less than or equal to 343°C (650°F). P-4 and P-5 steels may also be evaluated at this level, provided the proper precautions (e.g. preheating prior to pressurization) are taken to avoid brittle fracture due to in-service embrittlement.

2.

The equipment satisfies all requirements of a recognized code or standard (see Section 2, paragraph 2.2.2) at the time of fabrication.

3.

The nominal operating conditions have been essentially the same and consistent with the specified design conditions for a significant period of time, and more severe conditions (i.e., lower temperature and/or higher stress) are not expected in the future.

4.

The CET is greater than or equal to -29°C (-20°F).

5.

The nominal uncorroded governing thickness is not greater than 50.8 mm (2 inches).

6.

Cyclic service as defined in Appendix I is not a design requirement.

7.

The equipment is not in an active environmental cracking service (see Appendix G).

8.

The equipment is not subject to shock chilling (see Appendix I for a definition of shock chilling).

An assessment for brittle fracture is not required for the following: ·

ASME B16.5 ferritic steel flanges used at metal temperatures at and above -29°C (-20°F), and

·

Carbon steel components with a thickness less than 2.5mm (0.098 inches) used at a metal temperature at or above -48°C (-55°F).

Pressure vessels that are assessed using Method C of the Level 2 Assessment procedure are qualified for continued operation based on their successful performance demonstrated during past operation. However, if a repair is required, the guidelines in paragraph 3.6 should be followed to ensure that the risk of brittle fracture does not increase with continued operation.

Piping Systems – Method A Piping systems are acceptable at this level if it can be demonstrated that the operating pressure/temperature is within a safe envelope with respect to component design stress and the MAT. The provisions in paragraph 3.4.3.1 can be applied to piping to lower the MAT when the operating stress level is below the design allowable stress.

3.4.3.5

Piping Systems – Method B Piping systems are acceptable at this level if it can be demonstrated that the operating pressure and coincident temperature is within a safe envelope with respect to a hydrotest condition. The approach discussed in paragraph 3.4.3.2 that provides for a reduction in the MAT can be applied to piping.

3.4.3.6

Piping Systems – Method C Piping systems are acceptable at this level if the assessment criteria contained in Figure 3.7 and the accompanying notes are satisfied. This method is limited to piping components with a thickness of 38 mm (1.5 inch) or less.


Not for Resale

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criteria shall be assigned an MAT consistent with low-temperature operation. Note the MAT may be a single temperature or pressure-temperature operating envelope for the vessel.


3.4.3.7

Atmospheric and Low Pressure Storage Tanks a.

Atmospheric and low pressure storage tanks that operate at ambient temperature (including those which contain a heated product) shall meet the Level 2 Assessment criteria contained in Figure 3.2.

b.

Low pressure storage tanks constructed to API 620 shall be evaluated as a pressure vessel using the assessment procedures of paragraphs 3.4.3.1, 3.4.3.2 or 3.4.3.3.

c.

Atmospheric or low pressure storage tanks which contain a refrigerated product shall be evaluated using a Level 3 Assessment.

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3.4.3.8

If the component does not meet the Level 2 Assessment requirements, then a Level 3 Assessment can be performed.

3.4.4

Level 3 Assessment

3.4.4.1

Pressure vessels, piping and tankage which do not meet the criteria for Levels 1 and 2 assessments can be evaluated using a Level 3 assessment. Level 3 assessments will normally involve more detailed determinations of one or more of the three factors that control the susceptibility to brittle fracture: stress, flaw size and material toughness.

3.4.4.2

Section 9 can be used as a basis for a Level 3 Assessment. A risk analysis considering both the likelihood and potential consequences of a brittle fracture in the specific service should also be considered in a Level 3 Assessment.

3.4.4.3

At this assessment level, the judgment of the engineer involved (see Section 1, paragraph 1.4.1) may be used to apply some of the principles of Levels 1 and 2 without the specific restrictions used at those levels. Examples of some other approaches which may be considered are: a.

Perform a heat transfer analysis to provide a less conservative estimate of the lowest metal temperature which the vessel will be exposed to in service.

b.

If loadings are always quasi-static, consider additional credits due to the temperature shift between dynamic (e.g., Charpy V-notch) and quasi-static toughness.

c.

Inspect all seam welds and attachment welds to the pressure shell for surface cracks at the next scheduled turnaround, and provide guidance on acceptable flaw sizes based on a flaw assessment (see Section 9). The extent of subsequent inspections should be based upon the severity of the service considering the conditions given in paragraph 3.3.3. Ultrasonic examination from the outside is permissible if the inside surface cannot be inspected directly.

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3.4.4.4

It may be necessary to evaluate stresses using advanced techniques such as finite element analysis. Consideration should be given to all relevant loads including those which produce localized stresses (e.g. forces and moments at nozzles), thermal transient effects, and residual stress. These additional considerations may result in different criteria for different locations within a piece of equipment. Probable locations and orientations of crack-like flaws should be determined to guide the stress analyst.

3.4.4.5

A Level 3 assessment will normally rely on a determination of maximum expected flaw sizes at locations of high stresses. In general, these postulated flaws should be assumed to be surface breaking, and to be oriented transverse to the maximum stress. For welded structures, this often implies that the flaw is located within the residual stress field of a longitudinal weld. The maximum expected flaw size should be detectable with standard NDE techniques. The detectable flaw size will depend on factors such as surface condition, location, accessibility, operator competence, and NDE technique. Section 9 can be used to derive limiting sizes for crack-like flaws. In this assessment, the aspect ratio of the assumed flaw should be large enough to ensure that the calculations are not highly


Not for Resale


3.4.4.6

The use of material toughness data from appropriate testing is the preferred basis for a Level 3 assessment. Where this is not practical, appropriate and sufficiently conservative estimates must be determined. Methods for obtaining or estimating fracture toughness are described in Appendix F.

3.5

Remaining Life Assessment – Acceptability For Continued Service

3.5.1

Remaining life is not normally an issue associated with an equipment's resistance to brittle fracture. Therefore, equipment evaluated using a Level 1 or 2 assessment procedure should be acceptable for future operation as long as operating conditions do not become more severe and there is no active degradation mechanism that can result in loss of material toughness or the propagation of a cracklike flaw. If this is not the case, a Level 3 assessment should be performed, and a remaining life associated with the time a flaw grows to critical size can be calculated.

3.5.2

Pressure vessels constructed of materials which satisfy the requirements of a Level 1 or Level 2 assessment are considered acceptable for continued service. Pressure vessels can be fully pressurized within the limits of their design parameters at any metal temperature above the MAT.

3.5.3

Piping systems constructed of materials which satisfy the requirements of a Level 1 or Level 2 assessment are considered acceptable for continued service. Piping systems can be fully pressurized within the limits of their design parameters at metal temperatures above the MAT. The acceptability of piping systems for continued service can be determined by using similar methods as those to evaluate pressure vessels. There are two facts which distinguish piping from pressure vessels and make piping less likely to experience brittle fracture: (1) a lower MAT is more easily attainable because the component thickness is usually thinner (see Figure 3.3, Note 5); and (2) there is less likelihood to have to crack-like flaws orientated perpendicular to the highest stress in piping systems because there are fewer longitudinal weld seams (i.e. seamless pipe).

3.5.4

Atmospheric and low-pressure storage tanks constructed of materials which satisfy the requirements of a Level 1 or Level 2 assessment are considered acceptable for continued service. A Level 3 Assessment for storage tanks should follow the same general guidelines as used for pressure vessels. However, the analysis must reflect the special design considerations used for storage tanks such as the bottom plate-to-shell junction.

3.6

Remediation

3.6.1

A FFS analysis typically provides an evaluation of the condition of a component for continued operation for a period of time based upon a degradation rate. In the case of brittle fracture, a component is suitable for continued service as long as the operating conditions do not become more severe and/or there is no active material degradation mechanism that can result in loss of material toughness or the propagation of crack-like flaws. However, in many cases future degradation rates are very difficult to predict, or little or no further degradation can be tolerated. Therefore, the owneruser may choose to apply mitigation methods to prevent or minimize the rate of further damage.

3.6.2

Remediation methods are provided below. The methods cited are not inclusive for all situations, nor are they intended to be a substitute for an engineering evaluation of a particular situation. The owner-user should consult a qualified metallurgist/corrosion engineer and mechanical engineer as to the most appropriate method to apply for the relevant damage mechanism(s).

3.6.2.1

Limiting Operation – The limitation of operating conditions to within the acceptable operating pressure-temperature envelope is the simplest type of remediation effort. This method, however, may be impractical in many cases because of the requirements for stable process operation. The most successful, and effective, technique for limiting operation has been to implement a controlled start-up procedure. This is due to the fact that many petroleum and chemical processes that undergo


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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sensitive to small variations in flaw depth in the through thickness direction. To reduce this sensitivity, a minimum crack-like flaw aspect ratio of 6:1 is recommended.


this type of assessment for brittle fracture were originally designed for substantially warmer temperatures, above the temperature range where the risk of brittle fracture must be addressed. Postweld Heat Treatment (PWHT) – If the component has not been subject to PWHT, PWHT may be performed to enhance the damage tolerance to crack-like flaws and resistance to brittle fracture. The beneficial effect of PWHT is twofold: ·

It reduces the residual stresses that contribute to the driving force for brittle fracture.

·

It can de-embrittle metal at the tip of a pre-existing crack resulting in improved fracture toughness.

3.6.2.3

Hydrostatic Test – If the component has not been subject to a hydrotest, one may be performed to enhance the damage tolerance to crack-like flaws and resistance to brittle fracture. The beneficial effect of a hydrotest is that crack-like flaws located in the component are blunted which results in an increase in brittle fracture resistance. The beneficial effects of a hydrotest can be quantified using a Level 2 assessment (see paragraph 3.4.3.2) or a Level 3 assessment. If a hydrotest is performed, it should be conducted at a metal temperature that will permit plastic flow without the possibility of brittle fracture (i.e. conduct the test at a metal temperature that is in the upper shelf region of the transition curve). A typical hydrotest temperature that has been used is 17°C (30°F) above the MAT.

3.7

In-Service Monitoring

3.7.1

There is little that can be accomplished by in-service monitoring of equipment to alleviate the risk of brittle fracture because the factors that contribute to this phenomena, stress level, material toughness, and flaw size are difficult to monitor.

3.7.2

Monitoring for Degradation of Low Alloy Steel Notch Toughness – Certain materials, such as the chromium-molybdenum low alloy steels, experience a loss of notch toughness due to exposure at high temperatures. This degradation may be monitored over the service life by means of sentinel material included within a pressure vessel. Periodically, a portion of this material is removed and tested to monitor for the degradation of material toughness. The degradation of material properties is evaluated against a minimum acceptable brittle fracture criteria which have previously been established. A Level 3 Assessment is usually required to justify continued use when the material no longer meets this criteria.

3.7.3

Monitoring for Criticality of Growing Flaws – Flaws which develop or propagate during the service life of equipment can have a detrimental affect on the risk of brittle fracture. The assessment of each type of flaw is prescribed in other sections of this Recommended Practice, see Section 2 for an overview.

3.7.4

Assessment of Non-Growing Flaws Detected In-Service – In-service inspections may result in the detection of flaws that may include original material or fabrication flaws. These flaws may or may not be in excess of the requirements of the original design and construction code. While these flaws may have been innocuous relative to the original design code, their presence may affect current or altered design and operating parameters. Alternatively, flaws may have developed or resulted from service exposure, excessive operating conditions, or maintenance-related activities. The influence of such flaws on the increased susceptibility for brittle fracture should be assessed. This assessment will generally require either a Level 2 or 3 analysis.

3.8

Documentation

3.8.1

The documentation for each level of brittle fracture assessment should include the information cited in Section 2, paragraph 2.8 and the following specific requirements:

3.8.1.1

Level 1 Assessment – Documentation covering the assessment, the specific data used, and the criteria which have been met by the results obtained from that evaluation.

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Not for Resale

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3.6.2.2


3.8.1.2

Level 2 Assessment – The documentation should address the reason(s) for the assessment, the assessment level used, the engineering principles employed, the source of all material data used, identification of any potential material property degradation mechanisms and the associated influence on the propagation of flaws, and the criteria applied to the assessment procedure.

3.8.1.3

Level 3 Assessment – The documentation should cover the reason(s) for performing a Level 3 assessment and all issues pertaining to the fitness-for-service assessment. The documentation should also address the engineering principles employed including stress analysis methods and flaw sizing, the source of all material data used, identification of any potential material property degradation mechanisms and the associated influence on the propagation of flaws, and the criteria applied to the assessment procedure.

3.8.2

All documents pertaining to the assessment for brittle fracture should be retained for the life of the equipment in the equipment history file. This includes all supporting documentation, data, test reports, and references to methods and criteria used for such assessments and evaluations. For vessels exposed to identical conditions, a single document with appropriate references is adequate.

3.9

References

3.9.1

McLaughlin, J.E., Sims, J.R., "Assessment of Older Equipment for Risk of Brittle Fracture," ASME PVP-Vol. 261, American Society of Mechanical Engineers, New York, N.Y., 1993, pp. 257-264.

3.9.2

Findlay, M., McLaughlin, J.E., and Sims, J.R., “Assessment of Older Cold Service Pressure Vessels for Brittle Fracture During Temperature Excursions Below the Minimum Design Temperature,” ASME PVP-Vol. 288, American Society of Mechanical Engineers, New York, N.Y., pp. 297-305.

3.9.3

TWI, “Fracture -Safe Designs for Large Storage Tanks,” ed. A.A. Willoughby, The Welding Institute, 1986.

3.10

Tables And Figures

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Table 3.1 Overview Of Data For The Assessment Of Brittle Fracture Use this form to summarize the data obtained from a field inspection. Equipment Identification: Equipment Type: _____ Pressure Vessel Component Type & Location: Year Of Fabrication:

_____ Storage Tank

_____ Piping Component

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Additional Data Required For Level 2 Assessment (In Addition to the Level 1 Data): Weld Joint Efficiency (level 2) {V,P,T} : Corrosion Allowance {V,P}: Maximum Operating Pressure {V,P}: Charpy Impact Data, if available {V,P,T}:

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Data Required For A Level 1 Assessment (V – indicates data needed for pressure vessels, and P – indicates data needed for piping, and T – indicates data needed for tankage) Design Temperature {V,P,T}: Original Hydrotest Pressure {V,P}: Product Specific Gravity & Design Liquid Height {T}: Temperature During Original Hydrotest Pressure {V,P,T}: Nominal Wall Thickness of all components {V,P,T}: Critical Exposure Temperature (CET) {V,P,T}: Minimum Allowable Temperature (MAT) {V,P}: PWHT done at initial construction? {V,P,T}: PWHT after all repairs? {V,P,T}:


Not for Resale


Table 3.2 Procedure For Determining The MAT When Impact Test Results Are Not Available (1) Step

For the component under consideration, determine the following parameters: · Nominal uncorroded thickness (2), · Governing nominal uncorroded thickness t g (3), · · · · ·

Materials of construction, Applicable material toughness curve(s) of Figure 3.3 (4), All applicable loads and coincident Minimum Allowable Temperatures (5), Metal loss associated with the governing thickness, LOSS , Future corrosion allowance associated with the governing thickness, FCA ,

· ·

Weld joint efficiencies, E and E (6) (7) Required thickness in the corroded condition for all applicable loads, efficiency.

*

t r , using the applicable weld joint

2

Determine the MAT from Figure 3.3 based on the applicable toughness curve and current governing thickness which is equal to the nominal governing thickness minus the associated metal loss.

3

Determine the following ratio (7) (8):

Rts = 4 5

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1

Required Actions

tr E * S *E * = t g - LOSS - FCA SE

(3.1)

Use the ratio from Step 3 to enter ordinate of Figure 3.5 and determine the reduction to be applied to the MAT found in Step 2. Determine the adjusted MAT by subtracting the value obtained in Step 4 from the MAT obtained in Step 2. A lower limit to the resulting MAT is provided in Figure 3.5, Notes 6 and 7. Repeat Steps 1 through 5 for all components that make-up the piece of equipment being evaluated (e.g. pressure vessel or piping system). The MAT for the piece of equipment is highest value obtained in this calculation.

Notes: 1. The MAT can be based on Charpy Energy impact test results if available (see paragraph 3.4.2.1.c). 2. For welded pipe where a mill undertolerance is allowed by the material specification, the thickness after mill undertolerance has been deducted shall be taken as the nominal thickness. Likewise, for formed heads, the minimum specified thickness after forming shall be used as the nominal thickness. 3. The governing thickness is defined in paragraph 3.4.2.1.d. 4. The applicable material toughness curve can be determined once the material specification is known (see Table 3.3 and Table 3.4). Note that for some materials, the heat treatment and steel making practice must be known or established to determine a toughness curve. 5. A summary of the loads that should be considered are included in Table A.1 of Appendix A. Only those loads which result in general primary membrane tensile stress at the coincident MAT need to be considered. 6.

E is the joint efficiency (e.g. see Table UW-12 of the ASME Code, section VIII, Division 1) used in the calculation of t r . E * has a value equal to E except that E * shall not be less than 0.80. For castings, the quality factor or joint efficiency E, whichever governs design, should be used.

7.

Note that the ratio computed in Step 3 can be computed in terms of stresses, or thicknesses, and weld joint efficiencies where,

S * is the applied general primary stress, S

is the allowable stress value in tension, and

E

*

and E are defined in Note 5. 8.

S * for piping systems is computed using the guidelines in Figure 3.7, Note 5. For components with pressure temperature ratings, the stress ratio, Rts ,is computed as the pressure for the condition under consideration divided by the pressure rating at the design minimum temperature.


Not for Resale

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6


Table 3.3 Assignment Of Materials To The Curves In Figure 3.3

A

B

Material (1), (2), (6) 1.

All carbon and all low alloy steel plates, structural shapes and bars not listed in Curves B, C, and D below.

2.

SA-216 Grades WCB and WCC if normalized and tempered or water-quenched and tempered; SA -217 Grade WC6 if normalized and tempered or water-quenched and tempered

3.

The following specifications for obsolete materials: A7, A10, A30, A70, A113, A149, A150 (3).

4.

The following specifications for obsolete materials from the 1934 edition of the ASME Code, Section VIII: S1, S2, S25, S26, and S27 (4).

5.

A201 and A212 unless it can be established that the steel was produced by a fine-grain practice (5)

1.

SA-216 Grades WCA if normalized and tempered or water-quenched and tempered SA-216 Grades WCB and WCC for thicknesses not exceeding 2 inches if produced to a fine grain practice and water-quenched and tempered SA -217 Grade WC9 if normalized and tempered SA-285 Grades A and B SA-414 Grade A SA-442 Grade 55>1 in. if not to fine grain practice and normalized SA-442 Grade 60 if not to fine grain practice and normalized SA-515 Grades 55 and 60 SA-516 Grades 65 and 70 if not normalized SA-612 if not normalized SA-662 Grade B if not normalized Except for cast steels, all materials of Curve A if produced to fine grain practice and normalized which are not listed for Curve C and D below;

2.

C

3.

All pipe, fittings, forgings, and tubing not listed for Curves C and D below;

4.

Parts permitted from paragraph UG-11 of the ASME Code, Section VIII, Division 1, shall be included in Curve B even when fabricated from plate that otherwise would be assigned to a different curve.

5.

A201 and A212 if it can be established that the steel was produced by a fine-grain practice.

1.

SA-182 Grades 21 and 22 if normalized and tempered. SA-302 Grades C and D SA-336 Grades F21 and F22 if normalized and tempered SA-387 Grades 21 and 22 if normalized and tempered SA-442 Grades 55 < 1 in. if not to fine grain practice and normalized SA-516 Grades 55 and 60 if not normalized SA-533 Grades B and C SA-662 Grade A All material of Curve B if produced to fine grain practice and normalized and not listed for Curve D below

2.


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Curve


Table 3.3 Assignment Of Materials To The Curves In Figure 3.3 Curve D

Material (1), (2), (6)

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SA-203 SA-442 if to fine grain practice and normalized SA-508 Class 1 SA-516 if normalized SA-524 Classes 1 and 2 SA-537 Classes 1 and 2 SA-612 if normalized SA-662 if normalized SA-738 Grade A

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Notes: 1. When a material class or grade is not shown, all classes or grades are included. 2. The following apply to all material assignment notes. a. Cooling rates faster than those obtained in air, followed by tempering, as permitted by the material specification, are considered to be equivalent to normalizing and tempering heat treatments. b. Fine grain practice is defined as the procedures necessary to obtain a fine austenitic grain size as described in SA-20. 3. The first edition of the API Code for Unfired Pressure Vessels (discontinued in 1956) included these ASTM carbon steel plate specifications. These specifications were variously designated for structural steel for bridges, locomotives, and rail cars or for boilers and firebox steel for locomotives and stationary service. ASTM A 149 and A150 were applicable to high-tensile-strength carbon steel plates for pressure vessels. 4. The 1934 edition of Section VIII of the ASME Code listed a series of ASME steel specifications, including S1 and S2 for forge welding; S26 and S27 for carbon steel plates; and S25 for open-hearth iron. The titles of some of these specifications are similar to the ASTM specifications listed in the 1934 edition of the API Code for Unfired Pressure Vessels. 5. These two steels were replaced in strength grades by the four grades specified in ASTM A 515 and the four grades specified in ASTM A 516. Steel in accordance with ASTM A 212 was made only in strength grades the same as Grades 65 and 70 and has accounted for several known brittle failures. Steels in conformance with ASTM A 201 and A 212 should be assigned to Curve A unless it can be established that the steel was produced by fine-grain practice, which may have enhanced the toughness properties. 6. No attempt has been made to make a list of obsolete specifications for tubes, pipes, forgings, bars and castings. Unless specific information to the contrary is available, all of these product forms should be assigned to Curve A.


Not for Resale


Table 3.4 Impact Test Exemption Temperature For Bolting Materials Specification

Grade

SA-193 SA-193 SA-193

Impact Test Exemption Temperature

B5

mDia £ 635. mm b2.5 in.gr . mm b2.5 in.gr B7 mDia > 635 B7

(°C)

(°F)

-29

-20

-46

-50

-40

-40

SA-193

B7M

-48

-55

SA-193

B16

-29

-20

SA-307

B

-29

-20

SA-320

L7, L7A, L7M, L43

Impact Tested per Specification

Impact Tested per Specification

SA-325

1, 2

-29

-20

SA-354

BC

-18

0

SA-354

BD

-7

+20

SA-449

---

-29

-20

SA-540

B23/24

-12

+10

SA-194

2, 2H, 2HM, 3, 4, 7, 7M, and 16

-48

-55

SA-540

B23/B24

-48

-55

Bolting materials are exempt from assessment due to loading conditions.


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Note:

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Table 3.5 Equations For The Curves Included In Figures 3.3, 3.5, 3.6, and 3.8 Figure 3.3

Equation (see Note 1) Curve A

MAT = 18 MAT =

for 0 < t £ 0.394

-76.911 + 284.85t - 27.560t 2 1.0 + 17971 . t - 017887 . t2

(3.2)

for 0.394 < t £ 6.0

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Curve B

MAT = -20

for 0 < t £ 0.394

MAT = -135.79 + 17156 . t 0.5 + 103.63t 172.0t

1.5

2

+ 73.737t - 10.535t

(3.3)

2 .5

for 0.394 < t £ 6.0

Curve C

MAT = -55 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

for 0 < t £ 0.394 25550 . 287.86 196.42 69.457 9.8082 MAT = 10129 . + + t t2 t3 t4 t5

for 0.394 < t £ 6.0

(3.4)

Curve D

MAT = -55

for 0 < t £ 0.50

MAT = -92.965 + 94.065t - 39.812t 2 +

(3.5)

9.6838t 3 - 11698 . t 4 + 0.054687t 5 3.5

b

TR = 100.0 10 . - Rts

g

for 0.50 < t £ 6.0

for Rts ³ 0.6

TR = -9979.57 - 14125.0 Rts1.5 + 908811 . exp Rts - 17.3893 TR = 105.0 TR = 140.0 TR = 200.0


ln Rts Rts2

for 0.6 > Rts > 0.3 ( see Note 2)

for Rts £ 0.40 ( see Note 3) for Rts £ 0.35 ( see Note 4) for Rts £ 0.30 ( see Note 5)

Not for Resale

(3.6)


Table 3.5 Equations For The Curves Included In Figures 3.3, 3.5, 3.6, and 3.8 Figure 3.6

Equation (see Note 1)

bsee Note 6g ³ 0.75 b see Note 7g ³ 0.67 b see Note 8g

TRH = 20.0

for H R ³ 0.8

TRH = 26.0

for H R

TRH = 35.0

for H R

TRH = 20.411 + 16.811H R - 62.805H R2 + TRH = 105.0

(3.7)

21.078 HR

for 0.67 > H R > 0.25

for H R £ 0.25

TS = 30

for 0 < t £ 0.50 133.75 10.775 TS = 191.03 - 0.48321t 2 - 0.5 + 1.5 t t TS = 60 for 0.875 £ t £ 2.0

3.8

for 0.50 < t < 0.875

(3.8)

Notes: 1. Units for the equations in this table are as follows: t - The shell thickness is in inches, MAT - The Minimum Allowable Temperature is in degrees Fahrenheit, TR - The Reduction in MAT based on available excess thickness is in degrees Fahrenheit,

3. 4. 5. 6.

- The Reduction in MAT based on the operating-to-hydrotest ratio is in degrees Fahrenheit, and TS - The shell metal temperature is in degrees Fahrenheit. A temperature cut-off is assigned to this equation based on the room temperature design allowable stress of the original construction code, see notes 3, 4, and 5 below. See Note 2 of Figure 3.5. See Note 3 of Figure 3.5. See Note 4 of Figure 3.5. See Note 1 of Figure 3.6, H R is defined in Figure 3.6.

7.

See Note 2 of Figure 3.6,

2.

8.

H R is defined in Figure 3.6. See Note 3 of Figure 3.6, H R is defined in Figure 3.6.

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TRH

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Figure 3.1 Overall Brittle Assessment Procedure For Pressure Vessels And Piping

Obtain Original Equipment Design Data

Obtain Maintenance and Operational History

Determine the CET

Evaluation Method

Level 2 Method A

Level 1

No

MAT <= CET?

No

Operation within the MAT Envelope?

Yes

Level 2 Method B

No

Level 2 Method C

No


Yes

Level 3

No


Yes

Yes

Component Is Suitable For Service


Yes Component Is Not Suitable For Operation at the Stipulated CET

Maintain Inspection Per API 510 or API 570, As Applicable

Change In Service?

Yes

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No


Not for Resale


Figure 3.2 Brittle Fracture Assessment For Storage Tanks

Obtain Information for a Brittle Fracture Assessment

Level 1 Assessment

Tank Meets Toughness Requirements In Current Construction Code (1)(2)?

No

Yes

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No

Level 2 Assessment

Prior Hydrotest Demonstrates Fitness-For-Service (3)?

Yes

Yes

Is the Future Service More Severe (11)?

Tank Thickness <= 12.7 mm (0.5 inches) (4)? No

Yes

Operating Temperature Above 16 C (60 F) (5)? No

Yes

Membrane Stress <= 55.2 MPa (8 ksi) (6)? No

Yes

Tank Exempt from Impact Testing (7)? No

Yes

Tank Full at Lowest One Day Temperature (8)? No

Yes

Yes

Level 3 Assessment Satisfied?

Perform Level 3 Assessment?

No

Hydrotest to Demonstrate Fitness-For-Service (3)?

No

Yes

No Yes

Rerate Tank Based on Prior Operating History (9)? No Retire Tank

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Not for Resale

Yes

Tank Is Suitable for Continued Operation

No

No Yes

Tank Continues To Operate in the Same Service (10)?


Notes for Figure 3.2

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1.

Atmospheric storage tanks constructed in accordance with API Standard 650 (seventh edition or later) include requirements to minimize the risk of failure due to brittle fracture. Tanks constructed to earlier version of this Standard may also be shown to meet these the API 650 (seventh edition or later) toughness requirements by impact testing coupon samples from a representative number of shell plates.

2.

Many tanks continue to operate successfully in the same service that were not constructed to the requirements of API Standard 650 (seventh edition or later). These tanks are potentially susceptible to failure due to brittle fracture and require a Level 2 Assessment.

3.

For purposes of this assessment, hydrostatic testing demonstrates that an aboveground atmospheric storage tank in a petroleum or chemical service is fit for continued service and at minimal risk of failure due to brittle fracture, provided that all governing requirements for repair, alterations, reconstruction, or change in service are in accordance with API Standard 653 (including a need for hydrostatic testing after major repairs, modifications or reconstruction). The effectiveness of the hydrostatic test in demonstrating fitness for continued service is shown by industry experience.

4.

If a tank shell thickness is no greater than 12.7 mm (0.5 inches), the risk of failure due to brittle fracture is minimal, provided that an evaluation for suitability of service per API 653, Section 2 has been performed. The original nominal thickness for the thickest tank shell plate shall be used for this assessment.

5.

No known tank failures due to brittle fracture have occurred at shell metal temperatures of 16°C (60°F) or above. Similar assurance against brittle fracture can be gained by increasing the metal temperature by heating the tank contents.

6.

Industry experience and laboratory tests have shown that a membrane stress in tank shell plates of at least 55.2 MPa (8 ksi) is required to cause failure due to brittle fracture.

7.

Tanks constructed from steel listed in Figure 2-1 of API Standard 650 can be used in accordance with their exemption curves, provided that an evaluation for suitability of service per Section 2 of API Standard 653 has been performed. Tanks fabricated from steels of unknown toughness thicker than 12.7 mm (0.5 inches) and operating at a shell metal temperature below 16°C (60°F) can be used if the tank meets the requirements of Figure 3.8. The original nominal thickness for the thickest tank shell plate shall be used for the assessment. For unheated tanks, the shell metal temperature shall be the design metal temperature as defined in 2.2.9.3 of API Standard 650.

8.

The risk of failure due to brittle fracture is minimal once a tank has demonstrated that it can operate at a specified maximum liquid level at the lowest expected temperature without failing unless repairs or alterations have been made. For the purpose of this assessment, the lowest expected temperature is defined as the lowest one day mean temperature as shown in Figure 2-2 of API Standard 650 for the continental United States. It is necessary to check tank log records and meteorological records to ensure that the tank has operated at the specified maximum liquid level when the one-day mean temperature was as low as shown in Figure 2-2 of API Standard 650.

9.

An evaluation can be performed to establish a safe operating envelope for a tank based on the past operating history. This evaluation shall be based on the most severe combination of temperature and liquid level experienced by the tank during its life. The evaluation may show that the tank needs to be rerated or operated differently; several options exist: ·

Restrict the liquid level,

·

Restrict the minimum metal temperature,

·

Change the service to a stored product with a lower specific gravity, or

·

Combinations of the above.

10.

An assessment shall be made to determine if the change in service places the tank at greater risk of failure due to brittle fracture. The service can be considered more severe and creating a greater risk of brittle fracture if the service temperature is reduced (for example, changing from heated oil service to ambient temperature product), or the product is changed to one with a greater specific gravity and thus increasing stresses.

11.

A change in service must be evaluated to determine if it increase the risk of failure due to brittle fracture. In the event of a change to a more severe service (such as operating at a lower temperature or handling product at a higher specific gravity) it is necessary to consider the future service conditions in the fitness-for-service assessment.


Not for Resale

--``````-`-`,,`,,`,`,,`---

The assessment procedure as illustrated in Figure 3.2 shall be used for Level 2 assessment of aboveground atmospheric storage tanks in petroleum and chemical services. Each of the key steps on the decision tree are numbered corresponding to the explanation provided as follows:


Figure 3.3 Minimum Allowable Metal Temperature

Governing Plate Thickness, mm 10

20

30

40

50

60

70

80

90

100

110

120

130

140

150 60

Curve A

50 40

Curve B

100

30

80

20

Curve C 60

10 40

Curve D 0

20

-10

0

-20

-20

-30

-40

-40

-60

-50

-80 0.00

-60 0.394

1.00

2.00

3.00

4.00

5.00

6.00

Governing Plate Thickness, inches

Notes: 1. Curves A through D define material specification classes in accordance with Tables 3.3 and 3.4. 2. Equipment whose CET is above the appropriate material curve is exempt from further brittle fracture assessment. 3. This figure is from the ASME Code Section VIII, Division 1, paragraph UCS-66.

-8o C (18o F ) , Curve B intersects the MAT -axis at -29 o C ( -20o F ) , and Curves C and D intersect the MAT -axis at -48o C ( -55o F ) .

4.

Curve A intersects the MAT -axis at

5.

These curves can also be used to evaluate piping components designed to ASME B31.3. In this case, Curve B should be shifted to the right so that 12.7 mm (0.5 in.) corresponds to a temperature

-29 o C ( -20o F ) . To account for this shift in an assessment, an effective governing thickness equal to the actual governing thickness minus 2.69 mm (0.106 in.) can be used to determine the MAT. 6. 7.

The equations of the curves in this figure are provided in Table 3.5. A reduction in the MAT is permitted for components subject to PWHT (see paragraph 3.4.2.1.e).


Not for Resale

--``````-`-`,,`,,`,`,,`---

o

o

MAT: Minimum Allowable Temperature, F

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

120

MAT: Minimum Allowable Temperature, C

0 140


Figure 3.4 Some Typical Vessel Details Showing The Governing Thickness

tb X

2 1 ta

X

Section X-X

tb tg1=ta tg2=ta (seamless) or tb (welded) (A) Butt Welded Components

tc

tc tb

ta

tc

2 tb

ta

tb

3

--``````-`-`,,`,,`,`,,`---

1 tg1=min (ta, tc)

tg2=min (tb, tc)

tg3=min (ta, tb)

(B) Welded Connection with or without a Reinforcing Plate


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

ta


Figure 3.4 (continued) Some Typical Vessel Details Showing The Governing Thickness

1

1

Groove

ta

ta

Groove

2

tg1= ta/4 (for welded or nonwelded)

tg1= ta/4 (for welded or nonwelded)

2

tg2=tb Note: The governing thickness of the integral flat head or tubesheet is max (tg1, tg2)

tg2=tc tc

tb (D) Integral Flat Head or Tubesheet

(C) Bolted Flat Head or Tubesheet and Flange

Groove

1 A

ta

2 tg1= ta/4 (for welded or nonwelded) tg2=min (ta, tb) Note: The governing thickness of the integral flat head or tubesheet is max (tg1, tg2) tb (E) Flat Head or Tubesheet with a Corner Joint

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 3.4 (continued) Some Typical Vessel Details Showing The Governing Thickness

tb

ta

1

ta

1

Pressure Containing Part

tb

Pressure Containing Part

tg1=min(ta, tb) (F) Welded Attachments --``````-`-`,,`,,`,`,,`---

1

ta

tc

tg1=min (ta, tc) (G) Integrally Reinforced Welded Connection

Notes: 1. In general, the governing thickness is the thinner of the two parts at the welded joint. 2. In Details Figure 3.4(A) to (G), t gi , is the governing thickness at weld joint i . 3.

The MAT of a component is evaluated at each governing thickness,


t gi ,as applicable.

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

1


Figure 3.5 Reduction In The MAT Based On Available Excess Thickness For Carbon and Low Alloy Steel Vessels

TR, Temperature Reduction, oC 0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

105

110

1.0

* Rts=trE /(tg - Loss - FCA)

0.9 0.8 0.7 0.6 0.5 (Note 2)

0.4

(Note 3)

0.3

(Note 4)

0.2 0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

o TR, Temperature Reduction, F

Notes: 1. See Table 3.2 for definition of parameters. 2. Use this curve for components with a design allowable stress at room temperature less than or equal to 120.8 MPa (17.5 ksi). This curve can be used for vessels designed and constructed to the ASME Code, Section VIII, Division 1, Editions prior to 1999. 3. Use this curve for components with a design allowable stress at room temperature less than or equal to 137.8 MPa (20 ksi) but greater than 120.8 MPa (17.5 ksi) . This curve can be used for vessels designed and constructed to the ASME Code, Section VIII, Division 1, 1999 Edition and later. 4. Use this curve for components with a design allowable stress at room temperature less than or equal to 172.5 MPa (25 ksi) but greater than 137.8 MPa (20 ksi) . This curve can be used for vessels designed and constructed to the ASME Code, Section VIII, Division 2, and piping designed to ASME B31.3. 5. The equations for the curves in this figure are provided in Table 3.5. 4. The starting point for the MAT for use with the temperature reduction provided for in this figure is -48°C (-55°F). Note that this starting point cannot be below -48°C (-55°F) for components subject to PWHT (see paragraph 3.4.2.1.e). 5. The ending point for the MAT after application of the temperature reduction permitted by this figure is a function of Rts and the code allowable stress basis as defined in notes 3, 4, and 5 above. When Rts is

c

h

MAT = -104 o C -155o F . --``````-`-`,,`,,`,`,,`---

less than or equal to 0.4, 0.35, and 0.3 on the applicable curve, then


Not for Resale

//^:^^#


Figure 3.6 Allowable Reduction In The MAT Based On Hydrostatic Proof Testing

TRH , Temperature Reduction Below Hydrotest Temperature, oC

HR - Maximum Expected Operating Pressure/Hydrotest Pressure

0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110

1.0 0.9 (Note 1)

0.8

(Note 2)

0.7

(Note 3)

0.6 0.5 0.4 0.3 0.2 0.1 0.0 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 o TRH , Temperature Reduction Below Hydrotest Temperature, F

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes: 1. Use this curve when the hydrotest pressure is 125% of the design pressure. 2. Use this curve when the hydrotest pressure is 130% of the design pressure. 3. Use this curve when the hydrotest pressure is 150% of the design pressure. 4. The equations for the curves in this figure are provided in Table 3.5.

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 3.7 Level 2 Method C Assessment For Carbon Steel Piping

Piping Does Not Meet the Level 1 Assessment Criteria

Obtain Information For A Level 2 Assessment

Is CET < -104 C (-155 F) (1)?

Yes

No Is Shock Chilling Possible (2)?

Yes

No

Is Vibration Or Low Temperature Impact Possible (3)?

Yes

No

Piping Meets Level 2 Assessment Criteria

No

Is CET < -48 C (-55 F) (1)?

No

Yes

Is Nominal Pipe Wall Thickness > 12.7 mm (0.5 inches)? Yes Does Component Meet Operating Experience Criteria (4)?

Yes

Seamless Pipe?

Is the Long. & Cir. Stress <= 55.2 MPa (8ksi)?

No

Yes

No

Is the Long. Stress <= 55.2 MPa (8ksi)?

--``````-`-`,,`,,`,`,,`---


Not for Resale

Yes

Yes

No

Concern for Brittle Fracture - Level 3 Assessment Required

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

No


Notes for Figure 3.7 1.

Experience suggests that brittle fracture of piping is usually associated with unanticipated low temperature excursions.

2.

Shock chilling is a rapid decrease in metal temperature caused by a sudden flow of liquid, which is below -29°C (-20°F), and which is 56°C (100°F) or more, below the metal temperature of the equipment before cooling. In addition to a liquid, a two phase fluid may need to be considered when evaluating potential shock chilling. One example of this is a flare header that receives sub-cooled or flashing liquid from a safety valve discharge.

3.

Vibrations in a portion of the piping system could initiate cracks which are cause for a high level of concern of brittle fracture. If the system could be subject to cyclic operating or impact load while it is operating below -29°C (-20°F), then an assessment should be made to determine whether the resulting cyclic stresses could result in the initiation and propagation of a crack. If crack initiation and/or propagation is determined to be possible, then a Level 3 Assessment is required. Impact loads include hammering from flow or aggressive repeated strikes from tools or mobile equipment, etc. Minor impact loads from hand tools other than deliberate hammering are not generally a cause for concern.

4.

Acceptance based on successful operating experience is based on the following:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

5.

a.

The nominal operating conditions have been essentially the same and consistent for a significant period of time and more severe conditions (i.e., lower temperature and/or higher pressure or stress) are not expected in the future. In addition, the maximum design temperature and pressure have not been exceeded for a significant period of time. (Note safety valve discharge lines usually do not meet this criteria, see Note 1)

b.

The piping is not in a stress corrosion cracking environment such as non-PWHT piping in DEA, MEA, NaOH, or KOH. This restriction does not apply to seamless pipe in wet H2S service or seamless and welded pipe in anhydrous ammonia service unless there are clear indications of cracking in the piping.

c.

The piping system is in good condition as determined by an inspection using API 570 or other applicable inspection code or standard.

d.

The piping system has adequate flexibility by virtue of layout, freedom for thermal growth, and the supports as determined by visual inspection are in good condition.

Guidelines for stress calculations are as follows: a.

The circumferential stress should be calculated based on the nominal wall thickness minus the metal loss, future corrosion allowance, mechanical allowances, and the manufacturing mill tolerance.

b.

The longitudinal stress should be calculated based on the combined stress resulting from pressure, dead weight, and displacement strain. In calculating the longitudinal stress, the forces and moments in the piping system should be determined using section properties based on the nominal dimensions adjusted for metal loss and future corrosion allowance, and the stress should be calculated using section properties based on the nominal dimensions minus the metal loss, future corrosion allowance, and mechanical allowances. Stress intensification factors associated with pipe bends, elbows, tees, etc., do not need to be included in the longitudinal stress calculation. The thermal stress does not have to consider a full design range, such as would result from a system with a high design temperature. It should best reflect the actual stress imposed at low temperature.

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 3.8 Exemption Curve For Tanks Constructed From Carbon Steel Of Unknown Toughness Thicker Than o 12.7 mm (1/2 inch) And Operating At A Shell Metal Temperature Below 60 F

Shell Thickness, mm --``````-`-`,,`,,`,`,,`---

0

5

10

15

20

25

30

35

40

45

50

70 20 Safe for Use 60

15

5

40 Safe for Use

0 30

-5 20 -10 10 -15 0 0.0

0.5

0.875

1.0

1.5

2.0

Shell Thickness, inches

Note:

The above exemption curve between -1°C (30°F) and 16°C (60°F) is based on Curve A in Figure 3.3. The other parts of the curve were established based on successful operating experience.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

o

Shell Temperature, C

10

Additional Assessment Required

o

Shell Metal Temperature, F

50


3.11 3.11.1

Example Problems

Example Problem 1 – A pressure vessel, 1 inch thick, fabricated from SA-285 Grade C in caustic service was originally subject to PWHT at the time of construction. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine the MAT. Solution – Based on Curve A in Figure 3.3, a MAT of 68°F (20°C) was established for the vessel without any allowance for PWHT. Applying the allowance for PWHT reduces the MAT by 30°F (17°C) and established a new MAT of 38°F (3°C).

3.11.2

Example Problem 2 – A horizontal drum 1.5 inches (38 mm) thick is fabricated from A-516 Grade 70 steel which was supplied in the normalized condition. There is no toughness data on the steel. . The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine the MAT. Solution – Since SA-516 Grade 70 is manufactured to a fine grain practice and was supplied in this case in the normalized condition, Curve D of Figure 3.3 may be used. In this case, the MAT is found to be -15°F (-26°C).

3.11.3

Example Problem 3 – A reactor vessel fabricated from SA-204 Gr B (C-½ Mo) has the following material properties and dimensions. The reactors were designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Develop a table of MAT as a function of pressure based on paragraph 3.4.3.1 and the allowances given in Figure 3.5 and Table 3.2. Vessel Information Allowable stress

=

17,500 psi (121 MPa)

Design pressure

=

390 psi (2.69 MPa)

Inside Diameter

=

234 inches (5943.6 mm)

Operating pressure

=

240 psi (1.66 MPa)

Wall Thickness

=

2.72 inches (69 mm)

Startup pressure

=

157 psi (1.04 MPa)

Weld Joint Efficiency

=

1.0

Corrosion Allowance

=

1/

MAT at Design Pressure

=

110°F (43°C) (see Curve A of Figure 3.3)

16 in. (1.6 mm)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Impact test data is not available.

--``````-`-`,,`,,`,`,,`---


Not for Resale


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Appendix A):

234" - 0.0625 = 116.9" 2 t c = 2.72"-0.0625" = 2.66" Rc =

S *E * = P

FG 116.9 + 0.6IJ = 44.6 P H 2.66 K

Using this relationship, a table of MAT can be established as a function of pressure based on paragraph 3.4.3.1 and the allowances given in Figure 3.5 and Table 3.2.

P

S*E*

psi (MPa)

psi (MPa)

390 (2.69)

17,400 (120)

240 (1.66) 157 (1.08)

,T

MAT

°F (°C)

°F (°C)

1.00

0 (0)

110 (43)

10,700 (73.8)

0.61

38 (21)

72 (22)

7,000 (48.3)

0.40

105 to 260 (58 to 144)

5 to -155 (-15 to -104)

Rts =

S *E * SE

The operating pressures and corresponding values of the MAT in this table must be compared to the actual vessel operating conditions to confirm that the metal temperature (CET) cannot be below the MAT at the corresponding operating pressure.

3.11.4

Example Problem 4 – A sphere fabricated from BS 1501 – 213 Grade 32A LT (SA-414 Grade G equivalent) has the following material properties and dimensions. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Develop a table of MAT as a function of pressure based on paragraph 3.4.3.1 and the allowances given in Figure 3.5 and Table 3.2.

Allowable stress

=

25000 psi (172.4 MPa)

Design pressure

=

205 psig (1.41 MPa)

Inside Diameter

=

585.6 inches (14874.2 mm)

Wall Thickness

=

1.26 in. (32 mm)


=

1.0

Corrosion Allowance CA

=

1/ in. (1.6 mm) 16

MAT at Design Pressure

=

80°F (26.7°C), (see Curve A of Figure 3.3)

Impact test data is not available.

Solution – The membrane stress for a spherical pressure vessel as a function of pressure as (see Appendix A):


Not for Resale

--``````-`-`,,`,,`,`,,`---

Vessel Information


585.6" - 0.0625 = 292.7" 2 t c = 126 . "-0.0625" = 1198 . " Rc =

S *E * =

FG H

IJ K

P 292.7 + 0.2 = 122 P 2 1198 .

Using this relationship, a table of MAT can be established as a function of pressure based on paragraph 3.4.3.1, the procedure in Table 3.2 and the allowances given by the appropriate curve in Figure 3.5.

P

S*E*

psi (MPa)

psi (MPa)

205 (1.41)

25000 (172.5)

143 (0.99)

,T

MAT

°F (°C)

°F (°C)

1.0

0 (0)

80 (27)

17500 (121)

0.7

31.5 (17.5)

48.5 (9.2)

100 (0.69)

12500 (86.3)

0.5

58.5 (32.5)

21 ( -6)

57 (0.39)

7000 (48.3)

0.3

200 (111)

-120 (-84)

Rts =

S *E * SE

The operating pressures and corresponding values of the MAT in this table must be compared to the actual sphere operating conditions to confirm that the metal temperature (CET) cannot be below the MAT at the corresponding operating pressure.

3.11.5

Example Problem 5 – A spherical pressure vessel has the following properties and has experienced the following hydrotest conditions. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Using paragraph 3.4.3.2 and Figure 3.6, prepare a table showing the relationship between operating pressure and MAT. Hydrotest pressure

=

300 psi (2.07 MPa), or 150% of the design pressure

Design pressure

=

200 psi (1.38 MPa)

Metal temperature during hydrotest

=

50°F (10°C)

Solution – The maximum measured metal temperature during hydrotest was 50°F. To be conservative, 10°F is added to this and the analysis is based on a hydrotest metal temperature of 60°F.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~

--``````-`-`,,`,,`,`,,`---


Not for Resale


--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Operating Pressure

Operating Pressure/

Temperature Reduction

MAT

psi (MPa)

Hydrotest Pressure

°F (°C)

°F (°C)

200 (1.38)

0.67

35 (19.4)

25 (-4)

180 (1.24)

0.6

43 (24)

18 (-8)

150 (1.04)

0.5

55 (31)

5 (-15)

120 (0.83)

0.4

70 (39)

-10 (-23)

90 (0.62)

0.3

90 (50)

-30 (-34)

75 (0.52)

0.25

105 to 210 (58 to 117)

-45 to -155 (-43 to -104)

The operating pressures and corresponding values of the MAT in this table must be compared to the actual sphere operating conditions to confirm that the metal temperature (CET) cannot be below the MAT at the corresponding operating pressure.

3.11.6

Example Problem 6 – A demethanizer tower in the cold end of a ethylene plant typically operates colder in the top portion of the tower and warmer at the bottom of the tower. The bottom of the tower is kept warm with a side stream circulated through a reboiler. The top portion of the tower is constructed from a 3½% Ni steel which has been impact tested for toughness at -101°C (-150°F). The lower portion of the tower is constructed from a fully killed, fine grained and normalized carbon steel which is impact tested for toughness at -46°C (-50°F). A potential for brittle fracture exists if the reboiler does not operate because cold liquid will flow down the tower into the carbon steel section resulting in operating temperatures significantly lower than -46°C (-50°F). The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Perform a brittle fracture assessment of ethylene plant demethanizer tower considering all aspects of operation. The upset condition of the reboiler not operating properly should be included in the assessment. Solution – A brittle fracture assessment consistent with Paragraph 3.4.4 (Level 3 assessment) can be performed on the demethanizer tower. The approach is illustrated with reference to the demethanizer tower as illustrated in Figure 3.1E. The assessment to be utilized is based on the fracture mechanics principles presented in Section 9. In the assessment, the limiting flaw size in the tower will be established, and a sensitivity study will be performed to determine how the limiting flaw size changes as the temperature in the tower drops during an excursion. Based on the results of the assessment, a graph of limiting flaw size versus temperature will be constructed. This graph is referred to as a Fracture Tolerance Signature (FTS). The FTS provides an indication of the safety margin in terms of limiting flaw size. In addition, the FTS can be used to select a lower thermal excursion limit by establishing a flaw size that can be detected with sufficient confidence using an available NDE technique. The FTS can then be used to develop a modified MAT diagram, onto which the excursion limits can be superimposed. An assumption in the assessment is that the tower has been correctly fabricated to code standards at the time of construction. It is also a required that the vessel material specifications and inspection history are known and documented. These are essential to enable reasonable assumptions to be made about the material toughness properties, stress levels, and likelihood of fabrication or service induced flaws.


Not for Resale


Figure 3.1E Schematic Of Demethanizer Temperature ( oC)

-100 Feed 1

-50

0

Tray 62

Material: 3-1/2 % Ni

Feed 2

Normal Operation

Potential Excursion

Tray 33

Feed 3

Potential Violation

Tray 32

Material: Carbon Steel

29 mm (1.14 in.) Tray 24

Original MAT (based solely on Impact Tests)

Tray 1

Position

2300 mm

Detail A Typical Design

Detail B Temperature Profile Along The Length Of The Tower Material: ASTM A516 Grade 70 (KCS) Minimum YS @ 70oF: 447 MPa (64,784 psi) Pressure: 3.72 MPa-g (540 psig) Toughness: 33/32J @ -46oC (24.3/23.6 ft-lb @ -50oF) PWHT: Yes Weld Joint Efficiency: 1.0

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Assessment Approach The fracture analysis part of the assessment is based on the methodology presented in Section 9. In order to perform this analysis a flaw size must be assumed, and the applied stress and material toughness must be known. The fracture assessment is limited to the lower carbon steel section of the tower since this is the only section to experience an MAT violation (see Figure 3.1E).

A conservative yet representative hypothetical surface breaking elliptical crack with an aspect ratio of 6:1 (2c:a) is assumed to located on the inside surface of the vessel. The crack is also assumed to be parallel to a longitudinal weld seam. Other representative flaws elsewhere in the vessel could also be considered. However, as will be seen latter, the relative nature of the results as expressed by the FTS are not significantly affected by such variations, though the minimum excursion temperature will be. Applied Stress In order to utilize the assessment procedures of Section 9, the applied stress at the location of the flaw must be computed and categorized. Based on the operation sequence of the tower, four load sources are used describe the applied stress; the hoop stress from internal pressure, the residual stress in welds, local stress effects from nozzles and attachments, and thermal transient stresses during the upset. In addition, consideration should be given to occasional loads such as wind or earthquake loads. These loads are ignored in this example. Hoop Stress From Internal Pressure – The pressure stress is calculated using the code design equations. This stress is categorized as a primary membrane stress (see Appendix A). Residual Stress In Welds – The residual stress can be estimated based on whether post weld heat treatment (PWHT) has been performed (see Appendix E). Because the tower was subject to PWHT at the time of construction, the residual stress is taken as 15% of the weld metal room temperature yield strength. This stress is classified as a secondary bending stress. Local Stress Effects From Nozzles And Attachments – In this screening study, a detailed analysis of the local stresses at the nozzles and attachments were not performed. To account for a level of stress concentration at these locations a stress concentration factor is used. In this example a stress concentration factor 1.3 will be applied to all primary membrane and bending stresses. Transient Thermal Stresses – These stresses may be evaluated by using closed form solutions or a finite element analysis. In this example, a temperature excursion model consisting of a "cold front" of liquid is assumed to move down the tower. The liquid temperature in the cold front is defined by the process upset condition. The vessel wall is subsequently cooled from its pre-excursion steady-state temperature to the cold liquid temperature. Connective heat transfer from the cold fluid to the vessel shell is assumed to be instant, and heat loss to the atmosphere is neglected. The stress versus time history at a point on the vessel wall computed using a finite element analysis is shown in Figure 3.2E.


Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Assumed Flaw Size


Figure 3.2E Transient Thermal Stress Computed From A Finite Element Stress Analysis

45 40

35 Stress, MPa

30 25

20 15

10 5 0

0

20

40

60

100 120 140

80

160 180 200

Time, seconds The results from the finite element analysis confirm that the magnitude of the maximum transient stress can be readily evaluated from the following equation:

s=

Ea DT

F15. + 3.25 - 0.5expFG -16IJ I b1 - n g GH b H b K JK

>=

hL k

with,

E h k L ,T

= = = = =

= n I

= = =

Modulus of Elasticity, MPa, 2 o film coefficient, W/m - C, o thermal conductivity of the shell material, W/m- C, shell wall thickness, m. Temperature difference; the difference between the steady state wall temperature before the excursion and the temperature of the fluid causing the o excursion, C, o Thermal expansion coefficient, 1/ C, Poisson’s ratio, and Thermal stress, MPa.

Based on the results of the finite element analysis, the maximum stress is a through thickness bending stress with tension on the inside surface. The resultant transient stress is considered to be a primary stress and for further conservatism in this example, it is categorized into equal membrane and bending components. In this example, a thermal stress of 20 MPa (2900 psi) is computed based on a liquid temperature of -72°C (-98°F) and a shell temperature of -35°C (-31°F).

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

where,


A summary of the applied stresses is shown in Table 3.1E. Table 3.1E Summary Of Applied Stresses Magnitude And Classification Of Applied Stresses Source Of Stress

Magnitude Of Stress

Classification Of Stress

Hoop Stress From Internal Pressure

153 MPa (22,190 psi)

Pm = 153 MPa

Residual Stress In Welds

67 MPa (9720 psi)

Qm = 67 MPa

Local Stress Effects From Nozzles And Attachments

A stress concentration factor of 1.3 is used in the analysis.

A stress concentration factor of 1.3 is used in the analysis.

Transient Thermal Stresses

20 MPa (2900 psi)

Pm =

20 MPa = 10 MPa 2

Pb =

20 MPa = 10 MPa 2

Applied Stress Results For Use In Fracture Assessment Stress Category //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Primary Membrane Stress Primary Bending Stress Secondary Membrane Stress

Final Stress Result

b gb g P = b10 MPa gb1.3g = 13 MPa (1885 psi )

Pm = 153 MPa + 10 MPa 1.3 = 212 MPa (30,730 psi ) b

Qm = 67 MPa

Material Fracture Toughness Actual fracture toughness data is not normally available for process equipment; therefore, it is necessary to adopt a lower bound approach to describe the variation of toughness with temperature. The most widely used lower bound is the KIR curve from Figure F.3 in Appendix F. This curve is shown in Figure 3.3E. To use this curve it is necessary to estimate a reference temperature to position the temperature axis on an absolute scale. The reference temperature is typically taken as the Nil Ductility Temperature (NDT). In this example, the temperature at which a 40 Joules (30 ftlbs) Charpy V energy is obtained from a longitudinal specimen is selected as the NDT. It should be noted that Appendix F recommends the less conservative value of 20 J (15 ft-lbs). The use of this value would shift the FTS curve shown in Figure 3.4E upward. When an impact temperature corresponding to 40 J (30 ft-lbs) is not available, actual values are extrapolated to give an effective 40 J test temperature using the relationship: 1.5 J/°C (0.6 ft-lbs./°F). For this assessment the lowest average Charpy value was used for determining the NDT as opposed to the lowest minimum. The use of actual values is illustrated in Figure 3.3E.

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 3.3E Toughness Evaluation Using The KIR Curve

Temperature Difference (oC) -89

-67

-22

-44

200

Shabbiis (WCAP - 1623)

180

Ripling and Crosley HSST, 5th Annaula Information Meeting, 1971, Paper No. 9

160

0

22

44

67

89

111

0

40

80

120

160

200

Unpublished Data

140

MRL Arrest Data 1972 HSST Info MIG

120 100

80 60

40 20

-160

-120

-80

-40

Temperature Difference (oF) Notes: o o 1. Actual Charpy data: 38/32 Joules at -46 C (24.3/23.6 ft-lbs @ -50 F) o o o o 2. Equivalent temperature at 40 Joules from: -46 C + (40 C – 33 C)/1.5 = -41 C; therefore, o o NDT (0 F) in this figure, indexes to -41 C.

Material Properties Actual material properties obtained from equipment records should be used for yield strength and Charpy impact energy. Other properties can be determined using Appendix F. A correction can be adopted to increase the value of yield strength at low temperature. While this was used in the example its effect is primarily a higher plastic collapse limit, which is not a typical limiting factor for low temperature brittle fracture. Fracture Tolerance Signature (FTS) The applied stress, material properties, and fracture toughness parameter defined above are to create a plot of limiting law size versus temperature as illustrated in Figure 3.4E. The critical flaw depth is in the through thickness dimension and is expressed as a percentage of the wall thickness with a 6:1 aspect ratio maintained. The absolute factor of safety in the critical flaw size is undetermined, but is a function of the assumptions made with respect to lower bound toughness, stress, stress multiplier, and the NDT indexing temperature.


Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

KIR (ksi {nches} 0.5)

220


Figure 3.4E Fracture Tolerance Signature

100

80 For A Design Pressure of 37.2 Bar-g & Temperature Excursion of -36 oC to -72 oC

60

--``````-`-`,,`,,`,`,,`---

Crack Depth Percent

70

A

50 Crack Depth = 16% of the wall thickness

40

B

30 D

20

C

E 10 0 -140

-120

-100

-80

-60

-40

-20

0

20

Temperature (oC)

The influence of the transient operation on the limiting flaw size is shown in Figure 3.4E. Line segment A-B represents steady operation and defines the limiting flaw for gradual cool down to -36°C (-33°F) where the limiting flaw is 25% of the wall thickness. The exposure to cold liquid at -72°C (-98°F), begins at B and results in an almost instantaneous drop in limiting flaw size to 21% of the wall thickness at C. This occurs as a result of the applied thermal stress. The initial affect of the thermal transient decreases as the shell cools which results in a decrease of the temperature difference between the shell and the cold liquid. During this period the material toughness is reduced, but the thermal stress is also reduced, with the net result that the limiting flaw size is reduced to 17% of the wall thickness at Point D. At this point the metal temperature reaches equilibrium with the cold liquid, and from point D to E a return to steady state cool-down continues. The limiting flaw size is 12% of the wall thickness at Point E where the minimum temperature reached. The shape of the FTS curve in Figure 3.4E follows that of the KIR curve, and is modified only by the transient thermal effect. More or less conservative assumptions on stress and flaw size will lower or raise the curve vertically, respectively. Assuming a lower NDT will move the curve horizontally to the left. For example, using the less conservation KIC curve in place of the KIR curve in evaluating the toughness would shift the curve in Figure 3.4E upward resulting in a higher permitted crack depth. For this reason the curve provides useful insight into brittle fracture resistance during an excursion.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

90


The flatness of the curve between points C and E makes limiting temperature predictions highly sensitive to the minimum flaw size. This in turn is greatly influenced by type and extent of inspection and factors such as probability of detection (POD) of flaws. While work still needs to be done to clarify POD issues, application of detailed NDE to a vessel should enable a minimum flaw size to be assumed with sufficient confidence to enable the FTS to be used to specify a minimum excursion temperature. Based on the POD curve shown in Figure 3.5E, a flaw depth of 4.5 mm (0.177 in) should be detectable using a magnetic particle examination technique (MT) with a confidence level greater than 90%. For the 6:1 aspect ratio assumed in developing the FTS this equates a crack of length 27 mm (1.063 in). Figure 3.5E Comparison Of Inspection Methods - Probability Of Detection Curves 1

POD - Probability Of Detection

0.8

+

+ +

+

+

+

UT - Nordtest

0.6

+

+

0.4

Inspection Method UT20

+

UT - Nordtest

AE + UT

MPI

0.2

0 0

2

4

6

8

10

12

Flaw Depth, mm

Summary Of Results

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The evaluation of a potential thermal excursion for the demethanizer tower illustrated in Figure 3.1E is summarized in Figure 3.6E. The stresses and other factors assumed in conducting the evaluation are shown in Table 3.1E. An important aspect of the required data is a realistic estimate of the critical exposure temperature (CET). This is the actual metal temperature, or more likely the metal temperature predicted by process simulation programs during an excursion. The excursion temperature in the example illustrates that an MAT violation will not occur in the 3.5% Ni section above tray 33. Hence the evaluation need only consider the lower carbon steel section. The excursion temperature plotted in Figure 3.6E defines two cases to be considered. ·

Case 1 – The lowest temperature in the carbon steel section is at tray 32 with a pre-excursion temperature of -35°C (-31°F) and an excursion delta of -37°C (-67°F) to -72°C (-98°F).

·

Case 2 – The largest delta of -49°C (-88°F) occurs from a steady state temperature of -12°C (+10°F) at tray 24 to give an excursion temperature of -61°C (-78°F).

--``````-`-`,,`,,`,`,,`---


Not for Resale

14


Figure 3.6E Demethanizer MAT Versus Location 20 --``````-`-`,,`,,`,`,,`---

Normal operation

10

0

Excursion Temperature

-10

-20

Temperature ( oC)

-30

Coldest KCS Temperature = -72oC (-98oF)

Largest Excursion Temperature = -49 oC (-88oF)

-40

MAT

-50

-60

Excursion Limit

-70

-66oC (-87oF)

-80

-80oC (-112oF) -90

-100

-101oC (-150oF) -110

62

57

52

43

40

33

32

29

28

25

24

18

6

1

Tray Number

To illustrate the influence of inspection on the results, it is assumed that the tower has been 100% visually inspected internally. In addition, it is assumed that all internal weld seams are inspected by wet fluorescent magnetic particle methods, and angle probe ultrasonics, from the bimetallic weld to a circumferential weld between trays 24 and 25. It is further assumed that any flaw indications would be removed by light grinding. As part of such an assessment it would also be reasonable to conduct a hydrostatic test at 150% of design pressure. These assumptions allow the carbon steel section to be evaluated by two approaches: ·

The visually inspected region can be assessed using basic MAT principles in accordance with the "code compliant approach", or

·

The MT/UT inspected region can be assessed using the more sophisticated FTS approach.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The MAT approach for two constant flaw sizes is shown in Figure 3.7E. One is 22% of the wall thickness, and was selected to pass through original design conditions. For clarity, the effect of the transient stress is ignored in Figure 3.7E. The 22% curve illustrates that the excursion temperature at tray 24 of -61°C (-78°F) is within the acceptable MAT zone and, provided that additional transient stresses can be accommodated within the excursion margin, the MAT can be set at -66°C (-87°F) based on operating rather than design pressure. This check is made by evaluating the critical flaw size during the excursion, using an FTS for tray 24, and ensuring it is always above 22%. The check is made using tray 24 temperature and excursion conditions, with operating pressure applied rather than design. The check confirms that in this case -66°C (-87°F) is an acceptable excursion limit below tray 24.


Not for Resale

3-44 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________ Figure 3.7E Pressure Temperature Relationship for Constant Defect Size - Killed Carbon Steel Section 45

Potential Margin For Region Inspected Using MT

40

MAT as Defined by the Impact Test Temperature

Required Excursion Limit - Tray 32 = -72 oC (-98oF)

35

Pressure (bar-g)

32

30

Normal Operation

16% Defect (4.5mm, 0.177 in.)

Required Excursion Limit - Tray 24 = -61oC (-78oF)

25

22% Defect (6.2mm, 0.244 in.) Excursion Margin Tray 5 & Below = 5oC (9oF)

20

15 -140

-120

-100

-80

-60

-40

-36

-20

Temperature (oC)

The second feature apparent from the 22% curve is that a violation still exists at tray 32. Tray 32 is however, located in the section of the tower that was subject to MT/UT inspection. Thus it can be assessed on the basis of a smaller flaw size. The 16% of the wall thickness curve in Figure 3.7E represents this criterion as proposed earlier. It is clear that the -72°C (-98°F) excursion is accommodated, even at design pressure.

To be of value to operating personnel, and to compare it with the excursion temperature, it is useful to express the result in the form of an excursion limit for the tower, as shown in Figure 3.6E. This allows a direct comparison of normal operation, excursion temperature, MAT and excursion limits. The distinction between the MAT and the excursion limits is to differentiate between the "code compliant" and non code compliant aspects of the assessment. The purpose of the analysis is to establish reasonable excursion limits and to quantify the risk associated with excursions below the MAT. It is not meant to encourage normal operation at temperatures lower than the MAT. Recommendations and Conclusions For this particular type of Level 3 assessment only, the equipment to be evaluated should satisfy the following criteria: ·

Meets the design and fabrication requirements of a recognized code of construction,

·

Demonstrates, by measured values, minimum toughness of weld, HAZ and plate materials, and

·

An appropriate NDE technique is used to preclude the existence of flaws with sufficient confidence based on a risk assessment.

When a Level 3 assessment is made, its acceptability should be subjected to suitable criteria such as the following:

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The FTS curve in Figure 3.4E, indicates that a 4.5 mm (0.177 in.) limiting flaw is critical below -80°C (-112°F) when analyzed at full design pressure. In practice the contingency is unlikely to violate design conditions, hence there is an inherent conservatism over the more realistic operating case. An FTS for the operating case results in -111°C (-168°F) as the limiting temperature.


1.

Where no additional detailed inspection for a surface breaking flaw is performed by an appropriate NDE technique, the excursion limits should be no lower than the MAT as developed by a using the assessment procedures in this section.

2.

Where MT or equivalent is carried out around nozzles and attachments, the MAT may be based on a ¼-t or 6 mm (0.25 in) deep flaw, whichever is the smaller, with a 6:1 aspect ratio.

3.

Where an appropriate NDE technique is used to preclude the existence of flaws with sufficient confidence, the excursion limit can be based on a Fracture Tolerance Signature FTS approach.

4.

The assessment is only valid if the service conditions in the vessel are essentially unchanged or less severe than those experienced in the past.

5.

Poor operation in terms of control techniques leading to frequent cycling or process upsets should be discouraged by limiting the number of excursions allowed during the life of the vessel.

6.

Hydrostatic testing at a temperature at a level where the material toughness is above the lower shelf is recommended.

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

This is an example of a Level 3 Assessment. It is not intended to be a "prototype" for all Level 3 assessments, since there are many different approaches which can be used successfully at this level.


Not for Resale

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

SECTION 4 – Assessment Of General Metal Loss (Jan, 2000)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

4.1

General

4.1.1

Fitness-For-Service (FFS) assessment procedures for pressurized components subject to general metal loss resulting from corrosion and/or erosion are provided in this section. The procedures can be used to qualify a component for continued operation or for rerating. A flow chart for the assessment procedure for general metal loss is shown in Figure 4.1.

4.1.2

The assessment procedures in this section are based on a thickness averaging approach which provides a suitable result when applied to uniform metal loss. If local areas of metal loss are found on the component, the thickness averaging approach may produce conservative results. For these cases, the assessment procedures of Section 5, which require the use of detailed thickness profiles, can be utilized to reduce the conservatism in the analysis. The exact distinction between uniform and local metal loss cannot be made without knowing the characteristics of the metal loss profile. Therefore, the rules in this section have been structured to provide consistent results with Section 5. In addition, guidelines based on the characteristics of the thickness profile have been incorporated into the rules to direct the user to Section 5 when appropriate. Thus, for most evaluations, it is recommended to first perform an assessment using Section 4.

4.2

Applicability and Limitations of the Procedure

4.2.1

The assessment procedures in this section can be used to evaluate all forms of general metal loss (uniform or local) which exceeds or is predicted to exceed the corrosion allowance before the next scheduled inspection. The general metal loss may occur on the inside or outside of the component. Assessment procedures based on thickness profiles and point thickness readings are provided. The assessment procedure to be used in an evaluation is dependent on the type of thickness data available (point thickness readings or detailed thickness profiles, see paragraph 4.3.3), the characteristics of the metal loss (i.e. uniform or local), the minimum required wall thickness, and the degree of conservatism acceptable for the assessment. The methodology shown in Figure 4.2 can be used to determine the assessment procedure to be used in the evaluation.

4.2.2

Calculation methods are provided to rerate the component if the acceptance criteria in this section are not satisfied. For pressurized components (pressure vessels and piping), the calculation methods can be used to find a reduced maximum allowable working pressure (MAWP) and/or coincident temperature. For tank components (shell courses), the calculation methods can be used to determine a reduced maximum fill height (MFH).

4.2.3

Specific details pertaining to the applicability and limitations of each of the assessment procedures are discussed below.

4.2.3.1

The Level 1 or 2 assessment procedures in this section apply only if all of the following conditions are satisfied: a.

The original design criteria were in accordance with a recognized code or standard (see Section 1, paragraphs 1.2.2 or 1.2.3).

b.

The component is not operating in the creep range; the design temperature is less or equal to the value in Table 4.1. The Materials Engineer should be consulted regarding the creep range temperature limit for material not listed in this table.

c.

The region of metal loss has relatively smooth contours without notches (i.e. negligible local stress concentrations). --``````-`-`,,`,,`,`,,`---


4-1 Not for Resale


d.

The component is not in cyclic service. If the component is subject to less than 150 cycles (i.e. pressure and/or temperature variations including operational changes and start-up and shutdowns) through-out its previous and future planned operating history, or satisfies the cyclic service screening procedure in Appendix B, paragraph B.5.4, then the component is not in cyclic service.

e.

The component under evaluation does not contain crack-like flaws. If crack-like flaws are present, the assessment procedures in Section 9 shall be utilized.

f.

The component under evaluation has a design equation which specifically relates pressure (or liquid fill height for tanks) and/or other loads, as applicable, to a required wall thickness. Examples include:

g.

h.

i. 4.2.3.2

·

Pressure vessel cylindrical and conical shell sections

·

Spherical pressure vessels and storage tanks

·

Spherical, elliptical and torispherical formed heads

·

Straight sections of piping systems

·

Elbows or pipe bends which do not have structural attachments

·

Cylindrical atmospheric storage tank shell courses, except at the location of the bottom course-to-bottom plate shell junction

The Level 2 Assessment procedure for components which do not have a design equation which specifically relates pressure (or liquid fill height for tanks) and/or other loads, as applicable, to a required wall thickness is limited to the following components: ·

Pressure vessel nozzles, tank nozzles and piping branch connections

·

The reinforcement zone of conical transitions

·

Cylinder to flat head junctions

·

Integral tubesheet connections

·

Flanges

·

Piping systems

The following limitations on applied loads are satisfied: ·

Level 1 Assessment – Components listed in paragraph 4.2.3.1.f subject to internal and/or external pressure (i.e. supplemental loads are assumed to be negligible).

·

Level 2 Assessment – Components listed in paragraph 4.2.3.1.f , and paragraph 4.2.3.1.g subject to internal and/or external pressure and/or supplemental loads (see Appendix A, paragraph A.2.6).

A flaw categorized as a groove in accordance with Section 5, paragraph 5.2.1.1 has a groove radius which satisfies the requirements Section 5, paragraphs 5.4.2.2.e.1 and 5.4.2.2.e.2.

A Level 3 Assessment can be performed when the Level 1 and 2 Assessment procedures do not apply, or when these assessment levels produce conservative results (i.e. would not permit operation at the current design conditions). Examples include, but are not limited to the following. a.

b.

Geometries associated with major structural discontinuities not covered in a Level 1 or Level 2 Assessment such as: ·

Major structural discontinuities on shells such as shell-to-formed head junctions, stiffening rings, structural attachments, and support locations.

·

The bottom shell course of a tank close to the bottom course-to-plate junction with or without significant foundation settlement (see API 653).

Components subject to supplemental loads not covered in the Level 1 or Level 2 assessment procedures.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

c.

Components with a design based on proof testing (e.g. piping tee or reducer produced in accordance with ASME B16.9 where the design may be based on proof testing).

d.

Components operating in the creep range; the assessment should consider the effects of creep damage on the fitness-for-service calculations used to qualify the component for continued operation (see Section 10).

e.

Components in cyclic service or components where a fatigue analysis was performed as part of the original design calculations; the assessment should consider the effects of fatigue on the fitness-for-service calculations used to qualify the component for continued operation.

4.3

Data Requirements

4.3.1

Original Equipment Design Data An overview of the original equipment data required for an assessment is provided in Section 2, paragraph 2.3.1.

4.3.2

Maintenance and Operational History An overview of the maintenance and operational history required for an assessment is provided in Section 2, paragraph 2.3.2.

4.3.3

Required Data/Measurements For A FFS Assessment

4.3.3.1

Thickness readings are required on the component where the metal loss has occurred to evaluate general metal loss. An overview of the Level 1 and Level 2 assessment options are shown in Figure 4.2, and are described in paragraph 4.4.

4.3.3.2

a.

Two options for obtaining thickness data are presented: (1) individual point thickness readings and (2) thickness profiles. Point thickness readings can be used to characterize the metal loss on a component as general if there are no significant differences among the values obtained at inspection monitoring locations. If there is a significant variation in the thickness readings, the metal loss may be localized, and thickness profiles (thickness readings on a prescribed grid) should be used to characterize the remaining thickness and size of the region of metal loss.

b.

The thickness quantities used in this section for the assessment of general metal loss are the average measured thickness and the minimum measured thickness. If the thickness readings indicate that the metal loss is general, the procedures in this section will provide an adequate assessment. However, if the metal loss is localized and thickness profiles are obtained, the assessment procedures of this section may produce conservative results, and the option for performing the evaluation using the assessment procedures of Section 5 is provided.

If point thickness readings are used in the assessment, the assumption of general metal loss should be confirmed. a.

Additional inspection may be required such as visual examination, radiography or other NDE methods.

b.

A minimum of 15 thickness readings is recommended unless the level of NDE utilized can be used to confirm that the metal loss is general. In some cases, additional readings may be required based on the size of the component, the construction details utilized, and the nature of the environment resulting in the metal loss. A sample data sheet to record thickness readings is shown in Table 4.2.

--``````-`-`,,`,,`,`,,`---


Not for Resale


c.

4.3.3.3

If the Coefficient Of Variation (COV) of the thickness readings minus the Future Corrosion Allowance (FCA) is greater than 10%, then the use of thickness profiles should be considered for use in the assessment (see paragraph 4.3.3.3). The COV is defined as the standard deviation divided by the average. A template that can be used to compute the COV is provided in Table 4.3.

If thickness profiles are used in the assessment, the following procedure can be used to determine the required inspection locations and the Critical Thickness Profiles (CTP’s).

--``````-`-`,,`,,`,`,,`---

a.

Step 1 – Locate the region of metal loss on the component and determine the location, orientation, and length of the inspection plane(s). 1.

2.

Step 1.1 – To determine the inspection plane(s) for thickness readings the following should be considered: a)

Pressure Vessel Heads and Spheres – Both the circumferential and meridional directions should be set as inspection plane(s) (see Figure 4.3).

b)

Cylindrical Shells, Conical Shells and Elbows – The critical inspection plane(s) are meridional (longitudinal) if the circumferential stress due to pressure governs, and circumferential if the longitudinal stress due to pressure and supplemental loads governs (see Figure 4.4).

c)

Atmospheric Storage Tanks – The critical inspection plane(s) are in the meridional (longitudinal) direction (see Figure 4.5).

d)

Low Pressure Storage Tanks – The critical inspection plane(s) are assigned based on the component geometry (see subparagraph a and b. above).

e)

If the critical inspection plane(s) for a component are not known at the time of the inspection, a minimum of two planes at right angles to each other should be utilized to record thickness readings.

Step 1.2 – Mark each inspection plane on the component; the length of the inspection plane for the corroded/eroded region should be sufficient to characterize the metal loss.

t min (see Appendix A, paragraph A.2) for

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b.

Step 2 – Determine the minimum required thickness, the component containing the metal loss.

c.

Step 3 – Measure and record the wall thickness readings at intervals along each inspection plane and determine the minimum measured wall thickness, t mm . The spacing distance for thickness readings should be set such that an accurate characterization of the thickness profile can be determined. 1.

If the corroded surface is not accessible for visual inspection, then the recommended spacing distance for thickness readings along each inspection plane is given by the following equation; however, a minimum of five thickness readings is recommended for each inspection plane(s).

Ls = min 0.36 Dt min , 2t nom

(4.1)

where,

Ls D tnom


=

Recommended thickness profile spacing (mm:in),

= =

Inside diameter of the shell (mm:in), Nominal or furnished thickness of the component (mm:in), and

Not for Resale


d.

=

Minimum required thickness (mm:in).

2.

The above recommended spacing for thickness readings can be modified based on the actual size and extent of the region of metal loss. If visual inspection or NDE methods are utilized to quantify the metal loss, an alternative spacing can be used as long as the metal loss on the component can be adequately characterized. For example, if the region of metal loss is determined to be uniform based on a visual inspection, the spacing utilized to take thickness readings can be increased without a reduction in accuracy in the FFS assessment.

3.

A sample data sheet to record thickness readings is shown in Table 4.2. If more than four inspection planes are utilized, additional copies of this sheet can be used to record the thickness profile data.

Step 4 – Determine the Critical Thickness Profile (CTP) in the meridional and circumferential directions. The CTP in each direction is determined by projecting the minimum remaining thickness for each position along all parallel inspection planes onto a common plane as shown in Figure 4.6. The length of the profile is established by determining the end point locations where the remaining wall thickness is greater than t min in the meridional and circumferential directions. Note that the remaining wall thickness within the bounds of the CTP may exceed t min .

4.3.3.4

1.

The CTP in the meridional or longitudinal direction is obtained by projecting the minimum thickness at each interval along M1-M5 inspection planes onto a common plane. The length of the metal loss in the longitudinal direction, denoted as s , is determined using the CTP and t min as shown in Figure 4.6.

2.

The CTP in the circumferential direction is obtained by projecting the minimum thickness at each interval along C1-C5 inspection planes onto a common plane. The length of the metal loss in the circumferential direction, denoted as c , is determined using the CTP and t min as shown in Figure 4.6.

3.

If there are multiple flaws in close proximity to one another, then the size of the flaw to be used in the assessment is established considering the effects of neighboring flaws using the methodology shown in Figure 4.7. The final CTP for the flaw, or network of flaws, can be established as shown in Figure 4.8. The thickness profile for both the longitudinal and circumferential planes should be evaluated in this manner.

4.

For large regions of metal loss, it may be overly conservative to project the minimum thicknesses on to a single plane to determine a CTP. For these cases, more than one CTP in the longitudinal or circumferential directions may be utilized in the assessment. The number of CTP’s to be used in an assessment to achieve an optimum result is dependent on the uniformity of the metal loss. A sensitivity analysis (see Section 2, paragraph 2.4.3.1) can be performed to evaluate the benefits of using multiple CTP’s in the assessment of the longitudinal and circumferential directions.

If the region of metal loss is close to or at a major structural discontinuity, the remaining thickness can be established using the procedure in paragraph 4.3.3.2 or 4.3.3.3. However, additional thickness readings should be taken to include sufficient data points in the region close to the major structural discontinuity. This involves taking adequate thickness readings within the zones defined as follows for the components listed below: ·

Nozzle or branch connection (see Figure 4.9 for the thickness zone, Lv , Lno and Lni )

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Not for Resale

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t min


Lv )

·

Conical shell transition (see Figure 4.10 for the thickness zone,

·

Axisymmetric discontinuities (see Figure 4.11 for the thickness zone,

·

Flange connections (see Figure 4.12 for the thickness zone, Lvh and Lvt )

4.3.3.5

Additional thickness readings are required if discrepancies are noted in the reported thickness measurements. For example, if the latest thickness reading is greater than the reading at the time of the last inspection, additional readings may be required to resolve the discrepancies in the data.

4.3.4

Recommendations For Inspection Technique and Sizing Requirements

4.3.4.1

Thickness readings which are required to determine the metal loss on a component are usually made using straight beam ultrasonic thickness examination (UT). This method can provide high accuracy and can be used for point thickness readings and in obtaining thickness profiles (continuous line scans or area scans can also be used to obtain thickness profiles). The limitations of UT are associated with uneven surfaces and access. Examples include measuring the thickness at a weld and/or the thickness of a shell underneath a reinforcing pad from the outside of a vessel, respectively.

4.3.4.2

Obtaining accurate thickness readings using UT is highly dependent on the surface condition of the component. Surface preparation techniques vary depending on the surface condition, but in many cases wire brushing is sufficient. However, if the surface has a scale build-up or is pitted, grinding may be necessary. Temperature compensation and special UT couplants are required if the thickness readings are obtained on high temperature components.

4.3.4.3

All UT thickness readings should be made after proper calibration for the wall thickness and temperature ranges of the component. It may be preferable to obtain readings with probes less than 12.7 mm (1/2 inches) in diameter to provide greater assurance that pitting/localized corrosion is not present.

4.3.4.4

Radiographic examination (RT) may also be used to determine metal loss; however, accurate thickness data may only be obtained by moving the component containing the metal loss, or moving the source around the component to obtain multiple views. This type of manipulation is typically not possible for many pressure containing components. However, RT examination can be effectively used to qualify the existence, extent and depth of a region of metal loss, and has been used in conjunction with UT to determine whether the metal loss on a component is general or local.

4.4

Assessment Techniques and Acceptance Criteria

4.4.1

Overview

4.4.1.1

If the metal loss is less than the specified corrosion/erosion allowance and adequate thickness is available for the future corrosion allowance, no further action is required other than to record the data; otherwise, an assessment is required.

4.4.1.2

An overview of the assessment levels is provided in Figure 4.1. Level 1 assessments are limited to components which have a design equation which specifically relates pressure (or liquid fill height for tanks) and/or other loadings, as applicable, to a required wall thickness. Level 2 Assessments can be used to evaluate components which do not satisfy Level 1 criteria, and can also be used to evaluate components which do not have a design equation which specifically relates pressure to a required wall thickness. For example, the design rules for nozzle reinforcement in the ASME Code, Section VIII, Division 1 are provided in terms of reinforcement areas which result in a thickness interdependency between the required thickness of the shell and nozzle. Level 3 assessments can be used to evaluate components which are not covered or do not pass a Level 1 or Level 2 assessment. Detailed stress analysis techniques are normally utilized in a Level 3 assessment (see Appendix B).


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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Lv )


4.4.1.3

If the thickness readings indicate that the metal loss is localized and thickness profiles are obtained, the assessment procedures of this section can still be used for the assessment. However, the results may be conservative, and the option for performing the analysis using the assessment procedures of Section 5 is provided.

4.4.1.4

FFS assessments for the components listed below require special consideration because of the

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a.

Pressure Vessels Designed To The ASME Code, Section VIII, Division 2 – A user design specification is required which stipulates the operational parameters for the vessel was originally established for the design. In addition, detailed heat transfer and stress calculations, and a fatigue analysis may have been performed to satisfy the design-by-analysis rules required in this code.

b.

Low Pressure Storage Tanks Designed To API 620 – The design rules for low-pressure storage tanks contained within API 620 require an intimate knowledge of engineering mechanics in that the required thickness of a shell component is based upon the evaluation of free body diagrams, the development of equilibrium equations, and the consideration of a biaxial stress field to determine an allowable design stress.

c.

Piping Designed To ASME B31.3 – Metal loss in piping systems can be evaluated using a Level 1 Assessment by the Inspector if the supplemental loads on the piping system are negligible (see Appendix A, paragraph A.2.6). If these loads are not negligible, a piping stress analysis is required. The piping analysis should take into account thickness interdependency due to the relationship between the component thickness, piping flexibility, and the resulting stress (see paragraph 4.4.3.3).

4.4.2

Level 1 Assessment

4.4.2.1

The following assessment procedure can be used to evaluate components described in paragraph 4.2.3.1.f subject to the loads defined in paragraph 4.2.3.1.h. If the flaw is found to be unacceptable, the procedure can be used to establish a new MAWP or MFH.

t min (see Appendix A, paragraph A.2).

a.

Step 1 – Determine the minimum required thickness,

b.

Step 2 – Locate regions of metal loss on the component and determine the type of thickness data that will be recorded; point thickness readings in accordance with paragraph 4.3.3.2 or thickness profile data in accordance with paragraph 4.3.3.3. Based on these data, determine the minimum measured thickness, t mm . If thickness profile data are used, then proceed to Step 3. If point thickness readings are used, determine the Coefficient Of Variation (COV) based on the thickness readings and Future Corrosion Allowance (see Table 4.3). If the COV is less than or equal to 10%, then proceed to Step 6 to complete the assessment using the average thickness, tam . If the COV is greater than 10%, then the use of thickness profiles should be considered for the assessment (see paragraph 4.3.3.3), or a Level 3 Assessment can be performed.

c.

Step 3 – Determine the length for thickness averaging,


Not for Resale

L.

--``````-`-`,,`,,`,`,,`---

complexities associated with the design requirements of the original construction code. In each case, an Engineer knowledgeable and experienced in the design requirements of the applicable code should perform the assessment (see Section 1, paragraph 1.4.3). If the metal loss is in a component which was not subject to special design requirements per the original construction code (i.e. design requirements based on stress analysis), then the Level 1 or Level 2 assessment procedures may be applied. If the corrosion/erosion damage is in a component subject to special design requirements, then the calculations required in the original design to qualify the component should be repeated considering a reduced wall thickness.


1.

Step 3.1 – Compute the remaining thickness ratio,

Rt =

FG t H

mm

- FCA t min

Rt .

IJ K

(4.2)

where,

2.

FCA

=

t min

=

t mm

=

Future corrosion allowance (see Appendix A, paragraph A.2.7) (mm:in), Minimum required thickness (see Appendix A, paragraph A.2.1) (mm:in), and Minimum measured thickness (mm:in).

Step 3.2 – Compute the length for thickness averaging,

L:

L = Q Dt min

(4.3)

where, tmin is defined above, and =

--``````-`-`,,`,,`,`,,`---

Q

=

Inside diameter of the cylinder, cone (at the location of the flaw), sphere, or formed head; for the center section of an elliptical head an equivalent inside diameter of Kc Dc is used where Dc is the inside diameter of the head straight flange and Kc is a factor defined in Appendix A, paragraph A.3.6; for the center section of a torispherical head two times the crown radius of the spherical section is used (mm:in), and Factor from Table 4.4 based on an allowable Remaining Strength Factor (see Section 2) and the remaining thickness ratio,

Rt .

d.

Step 4 – Establish the Critical Thickness Profiles (CTP’s) from the thickness profile data (see paragraph 4.3.3.3), and determine s and c , the dimensions which define the region of metal loss in the longitudinal and circumferential directions, respectively. The dimensions s and c are determined from their respective CTP and t min (see paragraph 4.3.3.3.c and Figure 4.6).

e.

Step 5 – Based on the parameters L and s from Steps 3 and 4, respectively, perform the FFS assessment of the region of metal loss using one of the following methods (see Figure 4.2): 1.

For

bs £ Lg – The meridional or longitudinal extent of metal loss is acceptable if the

limiting flaw size criteria in Section 5, paragraph 5.4.2.2.d are satisfied. For spherical shells, formed heads and atmospheric storage tanks the assessment is complete. For cylindrical shells, conical shells and elbows, the circumferential extent of the metal loss must be checked using Section 5, paragraph 5.4.2.2.g to complete the assessment. 2.

For a)

bs > Lg – One of the following assessment methods may be used: A simple approach is to set the average thickness equal to the measured minimum thickness, or ( t am = t mm ) and proceed to Step 6 (Level 1 or Level 2, as applicable). This approach facilitates the FFS assessment; however, the results may be conservative if the remaining thickness ratio is small.


Not for Resale

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D

Jan, 2000

RECOMMENDED

W

PRACTICE

4-9


Determine the average and minimum measured thickness for the meridional and circumferential CTP’s as described below, then proceed to Step 6 (Level 1 or Level 2, as applicable) to complete the assessment.

1)

Determine the minimum measured thickness, t,, , considering all points on the longitudinal and circumferential

2)

CTP’s.

Compute the average measured thickness from the CTP in the meridional (i.e. longitudinal direction for cylindrical or conical shells) and circumferential directions and designate these values as t& and &, respectively. The average thickness is computed by numerically averaging the thickness readings over length L . The center or midpoint of the length for thickness averaging, L , should be located at t,, .

3)

For cylindrical and conical shells and pipe bends, t,, = tL

in a Level 1

Assessment. In a Level 2 Assessment, tim and tzmare used directly in the assessment to account for supplemental loads. 4)

For spheres and formed heads, t,,

= min[tzm,

tzm] in a Level 1 or 2

f.

c)

The region of metal loss can be evaluated using a Level 3 Assessment.

4

The region of metal loss can be evaluated using the Section 5 Assessment procedures for local metal loss.

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Assessment.

Step 6 - The acceptability for continued operation can be established using the following criteria. 1.

The average measured wall thickness should satisfy the following thickness criteria. Alternatively, the MI Iivp or MFH

calculated based on the thickness

Appendix A) should be equal to or greater than the current MAW liquid level, respectively.

(tarn-

FCA) (see

or maximum design

t,,,,- FCA 2 t,, 2.

(4.4)

The minimum measured wall thickness, t,,,, , should satisfy the following thickness criterion. For pressure vessels and piping systems,

tmm- FCA 2 max[ OSt,, , 2.5 mm (0.10 inches) ]

(4.5)

and for atmospheric storage tanks,

t mm- FCA 2 max[ 0.6t,, , 2.5 mm (0.10 inches)] 4.4.2.2

(4.6)

If the component does not meet the Level 1 Assessment requirements, then the following, or combinations thereof, can be considered: a.

Rerate, repair, replace, or retire the component.


March 2000 Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

b.

Adjust the FCA by applying remediation techniques (see paragraph 4.6).

C.

Adjust the weld joint efficiency or quality factor, I? , by conducting additional examination and repeat the assessment (Note: To raise the value of E from 0.7 to .85, or from .85 to 1.O, would require that the weld seams be spot or 100% radiographed, respectively, and the examinations may reveal additional flaws that will have to be evaluated).

d.

Conduct a Level 2 or Level 3 Assessment.

4.4.3

Level 2 Assessment

4.4.3.1

The Level 2 assessment procedure can be used to evaluate components described in paragraphs 4.2.3.? .f and 4.2.3.1 .g subject to the loads defined in paragraph 4.2.3.1 .h. If the flaw is found to be unacceptable, the procedure can be used to establish a new MA WY’ or MFH.

4.4.3.2

The following assessment procedure can be used to evaluate components described in paragraph 4.2.3.1 .f subject to the loads defined in paragraph 4.2.3.1 .h. Step 1 - Calculate the thickness required for supplemental loads, t,, , and the minimum required thickness, t,,

(see Appendix A, paragraph A.2).

b.

Step 2 - Locate regions of metal loss on the component and determine the type of thickness data that will be recorded. Determine the minimum measured thickness, t,, . If thickness profile data are used, then proceed to Step 3. If point thickness readings are used, then complete the assessment following the methodology in paragraph 4.4.2.1 .b.

C.

Step 3 - Determine the length for thickness averaging,

d.

Step 4 - Establish the Critical Thickness Profiles (CTP’s) and determine s and c (see paragraph 4.4.2.1 .d).

e.

Step 5 - Perform the FFS assessment of the region of metal loss using one of the methods in paragraph 4.4.2.1 .e.

f.

Step 6 - The acceptability for continued operation can be established using the following criteria. 1.

L (see paragraph 4.4.2.1 .c).

Pressure Vessels and Piping Systems

4

The average measured wall thickness for the CZ”P(s) should satisfy the following thickness criteria. Alternatively, the MAW?’ calculated based on the thicknesses (tam -

FCA)/RSF,

FCA - tsl)/RSF, (see Appendix A) should be equal to or exceed the design MAFKP. The allowable remaining strength factor, RSF, , can be determined from Section 2.

1)

Cylindrical and Conical Shells:

2)

and (tarn -

t(sm- FCA 2 RSF, . t&

(4.7)

t; - FCA 2 RSF, -t,&

(4.8)

Spherical Shells and Formed Heads:

March2000


Not for Resale

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a.

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4-10


t am - FCA ³ RSFa × t min b)

2.

4.4.3.3

The minimum measured wall thickness, criterion in paragraph 4.4.2.1.f.2.

(4.9)

t mm , for the CTP(s) should satisfy the

Shell Courses of API 650 Storage Tanks – The requirements are the same as for Level 1 (see paragraph 4.4.2.1.f) because of the higher allowable stress permitted for inservice tankage as stipulated in API 653.

The following assessment procedure can be used to evaluate components described in paragraph 4.2.3.1.g subject to the loads defined in paragraph 4.2.3.1.h. a.

Design rules for components at a major structural discontinuity typically involve the satisfaction of a local reinforcement requirement (e.g. nozzle reinforcement area), or necessitates the computation of a stress level based upon a given load condition and geometry and thickness configuration (e.g. flange design). These rules typically result in one component with a thickness which is dependent upon that of another component (for examples, see paragraph 4.2.3.1.g). Design rules of this type have a thickness interdependency, and the definition of a minimum thickness for a component is ambiguous.

b.

To evaluate components with a thickness interdependency, the MAWP should be computed based upon the average measured thickness minus the future corrosion allowance

bt

am

g

- FCA and the thickness required for supplemental loads (see Appendix A, paragraph

A.2.6) for each component using the equations in the original construction. The calculated MAWP should be equal to or exceed the design MAWP. c.

The average thickness of the region, thickness interdependency:

tam , can be obtained as follows for components with a

1.

Nozzles and branch connections – Determine the average thickness within the nozzle reinforcement zone shown in Figure 4.9 (see paragraph 4.3.3.4). The assessment procedures in Appendix A, paragraphs A.3.11 and A.5.7 can be utilized to evaluate metal loss at a nozzle or piping branch connection, respectively. The weld load path analysis in this paragraph should also be checked, particularly if the metal loss has occurred in the weldments of the connection.

2.

Axisymmetric Structural Discontinuities – Determine L using the procedure in paragraph 4.4.2.1.c and Lv based on the type of structural discontinuity listed below. The average thickness is computed based on the smaller of these two distances. If

L < Lv , the

midpoint of L should be located at

t mm to establish a length for thickness averaging unless the location of t mm is within L 2 of the zone for thickness averaging. In this case, L should be positioned so that it is entirely within Lv before the average thickness is computed.

3.

·

Conical shell transition (see Figure 4.10 for the zone for thickness averaging and Lv ).

·

Axisymmetric discontinuities (see Figure 4.11 for the zone for thickness averaging and Lv ).

·

Flange connections (see Figure 4.12 for the zone for thickness averaging and

Piping Systems – Piping systems have a thickness interdependency because of the relationship between the component thickness, piping flexibility, and the resulting stress.

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Lv ).

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


For straight sections of piping, determine L using the procedure in paragraph 4.4.2.1.c and compute the average thickness to represent the section of pipe with metal loss in the piping analysis. For elbows or bends, the thickness readings should be averaged within the bend and a single thickness used in the piping analysis (i.e. to compute the flexibility factor, system stiffness and stress intensification factor). For branch connections, the thickness should be averaged within the reinforcement zones for the branch and header, and these thicknesses should be used in the piping model (to compute the stress intensification factor). An alternative assumption is to use the minimum measured thickness to represent the component thickness in the piping model. This approach may be warranted if the metal loss is localized; however, this may result in an overly conservative evaluation. In these cases, a Level 3 assessment may be required to reduce the conservatism in the assessment (see paragraph 4.4.4.4). d.

4.4.3.4

The minimum measured wall thickness, 4.4.2.1.f.2.

t mm , should satisfy the criterion in paragraph



b.

Adjust the

c.

Adjust the weld joint efficiency factor, E , by conducting additional examination and repeat the assessment (see paragraph 4.4.2.2.c).

d.

Conduct a Level 3 Assessment.

FCA by applying remediation techniques (see paragraph 4.6).

Level 3 Assessment

4.4.4.1

The stress analysis techniques discussed in Appendix B can be utilized to evaluate regions of general or local metal loss in pressure vessels, piping, and tanks. The finite element method is typically used to compute the stresses in a component; however, other numerical methods such as the boundary element or finite difference method may also be used. Handbook solutions may also be used if the solution matches the component geometry and loading condition. The evaluation may be based on a linear stress analysis with acceptability determined using stress categorization, or a nonlinear stress analysis with acceptability determined using a plastic collapse load. Nonlinear stress analysis techniques are recommended to provide the best estimate of the acceptable load carrying capacity of the component. Guidelines for performing and processing results from a finite element analysis for a fitness-for-service analysis are provided in Appendix B.

4.4.4.2

If a component is subject to external pressure and/or other loads which result in compressive stresses, a structural stability analysis should be performed using the methods in Appendix B to determine suitability for continued service. In addition, methods to evaluate fatigue are also included in Appendix B if a component is subject to cyclic loading.

4.4.4.3

Thickness data per paragraphs 4.3.3 as well as the component geometry, material properties and loading conditions are required for a Level 3 Assessment. The thickness data can be used directly in finite element model of the component. If thickness profile data are available, the thickness grid can be directly mapped into a three dimensional finite element model using two or three dimensional continuum elements, as applicable. This information can also be used if the component is modeled using shell elements.

4.4.4.4

If the region of local metal loss is close to or at a major structural discontinuity, details of the component geometry, material properties, and imposed supplemental loads (see Appendix A, paragraph A.2.6) at this location are required for the assessment. Special consideration is required if there are significant supplemental loads at a nozzle, piping branch connection, or pipe bend. The

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4.4.4

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:


Not for Resale


location and distribution of the metal loss in these components may significantly effect both the flexibility and stress distribution in a manner that cannot be evaluated using the approaches employed in the design. In addition, the localized metal loss may significantly reduce the plastic collapse load capability depending on the nozzle geometry, piping system configuration, and/or applied supplemental loads. 4.5


4.5.1

Thickness Approach

4.5.1.1

The remaining life of a component may be determined based upon computation of a minimum required thickness for the intended service conditions, thickness measurements from an inspection, and an estimate of the anticipated corrosion rate. This method is suitable for determination of the remaining life if the component does not have a thickness interdependency (see paragraph 4.4.3.3.a).

Rlife =

t am - Kt min Crate

(4.10)

where, =

Anticipated future corrosion rate (mm/year:in/year),

=

Factor depending on the assessment level; for a Level 1 assessment K for a Level 2 Assessment; K = RSFa for pressure vessels and piping

Rlife = RSFa = tam = t min

=

= 10 . ,

components and K = 10 . for shell courses of tanks, Remaining life (years), Allowable remaining strength factor (see Section 2),

Average wall thickness of the component determined at the time of the inspection (mm:in), and Minimum required wall thickness, t min , of the component (see Appendix A, paragraph A.2).

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4.5.1.2

The remaining life determined using the thickness based approach may produce non-conservative results when applied to components which have a thickness dependency (see paragraph 4.4.3.3.a). For these cases, the remaining life should be established using the MAWP Approach.

4.5.2

MAWP Approach

4.5.2.1

The MAWP approach provides a systematic way of determining the remaining life of any pressurized component. This method is also the only method suitable for determining the remaining life of components with a thickness dependency (see paragraph 4.4.3.3.a). In addition, the MAWP approach ensures that the design pressure is not exceeded during normal operation if the future corrosion rate is appropriately established.

4.5.2.2

The following procedure can be used to determine the remaining life of a component using the MAWP approach. a.

t loss , by subtracting the average measured thickness from the time of the last inspection, tam , from the nominal thickness, tnom Step 1 – Determine the metal loss of the component, (see paragraph 4.3.3.2 or 4.3.3.3, as applicable).


Not for Resale

--``````-`-`,,`,,`,`,,`---

Crate K


b.

Step 2 – Determine the MAWP for a series of increasing time increments using an effective corrosion allowance and the nominal thickness in the computation. The effective corrosion allowance is determined as follows:

CAe = t loss + Crate × time

(4.11)

where,

Crate CAe t loss tnom tam

=

Anticipated future corrosion rate (mm/year:in/year),

=

Effective corrosion allowance (mm:in),

=

Metal loss, defined as

=

Nominal or furnished wall thickness of the component (mm:in),

=

time

=

Average wall thickness of the component determined at the time of the inspection (mm:in), and Time in the future (years).

c.

Step 3 – Determine the remaining life from a plot of the MAWP versus time. The time at which the MAWP curve intersects the design MAWP for the component is the remaining life of the component.

d.

Step 4 – Repeat the Steps 1, 2 and 3 for each component. The equipment remaining life is taken as the smallest value of the remaining lives computed for each of the individual components.

4.5.2.3

This approach may also be applied to tanks using the maximum fill height, MFH, instead of the MAWP.

4.6

Remediation

4.6.1

An FFS assessment provides an evaluation of the condition of a component for continued operation for a period of time based upon a future corrosion or degradation rate. However, in many cases future degradation rates are very difficult to predict, or little or no further degradation can be tolerated. Therefore, mitigation methods may be applied to prevent or minimize the rate of further damage.

4.6.2

Remediation methods for general corrosion/erosion as well as local corrosion/erosion and pitting are provided below. These methods may also be suitable for mitigation of crack-like flaws in some process environments. The methods cited are not inclusive for all situations, nor are they intended to be a substitute for an engineering evaluation of a particular situation. The owner-user should consult a qualified metallurgist/corrosion engineer and mechanical engineer as to the most appropriate method to apply for the relevant damage mechanism(s).

4.6.3

Remediation Method 1 – Performing Physical Changes to the Process Stream: a.

Increasing or decreasing the process temperature and/or pressure – If the degradation mode is temperature and/or pressure sensitive, a process change may minimize the progression of the damage. However, the component must be evaluated so that the design still meets the changed conditions. Note that a reduction in the pressure and/or temperature (for limited temperature ranges depending on the original construction code) may result in a reduction of the minimum required wall thickness; therefore, the service life of the component can frequently be increased.

b.

Increasing or decreasing the velocity of the stream – Some damage mechanisms, such as erosion, sour water corrosion, under-deposit corrosion , and naphthenic acid corrosion are very velocity sensitive. A slight decrease or increase in stream velocity can change the rate of damage.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

(t nom - t am ) , (mm:in),


c.

Installing scrubbers, treaters, coalescers and filters to remove certain fractions and/or contaminants in a stream.

Remediation Method 2 – Application of solid barrier linings or coatings to keep the environment isolated from the base metal, which has suffered previous damage.

4.6.4.1

Organic coatings – The coating must be compatible with the service (temperature and stream composition) and must be resistant to all service conditions, including steaming-out. Surface preparation, particularly filling of pits, cracks, etc., is critical to achieve a solid bond. Curing conditions are also very important to assure a reliable lining. These fall into the following general classes:

--``````-`-`,,`,,`,`,,`---

4.6.4

4.6.4.2

a.

Thin film coatings – Typically, these include epoxy, epoxy phenolic, and baked phenolic coatings applied in dry film thickness less than 0.25 mm (10 mils).

b.

Thick film coatings – Typically, these include vinyl ester and glass fiber reinforced coatings that are applied in dry film thickness greater than 0.25 mm (10 mils).

Metallic linings – These fall into three general classes: a.

Metal spray linings – Various metal spray processes are available. In general, higher velocity processes such as HVOF (high velocity oxy-fuel) produce denser coatings, which are less susceptible to spalling or undermining. Coatings are often applied in multiple layers, with different compositions in each layer. Top coat materials should be corrosion resistant. Surface preparation is critical in achieving a solid bond. One advantage of metal spray linings is that the base material is not heated to high temperatures as in welding.

b.

Strip linings – Thin strips of a corrosion resistant metal are applied to the area of concern. They are fastened to the backing metal by small welds, which helps to minimize the size of the weld heat affected zone. Strip linings unfortunately have a high incidence of cracking of the lining attachment weld and may need periodic maintenance.

c.

Weld overlay – A corrosion resistant metal is applied to the surface of the base material with a weld overlay process. The base material is heated to high temperature during the welding process, which can cause cracking problems in the case of hydrogen charged materials, unless the hydrogen is previously baked out. Weld overlay may necessitate a PWHT. If they can be applied, weld overlays are usually considered to be a permanent repair and mitigation method.

4.6.4.3

Refractory linings – Many materials fall into this category. Depending on the damage mechanism, insulating refractories can be used to decrease the metal temperature, erosion resistant refractories can be used for erosion protection, and corrosion resistant refractories can be used to protect the base material. Selection of the refractory type and anchoring system, and curing of the refractory are critical elements for this remediation method. A refractory specialist should be consulted for details.

4.6.5

Remediation Method 3 – Injection of water and/or chemicals on a continuous basis to modify the environment or the surface of the metal. Important variables to consider when injecting chemicals are: the particular stream contaminants, injection point location and design, rate of injection, eventual disposition and any adverse reactions, the effect of process upsets, and monitoring for effectiveness. Examples of this type are as follows: a.

Water washing to dilute contaminants – This strategy is often applied in fluid catalytic cracking light end units and hydrodesulfurization reactor outlet systems. Important variables to consider when considering a retrofit water wash installation are location of injection, distribution of water, water rate, water quality, injection point design and disengagement, and monitoring for effectiveness.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b.

Injection of chemicals to change the aggressiveness of the solution – Neutralizing chemicals as used in atmospheric distillation unit overheads, polysulfide, and oxygen scavengers all fall into this category. Important variables to consider are; the injection location and design, possible adverse side effects, and monitoring for effectiveness.

c.

Injection of filming type chemicals to coat the metal surface – Filming chemicals attach to the metal surface to form a thin barrier that protects the metal. Important variables to consider are; the injection location and design, response to upsets, and monitoring effectiveness.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

4.6.6

Remediation Method 4 – Application of weld overlay. In this case, new material is added to the component to provide the necessary increase in wall thickness to compensate for corrosion/erosion. However, this method does not eliminate/reduce the rate of degradation. The weld overlay may be added to either the inside or outside surface regardless of which surface the metal loss is occurring on. The weld overlay should have the same chemistry (P-Number) as the base metal of the component, and prior to welding, the weldability of the base metal should be evaluated. In addition, for some applications, a repair procedure can be developed which permits deposit of the weld overlay while the component is in operation. Since this process changes the geometry of the component, an analysis considering bending stresses should be made to determine the acceptability of the proposed design.

4.7


4.7.1

As discussed above, mitigation methods can be applied, but in some cases these are not feasible or, if they are applied, it still is important to confirm that they are effective. Therefore in-service monitoring methods can be applied to monitor directly any further damage or to monitor indirectly conditions which might lead to further damage.

4.7.2

Typical monitoring methods include the use of the following tools or procedures: ·

Corrosion probes

·

Hydrogen probes

·

Retractable corrosion coupons and physical probes

·

UT measurements and scanning

·

Radiographic examination

·

Stream samples for H2S, Cl, NH3, CO2, Fe, Ni, pH, water content, Hg, etc.

·

Infrared thermography

·

Thermocouples

4.7.3

Care must be exercised in defining the in-service monitoring method, determining the required measurement sensitivity of the method based on the environment, and locating monitoring stations on the component to insure that the damage mechanism resulting in the metal loss can adequately be measured and evaluated during operation.

4.8

Documentation

4.8.1

The documentation of the FFS Assessment should include the information cited in Section 2, paragraph 2.8.

4.8.2

Inspection data including all thickness readings and corresponding locations used to determine the average measured thickness, tam , and the minimum measured thickness, t mm , should be recorded and included in the documentation. A sample data sheet is provided in Table 4.1 for this purpose. A sketch showing the location and orientation of the inspection planes on the component is also recommended.


Not for Resale

--``````-`-`,,`,,`,`,,`---



4.9

References Osage, D.A., Buchheim, G.M., Brown, R.G., Poremba, J., "An Alternate Approach for Inspection Scheduling Using the Maximum Allowable Working Pressure for Pressurized Equipment," ASME PVP-Vol. 288, American Society of Mechanical Engineers, New York, 1994, pp. 261-273. Tables and Figures

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

4.10

--``````-`-`,,`,,`,`,,`---


Not for Resale


Table 4.1 Temperature Limit Used To Define The Creep Range Temperature Limit

Carbon Steel and C-1/2 Mo and Ferritic Stainless Steels

399°C (750°F)

Low Alloy Steels (Cr-Mo)

454°C (850°F)

Austenitic Stainless Steels

510°C (950°F)

Aluminum Alloys

93°C (200°F)

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Material

--``````-`-`,,`,,`,`,,`---


Not for Resale

RECOMMENDED

Jan, 2000

Inspection

PRACTICE

4-19


Table 4.2 Summary Required For The Assessment Of General Metal Loss

Use this form to summarize the data obtained from a field inspection. Equipment Identification: Equipment Type: Pressure Vessel Component Type & Location:

Storage Tank

Piping Component

Data Required for Level 1 And Level 2 Assessment Future Corrosion Allowance: Inside Diameter: Minimum Required Thickness: Flaw Dimensions (s & c): Enter the thickness data for each of the inspection planes in the table shown below. Inspection

Plane:-

Inspection

Plane:-

Inspection Plane:-

Inspection Plane:-

--``````-`-`,,`,,`,`,,`---

t mm

t mm

t mm

t mm

t am

t am

t am

t am



API RECOMMENDED

4-20

Template

For Calculating

The Coefficient

PRACTICE 579

Table 4.3 Of Variation

(COV)

Jan, 2000

For Point Thickness

Readings

N -

-

s, =$(I,-FCA)= i=l

s* = gtj

-FcA)2

=

i=l

--``````-`-`,,`,,`,`,,`---

ANotes 1. 2.

N is the total number of thickness readings, the number of thickness equal to 15 (see paragraph 4.3.3.2) The equation for the Coefficient Of Variation (WV) is:

cov =

t, =

tsD

readings

should be greater

than or

(4.12)

t, - FCA $ - (torn- FCA)’

(4.13)

t/FCA$

(4.14)

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 4.4 Parameters To Compute The Length For Thickness Averaging

RSFa

0.90

0.85

0.80

0.75

0.70

Rt

Q

Q

Q

Q

Q

0.900 0.895 0.875 0.850 0.845 0.825 0.800 0.795 0.775 0.750 0.745 0.725 0.700 0.695 0.675 0.650 0.625 0.600 0.575 0.550 0.525 0.500 0.475 0.450 0.425 0.400 0.375 0.350 0.325 0.300 0.275 0.250 0.200 .8

50.00 21.19 4.93 2.82 2.62 2.07 1.68 1.62 1.43 1.26 1.23 1.12 1.02 1.00 0.93 0.86 0.80 0.74 0.70 0.65 0.61 0.58 0.55 0.51 0.49 0.46 0.43 0.41 0.38 0.36 0.34 0.31 0.27 50.0

50.00 50.00 50.00 50.00 29.57 6.59 3.65 3.38 2.63 2.11 2.03 1.77 1.54 1.51 1.37 1.24 1.13 1.04 0.96 0.89 0.83 0.77 0.72 0.68 0.64 0.60 0.56 0.53 0.50 0.46 0.43 0.40 0.35 50.0

50.00 50.00 50.00 50.00 50.00 50.00 50.00 36.82 8.01 4.35 4.01 3.10 2.45 2.36 2.05 1.77 1.56 1.40 1.27 1.16 1.07 0.99 0.92 0.86 0.80 0.74 0.70 0.65 0.61 0.57 0.53 0.49 0.42 50.0

50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 42.94 9.20 4.93 4.53 3.47 2.73 2.26 1.95 1.71 1.53 1.38 1.26 1.15 1.06 0.98 0.91 0.84 0.78 0.73 0.67 0.63 0.58 0.49 50.0

50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 47.94 10.16 5.39 3.77 2.94 2.43 2.07 1.81 1.61 1.45 1.32 1.20 1.10 1.01 0.93 0.86 0.79 0.73 0.67 0.57 50.0

Notes: 1.

The equation for

Q is:

LF 1 - R I Q = 1123 . MG MNH 1 - R RSF JK t

t

Q = 50.0 2.

for

a

2

O - 1P PQ

0.5

for

Rt < RSFa

(4.15)

Rt ³ RSFa

(4.16)

The length for thickness averaging is given by Equation (4.3)

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure 4.1 Overview Of The Assessment Procedures To Evaluate A Component With General Metal Loss

Obtain Equipment Data

Metal Loss at a Major Structural Discontinuity?

Yes

No

No


Equipment is Acceptable per Level 1 Criteria? No

No

No

Perform a Level 2 Assessment?

No

No

Rerate Equipment?

No

Yes

Perform Rerate per Level 3 Criteria to Yes Reduce Pressure and/or Temperature

No

Yes

Yes

Repair, Replace, or Retire Equipment

Rerate Equipment?

Yes Remaining Life Acceptable per Level 3 Critiera?

Rerate Equipment?

Perform Rerate per Level 1 Criteria to Reduce Pressure and/or Temperature

Equipment is Acceptable per Level 2 Criteria? Yes


Equipment Acceptable per Level 3 Assessment?

Yes

No

No

--``````-`-`,,`,,`,`,,`---

4-22

No

Remaining Life Acceptable Per Level 2 Criteria?

Yes

Return the Equipment to Service



Remaining Life Acceptable per Level 1 Criteria?

Yes

Yes

No

Yes

Not for Resale

Yes


Figure 4.2 Assessment Procedure To Evaluate A Component With Metal Loss Using Section 4 and Section 5

Determine tmin (see Appendix A)

Locate Regions of Metal Loss on the Equipment

Assessment Using Thickness Profiles?

No

Take Point Thickness Readings and Use Addtional NDE to Confirm General Corrosion

Yes Determine Inspection Plane(s) and Take Thickness Profile Data

Determine tmm, tam and COV from the Thickness Data

Determine tmm and L

Determine s, c, and tam for the CTP's

Determine Average Thickness, tam, within the Zone For Thickness Averaging, see Paragraph 4.3.3.4 and 4.4.3.2

Yes

Metal Loss at Major Structural Discontinuity? No

Evaluate the MAWP Using a Section 4 Level 2 or 3 Assessment

Assessment Using Thickness Profiles?

No

COV > 10%? No

Yes

Is s<=L?

Yes

No

Use tam For Calculations

Longitudinal or Meridonal Extent Of Metal Loss Is Acceptable

Yes

Obtain Thickness Profiles?

Cylinder, Cone or Elbow?

Level 3 Assessment? Yes

Yes

No

Assessment Complete

Yes Evaluate Circumferential Extent Of Metal Loss Using Section 5, Level 1

Evaluation Option:

--``````-`-`,,`,,`,`,,`---

Simple Approach

Thickness Averaging

Stress Analysis

Localized Metal Loss

Use tam=tmm for Calculations

Determine tam Using Thickness Data Within Length L

Evaluate Using a Level 3 Assessment

Evaluate Using Section 5

Evaluate Using Section 4, Level 1 or Level 2 Assessment


No

Not for Resale

No

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Determine CTP's in The Longitudinal and Circumferential Directions


Figure 4.3 Inspection Planes For Pressure Vessel Heads And Spheres

--``````-`-`,,`,,`,`,,`---

Spherical Shell or Formed Head

Metal Loss

M1

M2 M3 C1 C2 Axis of Vessel, or Vertical Axis of Sphere

C3

Notes: 1.

M1 – M3 are meridional inspection planes and C1-C3 are circumferential inspection planes.

//^:^^#^~^^""~:@":^*^~$~"#:*~


Not for Resale


Figure 4.4 Inspection Planes For Cylindrical Shells, Conical Shells, And Pipe Bends CL

CL

Metal Loss

Metal Loss

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C1

C1

C2

C2

C3

C3

M3 M1 M2 M3

M1 M2 M3

M1 Cylindrical Shell

Conical Shell

M1

Extrados

C3 C2

CL

M2 M3

C1 Metal Loss Intrados

Elbow or Pipe Bend

Notes: 1. 2.

For cylindrical and conical shells, M1 – M3 are meridional (longitudinal direction) inspection planes and C1-C3 are circumferential inspection planes. For elbows and pipe bends, M1 – M3 are longitudinal inspection planes and C1-C3 are circumferential inspection planes.

--``````-`-`,,`,,`,`,,`---


Not for Resale

Figure 4.5 Inspection Planes For Atmospheric Storage Tanks Longitudinal Weld Seam

Tank Shell

M1 M2 M3 M4 Flaw

Circumferential Weld Seam

Notes: 1. 2.

M1 – M3 are meridional (longitudinal direction). Circumferential inspection planes are not required because the stress normal to this direction is negligibly small and does not govern the design thickness calculation.

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure 4.6 Method For Determining The Plane Of Maximum Metal Loss (Critical Thickness Profile)

M5

C1

C2

C3

C4

C5

C6

C7

M4 C

M3

CL

M2 M1 Line M - path of minimum thickness readings in the longitudinal direction

Line C - path of minimum thickness readings in the circumferential direction

Cylindrical Shell

(a) Inspection Planes and the Critical Thickness Profile

S

t

tmin

tmm

(b) Critical Thickness Profile (CTP) - Longitudinal Plane (Projection of Line M) c

t

tc tmm

(c) Critical Thickness Profile (CTP) - Circumferential Plane (Projection of Line C)

Notes: 1. t – Is the current shell thickness, typically the nominal or furnished thickness minus the metal loss. 2. M1 – M5 are meridional (longitudinal) inspection planes. 3. C1 – C5 are circumferential inspection planes. tnom - the nominal or furnished thickness. 4. 6.

s - extent of the metal loss established using the CTP in the longitudinal direction with t min . c - extent of the metal loss established using the CTP in the circumferential direction; note that t c = t min in a Section 4 Assessment, and t c = t nom - LOSS - FCA in a Section 5 Assessment.

7.

For a cylindrical or conical shell,

5.

C L t min = max[t min , t min ] (see Appendix A).

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 4.7 Sizing Of A Region Of With Multiple Areas Of Metal Loss For An Assessment 2s

s

c

c

2c

c

Shell

s

Step 1 - Draw a box that completely encloses the thin area. Measure the maximum longitudinal (axial) extent, s (in. or mm.) and the maximum circumferential extent, c (in. or mm.) of this box. These will be the dimensions of the thinned area used in the assessment.

--``````-`-`,,`,,`,`,,`---

s

Step 2 - Draw a second box twice the size of the first box (2s x 2c) around the thinned area.

2s s

c

2c c

s

Step 3 - If another thinned area is within the larger box, the dimensions s and c should be adjusted to include the additional thinned area. Go back to step 2.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 4.8 Sizing Of An Isolated Metal Loss Region And A Network Of Metal Loss Regions Flaw S

t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Path of Maximum Metal Loss

tmin tmm

Thickness Profile

(a) Isolated Flaw

S Flaw 2

Flaw 1

t

tmin

Thickness Profile

Note: Flaw 1 and Flaw 2 Are Combined Based on the Criterion Shown In Figure 4.7 To Form A Single Flaw For The Assessment )

(b) Network Of Flaws

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 4.9 Zone For Thickness Averaging – Nozzles And Fabricated Branch Connections C L

Nozzle

Reinforcement Zone Reinforcing Pad

tn Lno

te di

Shell

tv

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Lni

Lv

Lv

Notes: 1.

b

Lv = max d i , di 2 + t n + t v 4.4.3.3.c.1).

2.

b

Lno = min 2.5t v , 2.5t n + t e

g

g

(zone for thickness averaging in the horizontal direction, see paragraph (zone for thickness averaging in the vertical direction on the outside of

the shell, see paragraph 4.4.3.3.c.1). 3.

Lni = min 2.5t v , 2.5t n

4.

see paragraph 4.4.3.3.c.1). t v , t n , t e are the furnished vessel, nozzle and reinforcing pad thicknesses, respectively.

5. 6.

(zone for thickness averaging in the vertical direction on the inside of the shell,

di is the current inside diameter of the nozzle including the specified FCA . See paragraph 4.4.3.3.c.1 to determine the length for thickness averaging.


Not for Resale

--``````-`-`,,`,,`,`,,`---

Nozzle with a Reinforcement Element


Figure 4.10 Zone For Thickness Averaging – Conical Transitions CL

Small End Cylinder

tS

Lv Cone

Zones for Thickness Averaging - Small End

RS

Lv Lv

Lv

Zones for Thickness Averaging - Large End

Large End Cylinder

tL

Notes: 1.

Lv = 0.78 RS t S (thickness averaging zone for the small end cylinder , see paragraph 4.4.3.3.c.2).

2.

Lv = 0.78 RS t C (thickness averaging zone for the small end cone see, paragraph 4.4.3.3.c.2).

3.

Lv = 10 . RL t C (thickness averaging zone for the large end cone, see paragraph 4.4.3.3.c.2).

4.

Lv = 10 . RL t L (thickness averaging zone for the large end cylinder, see paragraph 4.4.3.3.c.2). t S , t C , t L are the furnished small end vessel, cone, and large end vessel thicknesses, respectively. RS , RL are the small end and large end vessel inside radii, respectively.

5. 6. 7.

See paragraph 4.4.3.3.c.2 to determine the length for thickness averaging.


Not for Resale

--``````-`-`,,`,,`,`,,`---

RL

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

tC


Figure 4.11 Zone For Thickness Averaging – Axisymmetric Discontinuities CL

Zone for Thickness Averaging Shell

LV

Zone for Thickness Averaging, AR

External Stiffening Ring

LV

tV LV L V Internal Tray Support Ring, AR

Zone for Thickness Averaging

LV

Skirt Attachment Detail

LV Alternative Skirt Attachment Detail

Note 4

LV

LV

--``````-`-`,,`,,`,`,,`---

Vessel Skirt


Notes: 1.

LV = 10 . RtV (thickness averaging zone, see paragraph 4.4.3.3.c.2).

2. 3.

The length for thickness averaging is determined using the procedure in 4.4.3.3.c.2. A stiffening or tray support ring is considered to be a major axisymmetric discontinuity when:

AR > 0.65 AR + 156 . t v Rt v 4.

Distance from the skirt attachment point to the bottom head tangent line or

10 . Rt v , whichever is

greater. 5.

t v , R , AR are the furnished shell thickness, inside radius, and ring cross-sectional area, respectively.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

LV


Figure 4.12 Zone For Thickness Averaging – Flange Connections Flange


Vessel Shell or Nozzle

tV

LVt

LVh //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

R

CL

Notes: 1. 2.

Lvh is thickness averaging zone for the hub. Lvt is thickness averaging zone for the flange.

--``````-`-`,,`,,`,`,,`---


Not for Resale


4.11 4.11.1

Example Problems

Example Problem 1 – Corrosion at a longitudinal weld seam in a pressure vessel has been found during an inspection. Details regarding the pressure vessel and inspection data are given below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Evaluate if the vessel shell is fit-for-service. Pressure Vessel Information Design Conditions

=

300 psig @ 350°F

Inside Diameter

=

48 inches

Nominal Thickness

=

0.75 inches

Uniform metal loss

=

0.0 inches

Future Corrosion Allowance =

0.10 inches

Material

=

SA 516 Grade 70


=

0.85

Inspection Data The grid and data used for the inspection are shown below. The grid spacing set by the Inspector in the circumferential and longitudinal directions is 1.5 inches based on the corrosion profile. Vessel Shell

C1

C2

C3

C4

C5

C6

C7

C8

M1

Inspection Grid

M2 M3 M4 M5 M6 M7

Weld Seam

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

RECOMMENDED

Jan, 2000

PRACTICE


4-35

Inspection Data (inches) Longitudinal Inspection Planes

C cumfe ential Inspection Planes l-r

Cl

I C8

C2

I

Circumferential CTP

0.75 1

0.75

0.75 I

0.48

0.75 1

0.55

0.47

--``````-`-`,,`,,`,`,,`---

0.58 1 0.57 1 0.48 1 0.62

0.55 10.36 1 0.48 1 0.49

Perform a Level 7 Assessment per paragraph 4.4.2

Step 7 - Calculate the minimum required thickness.

300psig(24"+0.10") *’

= 2(17500@)(0.85)

+ 0.4(3OOpsig)

= 0.242 '

tti = max[0.492", 0.242"]= 0.492" Step 2 - Thickness profiles are provided, the data for thickness readings is in the above table. Step 3 - Determine the length for thickness averaging. Step 3.1 - Determine the minimum thickness and remaining thickness ratio

tmm= 0.36'

R = 0.36-0.10 =0.528 f 0.492 Step 3.2 - Determine the length for thickness averaging. From Table 4.4 with Rt = 0.528 with RSF, = 0.9 (see Section 2, paragraph 2.4.2.2.d); Q = 0.62 or by equation



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

300psig(24"+0.10") = 0.492 " "in = 175OOpsi(O.85)-0.6(3OOpsig)

API RECOMMENDED

4-36

Jan, 2000

PRACTICE 579

L = (0.6 16)d48"(0.492") = 3.0" --``````-`-`,,`,,`,`,,`---

Step 4 - Thickness profiles where taken; therefore, determine the longitudinal and circumferential CT/%, (the thickness readings for the critical inspection planes are indicated in the above table and shown in the following figure) and determine the flaw dimensions. Lonaitudinal

CTP

0.75”

0.48”

0.47”

0.55”

0.36”

4

0.49”

0.75”

b

s

p-7

Note:

0.48”

spaces @ 1.5”--/

In this figure, the top number is the wall thickness at the time of the inspection in the parentheses is this wall thickness minus the future corrosion allowance

The flaw dimension

Circumferential

is: s =

and the number

5(1.5")+ ("oAs'~~~~~~~)(l~~~)+(ooA69~~~~~~~)(l.51.)= 8.71'I

CTP

The circumferential CTP does not need to be determined because the minimum required thickness based on the circumferential plane (longitudinal stress) is less than the average measured thickness (see Step 2). Note that in this example, c is not required because the minimum required thickness for the circumferential direction is less than the minimum measured thickness, or

(t& = 0.242")<(tmm - FCA = 0.36"-O.lO"= 0.26"). Step 5- Since (s = This evaluation

8.71")> (L

can be performed

=

3.0") , the

evaluation

by direct averaging

is performed the thickness

using paragraph

4.4.2.1 .e.2.

readings that reside within length

L.

t = tS _- 055"+0.36"+0.48" =0463,, am lam 3 Alternatively, the average thickness can be established more accurately using areas. The area method should normally be used to determine the average thickness when there is only a small number of thickness readings which reside within length L. As the number of thickness readings within this length increase, the average thickness determined by the direct averaging method and the area method will converge to the same result.

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


0.55"

0.47"

0.49"

0.48" 0.36"

1.5"

1

2

1.5"

1.5"

1.5"

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

L=3.0"

b0.55"+0.36"g b15. "g = 0.6825 in 2 b0.48"+0.36"g b15. "g = 0.63 in A = A1 =

2

2

2

2

2

and

. in å A = 1313

2

i

i =1

2

åA

i

t am = t

s am

=

i =1

L

in 2 1313 . = = 0.438" 3.0"

Step 6 – Determine if the component is acceptable for continued operation. Per paragraph 4.4.2.1.f.1:

bt

am

g c

h

C - FCA = 0.438"-0.10" = 0.338" ³ t min = 0.492"

False

Per paragraph 4.4.2.1.f.2:

bt

mm

g c

h

- FCA = 0.36"-010 . " = 0.26" ³ max 0.5 t min , 010 . " = 0.246"

The Level 1 Assessment criteria are not satisfied. If the vessel is derated, the Permissible MAWP based on a Level 1 Assessment is:

Rc = 24"+010 . " = 24.10" t c = 0.438"-010 . " = 0.338" MAWP C =

b17500 psiggb0.85gb0.338"g = 207 psig b24.10"g + 0.6b0.338"g

Perform a Level 2 Assessment per paragraph 4.4.3 Steps 1 through 5 – The procedure and results are the same as in Level 1. Step 6 – Determine if the component is acceptable for continued operation. --``````-`-`,,`,,`,`,,`---


Not for Resale

True


Per paragraph 4.4.3.2.f.1.a.1:

ct

s am

h c

b g

h

C - FCA = 0.438"-0.10" = 0.338" ³ RSFa × t min = 0.90 0.492" = 0.443"

False

Per paragraph 4.4.3.2.f.1.b

bt

mm

g c

h

- FCA = 0.36"-010 . " = 0.26" ³ max 0.5 t min , 010 . " = 0.246"

Tr ue

The Level 2 Assessment criteria are not satisfied. If the vessel is derated, the Permissible MAWP based on a Level 2 Assessment is:

Rc = 24"+010 . " = 24.10" 0.438"-010 . " tc = = 0.376" 0.9 17500 psig 0.85 0.376" MAWP C = = 230 psig 24.10" + 0.6 0.376"

4.11.2

gb gb g g b g

b

Example Problem 2 – A localized region of corrosion on a 2:1 elliptical head has been found during an inspection. The corroded region is within the spherical portion of the elliptical head. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel head is suitable for continued operation. Pressure Vessel Information

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Design Conditions

=

2.068 MPa @ 340 °C

Head Inside Diameter

=

2032 mm

Nominal Thickness

=

19 mm

Metal Loss

=

0 mm


3 mm

Material

=

SA 516 Grade 70


=

1.0 (Seamless head)


Not for Resale

--``````-`-`,,`,,`,`,,`---

b


Inspection Data The grid and data used for the inspection are shown below. The grid spacing is 100 mm. Inspection Data (mm) Meridional Inspection

Circumferential Inspection Planes Circumferential C1

C2

C3

C4

C5

C6

C7

C8

CTP

M1

20

20

19

20

20

19

20

20

19

M2

20

20

20

19

19

19

20

20

19

M3

19

19

19

19

19

19

19

20

19

M4

20

19

19

17

17

18

19

19

17

M5

19

19

19

17

14

15

19

19

14

M6

19

19

20

17

15

16

19

19

15

M7

20

20

19

19

20

19

19

19

19

M8

20

20

19

18

19

19

20

19

19

Meridional CTP

19

19

19

17

14

15

19

19

Perform a Level 1 Assessment per paragraph 4.4.2 Step 1 – Calculate the minimum required thickness. Note that an equivalent diameter based on the parameter Kc is used to compute the wall thickness because the region of metal loss is located in the spherical portion of the elliptical head (see Appendix A).

bg

bg bg b2.068 MPa gc2032 mm + 2l3 mmqhb0.9g = 15.75 mm = 2b120.658 MPa gb10 . g - 0.2b2.068 MPa g 2

3

Kc = 0.25346 + 0.13995 2 + 012238 . 2 - 0.015297 2 = 0.90 t min

Step 2 – Thickness profiles are provided, the data for thickness readings is in the above table Step 3 – Determine the length for thickness averaging. Step 3.1 – Determine the minimum thickness and remaining thickness ratio

t mm = 14 mm Rt =

14 mm - 3 mm = 0.698 15.75 mm

Step 3.2 – Determine the length for thickness averaging. From Table 4.4 with Rt equation:

//^:^^#^~^^""~:@":^*^~$~"#


= 0.698 with RSFa = 0.9(see Section 2, paragraph 2.4.2.2.d); Q »1.0 or by

Not for Resale

--``````-`-`,,`,,`,`,,`---

Planes


LF 1.0 - 0.698 I - 10. OP = 1013 Q = 1123 . MG MNH 1.0 - 0.698 0.90JK PQ . L = b1.013g b0.90 × 2032 mmgb15.75 mmg = 172 mm 2

0.5

Step 4 – Thickness profiles where taken; therefore, determine the longitudinal and circumferential CTP – The thickness readings for the critical inspection planes are indicated in the above table and shown in the above table. Meridional CTP Not required for the assessment of the spherical portion of an elliptical head since the stresses are approximately equal in both directions. Circumferential CTP Determine Of Circumferential CTP Circumferential Distance

Thickness Reading

Thickness – FCA

(mm)

(mm)

(mm)

0

19

16

100

19

16

200

19

16

300

17

14

400

14

11

500

15

12

600

19

16

700

19

16

Step 5 – Since

s = 381 mm

bs = 381 mmg > b L = 172 mmg , the evaluation can be performed using paragraph

4.4.2.1.e.2. This evaluation can be performed by directly averaging the thicknesses. Note that in this case, the length for thickness averaging includes only one data point if the length is centered on the minimum reading.

t am = 14 mm Alternatively, the average thickness can be determined using the area method (see Step 5 of Example Problem 1).

t am =

åA

i

L

=

2556 mm2 = 14.86 mm 172 mm

Step 6 – Determine if the component is acceptable for continued operation.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Based on the data in the above table, the flaw dimension is:



bt

am

g b

g

- FCA = 14.86 mm - 3 mm = 1186 . mm ³ t min = 15.75 mm

False


bt

mm

g c

h

- FCA = 14 mm - 3 mm = 11 mm ³ max 0.5 t min , 3 mm = 7.9 mm

True

The Level 1 Assessment criteria are not satisfied. Perform a Level 2 Assessment per paragraph 4.4.3 Steps 1 through 5 – The procedure and results are the same as in Level 1. Step 6 – Determine if the component is acceptable for continued operation. Per paragraph 4.4.3.2.f.1.a.2:

bt

am

g c

b g

h

- FCA = 14.85 mm - 3 mm = 1186 . mm ³ RSFa × t min = 0.9 15.75 mm = 14.2 mm

False

bt

mm

g c

h

- FCA = 14 mm - 3 mm = 11 mm ³ max 0.5 t min , 3 mm = 7.9 mm

True

The Level 2 Assessment criteria are not satisfied.

4.11.3

Example Problem 3 – A region of corrosion on a 12 inch Class 300 long weld neck nozzle has been found during the inspection of a pressure vessel. The corroded region includes the nozzle bore and a portion of the vessel cylindrical shell (see inspection data). The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel nozzle is suitable for continued operation. Pressure Vessel Information Design Conditions

=

185 psig @ 650°F

Shell Inside Diameter

=

60 inches

Shell Thickness

=

0.60 inches

Shell Material

=

SA 516 Grade 70

Shell Weld Joint Efficiency

=

1.0

Shell FCA

=

0.125 inches

Nozzle Inside Diameter

=

12.0 inches

Nozzle Thickness

=

1.375 inches

Nozzle Material

=

SA 105

Nozzle Weld Joint Efficiency =

1.0

Nozzle FCA

=

0.125 inches

Reinforcing Pad Material

=

SA 516 Grade 70

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Inspection Data A sketch of the nozzle and metal loss are shown below.

CL 1.375"

Reinforcement Zone

--``````-`-`,,`,,`,`,,`---

0.375"

Lno

Metal Loss 0.60"

Reinforcing Pad 18" OD x 0.50" Thick Lv

From the inspection data: ·

The average shell thickness in the nozzle reinforcement zone is 0.50 inches.

·

The average nozzle thickness in the nozzle reinforcement zone is 0.90 inches.

·

The corrosion is uniform for each inspection plane.

·

The thickness for the shell and nozzle to be used in the assessment were determined by averaging thicknesses within the nozzle reinforcement zone (see paragraph 4.4.3.3.c.1 and Figure 4.9).

Perform a Level 2 Assessment because the corrosion is at a major structural discontinuity From the inspection data: nozzle t am = 0.90 shell t am = 0.50 //^:^^#^~^^""~:@":^*^~$~"#:*~


Not for Resale


Required thickness of the shell:

. " LOSS s = 0.60"-0.50" = 010

. "+0125 . "g b185 psiggb30"+010 b17500 psigb1.0g - 0.6b185 psigg = 0.3216"

tr =

Required thickness of the nozzle:

. "-0.90" = 0.475" LOSSn = 1375 t rn =

b185 psiggb6"+0.475"+0.125"g = 0.0702" b17500 psigb10. g - 0.6b185 psigg

Check the nozzle reinforcement (see Appendix A): Required Area:

b

g

d c = 12.0"+2 1375 . "-0.90"+0125 . " = 13.2" F = 10 . f r 1 = 10 . \ B = 0.0

b gb

gb g

A = 13.2" 0.3216" 1.0 = 4.245 in 2 Available area:

f r 2 = 10 . f r 3 = 10 . f r 4 = 10 . cs = 0.6"-0.50"+0125 . " = 0.225" cn = 1375 . "-0.90"+0125 . " = 0.60" wn = 0.375" w p = 0.375" Dp = 18"

--``````-`-`,,`,,`,`,,`---

t e = 0.50" h = 0.0 \ A3 = 0.0 and A43 = 0.0


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


LMb13.2"gm1.0b0.60"-0.225"g - 1.0b0.3216"gr - 0.0, OP = 0.705 in . "-0.225"-0.60"qm1.0b0.60"-0.225"g - 10 . b0.3216gr - 0.0PQ MN2l0.60"+1375 L5b1.375"-0.60"-0.0702"gb10. gb0.60"-0.225"g, OP = 1322 in A = min M . . "-0.60"-0.0702"qm2.5b1.375"-0.60"g + 0.50"r - 0.0PQ MN2l1375 A = b0.375"g b1.0g = 0141 in . A = b0.375"g b10 in . g = 0141 . A = c18.0"-13.2"-2l1375 in . "-0.60"qhb0.50"gb10 . g = 1625 . A1 = max

2

2

2

2

2

2

2

41

42

2

5

Reinforcement check:

A1 + A2 + A41 + A42 + A5 ³ A

c0.705in

2

h c

+ 1.322 in 2 + 0.141in 2 + 0.141in 2 + 1625 . in 2 = 3.93 in 2 ³ A = 4.245 in 2

h

False

The area reinforcement calculation per the original construction code is not satisfied using the average thicknesses for the shell and nozzle in the nozzle reinforcement zone. An acceptable pressure can be established using the above equations with an iterative procedure (e.g. assume a pressure, compute areas, perform area check and continue until the required area matches the available area). In order to determine if this component is acceptable for the stated design conditions, a Level 3 Assessment must be performed. The Level 2 Assessment criteria is not satisfied.

4.11.4

Example Problem 4 – Corrosion on the cylindrical shell of a heat exchanger has been found during an inspection. Details regarding the heat exchanger and inspection data are given below. The heat exchanger was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the heat exchanger is suitable for continued operation. Pressure Vessel Information Design Conditions

=

3.85 MPa @ 380°C

Inside Diameter

=

484 mm

Nominal Thickness

=

16 mm

Metal Loss

=

3 mm


2 mm

Material

=

SA 516 Grade 60


=

1.0


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Analysis Results:

RECOMMENDED

Jan, 2000

PRACTICE

4-45


Inspection Data Based on a visual inspection, the corrosion loss is characterized as general, and point thickness readings will be used in the assessment (see paragraph 4.3.3.1 and 4.3.3.2).

Inspection Data - Point Thickness Readings Thickness Reading Number

Thickness Reading

1

(t - FCA)

(t - FCA)’

13

11

121

2

12

10

100

3

11

9

81

5

10

8

64

6

12

10

100

t

81 12

10

100

9

13

11

121

10

13

11

121

11

11

9

81

12

12

10

100

13

12

10

100

14

13

11

121

15

13

11

121

s, =151

s, = 1533

---

-

--``````-`-`,,`,,`,`,,`---

8

Perform a Level 1 Assessment per paragraph 4.4.2 Step 7 - Calculate the minimum required thickness (see Appendix A).

tC, = 3.85 MPa(242 mm + 2 mm + 3 mm) = 10.13 mm llllll 96.196 MPa( 1.0) - 0.6( 3.85 Mpa) tL, = 3.85 MPa(242 mm + 2 mm+ 3 mm) = 4.90 mm 2( 96.196 MPa)( 1.0) + 0.4( 3.85 Mpa)

t,, = max[lO.l3mm,


4.90 mm] = 10.13 mm


API RECOMMENDED

--``````-`-`,,`,,`,`,,`---

4-46

PRACTICE

579

Jan, 2000

Step 2 - Point thickness readings will be taken, the location of the readings is determined by the Inspector based on a visual examination. The COV is determined using Table 4.3.

t, = $-(tam -FcA)* }{&}l”

co)7 =

The

=({$3-(10.0667)*}{&}~

=0.9608

0.9608 mm tm = 0.095 or 9.5% t,, - FCA = 10.0667 mm

(COV = 9.5%) < 10% ; therefore, the average thickness to be used in the calculation is the

average thickness of the thickness distribution, or tam-

FCA = 10.07 mm

Steps 3, 4, and 5 - These steps are not required if point thickness readings are used in the assessment Step 6 - Determine if the component is acceptable for continued operation. Per paragraph 4.4.2.1 .f. 1.

(tk -FCA

= 10.07mm) 2 (t2n = 10.13mm)

(tk - FCA = 10.07mm) 2 (tJYh= 4.90mm)

False True

Per paragraph 4.4.2.1 .f.2 km -

FCA = 8mm) 2 (max[0.5tmi,, 2 mm] = 506mm)

The Level 1 Assessment criteria are not satisfied.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

March 2000


Not for Resale

True


Perform a Level 2 Assessment. Steps 1 through 5 – Are the same as in Level 1. Step 6 – Determine if the component is acceptable for continued operation. Per paragraph 4.4.3.2.f.1.a.1

ct ct

s am c am

h c - FCA = 10.07 mmh ³ c RSF × t

b g h = b0.9g4.90 mm = 4.41 mmh True

C - FCA = 10.07 mm ³ RSFa × t min = 0.9 1013 . mm = 9.17 mm True a

L min


bt

mm

g c

h

- FCA = 8 mm ³ max 0.5 t min , 2 mm = 5.06 mm

True


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

The Level 2 Assessment criteria are satisfied.

SECTION 5 – Assessment Of Local Metal Loss

General

5.1.1

Fitness-For-Service (FFS) assessment procedures for pressurized components subject to local metal loss resulting from corrosion/erosion and/or mechanical damage are provided in this section. In addition, these procedures can also be used to evaluate regions of local metal loss resulting from blend grinding of crack-like flaws. The procedures can be used to qualify a component for continued operation or for rerating. A flow chart for the assessment procedures for local metal loss is shown in Figure 5.1.

5.1.2

The assessment procedures of this section are for the analysis of local metal loss whereas the procedures of Section 4 are for general metal loss. The methodology shown in Section 4, Figure 4.2 can be used to determine whether the assessment procedures of Section 4 or Section 5 should be used in the evaluation. For most evaluations, it is recommended to first perform an assessment using Section 4. The assessment procedures for local metal loss in this section can only be established using thickness profiles because the size of the region of the metal loss is required as well as thickness data for the assessment.

5.1.3

Damage associated with pitting and blisters can also be evaluated using the assessment procedures in this section in conjunction with the assessment procedures of Sections 6 and 7, respectively.

5.2


5.2.1

The procedures in this section can be used to evaluate components subject to local metal loss from corrosion/erosion, mechanical damage, or blend grinding which exceeds, or is predicted to exceed, the corrosion allowance before the next scheduled inspection. The local metal loss may occur on the inside or outside of the component.

5.2.1.1

The type of flaws characterized as local metal loss are defined as follows:

5.2.1.2

a.

Locally Thin Area (LTA) – local metal loss on the surface of the component; the length of a region of metal loss is the same order of magnitude as the width,

b.

Groove-like flaw – the following flaws are included in this category; a sharp radius may be present at the base of a groove-like flaw. 1.

Groove – local elongated thin spot caused by directional erosion or corrosion; the length of the metal loss is significantly greater than the width.

2.

Gouge – elongated local mechanical removal and/or relocation of material from the surface of a component, causing a reduction in wall thickness at the defect; the length of a gouge is much greater than the width and the material may have been cold worked in the formation of the flaw. Gouges are typically caused by mechanical damage, for example, denting and gouging of a section of pipe by mechanical equipment during the excavation of a pipeline. Gouges are frequently associated with dents due to the nature of mechanical damage (see Section 8, Figure 8.9). If a dent is present, the assessment procedures for dents in Section 8 should also be used.

The geometry associated with local metal loss may contain a region with a sharp notch. Notches are common at the base of groove-like flaws, and may also be present in a region of the LTA. The severity of the notch and its effect on the load carrying capacity of the component can be characterized by a local radius, the applied stress, the component and overall flaw geometry, and the


5-1 Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

5.1

--``````-`-`,,`,,`,`,,`---

(Jan, 2000)


material flow stress and toughness. The Level 2 Assessment procedures in this section include a provision to evaluate the effects of a notch. 5.2.2


5.2.3


5.2.3.1

The Level 1 and 2 assessment procedures in this section apply only if all of the following conditions are satisfied:

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

5.2.3.2

a.

The original design criteria were in accordance with a recognized code or standard (see Section 1, paragraphs 1.2.2 or 1.2.3).

b.

The component is not operating in the creep regime (see Section 4, paragraph 4.2.3.1.b).

c.

The material is considered to have sufficient material toughness. If the user is uncertain about the toughness , a Section 3 assessment should be performed. If the component is subject to embrittlement during operation due to temperature and/or the process environment, a Level 3 assessment should be performed. Temperature and/or process conditions which result in material embrittlement are discussed in Appendix G, paragraph G.3.6.4.

d.

The component is not in cyclic service (see Section 4, paragraph 4.2.3.1.d).

e.

The component under evaluation does not contain crack-like flaws. If crack-like flaws are present, the assessment procedures in Section 9 shall be utilized.

f.

The component under evaluation has a design equation which specifically relates pressure (or liquid fill height for tanks) and/or other loads, as applicable, to a required wall thickness (see Section 4, paragraph 4.2.3.1.f). However, if the component is subject to external pressure, or if the metal loss is located in the knuckle region of an elliptical head (outside of the 0.8D region), torispherical or toriconical head, or conical transition, a Level 3 Assessment is required.

g.

The Level 2 Assessment procedure for components which do not have a design equation which specifically relates pressure (or liquid fill height for tanks) and/or other loads, as applicable, to a required wall thickness is limited to the components listed in Section 4, paragraph 4.2.3.1.g.

h.

The following limitations on applied loads must be satisfied when using the assessment procedures in this section. ·

Level 1 Assessment – components listed in Section 4, paragraph 4.2.3.1.f subject to internal pressure.

·

Level 2 Assessment – components listed in Section 4, paragraph 4.2.3.1.f subject to internal pressure; cylinders subject to internal pressure and/or supplemental loads (see Appendix A, paragraph A.2.6 ); components listed in Section 4, paragraph 4.2.3.1.g subject to internal and/or external pressure and/or supplemental loads.

A Level 3 Assessment can be performed when the Level 1 and/or 2 Assessment procedures do not apply, or when these assessment levels produce conservative results (i.e. would not permit operation at the current design conditions). Examples are provided in Section 4, paragraph 4.2.3.2. In addition, examples based on the specific rules and limitations of this section are shown below.


Not for Resale

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE 5-3 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

a.

The metal loss is located in the knuckle region of elliptical heads (outside of the 0.8D region), torispherical and toriconical heads, or in conical transitions.

b.

The component is subject to external pressure.

5.2.4

The assessment procedures in this section can be used to evaluate a region of local metal loss that is created when a crack-like flaw is removed by blend grinding.

5.3

Data Requirements

5.3.1

Original Equipment Design Data An overview of the original equipment data required for an assessment is provided in Section 2, paragraph 2.3.1. This data can be entered in the form provided in Section 2, Table 2.2, and Table 5.1 for each component under evaluation.

5.3.2

Maintenance And Operational History An overview of the maintenance and operational history required for an assessment is provided in Section 2, paragraph 2.3.2.

5.3.3


5.3.3.1

To assess general corrosion/erosion, thickness readings are required on the component in the area where the metal loss has occurred. If the metal loss is less than the specified corrosion/erosion allowance and adequate thickness is available for the future corrosion allowance, no further action is required other than to record the data.

5.3.3.2

The following information is required for a Level 1 and Level 2 Assessment. a.

Thickness Profiles – The region of local metal loss on the component should be identified and inspection planes should be established to record thickness data. Based on these inspection planes, Critical Thickness Profiles (CTP) and the minimum measured thickness, t mm , can be established for the flaw types shown below using the procedures in Section 4, paragraph 4.3.3.3. 1.

LTA – A grid should be established to obtain thickness readings and to establish the CTP in the meridional (longitudinal direction for a cylinder) and circumferential directions.

2.

b.

Groove-Like Flaw – For grove-like flaws oriented in the circumferential and longitudinal directions, a grid similar to that used for an LTA can be utilized. For all other groove-like flaw orientations, the inspection planes of the grid should be located parallel and perpendicular to the groove.

Flaw Dimensions – The following procedures can be used to establish the flaw dimensions.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

1.

LTA – The relevant dimensions are s and c (see Figure 5.2) which are defined as the longitudinal and circumferential dimensions, respectively, of the extent of the local metal loss based on the corresponding CTP. The CTP is determined using the procedure in Section 4, paragraph 4.3.3.3. Note that in the Level 1 and Level 2 Assessment procedures, the c parameter is defined as the current thickness (i.e. the nominal or furnished thickness minus the metal loss known at the time of the inspection) minus the future corrosion allowance.


Not for Resale


2.

Groove-Like Flaw – The relevant parameters are gl , g w , gr , and > the dimensions which define the length, width, radius and orientation of the groove-like flaw, respectively (see Figures 5.3 and 5.4). The flaw dimensions gl and g w are based on the

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

corresponding CTP measured parallel and normal to the groove. In the Level 1 and Level 2 Assessment procedures, the groove-like flaw is treated as an equivalent LTA with s = gl and c = g w . In a Level 2 Assessment, c is redefined as described in subparagraph (1) above. For cylinders and cones, if the groove is orientated at an angle to the longitudinal axis, then the groove-like flaw profile can be projected on to the longitudinal and circumferential planes using the following equations to establish the equivalent LTA dimensions (see Figure 5.4).

s = gl cos >

for > < 90 Degrees

(5.1)

c = gl sin >

for > < 90 Degrees

(5.2)

--``````-`-`,,`,,`,`,,`---

c.

Flaw-To-Major Structural Discontinuity Spacing – The distance to the nearest major structural discontinuity should be determined (see Figure 5.5).

d.

Vessel Geometry Data – The information required depends on the shell type as summarized in paragraphs 5.4.2 and 5.4.3 for a Level 1 and Level 2 Assessment, respectively.

e.

Materials Property Data – The information required are summarized in paragraphs 5.4.2 and 5.4.3 for a Level 1 and Level 2 Assessment, respectively.

5.3.3.3

The information required to perform a Level 3 Assessment is dependent on the analysis method utilized. In general, a limit load procedure using a numerical technique can be used to establish acceptable operating conditions. For this type of analysis, a description of the local metal loss including size and thickness profiles (similar to that required for a Level 2 Assessment) should be obtained along with the material yield strength (see paragraph 5.4.4).

5.3.4

Recommendations For Inspection Technique And Sizing Requirements

5.3.4.1

Recommendations for obtaining thickness measurements to characterize the local metal loss are covered in Section 4, paragraph 4.3.4.

5.3.4.2

The radius at the base of the groove-like flaw can be established by using a profile gauge. Alternatively, a mold can be made of the flaw using clay or a similar material and the radius can be directly determined from the mold.

5.3.4.3

In addition to thickness readings to establish the thickness profile, the following examination is recommended: a.

All weld seams within a “2s x 2c box” (see Figure 5.2), and the entire surface of the flaw should be examined using Magnetic Particle (MT) or Dye Penetrant (PT) techniques,

b.

Any portion of a weld seam within a “2s x 2c box” (see Figure 5.2), with a thickness less than the required thickness, t min , should be volumetrically examined with radiographic (RT) or ultrasonic (UT) techniques, and

c.

If crack-like flaws or porosity not meeting the acceptance criteria of the original construction code are found, they should be repaired or a Level 3 Assessment should be conducted.


Not for Resale

5.4


5.4.1

Overview

5.4.1.1

If the metal loss is less than the specified corrosion/erosion allowance and adequate thickness is available for the future corrosion allowance, no further action is required other than to record the data; otherwise, an assessment is required.

5.4.1.2

An overview of the assessment levels is provided in Figure 5.1. Level 1 Assessments are limited to components covered by a recognized code or standard which have a design equation which specifically relates pressure (or liquid fill height for tanks) to a required wall thickness. The only load considered is internal pressure, and a single thickness reading and one or two surface area dimensions are used to characterize the local metal loss. Level 2 Assessments can be used to evaluate components which do not satisfy Level 1 criteria. The Level 2 Assessment rules provide for a better estimate of the structural integrity of a component when significant variations in the thickness profile occur within the region of metal loss. More general loading is considered (e.g. net-section bending moments on a cylindrical shell), and rules are provided for the evaluation of local metal loss at a nozzle connection. Level 3 assessments can be used to evaluate components which are not covered or do not pass a Level 1 or Level 2 assessment. Level 3 Assessment rules are intended to evaluate more complex regions of localized corrosion/erosion, and/or components with details where only limited design rules are provided in the original construction code or standard. Detailed numerical stress analysis techniques are normally utilized in a Level 3 assessment.

5.4.2

Level 1 Assessment

5.4.2.1

The Level 1 Assessment procedures can be used to evaluate a component with local metal loss subject to internal pressure. The procedures can be used to determine acceptability and/or to rerate a component with a flaw. If there are significant thickness variations over the length of the flaw or if a network of flaws are closely spaced, this procedure may produce conservative results, and a Level 2 assessment is recommended.

5.4.2.2

The following assessment procedure can be used to evaluate components described in paragraph 5.2.3.1.f subject to the loads defined in paragraph 5.2.3.1.h. If the flaw is found to be unacceptable, the procedure can be used to establish a new MAWP or MFH. Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters:

D

FCA gr Lmsd

=

= = =

MAWP =

b.

MFH

=

RSFa

=

Inside diameter of the cylinder, cone (at the location of the flaw), sphere, or formed head; for the center section of an elliptical head an equivalent inside diameter of Kc Dc is used where Dc is the inside diameter of the head straight flange and Kc is a factor defined in Appendix A, paragraph A.3.6; for the center section of a torispherical head two times the crown radius of the spherical section is used (mm:in), Future Corrosion Allowance (mm:in), Radius at the base of a groove-like flaw (mm:in), Distance from the edge of the region of local metal loss under investigation to the nearest major structural discontinuity (mm:in), Maximum Allowable Working Pressure (see Appendix A, paragraph A.2), (MPa:psig), Maximum fill height of the tank, may be calculated (see Appendix A, paragraph A.2), (m:ft), and Allowable remaining strength factor (see Section 2, paragraph 2.4.2.2).



Not for Resale


--``````-`-`,,`,,`,`,,`---

a.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



d.

e.

Step 3 – Determine the minimum measured thickness, t mm , the remaining thickness ratio, using Equation (5.3), the flaw dimension, s , (see paragraph 5.3.3.2.b), and the shell parameter, l , using Equation (5.4).

Rt ,

Rt =

t mm - FCA t min

(5.3)

l=

1285 . s Dt min

(5.4)

Step 4 – Check the limiting flaw size criteria; if the following requirements are satisfied, proceed to Step 5; otherwise, the flaw is not acceptable per the Level 1 Assessment procedure.

Rt ³ 0.20

(5.5)

t mm - FCA ³ 2.5 mm (010 . inches)

(5.6)

Lmsd ³ 18 . Dt min

(5.7)

Step 5 – If the region of metal loss is categorized as an LTA (a groove or gouge is not present in the LTA), then proceed to Step 6; otherwise, check the following criteria for a groove-like flaw (see Figure 5.3). 1.

Step 5.1 – Compute the critical groove radius,

grc , using the following equation:

grc = max 0.25t min , 6.4 mm (0.25 inches) 2.

(5.8)

Step 5.2 – If both of the following equations are satisfied, then proceed to Step 5.3; otherwise, proceed to Step 5.7.

gr ³ grc

(5.9)

gr . ³ 10 1 - Rt t min

b

g

(5.10)

3.

Step 5.3 – If the flaw is categorized as a groove, then proceed to Step 5.6. Otherwise, characterize the flaw as a gouge and determine the Critical Exposure Temperature, CET, based on operating and design conditions (see Section 3, paragraph 3.1.3).

4.

Step 5.4 – Determine the allowable temperature, MAT , using Section 3, Figure 3.3. The thickness of the plate containing the gouge and the material specification must be known to utilize this figure (if the material specification is not known, Curve A of Figure 3.3 should be used). For example, for a 25.4 mm (1 inch) thick plate of SA 285 Grade B material (Curve B material based on the information in Section 3, Table 3.3),

c

h

MAT = -1o C 30o F .


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

c.

5.

Step 5.5 – If

c

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


h

CET ³ MAT + 14 oC MAT + 25 oF , then proceed to Step 5.6;

otherwise, proceed to Step 5.7.

f.

6.

Step 5.6 – Proceed to Step 6 (Level 1 or Level 2 Assessment procedure, as applicable) and complete the assessment.

7.

Step 5.7 – The groove-like flaw is not acceptable per the Level 1 Assessment procedure. Alternatively, the groove-like flaw may be re-evaluated as an equivalent crack-like flaw using the Section 9 Level 1 Assessment criteria. In this evaluation, the maximum depth and length of the groove-like flaw should be used to determine the equivalent crack-like flaw.

Step 6 – Enter Figure 5.6 with the calculated values of l and Rt . If the point defined by the intersection of these values is on or above and to the left of the curve, then the longitudinal extent (circumferential or meridional extent for spherical shells and formed heads) of the flaw is acceptable per Level 1. If the point is unacceptable, then the component can be rerated using the equations in Section 2, paragraph 2.4.2.2 with the remaining strength factor computed as shown below, or the recommendations provided in paragraph 5.4.2.3. can be used. If the component is a cylindrical, conical shell or elbow, then proceed to Step 7 to evaluate the circumferential extent of the flaw. Otherwise, the assessment is complete.

RSF =

Rt

b

1 11 - Rt Mt

(5.11)

g

where,

c

M t = 1 + 0.48l2 g.

0.5

(5.12)

Step 7 – For cylindrical and conical shells, evaluate the circumferential extent of the flaw using Figure 5.7. To evaluate the circumferential extent of the flaw, enter Figure 5.7 with the calculated values of c D and Rt . If the point defined by the intersection of these values is on or above the curve in this figure, then the circumferential extent of the flaw is acceptable; otherwise, the circumferential extent of the flaw is unacceptable.



b.

Adjust the FCA by applying remediation techniques (see Section 4, paragraph 4.6).

c.

Adjust the weld joint efficiency factor, E, by conducting additional examination and repeat the assessment (see Section 4, paragraph 4.4.2.2.c).

d.


5.4.3

Level 2 Assessment

5.4.3.1

The assessment procedures in Level 2 provide a better estimate of the Remaining Strength Factor than computed in Level 1 for local metal loss in a component subject to internal pressure loading if there are significant variations in the thickness profile. These procedures account for the local reinforcement effects of the varying wall thickness in the region of the local metal loss and ensure


Not for Resale

--``````-`-`,,`,,`,`,,`---

5.4.2.3

h

5-8 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

5.4.3.2

that the weakest ligament is identified and properly evaluated. The procedures can also be directly used to evaluate closely spaced regions of local metal loss, and to evaluate cylindrical and conical shells with supplemental loads. The following assessment procedure can be used to evaluate components described in paragraph 5.2.3.1.f subject to the loads defined in paragraph 5.2.3.1.h. If the flaw is found to be unacceptable, the procedure can be used to establish a new MAWP or MFH. a.

Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the parameters in paragraph 5.4.2.2.a.

b.

Step 2 – Calculate the minimum required thickness, supplemental loads,

c.

t min including the thickness required for

t sl (see Appendix A, paragraph A.2).

Step 3 – Determine the minimum measured thickness,

t mm , the remaining thickness ratio, Rt ,

using Equation (5.3), the flaw dimensions s and c (see paragraph 5.3.3.2), and the shell parameter, l , using Equation (5.4). d.

Step 4 – Check the limiting flaw size criteria in paragraph 5.4.2.2.d. In addition, the length of the flaw must satisfy the relationship: l £ 5.0 . If all of these requirements are satisfied, then proceed to Step 5; otherwise, the flaw is not acceptable per the Level 2 Assessment procedure.

e.

Step 5 – If the region of metal loss is categorized as an LTA (a groove or gouge is not present in the LTA), then proceed to Step 6; otherwise, check the groove-like flaw criteria in paragraph 5.4.2.2.e to continue the assessment.

f.

Step 6 – Determine the Remaining Strength Factor for the longitudinal CTP. If there are significant variations in the thickness profile, then the following procedure can be used to compute a less conservative value for the RSF when compared to the procedures of Level 1. 1.

Step 6.1 – Rank the thickness readings in ascending order based on metal loss.

2.

Step 6.2 – Set the initial evaluation starting point as the location of maximum metal loss, this is the location in the thickness profile where t mm is recorded. Subsequent starting points should be in accordance with the ranking in Step 6.1.

3.

Step 6.3 – At the current evaluation starting point, subdivide the thickness profile into a series of subsections (see Figure 5.8). The number and extent of the subsections should be chosen based on the desired accuracy and should encompass the variations in metal loss.

4.

Step 6.4 – For each subsection, compute the Remaining Strength Factor using the following equation. Alternatively, the Remaining Strength Factor can be computed using the equations in Appendix D, paragraph D.2.3.3 where RSF

FG A IJ HA K = 1 FAI 1G J M HA K

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

RSF

i o

h

i

(5.13)

i

i t


c

= 10 . M sNS .

i

1-

i

i

i o

Not for Resale


with,

Aoi = si t min

(5.14)

F 102 . + 0.4411cl h + 0.006124cl h I =G J GH 10. + 0.02642cl h + 1533 . (10 )cl h JK i 2

M ti

i 2

i 4

0.5

for cylindrical

i 4

-6

(5.15)

shells M ti =

c h c h 10 . + 0.50144cl h - 0.011067cl h

10005 + 0.49001 li + 0.32409 li .

i 2

i

2

for spherical shells

(5.16)

and formed heads where, =

Aoi = M ti =

Area of metal loss based on 2 2 5.8), (mm :in ), Original metal area based on

si including the effect of FCA (see Figure si , (mm2:in2),

Folias factor (see Appendix D, paragraph D.2.3) for a through-wall flaw computed using Equation (5.15) or (5.16), as applicable, with

si li

g.

=

Length increment of metal loss (see Figure 5.8), (mm:in), and

=

Shell parameter computed using Equation (5.4) with

l = li ,

s = si . //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Ai

i

5.

Step 6.5 – Determine the minimum value of the Remaining Strength Factors, RSF , found in Step 6.4 for all subsections (see Figure 5.8). This is the minimum value of the Remaining Strength Factor for the current evaluation point.

6.

Step 6.6 – Repeat Steps 6.3 through 6.5 of this calculation for the next evaluation point which corresponds to the next thickness reading location in the ranked thickness profile list.

7.

Step 6.7 – The Remaining Strength Factor to be used in the assessment, RSF, is the minimum value determined for all evaluation points.

Step 7 – Evaluate the longitudinal extent (circumferential or meridional extent for spherical shells and formed heads) of the flaw. If RSF ³ RSFa , then the region of local metal loss is acceptable per Level 2. If RSF < RSFa , then the component can be rerated using the equations in Section 2, paragraph 2.4.2.2.

5.4.3.3

Step 8 – For cylindrical and conical shells, evaluate the circumferential extent of the flaw using the following criteria. If supplemental loads are not present or are not significant, then circumferential dimension, c , of the flaw determined from the circumferential CTP should satisfy the criterion in paragraph 5.4.2.2.g. If the supplemental loads are significant, then the circumferential extent of the region of local metal loss shall be evaluated using the procedures in paragraph 5.4.3.3.

The assessment procedure in this paragraph can be used to determine the acceptability of the circumferential extent of a flaw in a cylindrical or conical shell subject to pressure and/or supplemental loads. Note that the acceptability of the longitudinal extent of the flaw is evaluated using paragraph 5.4.3.2.


Not for Resale

--``````-`-`,,`,,`,`,,`---

h.


a.

Supplemental Loads – These types of loads may result in a net section axial force, bending moment, torsion and shear being applied to the cross section of the cylinder containing the flaw (see Appendix A, paragraph A.2.6). Supplemental loads will result in longitudinal membrane, bending, and shear stresses acting on the flaw, in addition to the longitudinal and circumferential (hoop) membrane stress caused by pressure. 1.

The supplemental loads included in the assessment should include loads which produce both load-controlled and strain-controlled effects. Therefore, the net section axial force, bending moment, torsion, and shear should be computed for two load cases; weight and weight plus thermal. The weight load case includes pressure effects, weight of the component, occasional loads from wind or earthquake, and other loads which are considered as load controlled. The weight plus thermal load case includes the results from the weight case plus the results from a thermal case which includes the effects of temperature, support displacements and other loads which are considered as straincontrolled

2.

For situations where the results of a detailed stress analysis are unavailable, the following modification may be made to the procedure in subparagraph c. a)

Calculate the longitudinal stress due to pressure and designate this value as Slp .

b)

Subtract Slp from the allowable stress for load-controlled effects,

--``````-`-`,,`,,`,`,,`---

allowable stress for strain-controlled effects, c)

Sas .

Multiply each of the resulting stress values obtained in subparagraph b) above by the section modulus of the pipe in the uncorroded condition to obtain the maximum allowable load-controlled bending moment, M al , and the straincontrolled bending moment,

d)

Sal , and the

M as .

A I lm , for the two load cases using Equation (5.51) by setting the axial force term, F , to zero and substituting M al for both M x and M y to obtain the maximum load-controlled longitudinal stress, and M as for both M x and M y to obtain the maximum strain-controlled

Calculate the longitudinal stress at point A,

longitudinal stress. e)

B I lm , for the two load cases using Equation (5.51) by setting the axial force term, F , to zero and substituting M al for both M x and M y to obtain the maximum load-controlled longitudinal stress, and M as for both M x and M y to obtain the maximum strain-controlled

Calculate the longitudinal stress at point B,

longitudinal stress. f)

Proceed with Step 5.3 to evaluate the load-controlled and strain-controlled load cases values of

g) b.

A B I lm and I lm .

When evaluating the results in Step 6, set the shear stress,

J , to zero.

Special Requirements For Piping Systems – Should be considered because of the relationship between the component thickness, piping flexibility or stiffness, and the resulting stress.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~

1.


The forces and moments acting on the circumferential plane of the defect resulting from supplemental loads can be computed from a piping stress analysis. The model used in

Not for Resale


this analysis should take into account the effects of metal loss. Recommendations for modeling of piping components is provided in Section 4, paragraph 4.4.3.3 c.3. Alternatively, a maximum value of the moments can be computed using the procedure in paragraph 5.4.3.3.a.2. 2.

c.

Special consideration may be required if the local metal loss is located at an elbow or pipe bend (see Section 4, paragraph 4.4.4.4). A Level 3 Assessment using a detailed stress analysis performed using shell or continuum elements may be required in some cases.

Assessment Procedure – If the metal loss in the circumferential plane can be approximated by a single area (see Figure 5.9), then the following procedure can be used to evaluate the permissible membrane, bending and shear stresses resulting from pressure and supplemental loads. If the metal loss in the circumferential plane is composed of several distinct regions, then a conservative approach is to define a continuous region of local metal loss which encompasses all of these regions (as an alternative, see subparagraph d below). 1.

Step 1 – Determine the Critical Thickness Profiles(s) in the circumferential direction (see paragraph 5.3.3.2) and the following parameters:

c

=

Di

=

Do

=

FCA = t mm = I ys 2.

=

Circumferential extent of the flaw (see Figure 5.9); the circumferential length of the flaw is based on a region of local metal loss with a thickness less than the current thickness t minus FCA (see Figure 5.9 where t is typically the nominal thickness minus the metal loss) (mm:in), Inside diameter of the cylinder, corrected for metal loss and future corrosion allowance (mm:in), Outside diameter of the cylinder, corrected for metal loss and future corrosion allowance (mm:in), Future corrosion allowance applied to the region of local metal loss (mm:in), Minimum measured wall thickness determined from the Critical Thickness Profiles (mm:in), and Specified minimum yield stress (see Appendix F), (MPa:psi).

Step 2 – For the circumferential inspection plane being evaluated, approximate the circumferential extent of metal loss on the plane under evaluation as a rectangular shape (see Figure 5.9).

--``````-`-`,,`,,`,`,,`---

For a region of local metal loss located on the inside surface,

b

g

D f = Do - 2 t mm - FCA

(5.17)

and for a region of local metal loss located on the outside surface:

g

(5.18)

The circumferential angular extent of the region of local metal loss is:

G= 3.


FG IJ H K

c 180 Df F

(G in Degrees)

(5.19)

Step 3 – Determine the remaining strength factor, RSF, the maximum allowable working pressure, MAWPr, and supplemental loads on the circumferential plane. The remaining strength factor and maximum permissible pressure for the region of local metal loss can

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b

D f = Di + 2 t mm - FCA


be established using the procedures in paragraph 5.4.3.2. The supplemental loads are determined in accordance with paragraphs 5.4.3.3.a and 5.4.3.3.b. 4.

Step 4 – For the supplemental loads determined in Step 3, compute the components of the resultant longitudinal bending moment (i.e. excluding torsion) in the plane of the defect relative to the region of metal loss as shown in Figure 5.9. This will need to be done for both the weight and weight plus thermal load cases.

5.

Step 5 – Compute the maximum section longitudinal membrane stress for both the weight and weight plus thermal load cases at the centerline of the circumferential extent of the region of local metal loss (point A in Figure 5.10). a)

Step 5.1 – Compute the section properties of a cylinder without a region of local metal loss.

Aa =

F 2 Di 4

Am =

F 2 Do - Di2 4

(5.20)

c

IX = Iy =

h

(5.21)

F Do4 - Di4 64

c

h

(5.22)

where, variables have been previously defined, and

Aa Am IX IY --``````-`-`,,`,,`,`,,`---

b)

2

Cylinder aperture cross-section, (mm :in ),

=

Cylinder metal cross-section, (mm :in ),

=

Cylinder moment of inertia, (mm :in ), and

=

Cylinder moment of inertia, (mm :in ).

2

2

4

4

4

4

Step 5.2 – Compute the section properties of a cylinder with a region of local metal loss. For a region of local metal loss located on the inside surface:

Af =

G 2 D f - Di2 4

d

i

(5.23)

Aw = Aa + A f

d

(5.24)

3 3 1 sinG D f - Di y= 12 Am - A f

i

x A = 0.0 yA = y + xB =


2

=

(5.25)

(5.26)

Do 2

(5.27)

Do sin G 2

(5.28)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Do cosG 2

yB = y +

(5.29)

d

3 3 1 sinG D f - Di b= 12 Aa + A f

Df

R=

d=

i

(5.31)

2

dD

- Di

f

i

(5.32)

2

Atf =

(5.30)

d

c Do + D f

i

(5.33)

8

For a region of local metal loss located on the outside surface:

Af =

G 2 Do - D 2f 4

d

i

(5.34)

Aw = Aa y=

(5.35)

d

3 3 1 sinG Do - D f Am - A f 12

i

--``````-`-`,,`,,`,`,,`---

x A = 0.0

(5.37)

yA = y + Df

xB =

2

yB = y +

Df

(5.38)

2 sinG Df

(5.39)

cosG

2

b=0 R=

d=


(5.36)

(5.40) (5.41)

Do 2

(5.42)

dD - D i o

f

(5.43)

2

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Atf =

d

c Di + D f

i

(5.44)

8

with,

IJ (5.45) K LMFG1 - 3d + d - d IJ FGG + sinG cosG - 2 sin G IJ +OP G K P H 2R R 4R K H = R dM MM d sin G F d d I PP (5.46) MN 3R G b2 - d Rg GH1 - R + 6R JK PQ = I + A y - I - A b y + yg (5.47) LF 3d + d - d IJ bG - sin G cosG gOP (5.48) = R d MG 1 Q NH 2 R R 4 R K

y LX =

FG H

2 R sinG d 1 1- + 3G R 2-d R 2

3

2

I LX

2

3

3

2

2

2

2

IX

I LY

2

2

2

X

m

LX

f

2

3

2

LX

3

3

I Y = I Y - I LY

b

(5.49)

g b

0.5F Di + Do - c Di + Do

At =

g

(5.50)

8

where variables have been previously defined and,

Af =

Cross-sectional area of the region of local metal loss, (the

At

unshaded area labeled “Local Metal Loss” in Figure 5.10), 2 2 (mm :in ), Mean area to compute torsion stress for the region of the cross 2 2 section without metal loss (mm :in ), Mean area to compute torsion stress for the region of the cross

Atf =

2

Aw = b =

d = Df =

Location of the centroid of area Aw, measured from the x - x axis (mm:in), Circumferential extent of the region of local metal loss (see Figure 5.9) (mm:in), Maximum depth of the region of local metal loss (mm:in), Diameter at the base of the region of local metal loss (see Figure

IX =

5.10) (mm:in), Moment of inertia of inertia of the cross section with the region of

IY

local metal loss about the x -axis (see Figure 5.10) (mm :in ), Moment of inertia of inertia of the cross section with the region of

c

=

=

4

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:

local metal loss about the


2

section with metal loss, (mm :in ), 2 2 Effective area on which pressure acts, (mm :in ),

Not for Resale

4

y -axis (see Figure 5.10) (mm4:in4),

--``````-`-`,,`,,`,`,,`---

=


Moment of inertia of area Af about a local x-axis (see Figure 4 4 5.10) (mm :in ), Moment of inertia of area Af about the y-axis (see Figure 5.10) 4 4 (mm :in ), Outside radius of area Af (mm:in), Distance along the x-axis to Point A on the cross section shown in Figure 5.10 (mm:in), Distance along the x-axis to Point B on the cross section shown in Figure 5.10 (mm:in), Distance from the x - x axis measured along the y-axis to Point A on the cross section shown in Figure 5.10 (mm:in), Distance from the x - x axis measured along the y-axis to Point B on the cross section shown in Figure 5.10 (mm:in), Location of the neutral axis (see Figure 5.10) (mm:in),

I LX = I LY =

R = xA = xB = yA = yB =

y = y LX = G

=

Step 5.3 – Compute the maximum section longitudinal membrane stress for both the weight and weight plus thermal load cases considering points A and B in the cross section (see Figure 5.10):

b

g

F Aw + MAWPr + Am - A f Am - A f

A = I lm

yA IX

b gb

g

x y + b MAWPr Aw + M x + A M y IY

b

g

F Aw + MAWPr + Am - A f Am - A f

B = I lm

yB IX

(5.51)

b gb

g

x y + b MAWPr Aw + M x + B M y IY

A B I lm = max I lm , I lm

(5.52)

(5.53)


F

=

Mx =

My = I lm = 6.

Applied section axial force determined in Step 3 for the weight or weight plus thermal load case (see paragraph 319.2.3(c ) of ASME B31.3), as applicable (N:lbs), Applied section bending moment determined in Step 4 for the weight or weight plus thermal load case about the x-axis (see Figure 5.10), as applicable (N-mm:in-lbs), Applied section bending moment determined in Step 4 for the weight or weight plus thermal load case about the y-axis (see Figure 5.10), as applicable (N-mm:in-lbs), and Maximum longitudinal membrane stress, computed for both the weight and weight plus thermal load cases (MPa:psi).

Step 6 – Evaluate the results as follows: --``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

c.

Distance from the centroid of Af to the x-axis (see Figure 5.10) 4 4 (mm :in ), and Angle describing extent of the region of local metal loss on the cross section (see Figure 5.9 and Figure 5.10), radians.


a)

The following relationship should be satisfied for either a tensile and compressive longitudinal stress for both the weight and weight plus thermal load cases:

I 2cm - I cmI lm + I 2lm + 3J 2 £ HI ys

(5.54)

with,

I cm =

J=

FG H

IJ K

MAWPr Di + 0.6 E L × RSF Do - Di

MT V + 2 At + Atf d Am - A f

d

(5.55)

(5.56)

i


EL H MAWPr MT

RSF V I cm I lm

I ys J

--``````-`-`,,`,,`,`,,`---

b)

7.

d.

= Longitudinal weld joint efficiency, = Allowable stress factor depending on the load case being evaluated; use 0.75 for the weight case and 1.5 for the weight plus thermal load case (N-mm:in-lbs), = Maximum allowable working pressure computed per paragraph 5.4.3.2 (MPa:psi), = Applied net-section torsion determined in Step 3 for the weight or weight plus thermal load case, as applicable (Nmm:in-lbs), = Computed Remaining Strength determined in Step 3, = Applied net-section shear force determined in Step 3 for the weight or weight plus thermal load case, as applicable (N:lbs), = Maximum circumferential stress, typically the hoop stress from pressure loading for the weight and weight plus thermal load case, as applicable (MPa:psi), = Maximum longitudinal membrane stress computed for both the weight and weight plus thermal load cases (MPa:psi), = Yield stress (see Appendix F), (MPa:psi), and = Maximum shear stress in the region of local metal loss for the weight and weight plus thermal load case, as applicable (MPa:psi).

If the maximum longitudinal stress computed in Step 5 is compressive, then this stress should be less than or equal to the allowable compressive stress computed using the methodology in Appendix A, paragraph B.4.4 or the allowable tensile stress, whichever is smaller. When using this methodology to establish an allowable compressive stress, an average thickness representative of the region of local metal loss in the compressive stress zone should be used in the calculations.

Step 7 – If the longitudinal membrane stress computed in Step 5 does not satisfy the requirements of Step 6, then the MAWP and/or supplemental loads determined in Step 3 should be reduced, and the evaluation outlined in Steps 2 through 5 should be repeated. Alternatively, an analysis using subparagraph d below or a Level 3 Assessment can be performed.

Alternate Assessment Procedures – if the metal loss in the circumferential plane cannot adequately be approximated by a single area (see Figure 5.9) because of irregularities in the


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


thickness profile and/or extent of the local metal loss in the circumferential direction, then a numerical procedure may be used to compute the section properties and the membrane and bending stresses resulting from pressure and supplemental loads. The acceptance criteria for the stress results should be established using Step 6 in paragraph 5.4.3.3.c. 5.4.3.4

The assessment procedure in Section 4, paragraph 4.4.3.3 can be used to evaluate components described in paragraph 5.2.3.1.g subject to the loads defined in paragraph 5.2.3.1.h.

5.4.3.5

If the component does not meet the Level 2 Assessment requirements, then the following, or combinations thereof, can be considered:

5.4.4

a.


b.


c.


d.


Level 3 Assessment The recommendations for a Level 3 Assessment of local metal loss are the same as those for general metal loss (see Section 4, paragraph 4.4.4).

5.5


5.5.1

Thickness Approach

5.5.1.1

The remaining life of a component with a region of local metal loss can be estimated using a Level 1 assessment procedure based upon computation of a minimum required thickness for the intended service conditions, actual thickness and region size measurements from an inspection, and an estimate of the anticipated corrosion/erosion rate and rate of change of the size of the flaw. If this information is known, or can be estimated, the equations in paragraph 5.4.2.2 or 5.4.3.2 can be solved iteratively with the following substitutions to determine the remaining life:

RSF ® RSFa

t mm - (Crate × time) t min

(5.58)

for a LTA or groove-like flaw evaluated as an equivalent LTA; s s ® s + Crate × time

(5.59)

c c ® c + Crate × time

(5.60)

where,

Crate

=

anticipated future corrosion rate (mm/year:in/year),

s rate

=

Estimated rate of change of the meridional length of the region of local metal loss (mm/year:in/year),

C


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Rt ®

(5.57)

5-18 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

c Crate

=

c

=

RSF RSFa Rt s

= =

t min

=

t mm

=

time

=

= =

Estimated rate of change of the circumferential length of the region of local metal loss (mm/year:in/year), Circumferential length of the region of local metal loss at the time of the inspection (mm:in), Computed remaining strength factor, Allowable remaining strength factor (see Section 2), Remaining thickness ratio, Longitudinal length of the region of local metal loss at the time of the inspection (mm:in), the minimum required thickness for the component which governs the MAWP

(MFH) calculation ( see Appendix A), (mm:in). the minimum remaining thickness determined at the time of the inspection (mm:in), and Time in the future (years).

5.5.1.2

The rate-of-change in the size or characteristic length of a region of local metal loss can be estimated based upon inspection records. If this information is not available, engineering judgment should be applied to determine the sensitivity of this parameter on the remaining life of the component.

5.5.1.3

The remaining life determined using the thickness based approach can only be utilized if the region of local metal loss is characterized by a single thickness. If a thickness profile is utilized (Level 2 assessment procedure), the remaining life should be established using the MAWP Approach.

5.5.2

MAWP Approach

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The MAWP approach can be used to determine the remaining life of a pressurized component with a region of local metal loss characterized by a thickness profile. To use this approach, the methodology in Section 4, paragraph 4.5.2.2 is applied in conjunction with the assessment methods of this section. When determining a remaining life with the MAWP approach, the change in the flaw size should be considered as discussed in paragraph 5.5.1. 5.6

Remediation The remediation methods for general corrosion provided in Section 4, paragraph 4.6 are applicable to locally thin areas. Because of the localized damage pattern, it may be necessary in some cases to fill deep areas of metal loss with substances such as caulking, before applying linings.

5.7

In-Service monitoring The remaining life may be difficult to establish for some regions of local metal loss in services where an estimate of the future metal loss and enlargement cannot be adequately characterized. In these circumstances, remediation and/or in-service monitoring may be required to qualify the assumptions made to establish the remaining life. Typical monitoring methods and procedures are provided in Section 4, paragraph 4.7.

5.8

Documentation

5.8.1

The documentation of the FFS assessment should include the information cited in Section 2, paragraph 2.8.

5.8.2

Inspection data including all thickness readings and corresponding locations used to determine the minimum average measured thickness, tam , and the minimum measured thickness, t mm , should be recorded and included in the documentation. A sample data sheet is provided in Table 5.1 for this


Not for Resale


References

5.9.1

Bubenik, T.A., Olsen, R.J., Stephens, D.R. and Francini, R.B., “Analyzing the Pressure Strength of Corroded Line Pipe,” Offshore Mechanics and Arctic Engineering Symposium, OMAE Volume V-A, Pipeline Technology, American Society of Mechanical Engineers, pp. 225-231, 1992.

5.9.2

Bubenik, T.,A., Rosenfeld, M.,J., “Assessing the Strength of Corroded Elbows,” NG-18 Report No. 206, Pipeline Research Committee of the American Gas Association, 1993.

5.9.3

Chouchaoui, B.A., Pick, R.J., “A Three Level Assessment of the Residual Strength of Corroded Line Pipe,” Offshore Mechanics and Arctic Engineering Symposium, OMAE Volume V, Pipeline Technology, American Society of Mechanical Engineers, pp 9-18, 1994.

5.9.4

Eiber, ER.J., Maxey, W.A., Duffy, A.R. and Atterbury, T.J., “Investigation Of The Initiation And Extent Of Ductile Pipe Rupture,” BMI-1908, Battelle Columbus Laboratories, Ohio, 1971.

5.9.5

Folias, E.S., “On the Effect of Initial Curvature on Cracked Flat Sheets,” International Journal of Fracture Mechanics, Vol. 5, No. 4, December 1969, pp. 327-346.

5.9.6

Hantz, B.F., Sims, J.R., Kenyon, C.T., Turbak, T.A., “Fitness For Service: Groove Like Local Thin Areas on Pressure Vessels and Storage Tanks,” ASME PVP-Vol. 252, American Society of Mechanical Engineers, New York, 1992.

5.9.7

Herter, K.H., Julisch, P., Stoppler, W. and Sturm, D., “Behavior of Pipes Under Internal Pressure and External Bending Moment – Comparison between Experiment and Calculation,” Fracture Mechanics Verification by Large-Scale Testing, EGF/E5158, Edited by K. Kussmaul, Mechanical Engineering Publications, London, 1991, pp. 223-241.

5.9.8

Kastner, W., Rehrich, E., Schmitt, W. and Steinbuch, R., “Critical Crack Sizes in Ductile Piping,” International Journal of Pressure Vessels & Piping, 9, 1981, pp. 197-219.

5.9.9

Kiefner, J.F., Maxey, W.A., Eiber, R.J., and Duffy, A.R., “Failure Stress Levels Of Flaws In Pressurized Cylinders,” ASTM STP 536, American Society for Testing and Materials, 1973, pp. 461481.

5.9.10

Kiefner, J.F. and Vieth, P.H., “A Modified Criterion for Evaluating the Remaining Strength of Corroded Pipe,” RPC International Catalog No. L51609, 1989.

5.9.11

Leggatt, R.H., Hodgson, A.P., Hayes, B. and Chan, S.W.K., “Safety Factors In Flaw Assessment of Girth Welds,” For the American Gas Association, Contract No: PR 164 509, The Welding Institute, 1988.

5.9.12

Maxey, W.A., Kiefner, J.F., Eiber, R.J., and Duffy, A.R., “Ductile Fracture Initiation, Propagation, and Arrest In Cylindrical Shells,” ASTM STP 514, American Society for Testing and Materials, 1972, pp. 70-81.

5.9.13

Sims, J.R., Hantz, B.F., Kuehn, K.E., “A Basis for the Fitness For Service Evaluation of Thin Areas in Pressure Vessels and Storage Tanks,” ASME PVP-Vol 233, American Society of Mechanical Engineers, New York, 1992.

5.9.14

Stephens, D.R., Bubenik, T.,A., Francini, R.,B., “Residual Strength of Pipeline Corrosion Defects Under Combined Pressure and Axial Loads,” NG-18 Report No. 216, Pipeline Research Committee of the American Gas Association, 1995.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

5.9

--``````-`-`,,`,,`,`,,`---

purpose. A sketch showing the location and orientation of the inspection planes on the component is also recommended.

5.9.15

Stephens, D.R., Krishnaswamy, P, Mohan, R., Osage, D.A. and Wilkowski, G., “A Review of Analysis Methods and Acceptance Criteria for Local Thinned Areas in Piping and Piping Components,” 1997 Pressure Vessels and Piping Conference, Orlando, Florida, July, 1997.

5.9.16

Strum, D., Stoppler, W. and Schiedermaier, “The Behavior Of Dynamically Loaded Pipes With Circumferential Flaws Under Internal Pressure and External Bending Loads,” Nuclear Engineering and Design, 96, 1986, pp. 99-113.

5.9.17

Rosenfeld, M.J., Vieth, P.H. and Haupt, R.W., “A Proposed Corrosion Assessment Method And InService Safety Factors For Process And Power Piping Facilities,” PVP-Vol. 353, ASME, pp. 395-405, 1997.

5.9.18

Rosenfeld, M.J., “Serviceability Of Corroded Girth Welds,” RPC International, Catalog No. L 51742, 1996.

5.9.19

Turbak, T.A. and Sims, J.R., “Comparison of Local Thin Area Assessment Methodologies,” ASME PVP-Vol. 288, American Society of Mechanical Engineers, New York, 1994, pp. 307-314.

5.9.20

Turbak, T.A. and Sims, J.R., “Fitness-For-Service Local Thin Areas Comparison Of Finite Element Results To Physical Test Results,” ASME PVP-Vol. 315, American Society of Mechanical Engineers, New York, 1995, pp. 285-292.

5.9.21

Vieth, V.H. and Kiefner, J.F., “RSTRENG2 User’s Manual”, RPC International Catalog No. L51688, 1993.

5.9.22

Vieth, V.H. and Kiefner, J.F., “Database Of Corroded Pipe Tests”, RPC International Catalog No. L51689, 1993.

5.9.23

Wang, K.C. and Smith, E.D., “The Effect Of Mechanical Damage On Fracture Initiation In Linepipe Part II – Gouges,” Metals Technology Laboratories, Report MTL 88-16(TR), March, 1988.

5.9.24

Wilkowski, G.M. and Scott, P.M., “A Statistical Based Circumferentially Cracked Pipe Fracture Mechanics Analysis For Design Or Code Implementation,” Nuclear Engineering and Design, 111, 1989, pp. 173-187.

5.9.25

Willoughby, A.A., “A Survey of Plastic Collapse Solutions Used in the Failure Assessment of Part Wall Defects,” The Welding Institute, 1982. Tables and Figures //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

5.10

--``````-`-`,,`,,`,`,,`---



Not for Resale


Table 5.1 Data Required For The Assessment Of Local Metal Loss Use this form to summarize the data obtained from a field inspection. Equipment Identification: Equipment Type: _____ Pressure Vessel Component Type & Location:

_____ Storage Tank


Data Required For A Level 1 And Level 2 Assessment Future Corrosion Allowance: Inside Diameter: Minimum Required Thickness: Minimum Measured Wall Thickness: LTA Dimensions ( s & c) : Groove-Like Flaw Dimensions

( gl , g r , g w & > ) :

Additional Data Required For A Level 2 Assessment Distance to the Nearest LTA ( Llta ) : Distance to the Nearest Structural Discontinuity ( Lmsd ) : The thickness data for each of the inspection planes may be entered in a table as shown below. Inspection Plane:__ Location

Thickness

tmm

Inspection Plane:__ Location

Thickness

tmm


Thickness

tmm

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


tmm

Thickness

--``````-`-`,,`,,`,`,,`---

Figure 5.1 Overview Of The Assessment Procedures To Evaluate A Component With Local Metal Loss



No

Yes

Yes

Yes


Rerate Equipment?


No

Yes

No

Yes


Equipment is Acceptable per Level 2 Criteria?

Rerate Equipment?

No

Yes

Yes


Yes


No

No


Not for Resale


No

Yes



No

5-22 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Remaining Life Acceptable per Level 3 Critiera?

No


Yes

Yes

No

Rerate Equipment?

Yes



No


Figure 5.2 LTA Flaw Dimensions

Shell

2s

Longitudinal Weld Seam

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

s

2c

c

Locally Thin Area (LTA) Or Groove-Like Flaw --``````-`-`,,`,,`,`,,`---

Area Subject to Inspection (2s x 2c box)

Notes: 1. s - Longitudinal dimension of the Flaw. 2. c - Circumferential dimensions of the Flaw. 3. See Section 4, paragraph 4.3.3.3 for the procedure to determine s and c .


Not for Resale


Figure 5.3 Groove-Like Flaw Dimensions – Flaw Profile

A

gl

B

B

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A (a) Groove-Like Flaw -- Plan View gl

t

tmin

(b) Groove-Like Flaw Length -- Section A-A gw gr tmin

tmm (c) Groove-Like Flaw Width -- Section B-B

--``````-`-`,,`,,`,`,,`---


Not for Resale

t


Figure 5.4 Groove-Like Flaw Dimensions – Flaw Orientation On A Cylindrical Shell

F

M CL Circumferential Orientation P

Cylindrical Shell or Pipe

s=gl

Axial Orientation

--``````-`-`,,`,,`,`,,`---

c=gw

gl s

> Arbitrary Orientation at Angle b (b < 90°)

c c

s

CL M

F


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

s=gl

c=gc


Figure 5.5 Procedure to Determine Lmsd

Stiffening Ring

--``````-`-`,,`,,`,`,,`---

L1msd Nozzle L4msd Flaw L2msd

Pipe Support

L3msd

Conical Transition

Notes: 1. For the example shown above, the minimum distance to a major structural discontinuity is:

Lmsd = min L1msd , L2msd , L3msd , L4msd 2. Typical major structural discontinues associated with vertical vessels are shown in this figure. For horizontal drums, the saddles supports would constitute a major structural discontinuity and for a spherical storage vessel, the support locations (shell-to-leg junction) would constitute a major structural discontinuity. The location of the flaw from these support locations would need to be considered in determining Lmsd as well as the distances from the nearest nozzle, piping/platform support, conical transition, and stiffening ring. 3. The measure of the minimum distances defined in this figure is from the nearest edge of the region of local metal loss to the nearest weld of the structural discontinuity.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 5.6 Level 1 Screening Criteria For Local Metal Loss In A Shell

1.0

ACCEPTABLE

0.9 0.8 0.7 0.6

Rt

0.5

UNACCEPTABLE

0.4 0.3 0.2 0.1 0.0 0

1

2

3

4

5

6

7

8

9

10

l

Notes: 1. Nomenclature. s = D = FCA =

2.

Meridional (axial) dimension of the region of local metal loss (mm:in) Inside diameter (see paragraph 5.4.2.1.a), (mm:in), Future corrosion allowance (mm:in),

Rt

=

t mm - FCA t min

t min t mm

=

Required thickness per applicable code (mm:in),

=

Minimum measured thickness (mm:in), and

l

=

1285 . s Dt min

The permissible remaining strength factor for this curve is

RSFa = 0.90. Equations for the curves in this

figure are provided below where Mt is given by Equation (5.12).

Rt = 0.2

F RSF I F RSF I R = G RSF 10 . G J J M KH M K H t

a

a

t

Rt = 0.885

a

for l £ 0.3475

(5.61)

for 0.3475 < l < 10.0

(5.62)

for l ³ 10.0

(5.63)

-1

t

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 5.7 Level 1 Screening Criteria For The Maximum Allowable Circumferential Extent Of Local Metal Loss In A Cylinder

1.0

ACCEPTABLE

0.9 0.8 0.7 0.6

Rt

0.5

UNACCEPTABLE

0.4 0.3 0.2 0.1 0.0 0

1

2

3

c/D

Notes: 1. Nomenclature: c = Circumferential dimension of the region of local metal loss (mm:in), D = Inside diameter of component (see paragraph 5.4.2.1.a), (mm:in), and Rt = Remaining thickness ratio (see Figure 5.6) 2. An equation for the curve in this figure is provided below.

Rt = 0.2

2

(5.64)

for c D > 0.348

(5.65)

2

--``````-`-`,,`,,`,`,,`---

Rt =

b g . + 13838 . bc D g 10

-0.73589 + 10.511 c D

for c D £ 0.348


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 5.8 Definition Of Areas Used To Compute The RSF For A Region Of Local Metal Loss In A Level 2 Assessment

si+3 si+2 si+1 si s2 s1

t

tmin

Cross Hatched Area - Ai

Aio - Area Within Box

(a) Subdivision Process for Determining the RSF

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

RSFi Minimum RSF

Si

(b) Determining the Minimum RSF Value Notes:

Ai = Area of metal loss associated with length si (cross-hatched area). This area can be evaluated using a numerical integration technique (e.g. Simpson’s or Trapezoidal Rule).

Aoi = Total original area associated with length si and thickness tmin, or Aoi = si t min

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 5.9 Parameters For Permissible Bending Moment, Axial Force, And Pressure For A Cylinder With An LTA Circumferential Plane A

t My

V p F

Di 2

MT

Ri

MT

F Mx

Mx My

V

A My //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Region Of Local Metal Loss

t

c

G

G

Di 2

Mx

F

MT

P

Section A-A

Notes: 1. P is the internal pressure. F is the net-section axial force from supplemental loads excluding the pressure thrust. 2. V is the net-section shear force from supplemental loads. 3. 4. M T is the net-section torsional moment from supplemental loads. 5. 6.

M y is the component of net-section bending moment from supplemental loads which bisects the region of local metal loss. M x is the component of the net-section bending moment from supplemental loads which is perpendicular to

My . --``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 5.10 Parameters For Determining Section Properties Of A Cylinder With An LTA

y,y Metal Loss tmm

x

A

Dff 2

G

B

yLx

G

x

y

x

x

Di 2

Do 2

t --``````-`-`,,`,,`,`,,`---

(a) Region Of Local Metal Loss Located on the Inside Surface y,y

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

B

A G

Metal Loss

tmm

G

yLx

Df 2 x

y

x Do 2

Di 2 t

(b) Region Of Local Metal Loss Located on the Outside Surface


Not for Resale

x x


5.11 5.11.1

Example Problems

Example Problem 1 – A region of localized corrosion has been found on a pressure vessel during a scheduled turnaround. The vessel and inspection data are provided below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is acceptable for the current MAWP using a Section 5 Level 1 Assessment.

=

300 psi @ 650°F

Inside Diameter

=

96 inches

Fabricated Thickness

=

1.25 inches

Uniform Metal Loss

=

0.10 inches

FCA

=

0.125 inches

Material

=

SA 516 Grade 70


=

0.85

Inspection Data The grid and data used for the inspection are shown below. The distance from the region of local metal loss to the nearest structural discontinuity is 60 inches. Another region of local metal loss with a smaller amount of metal loss is located 16 inches from the region shown below. Pressure Vessel Shell

C1

C2

C3

C4

C5

C6

C7

C8

C9 Inspection Grid

M5 M4 M3 M2

Weld Seam

M1


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Design Conditions

--``````-`-`,,`,,`,`,,`---

Vessel Data

Jan, 2000

Recommended

5-33

Practice For Fitness-For-Service

Inspection Data (Inches) Longitudinal Inspection I

Circumferential lnst ection C6 1.15

M3

1 1.15 1 0.81 1 0.82 1 0.84 10.62

0.80

0.85

0.94

1.15

0.70

0.45

0.65

0.90

1.15

0.45

0.83

0.90

0.91

1.15

0.81

1.15

1.15

1.15

1.15

1.15

0.45

0.65 10.901 1.15 1

Notes: 1. Spacing of thickness readings in longitudinal direction is % inch. 2. Spacing of thickness readings in circumferential direction is 1.O inch. 3. The localized corrosion is located away from all weld seams.

Perform a Level 1 Assessment per paragraph 5.4.2.2 Step I - Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters -the thickness readings for the critical inspection planes are indicated in the above table and figure.

D = 96” FCA = 0.125” g, is not required for the analysis of an LTA Lmd = 60” MA WP = 300 psig RSF, = 0.90 Step 2 - Calculate the minimum required thickness, tmin, based on the current design pressure and temperature. Note that E = 1.0 since the LTA is remote from weld seams (see paragraph A.2.4 of Appendix A)

R, = 48”+0.1 0”+0.125” = 48.225” t’

(3OOpsi)(48.225”) = (175OOpsi)(l.O) - 0.6(3OOpsi) = o’835”

t& = t,,

(3OOpsi)(48.225”) + 0.0” = 0.4 12 ” 2(175OOpsi)(l.O) + 0.4(3OOpsi)

= max[0.835”, 0.412”] = 0.835”

--``````-`-`,,`,,`,`,,`---



API RECOMMENDED

5-34

PRACTICE 579

Step 3 - Determine the minimum measured thickness, tmm, the remaining dimensions (see paragraph 5.3.3.2) and the shell parameter, h.

Jan, 2000 thickness

The LTA being evaluated satisfies the spacing criteria in Section 4, paragraph the dimensions of the LTA do not need to be adjusted.

ratio,

Rt, the flaw

4.3.3.3.d.3;

therefore,

= 0.45” R = 0.45”-0.125” = o 389 t 0.835” * s = 3.34” c = 3.02” t,,

A = 1*285(3-34”) = 0 479 $iFo * Step 4 - Check the limiting flaw size criteria for a Level 1 Assessment. (R, = 0.389) 2 0.20

Tme

km, - FCA = 0.450”-0.125” = 0.325”) 2 0.10”

True

( Lmd = 60”) 2 (1.X,/-

True

= 16.1”)

Step 5 - Check the criteria for a groove-like flaw. localized metal loss is categorized as an LTA.

This step is not applicable

because

the region of

Step 6 - Evaluate the longitudinal extent of the flaw. From Figure 5.6 with

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

equations

the longitudinal

extent of the flaw is acceptable.

Using

(5.11) and (5.12):

ikft = (1 + 0.48(0.479)2)o’5 = 1.054

!

0.389

RSF = l- &(1 .

- 0.389)

Step 7 - Evaluate circumferential the circumferential

= 0.93 2 (RSF, = 0.9) I

extent of the flaw.

From Figure 5.7, with


The Level 1 Assessment

Criteria

are Satisfied

March 2000


Not for Resale

c 3-02” = 00315 -=D 96” ’ .R, = 0.389

Jan, 2000

5.11.2

Recommended

5-35


Example Problem 2 - A pressure

vessel shell has two groove-like flaws with the following dimensions. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is fit for continued operation.

Vessel

Design Data

Design Conditions

300 psig @ 250°F

Inside Diameter

90 inches

Thickness

1.125 inches

Uniform Metal Loss

0.0 inches

FCA

0.125 inches

Material

SA 516 Grade 70


1.0

Inspection

Data

Groove

1 & 2 Orientation

Longitudinal

Groove

1 & 2 Width

1.5 inches

Groove

1 & 2 Depth

0.65 inches

Groove

1 812 Length

8.0 inches

Groove

1 Radius

0.60 inches

Groove 2 Radius

0.10 inches

The groove-like flaws are located 20” apart from each other. Each of the groove-like flaws are located a minimum distance’of 36” away from the nearest structural discontinuity or weld. Based on process conditions and a visual examination, it was determined that both of the grooves were caused by fluid erosion; therefore, both of the groove-like flaws are characterized as a groove per paragraph 5.2.1 .I .b.

Perform

a Level

1 Assessment

per paragraph

5.4.2.2 - Groove

1

Step 7 - Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters - the required information is provided in the vessel and inspection data.

D = 90” FCA = 0.125” g, = 0.60” Lmd = 36” A42 WP = 300 psig RSF, = 0.90 Step 2 - Calculate the minimum required thickness, tmin, based on the current design pressure and temperature. . Note that E = 1.0 since the LTA is remote from weld seams (see paragraph A.2.4 of Appendix A).

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Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

March 2000

API RECOMMENDED

5-36

PRACTICE 579

Jan, 2000

R,=+go+ 0.125” = 45.125” (3OOpsig)(45.125”) = 0.782 ” tin = (175OOpsi)( 1.0) - 0.6( 3OOpsig) (3OOpsig)(45.125”) + 0.0” = 0.3 86 ” tA = 2(17500psi)(1.0) + 0.4(3oopsig) t,, = max[0.782”, 0.386”] = 0.782” Step 3 - Determine the minimum measured thickness, tmm, the remaining dimensions (see paragraph 5.3.3.2) and the shell parameter, )L.

thickness

ratio,

The groove-like flaw being evaluated satisfies the spacing criteria in Section 4, paragraph therefore, the dimensions of the flaw do not need to be adjusted.

Rt, the flaw 4.3.3.3.d.3;

t,, = 1.125”-0.65” = 0.475” R = 0.475”-0.125” = 0448 t 0.782” ’ s =

g,

=

8”

c=g,=1.5” p = 0.0 ;z = 1*285(8’o”) +iqiiF)

= 1225 -

--``````-`-`,,`,,`,`,,`---

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Step 4 - Check the limiting flaw size criteria for a Level 1 Assessment.

(R, = 0.448) 2 0.20

True

km - RX

True

= 0.475”-0.125” = 0.350”) 2 0.10”

( Lmd = 36”) 2 (1.8,/%fii?i@ Step 5 - Check

= 15.1”)

the criteria for a groove-like

Step 5.7 - Compute

flaw.

the critical groove radius:

March 2000


Not for Resale

True

Jan, 2000

Recommended Practice For Fitness-For-Service

5-37

g,” = max[ 0.25(0.782”), 0.25”] = 0.25” Step 5.2 - Check the groove dimensions

(g, = 0.6”) 2 (g; = 0.25”) (I- &,,

= (I- Om4$Om78211= l-3’

proceed to Step 5.3.

Step 5.3 - The groove-like

flaw is characterized

Step 5.6 - Proceed to Step 6 and complete Step 6 - Evaluate the longitudinal

as a groove; therefore,

to Step 5.6

the Level 1 Assessment.

, the longitudinal

can be computed

proceed

extent of the flaw.

From Figure 5.6 with pressure

True

’ lmo

using Equations

extent of the flaw is unacceptable.

The rerate

(5.1 I), (5.12), and (2.2), respectively:

M, = (1 + O.48(1.225)2)o’s = 1.311 0.448

RSF = l- -&l

= 0.774

- 0.448)

0.774 MAWP, = (300psig) (.090 ) = 258 psig 1.5” --=0.0167 5 - 90” R, = 0.448 C

Step 7 - Evaluate circumferential the circumferential

Perform

a Level

extent of the flaw.

From Figure 5.7 with


1 Assessment

per paragraph

5.4.2.2 - Groove

2

Step 7 - Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters; the required information is provided in the vessel and inspection data.

D = 90” FCA = 0.125” g, = 0.10” Lmd = 36” MA WP = 300 psig RSF, = 0.90 --``````-`-`,,`,,`,`,,`---



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Therefore

True

5-38

API RECOMMENDED

PRACTICE

579

Jan, 2000

Step 2 - Calculate the minimum required thickness, tmjn, based on the current design pressure and temperature (same as Step 2 for Groove 1).

&, = 0.782 ” Step 3 - Determine the minimum measured thickness, tmm,the remaining thickness ratio, dimensions (see paragraph 5.3.3.2) and the shell parameter, h.

Rt, the flaw

Note that the groove-like flaw is analyzed as an equivalent LTA in accordance with paragraph 5.3.3.2.b.2. tmm=

1.125”-0.65” = 0.475” R = 0.475”-0.125” = o 448 t 0.782” ’ s = g, = 8” c = g, = 1.5” p = 0.0” 1.285(8.0”) A=p@-g=1*225 Step 4 - Check the limiting flaw size criteria for a Level 1 Assessment.

(R, = 0.448) 2 0.20

True

km - FCA = 0.475”-0.125” = 0.350”) 2 0.10”

True

( Lmd = 36”) 2 (1.8dm

True

= 15.19

Step 5 - Check the criteria for a groove-like flaw. Step 5.7 - Compute the critical groove radius:

g,” = max[0.25(0.782”), 0.25”] = 0.25” Step 5.2 - Check the groove dimensions

(g, = 0.1”) 2 (g,” = 0.25”)

gr

False

0.1” = 0.23” (1- R,)t,, = (1 - 0.448)0.782”

2 1.0

False

Therefore proceed to Step 5.7.

Step 5.7 -The groove is not acceptable per Level 1. The groove can be re-evaluated as an equivalent crack like flaw with the following dimensions using the Level 1 procedures of Section 9.

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March 2000


Not for Resale

Recommended

Jan, 2000

a = 0.65"+0.125"=


5-39

0.775"

2c = s = 8.0” Groove

Perform

2 is not acceptable

per the Section

a Level 2 Assessment

5 Level 1 Assessment

per paragraph

5.4.3.2 - Groove

Criteria.

2

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The Level 2 screening criteria for groove-like flaws is the same as the Level 1 criteria; therefore, this groove will not satisfy the Level 2 Assessment procedure. As an alternative, the groove can be analyzed as an equivalent crack-like flaw using the Level 2 procedures in Section 9. Groove

5.11.3

2 is not acceptable

per the Section

5 Level 2 Assessment

Criteria.

Example Problem 3 - inspection of a process vessel indicates a region of local corrosion in the lower shell section. In addition to internal pressure, the vessel is also subjected to axial forces and bending moments. The vessel data is shown below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Evaluate the region of localized metal loss for pressure plus supplemental loads and determine acceptability for continued operation without repairs. Vessel

Data

Design Conditions

=

220 psig @ 350°F

Nominal Thickness

=

0.50 inches

Inside Diameter

=

42 inches

Uniform Metal Loss

=

0.0 inches

FCA

=

0.06 inches

Material

=

SA 516 Grade 70


=

1.0

Weight Case Loads

(see Figure 5.10 for definition of applied loads)

Applied Axial Force

=

500.0 Ibs

M, Applied Bending Moment

=

l.79(106)


=

0.0 in-lb

Applied Shear Force

=

137600 Ibs

Applied Torsional

=

l.63(105)

Moment

Thermal Case Loads

in-lb

in-lb

(see Figure 5.10 for definition of applied loads)

Applied Axial Force

=

2550 Ibs


=

3.81(106) in-lb


=

0.0 in-lb

Applied Shear Force

=

38400 Ibs

Applied Torsional

=

2.59(105) in-lb

Moment

Note: The weight case and thermal case loads are typically obtained from a stress analysis. applied forces and moments were computed at the location of maximum metal loss.


The


API RECOMMENDED

PRACTICE

579

Inspection Data The grid and data used for the inspection are shown below. This is the only region of localized metal loss found on the vessel during the inspection. The distance from the region of local metal loss to the nearest structural discontinuity is 28 inches

-

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M6 -

0

f -

M5 -

t

M4 -

-

-

M3 -

-

-

M2 -

-

-

Ml

:-

Cl

C2

1.. I ‘- .-

L c3

C4

c5

C6

c7 /

Inspection Data (Inches) Circumferential

M5

0.50

0.48

0.46

0.42

0.42

0.46

0.50

0.42

M6

0.50

0.48

0.47

0.48

0.49

0.49

0.50

0.49

0.50

0.35

0.33

0.28

0.24

0.35

0.50

Longitudinal CTP

Notes: 1. Spacing of thickness readings in longitudinal direction is 1 .O inch. 2. Spacing of thickness readings in circumferential direction is 3.0 inches.

--``````-`-`,,`,,`,`,,`---

March 2000


Not for Resale

Jan, 2000 Recommended Practice For Fitness-For-Service 5-41 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

Perform a Level 2 Assessment per paragraph 5.4.2.2 because of the presence of an external moment Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters (same as Step 1 for the Level 1 Assessment).

D = 42" FCA = 0.06" gr is not required for the analysis of an LTA Lmsd = 28" MAWP = 220 psig RSFa = 0.90 Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature. Note that the thickness required for supplemental loads is included in the calculation of the minimum required wall thickness (see Appendix A).

Rc = 21"+0.06" = 2106 . " C t min =

Rmc =

215 . "+2106 . " = 2128 . " 2 179 . 106 in - lbs

c h 500 lbs + = 0.0721" . gF b2128 . "g . "g 2b17500 psi gb10 b17500 psigb10. gF b2128 . "g b220 psiggb2106 = + 0.0721" = 0. 204" 2b17500 psi gb10 . g + 0.4b220 psig g

t sl = L t min

. "g b220 psiggb2106 b17500 psigb10. g - 0.6b220 psigg = 0.267 "

2

t min = max 0.267", 0.204" = 0.267" Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see paragraph 5.3.3.2), and the shell parameter, l. There is only one LTA in the vessel; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

t mm = 0.24" 0.24"-0.06" Rt = = 0.674 0.267" s = 2.72" based on t min = 0.267" c = 15" based on t nom - LOSS = 0.50" l=

b g = 1044 . 42" b0.267"g

1285 . 2.72"

Note that the circumferential extent of the flaw is, c, based on the nominal thickness minus the uniform metal loss because a Level 2 Assessment is being performed.


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FCA=0.06"

0.50" nom. tmin = 0.267" s = 2.7"

Longitudinal CTP Step 4 – Check the limiting flaw size criteria for a Level 2 Assessment.

--``````-`-`,,`,,`,`,,`---

b R = 0.674g ³ 0.20 . "g ³ 010 . " bt - FCA = 0.24"-0.06" = 018 b L = 28"g ³ e18. 42" b0.267"g = 6"j t

True

mm

True

msd

True

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA. //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Step 6 – Determine the Remaining Strength Factor for the longitudinal CTP – in this assessment, the remaining strength factor will be based on a Level 1 Assessment.

e

b

M t = 1 + 0.48 1044 . RSF =

gj

2 0.5

= 1234 .

0.674

b

1 1 - 0.674 11234 .

g

= 0.916

Step 7 – Evaluate the longitudinal extent of the flaw

b RSF = 0.916g ³ b RSF = 0.90g ; therefore the longitudinal extent of the flaw is acceptable for the a

stated design conditions, and

MAWPr = MAWP = 220 psig Step 8 – Evaluate the circumferential extent of the flaw – Because of the presence of a external bending moment, the extent of the flaw in the circumferential direction must be evaluated using the procedure in paragraph 5.4.3.3. Step 8.1 – Determine the Critical Thickness Profiles(s) in the circumferential direction (see paragraph 5.3.3.2) and the following parameters:


Not for Resale


c = 15"

b

g

Di = 42"+2 0.06" = 42.12" Do = 43" FCA = 0.06" LOSS = 0.0 t mm = 0.24" t nom = 0.5" I ys = 33.2 ksi for SA 516 Gr 70 @ 350 oF Step 8.2 – For the circumferential inspection plane being evaluated, approximate the circumferential extent of metal loss on the plane under evaluation as a rectangular shape.

b

g FG 180IJ = 15" FG 180IJ = 2016 H F K 42.64" H F K .

D f = 43"-2 0.24"-0.06" = 42.64 G=

c Df

0

Step 8.3 – Determine the remaining strength factor, permissible pressure and supplemental loads acting on the circumferential plane.

RSF = 0.9 MAWPr = 220 psig Weight Case Supplemental Loads F = 500.0 lbs

c h

M x = 179 . 106 in - lbs M y = 0.0 in - lbs V = 137600 lbs

c h

T = 163 . 105 in - lbs Thermal Case Supplemental Loads F = 2550.0 lbs

c h

. 106 in - lbs M x = 381 M y = 0.0 in - lbs V = 38400 lbs

c h

T = 2.59 105 in - lbs Step 8.4 – Determine the resultant bending moment in the plane of the defect. In this case, the moments stated in the problem were aligned with the flaw. In general, the moments will not be aligned with the flaw, and the moments results obtained from a stress analysis will need to be resolved to the axis of the flaw as shown in Figure 5.9.

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Weight Case

c h

M x = 179 . 106 in - lbs M y = 0.0 in - lbs Thermal Case

c h

M x = 381 . 106 in - lbs M y = 0.0 in - lbs Step 8.5 – Compute the maximum section stress, Im, at the centerline of the circumferential extent of the region of local metal loss (point A in Figure 5.10) due to the pressure, axial force and the bending moment determined in Step 4 using the following procedure: Step 8.5.1 – Compute section properties of a cylinder without an LTA.

b

g b g b b g b

F 2 42.12" = 1393.4 in 2 4 F 2 2 Am = 43.0" - 42.12" = 58.8 in 2 4 F 4 4 IX = 43.0" - 42.12" = 13322 in 4 64 I Y = I X = 13322 in 4

g g

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Aa =

Step 8.5.2 – Compute section properties for cylinder with LTA on inside surface.

FG 2016 F F IJ IJ . G H H 180K K b42.64"g - b42.12"g = 0

Af

2

2

4 Aw = 1393.4 in 2 + 388 . in 2 = 1397.3 in 2

c

b42.64"g - b42.12"g h c58.8 in - 388 . in h 3

2

3

2

= 147 . "

--``````-`-`,,`,,`,`,,`---

1 y = sin 2016 . 0 12

= 388 . in 2


Not for Resale


xa = 0.0 ya = 147 . "+

43.0" = 22.97" 2

c

h c

43.0" sin 2016 . 0 = 7.35" 2 43.0" yb = 147 . "+ cos 2016 . 0 = 2167 . " 2

xb = --``````-`-`,,`,,`,`,,`---

h

b

g b 3

g

3

42.64" - 42.12" 1 b = sin 2016 . 0 = 0.058" . in 2 12 1393.4 in 2 + 388 42.64" R= = 2132 . " 2 42.64"-42.12" d= = 0.26" 2 15.0" 43.0"+42.64" Atf = = 160.58 in 2 8

c

h

b

g

with,

g c

2

3

2

3

2

I LX

3

0

0

0

0

0

2

2

2

2

0

2

0

I LX = 0.61 in 4

c

hb g

c

2

hb

g

2

I X = 13322 in 4 + 58.8 in 2 147 . " - 0.61in 4 - 388 . in 2 20.79"+147 . " = 11526 in 4


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

y LX

OP LM h 0.26" 1 = M1 - . " + 2 - 0.26" PP = 20.79" 3b0.352 radiansg M 2132 N 21.32" Q U| R| 0.26"g b0.26"g - b0.26"g OP × || ||LM1 - 23b2132 + . "g PQ M|N b . "g b21.32"g 4b2132 ||LM OP ||| 2 sin c2016 . h |V | F F F IJ IJ .+ sinc20.16 h cosc2016 P = b2132 . "g b0.26"gSMG 20.16 G . hFG 2016 F F IJ IJ PP | ||MMH H 180K K . G H H 180K K Q || ||N F1 - 0.26" + b0.26"g I | . h b0.26"g sin c2016 | ||+ . " 6b21.32"g JK | 0.26" I GH 2132 F IIF F F |W |T 3b21.32"g GH 20.16 GH 180JK JK GH 2 - 21.32"JK b

2 21.32" sin 20.160


R|L1 - 3b0.26"g + b0.26"g - b0.26"g O × U| MM 2b2132 P . "g b2132 . "g 4b2132 . "g PQ | | N = b2132 . "g b0.26"gS V| O ||LMFG 20.16 FG F IJ IJ - sinc2016 . h cosc20.16 hP | QW TNH H 180K K 2

3

2

I LY

3

3

0

0

0

I LY = 70.58 in 4 I Y = 13322 in 4 - 70.58 in 4 = 13252 in 4 with,

At =

b

g

0.5F 42.12"+43.0" - 15" 42.12"+43.0" 8

= 1263 in 2

Step 8.5.3 – Compute maximum section longitudinal membrane stress. For the Weight Case, points A and B A I lm =

b

g

1397.3 in 2 500 lbs 220 psig + + 2 2 58.8 in - 388 58.8 in 2 - 388 . in . in 2 22.97" 147 . "+0.058" 220 psig 1397.3 in 2 + 179 . 106 4 11526 in

b

gb

gc

h e m r j in - lbs +

b0g b0g = 10098 psi 13252 in 4

B = I lm

b

g

1397.3 in 2 500 lbs + 220 psig + 2 2 58.8 in - 388 . in 58.8 in 2 - 388 . in 2 2167 . " 147 . "+0.058" 220 psig 1397.3 in 2 + 179 . 106 4 11526 in

b

gb

gc

h e m r j in - lbs +

b7.35g b0g = 9840 psi 13252 in 4

w I lm = max 10098 psi , 9840 psi = 10098 psi

For the Weight plus Thermal Case, points A and B

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000 Recommended Practice For Fitness-For-Service 5-47 _________________________________________________________________________________________________ A = I lm

g b

g

500 lbs + 2550 lbs 1397.3 in 2 220 psig + + 2 2 58.8 in - 388 . in 58.8 in 2 - 388 . in 2 22.97" 147 . "+0.058" 220 psig 1397.3 in 2 + 179 . 106 + 381 . 106 in - lbs + 11526 in 4

b

b

gb

b0g b0g = 17731 psi 13252 in

gc

h e m r

m rj

4

B = I lm

g b

g

500 lbs + 2550 lbs 1397.3 in 2 220 psig + + 2 2 58.8 in - 388 . in 58.8 in 2 - 388 . in 2 2167 . " 147 . "+0.058" 220 psig 1397.3 in 2 + 179 . 106 + 381 . 106 in - lbs + 11526 in 4

b

b

gc

gb

h e m r

m rj

b7.35"g b0g = 17038 psi 13252 in 4

wt I lm = max 17731 psi , 17038 psi = 17731 psi

Step 8.6 – Evaluate results Compute the maximum hoop stress in the region of metal loss

I

cm

b220 psigg L 42.12" + 0.6O = 11639 psi PQ . b0.916g MN 43.0"-42.12" 10

=

Compute the shear stress for the Weight Case

J=

c

c h

1.63 105 in - lbs 2

2 1263 in + 160.58 in

2

+

137600 lbs = 2725 psi . in 2 58.8 in 2 - 388

hb0.26"g c

h

Compute the shear stress for the Weight Plus Thermal Case

J=

c h 2c1263 in

c h + 160.58 in hb0.26"g

1.63 105 in - lbs + 2.59 105 in - lbs 2

2

+

137600 lbs + 38400 lbs = 3774 psi 58.8 in 2 - 388 . in 2

c

h

Equivalent stress check for the Weight Case:

. ksi g - b1164 . ksi gb101 . ksi g + b101 . ksi g + 3b2.73 ksi g b1164 1193 . ksi £ b0.75g33.2 ksi = 24.9 ksi 2

2

2

= True

Equivalent stress check for the Weight Plus Thermal Case:

. ksi g - b1164 . ksi gb17.73 ksi g + b17.73 ksi g + 3b3.77 ksi g b1164 16.92 ksi £ b15 . g33.2 ksi = 49.8 ksi 2

2

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2

= True


Therefore, the Level 2 Assessment Criteria are satisfied. 5.11.4

Example Problem 4 – Inspection of a cylindrical pressure vessel indicates a region of localized corrosion. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Perform an API 579 Level 2 Assessment per Section 5 to evaluate the acceptability for continued operation. Vessel Data

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Design Conditions

=

572 psig @ 650°F

Inside Diameter

=

60 inches

Wall Thickness

=

1.0 inches

Uniform Metal Loss

=

0.0 inches

FCA

=

0.0 inches

Material

=

SA 516 Grade 70


=

1.0

Inspection Data The critical thickness profile for the longitudinal plane is shown in the following table. The critical thickness profile for the circumferential plane can be approximated as rectangular area of metal loss with a length of 20 inch. This is the only region of localized metal loss found on the vessel during the inspection. The region of metal loss is located 72 inches away from the nearest structural discontinuity.

Inspection Location

Longitudinal Location (inches)

Measured Thickness (inches)

1

0

1.00

2

2

0.90

3

4

0.85

4

6

0.70

5

8

0.45

6

10

0.30

7

12

0.40

8

14

0.65

9

16

0.85

10

18

0.90

11

20

1.00

Perform a Level 2 Assessment per paragraph 5.4.3.2 Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters (same as Step 1 for the Level 1 Assessment).

--``````-`-`,,`,,`,`,,`---


Not for Resale


D = 60" FCA = 0.0" gr is not required for the analysis of an LTA Lmsd = 72" MAWP = 572 psig RSFa = 0.90 Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature (same as Step 2 for the Level 1 Assessment).

60" = 30" 2 572 psig 30" . " = = 10 . - 0.6 572 psig 17500 psi 10

Rc = C t min

--``````-`-`,,`,,`,`,,`---

L t min

b

gb g b gb g b g b572 psiggb30"g = + 0.0" = 0.487 " . g + 0.4b572 psig g 2b17500 psi gb10

. ", 0.487" = 10 . " t min = max 10 Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see paragraph 5.3.3.2), and the shell parameter, l. There is only one LTA in the vessel; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

t mm = 0.30" 0.30"-0.0" Rt = = 0.30 10 . " C s = 20.0" based on t min = 1.0" . " c = 20.0" based on t nom - LOSS = 10 l=

b g = 3.318 60" b10 . "g

1285 . 20"

Step 4 – Check the limiting flaw size criteria for a Level 2 Assessment.

b R = 0.30g ³ 0.20 . " bt - FCA = 0.30"-0.0" = 0.30"g ³ 010 b L = 72"g ³ e18. 60" b10. "g = 13.9"j t

True

mm

True

msd

True

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA. Step 6 – Determine the Remaining Strength Factor for the longitudinal CTP


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Step 6.1 – Rank the thickness readings in ascending order based on metal loss – based on the CTP data, inspection location 6 would be the starting point for the assessment. Step 6.2 – Set the initial evaluation starting point as the location of maximum metal loss, this is the location in the thickness profile where tmm is recorded – inspection location 6 has the minimum thickness equal to 0.30 inches. Step 6.3 – At the current evaluation starting point, subdivide the thickness profile into a series of subsections – the thickness profile will be subdivided into 10 sections each 2 inches long. Step 6.4 – For each subsection, compute the Remaining Strength Factor using Equation (5.13) and the data tabulated in the following table.

Data For Starting Point At Location 6 Of The Longitudinal CTP Subsection

I

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1 2 3 4 5 6 7 8 9 10

ssi (1)

sei (2)

si (3)

l i (4)

A i (5)

A io

9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0

11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0

2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

0.332 0.664 0.995 1.327 1.659 1.991 2.323 2.654 2.986 3.318

1.338 2.550 3.575 4.350 4.912 5.300 5.576 5.800 5.950 6.000

2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

(6)

M

1.032 1.096 1.194 1.317 1.458 1.610 1.770 1.933 2.098 2.264

Notes: 1. Starting location of metal loss region under consideration. 2. Ending location of metal loss region under consideration. 3. Length of metal loss for the region under consideration. i

4. Shell parameter evaluated using Equation (5.4) with s = s . 5. Area of metal loss evaluated using a numerical procedure. 6. Original metal area evaluated using Equation (5.14). i

7. Folias factor evaluated using Equation (5.15) with l = l . 8. Remaining strength factor; evaluated using Equations (5.13).

Sei Ssi 1

2

3

Si

9

4

8 5

6

7

--``````-`-`,,`,,`,`,,`---


Not for Resale

10

i (7) t

11

RSF i 0.941 0.866 0.801 0.777 0.767 0.768 0.777 0.785 0.795 0.807

(8)

Jan, 2000 Recommended Practice For Fitness-For-Service 5-51 _________________________________________________________________________________________________ i

Step 6.5 – Determine the minimum value of the Remaining Strength Factors, RSF , found in Step 6.4 for all subsections. The minimum value of the Remaining Strength Factor for the current evaluation is found to be at subsection 5 when point 6 is used as the subdivision starting point.

RSFmin = 0.767 Step 6.6 – Repeat Steps 6.3 through 6.5 of this calculation for the next evaluation point which corresponds to the next thickness reading location in the ranked thickness profile list; this step is not shown here. Step 6.7 – After the calculation has been completed for all thickness reading locations (or evaluation points), determine the minimum value of the Remaining Strength Factor for each evaluation point and designate this value as RSFmin. Based on the results in the above table, the minimum RSF is associated with subsection 5 with a value of:

RSF = RSFmin = 0.767 Step 8 – Evaluate the longitudinal extent of the flaw

b RSF = 0.767g < b RSF = 0.90g ; therefore the longitudinal extent of the flaw is unacceptable for the a

stated design conditions. An acceptable MAWP for operation is established as follows:

b

IJ = 487 psig g FGH 00.767 .90 K

MAWPr = 572 psig ×

Step 9 – Evaluate the circumferential extent of the flaw. In this example, the Level 1 Assessment

R| c = 20" = 0.25U| , the circumferential extent of the flaw method will be used. From Figure 5.7 with S D 60" |TR = 0.30 V|W t

is acceptable.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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Not for Resale


5.11.5

Example Problem 5 – A region of local metal loss has been found on a cylindrical pressure vessel during an inspection. The vessel and inspection data are shown below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel for acceptable for continued operation.

Design Conditions

=

2.068 MPa @ 340°C

Inside Diameter

=

2438 mm


=

32 mm

Uniform Metal Loss

=

2.5 mm


3.2 mm

Material

=

SA 516 Grade 60


=

1.0

Inspection Data

--``````-`-`,,`,,`,`,,`---

Vessel Data

Based on the inspection data, the critical thickness profile in the longitudinal direction has a length s = 191 mm and has a uniform measured thickness of 16 mm. The critical thickness profile in the circumferential direction has a length c = 250 mm with the same uniform thickness. The region of local metal loss is located 1520 mm away from the nearest structural discontinuity. This is the only region of local metal loss found in the vessel during the inspection. Perform a Level 1 Assessment per paragraph 5.4.2.2

D = 2438 mm FCA = 3.2 mm gr is not required for the analysis of an LTA Lmsd = 1520 mm MAWP = 2.068 MPa RSFa = 0.90 Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature.

Rc = 1219 mm + 2.5 mm + 3.2 mm = 1224.7 mm

b2.068 MPagb1224.7 mmg = 24.78 mm b103.421 MPagb10. g - 0.6b2.068 MPag b2.068 MPagb1224.7 mmg + 0.0 mm = 12.2 mm = 2b103.421 MPa gb10 . g + 0.4b2.068 MPa g

C t min =

L t min

t min = max 24.78 mm, 12.2 mm = 24.78 mm Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see paragraph 5.3.3.2), and the shell parameter, l.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters; the thickness readings for the critical inspection planes are provided in the inspection data.


There is only one LTA in the vessel; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

t mm = 16 mm 16 mm - 3.2 mm Rt = = 0.516 24.8 mm s = 191mm c = 250 mm

b

g

1285 . 191 mm

b

g = 0.998

2438 mm 24.8 mm


b R = 0.516g ³ 0.20 bt - FCA = 16 mm - 3.2 mm = 12.8 mmg ³ 2.5 mm b L = 1520 mmg ³ e18. Dt = 18. 2438 mmb24.78 mmg = 442.4 mmj t

True

mm

True

msd

min

True

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA. //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Step 6 – Evaluate the longitudinal extent of the flaw.


RSl = 0.998 UV , the longitudinal extent of the flaw is unacceptable. The rerate TR = 0.516W t

pressure can be computed using Equations (5.11), (5.12), and (2.2), respectively.

b

e

gj

M t = 1 + 0.48 0.998

2 0.5

= 1216 .

0.516

RSF =

= 0.857 1 1 - 0.516 11216 . 0.857 . MPa = 197 MAWPr = 2.068 MPa 0.90

b

b

g

gFGH

IJ K

Step 7 – Evaluate circumferential extent of the flaw. The circumferential extent of the flaw does not need to be evaluated because

bt

mm

g c

h

L = 16 mm > t min = 12.2 mm .

The Level 1 Assessment Criteria are not satisfied, a rerate was required.


Not for Resale

--``````-`-`,,`,,`,`,,`---

l=


5.11.6

Example Problem 6 – A region of corrosion on a 12 inch LWN (Long Weld Neck) nozzle has been found during the inspection of a pressure vessel. The corroded region is located in the nozzle (see inspection data). The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is suitable for continued operation. Pressure Vessel Information Design Conditions

=

185 psig @ 650°F

Shell Inside Diameter

=

60 inches

Shell Thickness

=

0.60 inches

Shell Material

=

SA 516 Grade 70

Shell Weld Joint Efficiency

=

1.0

Shell FCA

=

0.125 inches

Nozzle Inside Diameter

=

12.0 inches

Nozzle Thickness

=

1.375 inches

Nozzle Material

=

SA 105

Nozzle Weld Joint Efficiency =

1.0

Nozzle FCA

0.125 inches

=

Inspection Data The region of localized metal loss is shown in the following figure. The opening is located 45 inches from the nearest major structural discontinuity.

CL

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

1.375"

0.375"

Metal Loss 0.60"

From the inspection data: --``````-`-`,,`,,`,`,,`---


Not for Resale


·

The average thickness in the nozzle reinforcement zone is 0.875 inches

·

The corrosion is uniform for all inspection planes.

Perform a Level 2 Assessment per paragraph 5.4.3.4 because the corrosion is at a nozzle From the inspection data: shell t am = 0.60" nozzle t am = 0.875"

t vr =

. "g b185 psiggb30"+0125 b17500 psi gb1.0g - 0.6b185 psigg = 0.321"

Required thickness of the nozzle:

t nr =

. "-0.875"q + 0125 . "h b185 psiggc6"+l1375 b17500 psigb10. g - 0.6b185 psigg = 0.071"

Determine the corroded shell and nozzle thicknesses considering the FCA:

t vc = 0.60"-0125 . " = 0.475" t nc = 0.875"-0125 . " = 0.75" Determine the corroded shell and nozzle mean diameters:

c60"+2l0.60"qh + c60"+2l0.125"qh = 60.725" 2 . "-0.875"q + 2l0125 . "qh c12"+2l1.375"qh + c12"+2l1375 = = 14"

Dm = dm

2

Perform the assessment (see paragraph A.3.11.2 of Appendix A):

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Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Required thickness of the shell:


0.75" t nc . = = 1578 \ A = 54 t vc 0.475" 0.75" t nc . = = 1578 \ B = 318 t vc 0.475" l=

FG 14" IJ H 60.725"K

60.725" = 2.607 0.475"

t vr = t r = 0.321"

F 2 + 2FG 14" IJ FG 0.75" IJ + 125 I GG H 60.725"K H 0.475"K . b2.607g = 2.836JJ £ GG JJ F 14" IJ FG 0.75" IJ 1+ G H 60.725"K H 0.475"K H K FG 2.95" FG 0.475"IJ = 4.372IJ True H H 0.321" K K 3/ 2

1/ 2

3/ 2

F L54FG 0.75" IJ + 228FG 0.75" IJ FG 14" IJ + 318Ob2.607g + 155 I GG MMN H 0.475"K H 0.475"K H 60.725"K PPQ JJ GG 108 2.607 + L228F 14" I + 228O 2.607 + 152 = 1.026JJ ³ b g MM GH 60.725"JK PPb g GH JK N Q FG 0.93 + 0.005b2.607g FG 0.321" IJ = 0.637IJ True H 0.475"K K H 2

2

2

Analysis Results: The area reinforcement calculation using the limit analysis approach is acceptable using the corroded dimension of the nozzle configuration and the stated design conditions. The Level 2 Assessment criteria are satisfied.


Not for Resale

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1/ 2


5.11.7

Example Problem 7 – A region of corrosion on an atmospheric storage tank has been found during the inspection. The tank was designed to API 650. Determine if the tank is suitable for continued operation. Tank Information Diameter

=

80 feet

Shell Height

=

40 feet

Design Liquid Height

=

40 feet

Specific Gravity

=

1.0

Design Temperature

=

Ambient

Uniform Metal Loss

=

0.113 inches

FCA

=

0.05 inches

Material

=

ASTM A285 Grade C


=

1.0

Inspection Data The grid and data used for the inspection are shown below. The opening is located 57 inches from the nearest major structural discontinuity. 80 ft

0.25" 40 ft (4 Courses @ 10 ft)

0.375" 0.438" 0.563"

4.75 ft Location of the LTA

M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 C10 C9 C8 C7 C6 C5 C4 C3 C2 C1

//^:^^#^~^^""~:@":^*^~$~"#:*

--``````-`-`,,`,,`,`,,`---


Not for Resale


Inspection Data (inches) Circumferential Inspection

Meridional Inspection Planes

Meridional

--``````-`-`,,`,,`,`,,`---

Planes

(ft -in)

M1

M2

M3

M4

M5

M6

M7

M8

M9

M10

M11

M12

C1

4-3

0.46

0.46

0.46

0.47

0.47

0.47

0.45

0.45

0.46

0.46

0.46

0.47

0.45

C2

4-6

0.46

0.47

0.47

0.45

0.45

0.43

0.43

0.43

0.43

0.45

0.46

0.47

0.43

C3

4-9

0.46

0.47

0.45

0.43

0.41

0.36

0.33

0.33

0.40

0.42

0.46

0.46

0.33

C4

5-0

0.47

0.47

0.40

0.36

0.30

0.26

0.33

0.34

0.34

0.35

0.39

0.46

0.26

C5

5-3

0.44

0.41

0.36

0.31

0.26

0.24

0.24

0.24

0.34

0.35

0.37

0.43

0.24

C6

5-6

0.45

0.41

0.38

0.33

0.27

0.23

0.24

0.29

0.33

0.38

0.37

0.43

0.23

C7

5-9

0.46

0.40

0.35

0.31

0.33

0.27

0.26

0.30

0.34

0.34

0.35

0.44

0.26

C8

6-0

0.45

0.42

0.35

0.36

0.33

0.29

0.31

0.30

0.32

0.37

0.39

0.45

0.29

C9

6-3

0.46

0.45

0.41

0.37

0.38

0.36

0.35

0.38

0.41

0.44

0.46

0.47

0.35

C10

6-6

0.46

0.46

0.45

0.45

0.45

0.46

0.46

0.47

0.45

0.45

0.45

0.47

0.45

0.44

0.40

0.35

0.31

0.26

0.23

0.24

0.24

0.32

0.34

0.35

0.43

Circumferential CTP

Notes: 1. Spacing of thickness readings in meridional or longitudinal direction is 3.0 inches 2. Spacing of thickness readings in circumferential direction is 6.0 inches

Perform a Level 1 Assessment per paragraph 5.4.2.2 Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters; the thickness readings for the critical inspection planes are indicated in the above table and shown in the following figure.

b g

D = 80' 960"

FCA = 0.05" gr is not required for the analysis of an LTA Lmsd = 57"

b g

MFH = 40' 480" RSFa = 0.90

Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature in accordance with API 653, Section 2.

t min =

b gb gb g b gb g

2.6 80 ft 35.25 ft 10 . = 0.311" 23595 psi 10 .

Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see paragraph 5.3.3.2), and the shell parameter, l.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

CTP


There is only one LTA in the tank; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

t mm = 0.23" 0.23"-0.05" Rt = = 0.579 0.311" s = 19.25" based on t min = 0.311" c is not required for the assessment of an atmospheric storage tank t mm = 0.23" l=

b g = 1432 . 960" b0.311"g

1285 19.25" .


b R = 0.579g ³ 0.20 . "g ³ 010 . " bt - FCA = 0.23"-0.05" = 018 b L = 57"g ³ e18. 960" b0.311"g = 311. "j t

True

mm

True True

msd

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA. Step 6 – Evaluate the longitudinal extent of the flaw.


. RSl = 1432 UV , the longitudinal extent of the flaw is unacceptable. The rerate TR = 0.579W t

maximum fill height can be computed using Equations (5.11), (5.12), and (2.4), respectively.

e

b

M t = 1 + 0.48 1432 . RSF =

gj

2 0.5

= 1409 .

0.579

= 0.826 1 1 - 0.579 11409 . 0.826 = 36.7 ft MFH = 40 ft 0.90

b

b gFGH

g

IJ K

Step 7 – Evaluate circumferential extent of the flaw – this step is not applicable for atmospheric storage tanks since the meridional or longitudinal plane governs. The Level 1 Assessment criteria are not satisfied, a rerate was required.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


5.11.8

Example Problem 8 – A region of corrosion and/or erosion has been found on the extrados of a seamless long radius piping elbow during an inspection. A piping stress analysis has been performed on this system and the results indicate that the forces and moments from the weight and thermal load cases which act on the elbow are negligible. The piping system was designed to ASME B31.3. Determine if the pipe bend is suitable for continued operation. Piping System Information o

Design Conditions

=

600 psig @ 700 F

Pipe Diameter

=

NPS 12

Wall Thickness

=

Schedule 40

Uniform Metal Loss

=

0.0 inches

FCA

=

0.05 inches

Material

=

ASTM A234 Grade WPB

Inspection Data Thickness readings have been taken based on a inspection grid on the extrados of the elbow. The spacing to the nearest structural discontinuity is 32 inches. The thickness readings indicate that the LTA is located in the middle one-third section of the elbow. The critical thickness profiles in the longitudinal and circumferential directions are 6.5 inch and 3.0 inch in length, respectively. A visual inspection in conjunction with thickness readings indicates that the metal loss can be assumed to be uniform with the following minimum thickness reading.

t mm = 018 . " Perform a Level 1 Assessment per paragraph 5.4.2.2 Note that a Level 1 Assessment may be performed for piping bends subject to pressure loading only. In this example, it has been stated that the results of a piping stress analysis indicates that the forces and moments on the pipe bend are negligible. Step 1 – Determine the Critical Thickness Profiles(s) (see paragraph 5.3.3.2) and the following parameters.

D0 = 12.75"

l

q

D = 12.75"-2 0.406" = 11938 . "

Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature (see paragraph A.5.5 of Appendix A).

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

FCA = 0.05" gr is not required for the analysis of an LTA Lmsd = 32.0" MAWP = 600 psig RSFa = 0.90


Not for Resale


Rb = 18" 12.75"+11938 . " Rm = = 6172 . 4 18" + 0.5 . " L f = 6172 = 0.872 18" + 10 . 6172 . " 600 psig 12.75" C t min = 16500 psi 2 10 . + 600 psig 0.4 0.872

b

L t min

gb

g

= 0199 . " LMFG O IJ b g b gb gPQ K NH b600 psiggb12.75"g = + 0.0" = 0114 . " 4 b16500 psi gb10 . g + b600 psig gb0.4g

t min = max 0199 . ", 0114 . " = 0199 . " Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see paragraph 5.3.3.2), and the shell parameter, l. There is only one LTA in the elbow; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

. " t mm = 018 . "-0.05" 018 Rt = = 0.653 0199 . " s = 6.5" c = 3.0" l=

b g = 5.419 11938 . " b0199 . "g 1285 . 6.5"


b R = 0.653g ³ 0.20 . "-0.05" = 013 . "g ³ 010 . " bt - FCA = 018 . " b0199 . "g = 2.77"j b L = 32.0"g ³ e18. 11938 t

True

mm

True True

msd

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA. Step 6 – Evaluate the longitudinal extent of the flaw.


RSl = 5.419 UV , the longitudinal extent of the flaw is unacceptable. The rerate TR = 0.653W t

pressure can be computed using Equations (5.11), (5.12), and (2.2), respectively.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


b

e

M t = 1 + 0.48 5.419

gj

2 0.5

= 3885 .

0.653

RSF =

= 0.717 1 1 - 0.653 13885 . 0.717 = 478 psig MAWP = 600 psig 0.90

b

b

g

gFGH

IJ K

R| c = 3.0" = 0.25U| Step 8 – Evaluate circumferential extent of the flaw. From Figure 5.7 with S D 11938 . " V| , |TR = 0.653 W t

the circumferential extent of the flaw is acceptable.

--``````-`-`,,`,,`,`,,`---

The Level 1 Assessment criteria are satisfied.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@


Not for Resale

SECTION 6 – Assessment Of Pitting Corrosion (Jan, 2000) 6.1

General

6.2


6.2.1

The assessment procedures can be used to evaluate four types of pitting: widely scattered pitting which occurs over a significant region of the component, a LTA located in a region of widely scattered pitting, localized regions of pitting, and pitting which is confined to within an LTA. A flowchart which shows the details of the assessment procedures required for these four types of pitting damage are shown in Figure 6.2. Based on the type of pitting damage, a combination of assessment methods in Sections 5 and 6 are used in the evaluation.

6.2.2

Calculation methods are provided to rerate the component if the acceptance criteria in this section are not satisfied. For pressurized components (pressure vessels and piping), the calculation methods can be used to find a reduced maximum allowable working pressure (MAWP) and/or temperature. For tank components (shell courses), the calculation methods can be used to determine a reduced maximum fill height (MFH).

6.2.3


6.2.3.1

The Level 1 and 2 assessment procedures in this section apply only if all of the following conditions are satisfied. a.

The requirements of Section 5, paragraphs 5.2.3.1.a through 5.2.3.1.h are satisfied.

b.

A Level 2 Assessment should be performed if pitting damage is on both sides of the component.

c.

The pitting damage is composed of many pits; individual pits or isolated pairs of pits should be evaluated using the assessment procedures in Section 5.

6.2.3.2

A Level 3 assessment should be performed where Level 1 and 2 methods do not apply, such as the component geometry and loading conditions described in Section 5, paragraph 5.2.3.2. In addition, a Level 3 assessment is required if the pitting corrosion is located in a component with a non-uniform through-wall stress distribution (e.g. bending stress).

6.3

Data Requirements

6.3.1



6-1 Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The assessment procedures in this section can be utilized to evaluate metal loss from pitting corrosion. In this context pitting is defined as localized regions of metal loss which can be characterized by a pit diameter on the order of the plate thickness or less, and a pit depth that is less than the plate thickness. Assessment procedures are provided to evaluate both widespread and localized pitting in a component with or without a region of local metal loss. In addition, the procedures in this section can be used to assess a damaged array of blisters as described in Section 7. A flow chart for the evaluation procedure of equipment with pitting is shown in Figure 6.1.


6.3.2

Maintenance And Operational History

6.3.3


6.3.3.1

The depth and diameter of a pit must be carefully measured because of the variety of pit types that can occur in service (see Figure 6.3). If the pit has an irregular shape, a diameter and depth which encompasses the entire shape should be used in the assessment.

6.3.3.2

The measure of damage used to evaluate pitting is the pit-couple. A pit-couple is composed of two pits separated by a solid ligament (see Figure 6.4). The metal loss of each pit in a pit-couple is modeled as an equivalent cylinder. To define a pit-couple, the diameter and depth of each pit, and the length or pitch between the pit centers is required. For a Level 2 Assessment, the orientation of the pit-couple in the biaxial stress field is also required (see Figure 6.4).

6.3.3.3

The occurrence of pits and their relative size in a region of a component are typically random. Therefore, user discretion is required to select a population of pits that adequately represents the damage in the component. The following recommendations should be considered in selecting the pit-couples for an assessment. To evaluate a region with pitting, a representative number of pit-couples in the damaged area should be used. If the pitting is uniform, a minimum sample size of ten pit-couples is recommended. If the pitting is non-uniform, additional pit-couple data should be taken.

b.

The pit-couple samples used in the assessment should be chosen such that the pit-couples are independent. The following guideline can be followed to select the pit-couples for an assessment.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.

6.3.3.4

1.

Step 1 – Select a minimum of ten pits covering a broad area.

2.

Step 2 – Select the nearest neighbor to each of these ten pits to create a minimum of ten pit-couples (see Figure 6.4).

3.

Step 3 – If any pit is part of more than one pit-couple in Step 2, then select a new pit and repeat Step 2.

4.

Step 4 – Complete the assessment using paragraph 6.4.

c.

The orientation of the pit-couple in a biaxial stress field is used only in the Level 2 assessment. These data will typically not significantly improve the assessment results, unless the pitting damage is preferential (e.g. the pitting damage is concentrated along a longitudinal, circumferential, or spiral weld seam). Therefore, the extra effort and work associated with obtaining this information should be balanced with the potential increase in strength.

d.

To determine the effects that additional pit-couples couples would have on the assessment results, additional independent pit-couples can be included in the sample size, and the assessment can be repeated. This procedure can provide a measure of the sensitivity of the data with regard to assessment results (see Section 2, paragraph 2.4.3.1). Alternatively, distributions can be developed for the parameters which define a pit-couple (i.e. diameter and depth of each pit, and the length between the pit centers), and a probabilistic analysis (see Section 2, paragraph 2.4.3.2) can be performed using the assessment model of paragraph 6.4.

The future Pitting Progression Rate (PPR) should be estimated. This is not a straightforward procedure because pits can increase in size (depth and diameter), increase in density, and a region


Not for Resale

--``````-`-`,,`,,`,`,,`---

An overview of the maintenance and operational history required for an assessment is provided in Section 2, paragraph 2.3.2.


of local pitting may increase in size. All pit dimensions used in the assessments in this section should be based on the best estimate of future size. A discussion pertaining to the remaining life estimate for pitting is included in paragraph 6.5. The following information is required for a Level 1 and Level 2 Assessment. The specific information required for a Level 1 and Level 2 Assessment is summarized in paragraphs 6.4.2.2 and 6.4.3.2, respectively. The form shown in Table 6.1 can be used to record this information.

b.

The parameters s and c should be determined if the pitting damage is localized (see Figure 6.5) or if the pitting damage is confined to a localized region of metal loss (see Figure 6.6). In addition, the required parameters per Section 5 will need to be determined.

6.3.3.6

The information required to perform a Level 3 Assessment is dependent on the analysis method utilized. In general, a limit load procedure using a numerical technique can be used to establish acceptable operating conditions. For this type of analysis, a description of the pitting, similar to that required for a Level 2 Assessment, should be obtained along with the material yield strength and stress-strain curve.

6.3.4

Recommendation For Inspection Technique And Sizing Requirements

6.3.4.1

Precise measurement of pitting is difficult. Care must be taken to ensure that the correct dimensions are measured because pits often have irregular shapes as shown in Figure 6.3 or are filled with scale. Pit gauges are usually used to measure pit depth and rulers or calipers to measure pit diameter and the pit pitch. Ultrasonic methods can also be used to measure the wall thickness of pits with large diameters and the average plate thickness in the area of pitting.

6.3.4.2

It is difficult to detect small diameter pits or to measure the depth of pits using ultrasonic methods. Scanning techniques are advisable when measuring the thickness in a pitted or locally thinned region. Radiography (RT) may also be used to characterize the damage in pitted regions.

6.3.4.3

If the surface is scaled, dirty or has a damaged coating, cleaning (i.e. sandblasting) may be required in order to obtain accurate pit measurements.

6.4


6.4.1

Overview

6.4.1.1

If the depth of all of the pits is less than the specified corrosion/erosion allowance and adequate thickness is available for the future pitting damage (see paragraph 6.5.1), no further action is required other than to record the data; otherwise, an assessment is required.

6.4.1.2

An overview of the assessment levels is provided in Figure 6.1. Level 1 Assessments are limited to components covered by a recognized code or standard which have a design equation which specifically relates pressure (or liquid fill height for tanks) to a required wall thickness. The only load considered is internal pressure, and the average values of three pitting characterization parameters are used to describe the damage. The Level 1 Assessment procedures can be used to evaluate four categories of pitting: general pitting, localized pitting, pitting within a locally thin area, and a locally thin area in a region of general pitting. Level 2 Assessments can be used to evaluate components which do not satisfy Level 1 criteria. The Level 2 Assessment rules provide a better estimate of the structural integrity of a component by using six parameters to describe the damage. The same four categories of pitting damage described under the Level 1 Assessment can also be evaluated in a Level 2 Assessment. In addition, this assessment level can be used when the pitting damage occurs on both sides of the component. Level 3 assessments can be used to evaluate components which are not covered or do not pass a Level 1 or Level 2 assessment. The Level 3 Assessment procedures are intended to evaluate more complex regions of pitting, loading conditions, and/or


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.

--``````-`-`,,`,,`,`,,`---

6.3.3.5

components with details where only limited design rules are provided in the original construction code or standard. Detailed stress analysis techniques are normally utilized in a Level 3 Assessment. 6.4.2

Level 1 Assessment

6.4.2.1

The Level 1 Assessment technique is simplified in that it does not account for the orientation of the pit-couple with respect to the maximum stress direction; therefore, the results will be conservative. Guidance for conducting an assessment for the four categories of pitting described in paragraph 6.2.1 is shown in Figure 6.2.

6.4.2.2

The following assessment procedure can be used to evaluate components described in paragraph 6.2.3.1. If the flaw is found to be unacceptable, the procedure can be used to establish a new MAWP or MFH. a.

Step 1 – Determine the following parameters:

D

FCA RSFa t b.

= Inside diameter of the cylinder, cone (at the location of the flaw), sphere, or formed head; for the center section of an elliptical head an equivalent inside diameter of Kc Dc is used where Dc is the inside diameter of the head straight flange and Kc is a factor defined in Appendix A, paragraph A.3.6; for the center section of a torispherical head two times the crown radius of the spherical section is used (mm:in), = Estimated future corrosion allowance (mm:in), = Allowable remaining strength factor (see Section 2), and = Current thickness in the vicinity of the pitting damage, typically the nominal thickness minus the uniform metal loss (mm:in).

Step 2 – Determine the following parameters for each pit couple, k , being evaluated. It is recommended that at least ten pit-couples be included in the assessment to obtain a statistical average of the Remaining Strength Factor.

di , k d j ,k Pk wi ,k w j ,k

i in pit-couple k (mm:in), Diameter of the pit j in the pit-couple k (mm:in), Pit-couple spacing in pit-couple k (mm:in). Depth of the pit i in pit-couple k (mm:in), and Depth of the pit j in pit-couple k (mm:in).

= Diameter of the pit = = = =

c.

Step 3 – Determine the minimum required thickness, tmin (see Appendix A, paragraph A.2).

d.

Step 4 – Determine the depth of each pit below

t min in all pit-couples, wi ,k and w j ,k (see

wavg , considering all readings. In the following equations, the variable k represents the kth pit-couple and n is the total number of

Figure 6.4.b) and compute the average pit depth,

pit-couples recorded at the time of the inspection. In accordance with Step 2, at least 10 pitcouples (n=10) should be used in an evaluation.

b g = w - bt - FCA - t g dw + w i =

wi ,k = wi ,k - t - FCA - t min

(6.1)

w j ,k

(6.2)

wavg ,k

j ,k

min

i ,k

j ,k

(6.3)

2

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



wavg = e.

1 n å wavg ,k n k =1

(6.4)

Step 5 – Determine the average pit diameter and pit-couple spacing. The average pit diameter, d avg , is based on all pits included in the number of pit-couples recorded at the time of the inspection. The average pit-couple pitch or spacing between the pits in a pit-couple, Pavg , is evaluated for all pit-couples recorded at the time of the inspection considering only pits immediately adjacent to each other (i.e. nearest neighbors, see Figure 6.4).

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d avg ,k =

f.

dd

i ,k

+ d j ,k

i

(6.5)

2

d avg =

1 n å davg ,k n k =1

(6.6)

Pavg =

1 n å Pk n k =1

(6.7)

wavg £ 0.0, RSF = 10 . , then the Level 1 RSF criteria are satisfied and proceed to Step 8; otherwise, compute the RSF using

Step 6 – Calculate the Remaining Strength Factor, RSF. If the following equation and proceed to Step 7.

--``````-`-`,,`,,`,`,,`---

LMR| MNS|T

RSF = min 1.0 -

wavg t min

+

d

Eavg t - FCA + wavg - t min t min

i U|V, 10. OP |W PQ

(6.8)

where,

Eavg = m avg = g.

3 m avg 2

(6.9)

Pavg - d avg

(6.10)

Pavg

Step 7 – Evaluate results based on the type of pitting damage (see Figure 6.2): 1.

Widespread Pitting – For widespread pitting which occurs over a significant region of the component, if the computed RSF ³ RSFa , the pitting is acceptable per Level 1. If this criterion is not satisfied, then the component can be rerated using the equations in Section 2, paragraph 2.4.2.2. For cylindrical and conical shells, if the minimum required thickness determined in Step 3 is based on the thickness for longitudinal stress because of supplemental loads, then a Level 2 Assessment using the procedure in paragraph 6.4.3.3 should be performed.

2.

Localized Pitting – If the pitting damage is localized, then the damaged area will be evaluated as an equivalent region of localized metal loss (LTA, see Section 5 and Figure 6.5). The meridional and circumferential dimensions of the equivalent LTA should be based on the physical bounds of the observed pitting. The equivalent


Not for Resale


thickness,

t eq , for the LTA can be established using the following equation. To

complete the analysis, the LTA is then evaluated using the Level 1 or Level 2 assessment procedures in Section 5 with t mm set equal to t eq .

t eq = RSF × t min

(6.11)

where,

t eq RSF 3.

=

Equivalent thickness of localized region of pits (mm:in), and

=

Remaining Strength Factor for pitting damage calculated using paragraph 6.4.2.2.f (paragraph 6.4.3.2.f should be used if a Level 2 Assessment is performed).

Region Of Local Metal Loss Located In An Area Of Widespread Pitting – If a region of local metal loss (LTA) is located in an area of widespread pitting, then a combined Remaining Strength Factor can be determined using the following equation. If the RSFcomb ³ RSFa , then the pitting is acceptable per Level 1. If this criterion is not satisfied, then the component can be rerated using the equations in Section 2, paragraph 2.4.2.2 with the combined remaining strength factor.

--``````-`-`,,`,,`,`,,`---

RSFcomb = RSFpit × RSFlta

(6.12)

where,

RSFcomb =

Combined Remaining Strength Factor which includes the effects of

RSFpit

pitting damage and a locally thin area, Remaining Strength Factor for pitting damage calculated using

RSFlta //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

4.

h.

=

=

paragraph 6.4.2.2.f (paragraph 6.4.3.2.f should be used if a Level 2 Assessment is performed), and Remaining Strength Factor for a local thin area computed using the methods provided in Section 5 (note that individual pits should be ignored in this calculation).

Pitting Confined Within A Region Of Localized Metal Loss – If the pitting damage is confined within a region of localized metal loss (see Figure 6.6), then the results can be evaluated using the methodology in subparagraph 3 above.

Step 8 – Check the recommended limitations on the individual pit dimensions: 1.

Pit Diameter – If the following equation is not satisfied for an individual pit, then the pit should be evaluated as a local thin area using the assessment methods of Section 5. The size of the local thin area is the pit diameter and the remaining thickness ratio is defined below. This check is required for larger pits to ensure that a local ligament failure at the base of the pit does not occur.

d £ Q Dt min

(6.13)

Q in the above equation can be determined using Section 4, Table 4.4 and is a function of the remaining thickness ratio, Rt , for each pit as given by the following equation where w is the depth of the pit under evaluation as computed in Step 4. The value of


Not for Resale


Rt =

min

- w - FCA t min

IJ K

(6.14)

Pit Depth – The following limit on the remaining thickness ratio is recommended to prevent a local failure characterized by pin-hole type leakage. The criterion is expressed in terms of the remaining thickness ratio as follows:

Rt ³ 0.20 6.4.2.3

(6.15)

--``````-`-`,,`,,`,`,,`---



b.


c.

Adjust the weld joint efficiency factor, E , by conducting additional examination and repeat the assessment (see Section 2, paragraph 4.4.2.2.c).

d.


6.4.3

Level 2 Assessment

6.4.3.1

The assessment procedure in Level 2 provides a better estimate of the Remaining Strength Factor for pitting damage in a component subject to pressure loading, and supplemental loading for cylindrical and conical shells. This procedure accounts for the orientation of the pit-couple with respect to the maximum stress direction. Guidance for conducting an assessment for the four categories of pitting described in paragraph 6.2.1 is shown in Figure 6.2.

6.4.3.2

The following assessment procedure can be used to evaluate components described in paragraph 6.2.3.1. If the flaw is found to be unacceptable, the procedure can be used to establish a new MAWP or MFH. a.

Step 1 – Determine the parameters in paragraph 6.4.2.2.a.

b.

Step 2 – Determine the parameters in paragraph 6.4.2.2.b. In addition, determine the orientation of the pit-couple measured from the direction of the I 2 stress component,

Gk

(see Figure 6.4); for a conservative analysis set G k = 0.0 degrees. It is recommended that at least ten pit-couples be analyzed to obtain a statistical average of the Remaining Strength Factor. c.


d.

Step 4 – Determine the depth of each pit below


t min in all pit-couples, wi ,k and w j ,k (see

paragraph 6.4.2.2.d). e.

Step 5 – Calculate the components of the membrane stress field, I 1 and I 2 (see Figure 6.4). Membrane stress equations for shell components are included in Appendix A.

f.

Step 6 – For pit-couple


k , calculate the Remaining Strength Factor:

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.

FG t H


1.

Single Layer Analysis – This analysis can be used when the pitting occurs on one side of the component (see Figure 6.4). In this case, the RSF is adjusted for t min (see Figure 6.4b); if

wavg , k £ 0.0 then RSFk = 1.0 for this pit-couple.

LMR| MNS|T

RSFk = min 1.0 where,

wavg ,k

+

t min

d

Eavg ,k t - FCA + wavg ,k - t min t min

i U|V, 1.0OP |W PQ

(6.16)

wavg ,k and d avg ,k are defined in paragraph 6.4.2.2.d and 6.4.2.2.e, respectively,

and

LM F MN Y k

OP PQ

, 10 .

(6.17)

F k = m avg ,k × max r 1,k , r 2 ,k , r 1,k - r 2 , k

(6.18)

k

--``````-`-`,,`,,`,`,,`---

c csin G 4

hc h - c + sin 2G hc H h 2

Yk = cos G k + sin 2G k H 1, k 4

2

+

(6.19)

k

2 ,k

r 1, k =

s1 m avg ,k

(6.20)

r 2 ,k =

s2 m avg ,k

(6.21)

m avg ,k = 2.

h

3 sin 2 2G k H 1,k H 2 ,k

2

2

k

2

Pk - d avg ,k

(6.22)

Pk

Multiple Layer Analysis – This analysis is used to account for pitting on both sides of the component (see Figure 6.7). In this analysis, E avg ,k , is established for each independent layer considering all pit-couples. The selection of the number of layers, N , is based on the depth of pits on both sides of the component. The component thickness is divided into layers based on the pitting damage (see Figure 6.7), and the RSF is computed using the following equation considering all layers containing pits (the solid layer is not included in the summation, see Figure 6.7.a). This value of the RSF is not adjusted for t min ; therefore, the MAWP used with this expression should be based on the current component thickness, t . N

RSFk = 1 - å

L =1


FG t IJ d1 - E i HtK L

avg , k

Not for Resale

(6.23)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Eavg ,k = min


g.

Step 7 – Repeat Step 6 for all pit-couples, n , recorded at the time of the inspection. Determine the average value of the Remaining Strength Factors, RSFk , found in Step 6 and designate this value as RSF for the region of pitting.

6.4.3.3

1 n å RSFk n k =1

(6.24)

h.

Step 8 – Evaluate results based on the type of pitting damage using the criteria in paragraph 6.4.2.2.g.

i.

Step 9 – Check the individual pit dimensions using the criteria in paragraph 6.4.2.2.h.

The assessment procedures in this paragraph can be used to determine the acceptability of the longitudinal stress direction in a cylindrical shell or pipe with pitting damage subject to pressure and/or supplemental loads. The acceptability of the circumferential stress direction is evaluated using paragraph 6.4.3.2. a.

Supplemental Loads – These types of loads may result in a net section axial force, bending moment, torsion and shear being applied to the cross section containing the flaw (paragraph Appendix A, A.2.6). The supplemental loads included in the assessment should include loads which produce both load-controlled and strain controlled effects. Therefore, the net section axial force, bending moment, torsion, and shear should be computed for two load cases; weight and weight plus thermal (see Section 5, paragraph 5.4.3.3.a).

b.

Special Requirements For Piping Systems – Are required because of the relationship between the component thickness, piping flexibility or stiffness, and resulting stress (see Section 5, paragraph 5.4.3.3.b).

c.

Assessment For Widespread Pitting – The following procedure can be used to evaluate the permissible membrane, bending and shear stresses resulting from pressure and supplemental loads. 1.

Step 1 – Determine the following parameters:

Di

=

Do

=

FCA

=

LOSS t I ys

= = =

Inside diameter of the cylinder, corrected for metal loss and future corrosion allowance (mm:in), Outside diameter of the cylinder, corrected for metal loss and future corrosion allowance (mm:in), Future corrosion allowance applied to the region of local metal loss allowance (see Appendix A, paragraph A.2.7), (mm:in), Metal loss of the component (mm:in), Furnished thickness of the component (mm:in), and Yield stress (see Appendix F), (MPa:psi).

2.

Step 2 – Determine the remaining strength factor, RSF, the allowable remaining strength factor, RSFa, the maximum allowable pressure, MAWPr, and supplemental loads on the circumferential plane. The remaining strength factor, allowable remaining strength factor, and the maximum allowable pressure for the region with pitting damage can be established using the procedures in paragraph 6.4.3.2 (or paragraph 6.4.2.2). The supplemental loads are determined in accordance with paragraphs 6.4.3.3.a and 6.4.3.3.b.

3.

Step 3 – Compute the equivalent thickness of the cylinder with pitting damage.

b

t eq = B t - LOSS - FCA


g

(6.25)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

RSF =


B = min

LM RSF , 10. OP N RSF Q

(6.26)

a

where variable have been previously defined, and

t eq = RSF = RSFa = 4.

Equivalent thickness (mm:in), Computed remaining strength factor from Step 2, and Allowable remaining strength factor from Step 2.

Step 4 – Compute the maximum section longitudinal membrane stress for both the weight and weight plus thermal load cases. a.

Step 4.1 – Compute the section properties of the cylinder with pitting damage, include the previous uniform metal loss and the future corrosion allowance. Pitting Damage on the inside surface:

D f = Do - 2t eq

(6.27)

IX =

F Do4 - D 4f 64

Am =

F 2 Do - D 2f 4

i

At =

F Do + D f 16

i

a=

d

d

d

i

(6.28)

(6.29)

2

(6.30)

Do 2

(6.31)

Pitting Damage on the outside surface:

D f = Di + 2t eq

(6.32)

F D 4f - Di4 64

Am =

F 2 D f - Di2 4

At =

F D f + Di 16

a=

d

d

d

i

(6.33)

i

(6.34)

i

(6.35)

2

Df

(6.36)

2

with, --``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

IX =


Aa =

F 2 Di 4

(6.37)

where,

b.

2

2

Aa Am Df

=

Cylinder aperture cross-section (mm :in ),

=

Cylinder metal cross-section (mm :in ),

=

Modified cylinder diameter to account for pitting damage

Ix t eq

=

(mm:in), 4 4 Cylinder moment of inertia (mm :in ), and

=

Equivalent thickness (mm:in).

2

2

Step 4.2 – Compute the maximum section longitudinal membrane stress for both the weight and weight plus thermal load cases

--``````-`-`,,`,,`,`,,`---

I lm =

b

g

Aa F Ma MAWPr + + Am Am I X

(6.38)

where,

F

=

Applied section axial force determined in Step 2 for the weight or weight plus thermal load case, as applicable (N:lbs), Permissible MAWP determined in Step 2 (MPa:psi),

MAWPr = M = Applied section bending moment determined in Steps 2 for //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I lm

5

=

the weight or weight plus thermal load case, as applicable (N-mm:in-lbs), and Maximum section longitudinal membrane stress computed for both the weigh and weight plus thermal load cases (MPa:psi).

Step 5 – Evaluate the results as follows: a)

The following relationship should be satisfied for either a tensile and compressive longitudinal stress for both the weight and weight plus thermal load cases:

I 2cm - I cmI lm + I 2lm + 3J 2 £ HI ys

(6.39)

with,

I cm =

J=

F GH

I JK

MAWPr Di + 0.6 Ec 2t eq

MT V + 2 At t eq Am

(6.41)


Ec


=

(6.40)

Circumferential weld joint efficiency,

Not for Resale


b)

6.

MT

=

t eq V

=

I cm

=

I lm

=

I ys J

=

=

=

Allowable stress factor depending on the load case being evaluated; use 0.75 for the weight case and 1.5 for the weight plus thermal load case, Applied net-section torsion determined in Step 2 for the weight or weight plus thermal load case, as applicable (Nmm:in-lbs), Equivalent thickness from Step 3 (mm:in), Applied net-section shear force determined in Step 2 for the weight or weight plus thermal load case, as applicable (N:lbs), Maximum circumferential stress, typically the hoop stress from pressure loading for the weight and weight plus thermal load case, as applicable (MPa:psi), Maximum longitudinal stress computed in Step 4.2 computed for both the weight and weight plus thermal load cases (MPa:psi), Yield stress (see Appendix F), (MPa:psi), and

--``````-`-`,,`,,`,`,,`---

=

Maximum shear stress in the region of local metal loss for the weight and weight plus thermal load case, as applicable (MPa:psi).

If the maximum longitudinal stress computed in Step 4 is compressive, this stress should be less than or equal to the allowable compressive stress computed using the methodology in Appendix B, paragraph B.4.4 or the allowable tensile stress, whichever is smaller. When using the methodology in Appendix B, paragraph B.4.4 to establish an allowable compressive stress, the equivalent thickness determined in Step 3 should be used in the calculations.

Step 6 – If the equivalent stress criteria of Step 5 is not satisfied, the MAWP and/or supplemental loads determined in Step 2 should be reduced, and the evaluation outlined in Steps 1 through 5 should be repeated. Alternatively, a Level 3 Assessment can be performed.

Assessment For Localized Pitting – If the flaw is categorized as localized pitting, a region of widely scattered pitting with an LTA, or pitting confined to within the region of an LTA, the assessment procedure in Section 5, paragraph 5.4.3.3 can be used once an equivalent LTA has been derived using the procedures in paragraph 6.4.2.2.g.

6.4.3.4

The assessment procedure in Section 4, paragraph 4.4.3.3 can be used to evaluate components which do not have a design equation which specifically relates pressure (or liquid fill height for tanks) to a required wall thickness (see Section 4, paragraph 4.3.2.1.g). For this assessment, the remaining wall thickness for the nozzle and vessel can be established using the equations in paragraph 6.4.3.3.c.3.

6.4.3.5



b.


c.


d.



Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d.

H


6.4.4

Level 3 Assessment

6.4.4.1

The stress analysis techniques discussed in Appendix B can be utilized to assess pitting damage in pressure vessels, piping, and tankage in a Level 3 analysis. In general, the limit load techniques described in Appendix B, paragraph B.3 are typically recommended for this evaluation.

6.4.4.2

If a numerical computation (e.g. finite element method) is used to evaluate pitting, two alternatives for modeling the pits may be considered. In the first method, the pits can be modeled directly using three dimensional continuum finite elements. This method may be impractical based upon the pit density. In the second method, the reduced stiffness of the plate with pits can be approximated by using effective elastic constants or by developing an equivalent thickness. Effective elastic constants for plates with holes with triangular and rectangular pitch patterns are provided in the ASME B&PV Code, Section VIII, Division 1, Appendix AA. Either of these methods will facilitate modeling of pitting damage using either shell or continuum finite elements; however, representative values of the effective elastic constants or equivalent thickness must be chosen and validated for use in the assessment. In addition, if a limit analysis is being performed, the validity of the effective elastic constants or equivalent thickness in the plastic regime also would need to be investigated.

6.5


6.5.1

The MAWP approach provides a systematic way of determining the remaining life of a pressurized component with pitting. When estimating the remaining life of pitting damage, a Pit Propagation Rate should be determined based on the environmental and operating conditions.

6.5.1.1

Pits can grow in three different modes and suitable estimates for a propagation rate should be established for each mode. In addition to these individual modes, pitting damage can also grow from a combination of these modes. ·

Increase In Pit Size – an estimate as to how the pit size, characteristic diameter and depth, will increase with time should be made. For a given pit-couple, as the pit diameter and/or depth increases, the RSF decreases.

·

Increase In Pit Density – in addition to existing pits continuing to grow, new pits can form, which increases the pit density. This decreases the pit spacing distance and the RSF.

·

Increase In Pit Region Size – if the pitting is localized, future operation may result in an enlargement of the localized region. The enlargement of a local region with pits is similar to the enlargement of an LTA.

6.5.1.2

If an estimate of the propagation rates cannot be made, remediation methods may be used to eliminate future pitting damage.

6.5.2

The following procedure can be used to determine the remaining life of a component with pitting using the MAWP approach:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.

Step 1 – Determine the uniform metal loss in the region with pitting.

b.

Step 2 – Using the procedures described in Level 1 or Level 2, determine the MAWP for a series of increasing time increments using a Pit Propagation Rate applied to the pit depth and diameter. Extreme value statistical analysis [6.9.3} and [6.9.4] can be used to predict the likely depth of the deepest pit that was not measured, based on those that were measured. The extreme value can then be used in the formulas for current pit depth. This will ensure that perforation does not occur, unless leak of the fluid contents is considered acceptable.

c.

Step 3 – The effective pit size and rate of change in the characteristic dimensions are determined as follows:

w f = wc + PPR pit - depth × time


(6.42)

Not for Resale


d f = d c + PPR pit - diameter × time

(6.43)

where,

PPR pit - depth

=

PPR pit - diameter =

Estimated rate of change of pit characteristic depth (mm/year:in/year), Estimated rate of change of the pit characteristic diameter

wc dc wf

=

(mm/year:in/year), Current characteristic pit depth (mm:in),

=

Current characteristic pit diameter (mm:in),

=

Estimated future characteristic pit depth (mm:in), and

df

=

Estimated future characteristic pit diameter (mm:in).

d.

Step 4 – If remediation is not performed, an estimate of the future pit density should be made and included in the estimation of the MAWP in Step 2.

e.

Step 5 – If the pitted region is localized, an estimate of the future enlargement of this region should be made and included in the estimation of the MAWP in Step 2. If there is an interaction between pitting and a LTA, then this interaction must also be considered in a MAWP versus time calculation.

f.

Step 6 – Determine the remaining life from a plot of the MAWP versus time. The time at which the MAWP curve intersects the design MAWP for the component is defined as the remaining life of the component. The equipment MAWP is taken as the smallest value of the MAWP for the individual components.

6.5.2.3

This approach may also be applied to tankage; however, in this case, the liquid maximum fill height, MFH, is evaluated instead of the MAWP.

6.6

Remediation The remediation methods for general corrosion provided in Section 4 are typically applicable to pit damage. Nonetheless, it is very difficult to properly remediate active pitting because the environment in a pit can be different from the bulk fluid environment; therefore, chemical treatments may not be effective. In addition, because coatings depend on proper surface preparation, which is challenging when removing scale in pits, they may also be ineffective. Therefore, strip linings may be the remediation method of choice.

6.7

In-Service Monitoring The remaining life may be difficult to establish for some services where an estimate of the future metal loss and enlargement of the pitted region cannot be adequately characterized. In these circumstances, remediation and/or in-service monitoring may be required to qualify the assumptions made to establish the remaining life. Nonetheless, it is often difficult to monitor pit advance nonintrusively with ultrasonic methods. Radiography may be an alternative.

6.8

Documentation

6.8.1

The documentation of the FFS assessment should include the information cited in Section 2. paragraph 2.8.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

6.8.2

Inspection data including readings and locations used to determine the pitting damage RSF factor should be recorded and included in the documentation. A sample data sheet is provided in Table 6.1 for this purpose.

6.9

References

6.9.1

ASM, “Metals Handbook, Ninth Edition, Volume 13, Corrosion,” ASM International, Metals Park, Ohio, 1987, pp. 231-233.

6.9.2


6.9.3

Gumbel, E.J., “Statistical Theory of Extreme Values”, National Bureau of Standards, AMS 33, 1954.

6.9.4

Kowaka, Masamichi, “Introduction to Life Prediction of Industrial Plant Materials – Application of the Extreme Value Statistical Method for Corrosion Analysis”, Allerton Press, Inc., 1994.

6.9.5

Porowski, W.J., “Limit Analysis of A Shell with Random Pattern of Pits Subject to In-plane Biaxial Loading”, MPC Report, In Preparation.

6.9.6

Porowski, W.J., O’Donnell, W.J., Farr, J.R., “Limit Design of Perforated Cylindrical Shells per ASME Code”, Journal of Pressure Vessel Technology, American Society of Mechanical Engineers, N.Y., pp. 646-651, 1977.

6.9.7

O’Donnell, W.J. and Porowski, W.J., “Yield Surfaces for Perforated Materials”, Transactions of the ASME, Journal of Applied Mechanics, American Society of Mechanical Engineers, N.Y., pp. 263-270, 1973.

6.9.8

Porowski, W.J. and O’Donnell, “Effective Elastic Constants for Perforated Materials”, Transactions of the ASME, Journal of Pressure Vessel Technology, American Society of Mechanical Engineers, N.Y., pp. 234-241, 1974.

6.9.9

Daidola, J.C., Parente, J., Orisamolu, I.R., “Strength Assessment Of Pitted Panels”, SSC-394, Ship Structures Committee, D.C., 1997.

6.10

Tables And Figures


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---



Table 6.1 Required Data For Assessment Of Pitting Use this form to summarize the data obtained from a field inspection. Equipment Identification: Equipment Type: _____ Pressure Vessel Component Type & Location:

_____ Storage Tank


Data Required for Level 1: Average Pit Diameter, d avg : Average Pit Spacing, Average Pit Depth,

Pavg :

wavg :

Data Required for Level 1 and Level 2:

Pk

Gk

di ,k

wi ,k

d j ,k

w j ,k

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Pit-Couple


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure 6.1 Overview Of The Assessment Procedures To Evaluate A Component With Pitting



No

Yes


Rerate Equipment?

No


Yes

Not for Resale

Yes

Yes

No

Yes



Rerate Equipment?

No

Yes

Yes


Yes


No

No


No

Yes



No

6-17


No


Yes

Yes

No

Rerate Equipment?

Yes




--``````-`-`,,`,,`,`,,`---

No


Figure 6.2 Categories And Analysis Methodology Of Pitting Analysis Types

Obtain Pitting Damage Information from Inspection

Type of Pitting Damage:

Region of Local Metal Loss Located in an Area of Widespread Pitting

Pitting Damage Confined within a Region of Local Metal Loss, see Figure 6.6

Determine the RSF Resulting from Pitting Damage Using Paragraph 6.4.2.2 or 6.4.3.2

Determine the RSF Resulting from Pitting Damage (RSF_PIT) Using Paragraph 6.4.2.2 or 6.4.3.2

Determine the RSF Resulting from Pitting Damage (RSF_PIT) Using Paragraph 6.4.2.2 or 6.4.3.2; the calculations for RSF_PIT are Based on the LTA Average Thickness

Determine an Equivalent Thickness teq=RSF*tmin; Perform LTA Assessment Using Section 5.0 with an LTA Characterized by s, c, and teq

Determine the RSF for the LTA (RSF_LTA) Using Section 5.0

Widespread Pitting, see Figure 6.4

Localized Pitting, see Figure 6.5

Determine the RSF Using Paragraph 6.4.2.2 or 6.4.3.2

Damage from Widespread Pitting Acceptable?

No

Yes

Check Individual Pit Criteria Using Paragraph 6.4.2.2.h

Yes

LTA Acceptable?

Determine a Combined RSF; RSF_COMB=RSF_PIT*RSF_LTA.

No

Criteria Satisfied for All Pits?

Pitting Damage with LTA Acceptable?

Yes

No

Yes

No

Repair Individual Pits Failing Criteria

Rerate, Repair or Replace Equipment

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Determine the Remaining Life

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure 6.3 Variation In The Cross Sectional Shapes Of Pits UVARIATION IN THE CROSS SECTIONAL SHAPE OF PITSU

d

d

w

w

t

t

(b) Elliptical

d

--``````-`-`,,`,,`,`,,`---

(a) Narrow, Deep

d w

w

t

t

(c) Wide, Shallow

(d) Subsurface d

w

t

(e) Undercutting d

d

w

(Horizontal)

(Vertical) (f) Microstructural Orientation

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


w

t

t

Not for Resale

Figure 6.4 Parameters For The Analysis Of Pits

5

4

Pit 1 3

Pit 2

A

Gk

6

I2

Pk A 7

8

I1 Note: In the example above: Pk = P12 and Gk = G12 because the closest pit to pit 1 is pit 2 (i.e. pit 2 is the nearest neighbor to pit 1).

(a) Pit-couple in a Plate Subject to a Biaxial Membrane Stress Field with I1 > I2

dj,k

di,k

wi,k

wj,k

wi,k

tmin

wj,k

Pk

davg,k= 0.5(di,k + dj,k)

wavg,k= 0.5(wi,k + wj,k)

(b) Section A-A

--``````-`-`,,`,,`,`,,`---


Not for Resale

t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure 6.5 Additional Parameters For The Analysis Of A Localized Region Of Pits

Localized Region With Pitting

c

CL

A

CL

A s

Cylindrical Shell //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(a) Cylinder With Localized Pitting

s

t

tmin

(b) Section A-A

s

tmin

teq = RSF*tmin

(c) Equivalent Plate Section For LTA Analysis

--``````-`-`,,`,,`,`,,`---


Not for Resale

t


Figure 6.6 Pitting Damage Confined To An LTA LTA with Pitting Damage

CL

c

A

A

s

Cylindrical Shell

(a) Cylinder With Pitting Damage Confined to an LTA

--``````-`-`,,`,,`,`,,`---

s

t

tmin

Notes: 1. The dimensions s and c define the region of localized pitting damage. 2. A combined RSF is used in the assessment (see paragraph 6.4.2.2).


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(b) Section A-A


Figure 6.7 Layered Shell Model To Evaluate Pitting Damage On Both Surfaces t1

t2 t3 t4

t

t5 t6 (a) Pit Damage From Both Surfaces Does Not Overlap

t1 t2

t

t3

--``````-`-`,,`,,`,`,,`---

Notes: 1. In Figure 6.7(a) five of the six layers are used to model the pit damage, layer four designated by t4 is not included in the calculation of the RSF (see paragraph 6.4.3.2.f.2) because there is no pitting damage in this layer. 2. The number of layers used in the assessment are established based on the deepest penetration of the individual pits included in the pit-couple data. A layer is assigned based on the depth of each pit until all pits are accounted for. Using this procedure, a single layer of material will exist (see Detail (a) above) as long as the depth of pitting damage from the inside and outside surface of the component does not overlap (see Detail (b) above). 3. Overlapping pit damage from both surfaces is not acceptable in a Level 1 or Level 2 Assessment.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(b) Overlapping Pit Damage From Both Surfaces


6.11 6.11.1

Example Problems

Example Problem 1 – Widely scattered pitting has been discovered on the cylindrical section of a pressure vessel during an inspection. The vessel and inspection data are shown below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is acceptable for continued operation at the current MAWP and temperature. Vessel Data Design Conditions

=

500 psi @ 450°F

Inside Diameter

=

60 inches

Wall Thickness

=

1 – 1/8 inches

Uniform Metal Loss

=

0.03 inches

Future Corrosion Allow.

=

0.05 inches

Material

=

SA516 Grade 70


=

0.85

Inspection Data Pit-Couple

--``````-`-`,,`,,`,`,,`---

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Pk

Gk

di ,k

wi ,k

d j ,k

w j ,k

inches

Degrees

inches

inches

inches

inches

3.5 4.2 2.7 2.1 4.6 3.1 2.9 3.1 2.6 2.2 1.8 2.5 3.8 1.9 1.8 1.0 2.5 1.5 1.3

10 15 22 30 5 15 20 45 60 0 10 20 35 90 0 22 45 67 90

0.5 1.6 0.9 1.0 0.7 1.1 0.8 0.5 1.3 0.4 1.5 0.6 2.4 0.4 1.0 0.6 0.9 0.6 0.8

0.5 0.6 0.5 0.7 0.6 0.5 0.65 0.4 0.5 0.55 0.4 0.75 0.5 0.25 0.7 0.75 0.3 0.5 0.4

0.6 1.8 0.9 1.2 1.2 2.2 0.5 1.0 0.8 0.3 0.8 0.5 1.6 0.8 0.8 0.2 1.2 0.6 0.5

0.4 0.65 0.75 0.6 0.5 0.45 0.6 0.75 0.2 0.75 0.5 0.7 0.75 0.5 0.5 0.7 0.4 0.7 0.7

Perform a Level 1 Assessment per paragraph 6.4.2 Step 1 – Determine the following parameters:


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Inspection Data


D = 60" LOSS = 0.03" FCA = 0.05" RSFa = 0.9 t = t nom - LOSS = 1125 . "-0.03" = 1095 . " Step 2 – Determine the parameters for each pit couple being evaluated. The pit diameters, pit-couple spacing and orientation are shown in the table of inspection data. Step 3 – Calculate the minimum required thickness, temperature (see Appendix A) .

t min , based on the current design pressure and

60" + 0.03"+0.05" = 30.08 " 2 500 psig 30.08 " . " = = 1032 17500 psi 0.85 - 0.6 500 psig

Rc = C t min

L t min

b

gb g b gb g b g b500 psiggb30.08 "g = = 0.501" 2b17500 psigb0.85g + 0.4b500 psigg

. ", 0.501" = 1032 . " t min = max 1032

b g = 0.40"-b1095 . "-0.05"-1032 . "g = 0.387" b0.487"+0.387"g = 0.437" =

w1,1 = 0.50"- 1.095"-0.05"-1032 . " = 0.487" w2 ,1

wavg ,1

2

The average pit depth for all pits is:

wavg = 0.5435" Step 5 – Determine the average pit diameter and pit-couple spacing. The average diameter for the first pit-couple is:

d avg ,1 =

b0.50"+0.60"g = 0.55" 2

The average diameter and pit spacing for all pits is:

d avg = 0.9237" Pavg = 2.5842" Step 6 – Calculate the Remaining Strength Factor,


RSF :

Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Step 4 – Determine the actual depth of each pit in all pit-couples. For example, the actual and average depths for the first pit-couple are:


2.584 - 0.9237 = 0.6426 2.584 3 = 0.6426 = 0.5565 2

m avg =

b g LR 0.5435" + 0.5565b1095 O . "-0.05"+0.5435"-1.032"g U RSF = min MS1.0 , 1.0P = 0.7734 V 1.032" . " W Q NT 1032 Eavg

Step 7 – Evaluate results based on the type of pitting damage: Widespread pitting with

b RSF = 0.7734g < b RSF = 0.9g ; therefore a rerate is required. The a

reduced operating pressure for continued operation is:

MAWPr = MAWP

FG RSF IJ = b500 psiggFG 0.7734 IJ = 430 psig H 0.90 K H RSF K a

Step 8 – Check the recommended limitations on the pit dimensions. All pit depths should be checked. In this example problem, only the first pit of pit-couple number one is examined to illustrate the procedure. Pit Dimensions and Remaining Thickness Ratio:

w = w1,1 = 0.487" 1032 . "-0.487"-0.05" = 0.48 1032 . " Rt = 0.48 from Table 4.4; Q = 0.55 RSFa = 0.9

Rt =

RS UV T W bd = 0.5"g £ eQ

b

gb

g

j

Dt min = 0.55 2 × 30.08" 1032 . " = 4.3"

True

Pit Depth:

b R = 0.48g ³ 0.20 t

True

Perform a Level 2 Assessment per paragraph 6.4.3 Step 1 – Determine the following parameters (see Step 1 of the Level 1 Assessment).

D = 60" LOSS = 0.03" FCA = 0.05" RSFa = 0.9 t = 1095 . " Step 2 – Determine the parameters for each pit couple being evaluated. The pit diameters, pit-couple spacing and orientation are shown in the table of inspection data.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

RECOMMENDED

PRACTICE

6-27


Step 3 - Calculate the minimum required thickness, t,, temperature (see Step 3 of the Level 1 Assessment).

, based on the current design pressure and

t,, = 1.032” Step 4 - Determine the actual depth of each pit in all pit-couples (see Step 4 of the Level 1 Assessment): iv,,, = 0.487” W2,1= 0.387” Step 5 - Calculate the components of the membrane stress field, LT,and g2 (see Figure 6.4). t, = 1.095”-0.05” = 1.045” o,=o~=~(~+0.6)=50~~~~[~+0.6)=17285psi o2 =of

=&[2-0.4)=

ziy(E-0.4)=8348

psi

Step 6 - Compute the remaining strength factor for each pit couple - an example calculation for the first pit couple is shown below:

%vg,l= 0.437”

from Step 4 of Level 1

davg,l= 0.55”

porn Step 4 of Level 1

LJqT,l = ‘J= “J=

35”-055” = 0 8429~ 35”

-

17285 psi = 20507 psi 0.8429 8348 psi = 9904 psi 0.8429

@,’ = (0.8429)1nax[~20507~, 199041,120507 - 99040 = 17285 psi Yl = [ cos” 1O”+ sin2 (2.1 O”)](20507)2 - 3[sin2 ‘,’ ’ ’ “”

(20507)(9904) +

[ sin4 1O”+ sin2 (2.1 O”)]( 9904)2 Y, = 4.207(10*) psi2

--``````-`-`,,`,,`,`,,`---



API RECOMMENDED

6-28

1

E nvg,l= min ds,

RSF,,, = min

Jan, 2000

PRACTICE 579

1.0 = 0.8427

l.O--

0.437” + 0.8427(1.095”-0.05”+0.437”-1.032”) 1.032” 1.032”

= 0.9441

Step 7 - Repeat Step 6 for all pit-couples. Determine the average value of the total number, n , of the Remaining Strength Factors, RSF, , found in Step 6 and designate this value as RSF for the region of pitting. The caicuiation

I

The

resuits for aii pit-coupies

is shown

in the following

table.

E mg,k

Pit-couple I

RSF for the assessment

is taken as the average value for all pit-couples:

1 l9 RSF = 19 c RSF, = 0.849 1 k-l --``````-`-`,,`,,`,`,,`---

Step 8 - Evaluate results Widespread reduced

pitting with

operating

MAWI

based on the type of pitting damage:

(RSF = 0.8491) < (RSF, = 0.9) ; th ere f ore a rerate is required.

pressure

for continued

operation

= iK4JW[~)=(5OOpsig)(~)=471.7

Step 9 - Check the recommended limitations Assessment for an example calculation.

The

is:

on the dimensions,

pig see Step 8 of the Level 1

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


6.11.2

Example Problem 2 – A region of localized pitting has been found in a pressure vessel during an inspection The vessel data is shown below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. The inspection data for the localized pitting is provided in Example 1. The region of localized pitting is located 60 inches away from the nearest structural discontinuity. Determine if the vessel is acceptable for continued operation at the current MAWP and temperature. Vessel Data Design Conditions

=

280 psi @ 700°F

Inside Diameter

=

120 inches

Wall Thickness

=

1.375 inches

Uniform Metal Loss

=

0.03 inches


0.06 inches

Material

=

SA 285 Grade C


=

1.0

Inspection Data Pit-couple data – see Example 1. Characteristic dimensions of localized pitting (see Figure 6.5):

s = 40" c = 20" Region with localized pitting is away from all weld seams. Perform a Level 1 Assessment. Perform a Level 1 Assessment per paragraph 6.4.2.1 Step 1 – Determine the following parameters:

D = 120" FCA = 0.06" LOSS = 0.03" RSFa = 0.9 t = t nom - LOSS = 1375 . "-0.03" = 1345 . " Step 2 – Determine the parameters for each pit couple being evaluated. The pit diameters, pit-couple spacing and orientation are shown in the table of inspection data in Example Problem 1. Step 3 – Calculate the minimum required thickness, temperature (see Appendix A).

t min , based on the current design pressure and

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


120" + 0.03"+0.06" = 60.09" 2 280 psig 60.09" . " = = 1281 . - 0.6 280 psig 13,300 psi 10

Rc = C t min

L t min

b

gb g b gb g b g b280 psiggb60.09"g = + 0.0" = 0.630" . g + 0.4b280 psig g 2b13,300 psi gb10

. ", 0.630" = 1281 . " t min = max 1281 Step 4 – Determine the actual depth of each pit in all pit-couples. For example, the actual pit depth for the pits in the first pit-couple are:

b g = 0.40"-b1345 . "-0.06"-1.281"g = 0.396" b0.496"+0.396"g = 0.446" =

w1,1 = 0.50"- 1.345"-0.06"-1.281" = 0.496" w2 ,1

wavg ,1 --``````-`-`,,`,,`,`,,`---

2

The average pit depth for all pits is:

wavg = 0.5528" Step 5 – Determine the average pit diameter and pit-couple spacing.

d avg ,1 =

b0.50"+0.60"g = 0.55" 2

The average diameter and pit spacing for all pits is:

d avg = 0.9237" Pavg = 2.5842" Step 6 – Calculate the Remaining Strength Factor, RSF: //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.584 - 0.9237 = 0.6426 2.584 3 = 0.6426 = 0.5565 2

m avg =

b g LR 0.5528" + 0.5565b1345 O . "-0.06"+0.5528"-1281 . "g U RSF = min MS1.0 , 1.0P = 0.8103 V . " 1281 W Q NT 1.281" Eavg

Step 7 – Evaluate results based on the type of pitting damage. The pitting is localized; therefore, determine an equivalent remaining thickness for use in an LTA assessment and perform a Section 5, Level 1 Assessment.

b

gb

g

t eq = RSF × t min = 0.8103 1.281" = 1034 . "


Not for Resale


Determine the acceptability for continued operation – Perform a Section 5, Level 1 Assessment of the equivalent LTA. Step 7.1 – Determine the Critical Thickness Profiles(s) and the following parameters

D = 120" FCA = 0.06" gr is not required for the analysis of an LTA Lmsd = 60" MAWP = 280 psig RSFa = 0.90 t min , based on the current design pressure

t min = 1281 . " Step 7.3 – Determine the minimum measured thickness,

t mm , the flaw dimensions (see Section 5,

paragraph 5.3.3.2), and the shell parameter, l There is only one LTA in the vessel; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

t mm = t eq = 1034 . " 1034 . "-0.06" = 0.7603 1281 . " s = 40" c = 20" Rt =

l=

b g = 4.145 120" b1.281"g 1285 40" .

Step 7.4 – Check the limiting flaw size criteria for a Section 5, Level 1 Assessment.

b R = 0.7603g ³ 0.20 . "-0.06" = 0.974"g ³ 010 . " bt - FCA = 1034 . "g = 22"j b L = 60"g ³ e18. 120" b1281 t

True

mm

True True

msd

Step 7.5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA.

Step 7.6 – Evaluate the longitudinal extent of the flaw. From Figure 5.6 with

RSl = 4.145 UV , the TR = 0.7603W t

longitudinal extent of the flaw is unacceptable. The rerate pressure is:


Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Step 7.2 – Calculate the minimum required thickness, and temperature.


b

e

gj

M t = 1 + 0.48 4.145

2 0.5

= 3.041

--``````-`-`,,`,,`,`,,`---

0.7603

RSF =

= 0.8254 1 1 - 0.7603 13.041 0.8254 = 256.8 psig MAWPr = 280 psig 0.90

b

g

gFGH

b

IJ K

R| c = 20" = 0167 U . | Step 7.8 – Evaluate circumferential extent of the flaw. From Figure 5.7 with S D 120" , |TR = 0.7603 V|W t


Step 8 – Check the recommended limitations on the dimensions (all pits should be checked, only the ith pit in first pit-couple is evaluated in this example). Pit Dimensions and Remaining Thickness Ratio: //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

w = w1,1 = 0.496" 1281 . "-0.496"-0.06" = 0.565 1281 . " Rt = 0.565 from Table 4.4; Q » 0.67 RSFa = 0.9

Rt =

RS UV T W bd = 0.5"g £ eQ

Dt min = 0.67

. "g = 8.3"j b2 × 60.09"gb1281

True

Pit Depth:

b R = 0.565g ³ 0.20 t

True

Perform a Level 2 Assessment per paragraph 6.4.3.2 Step 1 – Determine the following parameters (the pit diameters, pit-couple spacing and orientation are shown in the table of inspection data, see Example Problem Number 1)

D = 120" LOSS = 0.03" FCA = 0.06" RSFa = 0.9 t = 1345 . " Step 2 – Determine the parameters for each pit couple being evaluated. The pit diameters, pit-couple spacing and orientation are shown in the table of inspection data in Example Problem 1. Step 3 – Calculate the minimum required thickness, t min , based on the current design pressure and temperature (see Step 3 of the Level 1 Assessment).


Not for Resale


t min = 1281 . " Step 4 – Determine the actual depth of each pit in all pit-couples. For example, the actual pit depth for the first pit in the first pit-couple is (see Step 4 of the Level 1 Assessment):

b g = 0.40"-b1345 . "-0.06"-1281 . "g = 0.396"

w1,1 = 0.50"- 1345 . "-0.06"-1281 . " = 0.496"

Step 5 – Calculate the components of the membrane stress field,

t c = 1345 . "-0.06" = 1285 .

FG H

IJ K

FG H

IJ K

I 1 and I 2 see Figure 6.4).

I 1 = I Cm =

280 psig 60.09" P Rc + 0.6 = + 0.6 = 13262 psi 10 1285 E tc . . "

I 2 = I mL =

280 psig 60.09" P Rc - 0.4 = 6491 psi - 0.4 = 2 10 1285 2 E tc . . "

FG H

IJ K

FG b gH

IJ K

Step 6 – Compute the remaining strength factor for each pit couple – an example on how to compute the remaining strength factor for a pit-couple is shown in Step 6 of the Level 2 Assessment in Example Problem Number 1. Step 7 – Repeat Step 6 for all pit-couples. Determine the average value of the total number, n , of the Remaining Strength Factors, RSFk , found in Step 6 and designate this value as RSF for the region of pitting. The calculation results for all pit-couples is shown in the following table. Pit-couple 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

RSFk

Eavg ,k 0.8429 0.5959 0.6708 0.4869 0.7934 0.4682 0.7791 0.8396 0.7853 0.8409 0.3611 0.7832 0.4932 1.0000 0.5000 0.6037 0.6424 0.8877 1.0000

0.9478 0.8058 0.8424 0.7426 0.9143 0.8058 0.8952 0.9309 0.9443 0.9222 0.7785 0.8803 0.7557 1.0000 0.7688 0.7787 0.9052 0.9504 1.0000

The RSF for the assessment is taken as the average value for all pit-couples:

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

w2 ,1


RSF =

1 19 å RSFk = 0.8720 19 k =1

Step 8 – Evaluate results based on the type of pitting damage. The pitting is localized; therefore, determine an equivalent remaining thickness for use in an LTA assessment and perform a Section 5, Level 1 Assessment. --``````-`-`,,`,,`,`,,`---

b

gb

g

t eq = RSF × t min = 0.8720 1.281" = 1117 . " Determine the acceptability for continued operation – Perform a Section 5, Level 1 Assessment of the equivalent LTA. Step 8.1 – Determine the Critical Thickness Profiles(s) and the following parameters

D = 120" FCA = 0.06" gr is not required for the analysis of an LTA Lmsd = 60" MAWP = 280 psig RSFa = 0.90 Step 8.2 – Calculate the minimum required thickness, and temperature.

t min , based on the current design pressure

t min = 1281 . " Step 8.3 – Determine the minimum measured thickness,

t mm , the flaw dimensions (see Section 5,

paragraph 5.3.3.2), and the shell parameter, l . There is only one LTA in the vessel; therefore, the flaw-to-flaw spacing criteria does not need to be checked.

t mm = t eq = 1117 . " 1117 . "-0.06" = 0.8251 1281 . " s = 40" c = 20" Rt =

l=

b g = 4.145 120" b1.281"g 1285 40" .

Step 8.4 – Check the limiting flaw size criteria for a Level 1 Assessment.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:


Not for Resale


b R = 0.8251g ³ 0.20 . "-0.06" = 1057 . "g ³ 010 . " bt - FCA = 1117 . "g = 22"j b L = 60"g ³ e18. 120" b1281

True

t

True

mm

True

msd

Step 8.6 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA.

Step 8.7 – Evaluate the longitudinal extent of the flaw. From Figure 5.8 with

RSl = 4.145 UV , the TR = 0.8251W t


b

e

gj

M t = 1 + 0.48 4.145

2 0.5

= 3.041

0.8251

RSF =

= 0.8755 1 1 - 0.8251 13.041 0.8755 = 272.4 psig MAWPr = 280 psig 0.90

b

b

g

gFGH

IJ K

R| c = 20" = 0167 U . | Step 8.8 – Evaluate circumferential extent of the flaw. From Figure 5.9 with S D 120" , |TR = 0.8251 V|W t


Step 9 – Check the recommendation for limitations on the pit dimensions, see Step 8 of the Level 1 Assessment for an example calculation.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\ --``````-`-`,,`,,`,`,,`---


Not for Resale

SECTION 7 – Assessment Of Blisters And Laminations (Jan, 2000)

7.1

General

7.1.1

Fitness-For-Service (FFS) assessment procedures for pressurized components with hydrogen blisters and laminations, excluding HIC or SOHIC damage, are provided in this Section. The assessment procedures for blisters and laminations are shown in the flow charts contained in Figures 7.1 and 7.2, respectively.

7.1.2

Hydrogen blistering is caused by hydrogen accumulation at imperfections in the steel, such as laminations or inclusions. Blistering typically occurs in low temperature wet H2S or hydrofluoric acid environments which charge atomic hydrogen into the steel. The hydrogen combines at imperfections to form molecular hydrogen which is too large to diffuse out. The hydrogen accumulates and results in the build-up of high pressure which causes local stresses that exceed the yield strength of the material in the vicinity of these imperfections. The yielding of the material and subsequent plastic deformation in the form of bulging due to pressure loading results in a blister. Sometimes cracks can extend from the periphery of a blister and can propagate in a through-wall direction, particularly if the blister is located near a weld.

7.1.3

Laminations are a plane of non-fusion in the interior of a steel plate that results during the steel manufacturing process. Laminations are usually detected during an ultrasonic examination. Laminations that are parallel to the plate surface and are not in close proximity to structural discontinuities are not detrimental, unless they are in a hydrogen charging service and are in close proximity of a weld.

7.2


7.2.1

The FFS assessment procedures described below may be used to evaluate the acceptability of blisters and laminations subject to the limitations in this section. The assessment procedures cover both internally and externally bulged blisters. The assessment procedures also include analysis methods for laminations which are parallel to the surface of the plate or that have a through-thickness component (i.e. the lamination is not parallel to the surface of the plate).

7.2.2


7.2.3


7.2.3.1

The Level 1 and 2 assessment procedures for blisters apply only if all of the following conditions are satisfied: The original design criteria were in accordance with a recognized code or standard (see Section 1, paragraphs 1.2.2 or 1.2.3).

b.

The operating temperature is less than 204.4°C (400°F) for carbon steel or low alloy steels, or is below the applicable design curve in API 941, whichever is greater. Blisters associated with high temperature hydrogen attack are specifically excluded from this assessment.


--``````-`-`,,`,,`,`,,`---

a.

7-1 Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


c.

The material is considered to be ductile and is not subject to embrittlement during operation due to temperature or the process environment (see Section 5, paragraph 5.2.3.1.c).

d.

The component is not in cyclic service (see Section 4, paragraph 4.2.3.1.d).

e.

There is physical bulging which is discovered by visual or UT examination. If physical bulging is not present, the defect should be evaluated as a lamination.

f.

The component geometry is one of those cited in Section 4, paragraph 4.2.3.1.f.

g.

The applied loads are limited to internal or external pressure.

h.

The assessment procedures in this section are not applicable to HIC or SOHIC damage (see Appendix G, paragraph G.3.5).

A Level 3 assessment for blisters should be performed when the requirements of paragraph 7.2.3.1 are not satisfied, the blister is located in close proximity to a weld seam (see paragraph 7.4.2.1.b.5) or major structural discontinuity (see paragraph 7.4.2.1.b.6). In addition, a Level 3 assessment is required to evaluate a component with a multitude of closely spaced blisters (see Figure 7.3).

7.2.3.3

The Level 1 and 2 assessment procedures for laminations apply only if the lamination is located parallel to the plate surface and does not have any through thickness cracking associated with it. If the lamination is not parallel to the surface of the plate, then the flaw shall be evaluated as a cracklike flaw using the procedures of Section 9.

7.3

Data Requirements

7.3.1


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7.2.3.2

An overview of the original equipment data required for an assessment is provided in Section 2, paragraph 2.3.1. 7.3.2

Maintenance And Operational History An overview of the maintenance and operational history required for an assessment is provided in Section 2, paragraph 2.3.2.

7.3.3


7.3.3.1

The required data and measurements for a blister evaluation are as follows: a.

Blister Dimensions – The size of the blister to be used in the assessment is based on the following requirements. 1.

//^:^^#^~^^""~:@"


Blister Diameter – The blister dimensions to be recorded depend on the assessment level and are defined below. a)

Level 1 Assessment – The largest dimension, s or c should be taken as the diameter (see Figure 7.4).

b)

Level 2 Assessment – The blister dimensions in the longitudinal and circumferential directions, s and c , should be recorded consistent with the method used to characterize a region of localized metal loss in Section 5.

Not for Resale

Jan, 2000

RECOMMENDED

2.

b.

PRACTICE

7-3


Blister-To-Blister Spacing, Lb - Measurements should be made to determine the blisterto-blister spacing (including all nearest neighbors, see Figure 7.3). This information should be detailed and provided on an inspection sketch. If there are multiple blisters in close proximity to one another, the size of the blister to be used in the assessment is established considering the effects of neighboring blisters using the criterion for local metal loss described in Section 5 (see Figure 5.5). In addition, if the distance between two adjacent blisters (measured edge-to-edge) is less than or equal to two times the nominal plate thickness, the blisters should be combined and evaluated as a single blister.

Bulge Direction and Projection,

BP - The blister bulge direction, inside or outside of the

pressure containing component, and the blister projection above the shell surface (see Figure 7.4) should be recorded. C.

Blister Minimum Measured Wall Thickness, t,,,,,,- For an internal blister this is the distance from the outside surface to the blister, and for an external blister, this is the distance from the inside surface to the blister (see Figure 7.4).

d.

Blister Periphery Cracking - The blister should be examined to determine if there are any cracks extending in the plane of the blister and/or in a through-thickness direction. This type of cracking typically occurs at the periphery of the blister and can lead to cracking in the through thickness direction.

e.

Blister Crown Cracking And Vent Ho/es - Cracks on the crown of blisters (see Figure 7.5) affect the strength calculation; therefore, the dimension s, should be recorded if cracks are present. Alternatively, the blister may have previously been vented (see Figure 7.6) to relieve the internal pressure thereby decreasing the possibility of future growth. If so, the diameter of the vent hole can be used for s, .

f.

Blister Spacing To Weld Joints, L, - Measurements should be made to determine the spacing of blisters from weld joints (see Figure 7.7). This information is important because if the blister is close to the weld, through wall cracking may occur. This information should be detailed and provided on an inspection sketch.

9.

Blister Spacing To Major Structural Discontinuities,

Lmd - Measurements should be made to

determine the location of the blister to major structural discontinuities such as cylindrical to conical transitions and nozzle attachments. This information should be detailed and provided on an inspection sketch. 7.3.3.2

The above information should be recorded in a format similar to the one shown in Table 7.1. In addition, the creation of a detailed sketch at the time of the inspection showing the information in paragraph 7.3.3.1 is recommended.

7.3.3.3

The required data and measurements for a lamination are similar to those of blisters, but are limited to paragraphs 7.3.3.1 .a, c, d, f, and g. The above information should be recorded in a format similar to the one shown in Table 7.1. In addition, the creation of a sketch at the time of the inspection showing the information in paragraph 7.3.3.1 is recommended.

7.3.4

Recommendations

7.3.4.1

Blisters are usually discovered by visual observation of surface bulging on either the inside or outside of the equipment. During an in-service inspection/monitoring blisters may also be discovered with UT examination.

For Inspection Technique And Sizing Requirements

--``````-`-`,,`,,`,`,,`---



7-4

API RECOMMENDED

PRACTICE 579

Jan, 2000

7.3.4.2

Ultrasonic examination can be used to determine the depth of the blister and remaining plate thickness at the blister location. UT examination should also be used to ensure that HIC and SOHIC cracking are not present. Details regarding this type of cracking and examination techniques are provided in NACE Standard RP0296.

7.3.4.3

The periphery of the blister should be inspected for cracking that can be associated with hydrogen blisters. The crown of the blister should also be examined to determine the presence and size of a crown crack. Inspection techniques to identify and size crack-like flaws are covered in Section 9, paragraph 9.3.7.

7.4

Assessment .

And Acceptance

Criteria

Awnnrimar WI". 1.1..

7.4.1.1

If the blister is located within the region of the specified corrosion/erosion allowance, the assessment procedures of this section should still be followed to evaluate any crack-like flaws associated with the blister, and the proximity of the blister to a weld joint.

7.4.1.2

An overview of the assessment levels for blisters is provided in Figure 7.1. The Level 1 assessment procedures provide a screening criteria to accept existing blisters. Blisters failing the screening criteria may be analyzed using a Level 2 assessment. The assessment procedures in Level 2 utilize the methodology of Section 5 to evaluate the blister as an equivalent region of local metal loss. The Level 3 assessment procedures are intended to evaluate more complex regions of blisters, loading conditions, and/or components with details where only limited design rules are provided in the original construction code or standard. Detailed stress analysis techniques are normally utilized in a Level 3 assessment.

7.4.1.3

An overview of the assessment levels for laminations is provided in Figure 7.2. The Level 1 assessment provides the criteria for the acceptability of laminations. The Level 2 assessment procedure is similar to the Level 1 procedure except it applies to components operating in a hydrogen charging environment. The Level 3 assessment procedures are intended to evaluate situations which do not satisfy the Level 1 or Level 2 assessment procedures such as a lamination close to weld joint in a hydrogen charging environment, or a lamination close to a major structural discontinuity such as a nozzle or skirt attachment location.

7.4.2

Level 1 Assessment

7.4.2.1

The following procedure can be used to determine component using a Level 1 Assessment.

> J

the acceptability

a.

Step 1 - Determine

b.

Step 2 - Check the blister acceptance following are satisfied:

criteria, blisters

1.

requirements

the information

The blister diameter

in paragraph

and venting

of a blister in a pressurized

7.3.3.1. are acceptable

without

meet one of the following

criteria.

4

The blister diameter (see paragraph 7.3.3.1 .a and Figure 7.4) is less than or equal to 50.8 mm (2 inches) and is vented or unvented (see Figure 7.6) or

b)

The blister diameter equal to thickness 7.6).

0.6,/c

(see paragraphs where

7.3.3.1 .a and Figure 7.4) is less than or

D is the shell inside diameter

of the shell containing

and t,,,, is

the wall

the blister, and the blister is vented (see Figure

March 2000


repair if all of the

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

744 . -7.

Techniques

2.

The blister projection,

Bp , above the surface is less than or equal to 10% of the blister

diameter (see Figure 7.4). 3.

The minimum measured thickness, t mm , measured from the side which is not bulged (see Figure 7.4), is greater than or equal to one-half of the nominal plate thickness,

4.

There are no periphery cracks directed towards the inside or outside surface of the component as shown in Figure 7.4.

5.

The distance between the edge of the blister and the nearest weld seam, Lw , is greater than or equal to 25.4 mm (1 inch) or twice the nominal plate thickness, whichever is greater (see Figure 7.7).

6.

The distance from the blister edge to a major structural discontinuity, than or equal to

7.4.2.2

Lmsd , is greater

18 . Dt nom where D and tnom are defined in subparagraph 1(b) above.

A lamination is acceptable, regardless of size, if all of the following are satisfied: a. The component is not operating in a hydrogen charging service. b. The distance from the edge of the lamination to a major structural discontinuity is greater than or equal to

7.4.2.3

18 . Dt nom where D and tnom are defined in paragraph 7.4.2.1.b.1.b.


The damaged plate may be replaced or repaired.

b.

In the case of a blister, the blister can be removed by blend grinding as shown in Figure 7.9; if the blister is blend ground it should be evaluated as a local thin area per the assessment procedures of Section 5.

c.

A Level 2 or Level 3 Assessment can be conducted.

7.4.3

Level 2 Assessment

7.4.3.1

The Level 2 assessment procedures for blisters are dependent on their location and direction of bulging (to the inside or outside of the pressure boundary, see Figure 7.4). A logic diagram for a Level 2 Assessment is shown in Figure 7.8. If an assessment is required, the blister is evaluated as an equivalent region of local metal loss using the assessment procedures of Section 5. Specific details and recommendations for the assessment are provided in the following paragraphs. a.

Step 1 – Determine the information in paragraph 7.3.3.1.

b.

Step 2 – Determine the acceptability of the blister based on its orientation and location: 1.

Blisters located near weld seams are assessed using the same assessment procedures used for blisters located away from welds (see subparagraphs (2) and (3) below), subject to the following additional requirements. a)

A blister is considered to be located at a weld seam if it lies within 25.4 mm (1 inch) or twice the plate thickness from the edge of the weld, whichever is greater (see Figure 7.7). Experience with the inspections of pressure containing equipment have shown that cracks which develop from these blisters may

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



propagate along the weld fusion line or in the heat affected zone in the throughthickness direction (see Figure 7.7), particularly if the welds were not originally subject to post weld heat treatment. Therefore, blisters at weld seams should be monitored in-service.

3.

If through-wall direction hydrogen related cracks are found at a weld during a shut-down inspection, the blister is not acceptable per Level 2 Assessment.

c)

If cracks are determined to be growing in a through-wall direction during in-service inspection/monitoring, the blister is not acceptable per a Level 2 Assessment and appropriate actions should be considered if the equipment is to remain in-service. A Level 3 Assessment and/or on-line repairs, or the application of a leak repair clamp/box may be required based on factors such as whether the weld was subject to PWHT and the consequences of through-wall cracking.

Blisters bulged to the inside surface of the component – recommendations and additional acceptance criteria are as follows: a)

Venting of the blister to the inside surface (see Figure 7.6) to prevent further growth is recommended. However, venting of a blister to the inside surface is not recommended for components in hydrofluoric acid service because of the safety concerns regarding contamination, decontamination as well as the potential for corrosion and scale build-up within the blister crevice.

b)

The blister is considered acceptable if it is free from cracking or only has periphery cracks directed towards the inside surface (see Figure 7.4), and the assessment procedures per Section 5 are satisfied. In this assessment, an equivalent region of local metal loss is used with a length equal to the blister diameter plus any crack growth extension at the periphery and a remaining thickness equal to t mm (see Figure 7.4).

Blisters bulged to the outside surface of the component – recommendations and additional acceptance criteria are as follows: a)

Venting of the blister to the outside surface is recommended to prevent further growth. If the equipment is in operation, on-line venting to the outside may entail some risk if there is a leak-path to the inside surface; therefore, it is advisable to first monitor and observe some blister growth, before venting.

b)

If the blister is vented, or up to the time that it is vented if currently in-service, the blister may be considered as acceptable provided that the in-service monitoring requirements per paragraph 7.7 are followed and the remaining criteria of this paragraph are satisfied.

c)

The blister is not severely bulged to the outside surface. Severe bulging is defined as a blister projection greater than 10% of the blister diameter (see Figure 7.4). If severe bulging is present, then the blister can be evaluated as a region of local metal loss with the bulged plate section neglected using the assessment procedures per Section 5.

d)

If the blister is free from periphery and crown cracks (see Figure 7.5), then it is acceptable regardless of size if the blister spacing criteria is satisfied. If the blister is cracked, acceptability is based on the following criteria. 1)


If the blister has periphery cracks directed towards the inside surface (see Figure 7.4), then the blister is considered to be not acceptable.

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

2.

b)

2)

If the blister has periphery cracks towards the outside surface with or without crown cracks, then the blister can be evaluated as a region of local metal loss using the assessment procedures per Section 5. The length of the region of local metal loss to use in this assessment is the blister diameter plus any crack growth extension at the periphery, and the remaining thickness is t mm (see Figure 7.4).

3)

If the blister has only crown cracks, the blister can be evaluated as a region of local metal loss using the assessment procedures per Section 5. For this case, the blister diameter or the length of the crown crack (see paragraph 7.3.3.1.e) can be used in the assessment with a remaining thickness equal to t mm (see Figure 7.5).

7.4.3.2

A lamination is acceptable in a component operating in a hydrogen charging service, regardless of size, if the criteria in 7.4.2.2.b is satisfied. In addition, if the distance between the edge of the lamination and the nearest weld seam is less than or equal to 25.4 mm (1 inch) or twice the nominal plate thickness, whichever is greater, then the same provisions as detailed in paragraphs 7.4.3.1.b.1 for blisters apply to ensure that through thickness cracking does not occur.

7.4.3.3


The damaged plate may be replaced or repaired.

b.

In the case of a blister, the blister can be removed by blend grinding as shown in Figure 7.9; if the blister is blend ground it should be evaluated as a local thin area per the assessment procedures of Section 5.

c.

A Level 3 Assessment can be conducted.

7.4.4

Level 3 Assessment

7.4.4.1

A level 3 assessment for blisters and laminations consists of performing a detailed stress analysis per the techniques discussed in Appendix B of this Recommended Practice. In general, the nonlinear stress analysis techniques described in Appendix B, paragraph B.3 are recommended for this evaluation. In addition, if cracks are detected by inspection, a fracture mechanics assessment in accordance with Section 9 of this Recommended Practice is required.

7.4.4.2

A Level 3 assessment is required if the component has a multitude of closely spaced blisters (see Figure 7.3). This assessment level is required because explicit rules for the analysis are not provided in the Level 1 and Level 2 Assessment procedures. A recommendation for this analysis is to first use the concepts of this section to evaluate individual blisters. If the criteria for an individual blister is satisfied, the array of blisters can then be modeled as equivalent pitting damage, and the assessment procedures of Section 6 can be used to evaluate the overall weakening effect due to the blister array.

7.5

Remaining Life Assessment The growth rate and the remaining life of a blister or lamination cannot be adequately evaluated using analytical techniques. However, a remaining life evaluation is not required because the presence of blisters or laminations in equipment does not have a direct effect on the internal inspection interval except for the special inspection requirements required for in-service monitoring.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---



Remediation

7.6.1

Blisters meeting acceptance criteria of any assessment level should be considered for venting if the blister is deeper than 3.2 mm (0.125 inches) from the bulged surface and the blister diameter exceeds 50.8 mm (2 inches).

7.6.1.1

Venting of blisters may involve risk and all applicable plant safety guidelines should be reviewed and followed. If the component is in-service, additional inspection is required prior to drilling (see paragraph 7.4.3.1.b.3).

7.6.1.2

Venting of blisters can typically be accomplished by drilling a small diameter hole (e.g. 3.2 mm (0.125 inches)) in the center of the blister from the surface where the bulging is observed. Blisters located on the inside surface of equipment may be vented to the inside, or may be vented from the outside during downtime periods provided:

--``````-`-`,,`,,`,`,,`---

7.6

·

The blister is parallel to the plate surface as confirmed by inspection.

·

The blister is not already vented to the inside by crown or periphery cracking.

·

The component is not in hydrofluoric acid surface.

7.6.1.3

Electric drills should not be used to vent blisters because of the presence of hydrogen in the blister cavity. Air-driven drills should be used, and suitable safety provisions (see NACE Standard RP0296) should be made to ensure that ignition of the hydrogen released during the drilling operation does not occur. An inert gas and other safety provisions can be utilized to purge the area to help ensure that ignition does not occur.

7.6.2

Consideration should be given for coating/strip lining the inside surface of the component, particularly the weld regions of equipment with blistered plate, to prevent further blistering. A coating (e.g., organic, inorganic, or metal spray) should be considered, even if the blister is found to be acceptable, to help prevent further hydrogen charging of the damaged plate material. In addition, process changes and/or inhibitor additions that would decrease the propensity for hydrogen charging should also be evaluated and considered.

7.6.3

Blend grinding and weld repair techniques can be used to repair cracked blisters and to prevent crack growth. Caution should be exercised when conducting weld repairs on hydrogen charged steel to prevent subsequent re-cracking. The application of a suitable coating after blend grinding or weld repairs should be considered. All blend ground areas should be checked using either MT or PT examination techniques.

7.6.4

If the plate material is severely damaged and cannot be accepted per the assessment procedures or repaired, it should be replaced. The metallurgy and design of the replacement plate, weld details and weld procedures should be reviewed by a materials engineer and a mechanical engineer (see Section 1, paragraph 1.4.3).

7.6.5

Additional information regarding remediation and repair of blisters can be found in NACE Standard RP0296.

7.7


7.7.1

Periodic monitoring of the process stream for hydrogen charging conditions and/or of the equipment for additional damage should be considered, once hydrogen blistering has been observed. Monitoring of blisters, particularly those adjacent to welds that are not vented, and laminations in hydrogen charging service adjacent to welds, is important since the driving force for blister formation and growth (i.e. hydrogen pressure in the blister cavity) has not been relieved.

7.7.2

Inspection methods can be used to monitor blister growth and weld associated hydrogen damage. Common methods are straight beam UT for blisters/laminations and angle beam UT for cracks. Various forms of hydrogen probes, both internal or external, can be used to monitor hydrogen charging levels. The inspection monitoring interval can be adjusted based on the measured


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


hydrogen charging levels (e.g. if high hydrogen charging levels are measured, frequent inspection should be considered). 7.7.3

If the blister is found to grow during the monitoring process, the evaluation procedures in paragraph 7.4 and the remediation guidelines in paragraph 7.6 should be reviewed and implemented based on the severity of the damage that is anticipated.

7.8

Documentation

7.8.1

The documentation of the FFS Assessment should include the information cited in Section 2, paragraph 2.8.

7.8.2

The location, size, spacing and condition of existing blisters should be recorded along with the results of the assessments performed. A sample data sheet is provided in Table 7.1 for this purpose.

7.8.3

If blister growth is detected during the monitoring process, the blister physical dimensions and location should be recorded along with the time period between measurements. In addition, the associated operating conditions and process stream constituents should be recorded in order to permit an evaluation of the hydrogen charging environment relative to the process operation of the equipment. This information may be valuable in determining suitable process changes in the operation of the equipment, if possible, to mitigate further damage.

7.9

References

7.9.1

Anderson, T.L., Merrick, R.D., Yukawa, S., Bray, D.E., Kaley, L. and Van Scyoc, K., Fitness-ForService Evaluation Procedures for Operating Pressure Vessels, Tanks, and Piping in Refinery and Chemical Service,” FS-26, Consultants Report, MPC Program on Fitness-For-Service, Draft 5, The Materials Properties Council, New York, N.Y., October, 1995.

7.9.2


7.9.3

Bagnoli, D.L., Yin, H., Walker, S.T. and Milton, D.J., “Fitness For Service Applications For Equipment in Wet H2S Services”, ASME PVP-Vol. 136, American Society of Mechanical Engineers, New York, 1996, pp. 1-16.

7.10

Tables and Figures

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table 7.1 Size, Location, Condition And Spacing For Blisters Enter the data obtained from a field inspection on this form. Inspection Date: Equipment Identification: Equipment Type: _____ Pressure Vessel _____ Storage Tank Component Type & Location:


Blister Number

Diameter s (1) (2)

Dimension c (1)

(mm:in)

(mm:in)

Edge-ToEdge Spacing To Nearest Blister Lb (1)

Bulge Direction (inside/ outside)

Blister Projection Bp

Remaining Thickness tmm

Cracking At Periphery

(mm:in)

(mm:in)

(Yes/No)

Crown Cracking or Venting (2)

Length Of Crown Cracks sc (2)

Spacing To Nearest Weld Joint Lw (3)

Spacing To Nearest major Structural Discontinuity Lmsd

(mm:in)

(mm:in)

(mm:in)

--``````-`-`,,`,,`,`,,`---

Data Required For Level 1 And Level 2 Assessment

Notes: 1. The blister-to-blister spacing may effect the size of the blister to be used in the evaluation (see paragraph 7.3.3.1.a and Figure 7.3) 2. If the blister has crown cracks, enter the length of the crack, see dimension sc in Figure 7.5. If the blister has a vent hole, indicate as such with the diameter of the hole (see Figure 7.6). 3. See Figure 7.7.

7-10


Not for Resale

(mm:in)


Figure 7.1 Overview Of The Assessment Procedure To Evaluate A Component With Blisters


Perform Level 1 Assessment


Yes

No

No


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Yes


Yes

No Rerate Equipment?

No


Yes Perform Rerate per Level 2 Criteria to Reduce Pressure and/or Temperature

Yes

Equipment Acceptable per Level 3 Assessment? Yes

Determine Remaining Life Establish In-Service Monitoring Program if Necessary, Apply Remediation if Necessary, Develop an Inspection Plan

No

Rerate Equipment?

No

Yes


Remaining Life Acceptable? Yes Return the Equipment to Service


No

--``````-`-`,,`,,`,`,,`---

Repair, Replace or Retire Equipment

No

Not for Resale


Figure 7.2 Overview Of The Assessment Procedure To Evaluate A Component With Laminations


Evaluate As a Crack-Like Flaw Using Section 9

Lamination is Parallel to the Component Surface?

No

Yes Perform Level 1 Assessment


Yes

No


No

Yes


Yes

No


No

Yes


Yes

No No

Rerate Equipment? Yes Perform Rerate per Level 3 Criteria to Reduce Pressure and/or Temperature

Determine Remaining Life Establish In-Service Monitoring Program if Necessary, Apply Remediation if Necessary, Develop an Inspection Plan

Repair, Replace or Retire Equipment

No

Remaining Life Acceptable? Yes Return the Equipment to Service

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

RECOMMENDED

Assessment

Figure 7.3 Requirements For Closely Spaced Blisters

Blisters are Evaluated as an Equivalent LTA Per Section 5.0 As Describeb in the Level 1 and Level 2 Assessment Procedures of this Section

r

I L----------------

Blisters are Evaluated as a Region of Equivalent Pits Per Section 6.0 as Recommended in the Level 3 Assessment procedures of this Section

Sheli

1

_----_-__---_

: IO

O

0

I 0 lo0

01 Il

ooooo

4

000 I

o”

0

oi

00 i

0

001 I

i I

f

O

P

Oo

I

O

0

10 I

f 0 I I ---------------


7-13


Oo

0

O

I

00

0

Ooo/ 0

0

I

O o”

0

/ 0’ :


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Additional

PRACTICE

--``````-`-`,,`,,`,`,,`---

Jan, 2ooo

API RECOMMENDEDPRACTICE 579

7-14

Jan, 2000

Figure 7.4 Typical Blister

Periphery of Blister \

Blister Plan View

Section A-A Cross Section Of Blister

Notes A

The blister diameter to be used in the assessment is defined in paragraph 7.3.3.1 .a.

March 2000


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

\

Blister Periphery Cracks Directed Towards Inside or Outside Surface, as Applicable

--``````-`-`,,`,,`,`,,`---

Component Inside or Outside Surface, as Applicable

Jan, 2000

RECOMMENDED

PRACTICE


7-15

Figure 7.5 Blister With A Crown Crack Periphery

of Blister -T

L

Crown Crack J

Blister

Blister Plan View

Inside or Outside

Surface

--``````-`-`,,`,,`,`,,`---

Crown Crack -

Section A-A Cross Section of Blister

dNotes 1. The dimension S, can be used to characterize the length of an equivalent LTA for a blister located on the outside surface; alternatively, the dimension max[s, c] can be used. 2.

The dimension max[s, c] is used to characterize the length of an equivalent LTA for a blister located on the inside surface.



API RECOMMENDED

7-16

Blister

Jan, 2000

PRACTICE 579

Figure 7.6 With A Vent Hole Component Inside or Outside Surface

Periphery of Blister

\

\

Drilled Vent Hole

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Blister Plan View

Section A-A Cross Section of Blister LNotes

The blister diameter

to be used in the assessment

is defined

--``````-`-`,,`,,`,`,,`---


March 2000

Not for Resale

in paragraph

7.3.3.1 .a.

Jan, 2000

RECOMMENDED

PRACTICE

7-17


Figure 7.7 Blister Periphery Cracks At A Weld Periphery

of Blister

Blister

a) Blister

Spacing

Close

Plan View

to a Weld

Seam

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Inside or Outside

r

Blister Periphery Line of the Weld

b) Blister

Periphery

Surface

--,

Cracks Following the Fusion in the Through Thickness Direction

Cracks

at the Weld

\

Joint

inch)].

--``````-`-`,,`,,`,`,,`---

Notes L The blister is considered to be close to a weld seam if L,,, I max[2t,, , 25.4 mm (1 1. The blister diameter to be used in the assessment is defined in paragraph 7.3.3.1 .a. 2.



API RECOMMENDED

7-18

PRACTICE

Jan, 2000

579

Figure 7.8 Level 2 Assessment Procedure For Blisters

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Venting of the Blister to the Outside Surface is Recommended

LI”Il.7 “y

<

,u

WA;;

m

I

Yes

No x Blister

.- ____.. lent. or Repair or ReDlace the \

Y

\

--``````-`-`,,`,,`,`,,`---

Return to Service; Monitor if Near a Structural Discontinuity or Weld Seam

March 2000


Not for Resale

Jan, 2000

RECOMMENDED

PRACTICE

7-19


Figure 7.9 Blend Ground Area Remaining After Removal Of A Blister

The Recommended Radius is t/4

Inspect Periphery Region of the Blister to Ensure There are no Cracks Present

Minimum

i

--``````-`-`,,`,,`,`,,`---

i Ln __----

i

Blend Grind Periphery of Blister to Provide Smooth Contour to Minimize Stress Concentration and/or to Remove any Cracks.

Note:


Blisters

Removed by Blend Grinding should be Evaluated Using the Assessment Procedures in Section 5.

as an LTA



7-20

Jan, 2000

7.11

Example Problems

7.11.1

Example Problem 7 - A cylindrical vessel with both internal and external blisters is shown below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is suitable for continued operation at the current MA m and temperature using the Level 1 Assessment criteria. Vessel Data Vessel Design Conditions

250 psi @ 350°F

Inside Diameter

96 inches

Nominal Wall Thickness

1.14 inches

Uniform Metal Loss

0.0 inches

Future Corrosion Allow.

0.125 inches

Material

SA 516 Grade 70

Allowable Stress

17,500 psi


0.85

Inspection Data

--``````-`-`,,`,,`,`,,`---

Pressure Vessel Shell with Blisters /-

0

External Blister

(0__.’ Internal Blister

March 2000


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The pressure vessel section containing the blister is shown below. The inspection data for the blisters is shown in the following table.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\ --``````-`-`,,`,,`,`,,`---

Inspection Data – Location, Size, Spacing and Condition for Isolated Blisters Dimension

s (1)

c (2)

10” 6” 6” 12” 2” 2” 11”

8” 5” 6” 10” 4” 2” 8”

Edge-toEdge Spacing to Nearest Blister Lb

18” 18” 12” 10” 6” 6” 12”

Bulge Projection

External External Internal Internal Internal Internal External

Blister Projection Bp

Remaining Thickness tmm

Cracking at Periphery

Crown Cracking or Venting

Length of Crown Cracks sc

Spacing to Nearest Weld Joint Lw

1.5” 0.3” 0.6” 0.8” 0.1” 0.1” 0.3”

0.70 0.80 0.60 0.60 0.90 0.60 0.60

No No No No No No Yes (3)

Crack Vent Crack Crack Vent No Crack

6” -2” 6” --5”

10” 5” 6” 8” 10” 6” 3”

Notes: 1. This dimension is in the longitudinal direction. 2. This dimension is in the circumferential direction. 3. Inspection indicates that the periphery cracks are growing in the through-wall direction.

7-21

Spacing to Nearest Major Structural Discontinuity Lmsd

25” 20” 30” 30” 40” 40” 24” Not for Resale

A B C D E F G

Diameter


Blister Identification


Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blister A Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied: The blister diameter and venting requirements meet one of the following (note that the blister-toblister spacing check satisfies therefore,

b

s = 10.0" ):

False bs = 10"g £ 2 inches & vented or unvented: . "g = 6.27"j & is vented: bs = 10"g £ e0.6 Dt = 0.6 b96"gb114

· ·

nom

False g i b = 0.70"g ³ b0.5t = 0.57"g :

·

dB bt

·

Blister Does Not Have Periphery Cracks:

·

· ·

p

mm

bL bL

w

g b

g

"2 s x 2c" box criteria and Lb = 18" ³ 2t nom = 2.28" ;

False

= 15 . " £ 01 . s = 1.0" : nom

g c = 25"g ³ d18 .

True True

h

= 10" ³ max 2t nom , 1 inch = 2.28" :

msd

i

Dt nom = 18.8" :

True

True

Therefore, Level 1 Assessment criteria are not satisfied.

Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blister B Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied: ·

The blister diameter and venting requirements meet one of the following (note that the blister-toblister spacing check satisfies

b

g b

g

"2 s x 2c" box criteria and Lb = 18" ³ 2t nom = 2.28" ; therefore

s = 6" ):

bs = 6"g £ 2 inches & vented or unvented: False = 0.6 b96"gb114 . "g = 6.27"j & is vented: · b s = 6"g £ e0.6 Dt d B = 0.3"i £ b0.1s = 0.6"g : True True bt = 0.80"g ³ b0.5t = 0.57"g : ·

nom

· ·

p

mm

nom

--``````-`-`,,`,,`,`,,`---


Not for Resale

True

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

·


· · ·


bL bL

w

g c = 20"g ³ d18 .

True

h

= 5" ³ max 2t nom , 1 inch = 2.28" :

msd

i

Dt nom = 18.8" :

True

True

Therefore, Level 1 Assessment criteria are satisfied.

Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blister C Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied: The blister diameter and venting requirements meet one of the following (note that the blister-toblister spacing check satisfies therefore,

b

s = 6" ):

bs = 6"g £ 2 inches & vented or unvented: False . "g = 6.27"j & is vented: bs = 6"g £ e0.6 Dt = 0.6 b96"gb114

· ·

nom

g True i b = 0.60"g ³ b0.5t = 0.57"g :

·

dB bt

·


·

· ·

p

mm

bL bL

w

g b

g


True

= 0.6" £ 0.1s = 0.6" :

True

nom

g c = 30"g ³ d18 .

--``````-`-`,,`,,`,`,,`---

·

True

h

= 6" ³ max 2t nom , 1 inch = 2.28" :

msd

i

Dt nom = 18.8" :

True

True


Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blister D Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied:


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


·

The blister diameter and venting requirements meet one of the following (note that the blister-toblister spacing check satisfies therefore,

b

s = 12" ):


· ·

nom

True g i b = 0.60"g ³ b0.5t = 0.57"g :

·

dB bt

·


·

· ·

p

mm

bL bL

w

g b

g


False

= 0.8" £ 01 . s = 12 . " :

True

nom

g c = 30"g ³ d18 .

True

h

= 8" ³ max 2t nom , 1 inch = 2.28" :

msd

i

Dt nom = 18.8" :

True

True


Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blisters E Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied: ·

The blister diameter and venting requirements meet one of the following (note that the blister-to-

b

g b

g

"2 s x 2c" box criteria and Lb = 10" ³ 2t nom = 2.28" , and that the c=4 inch dimension is used in a Level 1 Assessment rather than the s=2 inch dimension per paragraph 7.3.3.1.a; therefore, s = 4" ):

blister spacing check satisfies

·


·

Blister-to-blister spacing check satisfies

·

nom

·

b L = 6"g ³ b2t = 2.28"g : d B = 01. "i £ b01. s = 0.4"g : True bt = 0.90"g ³ b0.5t = 0.57"g :

·


b

·

"2 s x 2c" box criteria and True

nom

p

mm

True

nom

True

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

True

· ·

bL bL

w

g c = 40"g ³ d18 .

h

= 10" ³ max 2t nom , 1 inches = 2.28" :

msd

i

Dt nom = 18.8" :

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


True

True


Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blisters F Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied: ·

The blister diameter and venting requirements meet one of the following (note that the blister-toblister spacing check satisfies

b

s = 2" ):

True bs = 2"g £ 2 inches & vented or unvented: . "g = 6.27"j & is vented: bs = 2"g £ e0.6 Dt = 0.6 b96"gb114

· ·

nom

True g i b = 0.60"g ³ b0.5t = 0.57"g :

·

dB bt

·


·

· ·

p

mm

bL bL

w

g b

g

"2 s x 2c" box criteria and Lb = 6" ³ 2t nom = 2.28" ; therefore,

False

= 01 . " £ 01 . s = 0.2" :

True

nom

g c = 40"g ³ d18 .

True

h

= 6" ³ max 2t nom , 1 inch = 2.28" :

msd

i

Dt nom = 18.8" :

True

True

--``````-`-`,,`,,`,`,,`---


Perform a Level 1 Assessment per paragraph 7.4.2.1 on Blisters G Step 1 – Determine data for blister assessment – see the above table. Step 2 – Check the blister acceptance criteria, blisters are acceptable without repair if all of the following are satisfied: ·

The blister diameter and venting requirements meet one of the following (note the blister-toblister spacing check satisfies therefore,


b

g b

g


s = 11" ):

Not for Resale



· ·

nom

g i b = 0.60"g ³ b0.5t = 0.57"g :

·

dB bt

·


·

· ·

p

mm

bL bL

w

= 0.3" £ 01 . s = 11 ." :

True True

nom

g c = 24"g ³ d18 .

False

h

= 3" ³ max 2t nom , 1 inch = 2.28" :

msd

False

i

Dt nom = 18.8" :

True

True


7.11.2

Example Problem 2 – For the blisters in Example Problem 1 which do not meet the Level 1 Assessment criteria, determine if the vessel is suitable for continued operation at the current MAWP and temperature using the Level 2 Assessment criteria. Perform a Level 2 Assessment per paragraph 7.4.3.1 on Blister A. Step 1 – Determine the required data and measurements for blister evaluation – see the information for the Level 1 Assessment in Example Problem Number 1. Step 2 – Determine the acceptability of the blister based on orientation and location.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

·

The blister did not pass the Level 1 Assessment because of its size and projection.

·

Based on the Level 1 Assessment results, all spacing requirements are satisfied.

·

The blister is bulged to the outside surface and has a crown crack. If the blister projection criteria were satisfied, the blister could be accepted without further analysis. However, because of the bulge projection, a Section 5 Level 1 Assessment is required.

Perform a Section 5 Level 1 Assessment Step 1 – Determine the Critical Thickness Profiles(s) and the following parameters – The thickness readings for the critical inspection planes are indicated in the table containing the inspection data.

D = 96" FCA = 0.125" gr is not for the analysis of an LTA Lmsd = 25" MAWP = 250 psig RSFa = 0.90 --``````-`-`,,`,,`,`,,`---


Not for Resale


Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature.

Rc = 48"+0.0"+0125 . " = 48.125"

. "g b250 psigb48125 b17500 psigb0.85g - 0.6b250 psig = 0.817 " . "g b250 psigb48125 = = 0.403" 2b17500 psi gb0.85g + 0.4b250 psi g

C t min =

L t min

t min = max 0.817", 0.403" = 0.817 " Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see Section 5, paragraph 5.3.3.2), and the shell parameter, l. The flaw dimensions are taken as the measured blister dimensions. Note that in this calculation, the length of the flaw is taken as the full blister diameter. For an external blister, the length of the crown crack could have been used (see paragraph 7.4.3.1.b.3.d).

l=

b g

1285 . 10"

b

--``````-`-`,,`,,`,`,,`---

t mm = 0.70" . " 0.70"-0125 Rt = = 0.704 0.817" s = 10.0" c = 8.0" . g = 1451

96" 0.817"


b R = 0.704g ³ 0.20 . " = 0.575"g ³ 010 . " bt - FCA = 0.70"-0125 b L = 25"g ³ e18. 96" b0.817"g = 15.9"j t

True

mm

True True

msd

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA.

Step 6 – Evaluate the longitudinal extent of the flaw. From Figure 5.8 with

. RSl = 1451 UV , the TR = 0.704W t


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale


b gj

e

M t = 1 + 0.48 1451 .

2 0.5

= 1418 .

0.704

RSF =

= 0.89 1 1 - 0.704 11418 . 0.89 = 247 psig MAWPr = 250 psig 0.90

b

g

gFGH IJK

b

R| c = 8" = 0.0833U| , the circumferential extent of the flaw is acceptable. From Figure 5.9 with S D 96" V |TR = 0.704 |W t

Perform a Level 2 Assessment per paragraph 7.4.3.1 on Blister D Step 1 – Determine the required data and measurements for blister evaluation – see the information for the Level 1 Assessment in Example Problem Number 1. Step 2 – Determine the acceptability of the blister based on orientation and location.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

·

The blister did not pass the Level 1 Assessment because of its size.

·


·

The blister is bulged to the inside surface and has a crown crack. The crown crack will provide a natural vent for the blister. Because the blister is bulged to the inside, a Section 5 Level 1 Assessment must be performed.

Perform a Section 5 Level 1 Assessment Step 1 – Determine the Critical Thickness Profiles(s) (see Section 5, paragraph 5.3.3.3) and the following parameters – The thickness readings for the critical inspection planes are indicated in the above table and shown in the following figure.

D = 96" FCA = 0.125" gr is not required for the analysis of an LTA Lmsd = 30" MAWP = 250 psig RSFa = 0.90 Step 2 – Calculate the minimum required thickness, tmin, based on the current design pressure and temperature.


Not for Resale

--``````-`-`,,`,,`,`,,`---

Step 7 – Evaluate circumferential extent of the flaw, assume significant supplemental loads which result in longitudinal stresses.


Rc = 48"+0.0"+0125 . " = 48.125"

. "g b250 psigb48125 b17500 psigb0.85g - 0.6b250 psig = 0.817 " . "g b250 psigb48125 = = 0.403" 2b17500 psi gb0.85g + 0.4b250 psi g

C t min =

L t min

t min = max 0.817", 0.403" = 0.817 " Step 3 – Determine the minimum measured thickness, tmm, the remaining thickness ratio, Rt, the flaw dimensions (see Section 5, paragraph 5.3.3.2), and the shell parameter, l. The flaw dimensions are taken as the measured blister dimensions. Note that in this calculation, the length of the flaw is taken as the full blister diameter. For an external blister, the length of the crown crack could have been used (see paragraph 7.4.3.1.b.3.d).

0.60"-0125 . " = 0.581 0.817" = 0.60"

Rt = t mm

s = 12.0" c = 10.0" l=

b g

1285 . 12"

b

. g = 1741

96" 0.817"


b R = 0.581g ³ 0.20 . " = 0.475"g ³ 010 . " bt - FCA = 0.60"-0125 b L = 30"g ³ e18. 96" b0.817"g = 15.9"j t

True

mm

True True

msd

Step 5 – Check the criteria for a groove-like flaw. This step is not applicable because the region of localized metal loss is categorized as an LTA.

Step 6 – Evaluate the longitudinal extent of the flaw. From Figure 5.8 with

. RSl = 1741 UV , the TR = 0.581W t


b gj

e

M t = 1 + 0.48 1741 .

2 0.5

= 1567 .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0.581

RSF =

= 0.793 1 1 - 0.581 11567 . 0.793 = 220 psig MAWPr = 250 psig 0.90

b

b

g

gFGH

IJ K

--``````-`-`,,`,,`,`,,`---


Not for Resale


R| c = 10" = 0104 U . | Step 7 – Evaluate circumferential extent of the flaw. From Figure 5.9 with S D 96" , the V |TR = 0.581 |W t

circumferential extent of the flaw is acceptable.

Perform a Level 2 Assessment per paragraph 7.4.2.1 on Blister G

Step 2 – Determine the acceptability of the blister based on orientation and location. The blister did not pass the Level 1 Assessment because of its size and because of the presence of periphery cracks.

·


·

The inspection information indicate that the periphery cracks are growing in the through-wall direction. Therefore, a Level 2 Assessment cannot be performed. The remaining options to evaluate this flaw are to perform a Level 3 Assessment which would include a fracture mechanics evaluation, or to institute an in-service monitoring program to permit on-line inspection of the flaw until a planned unit shutdown. At that time, further evaluation or repair of the flaw can be made.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

·

--``````-`-`,,`,,`,`,,`---

Step 1 – Determine the required data and measurements for blister evaluation – see the information for the Level 1 Assessment of blister G in Example Problem Number 1.


Not for Resale

SECTION 8 – Assessment Of Weld Misalignment And Shell Distortions (Jan, 2000) 8.1

General Fitness-For-Service (FFS) assessment procedures for pressurized components with geometric irregularities are provided in this section. The geometric irregularities covered include weld misalignment and shell distortions including out-of-roundness, bulges and dents. A flow chart for the evaluation procedure of equipment with a geometric irregularity is shown in Figure 8.1. Applicability And Limitations Of The Procedure

8.2.1

The procedures in this section can be used to assess geometric irregularities associated with weld misalignment and shell distortions in components made up of flat plates; cylindrical, conical, and spherical shells; and formed heads. These types of flaws will be referred to as geometric irregularities in this section and are defined in the following paragraphs. In general, if the current geometry of the component is such that the original fabrication tolerances are satisfied, an assessment is typically not required. Exceptions include components subject to cyclic service and components which have a localized geometric irregularity such as a dent.

8.2.1.1

Weld Misalignment – Categories covered include centerline offset, angular (peaking), and a combination of centerline offset and angular misalignment of butt weld joints in flat plates, cylindrical shells and spherical shells (see Figures 8.2 through 8.6).

8.2.1.2

Shell Distortion – Categories of shell distortion are defined as follows:

--``````-`-`,,`,,`,`,,`---

8.2

8.2.2

a.

General Shell Distortion – A deviation of a shell from an ideal or perfect geometry which occurs in either the meridional or circumferential directions. This type of distortion is characterized by significant shape variation of the shell (multiple local curvatures) and typically requires an assessment based on a numerical analysis method. Flat spots on a shell are also classified as general shell distortion.

b.

Out-of-roundness – A deviation of the cross-section of a cylindrical shell and pipe bend from an ideally circular geometry. The out-of-roundness for a cylinder is assumed to be constant in the longitudinal direction (see Figure 8.7 and paragraph 8.2.3.2.g for a discussion of limitations), and either global (oval shape) or arbitrarily shaped in the circumferential direction. The out-of-roundness of a pipe elbow is assumed to be global (oval shape) in the mid-elbow region with an ovality at the end equal to 50% of the mid-elbow value.

c.

Bulge – An inward or outward deviation of a cross-section of a shell member from an ideally circular geometry which can be characterized by a local radius (see Figures 8.8 and 8.9). The local bulge geometry may be either spherical or cylindrical. Flat spots (infinite radius of curvature) are not considered as a bulge, and are classified as general shell distortion. Note that if the bulge is associated with a blister, then the analysis procedures in Section 7 should be utilized for the assessment.

d.

Dent – An inward or outward deviation of a cross-section of a shell member from an ideally circular geometry which is characterized by a small local radius or notch (see Figure 8.10).

Calculation methods are provided to rerate the component if the acceptance criteria in this section are not satisfied. For pressurized components (pressure vessels and piping) the calculation methods can be used to find a reduced maximum allowable working pressure (MAWP) and/or coincident temperature. For tank components( shell courses) the calculation methods can be used to determine a reduced maximum fill height (MFH).

//^:^^#^~^^""~:@"


8-1 Not for Resale

8.2.3


8.2.3.1

Level 1 assessment procedures are based on the criteria in the original construction code. In some cases, these criteria are not completely defined by the original construction code and are dependent on the original design specification of the owner-user. In addition, the Level 1 Assessment procedures should not be used if the component is in cyclic service. A screening procedure to determine if a component is in cyclic service is provided in Appendix B, paragraph B.5.4.

8.2.3.2

The Level 2 assessment procedures in this section only apply if all of the following conditions are satisfied:

8.2.3.3

a.

The geometric irregularity is due to weld misalignment, shell out-of-roundness (general or arbitrary), a bulge, or a dent (see paragraph 8.2.1.2).

b.

The original design criteria were in accordance with Section 2, paragraph 2.2.2.

c.

The component is not operating in the creep range (see Section 4, paragraph 4.2.3.1.b).

d.

The component geometry is one of the following: ·

Flat plate

·

Pressure vessel cylindrical and conical shell sections

·

Spherical pressure vessels and storage tanks

·

Formed heads including spherical, elliptical, and torispherical shapes

·

Straight sections of piping systems

·

Elbows or pipe bends which do not have structural attachments

·

Shell courses of atmospheric storage tanks

e.

The applied loads are limited to pressure and/or supplemental loads (see Appendix A) that result in a membrane state of stress in the component excluding the effects of weld misalignment and/or shell distortions (i.e. through-wall bending stresses in the component are a result of weld misalignment and shell distortion). The assessment procedures can be used to evaluate stresses resulting from both internal and external pressure; however, a structural stability assessment is only provided for cylindrical and conical shells.

f.

The component under evaluation does not contain LTAs, groove-like flaws (excluding a groove-like flaw located in a dent), pitting damage, blisters, or crack-like flaws in the region of the geometric irregularity.

g.

The component under evaluation is a cylinder with out-of-roundness, and the out-of-roundness is constant along the axis of the cylinder. An analysis based on this assumption will typically result in a conservative estimate of the induced localized bending stresses. However, if local deviations of the cylindrical shell occur in the longitudinal direction, high local bending stresses may result, and the Level 2 assessment procedure may produce non-conservative results.

h.

The additional requirements and limitations for bulges and dents covered in paragraphs 8.4.3.6 and 8.4.3.7, respectively, are satisfied.

A Level 3 assessment can be performed where Level 1 and 2 methods do not apply, such as for the following conditions: a.

The component normal operating or design temperature exceeds the limitations in paragraph 8.2.3.2.c.

b.

The geometric irregularity is classified as general shell distortion (see paragraph 8.2.1.2.a).

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



c.

The geometric irregularity occurs in a component with a complicated geometry or at a major structural discontinuity (e.g. knuckle region of torispherical heads, toriconical heads and conical transitions, or stiffening rings on a cylindrical shell).

d.

More complicated loading conditions are involved which result in significant stress gradients at the location of the geometric irregularity.

e.

The region of the component containing the geometric irregularity contains a flaw, see paragraph 8.2.3.2.f.

f.

The component is subject to a loading condition that results in compressive stresses where structural stability is a concern; note that Level 2 Assessment procedures are provided for cylindrical and conical shell subject to external pressure. However, the Level 2 assessment rules are not applicable to cylinders subject to external pressure in combination with supplemental loads which result in significant longitudinal compressive stresses. Guidelines for performing a structural stability assessment are provided in Appendix B, paragraph B.4.

8.3

Data Requirements

8.3.1

Original Equipment Design Data An overview of the original equipment data required for an assessment is provided in Section 2, paragraph 2.3.1. Maintenance And Operational History An overview of the maintenance and operational history required for an assessment is provided in Section 2, paragraph 2.3.2.

8.3.3


8.3.3.1

The information typically used for a Level 1 and Level 2 Assessment is covered in paragraphs 8.4.2 and 8.4.3, respectively. A summary of these data is provided in Table 8.1.

8.3.3.2

The information required to perform a Level 3 Assessment is dependent on the analysis method utilized. In general, a detailed stress analysis or limit load procedure using a numerical technique can be used to establish acceptable operating conditions. For this type of analysis, an accurate description of the geometric irregularity must be obtained along with the material properties including the elastic modulus and the yield stress (see Appendix F). The description of the geometric irregularity should include field measurements of the deformed shape that are necessary to adequately characterize it.

8.3.4

Recommendations For Inspection Technique And Sizing Requirements

8.3.4.1

Measurement of the radial (offset) and angular (peaking) misalignment at the weld joint is required to use the assessment procedures for weld misalignment. a.

For a flat plate geometry, these two quantities can be established by knowing the plate thicknesses, disposition of the surfaces of the plates in the weld joint (e.g. internal surfaces are flush), the maximum offset between the plate centerlines at the weld joint, and the effective length used to characterize the deviation.

b.

For a cylindrical or spherical shell geometry, the radial misalignment can be established by knowing the plate thicknesses and the disposition of the surfaces of the plates in the weld joint (e.g. internal surfaces are flush). The angular misalignment at the joint can be established by

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

8.3.2


using a template as shown in Figure 8.11. The arc length of the template should extend beyond the locally deformed region resulting from the angular misalignment (or the contact point, see Figure 8.11), and be established using the inside or outside radius of the cylinder, as applicable. Using this technique, the maximum deviation can be calculated using either of the following equations. For a center template,

@=

(a1 + a2 ) 2

(8.1)

@= where //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

8.3.4.2

(b1 + b2 ) 4

(8.2)

a1 , a2 , b1 , and b2 are defined in Figure 8.11.

Measurement of the radius and associated deviation from the mean radius at positions around the circumference are required to use the assessment procedures for circumferential out-of-roundness of cylindrical shells a.

For the case of global out-of-roundness, the maximum, minimum and mean diameters are required. These quantities may be difficult to measure in the field, and the measurement procedure for arbitrary out-of-roundness presented in item (b) below is recommended in these cases.

b.

An accurate measurement of the cylinder radius at various stations must be made in order to apply the assessment procedures for an arbitrary circumferential out-of-roundness. 1.

Radii at an even number of equally spaced intervals around the circumference of the cylinder sufficient to define the profile of the cross section under evaluation should be measured (see Figure 8.12). The recommended minimum number of measurement locations is 24. If access to the inside of the vessel is not possible, an alternative means for measurements will need to be developed. If the vessel has stiffening rings, the measurements for the shape deviation of the shell located between the stiffening rings can be made by placing a level on the outside diameter of the rings and measuring a radial offset to the deformed surface of the shell. This method can produce accurate results assuming the stiffening rings are not significantly out-of-round. If the vessel does not have stiffening rings, a vertical level or plumb line placed alongside the vessel shell can be established to measure the radial offset (see Section 11, Figure 11.4).

2.

In order to determine the deviation from the mean circle, the radius measurements should be corrected for the mean and for the error in positioning the center of measurement. The radius at any location defined by an angle G is given by:

R (G ) = Rm + A1 cosG + B1 sin G + A

(8.3)

where,

A1

=

B1

=

Rm RG

=

Correction factor or offset from the center of measurement to the true center of the mean circle (see Figure 8.12) (mm:in), Correction factor or offset from the center of measurement to the true center of the mean circle (see Figure 8.12) (mm:in), Mean radius (mm:in),

=

Radius at a location defined by G (mm:in),

bg


Not for Resale

--``````-`-`,,`,,`,`,,`---

and for a rocked template


3.

A

=

G

=

Deviation from the mean circle at a location defined by G (mm:in), and Angle defining a location on the cylindrical cross section, taken from a reference line through the center of measurement (see Figure 8.12) (degrees).

The corrected radius and deviation from the mean circle can be found by taking radius measurements of an out-of-round cylindrical shell at equally spaced intervals around the circumference and finding the coefficients in the following expression. A worksheet has been included in Table 8.2 for this calculation using 24 measurement locations.

Ric = Ri - A1 cosG i - B1 sin G i

(8.4)

A i = Ric - Rm

(8.5)

where,

Rm = --``````-`-`,,`,,`,`,,`---

A1 =

B1 = Gi =

N

1 N

åR

2 N

å R cosG

2 N

(8.6)

i

i =1 N

i

i

(8.7)

å R sinG

i

(8.8)

i =1 N

i

i =1

360i N

(8.9)

N

=

Ri

=

Number of measurement points around the circumference, a minimum of 24 points is recommended, Measured radius at point i (mm:in),

Ric Ai

=

Corrected radius at point

=

deviation from the true mean radius at point i ; this information is used in a Level 1 or Level 2 assessment (mm:in).

i (mm:in), and

8.3.4.3

An estimate of the local radius is required to use the assessment procedures for local imperfections in cylindrical shells subject to external pressure. The local radius, RL , can be estimated using the guidelines shown in Figure 8.13.

8.3.4.4

An estimate of the local bulge radii are required to use the assessment procedures for bulges of cylindrical and spherical shells. The local bulge radii can be estimated using the guidelines shown in Figures 8.8 and 8.9.

8.3.4.5

An estimate of the maximum depth of a dent and the minimum radius at the location of maximum deformation is required to use the assessment procedures for dents in cylindrical shells (see Figure 8.10).


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

with terms defined in item (2) above, and


8.4

Evaluation Techniques And Acceptance Criteria

8.4.1

Overview An overview of the assessment levels is provided in Figure 8.1. The Level 1 assessment is based on the fabrication tolerances of the original construction code. If the current geometry of the component is such that the original fabrication tolerances are satisfied, the Level 1 assessment criteria are satisfied, and additional analysis is not required unless the component is in cyclic service or has a dent. In these case, a Level 2 or Level 3 assessment is required. Level 2 assessments provide a means to estimate the structural integrity of a component with weld misalignment or shell distortion characterized as out-of-roundness, a bulge or dent. Pressure as well as supplemental loads are considered as well as more general geometries (e.g. pipes of differing thicknesses and locations of welds). Level 3 assessments are intended for the evaluation of components with general shell distortions, complex component geometries and/or loadings. Detailed stress analysis techniques including fracture, fatigue, and numerical stress analysis are normally used in a Level 3 assessment. Significant field measurements are typically required in a Level 3 assessment to characterize the geometric irregularity.

8.4.2

Level 1 Assessment

8.4.2.1

The Level 1 assessment procedures are based on the fabrication tolerances provided in the original construction code. An overview of these tolerances is provided for the following construction codes in Tables 8.3 through 8.7. ·

ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 and Division 2 – see Table 8.3

·

ASME B31.3 Piping Code – see Table 8. 4

·

API 620 Standard – see Table 8.5

·

API 650 Standard – see Table 8.6

·

API 653 Standard (reconstructed tanks) – see Table 8.7

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8.4.2.2

If the component does not meet the Level 1 Assessment requirements, then a Level 2 or Level 3 Assessment can be conducted.

8.4.3

Level 2 Assessment

8.4.3.1

The Level 2 assessment procedures provide a computational procedure for assessment of a geometric irregularity in a component subject to pressure and other supplemental loads. The geometric irregularities covered include weld misalignment and circumferential distortions in cylindrical shells. Calculation methods are provided to rerate the component if the acceptance criteria in this section are not satisfied.

8.4.3.2

Weld Misalignment a.

Step 1 – Identify the component and misalignment type (see Tables 8.8, 8.9, 8.10, and 8.11) and determine the following variables as applicable (see Figures 8.2 through 8.6).

A

=

e Ey F

= = =

FCA =

Area of the metal cross section, 2F Rt1 ; used for centerline offset of circumferential joints in cylinders when supplemental loads are present 2 2 (mm :in ), Centerline offset of the plate sections at the welded joint (mm:in), Young’s modulus (MPa:psi) Net section axial force; used only for centerline offset of circumferential joints in cylinders (N:lbs), Future corrosion allowance (mm:in),

--``````-`-`,,`,,`,`,,`---


Not for Resale


Hf

=

Factor dependent on whether the induced stress from the shape deviation is categorized as a primary or secondary stress (see Appendix B); the stress is secondary and

L

=

M

=

P R Sa t1

= = =

t2

=

t

=

=

--``````-`-`,,`,,`,`,,`---

RSFa = R1 = R2

=

Z

=

@

= =

n b.

H f = 3.0 if

H f = 15 . if the stress is primary (for most

applications the induced bending stress can be considered as secondary), Characteristic length used to establish the amount of angular misalignment (see Figures 8.4 and 8.6); the definition of this length is shown in Figure 8.6 (mm:in), Net section bending moment; used only for centerline offset of circumferential joints in cylinders (N-mm:in-lbs), internal pressure (MPa:psi), Mean radius of the cylinder or sphere (mm:in), Allowable stress per the governing code (MPa:psi), Current wall thickness of component 1 in the joint (where t 2 ³ t1 ); used only for centerline offset weld misalignment in cylindrical shell circumferential weld joints (see Figure 8.3) (mm:in), Current wall thickness of component 2 in the joint (where t 2 ³ t1 ); used only for centerline offset weld misalignment in cylindrical shell circumferential weld joints (see Figure 8.3) (mm:in), Current wall thickness of the component (if the wall thicknesses of the two components are different at the weld joint, then use the thinner wall thickness should be used in the assessment) (mm:in), Allowable remaining strength factor (see Section 2), Mean radius of component 1 with a wall thickness of t1 in the joint (only used for centerline offset in circumferential joints of cylinders, see Figure 8.3), (mm:in), Mean radius of component 2 with a wall thickness of t 2 in the joint (only used for centerline offset in circumferential joints of cylinders, see Figure 8.3), (mm:in), 2

Section modulus of the metal cross section, FR t ; used for centerline offset of 3 3 circumferential joints when supplemental loads are present (mm :in ), Height of the angular peaking (mm:in), and Poisson’s Ratio.

Step 2 – Determine the membrane stress,

I m , (see Appendix A). Note that for cylindrical

C m

L

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shells, I should be used for misalignment of longitudinal joints, and I m should be used for misalignment of circumferential joints. For centerline offset in flat plates and circumferential joints in cylindrical shells, determine the resulting membrane plus bending stress using the following equation if supplemental loads exist:

I ms = c.

F M + A Z

(8.10)

Step 3 – Calculate the ratios of the induced bending stress to the applied membrane stress using the equations in Tables 8.8, 8.9, 8.10, and 8.11 based on the type of component and weld misalignment. Note that this ratio is equal to zero if there is no centerline offset or angular misalignment. The quantity Rb is defined as the ratio of the induced bending stress to the applied membrane stress resulting from pressure loads while Rbs is defined as the ratio of the induced bending stress to the membrane stress resulting from supplemental loads. 1)


Flat Plates:

Rb = -10 .

(8.11)

Rbs = Rbspc + Rbspa

(8.12)

Not for Resale


3)

4)

d.

Cylinders – Circumferential Joints (Longitudinal Stress):

Rb = Rbccjc + Rbccja

(8.13)

Rbs = Rbsccjc + Rbsccja

(8.14)

Cylinders – Longitudinal Joints (Circumferential Stress):

Rb = Rbcljc + Rbclja

(8.15)

Rbs = -1.0

(8.16)

Spheres – Circumferential Joints (Circumferential Stress):

Rb = Rbscjc + Rbscja

(8.17)

Rbs = -1.0

(8.18)

Step 4 – Determine the remaining strength factor:

RSF = min

LM O H S , 10 . P NI b1 + R g + I b1 + R g Q f

m

e.

8.4.3.3

b

a

ms

--``````-`-`,,`,,`,`,,`---

2)

(8.19)

bs

Step 5 – Evaluate the results. If RSF ³ RSFa , then the angular weld misalignment is acceptable per Level 2; otherwise, refer to paragraph 8.4.3.8.

Out-Of-Roundness – Cylindrical Shells And Pipe Elbows a.

Step 1 – Determine the following variables based on the type of out-of-roundness. 1)

Variables for Global (see Figure 8.7) and General (Arbitrary Shape, see Figure 8.12) Out-Of-Roundness as defined in paragraph 8.4.3.2.a.

G 2)

=

Angle to define the location where the stress will be computed (e.g. can be utilized to compute the stress at a weld location, see Figure 8.5).

Variables for Global Out-Of-Roundness

Cs

=

Factor to account for the severity of the out-of roundness, for a purely oval

Cs = 0.5 ; for shapes which significantly deviate from an oval shape, use Cs = 01 . , Dm Do Dmax Dmin Lf 3)


=

Mean diameter (mm:in),

=

Outside diameter of a pipe bend (mm:in),

=

Maximum outside diameter (mm:in),

=

Minimum outside diameter (mm:in),

=

Lorenz factor (see Appendix A, paragraph A.5.5.1).

Variables for General (Arbitrary Shape) Out-Of-Roundness – Measure the cross sectional profile of the cylinder by taking radius measurements at various angles around the vessel circumference when the cylinder is not pressurized. These data can be represented by the following Fourier Series:

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

shape,

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE 8-9 _________________________________________________________________________________________________ N

m

b g

b gr

Ri = Rm + å An cos nG i + Bn sin nG i n =1

(8.20)

The coefficients of this Fourier series can be computed using the following equations:

Rm =

An =

Bn = Gi =

N

1 N

åR

2 N

å R cosbnG g

(8.22)

2 N

å R sinbnG g

(8.23)

(8.21)

i

i =1 N

i

i

i =1 N

i

i

i =1

360i N

(8.24)

where,

An Bn i n N

=

Coefficient of cosine term in the Fourier series (mm:in),

=

Coefficient of sine term in the Fourier series (mm:in),

= = =

Rm Ri Gi

=

current measurement point, Harmonic number associated with the Fourier series, Number of equally spaced measurement locations around the circumference, a minimum of 24 points is recommended, Mean radius (mm:in),

=

Measured radius at point

=

i (mm:in), and Circumferential angle at point i (degrees).

b.

Step 2 – Determine the membrane stress (see Appendix A).

c.

Step 3 – Determine the ratio of the induced circumferential bending stress to the circumferential membrane stress at the circumferential position (denoted by the angle G ) of interest. 1)

Global Out-Of-Roundness of a cylinder:

bg

Rbor q =

b

g

15 . Dmax - Dmin cos 2q

F I bt - FCAgG1 + C Pc1E- n h FGH t -DFCAIJK J H K 2

3

(8.25)

m

s

y

General (Arbitrary Shape) Out-Of-Roundness of a cylinder:

6 I R b A cos(nG ) + B sin(nG )g U b g FGH t - FCA JK å ST VW 1+ k

Rbor G =

N

n

n=2

n

n

where,


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(8.26)

--``````-`-`,,`,,`,`,,`---

2)


kn =

Dc = 3)

c

PR 3 n 2 - 1 Dc

(8.27)

h

b

E y t - FCA

c

12 1 - n 2

h

g

3

(8.28)

Global Out-Of-Roundness Of Long Radius Elbow (note: limitations for the following expression are shown below, see item 4 below if these limitations are not satisfied).

bg

Rbor G =

Cb × cos2G Lf

(8.29)

where, --``````-`-`,,`,,`,`,,`---

Cb = -0.007281 + 0.05671Y + 0.0008353 X + 0.01210 XY + 0.00001313 X 2 - 0.00008362 X 2Y + 0.04889W + 01827 . WY 0.003201WX - 0.01697WXY - 0.00003506WX 2 -

(8.30)

0.0001021WX 2Y - 01386 . W 2 - 0.09795W 2Y + 0.007906W 2 X + 0.004694W 2 XY - 0.00003833W 2 X 2 + 0.0002649W 2 X 2Y W=

1000 × PR E y t - FCA

X=

R t - FCA

b

b

g

valid for 0.045 £ W £ 0.50

g

valid for 20 £ X £ 40

100 Dmax - Dmin Do

Y= 4)

b

(8.31)

(8.32)

g

(8.33)

Global Out-Of-Roundness Of An Elbow Or Pipe Bend (no limitation on bend radius)

FG D g H

3R cos 2G t - FCA L f

max

- Dmin Do

IJ K

b g F b F PR I R I GH1 + 3.64GH E lt - FCAqJK FGH t - FCAIJK JK

Rbor G =

2

(8.34)

y

e.

Step 4 – Determine the remaining strength factor using Equation (8.19) with and

f.

Rb = abs Rbor

Rbs = -1.0 (the terminology abs[x] means the absolute value of x).

Step 5 – Evaluate the results. If RSF ³ RSFa , then the out-of-roundness is acceptable per Level 2; otherwise, refer to paragraph 8.4.3.8.

//^:^^#^~^^""~:@":^*^


Not for Resale


8.4.3.4

Combined Weld Misalignment and Out-Of-Roundness In Cylindrical Shells Subject To Internal Pressure a.

The ratio of the induced circumferential bending stress to the circumferential membrane stress, Rb, due to weld misalignment can be calculated at the location of the weld using the equations in paragraph 8.4.3.2. The Rb ratio due to out-of-roundness can be calculated at any location around the circumference using the equations in paragraph 8.4.3.3. In this evaluation, this calculation should be performed at the location of the longitudinal weld joint (i.e., the position of the weld is defined by G ).

b.

The assessment procedure for weld misalignment and out-of-roundness in cylindrical shells subject to internal pressure is as follows: 1.

Step 1 – Determine the membrane stress (Appendix A).

2.

Step 2 – Calculate the ratio of the induced bending stress to the applied membrane stress for weld misalignment using paragraph 8.4.3.2, and for circumferential out-of or

roundness using paragraph 8.4.3.3 (note: when computing Rb per paragraph 8.4.3.3, do not take the absolute value or the result as indicated in Step 4).

Rb = Rbcljc + Rbclja + Rbor 3.

Step 3 – Determine the remaining strength factor using Equation (8.19) with the value of Rb determined in Step 2 and Rbs = -1.0 .

4.

Step 4 – Evaluate the results. If RSF ³ RSFa , then the weld misalignment and out-ofroundness is acceptable per Level 2; otherwise, refer to paragraph 8.4.3.8.

Out-Of-Roundness – Cylindrical Shells Subject To External Pressure (Buckling Assessment) a.

Cylindrical shells subject to external pressure must satisfy the stress criteria in paragraph 8.4.3.3 or 8.4.3.4, as applicable, and the buckling criteria set out in this paragraph.

b.

The assessment procedure for out-of-roundness for cylindrical and conical shells subject to external pressure is as follows: 1.

Step 1 – Determine the following variables (see Figure 8.13):

e

=

Ey FCA FS L P PeL Ro RL

=

maximum inward deviation from a true cylinder, can be determined using the procedure in paragraph 8.3.4.2 (mm:in), Young’s modulus (MPa:psi),

= = = = =

Future corrosion allowance (mm:in), In-service margin (see Appendix A, paragraph A.4.3), Unsupported length (see Appendix A, paragraph A.4.3), (mm:in), External design pressure (MPa:psi), Elastic bucking pressure of a cylinder (Mpa:psi),

=

Outside radius of the perfect shell (see Figure 8.13), (mm:in),

=

t n I ys

= = =

Local outside radius of imperfect shell (see Step 3 and Figure 8.13), (mm:in), Current wall thickness of the cylinder (mm:in), Poisson’s Ratio, and Yield stress (MPa:psi).

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

8.4.3.5

(8.35)


2.

Step 2 – If a conical shell is being evaluated, determine the equivalent length and outside diameter as defined in Appendix A, paragraph A.4.8. The equivalent length and equivalent outside radius ( Ro = Do 2 ) are to be used in all subsequent steps.

3.

Step 3 – Find the value of n (the number of waves into which the cylinder will buckle in the circumferential direction to give a minimum value of PeL ) for the perfect cylinder ( e = 0.0 ). a)

Approximate method – determine the value of n using the equations in Appendix A, paragraph A.4.1.5.1 with Rm = Ro and t c = t - FCA .

b)

Exact method – determine the value of n in the following equation which results in a minimum value of PeL . In this calculation, the value of n is assumed to be a non-integer (i.e. a floating point number) and is determined by starting with n = 2 and increasing n in increments of 010 . until a minimum value of PeL is found.

FG E (t - FCA) IJ H R K LM cn + l - 1h FG t - FCAIJ + = n + 0.5l - 1 M 12c1 - n h H R K cn N y

2

PeL

2

2

2

2

2

2

o

OP (8.36) + l h PQ l4

o

2

2 2

with, //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

l=

pRo L

(8.37)

4.

Step 4 – Determine the value of the local radius, RL , of the imperfection using the procedure shown in Figure 8.13 with the measured value of the deviation from the true cylinder, e , and the value of n determined in Step 3.

5.

Step 5 – Substitute

6.

Step 6 – Determine the inelastic buckling pressure

RL for Ro into Equation (8.36) and find a new value of n along with the associated value of the elastic buckling pressure and designate this pressure as Pec .

a)

For carbon and low-alloy steels:

Pc =

b

g

Fhc t - FCA Ro

(8.38)

where,

Fhc = Fhe

for Fhe I ys £ 0.552

(8.39)

Fhc = 0.7I ys

FF I GH I JK

(8.40)

he

0 .4

for 0.552 < Fhe I ys < 2.439

ys

--``````-`-`,,`,,`,`,,`---


Not for Resale


Fhc = I ys

Fhe = b)

b

for Fhe I ys ³ 2.439

Pec Ro t - FCA

g

(8.41)

(8.42)

For all other materials – determine the geometry and material parameters, Aext and Bext , respectively, using the procedure in the ASME B&PV Code,

Do = 2 RL . When determining the material parameter, Bext , if the value of the geometry parameter, Aext , is to the left of the

Section VIII, Division 1 with

material/temperature line or on the straight portion of the curve, then the limiting stress is elastic, Fhc = Fhe , and:

Pc = Pec

(8.43)

otherwise,

Pc =

2 Bext

LM R OP N bt - FCAg Q

(8.44)

o

7.

Step 7 – Determine the permissible external pressure:

Pext =

(8.45)

Step 8 – Evaluate the results. If Pext ³ P , then the component is suitable for continued operation; otherwise, refer to paragraph 8.4.3.8.

8.

8.4.3.6

min Pec , Pc FS

Bulges a.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b.

The following assessment procedures can be used for outward bulges (i.e. non-axisymmetric) which occur in spherical or cylindrical shells subject to internal pressure loading. A Level 3 Assessment for general shell distortion should be performed if the component has any of the following: ·

Axisymmetric bulges

·

Flat spots (the radius of curvature of the bulge is infinite)

·

Inward bulges (the location of the radius of curvature is location outside of the shell)

·

External pressure or significant supplemental loading

The assessment procedure for bulges is as follows: 1.

Step 1 – Determine the following parameters; for a bulge in a cylindrical shell see Figure 8.8 and for a bulge in a spherical shell see Figure 8.9.

D E FCA P Lmsd

= = = = =

Inside diameter (mm:in), Weld joint efficiency, Future corrosion allowance (mm:in), Internal pressure (MPa:psi), Distance from the edge of the bulge under investigation to the nearest major structural discontinuity or adjacent flaw (mm:in),

--``````-`-`,,`,,`,`,,`---


Not for Resale


HM

=

RLC

=

RLM

=

VC

=

VM

=

Sa

=

tB t min

=

Temperature (°C:°F), Height of bulge in the circumferential direction measured from the inflection point (see Figure 8.8(b) or Figure 8.9(b), as applicable), (mm:in), Height of bulge in the meridional direction (longitudinal direction for a cylindrical shell) measured from the inflection point (see Figure 8.8(c) or Figure 8.9(c), as applicable), (mm:in), Local radius opposite the bulge radius in the circumferential direction measured at the inflection point (see Figure 8.8(b) or Figure 8.9(b), as applicable), (mm:in), Local radius opposite the bulge radius in the meridional direction (longitudinal direction for a cylindrical shell) measured at the inflection point (see Figure 8.8(c) or Figure 8.9(c), as applicable), (mm:in), Length of bulge in the circumferential direction measured from the inflection point (see Figure 8.8(b) or Figure 8.9(b), as applicable), (mm:in), Length of bulge in the meridional direction (longitudinal direction for a cylindrical shell) measured from the inflection point (see Figure 8.8(c) or Figure 8.9(c), as applicable), (mm:in), Allowable stress for the component at the assessment temperature based on the original construction code (MPa:psi), Minimum local wall thickness in the bulge (mm:in), and

=

Minimum required wall thickness of the shell containing the bulge (see Appendix A) (mm:in).

Step 2 – Determine the local bulge radii.

c

h

RBC =

1 HC2 + 4VC2 8VC

RBM =

1 H M2 + 4V M2 8V M

c

h

(8.47)

Step 3 – Determine the local membrane stress in the bulge based on the current design pressure. a)

If the bulged shape can be approximated by a spherical surface, then compute the maximum circumferential and meridional membrane stress using the following equation. lg e lg e I bu = I bu = mc mm

b)

P 2E

F GH bt

RBC + 0.2 B - FCA

g

I JK

(8.48)

If the bulged shape can be approximated by a cylindrical surface (this assumption should be used for all cases unless a spherical shape can be justified by field observation and measurement), then compute the maximum circumferential and meridional membrane stress using the following equations. lg e I bu = mc


(8.46)

P Bc Bm E

F GH bt

I JK

RBC + 0.6 B - FCA

g

Not for Resale

(8.49)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

3.

= =

--``````-`-`,,`,,`,`,,`---

2.

T HC

RECOMMENDED

Jan, 2000

PRACTICE


P R = 2B,E ( (t, -&4)

0 bulge mm

- 0.4 1

8-l 5

(8.50)

where,

(8.51)

B

=

(%M

-,)“.5

(8.52)

m 2RBhf

4.

Step 4 - Determine the remaining strength factor:

--``````-`-`,,`,,`,`,,`---

RSF = min 5.

Step 5 - Evaluate the results. If all of the following requirements are satisfied, then the component is acceptable per Level 2; otherwise, refer to paragraph 8.4.3.8:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

l

RSF 2 RSF,

l

Lmd > lS,/Dt,,

.

RLc 2 15(t, - FCA)

.

R,

2 15(t, - FCA)

The results of an inspection indicate that all parts of the weld seam within the region of the bulge do not contain crack-like flaws and the weld joint efficiency used in the calculations is representative of the weld quality.

l

The bulged surface does not contain any flaws such as a locally thin area, blister, groove or cracks.

l

The loading on the component is internal pressure and the stress due to supplemental loads are insignificant.

l

8.4.3.7

(8.53)

Dents With Gouges

a.

The following assessment procedures should only be utilized for spherical and cylindrical components subject to internal pressure. The procedures can be used to evaluate dents with a gouge (see Section 5, paragraph 5.2.1 .l .b). If the dent does not contain a gouge, then the assessment procedure in paragraph 8.4.3.3 can be used.

b.

The assessment procedure for dents is as follows: 1.

Step 1 - Determine the following parameters (see Figure 8.10):

a,

=

Depth of the gouge (mm:in),

c,

=

Constant for units conversion;

C,, = 1.0 if C,,tis expressed in ft-lbs and

C, = 1.355818 if C,, is expressed in Joules,


Not for Resale

API RECOMMENDED

8-16

ctls

PRACTICE


579

Jan, 2000

C, = 1.0if s is expressed in inches and

C, = 25.4 if s is expressed in millimeters,

c”* dd d LT FCA L msd 5

Two-thirds size Charpy energy, required only if the dent has a groove-like flaw (see Appendix F), (ft-lbs), Maximum depth of the dent at the instance of damage (mm:in), Depth of the dent after removal of damaging tool (mm:in), Inside diameter (mm:in), Future corrosion allowance (mm:in), Distance from the edge of the dent under investigation to the nearest major structural discontinuity or adjacent flaw (mm:in), Local radius of the dent or groove-like flaw located at the base of the dent at the point of impact (mm:in), Length of the groove-like flaw, required only if the dent has a groove-like flaw (see Section 5 for information on how to establish the length of a groove-like flaw), (mm:in), Current thickness, typically the nominal thickness minus the metal loss (mm:in), Circumferential or hoop stress, required only if the dent has a groove-like flaw (see Appendix A) (MPa:psi), Flow stress equal to cr,,s +

69 A4Pa (0, + 10,OOOpsi) (see Appendix

F, paragraph F.2.2.1) (MPa:psi), Circumferential or hoop stress when the measurement of the dent is taken (see Appendix A) (MPa:psi), and Yield stress at the assessment temperature (see Appendix F) (MPa:psi). Step 2 - The depth of the dent to be used in the assessment is the depth that occurs at the instant of damage. After the damaging tool is removed, the dent in a pressurized pipe will rebound. Therefore, if the dent is found while the component is in service, then the depth of the dent to be used in the assessment can be computed using the following equation.

dd = ddp.[ -0.22+$ 3.

(8.54)

Step 3 -Determine the limiting circumferential stress.

~cl_- [e,-300]“‘6 90 Of

(8.55)

where,

(8.56)

4.

Step 4 - Evaluate the results. If all of the following requirements are satisfied, then the component is acceptable per Level 2; otherwise, refer to paragraph 8.4.3.10:

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.

· ·

8.4.3.8

8.4.3.9

I cl 15 . rd ³ 0.25(t - FCA)

Ic £

·

dd £ 0.05 D + t - FCA

·

Lmsd ³ 18 . Dt

·

All parts of the deformed shell at the location of the dent do not contain a weld seam.

·

The loading of the component is internal pressure and the stress due to supplemental loads are insignificant.

·

If the dent contains a groove-like flaw, then pressure fluctuations are not permitted; otherwise, pressure fluctuations are limited to start-up and shut-down cycles which will not exceed 500 for the duration the component is in service.

·

The deformed surface, including the groove-like flaw if one is present, does not contain any crack-like flaws.

b

g

Rerating Components a.

If RSF ³ RSFa the component is acceptable per Level 2. If this criteria is not satisfied, then the component can be rerated using the equations in Section 2, paragraph 2.4.2.2.

b.

A Level 3 analysis must be performed to rerate a component with a dent.

Fatigue Analysis a.

If the component is subject to cyclic service, or if a fatigue analysis was performed as part of the original design calculations, the fatigue strength including the effects of the geometric irregularity should be checked. A screening procedure to determine if a component is in cyclic service is provided in Appendix B, paragraph B.5.4.

b.

The procedure for the fatigue assessment is as follows. This procedure is applicable to evaluate weld misalignment, shell out-of-roundness and a combination of weld misalignment and shell out-of-roundness subject to the restrictions in paragraphs 8.4.3.2, 8.4.3.3, or 8.4.3.4, respectively. The assessment procedure is not applicable to a component with bulges or dents; a Level 3 Assessment is required for these cases. 1.

Step 1 – Determine the nature of loading, the associated membrane stress (see Appendix A), and the number of operating cycles.

2.

Step 2 – Determine the ratio of the induced bending stress to membrane stress, resulting from weld misalignment, shell out-of-roundness or combination of weld misalignment and shell out-of-roundness, as applicable, using the procedures in paragraphs 8.4.3.2, 8.4.3.3, or 8.4.3.4, respectively.

3.

Step 3 – Determine the stress concentration factor, Kt (typically required only if the fatigue curve used in the assessment is based on smooth bar test specimens, see Appendix F, paragraphs F.6.2 and F.6.3).

4.

Step 4 – Using the loading history and membrane stress from Step 1, the Rb parameters from Step 2, and the stress concentration factor from Step 3, calculate the stress range, I r , (see Appendix B, paragraph B.5 for information regarding a fatigue evaluation): --``````-`-`,,`,,`,`,,`---


Not for Resale

Rb ,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Flat Plate – Weld misalignment:

c

h

I r = I ms 1 + Rbpc + Rbpa Kt b)

(8.57)

Cylinder, Circumferential Weld Joint – Weld misalignment:

c

c

h

h

I r = I m 1 + Rbccjc + Rbccja + I ms 1 + Rbsccjc + Rbsccja Kt c)

Cylinder, Longitudinal Weld Joint – Weld misalignment and out-of-roundness:

c

h

I r = I m 1 + Rbcljc + Rbclja + Rbor Kt d)

(8.58)

(8.59)

Spheres, Circumferential Weld Joint – Weld misalignment:

c

h

I r = I m 1 + Rbscjc + Rbscja Kt

(8.60)

5.

Step 5 – Compute the number of allowed cycles using the stress range determined in Step 4 and the applicable fatigue curve (see Appendix F, paragraphs F.6.2 and F.6.3).

6.

Step 6 – Evaluate the results. If the computed number of cycles determined in Step 5 are greater than or equal to the number of operating cycles in Step 1, then the component is acceptable per Level 2.

8.4.3.10 If the component does not meet the Level 2 Assessment requirements, then the following, or combinations thereof, can be considered: a.

Rerate, repair, replace or retire the component.

b.

Adjust the

c.

Adjust the weld joint efficiency factor, E , by conducting additional examination and repeat the assessment (see Section 4, paragraph 4.4.2.2.c).

d.


FCA by applying remediation techniques (see Section 4, paragraph 4.6).

8.4.4

Level 3 Assessment

8.4.4.1

The stress analysis techniques in Appendix B can be used to assess the geometric irregularities discussed in this section in pressure vessels, piping, and tankage.

8.4.4.2

Linear stress analysis and the stress categorization techniques discussed in Appendix B, paragraph B.2 can be used to analyze misalignment at weld joints. In the Level 2 Assessment, the induced bending stress resulting from misalignment is considered to be a secondary bending stress for most applications. In some cases, this stress can be taken as a primary bending stress if elastic follow-up occurs. The limit load techniques described in Appendix B, paragraph B.3 can be utilized for the analysis to resolve issues pertaining to stress categorization.

8.4.4.3

The non-linear stress analysis techniques described in Appendix B, paragraph B.3 should be utilized to analyze general shell distortions which occur in shell components. a.

Typically, the localized bending stresses resulting from general shell distortion will tend to decrease due to the rounding effect of the shell when subject to internal pressure. This effect is more pronounced in thinner shells and can be directly evaluated using a non-linear analysis that includes the effects of geometric nonlinearity. The rounding effect is introduced in a Level


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

a)


2 analysis of out-of-roundness through the correction factor,

C f . If material nonlinearity is

included in the analysis, the plastic collapse strength of the component can also be determined and used to qualify the component for continued operation. b.

An accurate representation of the deformed shell profile is critical in obtaining an accurate analysis results, and this is especially important for shell with significant deviations (or kinks) in the meridional and circumferential direction. To obtain an accurate profile of the shell geometry, a grid should be established over the deformed region and measurements taken to determine the actual profile of the shell. These data should then be curve-fit with piece-wise cubic splines to obtain an accurate representation of the deformed shape. The piece-wise cubic splines parameterization of the surface will ensure that the slope and curvature of the deformed shell profile is continuous, which is a condition necessary for shell analysis.

c.

If a kink or sharp bend exists in a shell, traditional shell theory will not provide an accurate estimate of the stress state. In this case, a continuum model including the effects of plasticity is recommended for the evaluation.

d.

For shell structures with significant localized distortion resulting from contact with another component or mechanical device, a nonlinear stress analysis to simulate the deformation process may be used to determine the magnitude of permanent plastic strain developed. To simulate the distortion process, an analysis including geometric and material nonlinearity as well as the contact interaction between the original undeformed shell structure, and the contacting body is performed. The contacting component may be explicitly modeled as a deformable body or as a simple rigid surface. The analysis should include applicable loadings to develop the final distorted configuration of the shell structure. The calculated inelastic strains should be compared to the allowable strain limits given in Appendix B.

8.4.4.4

If the component is subject to a compressive stress field, the nonlinear stress analysis techniques described in Appendix B, paragraph B.3 are recommended for the assessment. If geometric nonlinearity is included along with material nonlinearity in the assessment, the stability of the component can be evaluated in the same analysis utilized to determine the plastic collapse strength. Alternatively, the stress categorization and structural stability techniques discussed in Appendix B, paragraph B.4 can be utilized in the assessment.

8.4.4.5

If the component is operating in the creep range, a nonlinear analysis that includes both material (plasticity and creep) and geometric nonlinearity is recommended. Stresses due to localized geometric irregularities may not sufficiently relax with time due to the surrounding compliance of the component. In this case, creep strains can accumulate and may result in significant creep damage or cracking. If the component contains a dent or other geometric irregularity with highly localized stresses, a detailed non-linear stress analysis and assessment should be performed. This assessment should also include an evaluation of the material toughness requirements. Otherwise, repair or regular in-service monitoring of the component is recommended.

--``````-`-`,,`,,`,`,,`---

8.5


8.5.1

A remaining life assessment of components with geometric irregularities generally fall into one of the following three categories: a.

Metal Loss Resulting From A Corrosive/Erosive Environment – In this case, adequate protection from a corrosive/erosive environment can be established by setting an appropriate value for the future metal loss. The remaining life as a function of time can be established using the MAWP Approach described in Section 4, paragraph 4.5.2.

b.

Cyclic Loading – The Level 2 assessment procedures include a fatigue evaluation for weld misalignment and out-of-roundness (see paragraph 8.4.3.9 and Appendix B). The remaining life can be established by combining the results from this analysis with the operational history of the component.

//^:^^#^~^^""


Not for Resale

c.

High Temperature Operation – If the component is operating in the creep regime, the assessment procedures in Section 10 can be utilized to determine a remaining life.

8.5.2

If the component is not within one of the above categories, a detailed Level 3 analysis should be performed to determine the remaining life of the component.

8.6

Remediation

8.6.1

Geometric irregularities associated with weld misalignment, out-of-round and bulges may be reinforced using stiffening plates and lap patches depending on the geometry, temperature and loading conditions. The reinforcement, if utilized, should be designed using the principles and allowable stresses of the original construction code.

8.6.2

Cylindrical shell sections which are out-of-round can be brought to within original fabrication tolerances or to a shape which reduces the local stress to within acceptable limits by mechanical means. Hydraulic jacks have been used successfully to alter the out-of-round shape of stiffened cylindrical shells. The design of the jacking arrangement and loads should be carefully established and monitored during the straightening process to minimize the potential for damage to the shell and attachments.

8.6.3

In general, a dent represents the most damaging flaw because it is difficult to establish the condition (strength and ductility) at the location of maximum deformation. Therefore, unless the condition of the material can be adequately evaluated, repair or replacement of the component is recommended.

8.7


8.7.1

The geometric irregularities covered in this section do not normally require in-service monitoring unless there is an unusually corrosive environment and future corrosion allowance cannot adequately be estimated, or if the component is subject to a cyclic operation and the load history cannot be adequately established to perform a detailed assessment. In these cases, the in-service monitoring usually entails visual inspection and field measurements of the geometric irregularity in the component at regular intervals. The type of measurements taken depend on the assessment procedure utilized in the assessment.

8.7.2

In-service monitoring is typically required when a Level 3 assessment is performed to qualify a component for continued operation which contains geometric irregularities with a groove-like or crack-like flaw.

8.8

Documentation

8.8.1

The documentation of the FFS assessment should include the information cited in Section 2, paragraph 2.8.

8.8.2

Inspection data including all field measurements used to determine the extent of the geometric irregularity should be included in the documentation of the Fitness-For-Service analysis.

8.9

References

8.9.1

Becht IV, C., Cehn, Y., and Lyow, B., “Jacking to Correct Out-Of-Roundness Of A Ring-Stiffened Vessel,” PVP-Vol. 315, Fitness-For-Service and Decisions for Petroleum and Chemical Equipment, ASME, 1995, pp. 447-451.

8.9.2

Berge, S., and Myrhe, H., “Fatigue Strength of Misaligned Cruciform and Butt Joints,” Norwegian Maritime Research, No. 1, 1977, pp. 29-39.

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


8.9.3

Bizon, P.T, “Elastic Stresses At A Mismatched Circumferential Joint In A Pressurized Cylinder Including Thickness Changes And Meridional Load Coupling,” NASA TN D-3609, NTIS, Springfield, Va., D.C., September, 1966.

8.9.4

Bock, N. and Zeman, J.L., “On Bending Stress at Longitudinal Weld Joints of Cylindrical Shells Due to Peaking,” International Journal of Pressure Vessels & Piping, 60, 1994, pp 103-106.

8.9.5

Buchheim, M.B., Osage, D,.A., Brown, R.G., and Dobis, J.D., “Failure Investigation of A Low Chrome Long-Seam Weld in a High -Temperature Refinery Piping System,” PVP-Vol. 288, ASME, 1994, pp 363-386.

8.9.6

Chuse, R. and Carson, B.E., “The ASME Code Simplified,” 7th Ed., McGraw-Hill, Inc., New York, N.Y., 1993.

8.9.7

Connelly, L.M., and Zettlemoyer, N., “Stress Concentrations at Girth Welds of Tubulars with Axial Wall Misalignment,” Tubular Structures, E & FN Spon., 1993.

8.9.8

Eiber, R.J., Maxey, W.A., Bert, C.W., and McClure, G.M., “The Effects of Dents on the Failure Characteristics of Line Pipe,” Battelle NG-18 Report No. 125, May 8 , 1981.

8.9.9

Hopkins, P., Jones, D.G., and Clyne, A.J., “The Significance Of Dents And Defects In Transmission Pipelines,” C376/049, ImechE, 1989.

8.9.10

Haigh, B.P., “An Estimate of Bending Stresses Induced by Pressure in a Tube That is Not Quite Circular,” Appendix IX in the Welding Research Committee Second Report.

8.9.11

Johns, R.H. and Orange, T.W., “Theoretical Elastic Stress Distributions Arising From Discontinuities And Edge Loads In Several Shell-Type Structures,” NASA TR R-103, NTIS, Springfield, Va., September, 1966.

8.9.12

Kendrick, S., “The Measurement of Shape in Pressure Vessels,” Institute of Mechanical Engineers, C96/80, 1980, pp261-267.

8.9.13

Maddox, S.J., “Fatigue Strength of Welded Structures,” 2nd Ed., Abington Publishing, Cambridge, England, 1991.

8.9.14

Miller, C.D., “The Effect of Initial Imperfections on the Buckling of Cylinders Subjected to External Pressure,” WRC Bullentin 443, Report No. 1, Pressure Vessel Research Council, New York, N.Y., January, 1995.

8.9.15

Morgan, W.C. and Bizon, P.T, “Technical Note D-1200 – Experimental Investigation Of Stress Distributions Near Abrupt Change In Wall Thickness In Thin-Walled Pressurized Cylinders,” NASA TN D-1200, NTIS, Springfield, Va., September, 1966.

8.9.16

Morgan, W.C. and Bizon, P.T, “Comparison Of Experimental And Theoretical Stresses At A Mismatch In A Circumferential Joint In A Cylindrical Pressure Vessel,” NASA TN D-3608, NTIS, Springfield, Va., September, 1966.

8.9.17

Partanen, T., “Factors Affecting the Fatigue Behavior of Misaligned Transverse Butt Joints in Stiffened Plate Structures,” Engineering Design in Welded Constructions. Proceedings, International Conference, Madrid, Spain, Pergamon Press for the International Institute of Welding (IIW), Oxford, UK, Sept, 1992, pp. 65-72.

8.9.18

Ong, L.S., Hoon, K.H., “Bending Stresses at Longitudinal Weld Joints of Pressurized Cylindrical Shells Due to Angular Distortion,” Journal of Pressure Vessel Technology, Vol. 118, ASME, August, 1996, pp. 369-373.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---



8.9.19

Ong, L.S., “Allowable Shape Deviation in a Pressurized Cylinder,” Transactions of the ASME, Vol. 116, August 1994, pp. 274-277.

8.9.20

Rodabaugh, E.C. and Pickett, A.G., “Survey Report on Structural Design of Piping Systems and Components,” Report TID-25553, NTIS, December, 1970, pp. 10.3-10.7.

8.9.21

Schwarz, M., and Zeman, J.L., “Bending Stresses at Longitudinal Weld Joints of Pressurized Cylindrical Shells Due to Angular Misalignment,” Journal of Pressure Vessel Technology, Vol. 119, ASME, May, 1997, pp. 245-246.

8.9.22

Thomas, K., “The Effects of Geometric Irregularities on the Design Analysis of Thin-Walled Piping Elbows,” Journal of Pressure Vessel Technology, Vol. 102, ASME, November, 1980, pp. 410-418.

8.9.23

Tooth, A.S., and Ong, L.S., “The Derivation of the Stresses in a Pressurized Pipe or Cylindrical Vessel with Initial Geometric Imperfections,” Strain, February, 1988, pp. 7-13.

8.9.24

Zeman, J.L., “Aufdachung an Langsnahten Zylindrischer Schusse,” TU Bd. 34, Nr. 7/8, 1993, pp 292295.

8.9.25

Zeman, J.L., “On the Problem of Angular Misalignment at Longitudinal Weld Joints of Cylinder Shells,” International Journal of Pressure Vessels & Piping, 58, 1994, pp 179-184.

8.9.26

Sofronas, A., Fitzgerald, B.J., and Harding, E.M., “The Effect of Manufacturing Tolerances on Pressure Vessels in High Cyclic Service,” PVP Vol. 347, ASME, New York, N.Y.

8.10

Tables And Figures

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table 8.1 Data Required For The Assessment Of Weld Misalignment And Shell Distortions Use this form to summarize the data obtained from a field inspection. Equipment Identification: Equipment Type: _____ Pressure Vessel Component Type & Location:

_____ Storage Tank

Data required For Level 1 Assessment Future Corrosion Allowance: Out-Of-Roundness (Cylindrical Shell Subject to internal pressure) Maximum Measured Internal Diameter ( Dmax ): Minimum Measured Internal Diameter ( Dmin ): Nominal Diameter: Weld Misalignment Wall Thickness: Radial Misalignment ( e ) :

Data required For Level 2 Assessment General Temperature: Internal and/or External Pressure: Allowable Stress and Weld Joint Efficiency: Component Inside Diameter ( L ): Weld Misalignment Component Wall Thickness ( t or Component Geometry ( R or

R1

t1 and

and

t 2 ):

R2 ):

Measure Of Misalignment ( e or @ ) Characteristic Length ( L ): Net Section Force And Bending Moment ( F &

M

):

Out-Of-Roundness Component Wall Thickness ( t ): Mean Radius ( Ro ): Local Radius ( RL ):

Young’s Modulus ( t ): Bulges Component Wall Thickness ( t ): Minimum Wall Thickness in Bulge ( tb ):

VC & HC , RBM or V M & H M ,): Local radius Opposite Bulge Radius ( RLC and RLM ): Distance To Nearest Structural Discontinuity ( Lmsd ): Bulge Radius ( RBC or

Dents Component Wall Thickness: Depth Of Dent ( d dp ): Local Radius Of Dent ( rd ): Groove-like Flaw Depth ( a g ):

Distance To Nearest Structural Discontinuity ( Lmsd ): --``````-`-`,,`,,`,`,,`---


Not for Resale


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


--``````-`-`,,`,,`,`,,`---

Table 8.2 Worksheet To Determine The Out-Of-Roundness Parameters For A Cylindrical Shell Required For A Level 2 Assessment (2)

(3)

cosG

(4)

sin G

(6)

(7)

(8)

(9)

(10)

Ri

Ri cosG

Ri sin G

A1 cosG

B1 sin G

C = A1 cos G

24

15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330 345 360

inches 0.9659 0.8660 0.7071 0.5000 0.2588 0.0 -0.2588 -0.5000 -0.7071 -0.8660 -0.9659 -1.0 -0.9659 -0.8660 -0.7071 -0.5000 -0.2588 0.0 0.2588 0.5000 0.7071 0.8660 0.9659 1.0

1

1 å= 24 1

col(3) x col(5)

col(4) x col(5)

A1 x col(3)

B1 x col(4)

0.2588 0.5000 0.7071 0.8660 0.9659 1.0 0.9659 0.8660 0.7071 0.5000 0.2588 0.0 -0.2588 -0.5000 -0.7071 -0.8660 -0.9659 -1.0 -0.9659 -0.8660 -0.7071 -0.5000 -0.2588 0.0

å= Rm =

(11)

(12)

Rc = Rm + C A i = Ri - Rc

(13) c

Ri = Ri - C

+ B1 sin G

Degrees 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

(5)

col(8) + col(9)

Rm + col(10)

col(5) – Col(11)

col(5) – Col(10)

Not for Resale

G =i

360

A1 =

å= 2

å= 3

1 å= 12 2

B1 =

8-24 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

1 å= 12 3


(1) Point

RECOMMENDED

Overview Fabrication

Of Fabrication

PRACTICE

Tolerances

- ASME

Table 8.3 B&PV Code, Section

Tolerance

Cut-Of-Roundness Cylindrical Shells Under Internal Pressure

In

(Ii&, -D,iJmust D D:: D

In

VIII, Division

1 And Division

not exceed

= = =

1% of

The diameter

D

UG-80(a)

where:

Maximum

measured

internal

diameter

Minimum

measured

internal

diameter

Nominal

tolerance

{AF-130.1)

internal diameter is increased

for internal

pressure

by 2% of the inside should

UGSO(b)

be satisfied.

Using a chord length equal to twice the arc length determined from Figure 8.14, the maximum deviation from true circle shall not exceed the value e determined from Figure 8.15. Take measurements

on the unwelded

For shells with a lap joint, increase Do not include

future corrosion

tolerance

allowance

by 1.

in t.

The inside surface must not deviate outside the shape by more than 1.25% of the inside diameter nor inside the shape by more than 0.625% of the inside diameter.

Cylindrical Shell-ToHead Attachment Weld

The centerline (radial) misalignment be less than one-half the difference thicknesses.

Cenkdine offset WeId Misalignment Longitudinal Joints (Category A)

Fort<

between the shell and the head shall between the actual shell and head

mm (112 in)

For 12.7 mm (I/2 in) c tl

19.1 mm (314 in)

e = 3.2 mm (l/8 in) in)

in) c t I 50.8 mm (2 in)

Centerline Offset WeId Misalignment Circumferential Joints (Category B, C and D)

UW-13(b)(3) (AD-420)

{AF-142)

e = 3.2 mm (l/8 in)

e = min(t/l6,9.5 mm) or e = min(tll6, 3/8 in) and e is the allowable

For t I lg.1 mm (314 in)

centerline

offset. uw=33

e=tl4

For 19.1 mm (3/4 in) e t I 38.1 mm (l-1/2 For 38.1 mm (l-1/2

{AF-135)

e = 3.2 mm (l/8 in)

For t > 50.8 mm (2 in)

Where t is the plate thickness

UG-81

uw=33

e = t/4

For 19.1 mm (3/4 in) c t I 38.1 mm (l-1/2 For 38.1 mm (l-1/2

{AF-130.2)

plate surface.

Shape of Formed Heads

12.7

2

Code Reference

Requirement

At nozzle openings, this tolerance diameter of the opening. Out-Of-Roundness Cylindrical Shells Under External Pressure

8-25


in)

in) c t I 50.8 mm (2 in)

e = 4.8 mm (3/l 6 in) e = t/8 e = min(tl8,

For t > 50.8 mm (2 in)

{AF-142)

19.1 mm) or

e = min(ff8, 3/4 in.) Where Angular Weld Misalignment


t is the plate thickness

and e is the allowable

centerline

offset. --

None stated

March 2000

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Jan, 2000


Overview Geometric

Table 8.4 Of Fabrication Tolerances - ASME 831.3 Requirement

Defect

Out-Of-Roundness In Cylindrical Shells Under Internal Pressure

Jan, 2000

Default is the ASTM Standard the pipe was purchased to, for example:

Code Reference //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

8-26

ASTM 530 - For thin wall pipe, the difference in extreme outside diameter readings (ovality) in any one cross-section shall not exceed 1.5% of the specified outside diameter. This wall pipe are defined as having a wall thickness of 3% or less of tine outside diameter.

l

l

l

l

l

ASTM 358 - Difference between major and minor outside diameters, 1% ASTM 671 - Difference between major and minor outside diameters, 1% ASTM 672 - Difference between major and minor outside diameters, 1% ASTM 691 - Difference between major and minor outside diameters, 1%

For wrought steel buttwelding fittings (e.g. elbows, teets, reducers, weld caps), requirements are provided in ASME B16.9. ---

Out-Of-Roundness In Cylindrical Shells Under External Pressure

Same as for internal pressure

Centerline Offset Weld Misalignment Longitudinal Joints

Defaults to ASTM standard pipe is purchased to, or requirement stipulated for centerline offset misalignment of Circumferential joints.

328.4.3(b)

Centerline Offset Weld Misalignment Circumferential Joints

Inside surfaces of components at ends to be joined in girth or miter groove welds shall be aligned within dimensional limits in the WPS and the engineering design.

328.4.3(a)

Angular Weld Misalignment

None Specified

-

--``````-`-`,,`,,`,`,,`---


March 2000

Not for Resale


Table 8.5 Overview Of Fabrication Tolerances – API Standard 620 Fabrication Tolerance

Requirement

Code Reference

Out-Of-Plumbness For Tank Shells

Out of plumbness from top of shell to bottom of shell shall not exceed 1/200 of the total tank height.

4.5.2

Out-Of-Roundness For Tank Shells

Maximum allowable out-of-roundness for tank shells, measured as the difference between the maximum and minimum diameters, shall not exceed 1% of average diameter or 305 mm (12 inches), whichever is less, except as modified for flat bottom tanks for which the radii measured at 305 mm (12 inches) above the bottom corner weld shall not exceed the tolerances shown below.

4.5.3

D < 12.2 m (40 ft)

Tol = 12.7 mm (1/2 in)

12.2 m (40 ft) £ D < 45.7 m (150 ft)

Tol = 19.1 mm (3/4 in)

45.7 m (150 ft) £ D < 76.2 m (250 ft)

Tol = 25.4 mm (1 in)

D > 76.2 m (250 ft)

Tol = 31.8 mm (1-1/4 in)

Where D is the diameter of the tank in feet and Tol is the tolerance on the radius

--``````-`-`,,`,,`,`,,`---

Skirts or cylindrical ends of formed tops shall have a maximum difference between maximum and minimum diameters of 1% of the nominal diameter. Centerline Offset Weld Radial Misalignment – All Butt Joints

For t £ 6.4 mm (1/4 inch)

e = 1.6 mm (1/16 inch)

For t > 6.4 mm (1/4 inch)

e = min[t/4, 3.2 mm] or

4.14

e = min[t/4, 1/8 in] Where t is the plate thickness and e is the allowable radial misalignment or offset.

Local Deviations Such As Angular Weld Misalignment (Peaking) And Or Flat Spots

Using a 914 mm (36 in) horizontal sweep board with a radius equal to the nominal radius of the tank, peaking at vertical joints shall not exceed 12.7 mm (1/2 inch ) for steel shells and 25.4 mm (1 inch) for aluminum shells (see API 620, Appendix Q). Using a 914 mm (36 in) vertical straight sweep board, banding at horizontal joints shall not exceed 12.7 mm (1/2 inch ) for steel shells and 25.4 mm (1 inch) for aluminum shells (see API 620, Appendix Q). Flat spots shall not exceed appropriate flatness and waviness requirements specified in ASTM A6 or ASTM A20 for carbon and alloy steels, ASTM A480 for stainless steels, and Table 3.13 of ANSI H35.2 for aluminum.

//^:^^#^~^^


Not for Resale

4.5.4


Table 8.6 Overview Of Fabrication Tolerances – API Standard 650 Requirement

Code Reference

Out-of-Plumbness

The maximum out of plumbness of the top of the shell of revolution to the bottom of the shell shall not exceed 1/200 of the total tank height.

5.5.2


Radii measured at 304 mm (12 inches) above the bottom corner weld shall not exceed the tolerances shown below.

5.5.3

D < 12.2 m (40 ft)

Tol = 12.7 mm (1/2 in)

12.2 m (40 ft) £ D < 45.7 m (150 ft)

Tol = 19.1 mm (3/4 in)

45.7 m (150 ft) £ D < 76.2 m (250 ft)

Tol = 25.4 mm (1 in)

D > 76.2 m (250 ft)

Tol = 31.8 mm (1-1/4 in)

--``````-`-`,,`,,`,`,,`---

Fabrication Tolerance

Where D is the diameter of the tank in feet and Tol is the tolerance on the radius Centerline Offset Weld Misalignment – Longitudinal Joints

For t £ 15.9 mm (5/8 in)

e = 1.6 mm (1/16 in)

For t > 15.9 mm (5/8 in)

e = min[t/10, 3.2 mm] or

5.2.3.1

e = min[t/10, 1/8 in] Where t is the plate thickness and e is the allowable radial misalignment or offset. Centerline Offset Weld Misalignment Circumferential Joints

The upper plate shall not project by more than 20 percent of the thickness of the upper plate, with a maximum projection of 3.2 mm (1/8 in); however, for upper plates less than 8 mm (5/16 in) thick, the maximum projection shall be limited to 1.6 mm (1/16 inch).

5.2.3.2


Using a 914 mm (36 in) horizontal sweep board with a radius equal to the nominal radius of the tank, peaking at vertical joints shall not exceed 12.7 mm (1/2 in).

5.5.4

Using a 914 mm (36 in) vertical straight sweep board, banding at horizontal joints shall not exceed 12.7 mm (1/2 in). Flat spots shall not exceed appropriate flatness and waviness requirements specified in ASTM A6 or ASTM A20.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 8.7 Overview Of Fabrication Tolerances For Reconstructed Tanks – API Standard 653 Fabrication Tolerance

Requirement

Code Reference

Out-of-Plumbness

The maximum out of plumbness of the top of the shell of revolution to the bottom of the shell shall not exceed 1/100 of the total tank height, with a maximum deviation of 127 mm (5 in).

8.5.2.1


Radii measured at 304 mm (12 inches) above the bottom corner weld shall not exceed the tolerances shown below.

D < 12.2 m (40 ft)

Tol = 12.7 mm (1/2 in)

12.2 m (40 ft) £ D < 45.7 m (150 ft)

Tol = 19.1 mm (3/4 in)

45.7 m (150 ft) £ D < 76.2 m (250 ft)

Tol = 25.4 mm (1 in)

D > 76.2 m (250 ft)

Tol = 31.8 mm (1-1/4 in)

8.5.3

Where D is the diameter of the tank in feet and Tol is the tolerance on the radius --``````-`-`,,`,,`,`,,`---

Centerline Offset Weld Misalignment – Longitudinal Joints

8.4.4.1

For t £ 15.9 mm (5/8 in)

e = 1.6 mm (1/16 in)

For t > 15.9 mm (5/8 in)

e = min[t/10, 3.2 mm] or e = min[t/10, 1/8 in]

Where t is the plate thickness and e is the allowable radial misalignment or offset. Centerline Offset Weld Misalignment Circumferential Joints

The upper plate shall not project by more than 20 percent of the thickness of the upper plate, with a maximum project of 3.2 mm (1/8 in); however, for upper plates less than 7.9 mm (5/16 in) thick, the maximum projection shall be limited to 1.6 mm (1/16 inch).

8.4.4.2


Using a 914 mm (36 in) horizontal sweep board with a radius equal to the nominal radius of the tank, peaking at vertical joints shall not exceed 25.4 mm (1 in).

8.5.4 & 8.5.5


Using a 914 mm (36 in) vertical straight sweep board, banding at horizontal joints shall not exceed 25.4 mm (1 in).

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 8.8 Equations For The Ratio Of Induced Bending Stress To Applied Membrane Stress For A Plate With Centerline Offset And Angular Misalignment

Plate – Centerline Offset (see Figure 8.2) (1)

Equations For Rb

Rbspc

F G F 6e I G 1 = 1+ G J H t - FCAK GG 1 + F t - FCAI H GH t - FCA JK 1

2

1

Limitations: Plate – Centerline Offset (see Figure 8.2) (1)

Rbspa =

b

1.5

I JJ JJ K

(8.61)

None

3@ Cf t - FCA

g

(8.62)

For Fixed Ends:

tanh

Cf =

> 2

> 2

(8.63)

For Pinned Ends:

Cf =

2 tanh > >

>=

L t - FCA

(8.64)

with,

--``````-`-`,,`,,`,`,,`---

@=

b

g

(in radians)

LG p None

Rb is dimensionless.


(8.65)

(8.66)

4

Limitations: Notes: 1. The equation for

3I m Ey

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Type Of Misalignment


--``````-`-`,,`,,`,`,,`---

Table 8.9 Equations For The Ratio Of Induced Bending Stress To Applied Membrane Stress For The Circumferential Joints Of A Cylinder With Centerline Offset And Angular Misalignment Type Of Misalignment Centerline Offset (see Figure 8.3) (1)(3)

Equations For Rb

LM 12 F 0.25672 R t R C U + eR R C UI OP ST C VW 2 ST C VWJK P MN R t GH Q I F JJ G F 6e I G 1 = 1+ G H t - FCAJK GG 1 + F t - FCA I JJ H GH t - FCA JK K

Rbccjc = abs

2 2

1 1

Rbsccjc

a

1

3

2

1.5

1

(8.67)

3

(8.68)

2

1

with,

b gc

C1 = H - 1 H 2 - 1

h

(8.69)

C2 = H 2 + 2 H 1.5 + 1

(8.70)

c

h

b g

(8.71)

where t 2 ³ t1

(8.72)

2

C3 = H 2 + 1 + 2 H 1.5 H + 1 H=

t 2 - FCA t1 - FCA

e = R1 - R2

where e is a negative number if R2 > R1 ; otherwise, e is a positive number

Ra =

10 £

(8.74)

R1 R and 10 £ 2 t1 t2

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Limitations:

R1 + R2 2

(8.73)


Not for Resale


Table 8.9 Equations For The Ratio Of Induced Bending Stress To Applied Membrane Stress For The Circumferential Joints Of A Cylinder With Centerline Offset And Angular Misalignment Type Of Misalignment Angular Misalignment (see Figures 8.6) (1),(4)

Equations For Rb

Rbccja = max Rbpccja , Rbtccja

(8.75)

with,

Rbtccja =

C1 C2

(8.76)

Rbpccja =

C3 C4

(8.77)

d i

o d it + (8.78)

C1 = 0.023748 - 0.010087 ln S p + 0.0014571 ln S p 11631 . G p + 10.476G 2p - 23.792G p

3

d i o d it 0.0044239olnd S it + 0.20821G C = -0.037285 - 0.0051687 lnd S i + 0.0072395olnd S it + C2 = 10 . - 0.36581 ln S p + 0.062036 ln S p

2

3

p

(8.79)

p

3

p

2

p

2

14.865G p - 331636 . G p + 91061 . Gp

d i o d it 0.0054959olnd S it + 0.044263G 12c1 - n h PR = E bt - FCAg F 2@ I bin radiansg = arctanG J H LK 3

p

2

(8.80)

3

C4 = 10 . - 0.35912 ln S p + 0.065885 ln S p

--``````-`-`,,`,,`,`,,`---

Sp

2

2

(8.81)

p

3

3

(8.82)

y

Gp

Note: in the above equations,

(8.83)

G p is in radians. Equations for Rbsccja are

currently under development Limitations:

Notes: 1. The equation for

10 £

R1 £ 500 , 0o £ G p £ 10o , and 0.0 £ S p £ 67.5 t1



Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 8.10 Equations For The Ratio Of Induced Bending Stress To Applied Membrane Stress For The Longitudinal Joints Of A Cylinder With Centerline Offset And Angular Misalignment Type Of Misalignment

Rbcljc = with

C1 C2

(8.84)

S p from Equation (8.82), and

FG e IJ + 12377 FG e IJ C = 38392 . . . c10 h + 31636 HtK HtK 4.0582c10 hS + 3.4647(10 ) S + -3

1

-3

p

-4

2

-

2 p

(8.85)

31205 . (10 -6 ) S p3 C2 = 10 . + 0.41934

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Limitations:


10 £

FG e IJ + 9.7390c10 hS HtK -3

p

R e £ 400 , 0.0 £ £ 1.0 , and 10 . £ S p £ 50.0 t t

Not for Resale

(8.86)

--``````-`-`,,`,,`,`,,`---

Centerline Offset (see Figure 8.2) (1)

Equations For Rb


Table 8.10 Equations For The Ratio Of Induced Bending Stress To Applied Membrane Stress For The Longitudinal Joints Of A Cylinder With Centerline Offset And Angular Misalignment Type Of Misalignment Angular Misalignment (see Figures 8.4 and 8.5) (1)

Equations For Rb

Rbclja =

b

6@ Cf t - FCA

g

(8.87)

C f can be determined from Figure 8.16 using S p from Equation (8.82) and @ R , or by using the series For Local Peaking (see Figure 8.4.A) – values of

solution provided below:

Cf = 1-

Gp

-

3F

4 S p2 F G 2p

d

i

4 G p - sin G p F G 2p

dnG - sin nG i å n n -1+ S d i 100

n=2

p

3

(8.88)

p

2

2 p

with,

FG 1 IJ bin radiansg H 1+ @ RK

G p = arccos --``````-`-`,,`,,`,`,,`---

For Global Peaking (see Figure 8.5.B): when

when

S p2 < 1 k2 -1 F 1 C f = 0.5 cot kF + 2 2 2k 2k 2k - 1

(8.90)

k 2 = 1 - S p2

(8.91)

S p2 > 1 C f = 0.5 +

k2 +1 F 1 coth kF - 2 2 2k 2k k +1

k 2 = S p2 - 1 Limitations: //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes: 1. The equation for

(8.89)

10 £

R and 0.0 £ S p £ 30.0 t



Not for Resale

(8.92)

(8.93)


Table 8.11 Equations For The Ratio Of Induced Bending Stress To Applied Membrane Stress For The Circumferential Joints Of A Sphere With Centerline Offset And Angular Misalignment Type Of Misalignment Centerline Offset (see Figure 8.2) (1)

Equations For Rb scjc b

R

F e IJ - 0.24587FG e IJ = 9.6291c10 h + 3.0791G H t - FCAK H t - FCAK F e IJ + 0.059281FG e IJ 0.025734G H t - FCAK H t - FCAK 61979 . . . c10 hS + 19252 c10 hS + 19815 c10 hS 18194 . c10 hS + 2.0698c10 hS -3

3

-3

-7

with

Rbscja = with

+

4

p

4 p

-4

2 p

-9

5 p

-6

(8.94)

3 p

S p from Equation (8.82).

Limitations: Angular Misalignment (see Figures 8.4 and 8.5) (2)

2

10 £

R e £ 400 , 0.0 £ £ 1.0 , and 0.0 £ S p £ 50.0 t t

C1 C2

(8.95)

S p from Equation (8.82), and C1 = 3.082 + 1.7207(10-3 ) S p + 13641 . O+ 0.062407O 2 - 0.033961O 3

C2 = 10 . + 8.9503(10-3 ) S p - 2.8724(10 -4 ) S p2 + 5.0797(10 -6 ) S p3 - 0.21717O

O = ln

FG @ IJ HC K

(8.96)

(8.97)

(8.98)

ul

R £ 300 , 0o £ G p £ 25o ( G p is computed using Equation t (8.89)), and 0.0 £ S p £ 30.0

Limitations:

Notes: 1. 2.

10 £

Rb is dimensionless. In the equation for Rb , Cul = 10 . if the units of inches are used, and Cul = 25.4 if the units of

The equation for

millimeters are used.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure 8.1 Overview Of The Assessment Procedures To Evaluate A Component With Geometric Irregularities

Obtain Equipment Data and Perform a Level 1 Assessment

Perform Level 1 Assessment

Yes

Yes

Equipment is Acceptable per Level 1 Criteria? Not for Resale



No

Yes


No

Yes



Rerate Equipment?

No

Yes

Yes


Yes


No

No


No

Yes



No

Rerate Equipment? Yes

Yes

No


Yes


--``````-`-`,,`,,`,`,,`---

8-36 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

No

Repair, Replace, or Retire Equipment Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS

No

Jan,2000

RECOMMENDED

PRACTICE

8-37


Figure 8.2 Centerline Offset Weld Misalignment

In Butt Weld Joints

-P P-

(a) Same Thickness

-- Inside and Outside Surfaces

Not Aligned

-P P--``````-`-`,,`,,`,`,,`---

(b) Different Thickness

(c) Different Thickness


- Alignment

With One Surface

- Inside and Outside Surfaces

Not Aligned


8-38

API RECOMMENDED

PRACTICE

Figure 8.3 Centerline Offset Weld Misalignment In Cylindrical

579

Shell Circumferential

Jan, 2000

Weld Joints

--``````-`-`,,`,,`,`,,`---

7 ------(i D2

7 (a) Weld Misalignment - Equal Diameters (D, = D2)

.--------

1 ---D,

7 2

D2

----------

L

3 (b) Weld Misalignment - Unequal Diameters (D,k D2)

March 2000


----

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(ii


t1

e R1

R2

t2

D1

CL D2

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(a) Weld Misalignment - Equal Diameters (D1 = D2) t2

t1

D1

R1

R2

e

D2 CL

--``````-`-`,,`,,`,`,,`---

(b) Weld Misalignment - Unequal Diameters (D1= D2)


Not for Resale

Figure 8.4 Angular Misalignment In Butt Weld Joints

Gp

t

P

t

@

P

L

(a) Angular Weld Misalignment

e

G @

Gp2

P

Gp1

L

(b) Angular and Centerline Offset Weld Misalignment Notes:

The dimension L is established as shown in Figure 8.6.

--``````-`-`,,`,,`,`,,`---


Not for Resale

P

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure 8.5 Angular Misalignment In A Cylindrical Shell Longitudinal Weld And Spherical Shell Circumferential Weld 2Gp

@

Shell With Imperfections

Gp

Shell Without Imperfections

R

(a) Local Peaking - Cylinder and Sphere Shell With Imperfections

@


R

(b) Global Peaking - Cylindrical Shells Only

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 8.6 Angular Misalignment In a Cylindrical Shell Circumferential Seam t

t

@

R

R

P

P

L

Notes: 1. 2.

The dimension L is defined as the length of the base of a triangle established based on the line of force, P , and the height of the angular peaking, @ . Note that as the height of the angular peaking, @ ® 0 , L ® 0 .

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 8.7 Global Circumferential Out-Of-Roundness Dmax Dmin

Dmax

Dmax

Dmin

Dmin

(a) Examples of Differences Between Maximum and Minimum Diameters In Cylindrical, Conical, and Spherical Shells Shell Without Imperfections

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Dmin Dmax

D

(b) Global Out-Of-Roundness Extrados


G

Dmax Dmin

Crown

Intrados

(c) Ovalization of a Pipe Bend


Not for Resale

--``````-`-`,,`,,`,`,,`---



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure 8.8 A Bulge In A Cylindrical Shell

A

--``````-`-`,,`,,`,`,,`---

B

B A (a) Cylinder with Bulge

CL VM

Location of Inflection Point (Change in Local Curvature)


HC

RLC

RBC

RBM VC HM

(b) Section A-A RLM

(c) Section B-B


Not for Resale


Figure 8.9 A Bulge In A Spherical Shell

B A

A

B

(a) Sphere with Bulge


Location of Inflection Point (Change in Local Curvature) HC

RLC

HM RLM

RBC

RBM

VC

(c) Section B-B

(b) Section A-A

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

VM


Figure 8.10 A Dent In A Cylinder

Gouge Length(s)

s

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Pipe Axis

--``````-`-`,,`,,`,`,,`---

Pushed Out Center Region

(a) Longitudinal Section

Original Pipe Wall Position

dd

rd t ag

Deformed Pipe Wall

(b) Cross Section


Not for Resale


Figure 8.11 Method Of Measurement To Determine The Extent Of Peaking In A Shell Template

Contact Point

"Centered" Template

a2

a1

"Peaked Surface"

Template

"Rocked" Template

"Rock" Point

Contact

Template

"Rocked" Template b2

"Rock" Point Contact 4 3 2 1

"B" Seam Vertical Seam Weld

Measuring Locations "A" Seam

10 9 8 7 6 5 4 3 2 1

Bottom Tangent


Not for Resale

Datum for Taking Location Readings

--``````-`-`,,`,,`,`,,`---

b1

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Vessel True Radius


Figure 8.12 Method Of Measurement To Determine The Extent Of Out-Of-Roundness In A Cylinder 0°

A1 24 23

G

15° 30°

1

2

R1

R2

22

B1

R3

True Center of Mean Circle

21

45°

3 4 R4

5 6

20

R

19

7

18

8

Center of Measurement

17

9

16 15

14

10 13

11

12

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 8.13 Definition Of Local Radius Used To Compute The Permissible External Pressure In A Cylindrical Shell With A Geometrical Deviation

c Cylinder Without Imperfections

e h

m

RO G

Cylinder With Imperfections

RL

Notes: 1. 2. 3.

Ro is the outside radius of the shell without imperfections e is the maximum inward deviation which occurs within a 2G arc length RL is the local radius which defines the shape of the imperfection based on e . The following equations can be used to compute the local radius. The value n is computed using the equations in paragraph 8.4.3.5.b.

G=

90 n

b

h = Ro 1 - cosG

(8.99)

g

(8.100)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

c = Ro sinG

(8.101)

m= h-e

(8.102)

RL =

m2 + c 2 2m

(8.103)

--``````-`-`,,`,,`,`,,`---


Not for Resale


1000 800

Arc = 0.030DO

600 500 400

Arc = 0.035DO Arc = 0.040DO Arc = 0.045DO

300

Arc = 0.055DO

200

Arc = 0.065DO Arc = 0.075DO Arc = 0.085DO

100 80

Arc = 0.150DO

20

Arc = 0.175DO

10 0.01

Arc

Arc = 0.200DO

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

30

O

Arc = 0.125DO

=0 .39 0D

=0 .30 0D

O

Arc = 0.010DO

60 50 40

Arc

Outside Diameter Divided By Thickness, Do/t

Figure 8.14 Maximum Arc Of A Shell Used As A Basis To Determine The Deviation From Circular Form

Arc = 0.250DO 0.02

0.040.06 0.1

0.2

0.4 0.6

1

2

3 4 5 6 8 10

20

Design Length Divided By Outside Diameter, Lec/Do

Notes: 1. Cylindrical Shells –

Lec is the unsupported length of the cylinder and Do is the outside diameter. 2. Conical Shells – Lec and Do are established using the following equations for any cross section having a diameter Dx . In these equations DL and DS are the cone large end and small end outside diameters, respectively and L is the unsupported length of the conical section under evaluation.

Lec =

FG L IJ FG1 + D IJ FG D IJ H 2 KH D KH D K S

S

L

L

(8.104)

Do = Dx

(8.105)

Lec is one-half of the outside diameter and Do is the outside diameter of the sphere. 2. Elliptical Head – Lec is one-half of Ko Do (see Appendix A, paragraph A.4.6) and Do is the outside 1. Spherical Shell –

diameter of the cylinder at the head attachment point. 3. Torispherical Head – Lec is the crown radius and Do is the outside diameter of the cylinder at the head attachment point. 4. The value of t for all calculations is the current shell thickness.

--``````-`-`,,`,,`,`,,`---


Not for Resale


--``````-`-`,,`,,`,`,,`---

Outside Diameter Divided By Thickness, Do/t

Figure 8.15 Maximum Permissible Deviation From A Circular Form For Vessels Subject To External Pressure

1000 900 800 700 600 500 400 300

e = 1.0t e = 0.8t e = 0.6t e = 0.5t

200 150 100 90 80 70 60 50

e = 0.4t

e = 0.3t e = 0.25t e = 0.20t

40 30 25 0.05

0.1

0.2

0.3 0.4 0.50.6 0.8 1

2

3

4 5 6 7 8 910

Design Length Divided By Outside Diameter, Lec/Do

Notes: see Figure 8.11 for the definition of variables.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

RECOMMENDED

PRACTICE


Figure 8.16 Correction Factor For Angular Weld Misalignment In The Longitudinal

8-51

Joint Of A Cylindrical

Shell

1 .o 0.9 0.8 0.7

6/R=0.001

0.6

cf

.002 .003

0.5

.004 .006 .006 .Ol

0.4 0.3

.02 .03

0.2

.05 6/R=O.l

0.1 0.0 0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

%

--``````-`-`,,`,,`,`,,`---



PRACTICE 579

API RECOMMENDED

8-52

Jan, 2000

8.11

Example Problems

8.11.1

Example Problem 7 - A NPS 36 long seam welded pipe is to be used on a refinery project. Inspection of the pipe indicates peaking at the long seam weld. The pipe was designed and constructed to ASME 831.3. Determine if the pipe is suitable for service. Pipe Data

--``````-`-`,,`,,`,`,,`---

Pipe Outside Diameter

=

36”

Wall Thickness

=

0.5 inches

Material

=

ASTM A691 Class 41 (1% CR - % MO)

Design Pressure

=

315 psig

Design Temperature

=

800°F

Joint Efficiency

=

100%

FCA

=

0.05 inches

=

0.31”

Pipe Data Peaking distortion 6

Perform A Level 1 Assessment per paragraph

8.4.2.1

Limitations for weld peaking misalignment are not specified in ASME B31.3 (see Table 8.4). Typically, the rules for out-of-roundness are applied to this type of misalignment.

(1%3X- Dti}

= (36.3 1”-36”) = 0.3 1”) I (O.OlD = 0.36”)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


is Satisfied if the Out-Of-Roundness

Perform A Level 2 Assessment per paragraph

True Criterion is Applied

8.4.3.2

Step 1 - Identify the component and weld misalignment type (see Table 8.10) and determine the following variables as applicable (see Figures 8.2, 8.3, and 8.4) - The weld misalignment is peaking which occurs on a longitudinal weld seam. The following data is required for the assessment:

Ey = 25.5( 10”) psi

FCA = 0.05” Hf = 3.0 P=315 psig R = 17LW’ Inside Radius S, = 16800 psi

t = 0.5” 6 = 0.3 1” v = 0.30 Step 2 - Determine the membrane stress based on the current design pressure (see Appendix A).

March 2000


Not for Resale

Jan, 2000

RECOMMENDED

PRACTICE

8-53


+0.6 = 12579 psi Step 3 - Calculate the ratio of the induced bending stress to the applied membrane stress using the equations in Table 8.10 based on the type of component and weld misalignment.

%=/(2IyIo.!IJIyI.=2 12{1-(0.3)*}(315

6

0.3 1” z = (17.75”-0.05”)

prig) (17.75”-0.05”)-

= 0.0175

From Figure 8.15, with

RC””

=

b

6(

Oa3

“I)

(OS’-0.05”)

-

Cf =

0.83, and

(0.83) = 3.43

Step 4 - Determine the remaining strength factors - using the conservative assumption, set H=3.0 (the induced bending stress is evaluated as a secondary stress)

RSF = min

1

(3.0)(16800 psi) , 1.0 = 0.90 (12579 psi)( 1+ 3.43)

Step 5 - Evaluate the results.


8.11.2

Example Problem 2 -

True

Criteria is Satisfied.

Determine if the pipe in the Example Problem Number 1 can operate for 2000

cycles at 315 psig. Perform A Level 2 Assessment - Fatigue Analysis per Paragraph 8.4.3.9 (the analysis will be Performed Using fatigue curves based on smooth bar and welded test specimens, see Appendix 9

Step 7 -

Determine if the weld misalignment satisfies the requirements of paragraphs 8.4.3.2.

Based on the results shown in Example Problem Number 1, this requirement is satisfied.

Step 2 -

Determine the stress concentration factor

Fatiaue Analysis Usina A Fatique Curve Based On Smooth Bar Test Specimens --``````-`-`,,`,,`,`,,`---



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(RSF = 0.90) 2 (RSF, = 0.90)

Jan, 2000


8-54

K, =1.5 Fatique Analvsis Usinq A Fatique Curve Based On Welded Test Soecimens

K, = 1.0 Step 3 -

Calculate the stress range using the parameters required in Step 1 - based on the results in Example Problem Number 1:

CT,= 12579 psi --``````-`-`,,`,,`,`,,`---

Rlgc = 0.0 centerline offset not present -rrin - .Kc- = 5.45 Rr = 0.0 shell out -of -roundness not present Fatique Analvsis Usinq A Fatique Curve Based On Smooth Bar Test Soecimens

K, =1.5 CT,= (12579 psi)(l+O.O+3.43+0.0)(15)

= 83,587 psi

Fatique Analvsis Usinq A Fatique Curve Based On Welded Test Soecimens

K, = 1.0 CF~= (12579 psi)(l + 0.0 + 3.43+ O.O)(l.O)= 55,725 psi Step 4 - Compute the number of allowed cycles using the stress range determined in Step 3 and a fatigue curve (see Appendix B). Fatique Analvsis Usinq A Fatique Curve Based On Smooth Bar Test Specimens From Figure F.10 of Appendix F: %,t =

? E,,, =

= 49169 psi a n = 46OOcycZes

uTS<80 hi Alternatively,

i

the number of cycles can be computed using the data in Table F.9:

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

RECOMMENDED

PRACTICE


8-55

Si = 64 bi S = 49.169 ksi Sj = 48 krsi

5= log(+)

= log( 4E6Zsi)

= 09164

log(g%)

-

log[$)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Ni = 2000 cycles Nj = 5000 cycles

6

= (2000

Fatioue Analysis Usino A Fatinue Curve Based On Welded Test Soecimens Information regarding the weld detail and profile are not stipulated, assume a double welded joint with an ‘undressed profile”. For a long seam welded pipe, the maximum principal stress acts perpendicular to the weld joint. For this loading condition and weld geometry assign the weld joint to Class 80 per Figure F. 12 of Appendix F. The constants for the Class 80 fatigue curve are:

A = 1.02(1oL2)

m=3 The allowable number of cycles is:

f, = 1.0 3

the wall thickness is less than 25mm

E = 255( 106) psi or = 55725 psi -3

N = {1.02(1012)}(1.0)

(55725 psi)2.09(105) (255{106} psi)

1

= 10706 cycles

Step 5 - Evaluate the results. If the computed number of cycles determined in Step 3 are greater than or equal to the specified number of operating cycles (Iv,,,=2000 c@es), the component is acceptable per Level 2. Fatique Analvsis Usinq A Fatique Curve Based On Smooth Bar Test Soecimens

(N = 463 1 cycles) 2 (N,,, = 2000)

True

Fatiaue Analvsis Usina A Fatioue Curve Based On Welded Test Soecimens

True --``````-`-`,,`,,`,`,,`---

(N = 10706 cycles) 2 (N,,, = 2000)



8-56 8.11.3

API RECOMMENDED

Jan, 2000

PRACTICE 579

Example Problem 3 - An existing pressure

vessel is being repaired during a shutdown. After field PWHT, inspection of the vessel indicates that out-of-roundness along the length of the cylindrical section of the vessel has occurred. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is suitable for service. Vessel

Data

Design Conditions

=

500 psig @ 650 OF

Wall Thickness

=

1.875 inches

Inside Diameter

=

120 inches

Material

=

SA 516 Grade 70

Joint Efficiency

=

100%

FCA

=

0.125

D mar

=

120.5 inches

&in

=

119.4 inches

Inspection

Data

--``````-`-`,,`,,`,`,,`---

Based on other measurements, Perform

A Level

t-i4X The Level Perform

the deformed shape.

1 Assessment

per paragraph

- Dmin} = {120.5”-119.4”)

1 Assessment A Level

Step 1 - Determine

Criteria

2 Assessment the following

shape significantly

deviates

from the perfect oval

8.4.2

= 1.1”) I (O.OlD = 1.2”)

True

Are Satisfied per paragraph variables

8.4.3.3

based on the type of out-of-roundness.

E, = 26.1(106) psi FCA = 0.125” Hf = 3.0 P = 500 psig R = 60” So = 17500 psi t = 1.875” v = 0.3

8 = 0” chosen because this is the location of a longitudinal weld seam C, = 0.1 the deformed shape significantly deviates from a perfect oval D=2R=120” D,, = 120.5” Dti = 119.4” Step 2 - Determine

the membrane

stress

based on the current

design pressure

(see Appendix

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A).


Im =

I . "g b500 psigg FG b60"+0125 + 0.6J = 17479 psi . "-0.125"g b1.0g H b1875 K

Step 3 – Determine the ratio of the induced circumferential bending stress to the circumferential membrane stress:

OP LM PP MM . b120.5"-119.4"g cosc2 × 0 h 15 = abs = 0.593 P MM F I 500 psig ge1 - l0.3q j F b 122" IJ J PP . "-0125 . "gG 1 + b01 .g G MM b1875 . "-0.125" K J GH o26.1c10 h psit H 1875 K PQ N o

or b

R

2

3

6

Step 4 – Determine the remaining strength factor:

RSF = min

LM b3.0gb17500 psig , 10. OP = 1.0 N b17479 psigb1 + 0.593g Q

Step 5 – Evaluate the results. If RSF ³ otherwise, refer to paragraph 8.4.3.10.

RSFa , the out-of-roundness is acceptable per Level 2;

b RSF = 1.0g ³ b RSF = 0.90g

True

a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The Level 2 Assessment Criteria Are Satisfied

8.11.4

On further inspection of the vessel in Example Problem Number 3, the out-of-roundness was reclassified as weld misalignment on one of the longitudinal seams. The weld misalignment is categorized as centerline offset and peaking. Determine if the vessel is suitable for operation. Inspection Data

--``````-`-`,,`,,`,`,,`---

Dmax

=

120.5 inches

Dmin

=

119.4 inches

Based on additional field measurements, the deformed shape significantly deviates from the perfect oval shape.

e

=

0.25 inches

@

=

0.60 inches

Perform A Level 2 Assessment per paragraph 8.4.3.4 Step 1 – Determine the membrane stress based on the current design pressure (see Appendix A) – from Example Problem Number 3:

I m = 17479 psi


Not for Resale


Step 2 – Calculate the ratio of the induced bending stress to the applied membrane stress for weld misalignment using paragraph 8.4.3.2, and for circumferential out-of roundness using paragraph 8.4.3.3.

Rb for centerline offset misalignment:

Sp =

e l q jb500 psiggb61"g . "-0125 . "g e261. m10 rjb1875

12 1 - 0.3

2

3

= 2.98

3

6

FG 0.25" IJ + 12377 FG 0.25" IJ . c h H 1875 H 1875 . "-0.125" K . "-0125 . "K 4.0582c10 hb2.98g + 3.4647(10 )b2.98g + 31205 . (10 )b2.98g = 0.4721 F 0.25" IJ + 9.7390c10 hb2.98g = 10888 = 10 . + 0.41934G . H 1875 . "-0.125" K

C1 = 38392 . 10-3 + 31636 . -3

-4

Rbcljc =

-

2

3

-6

C2

2

-3

0.4721 = 0.434 10888 .

Rb for peaking misalignment S p = 2.98 @ 0.60" = = 0.010 61" R

R|S = 2.98 U| From Figure 8.15, with S @ Þ C » 0.87 , and V = 0 . 010 |T R |W 6b0.60"g R = b0.87g = 1.79 . "-0125 . "g b1875 p

f

clja b

Rb for centerline offset misalignment and peaking weld misalignment is: Rb = 179 . + 0.434 + 0.0 = 2.224

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Step 3 – Determine the remaining strength factor.

RSF = min

LM b3.0gb17500 psig , 1.0OP = 0.93 N b17479 psigb1 + 2.224g Q

Step 4 – Evaluate the results.

b RSF = 0.93g ³ b RSF = 0.90g a

True

Therefore,

MAWPr = 500 psig

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale

SECTION 9 – Assessment of Crack-Like Flaws

9.1

General

9.1.1

Fitness-For-Service (FFS) assessment procedures for evaluating crack-like flaws in components are covered in this section. These assessment procedures are based on the Failure Assessment Diagram (FAD) method. This method has evolved as the most broadly accepted methodology for the analysis of components containing a crack-like flaw. Details regarding the background and development of the methodology and assessment procedures can be found in Reference [9.9.3].

9.1.2

Crack-like flaws are planar flaws which are predominantly characterized by a length and depth, with a sharp root radius. Crack-like flaws may either be embedded or surface breaking. Examples of crack-like flaws include planar cracks, lack of fusion and lack of penetration in welds, sharp groovelike localized corrosion, and branch type cracks associated with environmental cracking.

9.1.2.1

In some cases, it is conservative and advisable to treat volumetric flaws such as aligned porosity or inclusions, deep undercuts, root undercuts, and overlaps as planar flaws, particularly when such volumetric flaws may contain microcracks at the root. This is because the results from an NDE examination may not be sensitive enough to determine whether microcracks have initiated from the flaw.

9.1.2.2

It may be necessary to use the assessment procedures in this section to compare the relative flaw tolerance or evaluate the risk of brittle fracture of an existing component for screening purposes. In this type of analysis, a standard reference flaw must be postulated to undertake the fracture mechanics calculations. A standard reference surface flaw that has been used has a depth equal to 25% of the wall thickness and a length equal to six time this depth.

9.1.3

It is recognized that environmental cracks are more common in refining and petrochemical equipment due to a wide variety of process environment/material interactions and material damage mechanisms.

9.1.3.1

An overview of the failure modes and damage mechanisms which occur in the refining and petrochemical industry are described in Appendix G. A knowledge of the damage mechanism may affect decisions regarding the following:

9.1.3.2

·

The choice of material properties to be used in a FFS assessment.

·

The choice of an appropriate crack growth rate.

·

The permissible amount of crack extension prior to the final fracture or the time between inspection intervals.

·

The mode of final failure (e.g. unstable fracture, yielding due to overload of remaining ligament, or leak).

·

Whether account should be taken of any interaction between damage mechanisms (e.g. corrosion and fatigue, creep and fatigue, hydrogen embrittlement and temper-embrittlement, environmental assisted cracking).

Environmental cracks typically occur in multiples and may be branched. The assessment procedures in this section can be applied to such cracks provided a predominant crack whose behavior largely controls the structural response of the equipment can be identified. The predominant crack in the presence of multiple cracks or branched cracks can be defined through the flaw characterization techniques described in paragraph 9.3.6. When a predominant crack cannot be defined even after recharacterization, then more advanced FFS techniques, such as damage mechanics (which are outside the scope of this document) are available.

9-1 Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS

--``````-`-`,,`,,`,`,,`---

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(Jan, 2000)


9.2


9.2.1

The assessment procedures of this section can be used to evaluate pressurized components containing crack-like flaws. The pressurized components covered include pressure vessels, piping, and tanks designed to a recognized code or industry standard.

9.2.2


9.2.2.1

The Level 1 and 2 assessment procedures in this section apply only if all of the following conditions are satisfied: a.

The original design criteria were in accordance with Section 2, paragraph 2.2.2.

b.

The component is not operating in the creep range (see Section 4, paragraph 4.2.3.1.b).

c.

Dynamic loading effects are not significant (e.g. earthquake, impact, water hammer, etc.).

d.

The crack-like flaw is subject to loading conditions and/or an environment which will not result in crack growth. If a flaw is expected to grow in service, it should be evaluated using a Level 3 assessment, and the remaining life should be evaluated using the procedures of paragraph 9.5.

e.

The following limiting conditions are satisfied for a Level 1 Assessment. 1.

Limitations on component and crack-like flaw geometries:

--``````-`-`,,`,,`,`,,`---

a)

The component is a flat plate, cylinder, or sphere.

b)

Cylinder and spheres are limited to geometries with R t ³ 5 where inside radius and t is the current thickness of the component.

c)

The component current wall thickness at the location of the flaw is less than 38 mm (1.5 inches).

d)

The crack-like flaw geometry can be of the surface or through-thickness type, specific limitations are included in the Level 1 assessment procedure.

e)

For cylindrical and spherical shell components, the crack-like flaw is oriented in the axial or circumferential direction and is located a distance greater than or

R is the

equal to 18 . Dt from any major structural discontinuity where D is the inside diameter and t is the current thickness of the component. For a flat plat, the crack-like flaw is orientated such that maximum principle stress directions is perpendicular to the plane of the flaw. 2.


Limitations on component loads: a)

The loading on the component is from pressure which produces only a membrane stress field. Pressurized components subject to pressure which result in bending stresses (e.g. head-to-cylinder junction, nozzle intersections, rectangular header boxes on air-cooled heat exchangers) and/or components subject to supplemental loading (see Appendix A) should be evaluated using a Level 2 or Level 3 Assessment.

b)

The membrane stresses during operation are within the limits of the original construction code and the component will not be subject to hydrotest conditions.

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3.

9.2.2.2

c)

If a component being evaluated is to be subject to a future hydrotest, the component's metal temperature shall be at least above the MAT (see Section 3, paragraph 3.1.4). After the hydrotest, the crack-like flaw shall be re-examined to ensure that the flaw has not grown.

d)

The weld joint geometry is either a Single-V or Double-V configuration; the residual stresses are based on the solutions provided in Appendix E.

The material meets the following limitations: a)

The material is carbon steel (P1, Group 1 or 2) with an allowable stress per the original construction code which does not exceed 172 MPa (25 ksi).

b)

The specified minimum yield strength for the base material is less than or equal to 276 MPa (40 ksi), the specified minimum tensile strength for the base material is less than or equal to 483 MPa (70 ksi), and the weldments are made with electrode compatible with the base material.

c)

The fracture toughness is greater than or equal to the lower bound K IC value obtained from Appendix F, paragraph F.4.4.1.c computed using a reference temperature from Appendix F, paragraph F.4.4.2. This will be true for carbon steels where the toughness has not been degraded because of environmental damage (e.g., fire damage, over-heating, graphitization, etc.).

A Level 3 Assessment should be performed when the Level 1 and 2 methods cannot be applied or produce overly conservative results. Conditions which typically require this assessment level include the following.

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a.

Advanced stress analysis techniques are required to define the state of stress at the location of the flaw because of complicated geometry and/or loading conditions.

b.

The flaw is determined or expected to be in an active subcritical growth phase or has the potential to be active because of loading conditions (e.g. cyclic stresses) and/or environmental conditions, and a remaining life assessment or on-stream monitoring of the component is required.

c.

High gradients in stress (either primary or secondary), material fracture toughness, or material yield and/or tensile strength exist in the component at the location of the flaw (e.g. mismatch between the weld and base metal).

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9.2.3

Assessment procedures to evaluate a notch at the base of a groove-like flaw are covered in Section 8. These rules include both a fracture mechanics and limit load criteria.

9.3

Data Requirements

9.3.1

General

9.3.1.1

For a Level 1 assessment, sufficient conservatism has been added to the assessment procedure to minimize the data requirements. A summary of the information required is shown below: ·

Original Equipment Design Data (see paragraph 9.3.2)

·

Maintenance and Operating History (see paragraph (9.3.3))

·

Material Properties (see paragraph 9.3.5, only the minimum specified material yield and tensile strengths are required, and the material allowable stress are required)

·

Flaw Characterization (see paragraph 9.3.6)


Not for Resale

9.3.1.2

Significant input data are required to perform Level 2 and Level 3 FFS assessments of a component with a crack-like flaw. Details regarding the required data are discussed in paragraphs 9.3.2 through 9.3.6. The accuracy of these data and stress conditions will determine the accuracy of the assessment by the procedures in this section. The choice of input data should be conservative to compensate for uncertainties in the NDE flaw sizing, the prevalent cracking mechanism, and high failure consequences.

9.3.1.3

The datasheet shown in Table 9.1 should be completed before the FFS assessment is started. This ensures that all of the pertinent factors are considered, communicated, and incorporated into the assessment. The information on this datasheet is used for a Level 1 or Level 2 assessment. In addition, this information is generally applicable for a Level 3 assessment. Guidelines for establishing the information to be entered on this datasheet are provided in paragraphs 9.3.2 through 9.3.7.

9.3.2


9.3.2.1

An overview of the original equipment data required for an assessment is provided in Section 2, paragraph 2.3.1.

9.3.2.2

Equipment data is required in order to compute the stress intensity factor and reference stress solution based on the geometry of the component at the crack location. a.

For pressure equipment with uniform thickness such as vessels, pipes, and tanks, the important dimensions are the mean diameter and wall thickness.

b.

For pressurized equipment with a non-uniform thickness, or where structural discontinuities are involved (e.g. vessel head-to-shell junctions, conical transitions, nozzles, piping tees, and valve bodies) the important dimensions are the diameter, wall thickness, and the local geometric variables required to determine the stress distribution at a structural discontinuity.

9.3.3

Maintenance And Operating History

9.3.3.1

An overview of the maintenance and operating history required for an assessment is provided in Section 2, paragraph 2.3.2.

9.3.3.2

Maintenance and operational input should be provided by personnel familiar with the operational and maintenance requirements of the component containing the crack-like flaw. This data provides a basis for determining the following: ·

The most probable mechanism of the cracking

·

Whether or not the crack is growing

·

Reasonable postulates on flaw size and geometry based on prior records of cracking or experience with other components in a similar service

·

The most probable mechanism of the failure expected

·

Potential remediation measures

9.3.4

Required Data/Measurements For A FFS Assessment – Loads and Stresses

9.3.4.1

Load Cases – The stress distribution at the cracked region of the component should be determined for all relevant loads based on the planned future operating conditions. An overview of the load cases to consider in a stress analysis are provided in Appendix A. It is important that the combination of pressure and temperature be determined for all load cases because of the dependence of the material fracture toughness with temperature.

9.3.4.2

Stress Computation – The stress distributions from each load case are calculated based on the uncracked component geometry using loads derived from the future operating conditions.


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A non-uniform stress distribution may occur through the wall thickness or along the surface of the component. Examples include the through-wall stresses in a pressurized thick wall cylinder, the stress attenuation which occurs at a major structural discontinuity (e.g. nozzle-toshell and head-to-shell junctions), and the stress distribution caused by a thermal gradient which typically occurs at a skirt-to-vessel attachment. The method used to determine the state of stress in a component should include capabilities to compute stress distributions based on loading conditions and structural configuration.

b.

The methods of stress analysis vary widely and may be based on handbook solutions if they accurately represent the component geometry and loading condition. Otherwise, numerical analysis techniques such as the finite element method may have to be utilized to determine the stress field at the crack location.

c.

The computed stress profiles may need to be linearized into membrane and bending stress components to compute a stress intensity factor and reference stress for certain crack geometries and load conditions. Guidelines for linearization of a stress field in the presence of a crack are included in Appendix B.

d.

If it can be verified that the crack-like flaw in the component occurred after application of load, then the stress distributed can be computed using an elastic-plastic analysis.

Stress Classification – The stress distributions at the cracked region of the component must be classified into the following stress categories in order to complete a Level 2 assessment. a.

Primary Stress – The primary stress distribution is developed by the imposed loading which is necessary to satisfy the laws of equilibrium of external and internal forces and moments (see Appendix B). In addition, the primary stress should also include any recategorized secondary stresses. The primary stress can be assumed to be a uniform membrane stress with a magnitude equal to the allowable design stress per the original construction code at the temperature being evaluated if the crack-like flaw is located away from all major structural discontinuities. If the flaw is located at a weld joint, the magnitude of stress should be divided by the applicable weld joint efficiency.

b.

Maximum Primary Stress – The maximum primary stress is developed in the same manner as the primary stress but is associated with the maximum loading condition the component is subjected to. In pressurized equipment, this is typically associated with a hydrotest condition. The maximum primary stress is only used in the assessment procedures to account for mechanical stress relief.

c.

Secondary Stress – The secondary stress distribution is developed by the constraint of adjacent parts or by self-constraint of a structure (see Appendix B). If it is uncertain whether a given stress is a primary or secondary stress, it is more conservative to treat it as primary stress. It should be noted that in certain cases secondary stresses which are self-equilibrating over the entire structure or component may still result in plastic collapse in the net section around a crack-like flaw. This can occur when the flaw is small compared to the spatial extent of the secondary stress distribution, or there is significant elastic follow-up from the surrounding structure. In these cases, the secondary stress should be treated as a primary stress in the assessment.

d.

Residual Stress – Crack extension can occur locally if the crack tip is located in a tensile residual stress field. Therefore, residual stresses resulting from welding need to be added to the secondary stresses caused by operational loads when performing an evaluation. The magnitude and distribution of residual stress can be determined using Appendix E.

9.3.5

Required Data/Measurements For A FFS Assessment – Material Properties

9.3.5.1

Material Yield and Tensile Strength – The yield and tensile strength of the material are required in the FFS assessment to determine the effects of plasticity on the crack driving force, estimate the


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9.3.4.3

a.


9.3.5.3

If heat-specific yield and tensile strengths for the material and/or weldment are not available, then estimates may be made using the information in Appendix F. Otherwise, the specified minimum values of yield stress and tensile stress for the base and weld material should be used.

b.

In general, use of minimum values of yield and tensile strengths will result in a conservative assessment. However, if there are residual stresses in the region of the crack-like flaw, the use of the specified minimum yield strength will tend to under estimate the magnitude of the residual stresses. Therefore, when estimating the magnitude of residual stresses the actual yield strength should be used. If the actual yield strength is not known, the value of the minimum yield strength should be adjusted using the procedure in Appendix E before the residual stresses are computed.

c.

The material yield strength for the regions(s) ahead of the crack tip should be adjusted, as appropriate, to take account of temperature, strain aging, thermal aging, or other forms of prevalent degradation.

d.

The material stress-strain curve or Ramberg-Osgood constants if a J integral evaluation is to be performed (see Appendix F) are required if an elastic-plastic stress analysis is performed as part of the assessment.

Material Fracture Toughness – The fracture toughness of the material is a measure of its ability to resist failure by the onset of crack extension to fracture. a.

Guidance for determining fracture toughness for various materials and environments is provided in Appendix F.

b.

The process environment, service temperature envelope, and any related material/service degradation mechanisms such as embrittlement should be accounted for when determining the fracture toughness (see Appendix F).

c.

Local variations in the fracture toughness in the vicinity of the crack tip should be considered in the assessment.

d.

When material specific toughness is not available, then lower bound values must be used from various correlations (see Appendix F).

Crack Growth Law – A crack growth law and associated constants are required if an estimate of the remaining life of the component with a crack-like flaw is to be made based on a fracture mechanics approach. An overview of crack growth laws is provided in Appendix F. The law chosen for the assessment should include environmental effects, and may be related to cyclic behavior time to failure

bda dt g , or both.

bda dN g ,

9.3.5.4

Material Physical Constants – material properties such as the elastic modulus, Poisson’s ratio, and the thermal expansion coefficient may be required to perform an evaluation. Guidelines for determining these quantities are provided in Appendix F.

9.3.6

Required Data/Measurements For A FFS Assessment – Flaw Characterization

9.3.6.1

Overview – Flaw characterization rules allow an existing or postulated crack geometry to be modeled by a geometrically simpler one in order to make the actual crack geometry more amenable to fracture mechanics analysis. The nomenclature and idealized shapes used to evaluate crack-like flaws are shown in Figure 9.1. The rules used to characterize crack-like flaws are necessarily conservative and


Not for Resale

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9.3.5.2

a.

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residual stress, and evaluate the fracture toughness using correlations with other material toughness parameters.


9.3.6.2

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intended to lead to idealized crack geometries that are more severe than the actual crack geometry they represent. These characterization rules account for flaw shape, orientation and interaction. Characterization Of Flaw Length – The flaw length is typically not difficult to determine for surface breaking flaws. If the flaw is oriented perpendicular to the plane of the maximum principal tensile stress in the component, then the flaw length to be used in calculations ( c or 2c ) is merely the measured length co or 2co . However, if the flaw does not lie in a principal plane, then an equivalent

a.

Conservative option – The flaw dimension, c , to be used in the calculations can be set equal to the measured length, co , irrespective of orientation. In general, such an assumption leads to a conservative analysis. For fracture assessments, the plane of the flaw should be assumed to be normal to the maximum principal tensile stress.

b.

Equivalent flaw length option – The recommended procedure for defining an equivalent Mode I flaw dimension is shown in Figures 9.2. 1.

Step 1 – Project the flaw onto a principal plane. In the case of uniaxial loading, there is only one possible principal plane. However, when the loading is biaxial (e.g., a pressurized component which is subject to a hoop stress and an axial stress), there is a choice of principal planes on which to project the flaw. In most cases, the flaw should be projected to the plane normal to the maximum principal tensile stress (the I 1 plane),

I 2 plane would be more appropriate (e.g., when the angle between the flaw and the principle plane = is greater than 45°). but there are instances where the

2.

bg

Step 2 – Compute the equivalent flaw length a)

For the plane of the flaw projected onto the plane normal to I1

b g

1 - B sin = cos = c = cos2 = + + B 2 sin 2 = co 2 b)

(9.1)

For the plane of the flaw projected onto the plane normal to I2:

b g

1 - B sin = cos = c cos2 = = + + sin 2 = 2 co B 2 B2 c)

In the above equations, the dimension c corresponds to the half flaw length (or total length for corner or edge cracks) to be used in calculations, co is the measured half length for the flaw oriented at an angle and B is the biaxiality ratio, defined as:

B= d)

(9.2)

I2 I1

= from the I 1 plane,

where I 1 > I 2 and 0.0 £ B £ 10 .

The above equation is only valid when both

(9.3)

I 1 and I 2 are positive. If I 2 is

compressive, B should be set to zero, and Equation (9.1) used to compute the equivalent flaw length. If stress gradients occur in one or more directions, the sum of membrane and bending components should be summed for the purpose


Not for Resale

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flaw dimension with a Mode I orientation may be inferred by one of the following options.


of computing to:

I 1 and I 2 . For uniaxial loading, B = 0 and Equation (9.1) reduces

sin = cos = c = cos2 = + 2 co e)

The basis of the above equations is given in Appendix F of Reference [9.9.3]. The relationship between c co and the biaxiality stress ratio is shown in Figure 9.3.

Characterization Of Flaw Depth – The part through-wall depth of a flaw can be considerably more difficult to estimate than the length. Either a default value or a value based on detailed measurements may be used for the flaw depth in the assessment. a.

Flaw Depth by Default Values 1.

Through-Wall Flaw – If no information is available about the depth of a flaw, a conservative assumption is that the flaw penetrates the wall (e.g., a = t for a surface flaw). In pressurized components, an actual through-wall flaw would most likely lead to leakage, and thus would not be acceptable in the long term. However, if it can be shown that a through-wall flaw of a given length would not lead to brittle fracture or plastic collapse, then the component should be acceptable for continued service with a partthrough-wall flaw of that same length. Additional special considerations may be necessary for pressurized components containing a fluid where a leak can result in autorefrigeration of the material near the crack tip or other dynamic effects.

2.

Surface Flaw – Flaw depths less than the full wall may be assumed if justified by service experience with the type of cracking observed. However, the assumed flaw depth should not be less than the following where length of the flaw is 2c (see Figure 9.1(b)).

a = max t , c b.

(9.5)

Flaw Depth from Actual Measurements 1.

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The definition of the appropriate depth dimensions ( a for a surface flaw, and 2a and d for an embedded flaw) when relatively accurate measurements are available is illustrated in Figures 9.1 and 9.4. If the flaw is normal to the surface, the depth dimension, a , is taken as the measured dimension, ao . However, if the flaw is not normal to the surface (e.g. a lack of fusion flaw that is parallel to the bevel angle or a lamination, see Figure 9.4), the following procedure may be used to compute the depth dimension, a . a)

Step 1 – Project the flaw onto a plane that is normal to the plate surface.

b)

Step 2 – Measure the angle to the flaw, G , as defined in Figure 9.4, and determine W using the following equation or Figure 9.5.

W = max[WTheta , 1.0] where


Not for Resale

(9.6)

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9.3.6.3

(9.4)


c h

c h

WTheta = 0.99999 + 10481 . 10 -5 G + 15471 . 10 -4 G 2 +

c h 4.5751c10 hG

c h + 18220 . c10 hG

c h

3.4141 10-5 G 3 -2.0688 10 -6 G 4 + 4.4977 10 -8 G 5 -10

c)

6

-12

(9.7)

7

ao by W to obtain the dimension a , which is used in calculations. Note that the dimension d for buried flaws may decrease when the Step 3 – Multiply

flaw depth is determined using this approach. 2.

9.3.6.4

If the remaining ligament is small, it may be necessary to recategorize the flaw depending on the remaining ligament size. An embedded flaw may be recategorized as a surface flaw and a surface flaw may be recategorized as a through-wall flaw. Rules for flaw recategorization are provided in paragraph 9.3.6.6.

Characterization Of Branched Cracks – Determination of an idealized flaw is complicated when a branched network of cracks forms in a component because the idealized flaw must be equivalent to the network of cracks from a fracture mechanics approach. The recommended methodology for assessing a network of branched cracks is shown in Figure 9.6. As shown in this figure, the network is idealized as a single planar predominant flaw by means of the following procedure:

2co ,

a.

Step 1 – Draw a rectangle around the affected region. Define the measured flaw length, as the length of the rectangle (see Figures 9.6(a) and 9.6(b)).

b.

Step 2 – Rotate the idealized flaw so that it is perpendicular to the maximum principle stress, I 1 . Define an effective length according to the procedure in paragraph 9.3.6.2. (see Figure 9.6(c)). Alternatively, for a conservative estimate of the flaw size, set c = co .

c.

a.

If two or more flaws are close to one another, they can be combined into a single equivalent flaw for the purpose of analysis. If the separation distance is sufficient to avoid interaction, the flaws can be analyzed independently. In the latter instance, only the worst-case flaw needs to be considered.

b.

The procedure for assessing multiple flaws in a local region is illustrated in Figures 9.7 and 9.8 and outlined below: 1.

Step 1 – Rotate each flaw so that it coincides with a principal plane, and determine the effective flaw length according to the procedure in paragraph 9.3.6.2. All flaws in the local region should now be parallel, as illustrated in Figure 9.7(b).

2.

Step 2 – Apply the criteria in Figure 9.8 to check for interaction between parallel flaws. Project all interacting flaws onto a single plane, as illustrated in Figure 9.7(c). Note that some flaws will be combined using this procedure.

3.

Step 3 – Estimate the depth of the flaws with the procedure outlined in paragraph 9.3.6.3. If two or more flaws were combined as a result of step 2 above, define the


Not for Resale

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Characterization Of Multiple Flaws – This section applies to multiple discrete flaws that are in close proximity to one another. A branched network of cracks is treated as a single flaw, as discussed in 9.3.6.4.

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9.3.6.5

Step 3 – Measure the maximum through-wall depth of the branched network, a0 , (see Figure 9.6(d)). If an actual depth measurement is made, then the flaw depth to be used in the assessment is shown in Figure 9.6(d). Alternatively, the default value defined in paragraph 9.3.6.3.a can be used if accurate measurements are not possible.


4.

c. 9.3.6.6

Step 4 – Apply the criteria in Figure 9.8 to check for interaction between flaws on a given plane. If interaction exists, the dimensions of the combined flaw are inferred from a rectangle inscribed around the interacting flaws.

Multiple flaws do not have to be combined into an equivalent flaw for evaluation if a stress intensity factor and limit load solution can be obtained for the interacting flaw geometries.

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Recategorization Of Flaws – Flaw recategorization is required for two reasons. (1) For an embedded flaw close to the surface or for a deep surface flaw where the remaining ligament is small, the results obtained in the assessment may be overly conservative because the reference stress (see Appendix D) in the remaining ligament may over estimate the plasticity effects on the crack driving force resulting in the assessment point falling outside of the failure assessment diagram. Recategorization of an embedded flaw to a surface flaw, or a surface flaw to a through-wall flaw, may result in the associated assessment point being inside of the failure assessment diagram. (2) Most of the stress intensity solutions in Appendix C are not accurate for very deep cracks due to high strain/plasticity effects. For example, the commonly published KI solutions for a semi-elliptical surface flaw are only accurate for a t £ 0.8 . Therefore, recategorization to a through-thickness flaw is required to achieve an accurate solution. a.

Flaw Recategorization Guidelines 1.

The initial and recategorized crack-like flaws for flaws that experience ligament yielding are shown in Figure 9.9. An embedded or buried flaw can be recategorized as a surface flaw, while a surface flaw can be recategorized as a through-wall flaw. The assumed flaw dimensions are modified as follows. a)

b)

An embedded flaw should be recategorized to a surface flaw when d t < 0.2 (see Figure 9.9(a)). The length and depth of the surface flaw are given by:

2cs = 2cb + 2d

(9.8)

a s = 2 ab + d

(9.9)

A surface flaw should be recategorized as a through-thickness flaw when a t > 0.8 (see Figure 9.9(b)). The length of the through-wall flaw is given by:

b

2ct = 2cs + 2 t - a s

g

(9.10)

2.

Note that the crack length is increased in each case by twice the ligament dimension. When the plastic strain on the remaining ligament is large, the flaw could grow to the free surface by ductile tearing, in which case the flaw might also extend in the length direction.

3.

After recategorization, the load ratio, Lr , is determined with the new flaw dimensions. For example, if a deep surface flaw in the axial orientation is found in a component and a local analysis indicates that the computed load ratio is greater than the maximum allowable value (i.e. Lr > Lr (max) ) the flaw can be recategorized as through-wall, and reanalyzed. Definitions for the computed load ratio and maximum allowable load ratio are provided in Figure 9.20 and Appendix D.


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depth, a , as the width of a rectangle inscribed around the combined flaw, as illustrated in Figure 9.7(d).

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b.

It is important to emphasize that the recategorized flaw dimensions should be used in the assessment. Another important point is that leak-before-break conditions are not necessarily guaranteed when an assumed through-wall flaw is shown to be acceptable. Additional requirements must be met before leak-before break can be ensured, as discussed in paragraph 9.5.2.

9.3.7

Recommendation For Inspection Technique And Sizing Requirements

9.3.7.1

Reliable sizing of the flaws by nondestructive examination (NDE) is important. Therefore the choice of the NDE method should be based on the ability to detect and size the depth and length of the flaw.

9.3.7.2

As previously discussed in paragraph 9.3.6, the crack dimensions required as input for an FFS analysis are the crack depth, crack length, crack angle with the plate surface, crack location from the surface, and the spacing between the cracks if the component has multiple cracks. a.

Surface Cracks – The crack length, angle relative to the principal stress direction (see Figure 9.2) and distance to other surface cracks may be determined using Magnetic Particle (MT) or Dye Penetrant (PT) examination technique. The depth of and angle of the flaw relative to the surface (see Figure 9.4) is typically determined using Ultrasonic (UT) examination techniques.

b.

Embedded Cracks – The crack depth, length, angle, and distance to other surface breaking or embedded cracks is typically determined using angle beam Ultrasonic (UT) examination technique (e.g., time-of-flight-diffraction (TOFD) or pulse echo techniques). The calibration settings may need to be more sensitive than are used for new construction weld quality inspections.

9.3.7.3

Accurate sizing of crack-like flaws depends both on the available technology and the skill of the inspector. Parameters to be considered in the uncertainties of flaw sizing include the crack length, depth, orientation of the flaw, whether or not the flaw is surface breaking, and the number of flaws (i.e. single flaw or multiple flaws). PT or MT should be used to enhance surface breaking flaws prior to determining the crack length. A visual examination should not be used to determine the length of the flaw because the ends of the crack may be closed.

9.3.7.4

Determination of the depth, orientation and position (i.e. the location below the surface for an embedded crack) of a crack-like flaw is usually done by using ultrasonic examination techniques. Radiographic examination techniques may also be used; however, accurate flaw depth and orientation information can be obtained only by moving the component containing the flaw, or moving the source around the component to obtain multiple views. This type of manipulation is typically not possible for many pressure containing components. A level of qualitative depth and orientation information can sometimes be obtained with electrical resistance (potential drop), magnetic leakage field, and eddy current techniques. The accuracy of the electrical resistance techniques is seriously affected by conditions in the crack (i.e. touching surface and impurities such as oxides). Therefore, ultrasonics is the recommended sizing technique for depth and inclination of crack-like flaws.

9.3.7.5

If part of a component is inaccessible for inspection due to the component configuration, materials used, or obstruction by other flaws, and a flaw is suspected in this region because of the surrounding conditions, the possibility of the existence of a flaw the size of the region which cannot be inspected should be considered in the assessment.

9.4


9.4.1

Overview

9.4.1.1

The Fitness-For-Service assessment procedure used to evaluate crack-like flaws is shown in Figure 9.10. The three assessment levels used to evaluate crack-like flaws are based on the data and


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details required for the analysis, the degree of complexity required for a given situation, and the perceived risk (see API 581). Level 1 Assessments are limited to crack-like flaws in pressurized cylinders, spheres or flat plates away from all structural discontinuities. Level 2 Assessments can be used for general shell structures including crack-like flaws located at structural discontinuities. A flow diagram for the Level 2 Assessment is provided in Figure 9.11. In Level 2 assessments, detailed information on material properties and loading conditions are required, and a stress analysis is typically performed to determine the state of stress at the location of the flaw. The stress analysis at this level may be based on code equations, closed form solutions, or a numerical analysis. A Level 3 Assessment can be used to evaluate those cases that do not meet the requirements of a Level 1 or Level 2 assessment. Level 3 assessments are also required for flaws which may grow in service because of loading or environmental conditions. 9.4.1.2

It should be noted that the assessment levels designated in this document are different from the levels of analysis specified in BS PD6493, BS 7910, and Nuclear Electric R-6 because of the definitions in Section 2.

9.4.2

Level 1 Assessment

9.4.2.1

The Level 1 assessment is applicable to components which satisfy the limitations in paragraph 9.2.2.1.

9.4.2.2

The following procedure can be used to determine the acceptability of a crack-like flaw using a Level 1 Assessment. a.

Step 1 – Determine the load cases and temperatures to be used in the assessment based on operating and design conditions (see paragraph 9.3.4). The CET, see Section 3, should be considered in establishing the temperature for the assessment.

b.

Step 2 – Determine the length and depth of the crack-like flaw from inspection data. The flaw should be characterized using the procedure in paragraph 9.3.6.

c.

Step 3 – Determine the Figure from the list below to be used in the assessment based on the component geometry and crack-like flaw orientation with respect to the weld joint.

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e.

·

Flat Plate, Crack-Like Flaw Parallel To Joint (Figure 9.12)

·

Cylinder, Longitudinal Joint, Crack-Like Flaw Parallel To Joint (Figure 9.13)

·

Cylinder, Longitudinal Joint, Crack-Like Perpendicular To Joint (Figure 9.14)

·

Cylinder, Circumferential Joint, Crack-Like Flaw Parallel To Joint (Figure 9.15)

·

Cylinder, Circumferential Joint, Crack-Like Flaw Perpendicular To Joint (Figure 9.16)

·

Sphere, Circumferential Joint, Crack-Like Flaw Parallel To Joint (Figure 9.17)

·

Sphere, Circumferential Joint, Crack-Like Flaw Perpendicular To Joint (Figure 9.18)

Step 4 – Determine the screening curve from the Figure selected in Step 3. The following should be noted when selecting a screening curve. ·

For each Figure in Step 3, two sets of screening curves, 1/4-t and 1-t crack depths, are provided for three conditions; base metal, weldment that has been subject to PWHT, and weld metal that has not been subject to PWHT.

·

If the depth of the flaw can accurately be determined using qualified NDE procedures, then the 1/4-t flaw curve can be used in the assessment; otherwise, the 1-t flaw curve should be used.

·

t £ 25.4 mm (1 inch) where t is the wall thickness of the component containing the flaw, then the ¼-t flaw curves are directly applicable and the limiting crack depth is 0.25t . If t > 25.4 mm (1 inch) , then the 1/4-t flaw curves are applicable when the absolute If


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Jan, 2000

RECOMMENDED

PRACTICE

9-13


crack depth is less than or equal to 6.3 mm (0.25 inch) . The through-wall flaw or l-t curves can be used for all wall thickness up to the screening curve limitation of

38 mm (1.5 inch). .

e.

If the location of the flaw is at or within a distance of two times the nominal plate thickness measured from the centerline of the weld, then the curves for weldments should be utilized; otherwise the curve for base metal may be used. Note that for flaws located at a weldment, the applicable assessment curve is based on heat treatment of the component. If there is question regarding the type and/or quality of PWHT, Curve C should be used. Step 5 - Determine the reference temperature. The assessment curves are based on a reference temperature, & assessment. I&

= -9.4” C

=

38°C (100”F),

and this value may be used in the

(15°F) may be used for steel plates and forgings that have been

given a normalizing heat treatment. Alternatively, a value of the reference temperature can be established using Section 3, Table 3.3 and Figure 3.3. The thickness of the plate containing the flaw and the material specification must be known to utilize Figure 3.3 (if the material specification is not known, Curve A of this figure should be used). For example, for a 25.4 mm (1 inch) thick plate made from A285 Grade B material (a Curve B based on the information in Table 3.3) Z& = f.

-1°C (30” F) .

Step 6 - Determine the maximum permissible crack-like flaw length. Enter the assessment Figure established in Step 3 with the assessment temperature and reference temperature determined in Steps 1 and 5, respectively, to determine the maximum length of the flaw using the applicable screening curve. Step 7 - Evaluate Results - if the permissible flaw size determined in Step 6 is greater than or equal to the length of the crack-like flaw determined in Step 2, then the component is acceptable for future operation.

If the component does not meet the Level 1 Assessment requirements, then the following, or combinations thereof, can be considered: The data used in the analysis can be refined and the Level 1 assessment can be repeated (i.e. refinement of data entails performing additional NDE to better characterize the flaw dimensions, and determining the future operating conditions accurately to establish the operating temperature envelope).

b.

Repair, replace, or retire the component.

C.


9.4.3

Level 2 Assessment

9.4.3.1

The Level 2 assessment is applicable to components and loading conditions which satisfy the conditions given in paragraph 9.2.2.1. The assessment procedure in Level 2 provides a better estimate of the structural integrity of a component than a Level 1 Assessment with a crack-like flaw. A flow diagram for a Level 2 assessment is shown in Figure 9.11.

9.4.3.2

The following procedure can be used to determine the acceptability of a crack-like flaw using a Level 2 Assessment. In this procedure, Partial Safety Factors (see Section 2) are applied to the independent variables (i.e. flaw size, material fracture toughness, and stress) to account for uncertainty. An alternative procedure which does not require the use of Partial Safety Factors is provided in paragraph 9.4.3.3. a.

Step 1 - Evaluate operating conditions and determine the pressure, temperature and supplemental loading combinations to be evaluated (see paragraph 9.3.4.1).



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a.

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9.4.2.3


9-14

b.

Jan, 2000

Step 2 - Determine the stress distributions (see paragraph 9.3.4.2) at the location of the flaw based on the applied loads in Step 1 and classify the resulting stresses into the following stress categories (see paragraph 9.3.4.3): 0

Primary stress

l

Maximum primary stress

l

Secondary stress

l

Residual stress

C.

Step 3 - Determine the material properties; yield stress, tensile strength and fracture toughness (K,,, ) for the conditions being evaluated from Step 1 (see paragraph 9.3.5). The yield and tensile strength should be established using nominal values (i.e. minimum specified per the material specification if actual values are unknown), and the toughness should be based on the mean value (see Table 9.2, note 6).

d.

Step 4 - Determine the crack-like flaw dimensions from inspection data. The flaw should be categorized using the procedure in paragraph 9.3.6.

e.

Step 5 - Modify the primary stress, material fracture toughness, and flaw size using the Partial Safety Factors ( PSF). 1.

Primary Membraneand Bending Stress - Modify the primary membrane and bending stress components determined in Step 2 ( P, and P6, respectively) using the PSF for stress (see Table 9.2).

P, = P, . PSFs pb =pb.PSFs 2.

(9.12)

Material Toughness - Modify the mean value of the material fracture toughness determined in Step 3 (KM,) using the PSFfor fracture toughness (see Table 9.2).

KmatE-!&L

PSF,

3.

Flaw Size - Modify the flaw depth determined in Step 4 using the PSI; for flaw size (see Table 9.2). If the factored flaw depth exceeds the wall thickness of the component, then the flaw should be recategorized as a through-wall flaw.

a =a.PSF,

(fir a surface flaw)

(9.14)

2a = 2a. PSF,

(for an embedded flaw)

(9.15)

2c = 2~. PSI;,

(for a through - wall jlaw)

(9.16)

Note: if a given input value is known to be a conservative estimate (e.g. lower-bound toughness or upper-bound flaw size), a PSF of 1.O may be applied to this value. f.

Step 6 - Compute the reference stress for primary stresses, aLf , based on the factored primary stress distribution and factored flaw size from Step 5 and the reference stress solutions in Appendix D.

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March 2000


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g.

Step 7 – Compute the Load Ratio or the abscissa of the FAD using the reference stress for primary loads from Step 6 and the yield stress from Step 3. P r

L = h.

P I ref

(9.17)

I ys P

Step 8 – Compute the stress intensity attributed to the primary loads, K1 , using the factored primary stress distribution and factored flaw size from Step 5, and the stress intensity factor

K1P < 0.0 , then set K1P = 0.0 .

solutions in Appendix C. If i.

Step 9 – Compute the reference stress for secondary and residual stresses,

SR I ref , based on

the secondary and residual stress distributions from Step 2, the factored flaw size from Step 5, and the reference stress solutions in Appendix D. j.

Step 10 – Compute the secondary and residual stress reduction factor,

Ssrf , using the

Ssrf

LR| . - I = min MS14 MN|T I

P ref f

U|V, 10. OP |W PQ

SR I ref > I ys

SR I ref £ I ys

Ssrf = 10 .

(9.18)

--``````-`-`,,`,,`,`,,`---

following equation:

(9.19)

where: P I ref

=

Reference stress associated with the primary stress or maximum primary stress, as applicable (see the Note below) (MPa:psi), and

If

=

Reference stress associated with the secondary and residual stress from

=

Step 9 (MPa:psi), and Flow stress (see Appendix F), (MPa:psi).

Note: that when computing ·

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I

SR ref

Ssrf , the following two conditions must be considered.

If the crack is present before the application of the load associated with the maximum primary stress, then

P I ref to be used in Equation (9.18) can be based on the maximum

primary stress from Step 2 and the reference stress solutions in Appendix D. ·

If the crack occurs after application of the load associated with the maximum primary stress, then

P I ref to be used in Equation (9.18) can be based on the factored primary

stress distribution and flaw size from Step 5 and the reference stress solutions in Appendix D, or the maximum primary stress from Step 2 and the reference stress solutions in Appendix D using zero flaw dimensions, whichever results in the largest secondary and residual stress reduction factor. k.

SR

Step 11 – Compute the stress intensity attributed to the secondary and residual stresses, K1 , using the secondary and residual stress distributions from Step 2, the factored flaw size from Step 5, the secondary and residual stress reduction factor from Step 10, and the stress intensity factor solutions in Appendix C. If


K1SR < 0.0 , then set K1SR = 0.0 . The value of K1SR

Not for Resale


should be determined at the same location along the crack front as that used to P

determine K1 . l.

Step 12 – Compute the plasticity interaction factor, 1.

. , using the following procedure:

K1SR = 0.0 , then set F = 10 . and proceed to Step 13. Otherwise,

Step 12.1 – If

I ys from Step 3. SR r

L = 2.

SR I ref

I ys

Ssrf

(9.20)

O and B using Tables 9.3 to 9.6 and compute . . 0 using the following equation. Alternatively, . . 0 can be determined from Figure 9.19.

Step 12.2 – Determine

F O = 1+ B F0 3.

(9.21)

Step 12.3 – Compute the plasticity interaction factor

. . If 0 < LSR r £ 4.0 , then set

F 0 = 1.0 and

F = 1+

O B

(9.22)

Otherwise, compute the stress intensity factor for secondary and residual stresses corrected for plasticity effects,

K1SRp and compute .0 and . using the following

equations

F0 =

K IpSR

(9.23)

K ISR

FG H

F = F0 1 +

O B

IJ K

(9.24)

The most accurate method to compute

K1SRp is to perform an elastic-plastic finite

element analysis of the cracked component with boundary conditions that model the residual stress and secondary loads, all of the primary loads should be set to zero. Guidelines for performing this analysis are provided in Appendix B. Based on the results from the elastic-plastic analysis, evaluate the J integral and compute

K1SRp from the

following equation (see Appendix F, paragraph F.4.2.1.a)

K


SR Ip

J SR E = 1- v2

(9.25)

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SR LSR r using the following equation with I ref from Step 9, S srf from Step 10, and

compute


The following simplified method may be used to compute may produce overly conservative results.

F0

F a IJ =G HaK

aeff

F 1 IJ FG K IJ = a+G H 2FJ K H I K

. 0 ; however, this method

0.5

eff

(9.26)

with, 2

(9.27)

ys

where:

a aeff

= =

Depth of the crack-like flaw from Step 5 (mm:in), Effective depth of the crack-like flaw (mm:in),

K1SR J I ys

= = =

K1SR based on crack depth a from Step 11 (MPaÖm: ksiÖin) Factor equal to 1.0 for plane stress and 3.0 for plane strain, and Yield stress at the assessment temperature (see Appendix F), (MPa:psi).

As an alternative, the methods in Reference [9.9.32], which are less complicated than equation(9.23) and more accurate than equation (9.26) may be used to estimate m.

Step 13 – Determine toughness ratio or ordinate of the FAD assessment point where

K1SRp . K1P is

SR

the applied stress intensity due to the primary stress distribution from Step 8, K1 is the applied stress intensity due to the secondary and residual stress distributions from Step 11, Kmat is the factored material toughness from Step 5, and . is the plasticity correction factor from Step 12.

Kr = n.

K1P + FK1SR Kmat

(9.28)

Step 14 – Evaluate results; the FAD assessment point for the current flaw size and operating conditions (stress levels) is defined as

cK , L h . r

P r

LrP -axis of the FAD (see Figure 9.20).

1.

Step 14.1 – Determine the cut-off for the

2.

Step 14.2 – Plot the point on the FAD shown in Figure 9.20. If the point is on or inside the FAD (on or below and to the left), then the component is acceptable per the Level 2 Assessment procedure. If the point is outside of the FAD (above and to the right), then the component is unacceptable per the Level 2 Assessment procedure. Note that the P

SR

value of K1 and K1 will vary along the crack front; therefore, the assessment may have to be repeated at a number of points along the crack front to ensure that the critical location is found. 9.4.3.3

The following alternative Level 2 procedure can be used to determine the acceptability of a crack-like flaw. In this procedure, conservative assumptions are made in determining the material fracture

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SR 1


a.

Step 1 – The same as given in paragraph 9.4.3.2.a.

b.

Step 2 – The same as given in paragraph 9.4.3.2.b. except that the maximum value obtained from each stress distribution is assumed as a membrane stress in the assessment.

c.

Step 3 – The same as given in paragraph 9.4.3.2.c except a lower bound value is used for the material fracture toughness.

d.

Step 4 – The same as given in paragraph 9.4.3.2.d. except an upper bound value is used for the flaw size.

e.

Step 5 – Partial Safety Factors are not used. The primary stress is taken directly from Step 2, the material fracture toughness from Step 3, and the flaw size from Step 4.

f.

Step 6 – The same as given in paragraph 9.4.3.2.f.

g.

Step 7 – The same as given in paragraph 9.4.3.2.g.

h.

Step 8 – The same as given in paragraph 9.4.3.2.h.

i.

Step 9 – The same as given in paragraph 9.4.3.2.i.

j.

Step 10 – The same as given in paragraph 9.4.3.2.j.

k.

Step 11 – The same as given in paragraph 9.4.3.2.k.

l.

Step 12 – The same as given in paragraph 9.4.3.2.l.

m.

Step 13 – The same as given in paragraph 9.4.3.2.m.

n.

Step 14 – Evaluate results; the FAD assessment point for the current flaw size and operating conditions (stress levels) is defined as

c K , L h . If K £ 0.7 and L r

P r

r

P r

--``````-`-`,,`,,`,`,,`---

toughness and applied stress, and a lower-bound failure assessment diagram is utilized to compensate for uncertainty in the assessment procedure.

£ 0.8 (see Figure

9.20), then the component is acceptable per the Level 2 Assessment procedure. If this criteria is not satisfied, then the flaw is unacceptable; refer to paragraph 9.4.3.6 for recommendations. A limiting flaw size can be established using the following procedure. Determination of the limiting flaw size may be useful in selecting an appropriate NDE technique for retrospective inspection. a.

Increase the crack-like flaw dimensions by a small increment; for a surface flaw compute a = a0 + Da and c = c0 + Dc where ao and co are the initial flaw sizes found at the time of the inspection. The flaw increments should be proportioned based on the flaw aspect ratio or ratio of the stress intensity factor values at the surface and deepest part of the crack.

b.

For the new flaw size, complete the steps outlined in paragraph 9.4.3.2 or 9.4.3.3 and determine if the new flaw size is inside of the FAD curve. Partial Safety Factors should be used for stress and toughness, but not for flaw size in this calculation.

c.

Continue to increment the crack size until the calculated assessment point is on the FAD curve. The resulting crack size is defined as the limiting flaw size. If partial safety factors for flaw size are used in the assessment, then this limiting flaw size should be divided by the partial safety factor in a manor consistent with paragraph 9.4.3.2.e.


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9.4.3.4

In certain cases, an acceptable flaw size may be predicted using the Level 2 Assessment procedure although smaller flaw sizes may be unacceptable. This condition is a result of the assumptions used for input data and the mathematical form of the equations used in the analytical procedure, and is referred to as a “non-unique solution” (see Reference [9.9.26]). Non-unique solutions can also effect the limiting values of other input parameters such as stress results. Non-unique solutions are most likely to occur where stress distributions decrease through the section (e.g. stress gradients associated with a bending stress or stress concentration at the toe of a fillet weld), or where increasing the primary stresses results in increased relaxation of the secondary stress. A sensitivity analysis (see Section 2, paragraph 2.4.3.1) should be performed for these cases to determine acceptability based on a specific situation. In some cases, a more detailed analysis (i.e. Level 3) may need to be performed based on the results of the sensitivity analysis.

9.4.3.6


The data used in the analysis can be refined and the Level 2 assessment can be repeated. Refinement of data entails performing additional NDE to better characterize the flaw dimensions, reviewing equipment documentation to justify the use of other than lower bound material properties, and determining the future operating conditions and associated stress levels more accurately. If the assessment point lies within the Level 2 FAD after data refinement, the component is acceptable for continued operation.

b.

Rerate, repair, replace, or retire the component, and/or

c.

A Level 3 Assessment can be performed.

9.4.4

Level 3 Assessment

9.4.4.1

The assessment procedure in Level 3 provides the best estimate of the structural integrity of a component with a crack-like flaw. In addition, this assessment level is required if subcritical crackgrowth is possible during future operation. Five methods are permitted in a Level 3 Assessment. a.

Method A Assessment – The basis of this method is the Level 2 assessment procedure except that the FAD in Figure 9.20 is utilized for the acceptance criteria with user specified Partial Safety Factors based on a risk assessment. Alternatively, a probabilistic analysis can be performed.

b.

Method B Assessment – The basis of this method is the Level 2 assessment procedure except that the FAD is constructed based on the actual material properties. This method is only suitable for base and weld material because it requires a specific material dependent stressstrain curve; the method should not be used for assessment of crack-like flaws in the HAZ. The procedure for the assessment is as follows: 1.

Step 1 – Obtain engineering stress-strain data for the material containing the crack-like flaw at the assessment temperature. If a stress-strain curve for the actual material containing the flaw cannot be obtained, a stress-strain curve for a material with the same specification and similar stress-strain response can be used. The 0.2% offset yield strength, tensile strength, and modulus of elasticity should be determined together with sufficient data points to accurately define the stress-strain curve. It is recommended that the engineering stress-strain curve be accurately defined at the following ratios of . , 102 . , 11 . , 12 . and intervals of applied stress to yield stress: I I ys = 0.7, 0.8, 0.98, 10

01 . up to I uts . 2.


Step 2 – Convert the engineering stress-strain curve obtained in Step 1 to a true stressstrain curve. The true stress and strain can be computed from the engineering strain as shown in Appendix F, paragraph F.2.3.1.

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9.4.3.5

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3.

Step 3 – Determine the material-specific FAD using the following equation:

F EA c L h I K (L ) = G GH L I + 2 EA r

ref

P r

P r

ys

P 3 r

ref

ys

I JJ K

Kr ( LrP ) = 10 .

-1/ 2

for 0.0 < LrP £ LrP(max) for LrP = 0.0

(9.29)

(9.30)

where:

E LrP

=

Young’s Modulus (MPa:psi),

=

Load ratio which varies from

LrP(max) A ref

=

Maximum value of the load ratio (see Figure 9.20),

=

Reference strain obtained from the true stress-strain curve at a true stress equal to

I ys

=

0.0 to LrP(max) ,

LrPI ys , and

Yield stress (true stress value from Step 2) at the assessment temperature (see Appendix F), (MPa:psi).

4. --``````-`-`,,`,,`,`,,`---

Step 4 – Complete the assessment using the Level 2 assessment procedure except the material-specific FAD is utilized in Step 14 (see paragraph 9.4.3.2.n). Partial Safety Factors should be used in the assessment. Alternatively, a probabilistic analysis can be performed.

c.

Method C Assessment – The basis of this method is the Level 2 assessment procedure except that the FAD is constructed based on the actual loading conditions, component geometry and material properties. A procedure to construct the geometry and material dependent FAD, and to complete the assessment for a known crack-like flaw are covered in Appendix B, paragraph B.6.4.3. Partial Safety Factors should be used in the assessment. Alternatively, a probabilistic analysis can be performed.

d.

Method D Assessment – This method is a ductile tearing analysis where the fracture tearing resistance is defined as a function of the amount of stable ductile tearing. This method should only be used for materials that exhibit stable ductile tearing (e.g. ferritic steels on the upper shelf and austenitic stainless steels). Partial Safety Factors should be used in the assessment. Alternatively, a probabilistic analysis can be performed. The procedure for the assessment is as follows: 1.

Step 1 – Obtain a JR-curve for the material containing the crack-like flaw at the assessment temperature (see Appendix F). If a JR-curve for the actual material containing the flaw cannot be obtained, a JR-curve for a material with the same specification and similar ductile tearing response can be used.

2.

Step 2 – Determine a FAD to be used in the assessment from Methods A, B, or C as defined above.

3.

Step 3 – Follow Steps 1 through 13 of the Level 2 assessment procedure to generate a series of assessment points. For each assessment point, the crack depth, a , is determined by adding a crack depth increment, Da j , to the measured or initial crack

ai (i.e. the first point is a = ai + Da1 , the second point is a = ai + Da1 + Da2 , the third point is a = ai + Da1 + Da2 + Da3 , etc.). The magnitude of the crack depth increment, Da j , used to generate the series of assessment points can be inferred from depth,


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


the JR-curve. For surface and embedded flaws, the magnitude of crack depth increment should also be applied to the flaw length. The material fracture toughness used for each assessment point is determined from the JR-curve ( J can be converted to K using the procedures in Appendix F) at the crack depth associated with ductile tearing, a JR (i.e. the first point is a JR = Da1 , the second point is a JR = Da1 + Da2 , the third point is a JR = Da1 + Da2 + Da3 , etc.). Note that for a rising JR Curve, the fracture toughness will increase with the crack depth.

Method E Assessment – The recognized assessment procedures listed below are subject to supplemental requirements which may include the use of Partial Safety Factors or a probabilistic analysis. ·

BS PD6493 or BS 7910 (see Section 1, Table 1.1)

·

Nuclear Electric R-6 (see Section 1, Table 1.1)

·

SAQ/FoU Report 96/08 (see Section 1, Table 1.1)

·

WES 2805 – 1997 (see Section 1, Table 1.1)

·

DPFAD Methodology (see References [9.9.5] and [9.9.6])

·

EPFM using the J-integral (see References [9.9.10] and [9.9.11])

·

The J-integral-Tearing Modulus method (see References [9.9.18] and [9.9.33])

9.4.4.2

It is the responsibility of the Engineer to meet all limitations and requirements imposed by the selected method. In addition, the Engineer must ensure that the method used including all assumptions, analysis parameters, results and conclusions are clearly documented.

9.4.4.3

A sensitivity analysis (see Section 2, paragraph 2.4.3.1) should be performed as part of the assessment regardless of the method chosen.

9.5


9.5.1

Subcritical Crack Growth

9.5.1.1

Overview – There is special emphasis in the assessment procedures in this section for evaluating subcritical crack-growth in pressure containing components. In the refining and petrochemical industry there is a wide variety of process environments and material degradation mechanisms which increase the occurrence of environmentally and service induced cracking (see Appendix G). a.

For purposes of this document, in-service crack growth may be categorized into four main types; crack growth by fatigue, crack growth by stress corrosion cracking, crack growth by hydrogen assisted cracking, and crack growth by corrosion fatigue. Details regarding these crack growth mechanisms are covered in Appendix F, paragraph F.5.

b.

The methodology for crack growth evaluation used in this document is based on fracture mechanics. In this methodology, the growth of a pre-existing crack is controlled by a crack tip


Not for Resale

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e.

--``````-`-`,,`,,`,`,,`---

Step 4 – Plot the series of assessment points on the FAD. The three possible outcomes of a tearing analysis are shown on Figure 9.21(b). If all of the assessment points fall inside of the FAD, then unstable crack growth will not occur. If the first few assessment points fall outside of the FAD and subsequent points fall within the FAD, then a finite amount of crack growth or stable ductile tearing will occur. Ductile instability is predicted when all of the assessment points fall outside of the FAD. If the load is fixed, the locus of the assessment typically exhibits a “fish hook” shape where Kr reaches a minimum and then increases. The point of instability occurs when the locus of the assessment points is tangent to the FAD.

4.


stress intensity factor. In addition, it is assumed that the growth of a crack is controlled by a crack growth law for each combination of material, environment, and crack tip stress intensity factor which can be measured or determined independently and applied to a component with a crack-like flaw. An important requirement for this methodology is that the material properties such as yield and flow stress, material toughness, and crack growth law including appropriate coefficients should be determined as closely as possible from conditions which represent the combination of material, equipment age, environment and loading conditions (applied stress intensity level) for the component being evaluated.

9.5.1.2

c.

A major difficulty that must be addressed with environmental cracking data is that crack growth rates can be highly sensitive to changes in the process environment. While the environment is usually carefully controlled in an experiment, the composition and temperature of an actual process is subject to fluctuations, and the applicability of laboratory data is inappropriate in many cases. Another problem with predicting crack growth rates in structures is that the cracking often occurs as the result of an upset in operating conditions. For example, cracking that is detected after several years of service may have occurred over the space of several hours or days when atypical operating conditions were present; no cracking occurred before or after this upset. An average crack growth rate, obtained by dividing the crack size by the total time in service, would be meaningless in such instances.

d.

For cases involving fatigue, or environmentally assisted cracking, new cracks can initiate at other locations in the structure remote from the known cracks being analyzed. This occurs because corrosion, erosion, local cyclic or static stresses or local concentration of the environment are such that threshold values for crack extension are exceeded. Hence, when assessing the significance of known or postulated cracks for in-service crack extension and structural failure, the implications of exceeding such threshold values elsewhere in the structure must be considered.

e.

Closed form estimates for the time to reach a limiting flaw size are complicated by random loading, fatigue threshold and retardation effects, and the complexity of the stress intensity solution. Therefore, crack growth is typically done using a numerical algorithm which explicitly increments the crack growth for some repeated block of representative service loading. For complicated loading histories, load blocks may be developed for a representative time period using the "rainflow” cycle-counting method (see Appendix B).

f.

In addition to the complexities described above, sources of error in computing the time to reach a limiting flaw size include uncertainty in sizing the initial defect, variability in material behavior, and oversimplification of the load spectrum. Despite the difficulties of performing crack-growth calculations, estimates of crack-growth time to failure may be useful for establishing inspection intervals and prioritizing repairs.

g.

All cases in which subcritical crack growth is included in the assessment should be referred to and analyzed by an engineer sufficiently knowledgeable about the interactions between cracks, environment, component (structural) design, and loading history (including cyclic loads) using Level 3 procedures of this document.

h.

In cases where subcritical crack growth data is minimal or nonexistent, periodic monitoring of crack growth using appropriate NDE methods is recommended. The incremental growth data resulting from the periodic monitoring can be used as input data to an assessment.

Evaluation And Analysis Procedures For Components With Growing Cracks – Analysis of equipment containing growing cracks requires specialized skills, expertise, and experience because of the inherent uncertainties with the methodology. The analysis involves the use of a Level 3 assessment per paragraph 9.4.4 and the numerical integration of a crack growth law. The overall evaluation methodology for growing cracks is shown in Figure 9.22. Guidance for conducting a crack growth analysis is shown in Figure 9.23. Highlights of the evaluation include the following.

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Step 1 – Perform a Level 3 assessment for the initial crack size. If the component is demonstrated to be acceptable per a Level 3 assessment, then an attempt to apply remedial measures to prevent further crack growth should be made (see paragraph 9.6).

b.

Step 2 – If effective remedial measures are not possible and slow subcritical crack growth is expected, then determine if a crack growth law exists for the material and service environment. If a crack growth law exists, then a crack growth analysis can be performed. Otherwise, a leak-before break analysis should be performed to determine if an acceptable upper bound crack size can be established (see paragraph 9.5.2).

c.

Step 3 – Compute the stress at the flaw based on the future operating conditions. In these calculations, all relevant operating conditions including normal operation, start-up, upset, and shut-down should be considered.

d.

Step 4 – Determine an increment in crack growth based on the previous flaw size (to initialize the process, the previous flaw size is the initial flaw size determined in Step 1), stress, estimated stress intensity, and the crack growth law. For surface and embedded flaws, the increment of crack growth will have a component in the depth and length dimension. For embedded flaws, the increment of crack growth may also include a component to model the flaw location in the wall thickness direction. The increment of crack growth is established based on the applied stress intensity associated with the component of the crack and the crack growth law. For example, if a surface flaw is being evaluated, the crack depth is incremented based on the stress intensity factor at the deepest portion of the crack and the length is incremented based on the stress intensity factor at the surface. The flaw size to be used in Step 5 is the previous flaw size plus the increment of crack growth. A description of methodologies for performing crack growth calculations subject to constant amplitude and variable amplitude loading is contained in References [9.9.29], [9.9.30], [9.9.31], and [9.9.34].

e.

Step 5 – Perform a Level 3 assessment for the current crack size. Demonstrate that for the current crack size, the applied stress intensity factor is less than the critical stress intensity factor for the applicable crack growth mechanism. If the assessment point for the current flaw size is outside of the FAD or the crack is recategorized as a through-wall crack (see paragraph 9.3.6.6), then go to Step 6; otherwise, go to Step 4 and continue to grow the crack.

f.

Step 6 – Determine the time or number of stress cycles for the current crack size ( ao , co ) to reach the limiting flaw size. The component is acceptable for continued operation provided:

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a.

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g.

·

The time or number of cycles to reach the limiting flaw size, including an appropriate inservice margin, is more than the required operating period.

·

The crack growth is monitored on-stream or during shut-downs, as applicable, by a validated technique.

·

The observed crack growth rate is below that used in the remaining life prediction as determined by an on-stream monitoring or inspections during shutdowns.

·

Upset conditions in loading or environmental severity are avoidable.

·

If the depth of the limiting flaw size is recategorized as a through-wall thickness crack, the conditions for an acceptable leak before break (LBB) criteria should be satisfied (see paragraph 9.5.2).

Step 7 – At the next inspection, establish the actual crack growth rate, and re-evaluate the new flaw conditions per procedures of this section. Alternatively, repair or replace the component or apply effective mitigation measures.

9.5.2

Leak Before Break Analysis

9.5.2.1

Overview – In certain cases, it may be possible to show that a flaw can grow through the wall of a component without causing a catastrophic failure. In such cases, a leak can be detected (taking into


Not for Resale


consideration the contained fluid and type of insulation) and remedial action could be initiated to avoid a component failure. This type of examination is called a Leak-Before-Break (LBB) analysis. The leak-before-break methodology may be useful to determine an upper bound for a part-through flaw that is growing at an unknown rate; although the remaining life cannot be determined, detection of a leak can serve as an early warning. A leak-before-break analysis begins by recategorizing the flaw as through-wall, and evaluating the new geometry according to the procedures in paragraph 9.4.3 or 9.4.4. If the postulated through-wall flaw is acceptable, the existing flaw can be left in service as long as it does not grow through the wall.

9.5.2.3

Limitations Of LBB – There are limitations of the leak-before-break methodology. This approach should not be applied to certain situations which are outlined below. a.

The leak should be readily detectable. The LBB approach may not be appropriate if the affected area is covered by insulation, or if the cracking mechanism produces very tight cracks that do not produce leaks when they grow through the wall. The ability to detect a leak may also be influenced by the contained fluid (e.g. liquid or gas).

b.

The LBB methodology may not be suitable for flaws near stress concentrations or regions of high residual stress. The pitfalls of LBB in these situations is illustrated in Figure 9.24. When the stresses are higher on the surface than in the interior of the wall, the flaw may grow faster in the surface direction than in the depth direction. In some cases, the flaw can grow virtually around the entire circumference of the vessel before advancing in the depth direction. Therefore, LBB should not be applied to non-post weld heat treated cylindrical shell components with cracks in a circumferential weld joint (e.g. girth seams and head-to-shell junctions) or shell-to-nozzle junctions with circumferential cracks unless it can be shown that the stress distribution will not promote accelerated crack growth at the surface.

c.

The LBB approach should not be applied when the crack growth rate could potentially be high. When a leak occurs, adequate time must be available to discover the leak and take the necessary action. This consideration is particularly important when the component is subject to pneumatic pressure.

d.

The possible adverse consequences of developing a leak must be considered, especially when the component contains hazardous materials, fluids operating below their boiling point, and fluids operating above their auto-ignition temperature. Pressurized components which contain gas at high pressure can experience pneumatic loading or other dynamic effects at the crack tip making LBB impractical. Pressurized components which contain light hydrocarbon liquids, or other liquids with a low boiling point, can experience autorefrigeration which also make LBB impractical.

LBB Procedure – The procedure for assuring that a leak before break criteria is satisfied is shown below. a.

Step 1 – Using methods of paragraph 9.4.3 or 9.4.4, demonstrate that the largest initial flaw size left in the structure will not lead to fracture during the life of the component.

b.

Step 2 – Using methods of paragraph 9.4.3 or 9.4.4, determine the largest (critical) crack length of a full through-wall crack below which catastrophic rupture will not occur for all applicable load cases.

c.

Step 3 – Compute the corresponding leak areas associated with the critical crack lengths determined in Steps 1 and 2.

d.

Step 4 – Determine the leakage rate associated with the crack area computed in Step 3, and demonstrate that the associated leaks are detectable with the selected leak detection system (see paragraph 9.5.2.5). --``````-`-`,,`,,`,`,,`---


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9.5.2.2


9.5.2.4

Flaw Dimensions For LBB – The crack-like flaw dimension to be used in a LBB analysis are determined as follows: a.

If the component meets all of the conditions outlined in paragraph 9.5.2.2, the assumed LBB flaw can be defined as follows:

2c LBB = 2c + 2t

(9.31)

where,

c = half-length of the existing flaw (mm:in), and cLBB = half-length of the postulated through-wall flaw (mm:in). b.

9.5.2.5

The above equation, which applies to both surface and buried flaws, is more restrictive than the recategorization procedure in paragraph 9.3.6.6. The latter was applied to flaws that experienced ligament yielding. If the current flaw was initially recategorized as a through-wall flaw to account for ligament yielding, the length of the flaw should be redefined using (a) above if an LBB analysis is to be applied.

Leak Area Calculations for LBB Analysis – The crack opening area (COA) of a potential through-wall crack-like flaw is required to estimate leakage flow rates. The COA depends on the crack geometry (effective length, shape, orientation, etc.), component geometry, material properties, and the loading conditions. a.

The calculation methods for COA can be classified into three categories; linear elastic models, linear elastic models incorporating a small scale plasticity correction, and elastic-plastic models. Their accuracy varies with geometry, crack size, and the type and magnitude of the applied loads. A comparison of these solutions and numerical results based on finite element analysis is provide in Reference [9.9.19].

b.

The following equations can be used to provide a conservative approximation for the COA if the crack is located away from a major structural discontinuity and through-wall bending stresses are absent or can be ignored (see Reference [9.9.25]). These equations were derived using thin-wall, shallow-shell theory and are strictly valid only when R t ³ 10 , and the crack length does not exceed the radius of the shell. 1.

For a plate with a through-wall crack of length (2c) that is much less than the width and length of the plate,

2FIc 2 COAp = E¢

(9.32)

where,

COAp c E' I n 2.

2

2

=

crack opening area of a plate (mm :in ),

=

half-length of a though-wall flaw (mm:in),

=

E for plane stress and E 1 - n 2 for plane strain (MPa:psi),

= =

applied tensile stress (MPa:psi), and Poisson’s ratio.

c

h

For a cylindrical or spherical shell with a through-wall flaw,

d

COAs = = COAp

i

(9.33)

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where,

3.

The curvature correction factor is shown below for simple geometries (see Reference [9.9.25]) as a function of the shell parameter l (see Appendix C). a)

Longitudinal cracks in a cylinder (valid for l£ 8):

a = 1 + 01 . l + 016 . l2 b)

Circumferential cracks in cylindrical shell (valid for

c

a = 1 + 0117 . l2 c)

h

(9.34)

l£ 5):

0.5

Circumferential cracks in a spherical shell (valid for

(9.35)

l£ 5):

a = 1 + 0.02l + 0.22l2 4.

Plasticity at the crack tip tends to alter the effective length of the leakage. Therefore, a plasticity correction factor g is often required to correct for this effect. The leak areas for a plate and shell including the effects of plasticity can be computed using the following equations where the value of g as a function of normalized applied stress is shown in Table 9.7.

COAp =

2FIc 2 C E¢

d

(9.37)

i

COAs = = COAp C c.

d.

(9.36)

(9.38)

Alternative methods to compute the COA are covered in References [9.9.12], [9.9.17], [9.9.19], [9.9.21], and [9.9.22]. Elastic-plastic analysis, either by published closed form solutions or finite element analysis, is recommended for accurate assessments of the COA. This type of analysis is also recommended to compute the COA for cases where: ·

The membrane loading results in Lr > 0.4 (i.e. elastic analysis results with the plasticity correction give conservative results)

·

Complex geometries (e.g. though-wall crack at a major structural discontinuity such as a nozzle or head to shell weld), and

·

Unusual crack configurations.

The following should be considered in the determination of the COA. 1.


The solutions for plates and cylinders effectively assume that the cracks are in the center of an infinite body. For many geometries this will be a reasonable approximation. However, if the crack is close to a major structural discontinuity (e.g. a pipe nozzle intersection) then local effects can influence COA.

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--``````-`-`,,`,,`,`,,`---

COAp = crack opening area of a plate (in2:mm2), COAs = crack opening area of a shell (in2:mm2), and = = curvature factor.

Mean material properties should be used to provide a best estimate of COA. These properties must be relevant to the expected condition of the component; that is, time dependent changes in properties, such as degradation, relaxation and redistribution processes must be taken into consideration. LBB assessments are typically performed for cracks at welds. The variation in material properties at welds, the influence of the weld preparation angle, and the presence of residual welding stresses all affect the COA.

3.

Through-wall bending stresses can induce elastic crack face rotations which reduce effective crack opening area. If complete crack closure occurs, a LBB analysis cannot be justified. Significant local through-wall bending stresses may be present in thick wall shells subject to internal pressure, associated with geometric discontinuities, or thermal gradients. Generally all of the models, except for results based on detailed finite element analysis, estimate the COA at the mid-surface position; they do not account for the crack taper resulting from through-wall bending loads. A method to account for crack taper is discussed in Reference [9.9.14]. The effects of residual stress due to welding should also be evaluated (see Reference [9.9.7]) with regard to crack face rotations.

4.

The orientation of the resultant bending moment with respect to the through-wall crack should be considered when determining the COA in a cylindrical or conical shell subject to a net section bending moment. The orientation of the resultant bending moment may cause asymmetric crack openings, partial crack closure, or complete crack closure if the crack is located entirely on the compressive side of the shell section.

5.

For thick-walled geometries the crack-face pressure, which tends to open the crack, will be a function of crack opening; for tight cracks the mean pressure will be lower than for wide cracks. To assess the significance of the crack-face pressure, it is recommended that 50% of the internal pressure should be added to the membrane stress on the crack face. This value should then be reassessed when undertaking the leakage flow calculations.

6.

The initial leakage rate through a defect, which has just broken through the pressure boundary, may be significantly less than that predicted, assuming a uniform crack length equal to the re-characterized defect length. This is because when ligament failure first occurs, the defect may not penetrate the wall along its entire length, and because the recharacterization rules may over estimate the actual defect length.

9.5.2.6

Leak Rate Calculations For Through-Wall Cracks – The calculation of the fluid flow or leak rate through a crack is a problem which involves the crack geometry, the flow path length, fluid friction effects, and the thermodynamics of the flow through the crack. A method to compute the leak rate using approximate solutions for isothermal or polytropic flows of gases is provided in Reference [9.9.8]. Methods to compute the leak rate for two phase flow of steam/water mixtures are provided in Reference [9.9.17].

9.5.2.7

Analysis of Critical Leak Length (CLL) of Through-Wall Cracks – If a leak is expected and acceptable, and if conditions for LBB methodology are met, then the critical length of a through-wall crack for the component under the conditions of the prevalent stresses and material properties shall be performed using paragraph 9.4.3 or 9.4.4. The acceptance criteria of the CLL will depend on inspection monitoring and the leak detection system capability and reliability.

9.6

Remediation

9.6.1

A FFS analysis provides the remaining life of a component containing a flaw so that operation can be assured until the next scheduled inspection. The remaining life of crack-like flaws can only be determined if information about the crack growth rate in the service environment is known. Typically


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2.

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Remediation measure for crack-like flaws generally fall into one of the categories shown below. One or a combination of these methods may be employed.

9.6.2.1

Remediation Method 1 – Removal or repair of the crack. The crack may be removed by blend grinding. The resulting groove is then repaired using a technique to restore the full thickness of material and the weld repair is subject to PWHT in accordance with the in-service inspection code. Alternatively, repair of the groove is not required if the requirements of FFS assessment procedures in Section 5 are satisfied.

9.6.2.2

Remediation Method 2 – Use of a crack arresting detail or device. For components which are not a pressure boundary, the simplest form of this method is to drill holes at the end of an existing crack to effectively reduce the crack driving force. For example, this method has been used to control crack growth at the edge of slots located on coker reactor support skirts. For pressurized components, a device can be added to the component to control unstable crack growth (for example, crack arresting devices for pipelines, see Reference [9.9.24]).

9.6.2.3

Remediation Method 3 – Performing physical changes to the process stream (see Section 4, paragraph 4.6.3). This method can be used to reduce the crack driving force (reduction in pressure) or to provide an increase in the material toughness at the condition associated with highest stress state. This may involve the introduction of a warm start-up and/or shut-down cycle into equipment operating procedures such that the temperature of the component is high enough to ensure adequate material toughness at load levels associated with the highest state of stress.

9.6.2.4

Remediation Method 4 – Application of solid barrier linings or coatings to keep the environment isolated from the base metal (see Section 4, paragraph 4.6.4). In this method, the flaw is isolated from the process environment to minimize the potential for environmentally assisted subcritical crack growth.

9.6.2.5

Remediation Method 5 – Injection of water and/or chemicals on a continuous basis to modify the environment or the surface of the metal (see Section 4, paragraph 4.6.5). In this method, the process environment is controlled to minimize the potential for environmentally assisted subcritical crack growth.

9.6.2.6

Remediation Method 6 – Application of weld overlay (see Section 4, paragraph 4.6.6). In this method, weld overlay is applied to the component surface opposite to the surface containing the cracks to introduce a compressive residual stress field at the location of the crack (for an example, see Reference [9.9.9]). The compressive residual stress field should eliminate any future crack growth. This type of repair also increases the structural integrity of the component containing the flaw by the addition of extra wall thickness provided by the weld overlay.

9.6.2.7

Remediation Method 7 – Use of leak monitoring and leak-sealing devices.

9.7


9.7.1

In all cases where subcritical in-service crack growth is permitted by the methods of this document, in-service monitoring or monitoring at a shutdown inspection, as applicable, of the crack growth by NDE is required. The applicable NDE method will depend on the specific case.

9.7.2

Before returning the component to service, the monitoring method should be validated to ensure that it can adequately detect the size of the flaw under service conditions. The NDE sensitivity and flaw

--``````-`-`,,`,,`,`,,`---

9.6.2


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this information is not readily available or established for many of the process environments which occur in the refining and petrochemical industry. Therefore, a combination of analytical techniques (i.e. LBB, see paragraph 9.5.2), in-service monitoring (see paragraph 9.7), and remediation methods may be used to provide assurance that a component can be operated until the next scheduled inspection.


sizing uncertainty associated with the in-service monitoring procedure should be taken into account when specifying a limiting maximum flaw size for continued operation.

--``````-`-`,,`,,`,`,,`---

9.8

Documentation

9.8.1

The documentation of the FFS Assessment should include the information cited in Section 2, paragraph 2.8. Additional documentation requirements are essential because of the complexity associated with the assessment. This information should be permanently stored with the equipment record files.

9.8.1.1

The following information should be documented for a structural integrity assessment carried out according to the procedures of this section. a.

Assessment Level – Any deviations or modifications used at a given level of analysis (Levels 1, 2 and 3).

b.

Loading Conditions – normal operation and upset condition (see Appendix A for a summary of loading conditions); additional loads and stresses considered in the assessment (e.g. stresses from supplement loads, thermal gradients and residual stresses); the stress analysis methods (handbook or finite-element); and categorization of stress results (Levels 1, 2, and 3).

c.

Material Properties – The material specification of the component containing the flaw; yield stress, ultimate tensile stress, and fracture toughness at the temperature of interest (including whether the data was obtained by direct testing or indirect means and the source and validity of data); and a description of the process environment including its effect on material properties (Levels 1, 2 and 3).

d.

Characterization Of Flaw – The flaw location, shape and size; NDE method used for flaw sizing and allowance for sizing errors; and whether recharacterization of the flaw was required (Levels 1, 2 and 3).

e.

Partial Safety Factors – A list of the Partial Safety Factors used in the analysis; in a Level 3 assessment, a technical summary should be provided if alternative factors are utilized in the assessment (Level 2 and 3).

f.

Reference Stress Solution – The source of the reference stress solutions (e.g. handbook solution or finite-element analysis) used in the assessment including whether the local and/or global collapse was considered (Levels 2 and 3).

g.

Stress Intensity Factor Solution – The source of stress intensity factor solutions (e.g. handbook solution or finite-element analysis) used in the assessment (Levels 2 and 3).

h.

Failure Assessment Diagram – whether the Level 2 recommended curve, a material specific curve (including the source and validity of stress-strain data), or a curve derived from Janalysis is used in the assessment (Level 3).

i.

Flaw Growth – whether any allowance is made for crack extension by sub-critical crack growth mechanism (e.g. fatigue or stress corrosion cracking); the crack growth laws and associated constants utilized (from technical publication or laboratory measurements) should be summarized (Level 3).

j.

In-Service Margins – The results calculated for each loading condition of interest and for each category of analysis undertaken; assessment points should be displayed on the appropriate failure assessment diagram (Level 3).


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k.

Sensitivity Analysis – A listing of the input parameters used to perform sensitivity studies (e.g. loads, material properties, flaw size, etc.); the results of each individual study should be summarized (Level 3).

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9.8.1.2

All conservative assumptions used in the assessment procedures should be documented. In addition, all departures from the procedures in this section should be reported and separately justified. A separate statement should be made about the significance of potential failure mechanisms remote from the defective areas, if applicable.

9.8.2

If an in-service monitoring system is instituted because of the potential for sub-critical crack growth (see paragraph 9.7) or a leak detection system is installed as the result of a LBB assessment (see paragraph 9.5.2.7), the following documentation should be kept with the equipment files; the specification for the system, procedures for installation, system validation and calibration, procedures for recording data, and all in-service readings.

9.9

References

9.9.1

Anderson, P., Bergman, M., Brickstad, B., Dahlberg, L.“A Procedure for Safety Assessment of Components with Cracks – Handbook,” 3rd Edition, SAQ/FoU-Report 96/08, SAQ Kontroll AB, Sweden, 1997.

9.9.2

Anderson, T.L., “Fracture Mechanics – Fundamentals And Applications,” 2nd Edition, CRC Press, Boca Raton, Florida, 1995.

9.9.3

Anderson, T.L., Merrick, R.D., Yukawa, S., Bray, D.E., Kaley, L. And Van Scyoc, K., “Fitness-ForService Evaluation Procedures For Operating Pressure Vessels, Tanks, And Piping In Refinery And Chemical Service,” FS-26, Consultants’ Report, MPC Program On Fitness-For-Service, Draft 5, The Materials Properties Council, New York, N.Y., October, 1995.

9.9.4

Ainsworth, R.A., “The Treatment of Thermal and Residual Stresses in Fracture Assessments,” Engineering Fracture Mechanics, Vol. 24, No. 1, pp. 65-76, 1986.

9.9.5

Bloom, J.M., “Deformation Plasticity Failure Assessment Diagram (DPFAD) For Materials With NonRamberg-Osgood Stress-Strain Curves,” Journal Of Pressure Vessel Technology, American Society Of Mechanical Engineers, Vol. 117, November 1995.

9.9.6

Bloom, J.M., “Deformation Plasticity Failure Assessment Diagram (DPFAD) Approach / A FitnessFor-Purpose Fracture Mechanics Based Methodology for Use in the Petrochemical Industry,” PVPVol. 315, Fitness-for-Service and Decisions for Petroleum and Chemical Equipment, ASME, pp. 131144, 1995.

9.9.7

Dong, P., Rahman, S., Wilkowski, G., Brickstad, B., Bergman, M., “Effects Of Weld Residual Stresses On Crack Opening Area Analysis Of Pipes For LBB Applications,” LBB95; Specialist Meeting On Leak-Before-Break In Reactor Piping And Vessels, Lyon, France, October, 1995.

9.9.8

Ewing, D.J.F., “Simple Methods For Predicting Gas Leakage Flows Through Cracks,” Paper C376/047 In Proceedings Of International Conference On Pipework Engineering And Operation, I. Mech. E., London, 21-22, Pp. 307-314, February, 1989.

9.9.9

Hazelton, W.S., “Technical Report On Material Selection And Processing Guidelines For BWR Coolant Pressure Boundary Piping (Draft Report),” NUREG -0313, Rev. 2, June, 1986.

9.9.10

Kumar, V., German, M.D., Shih, C.F., “An Engineering Approach For Elastic-Plastic Fracture Analysis,” EPRI Report NP-1931, EPRI Palo Alto, CA, 1981.

9.9.11

Loushin, L.L., “Assessment of Structural Integrity in Pressure Vessels – Predictions and Verification,” PVP Vol. 336, ASME, pp. 97-104, 1996. --``````-`-`,,`,,`,`,,`---


Not for Resale


9.9.12

Langston, D.B., “A Reference Stress Approximation For Determining Crack Opening Displacements In Leak-Before-Break Calculations,” TD/SID/REP/0112, Nuclear Electric Document, 1991.

9.9.13

Langston, D.B., Haines, N.F. And Wilson, R., “Development Of A Leak-Before-Break Procedure For Pressurized Components,” CEGB, UK, pp. 287-292.

9.9.14

Miller, A.G., “Elastic Crack Opening Displacements And Rotations In Through Cracks In Spheres And Cylinders Under Membrane And Bending Loading,” Engineering Fracture Mechanics, Vol. 23, 1986.

9.9.15

Milne, I., Ainsworth, R.A., Dowling, A.R., And Stewart, A.T., “Assessment Of The Integrity Of Structures Containing Defects,” Int. J. Pres. Vessel & Piping, 32, 1988, pp. 3-104.

9.9.16

Milne, I., Ainsworth, R.A., Dowling, A.R., And Stewart, A.T., “Background To And Validation Of CEGB Report R/H/R6-Revision 3,” Int. J. Pres. Vessel & Piping, 32, 1988, pp. 105-196.

9.9.17

Paul, D.D., Ahmad, J., Scott, P.M., Flanigan, L.F. And Wilkowski, G.M., “Evaluation And Refinement Of Leak-Rate Estimation Models,” NUREG/CR-5128, Rev. 1, June 1995.

9.9.18

Paris, P.C., and Johnson, R.E., “A Method of Application of Elastic-Plastic Fracture Mechanics to Nuclear Vessel Analysis,” Elastic-Plastic Fracture: Second Symposium, Volume II-Fracture Resistance Curves and Engineering Applications, ASTM STP 803, 1983, pp. Ii-4-ii-40.

9.9.19

Rahman, S., Brust, F., Ghadiali, N., Choi, Y.H., Krishnaswamy, P., Moberg, F., Brickstad, B. And Wilkowski, G., “Refinement And Evaluation Of Crack Opening Area Analyses For Circumferential Through-Wall Cracks In Pipes,” NUREG/CR-6300, 1995.

9.9.20

Rahman, S., Ghadiali, Paul, D. And Wilkowski, G., “Probabilistic Pipe Fracture Evaluations For LeakRate-Detection Applications,” NUREG/CR-6004, April, 1995.

9.9.21

Scott, P.M., Anderson, T.L., Osage, D.A., and Wilkowski, G.M., “Review of Existing Fitness-ForService Criteria for Crack-Like Flaws,” WRC Bulletin 430, Welding Research Council, 1998.

9.9.22

Sharples, J.K. And Bouchard, P.J., “Assessment Of Crack Opening Area For Leak Rates,” LBB95; Specialist Meeting On Leak-Before-Break In Reactor Piping And Vessels, Lyon, France, October, 1995.

9.9.23

Smith, E., “The Opening Of Through-Wall Cracks In BWR Coolant Lines Due To The Application Of Severe Overloads,” NUREG/CP-0051, August, 1984.

9.9.24

Wilkowski, G., Scott, P. And Maxey, W., “Design And Optimization Of Mechanical Crack Arrestors For Pipelines,” NG-18 Report No. 134, American Gas Association, July, 1983.

9.9.25

Wuthrich, C. “Crack Opening Areas In Pressure Vessels And Pipes,” Engineering Fracture Mechanics, Vol. 18, No. 5, pp. 1049-1057, 1983.

9.9.26

Phaal, R, “Non-unique Solutions in PD6493: 1991 Fracture Assessment Procedures,” ASME PVPVol. 260, American Society of Mechanical Engineers, pp. 149-155, 1993.

9.9.27

Dijkstra, O.D. and Straalen, J.J., van, “Fatigue Crack Growth Program FAFRAM (Fatigue FRActure Mechanics),” TNO Building and Construction Research, Report BI-91-051.

9.9.28

Wirsching, P.H. and Mansour, A.E., “Incorporation of Structural Reliability Methods into Fitness-ForService Procedures,” The Materials Properties Council, Inc., May, 1998.

9.9.29

Liu, A.F., “Structural Life Assessment Methods,” ASM International, Materials Park, Ohio, 1998.

9.9.30

Ellyin, F., “Fatigue Damage Crack Growth and Life Prediction,” Chapman & Hall, Boundary Row, London 1997. --``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Bockrath, G. and Glassco, J., “Fatigue and Fracture Mechanics of High Risk Parts – Application of LEFM & EMDM Theory,” Chapman & Hall, New York, N.Y., 1997.

9.9.32

Hooton, G.H. and Budden, P.J., “R6 Developments In The Treatment Of Secondary Stresses,” PVPVol. 304, ASME, 1995, pp 503-509.

9.9.33

Popelar, C.H., “A Tearing Instability Analysis for Strain Hardening Materials,” ASTM STP 833, 1984.

9.9.34

Farahmand,B., Bockrath, G., and Glassco, J., “Fatigue and Fracture Mechanics of High Risk Parts – Application of LEFM & FMDM Theory,” Chapman Hall, New York, N.Y., 1997.

9.10

Tables And Figures

--``````-`-`,,`,,`,`,,`---

9.9.31

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale


Table 9.1 Data Required For The Assessment Of A Crack-Like Flaw A summary of the data that should be obtained from a field inspection is provided on this form. _____ Storage Tank


Data Required for Level 1: Assessment Temperature (typically the minimum temperature at full pressure): Assessment Pressure: Location of Flaw (Base Metal, Weld Metal or HAZ): Surface Location (ID, OD or Through-wall): Flaw Type (Surface or Embedded): Flaw Orientation To Weld Seam (Parallel or Perpendicular): Flaw Length (2c): Flaw Depth (a): Flaw Depth Below Surface (d – Embedded Flaw): Axial or Circumferential Crack : Post Weld Heat Treated (PWHT): Design Code: Base Material Specification: Weld Material Specification: Wall Thickness: MAWP: Process Environment: Design Pressure & Temperature: Cyclic Loading Conditions: Inspection Method – Flaw Length: Inspection Method – Flaw Depth: Inspection Method – Flaw Depth Below Surface: Additional Data Required for Level 2 (In Addition to the Level 1 Data): Yield Stress (Base Metal): Tensile Stress (Base Metal): Fracture Toughness (Base Metal): Source Of Material Data (Base Metal): Yield Stress (Weld Metal): Tensile Stress (Weld Metal): Fracture Toughness (Weld Metal): Source Of Material Data (Weld Metal): Yield Stress (HAZ): Tensile Stress (HAZ): Fracture Toughness (HAZ): Source Of Material Data (HAZ): Probability Of Failure Category: Coefficient Of Variation – Loads ( COVs ) : Partial Safety Factor – Loads ( PSFs ): Partial Safety Factor – Material Fracture Toughness ( PSFs ): Partial Safety Factor – Flaw Size ( PSFs ):


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Equipment Identification: Equipment Type: _____ Pressure Vessel Component Type & Location:


Table 9.2 Partial Safety Factors For The Assessment Of Crack-Like Flaws

a < 5 mm (0.2 inches) (1)

Shallow Cracks:

c h

COVs (3)

Rky £ Rc (5),(6)

Rc (4)

Rky > Rc (5),(6)

PSFs

PSFk

PSFa

PSFs

PSFk

PSFa

p f = 2.3 10 -2

0.10

1.0

1.20

1.43

1.08

1.25

1.0

1.0

( > = 2.0)

0.20

1.0

1.30

1.43

1.08

1.50

1.0

1.0

0.30

1.0

1.55

1.43

1.08

1.75

1.0

1.0

p f = 10-3

0.10

1.4

1.40

1.43

1.20

1.50

1.0

1.0

( > = 3.09)

0.20

1.4

1.50

1.82

1.10

2.0

1.0

1.0

0.30

1.4

2.00

2.0

1.05

2.50

1.0

1.0

p f = 10-6

0.10

2.0

1.75

2.0

1.35

2.00

1.0

1.0

( > = 4.75)

0.20

2.0

2.50

2.0

1.50

3.10

1.0

1.0

0.30

2.0

2.6

2.0

1.50

4.10

1.0

1.0

Deep Cracks: Probability Of Failure Category (2)

c h

COVs (3)

a ³ 5 mm (0.2 inches) (1)

Rky £ Rc (5),(6)

Rc (4)

Rky > Rc (5),(6)

PSFs

PSFk

PSFa

PSFs

PSFk

PSFa

p f = 2.3 10 -2

0.10

1.8

1.20

1.33

1.10

1.25

1.0

1.0

( > = 2.0)

0.20

1.3

1.40

1.54

1.10

1.50

1.0

1.0

0.30

1.1

1.60

1.67

1.10

1.75

1.0

1.0

p f = 10-3

0.10

1.9

1.40

1.67

1.15

1.50

1.0

1.0

( > = 3.09)

0.20

1.5

1.80

1.43

1.10

2.0

1.0

1.0

0.30

1.3

2.30

1.43

1.10

2.50

1.0

1.0

p f = 10-6

0.10

1.8

1.70

2.0

1.25

2.00

1.0

1.0

( > = 4.75)

0.20

1.5

2.60

1.82

1.25

3.10

1.0

1.0

0.30

1.5

3.50

1.67

1.25

4.10

1.0

1.0


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Probability Of Failure Category (2)


Notes For Table 9.2: 1. The flaw depth is the maximum value measured. The PSF factors for flaw depth in this table were established considering flaw size distributions obtained using accurate UT techniques such as crack-tip diffraction methods (TOFD) or focused beam methods. If the accuracy of the UT technique used to determine the flaw depth is less accurate (i.e. potential drop method), then a conservative estimate of the mean flaw depth should be used in the assessment with the PSF factors in this table. 2. In the Probability Of Failure Category column, p f is the probability of failure and > is the associated 3.

safety index. COVs is the coefficient of variation (standard deviation divided by the mean) used to define the uncertainty in the primary stress distribution. The primary stress to be used in the assessment should be based on the average expected value. Three categories are provided. COVs = 010 . – The primary loads and corresponding primary stresses in the region of the flaw are · computed or measured, and are well known. ·

COVs = 0.20 – The primary loads and corresponding primary stresses in the region of the flaw are computed or measured, and are reasonably well known. The uncertainty in the primary stresses is due to the possible variations in applied loads, or modeling estimates in the stress analysis.

·

COVs = 0.30 – estimates of the primary stresses are significantly uncertain. The uncertainty in the primary stresses result from the unknown or random nature of applied loading and/or modeling estimates in the stress analysis.

4.

Rc is a cut-off value used to define the regions of brittle fracture/plastic collapse and plastic collapse, and

5.

the corresponding category of Partial Safety Factors to be used in an assessment. Rky is used in conjunction with Rc to determine the Partial Safety Factors to be used in an assessment (see note 4 above). The definition of

Rky =

Rky is given by the following equation:

mean Kmat Cu I ys

(9.39)

where

Cu

=

conversion factor; if the units of the units of

mean Kmat = I ys =

mean Kmat are ksi in and I ys are psi then Cu = 1.0 , if

mean Kmat are MPa m and I ys are MPa then Cu = 6.268 .

Average value of the material fracture toughness (

MPa m: ksi in ), and

Nominal yield stress taken as the specified minimum value (MPa:psi).

6. If the only source of fracture toughness data is the lower bound estimate in Appendix F, paragraph F.4.4, then the mean value of toughness described in paragraph F.4.4.1.e should be used in the assessment. The mean value of fracture toughness is used because the Partial Safety Factors are calibrated against the mean fracture toughness. 7. The background for the Partial Safety Factors is provided in Reference [9.9.28].

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 9.3 Tabular Data For The O-Factor

O

LrP

LSr

--``````-`-`,,`,,`,`,,`---

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

³ 5.0

0.0

0.0

0.000

0.000

0.000

0.000

0.000

0.000

0.000

0.000

0.000

0.000

0.1

0.0

0.020

0.043

0.063

0.074

0.081

0.086

0.090

0.095

0.100

0.107

0.2

0.0

0.028

0.052

0.076

0.091

0.100

0.107

0.113

0.120

0.127

0.137

0.3

0.0

0.033

0.057

0.085

0.102

0.114

0.122

0.130

0.138

0.147

0.160

0.4

0.0

0.037

0.064

0.094

0.113

0.126

0.136

0.145

0.156

0.167

0.180

0.5

0.0

0.043

0.074

0.105

0.124

0.138

0.149

0.160

0.172

0.185

0.201

0.6

0.0

0.051

0.085

0.114

0.133

0.147

0.159

0.170

0.184

0.200

0.215

0.7

0.0

0.058

0.091

0.117

0.134

0.147

0.158

0.171

0.186

0.202

0.214

0.8

0.0

0.057

0.085

0.105

0.119

0.130

0.141

0.155

0.169

0.182

0.190

0.9

0.0

0.043

0.060

0.073

0.082

0.090

0.101

0.113

0.123

0.129

0.132

1.0

0.0

0.016

0.019

0.022

0.025

0.031

0.039

0.043

0.044

0.041

0.033

1.1

0.0

-0.013

-0.025

-0.033

-0.036

-0.037

-0.042

-0.050

-0.061

-0.073

-0.084

1.2

0.0

-0.034

-0.058

-0.075

-0.090

-0.106

-0.122

-0.137

-0.151

-0.164

-0.175

1.3

0.0

-0.043

-0.075

-0.102

-0.126

-0.147

-0.166

-0.181

-0.196

-0.209

-0.220

1.4

0.0

-0.044

-0.080

-0.109

-0.134

-0.155

-0.173

-0.189

-0.203

-0.215

-0.227

1.5

0.0

-0.041

-0.075

-0.103

-0.127

-0.147

-0.164

-0.180

-0.194

-0.206

-0.217

1.6

0.0

-0.037

-0.069

-0.095

-0.117

-0.136

-0.153

-0.168

-0.181

-0.194

-0.205

1.7

0.0

-0.033

-0.062

-0.086

-0.107

-0.125

-0.141

-0.155

-0.168

-0.180

-0.191

1.8

0.0

-0.030

-0.055

-0.077

-0.097

-0.114

-0.129

-0.142

-0.155

-0.166

-0.177

1.9

0.0

-0.026

-0.049

-0.069

-0.086

-0.102

-0.116

-0.129

-0.141

-0.154

-0.162

³ 2.0

0.0

-0.023

-0.043

-0.061

-0.076

-0.091

-0.104

-0.116

-0.126

-0.137

-0.146

Notes:

Equations to determine the


O-Factor are provided in Table 9.4.

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 9.4 Equations For Determination Of The O-Factor (1)

LSr

C1

C2

C3

C4

C5

C6

C7

C8

C9

C10

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.5

-2.66913E-05

25.6064

0.735321

-96.8583

-1.83570

134.240

1.59978

-83.6105

-0.493497

19.9925

1.0

-4.71153E-07

234.535

9.76896

-802.149

-23.3837

1066.58

19.9783

-648.697

-6.27253

153.617

1.5

-3.75189E-06

66.9192

4.64800

-224.507

-10.9901

288.872

8.92887

-169.271

-2.55693

38.3441

2.0

-1.07886E-05

45.9626

4.06655

-160.787

-10.1655

213.567

8.70602

-128.938

-2.58722

29.9699

2.5

-1.27938E-05

34.0140

3.56530

-126.974

-9.61991

176.724

8.85143

-111.226

-2.78480

26.8421

3.0

-4.62948E-06

27.5781

3.27165

-107.412

-9.20683

154.070

8.85151

-99.6994

-2.90516

24.7475

3.5

8.52189E-07

22.9360

3.03726

-90.9947

-8.63816

131.216

8.37438

-85.1256

-2.76449

21.1760

4.0

1.02755E-04

22.8427

3.04482

-64.9361

-5.39829

93.8627

5.79484

-75.1903

-3.28616

26.1201

4.5

4.44068E-05

19.6562

3.12233

-96.3032

-11.0348

164.591

13.2860

-123.811

-5.35151

35.4213

³ 5.0

8.19621E-05

21.1804

3.37642

-82.4411

-9.11191

146.507

12.5521

-125.246

-6.70084

42.6723

Notes: 1.

S

The equation to determine O-Factor for a given Lr is shown below where the coefficients are defined in the table.

O=

P r

10 . + C2 L

4

P 2 r

2

P 3 r

7

6

P 3 r

8

Interpolation may be used for intermediate values of

9

P 4 r

P 4 r

10

P 5 r

(9.40)

LSr .


--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.

c h + C cL h + C cL h + C cL h + C cL h + C cL h + C cL h

C1 + C3 LrP + C5 LrP

Not for Resale


Table 9.5 Tabular Data For The B-Factor

B

LrP

LSr

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

³ 5.0

0.0

0.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

1.0

0.1

0.0

0.815

0.869

0.877

0.880

0.882

0.883

0.883

0.882

0.879

0.874

0.2

0.0

0.690

0.786

0.810

0.821

0.828

0.832

0.833

0.833

0.831

0.825

0.3

0.0

0.596

0.715

0.752

0.769

0.780

0.786

0.789

0.789

0.787

0.780

0.4

0.0

0.521

0.651

0.696

0.718

0.732

0.740

0.744

0.745

0.743

0.735

0.5

0.0

0.457

0.589

0.640

0.666

0.683

0.693

0.698

0.698

0.695

0.688

0.6

0.0

0.399

0.528

0.582

0.612

0.631

0.642

0.647

0.648

0.644

0.638

0.7

0.0

0.344

0.466

0.522

0.554

0.575

0.587

0.593

0.593

0.589

0.587

0.8

0.0

0.290

0.403

0.460

0.493

0.516

0.528

0.533

0.534

0.534

0.535

0.9

0.0

0.236

0.339

0.395

0.430

0.452

0.464

0.470

0.475

0.480

0.486

1.0

0.0

0.185

0.276

0.330

0.364

0.386

0.400

0.411

0.423

0.435

0.449

1.1

0.0

0.139

0.218

0.269

0.302

0.326

0.347

0.367

0.387

0.406

0.423

1.2

0.0

0.104

0.172

0.219

0.256

0.287

0.315

0.340

0.362

0.382

0.399

1.3

0.0

0.082

0.142

0.190

0.229

0.263

0.291

0.316

0.338

0.357

0.375

1.4

0.0

0.070

0.126

0.171

0.209

0.241

0.269

0.293

0.314

0.333

0.350

1.5

0.0

0.062

0.112

0.155

0.190

0.220

0.247

0.270

0.290

0.309

0.325

1.6

0.0

0.055

0.100

0.139

0.172

0.200

0.225

0.247

0.267

0.285

0.301

1.7

0.0

0.048

0.089

0.124

0.154

0.181

0.204

0.224

0.243

0.260

0.276

1.8

0.0

0.042

0.078

0.110

0.137

0.161

0.183

0.202

0.220

0.236

0.250

1.9

0.0

0.036

0.068

0.096

0.120

0.142

0.162

0.180

0.196

0.211

0.225

³ 2.0

0.0

0.031

0.058

0.083

0.104

0.124

0.141

0.170

0.172

0.186

0.198

Notes: Equations to determine the


B-Factor are provided in Table 9.6.

Not for Resale


Table 9.6 Equations For Determination Of The B-Factor (1)

--``````-`-`,,`,,`,`,,`---

LSr

C1

C2

C3

C4

C5

C6

C7

C8

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.5

1.00001

-2.22913

-2.41484

2.93036

1.93850

-2.93471

-0.509730

1.31047

1.0

1.00001

-2.13907

-2.38708

1.90283

1.89948

-1.11292

-0.498340

0.400603

1.5

0.999999

-2.04828

-2.36097

1.45152

1.86492

-0.457048

-0.488331

0.101387

2.0

0.999987

-2.02808

-2.36632

1.30047

1.87918

-0.225165

-0.495719

0.000000

2.5

0.999961

-2.08565

-2.42584

1.34991

1.97702

-0.215801

-0.532519

0.000000

3.0

0.999951

-2.15806

-2.49971

1.43002

2.09759

-0.222316

-0.578002

0.000000

3.5

0.999910

-2.15424

-2.49570

1.41869

2.08859

-0.213589

-0.571688

0.000000

4.0

0.999978

-2.20511

-2.57332

1.42094

2.23701

-0.0755321

-0.636324

-0.0763128

4.5

0.999976

-2.27554

-2.66103

1.48947

2.39550

-0.0340309

-0.699994

-0.101608

³ 5.0

0.999977

-2.33094

-2.73542

1.54184

2.52395

-0.00694071

-0.750359

-0.119742

Notes: 1.

S

The equation to determine B -Factor for a given Lr is shown below where the coefficients are defined in the table.

B= 2.

c h

C1 + C3 LrP

c h

10 . + C2 LrP

0.5

0.5

c h

+ C5 LrP + C7 LrP

c h

+ C4 LrP + C6 LrP

1.5

1.5

c h

+ C8 LrP S

Interpolation may be used for intermediate values of Lr .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale

2

(9.41)


Table 9.7 Plasticity Correction Factor – C Stress Ratio (1) –

S=

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes: 1.

Plasticity Correction Factor – C (2)

0.1

1.008

0.2

1.031

0.3

1.069

0.4

1.123

0.5

1.198

0.6

1.302

0.7

1.450

0.8

1.680

0.9

2.117

The stress ratio is determined based on the component geometry, loading conditions and material properties (material properties are only required if the component is statically indeterminate). For example, for a cylindrical shell or radius (R) and thickness (t) subject to pressure (p):

I1 =

pR t

(9.42)

I2 =

pR 2t

(9.43)

S=

2.

I2 with I 1 > I 2 I1

I2 = 0.5 I1

(9.44)

The equation for the Dugdale correction factor is:

C =

LMb g N FG1 - 1 IJ LM 2 FG sec H S K MNF H

b g FS I - 1J + b1 - S g sec K 2 0.5

2

--``````-`-`,,`,,`,`,,`---


FG H FS O P 2 PQ

1 FS 4 FS 8 FS 2 1 - S sec 2 + 1 - S tan - ln cos S 2 F 2 F 2

Not for Resale

2

IJ OP + KQ

(9.45)

RECOMMENDED

Jan, 2000

PRACTICE

9-41


Figure 9.1 Nomenclature And Idealized Shapes of Crack-Like

Actual

Flaws

Idealized

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(a) Through-wail flaw

(b) Surface flaw

4

2c

b

4

2c

b

A f,D$2

$2; td

td (c) Embedded flaw

--``````-`-`,,`,,`,`,,`---

(d) Edge crack

(e) Corner flaw



API RECOMMENDED

9-42

PRACTICE

579

Jan, 2000

Figure 9.2 Procedure For Defining An Effective Flaw Length On A Principal Stress Plane

Use Equation (9.1)

or

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Use Equation (9.2)

--``````-`-`,,`,,`,`,,`---

March 2000


Not for Resale


Figure 9.3 Equivalent Mode I Crack Length As A Function Of The > Angle And The Stress Biaxiality Ratio

1.2 B=1.0

1.0

0.8

c/co

B=0.75

0.6

0.4

B=0.50

B=0.25

0.2

B=0

0.0

0

15

30

45

60

=, Degrees

Notes: 1. The figure is a plot of Equation (9.1) 2. B in this figure is the biaxial stress ratio, see Equation (9.3)

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

75

90


Figure 9.4 Procedure For Defining The Effective Depth Of A Flaw That Is Oriented At An Oblique Angle

t

aO

G

t

a

t

2a

t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2aO

G dO

d a = Wao, W is determined using Figure 9.5

Project the flaw onto the principal plane.

aO

t

t

a

t

2a

G 2aO

t

G dO

d

Project the flaw onto the principal plane.

a = Wao, W is determined using Figure 9.5

(b) Stepwise Crack-Like Flaw Note:

For an embedded flaw,


d o and d are the minimum distance from the flaw to the surface

Not for Resale

--``````-`-`,,`,,`,`,,`---

(a) Planar Crack-Like Flaw


Figure 9.5 Equivalent Mode I Crack Depth As A Function Of The G Angle

1.20

1.15

WTheta

1.10

1.05

1.00

0.95

0.90

0

20

40

60

80

Theta, Degrees

Notes: 1. The figure is a plot of Equation (9.7) 2. Theta in this figure is the angle of the flaw measured from the normal in the through-thickness direction (see Figure 9.4)

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 9.6 Procedure For Treating Branched Cracking

I1

I1

2cO

2cO

I2

I2

(b) Idealize the area as a planar flaw with length equal to the length of the rectangle.

(a) Draw a rectangle around the affected area.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I1

t

aO

2c

I2 --``````-`-`,,`,,`,`,,`---

t

(d) Define the effective flaw depth as 1.2 times the maximum depth of the branched network.

(c) Define an effective flaw length on a principal stress plane. (I1 > I )


a = 1.2aO

Not for Resale


Figure 9.7 Treatment Of Multiple Crack-Like Flaws

I2

I2

2c1

2c2

I1

I1

(a) Initial configuration.

(b) After application of the equivalent flaw length rules in paragraph 9.3.6.2.

--``````-`-`,,`,,`,`,,`---

I2

2c 2c1

I1

2c2 a t

2c3

(c) After projecting interacting flaws onto a single plane


(d) Definition of effective dimensions of flaws that overlap after projection onto a single plane.

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2c3


Figure 9.8 Interaction Of Coplanar Flaws Multiple Crack-Like Flaw Configuration

2c1

s

2c2

Criterion For Interaction

Effective Dimensions After Interaction

c1 + c2 ³ s

2c = 2c1 + 2c2 + s a = max a1 , a2

a1 a2

2a2

2c2

s

a1 + a2 ³ s

2a1

2a = 2a1 + 2a2 + s 2c = max 2c1 , 2c2

2c1

2c2

s

c1 + c2 ³ s

2c1

2c = 2c1 + 2c2 + s 2a = max 2a1 , 2a2

2a1 2a2

2c1

a1 + a2 ³ s a1

a

s

a = a1 + 2a2 + s 2c = max 2c1 , 2c2

2c2

--``````-`-`,,`,,`,`,,`---

2a2


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 9.8 Interaction Of Coplanar Flaws Multiple Crack-Like Flaw Configuration s1 2c2

s2

2a2

2a1

Criterion For Interaction

Effective Dimensions After Interaction

c1 + c2 ³ s2

2c = 2c1 + 2c2 + s2

and a1 + a2 ³ s1

2a = 2a1 + 2a2 + s1

c1 + c2 ³ s2

2c = 2c1 + 2c2 + s2

and a1 + a2 ³ s1

a = a1 + 2a2 + s1

2c1

a1 s2

2c1

2c2

s1 2a2

c1 + c2 ³ s 2c2

2c = total length of projection based on cracks defined by 2c1 and 2c2

s 2c 2c1

c1 + c2 ³ s1 2c2

Project flaws onto the same plane.

and c1 + c2 ³ s2

s1

Project flaws onto the same plane.

2c = 2c1 + 2c2 + s2

s2 2c1

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 9.9 Procedure For Recategorizing Flaws That Experience Ligament Yielding

2cs

d

as

2ab 2cb

--``````-`-`,,`,,`,`,,`---

2cs = 2cb + 2d as = 2ab + d (a) Embedded flaw recategorized as a surface flaw when d/t < 0.2

2cs

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

t

2ct

as

2ct = 2cs + 2(t - as) (b) Surface flaw recategorized as a through-wall flaw when as/t > 0.8


Not for Resale


Figure 9.10 Overview Of The Assessment Procedures To Evaluate A Component With Crack-Like Flaws

Obtain Equipment and Preliminary Inspection Data

Evalute Resulting Groove Using the Section 5.0 Assessment Criteria

Can the Crack-Like Flaw be Removed by Blend Grinding?

Yes

No Characterize the Shape and Size of the Flaw

Perform a Level 1 Assessment

Equipment is Acceptable Per Level 1 Screening Criteria?

Yes

--``````-`-`,,`,,`,`,,`---

No

Perform a Level 2 Assessment (See Figure 9.11)?

No

Yes Equipment Acceptable per Level 2 Assessment?

Yes

No

No

No


Yes

Yes

Yes

Rerate Equipment?

Perform Rerate per Level 2 Criteria to Modify Pressure and/or Temperature

Equipment Acceptable per Level 3 Assessment? No Rerate Equipment?

Repair or Replace Equipment

No

Yes Perform Rerate per Level 3 Criteria to Modify Pressure and/or Temperature

Potential for Crack-Like Flaw to Grow In-Service?

No

Return the Component to Service

Yes Evaluate Using the Assessment procedures in Paragraph 9.5 and Figure 9.23


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 9.11 Overview Of The Level 2 Assessment Procedure For A Non-Growing Crack-Like Flaw --``````-`-`,,`,,`,`,,`---

Start of Level 2 FAD Assessment for Crack-Like Flaws

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Determine Operating Conditions and Loading Combinations

Determine Crack-Like Flaw Dimensions

Determine Material Yield, Tensile and Toughness Properties

Determine Stress Distributions at the Flaw Location

Apply PSF's if Utilized in the Assessment

Compute Lr & Kr Evaluate Results Using FAD Criteria

Flaw Accepatble?

Yes

No

Yes

Can NDE be Improved?

If Required, Determine the Limiting Flaw Size

No

Perform Additional NDE

Yes

Can a Better Estimate of Material Properties Be Made?

Evaluate Potential for Non-Unique Solutions

No

Refine Material Properties

Yes

Can Loads and Stresses Be Determined More Accurately? No

Refine Estimates of Loads and/or Calculation Procedures to Determine Stresses


Component Not Acceptable per the Level 2 Assessment Criteria

Not for Resale

Flaw Is Acceptable per Level 2

Jan,2000

RECOMMENDED

PRACTICE

9-53


Figure 9.12 Level 1 Assessment - Flat Plate

(T - Tref + 55.6), ‘C 0

10

20

30

40

50

60

70

80

90

100

110

6

150

5

125

.-e - 4 cy”

100

3

75

2

50

1

25

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0

E rn 2

0 0

50

100

150

200

(T - Tref + IOO), OF

Notes 1.

2. 3. 4.

Definition of Screening Curves (solid line X-t flaw, dashed line l-t flaw): AAllowable flaw size in base metal. Allowable flaw size in weld metal that has been subject to PWHT. B Allowable flaw size in weld metal that has not been subject to PWHT. CCrack dimension for a l-t and ‘X-t flaw are shown in Appendix C, Figures C.l & C.2. See paragraph 9.2.2.1 for restrictions and limitations. Guidelines for establishing the Reference Temperature, & , are covered in paragraph 9.4.2.2.e. The maximum permitted flaw length from this curve is

2c = 203.2 mm (8 inch).

--``````-`-`,,`,,`,`,,`---



API RECOMMENDED

9-54

Level 1 Assessment

PRACTICE

579

Jan, 2000

Figure 9.13 - Cylinder, Longitudinal Joint, Crack-Like Flaw Parallel To The Joint

(T - Tref + 55.6), ‘C 0

10

20

30

40

50

60

70

80

90

100

110

8

6

0 0

50

100

150

200

(T - Tref + IOO), OF

Notes 1.

2. 3. 4.

Definition of Screening Curves (solid line X-t flaw, dashed line l-t flaw): AAllowable flaw size in base metal. BAllowable flaw size in weld metal that has been subject to PWHT. cAllowable flaw size in weld metal that has not been subject to PWHT. Crack dimension for a Y&t and l-t flaw are shown in Appendix C, Figures C.10 & C.14. See paragraph 9.2.2.1 for restrictions and limitations. Guidelines for establishing the Reference Temperature, &, are covered in paragraph 9.4.2.2.e.

5.

The maximum permitted flaw length from this curve is

March 2000


2c = 203.2 mm (8 inch).

--``````-`-`,,`,,`,`,,`---

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 9.14 Level 1 Assessment – Cylinder, Longitudinal Joint, Crack-Like Perpendicular To The Joint

o (T - Tref + 55.6), C 0

10

20

30

40

50

60

70

80

90

100

8

200 A

175

B

150

5

125

4

100 C

3

75 A

2

50 B

1

C

0

25

0

0

50

100

150

200

o (T - Tref + 100), F //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes: 1.

2. 3. 4.

Definition of Screening Curves (solid line ¼-t flaw, dashed line 1-t flaw): A – Allowable flaw size in base metal. B – Allowable flaw size in weld metal that has been subject to PWHT. C – Allowable flaw size in weld metal that has not been subject to PWHT. Crack dimension for a 1-t and ¼-t flaw are shown in Appendix C, Figures C.11 & C.15. See paragraph 9.2.2.1 for restrictions and limitations. Guidelines for establishing the Reference Temperature, Tref , are covered in paragraph 9.4.2.2.e.

5.



Not for Resale

2c = 203.2 mm (8 inch) .

--``````-`-`,,`,,`,`,,`---

6

2c, mm

7

2c, in.

110


Figure 9.15 Level 1 Assessment – Cylinder, Circumferential Joint, Crack-Like Flaw Parallel To The Joint

o (T - Tref + 55.6), C 0

10

20

30

40

50

60

70

80

90

100

8

110 200

7

175

A C

6

150

--``````-`-`,,`,,`,`,,`---

125

4

100 A

3 2

50

B

1

75

C

0

25

0

0

50

100

150

200

o (T - Tref + 100), F

Notes: 1.

2. 3. 4.


5.



2c = 203.2 mm (8 inch) .

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2c, mm

2c, in.

B

5


Figure 9.16 Level 1 Assessment – Cylinder, Circumferential Joint, Crack-Like Flaw Perpendicular To The Joint

o (T - Tref + 55.6), C 0

10

20

30

40

50

60

70

80

90

100

110

8

200

7

175 A B

150

5

125

4

100

75

C A

2

B

1

C

0

50

25

0

0

50

100

150

200

o (T - Tref + 100), F

Notes: 1.

2. 3. 4.


5.



2c = 203.2 mm (8 inch) .

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

3

2c, mm

2c, in.

6


Figure 9.17 Level 1 Assessment – Sphere, Circumferential Joint, Crack-Like Flaw Parallel To The Joint --``````-`-`,,`,,`,`,,`---

o (T - Tref + 55.6), C 10

20

30

40

60

70

80

90

100

110 200

7

175

6

150

5

2c, in.

50

125

B A

4

100 A

3

75

2

B C

1

50

25 C

0

0

0

50

100

150

200

o (T - Tref + 100), F

Notes: 1.

2. 3. 4.


5.



2c = 203.2 mm (8 inch) .

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2c, mm

0

8


Figure 9.18 Level 1 Assessment – Sphere, Circumferential Joint, Crack-Like Flaw Perpendicular To The Joint

o (T - Tref + 55.6), C 10

20

30

40

50

60

70

80

90

100

110 200

7

175

6

150

2c, in.

A

B

5

125

4

100 A

3

2c, mm

0

8

75 C

2

50

B

1 C

0

0

0

50

100

150

200

o (T - Tref + 100), F

Notes: 1.

2. 3. 4.


5.


--``````-`-`,,`,,`,`,,`---


Not for Resale

2c = 203.2 mm (8 inch) .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

25


Figure 9.19 Determination Of The Plasticity Interaction Factor

1.4

1.3

F/Fo

1.2 Lsr=0.5 Lsr=1.0

1.1

Lsr=1.5 Lsr=2.0 Lsr=2.5 Lsr=3.0 Lsr=3.5

1.0

Lsr=4.0 Lsr=4.5 Lsr=5.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Lpr

Notes:

. . o for values of LrP £ 10 . are shown in this figure. For value of

1.

The plasticity interaction factor,

2.

LrP > 1.0 greater than 1.0, . .o can be computed using the methodology in paragraph 9.4.3.2.l.1. P S Interpolation may be used to determine . . o for intermediate values of Lr and Lr .

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0.9


Not for Resale

Figure 9.20 The Failure Assessment Diagram

1.2

1.0 UNACCEPTABLE REGION

0.8

Kr

--``````-`-`,,`,,`,`,,`---

Cut-off For Steels with a Yield Plateau

0.6 ACCEPTABLE REGION

0.4

Cut-off for ASTM A508

(Inside the Lr Cut-off)

Cut-off for C-Mn Steels Cut-off for Stainless Steels

0.2

0.0 0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

LPr Notes: 1.

The FAD is defined using the following equation:

c h jFH 0.3 + 0.7 exp -0.65c L h IK

e

Kr = 1 - 014 . LrP 2.

2

P 6 r

for

LrP £ LrP(max)

(9.46)

P

The extent of the FAD on the Lr axis is determined as follows: a.

LrP(max) = 100 . for materials with yield point plateau (strain hardening exponent > 15),

b.

LrP(max) = 125 . for carbon-Mn steels,

c.

LrP(max) = 180 . for austenitic stainless steels, and

d.

LrP(max) =

If I ys

for other materials where

I f is the flow stress (see Appendix F) and I ys is the

yield stress; the flow stress and yield stress are evaluated at the assessment temperature. 3.

If the strain hardening characteristics of the material are not known, then

LrP(max) = 10 . should be

used in the assessment. 4.

The value of

LrP(max) may be increased for redundant components (see Appendix D, paragraph

D.2.5.2.b). 6.

If

LrP(max) = 10 . , then the FAD may be defined using following equation:

e c h j

Kr = 10 . - LrP 6.

2 .5 0.20

P

for Lr (max) = 10 .

The FAD in the dashed line is used with the assessment procedure in paragraph 9.4.3.3.


Not for Resale

(9.47)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure 9.21 Ductile Tearing Analysis

J

Kr

Increasing Crack Size

aJR Material JR Curve

--``````-`-`,,`,,`,`,,`---

Lr

(a) Obtaining a locus of assessment points from a JR-curve

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Stable Crack Growth

Ductile Instability Kr

No Crack Growth

Lr

(b) Three possible outcomes of a ductile tearing analysis


Not for Resale


Figure 9.22 Overview Of The Assessment Procedures To Evaluate Growing Crack-Like Flaws

Complete Evalution as Non-growing Crack (See Paragraph 9.4)

Can Crack Growth be Prevented?

Yes

Apply Preventative Measures

No

Estimate Remaining Life by Performing A Crack Growth Analysis (See Section 9.5)

Yes

Is a Crack Growth Equation Available? No

No

Refine Analysis? Yes

Refine Estimates for Material Properties and Crack-Growth Equation

No

Can Leak-Before-Break Analysis be Applied?

Life Adequate? Yes

No

Develop Monitoring Program and Return the Component to Service

Recategorize Crack-Like Flaw as Through-Wall

--``````-`-`,,`,,`,`,,`---

Refine Estimates of Loads (Including History) and/or Calculation Procedures to Determine Stresses

No

Yes

Yes

Repair and/or Remediate, or Replace the Component

Can The Falw be Monitored In-Sevice?

Evaluate as Non-Growing Flaw (See Paragraph 9.4)

Flaw Size Acceptable?

No

Yes

Evaluate Leakage Potential

Consequences of Leakage Acceptable?

No

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Yes


Not for Resale


Figure 9.23 Methodology For Crack Growth Analysis.

Start of Crack Growth Analysis

Determine Operating History and a Representative Load Histogram for Continued Operation

Determine Stresses for Points in the Load Histogram

Determine Material Tensile and Toughness Properties for Temperatures Defined in the Load Histogram

Determine Material Constants for Crack-Growth Equation for Conditions Defined in the Load Histogram

Determine the Initial Flaw Dimensions.

Compute Lr and Kr for the Current Flaw Size

Yes

--``````-`-`,,`,,`,`,,`---

No

Increment Flaw Sizes Based on Crack-Growth Equation

End of Specified Load Histogram Is Reached?

Point Inside the FAD?

No

Record Limiting Flaw Dimensions

Yes

Crack Growth Analysis For the Current Specified Data Is Complete

Sensitivity Analysis Complete?

No

Yes Crack Growth Analysis Complete


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

RECOMMENDED

Leak-Before-Break

PRACTICE


9-65

Figure 9.24 For Flaws Near A Stress Concentration

--``````-`-`,,`,,`,`,,`---

stress

(a) Flaw at a stress concentration

residual stress

(b) Flaw subject to high residual stresses.

.:

(c) Flaw growth predominantly


in the length direction.


API RECOMMENDED

9-66

PRACTICE 579

Jan, 2000

9.11

Example

Problems

9.11.1

Example Problem 7 - A crack-like flaw has been found on a cylindrical shell of a pressure vessel during a scheduled turnaround. The vessel and inspection data are provided below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is acceptable for continued operation using a Level 1 Assessment. Data

Design

Conditions

300 psi @ 650°F

Inside Diameter

96 inches

Fshrieatd . II..-“.“-

1.25 inches

Thirknacc . . ..-....--I

Uniform

Metal Loss

0.10 inches

FCA

0.125 inches

Material

SA 516 Grade 70


0.85

PWHT

Yes, Original Fabrication

Inspection

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Vessel

Requirement

Data

The flaw is located in the HA2 of a longitudinal weld seam on the inside of a cylindrical vessel. The flaw is parallel to the weld joint. The depth of the flaw was established by UT; however, many different values were obtained during the inspection with a maximum value of 0.25 inches being reported. The flaw length was established by MT and is 1 .l inches. The distance of the crack-like flaw to the nearest structural discontinuity is 60 inches. Perform

a Level

1 Assessment

per paragraph

9.4.2.2

Step I - Determine the temperature to be used in the assessment based on operating and design conditions - based on the operating constraints of the unit, the vessel is not fully pressurized until the temperature is 100 OF.

T= 100°F Step 2 - Determine

the length and depth of the crack-like

flaw from inspection

data.

a = 0.25” 2c = 1.1” Step 3 - Determine the figure to be used in the assessment - The flaw is located in a longitudinal weld seam in a cylindrical vessel and is parallel to the weld joint; therefore, Figure 9.13 will be used. Step 4 - Determine

the screening

curve.

l

The flaw is located at the HA2 of a weldment.

l

The maximum

l

The current component

flaw depth reported from UT measurements thickness

is

1.25inch - 0.10 inch = 1.15 inch

1 inch ; therefore, the maximum permissible

0.25 inch.

flaw depth for a screening

Based on NDE results, this is the maximum

March 2000


is 0.25 inches.

Not for Resale

which

is greater

assessment

flaw depth reported.

is

than

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


·

The flaw is in a weldment and the vessel was subject to PWHT at the time of construction.

Based on the above, use the ¼-t (solid line) Curve B of Figure 9.13 Step 5 – Determine a Reference Temperature –

Tref can established using Table 3.3 and Figure 3.3

in Section 3. ASTM A516 Grade 70 is a Curve B material, therefore:

. " RSt = 125 UV Þ T TCurve B Material W

ref

» 40 o F

R|c100 F - 40 F + 100 F h = 160 S|1 / 4t - Curve B of Figure 9.13 T o

o

o

o

F

U| Þ 2c » 8" V| W

Step 7 – Evaluate Results. Since

e2c

Screening Curve

j c

h

= 8" > 2c Measured = 11 . " , the flaw is acceptable.

The Level 1 Assessment Criterion are Satisfied

9.11.2

Example Problem 2 – A crack-like flaw has been found in the longitudinal seam on the inside surface of a cylindrical pressure vessel during a scheduled turnaround. The vessel and inspection data are provided below. The vessel was designed and constructed to the ASME B&PV Code, Section VIII, Division 1. Determine if the vessel is acceptable for continued operation if it is fully pressurized at 30°F. Vessel Data Design Conditions

=

200 psi @ 750°F

Inside Diameter

=

120 inches


=

1.0 inches

Uniform Metal Loss

=

0.0 inches

FCA

=

0.0 inches

Material

=

SA 516 Grade 70


=

0.85

PWHT

=

No

Inspection Data The flaw is located in the HAZ of a longitudinal weld seam on the inside of the vessel. The longitudinal seam is a double V-groove weld. The flaw is parallel to the weld seam. The depth of the flaw was established by UT; consistent readings where noted and a final value for the flaw depth was established at 0.20 inches. The flaw length was established by MT and is 3.2 inches. The distance of the crack-like flaw to the nearest structural discontinuity is 30 inches. Perform a Level 1 Assessment per paragraph 9.4.2.2


Not for Resale

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Step 6 – Determine the maximum permissible crack-flaw length using Figure 9.13 (see Step 3). Since there is variation in the measured flaw depth, the screening curve for a ¼-t flaw will be used.


Step 1 – Determine the temperature to be used in the assessment based on operating and design conditions – based on the operating constraints of the unit, the vessel is not fully pressurized until the o temperature is 30 F.

T = 30 o F Step 2 – Determine the length and depth of the crack-like flaw from inspection data.

a = 0.20" 2c = 3.2" Step 3 – Determine the figure to be used in the assessment – The flaw is located in a longitudinal weld seam in a cylindrical vessel and is parallel to the weld joint; therefore, Figure 9.13 will be used. Step 4 – Determine the screening curve. ·

The flaw is located at the HAZ of a weldment.

·

The maximum flaw depth reported from UT measurements is 0.20 inches.

·

The current component thickness is

b

1 inch ; therefore, the maximum permissible flaw depth for

g

0.25 × 10 . inch = 0.25 inch . Based on NDE results, the maximum flaw depth reported is 0.20 inch a screening assessment is

The flaw is in a weldment and the vessel was not subject to PWHT at the time of construction.

Based on the above, use the ¼-t (solid line) Curve C of Figure 9.13 Step 5 – Determine a Reference Temperature –

Tref can established using Table 3.3 and Figure 3.3

in Section 3. ASTM A516 Grade 70 is a Curve B material, therefore:

RSt = 10. " UV Þ T TCurve B Material W

ref

= 30 o F

Step 6 – Determine the maximum permissible crack-flaw length using Figure 9.13 (see Step 3).

R|c30 F - 30 F + 100 F h = 100 S|Curve C of Figure 9.13 T o

o

o

o

F

U| Þ 2c » 0.2" V| W

Step 7 – Evaluate Results. Since

e2c

Screening Curve

j c

h

= 0.2" < 2c Measured = 3.2" , the flaw is not acceptable.

The Level 1 Assessment Criterion are Not Satisfied Perform a Level 2 Assessment per paragraph 9.4.3.2 Step 1 – Evaluate operating conditions and determine the pressure, temperature and supplemental loading combinations to be evaluated – There are no significant supplemental loads, pressure is the only significant load.


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·


T = 30 o F P = 200 psig Step 2 – Determine the primary stress distribution at the location of the flaw based on the applied loads. Primary Stress The flaw is located away from all major structural discontinuities. Therefore, the primary stress at the weld joint perpendicular to the crack face is a membrane hoop stress. From Appendix A:

Rc = 60" t c = 1.0" Pm = I Cm =

b200 psigg FG b60"g + 0.6IJ = 14259 psi b0.85g H b10. "g K

Pb = 0 psi Maximum Primary Stress It has been verified that the crack-like flaw was in the vessel during a field hydrotest previously performed as part of a rerate. Therefore, the maximum primary stress is:

S = 14800 psi @ 750° F S = 17500 psi @ Ambient

b

Pmmax = 15 . 14259 psi

IJ = 25289 psi g FGH 1417..85 ksi ksi K

Secondary Stress Thermal gradients do not exist in the vessel at the location of the flaw, and the flaw is located away from all major structural discontinuities. Therefore, there are no secondary stresses. Residual Stress The flaw is located at a weldment in a vessel that was not subject to PWHT at the time of fabrication. From Appendix E, paragraphs E.3 and E.4.2.1 of Appendix E.

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I rys = 38 ksi + 10 ksi = 48 ksi I r ( x ) = 48 ksi Step 3 – Determine the material properties; yield stress, tensile strength and fracture toughness. Material properties for the plate containing the flaw are not available; therefore, the specified minimum specified yield and tensile stress are used. Based on the material specification and grade, the material fracture toughness is established using the low-bound curve in Appendix F, paragraph F.4.4.


Not for Resale


I uts = 70 ksi I ys = 38 ksi Tref = 30° F

( see Step 4 of the Level 1 Assessment )

c

h

K IC = 33.2 + 2.806 exp 0.02 30o F - 30o F + 100o F = 53.9 ksi in Step 4 – Determine the crack-like flaw dimensions from inspection data.

a = 0.20" 2c = 3.2" Step 5 – Modify the primary stress, material fracture toughness, and flaw size using Partial Safety Factors. Based on a risk assessment, it was decided that the most appropriate probability of failure to use in the FFS assessment would be minimum yield stress ratio,

p f = 10-3 . The mean fracture toughness to specified

Rky , is required to determine the Partial Safety Factors. Using the mean Kmat K IC

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information in Notes 5 and 6 of Table 9.2 (Note that sigma=1 is used in calculating the ratio):

DT = T - Tref = 30o F - 30o F = 0o F mean Kmat K IC

K

mean mat

Rky =

= sigma =1

10 . . = 163 0.61401

b g

. K IC = 163 . 53.9 = 87.9 ksi in = 163 87.9 ksi in = 2.3 in 38 ksi

g i b R|ba = 0.20"g ³ 0.20"U| R| PSF = 15. U| . S|COV = 010 V| Þ S| PSF = 10. V| TR = 19. W T PSF = 10. W

From Table 9.2, with

dR

ky

= 2.3 > Rc = 19 . , the Partial Safety Factors are: s

s

c

k

a

The primary stress, fracture toughness, and flaw size are factored by the Partial Safety Factors as follows:

b gb g P = b0 psi gb15 . g = 0 psi K = d87.9 ksi in ib10 . g = 87.9 ksi a = b0.20"gb10 . g = 0.20" Pm = 14259 psi 15 . = 21387 psi b

mat

in

Step 6 – Compute the reference stress for the primary stress. From Appendix C, Table C.1, the flaw geometry, component geometry, and loading condition correspond to RCSCLE2. The reference stress solution for RCSCLE2 is provided in Appendix D, paragraph D.5.10.


Not for Resale


a = 0.20" 3.2" = 1.6" 2 t = 1.0" Ri = 60" c=

b g = 0.8397 60" b0.2"g L 102 . + 0.4411b0.8397g + 0.006124b0.8397g O P M bl g = M . c10 hb0.8397g PQ MN1.0 + 0.02642b0.8397g + 1533 1 M = . = 1026 0.20" I 0.20" F 1 I F 1- G J H 10. " JK + 10. " GH 1144 . K 0 + {b0g + 9 b1.026gb21387 psi g } = 21943 psi s = la =

1818 . 1.6"

2

t

a

4

2

-6

4

0.5

. = 1144

NS s

P ref

3

Step 7 – Compute the Load Ratio (Lr) or abscissa of the FAD.

s ys = 38 ksi Lr =

21943 psi = 0.5774 38000 psi P

Step 8 – Compute K1 - . From Appendix C, Table C.1, the flaw geometry, component geometry, and loading condition correspond to KCSCLE2. The reference stress solution for KCSCLE2 is provided in Appendix C, paragraph C.5.11. Note that because the applied loading is a membrane stress, only the data required to evaluate the G0 influence coefficient is required to compute the stress intensity factor. The flaw ratios and parameters to determine the

R| A R| R = 60" = 60 U| | A || ct 161. "" || || A S| a = 0.2" = 8 V| Þ S| A || a = 0.2" = 0.2|| || A T t 10. " W | A |T A

0, 0

1, 0 2 ,0 3, 0 4 ,0

5, 0 6, 0

G0 influence coefficient from Table C.11 are:

U| = 1.256757 | = 1.047563 | | = -3.69639 V = 2.838158 | | = -0.26624| | = -0.39326|W = 0.414027

The influence coefficients required for the assessment are: At the base of the flaw


j = 90o :

Not for Resale

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2 0.5

2


j = 900

FG p IJ Þ b = 2 FG p IJ = 1 Þ G = 1.2006 H 2K p H 2K 0

At the edge of the flaw

j = 00 Þ b =

j = 0o :

bg

2 0 = 0 Þ G0 = 0.414027 p

The stress intensity factors are:

F aI Q = 10 . + 1464 . G J H cK

1.65

At the base of the flaw

K1P = G0I 0

1.65

= 1047 .

j = 90o :

b

gb

Fa = 12006 . 21387 . ksi Q


K1P = G0I 0

F 0.2"IJ = 1.0 + 1464 . G H 16. " K

b0.2"g = 19.89 ksi g F1047 .

in

j = 0o :

b

gb

Fa = 0.414027 21387 . ksi Q

b0.2"g = 6.86 ksi g F1047 .

Step 9 – Compute the reference stress for secondary stresses. Note that

in

SR I ref used in this

{b g

b

gb

g}

2 0.5

3

= 49248 psi

Step 10 – Compute the secondary stress reduction factor. Note that based on the maximum primary stress from Step 2.


--``````-`-`,,`,,`,`,,`---

SR = I ref

2

0 + 0 + 9 1026 . 48000 psi

Not for Resale

P I ref used in this calculation is

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r

calculation is based on the residual stress ( I ys ) from Step 2.


P I ref =

{b g

b

2

gb

0 + 0 + 9 1026 25289 psi .

g}

2 0.5

3

= 25946 psi

I ys = 38000 psi I uts = 70000 psi 38000 + 70000 If = = 54000 psi 2 SR Since I ref = 49248 psi > I ys = 38000 psi , then

d

i d

LMRS NT

S srf = min 1.4 -

i

UV OP W Q

25946 psi , 10 . = 0.92 54000 psi

SR

Step 11 – Compute K1 . Details regarding the calculation of the stress intensity factor are provided --``````-`-`,,`,,`,`,,`---

in Step 8. Note that

S srf = 0.92 computed in Step 10 is applied to the secondary membrane stress

in this calculation. The stress intensity factors are:

F aI Q = 10 . + 1464 . G J H cK

1.65


K1SR = G0I 0

1.65

j = 90o :

b

gb

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

|RS L |T L

P r

SR r

b

gb

Fa = 0.414027 0.92 × 48 ksi Q

b g

49248 psi 0.92 = 1192 . 38000 psi

|UV Þ RSO = 0.094UV |W TB = 0.562 W = 1192 .

= 0.5774

and,


b0.2"g = 411. ksi g F1047 .

in

j = 0o :

Step 12 – Compute the plasticity interaction factor

LSR r =

= 1047 .

Fa = 12006 . 0.92 × 48 ksi Q


K1SR = G0I 0

F 0.2"IJ = 1.0 + 1464 . G H 16. " K

Not for Resale

b0.2"g = 14.2 ksi g F1047 .

in


0.094 F = 10 . + = 117 . 0.562 Fo Since

c

h

0 < LSR . £ 4.0 , then F o = 10 . and F = 117 . r = 1192

Step 13 – Determine toughness ratio or ordinate of the FAD assessment point.

Kr =

b g

19.89 ksi in + 117 . 411 . ksi in 87.9 ksi in


Kr =

j = 90o : = 0.78

j = 0o :

b g

6.86 ksi in + 117 . 14.2 ksi in 87.9 ksi in

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= 0.27

Step 14 – Evaluate the results. Step 14.1 – Determine the cut-off for the Lr-axis of the FAD – since the hardening characteristics of the material are not known, the following value can be used (see Figure 9.20, Note 3):

Lr b max g = 10 . Step 14.2 – Plot the assessment point on the FAD shown in Figure 9.20. Note that since Partial Safety Factors are used in the assessment in Step 5, the full FAD may be used. At the base of the flaw

j = 90o :

e L , K j = b0.58, 0.78g ; the point is inside of the FAD r


j = 0o :

e L , K j = b0.58, 0.27g ; the point is inside the FAD r

r

The Level 2 Assessment Criterion are Satisfied


Not for Resale

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r

SECTION 10 – Assessment Of Components Operating In The Creep Regime

This section is currently being developed by the API CRE Task Group on Fitness-For-Service. When this section is complete, it will be sent to all registered purchasers of API 579. Until this time, questions regarding the contents and completion schedule for this appendix should be submitted to the Manager of the Downstream Segment, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005.


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(Jan, 2000)

SECTION 11 – Assessment Of Fire Damage (Jan, 2000) 11.1

General

11.1.1

Pressure vessels, piping and tanks subject to the extreme heat of a fire can experience visual structural damage, and less apparent degradation of mechanical properties (e.g., decrease in yield strength or fracture toughness) that may make the equipment unsuitable for continued service. It is therefore appropriate that a Fitness-For-Service (FFS) assessment of vessels, piping and tanks exposed to a fire be made to determine their suitability for continued service.

11.1.2

This section provides FFS procedures for pressurized components (i.e. internal and/or external pressure) that were potentially damaged by exposure to the extreme heat of a fire. Typically, this would be due to a fire external to the pressurized component; however, the assessment procedures are also applicable for fires internal to the component. Guidelines are given to assist in the definition of which components require a fitness-for-service evaluation before being returned to service. Some of these guidelines will be helpful in rerating components that have been judged to have experienced changes in mechanical properties.

11.1.3

The FFS procedures in this section can also be used to evaluate components subject to process upset which result in temperature excursions.

11.1.4

If the results of the fitness-for-service evaluation indicate that the equipment is not suitable for current design conditions, either:

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·

A new MAWP (or tank fill height), maximum design temperature, and/or minimum design metal temperature can be established using the appropriate evaluation procedures contained in other sections of this recommended practice.

·

Defective sections of the equipment can be repaired/replaced.

·

The equipment can be retired from service.

11.1.5

A flow chart for the assessment procedure for components subject to fire damage is shown in Figure 11.1.

11.2


11.2.1

The procedures in this section are used to identify and evaluate components subject to fire damage. This potential damage includes changes in mechanical properties (e.g.-spheroidization of carbon steel, grain growth and a decrease in toughness), decreases in corrosion resistance (e.g.sensitization of austenitic stainless steels) and, distortion and cracking of pressure boundary components.

11.2.2

The pressurized equipment covered in this section includes all pressure boundary components of pressure vessels, piping, and shell courses of storage tanks. Fitness-for-service procedures for tank fixed and floating roofs, and bottom tank plates are covered in Section 2 of API-653.

11.2.3

Structural steel, ladders and platforms are typically distorted during a fire. Some guidelines in this section, such as estimating tensile strength from hardness testing, can be helpful in making repair and replacement decisions for these structures. However, this section does not address such nonpressure containing structures. The distortion of equipment extremities such as platforms does not necessarily mean that the pressure envelope of the equipment is no longer suitable for continued service. The process fluid inside the vessel may have served as a cooling medium during the fire, thus preserving the mechanical properties of the equipment.

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11-1 Not for Resale


11.2.4

Instrumentation and wiring are commonly damaged during a fire. Such equipment requires a detailed analysis of the potential damage before pressure vessels, piping and other equipment are returned to service. With the exception of pressurized components such as piping attached to instruments, assessment of instrumentation and wiring are not addressed in this section.

11.3

Data Requirements

11.3.1


11.3.2

Maintenance And Operational History An overview of the maintenance and operational history required for an assessment is provided in Section 2, paragraph 2.3.2. Required Data/Measurements For A FFS Assessment

11.3.3.1 Evidence of fire damage may be collected both during the course of a fire and after the fire is extinguished. The objective of collecting such evidence is twofold: (a) To determine why the fire occurred, and (b) to determine the nature and extent of damage so that equipment may be returned to service. a.

Since an accidental fire is a random event, extensive data collection during an accidental fire is seldom possible. However, alert observers can learn significant facts about fires in progress, and occasionally a fire that burns for several hours allows a certain amount of remote measurement and documentation.

b.

Industrial plant fires take many different forms. Some are confined to a rather small area. Others are widespread yet patchy due to flammable material released under pressure into ditches, trenches, or roadways. In the latter case, fire damage may be severe along the channels into which fuel was spilled, while equipment between channels is less affected. If an incident begins with an explosion, fragmentation or blast, the resulting damage may produce multiple fuel sources and several essentially independent fires. The investigator must be alert to such possible variations when studying the fire scene.

c.

Although each fire investigation is unique, data are normally collected to determine: ·

The temperature extremes to which various components were subjected

·

The nature of the fuel

·

The location of ignition source or sources

·

The time at temperature

·

The cooling rate

d.

Of the items in (c.) above, the first three are the easiest to obtain. The time at temperature can often be deduced from logbooks and fire department records. An estimate of the cooling rate is the most difficult to obtain and may not be possible.

e.

Where circumstances and manpower permit, a videotape of a fire in progress can be an extremely useful tool for analyzing the nature and extent of fire damage. A fire in progress is always dangerous and may be unpredictable. Videotaping a fire in progress should not be attempted without the understanding and approval of the fire department in control of the scene, and all applicable site safety procedures should be followed. However, when videotape


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11.3.3


evidence is available, it may be possible to deduce the nature of the fuel, the fire’s progression from its ignition source, and temperature extremes from visual evidence on the tape. f.

Initial damage investigation and assessment should be thoroughly documented with photographs for later study. Memory of plant personnel can be inaccurate in recalling many details. Videotaping offers an excellent technique for recording the overview of the firedamaged area.

11.3.3.2 A record of the fire incident including, but not limited to, the following should be developed to help identify the equipment that needs to be evaluated before being returned to service. ·

A plot plan of the area showing the location of the equipment.

·

The locations of the primary and other fire sources, and wind direction during the incident shown on the plot plan.

·

The location, flow directions and the type of water used by fire monitors and hoses to control the incident.

·

The length of time of the incident.

·

The nature of the reactants (fuel) producing the flame in order to estimate flame temperatures and the compatibility of the reactants with the equipment.

·

The temperature, pressure and relief valve release data for the equipment prior to and during the incident – note that in many instances computer storage of process operating conditions are retained for a limited time; this information should be retrieved as soon as possible.

a.

A Heat Exposure Zone is established for a component based on the maximum exposure temperature incurred during the fire. This temperature is typically established after the fire is out, and must be determined based on field observations and a knowledge of the degradation associated with fire-damaged equipment. The concept of a Heat Exposure Zone implies a physical region that was exposed to a certain temperature. This generally is a helpful method to quickly screen equipment, however, adjacent components may have been exposed to varying levels of heat and thereby suffered varying damage, because one of the components was insulated or fireproofed while the other was not. Ultimately, the goal is to establish the heat exposure zone for the pressure boundary. In the case of completely insulated or fireproofed equipment, this may require a second evaluation pass to re-classify the pressure boundary heat exposure zone downward from that initially determined based on the condition of unprotected components.

b.

A wide range of temperature-indicating observations may be used to categorize fire-damaged equipment into appropriate Heat Exposure Zones. The basis for these observations is knowledge of the changes of state that take place in materials as temperature increases. Oxidation of polymers and metals, scale formation on metals, melting points, boiling points, and solid-state phase changes are all possible temperature indicators if properly interpreted. A knowledge of the forms of degradation, and an overview of observations associated with fire damage that can be used to deduce the temperature to which a component was exposed to are shown in Tables 11.2 through 11.5. Additional information pertaining to temperature indications that can be used to establish a Heat Exposure Zone are provided in Table 11.6. Temperature indicators based on a knowledge of the damage a component exposed to a fire has sustained are provided in Table 11.7.

c.

The highest Heat Exposure Zone for a component exposed to more than one fire zone shall be used in the assessment. The component should be assigned to the next most severe fire zone if the information gathered during the investigation is insufficient to adequately categorize a component. As described in paragraph 11.3.3.3.a., adjacent components may have been exposed to varying degrees of heat because of differences in insulation and fireproofing. Although a component may have been geographically close to the fire source, it may be


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11.3.3.3 A Heat Exposure Zone will need to be defined for each pressure vessel, tank and piping circuit subject to fire damage in order to determine the components that will require an assessment. A description of the Heat Exposure Zones is provided in Table 11.1.


relatively unaffected if it was insulated. Nonetheless, caution must be exercised before categorizing equipment. For example, it may not be appropriate to categorize all parts of a insulated vessel completely into a low Heat Exposure Zone, since flanges, piping, and other appurtenances, which are not insulated may have suffered damage and therefore should be assigned to a higher Heat Exposure Zone. The default should be to categorize these uninsulated components similar to adjacent uninsulated components. d.

A knowledge of the source of the fire can assist in the determination of a Heat Exposure Zone. The damage from fire and its extreme heat usually extends outward from the fuel source and upward (see Figures 11.2 and 11.3). Exceptions are in the cases of high-pressure fuel sources, where a flame jet or torch can be highly directional.

e.

Temperatures associated with the fire can also be determined directly from infrared surveys or optical pyrometer readings taken during the course of the fire. More typically, such instruments will not be available during the fire, and temperature extremes must be estimated after the fire is out. If videotape is available, temperatures may be estimated based on radiation colors observed on steel surfaces during the fire. Radiation colors corresponding to a range of different temperatures are shown in Table 11.8.

f.

Knowledge of the nature of the fuel in a fire and the ignition source may be useful in establishing a Heat Exposure Zone. 1.

If the source of the fire is known, the fuel being consumed will often be obvious based on known flammable products in the area. However, this is not always the case, and observers on the scene may be able to characterize the fuel based on the color of the smoke (see Table 11.9).

2.

Ignition sources in refinery and petrochemical plants include electrical sparks, open flames, and exposed hot surfaces. Flammable mixtures of organic vapors and air typically exhibit an autoignition temperature above which the mixture will ignite without a spark or additional energy source. For example, a hot surface with a temperature in excess of the autoignition temperature could be an ignition source. Autoignition temperatures for fuels are shown in Tables 11.10 and 11.11, respectively.

·

Softening, sagging (plastic deformation) and over aging of aluminum alloys

·

Softening and sagging (plastic deformation) of copper alloys

·

Hardening and/or tempering of heat treatable steels (e.g. ASTM A193 B7 stud bolts)

·

Grain growth, softening, sagging (plastic deformation), hardening or loss of toughness of carbon and low alloy steels, e.g., loss of a normalized microstructure

·

Short term creep and creep rupture

·

Spheroidization of carbon steels

·

Stress relieving of stainless steels and nickel alloys (e.g. resulting in tube roll leaks in heat exchangers)

·

Sensitization of stainless steels

·

Halide contamination of austenitic stainless steel or other austenitic alloy surfaces, especially under wet insulation or if salt water is used for fire fighting

·

Liquid metal corrosion or cracking, such as, molten zinc dripping on austenitic stainless steel piping and causing liquid metal cracking

·

Incipient melting of alloys (e.g. localized melting of low melting point segregation and eutectics),

·

Excessive oxidation of metals leading to wall loss

·

Deterioration of gaskets and valve packing --``````-`-`,,`,,`,`,,`---


Not for Resale

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11.3.3.4 A specific inspection plan should be created for each component subject to fire damage, based on first assigning a Heat Exposure Zone (see paragraph 11.3.3.3) and then taking into account the following forms of degradation associated with heat exposure as listed in Table 11.6:


·

Damage to coating systems, especially coatings applied for under insulation corrosion protection

·

High residual stresses due to distortion, restraint, and loss of supports

·

Cracking of metals due to distortion and restraint, for example, restraint of cooler internal components cracking attachment welds

·

Embrittlement of some grades of steels when cooled through critical temperature ranges

·

Formation of a cast iron structure due to carburization and localized melting of the carbon rich alloy (most likely in furnace tubes processing hydrocarbons)

·

Diametrical and circumferential variations of cylindrical vessels

·

Dimension profiles of vertical and horizontal vessels

·

Straightness of shell and piping sections

·

Nozzle orientations

·

Vertical plumb measurements

·

Hardness tests of the base metal and welds

·

Removal of coupons for mechanical testing

·

Wall thickness measurements of pressure containing components

·

In-situ metallography and microstructure replication

·

Surface crack detection techniques such as magnetic particle and dye penetrant

·

Surface condition of equipment with respect to scale formation, melting, coating damage, insulation condition, and weather barrier construction and condition

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11.3.3.5 Collection of the following data and measurements should be considered for components assigned to a Heat Exposure Zone where mechanical property changes and dimensional changes can occur:

11.3.3.6 Components subjected to temperatures at which changes in mechanical properties may be experienced should be evaluated to determine if the material has retained the necessary strength and toughness properties stipulated in the original construction code. The effects of temperature on mechanical properties of various metals is included in Table 11.6. If mechanical properties have been degraded, the actual strength and toughness properties need to be determined in order to rerate the affected component. In this context, components include: ·

Pressure Vessels – Shell sections, heads, nozzle necks, flanges, vessel supports

·

Piping Systems – Pipe sections, elbows, tees, reducers, flanges and piping supports

·

Tankage – Tank shell courses and nozzle necks

b.

Hardness testing is a helpful aid in assessing the loss of tensile strength in carbon and low alloy steels, and to a lessor extent changes in other material properties such as toughness and ductility. For example, hardness can be measured in areas of a carbon steel pressure vessel known to be in Heat Exposure Zones I through IV (see paragraph 11.3.3.3). These results can be compared to hardness measurements obtained in areas suspected of being exposed to higher temperatures, Zones V and VI.

c.

In-situ metallography or replication can be performed on surfaces of components having hardness values that are out of specification, either high or low, or if a certain microstructure is required, such as having a normalized microstructure in carbon steel equipment for minimum metal temperature toughness requirements. In-situ metallography or replication should also be performed at areas of the pressure component away from the suspected heat affected sample locations, if possible, to compare these microstructures to the fire exposed microstructures. Interpretation of the microstructures requires an experienced metallurgical engineer.

d.

In-situ metallography can be helpful in assessing non-carbon steel components if metallographic sample locations can be located both inside the fire affected zone, and in a


Not for Resale

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a.


lower temperature zone of the same pressurized component. Comparison of microstructure will be helpful in assessing degradation. In-situ metallography can also be helpful in assessing sensitized austenitic stainless steel or other alloy microstructures. --``````-`-`,,`,,`,`,,`---

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11.3.4

e.

Hardness testing can sometimes give an indication of a loss of toughness; however, since there is no direct correlation between hardness and toughness, this is not always reliable. Softening due to tempering below the lower critical temperature (approximately 718°C (1325°F) for carbon steels) usually results in only small changes in toughness for most steels used in the construction of pressure vessels, piping, tankage, and structural components. Therefore, heat exposure to temperatures below this limit is not normally of a concern. By contrast, heating above the lower critical temperature results in a phase transformations that can dramatically affect toughness. Depending on the time of the heat exposure, the material temperature level, and in particular the cooling rate, the material may either have the same or a different hardness as the component in the pre-heat exposure condition. In such cases, degradation of toughness cannot be inferred from the results of hardness testing. Hardness testing has a better chance of detecting this condition if it is done in multiple areas on a component (i.e. a grid pattern). Areas heated above the lower critical temperature will often be bounded by areas of tempering that show low hardness, so an anomalous hardness pattern will result. In this case, field metallography, removal of samples for mechanical testing, or other methods may be required to estimate the toughness.

f.

If hardness readings and in-situ field metallography are inconclusive with respect to determining whether carbon steel or low alloy steel equipment has experienced a decrease in mechanical properties, then consideration should be given to removing a coupon from the wall of the component for destructive evaluation. Destructive evaluation should include tensile tests, toughness tests or Charpy impact tests, and metallographic examination of the fire side surfaces and cross sectional planes.

Recommendations For Inspection Techniques And Sizing Requirements

11.3.4.1 Shell dimension profiles should be taken for equipment subject to fire damage. Dimensional profiles of vertical vessels can be obtained by dropping a reference vertical line from the top of the vessel, and measuring the bulges and dents of the shell sections relative to this vertical line at appropriate increments. An example on how to measure a profile for a vertical vessel is illustrated in Figures 11.4 and 11.5. Dimension profiles of horizontal drums can be taken in a similar way using a horizontal level. Additional methods to determine shell distortions using field measurement techniques are covered in Section 8. 11.3.4.2 Hardness measurements should be taken on all equipment subject to fire damage in order to evaluate the post fire-damaged strength of the material (see paragraph 11.3.3.6b). When making field hardness measurements the removal of about 0.5 mm (0.02 inches) of metal surface is recommended in the area of the reading to remove oxide scale and surface carburization or decarburization. 11.3.4.3 Other inspection techniques, such as magnetic particle testing and dye penetrant testing may be needed based on the observed or plausible deterioration mode (see paragraph 11.3.3.4). 11.3.4.4 Non-destructive material examination by means of replication is a metallographic examination method which exposes (or replicates) the microstructure of the surface material (see paragraph 11.3.3.6.c). a.

Method – Portable equipment is typically used for the examination. Surface preparation is conducted by progressive grinding to remove scale, surface carburization, and other surface material. After final grinding, the surface must be polished in the following ways; electrolytic polishing or mechanical polishing using polishing discs and diamond paste (particle size of 1m to 7m). After polishing, the surface must be cleaned thoroughly and dried. It is particularly important to thoroughly clean the surface after electropolishing to prevent corrosion on the newly polished surface from the aggressive electrolyte. A strip of acetate tape is softened in a


Not for Resale


solvent and pressed against the polished surface. Once the tape dries it is removed and can be coated with carbon or gold and can be viewed for features. b.

Application – The replication method can be used for the examination of all metallic materials. Replication is typically used for evaluating microstructure of the materials and determination of crack type. This method is restricted to relatively small areas for examination and evaluation as a follow-up to other detection methods such as magnetic particle or eddy current. Creep cracks can be identified at a much earlier stage using the replication method than with other NDE methods. This early detection allows time to plan repairs and/or replacements thus avoiding unscheduled repairs.

c.

Flaw Detection – Because each type of crack has specific characteristics, a damage type determination is usually possible with this method. If further evaluation is desired for metallurgical and microstructural components (such as carbides, cavities, etc.), replicas can be coated with a reflective, conductive material and studied in a scanning electron microscope.

d.

Limitations – The replication method can only be used on surfaces that are readily accessible. The surface conditions must be exposed, dry, and at ambient temperature, between about (-18°C to 32°C (0°F to 90°F)).

11.3.4.5 Leak testing of mechanical equipment subject to fire-damage in Heat Exposure Zones IV and higher should be considered prior to returning the equipment to service. The types of equipment includes but is not limited to: ·

Flanged connections

·

Threaded connections which are not seal-welded

·

Valves (i.e. both shell and closure test per API 598 should be considered)

·

Gaskets and packing

·

Heat exchanger tube sheet rolled joints

11.4


11.4.1

Overview An overview of the assessment levels is provided in Figure 11.1. The Level 1 assessment procedure is a screening criteria where the acceptability for continued service is based on the assigned Heat Exposure Zone and metallurgy of the component being evaluated. The screening criteria are conservative, and calculations are not required to establish suitability for continued service. The Level 2 assessment rules provide a better estimate of the structural integrity of a component by providing a means to evaluate the material strength of a fire damaged component. Assessment procedures are included for rerating including evaluation methods for flaws and damage incurred during the fire (e.g. local thin areas, crack-like flaws and shell distortions). These assessment procedures are typically applied to components subject to a Heat Exposure Zone of V and higher, or when dimensional changes are noted during a visual inspection. The Level 3 Assessment procedures can be utilized if the simplified stress analysis techniques and the current material strength of the component established using the Level 2 Assessment procedures result in an unacceptable evaluation. Detailed stress analysis techniques and in-situ field metallography or removal of material samples and testing may be utilized in a Level 3 assessment to remove some of the conservatism in the evaluation.

11.4.2

Level 1 Assessment

11.4.2.1 The objective of this Level 1 assessment is to gather and document the observations and data used to justify assigning a component to a Heat Exposure Zone. Components assigned to a Heat Exposure Zone in which mechanical properties or component dimensions have not changed, and are thus suitable for continued operation without the need for more in depth evaluation. The Heat


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Exposure Zone levels for the materials of construction that are acceptable per a Level 1 assessment are shown in Table 11.12. 11.4.2.2 Gasket inspections and leak checking of flange joints should be included in a start up check list for components passing a Level 1 assessment. 11.4.2.3 Protective coating damage can occur for some components that satisfy the Level I acceptance criteria. Although protective coatings are not considered in the fitness-for-service assessment, the condition of coatings applied to the components for under insulation corrosion protection should be considered when listing remedial action prior to start-up of the accepted equipment. Furthermore, if an internal coating is present to prevent degradation (e.g. corrosion and stress corrosion cracking), the integrity of the coating should be verified, particularly if an earlier FFS evaluation concluded that the coating was necessary. 11.4.2.4 If the component does not meet the Level 1 Assessment requirements, then the following, or combinations thereof, can be considered:

11.4.3

·

Repair, replace or retire the component, and/or

·


Level 2 Assessment

11.4.3.1 Pressurized components which do not pass a Level 1 Assessment can be evaluated for continued service using a Level 2 Assessment. This evaluation should consider the degradation modes described in paragraph 11.3.3.4. 11.4.3.2 An overview of the Level 2 assessment procedure is provided in Figure 11.6.

b.

The first step in the assessment is to conduct dimensional checks on pressure components. The dimensional checks generally take the following forms; overall out-of-plumb or sagging of a component(s) and localized shell distortion. As listed below, the forms of overall out-ofplumbness or sagging are dependent on equipment type whereas local shell distortions such as bulges are common for all equipment types: 1.

Vertical Pressure Vessels – Determine the out-of-plumbness from the vertical plane. The eccentricity of the vessel weight caused by out-of-plumbness results in additional bending stresses in the vessel and increased loads on anchor bolts.

2.

Horizontal Pressure Vessels – Determine the sag measured from the horizontal plane. Severe sagging may result in an increase of the localized stress at the saddle support locations.

3.

Storage Spheres – Determine the out-of-plumbness of the vertical support legs. Out-ofplumbness of the support legs may result in an increase of the localized stress at the leg-to-shell attachment locations.

4.

Atmospheric Storage Tanks – Determine the out-of-plumbness of the tank shell. Out-ofplumbness may result in higher shell stresses and out-of-roundness of the shell which may result in operational problems (e.g. binding of an internal or external floating roof)

5.

Piping Systems – Determine out-of-plumbness from the vertical and sag from the horizontal. Overall distortions of a piping configuration may result in increased stresses.

Hardness testing is used to determine the approximate tensile strength of a fire exposed component. The information is subsequently used with the rerating procedures in this document to establish an acceptable MAWP. Further evaluation is required to assess specific damage from localized thinning, shell distortions and creep.

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a.


c.

Components which experience dimensional changes provide insight into the additional evaluations that are required. This insight is based on the observation that carbon steel equipment does not experience a significant reduction in short term high temperature strength properties which would result in a dimension change (i.e. out-of-plumb, sagging or bulging) until a temperature in excess of 427°C (800°F) is reached.

11.4.3.3 The following procedure can be used to evaluate a pressurized component constructed of carbon or low alloy steels for continued operation if the mechanical strength properties are suspected to have been degraded by the fire exposure. a.

Step 1 – If the components is fabricated from carbon and/or low alloy steels, then perform a hardness test on the component and convert the resulting hardness value into an estimated ultimate tensile strength using Table F.1 of Appendix F. If the component is fabricated from high alloy of nickel base materials, an alternative method is usually required to determine an acceptable stress level to for a fitness-for-service assessment. Additional materials evaluation may need to be performed depending on the observed severity of damage and future service requirements. This evaluation may include in-situ field metallography to determine the condition of a component (see paragraph 11.3.3.6.c). Guidelines for this type of evaluation are provided in Figure 11.7.

b.

Step 2 – Determine an allowable stress for the fire damaged component based upon the ultimate tensile stress determined in (a) using the following formula:

LMR MNST

ht Safd = min Cism Suts

FG S HS

aT aA

IJ UV, KW

SaT

OP PQ

(11.1)

where, =

In-service margin, 0.25 is recommended,

=

Allowable stress for a fire damaged material (MPa:psi),

SaA

=

SaT

=

The allowable stress of the original design code or standard at the ambient temperature when the hardness tests are taken (MPa:psi), The allowable stress of the original design code or standard at the specified design temperature (MPa:psi), and

ht Suts

=

Ultimate tensile strength based on a hardness test from Step 1 (MPa:psi).

c.

Step 3 – Perform the necessary MAWP calculations using the value of allowable stress derived in Step 2 and equations in Appendix A.

d.

Step 4 – If additional forms of damage are present, the MAWP should be further modified using the appropriate sections in this document:

e.

·

General thinning – Section 4

·

Local thinning – Section 5

·

Pitting – Section 6

·

Blisters and laminations – Section 7

·

Shell distortions including out-of-roundness and bulges – Section 8

·

Crack-like flaws – Section 9

Step 5 – Evaluate creep damage of the component using Section 10. Normally, components subject to high temperatures during a fire do not experience significant creep damage because the time at temperature is short and significant creep strains and associated damage can not accumulate.

--``````-`-`,,`,,`,`,,`---


Not for Resale

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Cism Safd


11.4.3.4 Other effects that should be considered in the assessment include:

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a.

Internal attachments that may have been subject to large thermal gradients during a fire should be inspected for cracks on the plate surface and at the attachment weld. Large thermal gradients between shell and internal components can occur because of process cooling effects. This inspection is especially important for internal components fabricated from materials with a coefficient of thermal expansion significantly different from that of the shell (e.g. austenitic stainless steel internal attachment support welded to a carbon steel shell).

b.

Pressure components being rerated because of the reduction in mechanical properties should be assessed for possible changes in corrosion resistance in the service which the vessel will be exposed (The future corrosion allowance may need to be increased).

c.

Local areas which accumulate liquid (or ponding) may result from out-of-plumbness, sagging and localized shell distortions of components. Liquid in these areas may result in accelerated corrosion or operational problems.

11.4.3.5 The beneficial effects of PWHT (stress relief) may have been compromised because of heat exposure. Pressurized components that were subject to PWHT in accordance with the original construction code (i.e. based on shell thickness) or for service resistance (e.g. carbon steel in caustic SCC and wet H2S cracking services) need to be evaluated to ascertain whether the benefits of the PWHT have been compromised: a.

For carbon steel, the issue is usually one of relief of residual stresses, but sometimes also for relieving hard zones in the microstructure or for improved toughness. Distortion and/or quenching in fire fighting efforts can leave the component with higher residual stresses that could lead to service related cracking.

b.

For low alloy steels, the issue is usually one of retaining mechanical properties. The original PWHT was conducted to temper a hard microstructure and/or to improve toughness. Heat exposure can lead to a very hard/brittle microstructure in the component, which if left in place can lead to premature failure.

11.4.3.6 If the component does not meet the Level 2 Assessment requirements, then the following, or combinations thereof, can be considered:

11.4.4

·

Repair, replace or retire the component,

·

Adjust the FCA by applying remediation techniques (see Section 4, paragraph 4.6),

·

Adjust the weld joint efficiency factor, E, by conducting additional examination and repeat the assessment (see Section 4, paragraph 4.4.2.2.c), and/or

·


Level 3 Assessment

11.4.4.1 A Level 3 assessment of a fire damaged component can be performed if the component does not satisfy the Level 1 or Level 2 Assessment criteria. A Level 3 assessment is usually performed for the following reasons: a.

The simplified stress analysis techniques associated with a Level 2 Assessment cannot be used to adequately represent the current condition of the component. In many cases, the component may be severely deformed or shell distortions may be located in the region of a major structural discontinuity. In these cases, the stress analysis techniques discussed in Appendix B can be utilized in the evaluation.

b.

The current strength of the material established from a hardness test may be conservative resulting in a lowering of the MAWP. In-situ field metallography (see paragraph 11.3.3.6) or

--``````-`-`,,`,,`,`,,`---


Not for Resale


testing on material samples can be performed to develop a better estimate of the strength of the material.

--``````-`-`,,`,,`,`,,`---

11.5


11.5.1

The applicable sections of this document can be used to assess remaining life for the damage mechanisms cited in paragraph 11.4.3.3.d.

11.5.2

Creep damage and the associated remaining life can be calculated using the assessment procedures of Section 10.

11.6

Remediation

11.6.1

Remediation techniques for the damage mechanisms cited in paragraph 11.4.3.3.d are covered in the applicable sections of this document.

11.6.2

If the component is badly distorted or sagged, supports can be added to help reduce stresses associated with the deformed condition. For example, the increased bending stress resulting from out-of-plumbness of a process tower may be acceptable if guy wires or some other form of support is introduced to minimize the bending stress associated with wind loads. Note that added supports must be designed to accommodate thermal expansion of the equipment.

11.7

In-Service Monitoring Recommendations for in-service monitoring for the damage mechanisms cited in paragraph 11.4.3.3.d are covered in the applicable sections of this document.

11.8

Documentation

11.8.1

The documentation of the FFS Assessment shall include the information cited in Section 2, paragraph 2.8.

11.8.2

Information used to assign the Heat Exposure Zones, measurements to quantify component distortions, mechanical property changes, calculations for the MAWP, and remaining life calculations should be summarized and documented.

11.8.3

All documentation including the calculations used to determine the fitness-for-service of a pressurized component should be kept with the inspection records for the component or piece of equipment in the owner-user inspection department.

11.9

References

11.9.1

ASM, “Powder Metallurgy,” Metals Handbook, Volume 7, 8th Edition, American Society of Materials, p 133, 1972

11.9.2

ASM, “Properties and Selection: Iron and Steels,” Metals Handbook, Volume 1, 9th Edition, American Society of Materials, p 204, 1978


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11.4.4.2 A Level 3 assessment is required if, at a future time, an increase in the MAWP (or temperature) beyond the current MAWP (before the fire) of a known fire-damaged component is required. A material sample should be tested to establish an acceptable allowable stress value for use in the rerating calculations. Estimates of changes in mechanical properties based only on hardness measurements and microstructure should not be used to increase the allowable stress value of a component subject to fire damage.

11.9.3

Hau, J. L., "Assessment Of Fire Damage To Pressure Vessels In A Refinery Unit", Corrosion, pp 420437, Vol. 49, No.5, 1993

11.9.4

MTI, “Guidelines for Assessing Fire and Explosion Damage,” MTI Publication No. 30, Materials Technology Institute of the Chemical Process Industries, Inc., 1990.

11.9.5

MTI, “Guidelines for Preventing Stress-Corrosion Cracking in the Chemical Process Industries,” MTI Publication No. 15, Materials Technology Institute of the Chemical Process Industries, Inc., 1990.

11.9.6

Treseder, ed., Corrosion Engineer's Reference Book, National Association of Corrosion Engineers, Houston, TX, p. 177, 1980.

11.10

Tables and Figures

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Table 11.1 Description Of Heat Exposure Zones to Evaluate Fire Damage (1) Heat Exposure Zone

Description

Thermal Effects On Materials In The Fire Zone

I

Ambient temperature during fire event, no fire exposure

---

II

Ambient to 66°C (150 F); smoke and water exposure

III

66°C to 204°C (150 F to 400 F); light heat exposure

IV

> 204°C to 427°C (>400 F to 800 F); moderate heat exposure

V

> 427°C to 732°C (>800 F to 1350 F); heavy heat exposure

VI

> 732°C (>1350 F); severe heat exposure

Notes:

o

o

o

o

o

o

o

o

--Table 11.2 Table 11.3 Table 11.4 Table 11.5

An overview of the damage that is likely to occur in each fire zone is provided in Table 11.6.

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Table 11.2 Guidelines for Observing Fire Damage – Thermal Effects on Materials o o o o Heat Exposure Zone III, 66 C To 204 C (150 F To 400 F) Temperature (1)

Materials of Construction

Forms or Usage

--``````-`-`,,`,,`,`,,`---

°C

°F

93

200

Vinyl coatings (3) (4) (5)

Paints on tanks, structural steel, etc.

149

300

Alkyd coatings (6)

400

750

Inorganic zinc silicate (10)

Paints on tanks, structural steel, etc. Paints on tanks, structural steel, etc.

204

400

Epoxies & polyurethanes (11)

Paints on tanks, structural steel, etc.

190

375

UHMW HD Polyethylene (7)

Pipe

177

350

Elastomers, neoprene (2) (8)

Hose, diaphragms, gaskets

182

360

Lead / tin solder

260

500

Baked phenolic (9)

Electrical equipment connectors Fiberglass mat binder, micarta tank linings

204

400

Acrylic mastic

Weatherproof coating for insulation

Thermal Effects Begins to melt, flow, and bubble; may burn Color change visible; surface crazing Begins to melt, flow, and bubble; may burn Color change visible; blistering and charring Softening and melting Softening, melting; some burning / charring Melts Surface discoloration; blistering "Mud" cracking; charring

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Notes: 1. The temperatures listed in this table are the lower limits of temperature where significant damage is observed. Similar effects may occur at higher temperatures in shorter times 2. Effects of heat on synthetic rubber materials vary greatly due to formation of the particular elastomer and end product. Do not attempt to be too specific based on observations of elastomer condition. 3. The term vinyl can mean two different things when it comes to paint. Solution vinyls are single package paints with polymeric resin dissolved in strong hydrocarbon solvent. The other type of vinyl is similar to latex house paint; these water based paints are typically vinyl acrylic, but they may also be vinyl acetate and other polymer types. 4. Solution vinyl coatings (thermoplastics) have a maximum continuous service temperature of about 60 to 66°C (140 to 150°F) and soften in the 66 to 82°C (150 to 180°F) range; above 93°C (200°F) these coatings will begin to melt and flow, (giving up HCl as a by-product.) They may blister but are generically not good candidates for burning and charring. The significant halogen content stifles burning initially. This will occur with some bubbling which may be a little different than blistering. 5. Vinyl latex paints are also thermoplastic paints but these do not generally contain chlorine or other halogen. Above 93°C (200°F) these materials will begin to melt and flow much like solution vinyls but they burn differently. 6. Alkyds thermoset and as such they have much better temperature resistance than do the vinyls. Alkyds can handle 107 to 121°C (225 to 250°F) (continuously for months or years. A good alkyd can handle 149°C (300°F) for several hours. The first symptoms of heat/oxidation damage would be yellowing and surface crazing. Different colors mean different pigments and color changes could be important.


Not for Resale


--``````-`-`,,`,,`,`,,`---

Notes (Table 11.2 Continued): 7. UHMW and HD polyethylene used as pipe, has a temperature rating of 66 to 71°C (150 to 160°F) depending on commodity and pressure. The softening temperature is about 127°C (260°F); it takes some time at temperatures well above 149°C (300°F) to cause appreciable melting. Consider that HDPE pipe is welded at 204 to 260°C (400 to 500°F), depending on the technique. 8. Neoprene has a dry temperature rating of 149 to 177°C (300 to 350°F) depending on formulation specifics. Flame and heat aging/air oxidation resistance are very good for rubber. Neoprene is a type of chlorinated rubber and so it resists burning. 9. Baked phenolics thermoset, typically bake cured in the 163 to 204°C (325 to 400°F) range. Phenolics are typically red, brown, or black initially, so a color change may be difficult to observe. While this generic class may degrade over a range of temperature, the materials would need to be at temperatures close to 260°C (500°F) before major degradation would be observed. 10. For zinc silicate primers, the silicate binders can handle up to about 538°C (1000°F). However, the metallic zinc pigment can be impacted above the melting point near 399°C (750°F). 11. Epoxies and polyurethanes can typically withstand temperatures to about 149°C (300°F) with no real impact. These paints may begin to blister and/or char once the temperature exceeds 204°C (400°F). As with the alkyd paints, color changes may occur. For example, a common yellow finish color is obtained with hydrated ferric oxide and as you get hot the water of hydration is driven off and the coating starts to turn pink.


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Table 11.3 Guidelines For Observing Fire Damage – Thermal Effects On Materials 0 0 0 0 Heat Exposure Zone IV, >204 C To 427 C (>400 F To 800 F) Temperature (1)

Material of Construction

Forms or Usage

Thermal Effects

--``````-`-`,,`,,`,`,,`---

(°C)

(°F)

204

400

Tempered aluminum alloys

Pipe and tanks of T6 or other temper

Reduced strength (check hardness & elec. Conductivity)

232+

450+

Wood – various

Various

Charring, burns

260

500

Steel – machined or polished

Machinery or instrument parts

Develops blue temper color

271

520

Babbitt(2) -- lead based

Sleeve bearings

Melts

282

540

Copper -- cold drawn, bright annealed

Instrument and condenser tubing

Softens, sags, grain coarsening occurs

330

623

Lead (soft)

Lining in pipe and tanks

Melts

388

730

Zinc/aluminum die casting

Small valve handles and instrument parts

Melts

421

790

Zinc

Galvanized coating for steel structures

Melts

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Notes: 1. The temperatures listed in this table are the lower limits of temperature where significant damage is observed. Similar effects may occur at higher temperatures in shorter times. 2. Trade Name


Not for Resale


Table 11.4 Guidelines For Observing Fire Damage – Thermal Effects On Materials 0 0 0 0 Heat Exposure Zone V, >427 C To 732 C (>800 F To 1350 F) Material of Construction

Forms or Usage

Thermal Effects

(°C)

(°F)

482

900

Quenched and Tempered Steels

Springs, fasteners, 4140, et al., (particularly socket head cap screws)

Tempering to lower strength

510

950

Glass

Light bulbs

Distort and melt

538

1000

18-8 Stainless Steel

Vessels, piping etc.

Sensitized (carbide PPT) and reduced corrosion resistance

593

1100

Steel

Vessels and piping

Thermal distortion and creep, some heat scale

621

1150

Precipitation Hardened Stainless Steel

Machinery and valves

Overages -- reduced strength

649

1200

Steel

Vessels, piping, structures

Rapid oxidation -- thick black scale

657

1215

Aluminum

Tanks, piping, accessories

Melts

695

1285

Glass

Windows

Melts

704

1300

Copper

Tubing, pipe, vessels

Rapid oxidation -- black

710

1310

Glass

Pyrex(2) –pipe, sight glass

Melts

732

1350

Silver Solder

Brazed joints on accessories

Melts (may start at lower temperature)

--``````-`-`,,`,,`,`,,`---

Temperature (1)

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Notes: 1. The temperatures listed in this table are the lower limits of temperature where significant damage is observed. Similar effects may occur at higher temperatures in shorter times. 2. Trade Name


Not for Resale


Table 11.5 Guidelines For Observing Fire Damage – Thermal Effects On Materials 0 0 Heat Exposure Zone VI, >732 C (>1350 F) Temperature (1)(2)

Material of Construction Forms or Usage

Thermal Effects

(°C)

(°F)

760

1400

Steel

Vessels and piping

Iron carbide (cementite) spheroidizes

816

1500

Steel

All forms -- low alloy most susceptible

Austenitizes -- slow cool equals anneal, fast quench turns hard and brittle

904

1660

Zinc

Galvanizing on steel

Oxidizes to white powder or vaporizes

982

1800

Cellular glass

Thermal insulation

Melts

1093

2000

Copper

Tubing, pipe etc.

Melts

1307

2385

Alloy C-276

Vessels, pipe

Melts

1399

2550

316 SS – cast

Pumps, valves

Melts

1454

2650

316 SS – wrought

Vessels, pipe

Melts

1516

2760

Steel

Various

Melts

1685

3065

Titanium

Vessels, pipe etc.

Melts

Notes: 1. The temperatures shown are those in which significant damage begins to occur to the material of construction listed. 2. The temperatures listed in this table are the lower temperatures where heat effects begin. Similar effects may occur at higher temperatures in shorter times.

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Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 11.6 Guidelines For Assessing Fire Damage Effects Description Of The Types Of Damage That May Occur In The Heat Exposure Zone Categories Heat Exposure Zone

Temperature Range °C (°F)

Heat/Temperature Effects

Observations and Conclusions

ZONE I No evidence of heat, flame, or smoke contact

AMBIENT

Equipment clean. Paint, plastic and elastomer items unaffected.

·

No damage, acceptable to operate

ZONE II Smoke and water contact but no heat exposure.

AMBIENT

Equipment dirty, sooty and wet. No effects on paint, elastomer or plastic items.

·

No damage to major equipment. Water and smoke may have damaged insulation, insulation jackets and delicate mechanisms or electronics.(1)

·

Smoke or fumes from burning chlorinated compounds, i.e. PVC, will release chlorine or HCl, can damage electronics or contaminate insulation.(2)

·

No damage to major equipment. Some damage to non-metallics. Check packing and gaskets for heat effects.(3)

·

Electrical wiring and electronic components damaged.(4)

·

Belts on machinery drives need replacing.

·

Check for chlorine or HCl contact from burning organic chlorides. (2)

Organic coatings blistered or burned off. Plastics and rubber melted or charred. Insulation on electric wiring destroyed.

·

Severe general damage to ancillary equipment such as electrical wiring, circuit boards and motors.

·

All gaskets and packing must be replaced except those made from metallic, spiral or graphite

Springs will be tempered and softened. Valves, gauges out of calibration.

·

Springs in pressure relief valves, check valves etc., will be tempered out of calibration. Rupture discs may also be affected by heat and should be replaced. (5)

Cold drawn copper alloys lose strength. Solution annealed copper alloys are less affected.

·

Roll joints in heat exchangers might be affected. Sagging tubing joints on instrument tubing might leak. Consult mechanical engineers about copper alloy pressure components if loss of copper alloy strength is observed. (6)

ZONE III Light heat exposure

to 66°C (150°F)

>66°C (150°F) to 204°C (400°F)

ZONE IV Medium heat exposure

>204°C (400°F) to 427°C (800°F)

Vinyl and alkyd paints blistered, paints darkened to black, elastomers hardened or charred, plastics charred or melted, lead-tin solder melts.

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Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 11.6 Guidelines For Assessing Fire Damage Effects Description Of The Types Of Damage That May Occur In The Heat Exposure Zone Categories Heat Exposure Zone

Temperature Range °C (°F)

Zone IV Medium heat exposure (Continued)

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ZONE V Severe heat exposure. Direct exposure to flames, no impingement. This is the most important area of fire damage effects. Major equipment has been exposed to severe radiant heat, but not enough to destroy it.


>427°C (800°F) to 732°C (1350°F)



Aluminum alloys may experience considerable loss in strength due to over-aging and recrystallization. Distortion of aluminum alloys may occur. Structural steels, stainless steels, solution annealed nickel alloys, non-heat treated titanium and zirconium alloys generally unaffected. Possibility of liquid metal embrittlement begins and may affect the integrity of equipment.

·

Aluminum equipment often requires replacement. (6)

·

Usually can be returned to service. (7)

·

Refurbish susceptible metallic items that have had molten metal dripped on them by repairing damaged areas (by welding and/or grinding) and inspecting for cracking. (8)

Nonmetals destroyed or consumed.

·

All ancillary equipment and small piping, tubing, copper materials should be replaced. Concentrate on major equipment.

·

All gaskets and packing should be replaced.

The cold-rolled tube ends in heat exchangers may be stress relieved causing leaks.

·

Major equipment, including pressure vessels, heat exchangers and rotating equipment should be cleaned, inspected and pressure tested. (9)

Heat-treated or cold-worked metals may be softened. Check springs on pressure relief valves. Check A193-B7 stud bolts in flanges for softening. Check for localized heating and stressing of steel equipment in critical service.

·

In areas of highest temperature, replace all B7 bolts. (10) Pressurized components may need metallurgical sampling to determine exact degree of effects by high-temperature exposure. (13)

Long exposure to these temperatures may affect grain structure, properties and corrosion resistance of steels and stainless steels.

·

Vessel, piping, and tankage components, and associated structural steel supports, that are warped or distorted may require repaire or replacement. Regular carbon stainless steels are sensitized, may need replacing. 10)(11)(12)

Steel starting to oxidize, the thicker the scale the hotter the temperature.

·

Remove oxide scale and determine amount of physical damage. (13)

Copper tubing oxidizing to black scale, softened and distorted.

·

Replace copper tubing which has black oxide scale.

Aluminum, pyre and some silver solders melting.

Not for Resale


Table 11.6 Guidelines For Assessing Fire Damage Effects Description Of The Types Of Damage That May Occur In The Heat Exposure Zone Categories Heat Exposure Zone ZONE VI Extreme heat exposure, indicating vicinity of fire source or flame impingement.

Temperature Range °C (°F) >732°C (1350°F)



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Copper and copper alloys destroyed or melted.

·

Almost everything will have to be scrapped. Critical equipment that was protected by insulation, water spray or fire proofing construction will have to be thoroughly inspected and tested.

Heavily scaled steel may be distorted due to thermal stresses.

·

Check areas of severe oxidation. (13)

·

Possibility of liquid metal cracking (LMC) is greatest at these temperatures. Check areas exposed to molten metal for LMC. (8)

·

Check piping and vessels in lowtemperature service for increase in grain size and loss of toughness. (14)

·

Check bolting, vessels and piping components for metallurgical changes.

Grain growth of fine grained steels.

Steel that is water quenched may harden, lose ductility. All heat-treated or cold-worked materials may have altered properties.

(10)(11)(12)

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Notes: 1. Equipment heavily contaminated with smoke and water will require cleaning. Consider the potential effect of chloride-bearing fire water as a source of external stress-corrosion cracking or corrosion under insulation during service at a later date. 2. Consumption of organic chlorides (e.g. vinyl chloride or polyvinyl chloride (PVC)) in the fire may generate chlorine, HCl, or both. These gaseous products will be carried by the smoke and water spray onto the surrounding equipment. If so, decontamination, neutralizing, cleaning, and testing will be required to ensure that HCl corrosion has not and will not damage the equipment. If the fire water has carried acid chlorides onto stainless equipment, rapid external stress corrosion cracking failures could result from further service. A chloride spot check of uninsulated stainless equipment should reveal whether or not decontamination is required. 3. Temperatures in the range of 66°C to 204°C (150°F to 400°F) may begin to melt, char, harden, or change the color of paints, coatings, plastic tubing, and elastomers. Such changes will normally signal the need for replacement or re-coating of such organic components. Flange gaskets, O-ring seals, valve packing, and so forth should be checked for possible deterioration. These items are largely confined, so their deterioration may not be evident on first inspection. 4. As temperatures approach 204°C (400°F) electrical motors may be damaged due to the thermal decomposition of wiring and electrical insulation. Lead-tin solders begin to melt in this temperature range, breaking some electrical connections.


Not for Resale


Notes (Table 11.6 Continued): 5. Steels of extremely high hardness (tool steels, springs, etc.) are tempered in this temperature range so accidental fire exposure may lower their hardness. Rupture disks, pressure relief valve springs, and pressure gauges may all be out of calibration due to exposure in the 204°C to 427°C (400°F to 800°F) range.

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Since the early 1980s, counterfeit bolts and cap screws have been used in some components and many of these bolts do not meet the strength and alloy requirements of ASTM or Society of Automotive Engineers (SAE) standards. Such substandard bolts may lose substantial strength at temperatures where ASTM or SAE standard fasteners are unaffected. For example, SAE low alloy steel with boron additions (or, worse yet, plain carbon steel) have been substituted for SAE grade 8 low alloy steel cap screws. These substandard cap screws will lose substantial strength if exposed to temperatures in excess of about 316°C (600°F) while standard SAE grade 8 cap screws would be completely unaffected by such exposure. Therefore, investigators should be alert to the possibility of lowered strength on flange connections and valve bonnets due to low-temperature tempering of such substandard bolting alloys. 6. Cold-drawn copper and copper alloys lose significant strength due to annealing and recrystalization in the range of 204°C to 427°C (400°F to 800°F). Roll joints in heat exchangers are commonly affected; leak testing and re-rolling will often be necessary. Sagging and deformation of copper instrument tubing will be observed, and tubing joints will often leak. Solution-annealed copper alloys suffer relatively little from exposure in the 204°C to 427°C (400°F to 800°F) range; pressurized components should be checked to determine if any observed loss of strength affects the structural integrity. Aluminum alloy equipment may suffer considerable loss of strength due to over-aging and recrystallization in the 204°C to 427°C (400°F to 800°F) range. The great thermal expansion of aluminum may cause widespread warping and tensile failures as well. Aluminum equipment exposed in this temperature range will often require replacement. 7. Low carbon structural steels, stainless steels, solution-annealed nickel alloys, non-heat-treated titanium and zirconium alloys are largely unaffected by exposure in the 204°C to 427°C (400°F to 800°F) range and may often be returned to service with no serious damage.

9. The onset of many severe metallurgical effects that affect vessel integrity and future service occurs in the range of 427°C to 732°C (800°F to 1350°F). Therefore, equipment exposed in this temperature range will require extra attention from the materials engineer and inspection team. Spheroidization or tempering may significantly lower the strength of materials used in the construction of pressurized components. If there is evidence of such metallurgical change, tests should be performed on samples removed from the equipment in question to ensure that the properties still meet specification. Stress relief of stainless steel and nickel alloys will begin in this temperature range. In the absence of thermal distortion or sensitization, such stress relief is not, of itself, cause for concern. However, rolled joints in shell and tube heat exchangers will often relax and leak, requiring resealing.


Not for Resale

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8. Contact of molten tin, lead, zinc and their alloys with structural alloys may seriously affect the integrity of equipment due to liquid metal cracking (LMC). Threshold temperatures and times for cracking are not well established although susceptible combinations of low-melting alloys and structural alloys have been documented (see reference [11.9.5]). There is a possibility of LMC in the temperature range 204°C to 427°C (400°F to 800°F); however, the risk of serious damage gets worse as temperatures go up in heat exposure Zones V and VI. If a low-melting alloy has dripped onto a structural item, refurbishment should include a careful and thorough removal of the low-melting alloy and a careful check for intergranular cracking.


Notes (Table 11.6 Continued): 10. The normal tempering temperature is approximately 593°C (1100°F) for AISI alloy 4140 stud bolts. These bolts are commonly used in refinery and petrochemical plants to ASTM specification A193 Grade B7. If the fire exposes such bolts to temperatures in excess of approximately 663°C (1225°F), the bolts will be softened below their required minimum strength level. Bolts with low strength may yield on re-torquing, producing leaks during unit restart. Low carbon steel used for piping and structures will be relatively unaffected by exposure for short times at temperatures in the range 427°C to 732°C (800°F to 1350°F); long-term exposure may lead to strength loss by spheroidization as described above. Scaling due to oxidation in air begins on carbon steels in this temperature range. The scale itself is essentially equivalent to the mill scale often encountered on newly delivered steel products. The problems of dealing with such heat scale are similar to the problems of dealing with mill scale; such scale may promote pitting and localized attack in service and makes a poor anchor for protective coatings. For these reasons the heat scale should be removed, as mill scale is, by abrasive blasting. 11. Radiant heating or uneven heat flux to a portion of a vessel or pipe can cause severe residual stresses to develop during thermal expansion and contraction. If the various temperature indicators point to localized metal temperatures in excess of 538°C (1100°F), potentially harmful residual stresses should be considered in a fitness-for-service assessment. A field stress relief may be needed to reduce uneven or undesirable residual stresses. 12. Sensitization of austenitic stainless steels and other austenitic alloys may occur on exposure to temperatures above 427°C (800°F) and is normally most severe at temperatures around 677°C (1250°F). A sensitized austenitic stainless steel will lose considerable corrosion resistance in many environments; depending on the service such sensitized materials may not be suitable for further use. The mechanical properties of AISI Type 300 stainless steels are not significantly reduced by sensitization. 13. Oxidation of low carbon steel occurs rapidly above 732°C (1350°F) resulting in heavy scale build-up. Damage may be less than it appears initially, since the volume of scale is from seven to 20 times greater than that of the metal from which it formed. Heavily scaled parts should be cleaned of scale, checked for thickness, grain structure, and hardness to facilitate decisions regarding reuse. After exposure to temperatures in excess of 732°C (1350°F), hardenable steels may exhibit a wide range of hardness, toughness and grain structure depending on exposure temperature and cooling rate. If high-temperature (in excess of 732°C (1350°F)) exposure is followed by rapid cooling due, for instance, to fire water quenching, steels may show extremely high hardness and low toughness. Such hardened material is extremely prone to delayed brittle fracture or hydrogen-assisted cracking and therefore must be identified and removed prior to returning the equipment to service.

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14. The grain growth that occurs in carbon steels exposed to temperatures above about 1500°F is extremely detrimental to toughness. Common structural steels such as ASTM A53 show a gradual coarsening of the grain as temperatures increase; above about 954°C (1750°F), the grain size may be large enough to raise the ductile-to-brittle transition temperature well above the ambient temperature. Fine-grained lowtemperature steels such as ASTM A516 and A333 tend to show grain coarsening more abruptly over a narrow range of temperatures beginning at about 1038°C (1900°F). Once again, the primary concern for the presence of such coarse grains is the severe loss in toughness. It is seldom practical to refine the grain size of grain-coarsened steels in the field. In some circumstances, a normalization treatment in a heat-treating shop may be used to restore original grain size and toughness.


Not for Resale


Table 11.7 Temperature Indicators That Can Be Used To Categorize Fire Damaged Components Temperature Indicators Melting, Charring And Ignition

Description Melting points make excellent temperature indicators, since a piece of melted equipment is easy to identify and the melting ranges of alloys are largely unaffected by time. Only eutectic alloy compositions have a true melting point; all other alloys melt across a range of temperatures (e.g., the lead-based Babbitt frequently used for sliding bearings in pumps and compressors has a solidus temperature of 239°C (463°F), and a liquidus temperature of 272°C (522°F)). The liquidus temperatures for a wide variety of refining and petrochemical plant materials are shown in Table 11.13. Ignition of wood is affected by species, temperature, and time. The ignition temperature for some types of woods are shown in Table 11.14. Glass will melt at high temperature and will crack if subjected to even moderately high cooling rates. Consequently, the condition of sight glasses, flow meters, gauge faces, and other glass items may give useful indications of temperature and cooling rates. Glasses are noncrystalline even at room temperature; their transition to liquid is somewhat different from that of metal alloys. As the temperature of glass increases, it reaches a point where it begins to soften. Higher temperatures produce lower hardness and lower shear strength until, at the “working temperature,” the glass is essentially a syrupy liquid. The softening point and working temperatures of many glasses are shown in Table 11.15.

Oxidation Of Metals

The onset of high-temperature scaling on carbon steels or stainless steels exposed to air is largely temperature controlled. Below a certain temperature (approximately 538°C (1000°F) for carbon steels, and 843°C (1550°F) for 18Cr-8Ni stainless steels), essentially no high-temperature oxidation will be observed. Above that threshold temperature, a significant oxide scale may form, even in the short-term exposures (15 minutes to several hours) characteristic of accidental fires. The friable nature and logarithmic growth curve of some high-temperature oxides make time or temperature estimates from oxides thickness difficult to interpret. The presence of scale itself is, however, indicative of temperatures at least as high as the threshold. The scaling temperatures for a variety of common refinery and petrochemical plant materials are shown in Table 11.16.

Tempering Of Steels

In the range of 204°C to 482°C (400°F to 900°F), cold-worked and heat-treated steels of high hardness begin to lose strength. Bearing assemblies, springs, aircraft-grade fasteners, and other items are affected. The reduction in hardness may be used to estimate time and temperature of exposure based on the tempering curves of the alloy in question. One of the more common bolting materials in refinery and petrochemical plants is ASTM A193 Grade B7. Its response to heat exposure is fairly well known and can be used to help assess the heat to which adjacent piping or vessels were subjected. Different tempering temperatures produce different characteristic colors on clean steel surfaces such as pump shafts. (Temper colors will not develop, obviously, on painted steel or rusty surfaces.) The temper colors commonly observed on steel as a function of temperature are shown in Table 11.17.


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The discoloration and charring of some organic materials such as polyurethane foam, phenolic resin, and acrylic resins are also largely controlled by temperature.


Table 11.7 Temperature Indicators That Can Be Used To Categorize Fire Damaged Components Description

Grain Growth Of Carbon Steel

General purpose carbon steels such as ASTM A53 show a gradual coarsening of the grains as the temperature is increased above the austenitizing temperature. Exposure above about 1700°F produces very large grains. The effect of temperature on grain growth of carbon steel is shown in Figure 11.8. Fine-grained carbon steels of high toughness are used for low-temperature service; typical specifications included ASME SA 333 for pipe and SA 350 for flanges. The fine grain size is produced by deoxidizing practice (usually aluminum additions), normalizing, and cooling at a controlled rate. Steels made to fine-grained practice (ASTM 333, 516, etc.) show little grain coarsening between the austenitizing temperature and 1032°C (1900°F). Between 1032°C to 1093°C (1900°F to 2000°F), the grain size increases dramatically.

Grain Growth In Copper And Associated Alloys

In the range of 204°C to 427°C (400°F to 800°F), copper and copper alloys will soften and begin to show grain growth. Laboratory determination of hardness and grain size, when compared with equipment not exposed to the fire, may be useful for estimating the time and temperature of exposure. The effect of temperature on grain growth of cold-drawn, commercially pure copper is shown in Figure 11.9. The effects of temperature on grain size and hardness of cold-drawn admiralty brass are shown in Figures 11.10 and 11.11, respectively.

Spheroidization Of Carbon Steel

Long-term (several hours) exposure to temperatures in the range of 649°C to 732°C (1200°F to 1350°F) may spheroidize carbon steel if the cooling rate is slow.

Sensitization Of Austenitic Stainless Steels

The well-known sensitization reaction of austenitic stainless steels can be a useful temperature indicator. In the temperature range of 427°C to 899°C (800°F to 1650°F) chromium carbide precipitation in the grain boundaries leaves a distinctive ditching pattern when these alloys are examined metallographically using the ASTM A262 practice A test. Much of the chromium-nickel austenitic stainless steel produced in recent years is of the low carbon variety, to avoid sensitization during welding. Such low carbon stainless steel may still be sensitized during accidental fires if the time of exposure exceeds approximately 10 hours (See Figure 11.12).

Distortion Of Structural Steel

Gross plastic deformation of low carbon steel I-beams, channel sections, and other structural members is sometimes observed if the temperature is high enough to reduce the yield stress below the applied stress. Above 760°C (1400°F), the yield stress of carbon steel has dropped to only 25.9 MPa (3750 psi ) and gross plastic flow is possible at relatively low stress levels (see Figure 11.13). Therefore, the presence of structural steel grossly deformed by a fire is indicative of temperatures of 760°C (1400°F) or above.

Softening Of Aluminum Alloys

Aluminum alloys rapidly lose strength above about 149°C (300°F) ( See Figure 11.14). Sagging or warping of aluminum piping for fittings is suggestive of temperatures at least that high.

Stress Relief Of Austenitic Stainless Steel And Nickel Alloys

Exposure to temperatures above about 482°C (900°F) for more than 15 to 30 minutes will begin to produce significant stress relief of many austenitic stainless steels and nickel alloys.


Observations involving stress relief of stainless items include leaking joints in rolled-in heat exchanger tubes, leaking fittings on swaged instrument tubing joints, and softened bourdon tubes on pressure gauges.

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Temperature Indicators


Table 11.8 Temperature Of Steel Based On The Visible Radiation Spectrum Radiation Color During A Fire

Approximate Temperature (°C)

(°F)

Black

540

1000

Faint Dark Red

590

1100

Cherry Red (Dark)

650

1200

Cherry Red (Medium)

700

1300

Red

760

1400

Light Red

815

1500

Reddish-Orange

870

1600

Orange

930

1700

Orange To Pale Orange-Lemon

980

1800


1040

1900


1090

2000

Lemon

1150

2100

Light Lemon

1205

2200

Yellow

1260

2300

Light Yellow

1315

2400

Yellowish-Grey: "White"

1370

2500

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Not for Resale


Table 11.9 Color Of Smoke From Fuel Burned In Air Fuel

Color Of Smoke

Hay/Vegetable Compounds

White

Phosphorus

White

Benzene

White To gray

Nitro-Cellulose

Yellow To Brownish Yellow

Sulfur


Sulfuric Acid, Nitric Acid, Hydrochloric Acid


Gunpowder


Chlorine Gas

Greenish Yellow

Wood

Gray To Brown

Paper

Gray To Brown

Cloth

Gray To Brown

Iodine

Violet

Cooking Oil

Brown

Naphtha

Brown To Black

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Lacquer Thinner

Black

Turpentine

Black

Acetone

Black

Kerosene

Black

Gasoline

Black

Lubricating Oil

Black

Rubber

Black

Tar

Black

Coal

Black

Foamed Plastic

Black

Butadiene

Black


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 11.10 Ignition Temperature Of Gases Gas

Temperature

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(°C)

(°F)

Ammonia (Anhydrous)

649

1200

Butane

405

761

Carbon Monoxide

609

1128

Ethane

515

959

Ethylene

490

914

Hydrogen

400

752

Hydrogen Sulfide

260

500

Methane

540

1004

482-632

900-1170

Propane

450

842

Propylene

460

860

Natural Gas

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Not for Resale


Table 11.11 Ignition Temperature Of Liquids Flash Point (1)

Autoignition Temperature (2)

(°C)

(°F)

(°C)

(°F)

Castor Oil

229

450

449

840

Corn Oil

254

490

393

740

Creosote Oil

74

165

335

635

Denatured Alcohol

16

60

399

750

Ethyl Alcohol, Ethanol

13

55

365

689

Ethyl Ether

-45

-49

160

320

Fuel Oil No. 1

38-74

101-165

210

410

Fuel Oil No. 2

43-88

110-190

257

495

Fuel Oil No. 3

43-110

110-230

260

500

Fuel Oil No. 4

54-66

130-150

263

505

Fuel Oil No. 5

54-66

130-150

NA

NA

Fuel Oil No. 6

66

150

407

765

Gasoline

-43

-45

257

495

Glycerin

160

320

370

698

Kerosene

38-74

100-165

210

410

Lacquer

-18-27

0-80

NA

NA

Linseed Oil

221

430

343

650

Methyl Alcohol

11

52

385

725

Methyl Ethyl Ketone

-6

21

516

960

38-60

100-140

235

455

Naphthalene

79

174

526

979

Olive Oil

227

440

343

650

Peanut Oil

282

540

446

835

Soybean Oil

282

540

446

835

Toluene

4

40

480

896

Tung Oil

288

550

457

855

Turpentine

35

95

253

488

27-32

81-90

464-529

867-984

Naphtha, Safety Solvent

Xylene Notes: 1. 2.

Flash Point – The lowest temperature at which a liquid exposed to air gives off sufficient vapor to form a flammable mixture near the surface of the liquid. Autoignition – The lowest temperature required to cause a self-sustaining combustion, without initiation by a spark or flame, of a flammable material when its vapor pressure is mixed with air in a flammable concentration.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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Liquid


Table 11.12 Heat Exposure Levels For Materials Of Construction Which Satisfy The Level 1 Assessment Criteria Materials

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Typical ASTM Specifications For Pressurized Components

Heat Exposure Zone Levels Which Satisfy The Level 1 Assessment Criteria

Carbon Steels

A36, A53, A105, A106, A131, A139, A181, A216, A234, A266, A283, A285, A333, A350, A352, A420, A515, A516, A537, A671, A672, API 5L

I, II, III, IV

Low Alloy Steels

A182, A217, A234, A335, A336, A387, A691

I, II, III, IV

Austenitic Stainless Steels (1)

A312, A358, A240, A403, A351

I, II, III, IV

Alloy 20

B366, B462, B463, B464, B729, B744

I, II, III, IV

Alloy 400

B127, B164, B165, B366, B564, A494

I, II, III

Duplex Stainless Steels (2)

A182, A240, A789, A790, A815

Alloy 2205

(UNS S31803, UNS J92205)

Alloy 2507

(2507 – UNS S39275)

Alloy 800, 800H

B163, B366, B407, B409, B564

I, II, III, IV

Alloy 825

B163, B366, B423, B424, B704, B705

I, II, III, IV

Alloy 600

B163, B168, B366, B564

I, II, III, IV

Alloy 625

B167, B366, B443, B444, B564, A494

I, II, III, IV

Alloy C-276

B366, B575, B622

I, II, III, IV

Copper Alloys

B68, B96, B111, B169, B171, B395, B584

I, II

Aluminum Alloys

B209, B210, B241, B247

I, II

Precipitation Hardened Alloy Steels (3)

17-4PH, 17-7PH

I, II

I, II, III

Notes: 1. If the austenitic stainless steel components: are insulated, are not coated for under insulation stress corrosion cracking protection, and normally operate between 49°C and 177°C (120°F and 350°F), then preventative maintenance may be required to assure that halide contamination of the insulated surfaces has not occurred. The concern in this case is halide induced stress corrosion cracking of contaminated insulated surfaces after the equipment is returned to service. 2. Above 316°C (600°F), Duplex alloys will undergo a loss of toughness with time and temperature. In addition, severe loss in ductility (sigma phase formation) with short term exposure to 593°C and 927°C (1100°F and 1700°F) can also occur. 3. Precipitation hardened alloys may experience a loss in toughness when heated above 260°C (500°F), and slowly cooled.


Not for Resale


Table 11.13 Melting Points Of Metals And Alloys UNS Number

Melting Point (1) (°C)

(°F)

Commercially Pure Aluminum

A91050

657

1215

Aluminum Alloy

A96061

652

1206

Red Brass

C23000

1027

1880

Yellow Brass

C26800

932

1710

Admiralty Brass

C44300

938

1720

Naval Brass

C46400

899

1650

70/30 Copper Nickel

C71500

1238

2260

Silicon Bronze (2)

C87200

916

1680

Tin Bronze (2)

C90300

1000

1832

2.52% Carbon Gray Iron (2)

F11701

1293

2359

Ductile Iron (2)

F32800

1160

2120

0.15% Carbon Steel

G10150

1527

2781

CA15 (2)

J91150

1510

2750

--

1480

2696

CF-8 (2)

J92600

1425

2597

CF-8M (2)

J92900

1400

2552

CK-20 (2)

J94202

1425

2597

CN-7M (2)

--

1455

2651

1 ¼ Cr – ½ Mo

K11597

1511

2752

2 ¼ Cr – 1 Mo

K21590

1515

2759

5 Cr – ½ Mo

K41545

1512

2754

9 Cr – 1 Mo

K90941

1498

2728

Nickel 200

N02200

1447

2637

Alloy 400 (Monel (3))

N04400

1349

2460

Alloy K-500 (Monel (3))

N05500

1349

2460

Alloy X (Hastelloy (3))

N06002

1315

2399

Alloy G (Hastelloy (3))

N06007

1343

2449

Alloy 600 (Inconel (3))

N06600

1415

2579


N06601

1368

2494


N06625

1350

2462


N07718

1336

2437

Alloy X-750 (Inconel (3))

N07750

1427

2601

CD-4Mcu (2)


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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Material


Table 11.13 Melting Points Of Metals And Alloys UNS Number

Melting Point (1) (°C)

(°F)

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Alloy 20 (20Cb3 (3))

N08020

1427

2601

Alloy 800 (Incoloy (3))

N08800

1385

2525


N08801

1385

2525


N08825

1400

2552


N09925

1366

2491

Alloy C-276 (Hastelloy (3))

N10276

1315

2399

Alloy B-2 (Hastelloy (3))

N10665

1382

2520

17-4 PH

S17400

1440

2624

Type 304

S30400

1450

2642

Type 310

S31000

1450

2642

Type 316

S31600

1400

2552

Type 321

S32100

1425

2597

Type 347

S34700

1425

2597

Titanium Grade 2

R50400

1704

3099

Stellite 6 (3)

W73006

1354

2469

Copper (4)

--

1083

1981

Gold (4)

--

1063

1945

Iron (4)

--

1536

2797

Lead (4)

--

328

622

Magnesium (4)

--

650

1202

Tin (4)

--

232

450

Silver (4)

--

961

1762

Zinc (4)

--

420

788

Zirconium (4)

--

1852

3366

54320

312

594

97.5/2.5 Lead-Silver Solder (5)

--

304

579

Lead Babbitt – Alloy 7 (6)

--

268

514

95/5 Lead-Tin Solder

Notes: 1. Pure metals melt at a specific temperature. Metal alloys melt over a temperature range. The temperature shown for alloys is the liquidus temperature; that is, the temperature at which the alloy is completely liquid. The temperature at which the alloy begins to melt (solidus temperature) is somewhat lower 2. Casting 3. Trade Name 4. Pure element 5. ASTM Alloy Grade 2.5S 6. ASTM B23


Not for Resale

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Material


Table 11.14 Ignition Temperature Of Wood Approximate Ignition Temperature (°C)

(°F)

Douglas Fir

260

500

Paper Birch

200

400

Spruce

260

500

Western Red Cedar

190

380

White Oak

200

400

White Pine

260

500

Notes: 1. The ordinary ignition temperature of wood is between 450°F and 800°F (230°C and 430°C). The values in the table represent average ignition temperatures for selected wood types. 2. It is important to note that when wood is exposed to prolonged heat, it undergoes a chemical change and becomes pyrophoric carbon with an ignition temperature that can be as low as 300°F (150°C). The prolonged heat will also greatly reduce the amount of time for ignition. For example, a long leaf pine will ignite when subject to: · 180°C (356°F) for 14.3 minutes, ·

200°C (392°F) for 11.8 minutes,

·

225°C (437°F) for 8.7 minutes,

·


·


·

350°C (662°F) for 1.4 minutes, and

·

400°C (752°F) for 0.5 minutes.


Not for Resale

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Type of Wood


Table 11.15 Properties Of Commercial Glass Glass type

Principal Use

1/8 inch Thick

1/4 inch Thick

1/2 inch Thick

Thermal Stress Resistance

Softening Working Point Point

(Mpa)

(oC)

(oC)

(oC)

(oC)

(oC)

(oC)

91(10)-7

6.21(104)

65

50

35

19

626

970

84(10)-7

--

70

60

40

19

648

--

Lamp bulbs

92(10)-7

6.76(104)

65

50

35

17

696

1000

-7

--

65

50

35

17

630

975

135

115

75

29

915

1200

Potash-soda lead

0041

Potash-soda- Thermometers lead Soda-line

Thermal Shock Resistance

(oC-1) 0010

0080

Thermal Modulus Of Elasticity Expansion Coefficient

Lamb tubing

0120

Potash-sodalead

Lamb tubing

89(10)

1710

Hard lime

Cooking utensils

42(10)-7

8.76(104)

1770

Soda-lime

General

82(10)-7

--

70

60

40

19

710

--

2405

Hard red

General

43(10)-7

--

135

115

75

36

802

--

2475

Soft-red

Neon signs

91(10)-7

--

65

50

35

17

693

--

3321

Hard green sealing

Sealing

40(10)-7

--

135

115

75

39

780

--

4407

Soft green

Signal ware

90(10)-7

--

65

50

35

17

695

--

6720

Opal

General

80(10)-7

--

70

60

40

19

775

--

-7

6750

Opal

Lighting ware

87(10)

--

65

50

35

18

672

--

6810

Opal

Lighting ware

69(10)-7

--

85

70

45

23

768

--

-7

7050

Borosilicate

Series sealing

46(10)

--

125

100

70

34

703

--

7052

Borosilicate

Kovar sealing

46(10)-7

--

125

100

70

34

708

1115

7070

Borosilicate

Low-loss electrical

32(10)-7

4.68(104)

180

150

100

70

---

1100

7250

Borosilicate

Baking Ware

36(10)-7

---

160

130

90

43

775

---

7340

Borosilicate

Gauge Glass

67(10)-7

7.93(104)

85

70

45

20

785

---

7720

Borosilicate

Electrical

36(10)-7

6.55(104)

160

130

90

45

755

1110

-7

6.76(104)

180

150

100

48

820

1220

7740

Borosilicate

General

32(10)

-7

4

7760

Borosilicate

Electrical

34(10)

6.27(10 )

160

130

90

51

780

1210

7900

96% Silica

High Temperature

8(10)-7

6.69(104)

1250

1000

750

200

1500

---

7910

96% Silica

Ultraviolet Transmission

8(10)-7

6.69(104)

1250

1000

750

200

1500

---

7911

96% Silica


8(10)-7

6.69(104)

1250

1000

750

200

1500

---

8870

High Lead

Sealing or Electrical

91(10)-7

5.24(104)

65

50

35

22

580

---

9700

---


37(10)-7

---

150

120

80

42

804

1195

9741

---


39(10)-7

---

150

120

80

40

705

---

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Not for Resale

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Glass Code


Table 11.16 Scaling Temperatures Of Alloys In Air Alloy Designation

Composition

Scaling Temperature (°C)

(°F)

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Carbon Steel

Fe-0.10C

482

900

Low Alloy Steel

1-1/4Cr-1/2Mo

621

1150

Low Alloy Steel

2-1/4Cr-1Mo

621

1150

Low-Alloy Steel

5Cr-0.5Mo

621

1150

Low Alloy Steel

7Cr-1Mo

649

1200

Low Alloy Steel

9Cr-1Mo

677

1250

Type 410 Stainless Steel

12Cr

760

1400


17Cr

843

1550


21Cr

954

1750


27Cr

1038

1900


18Cr-8Ni

899

1650


18Cr-10Ni-Ti


18Cr-10Ni-Cb


23Cr-12Ni

1093

2000


25Cr-20Ni

1149

2100


18Cr-8Ni-2Mo

899

1650

Duplex 2205

22Cr-5Ni-3Mo

1038

1900

Duplex 2507

25Cr-7Ni-4Mo

Alloy 600

72Ni-15Cr-8Fe

1038

1900

Alloy 625

60Ni-22Cr-9Mo-3.5Cb

Alloy 800

33Ni-42Fe-21Cr

1038

1900

Alloy 825

42Ni-Fe-21.5Cr-3Mo-2.3Cu

N-155

Fe-based superalloy

1038

1900

S-816

Co-based superalloy

982

1800

M-252

Ni-based superalloy

982

1800

Hs-21

Co-based superalloy

1149

2100

Cr-based superalloy

899

1650

Ni-based superalloy

788

1450

Cu-based superalloy

454

850

Brass

70Cu-30Zn

704

1300

Alloy B-2

Ni-based superalloy

760

1400

Alloy C-276

Ni-based superalloy

1149

2100


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table 11.16 Scaling Temperatures Of Alloys In Air Alloy Designation

Composition

Scaling Temperature (°C)

(°F)

Alloy X

Ni-based superalloy

1204

2200

HW

12Cr-60Ni-bal Fe

1121

2050

HT

15Cr-66Ni-bal Fe

1149

2100

HX

17Cr-66Ni-bal Fe

1149

2100

Notes: 1. The temperature below which the oxidation rate is negligible. Negligible is often defined as less than 0.002 g weight gain per square inch per hour.

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Not for Resale


Table 11.17 Tempering Colors Of Steel Temper Color

Approximate Temperature (°C)

(°F)

Pale Yellow

193

380

Straw Yellow

215-226

420-440

Yellowish-Brown

238-249

460-480

Bluish-Purple

260-282

500-540

Violet

282-293

540-560

Pale Blue

293-304

560-580

Blue

316-338

600-640

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Not for Resale


Figure 11.1 Overview of the Procedure To Evaluate A Component With Fire Damage

Obtain Record Of Fire Incident.

Perform Preliminary Inspection Of The Fire Damaged Component.

Assign the Component to a Heat Exposure Zone.

Perform a Level 1 Assessment.

Yes

Equipment is Acceptable Per Level 1 Screening Criteria? No

--``````-`-`,,`,,`,`,,`---

No

Perform a Level 2 Assessment? Yes


Yes


No


Yes

Perform Rerate per Level 2 Criteria to Reduce Pressure and/or Temperature.

Yes

Equipment Acceptable per Level 3 Assessment? Yes

No

Remaining Life Aceptable?

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Yes Return the Equipment to Service!


No

Rerate Equipment? Yes Perform Rerate per Level 3 Criteria to Reduce Pressure and/or Temperature.

Determine the Remaining Life.

Repair or Replace Equipment!

No

Not for Resale

No


Figure 11.2 Idealized Representation Of Plant Equipment Exposed To Different Fire (Heat) Zones III Through VI

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Heat Exposure Zones III Light IV Moderate V Heavy VI Severe

III

IV

"Rupture"

Note:

VI

V

See Table 11.6 for definitions of the Heat Exposure Zones.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 11.3 Idealized Fire (Heat) Pattern And Equipment Exposure With Zones I Through VI Shown.

Wind Direction

PLAN VIEW

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Zone I Zone II

Zone III Zone IV

Zone V

Zone VI

Fire Source

Note:

ELEVATION VIEW

See Table 11.6 for definitions of the Heat Exposure Zones.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure 11.4 Sketch Illustrating The Procedure For Measuring The Vertical Shell Profile To Detect Vessel Distortion Bracket attached to vessel Tangent Line

Tension wire to remove distortions - If the wire between brackets is not parallel to vessel shell the correction procedure illustrated in Figure 11.5 can be utilized.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Vessel Wall

Saw slot in bracket for wire

DETAIL OF BRACKETS

Tangent Line

Bracket attached to vessel

SKIRT


Not for Resale

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Overall Length

Use a Depth Gage or Slide Caliper to measure this distance; measurements should be taken at small intervals (e.g. 250mm), starting from the support itself.


Figure 11.5 Illustration Of Vertical Wire Offset For Measuring Profile For The Ideal Situation And When The String Is Not Parallel To The Vessel.

Offset

Top Support

2

3

3

4

4

5

5

7 8 9 10

Correction Factor to be used varies with vertical distance

6

Vessel Wall

6

8 9 10 11

12

12

13

13

14

14

15

17 Bottom Support

15

Measured Offset on bottom

16 17 Bottom Support

Depth, mm

Note:

7

11

16

Top Support

1

2

Wire

Vessel Wall

Wire

1

0

Measured Offset on Top

Depth, mm

The correction factor is applied to the offset measurements to account for a non-vertical datum (vertical wire used as a reference line)


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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0


Figure 11.6 Level 2 Assessment Procedure For Fire Damage

Component Fails Level 1 Assessment - Perform Level 2 Assessment.

Equipment Type:

Vertical Pressure Vessel

Horizontal Pressure Vessel

Storage Sphere

Tank

Piping System

Measure Overall Out-Of-Plumb Of Shell From Vertical.

Measure Overall Sag Of Shell From Horizontal.

Measure Out-Of-Plumb Of Support Legs.

Measure Out-Of-Plumb Of Shell Tank Courses.

Measure Sag From Horizontal and Vertical.

Measure Localized Shell Distortions.

--``````-`-`,,`,,`,`,,`---

Perform Hardness Tests.

Yes

Hardness Acceptable?

Estimate Tensile Strength and Determine MAWP Using Appendix A.

No

No

Yes

MAWP Acceptable?


Repair or Replace the Component!

Complete Level 3 Assessment!

Yes

Yes

Other Forms Of Damage Present?

Evaluate Damage Using: Section 4 - General Thining Section 5 - Local Thining Section 6 - Pitting Section 7 - Blisters & Laminations Section 8 - Shell Distortions Section 9 - Crack-Like Flaws.

No

MAWP Acceptable?

Creep Damage From Fire?

Evaluate Creep Damage and Remaining Life Using Section 10.

Yes

No


No

Yes

Remaining Life Acceptable?

No

Leak Check Component, Paint And/Or Insulate.

Return To Service!

Yes

No

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure 11.7 Flow Diagram For Metallurgical Assessment Of Fire Damage To Carbon And Low Alloy Steels

Obtain Information Required For A Metallurgical Review.

Hardness Limits:

Acceptable

Above

Below

Hardness Above Acceptable Limits.

Check The Microstructure.

Check The Microstructure:

Microstructure Acceptable? No

Material Carburized

Microstructure Acceptable

Replace Component!

Heat Treatment Required For Process Enviornment?

Microstructure Unacceptable

Yes

Field Heat Treatment Possible?

Microstructure Coarsened.

No

Yes

No

Heat Treat The Component.

Re-check Hardness.

Hardness Acceptable?

No

Yes Evaluate Requirements for the MAT & CET (see Section 3).

Complete Level 2 Analysis!

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Not for Resale

Yes


Figure 11.8 Coarsening Behavior Of Carbon Steels As A Function Of Temperature (From: ASM Metals Handbook, 1948, ASM International)

o

Heating Temperature, C 700

800

900

1000

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Austenite Grain Size, ASTM Number

8

1100

A All fine

6

Prolonged heating Mixed grain size

4

Brief heating

B 2

0

-2 1200

All coarse

1400

1600

1800

2000

o

Heating Temperature, F

Curve A – killed steel with a fine austenitic grain size (e.g. ASTM A 516). Curve B – killed steel with a coarse austenitic grain size (e.g. ASTM A 515).

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Notes: 1. 2.


Not for Resale


Figure 11.9 Effect Of Heat On The Grain Size Of Copper

Temperature, oC 0

100

200

200

400

300

400

500

600

700

800

50

45

Grain Size - 0.001mm

40

35

30

25

20

15

10

0 0

600

800

1000

Temperature, oF

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Not for Resale

1200

1400

1600

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5


Figure 11.10 Effect Of Heat On The Grain Size Of Admiralty Brass Tubing Cold Drawn 50%.

Temperature, oC 0

100

200

200

400

300

400

500

600

700

800

150

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Grain Size - 0.001mm

125

100

75

50

25

0 0

600

800

1000

Temperature,oF


Not for Resale

1200

1400

1600


Figure 11.11 Effect Of Heat (Based On A One Hour Exposure) On The Hardness Of Admiralty Brass Tubing Cold Drawn 50%.

0

100

200

200

400

300

400

500

600

700

800

110 --``````-`-`,,`,,`,`,,`---

100

90

Hardness, RF

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Temperature, oC

80

70

60

50 0

600

800

1000

Temperature, oF


Not for Resale

1200

1400

1600


Figure 11.12 Sensitization Of 300 Series Stainless Steels.

1700 0.080

Temperature, oC

0.062 800

1600

0.056 0.058

1500 1400 0.052 1300

700 0.042

0.030

1200 0.019% Carbon

600

1100

Temperature, oF

900

1000 500

900 800

400 0.01

0.1

1

10

100

1000

10000

Notes: 1. 2. 3.

The time required for formation of carbide precipitation in stainless steels with various carbon contents is shown in the above graph. Carbide precipitation forms in the areas to the right of the various carbon-content curves. Within the time periods applicable to welding, chromium-nickel stainless steels with 0.05% or less carbon would be quite free from grain boundary precipitation. The figure is from Stainless Steels For Acetic Acid Service, American Iron And Steel Institute, 1977)

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Not for Resale

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Hours


Figure 11.13 High Temperature Yield Strengths Of Some Low Carbon Steels

Temperature, oC 200

300

400

500

600

700

0.2% Offset Yield Strength (ksi)

35

800

900 1000 1100 1200 28 ASTM A285 ASTM A201 ASTM A36 ASTM A106 Grade B ASTM A516 Grade 55

30 25

24 20 16

20 12

15

8

10 5

4

0

0 0

200

400

600

800

1000 1200 1400 1600 1800 2000 Temperature, oF

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Not for Resale

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100

0.2% Offset Yield Strength (MPa)

0 40


Figure 11.14 Effect Of Heat Exposure On The Strength Of Aluminum Alloy 6061-T6.

Temperature, oC 50

100

150

200

250

300

350

50 300 Tensile Strength Yield Strength

250

200

150

20

100 10 50

0

0 100

200

300

400

500

Temperature, oF


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

600

700

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30

Strength, MPa

Strength, ksi

40


11.11 Example Problems 11.11.1 Example Problem 1 – A 75 feet high by 60 inch inside diameter by 5/8 inch thick wall low carbon steel insulated distillation column is subject to fire damage. The vessel is not stress relieved and the weather barrier is galvanized carbon steel. The vessel is used to distill light fuel oil/gasoline type products during normal operation. Perform A Level 1 Assessment per Paragraph 11.4.2

b.

Observations After Fire: ·

The galvanize coating on the weather barrier is discolored but there is no indication of molten zinc running down the barrier.

·

The aluminum conduit on the side of the vessel is intact.

·

The alkyd coating on the vessel under the insulation is not blistered.

·

Light bulbs on the vessel structure are not distorted.

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a.

Conclusions: The temperature experienced by the vessel can be determined from the following conditions: ·

Since the coating is only discolored, the surface temperature during the fire never reached o o 421 C (790 F), in accordance Table 11.3.

·

The temperature is below 657 C (1215 F) at which point aluminum melts (see Table 11.4).

·

The temperature of the vessel below the insulation did not exceed 149 C (300 F) at which alkyd coatings discolor (see Table 11.2).

·

Light bulbs distort and melt at 510 C (950 F).

o

o

o

o

o

o

c.

d.

Further Action: ·

Leak check the vessel components and consider replacing the discolored areas of the weather barrier.

·

Document in the inspection files that the vessel was assessed for fire damage and that the vessel’s pressure envelope was not affected by the fire exposure.

Instructional Comment: The objective of a Level I assessment is to document the observations that led to the conclusion that the pressure containing component was not degraded by the fire exposure.

The Level 1 Assessment Criteria are Satisfied.

11.11.2 Example Problem 2 – A horizontal vessel with an inside diameter of 150 inch, a thickness of 9/16 inch, and a length of 35 feet is subject to fire damage. The distance from the tangent point to the centerline of the saddles is 3 feet and the height of the head is 37.5 in (i.e. the head is a 2:1 elliptical head. The vessel is fabricated from SA 516 Grade 70 carbon steel, is not insulated, and is coated on the exterior with an epoxy phenolic system. The vessel is not stress relieved and contains a heavy o diesel type product during normal operation. The vessel design conditions are 80 psig at 650 F, and the weld joint efficiency. A future corrosion allowance of 1/16 inch is required for operation. Perform A Level 1 Assessment per Paragraph 11.4.2 a.

Observations After Fire:


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The above observations indicate that the Heat Exposure Zone for the vessel is IV or below.

The aluminum conduit next to the vessel has melted.

·

The vessel is not sagged based on a visual inspection.

·

Iron oxide scale has spalled off of the side of the vessel facing the fuel source of the fire.

·

Paint discoloration of the vessel surface on the opposite side of the fuel source is visible.

·

An internal inspection of the vessel indicates no damage.

·

Thickness readings indicate a 0.03 inch metal loss (attributed to past operation).

·

The formation of coke like products were not observed from the heating of the fuel oil inside of the vessel.

Conclusions: ·

The aluminum conduit next to vessel has melted; therefore, the surface temperature of the o o vessel during the fire could have been in excess 657 C (1215 F) in accordance with the information in Table 11.4.

·

The Heat Exposure Zone for the vessel is possibly greater than Zone IV.

The Level 1 Assessment Criteria are Not Satisfied. Inspection Results ·

Sagging of the vessel from the horizontal has not occurred based on actual field measurements.

·

Localized shell distortions have not been found based on an internal inspection of the vessel.

·

Hardness test are performed to determine the condition of the shell material.

Perform A Level 2 Assessment per Paragraph 11.4.3 Step 1 – Hardness Test Results: ·

Vessel Hot Side – 132 HB, corresponds to a tensile strength of 65 ksi

·

Vessel Cool Side – 152 HB, corresponds to a tensile strength of 75 ksi

Step 2 – Determine an allowable stress for the vessel based on the material strength for the Hot Side

Safd = min

LMRb0.25gb65 ksi gF 17.5 ksi I U, 17.5 ksiOP = 16,250 psi GH 17.5 ksi JK VW MNST PQ

Step 3 – Determine the MAWP for the shell section in the Hot Side. Circumferential Stress (From Appendix A):

t c = 0.5625 in - 0.0625 in - 0.03 in = 0.47 in Rc = 75 in + 0.0625 in + 0.03 in = 75.0925 in MAWPc =

b16250 psi gb0.85gb0.47 ing = 86.4 psig 75.0925 in + 0.6b0.47 ing

Longitudinal Stress (From Appendix A):


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b.

·

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Q = 197,350 lb L = 35 ft = 420 in H = 37.5 in A = 36 in Rm = 75.28 in

OP LM 2{b75.28 ing - b37.5 ing } 1+ 4b36 ing P b197,350 lbgb420 ing MM b420 ing t = P = 0.05 in 4b37.5 ing 420 ing P b 4b16,250 psi gF b0.85gb75.28 ing M 1+ PP MM 3b420 ing Q N 2b16,250 psi gb0.85gb0.47 in - 0.05 ing MAWP = b75.0925 ing - 0.4b0.47 in - 0.05 ing = 155 psig 2

2

2

sl

2

Results:

MAWP = min 86 psig , 155 psig = 86 psig Step 4 – Evaluate component for other forms of damage ·

Iron oxide scale was removed from the vessel wall, subsequent inspection of the surface indicates no visible damage ( e.g. local thinning, blisters, shell distortions, and crack-like flaws).

·

Field metallographic examination indicates that the steel microstructure representative of the Hot Side of the vessel has noticeable grain coarsening compared to the Cool Side of the vessel where the coating is only discolored; an evaluation for MAT and CET requirements in accordance with Section 3 is recommended.

Step 5 – Evaluate the potential for creep damage An evaluation for creep damage in accordance with Section 10 is recommended.

The Level 2 Assessment Criteria are Satisfied Pending the Outcome of the Brittle Fracture Assessment per Section 3.

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L

APPENDIX A – Thickness, MAWP And Stress Equations For A FFS Assessment (Jan, 2000) A.1

General

A.1.1

The minimum required wall thickness, MAWP and membrane stress for common pressure components are required for many of the Level 1 and Level 2 fitness-for-service assessments in this document. These parameters may be computed using the appropriate equations from the construction code. Alternatively, equations for thickness, MAWP and membrane stress for internal pressure and external pressure are provided in this appendix. The equations in this appendix are based on the following publications: the ASME B&PV Code; Section VIII, Division 1; WRC 406 and ASME B&PV Code Case 2286; and ASME B31.3. The equations are presented in an organized fashion to facilitate use, and are adjusted for metal loss and future corrosion allowance.

A.1.2

In this appendix, the safe operating pressure capability of a pressure vessel is described in terms of MAWP. This terminology is also used for piping instead of the usual term, maximum allowable operating pressure. For atmospheric storage tanks, the pressure capability is defined in terms of a maximum fill height (MFH).

A.1.3

Computation of the minimum wall thickness, MAWP and membrane stress for existing equipment typically requires judgment on the part of the user to determine factors and parameters which may significantly affect the final results (e.g. code revisions, determination of allowable stresses for inservice components, weld joint efficiency in corroded regions). Methods to determine these factors and parameters for in-service equipment are provided in Paragraph A.2.

A.2

Calculation of Minimum Required Wall Thickness, MAWP

A.2.1

Minimum Required Wall Thickness and MAWP (MFH) – The minimum wall thickness and MAWP (MFH) of a component can be determined as follows.

(MFH), And Membrane Stress

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a.

The minimum required wall thickness for a component can be taken as the furnished thickness minus the original specified corrosion allowance, and the MAWP or MFH can be taken as the design pressure or maximum design liquid level, respectively, if the original design conditions have not been changed. If the design conditions have been changed, then this thickness and MAWP or MFH may also be used if all alterations and/or rerates have been made in accordance with a recognized code or standard.

b.

The minimum required wall thickness for pressure vessel and piping components can be computed if the component geometry, design pressure (including liquid head) and temperature, material specification, allowable stress, and the thickness required for supplemental loads (see paragraph A.2.6) are known. The MAWP can be computed if the current measured thickness(es) for the components under consideration and future corrosion allowance are known. The thickness used in this calculation is the current measured thickness less the thickness required for future corrosion allowance and supplemental loads. For components containing a flaw, the MAWP is also a function of the Remaining Strength Factor (see Section 2, paragraph 2.4.2.2.b).

c.

The minimum required wall thickness of atmospheric storage tank shell courses can be computed if the tank geometry, maximum design liquid level (see API 650), liquid specific gravity, design temperature, material specification, allowable stress, and the thickness required for supplemental loads are known. The MFH can be computed if the current measured


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A-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

thickness for the tank shell course amd other components under consideration and the future corrosion allowance are known. The thickness used in this calculation is the current measured thickness less the thickness required for future corrosion allowance and supplemental loads. For components containing a flaw, the MFH is also a function of the Remaining Strength Factor (see Section 2, paragraph 2.4.2.2.c).

A.2.2

A.2.3

Code Revisions – The minimum wall thickness, MAWP (MFH), and membrane stress of a component can be determined using the latest version of the applicable construction code if the following essential details are known to comply with that code. If any of the essential details do not comply with the latest edition of the code, the minimum thickness, MAWP (MFH), and membrane stress may be established using the version of the code to which the component was originally constructed. However, an assessment of the component using the latest edition of the code should be made to ensure that the original construction code rules provide an adequate margin of safety. ·

Material specifications

·

Upper and/or lower temperature limits for specific materials

·

Design details (e.g. nozzles, nozzle reinforcement, and conical transitions)

·

Special design requirements for cyclical and/or high temperature design conditions

·

Fabrication details and quality of workmanship

·

Inspection requirements

·

Weld joint efficiency

·

Material toughness (Charpy Impact) requirements

Determination Of Allowable Stresses – The allowable stress to be used in the calculation of the minimum required wall thickness and MAWP (MFH) can be determined based on one of the following items. a.

The allowable stress for all components can be based on the original construction code. Recommendations pertaining to the revision of the construction code to use for an assessment are contained in paragraph A.2.2.

b.

If a pressure vessel was constructed to the ASME B&PV Code, Section VIII, Division 1 (Code), the allowable stress may be determined from ASME B&PV Section VIII, Division 1, 1999 Addenda subject to all of the following: 1.

The pressure vessel was constructed to the 1968 or later edition of the Code,

2.

The essential details listed paragraph A.2.2 comply with the latest edition of the Code, and

3.

The pressure vessel satisfies one of the assessment levels of Section 3 of this recommended practice (note that pressure vessels constructed to the 1987 edition of the code, or later edition, automatically satisfy this requirement),

c.

If a pressure vessel was constructed to the ASME B&PV Code, Section VIII, Division 1 and the flaw is located in the base material of a cylindrical, conical or spherical shell outside of the weld band (see paragraph A.2.4.b), the allowable stress may be determined using the ASME B&PV Code, Section VIII, Division 2. This provision also applies to other construction codes which permit higher design allowable stresses in conjunction with design-by-analysis rules.

d.

If the specification for the material of construction cannot be identified, an allowable stress can be estimated based on the material chemistry determined by chemical analysis, methods used for positive materials identification (see API 578), or other physical attributes, e.g. magnetic properties, atmospheric corrosion behavior, hardness, color, etc. This chemistry can then be compared to material specifications and grade in the original construction code. The allowable


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Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE A-3 _________________________________________________________________________________________________

stress should be based on a specification and grade with a comparable chemistry that results in the lowest value of the code allowable stress at the design temperature. e.

A.2.5

Treatment of Weld Joint Efficiency (or Quality Factor) and Ligament Efficiency – The minimum thickness, MAWP (MFH), and membrane stress of a component shall include the appropriate weld joint or ligament efficiency utilized in the original design unless alternative values for these parameters can be established by stress analysis and/or inspection. a.

For damaged regions (e.g. corrosion/erosion, pitting, etc.) at a weld joint, the weld joint efficiency or weld joint quality factor, as applicable, shall be included in the minimum thickness and MAWP calculations. A damaged region is considered to be at a weld joint if any part of it is located within the weld band. The weld band is defined to be centered on the weld, and has a width of 50.8 mm (2 inches) or twice of the furnished plate thickness, whichever is greater.

b.

For damaged regions (e.g. corrosion/erosion, pitting, etc.) outside of the weld band (see subparagraph a above) in components without closely-spaced openings, a joint efficiency of 1.0 can be utilized in the minimum thickness and MAWP (MFH) calculations. For components with multiple closely spaced openings, the ligament efficiency associated with the hole pattern shall be utilized in the calculations.

Treatment of Damage in Formed Heads – If damage (e.g. corrosion/erosion, pitting, etc.) occurs in the center section of an elliptical or torispherical head, the minimum thickness, MAWP, and membrane stress can be determined as follows: a.

b.

Elliptical Heads: 1)

The minimum thickness and MAWP of the knuckle region for an elliptical head may be calculated by the equations in paragraph A.3.6.

2)

The minimum thickness and MAWP of the spherical region of an elliptical head may be calculated by the equation for spherical shells in paragraph A.3.5 using an equivalent radius. The spherical region of an ellipsoidal head is that area located entirely within a circle whose center coincides with the center of the head and whose diameter is equal to 80 percent of the shell diameter. The equivalent radius of the spherical segment is the equivalent spherical radius Kc D where Kc is given in Paragraph A.3.6 and D is the inside shell diameter and.

Torispherical Heads: 1)

The minimum thickness and MAWP of the knuckle region for a torispherical head may be calculated by the equations in paragraph A.3.7.

2)

The minimum thickness and MAWP of the spherical region of a torispherical head may be calculated by the equation in paragraph A.3.7 with M = 10 . .

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A.2.4

If a component was constructed to more stringent requirements than required by the original construction code, the allowable stress may be established considering the higher quality aspects of the component while taking into account the basis for establishing the design allowable stress in the code. Examples include guaranteed strength properties, increased inspection, design details which minimize stress concentration, and/or material selection to mitigate the effects of environmental damage and/or to provide a higher fracture toughness. If the allowable stresses are established based on the enhanced quality of the component, the basis should be documented and included in the assessment records.

A-4 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

Thickness for Supplemental Loads – The thickness necessary for supplemental loads shall be considered in the determination of the minimum thickness, t min , MAWP (or MFH), and/or membrane stress. Supplemental loads include, but are not limited to: the weight of the component, contained fluid, insulation or refractory; loads resulting from the constraint of free thermal expansion, thermal gradients or differences in thermal expansion characteristics; occasional loads due to wind, earthquake, snow, and ice; loads due both to environmental and operating conditions; reaction forces from fluid discharges; loads resulting from support displacements; and loads due to process upset conditions.

b.

An overview of supplemental loads, loading conditions, and allowances for pressure and/or temperature variations that should be considered in an assessment are shown in Table A.1.

c.

Supplemental loads may be considered to be negligible if these loads do not effect the minimum required thickness or MAWP (MFH) of a component. Otherwise, these loads are considered to be significant and must be included in an assessment.

d.

Typical pressure vessel and piping configurations and flaw locations where the required thickness for supplemental loads may be significant are listed below. ·

Vertical vessels subject to wind or earthquake loading, with flaw located in the lower section of the vessel (see paragraph A.7.3)

·

Horizontal pressure vessels, with the flaw located in the mid-span between saddle support points or close to the saddle (see paragraph A.7.4)

·

Piping systems, with the flaw located at support point locations or in the mid-span of piping sections

A.2.7

Determination of the Future Corrosion Allowance – The Future Corrosion Allowance (FCA) must be established for the intended operating period. This corrosion allowance may be established based upon previous thickness measurements, from corrosion rates on equipment in a similar service, or from information obtained from corrosion design curves. Metal loss on both the inside and outside of a component should be considered when determining a future corrosion allowance.

A.2.8

Required Thickness for Future Operation – The required thickness for future operation can be established from the minimum thickness using the following equation:

t req = t min + FCA

(A.1)

where,

t req = t min = FCA =

Required thickness for future operation (mm:in), Minimum thickness computed using the equations of this Appendix (mm:in), and Future corrosion allowance (see paragraph A.2.7) (mm:in).

A.2.9

Treatment of Shell Distortions – While in-service, components may evolve into a configuration which no longer satisfies the fabrication tolerances of the original design code. This distortion in shape may result in areas with high localized stresses, and for components subject to a compressive stress field, a reduction in structural stability. Assessment procedures for shell out-of-roundness and/or shell misalignment are covered in Section 8.

A.3

Pressure Vessels – Internal Pressure

A.3.1

Overview – The minimum required thickness and MAWP of a pressure vessel component subject to internal pressure may be calculated based on the original construction code. Alternatively, the equations in this section may be utilized in the calculation of these parameters. The equations are


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a.

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A.2.6


Metal Loss – The equations in this paragraph are written in terms of inside diameter of the component with the metal loss and future corrosion allowance applied to the inside surface. If metal loss has only occurred on the outside surface of the component (e.g. corrosion under insulation), the metal loss term in the equations should be set to zero. If metal loss has occurred on both the inside and outside surface, the loss term in the equations should be that for the inside surface.

A.3.3

Symbol Definitions – The following symbols defined below are used in this section.

Co Cr Crc D Dc Do DL DS E Ey F

= = = = = = = = = = =

FCA = Lc = LOSS = P M

= =

MAWP = R = Rc = Rell = RL = RLc = Ro = RS = RSc = rk = rkc rf rfc S

= = = =

t

=


Outside Crown radius of a torispherical head (mm:in), Inside crown radius of a torispherical head (mm:in), Cr + LOSS + FCA (mm:in), Inside diameter of the shell under consideration (mm:in), D + 2(LOSS + FCA) (mm:in), Outside diameter of cylindrical shell (mm:in), Cone outside diameter, large end (mm:in), Cone outside diameter, small end (mm:in), Weld joint efficiency from the original construction code, if unknown use 0.7, Modulus of elasticity at the assessment temperature (MPa:psi), Applied net-section axial force, use a negative value if the axial force produces a compressive stress at the location of the assessment point (N:lbs), Specified future corrosion allowance (see paragraph A.2.7) (mm:in), Total length of a conical transition (see Figure A.3 and A.4) (mm:in), Metal loss in the shell prior to the assessment equal to the nominal (or furnished thickness if available) minus the measured minimum thickness at the time of the inspection (mm:in), Internal design pressure (MPa:psi), Applied net-section bending moment, use a negative value if the bending moment produces a compressive stress at the location of the assessment point (N-mm:in-lbs), Maximum allowable working pressure (MPa:psi), Inside radius; R = D 2 (mm:in),

R + LOSS + FCA (mm:in), Ratio of the major-to-minor axis of an elliptical head (see Figure A.1), Inside radius of large cylinder at a conical transition (mm:in), RL + LOSS + FCA (mm:in), Shell outside radius (mm:in), Inside radius of small cylinder at a conical transition (mm:in), RS + LOSS + FCA (mm:in), Inside knuckle radius of a torispherical head, toriconical head, or conical transition (mm:in), rk + LOSS + FCA (mm:in), Inside radius of the flare at a conical transition (mm:in), rf + LOSS + FCA (mm:in), Allowable tensile stress of the shell material evaluated at the design temperature per the applicable construction code (MPa:psi), Nominal or furnished thickness of the shell, or cylinder thickness at a conical transition for a junction reinforcement calculation (mm:in),

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A.3.2

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based on the ASME B&PV Code, Section VIII, Division 1. The effects of supplemental loads (see paragraphs A.2.6 and A.7) are included in these equations only for cylindrical and conical shells (i.e. longitudinal stress direction) subject to a net section axial force and/or bending moment. The effects of supplemental loads for other component geometries and loading conditions can be evaluated using the stress analysis methods in Appendix B.


tc tk tkc tf tfc tmin tsl

= = = = = = =

t – LOSS – FCA (mm:in),

ts t cs tc t cc Im =

=

Minimum required thickness (mm:in), Thickness required for supplemental load based on the longitudinal stress (see paragraph A.7), (mm:in), Nominal or furnished small end cylinder thickness in a conical transition (mm:in),

=

ts – LOSS – FCA (mm:in).

=

Nominal or furnished cone thickness in a conical transition (mm:in),

=

tc – LOSS – FCA (mm:in).

= =

Nominal membrane stress (MPa:psi), and One-half apex angle of the cone in a conical shell or toriconical head (degrees).

Nominal or furnished thickness of the knuckle (mm:in),

tk – LOSS – FCA (mm:in), Nominal or furnished thickness of the flare at a conical transition (mm:in),

tf – LOSS – FCA (mm:in),

A.3.4

Cylindrical Shells – The minimum thickness, MAWP and membrane stress equations are as follows (see ASME B&PV Code, Section VIII, Division 1, paragraph UG-27):

A.3.4.1

Circumferential Stress (Longitudinal Joints):

PRc SE - 0.6 P

MAWP C =

I Cm =

(A.3)

IJ K

P Rc + 0.6 E tc

(A.4)

Longitudinal Stress (circumferential Joints): L t min =

PRc + t sl 2 SE + 0.4 P

MAWP L =

I mL = A.3.4.3

SEt c Rc + 0.6t c

(A.5)

2 SE (t c - t sl ) Rc - 0.4(t c - t sl )

FG H

P Rc - 0.4 2 E t c - t sl

(A.6)

IJ K

(A.7)

Final Values: C L t min = max (t min , t min )

(A.8)

MAWP = min( MAWP C , MAWP L )

(A.9)

I max = max (I Cm , I mL )


(A.10)

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A.3.4.2

FG H

(A.2) //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C t min =


A.3.5

Spherical Shell or Hemispherical Head – The minimum thickness, MAWP and membrane stress equations are as follows (see ASME B&PV Code, Section VIII, Division 1, paragraph UG-27).:

t min =

PRc 2 SE - 0.2 P

MAWP =

Im = A.3.6

(A.11)

2 SEt c Rc + 0.2t c

(A.12)

IJ K

(A.13)

FG H

P Rc + 0.2 2 E tc

Elliptical Head – The minimum thickness, MAWP and membrane stress equations are as follows (see Figure A.1 and the ASME B&PV Code, Section VIII, Division 1, Appendix 1):

t min =

PDc K 2 SE - 0.2 P 2 SEt c KDc + 0.2t c

(A.15)

P Dc K + 0.2 2 E tc

IJ K

(A.16)

c

(A.17)

MAWP =

Im =

(A.14)

FG H

where,

K=

1 2.0 + R 2ell 6

h

Note: To compute the minimum thickness, MAWP, and membrane stress for the center section of an elliptical head (a section within 0.8D centered on the head centerline), use Kc instead of K in the above equations:

Kc = 0.25346 + 013995 . Rell + 012238 . Rell2 - 0.015297 Rell3

Torispherical Head – The minimum thickness, MAWP and membrane stress equations are as follows (see Figure A.1 and the ASME B&PV Code, Section VIII, Division 1, Appendix 1):

t min =

PCrc M 2 SE - 0.2 P

MAWP =

Im =


(A.19)

2 SEt c Crc M + 0.2t c

FG H

(A.20)

IJ K

P Crc M + 0.2 2E tc

(A.21)

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A.3.7

(A.18)

A-%

API RECOMMENDED

PRACTICE

579

Jan, 2000

where,

Note: To compute the minimum thickness, torispherical head, use the above equations

m with

WP,and

membrane M = 1.0.

stress for the center

A.3.8

ConicalShe//- The minimum thickness, u4 WP and membrane stress equations Figure A.2 and the ASME B&PV Code, Section VIII, Division 1, Appendix 1):

A.3.8.1

Circumferential

(Longitudinal

Longitudinal

Stress

2SEtc cosa D, + 1.2t, cosa

(A.24)

(A.25)

(Circumferential

Joints):

PD, t$,= 2cosa(2SE + 0.4P) + ts, MA wpL

_

4sW,

(A.26)

- t,,)cosa

(A.27)

DC- 0.8(t, - t,,) cosa P DC - 0.4 Ok =2E t 2(tc - t,,)cosa 1 A.3.8.3

(see

(A.23)

0: =$[-&+1.2) A.3.8.2

are as follows

Joints):

PO, tzi,= 2cosa(SE -0.6P) MWPC =

of a

(A.28)

Final Values (A.29)

M4WP=min(MWPC,MAWPL) 0

(A.30)

max= max(oz,ok)

(A.31)

A.3.8.4

When determining the minimum thickness or w WP of a corroded area on a conical shell section, the inside diameter at the location of the minimum thickness reading adjusted for metal loss and corrosion allowance may be used in the above equations instead of maximum cone diameter.

A.3.8.5

The minimum thickness of an eccentric cone shall be taken as the greater of the two thicknesses obtained using both the smallest and largest a in the calculations (see Figure A-3).


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Stress

section

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(A.22)


A.3.9

Toriconical head – The minimum thickness, MAWP, and membrane stress equations are computed on a component basis (see Figure A.2 and the ASME B&PV Code, Section VIII, Division 1, paragraphs UG-32 and UG-33, and Appendix 1):

A.3.9.1

Conical Section – The equations in paragraph A.3.8 can be used to compute the minimum required thickness, MAWP and membrane stress of the cone section, designate these values as c c c t min , MAWP , and I m , respectively.

Knuckle Section – The following equations can be used to compute the minimum required thickness, MAWP and membrane stress: k t min =

PLkc M 2 SE - 0.2 P

MAWP k =

(A.32)

2 SEt kc Lkc M + 0.2t kc

P Lkc M + 0.2 2 E t kc

IJ K

(A.34)

Lkc =

Rc - rkc (1 - cos = ) cos =

(A.35)

M=

1 3.0 + 4

I mk =

FG H

(A.33)

where,

--``````-`-`,,`,,`,`,,`---

A.3.9.3

A.3.10

F GH

Lkc rkc

I JK

(A.36)

Final Values – Expressions for the minimum required wall thickness, MAWP, and membrane stress are provided on a component basis in paragraph A.3.9.1 and A.3.9.2. The values of these quantities to use in an assessment depends on the location of the flaw. The following equations can be used If a single expression is required for the cone-knuckle configuration. c k t min = max (t min , t min )

(A.37)

MAWP = min( MAWP c , MAWP k )

(A.38)

I max = max (I cm , I mk )

(A.39)

Conical Transition – The minimum thickness, MAWP and membrane stress equations are computed on a component basis (see Figure A.3).

A.3.10.1 Conical Section – The equations in paragraph A.3.8 can be used to compute the minimum required thickness, MAWP, and membrane stress of the cone section, designate these values as c c c t min , MAWP , and I m , respectively.

A.3.10.2 Knuckle Section (If Used) – Use the following equations to compute the minimum required thickness, MAWP, and membrane stress.


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A.3.9.2


PLkc M 2 SE - 0.2 P

k t min =

MAWP k =

(A.40)

2 SEt kc Lkc M + 0.2t kc

--``````-`-`,,`,,`,`,,`---

FG H

(A.41)

IJ K

P Lkc M + 0.2 2 E t kc

(A.42)

Lkc =

RLc - rkc (1 - cos = ) cos =

(A.43)

M=

1 3+ 4

I mk = where,

F GH

Lkc rkc

I JK

(A.44)

A.3.10.3 Flare Section (If Used) – Use the following equations to compute the minimum required thickness, MAWP, and membrane stress. a.

Equations based on modification of knuckle equations (see paragraph A.3.10.2) f t min =

PL fc M

MAWP f =

I mf =

(A.45)

2 SE - 0.2 P 2 SEt fc

(A.46)

L fc M + 0.2t fc

F GH

I JK

P L fc M + 0.2 2 E t fc

(A.47)

where,

L fc =

M= b.

b

RSc + rfc 1 - cos =

g

(A.48)

cos =

F GH

1 3+ 4

L fc rfc

I JK

(A.49)

Equations based on a pressure-area force balance procedure f t min =

F 1 GH = r

r fc


I F Pl K + K + K q - K - K I JK JK GH 15. SE 1

2

3

4

5

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(A.50)


FG t = r + K + K IJ H K +K +K K Pb K + K + K g = 15 . E dt = r + K + K i fc

MAWP f = 15 . SE

r fc

1

I mf

1

fc

2

4

2

5

3

4

r fc

(A.51)

3

(A.52)

5

where,

d

i

2

K1 = 0125 . 2rfc + D1 tan = -

= r rfc2 2

c h

K2 = 0.28 D1 D1t cs

1/ 2

(A.54)

c h K = 0.78t c K t h K = 0.55t c D t h D + 2r b1 - cos = g K = K3 = 0.78 K6 K6t cc

(A.53)

1/ 2

(A.55)

4

c c

c 1/ 2 6 c

(A.56)

5

s c

s 1/ 2 1 c

(A.57)

1

fc

6

=r ==

(A.58)

2 cos =

FG F IJ H 180K

(A.59)

D1 = 2 Rs

(A.60)

A.3.10.4 Final Values – Expressions for the minimum required wall thickness, MAWP, and membrane stress are provided on a component basis in paragraphs A.3.10.1, A.3.10.2, and A.3.10.3. The values of these quantities to use in an assessment depends on the location of the flaw. The following equations can be used If a single expression is required for the conical transition. a.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b.

Case 1 – The conical transition only contains a cone (Figure A.3(a)). c t min = t min

(A.61)

MAWP = MAWP c

(A.62)

I max = I cm

(A.63)

Case 2 – The conical transition contains a cone and knuckle (Figure A.3(b)).

c

c k t min = max t min , t min

h

(A.64)

--``````-`-`,,`,,`,`,,`---


Not for Resale


c

MAWP = min MAWP c , MAWP k

h

(A.65)

I max = max (I cm , I mk ) Case 3 – The conical transition contains a cone, knuckle and flare (Figure A.3(c)).

c

c k f t min = max t min , t min , t min

h

(A.67)

c

MAWP = min MAWP c , MAWP k , MAWP f

h

I max = max (I cm , I mk , I mf )

(A.69)

Case 4 – The conical transition contains a knuckle and flare (Figure A.3(d)).

c

k f t min = max t min , t min

h

(A.70)

c

MAWP = min MAWP k , MAWP f

h

I max = max (I mk , I mf ) e.

(A.71) (A.72)

Case 5 – The conical transition contains a cone and flare (Figure A.4(d)).

c

c f t min = max t min , t min

h

(A.73)

c

MAWP = min MAWP c , MAWP f

h

I max = max (I cm , I mf )

(A.74) (A.75)

A.3.10.5 The half-apex angle of a conical transition can be computed knowing the shell geometry with the following equations. These equations were developed with the assumption that the conical transition contains a cone section, knuckle, and flare. If the transition does not contain a knuckle or flare, the radii of these components should be set to zero when computing the half-apex angle. If

( RL - rk ) > ( RS + rf ) : = = > +B

> = arctan If

(A.76)

LM ( R N

L

- rk ) - ( RS + rf ) Lc

OP Q

(A.77)

( RL - rk ) < ( RS + rf ) : = = > -B


(A.78)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d.

(A.68)

--``````-`-`,,`,,`,`,,`---

c.

(A.66)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


> = arctan

LM ( R + r ) - ( R L N S

f

L

c

- rk )

OP Q

(A.79)

with,

B = arcsin A.3.11

LM (r N

f

+ rk ) cos > Lc

OP Q

(A.80)

Nozzles Connections In Shells – Two procedures are provided, area replacement and limit load. The area replacement procedure must be used for all nozzles in spherical shells or formed heads and for pad reinforced nozzles in cylinders. The limit load procedure may be used for unreinforced nozzles in cylindrical shells. Note that in both of these procedures the effects of nozzle loading are not included. Therefore, if nozzle loads are significant, a stress analysis must be performed to evaluate the acceptability of the nozzle configuration.

A.3.11.1 Required Reinforcement, Area Replacement Method – This assessment procedures is the one used for design of nozzles in the ASME Code, Section VIII, Division 1 (see paragraphs UG-37 through UG42). The procedure can be used for nozzle connections to most shell types both with or without a reinforcing pad. The procedure is known to produce conservative results for small nozzles. Definitions of variables (see Figure A.5):

cn cs dc

= = =

D Dp E E1

= = = =

fr1 fr2 fr3 fr4 F FCA h LOSSn

= = = = = = = =

LOSSs = J

=

Sn Sv Sp t

= = = =


LOSSn + FCA (mm:in), LOSSs + FCA (mm:in), Diameter of the circular opening, or chord length at the vessel wall mid-surface of a non-radial opening, in the plane under consideration including the effects of metal loss and future corrosion allowance (mm:in), Inside shell diameter (mm:in), Outside diameter of the reinforcing pad (mm:in),

1.0, 1.0 when the opening is in solid plate or in a Category B butt joint, otherwise, the joint efficiency of the weld joint the nozzle intersects, Strength reduction factor; = Sn/Sv for a set-in nozzle, = 1.0 for a set-on nozzle, Strength reduction factor; = Sn/Sv, Strength reduction factor; = min(Sn, Sp)/Sv, Strength reduction factor; = Sp/Sv,

1.0, Specified future corrosion allowance (see paragraph A.2.7), (mm:in), Inside projection of the nozzle beyond the vessel wall inner surface (mm:in), Metal loss in the nozzle from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection (mm:in), Metal loss in the shell from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection (mm:in), Load factor; in general, J=1.0 for internal pressure and J=0.5 for external pressure (see paragraph A.4.11 for restrictions) , Allowable stress for the nozzle (MPa:psi), Allowable stress for the vessel (MPa:psi), Allowable stress for the reinforcing pad (MPa:psi), Nominal thickness of the vessel wall (mm:in),

Not for Resale

--``````-`-`,,`,,`,`,,`---

a.


b.

te ti tr

= = =

Nominal thickness of the reinforcing pad (mm:in), Nominal thickness of the of the internal projection of the nozzle wall (mm:in), Required thickness of the vessel wall computed with E=1.0 (imm:in), (1) Cylindrical shell (see paragraphs A.3.4 and A.4.4). (2) Spherical shell (see paragraphs A.3.5 and A.4.5). (3) Elliptical head (see paragraphs A.3.6 and A.4.6); for the internal pressure calculation, when the nozzle opening and its reinforcement are completely within a circle the center of which coincides with the center of the head and the diameter of which is 80% of the shell diameter, the required wall thickness shall be determined using Kc instead of K. (4) Torispherical head (see paragraphs A.3.7 and A.4.7); for the internal pressure calculation, when the nozzle opening is entirely within the spherical of a torispherical head the required wall thickness is computed using M=1.0. (5) Conical shell (see paragraphs A.3.8 and A.4.8); when the nozzle opening is in a cone, the required wall thickness is determined based on the shell diameter where the nozzle axis intersects the conical shell.

tn trn wn

= = =

wh

=

wp

=

Nominal thickness of the nozzle wall (mm:in), Required thickness of a seamless nozzle wall (mm:in), Weld leg size of the nozzle-to-vessel or nozzle-to-reinforcing pad (if a pad is used) attachment weld (mm:in), Weld leg size of the nozzle-to-vessel attachment weld on the inside surface of the vessel (mm:in), and Weld leg size of the reinforcing pad-to-vessel attachment weld (mm:in).

Limitations: 1.

--``````-`-`,,`,,`,`,,`---

2. c.

For openings in cylindrical shells, the opening does not exceed the following; for nozzles which do not meet this criteria, stress analysis techniques using either stress categorization or plastic collapse are recommended to determine an acceptable MAWP. a)

For vessels 1524 mm (60 inches) in diameter and less, min[ D 2 , 508 mm (20 inches)] , and

b)

For vessels over 1524 mm (60 inches),

min[ D 3 , 1016 mm (40 inches)] .

For openings in spherical shells or formed heads there is no restriction on the opening size.

The condition required for satisfactory reinforcement of a branch nozzle connection is given by the following:

b

A = d c t r F + 2t n t r F 1 - f r 1

g

(A.81)

LMnd c E bt - c g - Ft h - Bs, OP MN n2bt + t - c - c gc E bt - c g - Ft h - BsPQ B = 2bt - c gc E bt - c g - Ft hb1 - f g A = min 5bt - c gbt - 2c g f , 5bt - 2c g f , 2hbt - 2c g f c

A1 = max

s

1

n

n

n

r

s

1

n

s

s

1

r

(A.82)

r

(A.83)

r1

2

3

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~


s

i

n

r2

n

Not for Resale

n

r2

i

n

r2

(A.84)


b

A43 = wh - cn

g

2

fr2

(A.85)

For nozzles without a reinforcing pad (see Figure A.5 for definition of areas):

A1 + A2 + A3 + A41 + A43 ³ JA

LMm5bt A = min MNm5bt 2

n

(A.86)

g b gr OP g f bt - c grPQ

- cn - t rn f r 2 t - cs ,

n - cn - t rn

r2

n

(A.87)

n

A41 = wn2 f r 2

(A.88)

For nozzles with a reinforcing pad (see Figure A.5 for definition of areas):

A1 + A2 + A3 + A41 + A42 + A43 + A5 ³ JA

(A.89)

LMm5bt - c - t g f bt - c gr, A = min MNn2bt - c - t gc2.5bt - c g + t h f r2

n

n

rn

n

n

rn

s

2

n

n

e

r2

OP sPQ

(A.90)

A41 = wn2 f r 3

(A.91)

A42 = w 2p f r 4

(A.92)

b

g

A5 = Dp - d c - 2 t n - cn t e f r 4 In the above equations, if

(A.93)

A1 < 0.0 use A1 = 0.0 , or if A2 < 0.0 use A2 = 0.0 .

A.3.11.2 Required Reinforcement, Limit Analysis Method – This assessment procedure can be utilized to evaluate nozzles in cylindrical shells subject to internal pressure that do not have a reinforcing pad (see ASME B&PV Code Case 2168). The procedure can be used to check a nozzle with a reinforcing pad if the pad is neglected in the analysis. The procedure cannot be used if the nozzle is subject to significant supplemental loading (i.e. applied net section forces and moments from piping loads). Any combination of thicknesses in the nozzle neck or vessel shell are acceptable provided all of the conditions listed below are met. This method is effective for evaluating a region of local metal loss at nozzles where an average thickness is used to represent the metal loss in the nozzle reinforcement zone (see Section 4, paragraph 4.3.3.4). Symbol definitions (in addition to those defined in paragraph A.3.11.1)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A B

=

=

Factor equal to 162 for

bt

g bt - c g > 10. , Factor equal to 210 for bt bt - c g bt - c g > 10. n

n

dm Dm L


= = =

bt

- cn

n

n

- cn

g bt - c g £ 1.0 ; and 54 for

n

- cn

g bt - c g £ 1.0 ; and 318 for

s

s

s

s

Nozzle or branch pipe mean diameter (mm:in), Vessel or run pipe mean diameter (mm:in), Axial length of nozzle with thickness tn (mm:in),

Not for Resale

--``````-`-`,,`,,`,`,,`---

a.


Ln

=

Lv

=

tn

=

Dimension to define the height of the reinforcement zone (see Figures A.6 and A.7) (mm:in), Dimension to define the width of the reinforcement zone (see Figures A.6 and A.7) (mm:in), Furnished nozzle wall thickness (see Figures A.6 and A.7) – For an integrally reinforced nozzle (see Figure A.7),

tp b.

=

b

g

t n = t p if L < 0.5 d m t n - cn (mm:in), and

Furnished wall thickness of the pipe section for an integrally reinforced nozzle (see Figure A.7), (mm:in),

Limitations – All the following must be satisfied: 1.

The opening is in a cylindrical vessel and is located a distance of

b

g

18 . Dm t - cs from

any major structural discontinuities.

c.

2.

The opening is circular with its axis normal to the surface of the vessel.

3.

The ratio

4.

The openings do not exceed the following:

b

g

Dm t - cs does not exceed 250.

a)

For vessels 1524 mm (60 inches) in diameter and less, min[ Dm 2 , 508 mm (20 inches)] , and

b)

For vessels over 1524 mm (60 inches),

min[ Dm 3 , 1016 mm (40 inches)] .

5.

The spacing between the centerlines of the opening and any other opening is more than three times the average diameters of the openings.

6.

The opening is fabricated from carbon steel and/or low alloy material with a design temperature less than or equal to 343°C (650°F).

7.

The opening is not subject to cyclic loading.

8.

The allowable stress of the material is less than or equal to 120.7 MPa (17.5 ksi).

Assessment Procedure – The following two equations must be satisfied:

F d I F t - c IJ + 125 2 + 2G J G H D K H t - c K . l £ 2.95FG t - c IJ H t K F d I F t - c IJ 1+ G J G H D K H t -c K 3/ 2

m

1/ 2

n

n

m

s

s

1/ 2

m

(A.94)

3/ 2

n

r

n

m

s

FG t - c IJ FG d IJ + BOPl + 155 H t - c K H D K PQ F t IJ ³ b0.93 + 0.005l gG L F d I + 228OPl + 152 Ht -c K 108l + M228G MN H D JK PQ

LM AF t - c I MN GH t - c JK n

n

2

+ 228

n

s

2

n

m

s

m

r

2

s

m

m

where, --``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(A.95)


l=

FG d IJ HD K m

m

Dm t - cs

(A.96)

A.3.11.3 Weld Strength Analysis a.

Definitions of variables (in addition to those defined in paragraphs A.3.11.1 and A.3.11.2):

do Swh

= =

Swn

=

Swng Swp Swpg wng

= = = =

Outside diameter of the nozzle (mm:in), Allowable stress for the nozzle-to-vessel (inside surface) attachment weld (MPa:psi), Allowable stress for the nozzle-to-reinforcing pad or nozzle-to-vessel fillet weld (MPa:psi), Allowable stress for nozzle-to-vessel groove weld (MPa:psi), Allowable stress for the shell to reinforcing pad fillet weld (MPa:psi), Allowable stress for the nozzle-to-pad groove weld (MPa:psi), Depth of nozzle-to-shell groove weld; for a set-on nozzle with a full penetration weld

b

g

wng = t n - cn ; for a set-in nozzle with a full penetration weld

b

g

wng = t - cs , (mm:in), and wpg

=

Depth of nozzle-to-pad groove weld; for a full penetration weld

w pg = t p

(mm:in). b.

If the nozzle connection is subject to corrosion, the corroded dimensions of the groove and fillet welds should be used in the strength calculations.

c.

The following analysis should be used when the nozzle neck is inserted through the vessel wall (set-in nozzle, see Figure A.8); the reinforcement areas, Ai , to be used in the calculations are defined in paragraph A.3.11.1. The required strength is:

b

(A.97)

W11

(A.98)

W22 W33 2.

g c b g h = b A + A + A + A gS = c A + A + A + A + 2bt - c gbt - c g f hS = c A + A + A + A + A + A + 2bt - c gbt - c g f hS

W = A - A1 + 2 t n - cn f r 1 E1 t - cs - Ftr Sv 2

41

42

2

3

41

2

3

5

5

v

43

41

n

42

n

s

43

r1

n

n

(A.99)

v

s

r1

v

(A.100)

The computed strength with a reinforcing pad is:

W c = min W11c , W22c , W33c

b

gb

F F Dp w p 0.49 S wp + d m t n - cn 0.7 Sn 2 2

d

i

g

(A.102)

--``````-`-`,,`,,`,`,,`---

W11c =

(A.101)


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

1.


b d

(A.103)

F F Dp w p 0.49 Swp + d o wng 0.74 S wng + 2 2 F d o wh 0.49 Swh 2

(A.104)

d

W33c =

b

3.

g i

F F d o wn 0.49 Swn + d o w pg 0.74 Swpg + 2 2 F F d o wng 0.74 Swng + d o wh 0.49 Swh 2 2

W22c =

d b

i

i

g

d

i

g

The computed strength without a reinforcing pad is:

W c = min W11c , W22c

(A.105)

b

g

b b

g g

b

gb

g

(A.106)

F F d o wn 0.49 S wn + d o wng 0.74 S wng + 2 2 F d o wh 0.49 Swh 2

(A.107)

F F d o wn 0.49 S wn + d m t n - cn 0.7 Sn 2 2

W11c =

W22c =

d

i

W33c = 0.0 4.

(A.108)

The acceptance criteria is:

Wc ³ W

(A.109)

or all of the following is true, (A.110)

W22c ³ min W22 , W

(A.111)

W33c ³ min W33 , W

(A.112)

The following analysis should be used when the nozzle neck abuts the vessel wall (set-on nozzle, see Figure A.9); the reinforcement areas, Ai , to be used in the calculations are defined in paragraph A.3.11.1. 1.

The required strength is:

W = A - A1 Sv

b

(A.113)

g

W11 = A2 + A5 + A41 + A42 Sv


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(A.114)

--``````-`-`,,`,,`,`,,`---

d.

W11c ³ min W11 , W


b

g

W22 = A2 + A41 Sv The computed strength with a reinforcing pad is:

--``````-`-`,,`,,`,`,,`---

W c = min W11c , W22c

3.

(A.116)

W11c =

F F Dp w p 0.49 S wp + d m wng 0.60S wng 2 2

W22c =

F F d o wn 0.49 Swn + d m wng 0.60S wng 2 2

d

i

d

b

g

d

i

(A.117)

i

(A.118)

The computed strength without a reinforcing pad is:

W c = W11c W11c =

(A.119)

b

g

F F d o wn 0.49 S wn + d m wng 0.60Swng 2 2

d

W22c = 0.0 4.

i

(A.120)

(A.121)

The acceptance criteria is:

Wc ³ W

(A.122)

or all of the following are true,

W11c ³ min W11 , W

(A.123)

W22c ³ min W22 , W

(A.124)

A.3.11.4 The reinforcement and weld strength calculations above are given in terms of thicknesses and/or areas. Therefore, to compute an MAWP, an iterative procedure is required. In this procedure, a pressure is assumed and the corresponding wall thicknesses, reinforcement areas, and weld strengths are computed are checked against required values. This process is repeated until a pressure is found which results in satisfaction of all required values. This resulting pressure is the MAWP of the nozzle component. A.3.12

Junction Reinforcement Requirements at Conical Transitions – For vessels subject to internal pressure, in lieu of a detailed stress analysis, the localized stresses and requirements for a cone-tocylinder junction stiffening ring can be evaluated using the following procedure pad (see ASME Code Case 2286). If there is an LTA at cylinder-to-cone junction, an average thickness should be used to represent the metal loss (see Section 4, paragraph 4.3.3.4).

A.3.12.1 Symbol Definitions – The following symbol definitions are in addition to those shown in paragraph A.3.3:

Ac DR

= =

Do

=


2

2

Cross sectional area of the stiffening ring (mm :in ), For an external ring, the diameter to the centroid of the composite ring section; for internal ring, the inside diameter (see Figure A.10), (mm:in), Cylinder outside diameter at the junction, DL or DS (mm:in), and

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2.

(A.115)


Ic

=

4

4

Moment of inertia of the stiffening ring about the ring centroid (mm :in ).

A.3.12.2 The longitudinal membrane and localized membrane plus bending stress requirements should satisfy the following requirements: 1.

2.

Determine the membrane stress in the cylindrical shell at the junction due to the pressure thrust and applied net section axial force and bending moment.

fx =

PDc2 4F + 2 2 Do - Dc F Do2 - Dc2

fb =

32 MDo F Do4 - Dc4

c

c

(A.125)

h

(A.126)

h

The longitudinal membrane and localized membrane plus bending stress in the cylinder at the junction should satisfy the following requirements:

bf

g F 0.6 D ct + t h I tan= J £ 3SE b f + f gGG1 + t JK H x

+ f b £ SE

o

x

c

(A.127)

c c

(A.128)

b

c

The longitudinal membrane and localized membrane plus bending stress in the cone at the junction should satisfy the following requirements:

gFGH t F b f + f gGG t H bf

x

x

4.

+ fb

b

c c

IJ K

tc £ SE cos=

(A.129)

c ch

h

I JJ K

0.6t c Do t c + t cc tc + tan = £ 3SE 2 c c cos = t cc

(A.130)

The circumferential membrane stress, fh, in the cylinder at the junction should satisfy the following requirements where fx and fb are given in the above paragraph A.3.12.2.

b

g

f h = 0.45

Do f x + f b tan = tc

(A.131)

f h £ SE

for hoop tension

(A.132)

f h £ Fha

for hoop compression

(A.133)

where Fha is computed using the equations in the paragraph A.4.4.1 with

--``````-`-`,,`,,`,`,,`---


Not for Resale

Fhe = 0.4tE y D .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

3.


A.3.12.3 If the cone-to-cylinder junction does not satisfy the requirements in the above paragraphs, the junction may be strengthened by increasing the cylinder thickness and/or cone thickness at the junction, or by providing a stiffening ring.

2.

The section properties of the stiffening ring are:

b

g

Ac ³

tDo f x + f b tan = I ys

Ic ³

tDo DR2 f x + f b tan= 8E y

b

g

(A.135)

In computing Ac and Ic, the effective length of the shell wall acting as a flange for the composite ring section shall be computed using the following equation (see Figure A.10):

be = 0.55 Do t c + A.3.13

(A.134)

Do t cc cos=

(A.136)

Other Components – Calculation procedures for the following components should be evaluated based on the original construction code. References for these components for the ASME Code and TEMA are cited below.

A.3.13.1 Integral tubesheet to cylinder connections (ASME B&PV Code, Section VIII, Division 1, Appendix AA or TEMA), A.3.13.2 Flat head to cylinder connections (ASME B&PV Code, Section VIII, Division 1, UG-34), and A.3.13.3 Bolted Flanges (ASME B&PV Code, Section VIII, Division 1, Appendix 2). //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A.4

Pressure Vessels – External Pressure

A.4.1

Overview – The minimum thickness and MAWP of a pressure vessel subject to external pressure may be computed based on the original construction code. Alternatively, the equations in the following paragraphs may be utilized in the calculation (see ASME B&PV Code Case 2286). These equations are less conservative than the equations in the ASME Code and have been experimentally verified with an extensive testing program. Additional information and requirements for using the equations in this appendix are provided below.

A.4.1.1

The buckling strength formulations presented in this section are based upon linear structural stability theory which is modified by reduction factors which account for the effects of imperfections, boundary conditions, non-linearity of material properties and residual stresses. The reduction factors are determined from approximate lower bound values of test data of shells with initial imperfections representative of the tolerance limits specified in paragraph A.4.1.5. Details regarding the derivation and experimental verification of the equations in this section can be found in WRC 406.

A.4.1.2

The equations in this section are applicable to Do t £ 2000 and t ³ 3 / 16 inches ( 4.8 mm) . In developing the equations in the section, the shell section is assumed to be axisymmetric with uniform thickness for unstiffened cylinders and formed heads. Stiffened cylinders and cones are also assumed to be of uniform thickness between stiffeners. Where nozzles with reinforcing plates or locally thickened shell sections exist, the thinnest uniform thickness in the applicable unstiffened or stiffened shell section should be used for the calculation of the allowable compressive stress.


Not for Resale

--``````-`-`,,`,,`,`,,`---

1.


A.4.1.3

The allowable stress equations apply directly to shells fabricated from carbon and low alloy steel plate materials given in the ASME B&PV Code, Section II, Part D. For other materials, see Appendix B, paragraph B.4.4.5. The maximum temperature limit permitted is defined in Table A.2.

A.4.1.4

The effects of supplemental loads (see paragraphs A.2.6 and A.7) are not included in these equations. The effects of supplemental loads can be evaluated using the stress analysis methods in Appendix B. In addition, special consideration shall be given to ends of components (shell sections) or areas of load application where stress distribution may be nonlinear and localized stresses may exceed those predicted by linear theory. When the localized stresses extend over a distance equal to one-half the buckling mode (approximately

12 . Do t ), the localized stresses should be considered as

a uniform stress around the full circumference. Additional stiffening may be required. The equations presented in this section are valid if the following out-of-roundness tolerances for the shell under evaluation are satisfied. The variables used to establish the tolerances are defined in paragraphs A.3.3 and A.4.3. 1.

Cylindrical and Conical Shells Subject To External Pressure – The tolerance requirements for diameter in the Level 1 Assessment of Section 8 should be satisfied. In addition, the maximum plus or minus deviation from a true circle, e, measured from a segmental circular template having the design inside or outside radius (depending on where the measurements are taken) and a chord length, Lch, should not exceed the following value:

e = min ec , 2t c

(A.137)

where

F e = 0.0165t G H c

c

I JK

Lec + 3.25 Rmt c

1.069

valid for 0.2t c £ ec £ 0.0242 Rm

(A.138)

and, --``````-`-`,,`,,`,`,,`---

Lch = 2 Rm sin

FG F IJ H 2n K

(A.139)

with

F n = NG H

Rm Rm × tc L

I JK

O

valid for 2 £ n £ 141 .

L FR I N = min M2.28G J MN H t K L FR I O = min M0.38G J MN H t K

0.54

m

c

m

c

2.

OP PQ

, 2.80

0.044

Rm tc

(A.140)

(A.141)

OP PQ

, 0.485

(A.142)

Cylindrical and Conical Shells Subject To Uniform Axial Compression and Axial Compression Due to a Bending Moment – The tolerance requirements for diameter in the Level 1 Assessment of Section 8 should be satisfied. In addition, the local inward deviation from a


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A.4.1.5


straight line, e, measured along a meridian over gauge length, Lx, shall not exceed the maximum permissible deviation, ex, given below:

ex = 0.002 Rm

(A.143)

and,

Lx = min 4 Rmt c , L

for cylindrical shells

Lx = min 4 Rmt cc cos = , Lc cos =

(A.144)

for conical shells

(A.145)

--``````-`-`,,`,,`,`,,`---

Lx = 25t c across circumferential welds

(A.146)

3.

Cylindrical and Conical Shells Subject To External Pressure And Uniform Axial Compression and Axial Compression Due to a Bending Moment – The tolerance requirements in subparagraphs (1) and (2) should be satisfied.

4.

Spherical Shells and Formed Heads – The tolerance requirements for diameter in the Level 1 Assessment of Section 8 should be satisfied. In addition, the maximum local deviation from true circle form, e, for spherical shells and any spherical portion of a formed head shall not exceed the shell thickness. Measurements to determine the maximum local deviation shall be made with a template with a chord length, Le, given by the following equation.

Le = 3.72 Rmt c

(A.147)

A.4.2

Metal Loss – The equations in this paragraph are written in terms of outside diameter of the component; therefore, the equations do not need to be adjusted for metal loss and future corrosion allowance which occurs on the inside surface. If metal loss has occurred on the outside surface of the component (e.g. corrosion under insulation), the geometry definition terms in the equations (i.e. outside diameter and outside radius) would need to be modified to account for this metal loss. The equations below are based on the future corrosion allowance and metal loss being applied to the inside surface of the shell.

A.4.3

Symbol Definitions – The following symbol definitions are in addition to those shown in paragraph A.3.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Af As Fha

= = =

Fhe

=

FS

=

h1 h2 Is Iss

= = = =

L

=


2

2

cross-sectional area of a large ring stiffener which acts as a bulkhead (mm :in ), 2 2 cross-sectional area of a ring stiffener (mm :in ), allowable hoop compressive membrane stress of a cylinder or formed head under external pressure alone (MPa:psi), elastic hoop compressive membrane failure stress of a cylinder or formed head under external pressure alone (MPa:psi), stress reduction factor, use 2.0; alternatively, a better estimate of the factor of safety can be obtained using Appendix B, paragraph B.4.4.4, Ring stiffener dimension (see Figure A.11), (mm:in), Ring stiffener dimension (see Figure A.11), (mm:in), 4 4 moment of inertia of a large or small ring stiffener about its centroidal axis (mm :in ), moment of inertia of a large or small ring stiffener plus effective length of shell about 4 4 centroidal axis of combined section (mm :in ), design length of a vessel section between lines of support; a line of support is; a circumferential line on a head (excluding conical heads) at one-third the depth of the

Not for Resale


--``````-`-`,,`,,`,`,,`---

LB

=

Lc Lct Lf

= = =

Ls

=

Lt Rm Ro RR

= = = =

t1 t2 Zc

= = =

Zs

=

I ys

=

head from the tangent line as shown in Figure A.12 or a stiffening ring that meets the requirement of paragraph A.4.4.3 (mm:in), length of cylinder between bulkheads or large rings designed to act as bulkheads (see Figure A.12), (mm:in), Total length of a conical transition (see Figure A.3 and A.4) (mm:in), Length of the cone section in a conical transition (see Figure A.4) (mm:in), one-half of the sum of the distances, LB, from the centerline of a large stiffening ring to the next large stiffening ring or head line of support on either side of the large ring, measured parallel to the axis of the cylinder (see Figure A.12), (mm:in), one-half of the sum of the distances from the centerline of a small stiffening ring to the next line of support on either side of the ring, measured parallel to the axis of the cylinder (see Figure A.12); a line of support is described in the definition for L (mm:in), overall length of vessel as shown in Figure A.12 (mm:in), Mean radius of shell; use the large end radius for a conical shell (mm:in), Outside radius of shell; use the large end radius for a conical shell (mm:in), radius to centroid of combined large ring and effective width of shell (see Figure A.11) (mm:in), Ring stiffener dimension (see Figure A.11), (mm:in), Ring stiffener dimension (see Figure A.11), (mm:in), radial distance from the outside of the shell to the combined centroid of the ring stiffener and shell section (defined as positive for outside rings, see Figure A.11) (mm:in), radial distance from the outside of the shell to the centroid of the ring stiffener (defined as positive for outside rings, see Figure A.11) (mm:in), yield stress of material at the assessment temperature (see Appendix F), (MPa:psi).

A.4.4

Cylindrical Shell – The minimum thickness and MAWP equations are as follows:

A.4.4.1

Determination of the MAWP

MAWP = 2 Fha

FG t IJ HD K c

(A.148)

o

Fha =

I ys

for

FS

Fhe ³ 2.439 I ys

F I GH JK

0.7I ys Fhe Fha = FS I ys

Fha =

Fhe =


Fhe FS

for

(A.149)

0.4

for 0.552 <

Fhe < 2.439 I ys

(A.150)

Fhe £ 0.552 I ys

(A.151)

16 . Ch E y t c

(A.152)

Do

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Ch

Ft I = 0.55G J HD K c

for

Mx

o

Ch = 112 . M

FD I ³ 2G J Ht K

0.94

o

(A.153)

c

-1.058 x

for 13 < M x

FD I < 2G J Ht K

0.94

o

(A.154)

c

0.92 M x - 0.579

Ch = 10 .

--``````-`-`,,`,,`,`,,`---

A.4.4.3

(A.155)

M x £ 15 .

for

(A.156)

L Ro t c

Mx = A.4.4.2

for 15 . < M x < 13

(A.157)

Determination of a Minimum Thickness – To determine a minimum thickness for a specified design pressure and temperature, an iterative procedure is required. A thickness is assumed, the MAWP is computed and this value is compared to the design pressure. If the computed MAWP is less than the design pressure, a larger thickness is assumed and the calculations are repeated. This process is continued until the computed MAWP is greater than the specified design pressure. Stiffening Ring Size – The following equations can be used to determine the size of a stiffening ring based on a loading condition. a.

Uniform Axial Compression and Axial Compression Due to Bending – when ring stiffeners are used to increase the allowable longitudinal compressive stress, the cross sectional area and moment of inertia of the stiffener shall satisfy the following equations (for a stiffener to be considered, M x < 15.0 ).

As ³

FG 0.334 - 0.063IJ L t HM K

I ss ³

5.33 Ls t c3 M s1.8

0 .6 s

s c

and

As ³ 0.06 Ls t c

(A.158)

(A.159)

where,

Ms = b.

Ls Ro t c

(A.160)

External Pressure 1.

Small Stiffening Ring – The required moment of inertia based on compressive stress is established using the following equations with Fhe evaluated using the equations in paragraph A.4.4.1 with


M x = M s = Ls

Not for Resale

Ro t c .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Ch =


. Fhe Ls RR2 t c 15 I ss ³ E y n2 - 1

c

(A.161)

h

where,

n=

2 Do1.5 3 LB t c0.5

where n is an integer; for n < 2 use n = 2,

(A.162)

and for n > 10 use n = 10

2.

As Z s2 Le t c Le t c3 I ss = I s + + As + Le t c 12

(A.163)

Le = 11 . Do t c

(A.164)

Large Stiffening Ring or Bulkhead – The required moment of inertia based on compressive stress is established using the following equations where Fhef is the average value of the hoop buckling stress, Fhe, evaluated using the equations in paragraph A.4.4.1 with

I ss ³

M x = Ms = Lf

Ro t c .

Fhef L f RR2 t c

(A.165)

2Ey

where Iss is given by the equation in subparagraph 1 above except that Le is evaluated using the following equations.

Le = 11 . Do t c

FG A IJ HA K 1

(A.166)

2

--``````-`-`,,`,,`,`,,`---

c.

A1 = As + Lt c

(A.167)

A2 = A f + Lt c

(A.168)

Shear – The required moment of inertia based on shear stress is established using the following equations with Cv evaluated using the equations in Appendix B, paragraph B.4.4.1.f with

M x = M s = Ls

Ro t c .

I ss ³ 0184 . Cv M s0.8t c3 Ls d.

(A.169)

Local Stiffener Geometry Requirements for all Loading Conditions – The following equations can be used to determine the stability of a stiffening ring. 1.


Flat bar stiffener, flange of a tee section and the outstanding leg of an angle stiffener (see Figure A.11).

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


F I GH JK

Ey h1 £ 0.375 t1 I ys

(A.170)

Web of a tee stiffener or leg of angle stiffener attached to the shell (see Figure A.11).

F I GH JK

Ey h2 £ t2 I ys

0.5

(A.171)

A.4.5

Spherical Shell or Hemispherical Head – The minimum thickness and MAWP equations are as follows:

A.4.5.1

Determination of the MAWP

MAWP = 2 Fha

FG t IJ HR K c

(A.172)

o

Fha =

Fha =

I ys FS

Fhe ³ 6.25 I ys

for

131 . I ys

F. +F I FS G 115 H I JK

for 16 . <

he

(A.173)

Fhe < 6.25 I ys

(A.174)

ys

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Fha =

Fha =

018 . Fhe + 0.45I ys FS

Fhe FS

Fhe £ 1.6 I ys

Fhe £ 0.55 I ys

for

Fhe = 0.075E y

for 0.55 <

(A.175)

(A.176)

FG t IJ HR K c

(A.177)

o

A.4.5.2

Determination of a Minimum Thickness – The minimum thickness is determined using the procedure in paragraph A.4.4.2.

A.4.6

Elliptical Head – The minimum thickness and MAWP for an elliptical head (see Figure A.1) can be determined using the equations for a spherical shell in paragraph A.4.5 by substituting KcDo for Ro. An equation for Kc is provided in paragraph A.3.6.

A.4.7

Torispherical Head – The minimum thickness and MAWP for an torispherical head (see Figure A.1) can be determined using the equations for a spherical shell in paragraph A.4.5 by substituting the outside crown radius for Ro.


Not for Resale

--``````-`-`,,`,,`,`,,`---

2.

0.5


A.4.8

Conical Shell – The minimum thickness and MAWP equations for a conical shell are as follows (see Figures A.2 to A.6).

A.4.8.1

Determination of the MAWP (a £ 60 Degrees) – The MAWP can be determined using the equations for a cylinder in paragraph A.4.4 by making the following substitutions:

b

g

0.5 DL + DS cos = is substituted for Do in the equations in paragraph A.4.4.1.

a.

The value of

b.

The value of Lc cos= is substituted for L in the equations in paragraph A.4.4.1 where Lc is determined as follows: 1.

For Sketches (a) and (b) in Figure A.4:

Lc = Lct 2.

(A.178)

For Sketch (c) in Figure A.4:

Lc = rk sin= + Lct 3.

(A.179)

For Sketch (d) in Figure A.4:

Lc = rf sin= + Lct 4.

(A.180)

For Sketch (e) in Figure A.4:

d

i

Lc = rk + rf sin= + Lct

(A.181)

A.4.8.2

Determination of a Minimum Thickness – The minimum thickness is determined using the procedure in paragraph A.4.4.2.

A.4.8.3

Intermediate Stiffening Rings – If required, intermediate circumferential stiffening rings within the conical transition can be sized using the equations in paragraph A.4.4.3.b with RR=D/2 where D is the cone diameter at the ring, t is the cone thickness, Ls is the average distance to the adjacent rings measured along the cone axis and Fhe is the average of the elastic hoop buckling stress computed for the two adjacent bays using the procedure in paragraph A.4.8.1.

A.4.8.4

Eccentric Cone – The minimum thickness of an eccentric cone is determined as defined in paragraph A.3.8.5.

A.4.9

Toriconical Head – The minimum thickness and MAWP equations for toriconical heads and transitions can be determined using the procedure of paragraph A.4.8.

A.4.10

Conical Transitions – The minimum thickness and MAWP equations for transitions can be determined using the procedure of paragraph A.4.8.

A.4.11

Nozzle Connections in Shells – The reinforcement for openings in single walled shells that do not exceed 10% of the cylinder diameter (or spherical shell or formed head diameter, as applicable) or 80% of the ring spacing into which the opening is placed may be designed in accordance with the rules provided in paragraphs A.4.4 through A.4.10. Openings in shells that exceed these limitations require a special analysis.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


A.4.11.2 For cases where the shell thickness is controlled by combinations of external pressure and axial load and/or applied bending moment, or by axial load and applied bending moment without external . (100% pressure, the reinforcement shall be in accordance with paragraph A.3.11.1 using J = 10 . . The required thickness in the unstiffened or stiffened shell section, as reinforcement) and F = 10 applicable, shall be the thickness used for the allowable stress calculation (see Appendix B, paragraph B.4.4). A.4.12

Junction Reinforcement Requirements at Conical Transitions – For a vessel subject to external pressure – In lieu of a detailed stress analysis, the localized stresses and requirements for a cone-tocylinder junction stiffening ring can be evaluated using the following procedure.

A.4.12.1 Symbol Definitions – The following symbol definitions are in addition to those shown in paragraph A.3.3:

D L1 Lc Fhe Fhec

= = = = =

Outside diameter of the cylinder at the junction (mm:in), Distance to the first stiffening ring in the cylinder section or line of support (mm:in), Distance to the first stiffening ring in the cone section or line of support (mm:in), Allowable elastic hoop stress for the cylinder (MPa:psi), Allowable elastic hoop stress for the cone treated as an equivalent cylinder (MPa:psi),

A.4.12.2 Stiffening Ring Requirements 1.

A stiffening ring at the cone to cylinder junction (large end and small end) is not required if f h < Fha where fh is the compressive hoop membrane stress in the cone at the junction given by the following equation, and Fha is determined using the equations in paragraph A.4.4.1 with

b

g

Fhe evaluated using Ch = 0.55 cos= t c Do . fh = 2.

PDo 2t cos=

(A.182)

c c

If a stiffening ring at the cone to cylinder junction (large end and small end) is required, the moment of inertia of the composite ring section should satisfy the following equation.

Ic ³

FG H

Do2 tcL F t c L1 Fhe + c c 2 hec 16 E y cos =

IJ K

(A.183)

A.4.13

Other Components – Calculation procedures for the other components are covered in paragraph A.3.13.

A.5

Piping Components

A.5.1

Overview – The minimum thickness and MAWP of a straight section or curved section of pipe subject to internal or external pressure with supplemental loads may be computed based on the original construction code. Alternatively, the equations in this section may be utilized in the calculation of these parameters. In addition, procedures to evaluate branch connections subject to internal pressure is provided. These equations are based upon the ASME B31.3 Piping Code. The effects of supplemental loads (see paragraphs A.2.6 and A.7) are included in these equations only for straight pipe (i.e. longitudinal stress direction) subject to a net-section axial force and/or bending moment.

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A.4.11.1 Reinforcement for nozzle openings in vessels designed for external pressure alone shall be in accordance with paragraph A.3.11.1 using J = 0.5 . The required thickness shall be determined using the equations in paragraphs A.4.4 through A.4.10, as applicable.


Metal Loss – The equations in this paragraph are written in terms of outside diameter of the pipe (OD); therefore, the equations do not need to be adjusted for metal loss and future corrosion allowance which occurs on the inside surface. If metal loss has occurred on the OD (e.g. corrosion under insulation), the geometry definition term in the equation, OD, would need to be modified to account for this metal loss.

A.5.3

Symbol Definitions – The following symbols defined below are used in this section.

--``````-`-`,,`,,`,`,,`---

A.5.2

E = FCA = LOSS = MA

=

Do P Rb Rm S t tc tmin tsl

= = = = = =

Y

=

= = =

Quality factor for ASME B31.3 Table A-1A or A-1B. E=1.0 for seamless pipe. Specified future corrosion allowance (see paragraph A.2.7), (mm:in), Metal loss in the shell from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection (mm:in), Mechanical allowances (thread or groove depth); for threaded components, the nominal thread depth (dimension h of ASME B.1.20.1) shall apply (mm:in), Outside diameter of the pipe (mm:in), internal design pressure (MPa:psi), Centerline bend radius (see Figure A.14), (mm:in), Mean radius of pipe (see Figure A.14), (mm:in), Allowable stress from the original construction code (MPa:psi), Nominal or furnished pipe thickness adjusted for mill tolerance (mm:in), t – LOSS – FCA (mm:in), Minimum required thickness including mechanical and corrosion allowances (mm:in), Supplemental thickness for mechanical loads other than pressure which result in longitudinal stress; this thickness is usually obtained from the results of a weight case in a stress analysis of the piping system (mm:in), and Coefficient from the following table valid for t min < Do 6 . The value of Y may be interpolated for intermediate temperatures. Materials

G

=

Temperature °C (°F) 482 (£ 900)

510 (950)

538 (1000)

566 (1050)

593 (1100)

621 (³ 1150)

Ferritic Steels

0.4

0.5

0.7

0.7

0.7

0.7

Austenitic Steels

0.4

0.4

0.4

0.4

0.5

0.7

Other Ductile Metals

0.4

0.4

0.4

0.4

0.4

0.4

Cast iron

0.4

...

...

...

...

...

Angle around the elbow circumference where results are to be computed (degrees).

A.5.4

Required Thickness and MAWP for Internal Pressure For Straight Pipe – The minimum thickness and MAWP equations for straight sections of pipe subject to internal pressure are as follows:

A.5.4.1

Circumferential stress (Longitudinal Joints):


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The effects of supplemental loads for other component geometries or loading conditions can be evaluated using the stress analysis methods in Appendix B.

--``````-`-`,,`,,`,`,,`---

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE A-31 _________________________________________________________________________________________________ C t min =

PDo + MA 2 SE + PY

b

g

b

LM Nb

g

(A.185)

OP g Q

(A.186)

Longitudinal stress (Circumferential Joints): L t min =

PDo + t sl + MA 4( SE + PY )

(A.187)

4 SE (t c - t sl - MA) Do - 4Y (t c - t sl - MA)

MAWP L =

F GH b

(A.188)

I g JK

P Do -Y E 4 t c - t sl - MA

I mL =

A.5.5

b

P Do -Y E 2 t c - MA

I Cm =

A.5.4.3

g

2 SE t c - MA Do - 2Y t c - MA

MAWP C =

A.5.4.2

(A.184)

(A.189)

Final Values: C L t min = max (t min , t min )

(A.190)

MAWP = min( MAWP C , MAWP L )

(A.191)

I max = max (I Cm , I mL )

(A.192)

Required Thickness and MAWP for Internal Pressure For Pipe Bends – The results for circumferential stress, and the minimum required thickness and MAWP are shown below for thin wall bends

bR

m

g

t c ³ 10 . Results for thick wall pipe bends which do not satisfy this criteria can be found

in DIN 2413, Parts 1 and 2. A.5.5.1

Circumferential stress – The results for any location defined by the angle G (see Figure A.14) are given by the following equations. In these equations, L f is the Lorenz factor which is a measure of the stress magnitude in a elbow relative to that in a straight pipe. When

L f = 10 . , the equations for

stress, minimum required wall thickness and MAWP are the same as those for straight pipe. If the pipe bend contains a flaw, the position defined by the angle G should coincide with the centerline of the location of the flaw if the flaw is located in the center section or middle one-third of the bend. If the flaw is not located in the center section of the bend, use L f = 10 . . C t min =

PDo

F2 SE + PY I + MA GH L JK

(A.193)

f


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


F SE I bt - MAg GH L JK MAWP = D - 2Y bt - MAg O PL L D I = - YP M E N 2bt - MAg Q 2

c

f

C

o

f

C m

(A.194)

c

o

(A.195)

c

where the Lorenz factor is given by:

F R + sinG I G R 2 JJ =G GH RR + sinG JK b

m

Lf

(A.196)

b

m

cG = -90 or G = 270 h the Lorenz factor is: F R - 0.5I G R JJ L =G GH RR - 10. JK and a the extrados cG = 90 h the Lorenz factor is: F R + 0.5I G R JJ L =G GH RR + 1.0 JK o

At the intrados

o

b

m

f

(A.197)

b

m

b

m

f

(A.198)

b

m

A.5.5.2

Longitudinal Stress – The equations in paragraph A.5.4.2. can be used.

A.5.5.3

Final Values – The equations in paragraph A.5.4.3. can be used.

A.5.5.4

If the bend angle, >, is greater than 2>a where >a is computed in degrees using the following equation, the equations in paragraph A.5.5.1 will give the correct value for the maximum hoop stress. Otherwise, the actual maximum hoop stress will be less than that given by these equations because of the strengthening effect of the attached straight pipe sections.

>a =

FG 1215.R IJ HR -R K m

b

A.5.6

m

t Rm

(A.199)

Required Thickness and MAWP for External Pressure – The minimum thickness and MAWP for straight and curved sections of pipe subject to external pressure can be determined using the methods in Appendix B, paragraph B.4.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

o


A.5.7

Branch Connections – Branch connections in piping systems have a thickness dependency and are evaluated in a Level 2 procedure. The following analysis method based on the area replacement rules in ASME B31.3 may be used for a Level 2 Assessment.

A.5.7.1

Definitions of variables (see Figure A.13):

LOSSb + FCA (mm:in), LOSSh + FCA (mm:in),

= = = = = = = = =

Effective length removed from the pipe at the branch location (mm:in), Half-width of reinforcement zone (mm:in), Outside diameter of the branch pipe (mm:in), Outside diameter of the run or header pipe (mm:in), Outside diameter of the reinforcing pad (mm:in), Specified future corrosion allowance (paragraph A.2.7), (mm:in), Metal loss in the branch pipe from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection (mm:in), Metal loss in the header pipe from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection (mm:in), Height of reinforcement zone (mm:in), Allowable stress for the header from the original construction code (MPa:psi), Allowable stress for the reinforcing pad from the original construction code (MPa:psi), Allowable stress for the weld metal from the original construction code (MPa:psi), Required thickness of the branch pipe, see paragraph A.5.4 (mm:in), Required thickness of the header or run pipe, see paragraph A.5.4; for welded pipe, when the branch pipe does not intersect the longitudinal weld on the run pipe, the basic allowable stress for the pipe may be used in determining the required wall thickness; when the branch pipe does intersect the longitudinal weld of the run pipe, the product of the basic allowable stress and the weld joint efficiency should be used in calculating the required wall thickness (mm:in), Nominal or furnished branch pipe thickness (mm:in), Nominal or furnished header or run pipe thickness (mm:in), Nominal or furnished thickness of the reinforcing pad (mm:in), Weld leg size of the branch to reinforcing pad or branch to run pipe attachment weld (mm:in), Weld leg size of the reinforcing pad to run pipe attachment weld (mm:in), and Angle between the axis of the header and branch pipe (degrees).

LOSSh =

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A.5.7.2

L4 S Sr Sw tb th

= = = = = =

Tb Th Tr wn

= = = =

wp >

= =

The condition for satisfactory reinforcement of a branch nozzle connection is given by the following:

A2 + A3 + A4 ³ A1

(A.200)

where,

b

A1 = t h d1 2 - sin >

b

g

(A.201)

gb

A2 = 2d 2 - d1 Th - t h - ch

A3 =


b

2 L4 Tb - tb - cb sin >

g

(A.202)

g

(A.203)

Not for Resale

--``````-`-`,,`,,`,`,,`---

cb ch d1 d2 Db Dh Dp FCA LOSSb


A4 = A41 + A42 + A43

(A.204)

A41 = wn2 f w

(A.205)

A42 = w 2p f w

(A.206)

d

i

A43 = Dp - Db sin > Tr f r

(A.207)

with

ncT - c ) + bT - c g + d 2hs L = min m2.5bT - c gr, m2.5bT - c g + T r LR S U . OP f = min MS V, 10 NT S W Q LR S U . OP f = min MS V, 10 NT S W Q

d 2 = max d1 ,

b

--``````-`-`,,`,,`,`,,`---

4

w

r

h

h

h

h

1

b

b

r

(A.208) (A.209)

w

(A.210)

r

(A.211)

In the above equations, if A.6

b

A1 < 0.0 use A1 = 0.0 , or if A2 < 0.0 use A2 = 0.0 .

API 650 Storage Tanks The equations to evaluate the minimum thickness and maximum fill height of an atmospheric storage tank are covered in Section 2 of API 653.

A.7

Thickness Equations For Supplemental Loads

A.7.1

Overview – Supplemental loads (see paragraphs A.2.6) may result in an axial force and/or bending moment being applied to the end of a cylindrical shell, conical shell or pipe section. This type of loading results in longitudinal membrane and bending stresses (stresses acting on a circumferential plane) in addition to the longitudinal and circumferential (hoop) membrane stress caused by pressure loading. The effects of supplemental loads for other loading conditions and/or shell geometries can be evaluated using the stress analysis methods in Appendix B.

A.7.2

Symbol Definitions – The following symbol definitions are in addition to those in paragraph A.3.3 and paragraph A.5.3.

A

=

H L Q Rm S

= = =

Length from the tangent line of the horizontal vessel to the centerline of a saddle support (mm:in), Height of the horizontal vessel head (mm:in), Tangent-to-tangent length of the horizontal vessel (mm:in), Saddle reaction resulting from the weight of the vessel and vessel contents (N:lbs),

=

Mean radius;

=

Allowable stress; the allowable tensile stress is from the original construction code and the allowable compressive stress may be taken from this code or from Appendix B, paragraph B.8.4.4 (MPa:psi),


b

g

0.25 Do + Dc (mm:in),

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


tsl

=

= G

= =

Supplemental thickness for mechanical loads other than pressure, longitudinal stress (see Paragraph A.2.6) (mm:in), One-half apex angle of the cone in a conical shell or toriconical head (degrees), and Angle of contact of the saddle with the shell (degrees).

A.7.3

Vertical Vessels Subject To Weight and Wind or Earthquake Loads – Use the equations in paragraph A.7.3 with F and M equal to the weight of the tower, attachments, and contents, and the bending moment from the wind or earthquake loading, respectively, above the point of interest. The loads resulting from wind and earthquake load may be calculated using the procedure in ASCE 7.

A.7.3.1

Thick shell:

t sl = A.7.3.2

2F 16 Do M + SEF Do + Dc cos = SEF Do + Dc Do2 + Dc2 cos =

(A.212)

F M + 2 SEF Rm cos = SEF Rm2 cos =

(A.213)

b

g

b

gc

h

Thin Shell:

t sl = A.7.4

Horizontal Vessels Subject To Weight Loads – The following equations can be used to determine the required thickness at the saddle and mid-span locations of the vessel.

A.7.4.1

Saddle Location: a.

Without Stiffening Rings At The Saddle:

t sl

b.

LM F FG sin D - cos DIJ OP H D K P =Z M MM D + sin D cos D - 2 sin D PP D Q N t

(A.214)

2

With Stiffening Rings At The Saddle:

t sl = Zt

(A.215)

where,

LM F 1 - A + R - H QL 4AG L 2 AL Z = 1M 4H 4 SEF R M L G 1+ MN GH 3L F F 5G I D= + 30J G K 180 H 12 2 m

t

A.7.4.2

2 m

2

I OP JJ P JK PPQ

(A.216)

(A.217)

Mid-span Location:

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


LM1 + 2c R - H h OP MM 4LH - 4LA PP MN 1 + 3L PQ 2 m

t sl =

3QL SEF Rm2

2

2

(A.218)

A.8

Stress Calculation Equations For Ring Stiffeners

A.8.1

Overview -The equations in the following paragraphs are provided for pressure containing components, and can be utilized for fitness-for-service assessments These equations are not readily available in the literature and are provided here for convenience.

A.8.2

Symbol Definitions – The following symbol definitions are in addition to those in paragraph A.3.3.

AR n A.8.3

2

= =

2

cross-sectional area of the ring stiffener (mm :in ), and Poison’s ratio.

Meridional Membrane And Bending Stress At A Cylindrical Shell Stiffening Ring – The results for the Meridional (longitudinal) stresses are shown below. These results are only applicable to thin wall shells

bR

m

g

t c ³ 10 when the stiffener spacing is greater than of equal to 2d (see paragraph

A.8.3.1). The meridional bending stress on the inside and outside surface at the location of the ring are given by the following equations:

FG 1 + f IJ H2 K F1 I I =I G - f J H2 K F 3 IJ FG1 - n IJ FG h IJ f =G H 1-n K H 2KH 1+ hK I s , ID = I mL

(A.219)

L m

s ,OD

(A.220)

0.5

(A.221)

2

D=

c=

where A.8.3.2

AR 2t c 2cRm

c

tc

12 1 - n 2

(A.222)

(A.223)

h

I mL is given by the equation in paragraph A.3.4.2.

The meridional membrane stress at the location of the ring is given by the following equation:

I s ,m =

I s , ID + I s ,OD 2

(A.224)

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A.8.3.1


References

A.9.1

Farr, J.R. and Jawad, M.H., “Guidebook For The Design of ASME Section VIII Pressure Vessels,” ASME, New York, N.Y., 1998.

A.9.2

Miller, C.D. and Mokhtarian, K, “A Comparisons of Proposed Alternative Rules with ASME Code Rules for Determining Allowable Compressive Stresses,” The Eight International Conference on Pressure Vessel Technology, Montreal, Canada, July, 1996.

A.9.3

Osage, D.A., Buchheim, G.M., Brown, R.G., Poremba, J., “An Alternate Approach For Inspection Scheduling Using the Maximum Allowable Working Pressure for Pressurized Equipment,” PVP-Vol. 288, American Society of Mechanical Engineers, 1994, pp. 261-273..

A.9.4

Steele, C.R., “Cylindrical Vessel with Ring Stiffeners,” Private Communication to D.A. Osage, January 1997.

A.9.5

Rodabaugh, E.C., Duffy, A.R., and Atterbury, T.J., “The Internal Pressure Capacity of Butt Welding Elbows,” American Gas Association, NG-18, Report No. 22, September, 1969.

A.9.6

WRC, “Review Of Area Replacement Rules for Pipe Connections in Pressure Vessels and Piping,” WRC-335, Welding Research Council, New York, October 1988.

A.9.7

WRC, “Proposed Rules for Determining Allowable Compressive Stresses for Cylinders, Cones, Spheres and Formed Heads,” WRC Bullentin 406, Welding Research Council, New York, 1995.

A.9.8

Zick, L.P., “Stresses in Large Horizontal Cylindrical Pressure Vessels on Two Saddle Supports,” Welding Research Journal Supplement, September, 1951.

A.9.9

Zick, L.P. and Germain, A.R., “Circumferential Stresses in Pressure Vessel Shells of Revolution,” Journal of Engineering for Industry, ASME, New York, N.Y., 1963.

A.10

Tables and Figures

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A.9


Not for Resale


Table A.1 Loads, Load Cases, And Allowable Design Stresses Loading Condition Erection

Hydrostatic Testing

Normal Operation

Normal Operation plus Occasional (note: occasional loads are usually governed by wind and earthquake; however, other load types such as snow land ice loads may govern, see ASCE7)

Abnormal or Startup Operation plus Occasional (see note above)

Design Loads

Allowable Stress

1.

Dead load of component less: insulation, fireproofing, piping, all loose internals, catalyst, packing, etc.

2.

Temporary loads and forces cased by erection

3.

Full wind or earthquake, whichever is greater.

1.

Dead load of component plus insulation, fireproofing, installed internals, platforms and other equipment supported from the component in the installed position.

2.

Piping loads including pressure thrust

3.

Applicable live loads excluding vibration and maintenance live loads.

4.

Pressure and fluid loads (water) for testing and flushing equipment and piping unless a pneumatic test is specified.

5.

Wind load for a wind speed of 56.3 Km/hr (35 mph).

1.

Dead load of component plus insulation, refractory, fireproofing, installed internals, catalyst, packing, platforms and other equipment supported from the component in the installed position.

2.


3.

Applicable live loads.

4.

Pressure and fluid loading during normal operation.

5.

Thermal loads.

1.


2.


3.


4.

Pressure and fluid loading during normal operation.

5.

Thermal loads

6.

Full wind, earthquake or other occasional loads, whichever is greater.

1.


2.


3.


4.

Pressure and fluid loading associated with the abnormal or start-up conditions

5.

Thermal loads

6.

Wind load for a wind speed of 35 mph.

Code of construction design allowable stress as determine in paragraph A.2.3.

Code of construction design allowable stress as determined in paragraph A.2.3. In addition, the following limits may be considered: 1.

Tensile membrane stresses shall not exceed 90% of the minimum specified yield strength at 38°C (100°F) multiplied by the applicable weld joint efficiency.

2.

Longitudinal compressive membrane stresses shall not exceed the allowable compressive stress calculated at 38°C (100°F).

Code of construction design allowable stress as determined in paragraph A.2.3.

Code of construction design allowable stress as determined in paragraph A.2.3 modified as follows: Vessels – per ASME B&PV Code, Section VIII, Division 1, the allowable stress may be increased by 20% in accordance with UG-23(d). However, this value of stress should not exceed the yield stress of the material at temperature. Piping – per Paragraph 302.3.5, limits for occasional loads per Paragraph 302.3.6 of the ASME B31.3 Piping Code.

Code of construction design allowable stress as determined in paragraph A.2.3 modified as follows: Vessels – Same as above Piping – per Paragraph 302.3.5, limits for occasional loads per Paragraph 302.3.6, allowances for pressure and temperature variations per Paragraph 302.2.4. of the ASME B31.3 Piping Code,

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table A.2 Temperature Limits For Compressive Stress Equations ASME B&PV Code Table In Which The Material Is Listed

Temperature Limit o

Section VIII, Division 2

UCS-23.1

ACS-1

427

800

UNF-23.1

ANF-1.1

149

300

UNF-23.2

ANF-1.2

66

150

UNF-23.3

ANF-1.3

482

900

UNF-23.4

ANF-1.4

316

600

UNF-23.5

---

316

600

UHA-23

AHA-1

427

800

UHT-23

AQT-1

371

700

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C

o

Section VIII, Division 1

F


Figure A.1 Elliptical And Torispherical Head Geometry CL t

A

B D Rell= B/A (a) Elliptical and Torispherical Head Geometries

CL

t

rk r

C

rk D

rk/Cr x 100 ³ 6% (b) Torispherical Head Geometry

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure A.2 Conical Transition And Toriconical Head Geometry C L

=

Stiffening Ring

L

D

(a) Conical Shell and Toriconical Head Geometries

D CL rk

rk

= Knuckle

L

=

Stiffening Ring

(b) Toriconical Head Geometry

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure A.3 Conical Transition Geometry RS

Lc

CL

RS

Lc

=

t

CL

t

= rk

= RL

RL

(a)

(b) CL

C L RS

RS

rf

rf

= Flare

t

Lc

=

Lc

Knuckle

rk rk

RL

RL (d)

(c)

Note: rk => max[0.12(RL + t), 3tc]; Rs has no dimensional requirements. =1 =2 (e)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~

--``````-`-`,,`,,`,`,,`---

=1 > =2 ; Therefore use =1 in design equations.


Not for Resale


Figure A.4 Conical Transition Geometry – Unsupported length For Conical Transitions

DL

DL

=

=

Portion of a cone

Lc=Lct

Lc=Lct

DS

(a)

DS DL

DLS

(b)

rk = Lc

=

= DL

Lct

Lc

Lct

DS

= rf

(c)

(d)

DS

DSS

DLS rk

= Lc

DL

=

Lct

DS

rf (e)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@


DSS

Not for Resale

--``````-`-`,,`,,`,`,,`---

=


Figure A.5 Nozzle Parameters – Area Replacement Method Dp tn tr n

Cn te

2.5t or 2.5tn + te Use smaller value

Include consideration of these areas if Sn / Sv < 1.0

tvr

Cs

--``````-`-`,,`,,`,`,,`---

2.5t or 2.5tn Use smaller value

h dc dc or Rnc + tn + t Use larger value

dc or Rnc + tn + t Use larger value For nozzle wall abutting the vessel wall

For nozzle wall inserted through the vessel wall

-A

Required reinforcement area

- A1

Available reinforcement area in the shell

- A2

Available reinforcement area in the nozzle

- A3

Available reinforcement area, inside nozzle projection

- A4 1

Available reinforcement area in the nozzle to pad or vessel weld

- A4 2

Available reinforcement area in the nozzle to weld, inside surface

- A4 3

Available reinforcement area in the reinforcing pad attachment weld

- A5

Available reinforcement area in the reinforcing pad


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

t

Rnc


Figure A.6 Nozzle Parameters – Limit Load Analysis C L

dm Nozzle

Reinforcement Zone

trn

tn Ln

Vessel

tr

t

Ln Dm Lv

Lv Nozzle Without Reinforcing Element Metal Loss

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure A.7 Nozzle Parameters (Integrally Reinforced Nozzle Neck) – Limit Load Analysis C L

dm

trn --``````-`-`,,`,,`,`,,`---

tp Nozzle

Reinforcement Zone

tn L

tr

t

Ln Dm Lv

Lv Integrally Reinforced Nozzle Metal Loss


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Vessel

Ln


Figure A.8 Definition Of Paths For A Nozzle Weld Strength Analysis – Set-in Nozzle

--``````-`-`,,`,,`,`,,`---

do dm

wn

wp

wpg wng

t wh

tn Dp (a) Nozzle and Weld Dimensions

tn //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Cn trn

2

1

3

3 1

t

1

tr Cs

3

3 2

2

A1

A41

A2

A42

A3

A43

A5 (b) Weld Strength Paths


2

Not for Resale

1


Figure A.9 Definition Of Paths For A Nozzle Weld Strength Analysis – Set-on Nozzle

do dm tn

wp

wn

t W ng

Dp (a) Nozzle and Weld Dimensions

tn Cn trn 2

2 1

t

1

1

2

2

1

tr

--``````-`-`,,`,,`,`,,`---

Cs

A1

A41

A2

A42

A5 (b) Weld Strength Paths


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


--``````-`-`,,`,,`,`,,`---

Figure A.10 Definition Of Lines Of Support For A Conical Transition

CL

0.5DR t

be=0.55[(Dot)1/2 +(Dotc/cos=)1/2]

t L1

L1 Lc

=

Internal Junction Ring

tc

Lc

=

t

CL 0.5D R L1

be

External Junction Ring (a) Stiffened


tc

(b) Unstiffened

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure A.11 Stiffening Ring Variables RR = Ro + Zc

RR=Ro+Zc

Zc

Zc

AF, IF

AS, IS

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Le

Le

t t Ro

Zs

Ro

Zs

(a) Large and Small Stiffening Rings

h1

h2

h2 t2

Shell

Shell t1

h1

Shell t1

(b) Stiffener Variables for Local Buckling Calculation


Not for Resale

t2

2h1

t1


Figure A.12 Definition Of Lines Of Support For Design Of Cylindrical Vessels Subjected To External Pressure

h/3

h/3

h

h

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Head (Effective as Bulkhead) Do

L LB1 Do

L=Lt Large Ring (Effective as Bulkhead)

L

0.5L1 0.5LB2

L1

LS

L2 LB2

0.5L2

Lt Lf

L LB3

Head (Effective as Bulkhead) h

0.5LB3 L

h

--``````-`-`,,`,,`,`,,`---

h/3

h/3

(b) Ring Stiffened

(a) Unstiffened


Not for Resale


Figure A.13 Definition of Variables For Branch Reinforcement Calculation In Piping Systems

Db

Tb Limits of reinforcement zone

C Tb

tb Mill tolerance Reinforcement areas Thickness, measured or minimum per purchase specification

A4

L4

Branch pipe or nozzle A3

A4

A3 Multiply this area by (2 - sin >) to get required area

A1

Tr

Reinforcement areas

Branch pipe or nozzle

Limits of reinforcement zone

Th c

Mill tolerance Nominal thickness

Run pipe

A2

d1

A2

d2

Dh

Run pipe

d2

> CL Pipe

Notes: A1 = Required reinforcement area (mm2:in2), A2 = Available reinforcement area resulting from excess thickness in the run pipe (mm2:in2), A3 = Available reinforcement area resulting from excess thickness in the branch pipe (mm2:in2), A4 = Available reinforcement area provided by the welds and reinforcement pad (mm2:in2), A41 = Available reinforcement area provided by the nozzle to pad or nozzle to pipe attachment welds 2 2 (mm :in ), A42 = Available reinforcement area provided by the reinforcement pad attachment welds (mm2:in2),and A43 = Available reinforcement area provided by the reinforcement pad (mm2:in2).

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

th Th


Not for Resale


Figure A.14 Definition of Variables For Piping Bends

G

Extrados Rm

Intrados

>

--``````-`-`,,`,,`,`,,`---

Rb (a) Bend Geometry

Flaw

G

Rb

(b) Flaw Location

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~


Not for Resale

APPENDIX B – Stress Analysis Overview For A FFS Assessment

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

B.1

Stress Analysis Methods In A Fitness-For-Service Assessment

B.1.1

The analytical methods contained within this section can be used for stress analysis when performing a Fitness-For-Service (FFS) Assessment of a component with a flaw. These methods are typically employed in either a Level 2 or Level 3 assessment.

B.1.2

Recommendations are provided on how to perform and utilize the results from a finite element stress analysis in a fitness-for-service assessment. Procedures for performing linear and non-linear analysis, determination of stress categories and classification of stress results obtained from a linear analysis, and a methodology to perform an elastic-plastic analysis to determine a collapse load or to perform a fatigue evaluation are among the items covered in this appendix.

B.1.3

The methods presented in this appendix can be used to evaluate volumetric flaws (i.e. general metal loss, localized metal loss, and shell distortions) and crack-like flaws. Linear or non-linear stress analysis can be used to evaluate volumetric flaws using stress categorization or by determining a plastic collapse load, respectively. The assessment criteria for crack-like flaws can also be based on linear or non-linear stress analysis. If a linear stress analysis is used, the acceptance criteria is based on a two parameter Failure Assessment Diagram (FAD) approach to evaluate the combined effects of fracture and plastic collapse (see Section 9). Alternatively, if a non-linear stress analysis is used, the crack-like flaw can be evaluated directly by using the J-integral. An overview of the assessment requirements for volumetric and crack-like flaws is provided below.

B.1.3.1

The following criteria should be satisfied to establish structural integrity of a component with a volumetric flaw.

B.1.3.2

B.1.4

a.

Allowable Stress – The requirements of paragraphs B.2 or B.3 should be satisfied.

b.

Structural Stability – For components subject to a compressive stress, buckling should be evaluated per paragraph B.4.

c.

Fatigue (Initiation) – For components subject to cyclic operation, the assessment procedures in paragraph B.5 should be satisfied.

d.

Creep-Fatigue (Initiation) – Assessment requirements for components subject to cyclic operation in the creep regime are covered in Section 10.

The following criteria should be satisfied to establish structural integrity of a component with a cracklike flaw: a.

Crack Stability and Growth (Low Temperature) – The assessment requirements for fracture are provided in Section 9; however, stress analysis results using information in this appendix are required for the assessment.

b.

Crack Stability and Growth (High Temperature) – The assessment requirements for creep crack growth are provided in Sections 9 and 10; however, stress analysis results using information in this appendix are required for the assessment.

c.

Structural Stability – For components subject to compressive stress fields, buckling should be evaluated per paragraph B.4.

The methods in this appendix are based on the design-by-analysis methods in the ASME Code, Section VIII, Division 2, Appendix 4 and Appendix 5; however, there are some noted differences


B-1 Not for Resale

--``````-`-`,,`,,`,`,,`---

(Jan, 2000)

B-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

such as the use of the Maximum Distortion Energy Yield Criterion and fatigue evaluation using plastic strains. The direct use of the ASME Code methods is also acceptable. B.2

Linear Elastic Stress Analysis Methods And Acceptance Criteria

B.2.1

Basis for Determining Stresses – A quantity known as the "equivalent intensity of combined stress" or "stress intensity" is computed at locations in the component and compared to an allowable value of stress intensity to determine if the component is suitable for the intended operating conditions.

B.2.1.1

The stress intensity at a point in a component is a measure of stress, calculated from stress components utilizing a yield criterion, which can be used for comparison with the mechanical strength properties of the material obtained in tests under uniaxial load.

B.2.1.2

The following yield criteria may be used to establish stress intensity. a.

Maximum Shear Stress Yield Criterion – The stress intensity is equal to twice the maximum shear stress which is equal to the difference between the algebraically largest and the algebraically smallest of the three principal stresses, I i , at the point:

S = 2J max = max I 1 - I 2 , I 2 - I 3 , I 3 - I 1 b.

(B.1)

Maximum Distortion Energy Yield Criterion – The stress intensity is equal to the von Mises equivalent stress; the use of this failure theory and stress intensity is recommended. Although this yield criterion is more complicated to apply when manual calculations are performed, it is the most common criterion for yield used in finite element analysis, and is generally recognized to give more accurate results than the maximum shear stress yield criterion.

S = I von Mises =

b

1 I1 -I 2 2

g + bI 2

2 -I 3

g + bI 2

3 -I1

g

2 0.5

(B.2)

B.2.2

Stress Categorization and Allowable Stress Intensities – In order to demonstrate structural integrity, the results from a stress analysis are categorized and compared to an associated limiting value.

B.2.2.1

The five basic stress intensity categories and associated limits which are to be satisfied are defined below. The terms general primary membrane stress, local primary membrane stress, primary bending stress, secondary stress, and peak stress are defined in Appendix I. a.

General Primary Membrane Stress Intensity

b P g , (see Figure B.1) is the stress intensity, m

derived from the average value across the thickness of a section, of the general primary stresses produced by the design internal pressure and other specified mechanical loads but excluding all secondary and peak stresses. The allowable value of this stress intensity is kSm where k is defined in Table B.1. The allowable stress, for different type of equipment. b.

Local Primary Membrane Stress Intensity

Sm , is evaluated per paragraph B.2.3

b P g , (see Figure B.1) is the stress intensity, L

derived from the average value across the thickness of a section, of the local primary stresses produced by the design pressure and specified mechanical loads but excluding all secondary and peak stresses. A region of stress in a component is considered as local if the distance over which the stress intensity exceeds 1.1Sm does not extend in the meridional direction more than Rt where R is the mid-surface radius of curvature measured normal to the surface from the axis of rotation and t is the minimum thickness in the region being considered. The allowable value of this stress intensity is 1.5kSm where k is defined in Table B.1.

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c.

Primary Membrane (General or Local) Plus Primary Bending Stress Intensity

b P + P g , (see L

b

Figure B.1) is the stress intensity, derived from the highest value across the thickness of a section, of the general or local primary membrane stresses plus primary bending stresses produced by design pressure and other specified mechanical loads but excluding all secondary and peak stresses. The allowable value of this stress intensity is 1.5kSm where k is defined in Table B.1. d.

Primary Plus Secondary Stress Intensity

b P + P + Qg , (see Figure B.1) is the stress L

b

intensity, derived from the highest value at any point across the thickness of a section, of the combination of general or local primary membrane stresses plus primary bending stresses plus secondary stresses, produced by specified operating pressure and other specified mechanical loads and by general thermal effects. The effects of gross structural discontinuities but not of local structural discontinuities (stress concentrations) shall be included. The maximum range of this stress intensity is limited to 3Sm . e.

Primary plus Secondary plus Peak Stress Intensity

b P + P + Q + F g , (see Figure B.1) is the L

b

stress intensity, derived from the highest value at any point across the thickness of a section, of the combination of all primary, secondary, and peak stresses produced by specified operating pressures and other mechanical loads and by general and local thermal effects and including the effects of gross and local structural discontinuities. This stress intensity is used in a fatigue evaluation in accordance with the ASME Code, Section VIII, Division 2, Appendix 5 to determine a permissible number of operating cycles (see paragraph B.5.2). B.2.2.2

Triaxial Stress Limits – The algebraic sum of the three primary principal stresses

bI

1

g

+ I 2 + I 3 at

the point being investigated should not exceed 4Sm . B.2.3

Establishment of the Allowable Stress Intensity – The allowable stress intensity,

Sm , to be used in

conjunction with paragraph B.2.2 in a FFS assessment is covered below. B.2.3.1

The allowable stress intensity is based on the type of equipment. a.

Pressure Vessels (API 510) – The stress value used in the original pressure vessel design shall be used for Sm but in no case shall Sm be greater than two-thirds of the specified minimum yield strength at temperature. Alternatively, for vessels constructed to the ASME B&PV Code, Section VIII, Division 1, Sm may be taken from ASME B&PV Code, Section VIII, Division 2 for use in a fitness-for-service assessment if the component has similar design details and NDE prerequisites as originally required for a Division 2 vessel design. In order to make this judgment, an evaluation by an engineer knowledgeable in the design of Division 1 and Division 2 pressure vessels is required.

b.

Piping (API 570) – The basic allowable stress from the applicable piping code (e.g. ASME B31.3) shall be used for Sm , but in no case shall Sm be greater than two-thirds of the specified minimum yield strength at temperature.

c.

Tankage (API 653) – The basic allowable stress from the applicable tank design standard shall be used for Sm . However, if the design stress is greater than the maximum of two-thirds of

(2 3×I ys ) or one-third of the specified minimum tensile strength at temperature (1 3×I ts ) , then the value of Sm shall be taken as the minimum value of (2 3×I ys ) and (1 3×I ts ) . the specified minimum yield strength at temperature

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B.2.3.2

3Sm in paragraph B.2.2 represents a limit on the primary plus secondary stress intensity range. Therefore, when evaluating this quantity, Sm shall be computed as the average of Sm at the

The quantity

highest and lowest temperatures in the cycle. In the determination of the maximum primary plus secondary stress intensity range, it may be necessary to consider the effects of multiple cycles where the total stress range may be greater than the stress range of any of the individual cycles. In this case, the value of 3Sm may vary with the specified cycle, or combination of cycles, being considered since the temperature extremes may be different in each case. Therefore, care must be exercised to assure that the applicable value of 3Sm for each cycle, or combination of cycles, is used (see paragraph B.5.2.3). B.2.4

Derivation and Categorization of Computed Stress Intensities – To determine the acceptability of a component with a flaw, the computed stress intensities for a component subject to loads shall not exceed the specified allowable stress intensity limits in paragraph B.2.2.

B.2.4.1

The following procedure can be used to compute and categorize the stress intensity at a point in a component. a.

Step 1 – Determine the types of loads the component will be subject to. In general, separate load cases should be analyzed to evaluate "load-controlled" loads such as pressure and externally applied reactions due to weight effects and "strain-controlled" loads resulting from thermal gradients and imposed displacements. An overview of the load cases to be considered is provided in Table A.1 of Appendix A.

b.

Step 2 – At the point on the vessel which is being investigated, calculate the stress tensor (six unique components of stress) for each type of load. Assign each of the computed stress tensors to one or to a group of the categories defined below. Assistance in assigning each stress tensor to an appropriate category for a component with or without a flaw can be obtained by using Figure B.1 and Table B.2.

c.

1.

General primary membrane stress Pm,

2.

Local primary membrane stress PL,

3.

Primary bending stress Pb,

4.

Secondary stress Q, and

5.

Peak stress F.

Step 3 – Sum the stress tensors (stresses are added on a component basis) assigned to each stress intensity category. The final result is a stress tensor representing the effects of all of the loads assigned to each stress intensity category. Note that in applying steps in paragraph B.2.4.1, a detailed stress analysis performed using a numerical method such as finite element analysis typically provides a combination of PL + Pb and PL + Pb + Q directly. Therefore, it is not necessary to determine the stress associated with a specific category. For example, if PL + Pb is computed directly in the analysis, it is not necessary to determine PL and Pb independently for the purpose of stress categorization. 1.

If a load case is analyzed that includes only "load-controlled" loads (e.g. pressure and weight effects), the computed stress intensities can be used to directly represent the total Pm , PL + Pb , or PL + Pb + Q . For example, for a vessel subject to internal

Pm stress intensities occur away from the head to shell junction, and PL and PL + Pb + Q stress intensities occur at the junction. pressure with an elliptical head;

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2.

If a load case is analyzed that includes only "strain-controlled" loads (e.g. thermal gradients), the computed stress intensities represent Q alone; the combination PL + Pb + Q would need to be derived from a load case developed from both "loadcontrolled" and "strain-controlled" loads.

3.

If the stress in category F is produced by a stress concentration, the quantity F is the additional stress produced by the stress concentration over and above the nominal stress level. For example, if a plate has a nominal stress intensity of S, and has a stress concentration characterized by a factor K, then: Pm = S , Pb = 0 , Q = 0 , and

b

g

F = Pm K - 1 . The peak stress intensity, is Pm + F , or with F = Pm + Pm K - 1 = Pm K .

b

g

d.

Step 5 – Determine the principal stresses of the sum of the stress tensors assigned to the stress intensity categories, and compute the stress intensity using either equation (B.1) or (B.2).

e.

Step 6 – Compare the computed stress intensity to the allowable stress intensity for each category of stress, see paragraphs B.2.2.

B.2.4.2

For components with a complex geometry and/or complex loading, the categorization of stresses requires significant knowledge and judgment on the part of the analyst. This is especially true for three-dimensional stress fields. Application of the plastic analysis methods in paragraph B.3.3 is recommended for cases were the categorization process may produce ambiguous results.

B.2.4.3

The use of stress classification to demonstrate structural integrity for heavy-wall pressure containing components, especially around structural discontinuities, may produce non-conservative results and is not recommended. The reason for the non-conservatism is related to the fact that the nonlinear stress distributions associated with heavy wall sections are not accurately represented by the implicit linear stress distribution utilized in the stress categorization and classification procedure. The misrepresentation of the stress distribution is enhanced if yielding occurs. For example, in cases where calculated peak stresses are above yield over a through thickness dimension which is more than five percent of the wall thickness, linear elastic analysis may give a non-conservative result. In these cases, an elastic/plastic analysis should be performed.

B.3

Nonlinear Elastic-Plastic Stress Analysis Methods And Acceptance Criteria

B.3.1

Overview – Structural evaluation procedures using either ASME Code formulas or linear elastic stress analysis techniques provide only a rough approximation of the loads which a component can withstand before collapse. A better estimate of the safe load carrying capacity of a component can be obtained using nonlinear stress analysis to develop limit and plastic collapse loads, evaluate deformation characteristics of the component including ratcheting, and to assess creep and/or fatigue damage.

B.3.1.1

In a nonlinear structural analysis, three forms of nonlinearity should be considered: geometric, material, and combined geometric and material nonlinearity. When geometric nonlinearity is included in a analysis, the strain-displacement relationships are nonlinear. When material nonlinearity is included in an analysis, the stress-strain relationships are non-linear, and may be either elastic or inelastic. If they are elastic, there is a unique relationship between stress and strain. If they are inelastic, plastic strains are produced and the stress-strain relationship becomes path dependent. The effects of both geometric and material nonlinearity are important when determining limit and plastic collapse loads, and the deformation characteristics of the component (ratcheting).

B.3.1.2

The calculated stress intensity computed using linear analysis need not satisfy the requirements in paragraph B.2 if a nonlinear stress analysis is utilized to determine the behavior of the component.

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B.3.1.3

a.

The limits on the general membrane intensity, local membrane stress intensity and primary membrane plus primary bending stress intensity have been placed at a level which conservatively assures the prevention of collapse as determined by the principles of limit analysis. These limits need not be satisfied at a specific location if it can be shown that the specified loads do not exceed two-thirds of the lower bound limit load or two-thirds of the plastic analysis collapse load.

b.

The limit on the primary plus secondary stress intensity has been placed at a level which assures shakedown to elastic action after a few repetitions of the stress cycle except in regions containing significant local structural discontinuities or local thermal stresses. These last two factors are considered only in the performance of a fatigue evaluation. In lieu of satisfying these limits, the structural behavior can be evaluated using an elastic-plastic stress analysis. The component is considered to be acceptable if shakedown occurs, as opposed to continuing deformation, and if the deformations which occur prior to shakedown do not exceed specified limits which would render the component inoperable or have an effect on structural integrity.

When a nonlinear stress analysis (geometric and/or material nonlinearity) is used to determine the safe load carrying capacity of a component, the following should be included as part of the assessment. The effects of plastic strain concentrations in areas of the component containing either major or local geometric discontinuities should be evaluated. An upper limit on the accumulated membrane, bending, and/or peak strain may need to be established to ensure structural integrity.

b.

The structural stability of the component should be evaluated if the applied loads result in a compressive stress field. If imperfections are present in the component (e.g. dents, bulges, out-of-roundness resulting from in-service loads), their effects should be included as part of the assessment because the structural stability of some components, especially shell type structures, may be reduced significantly. Recommendations for evaluating components subject to compressive stresses are covered in paragraph B.4.

c.

If the loading is cyclic, the component is considered to be acceptable if shakedown occurs, as opposed to continuing deformation with each cycle. If shakedown can be demonstrated, the peak stress intensity for comparison with the appropriate fatigue design curve should be computed using total strains derived from the analysis (see paragraph B.5.4). Note that if a weld is present, an additional fatigue strength reduction factor may be required if a fatigue evaluation is performed in accordance with the ASME Code, Section VIII, Division 2, Appendix 5 (see paragraph B.5.2).

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a.

B.3.2

Limit Loads – Limit loads can be utilized to evaluate both volumetric and crack-like flaws in components. A measure of the deformation characteristics of the component is usually not provided by a limit load solution. If deformation characteristics are important, a plastic collapse solution should be obtained. Despite this limitation, limit load solutions are still valuable in determining the load bearing capability of a component and have been used to determine the collapse loads for assessment of crack-like flaws (see paragraph B.5.2.4).

B.3.2.1

The theoretical limit load can be defined as the maximum load solution to an analytical model of a structure which embodies the following conditions: a.

The material response is rigid plastic or elastic-perfectly-plastic with an admissible yield function.

b.

The strain-displacement relations are those of small displacement theory.

c.

The internal stress and applied forces are related by the usual equations of equilibrium which ignore changes in geometry due to deformations.


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B.3.2.2

Lower and upper bound solutions can be developed to bracket the limit load. The efficiency of a limit load solution can be assessed by comparing the difference between the lower and upper bound limit load solution. a.

The Lower Bound Theorem of limit analysis – If any statically admissible stress field can be found for an applied load, then this load is a lower bound to the actual limit load. A statically admissible stress field is defined by a set of generalized stresses such that all equilibrium requirements are satisfied and the yield condition is not violated.

b.

The Upper Bound Theorem of limit analysis – If any kinematically admissible strain-rate field can be found for an applied load, then this load is an upper bound to the limit load. A kinematically admissible strain-rate field satisfies the strain-rate-velocity relations and the velocity boundary conditions. Corresponding to this strain-rate field, a stress field is determined using the flow law and yield function.

B.3.2.3

Closed form solutions for limit loads can be obtained for simple components subject to simple loading conditions. For general components subject to simple or complex loading conditions, an estimate of the limit load can be obtained using a numerical analysis technique (e.g. finite element method) by utilizing an elastic-perfectly-plastic material model and small displacement theory to obtain a solution. The limit load can be taken as the load which causes overall structural instability. This load corresponds to a point on the load-deformation curve at which the external work of applied loads does not balance the strain energy stored by the component. This point is indicated by the inability to achieve an equilibrium solution for a small increase in load; the solution will not converge.

B.3.2.4

Plasticity effects are included in the assessment of crack-like flaws by means of the load parameter Lr on the FAD (see Section 9). The value of Lr is defined as the ratio of the applied loading to the limit load of the component containing a flaw subject to the same loading condition. The applied loads to be used in determining the value of Lr are those that cause primary stresses (Pm, PL + Pb), i.e. those loads which can result in a plastic collapse of the component. A description and method for determining the limit load solution and associated load parameter for components with crack-like flaws is provided in Appendix D.

B.3.3

Plastic Collapse Loads – Plastic collapse loads can be utilized in the assessment of components containing either volumetric or crack-like flaws. If a plastic collapse load solution is used to assess a flaw in a component, the deformation and strain associated with the limit load should be evaluated and limited to prevent gross deformation in the component.

B.3.3.1

The plastic collapse load can be defined as the maximum load solution to an analytical model of a structure which embodies the following conditions:

B.3.3.2

a.

The material response is elastic-plastic with an admissible yield function and strain hardening.

b.

The strain-displacement relations are those of large displacement or strain theory (i.e. the internal stress and applied forces are related by equations of equilibrium which include changes in geometry due to deformations).

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Closed form solutions for plastic collapse loads are not readily available; therefore, numerical techniques (e.g. finite element method) can be utilized to obtain solutions. An estimate of the plastic collapse load can be obtained using a numerical analysis technique (e.g. finite element method) by incorporating an elastic-plastic material model and large displacement theory to obtain a solution. As with a numerically obtained limit load solution, the plastic collapse load can be taken as the load which causes overall structural instability. This point is indicated by the inability to achieve an equilibrium solution for a small increase in load; the solution will not converge. If an equilibrium solution is achieved and a plastic collapse load is computed, the local strains in the component should also be evaluated.

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Nonlinear Elastic-Plastic Stress Analysis Of Components With A Flaw – Nonlinear stress analysis techniques can provide a more accurate assessment of the safe load carrying capacity of a component relative to the criteria in paragraph B.2 because the actual structural behavior is more closely approximated. The redistribution of stress which occurs as a result of inelastic deformation (plasticity and/or creep) is considered directly in the analysis, rather than by the cumbersome and often inaccurate process of stress categorization. In addition, linear elastic analysis will under-predict the strain range at fatigue sensitive points in the low cycle regime. Results from a nonlinear stress analysis with material nonlinearity incorporated to account for plasticity and/or creep effects provide a more accurate representation of the actual strain ranges and accumulated inelastic strains.

B.3.4.1

The fitness-for-service of a component with or without a flaw can be established by taking two-thirds of the limit or plastic collapse load. If the deformation characteristics of the component are important (i.e. a limit on strain is required), the assessment should be based on a plastic collapse load. The plastic collapse load is determined from a finite element analysis using the following two criteria:

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B.3.4

a.

Global Criteria – A global plastic collapse load is established by performing an elastic-plastic analysis of the component subject to the specified loading conditions. The plastic collapse load is taken as the load which causes overall structural instability (see paragraph B.3.3.2).

b.

Local Criteria – A local plastic collapse load established based on a local criteria should be a measure of the local failure in the vicinity of the flaw as a function of the specified loading conditions. In this context, local failure can be defined in terms of a maximum peak strain in the remaining ligament of the flaw. One recommendation is to limit the peak strains at any point in the model to 5%. Alternatively, a measure of local failure can also be established by placing a limit on the net section stress in the remaining ligament of the flaw when material strain-hardening is included in the analysis. In addition, the following should also be considered: ·

The operational requirements of the component (i.e. local deformation).

·

Constraint effects related to the hydrostatic stress, material ductility, the effects of the environment.

·

The effects of localized strain which can result in zones of material hardness that may be subject to damage from the environment.

B.3.4.2

The concept of Load and Resistance Factor Design (LRFD) can be used as an alternate to the rigorous computation of a plastic collapse load to demonstrate the fitness-for-service of a component. In this procedure the actual applied loads are increased by a multiplier, and the resistance of the component to these increased loads is determined using an elastic-plastic finite element analysis. As with the rigorous plastic collapse solution, the global and local criteria described in paragraph B.3.4.1 should be evaluated when determining the resistance of the component to the applied loads. A procedure for evaluating a component containing a volumetric flaw using the LRFD approach is covered in paragraph B.6.4.1.

B.3.4.3

A general procedure for determining the fitness-for-service of a component with a volumetric flaw using nonlinear finite element stress analysis is provided in paragraph B.6.4.2. This procedure is based on the LRFD approach and can be used to evaluate components with or without flaws subject to plasticity, creep and fatigue.

B.3.4.4

If the component has a crack-like flaw, the stress analysis procedure provided in paragraph B.6.4.3 should be used in the assessment.

B.4

Assessment For Structural Stability

B.4.1

Overview – If a component with a flaw is subjected to external pressure or other loads which result in a compressive stress field, an analysis to determine the structural stability shall be performed to determine suitability for continued service. The flaw geometry shall be included in the model of the component used to assess structural stability.


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Jan, 2000

RECOMMENDED

PRACTICE

B-9


8.4.2

/n-service Margins - In addition to satisfying the allowable stress criteria (see paragraph B.2) an inservice margin for structural stability must also be satisfied to avoid buckling of components with a compressive stress field. The following in-service margins are recommended for use with shell components.

B.4.2.1

The in-service margins to be used in a structural stability assessment are based on the type of buckling analysis performed. The following in-service margins are recommended. a.

Type 1 - If a bifurcation buckling analysis is performed without including geometric and material nonlinearities in the solution to determine the pre-stress in the component, a minimum in-service margin of three (3) is recommended.

b.

Type 2 - If a bifurcation buckling analysis is performed including geometric and material nonlinearities in the solution to determine the pre-stress in the component, a minimum inservice margin of two (2) is recommended.

C.

Type 3 - If a plastic collapse analysis is performed in accordance with B.3.3, an in-service margin equal to one and one-half (1 S) is recommended.

B.4.2.2

Buckling loads determined from design standards or handbooks normally fall into a Type 1 analysis. However, an in-service margin need not be included in the assessment if a margin is already included in the buckling load formula (see paragraph B.4.4). An increase in the in-service margins may be warranted for the assessment of shell structures with significant deviations from the original structural configuration if these effects are not included in the model.

B.4.3

Structural Stability For Components with Flaws - The following items should be considered to determine the structural stability of a component with a flaw.

B.4.3.1

Assessment of the structural stability of a component with flaws should consider growth aspects and remaining life. The location, size and reduced thickness associated with a flaw will effect the structural stability of a component. Therefore, the assessment should be performed for the flaw size at the end of its useful life. For volumetric-type flaws, account should be taken of the possibility of increased metal loss and expansion of the corroded area with time. For crack-like flaws, account should be taken of the possibility of crack growth by fatigue, corrosion-fatigue, stress corrosion cracking and creep.

B.4.3.2

The significance of planar flaws parallel to a plate or shell surface in the direction of compressive stress (laminations, laminar tears, etc.) should be assessed by checking the buckling strength of each part of the material between the flaw and the component surface. This may be done by calculation as if the individual parts of the material are separate plates of the same area as the flaw using the distance between the flaw and the surface as an effective thickness.

8.4.3.3

If a flaw occurs parallel to the surface under the weld attaching a stiffener to a shell or plate loaded in compression, it will reduce the effective length over which the stiffener is attached to the plate. If a flaw of this type is located, it should be assessed assuming that the stiffener is intermittently welded to the plate and that the flaw forms a “space” between two welds. Rules for determining the allowable weld spacing for stiffener attachment from the original design code may be used in this evaluation.

8.4.3.4

The allowable compressive stress for a shell component with a flaw can be established using the compressive stress equations in paragraph B.4.4. The thickness to be used in the compressive stress calculation should be the minimum thickness less any future corrosion allowance unless another thickness can be justified.

8.4.4

Establishment Of Allowable Compressive Stresses For Shell Type Structures - The allowable stresses for cylindrical and conical shells subjected to loads which produce compressive stresses in this appendix are based on WRC 406 and ASME B&PV Code Case 2286 ( see Appendix A, paragraph A.4.1 .l for background and limitations). --``````-`-`,,`,,`,`,,`---



API RECOMMENDED

B-l 0

8.4.4.1

PRACTICE

579

Jan, 2000

Cylindrical Shells - The allowable compressive stresses for cylindrical shells can be computed using the following procedure for different load cases. a.

Symbol Definitions

A AS G

Cross-sectional area of cylinder (mm2:in2), Cross-sectional area of ring stiffener (mm2:in2), Coefficient whose value is established as follows: = 0.85 for compression members in frames subject to joint translation (sidesway). for rotationally restrained members in frames braced = 0.6-0.4(M,/M,)

Di DO J?Y F FCA fa h fh -fi fy FS K

L L LOSS M M, P t

= = = = =

smaller to large bending moment at the ends of the portion of the member that is unbraced in the plane of bending under consideration ( M,/M, is positive when the member is bent in reverse curvature and negative when the member is bent in single curvature). = 0.85 for compression members in frames braced against joint translation and subject to transverse loading between support points -The member ends are restrained against rotation in the plane of bending. = 1.O for compression members in frames braced against joint translation and subject to transverse loading between support points - The member ends are unrestrained against rotation in the plane of bending. = 1.O for an unbraced skirt supported vessel. Inside diameter of cylinder (including the effects of corrosion; Do- 2t,), (mm:in), Outside diameter of cylinder (mm:in), Modulus of elasticity of material at the assessment temperature (see Appendix F), (MPa:psi), Applied net-section axial compression load (N:lbs), Future corrosion allowance (mm:in), Axial compressive membrane stress resulting from applied axial load (MPa:psi), Axial compressive membrane stress resulting from applied bending moment (MPa:psi), Hoop compressive stress in the cylinder from external pressure (MPa:psi), Axial compressive membrane stress resulting from pressure load on the end of cylinder (MPa:psi), Shear stress from applied loads (MPa:psi), In-service margin or design factor (see paragraph B.4.4.4) Coefficient based on end conditions of a member subject to axial compression: = 2.1 for a member with one free and the other end fixed, = 1.O for a member with both ends pinned, = 0.8 for a member with one end pinned and the other end fixed, = 0.65 for a member with both ends fixed Design length of a vessel section between lines of support (see Appendix A, paragraph A.4.4) (mm:in), Unbraced length of cylindrical member that is subject to column buckling, equal to zero when evaluating the shell of a vessel under pressure (mm:in), Metal loss (mm:in), Applied net-section bending moment (N-mm:in-lbs), Shell parameter, Applied external pressure (MPa:psi), Thickness of the shell (mm:in), --``````-`-`,,`,,`,`,,`---

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against joint translation and not subject to transverse loading between their supports in the plane of bending; in this equation, M,/M, is the ratio of the


tc S Ro V a

I ys

t – LOSS – FCA, 3 3 Elastic section modulus of full shell cross section (mm :in ), Outside radius of a spherical shell (mm:in), Applied net-section shear force (N:lbs), One-half of the conical shell apex angle (degrees), and Yield stress of material at the assessment temperature (see Appendix F),

= = = = = =

(MPa:psi). Equations for section properties, nominal shell stresses and buckling parameters are provided below.

c

F Do2 - Di2

A=

S=

h

(B.3)

4

c

F Do4 - Di4

h

(B.4)

32 Do

fh =

PDo 2t c

(B.5)

fb =

M S

(B.6)

fa =

F A

(B.7)

PFDi2 fq = 4A

(B.8)

V A

(B.9)

fv =

rg = 0.25 Do2 + Di2 Mx =

(B.10)

L 0.5Do t c

F GH

KLu Fxa FS lc = Ey p rg

(B.11)

I JK

0.5

(B.12)

c.

The allowable hoop compressive membrane stress of a cylinder or formed head subject to external pressure acting alone, Fha, is computed using Appendix A, paragraph A.4.4.

d.

The allowable axial compressive membrane stress of a cylinder subject to an axial compressive load acting alone, Fxa, is computed using the following equations.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

b.

B-12 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

1.

For l c

£ 0.15 ( Local Buckling):

Fxa = min Fxa1 , Fxa 2

I ys

Fxa1 =

Do £ 135 tc

for

FS

(B.13)

466s ys

Fxa1 =

(B.14)

for 135 <

F DI FS G 331 + J H tK o

Do < 600 tc

(B.15)

c

0.5s ys

Fxa1 =

FS

Fxa 2 =

Fxe =

Cx

Do ³ 600 tc

for

(B.16)

Fxe FS

(B.17)

Cx E y t c

(B.18)

Do

LM OP 409c = min M MM F 389 + D I , 0.9PPP MN GH t JK PQ

for

o

Do < 1247 tc

(B.19)

c

Cx = 0.25c c = 2.64 c=

2.

For l c

for

313 . M x0.42

c = 1.0

Do ³ 1247 tc

for

M x £ 15 .

(B.21)

for 15 . < M x < 15 for

(B.22)

M x ³ 15

(B.23)

> 015 . and KLu rg < 200 (Column Buckling):

b

g

Fca = Fxa 1 - 0.74 l c - 015 . Fca =


(B.20)

0.88 Fxa l2c

0 .3

for l c ³ 1147 .

for 015 . < l c < 1147 .

(B.24)

(B.25)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


e.

The allowable axial compressive membrane stress of a cylinder subject to a bending moment acting alone, Fba, is computed using the following equations.

Fba = Fxa

Fba =

Do ³ 135 tc

for

466s ys

(B.26)

Do < 135 tc

F DI FS G 331 + J H tK

for 100 £

1081 . I ys

Do < 100 and C ³ 011 . tc

o

(B.27)

c

Fba =

Fba =

C =

FS

14 . - 2.9C I ys FS

Do < 100 and C < 011 . tc

for

I ys Do

(B.28)

(B.29)

(B.30)

E y tc

The allowable shear stress of cylinder subject to a shear load acting alone, Fva, is computed using the following equations.

Fva =

D v Fve FS

(B.31)

Fve = = v Cv E y

FG t IJ HD K c

(B.32)

o

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Cv = 4.454

M x £ 15 .

for

Cv =

FG 9.64 IJ c1 + 0.0239 M h HM K

Cv =

1492 . M x0.5

3 0.5 x

2 x


FG D IJ Ht K FD I ³ 4.347G J Ht K o

(B.34)

(B.35)

c

c

0.5

for

o

= v = 0.8

. < M x < 26 for 15

for 26 £ M x < 4.347

Ft I C = 0.716G J HD K v

(B.33)

for

Mx

o

(B.36)

c

Do £ 500 tc

(B.37)

Not for Resale

--``````-`-`,,`,,`,`,,`---

f.

for


FG D IJ Ht K

= v = 1389 . - 0.218 log10

o

for

c

D v = 10 .

(B.39)

FG I IJ + 01. for 0.48 < F I HF K F I IJ for F ³ 17. = 0.6 G I HF K ys

ve

ve

ys

ys

ve

ve

ys

< 17 .

(B.40)

(B.41)

The allowable compressive stress for the combination of uniform axial compression and hoop compression, Fxha, is computed using the following equations: 1.

For l c £ 0.15 ; Fxha is computed using the following equation with Fha and Fxa evaluated using the equations in subparagraphs (c) and (d.1), respectively.

LF 1 I - F C I + F 1 F = MG NH F JK GH C F F JK GH C F b F × FS + F × FS g - 1.0 C = 1

xha

2 xa

2

xa

ha

2 2

2 ha

-0.5

(B.42)

ha

1

(B.43)

I ys

fx fh

(B.44)

f x = fa + fq

(B.45)

C2 =

2.

xa

IJ OP KQ

015 . < l c £ 1147 . : Fxha is computed from the following equation with Fah1= Fxha evaluated using the equations in subparagraph (g.1) with fx= fa , and Fca evaluated

For

using the equations in subparagraph (d.2).

Fxha = min Fah1 , Fah 2

(B.46)

F GH

(B.47)

Fah 2 = Fca 1 3.

I ys

I JK

For l c £ 0.15 , the allowable hoop compressive membrane stress, following equation:

Fhxa =


fq

Fhxa, is given by the

Fxha C2

(B.48)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

g.

(B.38)

Fve £ 0.48 I ys

for

D v = 0.43

Dv

Do > 500 tc

h.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


The allowable compressive stress for the combination of a axial compression due to a bending moment and hoop compression, Fbha, is computed using the following equations. 1.

An iterative solution procedure is utilized to solve these equations for C3 with Fha and Fba evaluated using the equations in subparagraphs (c) and (e), respectively.

Fbha = C3C4 Fba

(B.49)

FG f IJ FG F IJ H f KH F K C cC + 0.6C h + C C4 = 2 3

ha

h

ba

2 4

n = 52.

b

4

2n 3

(B.50)

-1 = 0

(B.51)

4 Fha × FS I ys

(B.52)

The allowable hoop compressive membrane stress, equation:

Fhba = Fbha

Fhba, is given by the following

FG f IJ Hf K h

(B.53)

b

The allowable compressive stress for the combination of hoop compression and shear, Fvha, is computed using the following equations. 1.

The allowable shear stress is given by the following equation with Fva and Fha evaluated using the equations in subparagraphs (f) and (c), respectively.

Fvha

LF F I + F OP = MG NH 2C F JK Q 2 va

5

C5 = 2.

ha

0.5

-

Fva2 2C5 Fha

(B.54)

fv fh

(B.55)

The allowable hoop compressive membrane stress, equation:

Fhva = j.

2 va

Fhva, is given by the following

Fvha C5

(B.56)

The allowable compressive stress for the combination of uniform axial compression, axial compression due to a bending moment, and shear in the presence of hoop compression is computed using the following interaction equations. 1.


The shear coefficient is determined using the following equation with Fva from subparagraph (f).

Not for Resale

--``````-`-`,,`,,`,`,,`---

i.


F f IJ K = 10 . -G HF K

2

v

s

(B.57)

va

2.

For l c

£ 0.15 ; the acceptability of a member subject to compressive axial and bending stresses, fa and fb, respectively, is determined using the following interaction equation with Fxha and Fbha evaluated using the equations in subparagraphs (g.1) and (h.1),

FG f IJ + FG f IJ £ 1.0 HK F K HK F K 1.7

a

s

3.

b

xha

s

(B.58)

bha

. < lc For 015

£ 1147 . ; the acceptability of a member subject to compressive axial and bending stresses, fa and fb, respectively, is determined using the following interaction equation with Fxha and Fbha evaluated using the equations in subparagraphs (g.2) and (h.1), respectively.

FG f IJ + FG 8 D f H K F K H9 K F FG f IJ + FG D f H 2K F K H K F a

s

xha

s

a

s

D=

b

s

bha

Cm f × FS 1- a Fe

Fe =

fa ³ 0.2 Ks Fxha

for

fa < 0.2 Ks Fxha

(B.59)

(B.60)

(B.61)

F 2 Ey

F KL I GH r JK

for

bha

b

xha

IJ £ 10. K IJ £ 10. K

(B.62)

2

u

g

k.

The allowable compressive stress for the combination of uniform axial compression, axial compression due to a bending moment, and shear in the absence of hoop compression is computed using the following interaction equations: 1.

The shear coefficient is determined using the equation in subparagraph (j.1) with Fva from subparagraph (f).

2.

For l c

£ 0.15 ; the acceptability of a member subject to compressive axial and bending stresses, fa and fb, respectively, is determined using the following interaction equation with, Fxa and Fba evaluated using the equations in subparagraphs (d.1) and (e), respectively.

FG f IJ + FG f IJ £ 1.0 HK F K HK F K 1.7

a

s

b

xa

s

ba

--``````-`-`,,`,,`,`,,`---


Not for Resale

(B.63)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

respectively.


3.

For 015 . < lc

£ 1147 . ; the acceptability of a member subject to compressive axial and bending stresses, fa and fb, respectively, is determined using the following interaction equation with, Fca and Fba evaluated using the equations in subparagraphs (d.2) and

(e), respectively. The coefficient D is evaluated using the equations in subparagraph j.3.

FG f IJ + FG 8 D f IJ £ 10. H K F K H9 K F K FG f IJ + FG D f IJ £ 10. H 2K F K H K F K a

s

b

ca

s

a

s

B.4.4.2

B.4.4.3

s

fa ³ 0.2 Ks Fca

for

fa < 0.2 Ks Fca

ba

b

ca

for

ba

(B.64)

(B.65)

Conical Shells – Unstiffened conical transitions or cone sections between stiffening rings of conical shells with a half-apex angle, a, less than 60° can be evaluated for local buckling as an equivalent cylinder using the equations in paragraph B.4.4.1 with the following substitutions. The allowable stress must be satisfied at all cross-sections along the length of the cone. a.

The value of D/cos= is substituted for Do to determine the allowable compressive stress where D is the outside diameter of the cone at the point under consideration.

b.

The value of Lc/cos=, is substituted for L where Lc is the distance along the cone axis between stiffening rings.

Spherical Shells and Formed Heads – The allowable compressive stresses are based on the ratio of the biaxial stress state. a.

Equal Biaxial Stresses – The allowable compressive stress for a spherical shell subject to a uniform external pressure, Fha, is given by the equations in Appendix A, paragraph A.4.5.

b.

Unequal Biaxial Stresses, Both Stresses Are Compressive – The allowable compressive stress for a spherical shell subject to unequal biaxial stresses, I 1 and I 2 , where both

I 1 and I 2 are compressive stresses resulting from the applied loads are given by the following equations. Fha is determine using subparagraph (a) above. F1a is the allowable compressive stress in the direction of I 1 and F2a is the allowable compressive stress in the direction of I 2 .

F1a =

0.6 Fha 1 - 0.4 k

(B.66)

F2 a = kF1a

k= c.

I2 I1

(B.67)

where I 1 > I 2

(B.68)

Unequal Biaxial Stresses, One Stress Is Compressive And The Other Is Tensile – The allowable compressive stress for a spherical shell subject to unequal biaxial stresses, I 1 and I 2 , where I 1 is compressive and I 2 is tensile resulting from the applied loads are given by the following equation.

F1a is the allowable compressive stress in the direction of

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


I 1 and is the value of Fha determined using Appendix A, paragraph A.4.5 with Fhe computed using the following equations.

d

i

Fhe = Co + C p E y

Co =

102.2 R 195 + o tc

Co = 0125 .

Cp =

p= B.4.4.4

tc Ro

(B.69)

Ro < 622 tc

for

for

Ro ³ 622 tc

(B.71)

106 . 3.24 +

(B.70)

(B.72)

1 p

I 2 Ro E y tc

(B.73)

The allowable stresses are determined by applying a stress reduction factor, FS, to the predicted buckling stresses. The recommended values of FS are 2.0 when the buckling stress is elastic and 1.667 when the buckling stress equals the yield stress. A linear variation can be used between these limits. The equations for FS are given below where Fic is the predicted buckling stress which is determined by setting FS=1.0 in the allowable stress equations. For conservative results, a value of 2.0 can be used for FS. For combinations of earthquake loading or wind loading with other types of occasional loads, the allowable stresses are increased by a factors shown in Table B.1.

FS = 2.0

for Fic £ 0.55I ys

FF I GH I JK

FS = 2.407 - 0.741

ic

(B.74)

for 0.55I ys < Fic < I ys

(B.75)

ys

FS = 1667 .

for Fic = I ys

(B.76)

--``````-`-`,,`,,`,`,,`---

where,

B.4.4.5

Fic

=

I ys

=

Predicted buckling stress, which is determined by letting FS = 1 in the allowable stress equations, Yield stress (MPa:psi), and

FS

=

In-service margin or stress factor

The allowable stress equations apply directly to shells fabricated from carbon and low alloy steel plate materials given in Table UCS-23 of ASME B&PV Code, Section II. These equations can also be applied to other materials for which a chart or table is provided in Subpart 3 of ASME B&PV Code, Section II, Part D. The method for finding the allowable stresses for shells constructed form these materials is determined by the following procedures.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


a.

Step 1 – Calculate the value of factor A using the following equations.

A= b.

Fxe Ey

Fhe Ey

A=

Fve Ey

(B.77)

Step 2 – Using the value of A calculated in Step 1, enter the applicable material chart in Subpart 3 of ASME B&PV Code, Section II, Part D for the material under consideration. Move vertically to an intersection with the material temperature line for the design temperature. Use interpolation for intermediate temperature values. From the intersection point, move horizontally to the right to obtain the value of B. The tangent modulus, Eyt, is given by the following equation. When all values of A fall to the left of the applicable material/temperature line, Eyt = Ey.

Et = c.

A=

2B A

(B.78)

Step 3 – Calculate the allowable stresses using the following equations:

Fxa =

Fxe E yt FS E y

(B.79)

Fba = Fxa

(B.80)

Fha =

Fhe E yt FS E y

(B.81)

Fva =

Fve E yt FS E y

(B.82)

B.4.5

Components With Shell Distortions – While in service, components may evolve into a configuration which no longer satisfies the fabrication tolerances of the original design code. For components subject to a compressive stress field, the new structural configuration may result in a significant reduction in buckling strength, i.e. reduced structural stability under load. For example, the buckling strength pressure vessels and large diameter piping subjected to external pressure are sensitive to changes in structural configuration such as out-of-roundness. The significance of structural configuration changes can be evaluated using Section 8 or by using the nonlinear analysis procedures in this appendix.

B.5

Methods For Fatigue Evaluation

B.5.1

Overview – A fatigue evaluation should be performed if the component is subject to cyclic operation. The evaluation for fatigue is made on the basis of the number of applied cycles of a stress or strain range at a point in the component. The allowable number of cycles should be adequate for the specified duration of operation to determine the suitability for continued operation. The fatigue assessment methods covered in this appendix are based on preventing failure by crack initiation. The methods of Section 9 can be used to evaluate crack propagation if a crack already exists in a component which is then subject to cyclic loading.

B.5.1.1

Fatigue curves are typically presented in two forms; fatigue curves that are based on smooth bar test specimens and fatigue curves that are based on test specimens which include weld details. In general, the former curves are recommend when component locations not containing a weld joint are --``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


B.5.1.2

Stresses and strains produced by any load or thermal condition which does not vary during the cycle need not be considered in a fatigue analysis if the fatigue curves utilized in the evaluation are adjusted for mean stresses and strains. The design fatigue curves referenced in this appendix based on smooth bar test specimens are adjusted for the maximum possible effect of mean stress and strain; therefore, an adjustment for mean stress effects is not required. Alternatively, the computed values for alternating stresses and strains may be adjusted for mean stress using the Modified Goodman procedure if other fatigue curves are utilized in the assessment. The fatigue curves based on welded test specimens do not need to be modified for mean stress because results from fatigue tests indicate that failure of welded components is not significantly effected by mean stress.

B.5.1.3

A screening criteria is provided in paragraph B.5.4 which can be used to determine if a fatigue analysis should be included as part of a fitness for service assessment. If a fatigue analysis is required, the evaluation may be performed using the techniques in paragraphs B.5.2 and B.5.3. Other recognized fatigue analysis techniques may be utilized if approved by the Engineer.

B.5.2

Evaluation Procedures Using Fatigue Test Data Smooth Bar Test Specimens – The fatigue evaluation procedures that follow are based on the design rules presented in the ASME Code, Section VIII, Division 2. Two evaluation procedures are provided. The first is based on stresses determined using an elastic stress analysis and the second is based on plastic stains determined using an elastic-plastic analysis.

B.5.2.1

The stress analysis must include the effects of peak stresses which occur at local stress discontinuities. These effects shall be evaluated for all conditions using stress concentration factors determined from theoretical, experimental or finite element stress analysis techniques. Except for the case of crack-like flaws, the maximum value for a stress concentration factor that should be utilized in a fatigue evaluation is five.

B.5.2.2

If the fatigue analysis is based on linear elastic calculations, the following value of Poisson’s ratio should be used to determine the stress results:

n = 0.5 - 0.2

FG s IJ HS K ys

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

being evaluated, and the latter are recommended when there is a weld joint at the point being evaluated.

(B.83)

a

B.5.2.3

Sa

=

I ys

=

Alternating stress obtained from a fatigue curve for the specified number of operating cycles (MPa:psi), and Yield stress at the mean value of the temperature cycle (MPa:psi).

Fatigue Evaluation Procedure Based on Elasticity Calculated Stress Results – An effective total stress intensity amplitude is used to evaluate the fatigue damage for results obtained from a linear elastic stress analysis. The effective peak stress intensity amplitude is defined as one-half the effective total stress intensity range

b P + P + Q + F g , (see paragraph B.2.2) calculated for each L

b

cycle described in the loading history. The procedure in this paragraph can be used for the general case where the principal stress directions change during the loading cycle. a.

Step 1 – Determine a load history based on past operation and future planned operation. The load history should include all significant operating loads and events which the component will be subjected to.

b.

Step 2 – For a location in the component under evaluation, compute the stress components Iij and the equivalent stress for each point in the load histogram. Use this information to create an effective stress load histogram.


Not for Resale

--``````-`-`,,`,,`,`,,`---

where,


c.

Step 3 – Determine the cyclic stress range based on the effective stress histogram developed in Step 2 using the cycle counting method in ASTM E1049 (rainflow method).

d.

Step 4 – Determine the stress tensor at the start and end points for the “k ” cycle in the effective stress histogram counted in Step 3. Using these data, determine the stress range (difference between the stress components at the start and end points of the cycle) and

th

designate this quantity as e.

,I ijk . th

Step 5 – Compute an effective stress intensity range for the “k yield criteria. 1.

” using one of the following

Maximum Shear Stress Yield Criterion – Determine the principal stresses based on the change in stress components computed in Step 3, then compute the effective stress range intensity for the cycle. k DSrange = max DI 1 - DI 2 , DI 2 - DI 3 , DI 3 - DI 1

2.

Maximum Distortion Energy Yield Criterion – Using the change in stress components determined in Step 3, compute the effective equivalent stress intensity range for the cycle.

DS

f.

(B.84)

k range

1 = 2

LMbDI MNbDI

11

- DI 22

22

- DI 33

g + bDI - DI g + g + 6cDI + DI + DI 2

2

11

2

33

2 12

2 13

2 23

th

Step 6 – Determine the effective alternating stress intensity for the “k

OP hPQ

0.5

(B.85)

” cycle.

k k Salt = 0.5Kek DSrange

(B.86)

Kek = 10 .

(B.87)

with,

Kek = 10 . +

for DSnk £ 3Sm

b1 - ng FG S - 1IJ nbm - 1g H 3S K n

for 3Sm < DSnk < 3mSm

(B.88)

m

Kek =

1 n

for DSnk ³ 3mSm

(B.89)

where,

g.

th

Kek

=

Fatigue knock-down factor for the “k applicability and limitations),

,Snk m n

=

Range of primary plus secondary stress intensity for the “k

= =

Material constant (see Table B.3), and Material constant (see Table B.3).

” cycle (see Table B.4 for th

” cycle,

k

Step 7 – Determine the permissible number of cycles, N , for the alternating stress intensity computed in Step 6. Fatigue curves for ferritic materials are provided in Appendix F,

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


paragraph F.6.2.2. Additional fatigue curves for other materials are contained in ASME B&PV Code, Section VIII, Division 2, Appendix 5. th

Step 8 – Determine the fatigue damage for the “k

1 Nk

D kf =

(B.90)

i.

Step 9 – Repeat Steps 4 through 8 for all stress ranges identified in the cycle counting process in Step 3.

j.

Step 10 – Compute the accumulated fatigue damage using the following equation. The component is suitable for continued operation if this equation is satisfied. The permissible damage fraction, Df, is usually taken as 1.0 unless an alternative value is specified by the Engineer performing the assessment.

åD k. B.5.2.4

” cycle.

k f

£ Df

(B.91)

Step 11 – Repeat Steps 2 through 10 for each point in the component subject to a fatigue evaluation.

Fatigue Evaluation Procedure Based on Elastic-Plastic Calculated Strain Results – An effective peak stress intensity amplitude based upon a total strain range is used to evaluate the fatigue damage for results obtained from a nonlinear elastic-plastic analysis. The effective peak stress intensity amplitude is defined as one-half of the effective strain intensity range calculated for each cycle described in the loading history multiplied by Young's Modulus evaluated at the mean temperature of the cycle. The procedure in this paragraph can be used for the general case where the principal strain directions change during the loading cycle. a.

Step 1 – Determine a load history based upon past operation and future planned operation. The load history should include all significant operating loads and events the component will be subject to.

b.

Step 2 – For a location in the component under evaluation, compute the strain components Aij and the equivalent stress for each point in the load histogram. Use this information to create an effective stress load histogram.

c.

Step 3 – Determine the cyclic strain range based on the effective stress histogram developed in Step 2 using the cycle counting method in ASTM E1049 (rainflow method).

d.

Step 4 – Determine the strain tensor at the start and end points for the “k ” cycle in the effective stress histogram counted in Step 3. Using these data, determine the strain range (difference between the strain components at the start and end points of the cycle) and

th

designate this quantity as e.

th

Step 5 – Compute the equivalent strain range for the "k " cycle:

k DA range

f.

,A ijk .

2 = 3

LMbDA MNbDA

11

- DA 22

22 - DA 33

g + b DA - D A g + g + 6cDA + DA + DA 2

2

11

2

2 12

33

2 13

2 23

OP hPQ

0.5

(B.92)

th

Step 6 – Determine the effective alternating stress intensity for the “k

--``````-`-`,,`,,`,`,,`---


Not for Resale

” cycle.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

h.

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE B-23 _________________________________________________________________________________________________ k k Salt = 0.5Ert DA range

(B.93)

where,

Ert

=

Young's Modulus at room temperature k

--``````-`-`,,`,,`,`,,`---

g.

Step 7 – Determine the permissible number of cycles, N , for the alternating stress intensity computed in Step 6 (see paragraph B.5.2.3.g)

h.


i.


j.

Step 10 – Compute the accumulated fatigue damage and check the acceptance criteria (see paragraph B.5.2.3.j).

k.


th

” cycle (see paragraph B.5.2.3.h).

B.5.3

Evaluation Procedures Using Fatigue Test Data Obtained From Welded Specimens – The fatigue evaluation procedures that follow are based on the assessment procedures in Appendix C of BSI 5500.

B.5.3.1

The fatigue assessment is based on the primary plus secondary stress category, as opposed to the primary plus secondary plus peak stress intensity used in the procedure outlined in paragraph B.5.2. The stress range is computed based on a specific weld category as discussed in Appendix F, paragraph F.6.3. The full stress range is used, regardless of applied or effective mean stress. Details regarding the computation of the stress range are as follows (additional background information is contained in Reference B.7.21). a.

Stress range calculation for base material and weld material in butt joints – Sr is the maximum range of the direct or normal stress. Sr should be determined at all points where there is a risk of fatigue cracking as indicated for the individual weld details shown in Figures F.12 to F.16 of Appendix F. In some circumstances, not all stress directions need to be considered. 1.

Where stress cycling is due to the application and removal of a single load, Sr is the same as the maximum principal stress caused by the load acting alone.

2.

Where stress cycling is due to more than one load source but the directions of principal stresses remain fixed, Sr is the maximum range through which any one of the principal stresses changes as determined in the following equation. Tensile stresses are considered positive and compressive stresses are considered negative.

b

gb

gb

Sr = max I 1max - I 1min , I 2 max - I 2 min , I 3 max - I 3 min where,

I1max I1min I2max I2min I3max I3min


= = = = = =

Maximum principle stress in the 1-direction Minimum principle stress in the 1-direction Maximum principle stress in the 2-direction Minimum principle stress in the 2-direction Maximum principle stress in the 3-direction Minimum principle stress in the 3-direction

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g

(B.94)


3.

4.

b.

When the principal stress directions change during cycling between two load conditions, Sr may be calculated as follows. a)

Determine the stress tensor at each load condition with reference to a fixed axes.

b)

Calculate the algebraic difference between the stress tensors for each load condition on a component basis.

c)

Calculate principal stresses from the resulting stress differences in the usual way. Sr is the numerically greatest of these principal stresses.

Where cycling is of such a complex nature that it is not clear which two load conditions will result in the greatest value of Sr, they shall be established by carrying out the above procedure for all pairs of load conditions. Alternatively, it will always be safe to assume that Sr is the difference between the algebraically greatest and smallest principal stresses occurring during the whole cycle regardless of their directions.

Stress range calculation for weld metal in fillet or partial penetration joints – Sr is the maximum range of stress across the effective weld throat, calculated as the load carried by the weld divided by the weld throat area, with the assumption that none of the load is carried by bearing between the components joined. Since this can be expressed as a vector sum, Sr is the scalar value of the greatest vector difference between different stress conditions during the cycle. 1.

Where stress cycling is due to the application and removal and of a single load,

Sr = I 2 + J 2

(B.95)

where, = =

normal stress on the weld throat shear stress on the weld throat

2.

Where stress cycling is due to more than one load source, but the directions of the stresses remain fixed, Sr, is based on the maximum range of the load on the weld.

3.

Where the direction of the stress vector on the weld throat changes during a cycle between two extreme load conditions, Sr is the magnitude of the vector difference between the two stress vectors.

4.

Where cycling is of such a complex nature that it is not clear which two load conditions will result in the greatest values of Sr, then the vector differences shall be found for all pairs of extreme load conditions.

5.

Alternatively, it will always be safe to assume:

b

Sr = I max - I min

g + bJ 2

1 max - J 1 min

g + bJ 2

2 max - J 2 min

g

2 0.5

where,

Imax Imin J1max J1min


= = = =

Maximum normal stress at the weld Minimum normal stress at the weld Maximum shear stress in the 1-direction Minimum shear stress in the 1-direction

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(B.96)

--``````-`-`,,`,,`,`,,`---

I J


J2max J2min c.

= =

Maximum shear stress in the 2-direction Minimum shear stress in the 2-direction

Stress range calculation for elastic-plastic conditions – If the calculated pseudo-elastic stress range exceeds twice the yield strength of the material under consideration (i.e. Sr > 2Iys), it shall be corrected or modified by applying a plasticity correction factor computed based on the type of applied loads. 1.

The corrected stress range for mechanical loads (Srm is the stress range from mechanical or primary loads):

Srmk = k ml Srm

(B.97)

where M1, M2 and M3 are evaluated using Table B.4, and

k ml = M1

Srm -1 +1 2I ys

k ml = M 2 + M 3 2.

Sr 2I ys

for 2 £

for

Sr £3 I ys

Sr I ys

(B.98)

(B.99)

The corrected stress range for thermal loading is (Srt is the stress range from thermal loads):

Srtk = k tl Srt

(B.100)

where M1, M2 and M3 are evaluated using Table B.3, and

k tl =

(B.101)

Stress range based on loading conditions: a)

Mechanical Loads;

Sr = Srmk b)

(B.102)

Thermal Loads; or

Sr = Srtk c)

(B.103)

Combined loading;

Srk = Srmk + Srtk 4.


(B.104)

Elastic-plastic analysis – If the strain range ,A (elastic-plastic) due to any source of loading is known from theoretical or experimental stress analysis, the correction for plasticity is not required and

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3.

0.7 0.4I ys 0.5 + Sr


Sr = E rt DA

(B.105)

where,

Ert e.

=

Young's Modulus at room temperature

Stresses to be considered in the fatigue assessment:

--``````-`-`,,`,,`,`,,`---

1.

The fatigue lives of weld details which fall into weld Class 100 through weld Class 50 (see Appendix F, paragraph F.6.3) are expressed in terms of the primary plus secondary stress range acting on the base metal surface adjacent to the weld, ignoring any stress concentration due to the welded joint itself but including the effect of other stress concentrations.

2.

Short or discontinuous welds, where the relevant potential failure mode is by fatigue cracking from the weld end or weld toe shall be assessed on the basis of the maximum principal stress range, Sr, and classified on the basis that the weld is oriented in the least favorable direction with respect to Sr.

3.

Continuous welds (e.g. seams, ring stiffener welds) may be treated differently if the maximum principal stress range acts in a direction which is within 30° of the direction of the weld. Then the weld can be classified as being parallel to the direction of loading with respect to the maximum principal stress range and normal to the loading direction with respect to the minimum principal stress range.

4.

The fatigue lives of class W details are expressed in terms of the maximum stress range on the weld throat.

5.

Nozzles – Three possible stress concentrations due to structural discontinuities in nozzle shall be considered when calculating Sr (see Figure F.13). a)

Crotch corner – The weld Class 100 fatigue curve shall be used in conjunction with the maximum circumferential (with respect to the nozzle) stress range at the crotch corner.

b)

Weld toe in shell – The weld Class 63 fatigue curve, depending on the weld detail, shall be used in conjunction with the maximum stress range in the shell at the welded toe. Consideration shall be given to stresses in the shell acting in all radial directions with respect to the nozzle in order to determine the maximum stress at the weld toe. The possibility of stresses arising in the shell as a result of mechanical loading on the nozzle as well as pressure loading shall be considered.

c)

Weld toe in branch – This region shall be treated as described in subparagraph b above, except that the maximum stress range in the branch shall be used. Again, the possibility of mechanical as well as pressure loading shall be considered.

6.

Supports and attachments – Local concentrations of stress can arise in the shell where it is supported or loaded through an attachment. The appropriate fatigue design curve shall be used in conjunction with the maximum stress range in the shell at the weld toe determined using the same criteria as for nozzle weld toes in the shell (see Figures F.14 and F15).

7.

Shell distortions – Local increases in pressure-induced stresses in shells which arise as a result of secondary bending stresses due to discontinuities and departures from the intended shape shall be taken into account when calculating pressure stresses for the fatigue assessment of the shell at seams and attachments, even if the allowable assembly tolerances of the original construction code are satisfied. Methods to compute these stresses are covered in Section 8.


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B.5.3.2

Fatigue Evaluation Procedure – The procedure in this paragraph can be used for a fatigue evaluation of a component with a weld. a.

Step 1 – Determine a load history based on past operation and future planned operation. The load history should include all significant operating loads and events which the component will be subjected to.

b.

Step 2 – Based on the weld detail in the component under evaluation, determine a weld category to be used in the assessment based on the information in Appendix F, paragraph F.6.3. Compute the stress components I ij for each point in the load histogram at the weld location using the information in paragraph B.5.4.1 and develop a stress histogram.

c.

Step 3 – Determine the cyclic stress range based on the stress histogram developed in Step 2 using the cycle counting method in ASTM E1049 (rainflow method).

d.

Step 4 – Based on the start and end points obtained for the “k ” cycle in the stress histogram counted in Step 3, determine the stress range using the information in paragraph B.5.4.1 and

th

Srk . k

th

e.

Step 5 – Determine the permissible number of cycles, N , for the “k ” cycle using the procedure in paragraph B.5.5.4. Design fatigue curves for ferritic and austinetic materials and a method for determining the permissible number of cycles for a given stress are provided in Appendix F, paragraph F.6.3.2.

f.


g.


h.

Step 8 – Compute the accumulated fatigue damage and check the acceptance criteria (see paragraph B.5.2.3.j).

k.


th

” cycle (see paragraph B.5.2.3.h).

B.5.4

Screening Criteria To Determine If A Fatigue Analysis Is Required – The screening criteria contained in this paragraph are based on the concepts presented in paragraphs B.5.2 and B.5.3 with simplifying conservative assumptions to ensure a conservative result. Alternate screening criteria may be used be utilized based on the original construction code; however, allowances should be made to recognize the effects of a flaw in a component.

B.5.4.1

The following screening procedure can be used to determine if a fatigue analysis is required as part of a fitness-for-service assessment. a.

Step 1 – Determine a load history based on past operation and future planned operation. The load history should include all significant cyclic operating loads and events which the component has been or will be subjected to.

b.

Step 2 – Based on the load history in Step 1, determine the expected (design) number of fullrange pressure cycles including startup and shutdown.

c.

Step 3 – Based on the load history in Step 1, determine the expected number of operating pressure cycles in which the range of pressure variation exceeds 20% of the design pressure. (Cycles in which the pressure variation does not exceed 20% of the design pressure are not limited in number. Pressure cycles caused by fluctuations in atmospheric conditions need not be considered.)


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designate this quantity as


d.

Step 4 – Based on the load history in Step 1, determine the effective number of changes in metal temperature between any two adjacent points as defined below. The effective number of such changes is determined by multiplying the number of changes in metal temperature of a certain magnitude by the factor given in Table B.5, and by adding the resulting numbers. 1.

For surface temperature differences, points are considered to be adjacent if they are within the distance L computed as follows: for shells and dished heads in the meridional or circumferential directions,

L = 2.5 Rt

(B.106)

and for flat plates,

L = 35 .a

(B.107)

where,

d.

= =

t a

= =

Minimum distance between adjacent points (mm:in), radius measured normal to the surface from the midwall of the shell to the axis of revolution (mm:in), Thickness of the component under consideration (mm:in), and Radius of hot spot or heated area within a plate (mm:in).

For through-the-thickness temperature differences, adjacent points are defined as any two points on a line normal to any surface in the component.

Step 5 – Based on the load history in Step 1, determine the number of temperature cycles for components involving welds between materials having different coefficients of expansion which causes the value of

b=

1

g

- = 2 DT to exceed 0.00034, where a1 and a2 are the mean

f.

Step 6 – Determine the total number of expected operating cycles by adding the cycles determined in Steps 2, 3, 4 and 5.

g.

Step 7 – Determine the stress used to enter a design fatigue curve to establish a permissible number of operating cycles.

S fcs =

3Sa K 2

(B.108)

where,


K

=

Sa

=

Sfsc

=

Factor to compute the stress amplitude or range. If the screening criteria is evaluated using fatigue curves based on smooth bar test specimens, K is a stress concentration factor established using the values in Table B.6. If the screening criteria is evaluated using fatigue curves based on welded test specimens, K=2.0. Allowable stress based on the applicable construction code (MPa:psi), and Stress used to enter the fatigue curves to establish a permissible number of operating cycles (MPa:psi). If the screening criteria is evaluated using fatigue curves based on smooth bar test specimens, Sfsc is a stress

Not for Resale

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coefficients of thermal expansion and ,T is the operating temperature range (clad vessels are excluded from this calculation).

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2.

L R

Jan, 2000

RECOMMENDED

PRACTICE

B-29


amplitude. If the screening criteria is evaluated using fatigue curves based on welded test specimens, S& is a stress range. h.

Step 8 - Determine the permissible number of cycles by entering a design fatigue curve with the value of stress computed in Step 7. The fatigue curves in Appendix F, paragraph F.6.2.2 can be used if the number of permissible cycles is evaluated using fatigue curves based on smooth bar test specimens (see paragraph B.5.2). Alternatively, the fatigue curves in Appendix F, paragraph F.6.2.3 can be used with the weld class definitions in Table B.6 if the screening criteria is evaluated using fatigue curves based on welded test specimens (see paragraph 8.5.3).

i.

Step 9 - If the permissible number of cycles from Step 8 is greater than or equal to the expected number of operating cycles from Step 5, a fatigue analysis is not required as part of the FFS assessment. Alternatively, if the permissible number of cycles is less than the expected number of operating cycles, a fatigue analysis should be performed as part of the fitness-for-service assessment.

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B.5.4.2

The evaluation methods provided in B.5.2 and B.5.3 can be used if a fatigue analysis is required as part of the FFS assessment based on the screening criteria in paragraph 8.5.4.1.

B.6

Fitness-For-Service

B.6.1

Overview - The following paragraphs provide recommendations on how to perform and evaluate results from a finite element analysis used to qualify a component with a flaw.

B.6.2

Linearization Of Stress Results And Classification - Results from a finite element elastic stress analysis can be used to compute stress intensities for comparison to the limits in paragraph 8.2.3. The stress categorization procedure for stress intensities was originally developed for shell theory where membrane and bending stresses can be determined directly from shell stress resultants. In the finite element method using continuum elements, a stress distribution is obtained and linearization of this distribution is required for calculation and categorization of stress intensities (see Figure B.2).

B.6.2.1

Stress Results Derived From a Model Utilizing Shell Elements -The following approach is recommended:

Assessments

Using Finite Element Analysis

a.

The membrane stress intensities (I’, , Pb, Q) are derived from the stress tensor on the inside and outside surface of the shell averaged across the thickness of the section. The averaging should be performed at the stress component level.

b.

The membrane plus bending stress intensity limits ( PL + Pb, PL + Pb + Q) on the surface of a shell are derived directly from the stress tensor on the surface of the shell.

C.

The peak stress intensity limits are derived using a stress concentration factor, K applied

top,, PL+Pb or PL+Pb+Q. B.6.2.2

Stress Results Derived From a Model Utilizing two-dimensional or three-dimensional Continuum Elements - The options available for determining membrane and bending stress intensities are discussed below. a.

Stress classification methods to determine membrane and bending stress fall into three categories: 1.

Stress-at-a-point - This method is the simplest to apply, but it may also be the least accurate. It can be used for the assessment of structures with simple geometric shapes subject to simple loads. Its application assumes that the state of stress at a point --``````-`-`,,`,,`,`,,`---



API RECOMMENDED

PRACTICE

579

Jan, 2000

Stress-along-a-line - This method has been extensively applied to both two-dimensional and three-dimensional components. When applied to two-dimensional axisymmetric models, it represents a hybrid of the stress-along-a-plane approach. This method gives results closest to the average of all methods currently being utilized.

3.

Stress-along-a-plane - This method may appear to be the most fundamentally correct choice; however, it is difficult to apply and the results may vary significantly with the orientation of a stress plane, and also with the size of the plane.

b.

In addition to selection of a stress classification method, the technique utilized to process stress components along a stress line or stress plane to determine membrane and bending stress intensities may have a significant effect on the final results. Most users process stress components individually on a component basis to obtain the membrane and bending distributions. Variations to this approach include processing only principle stresses or select components of the stress tensor to obtain these distributions. Finally, some of the methods attempt to evaluate the validity of a chosen stress line or plane by evaluation of the stress distribution.

C.

The recommended procedure is the stress-along-a-line method with stress components averaged on an individual basis to determine membrane and bending stress intensities. Other methods may be utilized if in the judgment of the Engineer they would produce a more accurate assessment of the component.

8.6.3

Linearization of Stresses Results for Assessment of Crack-Like flaws - Results from a finite element elastic stress analysis can be used to compute the normal stress results at the location of a crack-like flaw. The stress results need to be categorized into primary and secondary stress for purposes of the assessment (see Section 9).

B.6.3.1

Stress Results Derived From a Model With Shell Elements - Membrane and bending stresses, normal to the crack face can be determined directly from the shell stress resultants using the method in paragraph B.6.2.1.

8.6.3.2

Stress Results Derived From a Model With Continuum Elements - Membrane and bending stresses normal to the plane of the crack can be developed by linearization of the stress components through the wall thickness with the same orientation using the method in paragraph B.6.2.2.

B.6.3.3

The linearization may be performed on the basis of the crack location within the wall thickness (see Figure 8.3) or the section thickness (see Figure 8.4).

B.6.4

Nonlinear Finite Element Analysis In Fitness-For-Service Assessments - The use of nonlinear finite element stress analysis is recommended to evaluate a component with a flaw. The response of a component obtained from a nonlinear finite element analysis provides insight relative to the overall structural behavior and possible failure modes. The assessment procedures shown below are recommended and general. Modifications to the procedures may be required based on the specific application, component configuration, material properties and loading conditions.

B.6.4.1

The following procedure has been used to demonstrate the fitness-for-service of a component with a volumetric flaw using a nonlinear finite element analysis. This procedure utilizes the LRFD approach (see paragraph 8.3.4.2) and is applicable to components which are subject to non-cyclic loads. A screening criteria for cyclic loading conditions is provided in paragraph 854.1. a.

Step 1 - Develop a finite element model of the component including all relevant geometry characteristics. The mesh used for the finite element analysis should be designed to

March 2000


Not for Resale

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2.

--``````-`-`,,`,,`,`,,`---

defines the local membrane and membrane plus bending conditions. As the geometric features of the component and loading conditions become more complex, the use of this method becomes inaccurate with respect to being able to assess failure modes, i.e. plastic collapse, local distortion and ratcheting.


Step 2 – Define all relevant loading conditions including pressure, supplemental loads and temperature distributions.

c.

Step 3 – An accurate representation of material properties should be included in the finite element model. An elastic-plastic material model with large displacement theory should be used in the analysis. The von Mises yield function and associated flow rule should be utilized if plasticity is anticipated. Material hardening or softening may be included in the analysis if the material stress-strain curve is available. If hardening is included in the plastic collapse load analysis, it should be based upon the kinematic hardening model, or a combined kinematic and isotropic model.

d.

Step 4 – Determine the load to be used in the analysis by applying a load multiplier of 1.5 to the actual load. If the component is subject to multiple loads, all of the actual loads should be proportionally scaled with the same multiplier.

e.

Step 5 – Perform an elastic-plastic analysis. If convergence is achieved in the solution, the component is stable under the applied loads, and the global criteria in paragraph B.3.4.1 is satisfied. Otherwise, the load as determined in Step 4 should be reduced and the analysis repeated. Note that if the applied loading results in a compressive stress field within the component, buckling may occur, and the effects of imperfections, especially for shell structures, should be considered in the analysis (see paragraph B.4.2).

f.

Step 6 – Review the results of the analysis in the area of high strain concentration and check the failure parameter chosen to categorize local failure (see paragraph B.3.4.1). If the local criteria is not satisfied, the applied loads should be reduced accordingly.

g.

Step 7 – If the global and local criteria are satisfied, the component is suitable for continued operation subject to the actual loads used in the assessment.

h.

Step 8 – A check for shakedown should be made if the component is to remain in-service during multiple start-up and shut-downs. This check can be made by removal and re-application of the actual load. A few cycles of this load reversal may be necessary to demonstrate shakedown. If significant incremental plastic strains occur during this load cycling (ratcheting), the permissible operating load should be reduced; otherwise, shakedown has occurred.

Note that if the assessment is to be based on a rigorous plastic collapse analysis, the collapse load is determined by increasing the load until structural instability is reached. The permissible operating load is taken as two-thirds of the plastic collapse load. This satisfies the global criteria in paragraph B.3.4.1. The local strains in the component should also be evaluated at the permissible operating load in order to satisfy the second criterion defined in paragraph B.3.4.1. B.6.4.2

The following procedure for the nonlinear analysis of a component with a non-crack-like flaw is one approach which has been used successfully to demonstrate the fitness-for-service. This procedure can be used to evaluate components subject to plasticity, fatigue and/or creep. This procedure can also be used to determine the stress field in the vicinity of a crack-like flaw for use in a fracture mechanics analysis. a.

Step 1 – Develop a finite element model of the component including all relevant geometry and flaw characteristics (see paragraph B.6.4.1.a).


Not for Resale

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b.

--``````-`-`,,`,,`,`,,`---

accurately model the component and flaw geometry. In addition, mesh refinement around areas of stress and strain concentrations should be provided. Based on the experience of the Engineer performing the analysis, the analysis of one or more finite element models may be required to ensure that an accurate description of the stress and strains in the component is achieved. This type of model evaluation is particularly important for non-linear analyses.


Step 2 – Define all relevant loading conditions including pressure, supplemental loads and temperature distributions. If the component is subject to cyclic loading or is in the creep regime, a histogram should be developed to determine the time dependency of the loads. If there is a concern about thermal stresses, a transient thermal analysis of the complete operating period may be required.

c.

Step 3 – Determine the maximum load combination based on the histogram in Step 2. This load combination should be selected as the one likely to govern the structural stability of the component. Evaluate the structural stability of the component using this load combination and the procedure in paragraph B.6.4.1 except that the check for shakedown should be based on the actual load histogram (see Step 4 below). Note that if a single load combination cannot be determined in the selection process, multiple load combinations may need to be evaluated.

d.

Step 4 – If cyclic loading is involved, peak elastic plus plastic strains should be evaluated for fatigue. A procedure to evaluate fatigue using the results of an elastic-plastic analysis is provided in paragraph B.5.2.4. In addition, for components operating below the creep regime, a check for shakedown should be made using the actual load histogram. If the component is operating in the creep regime, an evaluation including an assessment of the creep damage, and creep-fatigue interaction if cyclic loading is significant, should be made using the assessment procedures in Section 10.

e.

Step 5 – For components operating below the creep regime, if shakedown can be demonstrated, the check on fatigue damage is satisfied, and the strain in the vicinity of the flaw satisfies the limits in paragraph B.6.4.1.f, the component is suitable for continued operation. For components operating in the creep regime, if the check for creep/fatigue damage is satisfied, and the accumulated strain in the vicinity of the flaw satisfies the limits in paragraph B.6.4.1.f, the component is suitable for continued operation.

The following procedure has been used to demonstrate the fitness-for-service of a component with a crack-like flaw using the results of a nonlinear finite element analysis. The procedure cannot be used to evaluate cyclic loading or other conditions which may result in sub-critical crack growth. For these cases, special provisions and modifications are required to the procedure to account for subcritical crack growth (see Section 9). a.

Step 1 – Develop a finite element model of the component including all relevant geometry and flaw characteristics. The modeling of the crack tip is based on the component geometry and the type of analysis being performed. The following provides an overview for mesh design at the crack tip. Further details regarding finite element mesh design can be found in reference [B.7.1]. In addition, the users manual for the finite element program should also be consulted. 1.

Two-Dimensional (2-D) Small-Strain Analysis – The suggested (but not mandatory) mesh design for the crack tip region is a focused “spider web” mesh with elements concentrated at the crack tip. The first ring of elements is made up of quadrilaterals degenerated to triangles with several nodes coincident at the crack tip. It is important that these nodes not be tied together, nor merged into a single node (most commercial finite element programs will attempt to merge these nodes unless the user specifies otherwise). Subsequent rings of elements are quadrilaterals. The nodes on the crack face are not constrained. Under load, the nodes at the crack tip that are initially coincident move apart, resulting in a blunted crack. Note that the crack tip opening displacement (CTOD) can be inferred from the deformed mesh. Isoparametric 2-D elements (8 node or 9 node) are recommended, but linear (4 node) elements are acceptable provided the level of mesh refinement is sufficient to capture plastic strain gradients. One advantage of the degenerated isoparametric elements is that a 1 r strain singularity results at the crack tip, which is appropriate for elastic-plastic analysis (moving the mid-side nodes of isoparametric elements to the quarter point and tying the nodes at the crack tip will result in a appropriate for an elastic analysis).


Not for Resale

1 r 1/ 2 strain singularity which is

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B.6.4.3

b.

2.

Three-Dimensional (3-D) Small-Strain Analysis – The recommendations for the 2-D analysis are also applicable to a 3-D analysis. The main difference, is that 3-D continuum elements are used rather than 2-D continuum elements. Either isoparametric (20 or 27 node) bricks or 8 node bricks may be used, but the number of elements required for an accurate solution is greater for the 8 node bricks. It should be noted that constructing a 3-D crack mesh is extremely cumbersome. It is recommended that the user develop or acquire mesh generating software for this purpose.

3.

Two or Three-Dimensional Large-Strain Analysis – A “focused mesh” composed of 2-D or 3-D, as applicable, degenerated isoparametric elements at the crack tip is not appropriate when large strain theory is used in an analysis. Alternatively, the crack should be modeled as a notch with a finite radius. The initial undeformed crack tip radius should be chosen such that it is at least 5 times smaller than the deformed crack tip radius, where the deformed radius is approximately CTOD/2. Note that for smallstrain analyses, the finite crack tip radius mesh may be used as an alternative to the degenerated isoparametric element approach. Thus this mesh is appropriate when the user desires to perform both small- and large-strain analyses on the same geometry.

b.

Step 2 – Define all relevant loading conditions including pressure, supplemental load and temperature distributions. Crack face tractions should be applied where appropriate.

c.

Step 3 – An accurate representation of material properties should be included in the finite element model. The von Mises yield function and associated flow rule should be utilized if plasticity is anticipated. An elastic-plastic finite element analysis requires a stress-strain curve for the material of interest. Commercial finite element programs typically accept either a stress-strain data table or a parametric equation such as the Ramberg-Osgood power law. In the former case, the analysis treats the stress-strain curve as piece-wise linear. Some finite element codes offer the option of a bilinear stress-strain curve, but this option is not recommended here. If an accurate stress-strain curve is not available for the material of interest, there is little advantage to obtaining a failure assessment diagram (FAD) from an elastic-plastic J analysis. If the flaw of interest is in or near a weld, the weld metal and base metal flow behavior should be modeled.

d.

Step 4 – Perform the finite element analysis. 1.

A finite element program with automated procedures for performing a J analysis should be used in the analysis. Many commercial programs have built-in J post-processing routines. In its original definition, J is expressed as a line integral for 2-D problems and a surface integral in 3-D. However, this definition is not ideally suited to finite element analysis because numerical evaluation of a line integral or surface integral from finite element results is extremely inefficient and may be highly inaccurate. Alternatively, the J integral can be expressed as an area integral in 2-D problems and a volume integral in 3-D [B.7.4] and [B.7.6]. This approach, called the energy domain integral formulation is more efficient and accurate than contour or surface integration. It is the responsibility of the user to ensure that the J integral is evaluated accurately.

2.

Since the end results will be plotted as a FAD, an elastic J-solution must be obtained along with the elastic-plastic solution. There are two approaches to obtaining the elastic solution: ·

Evaluate J at an early load step when the plastic strains are negligible.

·

Perform a separate elastic analysis on the same model.

The elastic J is proportional to the square of the load, so it is necessary to evaluate the elastic J only at one load. For the elastic-plastic analysis, multiple load steps are required. For compound load cases, such as combined axial force and bending moment, the ratio of the various loads to one another must be fixed throughout the


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analysis. The analysis may be suspended when the total J exceeds 20 times the elastic component. There should be at least 10 load steps (and 10 corresponding J values) in the interval J elastic J total = 1.0 to J elastic J total = 0.05 . Since the functional relationship between J and load is normally not known in advance, some trial and error may be required to obtain sufficient load steps over the range of interest. e.

Step 5 – Construct the Failure Assessment Diagram (FAD) – The FAD (see Section 2 and 9) can be viewed as a non-dimensional plot of J versus the applied load (see Figure B.5). 1.

The toughness ratio, Kr, is the vertical axis of the FAD and is defined as the square root of the ratio of elastic J to total J. The y-coordinates of the points used to define the FAD can be determined using the results obtained in Step 4 with the following equation:

J elastic J total

Kr = 2.

(B.109)

The load ratio, Lr, is the horizontal axis of the FAD and is defined as ratio of the applied load to a normalizing or reference load. The x-coordinates of the points used to define the FAD can be determined using the results obtained in Step 4 with the following equation:

Lr =

P Pref

(B.110)

with Pref determined from the following relationship

= 1+ P = Pref

0.002 E y I ys

F GH

0.002 E y 1 + 1+ 2 I ys

I JK

-1

(B.111)

where,

Ey P

=

Modulus of Elasticity (MPa:psi),

=

Pref

=

Characteristic applied load (or stress) such as internal pressure, axial force, bending moment or a combination thereof, Reference load (or stress) defined as the load at which the ratio

J total J elastic reaches the value defined by Equation (B.111), and

I ys 3. f.

=

0.2% offset yield strength (MPa:psi).

The cut-off or limit of the horizontal axis (load ratio axis, Lr, see Step 2) of the FAD and is defined using the Section 9, Note 2 of Figure 9.17.

Step 6 – Complete the assessment for the specific flaw size and load case being evaluated by following the procedure in Section 9, paragraph 9.4.3.2 except that the FAD used to determine acceptability is taken from Step 5 above instead of the FAD shown in Section 9, Figure 9.17. 1.

The stress intensity factors for the primary and secondary loading conditions,

K1P and

K1S , respectively, can be determined using the solutions in Appendix C, or from an


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

J total J elastic


elastic J solution using the following equation, considering the specific flaw size and component stress for the loading condition to be evaluated. The toughness ratio, Kr, is then computed using Section 9, paragraph 9.4.3.2. If secondary and residual stresses are included in the J analysis described in Step 4, then the plasticity interation factor is not required in the calculation of Kr. Otherwise, the plasticity interaction factor can computed using the procedure in Section 9, paragraph 9.4.3.2 and included in the Kr calculation.

K=

J elastic E y

(B.112)

c1 - n h 2

where, Ey is previously defined, and Elastic J solution for the specific flaw and loading condition being evaluated, and Poisson’s ratio

J elastic =

n 2.

=

The load ratio, Lr, is defined as ratio of the reference stress to the material yield stress. The reference stress for the specific loading condition can be determined using the solutions in Appendix D or the following equation:

I ref =

FG I IJ I HI K

(B.113)

ys

L

where,

I ys is previously defined, and

I IL

= =

Applied stress (MPa:psi), and Applied stress when Lr = 10 . (MPa:psi).

B.7

References

B.7.1

Anderson, T.L., “Fracture Mechanics – Fundamentals And Applications,” 2nd Edition, CRC Press, Boca Raton, Florida, 1995.

B.7.2

Barsom, J.M., and Vecchio, R.S., “Fatigue Of Welded Components,” PVP Vol. 313-1, International Pressure Vessels and Piping Codes and Standards: Volume 1, ASME, 1995.

B.7.3

Brown, Robert, G., “Development of Elastic Stress Intensity Factor Solutions and Elastic-Plastic Failure Assessment Diagrams For Fillet Toe Cracks at Ring-Stiffened Cylindrical Shells,” Thesis, The University of Akron, December, 1996.

B.7.4

Dodds, R.H., Jr. And Vargas, P.M., “Numerical Evaluation of Domain and Contour Integrals for Nonlinear Fracture Mechanics.” Report UILU-ENG-88-2006, University of Illinois, Urbana, IL, August 1988.

B.7.5

Dowling, N.E., “Fatigue at Notches and the Local Strain and Fracture Mechanics Approaches,” Fracture Mechanics, ASTM STP 677, American Society for Testing and Materials, 1979.

B.7.6

Hibbitt, Karlson & Sorensen, Inc., “ABAQUS/Standard User’s Manual – Volume 1, Version 5.6,” Hibbitt, Karlson & Sorensen, Inc., Pawtucket, RI, 1997.

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B.7.7

IIW, “Stress Determination for Fatigue Analysis of Welded Components,” Edited by Erkki Niemi, Abington Publishing, Abington Hall, Abington, Cambridge, England, 1995, New York, 1995.

B.7.8

Miline, I., Ainsworth, R.A., Dowling, A.R., Stewart, A.T., “Assessment of the Integrity of Structures Containing Defects,” Int. J. Pres. Ves. & Piping 32, 1988, pp. 66-72.

B.7.9

Nelson, D.V., “Cumulative Fatigue Damage in Metals”, Ph.D. Dissertation, Stanford, California: Stanford University, 1978.

B.7.10

Shih, C.F., Moran, B., and Nakamura, T., “Energy Release Rate Along a Three-Dimensional Crack Front in a Thermally Stressed Body.” International Journal of Fracture, Vol. 30, 1986, pp. 79-102.

B.7.11

Wirsching, P.H., Wu, Y.T., “Probabilistic and Statistical Methods of Fatigue Analysis and Design,” Pressure Vessel and Piping Technology – 1985, American Society of Mechanical Engineers, New York, 1985, pp. 793-819.

B.7.12

WRC, “A Critical Evaluation of Plastic Behavior Data and a Unified Definition of Plastic Loads for Pressure Components,” WRC-254, Welding Research Council, New York, 1979.

B.7.13

WRC, “Fatigue of Welded Structures,” WRC-422, Welding Research Council, New York, 1997.

B.7.14

WRC, “Proposed Rules for Determining Allowable Compressive Stresses for Cylinders, Cones, Spheres and Formed Heads,” WRC-406, Welding Research Council, New York, 1995.

B.8

Tables and Figures

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Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table B.1 Stress Intensity K Factors For Various Load Combinations Load Combinations (1)

k

Design Loads – The design pressure, the dead load of the vessel, the imposed load of the mechanical equipment, and external attachment loads

1.0

Based on the corroded thickness at design metal temperature

Design loads plus wind load

1.2


Design loads plus earthquake load

1.2


Notes:

Calculated Stress Limit Basis

Structural instability or buckling must be considered for compressive stress fields.

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Not for Resale

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Table B.2 Examples Of Stress Classification

Any shell including cylinders, cones, spheres and formed heads

Location Shell plate remote from discontinuities

--``````-`-`,,`,,`,`,,`---

Near nozzle or other opening

Any location

Cylindrical or conical shell

Dished head or conical head

Flat head


Origin of Stress

General membrane Gradient through plate thickness

Pm Q

Axial thermal gradient Net-section axial force and/or bending moment applied to the nozzle, and/or internal pressure Temp. difference. between shell and head Internal pressure

Membrane Bending Local membrane Bending Peak (fillet or corner)

Q Q PL Q F

Membrane

Q

Bending Membrane Bending

Q Pm Q

Membrane Bending Membrane Bending Local membrane Bending Peak (fillet or corner)

Pm Pb PL Q (2) PL Q F

Membrane stress averaged through the thickness; stress component perpendicular to cross section Bending stress through the thickness; stress component perpendicular to cross section Membrane Bending Membrane Bending

Pm

PL Q PL Q

Membrane Bending Membrane Bending Membrane Bending Membrane Bending

Pm Pb PL (1) Q Pm Pb PL Q (2)

Internal pressure

LTA – Periphery

Internal pressure

LTA Near nozzle or other opening

Net-section axial force and/or bending moment applied to the nozzle, and/or internal pressure Net-section axial force, bending moment applied to the cylinder or cone, and/or internal pressure

Junction with head or flange LTA – Tank bottom course-to-shell junction Crown

Classification

Internal pressure

Shell distortions such as out-ofroundness and dents LTA – Center region

Any section across entire vessel

Type of Stress

Internal pressure Liquid Head Internal pressure

Knuckle or junction to shell Center region

Internal pressure Internal pressure

Junction to shell

Internal pressure

Not for Resale

Pb //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Vessel Component


Table B.2 Examples Of Stress Classification

Perforated head or shell

--``````-`-`,,`,,`,`,,`---

Nozzle

Location Typical ligament in a uniform pattern

Origin of Stress Pressure

Isolated or atypical ligament

Pressure

Cross section perpendicular to nozzle axis

Internal pressure or external load or moment

Nozzle wall

External load or moment Internal pressure

Differential expansion LTA – Nozzle wall

Internal pressure

Cladding

Any

Any

Any

Differential expansion Radial temperature distribution [note (3)]

Any Notes: 1. 2. 3. 4.

Any

Any

Type of Stress Membrane (average through cross section) Bending (average through width of ligament., but gradient through plate) Peak Membrane Bending Peak General membrane (average. across full section). Stress component perpendicular to section Bending across nozzle section General membrane Local membrane Bending Peak Membrane Bending Peak General membrane Local membrane Bending Peak Membrane Bending Equivalent linear stress [note (4)] Nonlinear portion of stress distribution Stress concentration (notch effect)

Classification Pm Pb

F Q F F Pm

Pm Pm PL Q F Q Q F Pm PL Q F F F Q F F

Consideration must also be given to the possibility of wrinkling and excessive deformation in vessels with large diameter-to-thickness ratio. If the bending moment at the edge is required to maintain the bending stress in the center region within acceptable limits, the edge bending is classified as Pb, otherwise, it is classified as Q. Consider possibility of thermal stress ratchet. Equivalent linear stress is defined as the linear stress distribution which has the same net bending moment as the actual stress distribution.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Vessel Component


Table B.3 Knock-Down Factors For Fatigue Analysis Tmax o

o

m

n

( C) (2)

( F) (2)

Low alloy steel

2.0

0.2

371

700

Martensitic stainless steel

2.0

0.2

371

700

Carbon steel

3.0

0.2

371

700

Austenitic stainless steel

1.7

0.2

427

800

Nickel-chromium-iron

1.7

0.2

427

800

Nickel-copper

1.7

0.2

427

800

Notes: 1. 2.

Fatigue knock-down factor The fatigue knock-down factor should only be used if all of the following are satisfied; · The range of primary plus secondary stress, excluding thermal stress, is less than 3Sm, · The component is not subject to thermal ratcheting, · The maximum temperature in the cycle is within the value in the table for the material, and · The material has a specified minimum yield strength to specified minimum tensile strength ratio of less than 0.8.

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Not for Resale

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Ke (1)

Material


Table B.4 Coefficients For Mechanical Loading Coefficient

Iys £ 500 MPa (72,519 psi)

500 MPa (72,519 psi) < Iys £

Iys > 800 MPa (116,030 psi)

800 MPa (116,030 psi) M1

0.443

M2

0.823

M3

0.164

Notes: 1. 2.

Csu Iys

= =

FG 2.5I C IJ H (10 ) K F 3.5I C IJ 0.998 - G H (10 ) K . I C I F 173 0.077 + G H (10 ) JK 0.318 +

ys 4

su

ys 4

su

ys 4

su

0.518

0.718

0.216

-3

6.894757(10 ) for stress in psi and 1.0 for stress (Mpa). Yield stress at the assessment temperature (Mpa).

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table B.5 Temperature Factors For Fatigue Screening Criteria

Notes: 1. 2.

Temperature Factor For Fatigue Screening Criteria

°C

°F

10 or less

50 or less

0

11 to 38

51 to 100

1

39 to 66

101 to 150

2

66 to 121

151 to 250

4

122 to 177

251 to 350

8

177 to 232

351 to 450

12

greater than 232

greater than 450

20

If the weld metal temperature differential is unknown or cannot be established, a value of 20 shall be used. As an example illustrating the use of this table, consider a component subject to metal temperature differentials for the following number of thermal cycles. Temperature Differential 10 °C (50 °F) 32 °C (90 °F) 204 °C (400 °F)

Temperature Factor Based On Temperature Differential 0 1 12

Number Of Thermal Cycles 1000 250 5

The effective number of thermal cycles due to changes in metal temperature is:

bg

bg b g

1000 0 + 250 1 + 5 12 = 310 cycles

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Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Metal temperature Differential


Table B.6 K-Factors For Determining The Permissible Number Of Cycles For The Fatigue Screening Criteria Flaw Type

General Corrosion

Local Thin Area

Groove-Like Flaw

Pitting

Notes: 1. 2.

Recommended K-Factor (1)

Recommended Weld Classification (2)

Within two plate thicknesses or at a weld joint

2.0

63

Away from weld joints

1.5

80

LTA with scratches, grooves, notches or pits

4 (3) RSF

40

LTA with smooth profile without scratches, grooves, notches or pits

2 (3) RSF

50

Groove-like flaw without a dent (4)

4 (3) RSF

50

Pits with sharp edges or bottoms

4 (5) RSF

40

Pits with rounded or smooth edges and bottoms

3 (5) RSF

50

The K-factor is used when the fatigue screening criteria is evaluated using fatigue curves based on smooth bar test specimens (see Appendix F, paragraph F.6.2), other values may be used based on the actual flaw configuration and the judgment of the Engineer. The weld classification is used when the fatigue screening criteria is evaluated using fatigue curves based on welded test specimens (see paragraph F.6.3 of Appendix F), other values may be used (see Appendix F, Table F.12) based on the actual flaw configuration and the judgment of the Engineer. The Remaining Strength Factor (RSF) is computed for these flaws using the procedures of Section 5. Grooves located in a dented region should be evaluated using Section 8. The Remaining Strength Factor (RSF) is computed using the procedures of Section 6.

--``````-`-`,,`,,`,`,,`---

3. 4. 5.

Description


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure B.1 Stress Categories And Limits Of Stress Intensity

Description (For examples, see Table 4-120.1

Primary General Membrane

Local Membrane Average stress across any solid section. Considers discontinuities but not concentrations. Produced only by mechanical loads.

Average primary stress across solid section. Excludes discontinuities and concentrations. Produced only by mechanical loads.

Symbol3

Pm

Pm

Secondary Membrane plus Bending

Bending Component of primary stress proportional to distance from centroid of solid section. Excludes discontinuities and concentrations. Produced only by mechanical loads.

PL

Self-equilibrating stress necessary to satisfy continuity of structure. Occurs at structural discontinuities. Can be caused by mechanical load or by differential thermal expansion. Excludes local stress concentrations.

Pb

Peak

1. Increment added to primary or secondary stress by a concentration (notch). 2. Certain thermal stresses which may cause fatigue but not distortion of vessel shape.

Q

F

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Stress Category

kSm Note 1

PL + Pb + Q

PL

3Sm

1.5kSm

Use design loads --``````-`-`,,`,,`,`,,`---

Note 2

Use operating loads PL + Pb

Notes: 1.

2. 3. 4.

1.5kSm

PL + Pb + Q + F

Sa

This limit applies to the range of stress intensity. The quantity 3Sm is defined as three times the average of the tabulated Sm values for the highest and lowest temperatures during the operation cycle. In the determination of the maximum primary-plus-secondary stress intensity range, it may be necessary to consider the superposition of cycles of various origins that produce a total range greater than the range of any of the individual cycles. The value of 3Sm may vary with the specific cycle, or combination of cycles, being considered since the temperature extremes may be different in each case. Sa is obtained from the fatigue curves, see Paragraph B.3.5. The Symbols Pm, PL, Pb, Q, and F do not represent single quantities, but rather sets of six quantities representing the six stress components Iij. The parameter k is defined in Table B.1.


Not for Resale


Figure B.2 Using Finite Element Stress Results To Elevate Stress Intensities Stress Classification Line Cylindrical Shell

Internal Pressure R

C L

Local Thickness Coordinate

(a) Stress Classification Line

Linearized Membrane and Bending Stress Distributions Linearized Membrane and Bending Stress Distributions

Computed Stress Results from Finite Element Analysis

Membrane

Bending

Peak

(b) Stress Along Stress Classification Line

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Not for Resale

Stress

--``````-`-`,,`,,`,`,,`---

Internal Support Ring


Figure B.3 Linearization Of Stresses For Assessment Of A Crack-Like Flaw – Linearization Over The Defect

I

I

I I

I 0

a

0

t

t I0

t

t

I

a

a

a

(a) Linearization Over the Defect - Surface Flaw

I I

I

I

I

I

I

t

0

2a

I0

2a

2a

t I0

t

(b) Linearization Over the Defect - Embedded Flaw Notes: 1.

The linearized membrane stress is:

2.

The linearized bending stress is:

I1 +I 2 2 I1 -I 2 Ib = 2 Im =

--``````-`-`,,`,,`,`,,`---


Not for Resale

t 2a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I

I


Figure B.4 Linearization Of Stresses For Assessment Of A Crack-Like Flaw – Linearization Over The Cross Section

I

I

I

I

I

I

I I a

a

I

a

a

t 0

t

0

t 0

t

(a) Linearization Over the Cross Section - Surface Flaw

I

I

I --``````-`-`,,`,,`,`,,`---

I

I

I 2a

I

I

I

2a

2a

2a

t 0

t

t 0

0

(b) Linearization Over the Cross Section - Embedded Flaw Notes: 1.

The linearized membrane stress is:

Im =

I1 +I 2 2

2.

The linearized bending stress is:

Ib =

I1 -I 2 2


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

t


Figure B.5 Construction Of A FAD From A J Versus Load Plot

JTotal

J

JElastic is Proportional to P2

Load - P

Pref

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(a) J Versus Applied Load Curves

Kr

Lr = P/Pref

(b) FAD Constructed From The J Versus Applied Load Curves


Not for Resale

APPENDIX C – Compendium of Stress Intensity Factor Solutions (Jan, 2000) --``````-`-`,,`,,`,`,,`---

C.1

General

C.1.1

Overview

C.1.1.1

This appendix contains stress intensity factor solutions for many crack geometries which are likely to occur in pressurized components. Stress intensity factor solutions are used in the assessment of crack-like flaws (see Section 9).

C.1.1.2

A summary of the stress intensity factor solutions is contained in Table C.1. These stress intensity factor solutions are recommended for most applications based on consideration of accuracy, range of applicability and convenience. However, additional cases and improved solutions are being produced for future incorporation into this appendix.

C.1.1.3

Stress intensity factors not included in this appendix may be obtained from handbooks (see references [C.15.2], [C.15.15], [C.15.21], [C.15.22] and [C.15.29]) if the tabulated solutions correspond to the component and crack geometry, and the loading condition. Otherwise, the stress intensity factor should be computed using a numerical approach such as the finite element method.

C.1.1.4

The stress intensity factor solutions for plates can be utilized to approximate the solution for a curved shell (cylinder and sphere) by introduction of a surface correction or bulging factor. This type of solution should only be utilized if a stress intensity factor equation is not listed in the sections covering shell type components.

C.1.1.5

An identifier has been assigned to each stress intensity factor solutions in this appendix (see Table C.1). This identifier is a set of alpha-numeric characters that uniquely identifies the component geometry, crack geometry, and loading condition. The identifier can be used to determine the associated reference stress solution to be used in an assessment of crack like flaws (see Section 9). For example, if a flat plate with a through-wall crack subject to a membrane stress is being evaluated, the stress intensity factor solution to be used is KPTC, and the associated reference stress solution is RPTC. A listing of the reference stress solutions is provided in Appendix D.

C.1.2

Symbol Definitions

C.1.2.1

The following symbols defined below are used in this appendix.

a Ar c B dn d1

= = = = =

Crack depth parameter (mm:in), 2 2 Cross sectional area of a stiffening or tray support ring (mm :in ), Crack length parameter (mm:in), Biaxial stress ratio, Mean nozzle diameter (see Figure C.26) (mm:in),

=

d2

=

F L

= =

M Mx

= =

Distance from plate surface to the center of an embedded elliptical crack (see Figure C.3) (mm:in), Distance from plate surface to the center of an embedded elliptical crack (see Figure C.3) (mm:in), Net section axial force acting on a cylinder (N:lbs), Length parameter used for stress intensity factor magnification factors and solutions at fillet weld locations (mm:in), Resultant net section bending moment acting on a cylinder (N-mm:in-lbs), Net section bending moment about the x-axis acting on a cylinder (N-mm:in-lbs),


C-1 Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

--``````-`-`,,`,,`,`,,`---

My p t tn rw Rb

=

Net section bending moment about the y-axis acting on a cylinder (N-mm:in-lbs),

= = =

Pressure (MPa:psi), Plate or shell thickness (mm:in), Nozzle thickness (see Figure C.26) (mm:in),

=

Root radius at the fillet weld (mm:in),

=

Rh Ri Rm Ro Rth x xg

=

Ratio of induced bending stress to the applied membrane stress (see Section 8, paragraphs 8.4.3.2, 8.4.3.3 and 8.4.3.4), Hole radius (mm:in),

=

Cylinder inside radius (mm:in),

=

Cylinder mean radius (mm:in),

=

Cylinder, round bar, or bolt outside radius, as applicable (mm:in),

= = =

Root Radius of a threaded bolt (mm:in), Radial local coordinate originating at the internal surface of the component, Global coordinate for definition of net section bending moment about the x-axis,

yg W

=

Global coordinate for definition of net section bending moment about the y-axis,

=

= j

= =

G n I ij

= = =

Distance from the center of the flaw to the free edge of the plate (see Figure C.1) (mm:in), Fillet weld angle (degrees), Elliptic angle, see Figure C.2 for surface cracks in plates and shells, Figure C.3 for embedded flaws, and Figure C.9 for surface cracks at holes, and Figure C.26 for radial corner cracks at nozzles (degrees), Half-angle of a circumferential crack (degrees), Poisson’s ratio, Stress component being evaluated,

I ij ,m I ij ,b Im Ib I0 I1 I2 I3 I4 I5

=

Equivalent membrane stress for a stress component,

=

Equivalent bending stress for a stress component,

=

Membrane stress component (MPa:psi),

=

Through-Wall Bending stress component (MPa:psi),

=

Uniform coefficient for polynomial stress distribution (MPa:psi),

=

Linear coefficient for polynomial stress distribution (MPa:psi),

=

Quadratic coefficient for polynomial stress distribution (MPa:psi),

=

Third order coefficient for polynomial stress distribution (MPa:psi),

=

Fourth order coefficient for polynomial stress distribution (MPa:psi),

=

I6

=

Bending stress from the net section bending moment about the x-axis acting on a cylinder (MPa:psi), and Bending stress from the net section bending moment about the y-axis acting on a cylinder (MPa:psi).

C.1.2.2

The above symbols are further defined for different component and crack geometries in Figures C.1 through C.32.

C.2

Stress Analysis

C.2.1

Overview


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Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE C-3 _________________________________________________________________________________________________

C.2.1.1

--``````-`-`,,`,,`,`,,`---

A stress analysis using handbook or numerical techniques is required to compute the state of stress at the location of a crack. The stress distribution to be utilized in determining the stress intensity factor is based on the component of stress normal to the crack face. The distribution may be linear (made up of membrane and/or bending distributions) or highly nonlinear based on the component geometry and loading conditions.

C.2.1.2

The stress distribution normal to the crack face should be determined for the primary, secondary, and residual loading conditions based on the service requirements that the uncracked component geometry is subjected to. If the component is subject to different operating conditions, the stress distribution for each condition should be evaluated and a separate fitness-for-service assessment should be performed for each.

C.2.2

Stress Distributions

C.2.2.1

Overview – The stress intensity factor solutions in this appendix are formulated in terms of the coefficients of a linear stress distribution (membrane and bending) or fourth order polynomial stress distribution, or in terms of a general stress distribution (weight functions). Therefore, if the stress intensity factor required for the assessment is written in terms of coefficients of a stress distribution, it is necessary to derive these coefficients from the results obtained from a stress analysis.

C.2.2.2

General Stress Distribution – A general stress distribution through the wall thickness can be obtained from a two or three dimensional elasticity solution (e.g. Lame solutions for a thick wall cylinder and sphere) or it can be determined using a numerical analysis technique such as the finite element method. In some cases, the stress distribution normal to the crack face may be highly non-linear. a.

b.

C.2.2.3

Statically equivalent membrane and bending stress components can be determined from the general stress distribution using the following equations; the integration is performed along a line assuming a unit width, see Appendix B.

z z

I ij ,m =

1 t I ij dx t 0

I ij ,b =

6 t2

t

0

I ij

(C.1)

FG t - xIJ dx H2 K

(C.2)

A general stress distribution can be used directly to determine a stress intensity factor by integration of this distribution with a suitable weight function. Weight functions have been provided in this appendix for a limited number of component and crack geometries.

Fourth Order Polynomial Stress Distribution – The fourth order polynomial stress distribution can be obtained by curve-fitting the general stress distribution. This distribution is utilized to obtain a more accurate representation of the stress intensity for a highly nonlinear stress distribution. Many of the stress intensity factor solutions in this appendix have been developed based on a fourth order polynomial stress distribution. a.

The general form of the fourth order polynomial stress distribution is as follows:

I ( x) = I o b.

F xI F xI +I G J +I G J HtK HtK 1

2

2

F xI +I G J HtK 3

3

F xI +I G J HtK 4

4

(C.3)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The equivalent membrane and bending stress distributions for the fourth order polynomial stress distribution are:

Im =I0 +


I1 I 2 I 3 I 4 + + + 2 3 4 5

Not for Resale

(C.4)


Ib = C.2.2.4

I 1 I 2 9I 3 6I 4 2 2 20 15

(C.5)

Fourth Order Polynomial Stress Distribution With Net Section Bending Stress – This distribution is used to represent a through-wall fourth order polynomial stress and a net section or global bending stress applied to a circumferential crack in a cylindrical shell.

F xI F xI F xI I ( x, x , y ) = I + I G J + I G J + I G J HtK HtK HtK F y IJ + I FG x IJ I G H R +tK H R +tK 2

g

g

o

1

2

3

g

5

F xI +I G J HtK 4

4

+ (C.6)

g

6

i

C.2.2.5

3

i

Membrane and Through-Wall Bending – The membrane and bending stress distribution is linear through the wall thickness and represents a common subset of the general stress distribution. This distribution occurs in thin plate and shell structures and can be computed using handbook solutions or by using a numerical technique such as finite element analysis. If finite element analysis is utilized in a fitness-for-service assessment, the results from plate and shell elements will directly yield membrane and bending stress distributions. The stress intensity factor solutions in this appendix can be used if a membrane and through-wall bending stress distribution is known. For the special case of weld misalignment and shell out-of-roundness, the bending stress solution can be computed using the membrane stress solution and the following equation:

I b = I m Rb

(C.7)

Surface Correction Factors

C.2.3.1

Surface correction or bulging factors are used to quantify the local increase in the state of stress at the location of a crack in a shell which occurs because of local bulging. The magnified state of stress is then used together with a reference stress solution for a plate with a similar crack geometry to determine the reference stress for the shell. Surface correction factors are typically only applied to the membrane part of the stress intensity solution because this represents the dominant part of the solution.

C.2.3.2

The surface correction factors for through-wall cracks in cylindrical and spherical shells subject to membrane stress loading are defined in Appendix D, paragraph D.2.3.2. The surface correction factors for surface cracks can be approximated using the results obtained for a though-wall crack by using one of the methods discussed in Appendix D, paragraph D.2.3.3. The surface correction factor based on net section collapse is recommended for use in this appendix.

C.3

Stress Intensity Factor Solutions for Plates

C.3.1

Plate – Through-Wall Crack, Through-Wall Membrane And Bending Stress (KPTC)

C.3.1.1

The Mode I Stress Intensity Factor [C.15.1], [C.15.36]

--``````-`-`,,`,,`,`,,`---

C.2.3

b

K I = I m + M bI b

g

F c fw

(C.8)

where,

0.302327 + 70.50193O + 110.305O 2 Mb = . + 110.960O + 98.7089O 2 + 0.753594O 3 10


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(C.9)


O= --``````-`-`,,`,,`,`,,`---

fw

(C.10)

L F Fc IJ OP = MsecG N H 2W K Q

1/ 2

(C.11)

Notes: a.

See Figure C.1 for the component and crack geometry.

b.

Crack and geometry dimensional limits:

c.

I m and I b can be determined using stress equations based on strength of materials concepts.

0.0 < c W < 10 . .

C.3.2

Plate – Surface Crack, Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (KPSCL1)

C.3.2.1

The Mode I Stress Intensity Factor [C.15.9]

KI C.3.2.2

L = MG I MN o

o

F aI F aI +GI G J +G I G J HtK HtK 1

1

2

2

2

F aI +G I G J HtK 3

3

3

F aI O +G I G J P H t K PQ 4

4

4

Fa

(C.12)

Notes: a.

See Figure C.2(b) for the component and crack geometry.

b.

The coefficients of the stress distribution to be used are defined in paragraph C.2.2.3.

c.

The influence coefficients

d.

Crack and geometry dimensional limits,

e.

The solution presented is for the case of no restraint on the ends of the plate.

G0 through G4 are provided in Table C.2. 0.0 < a t £ 0.8 .

C.3.3

Plate – Surface Crack, Infinite Length, Through-Wall Arbitrary Stress Distribution (KPSCL2)

C.3.3.1

The Mode I Stress Intensity Factor [C.15.3] The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.3.2.2.c.

C.3.3.2

Notes: see paragraph C.3.2.2.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.3.1.2

t c 10


C.3.4

Plate – Surface Crack, Semi-Elliptical Shape, Through-wall Membrane And Bending Stress (KPSCE1)

C.3.4.1


b

KI = M mI m + M bI b

g

Fa Q

(C.13)

where,

FG a IJ H cK FG c IJ Q = 10 . + 1464 . H aK

1.65

Q = 10 . + 1464 .

for a / c £ 10 .

(C.14)

for a / c > 10 .

(C.15)

1.65

The membrane correction factor is given by:

Mm

R| F aI = M SM + M G J HtK |T s

1

2

2

F a I U| + M G J V gf H t K |W 4

3

j

fw

(C.16)

where,

M s = 10 .

fw

(C.17)

|R F Fc a IJ |UV = SsecG |T H 2W t K |W

0.5

(C.18)

For a/c £ 1.0

M1 = 113 . - 0.09

M2 =

M3

FG a IJ H cK

(C.19)

0.89 - 0.54 a 0.2 + c

FG IJ HK

(C.20)

R F aIU = 0.5 + 14 S1 - G J V F aI T H cKW 0.65 + G J HK 1

24

(C.21)

c

|R . + 0.35FG a IJ |UVb1 - sinj g g = 1 + S01 H t K |W |T 2

2

--``````-`-`,,`,,`,`,,`---


Not for Resale

(C.22)

//^:^^


R|F a I = SG J |TH c K

fj

2

U| cos j + sin j V |W 2

0.25

2

(C.23)

For a/c > 1.0

F cI R F cIU M = G J S1 + 0.04G J V H aK T H aKW F cI M = 0.2G J H aK F cI M = -011 . G J H aK R| F c I F a I U| g = 1 + S0.1 + 0.35G J G J Vb1 - sinj g H a K H t K |W |T |RF c I |U f = SG J sin j + cos j V |TH a K |W 0.5

(C.24)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

1

4

(C.25)

2

4

(C.26)

3

2

2

(C.27)

0.25

2

2

2

j

(C.28)

The bending correction factor is given by:

M b = M m Hf w

(C.29)

--``````-`-`,,`,,`,`,,`---

where,

b

g

H = H1 + H2 - H1 sin q j

H2 = 1 + G1 For

FG a IJ + G FG a IJ HtK HtK

(C.30)

2

(C.31)

2

a c £ 1.0

FG a IJ + 0.6FG a IJ H cK H t K F aI F aIF aI H = 1 - 0.34G J - 0.11G J G J H t K H cKH t K F aI G = -122 . - 012 . G J H cK q = 0.2 +


(C.32)

1

(C.33)

1

(C.34)

Not for Resale


G2

F aI + 0.47G J H cK

0.75

1.5

(C.35)

a c > 10 .

FG c IJ + 0.6FG a IJ H aK H t K R F c I UF a I R| . FG c IJ H = 1 - S0.04 + 0.41G J VG J + S0.55 - 193 H a K WH t K |T H aK T F cI G = -2.11 + 0.77G J H aK F c I . FG c IJ G = 0.55 - 0.72G J + 014 H aK H aK q = 0.2 +

(C.36)

0.75

1

F cI + 138 . G J H aK

1.5

U|VFG a IJ |WH t K

1.5

(C.39)

2

--``````-`-`,,`,,`,`,,`---

C.3.4.2

(C.37)

(C.38)

1

0.75

2

Notes: a.


b.

Crack and geometry dimensional limits: 1.

0.0 < a t £ 0.8

for

0.0 < a c £ 0.2 ,

2.

0.0 < a t £ 10 .

for

0.2 < a c £ 2.0 ,

3.

0.0 < a c £ 2.0 ,

4.

0.0 < c W < 10 . , and

5.

0o £ j £ 180o .

c.

If c >> a , the solution approaches that of a plate with an edge crack (see Section 9, Figure 9.1(d).

d.

The solution presented can be used to determine a conservative estimate of the stress intensity factor for cylinders and spheres when Ri t > 10 . The following modifications are required: 1.

A surface correction factor, M s , should be used for longitudinal cracks or circumferential cracks in cylinders or circumferential cracks in spheres, see paragraph C.2.3,

2.

The finite width correction factor should be set equal to one,

3.

For internal cracks, the pressure loading on the crack faces should be included in the membrane stress.


Not for Resale

f w = 1.0 ,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

for

F aI = 0.55 - 105 . G J H cK


e.

The stress intensity factor solution presented above may be overly conservative for finite width plates. A more accurate estimate of the stress intensity factor can be obtained by using the following finite width correction factor for the membrane stress in Equation (C.16). The finite width correction factor for the bending stress is given by Equation (C.18) [C.15.21].

f wm

R| F pc IJ × FG a IJ b1 - 0.6 sin j g U|V = f SsecG |T H 2W K H t K |W

0.5

(C.40)

b

where

FG a IJ FG a IJ FG c IJ H cKH t KHW K

f b = 1 + 0.38 f.

2

cosj

(C.41)


Plate – Surface Cracks, Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KPSCE2)

C.3.5.1


--``````-`-`,,`,,`,`,,`---

C.3.5

KI C.3.5.2

L = MM G I MN s

o

o


1

2

2

2

F aI +G I G J HtK 3

3

3


4

4

Fa fw Q

(C.42)

Notes: a.

See Figure C.2(a) for the component and crack geometry.

b.


c.

The influence coefficients G0 through G4 are provided in Table C.3 for 01 . £ a c £ 10 . . The expressions for the influence coefficients in this table were developed by curve fitting the data provided in Tables A-3320-1 and A-3320-2 of Section XI, Division 1 of the ASME B&PV Code. . , the The curve fit equations cover the full range of data within 3%. If 0.02 < a c < 01 influence coefficients G0 and using the following equations:

G1 can be determined from the solution in paragraph C.3.4

Go = M m

G1 =

FG H

t M m - Mb 2 a

(C.43)

IJ K

(C.44)

0.0 < a c < 0.02 , the influence coefficients in paragraph C.3.4. should be used. The G2 , G3 , and G4 influence coefficients can be computed using paragraph C.14.3 or C.14.4.

If //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d.

The following coefficients have been previously defined:


Not for Resale


--``````-`-`,,`,,`,`,,`---

e.

f.

1.

Q by Equations (C.14) or (C.15),

2.

fw by Equation (C.18),

3.

Mm by Equation (C.16), and

4.

Mb by Equation (C.29).


0.0 < a t £ 0.8 ,

2.

0.0 < a c £ 1.0 ,

3.

0.0 < c W < 10 . , and

4.

0o £ j £ 180o .

See paragraph 3.4.2.d to determine

Ms .

C.3.6

Plate – Surface Crack, Semi-Elliptical Shape, Through-Wall Arbitrary Stress Distribution (KPSCE3)

C.3.6.1


LM hb x, agI b xgdxOP f Nz Q a

KI =

(C.45)

w

0

where h( x , a ) is a weight function, I ( x ) is the stress normal to the crack plane (when the component is in the uncracked state), x is the through-thickness distance measured from the free surface that contains the crack, and f w is the finite width correction factor given by Equation (C.18). The weight function at the deepest point of the crack

hj = 90

b x, ag = 2F ba - xg LMM1 + M FGH1 - ax IJK N 2

1

1/ 2

(j = 90o ) :

F xI F xI O + M G1 - J + M G1 - J P H a K H a K PQ 3/ 2

2

3

(C.46)

where Q is given by Equation (C.14) and,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

M1 =

b

g

F 24 4Yo - 6Y1 5 2Q

(C.47)

M2 = 3


(C.48)

Not for Resale


I JK F aI F aI Y = B +BG J +B G J HtK HtK F aI F aI B = 110190 . - 0.019863G J - 0.043588G J H cK H cK F aI F aI F aI B = 4.32489 - 14.9372G J + 19.4389G J - 8.52318G J H cK H cK H cK F aI F aI F aI B = -3.03329 + 9.96083G J - 12.582G J + 5.3462G J H cK H cK H cK F aI F aI Y = A +AG J +A G J HtK HtK FG a IJ - 0.046523FG a IJ A = 0.456128 - 0114206 . H cK H cK F aI F aI F aI A = 3.022 - 10.8679G J + 14.94G J - 6.8537G J H cK H cK H cK F a I . FG a IJ + 516354 FG a IJ A = -2.28655 + 7.88771G J - 110675 . H cK H cK H cK M3 = 2

F GH

F Yo - M1 - 4 2Q 2

o

o

(C.49)

4

1

(C.50)

2

2

(C.51)

o

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

2

3

(C.52)

1

2

3

(C.53)

2

2

1

o

4

1

(C.54)

2

2

(C.55)

o

2

3

(C.56)

1

2

2

The weight function at the free surface of the crack

hj = 0

LM MN

b g

FG IJ HK

x 2 x, a = 1 + N1 a Fx

1/ 2

3

(C.57)

(j = 0o ) :

F xI F xI +N G J+N G J H aK H aK 2

3/ 2

3

OP PQ

(C.58)

where,

b

g

(C.59)

F 60 F0 - 90 F1 + 15 4Q

b

g

(C.60)

b

(C.61)

N1 =

F 30 F1 - 18 Fo - 8 4Q

N2 =

N 3 = - 1 + N1 + N 2

g --``````-`-`,,`,,`,`,,`---


Not for Resale


F aI F = =G J H cK

>

(C.62)

0

F aI F aI = = 114326 . + 0.0175996G J + 0.501001G J HtK HtK FG a IJ - 0.398175FG a IJ > = 0.458320 - 0102985 . HtK HtK F aI F =CG J H cK FG a IJ + 0.484875FG a IJ C = 0.976770 - 0131975 . HtK HtK FG a IJ - 0.267775FG a IJ @ = 0.448863 - 0173295 . HtK HtK

2

(C.63)

2

(C.64)

@

(C.65)

1

(C.66)

2 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.3.6.2

2

(C.67)

Notes: a.


b.


0.0 < a t £ 0.8 ,

2.

01 . < a c £ 1.0 ,

3.

0.0 < c W < 10 . , and

4.

0o £ j £ 180o .

Plate – Embedded Crack, Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (KPECL)

C.3.7.1



--``````-`-`,,`,,`,`,,`---

C.3.7

Not for Resale


LMG |RI + I FG d IJ + I FG d IJ + I FG d IJ + I FG d IJ |U +OP H t K H t K H t K H t K V|W P MM S|T MMG R|SI + 2I FG d IJ + 3I FG d IJ + 4I FG d IJ U|VFG a IJ + PPP HtK HtK H t K |WH t K P MM |T PP R| F d I F d I U|F a I = MG SI + 3I G J + 6I G J VG J + H t K H t K |WH t K MM |T PP MMG RSI + 4I FG d IJ UVFG a IJ + PP H t K WH t K MM T PP MMG lI qFGH at IJK PP N Q 2

o

1

3

1

2

3

4

1

4

2

1

1

2

1

3

1

3

4

KI

2

2

3

1

2

2

1

1

1

4

Fa

(C.68) --``````-`-`,,`,,`,`,,`---

o

1

3

3

3

4

1

4

4

C.3.7.2

4

Notes:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.


b.


c.


d.


2.

3.

FG d - a IJ ³ 0.2 H t K FG d - a IJ ³ 0.2 H t K

Go through G4 for points A and B are provided in Table C.4.

1

when

d1 £

t , 2

2

when

d2 £

t , and 2

0.25 £ d1 t £ 0.75 . d1 = 0.0 .

e.

The datum for the stress distribution is at

f.

The solution presented can be used for cylinders and spheres when the finite width correction factor should be set to unity,

Ri t ³ 5 . In this case,

f w = 1.0 .

C.3.8

Plate – Embedded Crack, Elliptical Shape, Through-Wall Membrane and Bending Stress (KPECE1)

C.3.8.1


b

KI = M mI me + M bI be


g

Fa Q

(C.69)

Not for Resale


where Q is given by Equation (C.14). The local membrane and bending stress components acting on the crack face (see Figure C.4) are given by the following equations.

FG H

I me = I m + I b 1 -

I be = I b

IJ K

2d 2 t

(C.70)

FG 2a IJ HtK

(C.71)

The membrane correction factor is given by

M m = Hj f j f w

(C.72)

with fw given by Equation (C.18),

b

fj given by Equation (C.23), and

g

b

g

1 2 sin j H90 1 + sin j + H270 1 - sin j + H0 cos2 j 2

Hj =

(C.73)

with,

0

2

270

1

3

2

1

i

2

i

3

i

(C.75)

2

1

(C.76)

2

2

1

(C.74)

4

i

(C.77)

i

2

4

i

(C.78)

i

2

==

i

4

i

a c

(C.79)

(C.80)

>1 =

a d1

(C.81)

>2 =

a d2

(C.82)

The bending correction factor is:


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

b gb g H = h b= , > gh b= , > g H = h b= , > gh b= , > g 0.085 I F h b= , > g = 1 + G -0.04 + J > + b0.05 - 0.03= g> H 0.34 + = K 0.075 I F F 0.024 IJ > h b= , > g = 1 + G -0.03 + > + G 0.08 J H H 01. + = K 0.3 + = K 0.07 I F h b= , > g = 1 + G -0.06 + J > + b0.643 - 0.343= g> H 0.25 + = K H90 = h1 = , > 1 h3 = , > 2


M b = - 0.5 + 0.2591a 1.5 - 0.09189a 2.5 f j f W f b sin j

(C.83)

where terms are defined above, and

f> =

f 270 + f 90 f 270 - f 90 sin j 2 2

(C.84)

f 90 = 1 + exp -19249 . - 3.9087= 0.5 + 4.1067 > 2

3

(C.85)

f 270 = 1 + exp -19249 . - 3.9087= 0.5 + 4.1067> 13 C.3.8.2

(C.86)

Notes: a.


b.

See Figure C.4 for the definition of the membrane and through-wall bending stress components.

c.

See Figure C.5 for the sign convention of the bending stress.

d.


2.

--``````-`-`,,`,,`,`,,`---

e.

FG d - a IJ ³ 0.2 H t K FG d - a IJ ³ 0.2 H t K 1

when

d1 £

t , 2

2

when

d2 £

t , 2

3.

0.20 £ d1 t £ 0.80 ,

4.

0.0 < a c < 10 . ,

5.

0.0 < c W < 10 . , and

6.

0o £ j £ 360o .



f w = 1.0 .

C.3.9

Plate – Embedded Crack, Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KPECE2)

C.3.9.1


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@


Not for Resale


LMG R|I + I FG d IJ + I FG d IJ + I FG d IJ + I FG d IJ U| +OP H t K H t K H t K H t K V|W P MM S|T MMG |RSI + 2I FG d IJ + 3I FG d IJ + 4I FG d IJ |UVFG a IJ + PPP HtK HtK H t K |WH t K P MM |T PP R d I d I U|F a I | F F M = G SI + 3I G J + 6I G J VG J + H t K H t K |WH t K MM |T PP MMG RSI + 4I FG d IJ UVFG a IJ + PP H t K WH t K MM T PP MMG lI qFGH at IJK PP N Q 2

o

o

1

1

3

1

2

3

4

1

4

2

1

1

2

1

3

1

KI

2

2

3

4

3

4

2

1

1

1

2

1

Fa fw Q

(C.87)

3

3

3

4

1

4

4

C.3.9.2

4

Notes: a.


b.

The coefficients of the stress distribution to be used are defined in paragraph C.2.2.3

c.

The influence coefficients Go through G4. for inside and outside surface cracks can be determined using the following equations:

G0 = A0,0 + A1,0 > + A2 ,0 > 2 + A3,0 > 3 + A4 ,0 > 4 + A5,0 > 5 + A6,0 > 6

(C.88)

G1 = A0,1 + A1,1> + A2 ,1> 2 + A3,1> 3 + A4 ,1> 4 + A5,1> 5 + A6,1> 6

(C.89)

G2 = A0,2 + A1,2 > + A2 ,2 > 2 + A3,2 > 3 + A4 ,2 > 4 + A5,2 > 5 + A6,2 > 6

(C.90)

G3 = A0,3 + A1,3> + A2 ,3> 2 + A3,3> 3 + A4 ,3> 4 + A5,3> 5 + A6,3> 6

(C.91)

G4 = A0,4 + A1,4 > + A2 ,4 > 2 + A3,4 > 3 + A4 ,4 > 4 + A5,4 > 5 + A6,4 > 6

(C.92)

where,

b=

2j p

(C.93)

Aij , are provided in Table C.5. Solutions for d1 t = 0.25 and d1 t = 0.50 are defined in this table. The solution for d1 t = 0.75 can be derived as follows:

and the parameters,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

6

6

j =0

j =0

b g

Gi( 0.75) = å A(j ,0i.75) > j = å -1 A(j ,0i.25) > j c.

The parameter

j

Q is given by Equation (C.14), and f w is given by Equation (C.18).

--``````-`-`,,`,,`,`,,`---


Not for Resale

(C.94)


e.


1.

2.

FG ld - aqIJ ³ 0.2 H t K FG ld - aqIJ ³ 0.2 H t K 1

when

d1 £

t , 2

2

when

d2 £

t , 2

3.

0.25 £ d1 t £ 0.75 ,

4.

0.0 < a c £ 1.0 , and

5.

-90o £ j £ 90o . d1 = 0.0 .

f.

The datum for the stress distribution is at

g.



f w = 1.0 .

C.4

Stress Intensity Factor Solutions for Plates with Holes

C.4.1

Plate With Hole – Through-Wall Single Edge Crack, Through-Wall Membrane and Bending Stress (KPHTC1)

C.4.1.1


b

K I = M mI m + M bI b

g

Fa

(C.95)

The membrane correction factor is given by

M m = F1 + BF2

(C.96)

3.3539 + 7.7313z + 4.9282z 2 F1 = 1 + 4.3586z + 6.9091z 2

(C.97)

F2 =

10 . -0.88418 - 3.7618z - 6.9722z 2.5

(C.98)

and the bending correction factor is given by

e

c h

M b = 0.4 -6.327 10-3 - 12904 . z + 016219 . z 2 - 0.011274z 3 + 2.07z 0.5

j

(C.99)

with,

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


z= --``````-`-`,,`,,`,`,,`---

C.4.1.2

a Rh

(C.100)

Notes: a.


b.

See Figure C.6(b) for the definition of B; limitations on B are:

c.


d.

I m and I b can be determined using stress equations based on strength of materials

-10 . £ B £ 10 . .

z £ 10 . .

concepts.

C.4.2

Plate With Hole – Through-Wall Double Edge Crack, Through-Wall Membrane and Bending Stress (KPHTC2)

C.4.2.1


b


g

Fa

(C.101)

where the membrane correction factor is given by For B = -1.0

Mm =

0.26718 + 24.848z + 20.561z 2 + 24.922z 3 . z + 22.444z 2 + 24.743z 3 1 + 15128

(C.102)

For B = 0.0

. 019806 + 18.886z + 18.713z 2 + 26.651z 3 Mm = . z + 19.136z 2 + 26.629z 3 1 + 15144

(C.103)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

For B = 1.0

Mm =

. 013065 + 13.291z + 50.861z 2 + 54.142z 3 1 + 18.065z + 49.034z 2 + 54.363z 3

(C.104)

and the bending correction factor is given by

e

c h

M b = 0.4 -7.089 10-3 - 12934 . z + 0.2442z 2 - 0.058739z 2.5 + 2.0789z 0.5

j

(C.105)

with,

z=

a Rh


(C.106)

Not for Resale


C.4.2.2

Notes: a.


b.

See Figure C.7(b) for the definition of B; limitations on B are:

c.


d.


-10 . £ B £ 10 . .

z £ 10 . .

C.4.3

Plate With Hole – Surface Crack In Hole, Semi-Elliptical Shape, Through-Wall Membrane Stress (KPHSC1)

C.4.3.1


KI = M mI m

Fa Q

(C.107)

where, Q is given by Equation (C.14) or (C.15), and the membrane correction factor is given by

Mm --``````-`-`,,`,,`,`,,`---

L F aI = MM + M G J HtK MN 1

2

2

F aI O + M G J Pg g g f H t K PQ 4

3

1 2

3 j

fw

(C.108)

with,

M2 =

M3 =

0.05

F aI 011 . +G J H cK

(C.109)

1.5

0.29

(C.110)

F aI 0.23 + G J H cK FG a IJ 2.6 - 2FG a IJ HtK H t K cosj g = 10 . F aI 10 . + 4G J H cK 1.5

4

(C.111)

1

g2 =


10 . + 0.358z + 1425 . z 2 - 1578 . z 3 + 2.156z 4 10 . + 0.08z 2

Not for Resale

(C.112)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

concepts.


10 .

z=

FcI 10 . + G J cosb0.9j g HR K F aI = 10 . + 0.1b1 - cosj g G 1 - J H tK

(C.113)

h

g3

2

In the following equation, set C.4.3.2.c)

10

(C.114)

n = 2 for two cracks and n = 1 for one crack (see paragraph

FG F R IJ secFG F b2 R + ncg IJ H 2W K H 4bW - cg + 2nc K

f w = sec For

h

h

a t

a c £ 1.0 , fj is given by Equation (C.23) and M1 = 1.0

For

(C.116)

a c > 10 . , fj is given by Equation (C.28) and

M1 =

c a

(C.117)

a.


b.


c.

1.

0.0 < a t < 10 . ,

2.

0.2 £ a c £ 2.0 ,

3.

0.5 £ Rh t £ 2.0 ,

4.

b R + cg W < 0.5 , and

5.

-90o £ j £ 90o .

h

The stress intensity factor solution provided is for two cracks. To estimate the stress intensity factor for one crack, the following equation can be used:

K1-crack


F G =G GG H

I JJ JJ K

ac 4 + F 2tRh K2 - crack 4 ac + F tRh

(C.118)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes:

--``````-`-`,,`,,`,`,,`---

C.4.3.2

(C.115)


I m can be determined using stress equations based on strength of materials concepts.

C.4.4

Plate With Hole, Corner Crack, Semi-Elliptical Shape, Through-Wall Membrane and Bending Stress (KPHSC2)

C.4.4.1


--``````-`-`,,`,,`,`,,`---

b

KI = M mI m + M bI b

g

Fa Q

(C.119)

where Q is given by Equation (C.14) or (C.15). The membrane correction factor is given by:

R|S |T

M m = M1 + M 2

FG a IJ HtK

2

FG a IJ U|Vg g g g f H t K |W 4

+ M3

1 2

3 4 j

fw

(C.120)

where fw is given by Equation (C.115), and

g2 =

10 . + 0.358z + 1425 . z 2 - 1578 . z 3 + 2.156z 4 10 . + 013 . z2

1.0 c 10 . + cos mj Rh

z=

FG IJ b g H K

(C.122)

m = 0.85 For

(C.121)

(C.123)

a c £ 1.0 , fj is given by Equation (C.23) and

M1 = 113 . - 0.09

M2 =

M3

FG a IJ H cK

(C.124)

0.89 - 0.54 a 0.2 + c

FG IJ HK

(C.125)

R F aIU = 0.5 + 14 S1 - G J V F aI T H cKW 0.65 + G J HK 1

24

(C.126)

c

R| F a I U| g = 1 + S0.1 + 0.35G J Vb1 - sinj g H t K |W |T 2

2

1


Not for Resale

(C.127)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d.


FG a IJ OP 1 + 01. b1 - cosj g LM0.85 + 015 F aI . G J H cKQ HtK MN L F a I OLF a I OL F a I O = 1 - 0.7 M1 - G J P MG J - 0.2P M1 - G J P N H t K QNH c K QN H c K Q LM N

2

g3 = 1 + 0.04

g4 For

0.25

OP PQ

(C.128)

(C.129)

a c > 10 . , fj is given by Equation (C.28) and

FG c IJ RS1 + 0.04FG c IJ UV H aK T H aKW F cI M = 0.2G J H aK F cI M = -011 . G J H aK R| . + 0.35FG c IJ FG a IJ U|Vb1 - sin j g g = 1 + S01 H a K H t K W| T| L . - 0.09FG c IJ OP 1 + 01. b1 - cosj g LM0.85 + 015 F aI O g = M113 . G J P H aKQ H t K PQ N MN 0.5

M1 =

(C.130)

4

2

(C.131)

4

3

2

2

1

2

(C.132)

(C.133)

0.25

3

--``````-`-`,,`,,`,`,,`---

g4 = 10 .

(C.134)

(C.135)

The bending correction factor is given by:

Mb = M m H

(C.136)

where Mm is evaluated using the above equations with

F aI m = 0.85 - 0.25G J HtK

0.25

(C.137)

and,

b

g

H = H1 + H2 - H1 sin q j

(C.138)

F aI F aI F aI H = 1+ G G J + G G J + G G J HtK HtK HtK F aI F aI F aI H = 1+ G G J + G G J + G G J HtK HtK HtK 2

1

11

12

3

2

2


21

22

(C.139)

13

3

(C.140)

23

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


For

a c £ 1.0

FG a IJ + 0.6FG a IJ H cK H t K F aI F aI = -0.43 - 0.74G J - 0.84G J H cK H cK F aI F aI = 125 . - 119 . G J + 4.39G J H cK H cK F a I . FG a IJ = -194 . + 4.22G J - 551 H cK H cK F a I . FG a IJ = -15 . - 0.04G J - 173 H cK H cK F aI F aI = 171 . - 317 . G J + 6.84G J H cK H cK F aI F aI = -128 . + 2.71G J - 5.22G J H cK H cK

q = 0.2 +

G11

(C.141)

2

(C.142)

2

G12

G13

(C.143)

2

(C.144)

2

G21

(C.145)

2

G22

G23 For

(C.146)

2

(C.147)

a c > 10 .

FG c IJ + 0.6FG a IJ H aK H t K F cI = -2.07 + 0.06G J H aK F cI = 4.35 + 016 . G J H aK F cI = -2.93 - 0.3G J H aK F cI = -3.64 + 0.37G J H aK F cI = 587 . - 0.49G J H aK

q = 0.2 +

(C.148)

G11

(C.149)

G12

G13

G21

G22

(C.150)

(C.151)

(C.152)

(C.153)

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


FG c IJ H aK

G23 = -4.32 + 0.53 C.4.4.2

(C.154)

Notes: a.


b.


0.0 < a t £ 10 . for remote tension,

2.

0.0 < a t £ 0.8 for remote bending,

3.

0.2 £ a c £ 2.0 ,

4.

0.5 £ Rh t £ 2.0 ,

5.

b R + cg W < 0.5 , and

6.

0o £ j £ 90o .

h

c.

To estimate the stress intensity factor for one crack, use Equation (C.118).

d.


Stress Intensity Factor Solutions for Cylinders

C.5.1

Cylinder – Through-Wall Crack, Longitudinal Direction, Through-Wall Membrane and Bending Stress (KCTCL)

C.5.1.1


--``````-`-`,,`,,`,`,,`---

C.5

b


g

Fc

(C.155)

where the membrane and bending correction factors are given by

b = max b A

gb g, b A

M m = max Amm + Amb , Amm - Amb Mb

bm

+ Abb

bm

- Abb

g

g

(C.156) (C.157)

The parameters Amm , Amb , Abm and Abb are evaluated using the information in Table C.6 with l computed from the following equation:

l=

1818 . c Ri t


(C.158)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Notes: a.


b.

Crack and geometry dimensional limits: l £ 12.5 .

c.

The solution can be used for cylinders with

d.

If l exceeds the permissible limit, then the following equations can be used:

3 £ Ri t £ 100 ; for Ri t < 3 use the solution for Ri t = 3 and for Ri t > 100 use the solution for Ri t = 100 . Interpolation for values of Ri t other than those provided is recommended.

L10202 + 0.44108l + 6.1244(10 ) l O . =M . (10 ) l PQ N 1.0 + 0.026421l + 15329 -6.6351c10 h + 0.049633l - 8.7408(10 = 10 . + 19046 . (10 ) l + 5.7868c10 hl -3

2

Amm

-6

2

-3

Amb

e.

4

-3

2

(C.159)

4

2

-3

0.5

-3

)l4

4

(C.160)

Abm =

0.03178 + 0.32480l 1.0 + 0.55926l

(C.161)

Abb =

1006 . + 0.60216l + 0.091777l2 10 . + 0.60572l + 013773 . l2 + 4.3976(10-3 ) l3

(C.162)

For internal pressure loading only:

Im =

2 pRo2 +p Ro2 - Ri2 2

(C.163)

LM MN

FG IJ H K

pR t 3 t Ib = 2 o 2 Ro - Ri Ri 2 Ri

2

FG IJ OP H K PQ

9 t + 5 Ri

3

(C.164)

C.5.2

Cylinder – Through-Wall Crack, Circumferential Direction, Through-Wall Membrane and Bending Stress (KCTCC1)

C.5.2.1


b


g

Fc

(C.165)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


b

gb

g

M m = max Amm + Amb , Amm - Amb ×


FG IJ H K

2 Ri c tan 2 Ri c

Not for Resale

(C.166)

--``````-`-`,,`,,`,`,,`---

C.5.1.2


b

gb

M b = max Abm + Abb , Abm - Abb The parameters Amm , Amb , Abm and computed from Equation (C.158).

(C.167)

Abb are evaluated using the information in Table C.7 with l

Notes: a.


b.


For

Ri t = 3 ; Amm, Amb, Abm and Abb: l £ 6.5 ,

2.

For


3.

For


4.

For


5.

For

Ri t = 50 ; Amm, Amb, Abm and Abb: l £ 15.0 , and

6.

For

Ri t = 100 ; Amm, Amb, Abm and Abb: l £ 15.0 .

c.

The solution can be used for cylinders with 3 £

Ri t £ 100 ; for Ri t < 3 use the solution for Ri t = 3 and for Ri t > 100 use the solution for Ri t = 100 . Interpolation for values of Ri t other than those provided is recommended.

d.

If l exceeds the permissible limit for a specified Ri t , then the equations in paragraph C.5.3.2.d can be used for the membrane stress, equations for the through-wall bending stress are not available.

e.

For internal pressure with a net section axial force, 2

Im =

pRi F + 2 2 2 2 Ro - Ri F Ro - Ri

d

(C.168)

i

--``````-`-`,,`,,`,`,,`---

I b = 0.0

(C.169)

C.5.3

Cylinder – Through-Wall Crack, Circumferential Direction, Pressure With Net Section Axial Force and Bending Moment (KCTCC2)

C.5.3.1


d

K I = M mI m + M gbI gb where

i

Fc

(C.170)

M m is evaluated using the equations and values for Amm and Amb in paragraph C.5.2, and


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.5.2.2

g


d

id

M gb = max Ammgb + Ambgb , Ammgb - Ambgb where

i

(C.171)

Ammgb and Ambgb are evaluated using the information in Table C.8 with l computed from

Equation (C.158). --``````-`-`,,`,,`,`,,`---

C.5.3.2

Notes: a.


b.

Crack and geometry dimensional limits for C.5.2.2.b for

Ammgb and Ambgb are the as given in paragraph

Amm and Amb .

3 £ Ri t £ 100 ; for Ri t < 3 use the solution for Ri t = 3 and for Ri t > 100 use the solution for Ri t = 100 . Interpolation for values of Ri t other than those provided is recommended.

c.

The solution can be used for cylinders with

d.

If l exceeds the permissible limit for a specified used [C.15.32].

LM I OP N 2F= Q L I OP M =M N 2F= Q L pb O a I = M 8 c f - 10 . h+ P b Q k N L pb O a I = M 8 c g - 10 . h+ P b Q k N hb10 . - = cot = g f = 10 . +

Ri t , then the following equations can be

0.5

Mm =

o

(C.172)

0.5

gb

1

2

2

(C.173)

2

(C.174)

o

2

2

2

(C.175)

1

(C.176)

2=

L . + hc= + = cot = - cot = h OP sin = g = M10 4 MN PQ = 2

b=


2

F lF - = qIJ + cot G H 2 K

(C.178)

2 cot =

= 2k

(C.179)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

h=

(C.177)


==

c Rm

(C.180)

c

t × 12 1 - n 2 Rm

k=

h

-0.25

FG F IJ b - 0.029b H 16K F 8b I + FG 0179 . I >=G J H F K H b JK 2

> = 1+

0.5

e.

3

(C.181)

for b £ 10 .

(C.182)

. for b > 10

(C.183)

0.885

For internal pressure with a net section axial force, and net-section bending moment

pRi2 F Im = p+ 2 + 2 2 Ro - Ri F Ro - Ri2

c

I gb =

h c

MRo 0.25F Ro4 - Ri4

c

(C.184)

h

(C.185)

h

C.5.4

Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Internal Pressure (KCSCLL1)

C.5.4.1

The Mode I Stress Intensity Factor [C.15.9] Inside Surface 2

LM MN

FG IJ H K

FG IJ H K

LM MN

FG IJ H K

FG IJ H K

pR a a KI = 2 0 2 2Go - 2G1 + 3G2 Ri Ri R0 - Ri

2

FaI - 4G G J HR K

3

3

FaI O + 5G G J P H R K PQ

Fa

(C.186)


Fa

(C.187)

4

4

i

i

Outside Surface 2

pR a a KI = 2 i 2 2Go + 2G1 + 3G2 Ri Ri R0 - Ri C.5.4.2

2

FaI + 4G G J HR K 3

i

3

4

4

Notes:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.


b.


c.


G0 through G4 are provided in Table C.9.

0.0 £ a t £ 0.8 , and

--``````-`-`,,`,,`,`,,`---


Not for Resale

i


2 £ Ri t £ 1000 .

2. --``````-`-`,,`,,`,`,,`---

C.5.5

Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (KCSCLL2)

C.5.5.1


KI C.5.5.2

L = MG I MN o

o


1

2

2

2

F aI +G I G J HtK 3

3

3


4

4

Fa

(C.188)

Notes: a.

See paragraph C.5.4.2.

b.


C.5.6

Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Through-Wall Arbitrary Stress Distribution (KCSCLL3)

C.5.6.1

The Mode I Stress Intensity Factor The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.5.4.2.b.

C.5.6.2


C.5.7

Cylinder – Surface Crack, Circumferential Direction – 360 Degrees, Pressure With A Net Section Axial Force and Bending Moment (KCSCCL1)

C.5.7.1

The Mode I Stress Intensity Factor

LM N

K I = GoI o + G1I 1

FG a IJ OP H t KQ

Fa

(C.189)

where for an inside surface crack,

I 0 = I m -Ib

(C.190)

I 1 = 2I b

(C.191)

and for an outside surface crack,

I0 = Im +Ib

(C.192)

I 1 = -2I b

(C.193)


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


with,

b

g h

2 M Ro + Ri pRi2 F + + Im = 2 2 2 2 Ro - Ri F Ro - Ri F Ro4 - Ri4

c

Ib

o

4 o

h c

(C.194)

i

(C.195)

4 i

Notes: a.


b.


c.


G0 and G1 are provided in Table C.10.

1.

0.0 £ a t £ 0.8 , and

2.

2 £ Ri t £ 1000 .

d.

--``````-`-`,,`,,`,`,,`---

C.5.7.2

h c 2 MbR - R g = F cR - R h

This solution represents the maximum stress intensity on the cross section at the location of maximum bending stress. The stress intensity factor at other locations can be determined by using the appropriate value of bending stress.

C.5.8

Cylinder – Surface Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (KCSCCL2)

C.5.8.1


KI C.5.8.2

L = MG I MN o

o


1

2

2

2

F aI +G I G J HtK 3

3

3


4

4

Fa

(C.196)

Notes: a.


b.


c.



C.5.9

Cylinder – Surface Crack, Circumferential Direction – 360 Degrees, Through-Wall Arbitrary Stress Distribution (KCSCCL3)

C.5.9.1

The Mode I Stress Intensity Factor


Not for Resale

--``````-`-`,,`,,`,`,,`---


The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.5.7.2.b.

C.5.9.2


C.5.10

Cylinder – Surface Crack, Longitudinal Direction – Semi-Elliptical Shape, Internal Pressure (KCSCLE1)

C.5.10.1 The Mode I Stress Intensity Factor [C.15.37] Inside Surface 2

LM MN

FG IJ H K

FG IJ H K

LM MN

FG IJ H K

FG IJ H K

pR a a KI = 2 0 2 2Go - 2G1 + 3G2 Ri Ri R0 - Ri

2

FaI - 4G G J HRK

3

3


Fa Q

(C.197)


Fa Q

(C.198)

4

4

i

i

Outside Surface 2

pR a a KI = 2 i 2 2Go + 2G1 + 3G2 Ri Ri R0 - Ri

2

FaI + 4G G J HRK 3

i

3

4

4

i

C.5.10.2 Notes: a.


b.

The influence coefficients G0 and G1 for inside and outside surface cracks can be determined using the following equations:

G0 = A0,0 + A1,0 > + A2 ,0 > 2 + A3,0 > 3 + A4 ,0 > 4 + A5,0 > 5 + A6,0 > 6

(C.199)

G1 = A0,1 + A1,1> + A2 ,1> 2 + A3,1> 3 + A4 ,1> 4 + A5,1> 5 + A6,1> 6

(C.200)

> is given by Equation (C.93) and the parameters, Aij , are provided in Table C.11. The G2 , G3 , and G4 influence coefficients can be computed using paragraph C.14.3 or

where

c.

Q is determined using Equation (C.14) or (C.15).

d.


0.2 £ a t £ 0.8 ,

2.

1.0 £ c a £ 32.0 ,

3.

0o £ j £ 180o , and

4.

5 £ Ri t £ ¥ .


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.14.4.


Influence coefficients are provided in Table C.11 for values of 0.2 £ a t £ 0.8 . If a t < 0.2 , then the influence coefficients can be determined by interpolation using the values in Table C.11 and the following values for G0 and G1 at a t = 0.0. The equation for G1 is evaluated

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

e.

t = 0.01 , and the parameter H in this equation is computed using the equations in paragraph C.3.4.1 with a t = 0.01 . at a

LM N

FG a IJ OP 1 + 01. b1 - sinj g H cKQ F 1 - H IJ FG a IJ G =G G H 2 KH t K G0 = 113 . - 0.09

2

(C.201)

-1

1

f.

(C.202)

0

Influence coefficients are provided in Table C.11 for values of

1.0 £ c a £ 32.0 . For long

c a > 32 , the influence coefficients can be determined by interpolation using the values in Table C.11 and the following values for G0 and G1 . The influence coefficients cracks where

L

for the long flaw or infinite length solution ( G0 and using Table C.9.

FG 2j IJ HpK F 2j I G =G G J HpK

G1L ) in these equations can be computed

6

G0 = G0L

6

L 1

1

C.5.11

(C.203)

(C.204)

Cylinder – Surface Crack, Longitudinal Direction – Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KCSCLE2)

C.5.11.1 The Mode I Stress Intensity Factor [C.15.37]

KI

L = MG I MN o

o


1

2

2

2

F aI +G I G J HtK 3

3

3


4

4

Fa Q

(C.205)

C.5.12

a.


b.


Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Through-Wall Arbitrary Stress Distribution (KCSCLE3)

C.5.12.1 The Mode I Stress Intensity Factor


Not for Resale

--``````-`-`,,`,,`,`,,`---

C.5.11.2 Notes:


The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.5.10.2.b. C.5.12.2 Notes: see paragraph C.5.10.2.

C.5.13

Cylinder – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Internal Pressure and Net-Section Axial Force (KCSCCE1)

C.5.13.1 The Mode I Stress Intensity Factor [C.15.37] Inside Surface //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F pR GG R - R H 2

KI = Go

2

+

2

+

o

2

i

0

d

F 2

F R0 - Ri

2

I iJJK

Fa Q

(C.206)

I iJJK

Fa Q

(C.207)

Outside Surface

F pR GG R - R H 2

KI = Go

i

2

i

0

d

F 2

F R0 - Ri

2

C.5.13.2 Notes:

C.5.14


b.

The influence coefficient, G0 , can be determined using paragraph 5.14.2.c.

c.

The parameter

d.

Crack and geometry dimensional limits are shown in C.5.14.2.d.

--``````-`-`,,`,,`,`,,`---

a.

Q is given by Equation (C.14) or (C.15).

Cylinder – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution With Net Section Bending Stress (KCSCCE2)


KI

LMG I =M MNG I o

o

5

5


1

2

2

2

F aI +G I G J HtK 3

+ G6I 6

3

3

F aI O + G I G J +P HtK P PQ 4

4

4

Fa Q

(C.208)

C.5.14.2 Notes: a.


b.

The influence coefficients G0 , G1 , G5 , and G6 for inside and outside surface cracks can be determined using the following equations:


Not for Resale

G0 = A0,0 + A1,0 > + A2 ,0 > 2 + A3,0 > 3 + A4 ,0 > 4 + A5,0 > 5 + A6,0 > 6

(C.209)

G1 = A0,1 + A1,1> + A2 ,1> 2 + A3,1> 3 + A4 ,1> 4 + A5,1> 5 + A6,1> 6

(C.210)

G5 = A0,5 + A1,5> + A2 ,5> 2 + A3,5> 3 + A4 ,5> 4 + A5,5> 5 + A6,5> 6

(C.211)

G6 = A0,6 + A1,6 > + A2 ,6 > 2 + A3,6 > 3 + A4 ,6 > 4 + A5,6 > 5 + A6,6 > 6

(C.212)

> is given by Equation (C.93) and the parameters, Aij , are provided in Table C.12. The G2 , G3 , and G4 influence coefficients can be calculated using paragraph C.14.3 or where

C.14.4. c.

Q is determined using Equation (C.14) or (C.15).

d.


0.2 £ a t £ 0.8 ,

2.

1.0 £ c a £ 32.0 ,

3.

0o £ j £ 180o , and

4.

5 £ Ri t £ ¥ .

e.

Influence coefficients are provided in Table C.12 for values of 0.2 £ a t £ 0.8 . If a t < 0.2 , then the influence coefficients can be determined by interpolation using the values in Table C.12 and the following values for G0 and G1 at a t = 0.0. (see paragrapgh C.5.10.2.e).

f.


1.0 £ c a £ 32.0 . For long

c a > 32 , the influence coefficients can be determined by interpolation using the values in Table C.12 and the values for G0 and G1 computed using the equations in cracks where

paragraph C.5.10.2.f. The influence coefficients for the long flaw or infinite length solution L

( G0 and

G1L ) in these equations can be computed using Table C.10.

g.


h.

The net-section bending stress about the x-axis and y-axis are computed as follows:

I5 =

I6 =

c

M x Ro

F 4 Ro - Ri4 4

(C.213)

h

M y Ro

c

F 4 Ro - Ri4 4

(C.214)

h

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



C.5.15

Cylinder – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-Wall Arbitrary Stress Distribution (KCSCCE3)

C.5.15.1 The Mode I Stress Intensity Factor The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.5.14.2.b. C.5.15.2 Notes: see paragraph C.5.13.2.

C.5.16

Cylinder – Embedded Crack, Longitudinal Direction – Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (KCECLL)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.5.16.1 The Mode I Stress Intensity Factor solution in paragraph C.3.7 can be used C.5.16.2 Notes:

C.5.17

a.


b.

See paragraph C.3.7.

Cylinder – Embedded Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (KCECCL)


C.5.18

a.


b.

See paragraph C.3.7.

Cylinder – Embedded Crack, Longitudinal Direction – Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KCECLE)


C.5.19

a.


b.


Cylinder – Embedded Crack, Circumferential Direction – Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KCECCE)

C.5.19.1 The Mode I Stress Intensity Factor solution in paragraph C.3.9 can be used --``````-`-`,,`,,`,`,,`---


Not for Resale


C.5.19.2 Notes: a.


b.


C.6

Stress Intensity Factor Solutions for Spheres

C.6.1

Sphere – Through-Wall Crack, Through-Wall Membrane and Bending Stress (KSTC)

C.6.1.1


b


g

Fc

(C.215)


b = max b A

gb g, b A

M m = max Amm + Amb , Amm - Amb Mb

bm

+ Abb

bm

The parameters Amm , Amb , Abm and computed from Equation (C.158).

Amm

- Abb

g

(C.216)

g

(C.217)

Abb are evaluated using the following equations with l

. 10005 + 0.49001l + 0.32409l2 = . + 0.50144l - 0.011067l2 10

(C.218)

F 0.01764 + 0.37417l - 0.021l IJ =G . l + 0.010727 l K H 1.0 + 0.68139l - 01031 F -14799 . c10 h + 0.52715l IJ =G . l - 0.011347l K H 10. + 10615 2

Amb

2

3

Abb =

2

10 . + 14894 . l + 0.41053l2 10 . + 14854 . l + 0.3286l2 - 2.9346 10 -3 l3

c h

(C.220)

(C.221)

Notes: a.


b.

Crack and geometry dimensional limits: l £ 55 . .

c.

For internal pressure loading only:

Im =

pRo 2 +p Ro 2 - Ri 2

(C.222)

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.6.1.2

(C.219)

2

-4

Abm

2

3

LM F I F I MN GH JK GH JK

pR 3 t 3 t Ib = 3 o 3 2 Ri Ro - Ri 4 Ri

2

FG IJ OP H K PQ

9 t + 4 Ri

3

(C.223)

C.6.2

Sphere – Surface Crack, Circumferential Direction – 360 Degrees, Internal Pressure (KSSCCL1)

C.6.2.1


--``````-`-`,,`,,`,`,,`---

Inside Surface 3

LM MN

FG IJ H K

FG IJ H K

LM MN

FG IJ H K

FG IJ H K

pR a a KI = 3 0 3 15 . Go - 15 . G1 + 3G2 Ri Ri R0 - Ri

2

FaI - 5G G J HR K

3

3

FaI O + 7.5G G J P H R K PQ

Fa (C.224)


Fa (C.225)

4

4

i

i

Outside Surface 3

pR a a KI = 3 i 3 15 . Go + 15 . G1 + 3G2 Ri Ri R0 - Ri C.6.2.2

2

FaI + 5G G J HR K 3

i

3

4

4

i

Notes: a.


b.


c.



1.

0.0 < a t £ 0.8 , and

2.

2 £ Ri t £ 1000 .

C.6.3

Sphere – Surface Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (KSSCCL2)

C.6.3.1


LM MN

K I = GoI o + G1I 1 C.6.3.2

FG a IJ + G I FG a IJ HtK HtK 2

2

2

+ G3I 3

FG a IJ HtK

3

FG a IJ OP H t K PQ 4

+ G4I 4

Fa

Notes: a.


b.



Not for Resale

(C.226)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



C.6.4

Sphere – Surface Crack, Circumferential Direction – 360 Degrees, Through-Wall Arbitrary Stress Distribution (KSSCCL3)

C.6.4.1

The Mode I Stress Intensity Factor [C.15.3] The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.6.2.2.b

C.6.4.2


C.6.5

Sphere – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Internal Pressure (KSSCCE1)

C.6.5.1

The Mode I Stress Intensity Factor [C.15.37] Inside Surface 3

LM MN

FG IJ H K

FG IJ H K

LM MN

FG IJ H K

FG IJ H K

pR a a KI = 3 0 3 15 . Go - 15 . G1 + 3G2 Ri Ri R0 - Ri

2

FaI - 5G G J HRK

3

3


Fa (C.227) Q


Fa (C.228) Q

4

4

i

i

Outside Surface 3

pR a a KI = 3 i 3 15 . Go + 15 . G1 + 3G2 Ri Ri R0 - Ri C.6.5.2

2

FaI + 5G G J HRK 3

i

3

4

4

i

Notes: a.


b.

The influence coefficients G0 and G1 for inside and outside surface cracks can be determined using the following equations:

G0 = A0,0 + A1,0 > + A2 ,0 > 2 + A3,0 > 3 + A4 ,0 > 4 + A5,0 > 5 + A6,0 > 6

(C.229)

G1 = A0,1 + A1,1> + A2 ,1> 2 + A3,1> 3 + A4 ,1> 4 + A5,1> 5 + A6,1> 6

(C.230)

where > is given by Equation (C.93) and the parameters, The G2 , C.14.4

G3 , and G4 influence coefficients can be calculated using paragraph C.14.3 or

c.

The parameter Q is given by Equation (C.14) or (C.15).

d.


Aij , are provided in Table C.14.

0.2 £ a t £ 0.8 ,

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


2.

1.0 £ c a £ 32.0 ,

3.

0o £ j £ 180o , and

4.

5 £ Ri t £ ¥ .

e.

Influence coefficients are provided in Table C.14 for values of 0.2 £ a t £ 0.8 . If a t < 0.2 , then the influence coefficients can be determined by interpolation using the values in Table C.14 and the following values for G0 and G1 at a t = 0.0. (see paragrapgh C.5.10.2.e).

f.


1.0 £ c a £ 32.0 . For long

c a > 32 , the influence coefficients can be determined by interpolation using the values in Table C.14 and the following values for G0 and G1 computed using the cracks where

equations in paragraph C.5.10.2.f. The influence coefficients for the long flaw or infinite length L

solution ( G0 and g.

G1L ) in these equations can be computed using Table C.13.


Sphere – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KSSCCE2)

C.6.6.1


LM MN

K I = GoI o + G1I 1 C.6.6.2

FG a IJ + G I FG a IJ HtK HtK 2

2

2

+ G3I 3

FG a IJ HtK

3

FG a IJ OP H t K PQ 4

+ G4I 4

Fa Q

(C.231)

Notes: a.


b.


C.6.7

Sphere – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-Wall Arbitrary Stress Distribution (KSSCCE3)

C.6.7.1

The Mode I Stress Intensity Factor [C.15.3] The stress intensity factor can be determined using the weight function method (see paragraph C.14.5). The influence coefficients G0 and G1 required to compute M1 , M 2 , and M 3 can be determined using paragraph C.6.5.2.b.

C.6.7.2


C.6.8

Sphere – Embedded Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (KSECCL)


Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.6.6


C.6.8.1

The Mode I Stress Intensity Factor solution in paragraph C.3.7 can be used.

C.6.8.2

Notes: a.


b.


C.6.9

Sphere – Embedded Crack, Circumferential Direction – Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (KSECCE)

C.6.9.1

The Mode I Stress Intensity Factor solution in paragraph C.3.9 can be used.

C.6.9.2

Notes:

C.7

a.


b.


Stress Intensity Factor Solutions for Elbows And Pipe Bends The stress intensity factor solutions for cylinders can be used for elbows and pipe bends if the stress at the location of the crack is determined considering the bend geometry and applied loads. The netsection forces and moments applied to elbow, as well as internal pressure, should be considered when determining the stress at the crack location.

C.8

Stress Intensity Factor Solutions for Nozzles and Piping Tees

C.8.1

Nozzle – Corner Crack, Radial Direction, Quarter-Circular Shape, Membrane Stress At The Corner (KNCC1)

C.8.1.1


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b

K I = M f M b k taI nom + p

g 2 FF a

(C.232)

where

b

M f = 143 . - 0.24 sin j + cos j

Mb

F = 1 + 0.15G H

a t 2 + t n2

I JK

g

(C.233)

2

(C.234)

--``````-`-`,,`,,`,`,,`---


Not for Resale


k ta

F palsin j + cosjqI = 1 + b k - 1gG 1 + H 2ld - t q JK

-B

(C.235)

tn

n

n

with

B = 2-2

( for nozzles in spherical shells)

(C.236)

B = 2.7 - 2

tn dn

( for nozzles in cylindrical shells)

(C.237)

B = 3.3 - 2

tn dn

( for nozzles in plates)

(C.238)

Notes: a.

See Figure C.25 (Crack labelled G) and Figure C.26 for the component and crack geometry.

b.

The parameter k tn is the theoretical stress concentration factor that can be used to compute the maximum stress at the corner of a nozzle, or

k tn =

I max I nom

I max

=

I nom

=

(C.239)

where, Maximum stress at the nozzle corner where the crack is located (MPa:psi), and Nominal membrane stress away from the nozzle corner; for a spherical or cylindrical shell the membrane stress perpendicular to the crack face away from the nozzle (i.e. hoop stress for a spherical shell or cylindrical shell with a radial corner crack aligned with the longitudinal axis), for a plate, the maximum membrane stress perpendicular to the crack face (MPa:psi).

C.8.2

Nozzle – Corner Crack, Radial Direction, Quarter-Circular Shape, Cubic Polynomial Stress At The Corner (KNCC)

C.8.2.1


L K = M0.706I N I

C.8.2.2

0

F 2a I + 0.537G J I HFK

Fa I + 0.448G J I H 2K 2

1

F 4a IJ I OP + 0.393G H 3F K Q 3

2

3

Fa

(C.240)

Notes: a.

See Figure C.25 (Crack labelled G) and Figure C.26 for the component and crack geometry.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

C.8.1.2

tn dn


b.

--``````-`-`,,`,,`,`,,`---

c.

Crack and geometry dimensional limits (see Figure C.26 for definitions of 1.

0.0 £ a t £ 0.5 ,

2.

0.0 £ a t n £ 0.5 , and

3.

j = 45o .

t and t n ) :

The coefficients of the stress distribution to be used are defined below.

s ( x) = s 0 + s 1 x + s 2 x 2 + s 3 x 3

(C.241)

where,

x = Local coordinate for the stress distribution measured from the inside surface of the o corner crack radius at an angle of j = 45 (see Figure C.26); note that this stress distribution is not normalized with the wall thickness (see paragraph C.2.2.3).

C.8.3

Surface Cracks At Nozzles – General Solution The stress intensity factor solutions shown below can be used for surface cracks at nozzles if the stress distribution normal to the plane of the crack is determined based on the nozzle geometry and applied loads. The stress distribution normal to the plane of the crack, s ( x ) , should be computed for the component in the uncracked state considering the effects of the structural configuration and fillet weld geometry (see Figure C.32(b)). The net-section forces and moments applied to shell and nozzle, as well as internal pressure, should be considered when determining the stress distribution. The use of this method to compute the stress intensity factor will result in a conservative value as long as the geometry of the crack does not significantly reduce the stiffness of the cylinder-to-cylinder connection. If the geometry of the crack does result in a significant loss in stiffness, the resulting deformation will result in a higher value of the stress intensity factor. In these cases, an analysis of the cracked geometry is required to accurately determine the stress intensity factor. Nozzle Neck or Branch (see Figure C.25) ·

Crack A – Use KCTCC1, KCTCC2, KCSCCL3, KCSCCE3, KCECCL or KCECCE

·

Crack B – Use KCTCL, KCSCLL3, KCSCLE3, KCECLL or KCECLE

Shell or Run Pipe (see Figure C.25) ·

Crack D & F – Use KPTC, KPSCE3, KPECL, or KPECE2

·

Crack E & C – Use KPTC, KPSCE3, KPECL, or KPECE2

·

Crack G – Use KNCC1 or KNCC2

C.9

Stress Intensity Factor Solutions for Ring-Stiffened Cylinders

C.9.1

Ring-Stiffened Cylinder – Surface Crack At The Toe Of One Fillet Weld, Circumferential Direction – 360 Degrees, Pressure Loading (KRCSCCL1)


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


C.9.1.1


K I = pM 1pc p a C.9.1.2

(C.242)

Notes: a.


b.

The coefficients,

c.


M 1pc , are provided in Table C.15.

1.

0.2 £ a t £ 0.8 , and

2.

1.0 £ Ar t £ 32.0

3.

10 £ Ri t £ 300 ; for Ri t < 10 use Ri t = 10 and for Ri t > 300 use Ri t = 300

--``````-`-`,,`,,`,`,,`---

d.

The effects of the fillet weld on the stress field at the location of the fillet weld are included in the solution; a magnification factor is not required.

e.

This solution may be used for W, T, L and I sections attached by fillet welds to the inside of the vessel when the vessel is subject to a positive internal pressure.

f.

This solution may also be used for W, T, L, and I sections attached by fillet welds to the outside of the vessel when the vessel is subject to a partial or full vacuum. The results for this configuration and loading will be conservative because the membrane stress field in the vessel is compressive; the only tensile stress is a result of local through-wall bending at the ring to cylinder attachment location.

C.9.2

Ring-Stiffened Cylinder – Surface Crack At The Toe Of Both Fillet Welds, Circumferential Direction – 360 Degrees, Pressure Loading (KRCSCCL2)

C.9.2.1


K I = pM p2 c F a C.9.2.2

(C.243)

Notes: a.


b.

The coefficients,

c.

Refer to paragraph C.9.1.2 for other details regarding this solution.


M p2 c , are provided in Table C.15.

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Stress Intensity Factor Solutions for Sleeve Reinforced Cylinders The stress intensity factor solutions shown below can be used for surface cracks at sleeve-reinforced cylinders if the stress distribution normal to the plane of the crack is determined based on the nozzle geometry and applied loads. The stress distribution normal to the plane of the crack, s ( x ) , should be computed for the component in the uncracked state considering the effects of the structural configuration and fillet weld geometry (see Figure C.32(b)). The net-section forces and moments applied to cylindrical shell, as well as internal pressure, should be considered when determining the stress distribution. The use of this method to compute the stress intensity factor will result in a conservative value as long as the geometry of the crack does not significantly reduce the stiffness of the at sleeve-reinforced cylinder connection. If the geometry of the crack does result in a significant loss in stiffness, the resulting deformation will result in a higher value of the stress intensity factor. In these cases, an analysis of the cracked geometry is required to accurately determine the stress intensity factor. Cracks At Sleeve Reinforced Cylinders (see Figure C.28) ·


·


C.11

Stress Intensity Factor Solutions for Round Bars and Bolts

C.11.1

Round Bar, Surface Crack – 360 Degrees, Through-Wall Membrane and Bending Stress (KBSCL)

C.11.1.1 The Mode I Stress Intensity Factor [C.15.13], [C.15.19]

b


g

Fa

(C.244)

where,

c

M m = 0.50 z 1 + 0.5z + 0.375z 2 - 0.363z 3 + 0.731z 4

h

c

M b = 0.375 z 1 + 0.5z + 0.375z 2 + 0.313z 3 + 0.273z 4 + 0.537z 5

z = 1-

a Ro

(C.245)

h

(C.246)

(C.247)

C.11.1.2 Notes: a.

For the component and crack geometry see Figure C.29.

b.

Crack geometry dimensional limits:

c.


z < 10 . .

concepts.

C.11.2

Round Bar – Surface Crack, Straight Front, Through-Wall Membrane and Bending Stress (KBSCS)

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.10



b


g

Fa

(C.248)

where,

M m = 0.926 - 1771 . z + 26.421z 2 - 78.481z 3 + 87.911z 4

(C.249)

M b = 104 . - 3.64z + 16.86z 2 - 32.59z 3 + 28.41z 4

(C.250)

z=

a 2 Ro

(C.251)

C.11.2.2 Notes: a.


b.


c.


0.0625 £ z £ 0.625 .

concepts.

--``````-`-`,,`,,`,`,,`---

C.11.3

Round Bar, Surface Crack, Semi-Circular, Through-Wall Membrane and Bending Stress (KBSCC)


b


g

Fa

(C.252)

where,

b

M m = g 0.752 + 2.02z + 0.37 1 - sin y //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b

M b = g 0.953 + 0199 . 1 - sinO

FG H

184 . tan O F O g= cosO

IJ K

g

g

3

4

(C.253)

(C.254)

0.5

(C.255)

z=

a 2 Ro

(C.256)

O=

Fa 4 Ro

(C.257)


Not for Resale


C.11.3.2 Notes: a.


b.


c.


z £ 0.6 .

concepts.

C.11.4

Bolt, Surface Crack, Semi-Circular or Straight Front Shape, Membrane and Bending Stress (KBSC)

b


g

Fa

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.11.4.1 The Mode I Stress Intensity Factor [C.15.18] (C.258)

where,

M m = 2.043e -31.332z + 0.6507 + 0.5367z + 3.0469z 2 - 19.504z 3 + 45.647z 4

(C.259)

M b = 0.6301 + 0.03488z - 3.3365z 2 + 13.406z 3 - 6.0021z 4

(C.260)

z=

a 2 Rth

(C.261)

C.11.4.2 Notes: a.

For the component and crack geometry see Figure C.31; the solution applies to a semi-circular or straight front surface crack.

b.


c.

The solution provided is for UNF bolts. The solution for the bending stress does not include the effects of the thread.

d.

The solution for the membrane stress can be used for round bars if the exponential term is set to zero.

e.


0.004 £ z £ 0.5 .

C.12

Stress Intensity Factor Solutions for Cracks at Fillet Welds

C.12.1

Cracks at Fillet Welds – Surface Crack At A Tee Joint, Semi-Elliptical Shape, Through-Wall Membrane and Bending Stress (KFWSCE1)



Not for Resale

--``````-`-`,,`,,`,`,,`---

concepts.

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE C-47 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

b

KI = M km M mI m + M kb M bI b

g

Fa Q

(C.262)

Where M m and M b are determined using the equations in paragraph C.3.4.1 and Q is determined using Equation (C.14) or (C.15). The factors M km and Table C.16.

M kb are given by the following equations using the appropriate parameters from

cb F - F gF + F + F h, 10. = max cb F - F g F + F + F h, 10 .

M km = max

1

2

4

2

3

(C.263)

M kb

1

2

4

2

3

(C.264)

where,

L . - expRSFG P + P RS a UVIJ FG L IJ UVOP × LM10. + P FG a IJ OP Fr I F = 1.0 + P G J × sinb= g × M10 HtK MN TH T c WK H t K WPQ MN H c K PQ F aI g= P +PG J H cK F aI h= P + PG J H cK L . - P - P FG a IJ OP - P - P FG a IJ F = F M10 H cKQ H cK N L F aI F aI F aI F aI O F = M1.0 + P G J + P G J + P G J + P G J P × H c K H c K H c K H c K PQ MN LM P FG a IJ + P FG a IJ + P FG a IJ + P FG a IJ OP MN H t K H t K H t K H t K PQ g

1

2

1

P9

h

w

6

7

8

2

3

(C.266)

4

5

(C.267)

1

10

11

12

13

2

3

14

18

19

3

15

16

17

2

3

4

20

(C.268)

4

21

For the deepest point of the crack (Point B):


(C.265)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(C.269)


L F aI O F = P × exp M- P G J P + MN H t K PQ F aI L F aI F R a UI O P G J × exp M-G J × G P + P S VJ P + H c K MN H t K H T c WK PQ F LI L F a I F R L UI O P G J × exp M-G J × G P + P S VJ P + H t K MN H t K H T t WK PQ F t I L F aI F R t UI O P G J × exp M-G J × G P + P S VJ P + H r K MN H t K H T r WK PQ L F aI O P × sinb= g × exp M-G J × c P + P × sinb= ghP MN H t K PQ P24

4

22

23

P24

25

23

26

23

28

23

30

P24

27

(C.270)

P24

29

w

w

P24

31

23

32

For the surface point of the crack (Point A):

L F aI F = exp M- R × G J MN H t K F aI R= P +P G J H cK LM P + P FG a IJ H cK MN LM P + P FG a IJ H cK MN LM P + P FG a IJ H cK MN

OP + LM P PQ MN

P22

4

35

F aI +P G J H cK 36

P37

OP × FG a IJ PQ H t K

P38

(C.271)

P25

23

26

29

32

24

+ P28

27

P31

30

33

OPFG L IJ + PQH t K OPF t I + PQGH r JK OP × sinb= g PQ

(C.272)

w

P34

C.12.1.2 Notes: For the component and crack geometry see Figure C.32.

b.


0.0 < a t < 10 . ,

2.

0.0 < a c £ 1.0 ,

3.

0.01 £ rw t £ 0.07 ,

4.

30o £ = £ 60o , and


--``````-`-`,,`,,`,`,,`---

a.

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


5. c.

C.12.2

016 . £ L t £ 4.0 .


Cracks At Fillet Welds In Tee Junctions In Pressurized Components – General Solution The stress intensity factor solutions shown below can be used for surface cracks at fillet welds in pressue contiaing compoennts if the stress distribution normal to the plane of the crack is determined based on the nozzle geometry and applied loads. The stress distribution normal to the plane of the crack, I ( x ) , should be computed for the component in the uncracked state considering the effects of the structural configuration and fillet weld geometry (see Figure C.32(b)). The use of this method to compute the stress intensity factor will result in a conservative value as long as the geometry of the crack does not significantly reduce the stiffness of the tee junction connection. If the geometry of the crack does result in a significant loss in stiffness, the resulting deformation will result in a higher value of the stress intensity factor. In these cases, an analysis of the cracked geometry is required to accurately determine the stress intensity factor. Cracks At Fillet Welds of Tee Junctions In Pressurized Components (see Figure C.32)

C.13

·

Flat Plate Tee Junctions – Use KPTC, KPSCE3, KPECL, or KPECE2

·

Longitudinal Tee Junctions in Cylinders – Use KCTCL, KCSCLL3, KCSCLE3, KCECLL or KCECLE

·

Circumferential Tee Junctions in Cylinders – Use KCTCC1, KCTCC2, KCSCCL3, KCSCCE3, KCECCL or KCECCE

·

Circumferential Tee Junctions in Spheres – Use KSTC, KSSCCL3, KSECCL or KSECCE

Stress Intensity Factor Solutions Cracks In Clad Or Weld Overlayed Plates And Shells The stress intensity factor solutions in this appendix can be use to evaluate clad or weld overlayed plate and shell components if the modulus of elasticity between the clad or weld overlay is within 25% of the base material. If the difference between the elastic modulus is greater, the stress intensity factor should be computed numerically considering the actual properties of the materials. If the thermal expansion coefficients between the cladding and base material is different and the component is subject to a thermal load condition, a steep stress gradient will result at the cladding-tobase material interface. The weight function method should be used to compute the stress factor for this condition because it is the only method that can effectively capture the effects of the steep stress gradient.

·

Flat Plates – Use KPSCE3

·

Cylinders – KCSCLL3 or KCSCLE3

·

Spheres – Use KSSCCL3 or KSSCCE3


--``````-`-`,,`,,`,`,,`---

Cracks In Clad Or Weld Overlayed Plate

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


C.14

The Weight Function Method For Surface Cracks

C.14.1

Weight functions provide a means to infer stress intensity factors for nonuniform stress distributions. Consider a surface crack of depth a , subject to a normal stress I ( x ) that is an arbitrary function of x , where x is oriented in the crack depth direction and is measured from the free surface. The Mode I stress intensity factor for this case is given by the following equation where h( x , a ) is the weight function.

KI =

z

a

0

b gbg

h x , a I x dx

(C.273)

= 90o ) , the weight function can be represented by the following equation (see Reference [C.15.33]) where M1 , M 2 , and M 3 depend

For the deepest point of a semi-elliptical surface crack (j

on the component geometry and crack size. This equation also applies to an infinitely long surface crack.

h90 =

LM1 + M FG1 - x IJ H aK 2F ba - x g MN 2

1

For the surface point of the crack

LM MN

FG IJ HK

x 2 h0 = 1 + N1 a Fx

+ M2 1 -

IJ K

FG H

x x + M3 1 a a

IJ K

3/ 2

OP PQ

(C.274)

(j = 0o ) the weight function can be represented by [C.15.33]:

F xI F xI +N G J+N G J H aK H aK 2

3/ 2

3

OP PQ

(C.275)

M i and N i can be inferred from two reference stress intensity factor solutions. Normally, the K I solutions for uniform and linear loading are used to derive the weight function coefficients. For a uniform stress, I 0 , the stress intensity factor is given by the following equation where G0 is the influence coefficient, which depends on the component geometry and crack dimensions, and Q is given by Equations (C.14) or (C.15).

The weight function coefficients

K I = I o G0

Fa Q

(C.276)

For a linear stress distribution defined as

bg

I x = I1

FG x IJ HtK

(C.277)

the Mode I stress intensity factor is given by the following expression,

K I = I 1G1

FG a IJ HtK

Fa Q

(C.278)

At the deepest point of the surface crack, the weight function coefficients are given by the following equations (see Reference [C.15.34]) where the influence coefficients from the reference stress intensity factor solution, G0 and , G1 , are evaluated at


Not for Resale

j = 90o .

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.14.2

1/ 2

FG H

1/ 2


M1 =

b

g

2F 24 3G1 - G0 5 2Q

(C.279)

M2 = 3

M3 =

(C.280)

b

g

6F 8 G0 - 2G1 + 5 2Q

(C.281)

At the surface point of the surface crack, the weight function coefficients are given by the following equations (see Reference [C.15.34]) where the influence coefficients from the reference stress intensity factor solution, G1 and

C.14.3

b

G2 , are evaluated at j = 0o .

g

N1 =

3F 2G0 - 5G1 - 8 Q

N2 =

15F 3G1 - G0 + 15 Q

N3 =

3F 3G0 - 10G1 - 8 Q

b

(C.282)

g

b

(C.283)

g

(C.284)

The weight function coefficients defined above can be used to obtain a stress distribution defined as:

s ( x) = s o + s 1

FG x IJ + s FG x IJ HtK HtK 2

2

+s 3

FG x IJ HtK

3

+s 4

FG x IJ HtK

K I solution for a polynomial

4

(C.285)

The stress intensity solution is obtained by invoking the principle of superposition in summing contributions from each term in the polynomial.

KI

L = MI MN

o

F aI F aI +I G G J +I G G J HtK HtK 1

1

2

If the weight function coefficients

2

2

F aI +I G G J HtK 3

3

3

F aI O +I G G J P H t K PQ 4

4

4

Fa Q

(C.286)

M i and N i are known, it is possible to solve for the influence

coefficients, Gi . This is accomplished by substituting Equation (C.274) or Equation (C.275) into Equation (C.273) and integrating with the appropriate power-law stress distribution. The resulting expressions for Gi are given below (see Reference [C.15.34]). For the deepest point of a semi-elliptical surface crack

G2 =

G3 =

FG H 2Q F 32 1 32 + M + M G 315 F H 35 4

(j = 90o ) :

IJ K 1 I + M J K 20

2Q 16 1 16 1 + M1 + M2 + M3 15 3 105 12 F

1

2

(C.287)

(C.288)

3

//^:^^#^~^^""~:@":^*^~$~"

--``````-`-`,,`,,`,`,,`---


Not for Resale


FG H

2Q 256 1 256 1 + M1 + M2 + M3 F 315 5 3465 30

IJ K

(C.289)

The above expressions can also be applied an infinitely long surface crack by setting For the surface point of the crack

FG IJ H K Q F4 1 4 2 I + N + N + N J G H F 7 2 9 5 K Q F4 2 4 1 I + N + N + N J G H p 9 5 11 3 K

G3 =

1

G4 = C.14.4

(j = 0o ) :

Q 4 2 4 1 + N1 + N 2 + N 3 F 5 3 7 2

G2 =

Q = 1.

2

1

(C.290)

(C.291)

3

2

(C.292)

3

G0 and G1 influence coefficients are known for a given position along the crack front defined by the elliptic angle j , then the complete K I solution for a polynomial stress distribution defined by Equation (C.285) can be determined by computing the G2 , G3 and G4 influence coefficients using

If the

the following equations and substituting the results into Equation (C.286) (see Reference [C.15.35]). o

o

Note that if the K I solution is required at j = 90 or j = 0 , then the G2 , coefficients must be computed using the equations in paragraph C.14.3.

b

G3 and G4 influence

g + 144Dz h

G21 = 108 + 180z + 576z 2 - 864 z 3 + 1056 + 128 M1 @z 2.5

c

G22 = M 3 45D + 54Dz + 72Dz 2 - 315M z 2.5

b

Q G21 + G22 945F

G2 =

(C.293)

3

(C.294)

g

(C.295)

b

g

G31 = 880 + 1232 z + 2112 z 2 + 7040z 3 - 11264 z 4 + 13056 + 1280 M1 @z 3.5

c

G32 = M 3 385D + 440Dz + 528Dz 2 + 704Dz 3 - 3465Mz 3.5 + 1408Dz 4 G3 =

b

Q G31 + G32 13860F

g 4 .5

1

--``````-`-`,,`,,`,`,,`---


(C.297)

(C.298)

G41 = 1820 + 2340z + 3328z 2 + 5824 z 3 + 19968z 4 - 33280z 5 +

b37376 + 3072 M g@z

h

(C.296)

Not for Resale

(C.299)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

G4 =


F 819D + 909Dz + 1040Dz + 1248Dz +I =M G H1664Dz - 9009Mz + 3328Dz JK 2

G42

3

b

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

M2 =

M3 =

M4 =

(C.300)

5

g

(C.301)

M 2 and M 4 are only used in paragraph C.14.5)

where (note that

M1 =

4 .5

4

Q G41 + G42 45045F

G4 =

3

b

g

c

-1050FG1 + 105FG0 3 + 7 z - 4 Q 35 - 70z + 35z 2 + 189@z 0.5 + 61@z 1.5

b

g

Q 168 + 152 z z 0.5@

b

g

1 M1 - 3 3

e

h

(C.302)

(C.303)

c

2 -105FG1 + 45FG0 z + Q 28 + 24 z - 52 z 2 + [email protected]

c

h

Q -21 + 2 z + 19 z 2 D

b1 + M Dgz 3

hj

(C.304)

(C.305)

z -1

with,

z = sinj

(C.306)

@ = 1+ z

(C.307)

M = 1- z

(C.308)

1 -1 z

(C.309)

D= and C.14.5

Q determined using Equations (C.14) or (C.15).

The weight function method is recommended to compute the stress intensity factor for a through-wall arbitrary stress distribution. The stress distribution through the wall thickness of the component, s ( x ) , can be evaluated using the finite element method. The weight function, h( x , a ) , is evaluated as follows: ·

j = 90o and all infinitely long cracks, evaluate the influence coefficients G0 and G1 for the o applicable geometry at j = 90 and substitute the results into Equations (C.279), (C.280), and (C.281) to determine M1 , M 2 , and M 3 , respectively. Substitute M1 , M 2 , and M 3 into Equation (C.274) to compute the weight function; note that for an infinitely long crack, Q = 1 . For

The stress intensity factor is found by substituting the resulting equation into Equation (C.273) and completing the integration.


Not for Resale


·

j = 0o , evaluate the influence coefficients G0 and G1 for the applicable geometry at j = 90o and substitute the results into Equations (C.282), (C.283), and (C.284) to determine N1 , N 2 , and N 3 , respectively. Substitute N1 , N 2 , and N 3 into Equation (C.275) to compute

For

the weight function. The stress intensity factor is found by substituting the resulting equation into Equation (C.273) and completing the integration. ·

j , evaluate the influence coefficients G0 and G1 for the applicable j and substitute the results into Equations (C.302), (C.303), (C.304) and (C.305) to determine M1 , M 2 , M 3 and M 4 , respectively. Substitute M1 , M 2 , M 3 and M 4

For all other values of geometry at the angle

into the following equations to determine the weight functions.

h1 ( x , a ) =

LM1 + M F1 - x I + M F1 - x I OP GH a sin j JK GH a sin j JK P p ba sin j - x g MN Q 1 - sin j L F x - 1IJ + M FG x - 1IJ OP 1+ M G M H a sin j K H a sin j K PQ p b x - a sin j g MN 2

sin j + 1

1

2

(C.310)

1/ 2

h2 ( x , a ) =

3

4

(C.311)

The stress intensity factor is found by substituting the resulting equations into the following equation and completing the integration.

KI =

z

a sin j

0

h1 ( x , a )I ( x )dx +

z

a

a sin j

h2 ( x , a )I ( x )dx

(C.312)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.15

References

C.15.1

Newman, Jr., J.C., Raju, I.S., “Stress Intensity Factor Equations for Cracks in Three-Dimensional Finite bodies Subject to Tension and Bending Loads,” NASA Technical Memorandum 85793, April, 1984.

C.15.2

Rooke, DIP and Cartwright, D.J., “Compendium of Stress Intensity Factors,” Her Majesty’s Stationary Office (HMSO), London, 1974.

C.15.3

Cipolla, R.C., “Technical Basis for the Revised Stress Intensity Factor Equation for Surface Flaws in ASME Section XI Appendix A”, PVP-Vol. 313-1, International Pressure Vessels and Piping Codes and Standards: Volume 1 – Current Applications, American Society Of Mechanical Engineers, New York, N.Y., 1995, pp. 105-121.

C.15.4

Anderson, T.L., Unpublished Work, 1996.

C.15.5

Shen, G. and Glinka G. “Weight Functions for a Surface Semi-Elliptical Crack in a Finite Thickness Plate,” Theoretical and Applied Fracture Mechanics, Vol 15, 1991, pp. 247-255.

C.15.6

Vainshtok, V.A. and Varfolomeyev, I.V., “Stress Intensity Factor Equations for Part-Elliptical Cracks and Their Verification.” Engineering Fracture Mechanics, Vol 34, 1989, pp. 125-136.

C.15.7

Klecker, R., Brust, F.W., and Wilkowski, G., “NRC Leak before Break Analysis Method For Circumferentially Through-Wall Cracked Pipes Under Axial Plus bending Loads,” NUREG/CR-4572, U.S. Nuclear Regulatory Commission, May, 1986.

--``````-`-`,,`,,`,`,,`---


Not for Resale

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE C-55 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

C.15.8

Shin, C.S. and Wang, C.M. “Experimental Calibration of Stress Intensity Factors for Piping with Circumferential Through-Wall Crack,” International Journal of Pressure Vessels and Piping, 60, 1994, pp. 285-296.

C.15.9

Fuhrey, M. and Osage, D.A., “Stress Intensity Factor Solutions for Long Surface Cracks in Flat Plates, Cylinders and Spheres,” To Be Published.

C.15.10 Anderson, T.L., “Fracture Mechanics – Fundamentals and Applications,” 2nd Edition, CRC Press, Boca Raton, Florida, 1995. C.15.11 Erdogen, F. and Kibler, J.J., “Cylindrical and Spherical Shells with Cracks,” International Journal of Fracture Mechanics, 5, 1969, pp. 229-237. C.15.12 Folias, E.S., “On the Effect of Initial Curvature on Cracked Sheets,” International Journal of Fracture Mechanics, Vol. 5, No. 4, December, 1969, pp. 327-346. C.15.13 Murakami, Y., “Stress Intensity Factors Handbook,” Pergamon Press, Oxford, 1987, pp. 1356-1358. C.15.14 Eiber, R.J., Maxey, W.A., Duffy, A.R., and Atterbury, T.J., “Investigation of the Initiation and Extent of Ductile Pipe Rupture,” Battelle Report Task 17, June, 1971. C.15.15 Fu, B., Haswell, J.V., Bettess, P., "Weld Magnification Factors for Semi-Elliptical Surface Cracks in Fillet Welded T-Butt Joints," International Journal of Fracture, 63, 1993, pp. 155-171. C.15.16 Brust, F.W. and Gilles, P., “Approximate Methods for Fracture Analysis of Tubular Members Subjected to Combined Tensile and Bending Loads,” Journal of Offshore Mechanics and Arctic Engineering, Vol. 116, November, 1994. C.15.17 Green, D. and Knowles, J., “The Treatment of Residual Stress in Fracture Assessment of Pressure Vessels,” Journal of Pressure Vessel Technology, Vol. 116, American Society Of Mechanical Engineers, November 1994, pp. 345-352. C.15.18 James, L.A. and Mills, W.J., “Review and Synthesis of Stress Intensity Factor Solutions Applicable to Cracks in Bolts,” Engineering Fracture Mechanics, Vol. 30, No. 5, 1988, pp. 641-654. C.15.19 Tada, H., Paris, P.C. and Irwin, G.R, “The Stress Analysis Of Cracks Handbook – Second Edition,” Paris Productions Inc., St. Louis, Missouri, 1985. C.15.20 Sih, G.C., “Handbook of Stress Intensity Factors,” Institute of Fracture and Solid Mechanics, Lehigh University, Bethlehem, Pa. C.15.21 Newman, J.C., Reuter, W.G., and Aveline Jr, C.R., “Stress and Fracture Analysis of the Surface Crack,” Fatigue and Fracture Mechanics: 30th Volume, ASTM STP 1360, K.L. Jerina and P.C. Paris, ASTM, Philadelphia, PA, 1999.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.15.22 Niu, X. and Glinka, G., “Theoretical and Experimental Analyses of Surface Fatigue Cracks in Weldments,” Surface-Crack Growth: Models, Experiments, and Structures, ASTM STP 1060, W.G. Reuter, J.H. Underwood, and J.C. Newman Jr., Eds., ASTM, Philadelphia, Pa., 1990, pp. 390-413. C.15.23 Barsoum, R.S., Loomis, R.W., and Stewart, B.D., “Analysis of Through Cracks in Cylindrical Shells by the Quarter-Point Elements,” International Journal of Fracture, Vol. 15, No. 3, June 1979, pp. 259280. C.15.24 Chell,G.G, “Application of the CEGB Failure Assessment Procedure, R6, to Surface Flaws,” Fracture Mechanics: Twenty-First Symposium, ASTM STP 1074, J.P. Gudas, J.A. Joyce, and E.M. Hackett, Eds., ASTM, Philadelphia, 1990, pp. 525-544.


Not for Resale


C.15.25 Kramer, G.S., Wilkowski, G.M., and Maxey, W.A., “Flaw Tolerance of Spiral Welded Pipe,” Battelle NG-18 Report No. 154, January, 1987 C.15.26 Kiefner, J.F. and Vieth, P.H., “Project PR 3-805, A Modified Criterion for Evaluating the Remaining Strength of Corroded Pipe,” Battelle Report to the Pipeline Committee of the American Gas Association, 1989. C.15.27 Fett, T., and Munz, D., “Stress Intensity Factors and Weight Functions,” Computational Mechanics Publications, Southampton, UK, 1997. C.15.28 France, C.F., Green, D., Sharples, J.K., and Chivers, T.C., “New Stress Intensity Factor And Crack Opening Area Solutions For Through-Wall Cracks In Pipes And Cylinders,” PVP-Vol. 350, Fatigue and Fracture, Vol. 1, American Society Of Mechanical Engineers, New York, N.Y., 1997, pp. 143-195. C.15.29 Niu, X. and Glinka, G., “Stress-Intensity Factors For Semi-Elliptical Cracks In Welded Joints,” International Journal Of Fracture, Vol. 40, Kluwer Academic Publishers, Netherlands, 1989, pp. 255270. C.15.30 Brown, Robert, G., “Development of Elastic Stress Intensity Factor Solutions and Elastic-Plastic Failure Assessment Diagrams For Fillet Toe Cracks at Ring-Stiffened Cylindrical Shells,” Thesis, The University of Akron, December, 1996. C.15.31 HSE, “Development of Parametric Equations for MK-Factors for Semi-Elliptic Cracks in T-Butt Welds,” Offshore Technology Report – OTO 98 081, Health & Safety Executive, Research Admin, OSD, Bootle, Merseyside, August, 1998. C.15.32 Forman, R.G., Hickman, J.C., and Shivakumer, V., “Stress Intensity Factors for Circumferential Through Cracks in Hollow Cylinders Subjected to Combined Tension and Bending Loads,” Engineering Fracture Mechanics, Vol 21, No. 3, 1985, pp. 563-571. C.15.33 Shen, G. and Glinka, G., “Determination of Weight Functions from Reference Stress Intensity Solutions.” Theoretical and Applied Fracture Mechanics, Vol. 15, 1991, pp. 237-245. C.15.34 Zheng, X.J., Kiciak, A., and Glinka, G., “Weight Functions and Stress Intensity Factors for Internal Surface Semi-Elliptical Crack in Thick-Walled Cylinder.” Engineering Fracture Mechanics, Vol. 58, 1997, pp. 207-221. C.15.35 Anderson, T.L., private communication to D.A. Osage, 1998. C.15.36 Sih,G.C., “Mechanics Of Fracture 3, Plates and Shells with Cracks,” Noordhoff International Publishing Leydon, The Netherlands, 1977. C.15.37 Anderson, T.L., “Stress Intensity Factors For Surface Cracks In Cylinders and Spheres,” MPC Report, To Be Published. C.15.38 Guozhong, C. and Qichao, H., “Stress Intensity Factors of Nozzle Corner Cracks,” Engineering Fracture Mechanics, Vol. 38, No. 1, pp. 27-35, 1991.

C.15.40 Fife, A.B., Kobsa, I.R., Riccardella, P.C., and Watanabe, H.T., “Boiling Water Reactor Feedwater Nozzle/Spranger Interim Program Report,” NEDO-21480, 77NED125, Class I, General Electric, San Jose, CA,. July 1977. C.16

Tables and Figures

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C.15.39 Guozhong, C. and Qichao, H., “Approximate Stress-Intensity Factor Solutions for Nozzle Corner Cracks,” Int. J. Pres. Ves. & Piping, 42, pp. 75-96, 1990.


Component Geometry

Plate

Crack Geometry

Through-Wall Crack Surface Crack, Infinite Length Surface Crack, Infinite Length

Plate With A Hole

Cylinder

Surface Crack, Semi-Elliptical Shape Surface Crack, Semi-Elliptical Shape Surface Crack, Semi-Elliptical Shape Embedded Crack, Infinite Length Embedded Crack, SemiElliptical Shape Embedded Crack, SemiElliptical Shape Single Hole, Through-Wall Single Edge Crack Single Hole, Through-Wall Double Edge Crack Single Hole, Surface Crack, Semi-Elliptical Shape Single Hole, Corner Crack, Semi-Elliptical Shape Through-Wall Crack, Longitudinal Direction Through-Wall Crack, Circumferential Direction Through-Wall Crack, Circumferential Direction Surface Crack, Longitudinal Direction, Infinite Length Surface Crack, Longitudinal Direction, Infinite Length Surface Crack, Longitudinal Direction, Infinite Length Surface Crack, Circumferential Direction, 360 Degrees Surface Crack, Circumferential Direction, 360 Degrees Surface Crack, Circumferential Direction, 360 Degrees

Crack Loading

Stress Intensity Factor Solution

Reference Stress Solution

Through-Wall Membrane And Bending Stress Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Arbitrary Stress Distribution Through-Wall Membrane And Bending Stress Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Arbitrary Stress Distribution Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Membrane And Bending Stress Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Membrane And Bending Stress Through-Wall Membrane And Bending Stress Membrane Stress

KPTC (C.3.1) KPSCL1 (C.3.2) KPSCL2 (C.3.3) KPSCE1 (C.3.4) KPSCE2 (C.3.5) KPSCE3 (C.3.6) KPECL (C.3.7) KPECE1 (C.3.8) KPECE2 (C.3.9) KPHTC1 (C.4.1) KPHTC2 (C.4.2) KPHSC1 (C.4.3) KPHSC2 (C.4.4) KCTCL (C.5.1) KCTCC1 (C.5.2) KCTCC2 (C.5.3)

RPTC (D.3.1) RPSCL (D.3.2) RPSCL (D.3.3) RPSCE1 (D.3.4) RPSCE2 (D.3.5) RPSCE3 (D.3.6) RPECL (D.3.7) RPECE1 (D.3.8) RPECE2 (D.3.9) RPHTC1 (D.4.1) RPHTC2 (D.4.2) RPHSC1 (D.4.3) RPHSC2 (D.4.4) RCTCL (D.5.1) RCTCC1 (D.5.2) RCTCC2 (D.5.3)

KCSCLL1 (C.5.4) KCSCLL2 (C.5.5) KCSCLL3 (C.5.6) KCSCCL1 (C.5.7)

RCSCLL1 (D.5.4) RCSCLL2 (D.5.5) RCSCLL3 (D.5.6) RCSCCL1 (D.5.7)

KCSCCL2 (C.5.8)

RCSCCL2 (D.5.8)

KCSCCL3 (C.5.9)

RCSCCL3 (D.5.9)

Through-Wall Membrane And Bending Stress Through-Wall Membrane And Bending Stress Through-Wall Membrane And Bending Stress Pressure With A Net Section Axial Force And Bending Moment Internal Pressure (Lame Stress Distribution) Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Arbitrary Stress Distribution Pressure With Net Section Axial Force And Bending Moment Through-Wall Fourth Order Polynomial Stress Distribution with Net Section Bending Moments Through-Wall Arbitrary Stress Distribution

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.1 Summary Of Stress Intensity Factor Solutions


Table C.1 Summary Of Stress Intensity Factor Solutions Component Geometry

Cylinder

Crack Geometry

Crack Loading



Surface Crack, Longitudinal Direction, Semi-Elliptical Shape Surface Crack, Longitudinal Direction, Semi-Elliptical Shape Surface Crack, Longitudinal Direction, Semi-Elliptical Shape Surface Crack, Circumferential Direction, Semi-Elliptical Shape

Internal Pressure (Lame Stress Distribution) Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Arbitrary Stress Distribution Internal Pressure (Lame Stress Distribution) With Net Section Axial Force Through-Wall Fourth Order Polynomial Stress Distribution With Net Section Bending Moment Through-Wall Arbitrary Stress Distribution Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Fourth Order Polynomial Stress Distribution

KCSCLE1 (C.5.10) KCSCLE2 (C.5.11) KCSCLE3 (C.5.12) KCSCCE1 (C.5.13)

RCSCLE1 (D.5.10) RCSCLE2 (D.5.11) RCSCLE3 (D.5.12) RCSCCE1 (D.5.13)

KCSCCE2 (C.5.14)

RCSCCE2 (D.5.14)

KCSCCE3 (C.5.15) KCECLL (C.5.16) KCECCL (C.5.17)

RCSCCE3 (D.5.15) RCECLL (D.5.16) RCECCL (D.5.17)

Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Fourth Order Polynomial Stress Distribution With Net Section Bending Stress Through-Wall Membrane And Bending Stress Internal Pressure (Lame Stress Distribution) Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Arbitrary Stress Distribution Internal Pressure (Lame Stress Distribution) Through-Wall Fourth Order Polynomial Stress Distribution Through-Wall Arbitrary Stress Distribution Through-Wall Fourth Order Polynomial Stress Distribution

KCECLE (C.5.18) KCECCE (C.5.19)

RCECLE (D.5.18) RCECCE (D.5.19)

KSTC (C.6.1) KSSCCL1 (C.6.2) KSSCCL2 (C.6.3) KSSCCL3 (C.6.4) KSSCCE1 (C.6.5) KSSCCE2 (C.6.6) KSSCCE3 (C.6.7) KSECCL (C.6.8)

RSTC (D.6.1) RSSCCL1 (D.6.2) RSSCCL2 (D.6.3) RSSCCL3 (D.6.4) RSSCCE1 (D.6.5) RSSCCE2 (D.6.6) RSSCCE3 (D.6.7) RSECCL (D.6.8)

Through-Wall Fourth Order Polynomial Stress Distribution

KSECCE (C.6.9)

RSECCE (D.6.9)

See Discussion in Paragraph C.7.

(C.7)

(D.7)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Surface Crack, Circumferential Direction, Semi-Elliptical Shape Surface Crack, Circumferential Direction, Semi-Elliptical Shape Embedded Crack, Longitudinal Direction, Infinite Length Embedded Crack, Circumferential Direction, 360 Degrees Embedded Crack, Longitudinal Direction, Semi-Elliptical Shape Embedded Crack, Circumferential Direction, Semi-Elliptical Shape Sphere

Elbow And Pipe Bend

Through-Wall Crack Surface Crack, Circumferential Direction, 360 Degrees Surface Crack, Circumferential Direction, 360 Degrees Surface Crack, Circumferential Direction, 360 Degrees Surface Crack, Circumferential Direction, Semi-Elliptical Shape Surface Crack, Circumferential Direction, Semi-Elliptical Shape Surface Crack, Circumferential Direction, Semi-Elliptical Shape Embedded Crack, Circumferential Direction, 360 Degrees Embedded Crack, Circumferential Direction, Semi-Elliptical Shape General Solution

--``````-`-`,,`,,`,`,,`---


Not for Resale


Table C.1 Summary Of Stress Intensity Factor Solutions Component Geometry

Nozzle or Piping Tee

RingStiffened Cylinder

Sleeve Reinforced Cylinder Round Bar or Bolt

Cracks At Fillet Welds

Cracks In Clad Or Weld Overlayed Plate

Crack Geometry

Crack Loading



Corner Cracks, Radial Direction, Quarter-Circular Shape Corner Cracks, Radial Direction, Quarter-Circular Shape Surface Cracks At Nozzles – General Solution Surface Crack At The Toe Of One Fillet Weld, Circumferential Direction – 360 Degrees Surface Crack At The Toe Of Both Fillet Welds, Circumferential Direction – 360 Degrees General Solution

Membrane Stress

KNCC1 (C.8.1)

RNCC1 (D.8.1)

Cubic Polynomial Stress Distribution

KNCC2 (C.8.2)

RNCC2 (D.8.2)

See Discussion in Paragraph C.8. Pressure (Membrane and Bending Stress)

(C.8.3)

(D.8.3)

KRCSCCL 1 (C.9.1)

RRCSCCL 1 (D.9.1)

KRCSCCL 2 (C.9.2)

RRCSCCL 2 (D.9.2)

(C.10)

(D.10)

Round Bar, Surface Crack, 360 Degrees Round Bar, Surface Crack, Straight Front Shape Round Bar, Surface Crack, Semi-Circular Shape Bolt, Surface Crack, SemiElliptical Or Straight Front Shape Surface Crack, Infinite Length

Membrane And Bending Stress Membrane And Bending Stress Membrane And Bending Stress Membrane And Bending Stress

KBSCL (C.11.1) KBSCS (C.11.2) KBSCC (C.11.3) KBSC (C.11.4)

RBSCL (D.11.1) RBSCS (D.11.2) RBSCC (D.11.3) RBSC (D.11.4)

Membrane And Bending Stress See Discussion in Paragraph C.12.2

KFWSCE1 (C.12.1) (C.12.2)

RFWSCE1 (D.12.1) (D.12.2)

See Discussion in Paragraph C.13.

(C.13)

(D.13)

Cracks At Fillet Welds In Tee Junctions In Pressurized Components - General Solution General Solution

Pressure (Membrane and Bending Stress) See Discussion in Paragraph C.10.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table C.2 Influence Coefficients For A Infinite Length Surface Crack In A Plate (1)

a/t

G0

G1

G2

G3

G4

0.0

1.1200

0.6820

0.5245

0.4404

0.3791

0.1

1.1804

0.7028

0.5352

0.4473

0.3836

0.2

1.3587

0.7732

0.5753

0.4741

0.4043

0.4

2.0990

1.0526

0.7285

0.5741

0.4798

0.6

4.0082

1.7459

1.0998

0.8121

0.6526

0.8

11.8272

4.4792

2.5244

1.7069

1.2754

C3

C4

Influence Coefficients In Equation Form (2)

C0

C1

C2

G0

1.1202

6.0061

-1.3891

7.9260

31.914

G1

0.68109

2.3137

-0.71895

3.1140

10.702

G2

0.52360

1.3006

-0.56913

2.1463

5.0660

G3

0.43970

0.86873

-0.52507

1.7131

2.8443

G4

0.37831

0.64919

-0.28777

0.87481

2.2063

Notes: 1. Interpolation may be used for intermediate values of a t . 2. The equation to determine influence coefficients is shown below.

F aI G =C +C G J HtK 0

1

F aI +C G J HtK 2

4

F aI +C G J HtK 3

6

F aI +C G J HtK 4

8

(C.313) --``````-`-`,,`,,`,`,,`---

i

2


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

j

Coefficient

C0

C1

C2

C3

C4

C5

C6

C7

C8

C9

C10

0.0

G0

0.27389

-0.79900

-0.26714

1.4761

3.7226

0.16033

0.64383

-1.7330

-2.5867

0.55987

-0.54503

G1

0.028002

-1.1022

-0.033521

0.22057

0.52258

0.10846

0.065941

-3.1077

-0.93098

2.4443

0.18878

G2

0.012675

-1.1481

-0.015221

-0.082355

0.13759

0.041064

0.019569

-1.9848

-0.22151

2.9522

0.16896

G3

7.3602e-3

-1.1544

-6.5361e-3

-0.36173

0.049133

0.044540

8.9574e-3

-1.4999

-0.081464

3.0826

0.10436

G4

4.9892e-3

-1.2132

-4.3696e-3

-0.46223

0.020326

0.068641

4.1052e-3

-1.1912

-0.033493

3.2003

0.074990

G0

0.79807

0.041621

-0.55195

0.94721

-0.33668

0.52973

-0.93391

-0.064536

0.28786

-0.22806

---

G1

0.82407

0.023018

0.14705

0.15481

0.048556

0.16795

-0.12109

7.2007e-3

0.093079

-0.094413

---

G2

0.75607

1.8397e-3

0.28788

0.023688

0.12715

0.066900

0.012227

0.021628

0.041800

-0.051236

---

G3

0.68582

-1.6499e-3

0.30738

-0.033522

0.13604

0.029992

0.072309

0.022755

0.022788

-0.030355

---

G4

0.63097

8.4876e-3

0.30584

-0.067862

0.13547

0.025147

0.092532

0.022520

0.015831

-0.029806

---

90.0

Not for Resale

Table C.3 Influence Coefficients For A Finite Length Surface Crack In A Plate

Notes: The equation to determine influence coefficients for

FG a IJ + C FG a IJ + C FG a IJ H t K H 2c K H t K G = F aI F a I F aI 10 . +C G J +C G J +C G J H t K H 2c K H t K C0 + C2

4

2.

3

5

FG a IJ H 2c K FaI +C G J H 2c K

2

+ C8

6

i

1

2

j = 0o is shown below.

2

2

7

The equation to determine influence coefficients for

FG a IJ × FG a IJ H t K H 2c K F aI F a I + C G J ×G J H t K H 2c K

+ C10 9

j = 90o is shown below.

F aI F a I F aI L F aIO F aI F a I G = C + C G J + C lnG J + C G J + C MlnG J P + C G J × lnG J + H t K H 2c K H t K N H t K Q H t K H 2 c K F aI L F a IO F aI L F a IO F aI L F a IO C G J + C MlnG J P + C G J × MlnG J P + C G J × MlnG J P H t K N H 2c K Q H t K N H 2c K Q H t K N H 2c K Q 2

2

i

0

1

2

3

3

6

3

7

4

5

2

8

(C.314)

2

9

--``````-`-`,,`,,`,`,,`---

C-61

(C.315)


1.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\ --``````-`-`,,`,,`,`,,`---

Table C.4 Influence Coefficients For An Embedded Crack Of Infinite Length In A Plate Point A

Point B

d1 t

FG t - d - t IJ H2 2K

G0

G1

G2

G3

G4

G0

G1

G2

G3

G4

0.25

0.20

1.0211

-0.4759

0.4601

-0.3141

0.3025

1.0180

0.4777

0.4600

0.3165

0.3034

0.40

1.0923

-0.4804

0.4779

-0.3162

0.3113

1.0651

0.4757

0.4715

0.3155

0.3090

0.60

1.2628

-0.5129

0.5423

-0.3521

0.3638

1.1505

0.4806

0.5122

0.3372

0.3491

0.80

1.7105

-0.6027

0.6859

-0.4216

0.4634

1.3097

0.4740

0.5726

0.3551

0.4030

0.20

1.0259

-0.4758

0.4613

-0.3140

0.3031

1.0259

0.4784

0.4619

0.3168

0.3043

0.40

1.1103

-0.4993

0.5121

-0.3550

0.3587

1.1103

0.4987

0.5110

0.3553

0.3585

0.60

1.3028

-0.5299

0.5691

-0.3795

0.3974

1.3028

0.5292

0.5680

0.3790

0.3965

0.80

1.8103

-0.6451

0.7104

-0.4432

0.4754

1.8103

0.6446

0.7094

0.4425

0.4744

0.20

1.0180

0.4777

0.4600

0.3165

0.3034

1.0211

-0.4759

0.4601

-0.3141

0.3025

0.40

1.0651

0.4757

0.4715

0.3155

0.3090

1.0923

-0.4804

0.4779

-0.3162

0.3113

0.60

1.1505

0.4806

0.5122

0.3372

0.3491

1.2628

-0.5129

0.5423

-0.3521

0.3638

0.80

1.3097

0.4740

0.5726

0.3551

0.4030

1.7105

-0.6027

0.6859

-0.4216

0.4634

0.75

Notes:


d1 t and a

nct 2 - d - t 2 hs . 1

C-62


0.50

1

Not for Resale

a

--``````-`-`,,`,,`,`,,`---

a

FG t - d - t IJ H2 2K 1

1.0

0.25

0.20

0.40

0.60

0.75

1.0

0.50

0.20

0.40

Gi G0 G1 G2 G3 G4 G0 G1 G3 G3 G4 G0 G1 G3 G3 G4 G0 G1 G2 G3 G4 G0 G1 G2 G3 G4 G0 G1 G3 G3 G4

A0 0.998584271 0.000250000 0.063900054 -0.000595000 0.008863419 1.015009165 0.000819000 0.072201759 -0.000381000 0.015117034 1.025429249 -0.000546000 0.075269222 -0.000931000 0.016556218 1.042557478 -0.004758000 0.079656363 -0.002593000 0.018858910 1.007334948 0.000000000 0.070699543 0.000000000 0.014448826 1.020652771 0.000000000 0.073767327 0.000000000 0.017079074

A1

A2

A3

A4

A5

A6

-0.015684405 1.052208000 -0.005873878 0.164589000 0.013112109 -0.007527984 1.057810000 -0.003136456 0.166856000 0.009818073 -0.018899091 1.056583000 -0.005550366 0.167496000 0.008581266 -0.064163908 1.051391000 -0.015329611 0.167653000 0.004685976 0.000870055 1.055473000 -0.001362193 0.165942000 0.010547910 0.000801784 1.059402000 -0.001179798 0.167661000 0.010572735

-0.036381699 -0.007063000 1.371599317 0.005755000 0.408871502 -0.030901082 -0.005844000 1.334404588 0.005973000 0.432485193 -0.024097897 -0.009132000 1.326501131 0.004138000 0.430086076 -0.020997193 -0.032160000 1.317765236 -0.005711000 0.426645875 -0.032838214 -0.000686000 1.333568811 0.007078000 0.432404548 -0.024712475 -0.000822000 1.332170844 0.007030000 0.425339162

0.016835470 -0.426007000 0.019092306 1.139653000 -0.091415532 0.002446785 -0.429289000 0.009943038 1.138556000 -0.066636205 -0.001327875 -0.425212000 0.007215023 1.134758000 -0.067017213 -0.026481932 -0.395132000 -0.011036471 1.137499000 -0.079355448 -0.005828240 -0.425363000 0.008830077 1.139476000 -0.066712223 -0.005324946 -0.426893000 0.007611249 1.138310000 -0.066980615

0.092537522 0.007622000 -1.170752883 -0.011252000 0.888747275 0.081625558 0.006556000 -1.090502024 -0.010985000 0.775413394 0.088452123 0.007313000 -1.074798584 -0.010558000 0.773639321 0.175951198 0.004437000 -1.043201685 -0.019303000 0.777680934 0.083482720 -0.007413000 -1.089365482 -0.012172000 0.775485516 0.069424346 -0.006340000 -1.083972454 -0.012411000 0.787123919

-0.005774375 0.046894000 -0.020165332 -0.788627000 0.107038006 0.003223902 0.047572000 -0.010740384 -0.788519000 0.077664331 0.008861186 0.044664000 -0.007587478 -0.786476000 0.077920482 0.035161749 0.028163000 0.004665934 -0.787576000 0.084825188 0.006862204 0.043747000 -0.010340830 -0.788841000 0.077461660 0.006308417 0.043580000 -0.008927633 -0.788448000 0.077776462

-0.060056359 -0.003511000 0.346043199 0.004916000 -0.856287420 -0.054948926 -0.003170000 0.295820117 0.004677000 -0.761770606 -0.064283200 -0.002488000 0.285693318 0.004953000 -0.759862602 -0.131912649 0.007076000 0.266819298 0.014316000 -0.760302901 -0.055173296 0.007607000 0.295375705 0.005131000 -0.761576295 -0.047845412 0.006645000 0.291069508 0.005386000 -0.767555356

C-63

Not for Resale

d1 t


c a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.5 Influence Coefficients For An Embedded Crack Of Finite Length In A Plate

--``````-`-`,,`,,`,`,,`---

a

FG t - d - t IJ H2 2K 1

0.60

0.80

2.0

0.25

0.20

0.40

0.60

0.80


A0 1.039108276 0.000000000 0.078056663 0.000000000 0.019180533 1.076678038 0.000000000 0.086643226 0.000000000 0.022932023 0.717666984 0.000134000 0.035086215 -0.000314000 0.002949923 0.730289817 0.000220000 0.041978300 -0.000330000 0.007325023 0.743860006 -0.001394000 0.042902380 -0.000737000 0.008153066 0.760457635 -0.005280000 0.046198249 -0.002230000 0.010715187

A1

A2

A3

A4

A5

A6

0.000776094 1.062759000 -0.001199472 0.170220000 0.010460637 0.001492911 1.077683000 -0.001194164 0.177403000 0.010421058 -0.020379970 0.723947000 -0.001476090 0.073308000 0.010331869 -0.015679769 0.726457000 0.000007857 0.074159000 0.008144442 -0.021961927 0.711649000 -0.001773242 0.058020000 0.003901817 -0.048772674 0.701105000 -0.003950721 0.053570000 0.004106634

-0.005040028 -0.003182000 1.331264496 0.006127000 0.424202114 0.055210453 -0.006020000 1.338314056 0.006432000 0.428579211 0.936509609 -0.006780000 1.115369916 0.002381000 0.287094474 0.969475389 -0.006588000 1.088961601 0.002652000 0.300095439 1.005065084 -0.010184000 1.055271626 -0.001953000 0.251502514 1.138436317 -0.009052000 1.076766253 0.000871000 0.251023054

-0.005624372 -0.423205000 0.007707841 1.135403000 -0.066391952 -0.009914597 -0.374247000 0.007539950 1.156459000 -0.066204764 0.057694651 0.071199000 -0.004441738 1.079510000 -0.071217373 0.043222919 0.071565000 -0.011714980 1.079969000 -0.056600500 0.000001878 0.123002000 -0.016718227 1.123562000 -0.034795299 -0.087284081 0.189475000 -0.053235311 1.149157000 -0.057907805

0.064247996 0.000529000 -1.079096556 -0.010697000 0.785710752 0.119255103 0.012880000 -1.043217778 -0.012131000 0.798227072 -1.153294921 0.008381000 -0.702697754 -0.004861000 0.895005465 -1.201324821 0.007191000 -0.643703520 -0.005697000 0.830791533 -1.164803028 0.005080000 -0.523410320 -0.003418000 0.939929366 -1.229980111 -0.067278000 -0.515870810 -0.045224000 0.964621425

0.006871722 0.041231000 -0.008986242 -0.787366000 0.077226423 0.011779478 0.014321000 -0.008732292 -0.800413000 0.077072904 -0.056217909 -0.217568000 0.006067406 -0.718140000 0.082854390 -0.047816917 -0.218382000 0.013340348 -0.718580000 0.065467656 -0.007235289 -0.252337000 0.015064280 -0.744614000 0.035851352 0.034587063 -0.291822000 0.032110844 -0.759029000 0.048231684

-0.052375071 0.001284000 0.287330359 0.004307000 -0.766442955 -0.114726439 -0.010548000 0.260265261 0.005542000 -0.775999427 0.512093484 -0.004205000 0.087912411 0.001625000 -0.796597958 0.535517216 -0.003198000 0.051074322 0.002201000 -0.742353499 0.483331472 -0.000531000 -0.026169477 0.002782000 -0.790275753 0.494762659 0.048830000 -0.036005251 0.030020000 -0.808842838

C-64

Not for Resale

d1 t


c a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



1

2.0

0.50

0.20

0.40

0.60

0.80

4.0

0.25

0.20

0.40


A0 0.723986626 0.000000000 0.040720254 0.000000000 0.006760136 0.737302899 0.000000000 0.043920375 0.000000000 0.008774024 0.761394799 0.000000000 0.046658527 0.000000000 0.010802104 0.801960766 0.000000000 0.054810807 0.000000000 0.014770509 0.537695527 -0.000246000 0.014281154 -0.000107000 -0.000703126 0.547859669 -0.000456000 0.011184499 -0.000212000 -0.001172632

A1

A2

A3

A4

A5

A6

-0.007139158 0.726564000 0.001588252 0.074017000 0.008736135 -0.007297765 0.728397000 0.001719365 0.074923000 0.008724133 -0.003760176 0.717045000 0.001634146 0.059948000 0.005183375 0.004279781 0.719005000 0.004298563 0.059324000 0.006609293 -0.025921172 0.564125000 0.000287078 0.014103000 0.007997859 -0.027674442 0.564074000 0.000754926 0.014255000 0.005127981

0.955618560 -0.001605000 1.086529136 0.004101000 0.299515963 0.992434382 -0.002109000 1.088827252 0.004527000 0.297714084 1.051895618 -0.002967000 1.062532306 0.000684000 0.249832183 1.253179431 0.011393000 1.094039559 0.006812000 0.254210889 1.955145359 -0.002740000 1.050888300 0.000336000 0.251549721 1.990139008 -0.005148000 1.018531084 -0.000205000 0.193130761

0.044991035 0.070019000 -0.010068055 1.080085000 -0.055454411 0.045878738 0.072485000 -0.010916566 1.080519000 -0.055392418 0.022075510 0.131681000 -0.009691219 1.128646000 -0.030713916 0.010430514 0.251467000 -0.015009416 1.183994000 -0.036095604 0.120407231 0.343556000 -0.015054382 1.109461000 -0.055277310 0.108033605 0.343801000 -0.017088082 1.107599000 -0.038388681

-1.192714214 0.000591000 -0.642234981 -0.006328000 0.830799639 -1.233272672 0.002030000 -0.637684703 -0.007475000 0.835575581 -1.190796018 0.005004000 -0.520305634 -0.001600000 0.948557198 -1.203324795 -0.029449000 -0.474000961 -0.016429000 0.997467995 -2.938922405 0.005187000 -0.569579542 -0.000465000 0.855937243 -2.971917152 0.006167000 -0.428454161 -0.001989000 1.010172486

-0.052150622 -0.217340000 0.011690455 -0.718574000 0.064515509 -0.053049836 -0.219508000 0.012728972 -0.719037000 0.064431004 -0.023822187 -0.258490000 0.010499076 -0.747943000 0.033263046 -0.022751266 -0.328034000 0.013135224 -0.778236000 0.038652398 -0.125257567 -0.380079000 0.016957173 -0.725386000 0.063335896 -0.117768005 -0.380055000 0.018686125 -0.724060000 0.042986698

0.535845041 -0.000287000 0.051144417 0.002099000 -0.741818190 0.551959515 -0.001176000 0.046100236 0.002846000 -0.744572997 0.486505538 -0.002813000 -0.031081576 0.000673000 -0.795555770 0.437555224 0.018079000 -0.071147293 0.009714000 -0.832478523 1.497328520 -0.003435000 0.010361630 -0.000354000 -0.739814460 1.510430932 -0.003335000 -0.087797023 0.001017000 -0.826030314

C-65

Not for Resale

FG t - d - t IJ H2 2K

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a


d1 t

--``````-`-`,,`,,`,`,,`---

c a


a

FG t - d - t IJ H2 2K 1

0.60

0.80

4.0

0.50

0.20

0.40

0.60

0.80


A0 0.567564607 -0.001061000 0.015594944 -0.000456000 0.000207767 0.576341152 -0.003531000 0.017717555 -0.001407000 0.001281142 0.544045746 0.000000000 0.010169312 0.000000000 0.000225037 0.556659818 0.000000000 0.014997393 0.000000000 0.000296712 0.581807852 0.000000000 0.018123984 0.000000000 0.001851946 0.608272612 0.000000000 0.024348617 0.000000000 0.004477277

A1

A2

A3

A4

A5

A6

-0.020461284 0.571398000 0.000916155 0.016782000 0.004933221 -0.040645082 0.554035000 -0.000647742 0.012543000 0.004903509 -0.014364303 0.565516000 0.002381206 0.014335000 0.008197632 -0.014651378 0.566247000 0.002695497 0.014697000 0.005453894 -0.008650535 0.574804000 0.001634442 0.017797000 0.005267447 -0.008227244 0.561954000 0.002521146 0.013542000 0.004744411

1.969533205 -0.007944000 1.015393734 -0.001526000 0.203057408 2.158031225 -0.014173000 1.042167902 0.000852000 0.217941433 1.959108591 -0.001180000 1.014622450 0.001019000 0.254659474 2.024524450 -0.001445000 1.004418612 0.000740000 0.193812460 2.055695772 -0.000789000 1.042788506 0.000904000 0.206731319 2.345791578 -0.000788000 1.062774301 0.000593000 0.222326428

-0.009167116 0.342287000 -0.034519512 1.109613000 -0.044569548 -0.161776424 0.424091000 -0.079493247 1.129475000 -0.065569200 0.095271520 0.341811000 -0.015805501 1.109745000 -0.052066438 0.097215943 0.343967000 -0.017900053 1.109383000 -0.036215607 0.049933832 0.363279000 -0.009438507 1.120134000 -0.036054671 0.049046900 0.539207000 -0.017744772 1.186767000 -0.033387735

-2.705955029 -0.010781000 -0.386366516 -0.009983000 0.998682797 -2.691428661 -0.087946000 -0.354044884 -0.060002000 0.998170674 -2.959061146 0.002349000 -0.427708536 -0.001143000 0.850804865 -3.011442900 0.003157000 -0.387112886 -0.000451000 1.008949637 -2.712012529 0.000975000 -0.409391165 -0.002384000 1.009944320 -2.536022663 0.001266000 -0.244332820 -0.001749000 1.060651422

-0.016330346 -0.382996000 0.029948656 -0.727432000 0.046036392 0.064515099 -0.426653000 0.047244083 -0.733130000 0.050659008 -0.108773992 -0.378954000 0.018050963 -0.725493000 0.060585424 -0.111037679 -0.380215000 0.020447034 -0.725224000 0.041367345 -0.053153504 -0.395833000 0.010048167 -0.733520000 0.041702613 -0.052852552 -0.489579000 0.020773763 -0.761495000 0.039085969

1.293078780 0.010056000 -0.118726417 0.007257000 -0.819681048 1.222565532 0.063971000 -0.142868251 0.039306000 -0.817098200 1.512391806 -0.001650000 -0.087045237 0.000032000 -0.736277461 1.528936625 -0.002221000 -0.115022153 -0.000500000 -0.824311972 1.266471505 -0.000463000 -0.106125698 0.001419000 -0.828698397 1.042974591 -0.000686000 -0.230938986 0.001179000 -0.862353504

--``````-`-`,,`,,`,`,,`---

C-66 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Not for Resale

d1 t


c a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


FG t - d - t IJ H2 2K 1

8.0

0.25

0.20

0.40

0.60

0.80

8.0

0.50

0.20

0.40


A0 0.402472168 -0.002654000 -0.002027547 0.001862000 -0.003131000 0.423287302 -0.004337000 -0.000113367 0.000486000 -0.002569335 0.432988733 -0.004351000 0.001550407 0.000228000 -0.001650893 0.445541889 -0.005232000 0.003887496 -0.000904000 -0.000593060 0.452207506 0.000000000 0.000136745 0.000000000 0.000041900 0.460370034 0.000000000 0.000649770 0.000000000 0.000264715

A1

A2

A3

A4

A5

A6

-0.050527364 0.466214000 -0.011522302 0.008824000 0.002178000 -0.031729888 0.488376000 -0.012149093 0.002651000 -0.001079670 -0.033577092 0.486459000 -0.011964641 0.002766000 -0.000908507 -0.033047300 0.488237000 -0.004975302 -0.002210000 0.002201224 -0.017180284 0.515985000 -0.010746571 0.005191000 -0.004570000 -0.014353169 0.514400000 -0.011494149 0.004923000 -0.001302935

2.904406786 -0.066963000 0.899724305 -0.096953000 0.153341000 2.755031109 -0.018798000 0.951094687 -0.049583000 0.152314395 2.872620106 -0.027018000 0.969643116 -0.049174000 0.156156302 3.041505098 -0.017605000 0.999240696 -0.022680000 0.155599833 2.496135473 -0.006471000 0.903077602 0.000427000 0.184913000 2.597564697 -0.000381000 0.959328294 0.000370000 0.151837066

0.255471438 0.459261000 -0.037830871 0.958686000 -0.082397000 0.106002718 0.445002000 -0.003644595 1.025268000 -0.039286084 0.027124660 0.466641000 -0.021303291 1.036901000 -0.047469705 -0.234081879 0.521073000 -0.081999838 1.092769000 -0.064478561 0.096821368 0.418733000 -0.035133231 1.086222000 -0.033948000 0.086983338 0.431274000 0.003894663 1.088831000 -0.022124505

-4.947330952 0.146976000 -0.235938802 0.183063000 0.942617000 -4.356324673 0.042130000 -0.308412373 0.091154000 0.982607126 -4.359993458 0.031078000 -0.285069466 0.077402000 1.008257151 -4.127054691 -0.098628000 -0.187211588 -0.025501000 1.102857709 -3.887235641 0.011986000 -0.235300168 -0.001351000 0.832546000 -3.930643797 0.000350000 -0.301061720 -0.000894000 1.006404519

-0.281717867 -0.440574000 0.058484185 -0.620891000 0.092908000 -0.113843523 -0.442372000 0.015653433 -0.665949000 0.044717107 -0.064021170 -0.455126000 0.024773523 -0.671945000 0.048482072 0.097677328 -0.481469000 0.044134058 -0.702693000 0.042103145 -0.101878814 -0.430803000 0.056910519 -0.709040000 0.037795000 -0.094322875 -0.438897000 0.011213670 -0.710377000 0.027741110

2.736347914 -0.080979000 -0.195269406 -0.089157000 -0.762958000 2.276538134 -0.023399000 -0.149110302 -0.044010000 -0.778850794 2.235057831 -0.013517000 -0.171452820 -0.035391000 -0.797690511 2.009091854 0.071257000 -0.245910004 0.022851000 -0.860425115 2.006232023 -0.006741000 -0.196866214 0.000756000 -0.665999000 2.000951529 -0.000183000 -0.157400146 0.000399000 -0.796411634

C-67

Not for Resale

a


d1 t

--``````-`-`,,`,,`,`,,`---

c a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


FG t - d - t IJ H2 2K 1

0.60

0.80

Gi G0 G1 G2 G3 G4 G0 G1 G2 G3 G4

A0 0.470563471 0.000000000 0.002664581 0.000000000 0.000610358 0.481246084 0.000000000 0.006111201 0.000000000 0.001439426

A1

A2

A3

A4

A5

A6

-0.014111127 0.511104000 -0.011945072 0.004476000 -0.001640260 -0.013835795 0.495527000 -0.009233967 -0.002324000 -0.001643851

2.800145388 -0.000060000 0.985089541 0.000652000 0.158428669 3.156475782 0.000335000 1.017396569 0.000564000 0.150710672

0.085920550 0.482732000 0.005106864 1.106319000 -0.034544993 0.084019206 0.688092000 0.009921666 1.190456000 -0.020466875

-3.915485144 -0.000416000 -0.243500739 -0.001608000 1.039227009 -3.534390926 -0.000886000 -0.010110442 -0.000937000 1.217096567

-0.093347840 -0.468649000 0.010582664 -0.718463000 0.042712476 -0.091214538 -0.571261000 0.001465748 -0.751321000 0.026434405

1.914261580 0.000377000 -0.207032874 0.000880000 -0.820419967 1.522474766 0.000469000 -0.376234680 0.000289000 -0.936693668

Notes: Interpolation may be used for intermediate values of

c a , d1 t , and a

C-68

nct 2 - d - t 2 hs . 1

Not for Resale

a

--``````-`-`,,`,,`,`,,`---

d1 t


c a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C0

C1

C2

C3

C4

C5

3.0

Amm

1.0073E+00

8.3839E-01

1.5071E-01

5.4466E-02

-7.5887E-03

2.5248E-04

Amb

-5.7070E-03

8.1803E-02

-2.3171E-02

-1.5258E-01

2.4677E-02

-3.0187E-04

Abm

-6.0664E-04

5.5020E-02

1.7891E-01

4.0284E-04

---

---

Abb

-1.3128E-02

-4.0770E-01

0.0000E+00

3.3813E-01

-1.0957E-02

0.0000E+00

Amm

1.0048E+00

1.8860E-01

7.3172E-01

-8.4972E-02

6.1289E-03

-1.7729E-04

Amb

-2.3257E-03

1.4261E-01

-3.6873E-02

2.1666E-03

4.8189E-03

1.4505E-04

Abm

-1.4461E-04

7.1799E-02

3.6679E-01

-2.3437E-03

---

---

Abb

-5.4136E-04

-6.5893E-01

-2.9552E-02

1.0138E+00

-4.5494E-02

1.6372E-03

Amm

9.9652E-01

1.3041E-01

3.3780E-01

4.7232E-03

-2.7829E-03

1.3064E-04

Amb

-4.7919E-03

1.6845E-01

-3.8474E-02

8.8191E-02

-9.8223E-04

9.9173E-05

Abm

-5.4120E-05

5.7559E-02

2.6740E-01

2.7723E-03

---

---

Abb

-4.5087E-04

-1.5170E+00

-3.7096E-01

3.7600E+00

1.4390E-01

-1.3873E-03

Amm

1.0011E+00

1.2212E-01

4.4068E-01

-2.5824E-02

1.1045E-03

-2.3964E-05

Amb

-2.9633E-04

1.5835E-01

-3.2881E-02

-8.9569E-03

1.1153E-02

-4.4610E-04

Abm

3.6971E-05

4.7459E-02

2.0046E-01

3.4189E-03

---

---

Abb

-2.8088E-03

-1.3369E+00

-2.4049E-02

2.4901E+00

-1.4811E-01

5.4353E-03

5.0

10.0

20.0

--``````-`-`,,`,,`,`,,`---

Parameter

C-69


Ri t

Not for Resale

Table C.6 Parameters For A Through-Wall Longitudinal Crack In A Cylinder Subject To A Through-Wall Membrane And Bending Stress

Parameter

C0

C1

C2

C3

C4

C5

50.0

Amm

1.0010E+00

2.2135E-01

3.8500E-01

-9.8415E-03

-3.2277E-04

2.3126E-05

Amb

-1.3263E-04

1.7173E-01

-3.2485E-02

-3.4733E-03

9.5691E-03

-3.3192E-04

Abm

2.2444E-04

3.9606E-02

1.3682E-01

3.7372E-03

---

---

Abb

-2.5210E-03

-1.7256E+00

-9.1884E-02

3.4029E+00

-1.2368E-01

5.1002E-03

Amm

1.0115E+00

9.2952E-02

5.6457E-01

-5.7580E-02

4.4685E-03

-1.3837E-04

Amb

-4.0142E-04

1.8879E-01

-3.3723E-02

-1.6795E-02

1.3916E-02

-5.4210E-04

Abm

-1.6209E-03

3.5717E-02

8.3687E-02

5.8009E-03

---

---

Abb

-1.2900E-02

-2.7878E+00

-2.3967E-01

5.9592E+00

-1.7998E-01

1.0092E-02

100.0

Not for Resale

Ri t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.6 Parameters For A Through-Wall Longitudinal Crack In A Cylinder Subject To A Through-Wall Membrane And Bending Stress

Notes: 1. The equations to determine the coefficients are shown below. 0.5

(C.316)

C0 + C1l + C2 l2 Amb = 10 . + C3l + C4 l2 + C5l3

(C.317)

C0 + C1l 1.0 + C2 l + C3l2

(C.318)

Abm =

LM C + C l + C l OP N10. + C l + C l + C l Q 2

0

1

2

3

2.

2

4

(C.319)

3

5


Ri t .

C-70

--``````-`-`,,`,,`,`,,`---

Abb = exp


Amm = C0 + C1l + C2 l2 + C3l3 + C4 l4 + C5l5

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

C0

C1

C2

C3

C4

C5

C6

C7

3.0

Amm

1.0028E+00

2.7582E+00

-1.2070E+00

2.8138E-01

3.0813E-03

0.0000E+00

---

---

Amb

-6.6164E-05

3.0309E-01

-1.4663E-01

2.2028E-02

-2.5285E-03

0.0000E+00

0.0000E+00

0.0000E+00

Abm

3.5656E-03

1.6678E-01

-1.5113E-01

7.4153E-02

-1.5761E-02

1.1992E-03

---

---

Abb

9.8852E-01

4.5685E-01

3.3905E-02

---

---

---

---

---

Amm

1.0739E+00

2.1685E+00

-1.8605E+00

8.2538E-01

-1.4428E-01

9.8408E-03

---

---

Amb

1.2605E-02

2.2302E-01

-9.9866E-02

1.0074E-02

-3.3652E-04

-4.1729E-05

0.0000E+00

0.0000E+00

Abm

3.4529E-03

1.0410E-01

-5.7207E-02

1.7317E-02

-2.4783E-03

1.3821E-04

---

---

Abb

1.0027E+00

5.4578E-01

9.8971E-03

---

---

---

---

---

Amm

1.0036E+00

2.4813E-01

-2.1406E-02

3.7600E-02

-5.9734E-03

4.3077E-04

---

---

Amb

-2.0844E-03

1.5342E-01

-4.7168E-02

-1.7705E-03

9.4262E-04

-5.9505E-05

0.0000E+00

0.0000E+00

Abm

2.7372E-03

6.2194E-02

-2.4400E-02

4.8158E-03

-4.5005E-04

-1.6502E-05

---

---

Abb

1.0194E+00

6.5401E-01

-6.3194E-02

---

---

---

---

---

Amm

9.9890E-01

2.7663E-01

-2.4096E-02

2.1601E-02

-2.4683E-03

1.1871E-04

---

---

Amb

-8.3750E-03

1.6289E-01

-6.4962E-02

6.9647E-03

-3.4695E-04

5.7865E-06

0.0000E+00

0.0000E+00

Abm

2.3510E-05

4.5877E-02

-1.5305E-02

2.3741E-03

-1.6880E-04

4.5137E-06

---

---

Abb

1.0223E+00

7.2031E-01

-9.6237E-02

---

---

---

---

---

5.0

10.0

20.0

C-71

Not for Resale

Parameter


Ri t

--``````-`-`,,`,,`,`,,`---

Table C.7 Parameters For A Through-Wall Circumferential Crack In A Cylinder Subject To A Through-Wall Membrane And Bending Stress

--``````-`-`,,`,,`,`,,`---

Parameter

C0

C1

C2

C3

C4

C5

C6

C7

50.0

Amm

1.0066E+00

1.7032E-01

5.7435E-03

9.1296E-03

-8.4183E-04

2.6105E-05

---

---

Amb

-2.3750E-03

1.1858E-01

-4.2486E-02

3.8824E-03

-1.6389E-04

2.4611E-06

0.0000E+00

0.0000E+00

Abm

-1.2419E-03

3.4069E-02

-1.0262E-02

1.4635E-03

-9.6627E-05

2.3442E-06

---

---

Abb

1.0083E+00

8.1527E-01

-1.4042E-01

---

---

---

---

---

Amm

1.0312E+00

1.2255E-01

2.2317E-02

-2.4056E-04

0.0000E+00

0.0000E+00

---

---

Amb

-3.7251E-03

1.4018E-01

-6.0781E-02

8.1631E-03

-5.8354E-04

2.3247E-05

-4.8521E-07

4.1338E-09

Abm

-6.6962E-04

2.2863E-02

-5.9246E-03

7.0949E-04

-3.8222E-05

7.1346E-07

---

---

Abb

1.0021E+00

7.5257E-01

-1.2114E-01

---

---

---

---

---

100.0

Not for Resale

Ri t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.7 Parameters For A Through-Wall Circumferential Crack In A Cylinder Subject To A Through-Wall Membrane And Bending Stress

Notes: 1. The equations to determine the coefficients are shown below. (C.320)

Amb = C0 + C1l + C2 l2 + C3l3 + C4 l4 + C5l5 + C6l6 + C7 l7

(C.321)

Abm = C0 + C1l + C2 l2 + C3l3 + C4 l4 + C5l5

(C.322)

Abb = 2.

0.5

1.0 C0 + C1l + C2 l1.5


(C.323)

Ri t .

C-72


Amm = C0 + C1l + C2 l2 + C3l3 + C4 l4 + C5l5

C0

C1

C2

C3

C4

3.0

Ammgb

1.0017E+00

4.5697E-02

3.2958E-01

-1.6672E-01

2.6896E-02

Ambgb

-5.1419E-01

-3.5625E-01

-1.9591E-02

9.3757E-01

5.2087E-01

Ammgb

9.8878E-01

-3.6966E-01

2.4131E-01

-3.0143E-02

2.7631E-03

Ambgb

-5.0077E-01

2.8743E-01

-1.9205E-01

3.8470E-01

5.0601E-01

Ammgb

9.9235E-01

-6.4839E-02

8.7038E-02

-3.8788E-03

3.9153E-04

Ambgb

3.8004E-01

-2.8319E-04

-4.5114E-02

-3.9183E-02

-3.7925E-01

Ammgb

9.9979E-01

-1.1869E-01

1.5641E-01

-1.5488E-02

6.2630E-04

Ambgb

5.6688E-02

-3.2323E-02

-2.9781E-02

1.2962E-01

-5.2759E-02

Ammgb

9.9447E-01

1.5974E-03

9.3260E-02

-6.8911E-03

2.1016E-04

Ambgb

-5.8885E-02

-1.4501E-01

2.2014E-03

3.0541E-01

4.7178E-02

Ammgb

9.9360E-01

5.1424E-02

7.0378E-02

-3.9808E-03

9.1515E-05

Ambgb

7.1020E-01

-1.2457E-02

-6.6334E-04

-3.4158E-01

-7.0521E-01

5.0

10.0

20.0

50.0

100.0

Notes: 1. The equations to determine the coefficients are shown below.

Ammgb = C0 + C1l + C2 l2 + C3l3 + C4 l4

0.5

(C.324)

Ambgb = C0 + C1l + C2 l1.5 + C3l0.5 + C4 exp - l 2.


(C.325)

Ri t . C-73

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Not for Resale

Parameter


Ri t

--``````-`-`,,`,,`,`,,`---

Table C.8 Parameters For A Through-Wall Circumferential Crack In A Cylinder Subject To A Net Section Axial Force And Bending Moment

0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8

G0

5

10

20

40

60

1.12 1.24264 1.564166 1.998216 2.531611 1.12 1.307452 1.8332 2.734052 3.940906 1.12 1.332691 1.957764 3.223438 5.543784 1.12 1.345621 2.028188 3.573882 7.388754 1.12 1.351845 2.064088 3.780308 9.046439 1.12 1.353978 2.076759 3.85725 9.818255

G1 0.682 0.729765 0.853231 1.018826 1.247276 0.682 0.753466 0.954938 1.28757 1.739955 0.682 0.763153 1.002123 1.466106 2.300604 0.682 0.768292 1.028989 1.594673 2.946567 0.682 0.770679 1.042414 1.670205 3.526527 0.682 0.771359 1.04731 1.698243 3.796811

G2 0.5245 0.551698 0.620581 0.712669 0.849225 0.5245 0.564298 0.676408 0.857474 1.10621 0.5245 0.569758 0.702473 0.953655 1.398958 0.5245 0.57256 0.717256 1.023108 1.736182 0.5245 0.573795 0.724534 1.063426 2.038831 0.5245 0.574252 0.727245 1.078613 2.179989

Outside Surface

G3 0.4404 0.458464 0.503412 0.563725 0.657627 0.4404 0.466913 0.539874 0.656596 0.81823 0.4404 0.470495 0.556857 0.718048 1.000682 0.4404 0.472331 0.566433 0.762465 1.211533 0.4404 0.473108 0.571046 0.788181 1.400363 0.4404 0.473441 0.57288 0.797885 1.488012

G4 0.379075 0.392759 0.427226 0.472892 0.548973 0.379075 0.398757 0.454785 0.54072 0.661258 0.379075 0.401459 0.467621 0.585672 0.789201 0.379075 0.402984 0.475028 0.618437 0.936978 0.379075 0.403649 0.478588 0.637578 1.069409 0.379075 0.403767 0.479971 0.644619 1.131273

C-74

G0 1.12 1.299805 1.694919 2.320192 3.222963 1.12 1.324199 1.861734 2.864663 4.412961 1.12 1.338976 1.964321 3.270363 5.839919 1.12 1.348153 2.028188 3.584289 7.522466 1.12 1.352815 2.05888 3.783314 9.072502 1.12 1.354559 2.075495 3.85861 9.81499

G1 0.682 0.751137 0.902767 1.136251 1.484864 0.682 0.759716 0.964913 1.335823 1.903704 0.682 0.765213 1.004607 1.483681 2.403771 0.682 0.769051 1.028734 1.598763 2.992945 0.682 0.770943 1.039137 1.671252 3.534701 0.682 0.771574 1.046684 1.698758 3.795084

G2 0.5245 0.56329 0.647816 0.775993 0.972037 0.5245 0.567636 0.681357 0.883295 1.19155 0.5245 0.57077 0.703748 0.963144 1.452694 0.5245 0.572972 0.717129 1.025243 1.760192 0.5245 0.573978 0.721589 1.064248 2.042477 0.5245 0.574391 0.726942 1.079099 2.177882

G3 0.4404 0.465897 0.521143 0.604398 0.733888 0.4404 0.468987 0.542909 0.673156 0.871484 0.4404 0.471069 0.557628 0.724069 1.034485 0.4404 0.472583 0.566281 0.76384 1.226597 0.4404 0.473214 0.56869 0.78882 1.402231 0.4404 0.473496 0.572615 0.798289 1.486756

G4 0.379075 0.398423 0.440705 0.502437 0.600773 0.379075 0.400407 0.457058 0.553201 0.697846 0.379075 0.40185 0.468296 0.590347 0.812508 0.379075 0.403085 0.474824 0.619628 0.947337 0.379075 0.403667 0.477008 0.637814 1.070735 0.379075 0.403822 0.479723 0.644759 1.130544

Not for Resale

2

Inside Surface


a/t

--``````-`-`,,`,,`,`,,`---

Ri/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.9 Influence Coefficients For a Longitudinal Infinite Length Surface Crack in a Cylindrical Shell

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.9 Influence Coefficients For a Longitudinal Infinite Length Surface Crack in a Cylindrical Shell Inside Surface

G0 100

300

1000

Notes:

0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8

1.12 1.355721 2.088097 3.924228 10.55482 1.12 1.357654 2.098124 3.984819 11.43182 1.12 1.362669 2.107481 4.023909 11.68545

G1 0.682 0.772039 1.051685 1.722783 4.054112 0.682 0.772719 1.055171 1.744473 4.361182 0.682 0.775768 1.059637 1.759944 4.44755

Intepolation of the influence coefficients,

G2 0.5245 0.574618 0.729765 1.091988 2.314531 0.5245 0.575074 0.731561 1.10346 2.474754 0.5245 0.577169 0.734602 1.112458 2.518103

Outside Surface

G3 0.4404 0.473607 0.574481 0.806497 1.572029 0.4404 0.47405 0.575621 0.813729 1.671906 0.4404 0.475763 0.578123 0.819725 1.697986

G4 0.379075 0.403962 0.481203 0.650855 1.189801 0.379075 0.404119 0.481987 0.656089 1.260057 0.379075 0.405555 0.483688 0.660648 1.278424

G0 1.12 1.355914 2.086534 3.923337 10.53491 1.12 1.357654 2.098131 3.988986 11.41804 1.12 1.362492 2.106159 4.023909 11.90919

G1 0.682 0.772205 1.050936 1.722585 4.046475 0.682 0.772836 1.05542 1.746621 4.35619 0.682 0.77543 1.059018 1.759732 4.532179

G2 0.5245 0.574709 0.729261 1.091908 2.309298 0.5245 0.57512 0.73174 1.104648 2.471838 0.5245 0.577078 0.734066 1.112458 2.56558

G3 0.4404 0.473663 0.574252 0.806497 1.569106 0.4404 0.47405 0.575826 0.814588 1.670314 0.4404 0.475707 0.5777 0.819832 1.730506

G4 0.379075 0.404056 0.480917 0.650876 1.187672 0.379075 0.404212 0.482184 0.656975 1.258819 0.379075 0.40532 0.483457 0.660479 1.30138

Not for Resale

a/t

Gi , may be used for intermediate values of Ri t and a t .

--``````-`-`,,`,,`,`,,`---

C-75


Ri/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.10 Influence Coefficients For a Circumferential 360°° Surface Crack in a Cylindrical Shell

G0 2

5

10

20

40

60

0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8

1.12 1.130257 1.231783 1.418311 1.821886 1.12 1.210829 1.437161 1.764286 2.272892 1.12 1.254559 1.578769 2.054427 2.691796 1.12 1.286308 1.700591 2.354964 3.202288 1.12 1.308916 1.800221 2.649761 3.822034 1.12 1.318924 1.848413 2.813119 4.237503

G1 0.682 0.688023 0.730219 0.803088 0.99939 0.682 0.718943 0.807345 0.928708 1.156841 0.682 0.735816 0.860586 1.033913 1.302652 0.682 0.748129 0.906527 1.143036 1.480478 0.682 0.756949 0.944166 1.250285 1.696662 0.682 0.760855 0.962422 1.309799 1.84173

G2 0.5245 0.529018 0.553662 0.588954 0.719326 0.5245 0.546312 0.596196 0.656426 0.801593 0.5245 0.555784 0.625575 0.712856 0.877596 0.5245 0.562711 0.650941 0.771413 0.970278 0.5245 0.567677 0.671752 0.829036 1.083009 0.5245 0.569883 0.681854 0.861033 1.158696

Outside Surface

G3 0.4404 0.443165 0.459862 0.476433 0.576191 0.4404 0.454558 0.487609 0.519455 0.627635 0.4404 0.46081 0.506771 0.555383 0.675063 0.4404 0.465393 0.523329 0.592683 0.732879 0.4404 0.468679 0.536926 0.629406 0.803222 0.4404 0.470144 0.543524 0.649812 0.850454

G4 0.379075 0.381841 0.395293 0.416283 0.49261 0.379075 0.390464 0.415918 0.447584 0.528369 0.379075 0.395216 0.43019 0.47372 0.561238 0.379075 0.398716 0.442578 0.500911 0.601399 0.379075 0.401251 0.452764 0.527751 0.650398 0.379075 0.402374 0.45773 0.54269 0.683358

C-76

G0 1.12 1.24004 1.458299 1.796008 2.476159 1.12 1.263202 1.55417 1.966243 2.610699 1.12 1.28301 1.646171 2.176175 2.89526 1.12 1.301318 1.738126 2.426798 3.326522 1.12 1.316699 1.820527 2.691258 3.900213 1.12 1.32419 1.862482 2.842912 4.29851

G1 0.682 0.716765 0.798913 0.939337 1.217541 0.682 0.726351 0.835957 1.002411 1.26587 0.682 0.734415 0.871503 1.080225 1.36673 0.682 0.74179 0.906946 1.172917 1.518951 0.682 0.747945 0.938621 1.270496 1.7209 0.682 0.750929 0.954704 1.32636 1.860923

G2 0.5245 0.531545 0.576725 0.66837 0.83003 0.5245 0.537074 0.597311 0.702694 0.855722 0.5245 0.541694 0.617078 0.74504 0.908821 0.5245 0.545907 0.636767 0.79541 0.988743 0.5245 0.549407 0.654343 0.848362 1.0946 0.5245 0.551104 0.663258 0.878647 1.167928

G3 0.4404 0.432347 0.461617 0.534817 0.64399 0.4404 0.436025 0.474989 0.556948 0.660227 0.4404 0.439092 0.48785 0.584239 0.693565 0.4404 0.441883 0.500662 0.616676 0.74364 0.4404 0.444194 0.512094 0.650736 0.809896 0.4404 0.445314 0.517887 0.670199 0.855764

G4 0.379075 0.382879 0.404945 0.449742 0.536275 0.379075 0.385915 0.415406 0.466155 0.548031 0.379075 0.388405 0.425443 0.48642 0.571807 0.379075 0.390643 0.435407 0.510449 0.607331 0.379075 0.392491 0.444266 0.53562 0.654152 0.379075 0.39338 0.448742 0.549981 0.686511

Not for Resale

Inside Surface


a/t

--``````-`-`,,`,,`,`,,`---

Ri/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.10 Influence Coefficients For a Circumferential 360°° Surface Crack in a Cylindrical Shell

G0 100

300

1000

Notes:

0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8 0.0 0.2 0.4 0.6 0.8

1.12 1.328921 1.899528 3.004384 4.812997 1.12 1.326772 1.963785 3.332548 6.166579 1.12 1.322217 1.985705 3.550561 7.704234

G1 0.682 0.764758 0.981795 1.379555 2.042848 0.682 0.756593 0.994898 1.491534 2.493763 0.682 0.749276 0.991993 1.553001 2.997325


G2 0.5245 0.572095 0.692586 0.898565 1.263627 0.5245 0.563926 0.692884 0.957864 1.483156 0.5245 0.557422 0.684695 0.979529 1.722909

Outside Surface

G3 0.4404 0.471607 0.550532 0.673759 0.915957 0.4404 0.464829 0.546635 0.713772 1.041092 0.4404 0.459379 0.537194 0.719751 1.174144

G4 0.379075 0.403497 0.463005 0.560242 0.729154 0.379075 0.397395 0.460636 0.584192 0.819169 0.379075 0.392453 0.453928 0.589763 0.914488

G0 1.12 1.332125 1.908312 3.023794 4.859478 1.12 1.327958 1.967788 3.340673 6.185694 1.12 1.322614 1.988345 3.554007 7.714443

G1 0.682 0.754093 0.97225 1.392928 2.057938 0.682 0.75694 0.996347 1.493877 2.499017 0.682 0.749276 0.992918 1.554127 3.000386


C-77

G2 0.5245 0.552893 0.672981 0.914706 1.271054 0.5245 0.564112 0.69383 0.95905 1.485806 0.5245 0.557516 0.68527 0.980154 1.724431

G3 0.4404 0.446495 0.524206 0.693364 0.920244 0.4404 0.464942 0.547114 0.714507 1.042477 0.4404 0.459436 0.537439 0.720115 1.175261

G4 0.379075 0.394324 0.453612 0.567059 0.73193 0.379075 0.397435 0.460995 0.584442 0.81955 0.379075 0.392373 0.45414 0.589975 0.914895

Not for Resale

Inside Surface


a/t

--``````-`-`,,`,,`,`,,`---

Ri/t

Table C.11 Influence Coefficients For A Longitudinal Semi-Elliptical Surface Crack In A Cylinder

1

a/t 0.2 0.4 0.6 0.8

5

2

0.2 0.4 0.6 0.8

5

4

0.2 0.4 0.6 0.8

5

8

0.2 0.4 0.6 0.8

Inside Crack

Gi G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1

A0 1.20886 0.190256 1.249921 0.20501 1.328079 0.228104 1.429543 0.253926 0.883501 0.136141 0.968885 0.16423 1.124087 0.212063 1.31251 0.268793 0.620338 0.079509 0.721567 0.111933 0.904838 0.167658 1.186653 0.248998 0.413508 0.037224 0.490994 0.063093 0.62496 0.102289 0.850071 0.16566

A1 -0.87917 0.582508 -0.88353 0.564001 -1.04221 0.530502 -1.23629 0.494401 -0.55198 0.357504 -0.68414 0.317757 -1.07684 0.181392 -1.36031 0.062838 0.071697 0.244065 0.03749 0.259261 -0.13156 0.228912 -0.83428 0.080776 1.246405 0.312765 1.509877 0.364502 1.83259 0.466324 1.949 0.513359

A2 1.908351 0.723634 1.568502 0.708493 1.778359 0.676303 2.060968 0.776549 2.502802 1.022426 2.735877 1.088563 3.870392 1.47873 4.415758 1.859483 3.528479 1.676127 3.922691 1.64634 4.665482 1.775171 8.720578 2.465262 1.003186 1.451216 0.587689 1.582843 0.001321 1.473855 1.07588 1.730369

A3 -1.59472 -0.57144 -0.35878 -0.42156 -0.60332 -0.20747 -0.95738 -0.53106 -1.56182 -0.39111 -1.42013 -0.3372 -2.79876 -1.01907 -3.91515 -1.90252 -6.74503 -1.49697 -7.42224 -1.22628 -7.68409 -1.05788 -18.2575 -2.28643 -3.73475 -0.00297 -2.85874 -0.60876 -0.0015 -0.21497 -0.84026 -0.44172

A4 -0.86218 -1.23523 -2.82016 -1.51891 -2.45056 -1.83359 -1.81359 -1.02843 -2.91246 -1.28448 -3.87765 -1.58464 -3.8803 -0.75805 -1.60218 0.690165 4.888795 0.045149 5.354151 -0.59932 3.540441 -1.41265 18.40693 -0.37516 2.955754 -3.31484 2.811304 -1.84853 -1.50207 -1.93536 -2.23858 -1.90456

Outside Crack A5 2.308493 1.696861 3.771064 1.920712 3.360651 2.110526 2.614885 1.282325 4.469889 1.23202 5.55022 1.558331 6.763531 0.996139 4.366669 -0.10903 -0.94681 0.152257 -0.97861 0.782393 1.666319 1.726116 -8.86857 1.70208 -0.31659 3.316005 -1.12026 1.843525 1.64144 1.513131 3.187732 2.008435

A6 -1.05811 -0.65075 -1.47563 -0.71473 -1.29705 -0.75287 -0.97772 -0.46107 -1.75966 -0.3788 -2.14437 -0.49333 -2.78604 -0.34361 -1.87109 -0.05174 -0.29803 -0.0086 -0.37108 -0.2337 -1.46588 -0.60335 1.46455 -0.87182 -0.39471 -1.09458 0.02932 -0.59356 -0.68781 -0.43852 -1.44993 -0.85893

A0 1.257122 0.201921 1.339581 0.227594 1.47329 0.266094 1.644755 0.314082 0.920174 0.142889 1.037315 0.182769 1.248321 0.246609 1.531283 0.331258 0.633611 0.081884 0.742964 0.115178 0.93711 0.172681 1.26249 0.26029 0.413579 0.036026 0.470385 0.05324 0.56991 0.079906 0.743321 0.12461

A1 -0.93957 0.576141 -0.99952 0.560871 -1.20859 0.527913 -1.45922 0.439035 -0.63483 0.378221 -0.7658 0.301612 -1.12732 0.194699 -1.4214 0.071817 0.080973 0.236468 0.037831 0.265635 -0.02558 0.271719 -0.75771 0.243263 1.258662 0.299361 1.554191 0.36759 1.774176 0.429348 1.817277 0.467508

A2 1.876918 0.769398 1.615216 0.686725 1.82546 0.595258 1.973627 0.820631 2.922963 0.921394 3.186655 1.249469 4.262086 1.499603 4.990615 1.941243 3.669772 1.819398 4.501452 1.791545 5.140838 1.871117 10.5934 1.987065 1.196651 1.595427 0.546117 1.561673 0.846372 1.702653 2.797614 2.052894

A3 -1.1806 -0.82843 0.078266 -0.42153 -0.13244 -0.0963 -0.42616 -0.75539 -2.42933 -0.02305 -2.05649 -0.65508 -2.93426 -0.77177 -4.36837 -1.7261 -6.78458 -1.86889 -8.48699 -1.42703 -7.02478 -0.65469 -18.9882 1.180894 -3.93632 -0.34338 -1.3287 -0.15724 0.161191 -0.12138 0.275369 0.305849

A4 -1.73545 -0.67939 -3.99065 -1.44098 -3.66819 -1.84237 -2.69886 -0.64827 -1.8998 -1.8909 -3.5112 -1.21746 -4.69252 -1.45335 -2.36111 -0.11985 4.632099 0.653508 6.826836 -0.25618 1.513846 -2.19146 16.24573 -6.9845 3.13168 -2.66392 0.196127 -2.25283 -0.91925 -1.22111 -1.43262 -0.9948

--``````-`-`,,`,,`,`,,`---

C-78 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A5 3.104367 1.174647 4.959937 1.825733 4.592999 2.031386 3.294735 0.993076 3.834176 1.698719 5.52792 1.311973 7.808444 1.645282 5.141342 0.569928 -0.62982 -0.36532 -2.26387 0.399723 3.036568 2.114517 -7.73996 6.512576 -0.50924 2.678537 0.61567 1.814452 -0.50624 0.043347 -3.1035 -1.41184

A6 -1.32806 -0.4706 -1.90492 -0.67968 -1.73969 -0.70863 -1.15345 -0.36658 -1.59825 -0.5177 -2.19068 -0.42485 -3.17413 -0.55519 -1.96029 -0.19285 -0.42215 0.15693 0.05788 -0.09259 -1.76288 -0.6484 1.70988 -2.07453 -0.31706 -0.87193 -0.43574 -0.51898 0.36412 0.19482 2.18154 0.92457

Not for Resale

5

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\ --``````-`-`,,`,,`,`,,`---


16

a/t 0.2 0.4 0.6 0.8

5

32

0.2 0.4 0.6 0.8

10

1

0.2 0.4 0.6 0.8

10

2

0.2 0.4 0.6 0.8

Inside Crack


A0 0.281786 0.014245 0.328548 0.027006 0.39157 0.051503 0.526145 0.078574 0.234422 0.00852 0.231658 0.009042 0.263718 0.013281 0.349723 0.023558 1.216952 0.191645 1.269744 0.211284 1.356379 0.233837 1.458297 0.258345 0.892888 0.13783 0.979756 0.168328 1.139917 0.215653 1.310495 0.267352

A1 2.137082 0.301888 2.495861 0.428653 3.225085 0.417711 3.240597 0.657753 1.302174 0.764636 3.017434 0.392342 3.305552 0.52915 2.119214 0.51035 -0.84742 0.60032 -0.91837 0.532083 -1.102 0.53475 -1.30791 0.502809 -0.58781 0.362759 -0.65834 0.302505 -1.0507 0.189 -1.06679 0.11947

A2 -1.24025 1.929727 -2.0243 1.428912 -4.99454 2.347866 -1.38151 1.401751 11.11715 -1.66462 -3.67391 1.556576 -4.33855 0.817571 8.073903 1.502696 1.630538 0.630655 1.638439 0.927763 1.863836 0.637198 2.232862 0.674663 2.692181 0.974948 2.590596 1.206564 3.709622 1.44474 2.867532 1.517016

A3 -1.39795 -1.72416 0.861995 0.00996 12.18559 -3.08262 4.151931 1.153303 -54.4204 10.73457 3.348696 -0.1944 9.732845 2.972435 -27.5875 1.446778 -0.73396 -0.37163 -0.46752 -1.17255 -0.59927 -0.16199 -1.60024 -0.2815 -2.01658 -0.18183 -0.9807 -0.70306 -2.27682 -0.88546 -0.60202 -0.8642

A4 3.355648 -0.28644 2.474475 -2.23892 -13.4289 4.500277 0.51094 -1.68722 104.2185 -21.2424 3.495197 -1.23976 -4.94095 -4.46624 62.88392 1.43129 -2.17862 -1.4362 -2.73676 -0.24592 -2.74663 -1.81371 -0.64096 -1.38311 -2.30634 -1.68105 -4.50229 -0.99253 -4.76502 -1.03017 -5.16977 -1.03717

Outside Crack A5 -2.52638 0.800089 -4.06172 1.714364 5.681319 -4.83766 -8.14143 -0.64381 -90.7901 17.82151 -8.35829 0.429006 -4.65141 1.445697 -66.409 -6.03506 3.298831 1.782784 3.761656 0.883065 3.778085 2.042664 1.61676 1.55041 4.043883 1.5755 5.967682 1.083679 7.462531 1.239326 6.107101 1.24744

C-79

A6 0.61596 -0.31173 1.56065 -0.49643 -0.75293 1.7189 4.3185 0.50166 29.6224 -5.66166 3.7094 -0.02577 3.22187 -0.08594 24.3061 2.76985 -1.34968 -0.65998 -1.48715 -0.38975 -1.47009 -0.71951 -0.65026 -0.54086 -1.63793 -0.49092 -2.25126 -0.34607 -2.99086 -0.42196 -2.13082 -0.44529

A0 0.276715 0.012206 0.305204 0.021202 0.336457 0.031569 0.412365 0.041877 0.208156 0.00726 0.22 0.009106 0.234806 0.014519 0.286568 0.02069 1.247876 0.199397 1.323187 0.22293 1.445621 0.258809 1.597398 0.298889 0.913619 0.144247 1.028051 0.179683 1.233426 0.243496 1.503918 0.32149

A1 2.128015 0.280092 2.287508 0.30138 2.814142 0.351061 2.900861 0.601879 2.44627 0.609298 2.88817 0.345361 3.226181 0.510298 2.483466 0.640047 -0.93364 0.581625 -0.99211 0.564396 -1.20648 0.517424 -1.41509 0.456994 -0.62446 0.328767 -0.76371 0.312776 -1.13486 0.165645 -1.5034 0.05042

A2 -1.08549 2.027475 -0.90017 2.090446 -2.97035 2.242216 -0.88305 0.824716 -0.83143 -0.40903 -3.03279 1.71429 -4.48513 0.578838 4.14496 -0.02292 1.929976 0.726541 1.699324 0.681406 2.015609 0.656544 1.867267 0.718112 2.883441 1.227904 3.190679 1.158848 4.141111 1.626148 5.133579 1.957428

A3 -1.29971 -1.82842 -0.46605 -1.64203 9.564404 -1.90238 8.417456 3.981133 -6.23275 6.315998 2.777877 -0.53117 12.43305 3.968732 -13.5058 6.007267 -1.44095 -0.65183 -0.32373 -0.42391 -1.01478 -0.23057 -0.28309 -0.41644 -2.40875 -0.95574 -2.31854 -0.40622 -2.731 -1.22833 -5.1827 -1.9407

A4 2.900096 -0.08398 3.313116 0.634491 -9.96224 3.398886 -2.8151 -3.2906 15.21692 -13.4433 3.327422 -0.3691 -9.99646 -5.3534 45.15273 -3.11476 -1.23285 -1.0199 -3.22173 -1.41641 -1.95192 -1.71704 -2.74227 -1.20084 -1.84251 -0.45117 -2.85329 -1.61005 -4.96574 -0.71668 -1.02134 0.283218

A5 -2.13402 0.564767 -4.31183 -0.75595 2.710794 -4.57779 -9.69098 -1.57301 -14.1766 11.2371 -7.74048 -0.51184 -0.21697 1.823369 -55.4237 -3.79348 2.658565 1.479968 4.280673 1.794457 3.060946 1.997206 3.239174 1.439061 3.743365 0.605716 4.891191 1.635194 8.056155 1.09129 4.281751 0.302343

A6 0.49288 -0.22734 1.52914 0.27459 0.10816 1.68744 5.56669 1.1215 4.67049 -3.54667 3.39398 0.30258 1.58756 -0.23071 21.127 2.11792 -1.17902 -0.57368 -1.6779 -0.66758 -1.22649 -0.71588 -1.12129 -0.50911 -1.55862 -0.19332 -1.96747 -0.52929 -3.25817 -0.39306 -1.76362 -0.13299

Not for Resale

5

c/a


R/t


0.2 0.4 0.6 0.8

10

8

0.2 0.4 0.6 0.8

10

16

0.2 0.4 0.6 0.8

10

32

0.2 0.4 0.6 0.8

Inside Crack


A0 0.622923 0.078828 0.726924 0.114139 0.913694 0.169041 1.228561 0.260576 0.411683 0.037768 0.490083 0.062519 0.638346 0.107879 0.910604 0.182783 0.283738 0.013856 0.329482 0.029013 0.40588 0.056926 0.590872 0.100443 0.240586 0.008752 0.236202 0.010315 0.280327 0.017664 0.410845 0.045914

A1 0.085935 0.270868 0.03314 0.228272 -0.11282 0.236798 -1.38872 -0.11803 1.298795 0.29322 1.579706 0.379597 1.889679 0.441806 1.677832 0.531662 2.075445 0.304124 2.554728 0.402993 3.366222 0.445165 3.531446 0.713442 1.114239 0.532366 3.023283 0.397102 3.510681 0.638312 2.7858 0.644114

A2 3.456516 1.491305 4.054108 1.90943 4.777037 1.777582 13.42344 4.124364 0.672366 1.603725 0.245691 1.500782 0.165488 1.809349 4.174131 2.001115 -0.65585 1.915718 -2.2095 1.691276 -5.14829 2.394536 -0.69292 1.836374 12.87065 0.340876 -3.37463 1.637174 -4.3633 0.336248 7.19999 1.810985

A3 -6.38617 -0.84017 -7.67588 -2.05718 -7.7684 -0.92196 -33.6089 -7.69197 -2.53205 -0.46247 -1.41693 -0.22154 0.140547 -1.06009 -7.62741 -0.72387 -3.34522 -1.64226 1.831682 -0.77847 13.51345 -2.9719 3.314025 0.193019 -60.8235 3.484481 2.651422 -0.48265 9.283177 4.673656 -24.9664 0.15005

A4 4.201936 -1.06538 5.625477 0.7745 3.175614 -1.84201 42.33036 8.09939 0.941514 -2.56883 0.133055 -2.55344 -2.88878 -0.91042 2.695721 -2.5544 6.605211 -0.40547 0.537894 -0.95906 -16.6551 4.132803 -0.24954 -0.53885 115.5125 -8.57898 4.269107 -0.6416 -2.72031 -7.02999 63.83854 5.630371

Outside Crack A5 -0.36255 1.048442 -1.15881 -0.34252 2.132441 2.142969 -27.5 -4.96363 1.268497 2.715589 1.097961 2.405621 3.137433 0.783547 2.328333 2.79982 -5.17095 0.867548 -2.44288 0.651349 8.667153 -4.57752 -7.11013 -1.75087 -100.304 7.27117 -8.69801 -0.13767 -7.44743 3.3065 -72.4905 -11.3292

A6 -0.48588 -0.28749 -0.31802 0.12233 -1.60805 -0.73488 7.27344 1.22763 -0.87416 -0.90877 -0.65444 -0.76134 -1.14318 -0.1968 -1.61725 -1.03189 1.44608 -0.32513 1.06941 -0.15108 -1.72935 1.67277 4.11188 0.99171 32.6873 -2.29978 3.71981 0.16533 4.27352 -0.64 27.6356 4.91916

A0 0.631976 0.081649 0.747485 0.118095 0.966154 0.183027 1.334144 0.290713 0.417691 0.038865 0.488345 0.057924 0.614093 0.095637 0.860609 0.164364 0.277532 0.013904 0.313775 0.024357 0.360061 0.037143 0.469443 0.059849 0.205549 0.007795 0.22465 0.014875 0.249521 0.020047 0.340424 0.030666

A1 0.082077 0.241582 0.042511 0.248488 -0.13532 0.240795 -0.93928 0.022228 1.191739 0.251098 1.467644 0.395493 1.827441 0.449768 1.870742 0.463337 2.179749 0.260557 2.325856 0.307205 2.888485 0.420124 3.330519 0.706503 2.576379 0.452516 2.939734 0.376324 3.415958 0.625843 2.71013 0.685686

A2 3.626157 1.763434 4.371798 1.906422 5.746649 2.033367 11.45855 3.538267 1.706782 1.97709 1.404314 1.408514 1.076742 1.787567 3.999869 2.666458 -1.44387 2.239501 -0.85799 2.181436 -2.61053 2.006838 -1.83469 0.763297 -1.92003 0.99483 -3.08715 1.587636 -4.94048 -0.0433 5.474106 0.691668

A3 -6.74195 -1.69728 -8.19448 -1.90573 -9.36252 -1.28834 -22.4475 -4.29767 -5.82613 -1.68253 -4.499 0.379375 -0.61192 -0.28599 -2.22135 -1.0454 -0.18465 -2.63784 -0.90403 -1.98163 8.000811 -1.05509 11.80685 4.431982 -2.33839 1.12954 2.431032 -0.21476 13.04232 5.959214 -20.2718 2.553542

--``````-`-`,,`,,`,`,,`---

C-80

A4 4.645163 0.360897 6.253803 0.552677 4.907828 -1.37144 20.24804 1.537866 6.385956 -0.43863 5.363475 -3.37945 -0.6954 -1.52033 -1.499 -0.43379 1.06662 1.303768 4.276652 1.166317 -6.66597 2.069572 -5.54196 -3.15695 8.461898 -4.30424 4.869024 -0.69793 -8.3791 -8.13215 65.82877 5.934145

A5 -0.67953 -0.1198 -1.68987 -0.24484 0.758849 1.650357 -9.50951 0.162356 -3.16469 0.904692 -3.42403 2.873519 -0.14056 0.547265 -1.43661 -1.30645 -0.6499 -0.56009 -5.17457 -1.16787 -0.3626 -3.64218 -10.7636 -2.85922 -8.54495 3.594269 -9.54299 -0.3343 -3.16601 3.813733 -78.8076 -13.208

A6 -0.39553 0.07918 -0.14273 0.11074 -1.13909 -0.53968 1.99072 -0.19626 0.51634 -0.32458 0.80524 -0.87404 0.21398 0.026 1.69021 0.94296 0.02987 0.1234 1.8051 0.40256 1.12298 1.43688 6.8425 1.88931 2.86471 -1.10632 4.05406 0.25184 2.78636 -0.85041 29.7605 5.41846

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

4

a/t

Not for Resale

10

c/a


R/t


1

a/t 0.2 0.4 0.6 0.8

20

2

0.2 0.4 0.6 0.8

20

4

0.2 0.4 0.6 0.8

20

8

0.2 0.4 0.6 0.8

Inside Crack


A0 1.219955 0.19326 1.28226 0.211716 1.370374 0.237955 1.47406 0.262095 0.896041 0.139444 0.987595 0.170315 1.153521 0.218965 1.338794 0.27042 0.624251 0.080883 0.730309 0.114217 0.920251 0.170268 1.232296 0.24971 0.408123 0.035475 0.49177 0.061881 0.646005 0.109303 0.932744 0.192139

A1 -0.82426 0.592353 -0.97195 0.573873 -1.1028 0.527833 -1.2903 0.499982 -0.58268 0.349335 -0.66042 0.303766 -1.08466 0.182074 -1.38468 0.086394 0.093477 0.232807 0.032604 0.241806 -0.15401 0.223518 -1.44265 0.109779 1.396263 0.347634 1.548053 0.38799 1.835145 0.436654 1.964806 0.48721

A2 1.464118 0.687679 1.89287 0.634722 1.793047 0.669323 1.933306 0.668801 2.657088 1.072804 2.590442 1.212967 3.885314 1.497493 4.594746 1.735666 3.42225 1.780396 4.133217 1.82977 5.161938 1.897436 14.00362 2.40797 -0.07489 1.190583 0.540205 1.451541 0.82857 1.918129 3.15328 2.518337

A3 -0.24704 -0.57795 -1.14423 -0.2443 -0.49161 -0.29314 -0.75389 -0.33529 -1.87141 -0.49581 -0.90604 -0.73513 -2.68034 -1.04671 -4.61825 -1.52154 -6.22887 -1.79458 -7.89856 -1.76826 -8.80824 -1.23991 -35.2375 -1.70734 0.140191 0.950891 -2.18346 -0.01675 -1.6608 -1.32123 -4.82911 -1.97462

A4 -2.89829 -1.06699 -1.79684 -1.73538 -2.73265 -1.5654 -1.85256 -1.22128 -2.58104 -1.16512 -4.68434 -0.91455 -4.32005 -0.78257 -0.81553 -0.10702 3.92781 0.520187 6.015964 0.301807 4.580701 -1.40283 44.19969 -2.21867 -3.64291 -4.90756 1.219615 -2.87524 -0.48776 -0.57317 -1.91343 -1.32738

Outside Crack A5 3.826622 1.467493 3.117624 2.055523 3.649469 1.825575 2.483311 1.383466 4.287241 1.159125 6.135042 0.999363 7.224627 1.0459 3.849965 0.584301 -0.15306 -0.23044 -1.52176 0.020593 1.126215 1.812988 -28.7466 3.449448 5.018176 4.577334 0.2889 2.630131 1.338079 0.475322 5.112632 2.000274

A6 -1.50197 -0.55736 -1.31483 -0.74854 -1.40117 -0.64769 -0.89123 -0.48013 -1.71997 -0.36076 -2.30652 -0.31364 -2.94069 -0.36131 -1.665 -0.25095 -0.54601 0.10982 -0.18979 0.01444 -1.30665 -0.63079 7.70182 -1.37262 -2.0509 -1.48132 -0.41367 -0.82139 -0.55041 -0.06756 -1.94754 -0.71771

A0 1.239889 0.199063 1.314608 0.221716 1.427393 0.255387 1.566988 0.287327 0.910072 0.141387 1.018756 0.177791 1.219168 0.236895 1.467086 0.310865 0.630291 0.080604 0.746144 0.117507 0.970783 0.185556 1.336672 0.298261 0.411223 0.034233 0.492639 0.062728 0.642992 0.105782 0.953357 0.195255

A1 -0.86578 0.564996 -1.00242 0.540466 -1.17225 0.483923 -1.42439 0.48235 -0.61419 0.365786 -0.72522 0.309734 -1.16241 0.199095 -1.48746 0.02055 0.099799 0.258931 0.067798 0.267022 -0.1536 0.221463 -0.81155 -0.10941 1.371577 0.377896 1.572132 0.35287 1.913227 0.482643 1.859051 0.464974

A2 1.52174 0.848644 1.845476 0.838594 1.810774 0.902298 2.081699 0.633935 2.814161 0.983391 2.951062 1.178272 4.303999 1.366537 4.913156 2.111191 3.448613 1.643725 4.12321 1.751451 5.712369 2.097073 10.00899 4.399185 0.272578 0.976318 0.654425 1.799037 0.859937 1.709168 5.330009 3.076292

A3 -0.20899 -1.05231 -0.87447 -0.89902 -0.26717 -1.0407 -1.04066 -0.29531 -2.23131 -0.20731 -1.69653 -0.52074 -3.49566 -0.4508 -4.82174 -2.51011 -6.12962 -1.35262 -7.50001 -1.43643 -9.60384 -1.55227 -18.4329 -7.52596 -0.92206 1.772218 -2.03939 -1.04375 -0.16496 -0.07929 -6.31552 -2.13409

A4 -3.14947 -0.362 -2.25044 -0.67864 -3.30787 -0.36308 -1.46525 -1.20468 -2.07891 -1.62754 -3.74953 -1.36851 -3.52645 -1.93034 -1.41119 1.217713 3.570831 -0.15733 5.121192 -0.23205 5.1974 -1.08835 13.07452 6.738908 -1.92405 -6.32603 0.977903 -1.04283 -2.3392 -2.27975 0.967732 -0.3677

--``````-`-`,,`,,`,`,,`---

C-81 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A5 4.130517 0.954119 3.465469 1.227119 4.225811 0.890908 2.209288 1.324542 3.900605 1.518569 5.563018 1.413158 6.838974 2.035587 4.621322 -0.38628 0.23047 0.267189 -0.75142 0.406091 0.737336 1.571893 -2.97413 -3.74492 3.629081 5.732558 0.335433 1.029042 1.743137 1.398444 -0.94939 -0.41079

A6 -1.6204 -0.41119 -1.41644 -0.49694 -1.60621 -0.36619 -0.80444 -0.44693 -1.59914 -0.46958 -2.16796 -0.45344 -2.8685 -0.67959 -1.89735 0.05646 -0.68864 -0.03329 -0.43909 -0.09548 -1.17929 -0.54958 -0.22982 0.94584 -1.61833 -1.84443 -0.40676 -0.30341 -0.42438 -0.2595 1.25388 0.56268

Not for Resale

20

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


16

a/t 0.2 0.4 0.6 0.8

20

32

0.2 0.4 0.6 0.8

60

1

0.2 0.4 0.6 0.8

60

2

0.2 0.4 0.6 0.8

Inside Crack


A0 0.280372 0.014651 0.330079 0.027296 0.413411 0.057567 0.626497 0.112646 0.232353 0.008963 0.236097 0.01022 0.286106 0.01984 0.459693 0.061756 1.221644 0.195879 1.289119 0.213396 1.385161 0.242113 1.491501 0.265356 0.89738 0.138361 0.995992 0.173196 1.164034 0.222251 1.353221 0.27298

A1 2.161661 0.278644 2.568783 0.454514 3.390579 0.505684 3.554364 0.705805 1.36017 0.595386 3.057278 0.412402 3.590594 0.656222 2.680576 0.608905 -0.80311 0.564117 -0.9709 0.577466 -1.1646 0.51024 -1.32747 0.503822 -0.56547 0.379657 -0.697 0.288046 -1.07011 0.180165 -1.41068 0.087827

A2 -1.37115 2.109153 -2.27301 1.294 -4.88205 2.031914 0.791921 2.378499 10.73026 -0.19738 -3.49362 1.538415 -4.3735 0.381081 10.71803 2.852737 1.326548 0.844364 1.832512 0.607135 2.102501 0.755589 1.968341 0.629647 2.56536 0.88706 2.807357 1.289734 3.750801 1.493623 4.662153 1.721405

A3 -0.68856 -2.26319 2.448229 0.658591 13.35192 -1.48221 0.319437 -0.94843 -52.8247 5.449562 3.272192 -0.06178 9.648488 4.571407 -36.8898 -3.27153 0.134746 -0.98924 -0.94141 -0.16641 -1.42622 -0.53058 -0.78139 -0.30345 -1.67415 0.056734 -1.48836 -0.88387 -2.19761 -0.98306 -4.72976 -1.50869

A4 1.97606 0.60677 -0.90618 -3.37459 -17.1606 1.49549 2.082479 0.683212 101.2995 -11.9923 3.058013 -1.36755 -3.30654 -6.66774 86.52319 12.27468 -3.44234 -0.51809 -2.10037 -1.84865 -1.26635 -1.23371 -1.89387 -1.16137 -2.72192 -2.00651 -3.85805 -0.78616 -5.14159 -0.94759 -0.84795 -0.1139

Outside Crack A5 -1.36392 0.068106 -1.11523 2.556753 9.148894 -2.55834 -8.67482 -2.90865 -88.35 10.09033 -7.66155 0.432335 -7.06883 2.83062 -93.7594 -17.7359 4.216303 1.106454 3.331608 2.138667 2.519391 1.598488 2.573345 1.270709 4.264836 1.792755 5.542079 0.961899 7.880414 1.209031 3.968669 0.563375

--``````-`-`,,`,,`,`,,`---

C-82

A6 0.25062 -0.08299 0.63369 -0.72498 -1.80159 1.11454 4.88367 1.54398 28.8534 -3.19144 3.38593 -0.00654 4.15326 -0.45051 35.0815 7.20968 -1.61291 -0.46438 -1.37195 -0.77276 -1.06144 -0.58669 -0.93101 -0.42909 -1.67722 -0.54778 -2.13808 -0.31697 -3.13907 -0.41785 -1.70458 -0.23027

A0 0.279807 0.013043 0.321296 0.026096 0.373396 0.045601 0.522614 0.076938 0.213009 0.005788 0.22745 0.007009 0.253364 0.007365 0.349869 0.027355 1.23637 0.197516 1.306917 0.219593 1.414978 0.249234 1.540551 0.278874 0.906209 0.140578 1.013727 0.176003 1.200833 0.230849 1.422892 0.294814

A1 2.161703 0.302082 2.344803 0.342219 3.103322 0.383656 3.423439 0.718847 2.391763 0.944106 2.979486 0.378366 3.631361 0.711117 3.619092 0.897757 -0.86162 0.578836 -0.99036 0.541649 -1.21456 0.515865 -1.42861 0.484701 -0.58473 0.367456 -0.75171 0.30621 -1.14671 0.20303 -1.44376 0.060799

A2 -1.2437 1.921481 -0.74269 2.000518 -3.58897 2.560853 -0.65481 1.276976 -0.24572 -3.2516 -3.29173 1.6174 -6.2242 -0.62296 0.19689 -0.36758 1.551 0.750535 1.786662 0.830186 2.209937 0.702266 2.255387 0.649196 2.610018 0.97705 3.122658 1.196801 4.210714 1.359314 4.682268 1.870252

A3 -1.01073 -1.54385 -1.41942 -1.33364 11.52991 -2.75537 9.748554 3.580448 -8.57506 16.659 3.159303 -0.26614 17.31625 8.062759 -4.04123 5.55412 -0.41351 -0.72918 -0.64529 -0.85797 -1.65378 -0.40927 -1.59946 -0.32348 -1.58496 -0.21225 -2.29927 -0.59972 -3.41303 -0.55302 -4.543 -1.93792

A4 2.535727 -0.57445 5.011997 -0.05783 -12.9474 4.612923 -3.22359 -2.1787 19.49482 -31.5804 3.653372 -0.67952 -14.5951 -11.5518 46.26732 3.426951 -2.68248 -0.88862 -2.70412 -0.76163 -0.9621 -1.37695 -0.61019 -1.18525 -3.13859 -1.59091 -2.73111 -1.22689 -3.46013 -1.62999 -1.42618 0.508038

A5 -1.86871 0.983832 -5.68102 -0.12305 4.650861 -5.67179 -13.8776 -4.29286 -17.7926 26.38495 -8.4864 -0.28417 1.37271 6.554 -68.4234 -12.9111 3.675529 1.36985 3.884589 1.301776 2.311875 1.689677 1.57747 1.325701 4.758753 1.473248 4.737906 1.297361 6.698155 1.727651 4.478438 0.078584

A6 0.41734 -0.36088 1.95365 0.0775 -0.34272 2.10837 8.541 2.69874 5.82211 -8.3832 3.67686 0.212 1.38979 -1.73393 27.6219 5.65598 -1.45956 -0.53818 -1.56144 -0.52191 -1.00526 -0.61139 -0.62566 -0.45247 -1.8691 -0.45175 -1.90932 -0.4173 -2.8074 -0.56953 -1.83774 -0.07045

Not for Resale

20

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---


4

a/t 0.2 0.4 0.6 0.8

60

8

0.2 0.4 0.6 0.8

60

16

0.2 0.4 0.6 0.8

60

32

0.2 0.4 0.6 0.8

Inside Crack


A0 0.626098 0.080646 0.733025 0.116104 0.921029 0.170248 1.204733 0.247257 0.414027 0.03434 0.494848 0.062552 0.640993 0.108356 0.935679 0.191652 0.281579 0.014473 0.328784 0.028078 0.417685 0.057466 0.658253 0.122542 0.236863 0.00848 0.237295 0.010659 0.293768 0.022057 0.483835 0.07167

A1 0.080929 0.244567 0.054103 0.220339 -0.04657 0.249718 -0.78476 0.11716 1.256757 0.378263 1.479444 0.365634 1.965295 0.445316 1.873876 0.452476 2.120964 0.27969 2.592157 0.427692 3.407415 0.54991 3.512887 0.704622 1.219008 0.733744 3.056601 0.40959 3.587004 0.674075 3.156615 0.708413

A2 3.536152 1.701252 4.006431 2.000431 4.452187 1.727054 8.953312 2.365237 1.047563 0.944824 1.118527 1.64075 -0.16421 1.839994 3.89467 2.800269 -1.00808 2.100015 -2.41326 1.497351 -4.67535 1.777459 2.282823 2.756929 11.97428 -1.37968 -3.3944 1.608347 -3.8424 0.347481 8.803117 2.608596

A3 -6.58568 -1.52691 -7.36947 -2.3056 -6.37691 -0.64208 -17.7152 -1.49786 -3.69639 1.841651 -4.04441 -0.65546 2.200552 -0.90867 -6.06939 -2.62888 -1.94609 -2.21712 3.063419 0.028844 13.07859 -0.50991 -1.99243 -1.44382 -57.3416 9.724215 3.147773 -0.32609 8.444201 4.962931 -27.1648 -1.42574

A4 4.506952 0.084627 5.062726 1.17136 0.540359 -2.40415 14.21804 -2.70285 2.838158 -6.45231 4.328286 -1.74744 -7.42184 -1.37743 -1.94441 -0.71446 4.143327 0.536474 -1.95253 -2.34973 -17.0413 -0.12821 2.231004 0.619685 109.2355 -19.4011 3.153023 -0.80351 -1.46003 -7.35087 69.60191 9.365357

Outside Crack A5 -0.61634 0.110055 -0.73451 -0.66814 4.304832 2.60263 -4.31965 3.848974 -0.26624 5.855783 -2.25956 1.667014 7.058303 1.137353 5.689649 1.522154 -3.15958 0.117967 -0.3333 1.740264 8.788828 -1.43655 -8.66817 -3.16409 -94.9987 16.21325 -7.78652 -0.14639 -8.93392 3.173217 -82.4796 -16.6405

C-83

A6 -0.40324 0.00672 -0.43736 0.22449 -2.26137 -0.86865 0.11573 -1.47395 -0.39326 -1.88739 0.39035 -0.5089 -2.32305 -0.26543 -2.01061 -0.48385 0.81916 -0.0981 0.41446 -0.47582 -1.50846 0.8552 5.4793 1.9357 30.9817 -5.13061 3.45766 0.211 4.91193 -0.46593 32.6826 7.39403

A0 0.628055 0.080838 0.745785 0.118295 0.959876 0.181752 1.301025 0.281597 0.421187 0.038376 0.499193 0.063863 0.659447 0.112346 0.998626 0.210564 0.281323 0.0149 0.328113 0.029232 0.398379 0.053325 0.607481 0.105717 0.204248 0.007469 0.230678 0.010938 0.264712 0.018629 0.391607 0.037786

A1 0.121237 0.249865 0.006695 0.232483 -0.13126 0.231176 -0.8 0.00126 1.119926 0.273931 1.492933 0.357719 1.951305 0.47698 2.002529 0.500829 2.151721 0.261409 2.390181 0.34244 3.229895 0.454129 3.500036 0.7235 2.695761 0.717964 3.038805 0.402017 3.65577 0.659841 3.582448 0.931452

A2 3.297291 1.693001 4.517144 1.968253 5.37191 1.981924 9.528552 3.419849 2.233648 1.806056 1.318136 1.790387 0.703731 1.818037 4.781095 3.005438 -1.1658 2.276346 -0.80958 2.120615 -3.56092 2.396477 1.932419 2.319473 -2.82193 -1.24934 -3.47288 1.543803 -5.54725 0.094435 2.46296 -0.03497

A3 -5.73928 -1.4961 -8.9481 -2.14568 -8.86927 -1.34379 -18.1521 -4.63533 -7.75411 -1.15264 -4.62221 -1.12505 -0.13288 -0.61671 -6.07069 -2.39541 -1.29461 -2.82959 -1.42103 -1.81362 11.58598 -2.09909 4.007886 1.328679 0.780295 9.298838 3.638567 -0.03837 14.5853 5.520558 -10.9379 4.732139

A4 3.059687 0.041104 7.588564 0.87392 4.107657 -1.35287 13.24947 2.073505 9.672445 -1.3205 5.402623 -0.89363 -3.17905 -1.6918 -2.3363 -1.03748 2.938693 1.619641 4.841563 0.649824 -14.5389 2.977382 -0.67674 -0.98334 3.076442 -18.6567 2.907158 -1.04288 -8.91296 -6.86889 63.87855 7.310553

A5 0.560068 0.136036 -2.74058 -0.4224 1.666586 1.779564 -3.02692 0.092415 -5.82249 1.624897 -3.25101 0.914649 3.088103 1.165388 4.217571 1.041567 -2.12207 -0.80046 -5.43549 -0.65083 6.478023 -4.26001 -14.1704 -4.83843 -4.07344 15.58961 -7.92647 -0.05244 -4.16618 2.30006 -89.4185 -18.9855

A6 -0.77068 0.0005 0.17924 0.14616 -1.48603 -0.61368 -0.28605 -0.28503 1.34417 -0.54931 0.72159 -0.26407 -0.95715 -0.22296 -0.81704 -0.05342 0.47686 0.19717 1.87918 0.24693 -0.85745 1.74061 9.13009 3.15757 1.44314 -4.93456 3.51884 0.16909 3.36682 -0.26058 36.1302 8.44785

Not for Resale

60

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


0.2 0.4 0.6 0.8

100

2

0.2 0.4 0.6 0.8

100

4

0.2 0.4 0.6 0.8

100

8

0.2 0.4 0.6 0.8

Inside Crack


A0 1.224581 0.196161 1.291544 0.214856 1.387921 0.244211 1.495553 0.267129 0.897045 0.140302 0.999566 0.172616 1.170513 0.223486 1.356536 0.275449 0.62612 0.081135 0.735315 0.116398 0.932415 0.173755 1.221949 0.250084 0.413682 0.034571 0.492723 0.062523 0.645797 0.107943 0.933198 0.190018

A1 -0.83969 0.565444 -0.986 0.563366 -1.1637 0.483994 -1.32987 0.495335 -0.55138 0.345265 -0.72802 0.308779 -1.12429 0.176668 -1.37695 0.063526 0.089146 0.234843 0.033538 0.222291 -0.23415 0.191659 -1.14155 0.058065 1.265142 0.371764 1.544082 0.368375 1.845006 0.452342 1.848404 0.449358

A2 1.524542 0.810456 1.919818 0.667548 2.068166 0.94075 1.962699 0.644581 2.468019 1.122406 2.977673 1.14255 4.054356 1.505155 4.396418 1.87602 3.477679 1.779806 4.152984 1.985913 5.795789 2.130035 11.71292 2.819919 0.989883 1.002303 0.634178 1.626205 0.824811 1.7937 4.061046 2.824048

A3 -0.38457 -0.82093 -1.20487 -0.2672 -1.29564 -1.15415 -0.82424 -0.27409 -1.31873 -0.69631 -1.92775 -0.38622 -2.98516 -0.9863 -3.88145 -1.98071 -6.36499 -1.79309 -7.80356 -2.24661 -10.6432 -1.88311 -27.0807 -3.03137 -3.485 1.631504 -2.36453 -0.60185 -1.20278 -0.75301 -6.44884 -2.70636

A4 -2.72291 -0.85418 -1.69206 -1.80613 -1.49738 -0.18482 -1.74681 -1.3088 -3.37484 -0.78177 -3.2709 -1.63442 -4.11664 -0.98675 -2.2095 0.607078 4.09241 0.518402 5.733 1.074784 7.326651 -0.48079 29.83418 -0.16014 2.465448 -6.08024 1.507174 -1.83487 -1.61618 -1.60099 -1.5508 -0.5768

Outside Crack A5 3.70302 1.399012 3.019064 2.180366 2.714766 0.746203 2.412969 1.451708 4.835125 0.814308 5.150549 1.66456 7.229943 1.266954 5.01876 0.01907 -0.24349 -0.22467 -1.25139 -0.59828 -0.97084 1.139543 -16.9377 1.795148 0.050502 5.545805 0.017525 1.739256 2.268601 1.281097 5.352686 1.345795

C-84

A6 -1.46369 -0.55669 -1.27781 -0.8035 -1.12465 -0.32023 -0.87129 -0.50062 -1.86565 -0.2436 -2.03504 -0.54127 -2.97918 -0.44181 -2.01358 -0.06834 -0.53072 0.10505 -0.28138 0.20575 -0.66761 -0.43457 4.06005 -0.82967 -0.49775 -1.79003 -0.31905 -0.53382 -0.80268 -0.29971 -1.85084 -0.39581

A0 1.23689 0.198686 1.306977 0.218277 1.411893 0.248631 1.532735 0.275943 0.903151 0.143156 1.012539 0.17532 1.195615 0.229205 1.413989 0.289661 0.628536 0.081611 0.74275 0.118366 0.956789 0.18057 1.31001 0.265887 0.416137 0.035454 0.497299 0.062974 0.661354 0.112733 0.99691 0.210536

A1 -0.87835 0.557703 -1.02346 0.558399 -1.21285 0.507337 -1.40571 0.499318 -0.54863 0.318216 -0.75689 0.307337 -1.1378 0.206192 -1.49857 0.088203 0.102776 0.230076 0.047047 0.220292 -0.17255 0.222646 -1.4349 0.247431 1.242844 0.348653 1.538266 0.382106 1.908602 0.468187 1.963426 0.466131

A2 1.620956 0.862771 2.035175 0.712363 2.173169 0.768032 2.149327 0.57072 2.421462 1.293491 3.131131 1.198038 4.171844 1.330633 5.065764 1.682758 3.450696 1.847436 4.201345 2.068115 5.636206 2.017202 14.3766 1.494264 1.253705 1.203115 0.954369 1.582731 0.983258 1.875459 4.863342 3.228224

A3 -0.50772 -0.99834 -1.47905 -0.46284 -1.42369 -0.63446 -1.2998 -0.09606 -1.11084 -1.17571 -2.27527 -0.63404 -3.37229 -0.45132 -5.77038 -1.34905 -6.31275 -2.0378 -7.92403 -2.53513 -9.85805 -1.46299 -35.1681 1.791574 -4.35088 0.969956 -3.44969 -0.39228 -1.26322 -0.87961 -6.90464 -3.39264

A4 -2.69305 -0.56927 -1.29704 -1.42737 -1.48779 -0.98741 -1.05104 -1.52817 -3.75166 -0.08652 -2.83879 -1.13251 -3.44567 -1.81616 0.49737 -0.43545 4.066286 0.958491 5.91979 1.589297 5.806612 -1.18065 42.22156 -8.5849 3.865388 -4.98259 3.468701 -2.18325 -1.38634 -1.28837 -1.51482 0.484157

A5 3.777594 1.184961 2.722608 1.844368 2.825799 1.361727 1.899606 1.584141 5.14576 0.309134 4.866722 1.196838 6.651209 1.892133 3.032912 0.825361 -0.26857 -0.60301 -1.41763 -1.04033 0.295818 1.668343 -26.6115 8.677336 -1.0519 4.660856 -1.69869 2.001966 1.768116 0.884725 4.296328 0.039449

A6 -1.51088 -0.49573 -1.18904 -0.69171 -1.18742 -0.505 -0.7187 -0.52944 -1.96244 -0.09861 -1.95909 -0.37937 -2.78672 -0.62452 -1.41974 -0.30103 -0.51162 0.22813 -0.22539 0.34876 -1.06117 -0.58672 7.0832 -2.95768 -0.16258 -1.51562 0.24303 -0.6135 -0.57155 -0.14386 -1.03855 0.19745

Not for Resale

1

a/t


100

c/a

--``````-`-`,,`,,`,`,,`---

R/t

--``````-`-`,,`,,`,`,,`---


16

a/t 0.2 0.4 0.6 0.8

100

32

0.2 0.4 0.6 0.8

¥

1

0.2 0.4 0.6 0.8

¥

2

0.2 0.4 0.6 0.8

Inside Crack


A0 0.280819 0.01533 0.332163 0.02757 0.417431 0.059249 0.660989 0.123351 0.237563 0.008511 0.23711 0.011014 0.292163 0.02266 0.524376 0.083368 1.230123 0.1969 1.298948 0.216225 1.397118 0.244587 1.511701 0.270447 0.900059 0.139883 1.005806 0.174087 1.182601 0.227712 1.383338 0.282011

A1 2.143891 0.257257 2.490134 0.433852 3.395534 0.494284 3.463342 0.691073 1.193192 0.744034 3.064732 0.402503 3.692636 0.67159 2.252477 0.466589 -0.85148 0.568337 -0.9978 0.563305 -1.13484 0.532667 -1.32448 0.511328 -0.5476 0.365987 -0.73226 0.305163 -1.10725 0.170117 -1.39003 0.083923

A2 -1.18942 2.278658 -1.56293 1.46702 -4.56837 2.211117 2.848119 2.867832 12.20547 -1.48971 -3.45132 1.643757 -4.69253 0.438855 16.79348 4.744027 1.55097 0.811399 1.947954 0.704831 1.791874 0.593969 1.756835 0.535744 2.441677 0.983314 2.995194 1.207031 3.962364 1.549947 4.375578 1.725858

A3 -1.31 -2.82674 0.071197 0.074296 12.80625 -1.94533 -3.54839 -1.60231 -58.1949 10.18232 3.391711 -0.37276 11.90172 4.593061 -53.8032 -8.43369 -0.45381 -0.88111 -1.30027 -0.49345 -0.42026 -0.03618 -0.13379 -0.03273 -1.26885 -0.24055 -1.94592 -0.67205 -2.77813 -1.10512 -3.73726 -1.53581

A4 3.090358 1.562349 3.20886 -2.31371 -16.6034 2.224168 4.29001 0.589152 110.761 -20.2736 2.732437 -0.81197 -7.7448 -6.55494 114.1036 21.11563 -2.60572 -0.6993 -1.49401 -1.30788 -2.86793 -2.01631 -2.86293 -1.55702 -3.38153 -1.53708 -3.26135 -1.06513 -4.30973 -0.83337 -2.54032 -0.06356

Outside Crack A5 -2.33433 -0.71579 -4.59262 1.632858 8.355117 -3.31267 -10.6097 -3.16474 -96.2925 16.98798 -7.46713 -0.0858 -3.79995 2.317828 -119.702 -26.6845 3.613961 1.255667 2.830623 1.707866 3.768548 2.216701 3.295327 1.557097 4.786857 1.427492 5.142457 1.144559 7.277275 1.171706 5.3036 0.500678

C-85 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A6 0.57164 0.16318 1.75834 -0.42328 -1.33494 1.43452 6.33679 2.00376 31.3989 -5.39055 3.36741 0.17815 3.3544 -0.12519 44.9141 10.7853 -1.44075 -0.51193 -1.2126 -0.6406 -1.4405 -0.77822 -1.14124 -0.50946 -1.83739 -0.43719 -2.03062 -0.36448 -2.96482 -0.41945 -2.09324 -0.19822

A0 0.280212 0.013292 0.328052 0.026039 0.410317 0.055083 0.64916 0.117619 0.214167 0.004996 0.232407 0.009069 0.270279 0.013548 0.420163 0.045178 1.230123 0.1969 1.298948 0.216225 1.397118 0.244587 1.511701 0.270447 0.900059 0.139883 1.005806 0.174087 1.182601 0.227712 1.383338 0.282011

A1 2.183348 0.310165 2.59019 0.461293 3.437316 0.536134 3.596224 0.752713 2.41288 0.614027 3.053456 0.392929 3.674268 0.696643 3.22276 0.866082 -0.85148 0.568337 -0.9978 0.563305 -1.13484 0.532667 -1.32448 0.511328 -0.5476 0.365987 -0.73226 0.305163 -1.10725 0.170117 -1.39003 0.083923

A2 -1.39995 1.85527 -2.18942 1.26298 -4.72503 1.898106 2.097024 2.422576 -0.36389 -0.35826 -3.47918 1.658575 -5.4506 -0.14238 6.092687 0.678866 1.55097 0.811399 1.947954 0.704831 1.791874 0.593969 1.756835 0.535744 2.441677 0.983314 2.995194 1.207031 3.962364 1.549947 4.375578 1.725858

A3 -0.55282 -1.29591 2.345672 0.872011 14.02544 -0.68934 2.613164 0.907093 -8.21049 6.082972 3.628804 -0.41953 14.67372 6.588859 -21.407 3.143907 -0.45381 -0.88111 -1.30027 -0.49345 -0.42026 -0.03618 -0.13379 -0.03273 -1.26885 -0.24055 -1.94592 -0.67205 -2.77813 -1.10512 -3.73726 -1.53581

A4 1.766439 -1.0639 -0.32053 -3.58211 -17.0473 0.801483 0.524741 -1.02572 18.83925 -13.0843 2.853442 -0.46877 -9.61388 -8.92489 81.16587 9.882409 -2.60572 -0.6993 -1.49401 -1.30788 -2.86793 -2.01631 -2.86293 -1.55702 -3.38153 -1.53708 -3.26135 -1.06513 -4.30973 -0.83337 -2.54032 -0.06356

A5 -1.2254 1.428943 -1.96182 2.602928 7.43505 -2.6604 -14.9133 -4.52243 -17.2273 10.98476 -7.86404 -0.48952 -3.54698 3.951284 -105.684 -22.0588 3.613961 1.255667 2.830623 1.707866 3.768548 2.216701 3.295327 1.557097 4.786857 1.427492 5.142457 1.144559 7.277275 1.171706 5.3036 0.500678

A6 0.21277 -0.50931 0.96962 -0.72336 -0.83856 1.30663 9.60126 3.10168 5.64098 -3.47693 3.50801 0.30513 3.24025 -0.72754 42.3048 9.88179 -1.44075 -0.51193 -1.2126 -0.6406 -1.4405 -0.77822 -1.14124 -0.50946 -1.83739 -0.43719 -2.03062 -0.36448 -2.96482 -0.41945 -2.09324 -0.19822

Not for Resale

100

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


4

a/t 0.2 0.4 0.6 0.8

¥

8

0.2 0.4 0.6 0.8

¥

16

0.2 0.4 0.6 0.8

¥

32

0.2 0.4 0.6 0.8

Inside Crack


A0 0.627412 0.081291 0.739042 0.11645 0.946121 0.177805 1.245211 0.258564 0.41686 0.035319 0.491777 0.063427 0.659182 0.111604 0.980933 0.203995 0.282375 0.013699 0.326148 0.029412 0.416633 0.059846 0.654014 0.121478 0.211805 0.008992 0.235794 0.014514 0.290224 0.020889 0.516355 0.082546

A1 0.098006 0.235191 0.054816 0.247988 -0.18588 0.205668 -0.69219 0.154889 1.212456 0.354631 1.659232 0.37225 1.875914 0.47145 1.884632 0.480015 2.112379 0.301109 2.520087 0.369937 3.156647 0.434074 3.423192 0.697549 2.479586 0.647688 3.08224 0.4038 3.689205 0.701678 2.531083 0.497177

A2 3.427515 1.791658 4.084262 1.828252 5.586746 2.097921 8.326062 2.117024 1.451554 1.148 -0.10804 1.623167 1.02126 1.794059 4.802078 2.882243 -0.86611 1.927456 -1.8847 1.922085 -2.62489 2.681156 3.815805 2.971833 -0.97912 -0.63215 -3.57921 1.64227 -4.57391 0.163184 14.7129 4.606481

Notes for Table C.11: 1. Interpolation of the influence coefficients,

A3 -6.17118 -1.8449 -7.58831 -1.71699 -9.86349 -1.80395 -14.948 -0.491 -5.08051 1.140333 0.179324 -0.53065 -1.7698 -0.75576 -8.05802 -2.58901 -2.45033 -1.58246 2.179874 -1.20715 7.732591 -3.19366 -4.15869 -1.30365 -5.98247 7.012493 3.947689 -0.39061 11.70989 5.707216 -43.6218 -7.33267

A4 3.761013 0.639466 5.404753 0.191212 5.959687 -0.55587 8.693691 -4.61461 5.176111 -5.25021 -2.70761 -2.00074 -0.56536 -1.49017 0.444785 -0.9683 5.003528 -0.55641 -1.45971 -0.4394 -9.69278 4.075372 3.471533 -0.07549 14.91676 -14.649 1.913159 -0.64807 -6.375 -8.20758 101.0657 21.14862

Outside Crack A5 0.014548 -0.35485 -1.01461 0.116577 0.129644 1.14614 0.475579 5.455075 -2.17287 4.862799 3.368062 1.894378 1.247996 1.085218 3.477266 1.537237 -3.85544 1.010305 -0.18865 0.273755 3.64287 -4.69402 -10.3104 -3.04651 -13.9367 12.24961 -6.88722 -0.29403 -5.88941 3.456112 -116.081 -29.3451

A6 -0.60669 0.15531 -0.34834 -0.01861 -1.00261 -0.42066 -1.39266 -1.96633 0.20404 -1.57303 -1.34897 -0.58803 -0.43766 -0.21137 -1.05675 -0.37502 1.03217 -0.37761 0.23934 -0.03952 -0.0892 1.82855 6.628 2.167 4.58836 -3.86819 3.18968 0.25149 4.24524 -0.44547 46.1909 12.4914

A0 0.627412 0.081291 0.739042 0.11645 0.946121 0.177805 1.245211 0.258564 0.41686 0.035319 0.491777 0.063427 0.659182 0.111604 0.980933 0.203995 0.282375 0.013699 0.326148 0.029412 0.416633 0.059846 0.654014 0.121478 0.211805 0.008992 0.235794 0.014514 0.290224 0.020889 0.516355 0.082546

A1 0.098006 0.235191 0.054816 0.247988 -0.18588 0.205668 -0.69219 0.154889 1.212456 0.354631 1.659232 0.37225 1.875914 0.47145 1.884632 0.480015 2.112379 0.301109 2.520087 0.369937 3.156647 0.434074 3.423192 0.697549 2.479586 0.647688 3.08224 0.4038 3.689205 0.701678 2.531083 0.497177

A2 3.427515 1.791658 4.084262 1.828252 5.586746 2.097921 8.326062 2.117024 1.451554 1.148 -0.10804 1.623167 1.02126 1.794059 4.802078 2.882243 -0.86611 1.927456 -1.8847 1.922085 -2.62489 2.681156 3.815805 2.971833 -0.97912 -0.63215 -3.57921 1.64227 -4.57391 0.163184 14.7129 4.606481

A3 -6.17118 -1.8449 -7.58831 -1.71699 -9.86349 -1.80395 -14.948 -0.491 -5.08051 1.140333 0.179324 -0.53065 -1.7698 -0.75576 -8.05802 -2.58901 -2.45033 -1.58246 2.179874 -1.20715 7.732591 -3.19366 -4.15869 -1.30365 -5.98247 7.012493 3.947689 -0.39061 11.70989 5.707216 -43.6218 -7.33267

A4 3.761013 0.639466 5.404753 0.191212 5.959687 -0.55587 8.693691 -4.61461 5.176111 -5.25021 -2.70761 -2.00074 -0.56536 -1.49017 0.444785 -0.9683 5.003528 -0.55641 -1.45971 -0.4394 -9.69278 4.075372 3.471533 -0.07549 14.91676 -14.649 1.913159 -0.64807 -6.375 -8.20758 101.0657 21.14862

Gi , may be used for intermediate values of Ri t , c a ,and a t .

2.

The value of the influence coefficients at the surface point of the crack defined by

j = 00 are equal to: Gi = A0 .

3.

The value of the influence coefficients at the deepest point of the crack defined by

j = 900 are equal to: Gi = å An .

6

--``````-`-`,,`,,`,`,,`---

n=0

C-86

A5 0.014548 -0.35485 -1.01461 0.116577 0.129644 1.14614 0.475579 5.455075 -2.17287 4.862799 3.368062 1.894378 1.247996 1.085218 3.477266 1.537237 -3.85544 1.010305 -0.18865 0.273755 3.64287 -4.69402 -10.3104 -3.04651 -13.9367 12.24961 -6.88722 -0.29403 -5.88941 3.456112 -116.081 -29.3451

A6 -0.60669 0.15531 -0.34834 -0.01861 -1.00261 -0.42066 -1.39266 -1.96633 0.20404 -1.57303 -1.34897 -0.58803 -0.43766 -0.21137 -1.05675 -0.37502 1.03217 -0.37761 0.23934 -0.03952 -0.0892 1.82855 6.628 2.167 4.58836 -3.86819 3.18968 0.25149 4.24524 -0.44547 46.1909 12.4914

Not for Resale

¥

c/a


R/t

Table C.12 Influence Coefficients For A Circumferential Semi-Elliptical Surface Crack In A Cylinder

1

a/t 0.2

0.4

0.6

0.8

5

2

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 1.22453 -0.86759 1.629256 -0.6513 -2.00939 2.887804 -1.15618 1.235631 -0.84627 1.618854 -0.66683 -2.41778 3.601344 -1.47297 0.190434 0.590384 0.665812 -0.53963 -0.91759 1.221226 -0.46288 0.200429 0.574132 0.777278 -0.68972 -1.15441 1.703381 -0.66781

1.28273 -1.03763 2.019604 -1.29816 -1.15406 2.223313 -0.94993 1.297448 -0.89785 1.546486 -0.06844 -3.88915 0.209873 0.557807 0.6858 -0.55706 -0.79299 1.06438 -0.40757 0.219409 0.534541 0.961461 -1.1685 -0.55346

5.0715 -1.98567 1.31173 -0.55645

1.357359 -1.17045 1.875968 -0.34006 -2.53869 3.052277 -1.12495 1.390267 -1.05267 1.867108 -0.94376 -2.50117 3.920839 -1.58911 0.233928 0.525469 0.593133 -0.19291 -1.22905 1.299426 -0.45861 0.244031 0.513724 0.89743 -0.87855 -1.08818 1.728649 -0.66573

1.439434 -1.30987 1.77713 0.386089 -3.32538 3.253952 -1.07004 1.497836 -1.16405 1.83446 -1.11677 -1.60622 2.673173 -1.01653 0.257374 0.495123 0.650179 -0.54904 -0.14696 0.170227 -0.07188 0.269077 0.513828 0.771369 -0.58948 -1.29811 1.687765 -0.58895

0.889003 -0.58338 2.605624 -1.60142 -2.95441 4.480381 -1.75135 0.904956 -0.58054 2.813136 -2.49871 -1.46724 3.365403 -1.42996 0.132978 0.349381 1.018756 -0.24459 -1.60147 1.537656 -0.49431 0.143129 0.371325 0.999483 -0.29773 -1.46642 1.380556 -0.42231

Not for Resale

5

c/a

0.96265 -0.71113 2.661367 -0.71625 -5.14543 6.507539 -2.42132 1.001903 -0.65563 2.877541 -1.97872 -3.00039 4.925776 -1.97906 0.161464 0.29748 1.166086 -0.50872 -1.27263 1.287134 -0.41241 0.173894 0.335569 1.127052 -0.45783 -1.46231 1.50658 -0.48676

1.075175 -1.09832 3.991656 -2.78803 -3.95488 6.723596 -2.7469 1.158904 -0.91197 3.601943 -2.56132 -4.04148 6.867655 -2.81629 0.195423 0.196232 1.389571 -0.69788 -1.21179 1.318343 -0.44416 0.219581 0.25041 1.33442 -0.63429 -1.51377 1.684402 -0.56781

1.17278 -1.08901 3.514991 -1.902 -3.68893 5.264313 -1.98234 1.317528 -0.77142 2.579497 -1.16534 -3.43766 4.268269 -1.41215 0.222794 0.234926 1.030902 0.122412 -1.76174 1.348743 -0.3982 0.260221 0.319975 0.949212 -0.18394 -1.10099 0.668455 -0.09873

--``````-`-`,,`,,`,`,,`---

C-87


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~"


0.2

0.4

0.6

0.8

5

8

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 0.618741 0.029927 3.692827 -7.03304 5.226132 -1.16047 0.075972 0.249386 1.587426 -1.14322 -0.60024 0.739603

A6 A0 A1 A2 A6 A4 A5 A6 -0.252 0.630202 0.071637 3.71755 -7.20217 5.604809 -1.56601 -0.08931 -0.217 0.083005 0.244852 1.776558 -1.80268 0.632902 -0.42445 0.20064

0.680709 -0.01817 4.101012 -7.73421 5.778971 -1.27814 -0.30208 0.724394 0.098217 3.864905 -6.85721 4.447424 -0.46469 -0.46106 0.097722 0.234593 1.75714 -1.50322 -0.17823 0.468068 -0.1464 0.111616 0.242111 1.959851 -2.23664 1.267138 -0.90683 0.33672

0.764378 -0.10456 4.67805 -7.7826 3.609057 1.715428 -1.51652 0.859131 0.01565 4.841081 -7.69577 3.532935 1.147107 -1.08916 0.12315 0.198776 1.975688 -1.54702 -0.78987 1.302132 -0.48177 0.150629 0.241484 2.079275 -1.79646 -0.28062 0.698277 -0.23068

0.900503 -0.8174 9.134379 -18.3189 16.23302 -5.90928 0.33361 1.010973 -0.1571 7.068453 -11.6221 6.427465 -0.29494 -0.54705 0.15924 0.125445 2.223491 -0.9907 -3.21691 4.254132 -1.68007 0.194992 0.148612 2.991513 -3.45286 0.991203 0.303777 -0.20567

0.40346 1.269078 0.468652 -1.49917 -1.14398 3.249552 -1.59066 0.416472 1.193136 1.505216 -5.01085 4.978573 -2.05798 0.033726 0.304129 1.376953 0.506719 -4.57073 4.598465 -1.55196 0.035073 0.3352 1.308038 0.53042 -3.97663 3.64897

Not for Resale

4

a/t

0.19647 -1.156

0.433352 1.357053 0.644257 -1.61627 -0.99478 2.960476 -1.45987 0.447596 1.514472 0.702501 -2.49876 2.542672 -1.5532 0.36324 0.041414 0.32802 1.502228 -0.12095 -2.69839 2.450729 -0.74287 0.046939 0.350898 1.596263 -0.11174 -2.90027 2.737118 -0.88849

0.477833 1.638128 -0.44495 2.245242 -6.09804 5.555027 -1.82355 0.488166 1.65074 0.205056 2.143395 -4.52915 2.196329 -0.21683 0.056898 0.353998 1.677902 -0.61725 -1.61356 1.358995 -0.37171 0.056645 0.330996 1.981865 -0.91235 -0.44423 -0.45253 0.41997

0.567829 1.369979 2.182974 -2.25672 -3.76029 6.994104 -3.18 0.512125 1.570448 2.414313 0.249808 -4.32629 2.107335 -0.05753 0.08447 0.266721 2.54091 -2.29253 -0.17134 1.312617 -0.73589 0.056124 0.346566 2.321294 -0.62794 -1.04693 -0.28895 0.42449

C-88 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


5

c/a

--``````-`-`,,`,,`,`,,`---

R/t

--``````-`-`,,`,,`,`,,`---


16

a/t 0.2

0.4

0.6

0.8

10

1

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.266495 2.110259 -1.91517 2.621227 -5.40637 5.726542 -2.21788 0.265471 2.238411 -2.41793 4.180802 -7.23449 6.474941 -2.24531 0.017758 0.054998 3.914855 -9.40623 14.16818 -12.0517 4.01071 0.024467 -0.07071 4.730001 -10.5695 13.47782 -9.5035 2.65276

0.290506 2.261384 -2.02366 2.234869 -2.03843 0.848013 -0.17694 0.27466 2.429364 -2.80451 4.97945 -4.583 1.311506 -0.00226 0.026426 0.305086 1.745013 -0.63292 -1.78857 1.643928 -0.50055 0.062492 0.380176 1.259066 0.824841 -2.97828 1.728634 -0.35122

0.313679 2.239171 -0.96862 0.46444 0.911652 -2.17932 0.03937 0.348261 1.747076 -0.54629 -1.04888 0.352418

0.92556 0.353569 -0.00769 18.9768 -72.9224 135.8806 -119.792 0.03561 0.076012 -0.62009 9.993453 -31.1269 55.34591 -48.6111

39.6005 16.0335

0.330758 2.26658 -0.19221 0.225111 0.204968 -0.17913 -0.43439 0.279258 2.060573 0.342894 2.341133 1.744751 -7.55914 0.052604 0.331536 1.906451 -0.07278 -2.29722 2.258468 -1.0213 0.094297 0.274825 1.729841 0.689454 0.046663 -2.56629

3.52893 1.13456

1.225849 -0.83933 1.499205 -0.28275 -2.68859 3.498306 -1.35837 1.237192 -0.88019 1.714221 -0.74767 -2.43205 3.671201 -1.50793 0.189862 0.619116 0.520286 -0.12653 -1.57208 1.720263 -0.60525 0.201209 0.567773 0.803059 -0.80312 -0.88404 1.436442 -0.57598

Not for Resale

5

c/a

1.285913 -0.94875 1.600253 -0.18144 -2.97796 3.72951 -1.42413 1.303284 -0.98012 1.939669 -1.2179 -1.87983 3.332302 -1.41577 0.210241 0.581031 0.580096 -0.19154 -1.51301 1.696253 -0.60598 0.221236 0.538287 0.874731 -0.91348 -0.83486 1.456613 -0.58903

1.375315 -1.17021 2.021815 -1.01813 -1.59531 2.472822 -0.97984 1.399857 -1.09985 1.824235 -0.55174 -3.00505 4.16702 -1.63202 0.237641 0.519752 0.678519 -0.41245 -1.06829 1.266194 -0.4553 0.248537 0.507886 0.834619 -0.73742 -1.08 1.585458 -0.60013

1.468863 -1.30847 1.835631 -0.17962 -2.4202 2.604877 -0.86846 1.51249 -1.24821 1.817243 -0.74182 -1.95851 2.711487 -0.98201 0.259624 0.518594 0.507792 0.004241 -1.33281 1.257832 -0.42215 0.274517 0.494276 0.745005 -0.55118 -1.10084 1.406869 -0.49422

C-89 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


2

a/t 0.2

0.4

0.6

0.8

10

4

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.892348 -0.56612 2.581804 -1.56449 -3.06476 4.612133 -1.80044 0.901298 -0.55331 2.565941 -1.56402 -3.10211 4.706064 -1.84822 0.133763 0.353255 1.06498 -0.49146 -1.09361 1.057837 -0.32434 0.143912 0.366587 1.015279 -0.34727 -1.3588 1.268591 -0.3802

0.979714 -0.72548 2.949319 -1.78037 -3.39225 5.115045 -1.99007 1.001817 -0.65267 2.752506 -1.5008 -3.71796 5.398355 -2.09232 0.16347 0.303087 1.178026 -0.53821 -1.262 1.296022 -0.41713 0.177357 0.301216 1.276512 -0.83898 -0.90085 1.077153 -0.35648

1.115407 -1.06573 3.77272 -2.10087 -5.19315 7.785862 -3.08622 1.174417 -1.02665 3.923567 -3.06543 -3.60185 6.657817 -2.77254 0.204829 0.191342 1.436455 -0.8279 -1.08086 1.268753 -0.44104 0.225566 0.220228 1.384715 -0.69304 -1.43024 1.601399 -0.53732

1.243144 -1.11535 3.398414 -1.68643 -3.96636 5.374158 -1.95761 1.348939 -0.92352 2.670434 -0.69029 -4.70978 5.47252 -1.80889 0.238382 0.208213 1.174369 -0.38882 -0.98233 0.768977 -0.22403 0.273161 0.256365 1.054829 -0.27264 -1.08072 0.701264 -0.11962

0.618441 0.10897 3.321756 -5.89189 3.37405 0.305058 -0.70065 0.626156 0.114309 3.436849 -6.30326 4.114301 -0.36415 -0.46117 0.073772 0.254155 1.58987 -1.19364 -0.41549 0.523919 -0.13646 0.084972 0.247494 1.764253 -1.74973 0.498956 -0.29522 0.15928

0.705106 -0.02316 4.302381 -8.27756 6.593755 -1.94802 -0.08204 0.732618 0.036607 4.33804 -8.4916 7.116286 -2.55382 0.103037 0.24794 1.702747 -1.32463 -0.45401 0.687271 -0.21955 0.116607 0.255482 1.857056 -1.84771 0.558493 -0.33176

0.827244 -0.14733 4.831186 -7.71803 3.148878 2.082421 -1.59323 0.905804 -0.14196 5.512277 -9.56175 0.141229 0.201031 1.983964 -1.55112 -0.81838 1.348469 -0.50361 0.163312 0.260041 1.825916 -0.93865

Not for Resale

10

c/a

0.1732 0.16727

5.97649 -0.35927 -0.72662 -1.719 1.849916 -0.58036

0.984889 -0.59193 7.519862 -13.5101 8.816464 -0.48163 -1.16355 1.136295 -0.63227 8.993059 -17.1542 13.98648 -5.2792 0.77788 0.181668 0.205782 1.681088 0.697802 -6.07296 6.567973 -2.38642 0.226791 0.176145 2.352339 -1.31289 -2.67889 3.371922 -1.18142

--``````-`-`,,`,,`,`,,`---

C-90


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


0.2

0.4

0.6

0.8

10

16

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.407149 1.275307 0.661936 -2.20744 0.112163 2.155128 -1.22591 0.407861 1.41118 -0.12298 0.401791 -3.99815 5.157982 -2.03968 0.029996 0.334682 1.089345 1.426866 -5.9931 5.757879 -1.94196 0.044048 0.212151 2.354247 -3.04638 2.033382 -1.29635 0.42512

0.457024 1.408392 0.688715 -2.20963 0.847375 0.939313 -0.73355 0.475146 1.451004 1.079911 -3.53875 3.810827 -2.25622 0.51007 0.050418 0.329947 1.554532 -0.03976 -3.29789 3.28013 -1.09334 0.056037 0.33467 1.800475 -1.14198 -0.65627 0.570746 -0.12706

0.522307 1.519723 1.251787 -2.38057 -0.19061 1.95562 -1.00727 0.545574 1.711818 0.746041 0.367462 -3.2109 2.366074 -0.5373 0.068138 0.347099 1.848248 -0.69584 -1.92388 1.720244 -0.47984 0.074266 0.435578 1.541174 0.559045 -3.52443 2.576387 -0.66594

0.629493 1.436651 2.551755 0.41517 -14.3482 18.54737 -7.25024 0.631339 1.730331 1.866951 5.483011 -18.7497 15.98982 -4.45181 0.098203 0.333967 2.32188 -0.80354 -3.59082 4.224973 -1.56615 0.098293 0.350423 2.462583 0.354102 -5.23173 4.317319 -1.16044

0.275978 2.104379 -1.33224 -0.50576 1.252516 -0.43326 -0.14873 0.280132 2.07202 -0.70798 -2.84818 5.771448 -4.64857 0.019722 0.290969 1.826781 -0.95151 -2.20114 2.656906 -0.91794 0.013105 0.273105 2.1456 -2.52188 1.508614 -0.93892

0.301159 2.236935 -1.2366 -0.227 2.251246 -2.83872 0.035716 0.33908 1.584615 0.023157 -2.63464 2.044292

1.34382 0.26199

1.01234 0.291475 2.403025 -2.17427 3.077336 -1.67366 -1.02541 0.76395 -0.5487 0.018825 0.287094 1.96498 -0.48804 -2.69545 2.882303 -1.07997

0.322433 2.784889 -3.99337 11.32678 -16.755 10.9782 -2.78311 0.296657 2.679796 -3.78588 11.63494 -13.0489 4.442317 0.041083 0.231398 3.057756 -4.87771 6.313355 -5.79183 2.00041 0.028808 0.237904 2.48079 -2.12173 2.809571 -3.93304

0.0112 1.60598

0.411765 1.704418 7.413284 -24.6858 41.66298 -35.936 0.060944 0.059269 5.064858 -10.8339 16.2816 -14.0064

3.34631 0.83968

C-91

Not for Resale

8

a/t

11.8385 0.310521 2.159682 0.72527 4.209456 -2.96699 -4.85687 4.56037 0.055260 0.325908 1.687887 2.161601 -3.06812 -0.58939


10

c/a

--``````-`-`,,`,,`,`,,`---

R/t


0.2

0.4

0.6

0.8

20

1

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.21059 2.312121 -0.13262 -8.80205 19.37682 -17.3391 5.60916 0.186506 2.497137 0.410358 -14.277 33.04813 -31.1009 10.5291 0.009861 1.328788 -7.06092 30.84849 -56.3394 46.69106 -14.7144 0.008043 0.271707 2.240427 -1.57658 -2.94763 5.080884 -2.31876

0.215486 2.80035 -3.04539 2.053216 3.410859 -6.8487 2.97795 0.207054 2.753725 -2.87618 2.227162 3.973315 -8.08134 0.017858 0.307916 1.681398 -0.01661 -2.6394 2.207414 -0.69762 0.011418 0.384757 1.271624 0.396759 -1.16196 -0.4328

3.49664 0.45356

0.233493 2.780435 -2.06965 2.657911 1.45353 -5.8352 2.81259 0.208349 2.841662 -3.59319 9.533175 -7.90367 -0.46863 0.020541 0.388819 1.149927 2.487747 -5.73181 3.642785 -0.91726 0.017921 0.295862 1.827837 -0.74913 2.253206 -4.34805

1.63891 1.84069

0.24277 2.803535 -1.27137 5.462065 -6.13619 1.510885 0.030472 0.206744 2.970967 -3.25734 4.973979 -5.44645

11.4743 1.64176

0.0547 0.231842 2.060884 3.330136 -9.16926 24.91497 -29.8441 1.82856 0.025044 0.329503 1.377728 1.715174 -0.16127 -3.48163

1.228177 -0.85714 1.64914 -0.72349 -2.10408 3.127043 -1.26558 1.237365 -0.89345 1.769028 -0.89972 -2.14007 3.395658 -1.41248 0.189836 0.619568 0.513329 -0.04084 -1.81048 1.965467 -0.69191 0.201775 0.56226 0.829685 -0.90318 -0.6771 1.246072 -0.51304

Not for Resale

32

a/t

1.291315 -0.96501 1.805754 -0.91749 -1.82419 2.852755 -1.15957 1.304789 -0.99219 1.892573 -0.91007 -2.42228 3.76098 -1.54839 0.211291 0.571016 0.655601 -0.36237 -1.36245 1.643502 -0.60065 0.220655 0.570255 0.620375 -0.10482 -2.08059 2.405327 -0.87516

1.385229 -1.14701 1.919405 -0.71448 -2.28044 3.170269 -1.22747 1.404009 -1.11885 1.7571 -0.21604 -3.43385 4.387624 -1.6723 0.238974 0.523918 0.675763 -0.37199 -1.23561 1.448651 -0.51589 0.251665 0.493252 0.855991 -0.78686 -0.92838 1.422986 -0.54589

1.489488 -1.35114 2.131277 -1.25783 -0.80555 1.448803 0.264098 0.48334 0.743841 -0.68049 -0.38329 0.572737

-0.5327 1.52292 -1.33538 2.018106 -1.03742 -1.5224 2.329577 -0.85916 -0.2136 0.277661 0.490666 0.669306 -0.32811 -1.30019 1.473499 -0.5029


10

c/a

--``````-`-`,,`,,`,`,,`---

R/t

C-92 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


0.4

0.6

0.8

20

4

0.2

0.4

0.6

0.8

G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6

Outside Crack

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0.2

Inside Crack

Gi

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.892149 -0.53917 2.530731 -1.57301 -2.92228 4.445303 -1.73955 0.902161 -0.59389 2.792028 -2.1519 -2.29954 4.153491 -1.69758 0.133188 0.357528 1.045211 -0.39311 -1.30677 1.259464 -0.39415 0.145666 0.343303 1.142483 -0.69872 -0.83951 0.879246 -0.26431

0.987195 -0.69701 2.892247 -1.69638 -3.53657 5.259599 -2.04258 1.004994 -0.70402 2.936404 -1.71985 -3.74703 5.620522 -2.20244 0.164101 0.311629 1.174598 -0.56572 -1.19547 1.230337 -0.39327 0.177602 0.324323 1.085153 -0.19893 -1.93119 1.873507 -0.59389

1.141602 -1.09126 4.050481 -3.09746 -3.64152 6.625857 -2.74298 1.181681 -1.07416 3.999471 -2.98009 -3.98971 7.054781 0.210396 0.18696 1.486406 -0.96351 -0.91746 1.160405 -0.40736 0.230356 0.19664 1.452579 -0.83048 -1.23276 1.436885

-2.9051 -0.4815

1.285838 -1.06897 3.032382 -0.7046 -5.59568 6.677471 -2.33346 1.365757 -1.03711 2.887969 -0.75956 -5.17589 6.130371 -2.06795 0.247497 0.217533 1.10264 -0.16751 -1.38484 1.086184 -0.30807 0.279445 0.225549 1.090098 -0.25972 -1.15858 0.777397 -0.1447

0.619953 0.104258 3.502101 -6.58499 4.572773 -0.68018 -0.39077 0.624044 0.125565 3.384667 -6.14378 3.823354 -0.10499 -0.54798 0.072027 0.255715 1.574778 -1.10057 -0.58329 0.65904 -0.17935 0.086522 0.251852 1.73804 -1.65172 0.296591 -0.1122 0.10054

Not for Resale

2

a/t

--``````-`-`,,`,,`,`,,`---

20

c/a

0.712046 0.09973 3.700271 -6.39576 3.532436 0.471357 -0.82271 0.732936 0.085166 3.999392 -7.32749 5.049025 -0.79223 -0.3978 0.102436 0.239373 1.799183 -1.65742 0.154797 0.171592 -0.0598 0.119283 0.273674 1.722945 -1.37009 -0.32503 0.43576 -0.08171

0.870173 -0.20135 5.491611 -9.73042 6.12685 -0.13088 -0.94286 0.924796 -0.14703 5.553835 -9.79859 6.255566 -0.46776 -0.71431 0.146961 0.230001 1.800534 -0.90982 -1.90665 2.253983 -0.79983 0.175102 0.240244 1.965764 -1.36824 -1.11307 1.40686 -0.4424

1.066158 -0.682 0.203395 0.152657

8.23472 2.08571

-15.488 11.38461 -2.42135 -0.48766 1.196854 -0.76482 9.538822 -18.9684 16.30793 -6.57346 1.05692 -0.5861 -4.07884 4.976272 -1.87104 0.250788 0.064656 3.032021 -3.51981 0.704846 0.849548 -0.43707

C-93


R/t


0.2

0.4

0.6

0.8

20

16

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

8

a/t

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.405309 1.359428 0.217871 -0.8116 -2.13257 3.903326 -1.751 0.409327 1.35664 0.390447 -1.49279 -0.73432 2.497803 -1.21111 0.025027 0.372041 0.750804 2.602851 -7.82662 7.137545 -2.35362 0.042861 0.339277 1.438709 0.110848 -3.45856 3.278899 -1.02698

0.468062 1.518072 0.261454 -0.82974 -1.27856 2.464007 -1.15292 0.485426 1.470847 1.137514 -3.91363 4.411212 -2.67018 0.05261 0.345523 1.529331 -0.10187 -2.97463 2.94 -0.98952 0.06141 0.363429 1.702177 -0.80339 -1.27571 1.039943

0.62013 -0.2466

0.566516 1.576792 1.205982 -1.77762 -1.24002 2.589911 -1.14239 0.59754 1.733762 1.059041 -0.93815 -1.4454 1.27002 -0.24912 0.081748 0.350414 2.014082 -1.23646 -1.23405 1.407119 -0.46638 0.092819 0.410888 1.963655 -1.05892 -0.62773 0.022488 0.20863

0.714694 1.272546 4.866052 -7.40263 -0.92888 6.64832 -3.09947 0.777955 1.365907 5.918909 -8.07884 0.942464 2.034654 -0.43827 0.124282 0.261784 3.120477 -3.04719 -0.59553 2.107423 -0.92882 0.141437 0.335156 3.142784 -2.41758 -0.81656 0.913214 -0.10138

0.278452 2.097536 -1.03886 -1.68788 3.498143 -2.44726 0.53244 0.278981 2.151089 -1.295 -0.82318 2.281402 -1.75123 0.019683 0.251974 2.056009 -1.85496 -0.52517 1.370512 -0.58692 0.019674 0.224797 2.622522 -3.95587 3.671992 -2.68575

0.42128 0.84521

Not for Resale

20

c/a

0.308341 2.385585 -1.92183 1.980357 -1.03484 -0.37504 0.23656 0.306308 2.516374 -2.63013 4.451129 -4.00182 0.924404 0.13623 0.031282 0.343854 1.72884 -0.33687 -2.36717 2.06992 -0.60866 0.019364 0.418936 1.31179 0.66809 -2.94692 1.964796 -0.53152

0.40112 1.195553 10.28517 -38.4322 67.85784 -57.9926 0.04239 0.354881 2.140459 -1.33018 0.71235 -1.89561

18.745 0.349658 2.250205 1.282559 -5.61762 15.28539 -18.2272 7.06346 1.00726 0.024051 0.486146 1.165673 2.249645 -4.7554 2.48449 -0.50592

0.505861 0.610979 16.92296 -51.7085 81.15173 -66.0733 21.1833 0.435493 0.580314 15.80935 -46.0766 82.66331 -77.844 0.060908 0.440816 2.163456 0.620647 -3.84181 1.977736 -0.18314 0.038219 0.150727 3.795472 -4.02432 6.96083 -9.53295

--``````-`-`,,`,,`,`,,`---

C-94

27.6431 4.06521


R/t


0.2

0.4

0.6

0.8

60

1

0.2

0.4

0.6

0.8

Inside Crack


Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.22206 2.041495 2.40433 -18.1047 35.76643 -31.0194 9.95181 0.221753 1.54844 8.934596 -46.1315 89.73344 -78.9069 25.9069 0.009841 0.337096 1.792421 -1.30942 -0.69385 0.692134 -0.08216 0.008838 0.895514 -2.76058 14.43142 -27.1159 22.56994 -7.24956

0.233907 2.486697 -0.3945 -6.03773 16.35945 -17.0051 6.02733 0.212626 2.818308 -3.03302 2.700349 3.844809 -8.52014 0.015641 0.661412 -0.88932 8.000579 -14.1751 10.01939 -2.72454 0.011412 0.25787 1.992376 -0.27056 -2.82627 2.937993

3.76257 -1.1577

0.232156 3.261786 -5.35265 15.41107 -19.3707 9.764186 -1.68391 0.221826 2.684513 -1.02206 0.021195 0.285791 2.554554 -2.87742 4.471291 -5.37467 2.03201 0.018506 0.321327 1.474418

-1.7085 16.58343 -23.9882 1.21455 -0.79493 -2.3403

9.75487 1.34168

0.26468 3.089548 -2.79737 16.1803 -26.1326 16.06162 -3.63413 0.233473 2.192648 2.409249 -4.87956 23.22512 -33.5197 0.030454 0.326394 1.772593 3.214382 -6.91089 3.817756 -0.83924 0.02522 0.503957 -0.14353 7.339129 -7.53406 0.649287

13.8122 0.7706 Not for Resale

32

a/t

1.227244 -0.83221 1.563619 -0.5865 -2.20891 3.145646 -1.25494 1.236451 -0.88335 1.660995 -0.48945 -2.841 3.965751 -1.59197 0.191335 0.593112 0.678811 -0.49775 -1.17264 1.517881 -0.56622 0.201659 0.568561 0.775104 -0.73324 -0.92305 1.421656 -0.56341

1.293907 -0.94144 1.653191 -0.33544 -2.98735 3.923756 -1.52278 1.305727 -1.00082 1.857272 -0.6808 -2.82315 4.070933 -1.64114 0.212657 0.553272 0.777553 -0.69499 -0.91658 1.335911 -0.51261 0.223751 0.528818 0.857914 -0.82125 -0.93029 1.498214 -0.59934

1.391989 -1.12574 1.871387 -0.74404 -2.14743 3.031902 -1.17293 1.409752 -1.19587 2.113631 -1.17283 0.241095 0.510052 0.762927 -0.57218 -1.0394 1.354815 -0.49498 0.252809 0.496206 0.802983 -0.66098

1.502591 -1.32086 0.265958 0.48941

-1.9231 3.172229 -1.0059 1.404996

-1.2928 -0.5248

1.93121 -0.76701 -1.61111 2.118791 -0.73816 1.52611 -1.35769 1.959615 -0.74449 -1.85368 2.455851 -0.8665 0.6971 -0.48571 -0.80239 0.945581 -0.3278 0.279834 0.47884 0.692529 -0.44125 -0.97137 1.1277 -0.38283

C-95

--``````-`-`,,`,,`,`,,`---

20

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"


2

a/t 0.2

0.4

0.6

0.8

60

4

0.2

0.4

0.6

0.8

Inside Crack


Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 0.892834 -0.53489 2.582708 -1.83754 -2.41411 4.000823 -1.59308 0.898618 -0.54908 2.482265 -1.16574 0.133493 0.345473 1.140748 -0.68796 -0.84912 0.90668 -0.28726 0.146901 0.328932 1.210431 -0.85448

A4 A5 A6 -3.8572 5.347663 -2.05228 -0.6553 0.771722 -0.24002

0.993274 -0.68256 2.86827 -1.60359 -3.8094 5.56843 -2.15985 1.007429 -0.76277 3.293 -2.77665 -2.09303 4.32357 -1.80347 0.164205 0.323963 1.115855 -0.36632 -1.54561 1.521671 -0.48538 0.181032 0.283358 1.321869 -0.89224 -0.8601 1.045971 -0.34298

1.160583 -1.07632 4.019789 -3.03209 -3.87058 6.911263 -2.85428 1.185151 -1.10659 4.06043 -2.94805 -4.21099 7.280421 -2.97626 0.213941 0.19223 1.490657 -1.01345 -0.8145 1.059723 -0.36935 0.233528 0.182938 1.475845 -0.82948 -1.28266 1.490696 -0.49922

1.329237 -1.16151 3.653565 -2.88353 -2.12416 3.99405 -1.51021 1.376334 -1.17058 3.442652 -2.1143 -3.38951 4.921618 -1.7364 0.255574 0.224125 1.052971 -0.03137 -1.61924 1.259214 -0.34822 0.282014 0.23224 0.900523 0.487842 -2.46637 1.850033 -0.47973

0.618145 0.158592 3.235224 -5.81578 3.391581 0.217302 -0.6564 0.621872 0.144717 3.26704 -5.76907 3.202279 0.394112 -0.70165 0.070559 0.251924 1.614246 -1.24649 -0.28366 0.374078 -0.08069 0.088035 0.252389 1.735437 -1.61845 0.178476 0.023246 0.05021

Not for Resale

60

c/a

0.723086 0.076331 4.136926 -8.03193 6.359236 -1.86373 -0.08104 0.733106 0.098681 3.947255 -7.18894 4.783755 -0.54515 -0.48196 0.102834 0.253971 1.716387 -1.34076 -0.36686 0.564594 -0.17314 0.123723 0.246469 1.925584 -2.01448 0.642062 -0.27127 0.12238

0.904247 -0.18565 5.729124 -10.5508 7.28881 -0.96409 -0.69207 0.933072 -0.09102 5.151403 -8.5062 3.937245 1.552269 -1.37862 0.152959 0.254543 1.692264 -0.55359 -2.43354 2.596528 -0.87978 0.183558 0.217313 2.120103 -1.84191 -0.49592 1.029221 -0.35029

1.131688 -0.44198 6.705525 -9.95387 1.092488 6.397411 -3.29028 1.248088 -1.26679 13.23188 -31.7385 37.28331 -23.1222 6.12517 0.222158 0.026002 3.077342 -3.85637 1.22288 0.757223 -0.55984 0.261753 0.190769 1.983691 0.071851 -5.55866 6.083658 -2.09741


R/t

--``````-`-`,,`,,`,`,,`---

C-96 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


0.4

0.6

0.8

60

16

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.402016 1.465131 -0.42125 1.233709 -5.44407 6.505277 -2.54087 0.407474 1.380482 0.280836 -1.21888 -1.14269 2.818711 -1.31165 0.021121 0.366842 0.794775 2.378236 -7.21845 6.482394 -2.11366 0.048796 0.298759 1.878459 -1.50994 -0.75298 1.119326 -0.35741

0.475991 1.614929 0.05631 -0.38812 -1.80586 2.770215 -1.22882 0.486031 1.601403 0.417457 -1.78011 0.988449 0.045091 -0.211 0.047684 0.344882 1.400537 0.404961 -3.64996 3.393118 -1.12804 0.071623 0.390782 1.777201 -1.23796 -0.58787 0.493051 -0.06046

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0.2

Gi

0.604108 1.701839 1.297662 -2.34547 0.043552 1.162999 -0.57117 0.627006 1.915875 0.375014 0.724379 -4.31159 3.786541 -1.07343 0.087204 0.376779 1.921479 -0.95058 -1.42526 1.353735 -0.41197 0.109763 0.492544 1.713797 -0.40419 -1.8971 1.135454 -0.1307

0.801819 1.431166 5.137887 -7.59004 -1.72582 7.087092 -2.95937 0.883492 1.549975 5.952535 -9.37773 1.658256 2.624713 -0.79034 0.140921 0.313148 2.922217 -2.2316 -2.0494 3.181774 -1.208 0.182745 0.417024 3.064539 -2.26898 -1.88356 2.228041 -0.54604

0.279144 2.118699 -0.98025 -2.03738 0.019859 0.122056 2.501833 -2.85177

4.23735 -3.13727 0.76711 0.279269 2.147733 -1.11016 -1.70454 3.980062 -3.2401 0.96237 0.292507 -0.30982 0.029196 0.361359 2.099144 -2.41345 0.871465 -0.31761

0.91272 0.1149

Not for Resale

8

a/t

--``````-`-`,,`,,`,`,,`---

60

c/a

0.31772 2.478958 -2.06368 2.353408 -1.26879 -0.47711 0.31788 0.321257 2.516516 -2.00534 1.841965 0.563789 -2.8167 1.31301 0.037931 0.322569 1.764793 -0.7186 -1.37966 1.364092 -0.49726 0.030288 0.490594 1.319741 0.480319 -2.51626 1.280365 -0.16501

0.373139 3.029841 -3.69572 10.93337 -14.841 8.052859 -1.58497 0.376688 3.180761 -4.3574 13.45808 -16.9619 7.732542 -0.90398 0.051437 0.346661 2.506982 -2.53194 2.305525 -2.53414 0.95187 0.046492 0.505459 1.827252 -0.30105 0.319997 -2.6365 1.44216

0.51268 2.574607 4.100699 -6.70709 0.073539 0.394695 3.25618 -2.65153

7.19388 -9.52942 1.10693 -1.99051

C-97

4.71483 0.508937 2.869761 2.352832 1.820424 -0.78666 -10.8432 1.11242 0.074799 0.558113 2.451129 0.737529 -0.9973 -4.17817

7.58843 2.91417


R/t


0.4

0.6

0.8

100

1

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 0.219112 2.183684 1.415539 -14.6494 29.96804 -26.3528 0.00993 0.579087 -1.70218 12.69764 -26.627 23.62174

A6 A0 A1 A2 A6 A4 A5 A6 8.49846 0.225571 1.502637 9.49724 -48.3434 93.71256 -82.2705 26.9896 -7.8203 0.009072 1.077105 -3.74016 18.3772 -34.4463 28.42404 -8.92709

0.22735 2.899478 -3.07028 2.845911 2.435876 -6.30164 2.74114 0.223543 2.93739 -3.19946 2.78097 4.373897 -9.37529 0.018966 0.303749 1.883692 -0.63545 -1.91722 1.967167 -0.68974 0.015379 0.426271 1.437459 -0.03292 0.137297 -1.97203

4.12852 0.97672

0.259504 3.046036 -2.30266 5.147609 -0.25049 -7.06069 0.025718 0.372792 1.834776 0.718434 -1.95865 -0.5017

3.72962 0.231558 3.315269 -5.34871 15.8664 -14.2689 1.242696 1.82591 0.72191 0.019083 0.630364 -0.38987 7.420293 -10.4187 5.34501 -1.24646

0.312596 3.17917 -0.93084 13.40961 -18.1255 3.224809 0.03677 0.355318 2.261108 2.01258 -1.65028 -4.70438

2.49792 0.27842 1.619377 13.24939 -52.2191 129.9451 -142.768 3.26049 0.027425 -0.47089 10.87618 -36.9062 79.25838 -78.7432

54.2582 27.847

1.237421 -0.90121 1.78373 -0.92303 -2.04581 3.259078 -1.35259 1.237421 -0.90121 1.78373 -0.92303 -2.04581 3.259078 -1.35259 0.20047 0.590169 0.637213 -0.32664 -1.52273 1.851416 -0.6825 0.20047 0.590169 0.637213 -0.32664 -1.52273 1.851416 -0.6825

1.306466 -1.01524 1.935088 -0.89937 -2.4736 3.782566 -1.54721 1.306466 -1.01524 1.935088 -0.89937 -2.4736 3.782566 -1.54721 0.223571 0.533887 0.826362 -0.74393 -1.01252 1.532888 -0.60195 0.223571 0.533887 0.826362 -0.74393 -1.01252 1.532888 -0.60195

1.409899 -1.19432 2.068271 -0.98929 -2.22454 3.401071 -1.35944 1.409899 -1.19432 2.068271 -0.98929 -2.22454 3.401071 -1.35944 0.253076 0.49795 0.771147 -0.53734 -1.21193 1.56538 -0.5725 0.253076 0.49795 0.771147 -0.53734 -1.21193 1.56538 -0.5725

1.52568 -1.34151 1.783455 -0.09647 -2.9501 3.341272 -1.14256 1.52568 -1.34151 1.783455 -0.09647 -2.9501 3.341272 -1.14256 0.281529 0.457598 0.788296 -0.66084 -0.69791 0.95756 -0.34201 0.281529 0.457598 0.788296 -0.66084 -0.69791 0.95756 -0.34201

C-98

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

0.2

Gi

Not for Resale

32

a/t

--``````-`-`,,`,,`,`,,`---

60

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


2

a/t 0.2

0.4

0.6

0.8

100

4

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.898536 -0.56282 2.636997 -1.80068 -2.65794 4.291379 -1.70131 0.898536 -0.56282 2.636997 -1.80068 -2.65794 4.291379 -1.70131 0.146184 0.336602 1.201864 -0.93807 -0.38154 0.469019 -0.12577 0.146184 0.336602 1.201864 -0.93807 -0.38154 0.469019 -0.12577

1.006388 -0.74257 3.126026 -2.1867 -3.09312 5.129893 -2.05205 1.006388 -0.74257 3.126026 -2.1867 -3.09312 5.129893 -2.05205 0.178944 0.32069 1.101166 -0.27803 -1.73601 1.664871 -0.51472 0.178944 0.32069 1.101166 -0.27803 -1.73601 1.664871 -0.51472

1.187688 -1.15146 4.313443 -3.6414 -3.22481 6.578137 -2.77825 1.187688 -1.15146 4.313443 -3.6414 -3.22481 6.578137 -2.77825 0.234856 0.169401 1.531033 -0.92974 -1.20484 1.474713 -0.50378 0.234856 0.169401 1.531033 -0.92974 -1.20484 1.474713 -0.50378

1.376855 -1.18079 3.432775 -1.9675 -3.74229 5.258623 -1.85116 1.376855 -1.18079 3.432775 -1.9675 -3.74229 5.258623 -1.85116 0.282717 0.225806 0.913633 0.487159 -2.50463 1.901396 -0.50029 0.282717 0.225806 0.913633 0.487159 -2.50463 1.901396 -0.50029

0.622503 0.119799 3.469459 -6.47873 4.419235 -0.60945 -0.38377 0.622503 0.119799 3.469459 -6.47873 4.419235 -0.60945 -0.38377 0.087781 0.263726 1.66842 -1.44122 -0.05464 0.168573 0.01673 0.087781 0.263726 1.66842 -1.44122 -0.05464 0.168573 0.01673

Not for Resale

100

c/a

0.732995 0.099625 3.957373 -7.25266 4.91367 -0.66493 -0.44015 0.732995 0.099625 3.957373 -7.25266 4.91367 -0.66493 -0.44015 0.124453 0.243823 1.942652 -2.06094 0.695455 -0.30042 0.12921 0.124453 0.243823 1.942652 -2.06094 0.695455 -0.30042 0.12921

0.933585 -0.06714 4.985972 -8.00998 3.144457 2.175137 -1.56709 0.933585 -0.06714 4.985972 -8.00998 3.144457 2.175137 -1.56709 0.18616 0.187207 2.320879 -2.45919 0.428893 0.35508 -0.1581 0.18616 0.187207 2.320879 -2.45919 0.428893 0.35508 -0.1581

1.240705 -0.98327 11.03635 -24.419 25.07482 -13.2471 3.04485 1.240705 -0.98327 11.03635 -24.419 25.07482 -13.2471 3.04485 0.268532 0.068702 2.924279 -3.19358 -0.07249 1.661458 -0.72485 0.268532 0.068702 2.924279 -3.19358 -0.07249 1.661458 -0.72485

--``````-`-`,,`,,`,`,,`---

C-99


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


0.2

0.4

0.6

0.8

100

16

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 0.41407 1.204777 1.690217 -6.13659 7.236043 -4.04073 0.051207 0.263168 2.203952 -2.70762 1.33477 -0.61847

0.488463 1.573083 0.679425 -2.69427 0.072189 0.419684 1.572558 -0.5246

A6 A0 A1 A2 A6 A4 A5 0.84676 0.41407 1.204777 1.690217 -6.13659 7.236043 -4.04073 0.19805 0.051207 0.263168 2.203952 -2.70762 1.33477 -0.61847

2.46889 -1.09677 0.12794 0.488463 1.573083 0.679425 -2.69427 -1.882 1.618109 -0.43023 0.072189 0.419684 1.572558 -0.5246

A6 0.84676 0.19805

2.46889 -1.09677 0.12794 -1.882 1.618109 -0.43023

0.632565 1.961238 0.212464 1.067366 -4.85209 4.242828 -1.21876 0.632565 1.961238 0.212464 1.067366 -4.85209 4.242828 -1.21876 0.117102 0.457833 2.116802 -1.88948 0.575957 -0.8442 0.48755 0.117102 0.457833 2.116802 -1.88948 0.575957 -0.8442 0.48755

0.904467 1.660291 5.429361 -7.87417 -1.31829 5.438647 -1.75332 0.904467 1.660291 5.429361 -7.87417 -1.31829 5.438647 -1.75332 0.194705 0.409353 3.307649 -3.22508 -0.49734 1.292511 -0.29198 0.194705 0.409353 3.307649 -3.22508 -0.49734 1.292511 -0.29198

0.277854 2.162346 -1.29481 -0.9149 2.280673 -1.5076 0.24663 0.278704 2.168938 -1.26618 -1.18323 3.105412 -2.52499 0.019072 0.082898 2.479172 -2.44116 0.123556 1.029726 -0.55613 0.031491 0.345387 2.32357 -3.32649 2.438921 -1.5645

0.68583 0.49627

0.320208 2.506753 -2.0649 2.227828 -0.86236 -0.94327 0.49566 0.323438 2.541399 -2.01762 1.695905 0.927412 -3.16622 0.028406 0.270584 1.947826 -1.05799 -0.95048 1.1065 -0.45442 0.037033 0.490084 1.602022 -0.63851 -0.74121 -0.07101

1.43581 0.24474

Not for Resale

8

a/t

0.377521 3.240662 -4.82459 14.62968 -20.4559 12.07537 -2.70569 0.390524 3.257664 -4.31971 12.91827 -15.9472 6.851412 -0.59746 0.049618 0.334833 2.524177 -2.73218 3.109009 -3.42036 1.25094 0.059258 0.501495 2.35444 -2.28772 3.544442 -5.24082 2.28609

0.538092 2.719578 4.087174 -6.30083 7.147338 -10.8276 0.076044 0.410478 3.157604 -2.28964 1.020733 -2.39745

C-100

5.61527 0.558548 3.073305 2.711606 0.157017 1.195911 -12.2761 1.35655 0.096648 0.66476 2.451322 0.867953 -1.95125 -3.22155

8.15085 2.6751


100

c/a

--``````-`-`,,`,,`,`,,`---

R/t


0.2

0.4

0.6

0.8

¥

1

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.215848 2.299472 0.447928 -11.0688 23.63621 -21.0415 6.79789 0.230446 1.366535 10.74928 -53.0073 101.9654 -89.1984 29.2101 0.009536 0.561651 -2.21384 15.08135 -30.7855 26.97467 -8.86786 0.09086 1.038628 -2.76911 14.30135 -27.2244 22.40172 -6.99051

0.229132 2.927635 -3.07382 2.739746 2.960466 -6.97983 3.00834 0.22679 2.987436 -3.35966 3.314904 3.377962 -8.492 0.014203 0.219285 2.05648 -0.94896 -1.51323 1.963637 -0.85322 0.013227 0.489134 1.481022 -0.25056 0.351719 -2.27879

3.83265 1.18082

0.262335 3.209256 -3.23974 8.520427 0.024809 0.351354 2.070065 -0.52906

-5.122 -3.76658 0.0968 -1.49582

2.81565 0.245163 3.407357 -5.17546 15.02969 -12.2384 -1.05932 0.72413 0.037451 0.779048 -1.11977 10.26771 -14.3967 7.176713

2.75844 -1.3237

0.383599 1.703498 12.80512 -35.2911 68.8615 -71.7625 0.044869 0.090589 5.043191 -7.60137 13.74368 -16.2402

27.1027 0.300197 2.513347 4.557225 -10.6053 47.9099 -70.7214 6.54186 0.093687 0.445717 1.885641 0.489651 11.08897 -21.8341

30.7141 9.90554

1.230123 -0.85148 1.55097 -0.45381 -2.60572 3.613961 -1.44075 1.230123 -0.85148 1.55097 -0.45381 -2.60572 3.613961 -1.44075 0.1969 0.568337 0.811399 -0.88111 -0.6993 1.255667 -0.51193 0.1969 0.568337 0.811399 -0.88111 -0.6993 1.255667 -0.51193

1.298948 -0.9978 1.947954 -1.30027 -1.49401 2.830623 0.216225 0.563305 0.704831 -0.49345 -1.30788 1.707866

-1.2126 1.298948 -0.9978 1.947954 -1.30027 -1.49401 2.830623 -0.6406 0.216225 0.563305 0.704831 -0.49345 -1.30788 1.707866

Not for Resale

32

a/t

-1.2126 -0.6406

1.397118 -1.13484 1.791874 -0.42026 -2.86793 3.768548 -1.4405 1.397118 -1.13484 1.791874 -0.42026 -2.86793 3.768548 -1.4405 0.244587 0.532667 0.593969 -0.03618 -2.01631 2.216701 -0.77822 0.244587 0.532667 0.593969 -0.03618 -2.01631 2.216701 -0.77822

1.511701 -1.32448 1.756835 -0.13379 -2.86293 3.295327 -1.14124 1.511701 -1.32448 1.756835 -0.13379 -2.86293 3.295327 -1.14124 0.270447 0.511328 0.535744 -0.03273 -1.55702 1.557097 -0.50946 0.270447 0.511328 0.535744 -0.03273 -1.55702 1.557097 -0.50946


100

c/a

--``````-`-`,,`,,`,`,,`---

R/t

C-101 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


2

a/t 0.2

0.4

0.6

0.8

¥

4

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.900059 -0.5476 2.441677 -1.26885 -3.38153 4.786857 -1.83739 0.900059 -0.5476 2.441677 -1.26885 -3.38153 4.786857 -1.83739 0.139883 0.365987 0.983314 -0.24055 -1.53708 1.427492 -0.43719 0.139883 0.365987 0.983314 -0.24055 -1.53708 1.427492 -0.43719

1.005806 -0.73226 2.995194 -1.94592 -3.26135 5.142457 -2.03062 1.005806 -0.73226 2.995194 -1.94592 -3.26135 5.142457 -2.03062 0.174087 0.305163 1.207031 -0.67205 -1.06513 1.144559 -0.36448 0.174087 0.305163 1.207031 -0.67205 -1.06513 1.144559 -0.36448

1.182601 -1.10725 3.962364 -2.77813 -4.30973 7.277275 -2.96482 1.182601 -1.10725 3.962364 -2.77813 -4.30973 7.277275 -2.96482 0.227712 0.170117 1.549947 -1.10512 -0.83337 1.171706 -0.41945 0.227712 0.170117 1.549947 -1.10512 -0.83337 1.171706 -0.41945

1.383338 -1.39003 4.375578 -3.73726 -2.54032 5.3036 -2.09324 1.383338 -1.39003 4.375578 -3.73726 -2.54032 5.3036 -2.09324 0.282011 0.083923 1.725858 -1.53581 -0.06356 0.500678 -0.19822 0.282011 0.083923 1.725858 -1.53581 -0.06356 0.500678 -0.19822

0.627412 0.098006 3.427515 -6.17118 3.761013 0.014548 -0.60669 0.627412 0.098006 3.427515 -6.17118 3.761013 0.014548 -0.60669 0.081291 0.235191 1.791658 -1.8449 0.639466 -0.35485 0.15531 0.081291 0.235191 1.791658 -1.8449 0.639466 -0.35485 0.15531

Not for Resale

¥

c/a

0.739042 0.054816 4.084262 -7.58831 5.404753 -1.01461 -0.34834 0.739042 0.054816 4.084262 -7.58831 5.404753 -1.01461 -0.34834 0.11645 0.247988 1.828252 -1.71699 0.191212 0.116577 -0.01861 0.11645 0.247988 1.828252 -1.71699 0.191212 0.116577 -0.01861

0.946121 -0.18588 5.586746 -9.86349 5.959687 0.129644 -1.00261 0.946121 -0.18588 5.586746 -9.86349 5.959687 0.129644 -1.00261 0.177805 0.205668 2.097921 -1.80395 -0.55587 1.14614 -0.42066 0.177805 0.205668 2.097921 -1.80395 -0.55587 1.14614 -0.42066

1.245211 -0.69219 8.326062 0.258564 0.154889 2.117024

-14.948 8.693691 0.475579 -1.39266 1.245211 -0.69219 8.326062 -0.491 -4.61461 5.455075 -1.96633 0.258564 0.154889 2.117024

--``````-`-`,,`,,`,`,,`---

C-102 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

-14.948 8.693691 0.475579 -1.39266 -0.491 -4.61461 5.455075 -1.96633


R/t


0.2

0.4

0.6

0.8

¥

16

0.2

0.4

0.6

0.8


Inside Crack

Outside Crack

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

8

a/t

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.41686 1.212456 1.451554 -5.08051 5.176111 -2.17287 0.20404 0.41686 1.212456 1.451554 -5.08051 5.176111 -2.17287 0.20404 0.035319 0.354631 1.148 1.140333 -5.25021 4.862799 -1.57303 0.035319 0.354631 1.148 1.140333 -5.25021 4.862799 -1.57303

0.491777 1.659232 -0.10804 0.179324 -2.70761 3.368062 -1.34897 0.491777 1.659232 -0.10804 0.179324 -2.70761 3.368062 -1.34897 0.063427 0.37225 1.623167 -0.53065 -2.00074 1.894378 -0.58803 0.063427 0.37225 1.623167 -0.53065 -2.00074 1.894378 -0.58803

0.659182 1.875914 1.02126 -1.7698 -0.56536 1.247996 -0.43766 0.659182 1.875914 1.02126 -1.7698 -0.56536 1.247996 -0.43766 0.111604 0.47145 1.794059 -0.75576 -1.49017 1.085218 -0.21137 0.111604 0.47145 1.794059 -0.75576 -1.49017 1.085218 -0.21137

0.980933 1.884632 4.802078 -8.05802 0.444785 3.477266 -1.05675 0.980933 1.884632 4.802078 -8.05802 0.444785 3.477266 -1.05675 0.203995 0.480015 2.882243 -2.58901 -0.9683 1.537237 -0.37502 0.203995 0.480015 2.882243 -2.58901 -0.9683 1.537237 -0.37502

0.282375 2.112379 -0.86611 -2.45033 5.003528 -3.85544 1.03217 0.282375 2.112379 -0.86611 -2.45033 5.003528 -3.85544 1.03217 0.013699 0.301109 1.927456 -1.58246 -0.55641 1.010305 -0.37761 0.013699 0.301109 1.927456 -1.58246 -0.55641 1.010305 -0.37761

Not for Resale

¥

c/a

0.326148 2.520087 -1.8847 2.179874 -1.45971 -0.18865 0.23934 0.326148 2.520087 -1.8847 2.179874 -1.45971 -0.18865 0.23934 0.029412 0.369937 1.922085 -1.20715 -0.4394 0.273755 -0.03952 0.029412 0.369937 1.922085 -1.20715 -0.4394 0.273755 -0.03952

0.416633 3.156647 -2.62489 7.732591 -9.69278 3.64287 0.059846 0.434074 2.681156 -3.19366 4.075372 -4.69402

-0.0892 0.416633 3.156647 -2.62489 7.732591 -9.69278 3.64287 1.82855 0.059846 0.434074 2.681156 -3.19366 4.075372 -4.69402

-0.0892 1.82855

0.654014 3.423192 3.815805 -4.15869 3.471533 -10.3104 0.121478 0.697549 2.971833 -1.30365 -0.07549 -3.04651

6.628 0.654014 3.423192 3.815805 -4.15869 3.471533 -10.3104 2.167 0.121478 0.697549 2.971833 -1.30365 -0.07549 -3.04651

6.628 2.167

--``````-`-`,,`,,`,`,,`---

C-103


R/t

--``````-`-`,,`,,`,`,,`---


¥

c/a 32

a/t 0.2

0.4

0.6

0.8

Inside Crack

Gi G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6 G0 G1 G5 G6

Outside Crack

A0 A1 A2 A6 A4 A5 A6 A0 A1 A2 A6 A4 A5 A6 0.211805 2.479586 -0.97912 -5.98247 14.91676 -13.9367 4.58836 0.211805 2.479586 -0.97912 -5.98247 14.91676 -13.9367 4.58836 0.008992 0.647688 -0.63215 7.012493 -14.649 12.24961 -3.86819 0.008992 0.647688 -0.63215 7.012493 -14.649 12.24961 -3.86819

0.235794 0.014514

3.08224 -3.57921 3.947689 1.913159 -6.88722 0.4038 1.64227 -0.39061 -0.64807 -0.29403

3.18968 0.235794 0.25149 0.014514

3.08224 -3.57921 3.947689 1.913159 -6.88722 0.4038 1.64227 -0.39061 -0.64807 -0.29403

3.18968 0.25149

0.290224 3.689205 -4.57391 11.70989 -6.375 -5.88941 4.24524 0.290224 3.689205 -4.57391 11.70989 -6.375 -5.88941 4.24524 0.020889 0.701678 0.163184 5.707216 -8.20758 3.456112 -0.44547 0.020889 0.701678 0.163184 5.707216 -8.20758 3.456112 -0.44547

0.516355 2.531083 14.7129 -43.6218 101.0657 -116.081 0.082546 0.497177 4.606481 -7.33267 21.14862 -29.3451


46.1909 0.516355 2.531083 14.7129 -43.6218 101.0657 -116.081 12.4914 0.082546 0.497177 4.606481 -7.33267 21.14862 -29.3451

46.1909 12.4914 Not for Resale

R/t


2.



3.



6

n=0

5.

Influence coefficients for Ri t = 5 and c a = 32 are not provided in this table because this geometry represents a 360 degree crack. Influence coefficients for this case can be determined using Table C.11. Solutions for the G5 and G6 influence coefficients are being prepared.


4.

C-104 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.13 Influence Coefficients For a Circumferential 360°° Surface Crack in a Spherical Shell Inside Surface

G0 2

5

10

20

40

0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8

1.12 1.082756 1.075365 1.100683 1.221668 1.446289 1.894082 1.12 1.103301 1.115127 1.177157 1.415271 1.75895 2.297752 1.12 1.108615 1.129154 1.214669 1.548235 2.033355 2.688413 1.12 1.109939 1.132866 1.23289 1.654952 2.313398 3.17044 1.12 1.10672 1.129154 1.233528 1.727851 2.575276 3.748132

G1 0.682 0.660076 0.660394 0.673298 0.723809 0.821111 1.031408 0.682 0.666719 0.673609 0.695982 0.789345 0.92602 1.162919 0.682 0.667506 0.676718 0.706198 0.833006 1.018225 1.29069 0.682 0.666405 0.67501 0.707311 0.864381 1.108205 1.445533 0.682 0.662931 0.66939 0.699216 0.875389 1.185079 1.624554

G2 0.5245 0.509318 0.510553 0.519164 0.548551 0.60647 0.737721 0.5245 0.5124 0.516886 0.528877 0.580161 0.657926 0.801303 0.5245 0.512195 0.517697 0.532683 0.60082 0.702908 0.86271 0.5245 0.510964 0.515361 0.53066 0.612924 0.743888 0.935159 0.5245 0.508081 0.510348 0.522388 0.607334 0.773736 1.013576

Outside Surface

G3 0.4404 0.429462 0.430731 0.436599 0.455853 0.495534 0.588021 0.4404 0.431194 0.434249 0.441915 0.474188 0.525343 0.624584 0.4404 0.430804 0.43437 0.443396 0.485289 0.551016 0.659519 0.4404 0.429585 0.432069 0.440666 0.489863 0.572346 0.698728 0.4404 0.427061 0.427798 0.433221 0.478073 0.583393 0.737098

G4 0.379075 0.368984 0.370717 0.375976 0.392189 0.425106 0.503785 0.379075 0.37019 0.373337 0.378829 0.405897 0.446501 0.52826 0.379075 0.369757 0.373018 0.379499 0.414232 0.465383 0.552344 0.379075 0.368611 0.370909 0.376746 0.417989 0.481359 0.579813 0.379075 0.366476 0.367156 0.370142 0.412216 0.490483 0.607492 --``````-`-`,,`,,`,`,,`---

C-105

G0 1.12 1.135456 1.17202 1.262537 1.485895 1.79585 2.413845 1.12 1.124218 1.156245 1.249587 1.546794 1.953068 2.574511 1.12 1.123378 1.151243 1.252314 1.62213 2.152844 2.865317 1.12 1.115692 1.143927 1.251895 1.694893 2.384504 3.277447 1.12 1.10871 1.134717 1.243062 1.750478 2.616709 3.814046

G1 0.682 0.680892 0.695001 0.732636 0.816947 0.934668 1.188027 0.682 0.677493 0.688402 0.722068 0.834422 0.98762 1.243062 0.682 0.671737 0.684964 0.719666 0.858289 1.05542 1.34152 0.682 0.667977 0.679194 0.713993 0.877783 1.130006 1.475174 0.682 0.663406 0.671581 0.702548 0.886408 1.197704 1.642621

G2 0.5245 0.52093 0.528827 0.551175 0.597536 0.663221 0.811065 0.5245 0.519316 0.524943 0.542782 0.603652 0.688199 0.837873 0.5245 0.51424 0.522238 0.539728 0.61378 0.720965 0.885964 0.5245 0.511785 0.517596 0.534207 0.619735 0.754394 0.948252 0.5245 0.508287 0.51158 0.524143 0.616977 0.779703 1.021248

G3 0.4404 0.437092 0.442271 0.457089 0.486855 0.529983 0.630229 0.4404 0.436202 0.439534 0.450731 0.488737 0.543506 0.645142 0.4404 0.431826 0.43726 0.447812 0.493332 0.561704 0.672615 0.4404 0.429951 0.433524 0.442923 0.494049 0.578425 0.705919 0.4404 0.427159 0.428533 0.43437 0.487689 0.58683 0.74118

G4 0.379075 0.375097 0.379072 0.391076 0.413853 0.446039 0.525127 0.379075 0.374625 0.376947 0.385211 0.415653 0.456957 0.537022 0.379075 0.370189 0.375197 0.382744 0.41968 0.471242 0.557628 0.379075 0.368718 0.372045 0.37829 0.420723 0.484579 0.582125 0.379075 0.366458 0.367796 0.3709 0.416505 0.492296 0.608762

Not for Resale

a/t


Ri/t

--``````-`-`,,`,,`,`,,`---

Inside Surface

G0 60

100

300

1000

Notes:

0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8 0.0 0.05 0.1 0.2 0.4 0.6 0.8

1.12 1.103967 1.123564 1.22649 1.756462 2.71286 4.126269 1.12 1.09844 1.1123 1.208823 1.775773 2.860047 4.638121 1.12 1.070867 1.075365 1.133792 1.746727 3.051466 5.772142 1.12 1.024082 0.982026 0.969389 1.584413 2.990095 6.751458

G1 0.682 0.660076 0.664117 0.690153 0.875239 1.2202 1.735804 0.682 0.655289 0.654809 0.673259 0.870581 1.249167 1.877737 0.682 0.635287 0.62513 0.611639 0.796624 1.23445 2.124837 0.682 0.601169 0.555537 0.48418 0.640551 1.039894 2.106236


G2 0.5245 0.505804 0.505907 0.514444 0.600383 0.783173 1.057964 0.5245 0.501637 0.49849 0.500433 0.593351 0.783061 1.107159 0.5245 0.486127 0.4751 0.451255 0.510245 0.721692 1.136853 0.5245 0.459493 0.420873 0.351367 0.375023 0.508081 0.886556

Outside Surface

G3 0.4404 0.42519 0.424102 0.426569 0.468847 0.582943 0.755031 0.4404 0.421894 0.417996 0.414909 0.462736 0.572346 0.768207 0.4404 0.408884 0.399249 0.374918 0.378227 0.496415 0.715883 0.4404 0.387539 0.355007 0.294234 0.262572 0.285484 0.388222

G4 0.379075 0.364742 0.364056 0.364299 0.406373 0.491062 0.620864 0.379075 0.362018 0.358862 0.354317 0.398785 0.484799 0.63204 0.379075 0.351531 0.342505 0.320027 0.345428 0.434741 0.602916 0.379075 0.333594 0.305499 0.250941 0.253033 0.291371 0.392172

G0 1.12 1.104537 1.127294 1.23289 1.772076 2.742675 4.178392 1.12 1.09758 1.114656 1.212723 1.786084 2.879549 4.684553 1.12 1.067923 1.075365 1.134948 1.752724 3.059194 5.789161 1.12 1.020798 0.980903 0.969389 1.586151 2.993602 6.760196

G1 0.682 0.660076 0.665538 0.692392 0.884482 1.229196 1.750103 0.682 0.655129 0.655369 0.67466 0.874039 1.255034 1.89131 0.682 0.637431 0.624542 0.611982 0.808879 1.236715 2.129462 0.682 0.60239 0.554875 0.484342 0.641165 1.040903 2.108414


C-106

G2 0.5245 0.505596 0.506736 0.515615 0.610136 0.787404 1.064146 0.5245 0.501846 0.4987 0.501219 0.595117 0.785848 1.113538 0.5245 0.488495 0.474658 0.451429 0.528579 0.722661 1.138928 0.5245 0.461317 0.420499 0.351591 0.375198 0.508425 0.887591

G3 0.4404 0.425066 0.42472 0.427307 0.479525 0.585487 0.758412 0.4404 0.422044 0.418247 0.415415 0.46384 0.573872 0.771869 0.4404 0.411111 0.398986 0.375058 0.401085 0.496943 0.716981 0.4404 0.389214 0.355007 0.294144 0.262821 0.285546 0.38856

G4 0.379075 0.364628 0.364446 0.36481 0.410645 0.492297 0.621879 0.379075 0.362062 0.358839 0.354658 0.399489 0.485592 0.633612 0.379075 0.353835 0.342035 0.320071 0.354033 0.435008 0.603212 0.379075 0.335227 0.305194 0.251071 0.253176 0.291477 0.392167

Not for Resale

a/t


Ri/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.13 Influence Coefficients For a Circumferential 360°° Surface Crack in a Spherical Shell

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table C.14 Influence Coefficients For A Circumferential Semi-Elliptical Surface Crack In A Sphere

0.2 0.4 0.6 0.8

5

2

0.2 0.4 0.6 0.8

5

4

0.2 0.4 0.6 0.8

5

8

0.2 0.4 0.6 0.8

Inside Crack


A0 1.202179 0.184831 1.242247 0.201388 1.304612 0.222206 1.390842 0.248865 0.875562 0.129297 0.940103 0.155514 1.053788 0.192294 1.188461 0.238087 0.612795 0.074537 0.683509 0.100493 0.781164 0.130816 0.95162 0.185506 0.405009 0.035737 0.443016 0.045225 0.493973 0.059971 0.570313 0.083611

A1 -0.84251 0.592685 -0.97146 0.536435 -1.07905 0.524113 -1.24778 0.505852 -0.60633 0.346925 -0.74518 0.297019 -1.10936 0.18792 -1.29117 0.101008 0.025418 0.225775 -0.07624 0.213207 -0.14439 0.211497 -1.09142 -0.09499 1.232149 0.276546 1.348756 0.351693 1.610637 0.43279 1.533178 0.342692

A2 1.636246 0.664461 1.885279 0.841986 1.735636 0.654398 1.98968 0.623241 2.796852 1.049167 2.966456 1.157457 4.057995 1.380141 4.289815 1.608181 3.61172 1.719907 4.182209 1.801967 4.577991 1.786173 10.56435 3.728618 0.678443 1.593501 0.677866 1.357272 -0.47411 1.094406 0.196079 1.850494

A3 -0.74498 -0.53177 -0.99086 -0.98464 0.012846 -0.32287 -0.16645 -0.20596 -2.35823 -0.45249 -1.97494 -0.5681 -3.16325 -0.67462 -3.01352 -1.00267 -6.83388 -1.65703 -8.06638 -1.66331 -7.77094 -1.10923 -24.1386 -6.51509 -2.50573 -0.33808 -2.45327 0.164132 1.07253 0.840675 1.638149 -1.10438

A4 -1.86239 -0.92786 -1.65857 -0.19273 -3.18614 -1.08972 -2.7059 -0.96275 -1.62608 -1.14223 -2.89327 -1.0965 -3.13812 -1.2045 -3.08236 -0.64656 4.851983 0.265503 6.29037 -0.08244 4.023485 -1.31325 28.22147 6.811651 0.733352 -3.11741 1.000046 -3.13584 -2.48386 -3.52519 -5.17312 -0.54594

Outside Crack A5 2.786039 1.220279 2.648532 0.637713 3.63394 1.219277 2.965045 0.969567 3.387462 1.104886 4.644981 1.109809 6.014124 1.299745 5.639987 0.957821 -0.76996 0.075902 -1.55214 0.578951 1.375992 1.704317 -16.1943 -3.96978 1.676509 3.419437 1.182034 2.858551 2.232022 2.844646 6.20593 1.318202

C-107

A6 -1.12878 -0.45877 -1.08817 -0.28634 -1.32388 -0.43952 -1.04786 -0.35983 -1.40553 -0.34455 -1.83443 -0.34867 -2.53195 -0.44035 -2.37393 -0.4255 -0.40264 -0.02344 -0.27118 -0.23489 -1.47859 -0.62715 3.39407 0.79154 -1.08855 -1.18212 -0.89669 -0.89004 -0.86796 -0.88793 -2.91092 -0.87712

A0 1.267466 0.209983 1.368896 0.239275 1.518701 0.28367 1.706115 0.332593 0.867257 0.135019 0.987248 0.167919 1.181673 0.225353 1.413787 0.295376 0.573758 0.071766 0.654807 0.091884 0.736762 0.112705 0.823561 0.133631 0.365036 0.030362 0.382334 0.031678 0.37957 0.022018 0.374302 0.007572

A1 -0.92381 0.557726 -1.04408 0.532364 -1.17821 0.484493 -1.28688 0.467409 -0.33979 0.390878 -0.4453 0.376886 -0.762 0.26596 -0.91668 0.175153 0.504171 0.270873 0.490681 0.301251 0.532901 0.329346 0.049605 0.146859 1.728006 0.250871 1.745919 0.322613 1.95885 0.404378 1.735023 0.425533

A2 2.194068 0.80047 2.536126 0.855799 2.560336 0.931608 2.245458 0.858728 2.666705 1.056167 3.124547 1.127307 4.392908 1.582475 5.784941 2.289457 2.630815 1.828085 3.473567 1.867395 4.065276 1.92385 8.066059 3.257226 -1.04023 2.041354 -0.08283 1.526634 -1.14195 1.122881 -0.37046 0.686983

A3 -1.09356 -0.45714 -1.89014 -0.46132 -1.6965 -0.55725 -0.7754 -0.39811 -2.02482 -0.09799 -2.47611 -0.03446 -3.42356 -0.6755 -6.87192 -2.39051 -5.04973 -1.81472 -6.8787 -1.72192 -5.67898 -0.85505 -12.0672 -2.85931 2.117787 -1.92206 -0.55043 0.625355 4.157523 1.411468 7.014213 3.400888

A4 -2.72865 -1.24393 -1.78139 -1.48689 -2.21701 -1.48045 -3.33175 -1.5912 -2.74458 -1.9952 -2.81715 -2.33438 -4.4982 -1.83413 1.091081 0.653225 2.999738 0.69285 5.995558 0.715735 2.702096 -1.13573 10.88957 1.499683 -5.43374 0.402303 1.090492 -3.91143 -2.74234 -2.2682 -6.69944 -3.59338

A5 4.170131 1.452798 3.625787 1.786837 3.963391 1.838622 4.357856 1.796981 4.664963 1.796974 5.019464 2.164456 7.981611 1.94295 2.410809 -0.10217 0.106914 -0.60466 -2.60863 -0.78578 -0.07717 0.727023 -7.86213 -1.75451 5.516726 -0.10888 -1.52022 3.331029 -1.73433 0.044791 0.172409 0.281236

A6 -1.7078 -0.5189 -1.58049 -0.6475 -1.64818 -0.66237 -1.55892 -0.60175 -1.89126 -0.53874 -2.04915 -0.67274 -3.30457 -0.63509 -1.06905 0.0564 -0.53145 0.29579 0.37846 0.36757 -0.34376 -0.11694 2.66143 0.79321 -1.98251 0.05403 0.55484 -1.05074 1.2469 0.32505 0.62833 0.14355

Not for Resale

1

a/t

--``````-`-`,,`,,`,`,,`---

5

c/a


R/t


0.2 0.4 0.6 0.8

10

1

0.2 0.4 0.6 0.8

10

2

0.2 0.4 0.6 0.8

10

4

0.2 0.4 0.6 0.8

Inside Crack


A0 0.273117 0.015128 0.439976 0.025177 0.358271 0.025268 0.349974 0.026484 1.210278 0.188784 1.26386 0.205646 1.338505 0.228609 1.430644 0.252484 0.88371 0.130028 0.962879 0.159658 1.096737 0.199776 1.242483 0.247364 0.614005 0.074334 0.700269 0.104436 0.832781 0.144742 1.040898 0.209

A1 2.081572 0.326391 -1.46425 0.721645 1.131667 0.56247 2.291435 0.405197 -0.79251 0.585397 -0.96141 0.557956 -1.08055 0.534397 -1.26363 0.509576 -0.5753 0.383099 -0.71841 0.300691 -1.10709 0.195315 -1.30019 0.081939 0.117267 0.229889 -0.01129 0.209279 -0.14296 0.214331 -1.05724 -0.07381

A2 -1.36358 1.704366 28.04049 -1.54567 8.998108 -0.07745 -0.28319 1.586581 1.325211 0.711851 1.882203 0.736186 1.685194 0.608579 1.910082 0.63039 2.685008 0.852799 2.918922 1.177951 4.051375 1.3974 4.294143 1.827049 3.196605 1.734333 4.083941 1.949799 4.633564 1.826853 10.76592 3.713565

A3 -0.60122 -1.77827 -104.353 10.50411 -39.164 5.632144 -2.49922 -0.33649 0.159279 -0.61422 -1.17476 -0.63721 0.059588 -0.13087 -0.18006 -0.2703 -2.0132 0.169834 -1.80297 -0.56841 -3.02676 -0.76469 -3.29693 -1.85063 -5.55122 -1.66999 -7.70724 -2.21669 -7.45502 -1.13795 -25.1605 -6.37403

A4 1.310963 1.261591 181.4352 -20.5049 74.85094 -11.5732 9.79233 -0.36965 -3.33151 -0.93765 -1.34422 -0.85372 -3.44856 -1.59641 -2.80312 -1.00269 -2.26136 -2.15828 -3.2999 -1.1982 -3.69365 -1.08769 -2.75604 0.682335 2.843015 0.328485 5.697754 1.030415 3.127856 -1.42191 29.56341 6.079934

Outside Crack A5 -0.31835 -1.57411 -150.126 16.92535 -66.3382 9.278879 -11.1233 0.176902 3.975232 1.309349 2.430545 1.205809 4.013249 1.724166 3.15326 1.055648 3.959268 1.904739 5.046579 1.246293 6.646472 1.219684 5.309917 -0.12181 0.735933 -0.03345 -1.19537 -0.48287 1.998563 1.841381 -17.485 -3.22634

--``````-`-`,,`,,`,`,,`---

C-108

A6 -0.21849 0.74931 47.4394 -5.32341 21.8923 -2.92594 3.70941 -0.34916 -1.49825 -0.50013 -1.0245 -0.46154 -1.47157 -0.6053 -1.10392 -0.37549 -1.59989 -0.5862 -1.97418 -0.40266 -2.75856 -0.41389 -2.17237 -0.05581 -0.83615 0.02655 -0.32718 0.13772 -1.5759 -0.66923 4.01178 0.58881

A0 0.256933 0.01423 0.272975 0.036117 0.282136 0.051347 0.25708 0.064569 1.257289 0.206539 1.342742 0.232879 1.475713 0.272164 1.638996 0.314193 0.885431 0.141692 1.002985 0.177168 1.206404 0.238368 1.459466 0.312242 0.598904 0.078533 0.698793 0.107703 0.858944 0.152522 1.084552 0.21133

A1 2.08529 0.133844 2.310173 0.371264 1.614887 0.04516 2.147141 0.28617 -0.92975 0.554664 -1.01466 0.520985 -1.20472 0.467468 -1.36009 0.447066 -0.44695 0.341269 -0.57596 0.321997 -0.93218 0.203016 -1.14449 0.102429 0.319256 0.264553 0.344779 0.265188 0.263315 0.27601 -0.2782 0.254215

A2 -0.47832 2.768654 -2.1314 1.18268 4.842185 3.869138 -0.32953 1.42067 2.066713 0.842037 2.043616 0.929303 2.296349 0.970918 2.017802 0.843355 2.561834 1.246343 2.982162 1.255358 4.124017 1.628254 4.773246 2.085711 3.046618 1.772377 3.442438 2.001373 4.509792 2.085088 9.085535 2.384815

A3 -3.2955 -2.73787 2.797454 0.996814 -20.2233 -8.36251 4.717173 1.520745 -1.28778 -0.78165 -0.74782 -0.94157 -1.27903 -0.91305 -0.37441 -0.60421 -1.47679 -0.8009 -1.83098 -0.48651 -2.78321 -0.96529 -4.14516 -2.08342 -5.75071 -1.6888 -6.05177 -2.21239 -6.42073 -1.45629 -15.5432 -0.41946

A4 6.40219 -0.9947 -0.05976 -2.91123 42.13363 14.933 -3.27573 -1.76901 -1.86874 -0.76155 -3.17488 -0.62682 -2.27587 -0.7725 -3.25337 -0.98367 -3.57293 -0.83451 -3.81902 -1.64801 -5.12496 -1.35052 -2.96022 0.283979 3.644172 0.38834 3.604332 1.243341 1.930137 -0.67106 12.28714 -3.879

A5 -5.23094 3.054635 -3.23969 1.528592 -40.822 -14.3537 -2.33302 -0.13416 3.262798 1.173564 4.527086 1.126253 3.691608 1.266525 3.956049 1.228995 5.259445 0.914157 5.788766 1.69366 8.312746 1.629653 5.813935 0.311955 -0.15977 -0.24493 -0.04525 -0.98174 1.883945 0.727595 -5.77022 3.648836

A6 1.55541 -1.48401 1.67426 -0.2928 14.2422 4.90836 1.53207 -0.00772 -1.38225 -0.4592 -1.81451 -0.45277 -1.49816 -0.49013 -1.38893 -0.4219 -2.05681 -0.28 -2.27605 -0.54533 -3.36215 -0.55612 -2.1977 -0.11767 -0.4987 0.15506 -0.55329 0.38522 -1.20092 -0.17204 1.44203 -1.07788

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

16

a/t

Not for Resale

5

c/a


R/t

8

a/t 0.2 0.4 0.6 0.8

10

16

0.2 0.4 0.6 0.8

10

32

0.2 0.4 0.6 0.8

20

1

0.2 0.4 0.6 0.8

Inside Crack


A0 0.409327 0.032164 0.461753 0.053663 0.538072 0.075335 0.662887 0.108601 0.284282 0.01612 0.306942 0.017097 0.325281 0.032151 0.402906 0.041026 0.189224 0.004444 0.218843 0.007262 0.234356 0.009311 0.311606 0.025945 1.219034 0.188506 1.27755 0.207184 1.363088 0.234087 1.458861 0.257588

A1 1.211834 0.342651 1.462282 0.327602 1.621382 0.363743 1.404727 0.336423 1.812909 0.177265 2.266196 0.397488 2.911025 0.267005 2.513077 0.436965 2.482003 0.412109 2.805676 0.282275 2.942388 0.308874 1.211836 -0.10679 -0.85437 0.60307 -0.97172 0.573568 -1.13559 0.503742 -1.28297 0.490776

A2 1.101433 1.089603 0.215621 1.620914 0.465307 1.792529 2.781695 2.317837 0.855582 2.726718 -1.4011 1.270756 -5.03832 2.773864 -0.82652 1.638816 0.282887 1.338636 -3.22845 1.870155 -3.52061 1.721033 10.71379 5.04333 1.7643 0.602341 1.946579 0.634929 2.037755 0.824389 1.941154 0.719626

A3 -3.9158 1.343844 -0.88129 -0.45417 -0.53979 -0.83051 -4.14017 -1.71852 -7.7366 -3.96861 -0.18236 0.739843 13.33966 -4.21888 2.003631 0.334034 -13.8737 -0.89933 2.621647 -0.58286 6.591129 0.309729 -35.4327 -9.50306 -1.23369 -0.24582 -1.33273 -0.25674 -1.14217 -0.78793 -0.54007 -0.47543

A4 3.160535 -5.78831 -1.33284 -2.52785 -2.4739 -1.47516 -0.35878 -0.68243 12.99672 2.622463 2.587602 -3.59133 -17.9184 5.423193 0.844214 -1.6643 31.82774 0.382205 2.522784 -1.87127 -3.3423 -1.81075 63.44216 14.33327 -1.14456 -1.56691 -1.2496 -1.56846 -1.57647 -0.62135 -2.15957 -0.85877

Outside Crack A5 -0.40683 5.519543 2.787894 2.649762 3.735984 1.38957 4.249996 1.543233 -9.70524 -1.04559 -3.17905 2.760458 11.11743 -4.89251 -4.13269 0.83728 -29.5738 -1.17073 -6.00976 1.738281 -2.98682 0.435858 -55.8277 -12.2651 2.288332 1.820018 2.460115 1.819797 2.600181 0.987985 2.638547 1.02876

A6 -0.39791 -1.84044 -1.33883 -0.89458 -1.65067 -0.42131 -2.42677 -0.81178 2.69598 0.1827 1.0989 -0.77239 -2.80687 1.59744 1.73039 -0.39146 9.90131 0.66366 2.63892 -0.5959 2.12382 0.0592 18.2846 3.77874 -0.98852 -0.65749 -1.05337 -0.65665 -1.04837 -0.37916 -0.92999 -0.37295

A0 0.388346 0.034316 0.432551 0.045278 0.466246 0.051513 0.50042 0.050926 0.272677 0.031456 0.276962 0.013301 0.267924 0.012467 0.291237 0.000634 0.194272 0.004649 0.205118 0.005358 0.216796 0.007174 0.251789 0.08834 1.250014 0.204503 1.328065 0.228873 1.449884 0.264791 1.598647 0.300477

A1 1.518138 0.309941 1.701935 0.333441 1.846281 0.362792 1.565573 0.321058 1.946213 -0.30409 2.327692 0.293732 2.784228 0.220597 2.358301 0.459143 2.719898 0.244905 2.783346 0.336878 2.648252 0.232611 1.554224 0.318186 -0.91234 0.576045 -1.00672 0.542533 -1.20615 0.486856 -1.44001 0.463146

A2 -0.03539 1.61578 -0.05407 1.820513 0.118826 1.945363 2.186909 2.076457 0.432317 6.837241 -1.52515 1.849416 -4.63739 2.415394 -1.84944 0.451951 -3.53831 2.100511 -3.05068 1.643031 -1.88661 2.445532 7.500695 1.442474 1.856919 0.699163 1.884077 0.771876 2.160518 0.840278 2.279592 0.720319

A3 -0.75088 -0.43537 -0.27104 -1.14533 1.895146 -0.81983 2.200854 0.551979 -6.32214 -18.9502 0.565194 -0.6099 13.41556 -2.75409 8.932259 3.914963 4.377376 -1.09632 3.136843 -0.66596 3.986776 -2.90246 -22.5698 1.609246 -0.82675 -0.40137 -0.47187 -0.52723 -1.08882 -0.68309 -1.23604 -0.38845

--``````-`-`,,`,,`,`,,`---

C-109

A4 -1.26293 -2.31113 -0.2974 -0.22493 -2.22873 0.032051 -2.18792 -0.75782 11.23115 29.68576 3.460548 -1.28688 -13.9353 5.376582 -3.81852 -3.04456 -3.9935 -2.846 2.145293 0.330388 0.680633 5.645156 44.26953 -0.54744 -2.46499 -1.419 -3.3649 -1.29307 -2.22306 -0.97408 -1.66468 -1.13954

A5 2.535921 2.17772 0.18942 -0.07679 -0.64678 -1.033 -4.14593 -2.16633 -8.91517 -24.0452 -5.70444 0.944646 4.340989 -6.56789 -6.84744 -0.94519 2.080358 3.993396 -6.63277 -1.44507 -6.99602 -6.83918 -42.4463 -2.55228 3.702626 1.757507 4.560898 1.685327 3.452276 1.351834 2.610051 1.272242

A6 -1.1454 -0.65388 -0.08567 0.11965 0.74653 0.54095 2.87445 1.30443 2.64401 7.50171 2.29656 -0.29654 0.06025 2.4334 4.03042 0.61703 -0.5414 -1.64547 3.11085 0.71824 3.60219 2.53586 14.4383 1.14649 -1.5151 -0.65475 -1.80163 -0.6337 -1.38207 -0.50127 -0.96869 -0.42378

Not for Resale

10

c/a


R/t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


--``````-`-`,,`,,`,`,,`---


2

a/t 0.2 0.4 0.6 0.8

20

4

0.2 0.4 0.6 0.8

20

8

0.2 0.4 0.6 0.8

20

16

0.2 0.4 0.6 0.8

Inside Crack


A0 0.885462 0.130952 0.974681 0.160932 1.121993 0.204911 1.284052 0.25433 0.617451 0.071829 0.710238 0.103614 0.866844 0.148445 1.090479 0.209224 0.405392 0.031335 0.473102 0.05396 0.576893 0.087386 0.747633 0.135091 0.276663 0.018116 0.313252 0.024337 0.348774 0.036975 0.44098 0.051815

A1 -0.52572 0.360216 -0.67648 0.322151 -1.06181 0.211023 -1.36872 0.05233 0.096159 0.251003 0.043984 0.239899 -0.18535 0.250136 -0.88019 0.205149 1.344933 0.256538 1.459825 0.346875 1.673695 0.371843 1.525519 0.355541 2.07529 0.237787 2.412165 0.331976 2.927714 0.322875 2.440931 0.391964

A2 2.445901 1.0383 2.781725 1.082804 3.870644 1.310845 4.766019 2.049643 3.512532 1.592231 3.99024 1.771184 5.209401 1.631537 9.56124 1.613008 0.257048 1.721091 0.668658 1.514968 0.583902 1.931628 3.491101 2.641538 -1.20739 2.101277 -1.98831 1.875979 -3.91444 2.495838 2.191329 2.487924

A3 -1.31442 -0.42441 -1.47046 -0.27832 -2.61441 -0.42932 -4.92878 -2.53031 -6.64252 -1.16965 -7.46959 -1.5881 -9.00926 -0.45067 -20.31 0.948889 -1.00617 -0.83854 -2.43139 -0.11875 -0.41661 -1.17541 -5.9067 -2.40373 -0.22755 -1.79591 1.736132 -0.87948 10.75954 -2.78661 -4.07674 -1.1766

A4 -3.34561 -1.18948 -3.79221 -1.65696 -4.32636 -1.74173 -0.39169 1.598585 4.657258 -0.47635 5.374222 0.023924 5.129644 -2.57445 20.02358 -6.52255 -1.75609 -1.94306 1.439234 -2.97677 -2.92847 -1.18652 0.660976 -0.48934 0.02358 -0.94141 -0.27659 -1.63387 -15.1662 3.216224 5.862346 -0.03825

Outside Crack A5 4.784249 1.126834 5.41452 1.594614 7.132826 1.793341 3.564927 -0.76312 -0.72454 0.584595 -1.01526 0.283608 0.62876 2.743072 -9.42247 6.999506 3.572957 2.298428 0.317076 2.9842 3.812903 1.330743 3.859764 1.664463 0.902634 1.907122 -1.10918 1.635667 9.709167 -3.71816 -6.44143 -0.76494

A6 -1.84311 -0.34385 -2.08052 -0.50427 -2.89533 -0.59853 -1.62208 0.13875 -0.38324 -0.15902 -0.35834 -0.09095 -1.17779 -0.9382 1.59408 -2.55122 -1.6379 -0.82053 -0.49827 -1.01161 -1.52168 -0.44083 -2.16476 -0.80798 -0.61727 -0.80091 0.48343 -0.50853 -2.56972 1.47021 2.37016 0.35444

A0 0.894564 0.145218 1.009783 0.179973 1.20689 0.239439 1.457562 0.311033 0.611348 0.083875 0.721014 0.11592 0.920334 0.172931 1.215354 0.255827 0.401438 0.037001 0.463771 0.055982 0.55493 0.07671 0.678729 0.108382 0.272229 0.025277 0.294971 0.020443 0.293204 0.022605 0.312236 0.031367

A1 -0.52369 0.334184 -0.68749 0.305386 -1.01281 0.189505 -1.34927 0.084983 0.223792 0.252977 0.207974 0.279727 -0.01467 0.270071 -0.47444 0.197837 1.368139 0.41644 1.624502 0.366365 1.805579 0.457549 1.720755 0.400786 2.122222 0.004903 2.426327 0.254376 2.92379 0.223474 2.479824 0.392077

A2 2.687221 1.236445 3.233014 1.290909 3.959639 1.583211 4.983173 1.90842 3.226766 1.802161 3.869537 1.800683 5.670948 1.996927 9.091116 2.451139 0.834483 0.873396 0.482407 1.729766 0.932147 1.565832 3.502419 2.547658 -1.17408 4.371443 -1.93748 2.497804 -4.91162 2.890357 -1.443 1.152249

C-110 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A3 -1.83549 -0.84791 -2.55441 -0.74593 -2.33132 -1.05181 -4.98815 -1.77542 -5.94524 -1.80056 -7.21489 -1.52624 -9.97312 -1.27259 -15.7619 -0.79094 -3.53545 2.081299 -1.95744 -0.84348 -0.35788 0.482942 -0.79881 -0.56225 -0.4369 -9.94653 1.850547 -3.424 15.28175 -3.84738 9.729933 3.146729

A4 -2.85708 -0.7151 -2.59694 -1.10074 -5.6495 -0.99375 -1.40618 0.021232 3.654021 0.503105 5.158906 -0.09691 6.656886 -1.22869 10.34502 -4.10588 3.216413 -6.73104 1.85376 -0.97895 -0.53078 -2.53802 -2.62586 -0.9045 0.816727 13.83322 1.30489 4.301929 -17.5181 6.119555 -3.16018 -1.85416

A5 4.589319 0.817733 4.790589 1.210498 8.631388 1.257408 4.664817 0.46531 -0.01845 -0.27424 -1.05611 0.24722 -1.03939 1.379356 -2.24315 4.54707 -0.9838 5.885197 -1.08268 0.614079 -0.83505 1.086088 -1.52302 -1.24535 -0.1542 -10.9806 -3.94035 -4.08256 7.321047 -6.26767 -10.6685 -2.87799

A6 -1.82365 -0.25124 -1.96126 -0.38613 -3.43621 -0.42256 -1.89079 -0.16253 -0.57072 0.15076 -0.28467 -0.02594 -0.47921 -0.40544 -0.07605 -1.50644 -0.06674 -1.83032 0.21608 -0.07881 0.6371 -0.05263 2.05234 1.02783 -0.1656 3.44312 1.74529 1.35713 -0.89637 2.05743 6.26967 1.61544

Not for Resale

20

c/a


R/t

--``````-`-`,,`,,`,`,,`---


0.2 0.4 0.6 0.8

60

1

0.2 0.4 0.6 0.8

60

2

0.2 0.4 0.6 0.8

60

4

0.2 0.4 0.6 0.8

Inside Crack


A0 0.171377 0.008529 0.222378 0.016656 0.242834 0.021711 0.290257 0.027496 1.204993 0.18398 1.285418 0.209307 1.380433 0.237741 1.479192 0.259621 0.875583 0.127962 0.985835 0.162929 1.138681 0.209812 1.308368 0.249837 0.578046 0.064704 0.716818 0.103642 0.887611 0.153493 1.071471 0.216578

A1 3.095322 0.438707 2.857786 0.364768 2.968004 0.484376 2.319621 0.285217 -0.78706 0.612055 -0.9345 0.569691 -1.09265 0.517769 -1.25082 0.510084 -0.45772 0.376322 -0.65392 0.318597 -0.87678 0.24754 -1.02027 0.267465 0.737389 0.427202 0.138589 0.218527 0.000632 0.223468 0.512444 0.096765

A2 -5.01017 0.922945 -3.28047 1.598663 -2.71235 0.738522 4.246549 2.392744 1.469168 0.634277 1.707728 0.698647 1.726852 0.742516 1.740382 0.650811 2.210888 0.977114 2.756387 1.165293 3.11839 1.301203 2.780804 0.787851 0.684919 0.952475 3.645688 1.962918 4.334417 1.933537 -1.07876 2.494014

A3 5.652766 1.860793 3.29867 -0.81644 4.227628 3.735068 -13.6898 -0.4558 -0.4719 -0.50722 -0.66412 -0.52095 -0.34432 -0.56507 -0.55153 -0.54043 -0.89458 -0.27357 -1.48809 -0.57643 -1.56595 -0.6895 -0.25239 0.753672 -1.00598 -0.13049 -6.45713 -2.16478 -6.25279 -1.47801 17.59081 -1.97557

A4 -2.30497 -6.25534 1.307207 0.815595 1.971658 -7.38275 31.50016 0.719252 -2.28836 -1.00166 -2.28637 -1.10213 -2.73971 -0.9866 -1.4528 -0.44585 -3.74595 -1.41946 -3.71827 -1.149 -4.34919 -1.17176 -6.06626 -2.76968 -0.93882 -1.46384 3.805353 0.978261 0.675469 -0.78103 -45.713 -1.51514

Outside Crack A5 -1.28384 5.330135 -5.07305 -2.1386 -8.48569 4.996573 -34.0754 -2.5606 3.179724 1.299646 3.273554 1.427965 3.482474 1.284777 1.702313 0.51429 4.988729 1.316033 5.344338 1.178017 6.077143 1.261422 6.921051 2.099875 1.900047 1.159251 0.161978 -0.49411 4.026259 1.205612 44.36804 2.615867

A6 0.936065 -1.5596 2.33558 1.05938 4.07595 -1.46753 12.4991 1.01953 -1.26384 -0.48116 -1.30197 -0.52892 -1.31172 -0.47008 -0.55186 -0.16611 -1.89011 -0.40635 -2.05811 -0.3732 -2.29201 -0.40434 -2.37168 -0.59376 -0.81625 -0.31548 -0.70252 0.14917 -2.1571 -0.43263 -15.098 -1.03744

C-111

A0 0.203486 0.004857 0.208981 0.008044 0.205546 0.008247 0.236901 0.009071 1.221692 0.195875 1.31073 0.223533 1.421995 0.257568 1.544171 0.28558 0.883442 0.14245 1.008248 0.17969 1.187736 0.238406 1.412991 0.296697 0.577742 0.079925 0.733125 0.123718 0.935739 0.18462 1.200178 0.272226

A1 2.560386 0.77275 2.8283 0.26948 3.155514 0.303035 2.207404 0.535166 -0.87544 0.59238 -1.0156 0.555013 -1.17389 0.488188 -1.33253 0.486398 -0.51158 0.341105 -0.74563 0.320577 -0.92001 0.205047 -1.14632 0.191567 0.760416 0.451477 0.089498 0.260684 0.060083 0.254192 0.572199 0.180268

A2 -2.33163 -1.69889 -3.19985 1.943308 -5.59553 1.966889 2.879344 -0.0295 1.800708 0.646541 1.97075 0.695927 1.901668 0.819381 1.701996 0.635688 2.523081 1.179572 3.351018 1.107175 3.283068 1.513891 3.300682 1.178762 0.750124 1.022642 4.304878 1.882028 4.406518 1.965245 -0.85325 2.13042

A3 0.170458 10.56542 3.15051 -0.34711 15.95445 -1.93906 -8.98514 5.53716 -1.03913 -0.34621 -1.00399 -0.36768 -0.42747 -0.67935 0.006641 -0.42538 -1.57175 -0.78689 -3.03477 -0.204 -1.52319 -1.11768 -1.32331 -0.3009 -1.39 -0.53325 -8.50182 -1.852 -5.83885 -1.31965 18.99128 0.096883

A4 3.261337 -20.3699 3.403913 -2.39076 -15.8255 6.188543 32.27936 -3.53667 -1.85161 -1.50082 -2.27217 -1.52339 -3.09019 -0.95096 -2.78898 -0.69037 -2.99197 -0.74459 -1.60273 -1.9598 -5.04703 -0.74734 -4.97309 -1.25164 -0.12275 -0.71105 7.072692 0.384846 -0.58665 -1.28867 -50.3899 -5.86034

A5 -3.9339 17.02694 -8.36897 2.443843 4.114353 -8.77573 -41.3934 -2.51101 3.123559 1.853517 3.601086 1.874277 4.046793 1.338732 2.992644 0.713907 4.574389 0.840915 3.879918 1.90275 6.957505 1.026495 6.236219 0.883377 1.121848 0.436712 -2.45455 -0.08899 5.189378 1.599639 48.78014 6.264905

A6 1.37499 -5.52211 3.75883 -0.98101 0.50209 3.4765 16.2537 1.59821 -1.32165 -0.69332 -1.49046 -0.69445 -1.55021 -0.50111 -0.98459 -0.21458 -1.80058 -0.26402 -1.65272 -0.60358 -2.62532 -0.33886 -2.12811 -0.17396 -0.53794 -0.03888 0.12491 0.07273 -2.51175 -0.51415 -16.4171 -2.10598

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

32

a/t

Not for Resale

20

c/a


R/t

--``````-`-`,,`,,`,`,,`---


8

a/t 0.2 0.4 0.6 0.8

60

16

0.2 0.4 0.6 0.8

60

32

0.2 0.4 0.6 0.8

100

1

0.2 0.4 0.6 0.8

Inside Crack


A0 0.403196 0.02233 0.474227 0.051514 0.600774 0.091966 0.823688 0.150148 0.28438 0.019065 0.318963 0.019986 0.379861 0.044567 0.525596 0.079831 0.236097 0.009515 0.228461 0.01852 0.263663 0.026491 0.321013 0.045955 1.204927 0.184278 1.286695 0.209572 1.387513 0.238452 1.486398 0.260704

A1 1.212329 0.29405 1.448654 0.263961 1.77948 0.273872 1.42438 0.311077 1.869283 0.06174 2.503638 0.313944 3.100939 0.356643 2.806873 0.451532 1.174346 0.729346 2.937385 0.319316 3.006819 0.33828 2.819634 0.342756 -0.76688 0.613583 -0.91498 0.573678 -1.13421 0.524778 -1.2449 0.518678

A2 1.397554 1.307674 0.944143 1.946789 0.413254 2.695368 5.450441 3.073911 0.800003 2.877815 -2.1918 1.931052 -3.99598 2.539662 2.760439 3.073319 12.18299 -2.75865 -3.28781 1.84656 -1.75957 2.191691 2.341932 2.373047 1.351896 0.609994 1.602502 0.687153 1.991228 0.699127 1.632108 0.583282

A3 -4.77195 0.593549 -2.78303 -1.32224 1.28385 -3.53879 -9.35681 -2.92093 -7.56826 -3.91623 2.589311 -1.38334 11.50341 -2.77283 -3.30793 -2.3711 -57.8217 16.31238 3.234761 -0.54632 2.258403 -0.77962 -1.86803 0.805749 -0.15643 -0.39183 -0.40648 -0.51261 -1.19722 -0.4392 -0.18864 -0.3285

A4 4.770655 -4.03003 1.868228 -0.7999 -7.00747 2.755821 1.712267 -0.86515 12.87432 2.449927 -1.5926 -0.22621 -15.7193 2.690583 2.613192 0.999114 109.7081 -32.7755 2.081436 -1.94478 5.448391 0.693634 11.53755 0.788334 -2.74706 -1.24816 -2.62978 -1.09288 -1.36154 -1.1781 -2.08544 -0.79394

Outside Crack A5 -2.04502 3.712803 -0.26276 1.006913 7.505663 -1.911 4.494209 2.359321 -9.78597 -0.71085 -0.24606 0.389079 8.941533 -2.77646 -5.34754 -1.7909 -95.1341 28.6496 -6.15964 1.847381 -11.6174 -2.5355 -20.5232 -5.89507 3.528291 1.541317 3.510927 1.410255 2.389841 1.423678 2.231295 0.788112

C-112 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A6 0.2313 -1.19117 -0.20642 -0.33846 -2.69846 0.57898 -2.30859 -1.01796 2.77217 -0.04793 0.26465 -0.17443 -1.93927 1.00506 2.98142 0.92393 30.9502 -9.40407 2.73533 -0.61312 4.99948 1.28727 9.11518 3.18431 -1.37171 -0.56922 -1.36809 -0.52135 -0.97307 -0.50761 -0.71768 -0.24722

A0 0.400162 0.04856 0.482161 0.071647 0.624093 0.110227 0.880576 0.183708 0.278152 0.040525 0.314765 0.027952 0.355427 0.039647 0.444162 0.051484 0.198785 0.008243 0.21878 0.009759 0.222117 0.009471 0.2135 0.011307 1.22054 0.195948 1.305657 0.223275 1.418374 0.255125 1.532642 0.283095

A1 1.295359 0.294457 1.436977 0.322695 1.839185 0.445349 1.786663 0.442426 2.051183 -0.04031 2.529172 0.490246 3.169106 0.476199 2.873771 0.55322 2.765647 1.059545 2.920117 0.394314 3.286429 0.604192 3.492872 0.763771 -0.88844 0.58432 -0.98407 0.544949 -1.21355 0.501983 -1.30658 0.481165

A2 0.967302 1.918298 1.543983 2.174835 1.057203 2.07317 4.901883 3.118698 -0.57336 5.340558 -2.0919 1.247656 -4.78082 1.821023 0.286152 1.619754 -3.5505 -3.71555 -3.25414 1.557373 -5.61657 -0.27828 -5.75226 -1.17235 1.909202 0.700222 1.809406 0.77387 2.199351 0.754751 1.583841 0.667489

A3 -3.38153 -1.6315 -4.81986 -2.31674 -0.29164 -1.18594 -3.92615 -1.86914 -2.66504 -13.7539 2.114312 0.835084 15.069 -0.2332 8.226214 3.344268 3.564298 18.48382 2.77903 -0.52457 15.96204 6.320075 17.91447 8.183496 -1.45547 -0.5179 -0.67347 -0.65666 -1.49333 -0.56399 0.254367 -0.50459

A4 2.592033 -0.41845 5.639146 1.171859 -3.40307 -0.76754 -6.46861 -2.05963 4.629194 20.20743 0.558877 -3.05538 -17.9907 0.874041 -3.44958 -2.5539 -1.73471 -34.7667 4.935516 1.087159 -13.2858 -7.79011 2.558303 -3.40206 -1.1363 -1.24627 -2.58263 -1.01932 -1.22189 -1.03637 -3.02851 -0.60689

A5 -0.4419 0.677694 -3.65571 -1.00863 3.374064 0.258382 7.468062 1.677976 -3.24727 -16.0981 -3.12327 1.680919 7.608144 -3.4309 -13.2321 -4.33387 -0.20132 28.76288 -10.0963 -2.701 0.626351 3.290343 -28.4535 -4.78742 2.551674 1.672538 3.712298 1.456188 2.484768 1.35264 3.093099 0.685647

A6 -0.20911 -0.1606 0.9473 0.44031 -1.0492 0.12539 -1.8176 -0.18732 0.80024 5.05338 1.46329 -0.29439 -0.78078 1.70591 8.81354 3.04343 0.26444 -9.05558 4.37521 1.16448 1.71339 -0.77912 14.5473 2.38491 -1.14733 -0.64273 -1.4919 -0.56117 -1.05149 -0.49406 -0.9974 -0.21733

Not for Resale

60

c/a


R/t

--``````-`-`,,`,,`,`,,`---


2

a/t 0.2 0.4 0.6 0.8

100

4

0.2 0.4 0.6 0.8

100

8

0.2 0.4 0.6 0.8

100

16

0.2 0.4 0.6 0.8

Inside Crack


A0 0.875974 0.126642 0.989701 0.164714 1.147354 0.21277 1.323908 0.253462 0.580146 0.064294 0.721458 0.102241 0.8959 0.15467 1.084636 0.21634 0.405341 0.023358 0.479184 0.051142 0.609653 0.091266 0.840223 0.151326 0.275277 0.017839 0.320299 0.027954 0.382329 0.041127 0.55406 0.083603

A1 -0.45107 0.400776 -0.67377 0.301019 -0.8992 0.226886 -1.07644 0.251553 0.716102 0.431864 0.103365 0.258534 0.022979 0.234108 0.618317 0.178319 1.165322 0.260644 1.387011 0.253493 1.775412 0.27901 1.517734 0.315026 2.139052 0.121183 2.524597 0.295303 3.274725 0.361116 2.862062 0.431877

A2 2.201731 0.835495 2.931448 1.263535 3.266979 1.429398 3.131563 0.894412 0.823394 0.925784 3.980646 1.692533 4.276585 1.850567 -1.79056 1.869099 1.814917 1.550782 1.57423 1.990662 0.732959 2.649609 5.237891 3.046936 -1.4606 2.211517 -2.17795 1.774076 -4.89761 2.365671 3.577467 3.251222

A3 -0.92684 0.131638 -2.08703 -0.80872 -2.00937 -1.05382 -1.35941 0.418277 -1.39654 -0.0535 -7.60398 -1.29239 -6.03862 -1.12478 20.1534 0.236176 -6.24286 -0.20467 -5.02316 -1.39814 0.212629 -3.35626 -8.41863 -2.69137 0.585674 -1.35783 2.473391 -0.51125 14.49956 -2.19312 -5.45057 -2.7789

Outside Crack

A4 -3.6224 -2.01747 -2.72948 -0.88191 -3.69421 -0.6404 -4.39261 -2.26777 -0.35525 -1.56156 5.725155 -0.40455 0.258951 -1.44028 -50.3721 -5.3445 7.295091 -2.68803 5.752178 -0.67946 -5.21663 2.555822 -0.24645 -1.29041 -1.23556 -1.98758 -1.23254 -1.84411 -20.2053 2.045588 6.153719 1.794375

A5 4.8429 1.75102 4.559539 1.034915 5.59656 0.873014 5.675619 1.728736 1.453513 1.213831 -1.39175 0.565284 4.381588 1.768987 48.28967 5.754983 -4.12443 2.612383 -3.48995 0.90272 6.00343 -1.84361 5.934642 2.59957 1.833154 2.916953 -0.6552 1.80253 11.98139 -2.43658 -9.45865 -2.75188

A6 -1.83178 -0.52942 -1.81836 -0.34611 -2.15186 -0.29178 -2.00255 -0.48408 -0.67951 -0.32603 -0.21788 -0.16527 -2.26774 -0.61438 -16.3262 -2.01559 0.88824 -0.84385 0.81819 -0.30714 -2.20921 0.5793 -2.6149 -1.04075 -0.88761 -1.1853 0.4148 -0.65864 -2.71012 0.91744 4.85155 1.34333

A0 0.884802 0.140465 1.004501 0.180624 1.183626 0.236825 1.399229 0.292282 0.577215 0.079448 0.732919 0.124014 0.937004 0.186197 1.207361 0.272713 0.402889 0.0495 0.485088 0.073142 0.632818 0.11862 0.923918 0.201751 0.281913 0.040774 0.319877 0.035227 0.372479 0.052864 0.517186 0.081683

C-113 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

A1 -0.532 0.376588 -0.70168 0.300675 -0.93093 0.214619 -1.11311 0.207563 0.772559 0.467445 0.10746 0.268157 0.023072 0.24757 0.291972 0.160873 1.239951 0.291358 1.433201 0.363805 1.945087 0.431488 1.716507 0.440784 1.954104 0.035853 2.551157 0.509678 3.378584 0.5448 3.021028 0.646769

A2 2.610308 0.970926 3.00892 1.226004 3.290509 1.424241 2.964956 1.026387 0.64721 0.921567 4.067553 1.817758 4.554108 1.959076 1.006771 2.193932 1.367466 1.946442 1.583962 1.898462 0.3228 2.314443 5.85262 3.33287 0.291424 4.809723 -2.05367 1.438124 -5.52754 1.881354 1.871583 2.087271

A3 -1.86112 -0.24377 -1.97726 -0.58492 -1.60109 -0.84145 -0.30651 0.199668 -1.1169 -0.2646 -7.67395 -1.68059 -6.44705 -1.26925 12.27523 -0.24323 -4.75503 -1.73259 -5.0901 -1.40401 1.997375 -2.17259 -7.98822 -2.80521 -5.87984 -11.9249 1.797615 -0.06477 17.22659 -0.56374 3.600315 2.289412

A4 -2.49153 -1.47196 -3.26331 -1.35144 -4.84028 -1.19004 -6.52252 -2.08837 -0.48606 -1.08007 5.667631 0.139558 0.462838 -1.48771 -38.9701 -5.27568 4.892484 -0.29218 6.165509 -0.44938 -7.54295 0.785501 -0.83127 -1.11921 10.26464 16.94804 1.066115 -1.5756 -21.8289 1.115313 1.445434 -2.1269

A5 4.163474 1.325099 5.169822 1.430569 6.752496 1.380853 7.427646 1.577235 1.366207 0.689221 -1.31158 0.08355 4.36353 1.854934 39.62024 5.845749 -2.29444 0.61503 -4.11663 0.377128 6.99683 -0.90419 4.056757 1.448586 -7.91967 -13.3127 -3.49408 0.505801 10.68963 -3.57642 -16.7028 -4.57351

A6 -1.6724 -0.39014 -2.04417 -0.46123 -2.55367 -0.44936 -2.49191 -0.39789 -0.604 -0.10666 -0.22991 0.02741 -2.26155 -0.61736 -13.6034 -1.9946 0.36574 -0.15064 1.10401 -0.00651 -2.23077 0.47601 -1.00704 -0.22783 2.27865 4.15142 1.57687 0.08409 -1.6511 1.80376 10.2415 3.33129

Not for Resale

100

c/a


R/t


32

a/t 0.2 0.4 0.6 0.8

¥

1

0.2 0.4 0.6 0.8

¥

2

0.2 0.4 0.6 0.8

¥

4

0.2 0.4 0.6 0.8

Inside Crack


A0 0.230565 0.008715 0.229424 0.015401 0.267497 0.025753 0.374733 0.043467 1.230123 0.1969 1.298948 0.216225 1.397118 0.244587 1.511701 0.270447 0.900059 0.139883 1.005806 0.174087 1.182601 0.227712 1.383338 0.282011 0.627412 0.081291 0.739042 0.11645 0.946121 0.177805 1.245211 0.258564

A1 1.348388 0.607673 2.973813 0.251266 3.177315 0.380604 2.006346 0.128021 -0.85148 0.568337 -0.9978 0.563305 -1.13484 0.532667 -1.32448 0.511328 -0.5476 0.365987 -0.73226 0.305163 -1.10725 0.170117 -1.39003 0.083923 0.098006 0.235191 0.054816 0.247988 -0.18588 0.205668 -0.69219 0.154889

A2 10.72393 -2.57284 -3.36351 1.959342 -2.77385 1.847613 10.39928 4.702165 1.55097 0.811399 1.947954 0.704831 1.791874 0.593969 1.756835 0.535744 2.441677 0.983314 2.995194 1.207031 3.962364 1.549947 4.375578 1.725858 3.427515 1.791658 4.084262 1.828252 5.586746 2.097921 8.326062 2.117024

A3 -52.4932 16.38575 3.38934 -0.85265 6.322913 0.283894 -28.7893 -6.79313 -0.45381 -0.88111 -1.30027 -0.49345 -0.42026 -0.03618 -0.13379 -0.03273 -1.26885 -0.24055 -1.94592 -0.67205 -2.77813 -1.10512 -3.73726 -1.53581 -6.17118 -1.8449 -7.58831 -1.71699 -9.86349 -1.80395 -14.948 -0.491

A4 100.3807 -33.0903 2.170068 -1.4031 -1.1128 -1.47458 59.05812 12.19004 -2.60572 -0.6993 -1.49401 -1.30788 -2.86793 -2.01631 -2.86293 -1.55702 -3.38153 -1.53708 -3.26135 -1.06513 -4.30973 -0.83337 -2.54032 -0.06356 3.761013 0.639466 5.404753 0.191212 5.959687 -0.55587 8.693691 -4.61461

Outside Crack A5 -87.3605 28.90756 -6.5149 1.665783 -6.85125 -0.00343 -62.1022 -13.9297 3.613961 1.255667 2.830623 1.707866 3.768548 2.216701 3.295327 1.557097 4.786857 1.427492 5.142457 1.144559 7.277275 1.171706 5.3036 0.500678 0.014548 -0.35485 -1.01461 0.116577 0.129644 1.14614 0.475579 5.455075

A6 28.4704 -9.48603 2.91537 -0.70087 3.6651 0.18659 23.0333 5.34015 -1.44075 -0.51193 -1.2126 -0.6406 -1.4405 -0.77822 -1.14124 -0.50946 -1.83739 -0.43719 -2.03062 -0.36448 -2.96482 -0.41945 -2.09324 -0.19822 -0.60669 0.15531 -0.34834 -0.01861 -1.00261 -0.42066 -1.39266 -1.96633

A0 0.199484 0.008045 0.222815 0.011287 0.228214 0.018383 0.261529 0.022087 1.230123 0.1969 1.298948 0.216225 1.397118 0.244587 1.511701 0.270447 0.900059 0.139883 1.005806 0.174087 1.182601 0.227712 1.383338 0.282011 0.627412 0.081291 0.739042 0.11645 0.946121 0.177805 1.245211 0.258564

A1 2.776569 1.111761 2.973492 0.480266 3.516631 0.777313 2.733922 0.87795 -0.85148 0.568337 -0.9978 0.563305 -1.13484 0.532667 -1.32448 0.511328 -0.5476 0.365987 -0.73226 0.305163 -1.10725 0.170117 -1.39003 0.083923 0.098006 0.235191 0.054816 0.247988 -0.18588 0.205668 -0.69219 0.154889

A2 -3.65638 -3.63625 -3.42832 1.40738 -6.82364 -1.47523 1.590146 -2.00004 1.55097 0.811399 1.947954 0.704831 1.791874 0.593969 1.756835 0.535744 2.441677 0.983314 2.995194 1.207031 3.962364 1.549947 4.375578 1.725858 3.427515 1.791658 4.084262 1.828252 5.586746 2.097921 8.326062 2.117024

A3 4.0401 17.93994 3.393074 0.051089 20.4113 11.27875 -6.44032 11.24449 -0.45381 -0.88111 -1.30027 -0.49345 -0.42026 -0.03618 -0.13379 -0.03273 -1.26885 -0.24055 -1.94592 -0.67205 -2.77813 -1.10512 -3.73726 -1.53581 -6.17118 -1.8449 -7.58831 -1.71699 -9.86349 -1.80395 -14.948 -0.491

A4 -2.73525 -34.0494 3.787314 -0.09722 -20.3047 -15.8233 48.32267 -3.75842 -2.60572 -0.6993 -1.49401 -1.30788 -2.86793 -2.01631 -2.86293 -1.55702 -3.38153 -1.53708 -3.26135 -1.06513 -4.30973 -0.83337 -2.54032 -0.06356 3.761013 0.639466 5.404753 0.191212 5.959687 -0.55587 8.693691 -4.61461

A5 0.749981 28.3292 -9.11005 -1.89925 5.619412 8.643098 -70.868 -9.80425 3.613961 1.255667 2.830623 1.707866 3.768548 2.216701 3.295327 1.557097 4.786857 1.427492 5.142457 1.144559 7.277275 1.171706 5.3036 0.500678 0.014548 -0.35485 -1.01461 0.116577 0.129644 1.14614 0.475579 5.455075

A6 -0.0686 -8.93464 4.06013 1.03716 0.37835 -1.98935 29.3565 5.5705 -1.44075 -0.51193 -1.2126 -0.6406 -1.4405 -0.77822 -1.14124 -0.50946 -1.83739 -0.43719 -2.03062 -0.36448 -2.96482 -0.41945 -2.09324 -0.19822 -0.60669 0.15531 -0.34834 -0.01861 -1.00261 -0.42066 -1.39266 -1.96633

--``````-`-`,,`,,`,`,,`---

C-114 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Not for Resale

100

c/a


R/t


8

a/t 0.2 0.4 0.6 0.8

¥

16

0.2 0.4 0.6 0.8

¥

32

0.2 0.4 0.6 0.8

Inside Crack

Gi G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G1 G0 G2

A0 0.41686 0.035319 0.491777 0.063427 0.659182 0.111604 0.980933 0.203995 0.282375 0.013699 0.326148 0.029412 0.416633 0.059846 0.654014 0.121478 0.211805 0.008992 0.235794 0.014514 0.290224 0.020889 0.516355 0.082546

A1 1.212456 0.354631 1.659232 0.37225 1.875914 0.47145 1.884632 0.480015 2.112379 0.301109 2.520087 0.369937 3.156647 0.434074 3.423192 0.697549 2.479586 0.647688 3.08224 0.4038 3.689205 0.701678 2.531083 0.497177

A2 1.451554 1.148 -0.10804 1.623167 1.02126 1.794059 4.802078 2.882243 -0.86611 1.927456 -1.8847 1.922085 -2.62489 2.681156 3.815805 2.971833 -0.97912 -0.63215 -3.57921 1.64227 -4.57391 0.163184 14.7129 4.606481


A3 -5.08051 1.140333 0.179324 -0.53065 -1.7698 -0.75576 -8.05802 -2.58901 -2.45033 -1.58246 2.179874 -1.20715 7.732591 -3.19366 -4.15869 -1.30365 -5.98247 7.012493 3.947689 -0.39061 11.70989 5.707216 -43.6218 -7.33267

A4 5.176111 -5.25021 -2.70761 -2.00074 -0.56536 -1.49017 0.444785 -0.9683 5.003528 -0.55641 -1.45971 -0.4394 -9.69278 4.075372 3.471533 -0.07549 14.91676 -14.649 1.913159 -0.64807 -6.375 -8.20758 101.0657 21.14862

Outside Crack A5 -2.17287 4.862799 3.368062 1.894378 1.247996 1.085218 3.477266 1.537237 -3.85544 1.010305 -0.18865 0.273755 3.64287 -4.69402 -10.3104 -3.04651 -13.9367 12.24961 -6.88722 -0.29403 -5.88941 3.456112 -116.081 -29.3451

A6 0.20404 -1.57303 -1.34897 -0.58803 -0.43766 -0.21137 -1.05675 -0.37502 1.03217 -0.37761 0.23934 -0.03952 -0.0892 1.82855 6.628 2.167 4.58836 -3.86819 3.18968 0.25149 4.24524 -0.44547 46.1909 12.4914

A0 0.41686 0.035319 0.491777 0.063427 0.659182 0.111604 0.980933 0.203995 0.282375 0.013699 0.326148 0.029412 0.416633 0.059846 0.654014 0.121478 0.211805 0.008992 0.235794 0.014514 0.290224 0.020889 0.516355 0.082546

A1 1.212456 0.354631 1.659232 0.37225 1.875914 0.47145 1.884632 0.480015 2.112379 0.301109 2.520087 0.369937 3.156647 0.434074 3.423192 0.697549 2.479586 0.647688 3.08224 0.4038 3.689205 0.701678 2.531083 0.497177

A2 1.451554 1.148 -0.10804 1.623167 1.02126 1.794059 4.802078 2.882243 -0.86611 1.927456 -1.8847 1.922085 -2.62489 2.681156 3.815805 2.971833 -0.97912 -0.63215 -3.57921 1.64227 -4.57391 0.163184 14.7129 4.606481

A3 -5.08051 1.140333 0.179324 -0.53065 -1.7698 -0.75576 -8.05802 -2.58901 -2.45033 -1.58246 2.179874 -1.20715 7.732591 -3.19366 -4.15869 -1.30365 -5.98247 7.012493 3.947689 -0.39061 11.70989 5.707216 -43.6218 -7.33267

A4 5.176111 -5.25021 -2.70761 -2.00074 -0.56536 -1.49017 0.444785 -0.9683 5.003528 -0.55641 -1.45971 -0.4394 -9.69278 4.075372 3.471533 -0.07549 14.91676 -14.649 1.913159 -0.64807 -6.375 -8.20758 101.0657 21.14862

A5 -2.17287 4.862799 3.368062 1.894378 1.247996 1.085218 3.477266 1.537237 -3.85544 1.010305 -0.18865 0.273755 3.64287 -4.69402 -10.3104 -3.04651 -13.9367 12.24961 -6.88722 -0.29403 -5.88941 3.456112 -116.081 -29.3451

A6 0.20404 -1.57303 -1.34897 -0.58803 -0.43766 -0.21137 -1.05675 -0.37502 1.03217 -0.37761 0.23934 -0.03952 -0.0892 1.82855 6.628 2.167 4.58836 -3.86819 3.18968 0.25149 4.24524 -0.44547 46.1909 12.4914


2.



3.



4.

Influence coefficients for Ri t = 5 and c a = 32 are not provided in this table because this geometry represents a 360 degree crack. Influence coefficients for this case can be determined using Table C.13.

Not for Resale

¥

c/a

--``````-`-`,,`,,`,`,,`---

R/t

n=0

C-115 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


6


Table C.15 Coefficients For One And Two Cracks At The Toe Of A Fillet Weld Of A Ring Stiffened Cylinder Subject To Internal Pressure

Ri/t

Ar/t

a/t

M 1pc

M p2 c

10

1

0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8

11.106 10.428 11.463 13.562 16.369 12.717 11.659 12.328 14.174 16.691 15.156 13.452 13.474 14.740 16.789 16.514 14.560 14.041 14.854 16.423 17.276 14.826 13.902 14.359 15.789 17.649 14.860 13.486 13.607 14.808 19.269 18.759 22.239 28.552 36.175 22.159 21.068 24.104 30.009 36.920 27.603 25.406 27.389 32.190 37.716 31.262 28.564 29.584 33.343 37.377 34.441 30.598 30.707 33.518 36.815

10.707 9.564 9.438 10.255 12.590 12.261 10.689 10.134 10.736 12.900 14.644 12.425 11.326 11.640 13.533 15.941 13.486 12.001 12.083 13.613 16.862 14.080 12.488 12.526 13.970 17.440 14.532 12.956 12.938 14.193 18.769 17.561 18.858 21.683 26.663 21.552 19.680 20.277 22.710 27.288 26.846 23.693 23.099 24.732 28.528 30.328 26.601 25.029 25.978 27.814 33.532 28.778 26.632 27.214 29.750

2

4

8

16

32

20

1

2

4

8

16 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---


Not for Resale


Ri/t

Ar/t

a/t

M 1pc

M p2 c

20

32

30

1

0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8

36.535 31.740 30.505 31.891 34.014 27.137 26.846 33.060 44.379 58.493 30.669 30.063 35.781 46.776 59.767 38.831 36.414 40.976 50.576 61.329 44.710 41.641 44.887 52.987 61.249 50.589 45.798 47.902 54.624 61.231 54.929 48.707 48.797 53.038 56.949 42.373 42.679 54.728 77.789 108.432 47.993 47.448 59.055 81.723 111.144 60.278 57.556 67.696 88.740 113.738 70.395 66.013 75.063 94.910 116.860

35.879 30.526 28.082 25.247 30.330 26.548 25.383 28.564 34.219 42.370 30.098 28.385 30.696 35.734 43.291 37.948 34.273 34.996 38.833 45.094 43.574 39.072 38.289 40.955 45.531 49.352 43.140 41.291 43.252 47.163 53.818 46.566 44.041 45.271 48.127 41.659 40.812 48.412 61.044 77.271 47.208 45.328 51.864 63.725 78.974 59.142 54.808 59.067 68.963 81.561 69.008 62.587 65.135 73.402 83.943

2

4

8

16

32

50

1

2

4

8


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---




Ar/t

a/t

M 1pc

M p2 c

50

16

0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8

81.194 74.987 82.216 99.803 117.931 90.505 82.141 86.581 99.968 112.846 79.179 81.194 108.832 164.902 252.502 88.154 88.966 116.236 173.060 259.063 108.924 106.530 132.464 187.884 264.764 128.327 123.176 148.108 203.026 274.309 151.741 143.372 166.274 218.889 282.962 174.828 162.498 182.044 228.983 280.464 150.420 156.308 216.593 347.722 587.259 164.425 168.545 228.814 361.852 601.956 198.318 197.859 257.233 390.600 619.002

79.428 71.097 71.569 78.017 86.566 88.764 78.609 77.296 82.189 89.028 78.162 78.532 99.108 134.456 178.701 87.030 86.077 105.308 140.138 182.328 107.511 102.873 119.117 150.595 187.021 126.560 118.394 132.338 161.154 192.685 149.243 137.502 147.919 173.102 199.688 171.926 156.236 163.057 184.588 205.977 148.849 152.523 201.874 293.750 419.471 162.944 164.634 212.712 304.020 427.103 196.602 193.131 237.679 325.449 437.690

--``````-`-`,,`,,`,`,,`---

Ri/t

32

100

1

2

4

8

16

32

200

1

2

4


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Ri/t

Ar/t

a/t

M 1pc

M p2 c

200

8

0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0..2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8 0.1 0.2 0.4 0.6 0.8

232.986 228.011 287.511 423.357 640.233 279.311 269.046 326.872 463.529 670.028 330.530 313.114 369.008 502.465 685.282

230.791 221.767 263.983 348.986 450.670 276.031 263.426 298.360 378.446 468.110 326.493 303.480 335.703 409.708 485.817

219.626 229.605 322.659 532.144 955.006 238.716 246.132 340.143 553.121 976.452

217.842 224.306 304.104 460.036 691.338 237.289 241.842 320.429 475.768 703.323

282.843 284.925 378.344 594.759 1006.246 330.278 326.495 421.111 644.305 1047.281 397.141 386.084 480.278 708.066 1098.128 475.863 454.952 547.772 778.832 1140.055

281.077 279.572 354.437 507.204 720.786 327.755 319.091 392.473 543.771 743.266 393.356 376.539 444.954 591.154 772.214 471.069 443.355 505.320 645.850 804.194

16

32

300

1

2

4

8

16

32

Notes For Table C.15: Intepolation may be used for intermediate values of

--``````-`-`,,`,,`,`,,`---


Not for Resale

Ri t , Ar t , and a t .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Table C.16 Parameters for Mk-Factors – Surface Crack At A Tee Joint, Semi-Elliptical Shape, Through-Wall Membrane and Bending Stress Parameter

F1

F2

F3

Deepest point of the crack (Point B)

M km

M kb

M km

M kb

P1

1.04424

1.19137

0.47722

0.52011

P2

-0.09627

-0.14198

-0.46228

-0.36027

P3

0.03790

0.038086

0.19046

0.12547

P4

0.54616

0.86676

0.39777

0.54940

P5

-0.12508

-0.24951

0.22176

-0.098759

P6

-2.43313

-2.03967

-3.25447

-2.80066

P7

-0.07251

0.20231

-0.63489

-0.71090

P8

0.18353

0.40094

2.85835

1.50561

P9

0.87051

0.94855

1.95878

1.86540

P10

0.99924

1.00095

0.40489

0.96775

P11

0.04125

0.10217

0.34526

-0.21496

P12

-0.75765

-0.95780

-0.29917

-0.82377

P13

-0.000426

-0.075004

-0.77810

-0.25998

P14

-0.05692

-0.68779

41.72046

-8.77203

P15

1.19362

-8.67636

-78.8175

24.27778

P16

-1.43325

16.16166

34.10390

-28.1240

P17

0.61335

-8.14948

2.73640

11.4415

P18

1.05721

-0.152293

0.030034

2.64087

P19

-2.4052

-0.148843

-0.13126

-10.4940

P20

2.61759

1.77150

0.11538

12.8098

P21

-0.98207

-1.27776

0.040551

-5.98773

--``````-`-`,,`,,`,`,,`---


Surface point of the crack (Point A)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Function


Table C.16 Parameters for Mk-Factors – Surface Crack At A Tee Joint, Semi-Elliptical Shape, Through-Wall Membrane and Bending Stress Parameter

F4

Deepest point of the crack (Point B)

Surface point of the crack (Point A)

M km

M kb

M km

M kb

P22

1.06748

1.78291

0.53107

0.78365

P23

7.74090

8.37239

0.26223

-0.24718

P24

0.47714

0.41021

-0.24730

1.55530

P25

-0.21542

-0.95097

12.2781

0.049054

P26

-1.08081

1.64652

-0.059328

0.040332

P27

-0.002871

3.52508

-0.002740

-0.000146

P28

0.89122

31.9326

1.04175

-2.41618

P29

0.008454

0.000011

0.050788

0.002455

P30

0.14155

0.010084

-0.039354

0.013053

P31

0.48533

0.93093

1.39315

0.57026

P32

-2.12357

-2.52809

-10.8442

0.40172

P33

---

---

16.6945

0.35095

P34

---

---

0.12542

0.55589

P35

---

---

-1.39604

0.047656

P36

---

---

1.21456

0.042067

P37

---

---

0.69694

1.07535

P38

---

---

0.42960

-0.48462

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Function


Figure C.1 Plate – Through Wall Crack

c

c

t x

W

W

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\ --``````-`-`,,`,,`,`,,`---


Not for Resale


Figure C.2 Plate – Surface Crack, Semi-Elliptical Shape

c

c j

x

a t

x

W

W

(a) Finite Length Surface Crack

--``````-`-`,,`,,`,`,,`---

a

x t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(b) Infinitely Long Surface Crack (c>>a)


Not for Resale


Figure C.3 Plate – Embedded Crack, Elliptical Shape

d2

2c 2a

t

j

--``````-`-`,,`,,`,`,,`---

x W

d1 W

(a) Finite Length Embedded Crack

d2

B 2a

d1

A x

(b) Infinitely Long Embedded Crack (c>>a) //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale

t


Figure C.4 Plate – Embedded Crack, Definition of Membrane and Bending Stress

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Ib

d2

Ibe

2a t Ime d1 x

Im Note: The membrane and bending stress acting on the crack face can be computed using the equations in paragraph C.3.7.1.


Not for Resale


Figure C.5 Plate – Embedded Cracks, Sign Convention for Bending Stress Distribution

Ib

d2

2a t

d1 x

(a) Positive Ib

d2

2a t

d1 x

Ib (b) Negative Ib

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.6 Plate With Hole – Through-wall Single Edge Crack

--``````-`-`,,`,,`,`,,`---

Rh

t

x a (a) Through-Wall Single Edge Crack

I

BI

Rh

BI a

I (b) Biaxial Loading


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.7 Plate With Hole – Through-wall Double Edge Crack

Rh

t

x a

a

(a) Through-Wall Double Edge Crack

--``````-`-`,,`,,`,`,,`---

I

Rh

BI a

a

I (b) Biaxial Loading


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

BI


Figure C.8 Plate With Hole – Surface Crack, Semi-Elliptical Shape

w

w

Rh

t a a t

x

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

c

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure C.9 Plate With Hole – Corner Crack, Semi-Elliptical Shape

w

w Rh

t

x a

c (a) Crack Geometry

y

y

a

a j

j x

c

c

(a) a/c < 1

--``````-`-`,,`,,`,`,,`---

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(b) a/c > 1

(b) Coordinate System Used to Define the Parametric Angle


x


Figure C.10 Cylinder – Through-wall Crack, Longitudinal Direction

x

--``````-`-`,,`,,`,`,,`---

2c

Ri

t

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale


Figure C.11 Cylinder – Through-wall Crack, Circumferential Direction

2c

x

Ri

t --``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale


Figure C.12 Cylinder – Surface Crack, Longitudinal Direction, Infinite Length

x a

a

Ri

t

a

a

x

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Ri

t

(b) Outside Surface


Not for Resale

--``````-`-`,,`,,`,`,,`---

(a) Inside Surface


Figure C.13 Cylinder – Surface Crack, Circumferential Direction, 360 Degrees

x a

a a

Ri

Ri t t

(a) Inside Surface a x

Ri

Ri t a

t

(b) Outside Surface

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~


Not for Resale

--``````-`-`,,`,,`,`,,`---

a

--``````-`-`,,`,,`,`,,`---


Figure C.14 Cylinder – Surface Crack, Longitudinal Direction – Semi-elliptical Shape

x

a

2c

Ri

t (a) Inside Surface 2c

a

x

Ri

t (b) Outside Surface


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.15 Cylinder – Surface Crack, Circumferential Direction, Semi-elliptical Shape

x --``````-`-`,,`,,`,`,,`---

a 2c

Ri

t

(a) Inside Surface 2c

a x

Ri

t

(b) Outside Surface


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.16 Cylinder – Embedded Crack, Longitudinal Direction, Infinite Length

--``````-`-`,,`,,`,`,,`---

x

2a

2a d2 d1

x

Ri

Ri t

t

Infinitely Long Longitudinal Embedded Crack (Plane Strain) in a Cylindrical Shell


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.17 Cylinder – Embedded Crack, Circumferential Direction – 360 Degrees

2a x

d2 d1

2a Ri

Ri t

d1 d2

2a

t

--``````-`-`,,`,,`,`,,`---

360 Degree Circumferential Embedded Crack in a Cylindrical Shell

//^:^^#^~^^""~:@":^*^~


Not for Resale


Figure C.18 Cylinder – Embedded Crack, Longitudinal Direction, Elliptical Shape

2a d2 d1

x

2c

Ri

t

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale


Figure C.19 Cylinder – Embedded Crack, Circumferential Direction, Elliptical Shape

x d2

2a

d1

2c

Ri

t

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.20 Sphere – Through-wall Crack

2c

x x

Ri

t


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Axis of Symmetry


Figure C.21 Sphere – Surface Crack, Circumferential Direction, 360 Degrees

x

t

Ri a

a

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Axis of Symmetry

(a) Inside Surface

x

t

Ri a

Axis of Symmetry

(b) Outside Surface


Not for Resale

--``````-`-`,,`,,`,`,,`---

a

Figure C.22 Sphere – Surface Crack, Circumferential Direction, Semi-Elliptical Shape

x a 2c

Ri

t Axis of Symmetry

(a) Inside Surface

2c

a x

Ri

t Axis of Symmetry

(b) Outside Surface


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---



Figure C.23 Sphere – Embedded Crack, Circumferential Direction, 360 Degrees

x

Ri

d1 d2

2a

2a

Axis of Symmetry

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d2 d1

t


Figure C.24 Sphere – Embedded Crack, Circumferential Direction, Elliptical Shape

2c

x d1

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d2

2a

Ri

t

--``````-`-`,,`,,`,`,,`---

Axis of Symmetry


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.25 Cracks At Nozzles And Piping Branch Connections

CL

a A a

B

2c

D C

a

a G

--``````-`-`,,`,,`,`,,`---

2c

(a) Nozzle or Branch Connection

CL

a A

a

2c

a

C E

B

a

F a

a

G 2c

(b) Nozzle or Branch Connection with a Reinforcing Pad


Not for Resale

D 2c


Figure C.26 Nozzle Corner Cracks

CL dN

Nozzle

--``````-`-`,,`,,`,`,,`---

tN

Shell x t

a j

Corner Crack

Rm

CL


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.27 Ring Stiffened Cylinders – Edge Cracks At Fillet Welds

t

CL

Internal Pressure, P

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Fillet Weld First Crack a Second Crack Stiffening or Tray Support Ring with Cross Sectional Area, Ar R --``````-`-`,,`,,`,`,,`---

(a) Internal Ring, Internal Pressure t

CL Partial or Full Vacuum

Fillet Weld First Crack a Second Crack Stiffening or Tray Support Ring with Cross Sectional Area, Ar R (b) External Ring, Partial or Full Vacuum


Not for Resale


Figure C.28 Cracks At Sleeve Reinforced Cylinders

Reinforcing Sleeve

Cylinder

CL

2c A B

a

a

Longitudinal Semi-Elliptical Surface Crack

--``````-`-`,,`,,`,`,,`---


360° Circumferential Surface Crack or Circumferential Semi-Elliptical Surface Crack

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.29 Round Bar – Surface Crack, 360 Degrees

x

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a Ro

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure C.30 Round Bar – Surface Crack

Semi-Circular Crack

a

Straight Front Crack

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

x

--``````-`-`,,`,,`,`,,`---

Ro


Not for Resale


Figure C.31 Bolt – Surface Crack

Semi-Circular Crack --``````-`-`,,`,,`,`,,`---

a

Straight Front Crack

x Thread Depth

Rth


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure C.32 Crack At Fillet Weld – Surface Crack, Semi-Elliptical Shape

A

W

W

c

Fillet Weld

c

a

Point A t

Point B

A

(a) Tee-Joint -- End View

Fillet Weld

rw

=

I(x) a t

x Stress distribution at the location of the crack acting normal to the crack plane determine based on the structural configuration including the effects of the fillet weld geometry

(b) Section A-A

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~

--``````-`-`,,`,,`,`,,`---


Not for Resale

APPENDIX D – Compendium of Reference Stress Solutions (Jan, 2000)

D.1

General

D.1.1

Overview

D.1.1.1

This appendix contains reference stress solutions for many crack geometries which are likely to occur in pressurized components. Reference stress solutions are used in the assessment of crack-like flaws, see Section 9.

D.1.1.2

A summary of the reference stress solutions in this appendix is contained in Table C.1 of Appendix C. These reference stress solutions are recommended for most applications based on consideration of accuracy, range of applicability and convenience.

D.1.1.3

Reference stress solutions not included in this appendix may be obtained from publications (for example, see references [D.14.1] and [D.14.2]) if the tabulated solutions correspond to the component and crack geometry, and the loading condition. Otherwise, the reference stress should be computed using a numerical approach such as the finite element method.

D.1.1.4

The reference stress solutions for plates can be used to approximate the solutions for cylinders and spheres by introducing a surface correction (Folias or bulging) factor. This is an approximation that is supported by experimental results.

D.1.1.5

An identifier has been assigned to each reference stress solution in this appendix (see Table C.1 of Appendix C). This identifier is a set of alpha-numeric characters that uniquely identifies the component geometry, crack geometry, and loading condition. The identifier can be used to determine the associated stress intensity factor solution to be used in an assessment of crack like flaws (see Section 9). For example, if a flat plate with a through-wall crack subject to a membrane stress and/or bending stress is being evaluated, the reference stress solution is RPTC and the associated stress intensity factor solution to be used is KPTC.

D.1.2

Symbol Definitions

D.1.2.1

The following symbols defined below are used in this appendix.

a A Ao c dn d1

= = = = =

Crack depth parameter (mm:in), 2 2 Cross-sectional area of the flaw (mm :in ), 2 2 Cross-sectional area of the component computed for the flaw length (mm :in ), Crack length parameter (mm:in), Mean nozzle diameter (see Figure C.26) (mm:in),

=

F M Ms Mt p Pij Pij ,m

= = =

Distance from plate surface to the center of an embedded elliptical crack (see Appendix C, Figure C.3) (mm:in), Net section axial force acting on a cylinder (N:lbs), Resultant net-section bending moment acting on a cylinder (N-mm:in-lbs), Surface correction factor for a surface crack,

= =

Surface correction factor for a through-wall crack, Pressure (MPa:psi),

=

Primary stress component being evaluated,

=

Equivalent primary membrane stress for a stress component,

Pij ,b

=

Equivalent primary bending stress for a stress component, D-1

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

--``````-`-`,,`,,`,`,,`---

Pl Ply

=

Generalized loading parameter, such as applied stress, bending moment or pressure,

=

Value of the generalized loading parameter evaluated for the component with a crack-

Pm Pb P0 P1 P2 P3 P4 P5 P6 t tn Ri Rm Ro Rth x xg

=

like flaw at the yield stress, Primary membrane stress component (MPa:psi),

=

Through-Wall primary bending stress component (MPa:psi),

=

Uniform coefficient for polynomial primary stress distribution (MPa:psi),

=

Linear coefficient for polynomial primary stress distribution (MPa:psi),

=

Quadratic coefficient for polynomial primary stress distribution (MPa:psi),

=

Third order coefficient for polynomial primary stress distribution (MPa:psi),

=

Fourth order coefficient for polynomial primary stress distribution (MPa:psi),

=

Net-section primary bending stress about the x-axis (MPa:psi),

= = =

Net-section primary bending stress about the y-axis (MPa:psi), Plate or shell thickness (mm:in), Nozzle thickness (see Appendix C, Figure C.26) (mm:in),

=

Cylinder inside radius (mm:in),

=

Cylinder mean radius (mm:in),

=

Cylinder, round bar, or bolt outside radius, as applicable (mm:in),

= = =

Root Radius of a threaded bolt (mm:in), Radial local coordinate originating at the internal surface of the component, Global coordinate for definition of net section bending moment about the x-axis,

yg W l G I ref I ys

=

Global coordinate for definition of net section bending moment about the y-axis,

= = = =

Distance from the center of the flaw to the free edge of the plate (mm:in), Shell parameter used to determine the surface correction factors, Half-angle of the crack (degrees), Reference stress (MPa:psi), and

=

Yield stress (MPa:psi), see Appendix F.

D.1.2.2

The above symbols are also defined for different component and crack geometry’s in Appendix C, Figures C.1 through C.32.

D.2

Stress Analysis

D.2.1

Overview

D.2.1.1

A stress analysis using handbook or numerical techniques is required to compute the state of stress at the location of a crack. The stress distribution to be utilized in determining the stress intensity factor is based on the component of stress normal to the crack face. The distribution may be linear (made up of membrane and/or bending distributions) or highly nonlinear based on the component geometry and loading conditions.

D.2.1.2

The stress distribution normal to the crack face resulting from primary loads should be determined based on service loading conditions and the uncracked component geometry. If the component is subject to different operating conditions, the stress distribution for each condition should be evaluated and a separate fitness-for-service assessment should be performed.

D.2.1.3 In this appendix, the variable P is used for I to signify that stress calculations and the resulting stress distributions used to determine the reference stress and the Lr ratio for the assessment of a crack-like flaw using the FAD (see Section 9) are categorized as primary stress (see Appendix B).


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE D-3 _________________________________________________________________________________________________

The reference stress based on the secondary and residual stress distributions is required to determine the plasticity interaction factor, . , used in the assessment of crack-like flaws (see Section 9). In this case, the variable variable P can be used to represent the primary and/or residual stress. D.2.2

Stress Distributions

D.2.2.1

Overview – The reference stress solutions in this appendix are formulated in terms of the coefficients of a linear stress distribution (membrane and bending stress). Therefore, it is necessary to derive these coefficients from the results obtained from a stress analysis.

D.2.2.2

General Stress Distribution – A stress distribution through the wall thickness at the location of a crack-like flaw can be determined using an elastic solution or a numerical analysis technique such as the finite element method. In some cases, the stress distribution normal to the crack face may be highly non-linear. Statically equivalent membrane and bending stress components can be determined from the general stress distribution using the following equations; the integration is performed along a line assuming a unit width, see Appendix B.

D.2.2.3

z z

Pij ,m =

1 t Pij dx t 0

Pij ,b =

6 t2

t

0

Pij

(D.1)

FG t - xIJ dx H2 K

(D.2)

--``````-`-`,,`,,`,`,,`---

Fourth Order Polynomial Stress Distribution – The fourth order polynomial stress distribution can be obtained by curve-fitting a general stress distribution to obtain the coefficients of the best-fit fourth order polynomial. The equivalent membrane and bending stress distributions for use in the reference stress solutions in this appendix can be obtained directly from the coefficients of this polynomial. a.

The general form of the fourth order polynomial stress distribution is as follows:

F xI F xI P( x ) = P + P G J + P G J HtK HtK o

b.

2

3

3

F xI +PG J HtK

4

(D.3)

4

The equivalent membrane and bending stress distributions for the fourth order polynomial stress distribution are:

Pm = P0 + Pb = D.2.2.4

1

F xI +PG J HtK

2

P1 P2 P3 P4 + + + 2 3 4 5

(D.4)

P1 P2 9 P3 6 P4 - 2 2 20 15

(D.5)

Fourth Order Polynomial Stress Distribution With Net Section Bending Stress – This distribution is used to represent a through-wall fourth order polynomial stress and a net section or global bending stress applied to a circumferential crack in a cylindrical shell.

F xI F xI F xI P( x , x , y ) = P + P G J + P G J + P G J HtK HtK HtK F x IJ + P FG y IJ PG H R +tK H R +tK 2

g

g

o

1

2

3

g

5

F xI +PG J HtK 4

4

+ (D.6)

g

6

i


3

i

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


D.2.2.5

Membrane and Through-Wall Bending Stress Distribution – The membrane and bending stress distribution is linear through the wall thickness and represents a common subset of the general stress distribution (see paragraph D.2.2.2). Attributes of this stress distribution are discussed in Appendix C, paragraph C.2.2.5. The components of this stress distribution can be used directly in the reference stress solutions in this appendix.

D.2.3

Surface Correction Factor

D.2.3.1

A surface correction (also referred to as the Folias or bulging factor) is used to quantify the local increase in the state of stress at the location of a crack in a shell type structure which occurs because of local bulging. The magnified state of stress is then used together with a reference stress solution for a plate with a similar crack geometry to determine the reference stress for the shell. Surface correction factors are typically only applied to the membrane part of the reference stress because this represents the dominant part of the solution.

D.2.3.2

The surface correction factors for through-wall cracks in cylindrical and spherical shells subject to membrane stress loading are normally defined in terms of a single shell parameter, l, given by the following equation:

l=

1818 . c Ri t

(D.7)

However, recent work indicates that the surface correction factors for cylindrical shells are also a function of the shell radius-to-thickness ratio [D.14.9]. --``````-`-`,,`,,`,`,,`---

a.

Cylindrical shell – Longitudinal through-wall crack 1.

Data fit from references [D.14.10] and [D.14.11] (recommended for use in all assessments):

F 102 . + 0.4411l + 0.006124l I =G J . (10 ) l K H 10. + 0.02642l + 1533 2

Mt 2.

4

-6

2

c

M t = 0.01936l2 + 3.3

h

0.5

c

for l > 9.1

h

0.5

(D.9) (D.10)

(D.11)

General expression for membrane stress loading is given by the following equation where the coefficients Amm and Amb can be calculated using the equations in Appendix C, paragraph C.5.1. This expression is considered to be the most accurate and it includes an Ri t ratio dependency which can be significant.

b

gb

M t = max Amm + Amb , Amm - Amb b.

for l £ 9.1

Upper bound expression from reference [D.14.14]:

M t = 1 + 0.4845l2 4.

(D.8)

4

Approximate expression from references [D.14.12] and [D.14.13]:

M t = 1 + 0.3797l2 - 0.001236l4

3.

0.5

g

(D.12)

Cylindrical shell – Circumferential through-wall crack


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


1.

Data fit from reference [D.14.15] ] (recommended for use in all assessments):

F 10078 + 0.10368l + 3.7894(10 ) l I . =G J . (10 ) l K H 1.0 + 0.021979l + 15742 -4

2

Mt 2.

-6

2

b

4

(D.13)

gb

g

(D.14)

Spheres – Circumferential through-wall crack 1.

Data fit from references [D.14.10] and [D.14.11] (recommended for use in all assessments):

Mt = 2.

10005 . + 0.49001l + 0.32409l2 10 . + 0.50144l - 0.011067l2

c

3.

(D.15)

Approximate expression [D.14.16]:

M t = 1 + 0.427l2 + 0.00666l3

h

0.5

(D.16)

General expression for membrane stress loading is given by the following equation where the coefficients Amm and Amb can be calculated using the equations in Appendix C, paragraph C.6.1.

b

gb

M t = max Amm + Amb , Amm - Amb

g

(D.17)

The surface correction factors for surface cracks can be approximated using the results obtained for a through-wall crack by using one of the following methods. In all of these methods, the equations for M t are provided in paragraph D.2.3.2. a.

Cylindrical or Spherical Shell – The following is an empirical equation which does not produce consistent results when the crack approaches a through-wall configuration, see reference [D.14.14]. The factor C in the equation is used to define a model for the cross sectional area of the surface crack to be included in the analysis. A value of C = 10 . corresponds to a rectangular model and a value of C = 0.67 is used to model a parabolic shape. Experimental results indicate that a value of C = 0.85 provides an optimum fit to experimental data [D.14. 7], [D.14.8]. The results from this equation are usually associated with a local limit load solution; the superscript L in the following equation designates a local limit load solution.

FG a IJ FG 1 IJ H t KH M K F aI 1 - CG J HtK

1- C M sL =

t

(D.18)

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.2.3.3

0.5

General expression for membrane stress loading is given by the following equation where the coefficients Amm and Amb can be calculated using the equations in Appendix C, paragraph C.5.2.

M t = max Amm + Amb , Amm - Amb c.

4


b.

Cylindrical or Spherical Shell – This equation is based on a lower bound limit load solution and produces a consistent result as the crack approaches a through-wall configuration, see reference [D.14.17]. 1.

M t ( l c ) signifies that Mt is evaluated using the equations cited for a through-wall crack with the l a shell parameter as opposed to the l shell parameter (compare Equation (D.7) with Equation (D.20)). The results from this equation are usually associated with a net section limit load solution; the superscript NS In the following equation, the term

in the following equation designates a net section limit load solution. .

M sNS =

1

FG H

1 a a 1- + t t M t (l a )

IJ K

(D.19)

where,

la =

1818 . c Ri a

2.

In reference [D.14.17], the crack area is idealized as an equivalent rectangle with a area equal to the elliptical crack area. In this appendix, this approximation is not used and the area chosen to evaluate Mt is a rectangular area based on the component thickness and the full length of the crack. If desired, the equivalent elliptical area approximation can be introduced into the assessment by multiplying Equation (D.20) by F 4 .

3.

Equation (D.19) is written in terms of the component thickness and maximum depth of the flaw. If the flaw shape is characterized by a nonuniform thickness profile, Equation (D.19) can be written in terms of areas as follows:

M sNS =

c.

(D.20)

1 1 A A + 1Ao Ao M t ( l a )

FG H

IJ K

(D.21)

The results from equations (D.18) and (D.19) are approximately the same for flaws up to a t £ 0.5 . Above this value, the use of Equation (D.18) to compute M s will produce values which significantly exceed those obtained using Equation (D.19). This will result in conservatism in the computation of the stress intensity ratio ( Kr ), if the stress intensity factor is a function of M s , and the load ratio ( Lr ) in the FAD assessment for a given material toughness and yield stress. Experimental results indicate that Equation (D.19) produces consistent results for a t > 0.5 . Therefore, Equation (D.19) is recommended for use to compute the stress intensity factor (numerator in

Kr ) factor and reference stress (numerator

in Lr) unless additional conservatism is desired in the assessment. In summary, the following values can be used to compute the surface correction factor:

M s = M sL M s = M sNS

assessment based on local ligament criteria

b

(D.22)

g

assessment based on net section collapse recommended (D.23) --``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


D.2.4

Load Ratio and Reference Stress

D.2.4.1

The load ratio is the horizontal coordinate on the failure assessment diagram (see Section 9), and is defined as

Pl Ply

Lr = D.2.4.2

(D.24)

Alternatively, the load ratio can be written in terms of a reference stress:

Lr =

I ref

(D.25)

I ys

with,

F P II GH P JK

I ref =

l

(D.26)

ys

ly

D.2.4.3

This Appendix contains reference stress solutions for selected configurations. The solutions in paragraph D.2.4.2 can be converted into a yield load solution by rearranging equation (D.26). The limit load can be inferred by replacing the yield strength with an appropriate flow stress, see Appendix F.

D.2.5

Plastic Collapse In The Assessment Of Crack-Like Flaws

D.2.5.1

The position of an assessment point

b K , L g on the FAD represents a particular combination of r

r

flaw size, stresses and material properties. This point can be used to demonstrate whether the flaw is acceptable and an associated in-service margin can be computed based on the location of this point. If the flaw is unacceptable, the location of the assessment point on the FAD can indicate the type of failure which would be expected.

--``````-`-`,,`,,`,`,,`---

a.

The failure assessment diagram can be divided into three zones as illustrated in Figure D.1. If the assessment point lies in Zone 1, the predicted failure mode is predominantly fracture controlled and could be associated with brittle fracture. If the assessment point lies in Zone 3, the predicted failure mode is collapse controlled with extensive yielding resulting in large deformations in the component. If the assessment point lies in a Zone 2 the predicted failure mode is elastic plastic fracture.

b.

The significance of the Lr parameter in a FAD assessment can be described in terms of crack-tip plasticity. If fracture occurs under elastic plastic conditions, the

Kr value defined by

the failure assessment line at the corresponding Lr value represents the elastic component of the crack driving force. The limiting value of Kr reduces from unity as

Lr increases. Thus

b1- K g represents the enhancement of the crack driving force due to plasticity. Therefore, r

the value of the Lr parameter represents a measure of the crack tip plasticity as long as the

Lr parameter is less than the maximum permitted or cut-of value (see paragraph D.2.5.2.b). D.2.5.2

The value of a.

Lr depends on the type of plastic collapse load solution utilized in the assessment.

Plastic collapse solutions can be defined in three ways:


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


b.

1.

Local Collapse – Plastic collapse of the remaining ligament adjacent to the flaw being assessed. The reference stress solutions shown for plates in paragraphs D.3 and D.4 are based on a local collapse solutions. The reference stress solutions shown for cylinders and spheres which utilize the plate ligament equations (see paragraph D.3) with a surface correction factor, M s , based on a local limit load (see paragraphs D.2.3.3 and C.2.3.3 of Appendix C) are also considered to be local collapse solutions.

2.

Net Section Collapse – Plastic collapse of the structural section containing the flaw. The reference stress solutions shown for cylinders and spheres which do not utilize the plate ligament formulas of paragraph D.3 are considered to be net section collapse solutions. In addition, the reference stress solutions shown for cylinders and spheres which utilize the plate ligament equations (see paragraph D.3) with a surface correction factor, M s , based on a global limit load (see paragraphs D.2.3.3) are also considered to be net section collapse solutions. The reference stress solutions for bars and bolts in paragraphs D.11 are net section collapse solutions.

3.

Gross Collapse – Plastic collapse of the structure by unconstrained or gross straining throughout the structure. This occurs when a plastic collapse mechanism is formed in the structure and may be unaffected by the presence of the crack.

It is acceptable to use the local plastic collapse solution to determine the reference stress when computing the value of Lr . However, this may be excessively conservative for redundant structures. If the structure or component has degrees of redundancy, plasticity at the cracked ligament may be contained by the surrounding structure until conditions for gross collapse are reached. In such cases, it may be possible to use more appropriate estimates of Lr based on modified lower bound collapse solutions which are based on the response of the entire structure. For this approach to be adopted, it is essential to confirm by analysis that the plasticity at the cracked section is contained sufficiently by the remaining structure, so that the use of the standard assessment diagram gives conservative results. In ferritic steels, care must also be exercised to ensure that local constraint conditions are not sufficient to induce brittle fracture by a cleavage mechanism. Where global collapse can be shown to occur after the attainment of Lr b max g the Lr b cut - off g can be extended to the value relating to global collapse as described.

c.

If the assessment point falls outside the acceptable region, then recategorization of the flaw being evaluated can be undertaken and a reassessment made (see Section 9). In general, the recategorization procedures described in Section 9 will only be effective if the assessment point falls within the elastic plastic fracture controlled zone or beyond Lr b max g (in the collapse controlled zone).

D.2.5.3

The reference stress solutions in this appendix are based on the assessment of a single flaw. Multiple flaws which interact should be recategorized according to Section 9. However, multiple flaws which do not interact according to Section 9 may still effect the plastic collapse conditions, and allowances should be made to the collapse solutions to accommodate these effects.

D.2.5.4

It is recommended that a gross collapse assessment be performed to ensure that the applied stresses derived for local conditions do not cause failure of the structure in other regions. a.

In many cases a simple calculation can be performed to identify the highest applied stress condition which will result in the attainment of the flow strength on a significant cross section. In certain structures, gross collapse may occur in regions away from the flaw being assessed because of thinned areas, or where design conditions cause yielding of the general structure prior to collapse of the local regions.

b.

To facilitate understanding of the relative importance of local, net section and gross collapse loads, it is useful to calculate the minimum collapse load for regions away from the cracked --``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~


Not for Resale


section, as well as that involving the cracked section and determining the Lr parameter for both conditions. The minimum ratio of the gross collapse load for regions away from the cracked section to the local or net section collapse load at the cracked section represents a maximum value or cut off on the Lr -axis. The cut off limit may be less than one and in such cases the assessment diagram is effectively restricted by this cut-off. The failure assessment diagram is generally limited at higher values of Lr to a cut-off at Lr b max g which is based on --``````-`-`,,`,,`,`,,`---

material properties rather than structural behavior. In displacement controlled applications, the assessment diagram may be extended beyond the Lr b max g limit to the structural cut off limit.

D.3

Reference Stress Solutions For Plates

D.3.1

Plate – Through-Wall Crack, Through-Wall Membrane And Bending Stress (RPTC)

D.3.1.1

The Reference Stress is [D.14.3]:

I ref =

c

Pb + Pb2 + 9 Pm2

b g

h

0.5

(D.27)

3 1- =

where,

== D.3.1.2

c W

(D.28)

Notes: a.


b.

See paragraph D.2.2.3 for determination of Pm and Pb .

D.3.2

Plate – Surface Crack, Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (RPSCL1)

D.3.2.1

The Reference Stress is given by Equation (D.31) with the following definition of

== D.3.2.2

D.3.3

=:

a t

(D.29)

Notes: a.


b.


Plate – Surface Crack, Infinite Length, Through-wall Arbitrary Stress Distribution (RPSCL2)

//^:^^#^~^^""~:@":^*^~$~"#:*~


Not for Resale


D.3.3.1

The Reference Stress in paragrapgh D.3.2 can be used.

D.3.3.2

Notes: see paragraph D.3.2.2.

D.3.4

Plate – Surface Crack, Semi-Elliptical Shape, Through-wall Membrane And Bending Stress (RPSCE1)

D.3.4.1

The Reference Stress is [D.14.3], [D.14.18]: With bending restraint:

I ref =

b g + 9 P b1 - = g 3b1 - = g

gPb + gPb

2

2 m

2 0.5

(D.30)

2

With negligible bending restraint (e.g. pin-jointed):

I ref =

b

g + 9 P b1 - = g 3b1 - = g

Pb + 3 Pm= + Pb + 3 Pm=

2

2 m

2 0.5

(D.31)

2

where

a == t t 1+ c == D.3.4.2

D.3.5

0.75

=3

(D.32)

b g

for W ³ c + t

FG a IJ FG c IJ H t K HWK

(D.33)

b g

for W < c + t

(D.34)

Notes: a.


b.


c.

The normal bending restraint solution can be obtained by setting

d.

If

g = 10 . [D.14.18].

a > c , compute g based on a 2c = 0.5 .

Plate – Surface Cracks, Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (RPSCE2)

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

FaI g = 1 - 20G J H 2c K


--``````-`-`,,`,,`,`,,`---

D.3.5.1

The Reference Stress in paragraph D.3.4 can be used.

D.3.5.2

Notes: see paragraph D.3.4.

D.3.6

Plate – Surface Crack, Semi-Elliptical Shape, Through-wall Arbitrary Stress Distribution (RPSCE3)

D.3.6.1


D.3.6.2

Notes: see paragraph D.3.4.

D.3.7

Plate – Embedded Crack, Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (RPECL)

D.3.7.1


L R P + 3 P = + Mb P + 3 P = g + 9 P Sb1 - = g T N = = 4 d L OP 3Mb1 - = g + t Q N 2

b

I ref

m

b

2 m

m

2

4 d= + t

UVOP WQ

0.5

(D.35)

2

where,

d = d1 - a

== D.3.7.2

(D.36)

2a t

(D.37)

Notes: a.


b.


D.3.8

Plate – Embedded Crack, Elliptical Shape, Through-Wall Membrane and Bending Stress (RPECE1)

D.3.8.1

The Reference Stress is given by Equation (D.35) with following definitions of

d and = :

d = d1 - a

2a == t t 1+ c


(D.38)

b g

for W ³ c + t

(D.39)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


== D.3.8.2

FG 2a IJ FG c IJ H t KHW K

b g

for W < c + t

(D.40)

Notes: a.


b.


D.3.9

Plate – Embedded Crack, Elliptical Shape, Through-Wall Fourth-Order Polynomial Stress Distribution (RPECE2)

D.3.9.1


D.3.9.2

Notes: a.


b.


--``````-`-`,,`,,`,`,,`---

D.4

Reference Stress Solutions For Plates with Holes

D.4.1

Plate With Hole – Through-Wall Single Edge Crack, Through-Wall Membrane And Bending Stress (RPHTC1)

D.4.1.1


== D.4.1.2

=:

at t a+t

b g

(D.41)

Notes: a.


b.


D.4.2

Plate With Hole – Through-Wall Double Edge Crack, Through-Wall Membrane And Bending Stress (RPHTC2)

D.4.2.1


== D.4.2.2

2at t 2a + t

b

g

=: (D.42)

Notes: a.



Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


b.


D.4.3

Plate With Hole – Surface Crack, Semi-Elliptical Shape, Through-Wall Membrane Stress (RPHSC1)

D.4.3.1

The Reference Stress is:

L R 3 P = + Mb3 P = g + 9 P Sb1 - = g T N = 4 d= O L 3Mb1 - = g + t PQ N 2

m

I ref

m

2 m

2

4 d= + t

UVOP WQ

0.5

(D.43)

2

where,

D.4.3.2

d = t -c

(D.44)

2c == t t 1+ a

(D.45)

Notes:

--``````-`-`,,`,,`,`,,`---

a.


b.

See paragraph D.2.2.3 for determination of Pm .

D.4.4

Plate With Hole, Corner Crack, Semi-Elliptical Shape, Through-Wall Membrane and Bending Stress (RPHSC2)

D.4.4.1


== D.4.4.2

2ac t 2a + t

b

g

=: (D.46)

Notes: a.


b.


D.5

Reference Stress Solutions For Cylinders

D.5.1

Cylinder – Through-Wall Crack, Longitudinal Direction, Through-Wall Membrane and Bending Stress (RCTCL)


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


D.5.1.1

--``````-`-`,,`,,`,`,,`---

D.5.1.2

The Reference Stress is [D.14.1], [D.14.3]:

I ref =

l

e

Pb + Pb2 + 9 M t Pm

qj

2 0.5

(D.47)

3

Notes: a.


b.

See paragraph D.2.2.3 for determination of Pm and Pb . For internal pressure loading:

PRi t

Pm =

(D.48)

2

LM MN

FG IJ H K

pR t 3 t Pb = 2 o 2 Ro - Ri Ri 2 Ri c.

See paragraph D.2.3 to determine

2

FG IJ OP H K PQ

9 t + 5 Ri

3

(D.49)

M t for a through-wall crack in a cylinder.

D.5.2

Cylinder – Through-Wall Crack, Circumferential Direction, Through-Wall Membrane and Bending Stress (RCTCC1)

D.5.2.1


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I ref =

l qj

e

Pb + Pb2 + 9 ZPm

2 0.5

(D.50)

3

where,

Z=

c h b2 - J gR t b2= - G g

(D.51)

t Ro

(D.52)

F Ro2 - Ri2 o

J=

FG sin G IJ H 2K

= = arccos

(D.53)

c Rm

(D.54)

G= D.5.2.2

Notes: a.



Not for Resale


b.

See paragraph D.2.2.3 for determination of Pm and Pb . For internal pressure with a net section axial force:

Pm =

pRi2 F + 2 2 2 Ro - Ri F Ro - Ri2

c

(D.55)

h

Pb = 0.0

(D.56)

D.5.3

Cylinder – Through-Wall Crack, Circumferential Direction, Pressure With Net Section Axial Force and Bending Moment (RCTCC2)

D.5.3.1


I ref =

LM MN 2I

OP PQ

M I ys 2 3 ys Rm t 2 cos > - sin G - 2 pRm cos >

b

g

(D.57)

where,

F 2 >= 2I ys Rmt - pRm2 I ys RmtG +

G=

c Rm

(D.59)

Notes: a.


b.

If the net-section bending moment is zero, the solution in paragraph D.5.2. must be used.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.5.4

Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Internal Pressure (RCSCLL1)

D.5.4.1

The Reference Stress [D.14.1], [D.14.3]:

I ref =

l

Pb + Pb2 + 9 M s Pm

q

2 0.5

(D.60)

3

where,

Ms =

D.5.4.2

10 . 10 . -

(D.61)

a t

Notes:


Not for Resale

--``````-`-`,,`,,`,`,,`---

D.5.3.2

(D.58)


a.


b.

See paragraph D.5.1.2.b for determination of Pm and Pb .

D.5.5

Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (RCSCLL2)

D.5.5.1


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.5.5.2 Notes: see paragraph C.5.4.2.

D.5.6

Cylinder – Surface Crack, Longitudinal Direction – Infinite Length, Through-wall Arbitrary Stress Distribution (RCSCLL3)

D.5.6.1


D.5.6.2 Notes: see paragraph C.5.4.2.

D.5.7

Cylinder – Surface Crack, Circumferential Direction – 360 Degrees, Pressure With Net Section Axial Force And Bending Moment (RCSCCL1)

D.5.7.1


I ref

FG H

Mr M r2 2 = + Nr + 2 4

IJ K

0.5

(D.62)

For an inside surface crack

Nr =

Pm Ro2 - Ri2

b

Ro2 - Ri + a

g

(D.63)

2

LM MN

Ro4 - Ri4 3F 16 Ro4 - Ro Ri + a

M r = Pbg

b

OP g PQ

(D.64)

3

For an outside surface crack

Nr =

Pm Ro2 - Ri2 2

2 i

o

Mr

(D.65)

b R - ag - R OP R -R 3F L =P M 16 MN R b R - a g - R PQ 4 o

bg

o

o

4 i 3

(D.66)

4 i

--``````-`-`,,`,,`,`,,`---


Not for Resale


D.5.7.2

Notes: a.


b.

Pm and Pb are determined using the following equations:

Pm =

Pbg =

c

pRi2 F + 2 2 2 F Ro - Ri2 Ro - Ri

h c

--``````-`-`,,`,,`,`,,`---

MRo 0.25F Ro4 - Ri4

c

(D.67)

h

(D.68)

h

D.5.8

Cylinder – Surface Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (RCSCCL2)

D.5.8.1


I ref =

l qj

e

Pb + Pb2 + 9 ZPm

2 0.5

(D.69)

3

where,

L F 2 - 2J + xJ IJ OP Z = M1 - x G N H 2 -J KQ

D.5.8.2

-1

(D.70)

J=

t Ro

(D.71)

x=

a t

(D.72)

Notes:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.


b.


D.5.9

Cylinder – Surface Crack, Circumferential Direction – 360 Degrees, Through-wall Arbitrary Stress Distribution (RCSCCL3)

D.5.9.1


D.5.9.2

Notes: see paragragh D.5.8.2.


Not for Resale


D.5.10

Cylinder – Surface Crack, Longitudinal Direction – Semi-Elliptical Shape, Internal Pressure (RCSCLE1)

D.5.10.1 The Reference Stress is [D.14.3], [D.14.6]:

I ref =

b g + 9b M P g

gPb + gPb

2

2 0.5

s m

(D.73)

3

g is given by Equation (D.32) with the following definition of = :

where

a == t t 1+ c

(D.74)

D.5.10.2 Notes:

D.5.11

a.


b.


c.


M s for a surface crack in a cylinder.

Cylinder – Surface Crack, Longitudinal Direction – Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (RCSCLE2)

D.5.11.1 The Reference Stress in paragraph D.5.10.1 can be used.

D.5.12

Cylinder – Surface Crack, Longitudinal Direction – Semi-Elliptical Shape, Through-wall Arbitrary Stress Distribution (RCSCLE3)

D.5.12.1 The Reference Stress in paragraph D.5.10.1 can be used. D.5.12.2 Notes: see paragrapgh C.5.10.2.

D.5.13

Cylinder – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Internal Pressure and Net-Section Axial Force (RCSCCE1)

D.5.13.1 The Reference Stress is [D.14.2]:

I ref =

l qj

e

Pb + Pb2 + 9 ZPm

2 0.5

(D.75)

3

where,


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

D.5.11.2 Notes: see paragrapgh C.5.10.2.


Pm =

pRi2 F + 2 2 2 Ro - Ri F Ro - Ri2

c

(D.76)

h

Pb = 0.0

(D.77)

L 2= - xG FG 2 - 2J + xJ IJ OP Z=M N F F H 2 -J KQ = = arccosb A sin G g L b1 - J gb2 - 2J + xJ g + b1 - J + xJ g OP A = xM MN 2m1 + b2 - J gb1 - J gr PQ -1

(D.78)

(D.79)

2

(D.80)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

J=

t Ro

(D.81)

x=

a t

(D.82)

G=

Fc 4 Ri

for an internal crack

(D.83)

G=

Fc 4 Ro

for an external crack

(D.84)

D.5.13.2 Notes:

D.5.14

a.


b.

This solution can be used for any applied through-wall stress distribution if paragraph D.2.2.3 is used to determine of Pm and Pb .

Cylinder – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution With Net Section Bending Stress (RCSCCE2)


I ref =

M

a F I 2 R t G 2 sin > - sin G J H K t

(D.85)

2 m

where,

--``````-`-`,,`,,`,`,,`---


Not for Resale


>=

If

LM FG IJ FG a IJ - b P + P g OP MN H K H t K I PQ

F G 1F 2

m

b

(D.86)

ys

G=

Fc 4 Ri

for an internal crack

(D.87)

G=

Fc 4 Ro

for an external crack

(D.88)

bG + > g > F , I ref =

M a 2 Rm2 t 2 - I ys sin > t

FG H

IJ K

(D.89)

where,

F GH

F 1>=

b

P + Pb a - m t I ys a 2t

gIJ K

(D.90)

D.5.14.2 Notes:

D.5.15

a.


b.


c.

The inclusion of the term Pb in Equation (C.90) will produce conservative results.

d.

If the net section bending moment is zero, the solution in paragraph D.5.13 can be used with F = 0.0 and Pb equal to the value determined in subparagraph b above.

Cylinder – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-wall Arbitrary Stress Distribution (RCSCCE3)

D.5.15.1 The Reference Stress in paragraph D.5.13.1 can be used. D.5.15.2 Notes: a.


b.


--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~


Not for Resale


D.5.16

Cylinder – Embedded Crack, Longitudinal Direction – Infinite Length, Through-Wall Fourth Order Polynomial Stress Distribution (RCECLL)

D.5.16.1 The Reference Stress in paragraph D.3.7 can be used. D.5.16.2 Notes:

D.5.17

a.


b.


Cylinder – Embedded Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (RCECCL)


D.5.18

a.


b.


Cylinder – Embedded Crack, Longitudinal Direction – Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (RCECLE)

D.5.18.1 The Reference Stress is given by Equation (D.35) with the following definitions for

d and = :

d = d1 - a

(D.91)

2a == t t 1+ c

(D.92)

D.5.18.2 Notes:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.5.19

a.


b.


Cylinder – Embedded Crack, Circumferential Direction – Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (RCECCE)

D.5.19.1 The Reference Stress in paragraph D.5.18 can be used. D.5.19.2 Notes: a.

See Figure C.19 for the component and crack geometry. --``````-`-`,,`,,`,`,,`---


Not for Resale


b.


Reference Stress Solutions For Spheres

D.6.1

Sphere – Through-Wall Crack, Through-Wall Membrane and Bending Stress (RSTC)

D.6.1.1

The Reference Stress solution in paragraph D.5.1. can be used.

D.6.1.2

Notes: a.


b.

See paragraph D.2.2.3 for determination of Pm and Pb . For internal pressure loading only: 2

pR Pm = 2 i 2 Ro - Ri 3

(D.93)

LM F I F I MN GH JK GH JK

3 t 3 t pR Pb = 3 o 3 2 Ri Ro - Ri 4 Ri c.


2

FG IJ OP H K PQ

9 t + 4 Ri

3

(D.94)

M t for a through-wall crack in a sphere.

D.6.2

Sphere – Surface Crack, Circumferential Direction – 360 Degrees, Internal Pressure (RSSCCL1)

D.6.2.1


D.6.2.2

Notes: a.


b.


c.


M s for a surface crack in a sphere.

D.6.3

Sphere – Surface Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (RSSCCL2)

D.6.3.1


D.6.3.2


D.6.4

Sphere – Surface Crack, Circumferential Direction – 360 Degrees, Through-wall Arbitrary Fourth Order Polynomial Stress Distribution (RSSCCL3)


Not for Resale

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.6


D.6.4.1


D.6.4.2


D.6.5

Sphere – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Internal Pressure (RSSCCE1)

D.6.5.1

The Reference Stress in paragraph D.5.10. can be used.

D.6.5.2

Notes: a.


b.


c.


D.6.6

Sphere – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (RSSCCE2)

D.6.6.1


D.6.6.2


D.6.7

Sphere – Surface Crack, Circumferential Direction – Semi-Elliptical Shape, Through-wall Arbitrary Stress Distribution (RSSCCE3)

D.6.7.1


D.6.7.2


D.6.8

Sphere – Embedded Crack, Circumferential Direction – 360 Degrees, Through-Wall Fourth Order Polynomial Stress Distribution (RSECCL)

D.6.8.1


D.6.8.2

Notes: a.


b.


D.6.9

Sphere – Embedded Crack, Circumferential Direction – Elliptical Shape, Through-Wall Fourth Order Polynomial Stress Distribution (RSECCE)

D.6.9.1


--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

M s for a surface crack in a sphere.


D.7

Notes: a.


b.


Reference Stress Solutions For Elbows And Pipe Bends The reference stress solutions for cylinders can be used for elbows and pipe bends if the equivalent membrane and bending stress at the location of the crack is determined considering the bend geometry and applied loads. A discussion regarding the stress analysis for elbows is provided in Appendix C, paragraph C.7.

D.8

Reference Stress Solutions For Nozzles And Piping Tees

D.8.1

Nozzle – Corner Crack, Radial Direction, Quarter-Circular Shape, Membrane Stress At The Corner (RNCC1)

D.8.1.1


I ref

F 2.5t + lq - r qt I =PG H 2.5t + lq - r qt - 0.25Fa JK 2 n

m

2 n

n

2

(D.95)

n

where,

l

q = max 2rn , rn + t n + t rn = D.8.1.2

q

(D.96)

dn - tn 2

(D.97)

Notes: a.

See Figure C.25 (Crack labeled G) and Figure C.26 for the component and crack geometry.

b.

Pm is the primary membrane stress at the nozzle, the effects of the stress concentration are neglected in the calculation of the reference stress because this stress is localized.

D.8.2

Nozzle – Corner Crack, Radial Direction, Quarter-Circular Shape, Cubic Polynomial Stress Distribution (RNCC2)

D.8.2.1

The Reference Stress is computed using equations in paragraph D.8.2 with an equivalent membrane stress.

D.8.2.2

Notes: a.

See Figure C.25 (Crack labeled G) and Figure C.26 for the component and crack geometry.

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.6.9.2


b.

D.8.3

See paragraph D.2.2.3 for determination of Pm .

Surface Cracks At Nozzles – General Solution The reference stress solutions shown below can be used for nozzles if the equivalent membrane and bending stress at the location of the crack is determined considering the nozzle geometry and applied loads. A discussion regarding the stress analysis for nozzles is provided in Appendix C, paragraph C.8. Nozzle Neck or Branch (see Figure C.25) ·


·


Shell or Run Pipe (see Figure C.25) ·

Crack D & F – Use KPTC, KPSCE3, KPECL, or KPECE2

·

Crack E & C – Use KPTC, KPSCE3, KPECL, or KPECE2

·

Crack G – Use the solutions in paragraph D.8

D.9

Reference Stress Solutions For Ring-Stiffened Cylinders

D.9.1

Ring-Stiffened Cylinder – Internal Ring, Surface Crack At The Toe Of One Fillet Weld, Circumferential Direction – 360 Degrees, Pressure Loading (RRCSCCL1)

D.9.1.1

The Reference Stress in paragraph D.5.8 can be used with an equivalent membrane and bending stress.

D.9.1.2

Notes: a.


b.

See paragraph A.8.3 of Appendix A for determination of the equivalent membrane stress, Pm, and bending stress, Pb based on the stress results at the inside and outside surface, or

Pm =

Pb =

D.9.2

I s , ID + I s ,OD 2

(D.98)

I s , ID - I s ,OD

(D.99)

2

Ring-Stiffened Cylinder – Internal Ring, Surface Crack At The Toe Of Both Fillet Welds, Circumferential Direction – 360 Degrees, Pressure Loading (RRCSCCL2)

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


D.9.2.1

The Reference Stress in paragraph D.5.8 can be used with an equivalent membrane and bending stress.

D.9.2.2


D.10

Reference Stress Solutions For Sleeve Reinforced Cylinders The reference stress solutions shown below can be used for sleeve reinforced cylinders if the stress at the location of the crack is determined considering the actual component geometry and applied loads. A discussion regarding the stress analysis is provided for sleeve reinforced cylinders in Appendix C, paragraph C.10. Cracks At Sleeve Reinforced Cylinders (see Figure C.28) ·


·


D.11

Reference Stress Solutions for Round Bars and Bolts

D.11.1

Round Bar, Surface Crack – 360 Degrees, Membrane and Bending Stress (RBSCL)

D.11.1.1 The Reference Stress is:

I ref

FG H

M M2 = r + N r2 + r 2 4

IJ K

0.5

(D.100)

where,

Nr =

Pm Ro2

(D.101)

b R - ag OP R 3F L =P M 16 MN R b R - a g PQ 2

o

--``````-`-`,,`,,`,`,,`---

Mr

4 o

bg

(D.102)

3

o

o

D.11.1.2 Notes: a.


b.

The primary membrane and global bending stresses are computed using the following equations:

Pm =


F FRo2

(D.103)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Pbg =

D.11.2

4M FRo3

(D.104)

Round Bar – Surface Crack, Straight Front, Membrane and Bending Stress (RBSCS)


I ref =

FPm

F 1 + sin 2 > + > 2 2

+

3FPgb

(D.105)

16M

where,

FG R - a IJ H R K o

(D.106)

o

F a IJ M = 10002 . - 3.9927G H 2R K o

1.5

FG a IJ + 58491 . H 2R K

2 .5

o

F a IJ - 2.8550G H 2R K

3

(D.107)

o

D.11.2.2 Notes:

D.11.3

a.


b.

The primary membrane and global bending stresses can computed using the equations in paragrapgh D.11.2.b.

Round Bar, Surface Crack, Semi-Circular, Membrane and Bending Stress (RBSCC)


D.11.4

a.


b.

The semi-elliptical flaw is evaluated as an equivalent to a straight front flaw.

Bolt, Surface Crack, Semi-Circular or Straight Front Shape, Membrane and Bending Stress (RBSC)

D.11.4.1 The Reference Stress in paragraph D.11.2 can be used by replacing Ro with Rth. //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

D.11.4.2 Notes: a.


b.

The solution applies to a semi-circular or straight front surface crack.


Not for Resale

--``````-`-`,,`,,`,`,,`---

> = arcsin

D.12

Reference Stress Solutions For Cracks At Fillet Welds

D.12.1

Cracks at Fillet Welds – Surface Crack At A Tee Joint, Semi-Elliptical Shape, Through-Wall Membrane and Bending Stress (KFWSCE1)

D.12.1.1 The Reference Stress in paragraph D.3.4 can be used with an equivalent membrane and bending stress. D.12.1.2 Notes:

--``````-`-`,,`,,`,`,,`---

D.12.2

a.


b.


Cracks at Fillet Welds of Tee Junctions In Pressurized Components – General Solution The reference stress solutions shown below can be used for cracks at fillet welds in pressure containing components if the stress at the location of the crack is determined considering the actual component geometry and applied loads. A discussion regarding the stress analysis is provided in Appendix C, paragraph C.12. Cracks At Fillet Welds of Tee Junctions In Pressurized Components (see Figure C.32)

D.13

·

Flat Plate Tee Junctions – Use RPTC, RPSCE3, RPECL, or RPECE2

·

Longitudinal Tee Junctions in Cylinders – Use RCTCL, RCSCLL3, RCSCLE3, RCECLL or RCECLE

·

Circumferential Tee Junctions in Cylinders – Use RCTCC1, RCTCC2, RCSCCL3, RCSCCE3, RCECCL or RCECCE

·

Circumferential Tee Junctions in Spheres – Use RSTC, RSSCCL3, RSECCL or RSECCE

Reference Stress Solutions For Cracks In Clad Or Weld Overlayed Plates And Shells The reference stress solutions in this appendix can be use to evaluate clad or weld overlayed plate and shell components. A discussion regarding the stress analysis for clad and weld overlayed plate and shell components is provided in Appendix C, paragraph C.13.

D.14

References

D.14.1

Miller, A.G., “Review of Limit Loads of Structures Containing Defects,” International Journal of Pressure Vessels & Piping, Vol. 32, 1988.

D.14.2

Zahoor, A., "Ductile Fracture Handbook", Electric Power Research Institute, Palo Alto, CA, 1989.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



D.14.3

Willoughby, A.A. and Davey, T.G., “Plastic Collapse in Part-Wall Flaws in Plates,”Fracture Mechanics: Perspectives and Directions (Twentieth Symposium), ASTM STP 1020, R.P. Wei and R.P. Gangloff, Eds., American Society for Testing and Materials, Philadelphia, 1989, pp. 390-409.

D.14.4

Bamford, W.H., Landerman, E.I., and Diaz, E., “Thermal Analysis of Cast Stainless Steel, and its Impact on Piping Integrity,” Circumferential Cracks in Pressure vessels and Piping – Vol. II, ASME PVP – Vol. 95, G.M. Wilkowski, American Society of Mechanical Engineers, 1984, pp. 137-172.

D.14.5

Bergman, M., Bjorn, B., Dahlberg, L., Nilsson, F., and Sattari-Far, I., “A Procedure For Safety Assessment of Components with Cracks – Handbook,” SA/FoU-Report 91/01, The Swedish Plant Inspectorate, Stockholm, Sweden, December, 1991.

D.14.6

BSI, “Draft Revision to PD6493 Fracture Assessment”, TWI, March, 1996.

D.14.7

Kiefner, J.F. and Vieth, P.H., “Project PR 3-805, A Modified Criterion for Evaluating the Remaining Strength of Corroded Pipe,” Battelle Report to the Pipeline Committee of the American Gas Association, 1989.

D.14.8

Stephens, D.R., Krishnaswamy, P, Mohan, R., Osage, D.A., Sims, J.R., and Wilkowski, G., “A Review of Analysis Methods and Acceptance Criteria for Local Thinned Areas in Piping and Piping Components,” 1997 Pressure Vessels and Piping Conference, Orlando, Florida, July, 1997.

D.14.9

Green, D. and Knowles, J., “The Treatment of Residual Stress in Fracture Assessment of Pressure Vessels,” ASME, Journal of Pressure Vessel Technology, Vol. 116, November 1994, pp. 345-352.

D.14.10 Folias, E.S., “On the Effect of Initial Curvature on Cracked Sheets,” International Journal of Fracture Mechanics, Vol. 5, No. 4, December, 1969, pp. 327-346. D.14.11 Sih, G.C., “Handbook of Stress Intensity Factors,” Institute of Fracture and Solid Mechanics, Lehigh University, Bethlehem, Pa. D.14.12 Kramer, G.S., Wilkowski, G.M., and Maxey, W.A., “Flaw Tolerance of Spiral Welded Pipe,” Battelle NG-18 Report No. 154, January, 1987. D.14.13 Kiefner, J.F. and Vieth, P.H., “Project PR 3-805, A Modified Criterion for Evaluating the Remaining Strength of Corroded Pipe,” Battelle Report to the Pipeline Committee of the American Gas Association, 1989. D.14.14 Eiber, R.J., Maxey, W.A., Duffy, A.R., and Atterbury, T.J., “Investigation of the Initiation and Extent of Ductile Pipe Rupture,” Battelle Report Task 17, June, 1971. D.14.15 Murakami, Y., “Stress Intensity Factors Handbook,” Pergamon Press, Oxford, 1987, pp. 1356-1358. D.14.16 Tada, H., Paris, P.c. and Irwin, G.R, “The Stress Analysis Of Cracks Handbook – Second Edition,” Paris Productions Inc., St. Louis, Missouri, 1985. D.14.17 Chell,G.G, “Application of the CEGB Failure Assessment Procedure, R6, to Surface Flaws,” Fracture Mechanics: Twenty-First Symposium, ASTM STP 1074, J.P. Gudas, J.A. Joyce, and E.M. Hackett, Eds., American Society for Testing and Materials, Philadelphia, 1990, pp. 525-544. D.14.18 Sattari-Far, I., “Finite Element Analysis of Limit Loads For Surface Cracks in Plates,” Int. J. Pres. Ves. & Piping, 57, 1994, pp. 237-243.

D.15

Tables and Figures

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure D.1 Failure Regions On The Failure Assessment Diagram

1.6 Zone 1 Fracture (Elastic) Controlled

1.4 --``````-`-`,,`,,`,`,,`---

1.2

Unacceptable Region

Kr

1.0 Zone 2 Fracture (Elastic-Plastic) And Collapse Controlled

0.8 0.6

Acceptable Region

0.4 0.2

Zone 3 Collapse Controlled

0.0 0.0

0.2

0.4

0.6

0.8

1.0

Lr


1.2

1.4 1.6 Lr(max)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

APPENDIX E – Residual Stresses in a Fitness-For-Service Evaluation E.1

General

E.1.1

This appendix provides guidance for determining the magnitude and distribution of residual stresses at a welded joint. This information is required as input to perform a fitness-for-service assessment of a component containing a crack-like flaw (see Section 9).

E.1.2

The information from this appendix is used to compute the crack driving force associated with the residual stresses, and also serves as input data for determination of the plasticity interaction factor, . , (see Section 9) which quantifies the crack driving force that occurs under situations of combined loading (i.e. primary, secondary and residual stress).

E.2

Applicability and Limitations

E.2.1

The methodology provided herein apply to welded joints located in equipment that has been inservice, as well as to new construction. Residual stress distributions are provided for the following weld joint configurations: ·

Full Penetration Welds in Piping and Pressure Vessel Cylindrical Shells (see paragraph E.4)

·

Full Penetration Welds in Spheres and Pressure Vessel Heads (see paragraph E.5)

·

Full Penetration Welds in Storage Tanks (see paragraph E.6)

·

Full Penetration and Fillet Welds at Corner Joints (see paragraph E.7)

·

Fillet Welds at Tee Joints (see paragraph E.8)

·

Repair Welds (see paragraph E.9)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"

E.2.2

The residual stress distributions presented in this appendix are based on extensive numerical analyses and a literature survey of published results. The information obtained from the literature survey indicated a substantial scatter in the reported results. Therefore, the residual stress distributions in this appendix were obtained by developing an upper bound solution based on the published results and the results of the numerical analysis. Note that since the residual stress distributions are based on an upper bound solution, they are not necessarily self-equilibrating.

E.2.3

Residual stress distributions are provided for both the as-welded and PWHT conditions. The residual stress distribution for weld joints subject to PWHT are based on a uniform PWHT temperature applied to the component. Uncontrolled and/or local PWHT may result in significantly higher residual stresses. If the type of PWHT cannot be established, the residual stress distribution for the as-welded assessment should be used in the assessment. If the weld joint is in a component operating in the creep range (long-term operation), then the residual stress based on the PWHT condition may be used in the assessment.

E.2.4

Currently, a distinction is not made concerning the material of construction. It is currently assumed that stainless steel weldments can be assessed with equal accuracy using these equations. This assumption will be addressed in future revisions of this appendix.

E.2.5

The residual stress distributions at a welded joint are sensitive to the restraint condition. The distributions in this section are not applicable for closures welds where the degree of restraint against shrinkage is not known. For this case, a yield level membrane residual stress distribution should be used in the FFS assessment.

E.2.6

The residual stress distribution is also sensitive to the weld joint geometry. Currently, solutions are provided for single V-Type, double V-Type joint, fillet welds, and repair welds. The solutions for the

E-1 Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS

Not for Resale

--``````-`-`,,`,,`,`,,`---

(Jan, 2000)

--``````-`-`,,`,,`,`,,`---

double V-Type joint configuration should be used for joints that are back-gouged and predominantly welded from one side.

E.2.7

The residual stress distributions provided in this appendix are two dimensional; the stress distribution is provided through the wall thickness and in the plane of the component. The residual stress in the plane of the component diminishes with distance from the weld joint. The effects of this reduced residual stress may be used in the assessment.

E.2.8

The equations for the residual stress distributions provided in this appendix are referenced from the inside surface (i.e. the local coordinate, x , is referenced from the inside surface). If a surface breaking crack-like flaw is on the outside surface, then the distributions need to be modified so that the local coordinate is defined from the outside surface.

E.2.9

Results from the literature, testing, experimental analysis, or numerical analysis may be used to determine the residual stress at a welded joint as an alternative to the solutions provided in this appendix. For example, residual stresses measured in the field using the depth controlled hole drilling method can be used to determine the residual stress on the surface of a component. All assumptions used to determine the residual stress distribution by this alternative means should be documented with the assessment results. Residual stress distributions from a single literature source should not be used unless specific information is available to confirm their accuracy.

E.3

Data Requirements and Definition of Variables

E.3.1

The following data are required to estimate the residual stress field caused by a welded joint:

E.3.2

·

The material specification

·

The material specified minimum yield strength

·

The wall thickness of the component

·

The heat input used to make the weld

·

The type of weld (i.e. girth or circumferential joint, longitudinal seam, repair weld, or attachment weld)

·

The weld joint configuration (i.e. single V-groove, double V-groove, corner joint, fillet weld, or repair weld)

·

Whether the weld has experienced any of the following procedures aimed at reducing the residual stress level; hydrotest to 150% of the maximum allowable working pressure (MAWP) per the ASME Code, Section VIII, and/or post weld heat treatment per the original construction code.

Definition of symbols – The following variables are used in this appendix;

Cul

=

t x

= =

R I ys

= =

units conversion constant; equal to 1.0 if the thickness is expressed in mm and 25.4 if the thickness is expressed in inches, Nominal wall thickness of the component (mm:in), Local coordinate defined through the wall thickness of the component to define the residual stress distribution (mm:in), Mean radius of the pipe or cylindrical shell (mm:in), Specified minimum yield strength (MPa:psi),

I rys

=

The magnitude of the effective yield strength to be used to estimate the residual stress at a welded joint (MPa:psi),

I iph =

Primary circumferential stress at the inner surface in a cylindrical shell resulting from a hydrotest (MPa:psi),

I oph =

Primary circumferential stress at the outer surface in a cylindrical shell resulting from a hydrotest (MPa:psi),


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

E-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE E-3 _________________________________________________________________________________________________

I ir I ro I irh I rh o I rm I

Residual stress at the inner surface (MPa:psi),

=

Residual stress at the outer surface (MPa:psi),

=

Residual stress at the inner surface including the effects of hydrotest (MPa:psi),

=

Residual stress at the outer surface including the effects of hydrotest (MPa:psi),

=

Membrane component of the residual stress (MPa:psi), and

=

Bending component of the residual stress (MPa:psi).

I rys = I ys + 69 MPa

(E.1)

I rys = I ys + 10 ksi

(E.2)

E.4

Full Penetration Welds in Piping and Pressure Vessel Cylindrical Shells

E.4.1

Single V-Groove Circumferential (Girth) Welds (see Figures E.1 and E.2)

E.4.1.1

Residual Stress Perpendicular to The Weld Seam (Circumferential Flaw) a.

Residual Stress Distribution – The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equation. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface.

c

I r ( x ) = I ir + I ro - I ir

hFGH xt IJK

(E.3)

with,

I ro = 0.2I rys

(E.4)

for welds made with a heat input less than or equal to 2 kJ/mm (50kJ/in):

I ir = I rys

c

for t * £ 20 mm (0.79 in.)

h

I ir = 132 . - 0.016t * I rys

I ir = 0.2I rys

(E.5)

b

g

for 20 mm (0.79 in.) < t * < 70 mm 2.75 in.

for t * ³ 70 mm (2.75in.)

(E.6) (E.7)

and for welds made with a heat input greater than 2 kJ/mm (50kJ/in):

I ir = I rys


for t * £ 50 mm (2 in.)

Not for Resale

(E.8)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

In order to estimate the magnitude of the residual stress distribution at a weld joint, an estimate of the actual yield strength of the material must be made. If actual data does not exist or cannot be determined, the following equation may be used to estimate the magnitude of the yield strength. The elevation of the effective yield strength above the specified minimum yield strength accounts for the typical elevation of actual properties above minimum requirements. The properties of the base material should be used to determine the specified minimum yield strength.

--``````-`-`,,`,,`,`,,`---

E.3.3

r b

=


c

h

I ir = 180 . - 0.016t * I rys

I ir = 0.2I rys

for 50 mm (2 in.) < t * < 100 mm (4 in.)

for t * ³ 100 mm (4 in.)

(E.9) (E.10)

where,

for R t £ 10

(E.11)

LM 1 FG R IJ - 1OP + tC N10 H t K Q

t * = 3.90625

for 10 < R t < 50

ul

t * = tCul + 15.625

for R t ³ 50

(E.12)

(E.13)

The membrane and bending components of the residual stress distribution are:

I ir + I ro 2

(E.14)

I ir - I ro I = 2

(E.15)

I rm = r b

b.

Effects of Hydrotest – The methodology used to reduce the residual stress after overload or proof testing is covered in Section 9.

c.

Effects of PWHT – If the weld is known to have been subject to post weld heat treatment per the original construction code, then the residual stress is given by:

I r ( x ) = 0.2I rys E.4.1.2

(E.16)

Residual Stress Parallel to The Weld Seam (Longitudinal Flaw) a.

--``````-`-`,,`,,`,`,,`---


c


hFGH xt IJK

(E.17)

with,

I ro = I rys

(E.18)

and,

I ir = I rys

b

for t £ 20 mm (0.75 in)

g

I ir = 128 . - 0.014tCul I rys


(E.19)

for 20 mm (0.75in.) < t < 70 mm (2.75 in.) (E.20)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

t * = tCul

Jan,

RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE

2000

0; = 0.30' YS

for

t 2

70 mm (2.75in.)

E-5 (E.21)

b.

Effects of Hydrotest - The methodology used to reduce the residual stress after overload or proof testing is covered in Section 9.

C.

Effects of PWHll - If the weld is known to have been subject to post weld heat treatment per the original construction code, then the residual stress is given by:

d(x)=

o.30is

(E.22)

--``````-`-`,,`,,`,`,,`---

E.4.2

Double V-Groove Circumferential (Girth) Welds (see Figures E.l and E.3)

E.4.2.1


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Residual Stress Distribution - The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equations. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface.

cr’(x)=0,+0,(;)+-*(;)

(E.23)

CT, = 0;

(E.24)

where,

0,

=--(3:,+0.4(aj+d,)-30;

(E.25)

CT*

=20:,-0.4(aj+o;)+2aj

(E.26)

with 0: and 4 b.


C.

Effects of PWHT- If the weld is known to have been subject to post weld heat treatment per the original construction code, then the residual stress is given by:

d(x)= E.4.2.2

computed using the equations in paragraph E.4.1.1.

0.25

(E.27)


Residual Stress Distribution - The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equation. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface.

cf(x)=,;+(,;-0;) 0r Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS

Not for Resale

E-6


Jan, 2000

with,

0; =cJrYS

(E.29)

0: = 0.5a;s

(E.30)

--``````-`-`,,`,,`,`,,`---

b.


C.

Effects of PJYH7 - If the weld is known to have been subject to post weld heat treatment per the original construction code, then the residual stress is given by:

d(x)

= 0.3a;,

(E.31)

E.4.3

Single V-Groove Longitudinal (Seam) Welds (see Figures E.l and E.4)

E.4.3.1

Residual Stress Perpendicular to The Weld Seam (Longitudinal Flaw) a.

Residual Stress Distribution - The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equations. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface.

o’(x)=o,+cr,(;)++)

(E.32)

o(J = 0;

(E.33)

where,

0, = -0;

WW

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

LT* = 20; - 0.4(0; + a;) + 20;

(E.35)

0; = OS

(E.36)

0; = cTLs

(E.37)

b.


C.

Effects of PFW?T- If the weld is known to have been subject to post weld heat treatment per the original construction code, then the residual stress is given by:

d(x) E.4.3.2

+ 0.4( cr; + 0;) - 30;

= 0.2c5

(E.38)

Residual Stress Parallel To The Weld Seam (Circumferential Flaw)


Not for Resale


a.

Residual Stress Distribution:

I r ( x ) = I rys

(E.39)

b.


c.


I r ( x ) = 0.3I rys

(E.40)

E.4.4

Double V-Groove Longitudinal (Seam) Welds (see Figures E.1 and E.5)

E.4.4.1

Residual Stress Perpendicular to The Weld Seam (Longitudinal Flaw) a.


I r ( x ) = I rys

(E.41)

b.


c.


I r ( x ) = 0.2I rys E.4.4.2

(E.42)

Residual Stress Parallel To The Weld Seam (Circumferential Flaw) a.


I r ( x ) = I rys

(E.43)

b.


c.


I r ( x ) = 0.3I rys

(E.44)

E.5

Full Penetration Welds in Spheres and Pressure Vessel Heads

E.5.1

Single V-Groove Circumferential Welds (see Figure E.6 and E.7)

E.5.1.1

Residual Stress Perpendicular to The Weld Seam (Circumferential Flaw)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:

a.


--``````-`-`,,`,,`,`,,`---


Not for Resale


c

I r ( x ) = I ir + I ro - I ir with

hFGH xt IJK

(E.45)

I ro and I ir computed using the equations in paragraph E.4.1.1.

b.


c.


I r ( x ) = 0.2I rys --``````-`-`,,`,,`,`,,`---

E.5.1.2

(E.46)

Residual Stress Parallel to The Weld Seam (Meridional Flaw) a.


c

I r ( x ) = I ir + I ro - I ir with

hFGH xt IJK

(E.47)


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

b.


c.


I r ( x ) = 0.3I rys

(E.48)

E.5.2

Double V-Groove Circumferential Welds (see Figure E.6 and E.8)

E.5.2.1


Residual Stress Distribution – The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equations. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface.

I r ( x) = I 0 + I 1

FG x IJ + I FG x IJ HtK HtK

2

(E.49)

2

where,

I 0 = I ir

(E.50)

c

h

I 1 = -I ro + 0.4 I ir + I ro - 3I ir


(E.51)

Not for Resale


c

h

I 2 = 2I ro - 0.4 I ir + I ro + 2I ir with


b.


c.


I r ( x ) = 0.2I rys E.5.2.2

(E.52)

(E.53)

Residual Stress Parallel to The Weld Seam (Meridional Flaw) a.


c


hFGH xt IJK

(E.54)

with,

I ro = I rys

(E.55)

I ir = 0.5I rys

(E.56)

b.


c.


I r ( x ) = 0.3I rys

(E.57)

E.5.3

Single V-Groove Meridional (Seam) Welds (see Figures E.6 and E.9)

E.5.3.1

Residual Stress Perpendicular to The Weld Seam (Meridional Flaw) Residual Stress Distribution – The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equations. The residual stress distribution is approximated as two linear stress distributions intersecting at the mid-wall position. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface. r

I ( x) = I 0


2

2

(E.58) --``````-`-`,,`,,`,`,,`---

a.

where,


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I 0 = I ir

(E.59)

c - 0.4cI

h + I h + 2I

I 1 = -I ro + 0.4 I ir + I ro - 3I ir

(E.60)

I 2 = 2I ro

(E.61)

r i

r o

r i

with,

I ro = I rys

(E.62)

I ir = I rys

(E.63)

b.


c.


I r ( x ) = 0.2I rys E.5.3.2

(E.64)



I r ( x ) = I rys

(E.65)

b.


c.


I r ( x ) = 0.3I rys

(E.66)

E.5.4

Double V-Groove Meridional (Seam) Welds (see Figures E.6 and E.10)

E.5.4.1

Residual Stress Perpendicular to The Weld Seam (Meridional Flaw) a.


I r ( x ) = I rys

(E.67)

b.


c.


I r ( x ) = 0.2I rys


(E.68)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---



E.5.4.2



--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I r ( x ) = I rys

(E.69)

b.


c.


I r ( x ) = 0.3I rys

(E.70)

E.6

Full Penetration Welds in Storage Tanks

E.6.1

Single V-Groove Circumferential Welds (see Figure E.11)

E.6.1.1



c


hFGH xt IJK

(E.71)

with,

I ro = I rys

(E.72)

I ir = 0.0

(E.73)

b.


c.


I r ( x ) = 0.2I rys E.6.1.2

(E.74)



I r ( x ) = I rys b.

(E.75)



Not for Resale


c.


I r ( x ) = 0.3I rys

(E.76)

E.6.2

Double V-Groove Circumferential Welds (see Figure E.12)

E.6.2.1


Residual Stress Distribution – The residual stress distribution for this category of weld made remote from all geometric discontinuities can be approximated using the following equations. The local coordinate x for the stress distribution through the wall thickness is measured from the inside surface. r

I ( x) = I 0


2

(E.77)

2

where,

I 0 = I ir

c - 0.4cI

h + I h + 2I

I 1 = -I ro + 0.4 I ir + I ro - 3I ir

(E.79)

I 2 = 2I ro

(E.80)

r i

r o

r i

with,

--``````-`-`,,`,,`,`,,`---

E.6.2.2

I ro = I rys

(E.81)

I ir = I rys

(E.82)

b.


c.


I r ( x ) = 0.2I rys

(E.83)



c



hFGH xt IJK

(E.84)

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(E.78)


with,

I ro = I rys

(E.85)

I ir = 0.5I rys

(E.86)

b.


c.


I r ( x ) = 0.3I rys E.6.3

(E.87)

Single V-Groove Longitudinal Welds (see Figure E.11) The residual stress solution provided for the single V-groove circumferential weld joint in paragraph E.6.1 can be used for the single V-groove longitudinal weld joint.

E.6.4

Double V-Groove Longitudinal Welds (see Figure E.12) The residual stress solution provided for the double V-groove circumferential weld joint in paragraph E.6.2 can be used for the double V-groove longitudinal weld joint.

E.7

Full Penetration Welds at Corner Joints (Nozzles or Piping Branch Connections)

E.7.1

Corner Joint (see Figure E.13, Weld Joint A)

E.7.1.1

Residual Stress Perpendicular to The Weld Seam a.


I r ( x ) = I rys

(E.88)

b.

Effects of Hydrotest – The methodology used to reduce the secondary membrane stress (i.e. residual stress) after overload testing is covered in Section 9.

c.


I r ( x ) = 0.3I rys E.7.1.2

(E.89)

Residual Stress Parallel To The Weld Seam a.


I r ( x ) = I rys

(E.90)

b.


c.


--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


I r ( x ) = 0.3I rys E.7.2

(E.91)

Nozzle Fillet Weld (see Figure E.13, Weld Joint B) The results from paragraph E.8.1 can be used for this configuration.

E.7.3

Shell Fillet Weld With A Reinforcing Pad (see Figure E.13, Weld Joint C) The results from paragraph E.8.1 can be used for this configuration.

E.8

Full Penetration and Fillet Welds at a Tee Joint

E.8.1

Main Plate (see Figures E.14 and E.15)

E.8.1.1


Residual Stress Distribution – The residual stress acting perpendicular to the weld seam through the wall thickness in the plane of the fillet weld toe in the main plate is given as follows where the local coordinate x is defined in Figure E.14.

R|S c h |T

. I r ( x ) = I rys 8.571 10-3 - 01619

FG x IJ + 0.6286FG x IJ HtK HtK

2

FG x IJ U|V H t K |W 3

+ 0.5333

b.


c.


I r ( x ) = 0.2I rys E.8.1.2

(E.92)

(E.93)


Residual Stress Distribution – The residual stress acting transverse to the weld seam through the wall thickness in the plane of the fillet weld toe in the main plate is given as follows where the local coordinate x is defined in Figure E.14.

--``````-`-`,,`,,`,`,,`---

r

I ( x) = I

r ys

R|S8.571c10 h - 01619 FG x IJ + 0.6286FG x IJ . HtK HtK |T -3

2

F x I U| + 0.5333G J V H t K |W 3

(E.94)

b.


c.


I r ( x ) = 0.3I rys //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

E.8.2

Stay Plate (see Figure E.14)

E.8.2.1

Residual Stress Perpendicular to the Weld


(E.95)

Not for Resale


a.

Residual Stress Distribution – The residual stress acting perpendicular to the weld is:

I r ( x ) = I rys

(E.96)

b.


c.


I r ( x ) = 0.2I rys E.8.2.2

(E.97)


Residual Stress Distribution – The residual stress acting parallel to the Weld Seam is:

I r ( x ) = I rys

(E.98)

b.


c.


I r ( x ) = 0.3I rys

(E.99)

E.9

Repair Welds

E.9.1

Seam Welds (Figure E.16)

E.9.1.1


Residual Stress Distribution – The residual stress acting perpendicular to the repair weld through the wall thickness is given as follows where the local coordinate x is defined in Figure E.16. For

tw <

t : 2

b

I r ( x ) = 0.0

I r ( x ) = I rys

if x £ t - 2t w

FG x IJ Ht K

b

g

g

(E.100)

b

if t - 2t w < x < t - t w

g

(E.101)

w

I r ( x ) = I rys For

tw ³

b

if x ³ t - t w

g

(E.102)

t : 2

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


I r ( x ) = I rys

FG x IJ Ht K

if x < t - t w

b

g

(E.103)

b

g

(E.104)

w

I r ( x ) = I rys b.


c.

Effects of PWHT – If the weld is known to have been subject to post weld heat treatment per the original construction code, then the residual stress is given by: For

For

--``````-`-`,,`,,`,`,,`---

E.9.1.2

if x ³ t - t w

tw <

t : 2

b

g

I r ( x ) = 0.0

if x £ t - 2t w

I r ( x ) = 0.3I rys

if t - 2t w < x < t - t w

I r ( x ) = 0.3I rys

if x ³ t - t w

tw ³

b

g

b

(E.105)

b

g

g

(E.106) (E.107)

t : 2

b g x ³ bt - t g

I r ( x ) = 0.3I rys

if x < t - t w

(E.108)

I r ( x ) = 0.3I rys

if

(E.109)

w

Residual Stress Parallel To The Weld Seam The residual stress solution provided for the residual stress perpendicular to the weld seam in paragraph E.9.1.1 can be used.

E.9.2

Nozzle Welds

E.9.2.1

Residual Stress Transverse to the Weld a.

Residual Stress Distribution – The residual stress acting transverse to the weld is:

I r ( x ) = I rys

(E.110)

b.


c.


I r ( x ) = 0.2I rys E.9.2.2

(E.111)

Residual Stress Parallel To The Weld Seam


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


a.

Residual Stress Distribution – The residual stress acting parallel to the Weld Seam is:

I r ( x ) = I rys

(E.112)

b.


c.


I r ( x ) = 0.3I rys

(E.113)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

E.10

References

E.10.1

Anderson, P., Bergman, M., Brickstad, B., Dahlberg, L., Nilsson, F., and Sattari-Far, I., “A Procedure for Safety Assessment of Components with Cracks – Handbook,” SAQ/FoU-Report 96/08, SAQ Kontroll AB, SAQ Inspection Ltd, 1996.

E.10.2

Bate, S.K., Green, D. and Buttle, D., “A Review Of Residual Stress Distributions In Welded Joints For The Defect Assessment Of Offshore Structures,” Health and Safety Executive – Offshore Technology Report OTH 482, 1997.

E.10.3

Brickstad, Bjorn and Josefson, Lennart, “A Parametric Study of Residual Stresses in Multipass ButtWelded Stainless Steel Pipes,” SAQ/FoU-Report 96/01, SAQ Kontroll AB, SAQ Inspection Ltd, 1996.

E.10.4

BSI, “Guidance For Assessing The Acceptability Of Flaws In Fusion Welded Structures,” PD-6493: 1991, British Standards Institute, Aug. 1991.

E.10.5

Burdekin, F.M., “Local Stress Relief of Circumferential Butt Welds in Cylinders,” British Welding Journal, September 1963, pp. 483-490.

E.10.6

Downey, J.C., Hood, D.W., and Keiser, D.D., “Shrinkage in Mechanized Welded 16 Inch Stainless Pipe,” Welding Journal, March 1975, pp. 170-175.

E.10.7

Dubois, D., Devaux, J., and Leblond, J.B., “Numerical Simulation of a Welding Operation: Calculation of Residual Stresses and Hydrogen Diffusion, “ Fifth International Conference of Pressure Vessel Technology, Vol II, Materials and Manufacturing, ASME, 1984..

E.10.8

Finch, D.M. and Burdekin, F.M., “Effects of Welding Residual Stresses on Significance of Defects in Various Types of Welded Joint,” Engineering Fracture Mechanics, Vol. 41, No. 5, pp. 721-735, 1992.

E.10.9

Finch, D.M., “Effects of Welding Residual Stresses on Significance of Defects in Various Types of Welded Joint-II,” Engineering Fracture Mechanics, Vol. 42, No. 3, pp. 479-500, 1992.

E.10.10 Fujita, Y., Nomoto, T., and Hasegawa, H., “Deformations and Residual Stresses in Butt-Welded Pipes and Spheres,” IIW Doc. X-963-80, April 1980. E.10.11 Fujita, Y., Nomoto, T., and Hasegawa, H., “Welding Deformations and Residual Stresses Due to Circumferential Welds at the Joint Between Cylindrical Drum and Hemispherical Head Plate,” IIW Doc. X-985-81, July 1981. E.10.12 Guan Q., and Liu, J.D., “Residual Stress and Distortion in Cylindrical Shells Caused by a Single-Pass Circumferential Butt Weld – A Discussion with Appropriate Calculation Method,” IIW Document X92979.

--``````-`-`,,`,,`,`,,`---


Not for Resale


E.10.13 Health & Safety Executive, “A Review of Residual Stress Distributions in Welded Joints for the Defect Assessment of Offshore Structures,” OTH 482, HSE, 1997. E.10.14 Japan High Pressure Gas Institute as reported by T. Tanaka in "Local PWHT for Pressure Vessels" at the Spring 1991 API Refining Meeting, Nashville, Tennessee. E.10.15 Josefson, B.L., “Residual Stresses and Their Redistribution During Annealing of a Girth-Butt Welded Thin-Walled Pipe,” Transactions of the ASME, Journal of Pressure Vessel Technology, August 1982, pp. 245-250.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

E.10.16 Josefson, B.L., “Stress Distribution During Annealing of a Multi-Pass Butt Welded Pipe,” Journal of Pressure Vessel Technology, Vol. 105, May 1983, pp. 165-170. E.10.17 Kim, D.S., and Smith, J.D., “Residual Stress Measurements of Tension Leg Platform Tendon Welds,” Offshore Mechanics and Arctic Engineering Conference, Houston, Texas, Vol. III, pp. 31-36, 1994. E.10.18 Kim, D.S., MCFarland, D., Reynolds, J.T., Boswell, R.S.,”FFS Assessment Utilizing Field Measured Residual Stress Measurements” , ASME PVP Vol 315, pp 327-334, 1995. E.10.19 Kirk, M.T., Mohr, W.R., and Michaleris, P., “An Improved Treatment Of residual Stresses In Flaw Assessment Of Pipes and Pressure Vessels Fabricated From Ferritic Steels,” PVP-Vol. 359, ASME, pp 37-47, 1997. E.10.20 Koppenhoefer, K., “Incorporation of Residual Stresses Caused By Welding into Fracture Assessment Procedures,” EWI Project No. 40568-CSP, MPC No. FS-II-5, Sept. 15, 1998. E.10.21 Lazor, R.B., Leggatt, R.H., and Glover, A.G., “Experimental Stress Analysis of Pipeline Girth Welds,” American Gas Association Catalog No. L51490, August 1985. E.10.22 Leggatt, R.H., “Residual Stresses at Circumferential Welds in Pipes,” TWI Research Bulletin, June 1982, pp. 181-188. E.10.23 Leggatt, R.H., “Residual Stresses at Girth Welds in Pipes,” Welding in Energy-Related Projects, Welding Institute of Canada, Pergamon Press, 1984. E.10.24 Leung, C.K. and Pick, R.J., “Finite Element Analysis of Multi-Pass Welds,” WRC Bulletin 356, Welding Research Council, New York, N.Y., 1990. E.10.25 Leung, C.K., Pick, R.J., and Mok, D.H., “Finite Element Modeling of a Single Pass Weld,” WRC Bulletin 356, Welding Research Council, New York, N.Y., 1990. E.10.26 Makhnenko, V.I., Shekera, V.M., and L. A. Izbenko, L.A., “Special Features of the Distribution of Stresses and Strains Caused by Making Circumferential Welds in Cylindrical Shells,” Automatic Welding, 1970, No., 12, pp. 43-47. E.10.27 McGaughy, T.H., “Effects of Repair Welding on the Residual Stress Distribution and Fracture Toughness in Pipeline Girth Welds", Pipeline Research Committee final report PR-185-9104, August 1992. E.10.28 McGaughy, T.H., and Boyles, L., “Significance of Changes in Residual Stresses and Mechanical Properties Due to SMAW Repair of Girth Welds in Linepipe,” Pipeline Research Committee final report PR-185-905, October 1990. E.10.29 Michaleris, P., “Incorporation of Residual Stresses into Fracture Assessment Models,” EWI Project No. J7412, Nov. 13, 1996. E.10.30 Michaleris, P., Kirk, M., and Laverty, K. “Incorporation of Residual Stresses into Fracture Assessment Models,” MPC FS-30, Materials Properties Council, August 1996. --``````-`-`,,`,,`,`,,`---


Not for Resale


E.10.31 Mohr, W., “Internal Surface Residual Stresses in Girth butt-Welded Steel Pipes,” Proceeding of ASME Pressure Vessel and Pipe Conference, PVP-Vol. 327, Residual Stresses in Design, Fabrication, Assessment and Repair, 1996. E.10.32 Myers, P.S., Uyehara, O.A., and Borman, G.L., “Fundamentals of Heat Flow in Welding,” WRC Bulletin 123, Welding Research Council, New York, N.Y., 1967. E.10.33 Pavlovski, V.I. and Masubuchi, K., “Research in the USSR on Residual Stresses and Distortion in Welded Structures,” WRC Bulletin 388, Welding Research Council, New York, N.Y., 1994.

--``````-`-`,,`,,`,`,,`---

E.10.34 Roelens, J.B., “Numerical Simulation of Some Multipass Submerged Arc Welding Determination of the Residual Stresses and Comparison with Experimental Measurements,” IIW Document XIII-154994. E.10.35 Rybicki, E.F., Groom, J.J., Lemcoe, M.M., Mischler, H.W., Rodebaugh, E.C., Schmuster, D.W., Stonesifer, R.B., and Strenkowski, J.S., “Residual Stresses at Girth-Butt Welds in Pipes and Pressure Vessels,” NUREG Report 0376, November 1977. E.10.36 Rybicki, E.F., Groom, J.J., Lemcoe, M.M., Mishler, H.W., Rodabaugh, E.C., Schmuster, D.W., Stonesifer, R.B., and Strenkowski, J.S., “Residual Stresses at Girth-Butt Welds in Pipes and Pressure Vessels,” NUREG-0376 R5, NTIS, 1977. E.10.37 Scaramangas, A., “Residual Stresses in Cylinder Girth Butt Welds,” OTC 5024, 1985. E.10.38 Scaramangas, A., “Residual Stresses in Girth Butt Welded Pipes,” Ph.D. dissertation, Cambridge University, May 1984. E.10.39 Shack, W.J., “Measurement of Through-wall Residual Stresses in Large-Diameter Type 304 Stainless Steel Piping Butt Weldments,” Work Performed under EPRI Contract No. T114-2, Argon National Laboratory, March 1982. E.10.40 Ueda, Y., Fukuda, K., Nishimura, I., Yuma, H., Chiba, N., and Fukuda, M., “Three Dimensional Cold 2 Bending and Welding Residual Stresses in Penstock of 80 kgf/mm Class High Strength Steel Plate,” Transactions of the JWRI, Vol. 12, No. 2, 1983 pp. 117-126. E.10.41 Umemoto, T., and Furuya, S., “A Simplified Approach to Assess Weld Residual Stress Distribution Through Pipe Wall,” Nuclear Engineering and Design, Vol. 111, 1989, pp. 159171. E.10.42 Umemoto, T., and Tanaka, S., “A Simplified Approach to Calculate Weld Residual Stresses in a Pipe,” Ishikawajima-Harima Heavy Industries Engineering Review, Vol. 17, No. 3, 1984. E.10.43 Zhou, R.J., Pense, A.W., Basehore, M.L., and Lyons, D.H., “A Study of Residual Stresses in Pressure Vessel Steels,” WRC Bulletin 302, Welding Research Council, New York, N.Y., 1985.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

E.11

Tables and Figures


Not for Resale


Figure E.1 Weld Locations And Stress Directions In A Cylindrical Shell

Longitudinal or Seam Weld Longitudinal or Seam Weld

Circumferential (or Girth) Weld

(a) Identification of Welds

Longitudinal Stress

--``````-`-`,,`,,`,`,,`---

Circumferential or Hoop Stress

(b) Identification of Stresses

Definition Of Stress Directions Weld Seam

Stress Component Perpendicular To The Weld Seam

Stress Component Parallel To The Weld Seam

Longitudinal

Circumferential (Hoop) Stress

Longitudinal Stress

Circumferential (Girth)

Longitudinal Stress

Circumferential (Hoop) Stress


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure E.2 Residual Stress Surface And Through-Wall Distributions For Full Penetration Circumferential Single V-Groove Welds In Piping And Pressure Vessel Cylindrical Shells

Cylindrical Shell

I perp r

I (y)

y I r(y) 4w

-y

y

w

I para

w

-y

Weld Joint

w + 6t

Stress Distribution Perpendicular to Weld (see paragraph E.4.1.1)

Stress Distribution Parallel to Weld (see paragraph E.4.1.2)

(a) Surface Stress Distribution

w

x OD

x Ior

Ior

t

ID Weld Geometry

I ir

I perp

Stress Distribution Perpendicular to Weld (see paragraph E.4.1.1) (b) Through-Wall Stress Distribution

--``````-`-`,,`,,`,`,,`---


Not for Resale

I ir

Ipara


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

CL


Figure E.3 Residual Stress Surface And Through-Wall Distributions For Full Penetration Circumferential Double V-Groove Welds In Piping And Pressure Vessel Cylindrical Shells CL Cylindrical Shell

I perp

y r

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

I (x) 4w

-y

y

w

I para

w

-y

Weld Joint

w + 6t




x

x

w OD

Ior

ID

Iir

Ior

t

Weld Geometry

Iperp


--``````-`-`,,`,,`,`,,`---


Not for Resale

I ir

Ipara



Figure E.4 Residual Stress Surface And Through-Wall Distributions For Full Penetration Longitudinal Single V-Groove Welds In Piping And Pressure Vessel Cylindrical Shells

CL I

Cylindrical Shell

I perp

Weld Joint

para

r

I (x)

-y

-y

y

w

y

w + 1.5t --``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

w w + 1.5t Stress Distribution Perpendicular to Weld (see paragraph E.4.3.1)



x

x

w

I or

I or

OD t

ID Weld Geometry

I

i

r

I perp



Not for Resale

I ir

I

para


--``````-`-`,,`,,`,`,,`---


Figure E.5 Residual Stress Surface And Through-Wall Distributions For Full Penetration Longitudinal Double V-Groove Welds In Piping And Pressure Vessel Cylindrical Shells

CL Cylindrical Shell

I perp I

-y

I para

r (x)

Weld Joint

I r(x)

-y

y

w

y

w + 1.5t w w + 1.5t Stress Distribution Perpendicular to Weld (see paragraph E.4.4.1)


(a) Surface Stress Distribution w

x OD

x I or

I or

t

ID

Weld Geometry

I ir

I

perp

I ir




I para

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure E.6 Weld Locations and Stress Directions In A Spherical Shell or Formed Head

Meridional Weld

Circumferential Weld

(a) Identification of Welds --``````-`-`,,`,,`,`,,`---

Circumferential Stress Meridional Stress

(b) Identification of Stresses Definition of Stress Directions Weld Seam

Stress Component Perpendicular To The Weld Seam

Stress Component Parallel To The Weld Seam

Meridional

Circumferential Stress

Meridional Stress

Circumferential

Meridional Stress

Circumferential Stress


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Figure E.7 Residual Stress Surface And Through-Wall Distributions For Full Penetration Circumferential Single V-Groove Welds In Spherical Shells

CL I perp

Spherical Shell

r I (y)

y

I r(y)

-y

y

w

I para

w

4w

-y

Weld Joint

w + 6t




w

x

x OD

Ior

Ior

t

ID Weld Geometry

I ir

I perp


--``````-`-`,,`,,`,`,,`---


Not for Resale

I ir

Ipara


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure E.8 Residual Stress Surface And Through-Wall Distributions For Full Penetration Circumferential Double V-Groove Welds In Spherical Shells

CL I perp

Spherical Shell

yx

I r(x) 4w

-y

y

w

I para

w

-x -y

Weld Joint

w + 6t Stress Distribution Perpendicular to Weld (see paragraph E.5.2.1)



w

x

x OD

Ior

ID

I ir

Ior

t

Weld Geometry

Iperp


I ir

Ipara


(b) Through-Wall Stress Distribution

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure E.9 Residual Stress Surface And Through-Wall Distributions For Full Penetration Meridional Single V-Groove Welds In Spherical Shells

CL I

I perp

Spherical Shell

Weld Joint

para

r

I (x)

-y

-y

y

w

y

w + 1.5t

w w + 1.5t




x

x

I or

I or

OD

t

ID Weld Geometry

I

r i

I perp


I ir

para


(b) Through-Wall Stress Distribution

--``````-`-`,,`,,`,`,,`---


I

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure E.10 Residual Stress Surface And Through-Wall Distributions For Full Penetration Meridional Double V-Groove Welds In Spherical Shells

CL I perp

I

r (y)

I

-y

Weld Joint

para

-y

y

w

r (y)

--``````-`-`,,`,,`,`,,`---

I

Spherical Shell

y

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

w + 1.5t

w w + 1.5t




x

x OD

I or

I or

t

ID

Weld Geometry

I ir

I

perp



Not for Resale

I ir

I para



Figure E.11 Residual Stress Surface And Through-Wall Distributions For Full Penetration Circumferential And Longitudinal Single V-Groove Welds In Storage Tanks

I perp y

I r(y)

I w + 4t

-y

r (y)

I para

w

y

w

-y

w + 4t


Stress Distribution Parallel to Weld (see paragraph E.6.1.2) (a) Surface Distribution

x

x I or

I or

OD

t

ID

Weld Geometry

Iperp

I ir


(b) Through-Wall Thickness Distribution


Not for Resale

I ir

Ipara


--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

w


Figure E.12 Residual Stress Surface And Through-Wall Distributions For Full Penetration Circumferential And Longitudinal Double V-Groove Welds In Storage Tanks

I perp y

Ir(x)

Ir(x) w + 4t

-y

w

I para

y

w

-y

w + 4t



w

--``````-`-`,,`,,`,`,,`---

(a) Surface Distribution

x

x

OD

Ior

ID

I ir

Ior

t

Weld Geometry

Iperp


I ir


(b) Through-Wall Thickness Distribution


Ipara

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure E.13 Weld Locations and Stress Directions In A Corner Joint (Nozzle Attachment) C L

C L Nozzle

Nozzle Nozzle Fillet Weld Reinforcing Pad

Nozzle Fillet Weld x

B

x

Reinforcing Pad Fillet Weld

B

Shell

C x

A

Vessel Shell

x

x

A

Corner Joint

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(a) Identification of Welds

Nozzle

1

Reinforcing Pad 2

Vessel Shell

2 1 (b) Identification of Stresses

--``````-`-`,,`,,`,`,,`---


Not for Resale

1

- Stress Perpendicular to the Weld Direction

2

- Stress Parallel to the Weld Direction


Figure E.14 Weld Locations and Stress Directions In A Tee Joint

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Stay Plate

Plane Containing the Toe of the Fillet Weld in the Stay Plate 1 2

x

1 x 2 Plane Containing the Fillet Weld Toe in the Main Plate

Main Plate

--``````-`-`,,`,,`,`,,`---


Not for Resale

1

- Stress Perpendicular to the Weld Direction

2

- Stress Parallel to the Weld Direction

E-34 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________ --``````-`-`,,`,,`,`,,`---

Figure E.15 Residual Stress Surface And Through-Wall Distributions For Joints With Fillet Welds

Iperp r

I (y)

y I

r (y)

w 4w + t2 -y

t2

w

I para

y

2w + t2

-y


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

4w + t2


(a) Surface Distribution t2

x

x Iysr

Iysr

t1 Iperp

Weld Geometry

Stress Distribution Perpendicular to Weld (see paragraph E.8.1.1) (b) Through-Wall Distribution


Not for Resale

Ipara Stress Distribution Parallel to Weld (see paragraph E.8.1.2)


Figure E.16 Residual Stress Surface And Through-Wall Distributions For Repair Welds

Iperp I

y

r (y)

I

w

r (y)

w

Ipara

wr -y

w

y wr

-y

w + wr + tw

w

w + wr + tw




x

x I ysr tw t

Iysr

tw

tw

tw

tw Iperp

Weld Geometry


Ipara Stress Distribution Parallel to Weld (see paragraph E.9.1.2)

(b) Through-Wall Distribution

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

APPENDIX F – Material Properties For A FFS Assessment (Jan, 2000) F.1

General

F.1.1

The information in this appendix is intended to provide guidance on the materials information required for the Fitness-For-Service (FFS) Assessments covered in this document. Specific materials data is provided for many of the assessment methods; however, some of the materials data is provided in terms of references to published sources. To include, and keep up to date, all of the property information required by all of the assessment methods in this document would have been proven prohibitive. This is especially true of properties which are affected by the service environment.

F.1.2

The Fitness-For-Service assessment procedures in this document cover situations involving flaws commonly encountered in pressure vessels, piping and tankage that have been exposed to service for long periods of time. Therefore, when selecting materials properties for an analysis, care must be taken to evaluate these properties in terms of equipment that has been in-service; the properties used in the assessment should reflect any change or degradation, including aging, resulting from the service environment or past operation.

F.2

Strength Parameters

F.2.1

Yield and Tensile Strength

F.2.1.1

Estimates for the material yield strength and tensile strength to be used in a fitness-for-service assessment can be obtained as follows: a.

It may be necessary to obtain samples from a component and use a standard test procedure to directly determine the yield and tensile strength when accurate estimates of these properties can affect the results of an assessment. The yield strength and ultimate tensile strength for plate and pipe material can be determined in accordance with ASTM A370, ASTM E8, or an equivalent standard method, and reported on a mill test report for the particular heat of steel.

b.

Hardness tests can be used to estimate the tensile strength (see Table F.1). The conversions found in this table may be used for carbon and alloy steels in the annealed, normalized, and quench-and-tempered conditions. The conversions are not applicable for cold worked materials, austenitic stainless steels, or for non-ferrous materials.

c.

If the temperature for which a fitness-for-service assessment is to be made differs substantially from the temperature for which the yield and tensile strengths were determined, these values should be modified by a suitable temperature correction factor. The temperature correction factor derived from the MPC materials database (see paragraph 2.1.2) can be used in most cases.

d.

In the absence of heat specific data, mean values for the tensile and yield strength can be approximated using the following equations: min I mean = I uts + 69 MPa uts

(F.1)

min I mean = I uts + 10 ksi uts

(F.2)

I mean = I min ys ys + 69 MPa

(F.3)

and,


F-1 Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

I mean = I min ys ys + 10 ksi where,

I mean = uts

I

mean ys

Mean value of the ultimate tensile strength (MPa:ksi),

=

Mean value of the yield strength (MPa:ksi),

min I uts

=

Minimum specified ultimate tensile strength from the ASME B& PV Code, Section II, Part D (MPa:ksi), and

I min ys

=

Minimum specified yield strength from the ASME B& PV Code, Section II, Part D (MPa:ksi).

F.2.1.2

A method to compute the yield and tensile strength as a function of temperature for pressure vessel, piping and tankage materials is provided in Table F.2. The data used to develop these equations are from the MPC Materials Database. These data are recommended for use in most assessments.

F.2.1.3

A method to compute the yield and tensile strength as a function of temperature for pipe and tube materials are provided in Table F.3. The data used to develop these equations are from API RP530.

F.2.1.4

Values for the yield and tensile strength below the creep regime for pressure vessel, piping, and tankage steels can be found in the ASME Code, Section II, Part D. Other data sources for yield and tensile strength data for various materials are provided in paragraph F.8.2. These data sources provide values for the yield and tensile strength which are representative of new materials.

F.2.2

Flow Stress

F.2.2.1

The flow stress,

I f , can be thought of as the effective yield strength of a work hardened material.

The use of a flow stress concept permits the real material to be treated as if it were an elastic-plastic material which can be characterized by a single strength parameter. The flow stress can then be used, for example, as the stress level in the material that controls the resistance of a cracked structure to failure by plastic collapse. F.2.2.2

Several relationships for estimating the flow stress have been proposed which are summarized below. The flow stress to be used in an assessment will be covered in the appropriate section of this recommended practice. In the absence of a material test report for plate and pipe, and for weld metal, the specified minimum yield strength and the specified minimum tensile strength for the material can be used to calculate the flow stress. a.

Average of the yield and tensile strengths (recommended for most assessments):

If = b.

c.

dI

ys

+ I uts

i

(F.5)

2

The yield strength plus 69 MPa (10 ksi):

I f = I ys + 69 MPa

(F.6)

I f = I ys + 10 ksi

(F.7)

For austenitic stainless steels, a factor times the average of the yield and tensile strengths:

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

(F.4)

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE F-3 _________________________________________________________________________________________________

(F.8)

2

The maximum allowable stress ( Sm ) in accordance with the ASME Code, Section VIII, Division 2, multiplied by an appropriate factor:

I f = 2.4 × Sm

for ferritic steels

I f = 3 × Sm e.

i

(F.9)

for austenitic stainless steels

(F.10)

If Ramberg-Osgood parameters are available (see paragraph F.2.3), the flow stress can be computed using the following equation.

If =

I ys 2

LM FG 1 IJ MM1 + H 0.002n1K MN expFGH n IJK

1/ n

OP PP PQ

(F.11) --``````-`-`,,`,,`,`,,`---

d.

d

115 . × I ys + I uts

F.2.3

Ramberg-Osgood Stress-Strain Relationship

F.2.3.1

The stress-strain curve of a material can be represented by the following equation known as the Ramberg-Osgood equation. The exponent used in this equation may be required for a J-integral calculation.

FG IJ H K

I A I = += Io Ao I o

n

(F.12)

with

b

g

I = 1+ A e I e

b

A = ln 1 + A e

(F.13)

g

(F.14)

where,

A Ae Ao I Ie Io = n F.2.3.2

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

If =

= =

True strain, Engineering strain,

= = =

True reference strain equal to I o True stress (MPa:psi), Engineering stress (MPa:psi), and

= = =

True reference stress, usually the yield stress (MPa:psi), Data fitting constant, and Data fitting exponent.

E (MPa:ksi),

If multiple data points for a stress-strain curve are provided, the data fitting constants can be derived using regression techniques. If only the yield and ultimate tensile strength are known, the exponent, n , can be estimated by solving the following equation.


Not for Resale


I uts I ys

FG 1 IJ H 0.002n K = F 1I expG J H nK

The constant

==

1/ n

(F.15)

= can be determined from the following equation:

0.002 E - 10 . I ys

F.3

Physical Properties

F.3.1

Elastic Modulus

(F.16)

The elastic or Young’s modulus is required to perform stress analysis of a statically indeterminate component. Values for the elastic modulus for a full range in temperatures can be found in the ASME Code, Section II, Part D. Additional reference sources for the elastic modulus of various materials are provided in paragraph F.8.3. F.3.2

Poisson’s Ratio The value of Poisson’s ratio can normally be taken as 0.3 for steels. Data for specific steels are provided in Marks’ Standard Handbook for Mechanical Engineers.

F.3.3

Coefficient of Thermal Expansion

F.3.4

Thermal Conductivity The thermal conductivity is required to perform a heat transfer analysis of a component. The results from this analysis are utilized in a thermal stress calculation. Values for the thermal conductivity for a full range in temperatures can be found in the ASME Code, Section II, Part D.

F.3.5

Thermal Diffusivity The thermal diffusivity is required to perform a transient thermal heat transfer analysis of a component. The results from this analysis are utilized in a transient thermal stress calculation. Values for the thermal diffusivity for a full range in temperatures can be found in the ASME Code, Section II, Part D.

F.3.6

Density The material density is required to perform a transient thermal heat transfer analysis, and in cases where body force components are to be considered, a stress analysis of a component. The results from this analysis are utilized in a transient thermal stress calculation. Data for specific steels are provided in Marks’ Standard Handbook for Mechanical Engineers.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

The coefficient of thermal expansion is required to perform thermal stress analysis of a component. Values for the thermal expansion coefficient for a full range in temperatures can be found in the ASME Code, Section II, Part D. Additional reference sources for the thermal expansion coefficient of various materials are provided in paragraph F.8.3.

PRACTICE


F-5

F.4

Fracture Toughness

F.4.1

General

F.4.1.1

The fracture toughness of a material measures its ability to resist crack growth initiation and propagation. Several fracture toughness parameters are available, including critical stress intensity factor (K,,) , the critical value of the J integral ( Jtif) , and the critical crack tip opening

or S,,) . Any one of these parameters can be used for a fitness-for-service

displacement (CLOD

assessment of a component containing crack-like flaws. F.4.1.2

Ideally, the fracture toughness input to the FFS analysis should come from test data for the specific material of interest. In practice, however, heat-specific fracture toughness data are usually not available for an existing component. Consequently, alternative means must often be employed to obtain conservative estimates of fracture toughness. Guidelines for establishing a fracture toughness to use in an FFS analysis are provided in Figure F.l. The subsections that follow provide details to support the different options in this figure.

F-4.2

Fracture Toughness Parameters

F.4.2.1

For most materials and structures covered by this document, it is possible to measure toughness only in terms of J and CLOD; valid K,c data can only be obtained for brittle materials or thick sections. It is possible, however, to infer “equivalent” K,, values from Jand CZ’OD data by exploiting the relationships between these three parameters under plane strain linear elastic conditions. The fracture mechanics analysis can be expressed in terms of any one of the three parameters based on the relationships shown below. a.

For small scale yielding an equivalent value as follows:

KIc , denoted as K,, , can be derived from a critical J

--``````-`-`,,`,,`,`,,`---

KJc= JCritE J l-2

(F.17)

where, kc

b.

=

Fracture toughness derived from

Jet (MPadm:ksidin),

J value (Mpa-m:ksi-in),

Joit =

Critical

E

=

v

=

Young’s Modulus (MPa:ksi), and Poisson’s ratio.

An approximate relationship between the Jintegral and

Jtit = maf 6,

CTOD is: (F.18)

where,

Jc?i* =


m

=

Lit CTf

= =

Critical J value (Mpa-m:ksi-in), Conversion constant, 1.4 can be used in the absence of more reliable information, Critical CTOD value (m:in), and Flow stress (MPa:ksi).


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

RECOMMENDED

Jan, 2000

API RECOMMENDED

F-6 C.

By combining

the above equations,

Jan, 2000

PRACTICE 579

it is possible to derive equivalent

K,, values (K, ) from

CTOD data where all variables have been previously defined. K, =

(F.19)

F.4.2.2

Charpy impact tests can be used to provide a qualitative indication The results from these tests cannot be used directly to provide an However, correlations for use in a fitness-for-service assessment. estimate of fracture toughness to be made based on the results of paragraph F.4.5).

F.4.3

Fracture

F.4.3.1

Ideally, fracture toughness tests should be heat specific, which necessitates removing specimens from the material under consideration. This can be accomplished in one of three ways:

Testing

a.

Removal Of A Sample From A Component Currently In Service For Testing - Removal of a material sample from a component is an extreme step, but it is often the only way to obtain heat-specific fracture toughness data for a given structure. The value of component specific toughness data should be assessed versus the potential problems that may result from the procedure required to repair the region where the sample was obtained.

b.

Removal Of A Sample From A Retired Component In A Similar Service And Testing - Testing material from a retired component (preferably one that was fabricated from the same material heat) is beneficial because such data provide a relative indication of the toughness of similar vessels. However, these data must be used with caution because a material’s fracture toughness data can have significant heat-to-heat variations, and data from one component may not be necessarily applicable to another.

C.

Testing A Plate That Was Welded At The Time Of Fabrication - A test weldment will not normally be available for components that have been in service for some time; however, a plate can be produced at the time of fabrication for a new component. The steel in a test plate should come from the same heat as the material used in the actual structure, and it should be welded according to the same procedure and with the same batch of consumables as the structure. If possible, the same welders and equipment should be used for the test plate and structure. Finally, the weld joint should be subject to the same operating conditions to establish if these conditions cause embrittlement.

The following items should be noted if testing of a sample is to be performed fracture toughness of a material for a fitness-for-service assessment. of the

to determine

K, J, and CTOD fracture toughness

the

a.

Test methods for measurement covered in ASTM 1820.

b.

It is recommended that a minimum of three specimens be tested for each condition and temperature. If additional test results are available, the equivalent to the minimum of three test may be used (see Table F.4). If more than ten tests are available, the data may be fitted to the Master Curve (see paragraph F.4.9).

C.

Currently, an ASTM Standard A procedure to test weldments

d.

The results from a fracture toughness test can vary significantly. The use of the fracture toughness master curve approach can be used (see paragraph F.4.9) to quantify this variation.

covering fracture toughness testing of weldments is provided by BS 7448: Part 2.

March 2000


parameters

Not for Resale

are

does not exist.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

F.4.3.2

Toughness

of a material’s fracture toughness. indication of a material’s toughness are available which enable an Charpy impact values (see


e.

Charpy V-Notch Test (CVN) – The standard for CVN testing is ASTM Standard E23. The Charpy specimen is a rectangular bar with cross section measurements of 10 mm x 10 mm and length between end supports of 40 mm. A notch 2 mm deep is machined opposite the impact point with a 0.01 mm notch radius. The axis of the notch is usually oriented in the through-thickness direction with respect to the original material placement. When a component is less than 10 mm thick, “subsize” specimens are used. a.

b.

The thickness of the CVN specimen can influence both the absorbed energy and the transition temperature as described below (see Figure F.2): ·

Effect on Absorbed Energy – The reduced cross sectional area of a sub-size CVN specimen reduces its ability to absorb energy. Therefore, the absorbed energy values for sub-size CVN specimens will be less than those characteristic of standard size CVN specimens when both specimens are tested at the same temperature.

·

Effect on Transition Temperature – The reduced wall thickness of sub-size CVN specimens reduces the tri-axial constraint against plastic flow in comparison with that characteristic of a standard size CVN specimen. This reduced level of constraint makes cleavage fracture less likely to occur in a sub-size CVN specimen than in a standard size CVN specimen when both are tested at the same temperature. Therefore, the fracture mode transition will occur at lower temperatures in sub-sized CVN specimens than in standard CVN size specimens of the same material.

For plate materials used in pressure vessels, piping and tankage, the following correlations may be used for the energy and temperature shift. These correlations where derived based on the information in ASTM A370.

CVN std = CVN ss

FG t IJ Ht K std

(F.20)

ss

Tshift 18 .

c Ch

(F.21)

TTstd = TTss + Tshift

c Fh

(F.22)

TTstd = TTss +

o

o

with,

Tshift

LM1012899 Ft . - 9.730841G Ht =M MM 10. + 0.353215F t I GH t JK MN

ss

std

ss

std

IJ OP KP PP PQ

2

c Fh o

(F.23)

where,

CVN std

= Corrected Charpy impact energy for a standard size CVN specimen, (J:ft-lbs), --``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.4.3.3

The fracture toughness of a material tends to decrease with increasing crack tip triaxiality. Standard laboratory specimens used to determine a materials fracture toughness are usually highly constrained. Therefore, laboratory fracture toughness tests usually underestimate the fracture toughness of structural components of equivalent thickness that contain crack-like flaws, and flaw assessments based on standard fracture toughness data tend to be conservative.


CVN ss t ss t std Tshift TTstd TTss c.

= Charpy impact energy from the sub-size CVN specimen, (J:ft-lbs), = Thickness of sub-sized CVN specimen (mm:in), = Thickness of standard size CVN specimen (mm:in), = Temperature shift (temperature at the midpoint between the lower and upper shelf impact energies), (°C :°F), = Transition temperature for the standard size CVN specimen (temperature at the midpoint between the lower and upper shelf impact energies), (°C:°F), and = Transition temperature for the sub-size CVN specimen (temperature at the midpoint between the lower and upper shelf impact energies), (°C:°F).

The following equation from BS 7910 can also be used to determine the shift in transition temperature for sub-size specimens. A corresponding shit in impact energy is not provided in BS 7910.

c Ch c Fh

TTstd = TTss + Tshift TTstd = TTss + 18 . Tshift

o

(F.24)

o

(F.25)

with,

LM FG t IJ MN H 10K

Tshift = 514 . ln 2

0.25

OP PQ

c Ch o

-1

ss

(F.26)

where,

t ss d.

= Thickness of sub-sized CVN specimen (mm)

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

For pipeline materials (e.g. API 5L), the following procedure has been used to correlate the impact energies obtained from sub-size and full-size Charpy specimens. The expressions were derived from statistical analysis of data from tests on plain carbon and low alloy steels reported in [F.8.1.9] and [F.8.1.22]. The correlation is not exact because Charpy test data often exhibits scatter, particularly in the transition region. In addition, the use of the correlation may be inappropriate for materials that do not exhibit impact toughness behavior typical of plain carbon and low alloy steels. 1.

Step 1 – Obtain the following four quantities from the sub-size specimen (denoted with a S

S

S

S

superscript “S”) Charpy energy transition curve: CVN , CVNUS , SA and Tc . If only two or three of the quantities are available, the unknown quantities can be determined from the following equations. If only one of the quantities is known, the transformation cannot be performed.

FG CVN H CVN

SA S = 11 .

S CVNUS =


- 01 .

IJ K

(F.27)

CVN S 0.9 × SA S + 01 .

(F.28)

S

S US

Not for Resale

Jan, 2000

RECOMMENDED

PRACTICE

F-9


SAs = [ l+exp [ - (‘T-y+“}11

(F.29)

cs = T-Bln

(F.30)

where,

A&B

=

Parameter based on the size of the Charpy specimen, Size A B

cviv = cnv;, =

2.

l/4 22 19

l/3 28 24

112 36 30

213 41 32

Full 50 33

Charpy impact energy at the test temperature for the sub-size specimen, ft-lbs, Charpy upper shelf impact energy for the sub-size specimen, ft-lbs,

SA’

=

Shear area at the test temperature for the sub-size specimen expressed as percent divided by 100,

7y

=

T

=

85% Shear Area Transition Temperature (SATT) for the sub-size specimen, (“F), and Test or assessment temperature, as applicable (“F).

Step 2 - Calculate the full size specimen SATT:

T, = qs + 66(Nm)0~55({t,S}-o~7 - {tc}-O.,)

(F.31)

where, =

85% SATT for the sub-size specimen, (OF),

T,

=

85% SATT for the full-size specimen, (OF),

t,”

=

thickness of the sub-size specimen (in), and

t,

=

thickness of the full-size specimen (in).

Step 3 - Calculate the shear area of the full size specimen using the following equation (all variables have been previously defined).

SA= ( l+exp [ - {P’d”“}]1’ 4.

(F.32)

Step 4 - Calculate the upper shelf impact energy for the full size specimen using the following equation (all variables have been previously defined).

(F.33)

--``````-`-`,,`,,`,`,,`---



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

3.

Nominal wall thickness of the pipe (in),

NWT= qs

Jan, 2000


F-l 0

Step 5 - Calculate the impact energy for the full size specimen using the following equation (all variables have been previously defined).

5.

WA’ = CKVus (0.9 -SA + 0.1)

(F.34)

Note that if CI???’ is on the lower shelf or SA’ is less than five percent, and tf < t, , the impact energy for the full size specimen can be computed as:

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.4.3.4

A measure of the fracture tearing resistance as a function of the amount of stable ductile tearing are provided by determination of a JR curve. Typcial data for some materials are provided in Table F.5. Testing methods for determination of JR-Curves are covered in ASTM 1820. It should be noted that a JR curve may significantly change depending on loading rate; therefore, dynamic JR curve data should be used in the assessment of components under dynamic loading conditions.

F.4.4

Lower Bound Fracture Toughness

F.4.4.1

When fracture toughness data are not available, an indexing procedure based on a reference temperature can provide a conservative lower-bound estimate of fracture toughness for a ferritic material. The basic premise behind the approach is illustrated schematically in Figure F.3(a). Various ferritic steels, as well as different heats of the same steel, exhibit toughness-temperature curves with similar shapes, but with ductile-brittle transitions at different temperatures. When the toughness is plotted against a temperature relative to a reference transition temperature, these data tend to collapse onto a common trend, albeit with more scatter than in individual data sets. This additional scatter reflects the fact that the indexing temperature removes most, but not all, of the heat-to-heat variation in the fracture toughness curves.

b.

The indexing approach was originally developed for nuclear reactor pressure vessel steels, and this methodology is included in Section Xl of the ASME Boiler and Pressure Vessel Code. The reference temperature utilized is termed RT NDT, which is based on a combination of a drop weight nil-ductility transition temperature (NDTT) and the Charpy transition curve. In the late 1960s and early 197Os, a large fracture toughness data set was collected for multiple heats of low alloy pressure vessel steels and was plotted against relative temperature. Two curves were then drawn below the data. The K,, curve is a lower envelope to all of the

--``````-`-`,,`,,`,`,,`---

a.

fracture toughness tests loaded at quasi-static rates. The KIR curve, which is also known as the

Ku curve, is a lower envelope to all data, which include quasi-static initiation, dynamic

initiation, and crack arrest toughness results. C.

The ASME Section Xl basis reference curves have been adopted to estimate a lower bound fracture toughness, but RT NDT has been replaced by the temperature corresponding to the 20.3 Joules (15 ft-lb) impact energy for carbon steels and the 27.1 Joules (20 ft-lb) impact energy for Cr-Mo steels. The two reference curves are plotted in Figure F.3(b) and the equations are given by:

K,, = 365+3.084exp[O.O36(T-Td

+56)]

K,, = 33.2+2.806exp[O.O2(T-T,,

+lOO)]

March 2000


Not for Resale

(MPaJ;;;, (ksi&,

“C) “F)

(F.36)

(F-37)

Jan, 2000

RECOMMENDED

PRACTICE

F-II


and,

KIR = 29.5 + 1.344 exp [ 0.0260( T- Tef + 89)] KIR = 26.8+1.223exp[O.O144(T-

T,,r +160)]

(Mhh @s&z,

‘c)

(F.38)

OF)

(F.39)

where, =

Fracture toughness (MPadm:ksiJin),

KIR

=

Arrest Fracture toughness (MPadm:ksidin),

T TEf

= =

Temperature of the analysis (‘C:‘F), and Reference temperature (‘C:‘F). .

d.

Although the ASME Section XI reference curves were originally developed for nuclear grade pressure vessel steels, it has also been validated for carbon steel plates and weldments, as well as several heats of 2 114Cr - 1 MO steel (see References [F.8.1.2] and lF.8.1.341).

e

The equations for KIc and KIR , and the curves in Figure F.3(b), should be truncated as follows unless data are available that indicate higher maximum upper shelf toughness.

f.

.

110 MI%&

.

220 ma&i

(100 ksi&)

should be used for materials with an unknown chemistry.

(200 ksilr) zn can be used for low sulfur carbon steels (0.01 percent or less) or for J-controlled 2 l/4 Cr - 1 MO steels (J I 150, see paragraph F.4.7.3).

The mean value of the material fracture toughness can be estimated based on the low-bound value as described above using the correlations in Table F.6. The mean value of fracture toughness is used in the assessment of crack-like flaws (see Section 9).

The following indexing procedure can be used when fracture toughness data does not exist for a material. This procedure will typically result in a lower bound estimate of the material fracture toughness. a.

b.

The exemption temperature for fracture toughness testing (Charpy testing) that appear in the following construction codes can be used to establish the reference temperature for a given material specification and plate thickness: l

Figure UCS-66 in Section VIII, Division 1 of the ASME Code

l

Figure AM-218.1 in Section VIII, Division 2 of the ASME Code B&PV

l

Table R.2.2 in Appendix R of API Standard 620

Alternatively, a conservative default value of 38°C (100°F) or the value obtained using the plate thickness and Curve A of Figure 3.3 in Section 3, whichever is greater, can be set for the reference temperature, ref (see Reference [F.8.4.1 I]). Alternatively, a reference temperature can be established from Charpy impact test data, see paragraph F.4.5.2.

F.4.4.3

The lower bound curves in paragrapgh F.4.4.1 .c can also be used to estimate the fracture toughness at one temperature based on the value obtained at another temperature. This can be accomplished by calculating the reference temperature from known fracture toughness data using these equations. The fracture toughness at the new temperature can then computed using this reference temperature and these equations. Alternatively, this procedure can be performed graphically by locating the known toughness on the curve in Figure F.3(b) and moving up or down along the curve by the

--``````-`-`,,`,,`,`,,`---



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.4.4.2

Kc

API RECOMMENDED

F-12

appropriate difference in temperature (T-

PRACTICE 579

Jan, 2000

T,,) to read the new toughness value. Note that a

toughness estimate obtained in this manner may not be a lower bound value. F.4.5

Assessing Fracture Toughness From Charpy V-Notch

F.4.5.1

Although Charpy V-Notch impact test data do not represent true fracture toughness data, these data can be used as a starting point for determining the toughness to use in an assessment. The following provide guidance for estimating the fracture toughness from Cwdata. a.

Data

Lower Bound Fracture Toughness - The equations in paragraph F.4.4.1 .c can be used to establish a lower bound fracture toughness based on the value of the reference temperature, Tqp . The reference temperature to be used in the calculation is the temperature that

--``````-`-`,,`,,`,`,,`---

corresponds to 20.3 Joules (15 ft-lb) for carbon steels and 27 Joules (20 ft-lb) for low-alloy steels. This temperature can be determined from the Cmtemperature relationship in subparagraph (c) or(d). b.

Fracture Toughness Based On The Master Curve - The procedure in paragraph F.4.9.8 can be used to establish a fracture toughness based on a reference transition temperature, c . The reference transition temperature to be used in this calculation is the temperature that corresponds to the 27 Joules (20 ft-lb). This temperature can be determined from the CVNtemperature relationship in subparagraph (c) or (d).

C.

CFW-Temperature Relationship For Multiple Temperatures - If Charpy transition temperature curve is provided, the data can be curve-fit to the hyperbolic tangent equation shown below to determine the relationship between the Charpy impact energy and temperature. The characteristics of this equation are shown in Figure F.4(a). A typical curve-fit to CWdata is shown in Figure F.4(b).

CVN=A+Btanh

CTD> [ 1 C

(F.40)

where,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

d.

CVN

=-

A

=

;

= =

D T

= =

CVN-Temperature provided. 1.

Charpy V-notch impact value (Joules:ft-lbs), Curve-fit coefficient, Curve-fit coefficient, Curve-fit coefficient, Curve-fit coefficient, and Temperature (“C:“F). Relationship For A Single Temperature - The following two methods are

Method 7 - If Charpy data are available at a single temperature and they exceed 20.3 Joules (15 ft-lbs) for carbon steel and 27.1 Joules (20 ft-lbs) for low-alloy steel, the measured value can be extrapolated down to arrive at a reference temperature, Tel. The measured Charpy data can be extrapolated using a slope of

1.46 JouZe.,s/“C (0.60 ft - Zb/“F) . 2.

Method 2 - The 27 Joules (20 ft-lbs) Charpy transition temperature can be determined from the test temperature by extrapolation using the information in Table F.7.

March 2000


Not for Resale

Jan, 2000 F.4.5.2

RECOMMENDED

F-13

PRACTICE FOR FITNESS-FOR-SERVICE

Alternately, the Charpy V-Notch impact energy can be converted directly to a

KIc by using

KIc - CW correlations. a.

The value of the Charpy impact energy at the temperature of the assessment can be extrapolated, or read directly from a Charpy transition temperature curve (see paragraphs F.4.5.l.c and F4.5.1.d).

b.

The following equation know as the Rolfe-Novak Correlation can be used to establish a lower bound fracture toughness (see Reference [F.4.5.3]). This correlation represents a lower bound to a number of published Klc - CViV correlations, and is recommended for use when . a high degree of conservatism is desired.

K,, = 8.47( CYN)“‘63

(iwhh,

J)

KIc = 9.35( CvN)“‘63

(ksi&, fi-lb)

(F.41)

(F.42)

where, KIC cw C.

= =

Plane-strain fracture toughness (MPadm:ksi-din), and Charpy V-notch impact value (Joules:ft-lbs).

The following equation can be used to establish a lower bound dynamic fracture toughness for the transition temperature range (see Reference [F.4.5.4]).

Kid = 155( CW)“‘375

(MPa~,

J)

(F.43)

Kid = 15.873( CK’V)“.37J where, KM CVN d.

= =

Dynamic plane-strain fracture toughness (KPadm:ksi-din), and Charpy V-notch impact value (Joules:ft-lbs).

If the CWdata corresponds to upper shelf behavior (i.e. 100% shear fracture), the following equations can be used to calculate a lower bound to the upper shelf fracture toughness (see Reference [F.4.5.5]).

(F.45)

(ksi&,

ksi, B-lb)

(F.46)

where,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Kc

=

Plane-strain fracture toughness (MPadm:ksidin),

Oys CVN

= =

Yield stress (MPa:ksi), and Charpy V-notch impact value (Joules:ft-lbs).

--``````-`-`,,`,,`,`,,`---



API RECOMMENDED

F-14 e.

F.4.5.6

PRACTICE

579

Jan, 2000

Other K,, - cm correlations may be used depending on the material and region of the transition curve (e.g. lower shelf, transition, and upper shelf), see references [F.8.1.23] and [F.8.1.25].

There are two cautions in using Charpy V-Notch data to establish an estimate of the fracture toughness: The Charpy data used to estimate the reference temperature or KIc should be representative of the component being evaluated (i.e. they should be heat and heat treatment specific). These data should also come from a material with a representative microstructure. For example, Charpy data from the base metal may not be applicable when the flaw being evaluated is in the weld metal or in the HAZ.

b.

An appropriate temperature must be used to perform the assessment. In cases where the stress varies with temperature (e.g., a pressure vessel that is not fully pressurized until it reaches an elevated temperature) it may be necessary to perform the assessment at several temperatures to identify the worst-case loading.

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.

F.4.6

Fracture Toughness for Materials Subject to In-Service Degradation

F.4.6.1

The inherent fracture toughness of a material can be affected by the service environment. For example, hydrogen can diffuse into the steel and can result in a loss of fracture toughness. Temperature exposure can produce embrittlement, such as strain aging, temper embrittlement, 885 embrittlement, and sigma phase embrittlement. In these cases a lower fracture toughness which accounts for the loss of toughness resulting from the service environment must be used in the assessment.

F.4.6.2

Hydrogen dissolved in a ferritic steel can significantly reduce the apparent fracture toughness of a material (see Figure F.5). Fracture initiation is enhanced when hydrogen diffuses to the tip of a crack. Once unstable crack propagation begins, however, diffusing hydrogen cannot keep pace with the growing crack: thus the resistance to rapid crack propagation is unaffected by hydrogen. The Km curve defined by the equation in paragraph F.4.4.1 .c is a lower envelope to dynamic initiation and crack arrest toughness data. This curve represents a conservative estimate of the resistance of the material to rapid crack propagation, and can be used to estimate the toughness of a steel containing dissolved hydrogen. a.

The recommended procedure for inferring the toughness of a hydrogen charged steel is as follows: 1.

Step 1 - Determine the reference temperature, 7& , using paragraphs F.4.4 or F.4.5. Note that if Charpy V-Notch data is available it will normally be for the steel in the uncharged state. The Charpy impact energy is not significantly affected by hydrogen because of the dynamic attributes of the Charpy test.

2.

b.

Step 2 - Determine a lower-bound toughness by using the equation in paragraph F.4.4.1 .c or from the KIR curve in Figure F.3(b).

Flaws in hydrogen charged materials should be treated with extreme caution. The above procedure does not take account of the following two factors. 1.

If a material remains in a hydrogen charging environment in service, the cracks may grow by what is known as subcritical crack growth. Consequently, a flaw that is acceptable at its current size may grow to a critical size over time. If the applied K is above the threshold stress intensity for crack growth, the flaw will grow until the applied K exceeds a value from the Km curve, at which time unstable fracture will occur.

March 2000


Not for Resale


2.

There are several types of metallurgical embrittlement listed below that can reduce the ductility and fracture properties of carbon, alloy, and stainless steels below the K IR curve. a.

A brief description of the types of embrittlement currently encountered in the refining and petrochemical industry are described below. 1.

Strain Age Embrittlement Of Carbon And Carbon/Molybdenum Steels – occurs in the plastic zone at the tip of crack or at a strain concentration. It most typically occurs when a weld is made in close proximity of a crack, causing the material in the vicinity of the crack tip to be strained and heated in the 149°C (300°F ) to 260°C (500°F) range. Steels with an aluminum content greater than 0.015 wt % (i.e. killed steels) are not susceptible, and PWHT alleviates the problem for susceptible steels.

2.

Loss Of Tougness With Aging Of 1 1/4 Cr-1/2 Mo Steel – can occur in steels that has been in service in the 371°C (700°F) to 593°C (1100°F) temperature range (see Figure F.5). Embrittlement is thought to be related to carbide formation and/or the level of tramp element impurities (i.e. As, P, Sb, and Sn) present in the steel. Factors such as heat treatment condition and microstructure play a role. In many cases, older steels usually are more susceptible than newer generation steels. Toughness may be affected up to 149°C (300°F). In general steels are more susceptibe the higher the carbon content and steels above 0.15 wt% carbon are most susceptible. Although the correlation is not strong, the loss of toughness for 1-1/4 Cr-1/2Mo has been correlated to the

X factor (see paragraph F.4.7.2).

3.

Temper Embrittlement Of 2 1/4 Cr-1 Mo Steel – can occur in steels that have been in service in the 343°C (650°F) to 593°C (1100°F) temperature range (see Figure F.5). Embrittlement is related to the level of tramp element impurities (i.e Mn, P, Si, and Sn) present in the steel, and to the heat treatment condition and microstructure. In many cases, older steels usually are more susceptible than newer generation steels. Toughness may be affected up to 149°C (300°F) and more. The degree of susceptibility for 2¼ Cr-1 Mo have been correlated to the J TE factor (see paragraph F.4.7.3).

4.

885 (F) Embrittlement Of Ferritic Or Duplex Stainless Steels – can occur if a ferritic or duplex stainless steel is subjected to the temperature range of 371°C (700°F) to 566°C (1050°F). The material toughness for 885 embrittled steels is affected up to 149°C (300°F).

5.

Sigma Phase Embrittlement Of Austenitic Stainless Steels – sigma phase can form in austenitic stainless steels that contain ferrite in welds and are subject to heat treatment in the 649°C (1200°F) to 760°C (1400°F) temperature range, or irrespective of ferrite content if subjected to a 593°C (1100°F) to 816°C (1500°F) temperature range for prolonged periods. Toughness is affected most at ambient temperatures, but is affected even at operating temperatures.

If a material has experienced embrittlement because of the service environment, the toughness can be extremely low. In order to ascertain the toughness, samples may be removed and tests, such as CVN, could be conducted on the material to estimate the toughness. Otherwise the toughness values may be used based on the relative degree of embrittlement.

--``````-`-`,,`,,`,`,,`---

b.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.4.6.3

Long exposure to hydrogen may produce irreversible damage (e.g. microcracks) in the material. The apparent toughness could fall below the K IR curve in such cases.


Not for Resale


F.4.7

Temper Embrittlement and Other Aging Effects On The Fracture Toughness Of Cr-Mo Steels

F.4.7.1

The effect of embrittlement due to service conditions on the fracture toughness can be estimated for certain Cr-Mo steels based on chemistry. If the toughness calculated using the following temper embrittlement analyses is higher that that predicted by the methods in paragraphs F.4.2 through F.4.5 for a non-embrittled steel, then the temper embrittlement has no affect on the fracture toughness. However, if the fracture toughness predicted by the following temper embrittlement analyses is lower than that predicted by the methods in paragraph F.4.2 through F.4.5, then temper embrittlement may affect the fracture toughness and the lower value of the estimated fracture toughness should be used in the assessment.

F.4.7.2

The effect of tramp elements on the fracture toughness of 1 1/4 Cr – 1/2 Mo (see paragraph F.4.6.3.a.2) can be estimated based on a knowledge of the material chemistry using a two step correlation [F.8.4.8]. a.

In the first step, the FATT is estimated based on a material chemistry parameter X as shown below. A single correlation is available which corresponds to an upper bound. This correlation applies to both weld metal and base metal. This correlation only considers the effect of tramp elements on toughness. This prediction may be non-conservative if severe carbide embrittlement is possible. In such a case a higher estimated FATT should be used.

b

g

X = 10 × % P + 5 × % Sb + 4 × % Sn + % As × 100

(F.47)

where,

--``````-`-`,,`,,`,`,,`---

% As %P %Sb %Sn

= = = =

Weight percent Arsenic. Weight percent Phosphorous, Weight percent Antimony, Weight percent Tin.

and,

FATT upper bound = -87.355 + 11437 . X - 014712 . X2 b.

c Ch o

In the second step, the fracture toughness is determined using the equations for

(F.48)

K IC or K IR

Tref = FATT . If the material toughness is subject to degradation due to dissolved hydrogen, the fracture toughness should be based on the equation for K IR .

Alternatively, the Master Curve relationship (see paragraph F.4.9) can be used to determine the fracture toughness with

To = FATT - 75o C F.4.7.3

(F.49)

The effect of temper embrittlement on the fracture toughness of 2 ¼ Cr – 1 Mo (see paragraph F.4.6.3.a.3) can be estimated based on a knowledge of the material chemistry using a two step correlation [F.8.4.8]. a.

In the first step, the FATT is estimated based on a material chemistry parameter J TE as shown below. Three correlations are available corresponding to the mean, 95% confidence limit, and 99% confidence limit. These correlations apply to both weld metal and base metal.

b

gb

g

J TE = % Mn + % Si % P + % Sn × 10000 where,


Not for Resale

(F.50)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

in paragraph F.4.4.1 with


% Mn %P %Si %Sn

= = = =

Weight percent Manganese. Weight percent Phosphorous, Weight percent Silicon, and Weight percent Tin.

and,

c h - 8.5424c10 h J - 8.0043c10 h J

2 FATT mean = -77.321 + 0.57570 J TE - 5.5147 10-4 J TE

FATT 95% = -48.782 + 0.77455 J TE FATT 99% = -15.416 + 0.72670 J TE b.

-4

2 TE

-4

2 TE

c Ch c Ch c Ch o

(F.51)

o

(F.52)

o

(F.53)

In the second step, the fracture toughness is determined using the equations for

K IC or K IR

Tref = FATT . If the material toughness is subject to degradation due to dissolved hydrogen, the fracture toughness should be based on the equation for K IR .

To = FATT - 85o C

(F.54)

F.4.8

Fracture Toughness of Austenitic Stainless Steel

F.4.8.1

In most cases, austenitic stainless steels do not experience a ductile-brittle transition like ferritic steels. The fracture toughness is usually high, even at low temperatures, provided the material has not experienced a degradation in toughness as a result of exposure to the environment (see paragraph F.4.6.4.a.4). However, a toughness transition may occur in austenitic stainless steels with a high ferrite content (i.e. castings).

F.4.8.2

If specific information on the fracture toughness is not available, the following values can be used in an assessment provided the material has not experienced significant thermal degradation and does not exhibit a transition region. ·

Base material:

220 MPa m (200 ksi in )

·

Weld material:

132 MPa m (120 ksi in )

F.4.9

Probabilistic Fracture Toughness Distribution

F.4.9.1

The fracture toughness correlations discussed in the previous paragraphs are deterministic and conservative. Since there is a high degree of scatter in fracture toughness data, the actual toughness in a given situation can be considerably higher than the lower-bound curve predicts. Because of this substantial scatter, data should be treated statistically rather than deterministically. That is, a given steel does not have a single value of toughness at a particular temperature; rather, the material has a toughness distribution.

F.4.9.2

The ASTM E1921 standard can be used to determine this distribution for the ductile-brittle transition region. This standard utilizes a fracture toughness master curve approach to infer the toughness distribution of a material when fracture toughness data (J or CTOD) are available. It may not fit data in the lower shelf very well, and it is totally unsuitable for the upper shelf (the equations in paragraph F.4.9.5 increase without bound with increasing temperature).


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Alternatively, the Master Curve relationship (see paragraph F.4.9) can be used to determine the fracture toughness with

--``````-`-`,,`,,`,`,,`---

in paragraph F.4.4.1 with


F.4.9.3

The ASTM E1921 standard accounts for the temperature dependence of toughness through the use of a fracture toughness master curve (see Figure F.6). A wide range of ferritic steels have a characteristic fracture toughness-temperature curve, and the only difference between different grades and heats of steel is the absolute position of the curve with respect to temperature. Typically, high toughness steels have a low transition temperature and low toughness steels have a high transition temperature.

F.4.9.4

The fracture toughness distribution in ASTM E1921 is defined by a three-parameter Weibull distribution. With the threshold toughness Kmin equal to 20 MPa cumulative distribution function is given by the following equation.

L B F K - 20I OP F = 1 - exp MMN 25.4 GH K - 20 JK PQ L F K - 18.2 I OP F = 1 - exp M- BG MN H K - 18.2 JK PQ 4

m (18.2 ksi in ) the

dmm, MPa m i

Jc o

4

din, ksi in i

Jc o

(F.55)

(F.56)

where,

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

B F K Jc Ko F.4.9.5

= = =

Component thickness (mm:in), Cumulative probability, Fracture toughness (established by converting

=

(MPaÖm:ksivin), and rd 63 percentile fracture toughness ( F

J c to an equivalent K ),

= 0.63 when K Jc = Ko ), (MPaÖm:ksiÖin).

The temperature dependence of the median fracture toughness in the transition region can be estimated using the following equation. Note, that at T = To , the fracture toughness is

100 MPa m (91 ksi in ) , and Ko and (or a 1 inch fracture toughness specimen).

K Jc correspond to a 25.4 mm (1 inch) crack front length

K Jc ( median ) = 30 + 70 exp[0.0190(T - T0 )] K Jc ( median ) = 27 + 64 exp[0.0106(T - T0 )]

d MPa m i dksi in i

(F.57) (F.58)

where,

To = T = K Jc b median g = F.4.9.6

Reference transition temperature (°C:°F), Temperature of the assessment (°C:°F), and Median fracture toughness (MPaÖm:ksiÖin).

The following procedure can be used to develop a fracture toughness distribution for a specific assessment temperature based on K Jc test values (see ASTM E1921 for details). a.

Step 1 – Perform replicate fracture toughness tests at a constant temperature, the ASTM E1921 standard recommends at least 6 tests. Curve fit these data to the equations in paragraph F.4.9.4 to determine K0 and K Jc b mediumg at the test temperature. Note that this equation has the form of a three parameter Weibull distribution with two of the three parameters fixed, leaving only one degree of freedom. A distribution that contains only one

--``````-`-`,,`,,`,`,,`---


Not for Resale


parameter can be fit with a relatively small sample size. The only fitting parameter in this equation is K0 , which varies with temperature. b.

Step 2 – Compute T0 using the following equation obtained by rearranging the equations in paragraph F.4.9.5. The ASTM E1921 standard recommends applying this procedure at several test temperatures in order to obtain more than one estimate of T0 .

ln T0 = T ln T0 = T -

FG K H

Jc ( median )

FG K H

Jc ( median )

- 30

70 0.0190 - 27

64 0.0106

IJ K

d MPa m i

(F.59)

IJ K

dksi in i

(F.60)

where,

T = K Jc b median g = c.

Step 3 – Substitute the value of to compute

d.

Test temperature (°C:°F), and Median Fracture toughness from Step 1, (MPaÖm:ksiÖin).

T0 from Step 2 into one of the equations in paragraph F.4.9.5

K Jc b median g at the assessment temperature.

Step 4 – Solve for

K0 using the following equation obtained by rearranging the equations in = 0.5 and using the median fracture toughness from Step 1.

paragraphs F.4.9.4 with F

K0 =

K0 = e.

cK

Jc ( median )

bg

ln 2

cK

0.25

Jc ( median )

bg

ln 2

h + 20

- 20

- 18.2 0.25

h + 18.2

d MPa m i

(F.61)

dksi in i

(F.62)

Step 5 – With the computed value of Ko from Step 4 and the thickness of the component, B , the fracture toughness distribution is known for a specified assessment temperature using one of the equations shown below. Note that with these equations it is possible to infer median F = 0.5 , upper-bound F = 0.95 , and lower-bound F = 0.05 values for the fracture

b

g

b

g

b

g

toughness as a function of assessment temperature (see Figure F.6). 0.25

K Jc

0

0.25

K Jc f.

0

dmm, MPa m i din, ksi in i

(F.63)

(F.64)

Step 6 – Repeat Steps 3 through 5 to determine the fracture toughness distribution for different assessment temperatures.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

F 25.4 lnL 1 OIJ b K - 20g = 20 + G H B MN1 - F PQK F 1 L 1 OIJ b K - 18.2g = 18.2 + G ln M H B N1 - F PQK


F.4.9.7

In many applications, Charpy data are the only information available on material toughness. A number of empirical correlations between Charpy energy and fracture toughness have been developed over the years, but these tend to be unreliable. The following procedure can be used to develop a toughness distribution based on Charpy impact test values. Estimates of T0 obtained from the correlation in this procedure have a standard deviation of 15°C (27°F). This uncertainty can be accounted for by treating T0 as a random variable in a probabilistic analysis, or adding an appropriate margin to T0 (i.e. 15°C (27°F) for one standard deviation, 30°C (54°F) for two standard deviations, etc.) in a deterministic analysis.

F.4.9.8

F.4.10

a.

Step 1 – Determine the 27.1 Joules (20 ft-lb) transition temperature. If Charpy data is only available for sub-size specimens, then the temperature shift in accordance with paragraph F.4.3.4 should be used when determining this transition temperature.

b.

Step 2 – Estimate

T0 using the following equation.

T0 = T27 Joules - 18o C

(F.65)

T0 = T20 ft - lbs - 32.4 o F

(F.66)

c.

Step 3 – The same as given in paragraph F.4.9.6.c.

d.

Step 4 – The same as given in paragraph F.4.9.6.d.

e.

Step 5 – With the computed value of Ko , and the thickness of the component, B , the fracture toughness distribution is known for a specified assessment temperature using one of the equations in paragraphs F.4.9.6.e.

f.

Step 6 – Repeat Steps 3 through 5 to determine the fracture toughness distribution for different assessment temperatures.

The master curve approach may produce unconservative estimates of the fracture toughness in the following cases: ·

Charpy impact specimens exhibit unusual fracture behavior such as fracture path deviation.

·

Splits appear on the fracture surface of fracture toughness specimens due to crystallographic texture (this may give a lower fracture toughness than would be predicted from knowledge of the T27 J alone).

·

Through-thickness variation of microstructure and properties and the subsequent difficulty in ensuring that the Charpy specimen represents the same microstructure as that which initiates the fracture in the fracture toughness specimen (this is likely to be a problem with weld metals and HAZs, the weld root region could initiate a fracture in a CTOD test but be missed by Charpy testing).

·

Processes such as electron beam or laser welding which lead to narrow welds.

·

Components with weld mis-match induced constraint.

·

Components with cold worked material.

·

Certain high strength steels that exhibit unusual fracture modes such as quasi-cleavage.

Effect of Loading Rate on Toughness

F.4.10.1 Dynamic loading causes the ductile-brittle transition of ferritic steels to occur at higher temperatures relative to quasistatic conditions. When a high rate of loading is present, the corresponding effect on toughness should be taken into account.

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Jan, 2000

RECOMMENDED

PRACTICE

F-21


F.4.10.2 Three alternative methods are presented below to account for the effects of loading rate on toughness. For materials that do not exhibit a ductile-brittle transition, such as austenitic stainless steel, a loading rate adjustment on toughness is not necessary. Moreover, the upper shelf toughness of ferritic steels need not be adjusted for rate effects. a.

Method j - ASME K/R Cowe: The Km curve described in paragraph F.4.4 (Equations F.36 and F.37) represents a lower bound of dynamic and crack arrest toughness data. Consequently, this curve can be used to estimate toughness in situations where rapid loading may occur. The reference transition temperature, Teef, is used without adjustment.

b.

Method 2 - ASME K/C Curve with Temperature Shift: when using the lower-bound KIc curve in paragraph F.4.4 (Equations F.34 and F.35) a temperature shift should be added to the reference transition temperature,

Tref, where rz

is the reference transition temperature

under dynamic loading.

r: =Tt?f +Tshift

(F.67)

For impact loading, with nominal strain rates on the order of Ir = may be used to estimate the temperature shift [F.8.1.39].

qhift = 215- 1.50 YS

for

Thift = 0.0

lose1 , the following equations

36hi I oys I 14Ohi

fir

Oys >

14Oksi

(ksi:“F)

(F.68)

(ksi:“F)

(F.69)

and

Thift = 119.4 - 0.12080 ys

for

248 MPa I oys 5 966 MPa

(MPa:“c)

(F.70)

Thift = 0.0

for

oys > 966 MPa

(MPa:‘C)

(F.71)

For intermediate loading rates, with nominal strain rates in the range 10e3s-’ I ,kI following expressions may be used to adjust the transition temperature [F.8.1.39].

10~~ the

Thift = (215 - 1.50, 1i.O.”

for 36k.G I oys I14Ok.G

(ksi:“F:s-‘)

(F.72)

Thift = 0.0

for oys > 140 hi

(hi:“I;:s-‘)

(F.73)

(MPa:“Cs-‘)

(F.74)

(MPa:“Cs-‘)

(F.75)

and

Tshzft = (lo34- %) 6.895

qhifl = 0.0 C.

.0.17

for 248 MPa IO,

I966MPa

cc

for

oys > 966MPa

Method 3 - Master Curve with Temperature Shirk If the fracture toughness master curve approach, as described in paragraph 4.9, is used to infer toughness, the index temperature, To, should be adjusted with the equation below if high or intermediate loading --``````-`-`,,`,,`,`,,`---



API RECOMMENDED

F-22 rates are present. in paragraph

The temperature

PRACTICE 579

shift, q,,*,

can be estimated

Jan, 2000 using the procedure

outlined

F.4.10.2.b. (F.76)

of Fracture

Toughness

Sources

for fracture toughness

F.5

Material

Data for Crack

F-5.1

Categories

of Crack

Growth

Data data for various

materials

are provided

in paragraph

F.8.4.

Calculations

Growth

F.5.1 .l

Crack Growth by Fatigue - Crack growth by fatigue occurs when a component is subject to time varying loads which result in cyclic stresses. Each increment of crack extension correlates to a certain increment of stress cycles. Linear elastic fracture mechanics (LEFM) has been validated to relate the crack growth per cycle to the applied stress intensity range through a fatigue crack growth law. The simplest and most common form of fatigue crack growth law is the Paris Equation (see paragraph F.5.2.1). More advanced forms of fatigue crack growth laws which take explicit account of ’ such factors as stress ratio, ranges of K , effects of a threshold stress intensity factor, A&,, , and plasticity-induced crack closure are available for certain materials and environments. These laws should be considered in an assessment based on the applied loading, crack configuration, and service environment. The variation of fatigue crack growth rate with cyclic stresses which produce a range of hK and the associated fracture mechanisms is shown in Figure F.7. An overview of the fatigue crack growth laws and available data is provided in paragraph F.5.2 and F5.3, respectively.

F.5.1.2

Crack Growth 6y Stress Corrosion Cracking (KC) - Stress corrosion cracking results from the combination of a corrosive environment, a static applied or residual tensile stress, and a susceptible material. In the presence of these elements, the passivation, re-passivation and metal dissolution that occur locally at the crack tip are altered such that when the crack tip stress intensity factor exceeds a critical threshold value, SCC will initiate and grow for the specified condition. Active SCC usually accelerates initially until it attains an approximately uniform velocity which is independent of the stress intensity factor, but may be dependent on duration (time), material, temperature, and specific environmental factors. The different type relationships between crack velocity and stress intensity factor that can occur during stress corrosion cracking are shown in Figure F.8(a) for two different environments. The difference in the relationship between the crack velocity and applied stress intensity factor should be noted. An overview of the stress corrosion crack growth laws and available data is provided in paragraph F.5.4 and F5.5, respectively

F.5.1.3

Crack Growth by Hydrogen Assisted Cracking (/-/AC) - This covers a broad range of crack growth mechanisms that are associated with absorbed hydrogen in the metal. This includes hydrogen embrittlement, hydrogen induced cracking (HIC), stress-oriented hydrogen induced cracking (SOHIC), and sulfide stress cracking. In contrast to the other failure mechanisms, HAC susceptibility is highest at ambient and moderate temperatures and decreasing strain rate. a.

HAC occurs when hydrogen is absorbed by a material during a corrosion process, or by exposure to high-temperature and/or high pressure hydrogen gas, and diffuses to a preexisting flaw as atomic hydrogen, and stresses are applied (including residual stresses) to the flaw. The crack will continue to propagate at an increasing velocity until fracture occurs as long as the stress intensity factor resulting from the applied and residual stresses exceed a critical threshold value, Kth, and a critical concentration of atomic hydrogen is maintained in the vicinity of the crack tip either by continuous absorption of hydrogen from the external surface, or by redistribution of internal lattice hydrogen and internal sources such as hydrogen traps in the material. The fracture condition is dictated by the value of the material toughness

March 2000


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Sources

--``````-`-`,,`,,`,`,,`---

F-4.1 1

Jan, 2000

RECOMMENDED

PRACTICE

F-23


in the presence of absorbed hydrogen at the crack tip. This toughness is designated as

K IC-H b.

F.5.1.4

.

Within a LEFM methodology, a HAC crack growth law can be determined from test specimens that relate the crack growth rate to the combined applied and residual stress intensity factor, the material/environment constants, and loading (strain) rate. A simple form of the HAC crack growth curve is shown in Figure F.8(b). A typical crack growth law for HAC is shown in paragraph F.5.4.

Crack Growth by Corrosion Fatigue - The synergistic effect of combined SCC or HAC with fatigue under cyclic loading in an aggressive environment can produce significantly high crack growth per cycle compared to an inert environment where SCC or HAC is absent. This interaction can be very complicated, and makes development of a simple crack growth law difficult. a.

Corrosion fatigue crack propagation typically exhibits the three basic types of crack growth rate behavior shown in Figure F.9. True Corrosion Fatigue (TCF) - describes the behavior when fatigue crack growth rates are enhanced by the presence of aggressive environment at levels of applied K below K Iscc (see Figure F.g(a)). This behavior is characteristic of materials that do not exhibit

l

stress corrosion( i.e. l

l

b.

KIscc = K,,).

Stress Corrosion Fatigue (SCF) - describes corrosion under cyclic loading that occurs whenever the stress in the cycle is greater than K,,,, . This is characterized by a plateau in crack growth (see Figure F.g(b)) similar to that observed in stress-corrosion cracking. Combination TCF and SCF -this is the most common type of corrosion fatigue behavior (see Figure F.g(c)) which is characterized by stress-corrosion fatigue above KIscc, superimposed on true corrosion fatigue at all stress intensity levels.

Equations which describe corrosion fatigue behavior are available for limited stress intensity ranges and material/environment combinations. Therefore, it is advisable to establish and use upper bound crack growth laws for such cases.

F.5.2

Fatigue Crack Growth Equations

F.5.2.1

Overview Fatigue crack growth laws which have been used in the refining and petrochemical industry are summarized below. A complete discussion of all aspects of these crack growth laws is beyond the scope of the appendix. Further information on fatigue crack growth laws can be found in reference [F.8.1 .I] and [F.8.1.20].

F.5.2.2

Paris Equation a.

The Paris Equation is the simplest of the fatigue crack growth laws (see Figure F.7). The Paris Equation has the form:

f

= c(AK)”

(F.77)

where,

da/dN C n

=

Increment of crack growth for a given cycle,

= =

Material parameter, Material parameter, --``````-`-`,,`,,`,`,,`---



API RECOMMENDED

F-24

b. F.5.2.3

a.

Jan, 2000

AK

=

K,, - Kti ; if AK > AK, crack growth occurs; otherwise, if AK I AK, crack growth does not occur, or da/dN = 0.0,

K KZ

=

Maximum

stress

=

Minimum

stress

K/l

=

Threshold

stress

intensity for a given cycle, intensity for a given cycle, and intensity factor.

Note that in this model, the crack growth

Walker

PRACTICE 579

rate is independent

of the load ratio.

Equation The Walker Equation is a simple but significant Walker Equation has the form:

generalization

of the Paris Equation.

g = c&J

The

(F.78)

where,

b.

da/dN c n

= = =

&4 m AK

= = =

K,, Kti

= =

fwh R

= Threshold stress intensity factor, and = IcninlKmax~

Increment

of crack growth

for a given cycle,

Material parameter, Material parameter, @l-R)“, Material parameter, K,, - Kti ; if crack growth

occurs;

otherwise,

if AK I AI&,

crack

growth does not occur, or, Maximum stress intensity for a given cycle, Minimum stress

intensity for a given cycle,

The Walker Equation is the same as the Paris Equation except that AK is replaced by an effective AK which is now dependent on the load ratio. Therefore, while the Paris Equation is only dependent on AK, the Walker Equation is dependent on both AK and R . The appearance of R in the Walker Equation results in larger crack growth rates being predicted for larger values of even if AK is held constant. This behavior is intuitive and is also supported by experimental data for numerous metals. The effects of AK and K,, are more clearly seen by writing

AI&.

in the following

way:

(F.79) or

AKeg = { 1 - R}(l-m) K,, C.

(F.80)

m controls the relative importance of AK and K,, on AKefl, and thus on the crack growth rate. If m = 1.0, then AI& = AK and the Walker Equation simplifies to the Paris Equation. If m = 1.0, then the crack growth is only dependent only on K,, . The parameter m allows the load ratio dependence of the Walker Equation to be adjusted to fit

The parameter

--``````-`-`,,`,,`,`,,`---

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

RECOMMENDED

Jan, 2000

PRACTICE

F-25


available experimental data. As a result of this additional parameter, the Walker Equation parameters are slightly more difficult to determine than the Paris Equation parameters. F.5.2.4

Bilinear Equation a.

The Bilinear Equation reflects another approach to generalization of the Paris Equation. The form of the Bilinear Equation is:

g = c&K)”

for &I

g = C,(AK)“”

for AK 2 AI&,

-c AK -c 4rall

and (F.82)

where,

*I n, AK

b.

= = = = = =

Km K,, Kh

= = =

wrM

=

Increment of crack growth for a given cycle, Material parameter, Material parameter, Material parameter, Material parameter,

K,, - Kh ; if crack growth occurs; otherwise, if AK I A&

crack

growth does not occur, or, Maximum stress intensity for a given cycle, Minimum stress intensity for a given cycle, Threshold stress intensity factor, and Transition used to determine the constants in the crack growth law.

The Bilinear Equation is a combination of two Paris Equations. For k above the transition, AK,,, , one law is used; for a below the transition, the other law is used. Note that the above equations do not give the same crack growth rate at A&=,, ,

F.5.2.5

Modified Forman Equation a.

The Modified Forman Equation is a general crack growth law and can be used to represent the state of crack growth across the full regime of crack propagation (see Figure F.7). The form of the Modified Forman Equation is:

da dN

(F.83)

where,

da/dN

=


c

= =

Material parameter, Material parameter,

n



--``````-`-`,,`,,`,`,,`---

da/dN c, c,

API RECOMMENDED

F-26

;

= =

4 M

= =

Jan, 2000

Material parameter, Material parameter, Material parameter, K,,

- &,,

AK I AK,

; if AK > A&, crack growth stress


Minimum

stress


stress

4ninlKmax Equation

otherwise,

crack growth does not occur, or da/&I

if

= 0.0,

intensity factor,

Plain strain fracture

The Modified Forman

occurs;

Maximum Threshold

b.

PRACTICE 579

toughness,

and

* is similar to the Walker

Equation in that there is a (1 -

R)”

m in the Modified Forman Equation is not the same as in the Walker Equation due to the term appearing in the numerator, and also due to the (1- R)”

factor.

However,

the constant

term not being raised to the n power. If p and 4 are set to zero, then this law becomes equivalent to the Walker Equation with

mf = -m,

(F.84)

where,

mf m, C.

NASGRO a.

is the

m constant for the Modified Forman Equation, and

is the m constant

for the Walker

Equation.

The terms with the p and q exponents allow the law to accurately represent da/dN vs. AK data in the low growth rate (threshold) region, in the mid-range region, and in the high growth rate region (K,, approaching K,,) as shown in Figure F.7. The exponents p and q are in the range of zero to unity and are typically equal to each other. With such values, the factor with the p exponent tends to affect the behavior of the law primarily in the threshold region, while the factor with the q exponent tends to affect the behavior primarily near load levels approaching significance, data.

F.5.2.6

= =

KIc . It should be clear that the p and q exponents

have no physical the only real basis for their choice is in making the law fit actual crack growth

Equation

The NASGRO Equation represents the most general crack growth law, and except for special purpose laws, is the one which would best represent the state of the art in fatigue crack growth relationships. This law also incorporates the effects of fatigue crack closure. The form of the NASGRO Equation is:

da =C(ldN

R)“AK

l-f% p AK [ 1

1-[ 1 K

(F.85)

’

Kc

where,

da/dN

=

Increment

of crack growth

for a given cycle,

--``````-`-`,,`,,`,`,,`---

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


--``````-`-`,,`,,`,`,,`---

b.

=

C n p q ,K

= = = = =

Kmax - Kmin ; if DK > DKth crack growth occurs; otherwise, if DK £ DKth crack growth does not occur, or da dN = 0.0 ,

Kmax Kmin ,Kth K IC R

=

Maximum stress intensity for a given cycle,

=

Minimum stress intensity for a given cycle,

=

Threshold stress intensity factor,

=

Plain strain fracture toughness, and

=

Kmin Kmax .

parameter which reflects the amount of plasticity-induced crack closure that is present in the material, Material parameter, Material parameter, Material parameter, Material parameter,

Details regarding the NASGRO Equation can be found in References [F.8.5.8] and [F.8.5.9].

Collipriest Equation a.

The Collipriest Equation was an early attempt at addressing the shortcomings of the Paris and Walker Equations in terms of representing behavior in the threshold and large ,K regions of the da dN vs. ,K plot. The Collipriest Equation tries to compensate for the lack of nonlinear behavior of the simpler laws without introducing additional parameters and thus has a rather complicated form:

R| LM lnL DK O OPU| MN DK b1 - RgK PQ P| nI F K I | F M g × expSGH 2 JK lnGH DK JK × a × tanhM L b1 - RgK O PV || MM lnM DK P PP|| Q QW N N T 2

b

da = C DKth K IC dN

n 2

IC

th

IC

th

(F.86)

IC

th

where,

b.

F.5.2.8

da dN C n a ,K

=


= = = =

Material parameter, Material parameter, Current crack size, Kmax - Kmin ; if DK

Kmax Kmin ,Kth K IC R

=


=


=

Threshold stress intensity factor,

=

Plain strain fracture toughness, and

=

Kmin Kmax .

> DKth crack growth occurs; otherwise, if DK £ DKth crack growth does not occur, or da dN = 0.0 ,

The material parameters of the Collipriest law are the same as for the Paris Equation. This does not imply, however, that one can simply substitute Paris Equation parameters into the Collipriest Equation without verifying that the resulting model provides a reasonable representation of actual material behavior.

ASME Section XI Ferritic Steel Air and Water Equation


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.5.2.7

f


a.

The fatigue crack growth rate of the material is characterized in terms of the range of applied stress intensity factor. This characterization is generally of the form:

b g

da = C0 DK dN

n

(F.87)

da dN Co n ,K Kmax Kmin b.

F.5.2.9

=


= = =


=

Maximum stress intensity for a given cycle, and

=


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

where,

Kmax - Kmin ,

The material parameters should be based on flaw growth data obtained from specimens of the same material specification and product form, or suitable alternative. Material variability, environment, test frequency, mean stress and other variables that affect the data should be considered.

ASME Section XI Austenitic Stainless Steel Equations For In Air & Water Environments a.

Fatigue flaw growth rate in austenitic piping can be characterized in terms of the range of the applied stress intensity factor. This characterization is of the form:

b g

da = C0 DK dN

n

(F.88)

where,

da dN Co n ,K Kmax Kmin


= = =


=


=


Kmax - Kmin ,

The material parameters should be based on flaw growth data obtained from specimens of the same material specification and product form, or suitable alternative. Material variability, environment, test frequency, mean stress and other variables that affect the data should be considered.

F.5.3

Fatigue Crack Growth Data

F.5.3.1

Sources for fatigue crack growth data, da dN , for various materials and service environments are provided in paragraph F.8.5. When possible, fatigue crack growth data should be evaluated from test results in a similar environment since this can greatly affect the crack growth rate.

F.5.3.2

The fatigue crack growth equations shown below can be used with the Paris Equation (see paragraph F.5.2.2) in FFS assessments (see Reference [8.5.6]). These equations are valid for materials with yield strengths less than or equal to 600 MPa (87 ksi ) . These parameters correspond to upper bound crack growth data with a slope which is consistent with the S-N fatigue curves for welded joints


Not for Resale

--``````-`-`,,`,,`,`,,`---

b.

=


(see paragraph F.6.3.2). The following threshold stress intensity value can be used with all of these fatigue crack growth equations:

a.

Kth = 2.0 MPa in

(F.89)

Kth = 18 . ksi in

(F.90)

For ferritic and austenitic steels in air or other non-aggressive service environments at temperatures up to 100°C (212°F):

c h

--``````-`-`,,`,,`,`,,`---

da = 165 . 10-8 DK 3.0 dN

c h

da = 8.61 10 -10 DK 3.0 dN b.

for for

DK > DKth DK > DKth

dmm cycle , MPa m i din cycle , ksi in i

(F.91)

(F.92)

For ferritic and austenitic steels in air or other non-aggressive service environments at temperatures operating between 100°C (212°F) and 600°C (1112°F) with cyclic frequencies greater than or equal to 1 Hz:

c hFGH EE DKIJK F E DKIJ da = 8.61c10 hG dN HE K

3.0

da = 165 . 10-8 dN

ab

for

DK > DKth

at

-10

3.0

ab

for

DK > DKth

at

dmm cycle , MPa m i (F.93) din cycle , ksi in i

(F.94)

where,

Eab E at c.

=

Young’s modulus at ambient temperature, and

=

Young’s modulus at the assessment temperature.

For ferritic steels operating in a marine environment at temperatures up to 20°C (54°F):

c h

for

DK > DKth

dmm cycle , MPa m i

(F.95)

c h

for

DK > DKth

din cycle , ksi in i

(F.96)

da = 7.27 10-8 DK 3.0 dN da = 380 . 10 -9 DK 3.0 dN F.5.3.3

Alternatively, the fatigue crack growth equations shown below can be used with the Paris Equation (see paragraph F.5.2.2) in FFS assessments (see Reference [8.5.4]). These parameters correspond to upper bound crack growth data. The following threshold stress intensity values can be used with all of the fatigue crack growth equations:

b

DKth = 7 1 - 0.85R

b

g

DKth = 6.37 1 - 0.85R


d MPa m i dksi in i

g

(F.97) (F.98)

Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


where,

R Kmax Kmin //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

a.

=

Kmin Kmax ,

=


=

Minimum stress intensity for a given cycle.

For martensitic steels with a yield strength from 552 MPa (80 ksi) to 2068 MPa (300 ksi) at room temperature in air or an other non-aggressive environments:

c h

for

DK > DKth

dmm cycle , MPa m i (F.99)

c h

for

DK > DKth


da = 136 . 10-7 DK 2.25 dN da = 6.60 10 -9 DK 2.25 dN b.

For ferritic-pearlite steels at room temperature in air or an other non-aggressive environments:

c h

for

DK > DKth

dmm cycle , MPa mi (F.101)

c h

for

DK > DKth


da = 6.89 10 -9 DK 3.0 dN --``````-`-`,,`,,`,`,,`---

da = 3.60 10 -10 DK 3.0 dN c.

(F.102)

For austenitic stainless steels at room temperature in air or an other non-aggressive environments:

c h

da = 5.61 10-9 DK 3.25 dN

c h

da = 3.00 10 -10 DK 3.25 dN F.5.3.4

(F.100)

for for

DK > DKth DK > DKth

dmm cycle , MPa m i (F.103) din cycle , ksi in i

(F.104)

Fatigue crack growth parameters for use with the Bilinear Equation (see paragraph F.5.2.4) are given provided below. a.

Fatigue crack growth parameters are provided in Table F.8 is provided for different materials and service environments.

b.

The following fatigue crack growth parameters can be used for pipeline steels (e.g. API 5L) at ambient temperatures in crude oil service (see Reference [8.5.11]). Note that when these parameters are used, an effective ,K which is dependent on the load ratio is substituted for ,K in the Bilinear Equation.

DKth = 6 MPa in

b

da = Cl DK + BR dN l


(F.105)

g

nl

dmm cycle , MPa m i

Not for Resale

(F.106)


da dN

b

= Cu DK + BR

g

dmm cycle , MPa m i

nu

u

(F.107)

The following parameters can be used for sour crude oil (with H2S):

c h

c h

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Cl = 7.12 10 -16 × CH2 S + 3.40 10-13

(F.108)

nl = 6.40

(F.109)

c h

c h

Cu = 2.50 10 -11 × CH2 S + 1.48 10 -7

(F.110)

nu = 2.72

(F.111)

c h

Cl = 148 . 10-11

(F.112)

nl = 4.80

(F.113)

c h

Cu = 4.00 10-7

(F.114)

nu = 190 .

(F.115)

where,

B CH 2 S ,K

= =

Material parameter equal to 4 for pipeline steels (API 5L, Grade X60), H2S concentration in ppm,,

=

Kmax - Kmin ; if DK > DKth crack growth occurs; otherwise, if DK £ DKth crack growth does not occur, or DK = 0.0 ,

Kmax Kmin R

=


=

Minimum stress intensity for a given cycle, and

=

Kmin Kmax .

F.5.3.5

Fatigue crack growth parameters for use with the NASGRO Equation (see paragraph F.5.2.6) are given in reference [F.8.5.8] for different materials and service environments.

F.5.3.6

Fatigue crack growth parameters for ferritic steels in air and water environments (see paragraph F.5.2.8) are given in the ASME Code, Section XI, Paragraph A-4300, Article A-4000.

F.5.3.7

Fatigue crack growth parameters for austenitic stainless steel in air and water environments (see paragraph F.5.2.9) are given in the ASME Code, Section XI, Paragraph C-3210, Article C-3000.

F.5.4

Stress Corrosion Crack Growth Equations

F.5.4.1

Within the LEFM methodology, a Stress Corrosion Crack (SCC) growth law can be experimentally determined which relates the crack growth rate to the stress intensity factor ( K ), the material, service environmental, and time. This crack growth law can subsequently be used to characterize the crack growth behavior in equipment under a similar combination of stress, material, and service environment to that used in the experiment.


Not for Resale

--``````-`-`,,`,,`,`,,`---

The following parameters can be used for sweet crude oil (without H2S):


F.5.4.2

A overview of stress corrosion crack growth laws is provided in reference [F.8.1.20]. Examples of SCC crack growth laws that have been used are shown below. a.

The following three equations are representative of the crack growth laws used to model SCC.

da = C1 K n1 dt

for Kth £ K £ K IC

(F.116)

da = C2 t n2 dt


(F.117)

da = C3 dt


(F.118)

where,

--``````-`-`,,`,,`,`,,`---

b.

da dt C1 n1 C2 n2 C3 Kth

=

Increment of crack growth,

=

material/environment constant,

=


=


=


=


=

K IC K t

=

threshold stress intensity factor above which SCC will initiate and grow under predominantly plain strain conditions, material toughness measured in the environment under consideration,

= =

applied stress intensity factor, and time.

The following equation is a typical crack growth law for HAC.

da = CK n dt

for

Kth £ K £ K IC - H

(F.119)

where,

Kth

=

K IC - H =

Increment of crack growth, material/environment constant, material/environment constant, applied stress intensity factor. the threshold stress intensity factor for the material and environment, above which measurable crack extension will occur, and material toughness measured in the hydrogen charging environment.

F.5.5

Stress Corrosion Crack Growth Data

F.5.5.1

Sources for stress corrosion crack growth data

bda dt g for various materials are provided in

paragraph F.8.5. When possible, stress corrosion crack growth data should be evaluated from test results in a similar environment. An excellent overview of crack growth mechanisms and rates for several cracking mechanisms commonly observed in materials utilized for petroleum refinery applications is included in reference [F.8.5.1].


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

da dt = C = n = K =


F.5.5.2

An upper bound solution for a hydrogen assisted crack growth rate in 2 1/4Cr – ½ Mo and the associated threshold stress intensity factor are shown below. The tests for the data were conducted in a 500 ppm H2S solution.

c

h

da = 2.4 10-24 K 11.7 dt

for


Kth = 0.0014 × FATT 2 - 0.421 × FATT + 57.0

c h

da = 2.85 10 -25 K 11.7 dt

Kth =

for


0.0014 × FATT 2 - 0.421× FATT + 57.0 10988 .

dmm hour , MPa m i

(F.120)

d MPa m i

(F.121)

din hour , ksi in i

(F.122)

dksi in i

(F.123)

where,

da dt = FATT =

K = Kth = K IC - H =

Increment of crack growth (mm/hour:in/hour), Fracture appearance transition temperature (see paragraph F.4.7.3), note that the temperature is in centigrade for this correlation (°C), Applied stress intensity factor (MPaÖm:ksiÖin), the threshold stress intensity factor (MPaÖm:ksiÖin), and material toughness measured in the hydrogen charging environment temperature (see paragraph F.4.7.3) (MPaÖm:ksiÖin).

--``````-`-`,,`,,`,`,,`---

F.6

Fatigue Curves

F.6.1

General

F.6.1.1

Fatigue curves are required to evaluate the remaining life of a component subject to cyclic loading conditions. Crack growth after initiation is analyzed using a fracture mechanics analysis.

F.6.1.2

Most of the fatigue curves for crack initiation reported in the literature are based on testing in air at room temperature. There is evidence that these curves may be affected by the environment; an aggressive environment may result in a lowering of the number of cycles to failure. Therefore, if a fatigue curve for a similar environment to that which the component is subjected to is available, it should be utilized in the assessment. If a fatigue curve is not available, consideration should be given to the detrimental effects of the environment with regard to fatigue life.

F.6.1.3

Fatigue curves are typically presented in two forms; fatigue curves that are based on smooth bar test specimens and fatigue curves that are based on test specimens which include weld details. In general, the former curves are recommended when the point being evaluated is not at a weld joint, and the latter are recommended when there is a weld joint at the point being evaluated.

F.6.2

Fatigue Curves Based On Smooth Bar Test Specimens

F.6.2.1

Fatigue curves of this type are generated from fatigue test data obtained from smooth bar test specimens. The testing is carried out under load controlled, or for applied stresses exceeding yield, strain controlled conditions. Continuity between the low and high cycle regime is achieved by expressing the low-cycle data in terms of a pseudo-elastic stress range (i.e. applied strain amplitude multiplied by the elastic modulus).


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.6.2.2

Fatigue data that can be utilized for many materials for a limited temperature range of 38°C – 371°C (100°F – 700°F) is shown in Table F.9 (see Figure F.10). Fatigue curves for other materials used in the construction of pressure vessels and piping can be found in the ASME Code, Section VIII, Division 2, Appendix 5. A factor of two is applied to the stress range and 20 is applied to the number of cycles to failure to account for data scatter, size effect, surface finish and environment. In order to use this curve, an alternating stress range that includes membrane, bending and peak stress components must be derived (see Appendix B for details on the assessment methodology).

F.6.3

Fatigue Curves Based On Welded Test Specimens

F.6.3.1

The fatigue strength for welded components is expressed in terms of a series of fatigue curves, each applying to a particular construction detail. The curves are identified by the fatigue strength value 6 achieved at a fatigue life of 2(10 )cycles and are assigned a class at this value.

F.6.3.2

a.

The curves have been derived based on fatigue test data obtained from welded test specimens, fabricated to normal standards of workmanship, tested under load-control or, for applied strains exceeding yield (low-cycle fatigue), under strain control. Continuity from the low-cycle to high-cycle regime is achieved in terms of the pseudo-elastic stress range (i.e. strain range multiplied by elastic modulus). Fatigue data of this type have been found to be compatible with results obtained from pressure cycling tests on actual vessels when they are expressed in terms of the nominal stress range in the region of fatigue cracking.

b.

The fatigue curves are approximately two standard deviations of log(N) below the mean curve, fitted to the original test data by regression analysis. Thus, they represent a probability of survival of approximately 98%. The survival probability can be increased to approximately 99.9% by choosing the next lowest fatigue curve.

The fatigue data for welded test specimens are presented in the following format. a.

General form – the general equation for the fatigues curves is:

b

--``````-`-`,,`,,`,`,,`---

N = A I r Csu

g

-m

(F.124)

where,

b.

A = Csu =

Fatigue data constant dependent on the weld class (see Table F.10), Constant for units conversion; Csu = 10 . if I r is expressed in MPa and

m N Ir

Csu = 10 . 6.894757 if I r is expressed in ksi, Fatigue data exponent dependent on the weld class (see Table F.10) Permissible number of cycles, and Applied stress range (MPa:psi).

= = =

Effect of Material And Temperature – the same set of fatigue data is applicable for all steels (ferritic and austenitic) since the fatigue lives of weld details are independent of material yield strength. The fatigue data in Table F.10 (see Figure F.11) are related to a material with a 5 6 modulus of elasticity of 2.09(10 ) MPa (30.3(10 ) psi), which is the typical value for ferritic steel at ambient temperature. When other materials and/or temperatures are being considered, the following adjustment to the fatigue curves can be made. This adjustment is valid for materials not operating in the creep range.

F 2.09c10 hC I I GH E JK 5

I=

us

(F.125)

r

y

where,


Not for Resale


Cus =


Csu = 10 . if I r is expressed in MPa and

Csu = 10 . 6.894757 if I r is expressed in ksi,

Ey Ir I c.

=

Young’s Modulus evaluated at the mean temperature of the cycle (MPa:psi),

= =

Stress range for a particular life (MPa:psi), and Stress range obtained from the appropriate fatigue curve at the same life (MPa:psi).

Effect of plate thickness – the fatigue strength of members containing surface welds can decrease with increase in plate thickness. The fatigue data in Table F.10 apply to components with a section thickness, t , up to 25 mm (1.0 inch, nominal). If t > 25 mm (1.0 inch, nominal), then the stress range obtained from the fatigue data shown in Table F.10 should be

b25 t g

0.25

t is in mm. In all cases, fatigue cracking from the weld toe into a stressed member is being considered and t is the thickness of that member.

multiplied by the factor

where

d.

Effects Of Environment – environmental-assisted fatigue cracks can occur at lower levels of stress than in air thereby reducing the fatigue life of a component. Therefore, where environmental-assisted fatigue is anticipated and effective protection against the environment cannot be guaranteed, a factor to reduce the fatigue life should be chosen based on experience with components in a similar environment and/or testing.

e.

Effect Of Material Toughness – there are no restrictions on the use of the fatigue design curves for components which operate at cold temperatures provided the material has sufficient toughness to ensure that fracture will not initiate from a fatigue crack (see Section 3).

f.

Temperature Limitations – there is a lack of data on the influence of creep on the elevated temperature fatigue strength of steel; therefore, the fatigue curves are only applicable to components which operate at temperatures below the creep range of the material. Thus, the fatigue design curves are applicable up to 350°C (662°F) for ferritic steels and 430°C (806°F)for austenitic stainless steels.

g.

Adjusted Fatigue Equation – the final form of the fatigue equation, adjusted for material type, temperature, and the thickness of the component is given by the following equation.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F R| 2.09(10 ) U|I I N = Af f G S H |T E V|W JK 5

t

c

-m

(F.126)

r

y

with,

ft

F 25 IJ =G H tC K

m4

for t > 25 mm

(F.127)

tu

f t = 10 .

for t £ 25 mm

(F.128)

where,

A Ctu E fc m

= =

Fatigue data constant based on a weld class (see Table F.10), Constant for units conversion, Ctu = 25.4 if t is expressed in inches and

Ctu = 10 . if t is expressed in mm, = = =

Young’s Modulus (MPa:ksi), Factor to reduce fatigue life based on the environment (see subparagraph d), Fatigue data exponent based on a weld class (see Table F.10),

--``````-`-`,,`,,`,`,,`---


Not for Resale


N t Ir F.6.3.3

F.6.3.5

Permissible number of cycles, Section thickness of the component (mm:in), and Applied stress range (MPa:ksi).

Weld classification – for the purpose of a fatigue assessment, a component which contains a welded detail subject to fluctuating stress is placed into one of six classes (see Table F.10 and Figure F.11). An overview of weld details and the appropriate classifications are shown in Figures F.12 through F.16. Additional information on fatigue curves and the associated weld classes can be found in reference [F.8.1.5]. a.

F.6.3.4

= = =

The classification of a component containing a weld depends upon the following: ·

The direction of the fluctuating principal stress relative to the weld detail

·

The location of possible crack initiation at the weld detail

·

The geometrical arrangement and proportions of the weld detail

·

The methods of manufacture and inspection

b.

More than one class may apply for a given weld detail, since each class refers to one particular mode of fatigue failure. The potential mode of fatigue cracking and the position and direction of the relevant fluctuating stress are indicated in the details in Figure F.12 through F.16.

c.

It should be noted that the classification for a weld seam depends on the level of inspection. In particular, to justify the assigned weld class, the welds must be shown to be free from significant flaws. This requires 100% inspection. Flaws are significant if, as a result of their presence, the fatigue strength of the weld is reduced below that corresponding to fatigue failure from the weld toe. Seam welds which are not inspected are downgraded to the lowest design class. The need for 100% inspection of a weld does not necessarily mean that the entire component requires the same level of inspection. The choice depends on the detail classification required to achieve the required fatigue life.

d.

Except for partial penetration butt welds, which are not classified, details not covered in Figures F.12 through F.16 should be treated as Class 40. A higher classification may be used if superior resistance to fatigue is proved by testing or reference to relevant fatigue test results.

Change of Classification – the classification of some weld details may be raised if the conditions below are met. a.

Hot Spot Stress – Class 80 may be used for welds designated as Class 63 or Class 50 if the hot spot stress range, as opposed to the nominal stress range, is used in the assessment. Information pertaining to the calculation of the hot spot stress and how it is used in a fatigue analysis can be found in references [F.8.1.18] and [F.8.1.19].

b.

Weld Toe Dressing – The classification of fillet welds may be moved into a higher classification when dressing the toes is carried out. When joints are treated in accordance with paragraph F.6.3.5, the fatigue data one class higher than that for the untreated weld may be used in the assessment.

c.

Dressing Of Seam Welds – Class 100 may be used for Class 80 welds if dressing or flush grinding of the seam welds is performed. A fatigue strength higher than Class 100 is not used because of the possible presence of weld flaws which are too small for reliable detection by non-destructive inspection methods but are of sufficient size to reduce the fatigue strength of the joint.

Recommendations for reducing the risk of fatigue failure at a fillet weld – fatigue cracks may initiate at weld toes on stressed members, partly because of the stress concentration resulting from the weld shape but mainly because of the presence of inherent flaws. For members at least 13 mm thick (0.5 inches), the fatigue lives of welds which might fail from the toe may be increased by locally machining and grinding the toe to reduce the stress concentration and remove the inherent flaws [F.8.1.6].

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


a.

The weld toe is machined using a rotating conical tungsten-carbide machining burr. In order to ensure that weld toe flaws are removed, the required depth of machining is 0.5 mm (0.02 inches) below any undercut (see Figure F.17). The area should be examined using PT or MT. This examination is facilitated if the machined toe is ground using emery bands, a measure which will also increase the fatigue life. The resulting profile should produce a smooth transition from the plate surface to the weld; all machine marks should have a transverse orientation with respect to the weld toe. This technique is particularly suitable for treating weld toes. The ends of short or discontinuous welds can only be treated effectively if the weld can be carried around the ends of the attachment member to provide a distinct weld toe.

b.

Weld toe dressing will result in a region of reduced plate thickness. The stress concentration associated with this feature is less severe than the original weld; therefore, the loss of section in the weld toe region is acceptable based on fatigue resistance. However, it should be considered in thickness calculations to qualify a component based on material strength considerations (i.e. when calculating the minimum required thickness for pressure).

c.

Weld toe dressing only affects the fatigue strength of a welded joint from the point of view of failure from the weld toe. The possibility of fatigue crack initiation from other features of the weld (e.g. weld root in fillet welds) should also be considered.

d.

Weld toe dressing may not be effective in the presence of a corrosive service environment which can cause pitting in the dressed region.

F.7

Material Data for Creep Analysis

F.7.1

Creep Rupture Data Creep rupture data may be required to evaluate the remaining life of a component operating at a high temperature. Minimum and average creep rupture data are typically expressed in terms of the Larson-Miller parameter which combines the time to rupture and temperature into a single variable. The Larson-Miller parameter and the time to rupture are as follows:

b

gb

g

LMP (I ) = T + 460 C + Log10 L 10 -3

(F.129)

1000 × LMP(I ) -C T + 460

(F.130)

log10 L =

b

g

where,

C L LMP I T

bg

= = =

Material constant, Rupture Life, hours, Larson-Miller parameter as a function of stress, ksi, and

=

Temperature, (°F).

F.7.2

Creep Strain-Rate Data Sources for strain rate data for various materials are provided in paragraph F.8.2. Data for creep strain rate based on the MPC Project Omega program are provided in paragraph F.7.3.


Not for Resale

--``````-`-`,,`,,`,`,,`---

The minimum and average creep rupture data in terms of the Larson-Miller Parameter for pipe and tube materials are provided in Table F.11.


//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

F.7.3

MPC Project Omega Data

F.7.3.1

The assessment techniques developed under the MPC Project Omega program provide a methodology for estimating the remaining life of a component operating at high temperature that has been extensively used in the refining and petrochemical industry. The MPC Project Omega Method is a public domain assessment procedure with a proven record and associated property relations covering a wide range of materials used in the refining and petrochemical industry. In this methodology, a strain-rate parameter and multi-axial damage parameter (Omega) are used to predict the rate of strain accumulation, creep damage accumulation, and remaining time to failure as a function of stress state and temperature. An overview of the assessment procedure is described below.

F.7.3.2

The remaining life of a component,

L=

L , for a given stress state and temperature is expressed as:

1 W mA co

(F.131)

where,

Wm A co

=

Omega multiaxial damage parameter, and

=

Initial creep strain rate at the start of the time period being evaluated based on the stress state and temperature at this time.

The multiaxial damage parameter,

W m , is evaluated using the following equations:

Wm = W@n +1 + =n

b

(F.132)

g

W n = max W - n , 3.0

(F.133)

g LMN 4601+ T OPQ C + C S + C S

b

log10 W = Co + D cd +

1

2

2 3 l

l

+ C4 Sl3

b g

Sl = log10 I e Ie =

@ =>

b

(F.135)

1 I1 -I 2 2

FG I H

1

g + bI 2

1

-I 3

g + bI 2

2

-I 3

g

2 1/ 2

IJ K

+I 2 +I 3 . - 10 Ie

(F.136)

(F.137)

where,

C0 ® C4 L n T =

=

Material coefficients for the omega parameter (see Table F.12),

= = = =

>

=

Rupture Life (hours), Strain-rate exponent evaluated using the equations shown below, o Temperature ( F), Parameter based on the state-of-stress, = 3.0 – pressurized sphere or formed head = 2.0 – pressurized cylinder or cone = 1.0 – for all other components and stress states Prager factor equal to 0.33,

--``````-`-`,,`,,`,`,,`---


(F.134)

Not for Resale


, cd

=

9 9m @ Ie I1 I2 I3

= =

Omega uniaxial damage parameter, Omega multiaxial damage parameter,

= =

Damage parameter exponent, Effective stress (ksi),

=

Principal stress (ksi),

=

Principal stress (ksi), and

=

Principal stress (ksi).

Adjustment factor for creep ductility, a range of

-0.3 for ductile behavior can be used,

The strain rate exponent, n , and initial strain rate,

log10

A co , are computed using the following equations:

RSL 1 O C + 2C S + 3C S UV TMN 460 + T PQ W R L 1 OP C + C S + C S A = - SbC + D g + M N 460 + T Q T

n=-

2

co

o

3 l

4

+0.3 for brittle behavior and

2 l

sr

1

2

l

2 3 l

(F.138)

+ C4 Sl3

UV W

(F.139)

where variables are defined above and,

C0 ® C4

=

, sr

=

Material coefficients for the strain rate parameter based on average or most probable properties (see Table F.12), Adjustment factor to account for the material scatter band, a range of -0.5 for the bottom of the scatter band to +0.5 for the top of the scatter band can be used.

If the component is subject to multiple operating conditions (i.e. different temperatures and/or stress states), then the remaining life can be determined using a life fracture approach as follows:

Dc = å

ti £ Dca Li

(F.140)

where,

Dc Dca

=

Creep damage computed based on the loading history,

=

Allowable creep damage usually taken as

i

=

Rupture time for the loading history in time increment

=

Time increment or load duration for use in the damage calculation (hour).

L ti

t i (hours), and

Es =

I I + Ac E

R ¶A UV = RS ¶ FG - 1 ln 1 - A E =S T ¶ I W T ¶I H W

(F.141)

-1

t


c

co

IU Wt J V KW

-1

Not for Resale

(F.142)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

The MPC Project Omega data can also be used to determine the secant modulus and the tangent modulus. These parameters can be used to evaluate structural stability in the creep regime. The secant modulus, E s , and tangent modulus, E t , can be determined as follows. --``````-`-`,,`,,`,`,,`---

F.7.3.3

10 . ,


with

Ac = -

1 ln 1 - A co Wt W

(F.143)

E Es Et I t Ac

= =

Young’s Modulus (ksi), Secant Modulus (ksi),

= = = =

Tangent Modulus (ksi), Stress (ksi), The length of the time period being evaluated (hr), and Creep strain at the end of the time period being evaluated.

F.7.4

Isochronous Stress-Strain Curves

F.7.4.1

Sources for isochronous stress-strain curves for various materials for components operating at high temperatures are provided in paragraph F.8.2. Isochronous stress-strain curves may be required to evaluate the remaining life of a component operating at high temperature. These curves are particularly useful in evaluating the creep buckling potential of a component.

F.7.4.2

Isochronous stress-strain curves may be calculated by solving the Omega expressions in paragraph F.7.3 when stresses are low and primary creep can be neglected. Since 9 and A co are functions of the stress and temperature, specification of time of interest yields a closed form equation for an isochronous stress-strain curve, or

A=

I 1 - ln 1 - A co Wt E W

(F.144)

where,

E 9 t A A co F.7.5

= = = = =

Young’s Modulus (ksi), Omega uniaxial damage parameter, The length of the time period being evaluated (hr), Elastic plus creep strain, and Initial creep strain rate at the start of the time period being evaluated based on the stress state and temperature.

Creep Regime Fatigue Curves (Crack Initiation) Sources for fatigue curves (crack initiation) for various materials for components operating in the creep regime are provided in paragraph F.8.7.

F.7.6

Creep Crack Growth Data

F.7.6.1

Crack growth data may be required to evaluate the remaining life of a component operating at high temperature containing a crack. The creep crack growth rate can be correlated to the creep fracture mechanics parameter

C * ( Ct or C (t ) can also be used) by the following equation:

da = D( C * ) B dt


(F.145)

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--``````-`-`,,`,,`,`,,`---

where variables are defined above and,


where,

da dt C* D B F.7.6.2

=

Crack growth rate (mm/hr:in/hr),

= = =

Crack driving force (N/mm -mm-hr:ksi-in-hour), Coefficient of crack growth equation (material and temperature dependent), Exponent of crack growth equation (material and temperature dependent, usually between 0.70 and 1.0).

2

*

If the crack driving force is in terms of C , the following crack growth relationship can be used to estimate the crack growth for a wide range of materials.

c h

* da 3 C = dt A *f

0.85

(F.146)

where,

da dt C* A *f

=

Crack growth rate (mm/hr:in/hr),

=

Crack driving force (N/mm -mm-hr:ksi-in-hour),

=

Creep ductility appropriate to the state of stress at the crack tip. For plane stress

2

conditions it is taken equal to the uniaxial creep failure strain, strain conditions F.7.6.3

A f , and for plain

A f 50 .

The equation in paragraph F.7.6.2 has been used for remaining life assessment for high temperature components. However, the fracture strain in this model can be difficult to estimate for an in-service component where only limited materials data is available. In addition, the model does not provide a means to consider prior and ongoing damage in the material where the crack will grow. Another creep crack growth relationship, based on MPC Project Omega Methodology, that has been used is shown below.

b g

da W = Ct dt 500

n n +1

(F.147)

with,

LMF t I FGH IJK OP C =C G MNH t JK + 1PQ F A IJ K C =G H 1- D - D K I *

t

relax

n-3 n -1

bc

t relax

2 I

ref

*

(F.148)

ac

(F.149)

ref

0.91K I2 = n + 1 EC *

(F.150)

ti Libc

(F.151)

b g

Dbc = å //^:^^#^~^^""~:@":^*^~$~"#:*~^~$

--``````-`-`,,`,,`,`,,`---


Not for Resale


Dac = å

ti Liac

(F.152)

where,

da dt Ct

=

Local creep crack growth rate (in/hour),

=

Crack driving force related to the expansion of the creep zone (ksi-in-hour),

C Dbc

= =

Dac

=

E KI

= =

Crack driving force associated with global steady-state creep (ksi-in-hour), Local creep damage before the initiation of the crack, the damage is computed using the net section stress considering the pre-crack loading history, Local creep damage after the crack initiates, the damage is computed using the reference stress (see Appendix D) considering the post-crack loading history, Modulus of elasticity (ksi), Mode I stress intensity factor (see Appendix C) (ksivin),

Liac

=

Rupture time for the loading history after initiation of the crack applied for time

*

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increment

Libc

t i computed using the references stress (see paragraph F.7.3) (hours),

=

Rupture time for the loading history before initiation of the crack applied for time

n t ti trelax A ref

= =

increment t computed using the net section stresses (see paragraph F.7.3) (hours), Norton coefficient evaluated at the reference stress in the current load increment, Current time after initiation of the crack (hour),

= =

Time increment or load duration for use in the damage calculation (hour), Relaxation term in the crack driving force (hour),

=

Creep strain rate,

I ref 9

=

Reference stress (see Appendix D) (ksi), and

=

Uniaxial damage parameter computed using the reference stress considering the post-crack loading history (see paragraph F.7.3).

i

A co , evaluated at the reference stress (see paragraph F.7.3),

*

F.7.6.4

Data sources for creep crack growth data for C and other measures of the crack driving force (e.g. Ct or C (t ) ) for various materials are provided in paragraph F.8.6. Alternatively, if the MPC Project Omega Methodology is used for an assessment, then all required material parameters can be computed from the MPC Omega data coefficients in Table F.12 (see paragraph F.7.6.3).

F.8

References

F.8.1

Technical References

F.8.1.1

Anderson, T.L., “Fracture Mechanics – Fundamentals and Applications,” 2nd Edition, CRC Press, Boca Raton, Florida, 1995.

F.8.1.2

Anderson, TL, Merrick, R.D., Yukawa, S., Bray, D.E., Kaley, L. and Van Scyoc, K., “Fitness-ForService Evaluation procedures for Operating Pressure Vessels, Tanks, and Piping in Refinery and Chemical Service,” FS-26, Consultants’ Report, MPC Program on Fitness-For-Service, Draft 5, The Materials Properties Council, New York, N.Y., October, 1995.

F.8.1.3

API, “Characterization Study of Temper Embrittlement of Chromium-Molybdenum Steels,” API Publication 959, American Petroleum Institute, Washington, D.C., 1982.

F.8.1.4

Avallone, E.A., and Baumeister, T, “Marks’ Standard Handbook for Mechanical Engineers,” Ninth Edition, McGraw-Hill, New York, N.Y., 1978.

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Not for Resale


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F.8.1.5

Barsom, J.M. and Vecchio, R.S., “Fatigue of Welded Components,” WRC Bulletin 422, Welding Research Council, New York, N.Y., June, 1997.

F.8.1.6

Booth, G.S., “Improving the Fatigue Strength of Welded Joints By Grinding,” Metal Construction, 18, (7), 1986, pp 432-437.

F.8.1.7

Bockrath, G. and Glassco, J., “Fatigue and Fracture Mechanics of High Risk Parts – Application of LEFM & EMDM Theory,” Chapman & Hall, New York, N.Y., 1997.

F.8.1.8

McEvily, Jr., A.J. and Wei, R.P., “Corrosion Fatigue: Chemistry, Mechanics and Microstructure,” NACE, 1972, pp. 381-395.

F.8.1.9

Eiber, R.J., “Investigation of the Initiation and Extent of Ductile Pipe Rupture,” Battelle Report to USAEC, BMI-1908, June, 1971.

F.8.1.10 Ellyin, F., “Fatigue Damage Crack Growth and Life Prediction,” Chapman & Hall, Boundary Row, London 1997. F.8.1.11 Engineering Sciences Data, Fatigue Endurance Data Sub-series, 3, Stress Concentrations, ESDU International Ltd., London. F.8.1.12 EPRI, “Evaluation of Flaws in Austenitic Steel Piping, "EPRI NP-4690-SR, Electric Power Research Institute, Palo Alto, CA, July, 1986. F.8.1.13 EPRI, “Evaluation of Flaws in Ferritic Piping, "EPRI NP-6045, Electric Power Research Institute, Palo Alto, CA, October, 1988. F.8.1.14 Grosse-Wordemann, J. and Dittrich, S., ”Prevention of Temper Embrittlement in 2 ¼ Cr -1Mo Weld Metal by metallurgical Actions,” Welding Research Supplement, may, 1983, pp. 123-128. F.8.1.15 Gurney, T.R. and Maddox, S.J., “A Re-Analysis of Fatigue Data for Welded Joints in Steel,” Welding Research Int. 3, (4), 1972. F.8.1.16 Gurney, T.R., “Fatigue of Welded Structures,” Cambridge University Press, 1979.

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F.8.1.17 Harrison, J.D. and Maddox, S.J., “A Critical Examination of Rules for the Design of Pressure Vessels Subject to Fatigue Loading,” Proc. 4th Int. Conf. on Pressure Vessel Technology, I.Mech.E., 1980 (or IIW Doc. XIII-941-80, 1980). F.8.1.18 IIW, “Fatigue Design Of Welded Joints And Components,” A. Hobbacher, Abington Publishing, Abington Hall, Abington, Cambridge, England, 1996 F.8.1.19 IIW, “Stress Determination For Fatigue Analysis Of Welded Components,” Ed. E. Niemi, Abington Publishing, Abington Hall, Abington, Cambridge, England, 1995. F.8.1.20 Liu, A.F., “Structural Life Assessment Methods,” ASM International, Materials Park, Ohio, 1998. F.8.1.21 Maddox, S.J., “Fatigue Strength of Welded Structures,” 2nd Ed., Abington Publishing, Cambridge, England, 1991. F.8.1.22 Maxey, W.A., “Brittle Fracture Arrest in Gas Pipelines,” AGA Report No. 135, Catalog No. L51436, April, 1983. F.8.1.23 McNicol, R.C., “Correlation of Charpy Test Results for Standard and Nonstandard Size Specimens,” WRC 385, September, 1965. F.8.1.24 Neuber, H., “Theory of Stress Concentrations for Shear Strained Prismatic Bodies with Arbitrary Nonlinear Stress-Strain Law,” Trans. ASME Journal of Applied Mechanics, 1969, p. 544. F.8.1.25 Phaal, R., Macdonald, K.A., and Brown, P.A., “Correlations Between Fracture Toughness and Charpy Impact Energy,” Report from the Co-operative Research Programme for Industrial Members Only, TWI Report 504/1994, The Welding Institute, Cambridge, U.K., 1994. F.8.1.26 Prager, M. and Ibarra, S., “Approaches to Long Term Life prediction of Furnace and Boiler Tubes,” Fitness For Adverse Environments in Petroleum and Power Equipment, PVP-Vol. 359, ASME, 1997, pp. 339-352. F.8.1.27 Prager, M., “Development of the MPC Project Omega Method for Life Assessment in the Creep Range,” PVP-Vol. 288, ASME, 1994, pp. 401-421.


Not for Resale


F.8.1.28 Prager, M., “The Omega Method – An Effective Method for Life and Damage Prediction in Creep Tests and Service,” Oikawa (eds.), Strength of Materials, Japan Institute of Metals, 1994, pp. 571574. F.8.1.29 Prager, M., “Proposed Implementation of Criteria for Assignment of Allowable Stresses in the Creep Range,” ASME Journal of Pressure Vessel Technology, May, 1996, Vol. 335, pp. 273-293. F.8.1.30 Prager, M., “Generation of Isochronous Creep, Tubing Life and Crack Growth Curves Using the MPC Omega Method, Structural Integrity,” NDE, Risk and Material Performance for Petroleum, process and Power, PVP-Vol. 336, ASEM, 1996, pp. 303-322. F.8.1.31 Roberts, R. and Newton, C., “Interpretive Report on Small Scale Test Correlations with KIc Data,” WRC Bulletin 265, Welding research Council, New, York, N.Y., February, 1981. F.8.1.32 Spence, J., and Tooth, A.S. (Ed), “Pressure Vessel Design, Concept and Principles,” E.&F.N. Spon, London, 1994. F.8.1.33 IIW, “Fifth Draft (January 1995) Of Proposed Detailed Fatigue Assessment Method Based On Draft Eurcode 3,” The Welding Institute, Abington Hall, Abington, Cambridge, England, 1995. F.8.1.34 Scott, P.M., Anderson, T.L., Osage, D.A., Wilkowski, G.M., “Review of Existing Fitness-For-Service Criteria For Crack-like Flaws,” WRC 430, Welding Research Council, New York, N.Y., 1998. F.8.1.35 Klehn, R. and Laughlin, C., “Chevron’s Experience Using Omega Method Creep Tests for Life Assessment of Refinery Equipment,” PVP-Vol. 288, ASME, 1994, pp. 345-350. F.8.1.36 Buchheim, G.M., Osage, D.A., Brown, R.G., and Dobis, J.D., “Failure Investigation of a Low Chrome Long-Seam Weld in a High-Temperature Refinery Piping System,” PVP-Vol. 288, ASME, 1994, pp. 363-386. F.8.1.37 Ibarra and Konet, R.R., “Life Assessment of 1 ¼ Cr-1/2 Mo Steel Catalytic Reformer Furnace Tubes Using the MPC Omega Method,” PVP-Vol. 288, ASME, 1994, pp. 387-400.

F.8.1.39 Barsom, J.M. and Rolfe, S.T., “Fracture and Fatigue Control in Structures, “ Second Edition, Prentice Hall, Englewood Cliffs, New Jersey, 1987. F.8.2

Yield Strength, Tensile Strength, Creep Rupture Strength and Creep Strain Rate Data

F.8.2.1

ASM, “Atlas of Creep and Stress-Rupture Curves,” ASM International, Metals Park, Ohio, 1988.

F.8.2.2

ASME, “Boiler and Pressure Vessel Code, Section II, Part D – Properties,” ASME Code Section II, Part D, ASME, New York, N.Y.

F.8.2.3

ASME, “Subsection NH – Class 1 Components in Elevated Temperature Service,” ASME Code Section III, Division 1, ASME, New York, N.Y.

F.8.2.4

ASTM, “An Evaluation of the Elevated Temperature Tensile and Creep-Rupture Properties of Wrought,” ASTM Data Series DS 11S1, American Society for Testing Materials, Philadelphia, Pa., 1970.

F.8.2.5

ASTM, “An Evaluation of the Yield, Tensile, Creep, and Rupture Strengths of Wrought 304, 316, 321, and 347 Stainless Steels at Elevated-Temperatures,” ASTM Data Series DS 5S2, American Society for Testing Materials, Philadelphia, Pa., 1969.

F.8.2.6

ASTM, “Elevated-Temperature Properties of Carbon Steels,” ASTM Special Technical Publication No. 180, American Society for Testing Materials, Philadelphia, Pa., 1955.

F.8.2.7

ASTM, “Evaluation of the Elevated Temperature Tensile and Creep-Rupture Properties of 1/2 Cr – 1/2 Mo, 1 Cr – 1/2 Mo, and 1 1/4 Cr – 1/2 Mo-Si Steels,” ASTM Data Series DS 50, American Society for Testing Materials, Philadelphia, Pa., 1973.

F.8.2.8

ASTM, “Evaluation of the Elevated-Temperature Tensile and Creep Rupture Properties of 3 to 9 Percent Chromium-Molybdenum Steels,” ASTM Data Series DS 58, American Society for Testing Materials, Philadelphia, Pa., 1971.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

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F.8.1.38 Kim, D.S. and Mead, H.E. “Remaining Life Assessment of Refinery Heater Tubes,” PVP-Vol. 388, ASME, 1999, pp. 361-366.

F.8.2.9

ASTM, “Evaluations of the Elevated Temperature Tensile and Creep-Rupture Properties of C-Mo, Mn-Mo and Mn-Mo-Ni Steels,” ASTM Data Series DS 47, American Society for Testing Materials, Philadelphia, Pa., 1971.

F.8.2.10 ASTM, “Evaluations of the Elevated-Temperature Tensile and Creep Rupture Properties of 12 to 27 Percent Chromium Steels,” ASTM Data Series DS 59, American Society for Testing Materials, Philadelphia, Pa., 1980. F.8.2.11 ASTM, “Report on Elevated-Temperature Properties of Chromium Steels (12 to 27 percent),” ASTM Special Technical Publication No. 228, American Society for Testing Materials, Philadelphia, Pa., 1958. F.8.2.12 ASTM, “Report on Elevated-Temperature Properties of Stainless Steels,” ASTM Special Technical Publication No. 124, American Society for Testing Materials, Philadelphia, Pa., 1952. F.8.2.13 ASTM, “Supplemental report on the Elevated-Temperature Properties of Chromium-Molybdenum Steels,” ASTM Data series DS 6S1, American Society for Testing Materials, Philadelphia, Pa., 1966. F.8.2.14 ASTM, “Supplemental Report on the Elevated-Temperature Properties of Chromium-Molybdenum Steels (AN Evaluation of 2 1/4 Cr – 1Mo Steel),” ASTM Data series DS 6S2, American Society for Testing Materials, Philadelphia, Pa., 1971. F.8.2.15 ASTM, “Supplemental Report on the Elevated-Temperature Properties of Chromium-Molybdenum Steels,” ASTM Special Technical Publication No. 151, American Society for Testing Materials, Philadelphia, Pa., 1953. F.8.2.16 ASTM, “The Elevated-Temperature Properties of Weld-Deposited Metal and Weldments,” ASTM Special Technical Publication No. 226, American Society for Testing Materials, Philadelphia, Pa., 1958. F.8.2.17 Atkins, D.F. and Schwartzbat, H., “Stress-Rupture Behavior of Welded and Decarburized Tubular 2 1/4 Cr – 1 Mo Steel,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 205-223. F.8.2.18 Blackburn, L.D., “Isochronous Stress-Strain Curves for Austenitic Stainless Steels," The Generation of Isochronous Stress-Strain Curves, American Society of Mechanical Engineers, New York, N.Y., 1972. F.8.2.19 Booker, M.K., “An Analytical Treatment of the Creep and Creep-Rupture Behavior of Alloy 800H,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 1-27. F.8.2.20 Booker, M.K., “Use of Generalized Regression Models for the Analysis of Stress-Rupture Data,” Characterization of Materials for Service at Elevated Temperatures,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 459-499. F.8.2.21 Ellis, F.V., “Time-Temperature Parameter Based Incremental Creep Equation for Finite Element Analysis,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 29-49. F.8.2.22 Holt, J.M., Mindlin, H., and Ho, C.Y., “Structural Alloys Handbook,” Volumes 1, 2 and 3, CINDAS/Purdue University, Potter Engineering Center, West Lafayette, IN, 1995. F.8.2.23 Jaske, C.E., “Consideration of Experimental Techniques Used in the Development of Long-Term Properties of Pressure Vessel and Piping Alloys,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 129-144. F.8.2.24 MEP, “High Temperature Design Data for Ferritic Pressure Vessel Steels,” The Creep of Steels Working Party of the Institute of Mechanical Engineers, Mechanical Engineering Publications, Ltd, London, . F.8.2.25 Sikka, V.K., Booker, M.K., and Brinkman, C.R., “Relationships Between Short-And Long-Term Mechanical Properties of Several Austenitic Stainless Steels,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 51-82. F.8.2.26 Schill, T.V. and Bassfor, T.H., “Extrapolation of Incoloy Alloy 800 Creep-Rupture Data at 500°C to 650°C,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 95-105. F.8.2.27 USS, “Steels for Elevated Temperature Service”, United States Steel Corporation. --``````-`-`,,`,,`,`,,`---


Not for Resale

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F.8.2.28 VanEcho, J.A. and Roach, D.B., “Investigation of Mechanical, Physical, and Creep Rupture Properties of Reformer Materials,” Battelle Technical Report on Materials for Steam Reformer Furnaces, Battelle, Columbus, Ohio, 1973. F.8.2.29 Viswanathan, R. and Gandy, D.W., “A Review of High Temperature Performance Trends and Design Rules for Cr-Mo Steel Weldments,” EPRI, Palo Alto, CA, 1998, TR-110807. F.8.3

Physical Properties

F.8.3.1

ASME, “Subsection NH – Class 1 Components in Elevated Temperature Service,” ASME Code Section III, Division 1, ASME, New York, N.Y.

F.8.3.2

Holt, J.M., Mindlin, H., and Ho, C.Y., “Structural Alloys Handbook,” Volumes 1, 2 and 3, CINDAS/Purdue University, Potter Engineering Center, West Lafayette, IN, 1995.

F.8.3.3

USS, “Steels for Elevated Temperature Service”, United States Steel Corporation.

F.8.4

Fracture Toughness Data

F.8.4.1

Holt, J.M., Mindlin, H., and Ho, C.Y., “Structural Alloys Handbook,” Volumes 1, 2 and 3, CINDAS/Purdue University, Potter Engineering Center, West Lafayette, IN, 1995.

F.8.4.2

Hudson, C.M. and Ferrainolo, J.J., “A Compendium of Sources of Fracture Toughness and Fatigue Crack Growth Data for Metallic Alloys – Part IV”, International Journal of Fracture, 48, 1991.

F.8.4.3

Hudson, C.M. and Seward, S.K., “A Compendium of Sources of Fracture Toughness and Fatigue Crack Growth Data for Metallic Alloys”, International Journal of Fracture, 14, 1978.

F.8.4.4

Hudson, C.M. and Seward, S.K., “A Compendium of Sources of Fracture Toughness and Fatigue Crack Growth Data for Metallic Alloys – Part II”, International Journal of Fracture, 20, 1982.

F.8.4.5

Hudson, C.M. and Seward, S.K., “A Compendium of Sources of Fracture Toughness and Fatigue Crack Growth Data for Metallic Alloys – Part III”, International Journal of Fracture, 39, 1989.

F.8.4.6

NASA, “Derivation of Crack Growth Properties of Materials for NASA/FLAGRO 2.0,” Volumes I, II, and III, JSC-26254, National Aeronautics and Space Administration, Houston, Texas, 1994.

F.8.4.7

NASA, “fatigue Crack Growth Computer Program NASGRO Version 3.00,” Revision B, JSC-22267B, National Aeronautics and Space Administration, Houston, Texas, September, 1998.

F.8.4.8

Iwadate, T., “Pressurization Temperature Of Pressure Vessels Made Of Cr-Mo Steels,” PVP-Vol. 288, ASME, 1994, pg. 155-163.

F.8.4.9

Yukawa, S., “Review and Evaluation of the Toughness of Austenitic Steels and Nickel Alloys After Long-Term Elevated Temperature Exposure,” WRC 378, The Welding Research Council, New York., N.Y., 1993.

F.8.4.10 Zahoor, A., “Ductile Fracture HandbookReview – Volume 3,” Electric Powr Research Institue, Palo Alto, CA, 1991. F.8.4.11 Orth, F.C. and Mohr, W.C., "Storage Tanks: Correlations Between Charpy Absorbed Energy and The Fracture Toughness of Storage Tank Steels," EWI Project No. J6117, EWI, December 4, 1995. F.8.5

Fatigue and Stress Corrosion Crack Growth Data

F.8.5.1

Cayard, M.S. and Kane, R.D., “Fitness-For-Service Metrologies for the Assessment of Equipment nd Containing Corrosion Induced Damage,” Plenary Lecture at the 2 NACE Latin American Region Corrosion Congress, Rio do Janeiro, Brazil, September, 1996.

F.8.5.2

ASM, “Atlas of Fatigue Curves,” American Society for Metals, Metals Park, Ohio, 1986.

F.8.5.3

ASM, “Atlas of Stress Corrosion and Corrosion Fatigue Curves,” ASM International, Metals Park, Ohio, 1990.

F.8.5.4

Barsom, J.M., “Fatigue Behavior of Pressure-Vessel Steels,” WRC Bulletin 194, Welding Research Council, New York, N.Y., May, 1974.

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F.8.5.5

BSI, “Guidance on Methods for Assessing the Acceptability of Flaws in Fusion Welded Structures,” BS PD6493, British Standards Institute, 1991.

F.8.5.6

BSI, “Guide on Methods For Assessing the Acceptability of Flaws in Structures,” BS 7910, British Standards Institute (Pending).

F.8.5.7

Mukherjee, B. and Vanderglas, M.L., “Fatigue Threshold Stress Intensity and Life Estimation of ASTM A 106B Piping Steel,” Vol. 201., Transactions of the ASME, ASME, New York, N.Y., August, 1980, pp. 294-302.

F.8.5.8

NASA, “Derivation of Crack Growth Properties of Materials for NASA/FLAGRO 2.0,” Volumes I, II, and III, JSC-26254, National Aeronautics and Space Administration, Houston, Texas, 1994.

F.8.5.9

NASA, “Fatigue Crack Growth Computer Program NASGRO Version 3.00,” Revision B, JSC-22267B, National Aeronautics and Space Administration, Houston, Texas, September, 1998.

F.8.5.10 Woollin, P. and Tubby, P.J., “Fatigue Crack Propagation in C-Mn Steel HAZ Microstructures Tested in Air and Seawater,” TWI, 526/1995, Abington Hall, Abington, Cambridge, UK, November, 1995. F.8.5.11 Vosikovsky, O., Macecek, M. and Ross, D.J., “Allowable Defect Sizes in a Sour Crude Oil Pipeline for Corrosion Fatigue Conditions”, International Journal of Pressure Vessels & Piping, 13, pp. 197-226, 1983. F.8.5.12 Iwadate, T., Watanabe, J., and Tanaka, Y., “Prediction of the Remaining Life of HighTemperature/Pressure Reactors Made of Cr-Mo Steels,” Transactions of the ASME, Vol. 107, ASME, New York, N.Y., August, 1985, pp. 230-238. F.8.5.13 Barsom, J.M., “Fatigue Behavior of Pressure-Vessel Steels,” WRC Bulletin 194, Welding Research Council, New York, N.Y., May 1974. F.8.5.14 Woollin, P. and Tubby, P.J., “Fatigue Crack Propagation in C-Mn Steel HAZ Microstructures Tested in Air and Seawater,” TWI Report 526/1995, TWI, Cambridge, UK, November, 1995. F.8.5.15 Parkins, R.N. and Foroulis, Z.A., “The SCC of Mild Steel in Monoethanolamine Solutions,” Corrosion/87, Paper No. 188, NACE International, March, 1987. --``````-`-`,,`,,`,`,,`---

F.8.5.16 Parkins, R.N., “Slow Strain Rate Testing – 25 Years Experience,” Slow Strain Rate Testing for Evaluation of Environmentally Induced Cracking: Research and Engineering Applications, Ed. R.D. Kane, STP 1210, ASTM, W. Conshohocken, PA, 1993, pp. 7-21. F.8.5.17 Saiolu, F. and Doruk, M., “Correlation Between Yielding Fracture Mechanics Parameters and the Crack Growth Rate of Low Strength Steel in 2N(NH4)2CO3 at 75 C,” International Congress of Metallic Corrosion, Vol. 1, 1984. F.8.5.18 Slater, J.E., “An Approach to Reliability Analysis of Cracked Continuous Digesters,” Corrosion/82, Paper No. 92, NACE International, March, 1982. F.8.5.19 Speidel, M.O., “Stress Corrosion Cracking of Stainless Steels in NaCl Solutions,” Metallurgical Transactions, Vol. 12A, ASM International, May, 1981, pp. 779-789. F.8.5.20 Iwadate, T., “Hydrogen Effect on Remaining Life of Hydroprocessing Reactors,” Corrosion, Vol. 44, NACE International, February, 1988, pp. 103-112. F.8.5.21 Cayard, M.S. and Kane, R.D., Kaley, L., and Prager, M., “Research Report on Characterization and Monitoring of Cracking in Wet H2S Service,” Publication 939, American Petroleum Institute, October, 1994. F.8.5.22 Kane, et al., Slow Strain Rate Testing for Evaluation of Environmentally Induced Cracking: Research and Engineering Applications, Ed. R.D. Kane, STP 1210, ASTM, W. Conshohocken, PA, 1993, pp. 181-192. F.8.6

Creep Crack Growth Data

F.8.6.1

BSI, “Guide on Methods For Assessing the Acceptability of Flaws in Structures,” BS 7910, British Standards Institute (Pending).


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


F.8.6.2

Buchheim, G.M., Becht, C., Nikbin, K.M, Dimopolos, V., Webster, G.A., and Smith D.J., “Influence of Aging on High-Temperature Creep Crack Growth in Type 304H Stainless Steel,” Nonlinear Fracture Mechanics, ASTM STP 995, Volume 1, The American Society of Testing and Materials, Pa, 1988, pp. 153-172.

F.8.6.3

Dimopulos, V., Nikbin, K.M., and Webster, G.A., “Influence of Cyclic to Mean Load Ratio on Creep/Fatigue Crack Growth,” Metallurgical Transactions A, Volume 19A, pp. 873-880, May 1988.

F.8.6.4

Hollstein, T and Voss, B., “Experimental Determination of the High-Temperature Crack Growth Behavior of Incoloy 800H,” Nonlinear Fracture Mechanics, ASTM STP 995, Volume 1, The American Society of Testing and Materials, Pa, 1988, pp. 195-213.

F.8.6.5

Konosu, S. and Maeda, K., “Creep Embrittlement Susceptibility and Creep Crack Growth Behavior in Low-Alloy Steels: An Assessment of the Effects of Residual Impurity Elements and Postweld Heat Treatment Condition on Creep Ductility and Crack Growth,” Nonlinear Fracture Mechanics, ASTM STP 995, Volume 1, The American Society of Testing and Materials, Pa, 1988, pp. 127-152.

F.8.6.6

Liaw, P.K., Rao, G.V., and Burke, M.G., “Creep Fracture Behavior of 2 1/4 Cr – 1 Mo Welds from a 31- Year-Old Fossil Power Plant,” Materials Science and Engineering, A131, pp. 187-201, 1991.

F.8.6.7

Liaw, P.K., Saxena, A., and Schaefer, J., “Estimating Remaining Life of Elevated-Temperature Steam Pipes-Part I. Materials Properties,” Engineering Fracture Mechanics, Vol. 32, No. 5, pp. 675-708, 1989.

F.8.6.8

Nikbin, K.M., Smith, D.J., and Webster, G.A., “An Engineering Approach to the Prediction of Creep Crack Growth,” Journal of Engineering Materials and Technology, Vol. 108, The American Society of Mechanical Engineers, pp. 186-191, April 1986.

F.8.6.9

Sadananda, K. and Shahinian, P, “Effect of Specimen Thickness on Crack Growth Behavior in Alloy 718 Under Creep and Fatigue Conditions,” MPC-7, The American Society of Mechanical Engineers, New York, N.Y., 1978, pp. 107-127.

F.8.6.10 Saxena, A., Han, J., and Banerji, K, “Creep Crack Growth Behavior in Power Plant Boiler and Steam Pipe Steels,” Journal of Pressure Vessel Technology, The American Society of Mechanical Engineers, Vol. 110, pp. 137-146, May, 1988. --``````-`-`,,`,,`,`,,`---

F.8.6.11 Webster, G.A., “Lifetime Estimates of Cracked High Temperature Components,” International Journal of Pressure Vessels & Piping, 50, pp. 133-145, 1992. F.8.7

Fatigue Curves (Crack Initiation) for Components Operating in the Creep Regime

F.8.7.1

Austin, T.S.P. and Webster, G.A., “Application of a Creep-Fatigue Crack Growth Model to Type 316 Stainless Steel”, ESIS Publication 15, Behavior of Defects at High Temperatures, Mechanical Engineering Publications Limited, London, 1993.

F.8.7.2

Okazaki, M., Hashimoto, M., and Mochizuki, T., “Creep-Fatigue Strength of Long-Term Post-Service 2 1/4 Cr – 1 Mo Steel and Remaining Life Estimation,” Journal of Pressure Vessel Technology, Vol. 119, The American Society of Mechanical Engineers, pp. 549-555, 1991.

F.9

Tables and Figures


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Table F.1 Approximate Equivalent Hardness Number and Tensile Strength for Carbon and Low Alloy Steels in the Annealed, Normalized, and Quenched-and-Tempered Conditions Vickers Hardness No.

Approximate Tensile Strength

(3000 kg load)

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

441 433 425 415 405 397 388 379 369 360 350 341 331 322 313 303 294 284 280 275 270 265 261 256 252 247 243 238 233 228 219 209 200 190 181 171 162 152 143 133 124 114


(MPa) 470 460 450 440 430 420 410 400 390 380 370 360 350 340 330 320 310 300 295 290 285 280 275 270 265 260 255 250 245 240 230 220 210 200 190 180 170 160 150 140 130 120

1572 1538 1496 1462 1413 1372 1331 1289 1248 1207 1172 1131 1096 1069 1034 1007 979 951 938 917 903 889 876 855 841 827 807 793 779 765 731 696 669 634 607 579 545 517 490 455 427 393

Not for Resale

(ksi) 228 223 217 212 205 199 193 187 181 175 170 164 159 155 150 146 142 138 136 133 131 129 127 124 122 120 117 115 113 111 106 101 97 92 88 84 79 75 71 66 62 57

--``````-`-`,,`,,`,`,,`---

Brinell Hardness No.

--``````-`-`,,`,,`,`,,`---

Table F.2 MPC Yield and Tensile Data Yield and Tensile Parameter Constants (1), (2)

A0

A1

A2

A3

A4

A5

Carbon Steel with

I ys

3.5597435E-02

-5.5648438E-04

1.2182325E-06

-1.8210422E-09

1.2840057E-12

-3.7019131E-16

I ys £ 40 ksi

I uts

-3.1558675E-02

7.9423823E-04

-6.2091189E-06

1.5915891E-08

-1.6369700E-11

5.6191204E-15

C-1/2Mo

I ys

3.1111810E-02

-5.1713330E-04

1.3656653E-06

-1.9196382E-09

1.6006149E-12

-6.6169444E-16

I uts

5.7801897E-02

-8.0842027E-04

1.1756835E-06

8.7008977E-11

-6.7722618E-13

3.6235837E-17

1-1/4Cr-1/2Mo

I ys

3.1111810E-02

-5.1713330E-04

1.3656653E-06

-1.9196382E-09

1.6006149E-12

-6.6169444E-16

Annealed

I uts

5.7801897E-02

-8.0842027E-04

1.1756835E-06

8.7008977E-11

-6.7722618E-13

3.6235837E-17

1-1/4Cr-1/2Mo

I ys

4.5732479E-02

-7.3532107E-04

2.3268109E-06

-3.9803980E-09

3.4450521E-12

-1.2741522E-15

N&T

I uts

3.2332577E-02

-4.7810813E-04

7.7091662E-07

-7.8371239E-11

-5.6239737E-13

1.1351646E-16

2-1/4Cr-1Mo

I ys

3.1111810E-02

-5.1713330E-04

1.3656653E-06

-1.9196382E-09

1.6006149E-12

-6.6169444E-16

Annealed

I uts

5.7801897E-02

-8.0842027E-04

1.1756835E-06

8.7008977E-11

-6.7722618E-13

3.6235837E-17

2-1/4Cr-1Mo

I ys

4.5732479E-02

-7.3532107E-04

2.3268109E-06

-3.9803980E-09

3.4450521E-12

-1.2741522E-15

N&T

I uts

3.2332577E-02

-4.7810813E-04

7.7091662E-07

-7.8371239E-11

-5.6239737E-13

1.1351646E-16

2-1/4Cr-1Mo

I ys

4.5732479E-02

-7.3532107E-04

2.3268109E-06

-3.9803980E-09

3.4450521E-12

-1.2741522E-15

Q&T

I uts

3.2332577E-02

-4.7810813E-04

7.7091662E-07

-7.8371239E-11

-5.6239737E-13

1.1351646E-16

F-50

Not for Resale

Parameter


Material

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


2-1/4Cr-1Mo -V

3Cr-1Mo

5Cr-1/2Mo

9Cr-1Mo

9Cr-1Mo-V

Type 304

Type 310

Type 316

A1

A2

A3

A4

A5

I ys

4.5732479E-02

-7.3532107E-04

2.3268109E-06

-3.9803980E-09

3.4450521E-12

-1.2741522E-15

I uts

3.2332577E-02

-4.7810813E-04

7.7091662E-07

-7.8371239E-11

-5.6239737E-13

1.1351646E-16

I ys

3.1111810E-02

-5.1713330E-04

1.3656653E-06

-1.9196382E-09

1.6006149E-12

-6.6169444E-16

I uts

5.7801897E-02

-8.0842027E-04

1.1756835E-06

8.7008977E-11

-6.7722618E-13

3.6235837E-17

I ys

3.1111810E-02

-5.1713330E-04

1.3656653E-06

-1.9196382E-09

1.6006149E-12

-6.6169444E-16

I uts

5.7801897E-02

-8.0842027E-04

1.1756835E-06

8.7008977E-11

-6.7722618E-13

3.6235837E-17

I ys

3.1111810E-02

-5.1713330E-04

1.3656653E-06

-1.9196382E-09

1.6006149E-12

-6.6169444E-16

I uts

5.7801897E-02

-8.0842027E-04

1.1756835E-06

8.7008977E-11

-6.7722618E-13

3.6235837E-17

I ys

4.5732479E-02

-7.3532107E-04

2.3268109E-06

-3.9803980E-09

3.4450521E-12

-1.2741522E-15

I uts

3.2332577E-02

-4.7810813E-04

7.7091662E-07

-7.8371239E-11

-5.6239737E-13

1.1351646E-16

I ys

5.9527714E-02

-8.0108408E-04

8.8839967E-07

-6.7959435E-10

4.1633275E-13

-1.5462208E-16

I uts

6.4030209E-02

-9.7162665E-04

1.9728243E-06

-2.0912533E-09

1.2474493E-12

-3.7877139E-16

I ys

3.1508900E-02

-4.2692059E-04

1.7583667E-07

-8.1181739E-11

2.4384222E-13

-1.4829637E-16

I uts

6.7869440E-02

-1.0196125E-03

2.4225259E-06

-2.5773233E-09

1.2780471E-12

-2.9903240E-16

I ys

5.9527714E-02

-8.0108408E-04

8.8839967E-07

-6.7959435E-10

4.1633275E-13

-1.5462208E-16

I uts

6.7869440E-02

-1.0196125E-03

2.4225259E-06

-2.5773233E-09

1.2780471E-12

-2.9903240E-16

F-51

Not for Resale

A0

--``````-`-`,,`,,`,`,,`---

Parameter


Material


Type 316L

Type 321

Type 347

Alloy 800

Alloy 800H

Alloy 800HT

HK-40

A1

A2

A3

A4

A5

I ys

4.1417585E-02

-5.1405646E-04

-6.6183360E-07

2.8413154E-09

-3.0591105E-12

1.0751230E-15

I uts

4.4688237E-02

-6.5031112E-04

7.0857418E-07

6.5556837E-10

-1.4959792E-12

5.9465927E-16

I ys

3.1508900E-02

-4.2692059E-04

1.7583667E-07

-8.1181739E-11

2.4384222E-13

-1.4829637E-16

I uts

6.7869440E-02

-1.0196125E-03

2.4225259E-06

-2.5773233E-09

1.2780471E-12

-2.9903240E-16

I ys

3.1508900E-02

-4.2692059E-04

1.7583667E-07

-8.1181739E-11

2.4384222E-13

-1.4829637E-16

I uts

6.4030209E-02

-9.7162665E-04

1.9728243E-06

-2.0912533E-09

1.2474493E-12

-3.7877139E-16

I ys

3.4120476E-02

-5.4130027E-04

1.3532761E-06

-2.1291045E-09

1.6415489E-12

-4.9097668E-16

I uts

6.0469152E-02

-1.0856404E-03

4.1838363E-06

-7.5370902E-09

6.4648009E-12

-2.1585616E-15

I ys

2.3820566E-02

-3.3308410E-04

2.5629373E-07

-5.0382511E-10

5.7964773E-13

-2.3034381E-16

I uts

6.4682817E-02

-1.1795504E-03

4.7979861E-06

-9.2240164E-09

8.3640451E-12

-2.8838762E-15

I ys

2.3820566E-02

-3.3308410E-04

2.5629373E-07

-5.0382511E-10

5.7964773E-13

-2.3034381E-16

I uts

6.4682817E-02

-1.1795504E-03

4.7979861E-06

-9.2240164E-09

8.3640451E-12

-2.8838762E-15

I ys

7.8963366E-02

-1.2373209E-03

2.4983476E-06

-2.8401946E-09

1.6893116E-12

-4.0807498E-16

I uts

7.1604868E-02

-1.1820289E-03

2.5261369E-06

-2.2528977E-09

8.1118531E-13

-1.2119101E-16

F-52 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Not for Resale

A0


Parameter

--``````-`-`,,`,,`,`,,`---

Material

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes For Table F.2: 1. Units for the equations in this table are as follows: 2.

I ys and I uts are in ksi and the temperature, T , is in degrees Fahrenheit.

I ys is the value of the yield stress at temperature where I rtys is the value of the yield stress (minimum, average, or maximum as applicable) at room temperature.

I ys = I rtys 10 M

(F.153)

where

M = A0 + A1T + A4 T 2 + A4 T 3 + A4 T 4 + A5T 5 3.

(F.154)

I uts is the value of the ultimate tensile stress at temperature where I rtuts is the value of the ultimate tensile stress (minimum, average, or maximum as applicable) at room temperature.

I ut = I rtut 10 M

(F.155)

M = A0 + A1T + A4 T 2 + A4 T 3 + A4 T 4 + A5T 5

(F.156)

4. Temperature limitations for the equations in this table are defined in the following below: Classification

Lower Temperature Limit

Upper Temperature Limit

Ferritic Materials

70°F

1100°F

Austenitic Stainless and Nickel Base Alloys

70°F

1500°F

Not for Resale

where

--``````-`-`,,`,,`,`,,`---

F-53


5. The yield and tensile strength values tabulated in the ASME Code, Section II, Part D for elevated temperature may differ from the values derived using the temperature trend coefficient, M , derived from the coefficients in this table when the room temperature yield and tensile strength value from the Code is used. This difference is associated with the robust nature used in performing the regression of the yield and tensile strength data.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table F.3 Minimum Values Of Yield And Tensile Strength From API RP530

Low Carbon Steel (Figure 4A) A161 A192 Medium Carbon Steel (Figure 4B) A53 Grade B A106 Grade B

Parameter

Coefficients For Yield And Tensile Stress Data

Ao

A1

A2

A3

A4

A5

I ys

1.6251089E+00

-3.3124966E-03

5.0904910E-06

-3.3374441E-09

4.9690402E-13

0.0000000E+00

I uts

1.1720989E+00

-2.0580032E-03

7.6239020E-06

-9.9459690E-09

3.7189699E-12

0.0000000E+00

I ys

1.6434698E+00

-3.5201715E-03

5.8080277E-06

-4.2398160E-09

8.7536764E-13

0.0000000E+00

I uts

1.1872106E+00

-2.2083065E-03

8.0934859E-06

-1.0510434E-08

3.9529036E-12

0.0000000E+00

I ys

1.0875314E+00

-2.1270293E-04

-4.4780776E-07

8.4688943E-10

-5.6614129E-13

0.0000000E+00

I uts

-8.3107781E-02

6.7591546E-03

-1.3556423E-05

1.1122871E-08

-3.5429684E-12

0.0000000E+00

I ys

1.1345901E+00

-4.8648764E-04

3.9401132E-08

4.2209296E-10

-3.8709072E-13

0.0000000E+00

I uts

1.7526113E+00

-7.0066393E-03

2.3037863E-05

-3.2685799E-08

2.0963053E-11

-5.2442438E-15

A210 Grade A-1 C-1/2Mo (Figure 4C) A 161 T1 A 209 T1

Not for Resale

Materials

1-1/4Cr-1/2Mo (Figure 4D) A 213 T11 A 335 P11 A 200 T11

--``````-`-`,,`,,`,`,,`---

F-54


A 335 P1

--``````-`-`,,`,,`,`,,`---

Materials

2-1/4Cr-1Mo (Figure 4E) A 213 T22 A 335 P22

Parameter

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table F.3 Minimum Values Of Yield And Tensile Strength From API RP530 Coefficients For Yield And Tensile Stress Data

Ao

A1

A2

A3

A4

A5

I ys

1.2398072E+00

-1.5494280E-03

3.2430371E-06

-2.3756026E-09

3.1331338E-13

0.0000000E+00

I uts

2.0398036E+00

-7.5239262E-03

1.7967199E-05

-1.6168512E-08

4.6189330E-12

0.0000000E+00

I ys

1.3109507E+00

-1.8522910E-03

3.3285320E-06

-2.1885193E-09

2.7268140E-13

0.0000000E+00

I uts

1.2922744E+00

-1.7583742E-03

3.5081428E-06

-2.9914715E-09

6.7845610E-13

0.0000000E+00

I ys

1.1392352E+00

-1.3518395E-03

4.3886534E-06

-5.1308445E-09

1.6914766E-12

0.0000000E+00

I uts

1.2563698E+00

-1.9619215E-03

5.1583250E-06

-5.4836935E-09

1.7207470E-12

0.0000000E+00

I ys

1.2324252E+00

-1.6940271E-03

4.3681713E-06

-4.8983328E-09

1.6079702E-12

0.0000000E+00

I uts

1.2773067E+00

-2.3196405E-03

6.5893951E-06

-7.2379937E-09

2.3466718E-12

0.0000000E+00

I ys

6.9288533E-01

3.4867283E-03

-1.3498948E-05

2.2065464E-08

-1.6085361E-11

4.1090437E-15

I uts

9.9596073E-01

2.4796284E-05

3.3129703E-07

-1.4772664E-09

6.5165864E-13

0.0000000E+00

3Cr-1Mo (Figure 4F) A 213 T5 A 335 P5 A 200 T5 5Cr-1/2Mo (Figure 4G) A 213 T5 A 335 P5

Not for Resale

A 200 T22

5Cr-1/2Mo-Si (Figure 4H) A 213 T5b A 335 P5b 7Cr-1/2Mo (Figure 4I) A 213 T7 A 335 P7 A 200 T7

F-55


A 200 T5

Table F.3 Minimum Values Of Yield And Tensile Strength From API RP530 Materials

9Cr-1Mo (Figure 4J) A 213 T9 A 335 P9

Parameter


Ao

A1

A2

A3

A4

A5

I ys

1.3645782E+00

-2.4184891E-03

5.3798831E-06

-5.0826095E-09

1.4540216E-12

0.0000000E+00

I uts

1.6002250E+00

-3.8196855E-03

8.1545162E-06

-7.4536524E-09

2.1749553E-12

0.0000000E+00

I ys

1.1559737E+00

-1.3027523E-03

3.6718335E-06

-3.9082343E-09

1.1136278E-12

0.0000000E+00

I uts

1.3561147E+00

-2.5814516E-03

6.4611130E-06

-6.6563640E-09

2.0875274E-12

0.0000000E+00

I ys

1.6894159E+00

-3.3500871E-03

6.0887433E-06

-6.3277196E-09

3.4413453E-12

-7.8762940E-16

I uts

1.2907427E+00

-1.8958334E-03

4.2634694E-06

-3.7649126E-09

9.8390933E-13

0.0000000E+00

I ys

1.3224680E+00

-8.7683155E-04

-1.3646107E-07

8.9906963E-10

-4.2098578E-13

0.0000000E+00

I uts

1.2454373E+00

-1.6314830E-03

3.7350778E-06

-3.3393727E-09

8.7044694E-13

0.0000000E+00

9Cr-1Mo-V (Figure 4K) A 213 T91 A 335 P91

Not for Resale

A 200 T9

Type 304&304H (Figure 4L) A 213 Type 304&304H A 271 Type 304&304H A 312 Type 304&304H

--``````-`-`,,`,,`,`,,`---

A 200 T91

Type 316&316H (Figure 4M) A 213 Type 316&316H A 271 Type 316&316H


A 376 Type 304&304H

A 312 Type 316&316H A 376 Type 316&316H

F-56 //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table F.3 Minimum Values Of Yield And Tensile Strength From API RP530

(Figure 4N) A 213 Type 316L A 312 Type 316L Type 321 (Figure 4O) A 213 Type 321 A 271 Type 321


Ao

A1

A2

A3

A4

A5

I ys

1.6764367E+00

-2.7911113E-03

3.5200992E-06

-2.0849191E-09

3.9274747E-13

0.0000000E+00

I uts

1.4209808E+00

-2.3830395E-03

4.6717029E-06

-3.7247428E-09

9.0385624E-13

0.0000000E+00

I ys

1.6512149E+00

-2.5517760E-03

2.7303828E-06

-1.0524840E-09

3.6127158E-14

0.0000000E+00

I uts

1.1069812E+00

2.4195844E-04

-3.4616380E-06

7.9148731E-09

-6.6204087E-12

1.7648940E-15

I ys

1.5939147E+00

-2.2764479E-03

2.3000206E-06

-7.7700412E-10

-2.6637614E-14

0.0000000E+00

I uts

1.1972163E+00

-3.3091580E-04

-2.1198718E-06

6.4820833E-09

-5.9046170E-12

1.6286232E-15

I ys

1.3337499E+00

-7.4852863E-04

-8.1021768E-07

1.8974804E-09

-8.3958005E-13

0.0000000E+00

I uts

1.5437300E+00

-2.4368121E-03

3.3229020E-06

-1.5387323E-09

3.9373670E-14

0.0000000E+00

A 312 Type 321 A 376 Type 321 Type 321H (Figure 4P) A 213 Type 321H A 271 Type 321H

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Type 316L

Parameter

Not for Resale

Materials

A 312 Type 321H

Type 347&347H (Figure 4Q) A 213 Type 347&347H A 271 Type 347&347H A 312 Type 347&347H A 376 Type 347&347H

--``````-`-`,,`,,`,`,,`---

F-57


A 376 Type 321H

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table F.3 Minimum Values Of Yield And Tensile Strength From API RP530 Coefficients For Yield And Tensile Stress Data

A1

A2

A3

A4

A5

I ys

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

B407 Alloy 800H

I uts

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

HK-40

I ys

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

I uts

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

(see Note 2)

Alloy 800H (Figure 4R)

(Figure 4S) A608 Grade HK-40

--``````-`-`,,`,,`,`,,`---

Ao

F-58

Not for Resale

Parameter


Materials

--``````-`-`,,`,,`,`,,`---

Notes For Table F.3: 1. Data for tensile and yield strength in this table are from Figures 4-A through 4-S of API RP530 Calculation of Heater Tube Thickness in Petroleum Refineries. 2. Data for Figures 4R and 4S are not provided in RP 530. 3. Units for the equations in this table are as follows: I ys and I uts are in ksi and the temperature, T , is in degrees Fahrenheit. 4.

I ys is the value of the yield stress at temperature where I rtys is the value of the yield stress (minimum, average, or maximum as applicable) at the lower temperature limit defined in Note 6 below.

c

I ys = I rtys Ao + A1T + A2 T 2 + A3T 3 + A4 T 4 + A5T 5 5.

h

(F.157)

I uts is the value of the ultimate tensile stress at temperature where I rtuts is the value of the ultimate tensile stress (minimum, average, or maximum as applicable) at the lower temperature limit defined in Note 6 below.

c

rt I uts = I uts Ao + A1T + A2 T 2 + A3T 3 + A4 T 4 + A5T 5

h

(F.158)

Lower Temperature Limit

Upper Temperature Limit

A, B, C, D

300°F

1150°F

E, F, G, H, I, J

300°F

1350°F

K

300°F

1220°F

L, M, N, O, P

400°F

1550°F

N

400°F

1270°F

F-59


API RP 530Material Figure Identification

Not for Resale

6. Temperature limitations for the equations in this table are defined in the following below:

//^:^^#


Table F.4 Equivalent To The Minimum Of Three Tests Number of Fracture Toughness Tests

Equivalent To The Minimum Of Three Tests

3®5

Lowest value

6 ® 10

Second Lowest Value

11 ® 15

Third Lowest Value

16 ® 20

Fourth Lowest Value

21 ® 25

Fifth Lowest Vale

26 ® 30

Sixth Lowest Value

--``````-`-`,,`,,`,`,,`---


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Table F.5 J-R Tearing Resistance Curve Data Material

Temperature

Thickness

C

Ji

n

Reference

2

(F)

(in)

(in-lb/in )

(in-lb/in )

Generic CS-1

550

1.0

350

1808

0.277

F.8.4.10

Generic CS-2

550

1.0

600

2563

0.274

F.8.4.10

Generic CS-3

550

1.0

1050

5400

0.344

F.8.4.10

T 304 SS

75

1.0

6500

32758

0.519

F.8.4.10

Generic SS/SMAW

550

1.0

990

6033

0.391

F.8.4.10

Generic SS/SAW

550

1.0

650

4448

0.431

F.8.4.10

A508 Cl3

550

1.378

446

3443

0.329

F.8.4.10

A106 Gr B

120

0.54

2900

13008

0.334

F.8.4.10

75

0.34

8000

33642

0.435

F.8.4.10

2

(NPS 8 inch Pipe) TP 304 SS (NPS 4 inch pipe) Notes: 1. The values in this table represent typical values for the stated temperature and wall thickness, actual values should be used when available. 2. The equaton for the J-R curve is:

b g

J = C Da

n

(F.159)

--``````-`-`,,`,,`,`,,`---

//^:^^#^~


Not for Resale


Correlation

Sigma (1)

C0

C1

C2

C3

C4

C5

mean Kmat K IC

0

0.49920

-1.2103E-4

1.7924E-5

3.8591E-8

4.6627E-11

2.9800E-13

1

0.61401

2.2142E-4

2.1050E-5

5.9334E-8

8.3068E-11

2.9452E-13

2

0.74203

7.6452E-4

2.4899E-5

8.5761E-8

1.3869E-10

2.8014E-13

3

0.87961

1.5415E-4

2.9888E-5

1.1822E-7

2.1613E-10

2.7970E-13

0

0.36138

-1.2356E-3

6.1556E-6

3.8345E-9

-3.6769E-11

5.2537E-14

1

0.44397

-1.2400E-3

6.2434E-6

7.6693E-9

-4.0941E-11

5.1749E-14

2

0.53624

-1.1253E-3

6.1389E-6

1.1337E-8

-3.8371E-11

3.9580E-14

3

0.63577

-8.6564E-4

6.0413E-6

1.4613E-9

-3.0080E-11

5.8440E-14

mean Kmat K IR

Notes: 1. 2.

The number of standard deviations from the mean. The mean trend of the fracture toughness is taken as the medium master curve. The standard deviation on temperature used to determine the coefficients in this table is given in paragraph F.4.9.7. The equation for the mean-to-lower bound toughness ratio is: mean Kmat KI

= sigma

FG H C + C DT + C DT 0

1

2

2

10 . + C3 DT 3 + C4 DT 4 + C5DT 5

IJ K

(F.160)

where

DT = T - Tref 3.

The data in this table is valid for

(F.161)

d

i

-200o F £ T - Tref £ 400o F .

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table F.6 Correlations For The Mean-to-Lower Bound Fracture Toughness Ratio (1)

Jan, 2000

RECOMMENDED

PRACTICE

F-63


Table F.7 Estimation of the 27 J (20 ft-lb) Transition Temperature From Other Charpy Test Temperatures Oc (OF) Charpy lmapct Energy J (ft-lbs)

Difference Between Charpy Test Temperature and the 27 J (20 ft-lb) Charpy Transition Temperature -30 (-54)

I

-20 (-36)

10 (7.4)

-10 (-18)

18 (13.3)

-6.9 (-12.4)

Notes 1. 2.

5 (3.7)

I

I

20.3 (15)

0 (0)

27 (20)

10 (18)

41 (30.4)

20 (36)

61 (45.1)

I

I

The extrapolation method for in this table if taken from BS 7910. The extrapolation is valid for Charpy energy values of 5 Joules (3.7 ft - Zbs) I CVN I 61 Joules (45.1 ft - Ibs) . The downward limit to extrapolation from the 27 Joule transition temperature is -30°C, the upward limit is 20°C. These limit should be strictly adhered to as more modern day low carbon and/or low sulfur steels may have a steeper transition curve than that suggest by the equation. For Charpy values which exceed 61 J a maximum

3.

difference of 2o”c should be assumed. An example of the use of this information in this table is as follows: if 41 J is measured at I;,, =

4.

20°C, then (Z& -T,,,)

=

10°C and Z&J = -(lO’C-

rmt) = -3O’C.

The equation for the difference between the Charpy test temperature and the 27 J (20 ft-lb) Charpy transition temperature is:

Piest - T,J =

-40.676 + 1.49 11. CW 1+ 0.024956. CFW

(F.162)

where,

CVN AT

= =

Charpy impact energy (Joules), and Difference between the Charpy test temperature and the 27 Joule Charpy Transition Temperature (“C).

--``````-`-`,,`,,`,`,,`---



//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

K?st - T,,,)

Table F.8 Crack Growth Data For Use With The Bilinear

Fatigue

Service Environment

Lower Stage of Crack Growth Curve

Upper Stage of Crack Growth Curve

AK Transition

Mean Data

Mean Data

Between Lower and Upper Curves

R

caysI7OOMPa

R < 0.5 (101.5 hi)

Operating in air or other non-aggressive environments at temperatures up to 100°C

2.10E-14

Mean Data +20

n

G Steels with

Equation

G

8.16

7.59E-14

(1.79E-15)

R20.5

2.14E-10

n 8.16

(6.45E-15)

5.10

9.38E-10

(1.37E-11)

Cl 8.32E-9

Mean Data +2~

n

G

n

2.88

1.41 E-8

2.88

(4.29E-10)

5.10

1.22E-8

(7.31 E-l 0)

2.88

(6.32E-10)

(5.97E-11)

9.96

2.70E-8

(9.07)

2.88

4.55

(1.39E-9)

(4.14)

(212°F)

Steels with (T,,~ I6OOMPa

R < 0.5 (87

hi)

Operating in a freely corroding marine environment temperatures up to

4.05E-9

3.42

l.l5E-8

(2.20E-10)

R205

7.24E-9

3.42

(6.27E-10)

3.42

2.32E-8

(3.94E-10)

l.l3E-5

1.30

(5.04E-7)

3.42

(1.26E-9)

2.62E-5

1.72E-5

1.30

31.4

(28.6)

(7.66E-7)

1.11

3.37E-5

1.11

23.7

(1.47E-6)

(l.l5E-6)

(21.5)

20°C (68°F)

LNotes 1.

Units for crack growth data are: (mm /cycle,

2.

The threshold stress intensity factor may be taken as 2.0 APa&

3.

The conversion factor for fracture toughness

4.

In the above table, R = K,,,in/Km , where K,,,,

A4..a&)

is 1.098843 iMPa&

(1.82 ksi&z)

//^:^^#^~^^""~:@

Not for Resale

is for (i” / cycle, hi&)

for use with these data.

= 1.0 hi&.

and Kmi, are the maximum

--``````-`-`,,`,,`,`,,`---


. The crack growth data within the parenthesis

and minimum

stress intensity for a given cycle.

.

Table F.9 Fatigue Curves Based On Smooth Bar Test Specimens (1) Date For Fatigue Curves – Stress Amplitude Number Of Cycles

UTS £ 551.6 MPa (80 ksi) (MPa)

(ksi)

(MPa)

(ksi)

1

3999

580

2895.8

420

1

2826.8

410

2206.3

320

1

1896

275

1585.8

230

2

1413.4

205

1206.6

175

2

1068.7

155

930.8

135

2

723.9

105

689.5

100

3

572.3

83

537.8

78

3

441.3

64

427.5

62

3

330.9

48

337.8

49

1(10 ) 2(10 ) 5(10 ) 1(10 ) 2(10 ) 5(10 ) 1(10 ) 2(10 ) 5(10 ) 4

1(10 )

262

38

303.4

44

4

248.2

36

296.5

43

4

2(10 )

213.7

31

248.2

36

4

158.6

23

200

29

5

137.9

20

179.3

26

5

113.8

16.5

165.5

24

5

93.1

13.5

151.7

22

6

86.2

12.5

137.9

20

1.2(10 )

5(10 ) 1(10 ) 2(10 ) 5(10 ) --``````-`-`,,`,,`,`,,`---

1(10 )

Notes: 1. 2. 3. 4.

UTS 792.9 – 896.3 MPa (115-130 ksi)

See Figure F.10 for graphical display of fatigue curves. The fatigue data in this table are applicable to the following materials; Carbon, Low Alloy, Series 4XX, High Alloy Steels and High Tensile Steels for Temperatures Not Exceeding 371°C (700°F) Fatigue data is from the ASME B&PV Code, Section VIII, Division 2. Interpolation between tabular values is permissible using the following equation with Si > S > S j :

FN I N=NG J HN K

N

j

(F.163)

i

i

with

log N=

LMF S I F E I OP MNGH S JK GH 30c10 hJK PQ LS O log M P MN S PQ i

t

6

(F.164)

i

j

where

E t is Young’s Modulus at the assessment temperature in psi.


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Table F.10 Coefficients For Fatigue Curves Based on Welded Test Specimens Parameters of Fatigue Curves (2) – Stress Range (MPa) Weld

for

c h

N £ 5.0 106 cycles

for

c h

N > 5.0 106 cycles

Class

m

--``````-`-`,,`,,`,`,,`---

3. 4. 5.

m

c h

N = 5.0 10

6

Stress range at

c h

N = 10 . 108

cycles

cycles

A (3)

124+

3.5

4.25E+13

5.5

3.87E+17

95.0Csu

55.0Csu

100

3.0

2.00E+12

5.0

1.10E+16

74.0Csu

40.0Csu

80

3.0

1.02E+12

5.0

3.57E+15

59.0Csu

32.0Csu

63

3.0

5.00E+11

5.0

1.03E+15

46.0Csu

26.0Csu

50

3.0

2.50E+11

5.0

3.47E+14

37.0Csu

20.0Csu

40

3.0

1.28E+11

5.0

1.03E+14

29.0Csu

16.0Csu

Notes: 1. 2.

A (3)

Stress range at

I r > 766 MPa (111,099 psi ) or N < 3380 cycles , the use Class 100. The data in this table are based on E = 2.09 E + 5 MPa ( 30.313E + 6 psi ) . Csu = 10 . for stress in MPa and Csu = 1 6.894757 E - 3 for stress in psi. If

The equation for the fatigue curves is in paragraph F.6.3.2. The fatigue curves are shown in Figure F.11.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Table F.11 Average and Minimum Rupture Data In Terms of the Larson-Miller Parameter From API RP530 Materials

Low Carbon Steel

Parameter

Average and Minimum Larson-Miller Parameter Equation Constants

Constant

A0

A1

A2

A3

A4

C

LMPm

3.94730E+01

-1.81590E-01

0.00000E+00

-2.52453E+00

0.00000E+00

20

LMPa

3.98044E+01

-1.55223E-01

0.00000E+00

-2.62421E+00

0.00000E+00

20

LMPm

4.06695E+01

-1.00122E-01

-1.95592E-03

-2.88578E+00

0.00000E+00

20

LMPa

4.13897E+01

-8.29692E-02

-1.09590E-03

-2.84904E+00

0.00000E+00

20

LMPm

4.05724E+01

4.68116E-02

-1.74287E-03

-2.42877E+00

0.00000E+00

20

LMPa

4.12353E+01

3.77608E-02

-1.11890E-03

-2.44037E+00

0.00000E+00

20

LMPm

4.14713E+01

0.00000E+00

0.00000E+00

-2.61208E+00

0.00000E+00

20

LMPa

4.26001E+01

0.00000E+00

0.00000E+00

-2.62249E+00

0.00000E+00

20

(Figure 4A) A161 A192 Medium Carbon Steel (Figure 4B) A53 Grade B A210 Grade A-1 C-1/2Mo (Figure 4C) A 161 T1

Not for Resale

A106 Grade B

A 209 T1 A 335 P1 1-1/4Cr-1/2Mo (Figure 4D) A 213 T11 A 335 P11

--``````-`-`,,`,,`,`,,`---

F-67


A 200 T11


2-1/4Cr-1Mo

Parameter


Constant

A0

A1

A2

A3

A4

C

LMPm

4.55051E+01

4.54462E-02

-6.35204E-04

-4.30189E+00

-9.64012E+00

20

LMPa

4.56112E+01

-2.82477E-02

2.67540E-04

-3.65748E+00

-9.05122E+00

20

LMPm

4.40476E+01

0.00000E+00

0.00000E+00

-3.47620E+00

0.00000E+00

20

LMPa

4.47860E+01

0.00000E+00

0.00000E+00

-3.50144E+00

0.00000E+00

20

LMPm

4.40575E+01

0.00000E+00

0.00000E+00

-3.88271E+00

0.00000E+00

20

LMPa

4.55586E+01

0.00000E+00

0.00000E+00

-3.92851E+00

0.00000E+00

20

LMPm

4.34162E+01

0.00000E+00

0.00000E+00

-4.08536E+00

0.00000E+00

20

LMPa

4.51928E+01

0.00000E+00

0.00000E+00

-4.06518E+00

0.00000E+00

20

LMPm

4.45878E+01

0.00000E+00

0.00000E+00

-4.41509E+00

0.00000E+00

20

LMPa

4.57938E+01

0.00000E+00

0.00000E+00

-4.42502E+00

0.00000E+00

20

(Figure 4E) A 213 T22 A 335 P22 A 200 T22 3Cr-1Mo

A 213 T5 A 335 P5 A 200 T5 5Cr-1/2Mo

Not for Resale

(Figure 4F)

(Figure 4G) A 213 T5 A 335 P5 A 200 T5 5Cr-1/2Mo-Si (Figure 4H) A 213 T5b

7Cr-1/2Mo (Figure 4I) A 213 T7 A 335 P7 A 200 T7

--``````-`-`,,`,,`,`,,`---

F-68

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


A 335 P5b

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\ --``````-`-`,,`,,`,`,,`---


9Cr-1Mo

Parameter


Constant

A0

A1

A2

A3

A4

C

LMPm

4.34345E+01

0.00000E+00

0.00000E+00

-3.12645E+00

0.00000E+00

20

LMPa

4.47031E+01

0.00000E+00

0.00000E+00

-3.10233E+00

0.00000E+00

20

LMPm

6.21657E+01

-4.08043E-01

3.23598E-03

-1.14003E+00

0.00000E+00

30

LMPa

6.37694E+01

-3.11988E-01

1.78978E-03

-1.81489E+00

0.00000E+00

30

LMPm

4.16022E+01

0.00000E+00

0.00000E+00

-4.15945E+00

0.00000E+00

15

LMPa

4.31703E+01

0.00000E+00

0.00000E+00

-4.15807E+00

0.00000E+00

15

LMPm

4.07310E+01

0.00000E+00

0.00000E+00

-3.37948E+00

0.00000E+00

15

LMPa

4.14735E+01

0.00000E+00

0.00000E+00

-3.37421E+00

0.00000E+00

15

(Figure 4J) A 213 T9 A 335 P9 A 200 T9 9Cr-1Mo-V

A 213 T91 A 335 P91 A 200 T91 Type 304 & 304H

Not for Resale

(Figure 4K)

(Figure 4L) A 213 Type 304 & 304H A 271 Type 304 & 304H A 312 Type 304 & 304H A 376 Type 304 & 304H Type 316 & 316H

A 213 Type 316 & 316H A 271 Type 316 & 316H A 312 Type 316 & 316H A 376 Type 316 & 316H

F-69


(Figure 4M)


Type 316L

Parameter


Constant

A0

A1

A2

A3

A4

C

LMPm

4.00157E+01

0.00000E+00

0.00000E+00

-3.28310E+00

0.00000E+00

15

LMPa

4.07590E+01

0.00000E+00

0.00000E+00

-3.26423E+00

0.00000E+00

15

LMPm

3.78846E+01

0.00000E+00

0.00000E+00

-3.10462E+00

0.00000E+00

15

LMPa

3.98956E+01

0.00000E+00

0.00000E+00

-3.12309E+00

0.00000E+00

15

LMPm

4.04446E+01

0.00000E+00

0.00000E+00

-3.81729E+00

0.00000E+00

15

LMPa

4.21308E+01

0.00000E+00

0.00000E+00

-3.84328E+00

0.00000E+00

15

LMPm

4.09851E+01

0.00000E+00

0.00000E+00

-3.39864E+00

0.00000E+00

15

LMPa

4.16803E+01

0.00000E+00

0.00000E+00

-3.38401E+00

0.00000E+00

15

(Figure 4N) A 213 Type 316L A 312 Type 316L Type 321 (Figure 4O) A 213 Type 321 A 312 Type 321 A 376 Type 321 Type 321H

Not for Resale

A 271 Type 321

(Figure 4P) A 213 Type 321H A 271 Type 321H A 312 Type 321H A 376 Type 321H Type 347 & 347H (Figure 4Q) A 213 Type 347 & 347H


A 271 Type 347 & 347H A 312 Type 347 & 347H A 376 Type 347 & 347H

--``````-`-`,,`,,`,`,,`---

F-70

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Parameter


Constant

A0

A1

A2

A3

A4

C

LMPm

4.29998E+01

0.00000E+00

0.00000E+00

-4.47081E+00

0.00000E+00

15

B407 Alloy 800H

LMPa

4.39900E+01

0.00000E+00

0.00000E+00

-4.47340E+00

0.00000E+00

15

HK-40

LMPm

4.43554E+01

-2.02153E-01

0.00000E+00

-3.78086E+00

0.00000E+00

15

LMPa

4.52098E+01

-1.76138E-01

0.00000E+00

-3.77497E+00

0.00000E+00

15

Alloy 800H (Figure 4R)

A608 Grade HK-40

Notes: 1. Data for the minimum and average Larson-Miller parameters in this table are from Figures 4-A through 4-S of API RP530 Calculation of Heater Tube Thickness in Petroleum Refineries.

Not for Resale

(Figure 4S)

2. Units for the equations in this table are as follows: I are in ksi.

LMPm is the minimum Larson-Miller parameter based on minimum stress to rupture data, the equation for this parameter is:

LMPm = Ao + A1I + A2I 2 + A3 ln I + A4 exp -I 4.

(F.165)

LMPa is the average Larson-Miller parameter based on average stress to rupture data, the equation for this parameter is: LMPa = Ao + A1I + A2I 2 + A3 ln I + A4 exp -I

(F.166)

--``````-`-`,,`,,`,`,,`---

F-71


3.


Table F.12 Uniaxial Service Exposed Creep Coefficients From MPC Project Omega

Carbon Steel

Carbon Steel – Graphitized

C-1/2Mo

1-1/4Cr-1/2Mo – N&T

1-1/4Cr-1/2Mo – Annealed

2-1/4Cr-1Mo – N&T

2-1/4Cr-1Mo – Annealed

2-1/4Cr-1Mo – Q&T

2-1/4Cr-1Mo – V

5Cr-1/2Mo

9Cr-1Mo

9Cr-1Mo – V

12 Cr

Parameter

Omega and Strain Rate Parameter Constants

C0

C1

C2

C3

C4

A 0

-16.24

38102.0

-10966.0

2588.0

0.0

9

-1.0

3060.0

135.0

-760.0

247.0

A 0

-16.64

38102.0

-10966.0

2588.0

0.0

9

-1.0

3060.0

135.0

-760.0

247.0

A 0

-19.50

61000.0

-49000.0

33000.0

-8000.0

9

-1.30

4500.0

2000.0

-4500.0

2000.0

A 0

-23.35

62070.0

-47520.0

43800.0

-14790.0

9

-4.40

14510.0

-24671.0

29384

-10630.0

A 0

-23.5

50896.0

3509.0

-16677.0

5849.0

9

-2.65

6110.0

3000.0

-4440.0

1375.0

A 0

-21.56

55518.0

-10910.0

-1705

0.0

9

-1.12

5032.0

-360.0

-2320.0

1210.0

A 0

-21.86

51635.0

-7330.0

-2577.0

0.0

9

-1.85

7205.0

-2436.0

0.0

0.0

A 0

-21.56

55518.0

-10910.0

-1705

0.0

9

-1.12

5032.0

-360.0

-2320.0

1210.0

A 0

-24.2

50315.0

5358.06

-7580.0

450.0

9

-2.525

9000.0

-3500.0

225.0

450.0

A 0

-22.40

51635.0

-7330.0

-2577.0

0.0

9

-1.40

5035

-1330.0

423

0.0

A 0

-20.85

49672.0

-6038.0

-6178.0

0.0

9

-1.10

5400.0

-1600.0

-1000.0

0.0

A 0

-34.0

73201.8

-2709.0

-4673.0

-569.0

9

-2.00

7200.0

-1500.0

0.0

0.0

A 0

-30.29

67110.0

-21093.0

14556.0

-5884.0

9

-3.298

6508.0

3016.0

-2784.0

480.0

--``````-`-`,,`,,`,`,,`---


Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Materials

Jan, 2000

RECOMMENDED

PRACTICE


--``````-`-`,,`,,`,`,,`---

Table F.12 Uniaxial Service Exposed Creep Coefficients Materials

G EO

Q

Type 316 & 316H

From MPC Project Omega

Omega and Strain Rate Parameter Constants

Parameter

Type 304 & 304H

F-73

c,

G

G

c,

-19.17

53762.4

-13442.4

3162.6

-1685.2

-3.40

11250.0

-5635.8

3380.4

-993.6

Under Development By MPC

EO

Under Development By MPC

R Type 321

Notes 1. 2.

Coefficients in this table are estimates of the typical material behavior(center of scatter band) based on the MPC Project Omega Materials data from service aged materials at design stress levels. The coefficients in this table are intended to describe material behavior in the range of the ASME Code design allowable stress for a given material at a specified temperature. These coefficients may be used to estimate the stress relaxation resulting from creep over a wider stress range; however, these coefficients may not be applicable to predict the creep damage during this stress relaxation because of a possible change in the failure mode (i.e., high stress regions may fail in a transgranular mode whereas lower stressed regions typically fail in a intergranular mode).



Guidelines

for Establishing

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

J

--

t


Not for Resale

Figure F.l Fracture Toughness

In a &‘Fs Assessment


Figure F.2 Difference In CVN Transition Curve Generated Using Standard Size and Sub-Size Specimens

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Charpy Impact Energy

Standard Sized CVN

Sub-Sized CVN

Energy Shift

Temperature Shift

Temperature


Not for Resale


Figure F.3 The Fracture Toughness Indexing Approach

Heat 1

KIC

Heat 2

Heat 3

Heat 1,2,3

KIC

T-TREF

TEMPERATURE

(a) Concept Of Fracture Toughness Indexing

-100

-80

-60

-40

-20

0

20

40

60

80 275

Cut-off For Low Sulphur Steels

225 200 175 150 125

Cut-off For High Sulphur Steels

100

KIC Curve

75 KIR Curve

50 25 0

-100

0

100

200

(T - TRef), (oF)

(b) Lower-Bound Fracture Toughness Curves for Ferritic Steels


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

250 1/2

-120 250 240 230 220 210 200 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 -200

Fracture Toughness, (MPa(m) )

1/2

Fracture Toughness, (ksi (in) )

(T - TRef), (oC)


Figure F.4 Curve Fitting of Charpy Data

Absorbed Energy

Upper Shelf A+B

B Transition A

B

Lower Shelf A-B

C

C

--``````-`-`,,`,,`,`,,`---

Tm Temperature

(a) Characteristics of the Hyperbolic Tangent Function

200 180

Absorbed Energy (Ft - lbs)

160 140 120 100 80 60 40 20 0 -200

-100

0

100

200

Temperature (oF)

(b) Typical Hyperbolic Tangent Function Curve Fit to CVN data


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure F.5 Effect Of Temper Embrittlement and Hydrogen on the Toughness of 2¼ Cr- 1Mo Steel

KIC Level of Non-Embrittled Material

KIC

KIH

Hydrogen Embrittlement Effect of Hydrogen Content

--``````-`-`,,`,,`,`,,`---

Stress Intensity - K

Temper Embrittlement

H2 Saturated

KIH Level of Extremely Temper Embrittled Material Room Temperature

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

FATT - Fracture Appearance Transition Temperature


Not for Resale


Figure F.6 Fracture Toughness Master Curve

KJc = 100 MPa-m1/2 (91 ksi-in1/2)

KJc

F = 0.95 Median (F = 0.5)

F = 0.05

Experimental Data

To Temperature Notes: 1. 2.

F is the cummulative probability. K Jc is the fracture toughness.

3.

T0 is the temperature at which K Jc = 100 MPa in .

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure F.7 Crack Growth Behavior – Fatigue

Final Failure

REGIME A

Regime B

Non-Continuum Mechanisms

Continuum Mechanisms (Striation Growth)

da/dN

Large Influence Of: (i) Microstructure (ii) Mean Stress (iii) Environment

--``````-`-`,,`,,`,`,,`---

10-5

Effect of increasing mean stress (Increasing R-ratio)

Small Influence Of: (i) Microstructure (ii) Mean Stress (iii) Thickness da/dN=C(,K)n

10-7 Regime C m l

Large Influence Of: (i) Microstructure (ii) Mean Stress (iii) Thickness

Effect of Increasing Mean Stress

Threshold ,Kth


Log ,K

Not for Resale

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

10-9

"Static Mode" Mechanisms (Cleavage, Intergranular, or Fibrous)


Figure F.8 Crack Growth Behavior – Stress Corrosion Cracking and HAC

da/dt

Stage 3

Stage 2

Klc

KISCC Stage 1

LOG K

da/dt

--``````-`-`,,`,,`,`,,`---

(a) Crack Growth Rate and Stress Intensity Factor relationship For Two Environments

Rising Load Test

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Falling Load Test

KIH

KIC-H

Kth

KIC (air)

Log K

(b) Hydrogen Assisted Crack (HAC) Growth Curve


Not for Resale


Figure F.9 Crack Growth Behavior – Corrosion Fatigue

Aggressive

Aggressive

Log , K (b) Stress Corrosion Fatigue (SCF)

da/dN

Log , K (c) SCF with TCF

--``````-`-`,,`,,`,`,,`---

(a) True Corrosion Fatigue (TCF)

Inert Kmax = ,KlSCC

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Log , K

Inert ,K = ,KTH

Inert

Kmax = Klc

da/dN

da/dN

Aggressive


Not for Resale


Figure F.10 Fatigue Curves Based On Smooth Bar test Specimens

1e+7

1e+6

For UTS < 80 ksi

1e+6

1e+5 For UTS 115-130 ksi

1e+4 1e+1

Stress Amplitude, Sa, (kPa)

Stress Amplitude, Sa, (psi)

1e+7

1e+5 1e+2

1e+3

1e+4

1e+5

1e+6

Number of Cycles

See Table F.4 for the tabulated fatigue data. Stress Amplitude based on E=30E6 psi. 1.0 psi = 6.894757 kPa

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Notes: 1. 2. 3.

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure F.11 Fatigue Curves Based On Welded Test Specimens

--``````-`-`,,`,,`,`,,`---

1000

100

100 10

10 1e+2

1e+3

1e+4

1e+5

1e+6

Number of Cycles, N

Notes: 1. 2.

See Table F.9 for the tabulated fatigue data. 1 ksi = 6.894757 MPa


Not for Resale

1e+7

1e+8

1 1e+9

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Class 124+ Class 100 Class 80 Class 63 Class 50 Class 40

Stress Range, Sr, (ksi)

Stress Range, Sr (MPa)

1000


Figure F.12 Classification Of Weld Details – Seam Welds Joint Type

For Stresses Acting Essentially Along The Weld

--``````-`-`,,`,,`,`,,`---

Sketch of Detail

Class

Full penetration butt weld flush ground

Comments

100

Weld shall be proved to be free from surface-breaking defects and significant subsurface defects by NDE

Full penetration butt weld made from both sides or from one side on to consumable insert or temporary nonfusible backing.

100

Weld shall be proved free from significant defects by NDE.

Full penetration butt welds made from one side without a backing device

80

Weld shall be proved free from significant defects by NDE

Fatigue cracks usually initiate at weld flaws


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



For Stresses Acting Essentially Along The Weld Sketch of Detail

Class

Full penetration butt welds made from one side on to permanent backing device

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Not for Resale

Comments

80

Breaking strip shall be continuous and, if attached by welding, tack welds shall be ground out or buried in main butt weld, or continuous fillet welds shall be used. Weld shall be proved free from significant defects by non-destructive testing

80

Backing strip attached with discontinuous fillet weld.

80

Joggle joint; weld shall be proved free from significant defects by NDE


For Stresses Acting Essentially Along The Weld Sketch of Detail

Class

Comments

Fillet welded lap joint.

80

Welds shall be continuous. The fatigue strength is based on the stress range acting on the cross section of the weld.

Full penetration butt weld which is ground flush

100

Weld shall be proved free from surface-breaking defects and significant subsurface defects by NDE

80

Weld shall be proved free from significant defects by NDE and, for welds made from one side, full penetration. The bending stress resulting from centerline weld misalignment should be considered in the assessment.

Fatigue cracks usually initiate at weld flaws Full penetration butt weld made from both sides or from one side on to consumable insert or temporary nonfusible backing device

1 Max

4

80

80

Full penetration butt welds made from one side without a backing device.

---

--``````-`-`,,`,,`,`,,`---


Not for Resale

Not recommended for fatigue loaded joints since fatigue life critically dependent on root condition. If full penetration can be assured, then Class 80 can be used in the assessment. The weld shall be proved free from significant defects by NDE

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\



Figure F.12 Classification Of Weld Details – Seam Welds For Stresses Acting Essentially Along The Weld Sketch of Detail

Class

Full penetration butt welds made from one side on to permanent backing device.

Fillet welded lap joint.

A

63


63


A: 63

A: Class 63 refers to fatigue failure in shell from the weld toe (a one class increase can be used if the weld toe is dressed according to procedure in paragraph F.6.3.4.b.).

B: 40 B

Comments

B: Class 40 refers to fatigue failure in weld; the assessment is based on the stress range in weld throat.

Notes: 1.

2.

3.

The higher fatigue strength transversely loaded seams are full penetration butt welds made from both sides or from one side using consumable inserts or a temporary non-fusible backing medium. Then, in the absence of significant defects, the fatigue strength of the joint depends on the overfill shape. In general, the overfill profile requirement for Class 100 should be achieved with shop welds made in the flat position. However, special care may be needed in the case of submerged arc welding since it is known that very poor profiles can be obtained using this process. There is a reduction in the fatigue strength of transverse butt welds if they are made from one side only, unless a joint resembling one made from both sides can be achieved. This is possible using special consumable inserts or a temporary non-fusible backing medium. However, in all cases the weld should be inspected to ensure that full penetration and a satisfactory overfill shape has been achieved on the inside of the joint. As far as seem welds under longitudinal loadings are concerned, there is an incentive to avoid the introduction of any discontinuous welds. In the absence of significant defects, their fatigue strengths are only reduced if they contain discontinuous welds.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

--``````-`-`,,`,,`,`,,`---

Joint Type

Jan, 2000

RECOMMENDED

Classification Joint Type

PRACTICE

F-89


Figure F.13 Of Weld Details - Nozzles and Branch Connections Sketch Of Detail

Class

Comments

Crotch comer --``````-`-`,,`,,`,`,,`---

sketches show plane of crack Weld toe in

she’l

Weld toe in branch

member.



API RECOMMENDED

F-90

Classification

PRACTICE

579

Jan, 2000

Figure F.13 Of Weld Details - Nozzles and Branch Connections Sketch Of Detail

Joint Type

Class

Weld metal stressed along its length.

I Comments

Class 80 refers to a full penetration weld 11

Class63referstbafilletor partial penetration weld. The assessment is based on stress range acting on the weld cross section.

Cracks radiate from root or defect through welds

Full penetration weld

Partial penetration weld

Weld metal stressed normal to its length. --``````-`-`,,`,,`,`,,`---

The assessment is based on the stress range acting on the throat of the weld.

Notes 1.

The main sties for fatigue cracking in branch connections are the weld toes in the shell and the nozzle, and the crotch corner in the nozzle. In every case, account should be taken of the stress concentration in the region of potential fatigue cracking due to the gross structural discontinuity introduced by the nozzle.

March 2000


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure F.14 Classification Of Weld Details – Shell Attachments Joint Type

For Stresses Acting Essentially Along The Weld Sketch Of Detail

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Attachment of any shape with an edge fillet or bevel – butt welded to the surface of a stressed member, with continuous or discontinuous around the ends.

Attachments of any shape with surface in contact with stressed member, with continuous or discontinuous welds around the ends of the attachments.

Class

Comments

63

For details with return welds, the Weld Class can be increased if the weld toe is dressed according to procedure in paragraph F.6.3.5. The thickness correction is applicable where t is the plate thickness of the stressed member.

63

Class 63 is applicable when W £ 55 mm (2.17 inches).

L

Edge distance

W

50

Class 50 is applicable when W > 55 mm (2.17 inches). For details with welds which are continuous around the ends, the Weld Class can be increased if the weld toe is dressed according to procedure in paragraph F.6.3.5. The thickness correction is applicable where t is the plate thickness of the stressed member.

Edge distance

Attachments of any shape on or within 10 mm of the edge of a stressed member.


50

Not for Resale

For details with return welds, the Weld Class can be increased if the weld toe is dressed according to procedure in paragraph F.6.3.5. The thickness correction is not applicable.


Figure F.14 Classification Of Weld Details – Shell Attachments Joint Type

For Stresses Acting Essentially Along The Weld Sketch Of Detail

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Attachment of any shape with an edge fillet or bevel – butt welded to the surface of a stressed member, with continuous or discontinuous welds around the ends of the attachments.

Class

2.

The Weld Class can be increased if the weld toe is dressed according to procedure in paragraph F.6.3.5. The thickness correction is applicable where t is the plate thickness of the stress member.

63

Class 63 is applicable when W £ 55 mm.

50

W

Class 50 is applicable when W > 55 mm. For details with welds which are continuous around the ends, the Weld Class can be increased if the weld toe is dressed according to procedure in paragraph F.6.3.5. The thickness correction is applicable where t is the plate thickness of the stressed member.

Edge distance

Notes: 1.

63

Edge distance

Attachments of any shape with surface in contact with stressed member, with welds continuous around ends or not.

Comments

The most likely mode of fatigue failure at a welded attachment is from the weld toe, or the weld end in the case of welds lying essentially parallel to the direction of applied stress, into the stressed member. Transverse attachments welded only on one side may fail by fatigue crack propagation from the weld root, also into the stressed member. Such cracks are virtually undetectable and therefore this practice is not recommended. The fatigue strength of members with edge attachments is lower than that of members with only surface attachments; to allow for the accidental occurrence of edge welds, surface attachments less than 10 mm (0.394 inches) from an edge are assumed to be on the edge. Fatigue design is based on the normal strength in the stressed member in the vicinity of the attachment. The thickness correction (see paragraph F.6.3.2.c) is applicable as indicated above.

--``````-`-`,,`,,`,`,,`---


Not for Resale


Figure F.15 Classification Of Weld Details – Supports For Stresses Acting Essentially Along The Weld Sketch Of Detail Support on either horizontal or vertical vessel.

Class A: 63

A

Welded with fillet weld to vessel all around

B

B: 50 C: 40

Comments A: Class 63 refers to fatigue failure from the toe of a weld. B: Class 50 refers to fatigue failure from the toe of a weld. C: Class 40 refers to fatigue failure in the weld; the assessment is based on the stress range acting on the throat of the weld.

Backing plate

--``````-`-`,,`,,`,`,,`---

Joint Type

C

Trunnion support

A: 63 B: 50 C: 40

Backing plate

A

B

Notes: 1.

B: Class 50 refers to fatigue failure from the toe of a weld. C: Class 40 refers to fatigue failure in the weld; the assessment is based on the stress range acting on the throat of the weld.

C

Welded with fillet weld to vessel all around

50

Class 50 refers to fatigue failure from the toe of a weld.

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

Saddle support

A: Class 63 refers to fatigue failure from the toe of a weld.

The weld classes which refer to potential fatigue failure from the weld toe can be increased by one weld class, if the weld toes are dressed according to procedure in paragraph F.6.3.5. However, the class for potential fatigue failure through the weld throat is not affected. Therefore, for toe dressing to be effective, full penetration welds should be used for directly loaded welds.


Not for Resale


Figure F.16 Classification Of Weld Details – Flanges Joint Type

For Stresses Acting Essentially Along The Weld Sketch Of Detail Class

Full penetration butt weld made from both sides.

Fillet welded from both sides.

A

63

Class 63 refers to fatigue failure in the toe of a weld.

A: 63

A: Class 63 refers to fatigue failure in the toe of a weld.

B: 40

B: Class 40 refers to fatigue failure in the weld, the assessment is based on the stress range in the weld throat.

B Welded from both sides.

Comments

A: 63

A

B: 40

A: Class 63 refers to fatigue failure in the toe of a weld. B: Class 40 refers to fatigue failure in the weld, the assessment is based on the stress range in the weld throat.

B Fillet welded from both sides.

A: 63

A

B: 40

A: Class 63 refers to fatigue failure in the toe of a weld.

--``````-`-`,,`,,`,`,,`---

B: Class 40 refers to fatigue failure in the weld, the assessment is based on the stress range in the weld throat.

B Welded from both sides.

A: 63

A

B: 40

A: Class 63 refers to fatigue failure in the toe of a weld. B: Class 40 refers to fatigue failure in the weld, the assessment is based on the stress range in the weld throat.

B

Notes: 1.

The weld classes which refer to potential fatigue failure from the weld toe can be increased by one weld class, if the weld toes are dressed according to procedure in paragraph F.6.3.5. However, the class for potential fatigue failure through the weld throat is not affected. Therefore, for toe dressing to be effective, full penetration welds should be used.


Not for Resale //^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\


Figure F.17 Dressing Of A Fillet Weld To Reduce Fatigue Failure

Depth of grinding = 0.5 mm (0.020 in) below undercut

Stressed plate (a) Blend ground detail

45°

burr tool

--``````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~^~$~":~@~~~"^~:^:@:~*:$"\\

45°

(b) Method of burr grinding

Direction of travel

Grinding disk 30 to 45°

(c) Method of disk grinding


Not for Resale

Appendix

G - Deterioration

And Failure

Modes

(Jan, 2000)

Deterioration

and Failure

Modes

G.l .l

This appendix provides a general overview of the types of flaws and damage observed, concentrating on service-induced degradation mechanisms. It also provides general information in about mitigation and monitoring methods. A more complete overview of the damage mechanisms that occur in the refining industry is provided in API 571.

G.1.2

When conducting a FFS assessment it is very important to determine the cause(s) of the damage or deterioration observed to date and the likelihood and degree of further damage that might occur in the future. Flaws and damage that are discovered during an in-service inspection can be the result of a preexisting condition before the component entered service and/or could be service-induced. The root causes of deterioration could be due to inadequate design considerations including materials selection and design details, or the interaction with aggressive environments/conditions that the equipment is subjected to during normal service or during transient periods.

G.2

Pre-Service

G.2.1

The types of pre-service

Deficiencies deficiencies

that can be present

before equipment

enters service

are:

.

Material Production Flaws - Flaws which occur during production including laminations in wrought products, and voids, segregation, shrinks, cracks, bursts in cast products.

.

Welding Related Flaws - Flaws which occur as a result of the welding process including lack of penetration, lack of fusion, delayed hydrogen cracking, porosity, slag, undercut, weld cracking, hot shortness.

.

Fabrication roundness,

.

Heat Treatment Related Flaws Or Embrittlemenf - Flaws associated with heat treatment or inservice elevated temperature exposure including reheat cracking, quench cracking, sensitization, 475°C (885°F) embrittlement, and sigma phase embrittlement.

and laps

Related Flaws - Imperfections associated with fabrication including out-offorming cracks, grinding cracks and marks, and lamellar tearing.

G.2.2

In most instances, one or more of these pre-service deficiencies do not lead to an immediate Usually, only gross errors cause a failure during a pre-service hydrostatic or pneumatic test.

G.2.3

Flaws or damage associated with pre-service deficiencies or damage are often only discovered during an In-Service Inspection (ISI), because in many cases the ISI techniques used are more sensitive or the inspection scope is wider than the inspection techniques or extent of inspection used during the original construction. Some damage can be classified relatively easily as pre-service, based on its characteristics and location ( e.g. void in the interior of a weld is porosity). However some pre-service damage is indistinguishable from service induced damage (e.g. delayed hydrogen cracking and sulfide stress cracking). Therefore, the key decision that needs to be made is whether the flaw and associated deterioration (regardless of its origin) is likely to progress in the future based on the material, stress, service conditions, and flaw size.

6.3

In-Service

G.3.1

Overview

G.3.1 .l

Once equipment enters service, it is subjected to operating and/or downtime conditions which can deteriorate or damage the equipment. One factor that complicates a FFS analysis for petrochemical equipment is that material/environmental condition interactions are extremely varied; many

Deterioration

failure.

and Damage

G-l Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS


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G.l


G-2

Jan, 2000

refinery/chemical plants contain over 30 different processing units, each having its own combination of numerous aggressive process streams and temperature/pressure conditions. In general, the following types of damage are encountered in petrochemical equipment:

G.3.1.2

. .

General and local metal loss due to corrosion and/or erosion

.

Subsurface cracking

.

Microfissuring/microvoid

.

Metallurgical changes

Surface connected cracking formation

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Each of these general types of damage is caused by a multitude of damage mechanisms, which are specific types of corrosion (e.g. naphthenic acid corrosion of carbon steel), stress corrosion cracking (SCC - e.g. polythionic acid stress corrosion cracking of sensitized austenitic stainless steels (PSCC)), or types of embrittlement (e.g. temper embrittlement of 2-l/4 Cr -1 MO alloy steel). Each of the damage mechanisms occur under very specific combinations of materials, process environments, and operating conditions. General guidance as to the most likely damage mechanisms for common alloys used in the petroleum industry is provided in API 571.

G.3.1.3

The following sections of this Appendix describe each of the damage types and provide some typical examples of damage mechanisms encountered in the petrochemical industry and potential mitigation methods. These sections are intended to provide an introduction to the non-specialist in corrosion/metallurgy. The user is urged to consult with engineers familiar with degradation modes and to refer to publications such as API 571 which provide a more detailed description of damage mechanisms in the petroleum industry.

G.3.1.4

When performing a F’,S assessment it is important that the potential for further degradation or damage is considered or that steps are taken to preclude further damage from occurring by means of mitigation methods. A list of the types of information needed for a specialist to judge whether, and at what rate, further degradation is likely to occur is provided in Table G.l.

G.3.2

General Metal Loss Due to Corrosion and/or Erosion

G.3.2.1

General metal loss is defined as relatively uniform thinning over a significant area of the equipment. Corrosion and erosion are never totally uniform; a rule of thumb is that if the metal loss rate among different points in an area vary by a factor of four or less, then damage is considered general. Examples of general corrosion for carbon steel and low alloy steels are sulfidation in crude units, HdHpS corrosion in hydrotreaters, and sour water corrosion in moderate velocity situations in sour water strippers.

G.3.2.2

A corrosion rate can usually be calculated from past and current thickness readings, for example see API 510, API 570, and API 653. The corrosion rate can also be predicted from standard corrosion curves/references, such as the modified McConomy Curves for sulfidation of carbon and low alloy steels (these curves are a function of temperature and sulfur content versus alloy). The measured or calculated rate, or a modified rate if conditions have changed, can be factored into a FFS assessment to evaluate future operation.

G.3.2.3

Remediation and monitoring methods for general metal loss are described in Section 4, paragraphs 4.6 and 4.7, respectively.

G-3.3

Localized Metal Loss Due to Corrosion and/or Erosion

G.3.3.1

Unlike general metal loss, localized metal loss rates can vary significantly within a given area of equipment. Examples of localized metal loss are under deposit corrosion in crude unit overhead systems, naphthenic acid corrosion, injection point corrosion, and corrosion under insulation. Localized corrosion can take many forms, such as pitting resulting in numerous surface cavities, selective galvanic corrosion in the region between two electrochemically different metals, selective

March 2000


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Jan, 21DO0

RECOMMENDED

PRACTICE


G-3

G.3.3.2

When localized metal loss is detected, it is important to locate and characterize all of the locally thinned areas and obtain accurate measurements to calculate a metal loss rate. Predicting a localized corrosion rate is difficult, since the damage may only occur under very specific operating conditions (temperatures, chemical species, flow velocity) and is more of an on/off situation and usually does not occur at a steady constant pace. Since localized corrosion rates are extremely sensitive to minor variations in process conditions/materials it is difficult to find applicable reference sources of corrosion data.

G.3.3.3

Remediation and monitoring methods for local metal loss are described in Section 5, paragraphs 5.6 and 5.7, respectively.

6.3.4

Surface Connected Cracking

G.3.4.1

Most service-induced cracking mechanisms initiate at the surface of the component. Examples of service-induced surface cracking are mechanical and thermal fatigue and various forms of stress corrosion cracking, such as polythionic acid stress corrosion cracking (PASCC) or chloride SCC of austenitic stainless steels, amine type cracking of carbon steels, and sulfide stress cracking of carbon and low alloy steels. Fatigue cracking data is available from a number of reference sources (see Appendix F) and future crack growth rate can be calculated if the stresses can be characterized.

G.3.4.2

The occurrence of SCC requires that a combination of three conditions to be present: a susceptible material or material condition, a chemically aggressive environment, and a sufficiently high tensile stress. Since three factors are involved, generalizations about environments that can cause SCC are difficult even when restricted to a specific class of material. However, experiments and service experience have identified environments that can or have caused SCC in carbon and low alloy steels, and these have been tabulated and described in API 571.

G.3.4.3

The metallurgical condition of the material is an important determinant of the severity of the SCC problem. For example high hardness and strength make a steel, particularly the HA2 of welds, more susceptible to sulfide stress cracking. Another material condition is sensitization of austenitic steels (chromium-rich carbide precipitation at grain boundaries) which is necessary for PASCC. The environmental and operating conditions of the component are also important. For example, there is a threshold level of caustic concentration and temperature which must be exceeded before carbon steel is susceptible to caustic cracking. In general, the greater the concentration of the causative agent, Cl, ammonia, H2S, CN, etc., the greater the likelihood of SCC. For some mechanisms increasing temperature increases susceptibility, while for others it decreases susceptibility. Concentration of the causative agents due to boiling, crevices, etc. can lead to problems where bulk stream composition would not predict susceptibility. Tensile stress is the third required ingredient for SCC. High tensile stresses, both applied and residual, increase the severity of the problem. Residual stress estimation is very important, because many cracks in practice arrest when they enter a lower residual stress field.

G.3.4.4

Surface cracks often are found by surface inspection techniques, such as visual, PT and MT, although UT methods and AET are also used to detect cracks. Sizing surface connected cracking, in particular SCC, is very difficult, because in many cases the cracks are branched. PT or MT examination methods can be used to determine the length of surface cracks and UT examination methods can be used to determine the depth of cracking. Crack depth can also be determined by destructive grinding.

G.3.4.5

Predicting crack growth rates for SCC is also very difficult, because of a lack of relevant data and lack of precise knowledge of the environmental conditions near the crack tip, which can be different from the bulk stream composition. SCC is also more of an on/off damage type, i.e. cracks can grow very rapidly if all the conditions are conducive, but it can also be dormant for a very long time.



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corrosion attack along a weld heat affected zone (HAZ), corrosion attack in crevices resulting from the concentration of aggressive chemical specie(s), or local grooving due to impingement. In general, the more resistant an alloy is to general corrosion, the more likely it is that corrosion, if it occurs, will be localized.

API RECOMMENDED

G-4

PRACTICE 579

Jan, 2000

G.3.4.6

Mitigation methods to slow/prevent further SCC without removing cracks are somewhat limited. Strip lining the area and possibly coating the area if the cracks are tight is possible. Other methods are to alter the environment by means of chemical treatments, changing the temperature, or removing contaminants. Monitoring methods consist of periodic UT measurements or continuous passive AET Stream sampling/analysis and process variable monitoring to predict when conditions monitoring. conducive to SCC are present can also be used.

G.3.4.7

If cracks are removed, additional mitigation options are available, such as PWHT or heat treatment to remove residual stresses and/or improve the metallurgical condition, and weld overlays and coatings to isolate the susceptible material from the environment.

6.3.5

Subsurface

G.3.5.1

Service-induced damage that is not surface connected or initiates subsurface falls into the general class of low-temperature hydrogen related phenomena or high temperature mechanisms such as creep and hydrogeh attack. Hydrogen damage consisting of blistering, HIC, and SOHIC is primarily Much of refinery equipment encountered in carbon steels operating in wet H2S or HF environments. is subject to wet H2S charging conditions during service or shutdown conditions. For example, deethanizers in fluid catalytic cracking light ends units typically have an environment with a high pH and cyanides that causes severe hydrogen charging leading to damage. Low-temperature hydrogen related damage occurs as a result of a local surface corrosion reaction which allows hydrogen atoms to diffuse into the steel. Once the hydrogen reaches a threshold concentration damage can occur. Subsurface service-induced hydrogen damage can also eventually connect with the surface or this type of damage can initiate as a result of surface cracks, such as sulfide stress cracking.

G.3.5.2

This mechanism is similar to SCC in that susceptible material and an aggressive environment must be present. Hydrogen blistering and HIC are however not stress related, but SOHIC is. Hydrogen damage often is an on-off mechanism, occurring under very specific environmental conditions that may be present only during upsets and startup/shutdowns. Damage often occurs very quickly at first and once surface films buildup they inhibit further damage, although if films are disturbed in service or intentionally during inspections accelerated damage can recur. Since hydrogen charging normally only occurs from the process side of the equipment, the hydrogen concentration decreases through the wall and in practice many cracks arrest mid-wall and blisters are less prevalent on the external surfaces.

G.3.5.3

Metallurgical and microstructural details (e.g. the sulfur impurity level of the steel) affect the susceptibility to damage or threshold level for damage by a certain level of hydrogen charging. Environmental variables, such as pH, temperature, CN, H2S content, and stream velocity influence the level of hydrogen charging. Applied and residual stress also influence SOHIC susceptibility. Much of the equipment that will be evaluated for FFS will contain hydrogen damage. It is recommended that an expert in this field be consulted because it is very important to assess the future potential and rate of hydrogen damage. Reference publications that can be used in this assessment are: API 571; NACE Publications 8X194,8X294, and RP0296; and API 939.

G.3.5.4

Finding subsurface hydrogen damage is normally accomplished by visual inspection and various UT methods. Characterizing the damage is very difficult because this type of damage is more a damage mechanics than fracture mechanics problem, since there often is no discreet single crack, cracks may be interconnected, and stacked in arrays. Various UT methods are used to characterize the damage.

G.3.5.5

Mitigation for low temperature hydrogen damage can consist of chemical treatment and/or water washing to minimize hydrogen charging, strip lining or coatings to isolate the steel from the environment, and venting for blisters to relieve the internal stress. If properly performed, PWHT may also reduce the propensity for SOHIC cracking by lowering the residual stress. Monitoring methods consist of hydrogen probes that measure hydrogen flux and periodic UT inspections to monitor damage extent.

Cracking

and MicrofissuringlMicrovoid

Formation

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Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE G-5 _________________________________________________________________________________________________

G.3.5.6 Creep and/or high temperature hydrogen attack (HTHA) are mechanisms that form voids and fissuring only during latter stages of damage. These mechanisms can be either surface-connected or initiate subsurface. The variables that affect creep damage are the creep strength and strain capability of the material and the exposure conditions (stress and temperature). The variables that affect hydrogen attack are similar, but in addition the hydrogen partial pressure in the process stream and the alloy chemistry are very important. Subsurface creep and hydrogen attack damage which is detectable with UT methods, indicates that the component is at late stages of life for most common alloys. Creep and hydrogen attack damage rates can only be reduced by lowering the severity of the operating conditions. Field metallography may be affective for monitoring creep; however, the best monitoring method involves removing samples and conducting destructive tests while recording the temperature and pressure of the process. G.3.6

Metallurgical Changes

G.3.6.1 Metallurgical properties, such as strength, ductility, toughness, and corrosion resistance can change while a component is in-service due to microstructural changes as a result of thermal aging at elevated temperatures. For example, carbon steels can strain age embrittle, spheroidize, or graphitize, ferritic and austenitic stainless steels can form sigma phase or can sensitize, ferritic stainless steels can suffer from 475°C (885°F) embrittlement, and 2-1/4 Cr-Mo Steel can temper embrittle. Properties can also change as a result of hydrogen charging. G.3.6.2 These changes in properties are often difficult to detect, since damage may not have occurred yet. Sometimes inferences can be made from examining samples or surface replicas. Steel composition and microstructure, operating temperature, and accumulated strain are the most important factors that determine susceptibility to metallurgical changes. Often an equilibrium state of change is reached and further changes will not occur. Hydrogen charging, even without material damage, will in many cases lower the ductility and possibly even the toughness of the material. Hydrogen charging is a reversible reaction and if it does not cause damage, has no permanent effect. G.3.6.3 Once the metallurgical properties are changed in-service, they usually are not recovered. Heat treatment can be effective, although this often is only a temporary solution. To prevent further degradation operating conditions can be adjusted to a lower severity. If the degradation in properties is known, then operating precautions such as start-up and shut-down procedures can be altered to prevent damage from occurring despite the degraded physical properties.

·

Carbon steel in wet H2S service and hydrofluoric acid service (hydrogen embrittlement)

·

Carbon steel and C-1/2 Mo between 149°C -316°C (300°F – 600° F) (strain age embrittlement)

·

Carbon steel above 427°C (800°F) (graphitization)

·

Carbon steel, low alloy steels (i.e. 1/2 Cr to 9 Cr), and 12 Cr in fire situation when temperatures exceed 704°C (1300°F) (various damage mechanisms, see Section 11)

·

Alloy steels (1/2 Cr – 9 Cr) above 593°C (1100 °F) (carburization)

·

1-1/4 Cr-1/2 Mo above 482°C (900°F) (reheat cracking/creep embrittlement)

·

2-1/4 Cr-1 Mo above 399°C (750°F) (temper embrittlement)

·

12 Cr above 371°C (700°F) (475°C (885°F)embrittlement)

·

Austenitic stainless steel above 593°C (1100°F) (sigma phase embrittlement)


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G.3.6.4 As previously discussed, loss of toughness can occur in service as a result of the process environment and service conditions. This form of metallurgical damage will have significant impact on the structural integrity of a component containing a crack-like flaw. In addition, experimental evidence indicates that loss of toughness may also have an effect on the structural integrity of components with blunt flaws that are typically associated with localized corrosion, groove-like flaws or pitting. Some of the service and materials combinations that may be susceptible to loss of toughness are listed below. An evaluation of the materials toughness may be required depending on the flaw type, the severity of the environment, and the operating conditions.

G-6 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

G.4

References

G.4.1

API, "Research Report on Characterization and Monitoring of Cracking in Wet H2S Service," API Publication 939, American Petroleum Institute, Washington D.C., 1994.

G.4.2

Logan, H.L., The Stress Corrosion of Metals, Wiley, 1966.

G.4.3

McConomy, H.F., "High Temperature Sulfuric Corrosion in Hydrogen Free Environments," Proc. API, Vol. 43 (III), pp. 78-96, 1963.

G.4.4

NACE, " Guidelines for Detection, Repair, and Mitigation of Cracking of Existing Petroleum Refinery Pressure Vessels in Wet H2S Environments,” NACE Publication RP0296, National Association of Corrosion Engineers, Houston, TX, 1996.

G.4.5

NACE, "Materials and Fabrication Practices for New Pressure Vessels Used in Wet H2S Refinery Service,” NACE Publication 8X194, National Association of Corrosion Engineers, Houston, TX, 1994.

G.4.6

NACE, "Review of Published Literature on Wet H2S Cracking of Steels Through 1989,” NACE Publication 8X194, National Association of Corrosion Engineers, Houston, TX, 1994.

G.5

Tables and Figures

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Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE G-7 _________________________________________________________________________________________________

Table G.1 Information to Determine Degradation Mechanisms General Information

Data

Processing Unit/Item Year of Construction Material Specification Material Chemical Composition PWHT (Yes/No) Lining/Coating Material

Item (1)

Operating Information (2) Start-Up /Shutdown

Normal

Upset

Crude Fraction Sulfur Content (%) Crude Fraction Neut Number Water Content (%/pH) H2S (ppm in water) NH3 (ppm in water) NH3 (%) H2S (%) HCl (%) Chlorides (%) Sulfuric Acid (%) HF Acid (%) Amine Type (MEA/DEA/etc.) Amine Concentration (%) Amine Loading (mole H2S & CO2/mole amine) Caustic Concentration (%) H2S Partial Pressure (bar:psia) H2 Partial Pressure (bar:psia) Cyanides (Yes/No) Water Wash/Injection (Yes/No) Polysulfide Injection (Yes/No) Neutralizing Amine Injection (Yes/No) Filming Amine Injection (Yes/No) Caustic Injection (Yes/No) Hydrogen Absorption Injection Inhibitor Temperature (°C:°F) Pressure (bar:psig) Flow Velocity (m/sec:ft/sec)

Notes: 1. Other process stream constituents or operating parameters that may affect the fitness-for-service assessment can be entered at the end of this list. 2. Values for the process stream constituents and operating parameters for the start-up, shut-down, and upset conditions, as well as the normal operating condition, need to be defined because significant damage may occur during these phases of operation.

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APPENDIX H - Validation (Jan, 2000)

This appendix is currently being developed by the API CRE Task Group on Fitness-For-Service. When this appendix is complete, it will be sent to all registered purchasers of API 579. Until this time, questions regarding the contents and completion schedule for this appendix should be submitted to the Manager of the Downstream Segment, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005.

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H-1 Copyright American Petroleum Institute Reproduced by IHS under license with API No reproduction or networking permitted without license from IHS

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APPENDIX I – Glossary Of Terms And Definitions (Jan, 2000)

Abs[a] or |a| – The definition of a mathematical function which indicates that the absolute value of the arguments, a, is to be computed.

I.2

AET – Acoustic Emission Testing.

I.3

Alteration – The definition is dependent on the equipment type as shown below: ·

Pressure vessels (API 510) – A physical change in any component having design implications that affect the pressure-containing capability of a pressure vessel beyond the scope of the items described in existing data reports. It is not intended that any comparable or duplicate replacement, such as the addition of any reinforced nozzle equal to or less than the size of existing reinforced nozzles, the addition of nozzles not requiring reinforcement, or rerating be considered an alteration.

·

Piping Systems (API 570) – A physical change in any component or pipe routing (including support system modifications) which have design implications affecting the pressure-containing capability of the piping system, including the pressure vessels, tanks and/or equipment it services. For example, an alteration which installs a heavy valve near a vessel nozzle may have design implications for the pressure vessel as well as the piping system itself.

·

Storage tanks (API 653) – Any work necessary to restore a tank to a condition suitable for safe operation.

I.4

ASCC (Alkaline Stress Corrosion Cracking) – Cracking of a metal produced by the combined action of corrosion in an aqueous alkaline environment containing H2S, CO2, and tensile stress (residual or applied). The cracking is branched and intergranular in nature, and typically occurs in carbon steel components that have not been subjected to PWHT. This form of cracking has often been referred to as carbonate cracking when associated with alkaline sour waters, and as amine cracking when associated with alkanolamine treating solutions.

I.5

Authorized Inspection Authority – the inspection organization of the jurisdiction in which the pressure vessel is used, or the inspection organization of an insurance company which is licensed or registered to (and does) write pressure vessel insurance, or an owner or user of pressure vessels who maintains an inspection organization for activities relating only to his equipment, excluding vessels intended for sale or resale, or an independent organization licensed or organized by the jurisdiction in which the pressure vessel is used who is employed by or acting under the direction of the owner or user.

I.6

Authorized Inspector, or Inspector – An employee of an Authorized Inspection Agency who is qualified and certified to perform inspections under API 510, API 570 or API 653.

I.7

Bending Stress – The variable component of normal stress; the variation may or may not be linear across the section thickness (see Appendix B).

I.8

CET (Critical Exposure Temperature) – The lowest process or atmospheric temperature at which the equipment metal will be exposed to a given stress under either normal or upset conditions. The CET is derived from the operating conditions to which the component is subjected. The CET may be a single temperature at an operating pressure or an envelope of temperatures and pressures, e.g. I-1


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I.1

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This Appendix contains definitions of terms that are used in this recommended practice, or terms that may be found elsewhere in documents related to fitness-for-service evaluation.

I-2 API RECOMMENDED PRACTICE 579 Jan, 2000 _________________________________________________________________________________________________

Coefficient Of Variation (COV) – A statistical measure of a distribution defined as the ratio of the standard deviation of the distribution to the mean of the distribution.

I.10

Corrosion – The deterioration of metal caused by chemical or electrochemical attack (see Section 4).

I.11

Crack-Like Flaw – A flaw which may or may not be the result of linear rupture, but which has the physical characteristics of a crack when detected by an NDE technique (see Section 9).

I.12

Creep – The special case of inelasticity which characterizes the stress induced time-dependent deformation under load, usually occurring at elevated temperatures (see Section 10).

I.13

Creep Damage – In polycrystalline materials (e.g. metals) creep damage results from the motion of dislocations within grains, grain boundary sliding and microstructural diffusion processes within the crystalline lattice. The resultant grain boundary voids, or grain and grain boundary distortions (damage), generally impairs the materials strain hardening capability (see Section 10).

I.14

Creep Rupture – An extension of the creep process to the limiting condition of gross section failure (frequently termed creep fracture). The stress that will cause creep fracture at a given time in a specified environment is the creep rupture strength (see Section 10 and Appendix F).

I.15

Cyclic Service – A service in which fatigue becomes significant due to the cyclic nature of mechanical and/or thermal loads. A screening criteria is provided in Appendix B, paragraph B.5.4 which can be used to determine if a fatigue analysis should be included as part of a fitness for service assessment.

I.16

Damage Mechanism – A phenomena which induces deleterious micro and/or macro material changes that are harmful to the material condition or mechanical properties. Damage mechanisms are usually incremental, cumulative, and unrecoverable. Common damage mechanisms are associated with chemical attack (or corrosion, and the special case of stress-corrosion), creep, erosion, fatigue, fracture, and thermal aging (see Section 2).

I.17

Ductility – The ability of a material to plastically deform without fracturing. One measure used to define ductility from a tensile test specimen is the reduction of area (RA), defined as the ratio of the change in area (taken as the necked area at fracture) to the initial cross sectional area.

I.18

Erosion – The destruction of metal by the abrasive action of a liquid or vapor (see Section 4).

I.19

FAD – The Failure Assessment Diagram (FAD) used for the evaluation of crack-like flaws in components (see Section 2 and Section 9).

I.20

Fatigue – The conditions leading to fracture under repeated or fluctuating stresses having a maximum value less than the tensile strength of the material (see Appendix B).

I.21

Fatigue Endurance Limit – The maximum stress below which a material can undergo an infinite number of alternating stress cycles without failure.

I.22

Fatigue Strength – The maximum stress that a material can sustain for a specific number of cycles without failure (see Appendix F).

I.23

Fatigue Strength Reduction Factor – A stress intensification factor which accounts for the effect of a local structural discontinuity (stress concentration) on the fatigue strength. Values for some specific cases are empirically determined (e.g. socket welds). In the absence of experimental data, the stress


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vapor pressure curve for LPG streams. The methodology used to determine the CET for pressure vessels, piping, and tankage is covered in Section 3.0.

Jan, 2000 RECOMMENDED PRACTICE FOR FITNESS-FOR-SERVICE I-3 _________________________________________________________________________________________________

FCA (Future Corrosion Allowance) – The corrosion allowance required for future operation of a component.

I.25

Fillet Weld – A weld of approximately triangular cross section joining two surfaces approximately at right angles to each other in a lap joint, tee joint, or corner joint.

I.26.

Fitness-for-Service Evaluation – A methodology whereby flaws contained within a structure are assessed in order to determine the adequacy of the structure for continued service without failure (see Section 2).

I.27

Flaw – A discontinuity or irregularity which is detected by inspection.

I.28

Fracture Mechanics – an engineering discipline concerned with the behavior of cracks in materials. Fracture mechanics models provide mathematical relationships for critical combinations of stress, crack size and fracture toughness that lead to crack propagation. Linear Elastic Fracture Mechanics (LEFM) approaches apply to cases where crack propagation occurs during predominately elastic loading with negligible plasticity. Elastic-Plastic Fracture Mechanics (EPFM) methods are suitable for materials that undergo significant plastic deformation during crack propagation.

I.29

Girth Weld – A butt weld joining plate sections along the circumferential direction of a cylinder or cone.

I.30

Gouge – An elongated local mechanical removal and/or relocation of material from the surface of a component, causing a reduction in wall thickness at the defect; the length of a gouge is much greater than the width and the material may have been cold worked in the formation of the flaw. Gouges are typically caused by mechanical damage, for example, denting and gouging of a section of pipe by mechanical equipment during the excavation of a pipeline (see Section 5).

I.31

Groove – A local elongated thin spot caused by directional erosion or corrosion; the length of the metal loss is significantly greater than the width (see Section 5).

I.32

Gross Structural Discontinuity – A source of stress or strain intensification which affects a relatively large portion of a structure and has a significant effect on the overall stress or strain pattern or on the structure as a whole. Examples of gross structural discontinuities are head-to-shell and flange-to-shell junctions, nozzles, and junctions between shells of different diameters or thicknesses.

I.33

Groove-Like Flaw – A surface flaw with a small, but finite, tip (or frontal) radius wherein the flaw length is very much greater than its depth. Groove-like flaws are categorized as either a groove or gouge (see Section 5).

I.34

Heat-Affected Zone (HAZ) – A portion of the base metal adjacent to a weld which has not been melted, but whose metallurgical microstructure and mechanical properties have been changed by the heat of welding, usually with undesirable effects.

I.35

HIC (Hydrogen-Induced Cracking) – Stepwise internal cracks that connect adjacent hydrogen blisters on different planes in the metal, or to the metal surface. No externally applied stress is needed for the formation of HIC. In steels, the development of internal cracks (sometimes referred to as blister cracks) tends to link with other cracks by a transgranular plastic shear mechanism because of internal pressure resulting from the accumulation of hydrogen. The link-up of these cracks on different planes in steels has been referred to as stepwise cracking to characterize the nature of the crack appearance. HIC is commonly found in steels with (a) high impurity levels that have a high density of large planar inclusions, and/or (b) regions of anomalous microstructure produced by segregation of impurity and alloying elements in the steel.


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I.24

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intensification factor can be developed from a theoretical stress concentration factor derived from the theory of elasticity.


I.36

Hydrogen Blistering – The formation of subsurface planar cavities, called hydrogen blisters, in a metal resulting from excessive internal hydrogen pressure. Growth of near-surface blisters in lowstrength metals usually results in surface bulges. Hydrogen blistering in steel involves the absorption and diffusion of atomic hydrogen produced on the metal surface by the sulfide corrosion process. The development of hydrogen blisters in steels is caused by the accumulation of hydrogen that recombines to form molecular hydrogen at internal sites in the metal. Typical sites for the formation of hydrogen blisters are large nonmetallic inclusions, laminations, or other discontinuities in the steel. This differs from the voids, blisters, and cracking associated with high-temperature hydrogen attack.

I.37

Inclusion – Non-metallic material (oxides, silicate, etc.) held mechanically in a metallic matrix as unintentional impurities.

I.38

Incomplete Fusion – Lack of complete melting and coalescence (fusion) of some portion of the metal in a weld joint.

I.39

Incomplete Penetration – Partial penetration of the weld through the thickness of the joint.

I.40

Indication – A discontinuity or irregularity which is detected by inspection.

I.41

In-Service Margin – In terms of applied loads, the ratio of the load that will produce a limiting condition to the applied load in the assessed condition. Similar definitions may be developed for parameters other than load. For example, the safety margin on fracture toughness (see Section 9) is defined as the ratio of the fracture toughness of the material being assessed to the fracture toughness to produce a limiting condition.

I.42

Jurisdiction – A legally constituted government administration which may adopt rules relating to pressure vessels.

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I.43

Limit Analysis – Limit Analysis is a special case of plastic analysis in which the material is assumed to be ideally plastic (non-strain-hardening). In limit analysis the equilibrium and flow characteristics at the limit state are used to calculate the collapse load (see Appendix B).

I.44

Limit Analysis Collapse Load – The methods of limit analysis are used to compute the maximum load a structure made of an ideally plastic material can carry. The deformations of an ideally plastic structure increase without bound at this load, which is termed the collapse load (see Appendix B).

I.45

Local Primary Membrane Stress – Cases arise in which a membrane stress produced by pressure, or other mechanical loading associated with a primary and/or a discontinuity effect would, if not limited, produce excessive distortion in the transfer of load to other portions of the structure. Conservatism requires that such a stress be classified as a local primary membrane stress even though it has some characteristics of a secondary stress (see Appendix B).

I.46

Local Structural Discontinuity – A source of stress or strain intensification which affects a relatively small volume of material and does not have a significant effect on the overall stress or strain pattern, or on the structure as a whole. Examples are small fillet radii, small attachments, and partial penetration welds (see Appendix B).

I.47

Longitudinal Weld – A full penetration butt weld joining plate sections along the longitudinal axis of a cylinder or cone.

I.48

LTA – Locally Thinned Area (see Section 5).

I.49

Major Structural Discontinuity – A source of stress or strain intensification which affects a relatively large portion of a structure and has a significant effect on the overall stress or strain pattern of the structure as a whole. Examples are: head-to-shell and flange-to-shell junctions, nozzles, and, junctions between shells of different diameters or thicknesses (see Appendix B).


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I.50

MAT (Minimum Allowable Temperature) – The permissible lower metal temperature limit for a given material at a specified thickness based on its resistance to brittle fracture. It may be a single temperature, or an envelope of allowable operating temperatures as a function of pressure. The MAT is derived from mechanical design information, materials specifications, and/or materials data.

I.51

MAWP (Maximum Allowable Working Pressure) – The maximum gauge pressure adjusted for liquid head for a component in its operating position at the design temperature, based on calculations using the current minimum thickness, exclusive of thickness required for future corrosion allowance and supplemental loads. Note that this term is also applied to piping components. For components containing a flaw, the MAWP is also a function of the Remaining Strength Factor (see Section 2).

I.52

Max[a1,a2,a3,..,ai] – The definition of a mathematical function which indicates that the maximum value of all of the arguments, ai, is to be computed.

I.53

Membrane Stress – A normal stress or a shear stress which is necessary to satisfy the simple laws of equilibrium due to the externally applied forces and moments. The basic characteristic of a primary stress is that it is not self-limiting. Primary stresses which considerably exceed the yield strength will result in failure, or at least in gross distortion. A thermal stress is not classified as a primary stress. Primary membrane stress is divided into general and local categories. A general primary membrane stress is one that is distributed in the structure such that no redistribution of load occurs as a result of yielding (see Appendix B).

I.54

MFH (Maximum Fill Height) – The maximum height permitted for a liquid with a given specific gravity in an atmospheric storage tank at the design temperature based on calculations using the current minimum thickness for all critical shell elements, exclusive of thickness required for future corrosion allowance and supplemental loads. For components containing a flaw, the MFH is also a function of the Remaining Strength Factor (see Section 2).

I.55

Min[a1,a2,a3,..,ai] – The definition of a mathematical function which indicates that the minimum value of all of the arguments, ai, is to be computed.

I.56

Minimum Allowable Shell Thickness – The thickness required for each element of a vessel based on calculations considering temperature, pressure, and all loadings (see Appendix A).

I.57

Minimum Design Metal Temperature (MDMT) – The lowest temperature at which a significant load can be applied to a pressure vessel as defined by the ASME Code, Section VIII, Division 1, paragraph UG-20 (see Section 3).

I.58

Minimum Safe Operating Temperature (MSOT) – Minimum acceptable operating temperature for an existing vessel based on material brittle fracture considerations (see Section 3).

I.59

MT – Magnetic particle examination.

I.60

NDE – Non-destructive examination.

I.61

Nil-Ductility Temperature – A temperature at which an otherwise ductile material, under a light load, cracks in a manner characteristic of a brittle fracture.

I.62

Normal Stress – The component of stress normal to the plane of reference (this is also referred to as a direct stress). Usually the distribution of normal stress is not uniform through the thickness of a part, so this stress may be considered to be made up of two components. One stress component is uniformly distributed and equal to the average value of stress across the thickness of the section under consideration, and the other stress component varies with the location across the section thickness.

I.63

Notch Sensitivity – A measure of the reduction in the strength of a metal caused by the presence of a stress concentration.


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I.64

Notch Toughness – The ability of a material to resist brittle fracture under conditions of high stress concentration, such as impact loading in the presence of a notch.

I.65

On-Stream Inspection – The use of any of a number of nondestructive examination procedures to establish the suitability of a pressure vessel for continued operation. The vessel may, or may not, be in operation while the inspection is being carried out (API 510).

I.66

Operational Cycle – An operational cycle is defined as the initiation and establishment of new conditions followed by a return to the conditions that prevailed at the beginning of the cycle. Three types of operational cycles are considered: the startup-shutdown cycle, defined as any cycle which has atmospheric temperature and/or pressure as one of its extremes and normal operating conditions as its other extreme; the initiation of, and recovery from, any emergency or upset condition that must be considered in the design; and the normal operating cycle, defined as any cycle between startup and shutdown which is required for the vessel to perform its intended purpose.

I.67

Peak Stress – The basic characteristic of a peak stress is that it does not cause any noticeable distortion and is objectionable only as a possible source of a fatigue crack or a brittle fracture. A stress which is not highly localized falls into this category if it is of a type which cannot cause noticeable distortion (see Appendix B). Examples of peak stress are: the thermal stress in the austenitic steel cladding of a carbon steel vessel, the thermal stress in the wall of a vessel or pipe caused by a rapid change in temperature of the contained fluid, and the stress at a local structural discontinuity.

I.68

Pitting – Localized corrosion in the form of a cavity or hole such that the surface diameter of the cavity is on the order of the plate thickness (see Section 6).

I.69

Plastic Analysis – A stress analysis method where structural behavior under load is computed for a structure considering the plasticity characteristics of the material including strain hardening and stress redistribution (see Appendix B).

I.70

Plastic Instability Load – The plastic instability load for a structure under predominantly tensile or compressive loading is defined as the load at which unbounded plastic deformation can occur without further load increase. At the plastic tensile instability load, the true stress in the material increases faster than the strain hardening can accommodate (see Appendix B).

I.71

Plasticity – A general characterization of material behavior in which the material undergoes time independent non-recoverable deformation (see Appendix B).

I.72

POD (Probability Of Detection) – A measure of the ability to detect a flaw or indication in a component using a standard NDE technique on a consistent basis.

I.73

Primary Stress – A normal or shear stress developed by the imposed loading which is necessary to satisfy the laws of equilibrium of external and internal forces and moments. The basic characteristic of a primary stress is that it is not self-limiting. Primary stresses which considerably exceed the yield strength will result in failure or at least in gross distortion. A thermal stress is not classified as a primary stress. Primary membrane stress is divided into general and local categories. A general primary membrane stress is one that is distributed in the structure such that no redistribution of load occurs as a result of yielding. Examples of primary stress are general membrane stress in a circular cylindrical or a spherical shell due to internal pressure or to distributed live loads and the bending stress in the central portion of a flat head due to pressure. Cases arise in which a membrane stress produced by pressure or other mechanical loading and associated with a primary and/or a discontinuity effect would, if not limited, produce excessive distortion in the transfer of load to other portions of the structure. Conservatism requires that such a stress be classified as a local primary membrane stress even though it has some characteristics of a secondary stress. Finally a primary bending stress can be defined as a bending stress developed by the imposed loading which is necessary to satisfy the laws of equilibrium of external and internal forces and moments (see Appendix B).


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I.74

PSF (Partial Safety Factor) – A deterministic parameter (derived from statistical considerations) which represents a level of uncertainty or importance for a specific field variable. For example, in a fracture mechanics analysis, distinct PSF’s may be applied to each of the loading, material toughness and crack sizing variables. In combination these factors yield a desired level of confidence (i.e. degree of safety) in the calculated fracture assessment result. Where the method is prescribed, tabulations are provided which map the required (or critical) analysis variables to a user selected risk level and the associated PSF multiplier. As an application example, the PSF methodology is well established in the Load and Resistance Factor Design Manual of the American Institute of Steel Construction (see Section 2).

I.75

PT – Liquid penetrant examination.

I.76

PWHT (Postweld Heat Treatment) – Uniform heating of a weldment to a temperature below the critical range to relieve the major part of the residual stresses, followed by uniform cooling in still air.

I.77

Ratcheting – is a progressive incremental inelastic deformation or strain that can occur in a component subjected to variations of mechanical stress, thermal stress, or both (thermal stress ratcheting is partly or wholly caused by thermal stress).

I.78

Recognized Code or Standard – is a term used to define a code or standard that is recognized by a local jurisdiction (see Section 1, paragraphs 1.2.2 and 1.2.3).

I.79

Repair – restoration of a pressure containing component, the definition is dependent on the equipment type as shown below: a.

Pressure vessels (API 510) – The work necessary to restore a vessel to a condition suitable for safe operation at the design conditions. Repairs also include the addition or replacement of pressure or non-pressure parts which do not change the rating of a vessel.

b.

Piping systems (API 570) – The work necessary to restore a piping system to a condition suitable for safe operation at the design conditions. Such repairs are typically completed in compliance with the schedule and pressure class requirements of the piping system. Repairs resulting in schedule/class deviations (e.g. use of lower pressure class fittings) may impact the system design conditions.

c.

Storage tanks (API 653) – any work on a tank involving, cutting, burning, welding, or heating operations that changes the overall physical dimensions and/or configuration of a tank.

I.80

Rerating – A change in either or both the temperature rating or the maximum allowable working pressure rating of a vessel.

I.81

RSF (Remaining Strength Factor) – Ratio of the collapse pressure of a shell with a locally thinned area to the collapse pressure of the shell without a locally thinned area (see Section 2).

I.82

RT – Radiographic examination.

I.83

Secondary Stress – A normal stress or a shear stress developed by the constraint of adjacent parts or by self-constraint of a structure. The basic characteristic of a secondary stress is that it is selflimiting. Local yielding and minor distortions can satisfy the conditions which cause the stress to occur and failure from one application of the stress is not to be expected (see Appendix B). Examples of secondary stress are a general thermal stress; and the bending stress at a gross structural discontinuity.

I.84

Sensitivity Analysis – A statistical or parametric process of varying the independent variables (or inputs) in order to determine the response (or sensitivity ) of the dependent variables (or outputs). For example, in a fitness-for-service analysis, determination of the maximum permissible crack length may have a strong sensitivity to temperature variation if the material fracture toughness (a material property) is also strongly influenced by temperature (see Section 2).

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I.85

Shakedown – Shakedown of a structure occurs if, after a few cycles of load applications, ratcheting ceases. The subsequent structural response is elastic, or elastic-plastic, and progressive incremental inelastic deformation is absent. Elastic shakedown is the case in which the subsequent response is elastic (see Appendix B).

I.86

Shear Stress – The component of stress tangent to the plane of reference.

I.87

Shock Chilling – A rapid decrease in equipment temperature caused by a sudden flow of fluids o o colder than -29 C (-20 F); or a rapid change in temperature that is lower than the initial temperature o o of the equipment component by at least 38 C (100 F), regardless of pressure. Consideration of the Biot and Fourier numbers (as derived for transient heat transfer analyses) are also useful in assessing the merit of shock chilling. A Biot number which is less than 3, or the product of the Biot and Fourier numbers being less than one, are generally indications of benign conditions for a onetime transient.

I.88

SOHIC (Stress-Oriented Hydrogen-Induced Cracking) – Arrays of cracks, aligned nearly perpendicular to the stress, that are formed by the link-up of small HIC cracks in steel. Tensile stress (residual or applied) is required to produce SOHIC. SOHIC is commonly observed in the base metal adjacent to the heat-affected zone (HAZ) of a weld, oriented in the through-thickness direction. SOHIC may also be produced in susceptible steels at other high stress points such as from the tip of mechanical cracks and defects, or from the interaction among HIC on different planes in the steel.

I.89

Strain Limiting Load – When a limit is placed upon a strain, the load associated with the strain limit is called the strain limiting load.

I.90

Stress Concentration Factor – The ratio of the maximum stress to the average section stress.

I.91

Stress Cycle – A stress cycle is a condition in which the alternating stress difference goes from an initial value through an algebraic maximum value and an algebraic minimum value and then returns to the initial value. A single operational cycle may result in one or more stress cycles.

I.92

Stress Intensity – The equivalent intensity of combined stress, or in short the stress intensity, is defined as twice the maximum shear stress. In other words, the stress intensity is the difference between the algebraically largest principal stress and the algebraically smallest principal stress at a given point (see Appendix B).

I.93

Stress Intensity Factor – A measure of the stress-field intensity near the tip of an ideal crack in a linear elastic medium when deformed so that the crack faces are displaced apart, normal to the crack plane (i.e. crack opening mode or Mode I deformation). The Mode I stress intensity factor (KI) is directly proportional to the applied load and depends on specimen geometry (see Appendix C).

I.94

Sulfide Stress Cracking (SSC) – Cracking of a metal under the combined action of tensile stress and corrosion in the presence of water and H2S (a form of hydrogen stress cracking). SSC involves hydrogen embrittlement of the metal by atomic hydrogen that is produced by the sulfide corrosion process on the metal surface. The atomic hydrogen can diffuse into the metal and produce embrittlement. SSC usually occurs more readily in high-strength steels or in hard weld zones of steels.

I.95

Tensile Strength – The maximum load per unit of original cross sectional area which a tensile test specimen of a material sustains prior to fracture. The tensile strength may also be identified as the ultimate tensile strength (see Appendix F).

I.96

Thermal Stress – A self-balancing stress produced by a nonuniform distribution of temperature or by differing thermal coefficients of expansion. Thermal stress is developed in a solid body whenever a volume of material is prevented from assuming the size and shape that it normally should under a change in temperature. For the purpose of establishing allowable stresses, two types of thermal stress are recognized, depending on the volume or area in which distortion takes place. A general thermal stress which is associated with distortion of the structure in which it occurs. If a stress of this


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type, neglecting stress concentrations, exceeds twice the yield strength of the material, the elastic analysis may be invalid and successive thermal cycles may produce incremental distortion. Therefore this type is classified as a secondary stress. Examples of general thermal stress are: the stress produced by an axial temperature distribution in a cylindrical shell, the stress produced by the temperature difference between a nozzle and the shell to which It is attached, and the equivalent linear stress produced by the radial temperature distribution in a cylindrical shell. A Local thermal stress is associated with almost complete suppression of the differential expansion and thus produces no significant distortion. Such stresses shall be considered only from the fatigue standpoint and are therefore classified as local stresses. Examples of local thermal stresses are the stress in a small hot spot in a vessel wall, the difference between the actual stress and the equivalent linear stress resulting from a radial temperature distribution in a cylindrical shell, and the thermal stress in a cladding material which has a coefficient of expansion different from that of the base metal. I.97

Toughness – The ability of a material to absorb energy and deform plastically before fracturing (see Appendix F).

I.98

Transition Temperature – The temperature at which a material fracture mode changes from ductile to brittle.

I.99

Undercut -An intermittent or continuous groove, crater or channel that has melted below, and thus undercut, the surface of the base metal adjacent to the toe of a weld and is left unfilled by weld metal.

I.100

UT – Ultrasonic examination.

I.101

Volumetric Flaw -A flaw characterized by a loss of material volume or by a shape imperfection. Examples include general and local corrosion, pitting, blisters, out-of-roundness, bulges, dents and weld misalignment.

I.102

Weld – A localized coalescence of metal wherein coalescence (i.e. fusion) is produced by heating to suitable temperatures, with or without the application of pressure, and with or without the use of filler metal. The filler metal typically has a melting point approximately the same as that of the base metal.

I.103

Yield Strength – The stress at which a material exhibits a specified deviation from the linear proportionality of stress versus strain (see Appendix F).

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Appendix J – Technical Inquiries (Jan, 2000) J.1

Introduction API will consider written requests for interpretations of API Recommended Practice 579. API staff will make such interpretations in writing after consulting, if necessary, with the appropriate committee officers and committee members. The API committee responsible for maintaining RP 579 meets regularly to consider written requests for interpretations and revisions and to develop new criteria dictated by technological development. The committee’s activities in this regard are limited strictly to interpretations of the document and to the consideration of revisions to the current edition of the document on the basis of new data or technology. As a matter of policy, API does not approve, certify, rate, or endorse any item, construction, proprietary device, or activity, and accordingly, inquiries that require such consideration will be returned. Moreover, API does not act as a consultant on specific engineering problems or on the general understanding or application of RP 579. If, based on the inquiry information submitted, it is the opinion of the committee that the inquirer should seek other assistance, the inquiry will be returned with the recommendation that such assistance be obtained. All inquiries that cannot be understood because they lack information will be returned.

J.2

Inquiry Format

J.2.1

Inquiries shall be limited strictly to requests for interpretation of RP 579 or to the consideration of revisions to the document on the basis of new data or technology. Inquiries shall be submitted in the format described in J.2.2 through J.2.5.

J.2.2

The scope of an inquiry shall be limited to a single subject or a group of closely related subjects. An inquiry concerning two or more unrelated subjects will be returned.

J.2.3

An inquiry shall start with a background section that states the purpose of the inquiry, which would be either to obtain an interpretation of RP 579 or to propose a revision to the document. The background section shall concisely provide the information needed for the committee’s understanding of the inquiry (with sketches as necessary) and shall cite the applicable edition, revision, paragraphs, figures, and tables.

J.2.4

After the background section, an inquiry’s main section shall state the inquiry as a condensed, precise question, omitting superfluous background information and, where appropriate, posing the question so that the reply could take the form of “yes” or “no” (perhaps with provisos). This inquiry statement should be technically and editorially correct. The inquirer shall state what he or she believes the document requires. If the inquirer believes a revision to RP 579 is needed, he or she shall provide recommended wording.

J.2.5

The inquirer shall include his or her name and mailing address. The inquiry should be typed; however, legible handwritten inquiries will be considered. Inquiries should be submitted to the director of the Manufacturing, Distribution and Marketing Department, American Petroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005.

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