Guidelines for Interpretation and Application of API 1104

Catalog No. L52306

Guidelines for Interpretation and Application of API 1104 PR-82681361-6

Prepared for the

Pipeline Research Council International, Inc.

Prepared by: DNV Columbus, Inc. Asset Risk Management 5777 Frantz Road Dublin, OH 43017-1386

Publication Date: April 2010

ACKNOWLEDGEMENTS This report is furnished to Pipeline Research Council International, Inc. (PRCI) under the terms of PRCI Contract No. PR-82681361-6 between PRCI and Det Norske Veritas (DNV). The contents of this report are published as received from DNV. The opinions, findings, and conclusions expressed in the report are those of the authors and not necessarily those of PRCI, its member companies, or their representatives. Publication and dissemination of this report by PRCI should not be considered an endorsement by PRCI or DNV, or the accuracy or validity of any opinions, findings, or conclusions expressed herein. In publishing this report, PRCI makes no warranty or representation, expressed or implied, with respect to the accuracy, completeness, usefulness, or fitness for purpose of the information contained herein, or that the use of any information, method, process, or apparatus disclosed in this report may not infringe on privately owned rights. PRCI assumes no liability with respect to the use of, or for damages resulting from the use of, any information, method, process, or apparatus disclosed in this report. The text of this publication, or any part thereof, may not be reproduced or transmitted in any form by any means, electronic or mechanical, including photocopying, recording, storage in an information retrieval system, or otherwise, without the prior, written approval of PRCI.

Pipeline Research Council International Catalog No. L52306

Copyright 2010 All Rights Reserved by Pipeline Research Council International, Inc. PRCI Reports are published by Technical Toolboxes, Inc. 3801 Kirby Drive, Suite 520 Houston, Texas 77098 Tel: 713-630-0505 Fax: 713-630-0560 Email: [email protected]

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Final Report for Pipeline Research Council International, Inc. Guidelines for Interpretation and Application of API 1104

This report is furnished to Pipeline Research Council International, Inc. (PRCI) under the terms of PRCI Contract No. API-1-2 between PRCI and DNV Columbus, Inc. (DNV). The contents of this report are published as received from DNV. The opinions, findings, and conclusions expressed in the report are those of the authors and not necessarily those of PRCI, its member companies, or their representatives. Publication and dissemination of this report by PRCI should not be considered an endorsement by PRCI or DNV, or the accuracy or validity of any opinions, findings, or conclusions expressed herein. In publishing this report, PRCI makes no warranty or representation, expressed or implied, with respect to the accuracy, completeness, usefulness, or fitness for purpose of the information contained herein, or that the use of any information, method, process, or apparatus disclosed in this report may not infringe on privately owned rights. PRCI assumes no liability with respect to the use of, or for damages resulting from the use of, any information, method, process, or apparatus disclosed in this report. The text of this publication, or any part thereof, may not be reproduced or transmitted in any form by any means, electronic or mechanical, including photocopying, recording, storage in an information retrieval system, or otherwise, without the prior, written approval of PRCI.

Revision No.: 1 Date: April 30, 2010

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Table of Contents 1.

INTRODUCTION ................................................................................................................. 1

2.

BACKGROUND ................................................................................................................... 1

3.

REVIEW OF INDUSTRY NEEDS AND PRACTICES....................................................... 2

4.

FORMAT DEVELOPMENT ................................................................................................ 2

5.

DEVELOPMENT OF GUIDANCE MATERIAL ................................................................ 3 5.1

Example 1 – Wall Thickness Groupings For Specification Information...................... 4

5.2

Example 2 – Essential Variable for Joint Design ......................................................... 4

6.

INDUSTRY REVIEW........................................................................................................... 5

7.

RESULTING GUIDANCE DOCUMENT............................................................................ 5

8.

SUMMARY AND CONCLUSIONS .................................................................................... 6

9.

ACKNOWLEGEMENTS...................................................................................................... 6

10.

REFERENCES ...................................................................................................................... 8

Appendix A. Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities


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1.

INTRODUCTION

The application of requirements contained in many industry codes and standards requires some interpretation by the user and by the regulator who is called upon to enforce their use. There are often differences in the way requirements are interpreted because of unclear rationale behind the requirements or novel or non-traditional applications. Some industry codes and standards contain guidance in the form of commentary sections or companion documents. This is not the case for API Standard 1104 – Welding of Pipelines and Related Facilities, where requests for interpretation are common because of unclear requirements or an absence of information pertaining to rationale. Since API 1104 is written in the form of a specification, it cannot present background information or discuss the intent of the API 1104 committee. The intent of the API 1104 committee, and the rationale pertaining to how some of the requirements in API 1104 came about, lies with individuals who have been or were members of the committee for many years. Unfortunately, many of these individuals are no longer with us. The objective of this project was to develop guidance material for API 1104. The use of this guidance material will allow users and regulators to better understand the intent regarding interpretation of some requirements in API 1104, the rationale behind the requirements, and the applicability of the requirements to both conventional and modern high-strength pipelines.

2.

BACKGROUND

API Standard 1104 – Welding of Pipelines and Related Facilities,(1) is the most widely-used industry standard in the world for pipeline construction. For the majority of cross country pipelines constructed in the United States, the use of certain sections of API 1104 is mandated by Federal regulations. Many changes in the pipeline industry have occurred since the First Edition of API 1104 was introduced in 1953, although many of the construction practices that were used then are still used today. Significant changes include the development of higher strength line pipe materials and the development of high-productivity mechanized welding equipment. Many new long-distance transmission pipelines are constructed today using high-strength line pipe materials and highproductivity mechanized welding equipment, and the completed girth welds are inspected using automated ultrasonic testing (AUT) equipment. In spite of these developments, many pipelines are still constructed using lower-strength material and conventional “stove-pipe” welding practices and the completed girth welds are inspected using radiographic testing (RT). API 1104 is revised regularly to adapt to changing pipeline construction practices. The current version, which was issued in November 2005, is the Twentieth Edition. An addenda/errata to the Twentieth Edition was issued in July 2007. In spite of these revisions, there are many requirements in API 1104 that are subject to interpretation. For example, many of the suggested ranges for procedure and welder qualification are nearly always taken literally, whereas the Revision No.: 1 Date: April 30, 2010

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intent is to allow flexibility. Where the user does elect to specify another range or grouping, no guidance is given as to what constitutes an acceptable range or grouping. This can result in procedures that are less than completely sound when ranges that are too wide are specified or difficult to execute in the field when ranges that are too narrow are specified. The lack of guidance gives regulators little support in terms of enforcement. There is a formal procedure for handling requests for interpretations within the API 1104 committee structure, but these can take weeks and sometimes take up to a full year to resolve. There is also a database of previous requests for interpretations (technical inquiries), but this only contains relatively recent inquiries (from 1996) and the existence of this database may not be apparent to the typical user. The development of a guidance document for API 1104, similar to the commentary section contained in AWS D1.1, Structural Welding Code – Steel,(2) would alleviate some of the concerns raised above. AWS D1.1 is the most widely used reference for structural steel welding. The commentary section of this code provides users with valuable information pertaining to interpretation, rationale, and applicability of the code. The Canadian standard CSA Z662- Oil and Gas Pipeline Systems(3) also contains a commentary document for this purpose.

3.

REVIEW OF INDUSTRY NEEDS AND PRACTICES

The needs of the industry with respect to what sections of API 1104 require clarification or supplementary guidance were reviewed. This included a review of the API 1104 database for technical inquiries(4) to determine what topics or sections require the most frequent need for interpretation. This on-line document includes inquiries that have been submitted from 1996 to the present. Representatives from PRCI member companies were also informally surveyed to better define areas of concern. Other industry standards that contain guidance pertaining to topics of concern were also reviewed. For example, AWS B2.1-84, Standard for Welding Procedure and Performance Qualification,(5) is a universal document that contains requirements for the qualification of welding procedures and for the performance qualification of welders and welding operators. A literature search was also performed to identify published journal articles, conference papers, etc.,(6-8) that contain guidance that could be included in the document. In addition, a very useful document that is part of the American Welding Society Certified Welding Inspector program was identified and used (with permission from AWS). This document, AWS API-M:2006, Study Guide for API Standard 1104,(9) contains section-by-section guidance pertaining to understanding and learning how to apply API 1104.

4.

FORMAT DEVELOPMENT

The required format for the guidance document was developed. From the onset of this project, it is anticipated that the format would follow the format of the API 1104 document itself. Where additional guidance and/or a description of the rationale behind the requirement was determined


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to be necessary, it was developed and included in a draft of the guidance document. Where the requirement is self-explanatory, this was indicated in the draft document. The draft of the guidance document included two parallel columns; one contained the text of API 1104 and the other contained the corresponding guidance material. The benefit of this format is that it allowed side-by-side comparison of the text in API 1104 with the guidance material. Discussions were held with personnel at API regarding the use of the API 1104 text in the guidance document. Since API 1104 is a top-selling document for API, they were reluctant to allow the text of API 1104 to be reproduced in the guidance document. API eventually declined a request to allow the use of the API 1104 text in the guidance document, either outright or through a revenue sharing agreement. The resulting guidance document therefore contains only the guidance material, which will require that both documents be available to the user for effective use of the guidance document. The outline of the guidance document follows the outline in the API 1104 document itself. Sections of the guidance document are preceded with the letter “G” for “guidance”. For example, 5.3.2.11 in API 1104 is titled “Type and Removal of Lineup Clamp”. In the guidance document, guidance material for this section can be found in G5.3.2.11. Tables and figures in the guidance document are also preceded with the letter “G” to differentiate between these and the tables and figures in API 1104 itself. Some of the guidance material is repeated in several places in the guidance document. It is anticipated that this document will not be read cover-to-cover, but that certain sections will be referred to on as needed basis (i.e., it will be used as a look-up document) This repetition is intentional and is intended to provide the required guidance in each of the places where it is needed. For example, someone who is qualifying procedures for mechanized welding (Section 12) may not think to look in Section 5 (procedure qualification for manual welding) for essential variable guidance pertaining to preheating and inter-pass temperature, so the guidance material is provided in both places.

5.

DEVELOPMENT OF GUIDANCE MATERIAL

The majority of the effort for this project focused on the development of material for the guidance document. Where necessary, items that were determined to be in need of guidance were researched to identify the source of the requirement and the rationale behind the requirement. The guidance material was developed from this and using a variety of resources. These resources included: •

AWS API-M:2006 – Study Guide for API Standard 1104

•

API 1104 Technical Inquiries Database

•

CSA Z662 – Oil and Gas Pipeline Systems – code and commentary

•

ASME Section IX – Welding and Brazing Qualifications(10)


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•

AWS B2.1-84 – Standard for Welding Procedure and Performance Qualification

•

AWS D1.1:2000, Structural Welding Code – Steel

•

Proposed revisions to API 1104 (from committee member correspondence)

•

Project team member experience

•

Inquiries to PRCI member company representatives

To the extent that it was possible, the guidance that was developed pertains to both conventional pipelines constructed using conventional stove-pipe welding practices and modern high-strength pipelines constructed using high-productivity mechanized welding equipment. Guidance pertaining to Appendix A of API 1104 (alternative acceptance standards based on fitness-forpurpose criteria) was developed by Yong-Yi Wang at Center for Reliable Energy Systems, LLC. Guidance pertaining to Appendix B of API 1104 (in-service welding) was also developed. Two examples that describe the development of the guidance material, both of which pertain to qualification of welding procedures (Section 5 in API 1104), are provided below:

5.1

Example 1 – Wall Thickness Groupings for Specification Information

When developing a welding procedure, 5.3.2.3 of API 1104 (specification information for diameters and wall thicknesses) indicates: The ranges of outside diameters and wall thicknesses over which the procedure is applicable shall be identified. Examples of suggested groupings are shown in 6.2.2, items d and e. The guidance material for 5.3.2.3, in part, indicates: The suggested groupings shown in 6.2.2, items d and e are just that – suggested groupings. Other groupings can be used provided that there is technical justification for doing so based on sound engineering judgment. Guidance can be found in a variety of other codes and standards. For example, some codes limit wall thickness to which the procedure is applicable from some minimum thickness to 2t, where t is the wall thickness used for procedure qualification. The suggestion that some minimum thickness to 2t might be a reasonable alternative to the wall thickness groupings shown in 6.2.2 was taken from ASME Section IX (QW-451). For procedures qualified on material that is over 3⁄8 inch (10 mm) thick but less than 3⁄4 inch (19 mm) thick, the thickness range qualified according to ASME Section IX is 3⁄16 inch (5 mm) to 2t. AWS B2.1-84 includes this same provision (Paragraph 2.4.1).

5.2

Example 2 – Essential Variable for Joint Design

When determining the applicability of a qualified welding procedure, 5.4.2.3 of API 1104 (essential variable requirements for joint design) indicates: Revision No.: 1 Date: April 30, 2010

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A major change in joint design (for example, from V groove to U groove) constitutes an essential variable. Minor changes in the angle of bevel or the land of the welding groove are not essential variables. The guidance material for 5.4.2.3, in part, indicates: API 1104 does not define what constitutes a minor change in joint design. It would seem reasonable to allow changes to the bevel angle of up to + 20%/-5% of the nominal value and changes to the root opening or land of up to +/- 50% of the nominal value without the need for requalification. The suggested ranges given in the guidance material were taken from CSA Z662 (Clause 7.6.5) for manual or semi-automatic welding. The guidance material for 5.4.2.3 also indicates A change from a butt weld to a fillet weld is a major change in joint design, thus requiring that a new procedure be qualified. A change from a fillet weld to a groove weld of a branch connection is also a major change in joint design, thus requiring that a new procedure be qualified. However, a branch connection can consist of a groove weld and a fillet weld. Therefore, for welding fullencirclement sleeves that involve only fillet welds, a welding procedure qualified for a branch connection (groove and fillet weld) is sufficient. However, a welding procedure qualified by welding a full encirclement sleeve (fillet weld only) is not sufficient for welding a branch connection that includes a groove weld. This guidance material was derived from a combination of responses listed in the API 1104 Technical Inquiries Database (Inquiry Nos. 1104-I-0810-96, 1104-I-1122-96, and 1104-I-0608-04).

6.

INDUSTRY REVIEW

As draft sections of the guidance document were developed, these were sent to various industry representatives for review. These included current members of the API 1104 committee, former (retired) committee members, representatives from PRCI member companies, federal regulators in the US, and other interested individuals. Comments and suggestions from these individuals were incorporated into the draft sections, as appropriate.

7.

RESULTING GUIDANCE DOCUMENT

Following review and revision, each the draft sections was used to develop a final version of the guidance document. The primary focus of this task was the development of an easy to read, cohesive document that will be useful to both users and regulators. The final version of the guidance document is provided in the appendix of this report. The guidance material that was developed pertains to the Twentieth Edition of API 1104 (November 2005) as amended by the addenda/errata that was issued in July 2007. Periodic


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updates to the guidance document will be required as subsequent editions of API 1104 are published. The guidance document contains a disclaimer in the Forward section that reads as follows: The guidance material contained in this document is not part of the API 1104 standard and it has not been reviewed or approved by the committee responsible for API 1104 (API-AGA Joint Committee on Oil and Gas Pipeline Field Welding Practices). Accordingly, this guidance material does not provide formal interpretations of the standard. To request formal interpretations by the committee, the procedure outlined in the Forward section of API 1104 should be followed. The Forward section goes on to say the following: The guidance material contained in this document includes the opinions of the authors and contributors and not necessarily those of API or PRCI. While the authors believe that guidance document provided in the appendix of this report will indeed be useful to both users and regulators, there are certainly improvements that are possible. For example, the guidance material for some sections is more comprehensive than for others. In addition to periodic updates, further revisions of the guidance document can incorporate expanded guidance for these less-comprehensive sections.

8.

SUMMARY AND CONCLUSIONS

The use of the resulting guidance document will allow both users and regulators to better understand the intent regarding the interpretation of some requirements, the rationale behind the requirements, and the applicability of API 1104 to both conventional and modern high-strength pipelines. The use of this document will also increase the safety and reliability of newly constructed pipeline by avoiding misinterpretation of requirements. It will also allow users to confidently tailor welding procedures to better fit the requirements for their specific needs without fear of violating arbitrarily established ranges and groupings. This may in turn reduce the cost of pipeline construction and maintenance activities. While the authors believe that the guidance document provided in the appendix of this report will indeed be useful to both users and regulators, a planned update and refinement of this document will be beneficial.

9.

ACKNOWLEGEMENTS

The authors would like to thank those individuals who contributed to the development of the guidance material, either through direct contributions of material or by reviewing drafts of the guidance material. These individuals include, but are not limited to, Alan Beckett (Alyeska Pipeline Service Company), Geoff Rogers (Spectra Energy), Jan van der Ent (Applus RTD), James Barber (Marathon Pipe Line LLC), Ken Lee (Lincoln Electric Company, now with US Revision No.: 1 Date: April 30, 2010

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Department of Transportation), Jim McHaney (Microalloying International), Gery Bauman (US Department of Transportation), Joe Kiefer (ConocoPhillips), and Bob Wright (retired API 1104 committee member). Permission from American Welding Society for the use of the existing guidance material in AWS API-M:2006 (Study Guide for API Standard 1104) is also greatly appreciated. The authors would also like to thank Steve Rapp (Spectra Energy), who conceived the idea of this project and acted as the project leader for PRCI, the PRCI project team members, and Tara Podnar and Libby Brannon at DNV for their contributions in the early stage of this project.


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10.

REFERENCES

1.

API Standard 1104, Welding of Pipelines and Related Facilities, American Petroleum Institute, Washington, D.C., 2005.

2.

AWS D1.1:2000, Structural Welding Code – Steel, American Welding Society, Miami, Florida, 2000.

3.

CSA Z662-03, Oil and Gas Pipeline Systems, Canadian Standards Association, Mississauga, Ontario, Canada, 2003.

4.

API 1104 Technical Inquiries Database – http://committees.api.org/standards/tech/ pplnti.html

5.

AWS B2.1-84, Standard for Welding Procedure and Performance Qualification, American Welding Society, Miami, Florida, 1984.

6.

Bruce, W. A., “Recent Changes in Code Requirements for Repair of In-Service Pipelines by Welding,” International Pipeline Conference – IPC 2000 (Calgary), 2000.

7.

Underwood, A. C., “It Pays to Understand Pipeline Standards,” Welding Design & Fabrication, February 1979.

8.

Wang Y.-Y, Liu, M., Horsley, D., and Bauman, G., “A Tiered Approach to Girth Weld Defect Acceptance Criteria for Stress-Based Design of Pipelines”, International Pipeline Conference – IPC 2006 (Calgary), 2006.

9.

AWS API-M:2006, Study Guide for API Standard 1104, American Welding Society, Miami, Florida, 2006.

10.

ASME Boiler and Pressure Vessel Code, Section IX: Welding and Brazing Qualifications, American Society of Mechanical Engineers, New York, New York, July 2007.


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Appendix A Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities PRCI Project No. API 1-2 – Interpretation and Guidelines for Application of API 1104 DNV Columbus, Inc.1 William A. Bruce, P.E., IWE William E. Amend, P.E. Center for Reliable Energy Systems, LLC2 Yong-Yi Wang, Ph.D.

1 2

Except Appendix A Appendix A only

Revision 1 – April 30, 2010


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Forward The objective of this document is to provide guidance material for American Petroleum Institute (API) Standard 1104 – Welding of Pipelines and Related Facilities that will allow users and regulators to better understand the intent regarding interpretation of some requirements in API 1104, the rationale behind the requirements, and the applicability of the requirements to both conventional and modern high-strength pipelines. The guidance material contained in this document is not part of the API 1104 standard and it has not been reviewed or approved by the committee responsible for API 1104 (API-AGA Joint Committee on Oil and Gas Pipeline Field Welding Practices). Accordingly, this guidance material does not provide formal interpretations of the standard. To request formal interpretations by the committee, the procedure outlined in the Forward section of API 1104 should be followed. The guidance material contained in this document pertains to the Twentieth Edition of API 1104 (November 2005) as amended by the Errata/Addenda issued in July 2007. Updates to this guidance material will be required as subsequent editions of API 1104 are released. It was not possible to include the text of API 1104 in this document because of copyright restrictions. It is therefore necessary to use this document in conjunction with a copy of the API 1104 standard itself. However, the outline of this document follows that in API 1104. The guidance material contained in this document includes the opinions of the authors and contributors and not necessarily those of API or Pipeline Research Council International (PRCI).

General Comments 1. As indicated in the Forward section above, it was not possible to include the text of API 1104 in this document. Therefore, it is necessary to have a copy of API 1104 open in front of you for the guidance material to make much sense. It is strongly suggested that you read the paragraph in API 1104 and then read the guidance material that corresponds to that paragraph. It makes little sense to read the guidance material only. 2. A common source of error when using API 1104 is confusing requirements for welding procedure qualification (Section 5) and those for welder qualification (Section 6), and vice versa. Both have similar requirements for making a test weld and then subjecting that weld to a variety of tests. While similar, there are subtle differences between these two sections. Another common source of error is misunderstanding essential variable requirements. The essential variables for welding procedure qualification are different than those for welder qualification. Special attention should be given to assure that the requirements in Section 5 are applied to welding procedure qualification and the requirements in Section 6 are applied to welder qualification.



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Contents G1 General ...................................................................................................................................... 1 G1.1 Scope.................................................................................................................................. 1 G2 Referenced Publications............................................................................................................ 1 G3 Definition of Terms................................................................................................................... 2 G3.1 General ............................................................................................................................... 2 G3.2 Definitions.......................................................................................................................... 2 G4 Specifications ............................................................................................................................ 4 G4.1 Equipment .......................................................................................................................... 4 G4.2 Materials............................................................................................................................. 4 G5 Qualification of Welding Procedures for Welds Containing Filler-metal Additives................ 5 G5.1 Procedure Qualification ..................................................................................................... 5 G5.2 Record ................................................................................................................................ 5 G5.3 Procedure Specification ..................................................................................................... 5 G5.4 Essential Variables............................................................................................................. 9 G5.5 Welding of Test Joints-Butt Welds.................................................................................. 11 G5.6 Testing of Welded Joints-Butt Welds .............................................................................. 11 G5.7 Welding of Test Joints-Fillet Welds ................................................................................ 14 G5.8 Testing of Welded Joints-Fillet Welds............................................................................. 14 G6 Qualification of Welders......................................................................................................... 15 G6.1 General ............................................................................................................................. 15 G6.2 Single Qualification ......................................................................................................... 15 G6.3 Multiple Qualification...................................................................................................... 16 G6.4 Visual Examination.......................................................................................................... 17 G6.5 Destructive Testing .......................................................................................................... 17 G6.6 Radiography-Butt Welds Only......................................................................................... 18 G6.7 Retesting........................................................................................................................... 18 G6.8 Records............................................................................................................................. 19 G7 Design and Preparation of a Joint for Production Welding .................................................... 19 G7.1 General ............................................................................................................................. 19 G7.2 Alignment......................................................................................................................... 19 G7.3 Use of Lineup Clamp for Butt Welds .............................................................................. 20 G7.4 Bevel ................................................................................................................................ 20 G7.5 Weather Conditions.......................................................................................................... 20 G7.6 Clearance.......................................................................................................................... 20 G7.7 Cleaning Between Beads ................................................................................................. 20 G7.8 Position Welding.............................................................................................................. 21 G7.9 Roll Welding .................................................................................................................... 21 G7.10 Identification of Welds................................................................................................... 21 G7.11 Pre- and Post-Heat Treatment ........................................................................................ 21 Revision 1 – April 30, 2010


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Contents (continued) G8 Inspection and Testing of Production Welds .......................................................................... 22 G8.1 Rights of Inspection ......................................................................................................... 22 G8.2 Methods of Inspection...................................................................................................... 22 G8.3 Qualification of Inspection Personnel.............................................................................. 23 G8.4 Certification of Nondestructive Testing Personnel.......................................................... 23 G9 Acceptance Standards for Nondestructive Testing ................................................................. 23 G9.1 General ............................................................................................................................. 23 G9.2 Rights of Rejection........................................................................................................... 24 G9.3 Radiographic Testing ....................................................................................................... 24 G9.4 Magnetic Particle Testing ................................................................................................ 26 G9.5 Liquid Penetrant Testing.................................................................................................. 27 G9.6 Ultrasonic Testing ............................................................................................................ 27 G9.7 Visual Acceptance Standards for Undercutting ............................................................... 33 G10 Repair and Removal of Defects ............................................................................................ 33 G10.1 Authorization for Repair ................................................................................................ 33 G10.2 Repair Procedure............................................................................................................ 33 G10.3 Acceptance Criteria........................................................................................................ 34 G10.4 Supervision..................................................................................................................... 34 G10.5 Welder............................................................................................................................ 34 G11 Procedures for Nondestructive Testing................................................................................. 34 G11.1 Radiographic Test Methods ........................................................................................... 34 G11.2 Magnetic Particle Test Method ...................................................................................... 36 G11.3 Liquid Penetrant Test Method........................................................................................ 37 G11.4 Ultrasonic Test Methods ................................................................................................ 37 G12 Mechanized Welding with Filler Metal Additions ............................................................... 40 G12.1 Acceptable Processes ..................................................................................................... 40 G12.2 Procedure Qualification ................................................................................................. 40 G12.3 Record ............................................................................................................................ 40 G12.4 Procedure Specification ................................................................................................. 40 G12.5 Essential Variables......................................................................................................... 44 G12.6 Qualification of Welding Equipment And Operators .................................................... 45 G12.7 Records OF Qualified Operators.................................................................................... 46 G12.8 Inspection and Testing of Production Welds ................................................................. 46 G12.9 Acceptance Standards for Nondestructive Testing ........................................................ 46 G12.10 Repair and Removal of Defects ................................................................................... 47 G12.11 Radiographic Testing ................................................................................................... 47 G13 Automatic Welding Without Filler- metal Additions ........................................................... 47 G13.1 Acceptable Processes ..................................................................................................... 47 G13.2 Procedure Qualification ................................................................................................. 47



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Contents (continued) G13.3 Record ............................................................................................................................ 48 G13.4 Procedure Specification ................................................................................................. 48 G13.5 Essential Variables......................................................................................................... 48 G13.6 Qualification of Equipment and Operators .................................................................... 48 G13.7 Records of Qualified Operators ..................................................................................... 49 G13.8 Quality Assurance of Production Welds........................................................................ 49 G13.9 Acceptance Standards for Nondestructive Testing ........................................................ 49 G13.10 Repair and Removal of Defects ................................................................................... 49 G13.11 Radiographic Procedure............................................................................................... 49

Appendix A. Alternative Acceptance Standards for Girth Welds GA.1 General ................................................................................................................................ 50 GA.2 Stress Analysis .................................................................................................................... 51 GA.2.1 Axial Design Stress ...................................................................................................... 51 GA.2.2 Cyclic Stress................................................................................................................. 52 GA.2.3 Sustained-Load Cracking ............................................................................................. 52 GA.2.4 Dynamic Loading......................................................................................................... 52 GA.2.5 Residual Stress ............................................................................................................. 53 GA.3 Welding Procedure.............................................................................................................. 53 GA.3.1 General ......................................................................................................................... 53 GA.3.2 Mechanical Property Testing ....................................................................................... 55 GA.4 Qualification of Welders ..................................................................................................... 56 GA.5 Inspection and Acceptable Limits....................................................................................... 57 GA.5.1 Planar Imperfections .................................................................................................... 57 GA.5.2 Acceptable Limits of Volumetric Imperfections.......................................................... 58 GA.5.3 Arc Burns ..................................................................................................................... 58 Ga.5.4 Imperfection Interaction................................................................................................ 58 GA.6 Record ................................................................................................................................. 58 GA.7 Repairs................................................................................................................................. 58 GA.8 Nomenclature ...................................................................................................................... 58



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Contents (continued) Appendix B. In-Service Welding GB.1 General ................................................................................................................................ 59 GB.2 Qualification of In-service Welding Procedures ................................................................. 60 Gb.2.1 Procedure Specification ................................................................................................ 60 GB.2.2 Essential Variables ....................................................................................................... 62 GB.2.3 Welding of Test Joints.................................................................................................. 62 GB.2.4 Testing of Welded Joints.............................................................................................. 63 GB.3 In-Service Welder Qualification ......................................................................................... 66 GB.3.1 Welding of Test Joint ................................................................................................... 67 GB.3.2 Testing of Welded Joints.............................................................................................. 67 GB.3.3 Records......................................................................................................................... 67 GB.4 Suggested In-service Welding Practices ............................................................................. 67 GB.4.1 Alignment..................................................................................................................... 68 GB.4.2 Welding Sequence........................................................................................................ 68 GB.5 Inspection and Testing of In-service Welds ........................................................................ 69 GB.6 Standards of Acceptability: Nondestructive Testing (Including Visual) ............................ 69 GB.7 Repair and Removal of Defects........................................................................................... 69



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which each method of application is generally applicable are shown in Table G1.

G1 General G1.1 SCOPE Common industry abbreviations and nonstandard names for the welding processes covered in API 1104 are: • Shielded metal arc welding (SMAW), also called stick welding. • Submerged arc welding (SAW), also called subarc welding. • Gas tungsten arc welding (GTAW), also called tungsten inert gas (TIG) and heliarc welding. • Gas metal arc welding (GMAW), also called metal inert gas (MIG) or metal-active gas (MAG) welding. • Flux-cored arc welding (FCAW). • Plasma arc welding (PAW). • Oxyacetylene welding (OAW) or oxy-fuel welding (OFW), also called gas welding. • Flash butt welding (FW). In addition, several of the welding processes listed above have process variations, such as: • Pulsed gas metal arc welding (GMAW-P). • Gas-shielded flux-cored arc welding (FCAWG). • Self-shielded flux-cored arc welding (FCAWS). Methods of application that are covered in API 1104 include manual, semiautomatic, mechanized, or automatic. Definitions of these are provided in Section 3 of API 1104. The welding processes for

Common industry abbreviations and nonstandard names for the nondestructive testing (NDT) techniques covered in API 1104 are: • Radiographic testing (RT), also called x-ray or gamma radiation testing. • Ultrasonic testing (UT), also called Sonaray testing. • Automated Ultrasonic testing (AUT) • Magnetic particle testing (MT), also called Magnaflux® or MPI. • Liquid penetrant testing (PT), also called dye testing or dye penetrant testing. • Visual testing (VT). The use of nonstandard names for welding processes and NDT techniques should be avoided. While API 1104 is comprehensive, it may not address all issues that may arise during work included in this scope. The absence of guidance or requirements should not be considered to prohibit a particular activity or approach that is based upon sound engineering judgment. Established industry practice and other industry standards may provide useful reference to establish sound engineering practice.

G2 Referenced Publications The footnotes provide full names and contact information for the organizations identified by acronyms in this section.

Table G1 – Welding Processes and Generally Applicable Methods of Application Process

Manual

Semiautomatic

Mechanized

SMAW 1 SAW 2 1 GTAW 1 2 GMAW 1 1 FCAW 1 2 PAW 1 2 OAW 1 FW 1. Common applications used in industry. 2. Non-typical applications requiring additional equipment.

Automatic

2

1



G3 Definition of Terms G3.1 GENERAL Welding terms used in API 1104 are based on definitions in AWS A3.0, Standard Welding Terms and Definitions, with additions and modifications as shown in 3.2 G3.2 DEFINITIONS Definitions for key terms that appear in API 1104 are provided in 3.2. Definitions for additional key terms that appear in API 1104 that are not included in 3.2 are shown below: bend test: A soundness and ductility test in which a specimen is placed across the shoulders of a die. A plunger is positioned such that the area of interest is opposite the plunger. The plunger is forced toward the die, causing the specimen to bend into a U shape. butt weld: A nonstandard term for a weld in a butt joint, which is a joint between two members aligned approximately in the same plane. classification number: A number/letter designation in an American Welding Society (AWS) or other numbering system that identifies electrodes and filler metals according to their chemistry and operating characteristics. Examples of AWS classifications include for SMAW - E7018, for GMAW - ER70S-6, and for GTAW - EWTH-2. destructive testing: Testing that renders the material or weld useless for service, performed to obtain information on material properties and soundness. discontinuity: An interruption or irregularity in an otherwise uniform structure. See Section 9 for a list of types of imperfections and the criteria that may allow them in a weld. API 1104 does not use the word discontinuity but rather calls them indications or imperfections. Not all discontinuities, imperfections, or indications are rejectable. essential variable: A component of a welding procedure specification that requires requalification if changed beyond certain limits specified in the applicable code. face reinforcement: A weld metal build-up, raised above the surface of the parent metal in excess of what is required to fill a groove joint on the side of the base metal from which welding was done.

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faying surface: The mating surfaces of two parts that are to be welded together. filler metal: The metal or alloy to be added in making a brazed, soldered, or welded joint. fillet weld: A weld of approximately triangular cross section joining two surfaces approximately at right angles. fisheye: An imperfection attributed to the presence of hydrogen in the weld, observed on the fracture surface of a weld in steel that consists of a small pore or inclusion surrounded by a round bright area. See Figure G1 in Section G5. flux: A substance that hinders or prevents oxide formation, and promotes the union of the metals being joined. image quality indicator (IQI): Previously referred to as a penetrameter in API 1104. A device used to measure the quality of radiographic images. It is placed on the weld prior to radiography and must be visible when viewing the resulting film. lineup clamp: An external or internal device used to bring two pipe segments into acceptable alignment for pre-weld tacking or for welding. nick-break test: A destructive test that judges the soundness of a weld by fracturing the specimen through the weld so the fractured surfaces can be examined for the presence of imperfections. post-heat: The heat applied after completion of welding. Also referred to as maintenance of preheat temperature. post-weld heat treatment: Heat treatment carried out at high temperature (1100 to 1250°F [600 to 675°C]) after completion of welding to relieve residual welding stresses and/or to temper hard weld microstructures. preheat: The heat applied to a base metal immediately before welding. Also used to describe the temperature of the base metal immediately before welding. See guidance in G5.3.2.13 and G7.11. procedure qualification record (PQR): A document containing the actual values recorded during welding of a test weld and the test results necessary to comply with a given code or standard.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities relevant indication: An indication produced by nondestructive testing that is caused by an imperfection (as opposed to a geometric feature, for example).

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wagon tracks: Parallel elongated slag inclusions in the root region that are separated by approximately the width of the root bead.

shielding atmosphere: A protective gas or vacuum envelope surrounding the welding arc to prevent or reduce contamination of the weld by the ambient atmosphere.

welder qualification test report (WQTR): A document that identifies the variables and the test results necessary to verify a welder’s ability to perform a procedure to the requirements of a given code or standard.

socket weld: A fillet weld joining two pipes or pipe fittings, one of which is inserted into the other.

welding bug: A mechanized device that provides movement of the welding torch around the pipe.

sound metal: The metal that remains after a defect has been removed.

welding procedure: An activity undertaken according to a set of specific instructions provided in a welding procedure specification. Also an abbreviated form of welding procedure specification.

soundness: Freedom from defects. specification number: The number assigned to a document that describes the attributes of some item or operation. Examples include AWS A5.1, Specification for Covered Carbon Steel Arc Welding Electrodes, ASTM A 514, Standard Specification for High Yield Strength, Quenched and Tempered Alloy Steel Plate, and AWS D14.4, Specification for Welded Joints in Machinery and Equipment. speed of travel: The rate of welding progression along the weld joint. stripper beads: Weld passes deposited primarily on the sides of pipeline girth welds in the fixed position to even out the weld cross-sectional thickness prior to depositing the cap pass. tensile-strength test (also called tension test): A test in which the specimen is subjected to a pulling load until failure occurs. Test results are expressed in pounds per square inch (psi) or megapascals (MPa). trepanning: A process for removing a specimen from a welded seam, using a hole saw for example, for examination of the weld. The hole is cut so the inspector can look inside the pipe to verify the degree of penetration or so the portion of the weld that is removed can be destructively examined. Trepanning is generally not permitted for production piping applications. underfill: Weld metal that is insufficient in meeting the full thickness of the parent metal due to inadequate filling of a groove joint from the side of the base metal from which welding was done.

welding procedure specification (WPS): A document that provides the welding variables required for a specific application to assure repeatability by properly trained welders and welding operators to the requirements of a given code or standard. yield strength: The amount of stress necessary to make a material exhibit a specified permanent deformation under load, expressed in pounds per square inch (psi) or megapascals (MPa). G3.2.1 automatic welding: For methods of applications that are applicable for various welding processes, see Table G1-1 in Section G1. G3.2.2 branch weld: This revised definition of ‘branch weld’ appeared in the July 2007 errata/addendum to API 1104 and was intended to alleviate the confusion caused by Figure 10, which seems to imply that a branch weld is a fillet weld. A branch weld can consist of a groove and/or fillet weld. The branch can be welded to the outside of the pipe wall (i.e., set on the pipe) or it can be set into the pipe wall. The branch can consist of a pipe or a fitting. G3.2.3 company: No guidance material required. G3.2.4 contractor: No guidance material required. G3.2.5 defect: No guidance material required. G3.2.6 imperfection: required.

No

guidance

material

G3.2.7 indication: No guidance material required.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities G3.2.8 internal concavity: Also called suck-back. G3.2.9 mechanized welding: For methods of applications that are applicable for various welding processes, see Table G1. G3.2.10 position welding: No guidance material required. G3.2.11 qualified welder: No guidance material required. G3.2.12 qualified welding procedure: No guidance material required. G3.2.13 radiographer: No guidance material required. G3.2.14 repair: Repair refers to repair of welds. Not to be confused with pipeline repair using fullencirclement sleeves, for example. G3.2.15 roll welding: Roll welding refers to rolling the pipe while the weld metal is being deposited. Welding while the pipe is stationary, rolling the pipe, and then welding again (sometimes referred to as quarter welding) is position welding (not roll welding). G3.2.16 root bead: No guidance material required. G3.2.17 semiautomatic welding: For methods of applications that are applicable for various welding processes, see Table G1-1 in guidance material for 1.1. G3.2.18 shall: No guidance material required. G3.2.19 weld: No guidance material required. G3.2.20 welder: Refers to a person. Not to be confused with a welding machine. Weldor is a nonstandard term.

G4 Specifications Several pertinent aspects related to equipment and materials for welding of pipelines and related facilities are specified in this section. G4.1 EQUIPMENT Appropriate equipment should be used to ensure that all of the variables specified in the welding procedure can be achieved in safe manner.

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G4.2 MATERIALS G4.2.1 Pipe and Fittings Pipe and fitting materials must conform to API Spec 5L, an applicable ASTM specification, or have chemical and mechanical properties that comply with one of these specifications. It is common for companies to consider this standard applicable not only to pipe and fittings (e.g., elbows, tees, reducers, etc.), but to flanges and valves as well. G4.2.2 Filler Metal G4.2.2.1 Type and Size Filler metals must conform to one of the AWS filler metal specifications listed, or must be separately qualified for use in accordance with the requirements of Section 5 of API 1104. New AWS filler metal specifications are occasionally introduced. Until these are included in 4.2.2.1, their use requires a separate qualification in accordance with the requirements of Section 5. G4.2.2.2 Storage and Handling of Filler Metals and Fluxes API 1104 requires protection of filler metals and fluxes from damage, deterioration, and excessive changes in moisture. Low-hydrogen electrodes (predominantly AWS EXX18-type, where “XX” represents the ultimate tensile strength level in ksi) should not be allowed to pick up (absorb) an excessive amount of moisture from atmospheric exposure prior to use. Excessive moisture can lead to elevated weld hydrogen levels and can contribute to heat-affected zone (HAZ) and weld metal hydrogen cracking. Manufacturers recommend that, after opening their container, lowhydrogen electrodes should be stored in heated, vented ovens at prescribed temperatures. Since different low-hydrogen electrodes behave differently with respect to moisture absorption, it is important to follow the specific electrode manufacturer’s recommendations for storage and handling. Low-hydrogen electrodes that have exceeded their atmospheric exposure limit must be discarded or reconditioned (re-dried). Low-hydrogen electrodes from some manufacturers may require conditioning (drying) prior to use. As with storage and handling,


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities reconditioning guidelines specified by the manufacturer for the particular brand of electrode being used should be followed. Electrode drying/reconditioning should be carried out in a purpose-built oven. Drying/reconditioning ovens are capable of attaining temperatures well in excess of those attainable in electrode storage ovens and have the capability for air circulation. General guidelines for the use and handling of low-hydrogen electrodes are available from a variety of sources, including manufacturers, and other industry codes. Cellulosic-coated electrodes (AWS EXX10-type) should not be allowed to dry out excessively prior to use. Cellulosic-coated electrodes that have been allowed to dry out are known to produce welds that are susceptible to weld metal hydrogen cracking.3 G4.2.3 Shielding Gases G4.2.3.1 Types Active gases combine with the weld to contribute to weld properties. Inert gases protect the weld but do not combine with the weld. Examples of active gases include carbon dioxide and oxygen. Examples of inert gases include argon and helium. The gas, or mixture of gases, must have adequate purity and dryness for welding. G4.2.3.2 Storage and Handling A crucial prohibition with respect to shielding gases involves field intermixing. Never try to force one kind of gas into a cylinder containing another, or bring gases to the arc in multiple hoses.

G5 Qualification of Welding Procedures for Welds Containing Filler-metal Additives The word “additives” in the title of this section refers to filler metal in general and is intended to differentiate between welding procedures covered by this section and welding procedures for autogenous (no filler metal added) welding.

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G5.1 PROCEDURE QUALIFICATION The phrase “before production welding is started” has no specific time limit. It is only necessary that the welding procedure specification (WPS) to be used for production welding be established and qualified sometime prior to the start of production welding. A WPS need not be established and qualified by the company itself. However, it is common practice for the company to approve each qualified WPS that will be used for production welding. Other codes and standards require that welding procedures be requalified if they are transferred to and used by a different company. G5.2 RECORD A qualified welding procedure consists of a WPS and a procedure qualification record (PQR). API 1104 also refers to the latter as a coupon test report. A PQR ‘supports’ a WPS. A WPS can be supported by more than one PQR. It is common, but not mandatory to list the PQRs that support a particular WPS. Figure 1 in API 1104 is a sample WPS. Figure 2 is a sample PQR, which can also be used as a welder qualification test record (WQTR). The use of Figures 1 and 2 is not mandatory, although forms similar to these should be used. It is common, but not mandatory, for both to include a space for a revision number, which may be required eventually. A welder who performs a test joint that qualifies a WPS becomes qualified to perform that procedure provided that all of the testing required for a welder qualification is performed and passed. Other welders then may qualify to perform the same welding procedure. Note that the qualification of a welder who performs a test joint for a procedure qualification may be limited by the essential variables of a single qualification in 6.2.2. More specifically, the diameter and wall thickness ranges listed in a WPS may be different from the mandatory diameter and wall thickness groups in 6.2.2. See additional guidance provided in G5.3.2.3. G5.3 PROCEDURE SPECIFICATION

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Fiore, S., and Boring, M. A., "Evaluation of Hydrogen Cracking in Weld Metal Deposited using Cellulosic-Coated Electrodes," Final Report to Pipeline Research Council International and U.S Department of Transportation, PHMSA Research and Development for PRCI Project No. PR-185-04508, Edison Welding Institute, Columbus, Ohio, June 2009.

G5.3.1 General Only the welding variables that are applicable to the welding process and welding method to be used


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities need be documented. All of the applicable welding variables described in 5.3.2 must be included in the WPS. Many of these variables are limited by the essential variable changes given in 5.4. Changes to welding variables that are not listed in 5.4 are allowed by simply revising the WPS without the need for requalification, although sound engineering judgment should be used. A revised WPS should be identified by a revision number. G5.3.2 Specification Information G5.3.2.1 Process Eight possible welding processes are listed in 1.1. Welding methods (or methods of application) include manual, semiautomatic, mechanized, or automatic, and combinations of these methods. Not all welding methods are applicable to all welding processes. Table G-1 in Section G1 shows which methods of application are generally applicable to which welding processes. G5.3.2.2 Pipe and Fitting Materials It is common, but not mandatory, to specify the industry standard or specification to which the base material was manufactured, as well as the grade of the base material. The latter establishes the basis for the tensile strength requirements in 5.6.2.3 and the basis for selecting the welding consumables to be used. It is not clear what constitutes an “acceptable ASTM specification.” This presumably refers to ASTM specifications that are acceptable to the company. Base materials and base material groupings are addressed in 5.4.2.2. To qualify a WPS for an entire group, the test joint must be made using the material with the highest specified minimum yield strength (SMYS) in the group. For production welding that involves joining base materials from two different strength groups, a WPS for the higher strength material must be employed. For material with a SMYS higher than 56,000 psi (386 MPa), it is good practice but not mandatory to document the carbon equivalent for all base materials used in the procedure qualification. For pipe that meets the requirements of more than one pipe grade (i.e., pipe that is ‘multi-graded’

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or ‘dual or triple stenciled’), it is not necessary to use a welding procedure that is qualified for the highest grade to which the pipe is certified. It is only necessary to use a welding procedure qualified for use on the grade for which the material will be used. For example, for pipe certified to both API 5L X42 and X52, a welding procedure qualified for use on X42 is acceptable provided that the material is being used as X42. However, for some applications (e.g., high longitudinal strains), it is good practice to at least match the actual yield strength of the pipe. The use of filler metal with yield strength that matches or overmatches the actual yield strength of the pipe material prevents longitudinal strains from accumulating in the weld region, which is more likely to contain imperfections than the pipe material. G5.3.2.3 Diameters and Wall Thicknesses The suggested groupings shown in 6.2.2, items d and e are just that – suggested groupings. Other groupings can be used provided that there is technical justification for doing so based on sound engineering judgment. Guidance can be found in a variety of other codes and standards. For example, some codes limit wall thickness to which the procedure is applicable from some minimum thickness to 2t, where t is the wall thickness used for procedure qualification. However, the size of the wall thickness range to which the procedure is applicable often depends on the actual value of t and the welding process that will be used. Wall thickness is an essential variable for procedure qualification, whereas diameter is not. It may be beneficial to select diameter and wall thickness groups for a WPS based on the diameter and wall thickness groups that are essential variables for single qualification of welders in 6.2.2. More specifically, if the diameter and wall thickness groups in a WPS are different from these essential variable groups for single qualification, a welder with single qualification might be qualified to weld only a portion of the joints permitted by a WPS. While control of this sort of situation is possible, it could be confusing to welders, inspectors, contractors, etc. For branch connections, 5.3.2.3 refers to the diameter and wall thickness of the branch and header piping. G5.3.2.4 Joint Design The joint type (fillet, groove, or a combination of fillet and groove) should be specified. A branch weld


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities can consist of a groove and/or fillet weld. A branch connection that includes the use of a beveled branch and a full penetration weld is considered a groove weld. If it also includes a fillet weld reinforcement, it is considered a combination fillet and groove weld. In addition to specifying the required bevel angle, it is common practice, but not mandatory, for the bevel angle tolerances to be specified also. Such tolerances may vary depending upon the type of bevel (machine-cut or torch-cut). The required root opening may be expressed as an approximate value or a specific value with applicable tolerances. In addition to specifying the required size of the root face, it is common practice, but not mandatory, for the root face tolerances to be specified.

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acceptable) is to be prohibited, this should be specified. If backwelding is to be permitted, it is good practice but not mandatory to weld and test joints with and without backwelds (i.e., it is good practice to consider the addition of a backweld to be an essential variable for procedure qualification). Backwelds are normally deposited last and do not benefit from the tempering associated with the thermal cycle from subsequent passes. Unlike cap passes, backwelds are relatively small beads that are deposited at relatively low heat input levels. It is good practice but not mandatory to specify the welding technique that should be used – e.g., stringer beads, weave beads, or a combination of both. If the welding procedure covers a range of wall thicknesses and a combination of techniques, the weld width (or wall thickness) at which the transition from one technique to another should occur should also be specified.

G5.3.2.5 Filler Metal and Number of Beads The filler metal to be used should be identified by its AWS (or other) specification and classification numbers. While not required, the trade name of the filler metal can also be listed for information purposes, if desired. However, it is insufficient to list trade name only Line pipe materials are designated by their specified minimum yield strength or SMYS (e.g., X60 has a SMYS of 60,000 psi), whereas filler metals (i.e., welding consumables) are designated by their specified minimum ultimate tensile strength or SMUTS, (e.g., E6010 has a SMUTS of 60,000 psi). To achieve matching or overmatching strength girth welds, it is normally necessary to specify the use of welding consumables with a higher designation than the pipe material (e.g., at least E7010 electrodes for X60 pipe material). It is permissible to list more than one filler metal diameter for each welding pass when the procedure will be qualified using only one diameter since filler metal diameter is not an essential variable for procedure qualification. If the welding procedure covers a range of wall thicknesses, it is appropriate to include the minimum number of beads for each wall thickness. The WPS is not required to contain a sketch of the sequence of beads. However, the sequence of beads must somehow be designated. If backwelding (i.e., depositing a weld pass from the inside to repair or otherwise make the root region of the weld

G5.3.2.6 Electrical Characteristics Current can be either alternating current (AC) or direct current (DC). For DC, polarity can be either electrode negative (straight polarity) or electrode positive (reverse polarity). If pulsed current is to be used, it is good practice to indicate this and to specify pulse parameters, etc. It is good practice to list an amperage and voltage range for each filler metal type and size. The specified range should reflect the minimum and maximum values that produce an acceptable weld (or a weld with desired toughness properties for example, if required). The limits of the range should be based on sound engineering judgment. Ranges for amperage and voltage specified by the electrode manufacturer can be used for guidance. The ranges specified should be wide enough so that the qualified welding procedure can be implemented in the field. The ranges should not be so wide that operating at the edges of the ranges produces an unacceptable weld. For example, the allowable range for amperage and voltage should be no larger than the median value +/- 20%. In addition to ranges for amperage, voltage, and travel speed, it is good practice, but not mandatory, to specify a heat input range for each welding pass. Heat input takes into account the collective effect of amperage, voltage, and travel speed on the thermal cycle of the weld. The specified range should reflect the minimum and maximum heat input values that produce an acceptable weld, not the calculated


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities minimum and maximum values from the amperage, voltage, and travel speed range. Actual values for amperage and voltage used during the procedure qualification test need not be recorded in the WPS; only the ranges need to be specified. The actual values used during the procedure qualification test should be recorded in the PQR. G5.3.2.7 Flame Characteristics The term “flame characteristics” refers to oxyfuel welding. Flame characteristics include carburizing (also called reducing), in which an excess of fuel gas results in a carbon-rich flame, oxidizing, in which an excess of oxygen results in an oxygenrich flame, and neutral, in which the mixture being burned contains a balance of fuel gas and oxygen. G5.3.2.8 Position A definition for “roll welding” is provided in 3.2.15. Roll welding refers to rolling the pipe while the weld metal is being deposited. There is no requirement in API 1104 to designate the position of the pipe material (e.g., horizontal, vertical, or some position in between). API 1104 has traditionally been used for construction of cross country pipelines, which involves girth welding with the pipe in the horizontal position. If welding is to be performed with the pipe in a position other than horizontal, it would seem to be prudent to indicate that here. For branch connection welding, there is no requirement in API 1104 to designate the position of the branch (e.g., top, side, or bottom of the pipe), although it would seem to be prudent to indicate that here.

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cracking to occur. The time between the completion of the root bead and the start of the second bead is most critical since the weld has less cross-sectional area at this stage. When determining what value to specify on a WPS for time between passes, the time-dependant nature of hydrogen cracking should be considered, as well as the probability of the weld to cracking. Shorter times decrease the chance that cracking can occur prior to the completion of the weld. Longer times can be justified when the probably of cracking is low (e.g., higher preheat/interpass temperatures, low-hydrogen electrodes, etc.). The possibility of unforeseen delays or interruptions during welding should also be considered when specifying the maximum allowable time between the completion of the root bead and the start of the second bead (see guidance in G5.4.2.8). G5.3.2.11 Type and Removal of Lineup Clamp Information pertaining to the type and removal of a lineup clamp in this section generally applies to production welding. For manual or semiautomatic welding, it is common for no lineup clamp to be used during the procedure qualification test (i.e., ‘stacked and tacked’) and for a lineup clamp to be specified for production welding. Also for manual or semiautomatic welding, it is common for an external lineup clamp to be used during the procedure qualification test and for an internal lineup clamp to be specified for production welding. Requirements/recommendations for root bead completion prior to lineup clamp removal are given in 7.3. The information specified in the WPS should comply with the requirements/recommendations given in 7.3. See guidance in G7.3. G5.3.2.12 Cleaning and/or Grinding

G5.3.2.9 Direction of Welding If welding is to be performed with the pipe in the vertical position, the direction of welding is horizontal. G5.3.2.10 Time between Passes The primary intent of this requirement is to prevent the weld from experiencing hydrogen cracking prior to completion. Specifying a maximum-allowable time between passes does this by a) preventing the weld from cooling excessively between passes and b) providing less time for

It is good practice, but not mandatory, to specify the extent of cleaning/grinding required for the weld bevel prior to welding and for each pass type (e.g., grinding for the root pass, power brushing only for the remaining passes). The use of the phrase “as required” is common. G5.3.2.13 Pre- and Post-heat Treatment Preheat is the minimum specified temperature of the entire weld zone immediately prior to the start of welding. In a multipass weld, it is also the temperature immediately before the second and


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities subsequent passes. It may be useful to think of preheat temperature as the “arc start temperature,” or the temperature of the weld zone during welding of any weld bead (i.e., not just the first weld bead). The primary reason for preheating is to prevent the weld from experiencing hydrogen cracking during welding or soon after completion. Preheating does this by driving off moisture and other contaminants prior to welding, slowing the weld cooling rate somewhat, which has a beneficial effect on the weld microstructures that develop, and allowing hydrogen to diffuse from the weld during welding and after completion. Post-heating and slow cooling can also have a beneficial effect on welds by allowing hydrogen diffusion after welding. If carried out at high enough temperatures, post-weld heat treatment (PWHT) can also temper hard weld microstructures and relieve residual welding stresses. A minimum-required preheating temperature is normally specified. Once welding begins, this temperature is generally referred to as the interpass temperature. For some applications, it is also common to specify a maximum-allowable interpass temperature. For some applications, preheating is specified only when the ambient or pipe surface temperature is below a certain value. Additional information pertaining to the application of pre- and post-heating is provided in the guidance material for 7.11. PWHT parameters for stress relief often include a temperature to which the joint can be heated without controlling the heating rate, a maximumallowable heating rate from this temperature to the PWHT temperature range, the hold time at the PWHT temperature range (usually expressed in hours per unit of wall thickness), and the maximumallowable cooling rate from this temperature. Common methods used to preheat pipelines prior to welding include gas torches and quartz lamps (radiation methods), electric resistance heaters (conduction methods), and induction heaters (induction methods). Common methods for temperature measurement include contact thermometers (digital or analog), non-contact infrared pyrometers, and temperature indicating crayons (e.g., Tempilsticks™). If used to expedite nondestructive testing (NDT) and/or joint coatings, the type of weld cooling after welding, such as air cooling or accelerated cooling

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with water, should be specified. The maximum metal temperature at which accelerated cooling is applied should also be specified. G5.3.2.14 Shielding Gas and Flow Rate AWS A5.32/A5.32M Specification for Welding Shielding Gases provides standard AWS classifications for common shielding gasses and gas mixtures that can be used in preparation of procedure specifications. AWS A5.32/A5.32M also provides purity requirements for the listed gases and mixtures. The specified range should reflect the minimum and maximum values that produce an acceptable weld. G5.3.2.15 Shielding Flux Shielding flux type refers to submerged arc welding. G5.3.2.16 Speed of Travel It is good practice to list a travel speed range for each filler metal type and size. The specified range should reflect the minimum and maximum values that produce an acceptable weld. It is unacceptable to list the travel speed as ‘manual’. Travel speed is measured in the direction of weld progression. Weave motion perpendicular to the direction of weld progression is not included in the travel speed measurement. The range specified should be wide enough so that the qualified welding procedure can be implemented in the field. The range should not be so wide that operating at the edges of the range produces an unacceptable weld. For example, the allowable range for travel speed should be no larger than the median value +/- 20%. G5.4 ESSENTIAL VARIABLES G5.4.1 General API 1104 allows some degree of departure from the variables used to qualify a WPS. However, departures from variables that affect the mechanical properties or soundness of completed welds are not allowed without requalification by preparing and testing another weld. These latter variables are referred to as essential variables.



G5.4.2 Changes Requiring Requalification Essential variables are those that require the procedure to be requalified, or a new procedure qualified, if the range specified in the WPS for any of those variables is exceeded.

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that might be considered within one of the grouping specified is carbon equivalent level. For a pipe material of a given grade, higher carbon equivalent materials generally have reduced weldability compared to lower carbon equivalent materials. G5.4.2.3 Joint Design

G5.4.2.1 Welding Process or Method of Application See guidance provided in G5.3.2.1. G5.4.2.2 Base Material To qualify a welding procedure for an entire group, the procedure qualification must be carried out on the material with the highest specified minimum yield strength in the group. The strength level grouping listed in 5.4.2.2 should be based on nominal strength levels. The actual strength levels that are now specified in API Spec 5L (Forty-fourth Edition) as the result of normalization need not be considered (i.e., it is not necessary to consider that API 5L-X42 now has an actual specified minimum yield strength, expressed in US Customary units, of 42,100 psi). A procedure qualified using a combination of materials only qualifies the procedure for that combination of materials. For example, a welding procedure qualified by welding API 5L-X42 to X65 only qualifies for welding X42 to X65, not all combinations of X42 and X65 (i.e., does not qualify for welding X42 to X42 or X65 to X65). For welding procedure qualification tests conducted on multi-graded or dual or triple stenciled pipe (e.g., pipe certified to both API 5L-X65 and X70) the test results can be used to support WPSs pertaining to any of the grades to which the pipe is certified. Using the example of pipe certified to both X65 and X70, a successful procedure qualification test qualifies the procedure for use in welding X70 to X70, X65 to X65, and X65 to X70. Even though 5.4.2.2 requires a separate qualification test for materials with a SMYS of 65,000 psi (448 MPa) and above, it would make little sense to perform two identical qualification tests (i.e., one considering it to be X65 and the other considering it to be X70) on the exact same material. Regarding the note provided in 5.4.2.2, sound engineering judgment should be used when determining the compatibility of the base materials. An example of a base material compatibility factor

API 1104 does not define what constitutes a minor change in joint design. It would seem reasonable to allow changes to the bevel angle of up to + 20%/-5% of the nominal value and changes to the root opening or land of up to +/- 50% of the nominal value without the need for requalification. It is good practice but not mandatory to consider the addition of a backweld as an essential variable for procedure qualification (see guidance provided in G5.3.2.5). A change from a butt weld to a fillet weld is a major change in joint design, thus requiring that a new procedure be qualified. A change from a fillet weld to a groove weld of a branch connection is also a major change in joint design, thus requiring that a new procedure be qualified. However, a branch connection can consist of a groove weld and a fillet weld. Therefore, for welding full-encirclement sleeves that involve only fillet welds, a welding procedure qualified for a branch connection (groove and fillet weld) is sufficient. However, a welding procedure qualified by welding a full encirclement sleeve (fillet weld only) is not sufficient for welding a branch connection that includes a groove weld. G5.4.2.4 Position See guidance provided in G5.3.2.8. G5.4.2.5 Wall Thickness See guidance provided in G5.3.2.3. Wall thickness is an essential variable for procedure qualification, whereas diameter is not. G5.4.2.6 Filler Metal If a filler metal is not listed in one of the groups of Table 1 in API 1104, it requires separate qualification. See the note under Table 1. In addition to numerous AWS specifications listed in Table 1, additional information pertaining to filler metal, electrode, and flux designations can be found in ASME Boiler and Pressure Vessel Code, Section II, Part C. Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities Regarding the note provided in 5.4.2.6, sound engineering judgment should be used when determining the compatibility of the filler metals within the groups specified in Table 1. G5.4.2.7 Electrical Characteristics See guidance provided in G5.3.2.6. G5.4.2.8 Time between Passes The maximum time between the completion of the root bead and the start of the second bead is an essential variable for procedure qualification, whereas the maximum time between the completion of the second bead and the start of other beads is not. Exceeding the maximum allowable value specified in the welding procedure for time between the completion of the root bead and the start of the second bead during production welding is grounds for rejection of that weld. Consequently, one common practice during procedure qualification is to delay welding of the hot pass after completion of the root pass by an appropriate amount of time. G5.4.2.9 Direction of Welding See guidance provided in G5.3.2.9. G5.4.2.10 Shielding Gas and Flow Rate A change from one shielding gas to another refers to nominal composition. API 1104 does not define what constitutes a major change in shielding gas flow rate. Even if a change in the shielding gas flow rate does not visually affect the weld (e.g., does not result in porosity), the weld properties (e.g., strength and toughness) may be adversely affected. It would seem reasonable to allow changes of up to +/- 20% of the nominal value without the need for requalification. G5.4.2.11 Shielding Flux See guidance provided in G5.3.2.15. G5.4.2.12 Speed of Travel See guidance provided in G5.3.2.16.

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G5.4.2.13 Pre-heat The addition of preheat or an increase in the preheat temperature is not an essential variable for procedure qualification. G5.4.2.14 Post-weld Heat Treatment (PWHT) See guidance provided in G5.3.2.13. Maintaining preheat temperature following the completing of welding (e.g., to allow hydrogen diffusion after welding) does not constitute post-weld heat treatment (PWHT) and should not be considered an essential variable for procedure qualification. G5.5 WELDING OF TEST JOINTS-BUTT WELDS There is no requirement for minimum length of the pipe nipples. However, the pipe nipples should be long enough so that adequate restraint and thermal mass are provided and that specimens of adequate length can be extracted. Test joints should be made using parameters that are specified in the WPS. Where a range is specified for a given parameter, is not necessary to test the limits of the range. The target value for welding parameters during welding of the test joint should be near the middle of the range specified. Target value for preheat temperature should be near the minimumrequired value. If after-weld cooling is to be used during production welding to expedite NDT and/or joint coatings, cooling should also be applied to the test joint. If the values recorded during welding of the test joint are outside the ranges specified in the WPS, the WPS should be revised accordingly to reflect the actual parameter ranges that were used to make the test joint. G5.6 TESTING OF WELDED JOINTS-BUTT WELDS It should be noted that some acceptance criteria for imperfections discovered during procedure qualification testing in 5.6 are more stringent than those for imperfections discovered by nondestructive testing of production welds in Section 9. This is intended to account for the more-favorable conditions that generally exist when welding procedures are normally qualified (e.g., welds made by what may be the most highly skilled welders available, in an enclosed welding shop as opposed to on a pipeline


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities right-of-way, on pipe nipples as opposed to full joints of pipe, etc.). There are no specific provisions in Section 5 of API 1104 for retesting during procedure qualification should any of the test specimens fail to meet the minimum requirements. However, retesting of failed tensile test specimens during procedure qualification is specifically prohibited by 5.6.2.3 (see guidance provided in G5.6.2.3). There is currently disagreement among industry experts as to the acceptability of the practice of retesting specimens that fail to meet the minimum requirements during procedure qualification testing. Specimens may fail because the parameters that were used to make the test joint were inadequate. Specimens may also fail because the location from which they were taken contains an imperfection that exceeds the acceptance criteria in 5.6, even though the parameters that were used are capable of producing acceptable production welds. Retesting of bend test specimens is allowed during welder qualification in 6.5.5 if, in the opinion of the company, the imperfection observed is not representative of the weld. In other codes and standards, retesting of failed test specimens during procedure qualification is allowed, often on a twofor-one basis. Since retesting of specimens other than tensile test specimens is not specifically addressed in Section 5, sound engineering judgment should be used when determining the acceptability of this practice.4 If it is determined that retesting of specimens (other than tensile test specimens) on a two-for-one basis is appropriate (e.g., if the quality of the weld in the area from which a failed specimen was taken is determined to be not representative of the weld), the test joint should be considered unacceptable if either of the replacement specimens fails to meet the minimum requirements. If a test joint is found to be unacceptable because the welding parameters that were used to make the weld were inadequate, the inadequacy should be diagnosed and revised welding parameters should be specified and used to weld a new test joint. G5.6.1 Preparation No guidance material required. 4

In the past, some regulators in the US have required operators to re-qualify a procedure that was originally qualified based on retesting of failed test specimens or to perform testing on production welds removed from the pipeline. This becomes problematic if requalification (or testing of production welds) produces unacceptable results, particularly if there are pipelines already built using the procedures in question..

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G5.6.2 Tensile-strength Test G5.6.2.1 Preparation Figure 4 illustrates the tensile-strength test specimen. The weld reinforcement is not removed and the specimen is full width and not a reduced section specimen. Specimens must have parallel edges so that questionable results are avoided. If a tensile test specimen is inadvertently tested with the weld reinforcement removed, and the results meet the minimum tensile strength requirement, then the results should be considered valid. G5.6.2.2 Method No guidance material required. G5.6.2.3 Requirements It is acceptable according to API 1104 for the measured tensile strength across the weld to be less than the actual tensile strength of the pipe material. However, some pipeline designs (e.g., high longitudinal strains) require matching or overmatching strength girth welds. The use of filler metal with yield strength that matches or overmatches the actual yield strength of the pipe material prevents longitudinal strains from accumulating in the weld region, which is more likely to contain imperfections than the pipe material. Such requirements should be specified in the contract documents. If a tensile test specimen breaks in the weld, it is also evaluated as if it is a nick-break test specimen. If the specimen breaks below the specified minimum tensile strength of the pipe material, no retesting is allowed. This can be problematic since API Spec 5L only requires that tensile strength requirements be met in the transverse (circumferential) direction for welded line pipe 8-5/8 in. (219.1 mm) diameter and larger. The cross-weld tensile test required in 5.6.2 is performed in the longitudinal direction and the longitudinal tensile strength of some line pipe materials can be lower than the transverse tensile strength. One exception to the no retesting requirement in 5.6.3.2 that would seem reasonable involves test results that are determined to be invalid. Because the API 1104 tensile test specimen does not utilize an


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities area of reduced cross section, test specimens will occasionally fail at a low value in the area of the grips (i.e., the grips deform or otherwise cause a stress concentration in the pipe material). In cases such as this, it would seem reasonable to allow a retest of a replacement specimen removed adjacent to the original specimen. Consideration should be given to replacing the grips if this becomes problematic for a particular testing machine.

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G5.6.3.2 Method

G5.6.3 Nick-break Test

The intent of this test is to provide an adequate fracture surface for subsequent examination. While methods for breaking the specimens are prescribed in this section, other convenient methods, such as supporting one end and bending the other end with a lever (a length of small-diameter pipe) or bending in alternating directions in a load frame, would also seem to be appropriate provided that an adequate fracture surface results.

G5.6.3.1 Preparation

G5.6.3.3 Requirements

The nick-break test is a subjective test that judges the soundness of a weld by fracturing the specimen through the weld so the fracture surfaces can be examined for the presence of imperfections. The term “nick-break” refers to the saw-cut notch that initiates fracture, making the specimen easier to break.

Figure 8 illustrates the exposed surface of such a specimen after breaking.

While nicking the specimen with a hack saw is preferred, it would seem to be appropriate to allow the specimen to be nicked with a narrow disk grinder as well. It is not appropriate to “nick” the specimens using an oxy-fuel torch. Figure 5 illustrates a nick-break test specimen with instructions on how to prepare the nick.

Fisheyes are features on exposed fracture surfaces caused by the presence of hydrogen in the weld. A fisheye consists of a small imperfection or defect that is surrounded by a circular or ellipticalshaped shiny or dull grey area. Only the actual imperfection in the center of the fisheye needs to be considered when evaluating nick-break test specimens, not the entire fisheye. Typical fisheyes are shown in Figure G1. The sooner nick-break specimens are tested after welding the more likely fisheyes are to appear due to the presence of hydrogen in the weld. The hydrogen that causes fisheyes will generally diffuse out of the weld over time.

Figure G1 – Typical Fisheyes on Fracture Surface of Nick-Break Specimen (photo courtesy of Lincoln Electric Company)



G5.6.4 Root- and Face-bend Test G5.6.4.1 Preparation The root- and face-bend testing involves determining the soundness and ductility of a weld by placing a test specimen across the shoulders of a die. A plunger is positioned such that the area of interest is opposite the plunger. The plunger is forced toward the die, causing the specimen to bend into a U shape. The root- and face-bend test is for pipes with a wall thickness less than or equal to 1/2 in. (12.7 mm). API 1104 Figure 6 illustrates a root- and facebend test specimen. Note that weld reinforcement must be removed prior to testing. It is not permissible to grind or machine to below the surface of the specimen (e.g., to remove undercut). Deep scratches or grinding marks that are parallel to the weld (i.e., perpendicular to the specimen) may cause an otherwise acceptable weld to fail. G5.6.4.2 Method Figure 9 illustrates an example of a guided bend test jig. It should be noted that the diameter of the plunger and die are specified and not determined by material thickness and strength as in other codes. The current wording in 5.6.4.2 would seem to prohibit the use of guided bend test machines that employ the alternative ‘wrap-around’ method, although the use of this method would seem to be reasonable from a practical point of view. The use of the wrap around method is actually preferred when testing specimens when there is a significant difference in weld and base material yield strength as non-uniform bending (kinking) is avoided. G5.6.4.3 Requirements Causes of failure may include lack of ductility, cracks, incomplete fusion or penetration, porosity, and/or trapped slag. G5.6.5 Side-bend Test G5.6.5.1 Preparation The side-bend test is similar to the root- and face-bend test, except that the bending occurs on the cross section surface of the specimen.

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required thickness of side-bend test specimens is 1/2 in. (12.7 mm), which is different from other codes. Figure 7 illustrates a side-bend test specimen. Note that the weld reinforcement must be removed. G5.6.5.2 Method See guidance provided in G5.6.4.2. G5.6.5.3 Requirements See guidance provided in G5.6.4.3. G5.7 WELDING OF TEST JOINTS-FILLET WELDS Figure 10 shows three possible configurations. The bottom two are fillet welds typical of those used for a full-encirclement reinforcing sleeve and a belland-spigot joint, respectively. The top configuration shows a branch connection that consists of a groove weld and a fillet weld reinforcement. In API 1104, a change from a butt weld to a fillet weld is a major change in joint design, thus requiring that a new procedure be qualified. Unlike other codes, a procedure for butt welding cannot be used for fillet welding. A welding procedure qualified for a branch connection will also qualify for welding a fullencirclement sleeves that involves only fillet welds, provided that the branch connection consists of a groove weld and a fillet weld reinforcement. G5.8 TESTING OF WELDED JOINTS-FILLET WELDS It should be noted that some acceptance criteria for imperfections discovered during procedure qualification testing are more stringent than those for imperfections discovered by nondestructive testing of production welds. This is intended to account for the more-favorable conditions that generally exist where welding procedures are normally qualified (e.g., in an enclosed welding shop as opposed to on a pipeline right-of-way). To qualify a welding procedure for a branch connection, the testing requirements for both the groove and fillet portion of the weld are the same as those for a fillet weld.

The side-bend test is for pipes with a wall thickness greater than 1/2 in. (12.7 mm). The Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities G5.8.1 Preparation The flame and hacksaw cuts shown in Figure 11 must be sufficient to ensure that the specimen breaks in the weld. G5.8.2 Method This is a subjective test that judges the soundness of a weld by fracturing the specimen through the weld so the fracture surfaces can be examined for the presence of imperfections.

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satisfactory welder qualification welds are more stringent than for production welds, and a welder may be inclined to take more care with a qualification weld than some production welds. Consequently, the “pace” or “elapsed time” for a production weld will tend be different from a qualification weld. A welder need not be qualified by the company itself. However, welders must be qualified in the presence of a representative that is acceptable to the company..

G6 Qualification of Welders

The phrase “segments of pipe nipples” refers to a single qualification in accordance with 6.2. Two welders can be qualified on a single pipe nipple as long as an appropriate number of test specimens are removed and tested from the typical flat, vertical, and overhead positions of the weld made by each welder. The qualification of two welders in this manner is typically referred to as the “brother-in-law” technique. Each welder must weld the entire wall thickness of their particular segments. It is not appropriate for two welders to weld in combination to fill up one weld groove. Each welder must weld the entire wall thickness of a particular segment when qualifying.

G6.1 GENERAL

G6.2 SINGLE QUALIFICATION

This section refers to the use of previously qualified procedures because a welder qualification test is intended to evaluate welder skill, not the suitability of the welding procedure. A welder who makes a procedure qualification weld is also qualified as a welder, however, as long as the requirements in Section 6 are also met.

A single qualification accordance with 6.2 allows a welder to make welds within the limits of the essential variables described in 6.2.2. A multiple qualification in accordance with 6.3 allows a welder to make welds over a wider range of applications.

The phrase “before any production welding is performed” has no specific time limit. It is only necessary that welders to be used for production welding be qualified sometime prior to the start of production welding.

The use of the word “plane” in 6.2.1 can be confusing. When the welder is qualifying in the fixed position, the axis of the pipe shall be horizontal, vertical, or inclined from horizontal at an angle of not more than 45°. AWS designations are typically used to describe pipe positions. If the axis of the pipe is:

Breaking specimens from relatively highstrength, thin-wall pipe through the weld can present challenges. If the specimen does not break through the weld because the flame and hacksaw cuts were not sufficient, it would seem to be appropriate to allow a duplicate specimen removed adjacent to the original to be used for a retest. G5.8.3 Requirements No guidance material required.

API 1104 does not address time intervals over which a welder qualification is valid. Required welder requalification intervals are left to the discretion of the user and are addressed in a variety of other codes and regulations. During the welder qualification test, the welder should follow the requirements of the previously qualified procedure as outlined in the WPS. The word “speed” applies to the “pace” or “elapsed time” of welding. The travel speed used by the welder during a welder qualification test should be within the range specified in the WPS. The requirements for

G6.2.1 General

• Horizontal, and the pipe is rotated, the position is 1G. • Horizontal, and the pipe is fixed, the position is 5G. • Vertical, the position is 2G (whether the pipe is fixed or rotated). • 45° incline from the horizontal, and the pipe is fixed, the position is 6G. If a welder qualifies by making a weld in accordance with 6.2, that welder is limited by the essential variables listed in 6.2.2.



G6.2.2 Scope While the title of this section is “Scope”, it contains a list of essential variables for welders with a single qualification, which require that the welder be requalified if changes beyond the limits listed are exceeded. It should be noted that the essential variables for welder qualification are different than those for welding procedure qualification. Specific guidance for each item listed, as appropriate, is provided below. a. See guidance material below. 1. The eight possible welding processes are listed in 1.1. 2. To be qualified to make a weld with a combination of processes, the welder can qualify using that combination of processes or the welder can qualify using each process separately. If the welder qualifies using a combination of processes, this does not qualify that welder to make complete welds using only one of those processes. b. In addition to vertical uphill and vertical downhill, the direction of welding is horizontal if welding is to be performed with the pipe in the vertical position. c. If a welder qualifies using a combination of filler metals (e.g., root pass from Group 1 or 2 and fill and cap from Group 3), this does not qualify that welder to make complete welds using electrodes from only Group 1 or 2 or from only Group 3. Qualification using a combination of filler metals only qualifies the welder to make welds using that combination. d. Pipe diameter is an essential variable for welder qualification but not for procedure qualification. For branch connections, this requirement appears to refer to the diameter of both the branch and the header piping. e. Wall thickness is an essential variable for both welder and welding procedure qualification. For branch connections, this requirement seems to refer to the wall thickness of both the branch and the header piping. f. A welder who qualifies for butt welds in the 6G position is qualified not only to make butt welds in all positions, but is also qualified to make lap fillet welds. A welder who qualifies in any position other than the 6G position is only qualified for that particular position. API 1104 does not define tolerances for changes in position. It would seem reasonable to allow a welder who has qualified in a particular position (e.g., 5G or horizontal-fixed position) to make production welds with the pipe inclined an angle of up to +/- 15° from that position without the need for requalification.

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g. A change in joint design constitutes an essential variable. A change from a butt weld to a fillet weld is a change in joint design. Except as indicated in “f” above, a welder qualified for only butt welds is not qualified for fillet welds. That is contrary to some other standards, such as ASME Section IX, that allow welders who are qualified to make butt welds to also make fillet welds without a separate qualification. Changes to variables that are not listed in 6.2.2 are allowed by simply revising the welder qualification test record (WQTR) without the need for requalification, although sound engineering judgment should be used. A revised WQTR should be identified by a revision number. G6.3 MULTIPLE QUALIFICATION Multiple qualification allows a welder to weld in all positions, on all wall thicknesses, joint designs, and fittings, and on all pipe diameters within the limits of the essential variables described in 6.3.2. G6.3.1 General See guidance pertaining to pipe positions in G6.2.1. Multiple qualification requires the welder to complete two tests: • A butt weld test with the pipe fixed in the 5G or 6G position on pipe with a minimum outside diameter of 6.625 in. (168.3 mm) and a minimum wall thickness of 0.250 in. (6.4 mm). No backing strip may be used. • A branch-on-pipe connection test (i.e., a set-on branch), which requires the welder to lay-out, cut, and fit two pipes together in the form a branch connection. The welder performing the test must lay-out, cut, and fit the two pipes together and make the weld. The nominal diameter of the branch must match the nominal diameter of the run pipe and the hole in the run pipe must be the same size as the inside diameter of the branch. The branch must be located at the 6 o’clock position. Successful qualification requires that the completed weld “exhibit a neat, uniform workmanlike appearance”, and not contain burn-throughs exceeding the size limits of 6.3.1. While “neat, uniform workman-like appearance” is not defined, it is common to apply the visual examination standards given in 6.4. In addition, four nick-break specimens


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities removed from locations described in Figure 10 must be tested and meet the requirements of 5.8.3 The phrase “using qualified procedures” refers to both tests. A welder who makes a procedure qualification weld is also qualified as a welder, however, as long as the requirements in Section 6 are also met. G6.3.2 Scope While the title of this section is “Scope”, it contains a list of essential variables for welders with a multiple qualification, which require that the welder be requalified if changes beyond the limits listed are exceeded. It should be noted that the essential variables for welder qualification are different than those for welding procedure qualification. The essential variables for multiple qualification are also different than those for single qualification. Specific guidance for each item listed, as appropriate, is provided below. a. See guidance material below. 1. The eight possible welding processes are listed in 1.1. 2. To be qualified to make a weld with a combination of processes, the welder can qualify using that combination of processes or the welder can qualify using each process separately. If the welder qualifies using a combination of processes, this does not qualify that welder to make complete welds using only one of those processes. b. In addition to vertical uphill and vertical downhill, the direction of welding is horizontal if welding is to be performed with the pipe in the vertical position. c. If a welder qualifies using a combination of filler metals (e.g., root pass from Group 1 or 2 and fill and cap from Group 3), this does not qualify that welder to make complete welds using electrodes from only Group 1 or 2 or from only Group 3. Qualification using a combination of filler metals only qualifies the welder to make welds using that combination. Changes to variables that are not listed in 6.3.2 are allowed by simply revising the welder qualification test record (WQTR) without the need for requalification, although sound engineering judgment should be used. A revised WQTR should be identified by a revision number. G6.4 VISUAL EXAMINATION Visual examination of the test weld is a requirement for welder qualification and generally

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precedes preparation and testing of samples for mechanical testing. If the visual examination reveals that the weld contains imperfections that exceed the limits given in 6.4, rejection is automatic and no additional testing need be performed. The phrase “shall be free from” indicates that there is no acceptable extent for cracks, inadequate penetration, and burn-through. In addition to the objective criteria for rejection, a weld may be rejected at the discretion of the inspector based on poor workmanship or if too much filler wire protrudes into the interior of the pipe (also called whiskers). G6.5 DESTRUCTIVE TESTING It should be noted that some acceptance criteria for imperfections discovered during welder qualification testing are more stringent than those for imperfections discovered by nondestructive testing of production welds. This is intended to account for the more-favorable conditions that generally exist where welders are normally qualified (e.g., in an enclosed welding shop as opposed to on a pipeline right-ofway). G6.5.1 Sampling of Test Butt Welds Figure 12 shows sample locations for welder qualification welds. This figure is very similar to and should not be confused with Figure 3, which shows sample locations for procedure qualification welds. The phrase “segments of pipe nipples” refers to the qualification of two welders on a single pipe nipple using the “brother-in-law” technique. If two welders are qualified on a single pipe nipple, the total number of specimens specified in Table 3 is required for each welder and the locations of test specimens for each welder must be representative of each location illustrated in Figure 12. The locations of the specimens shown in Figure 12 are rotated in accordance with Note 1 in Figure 12 so that the appropriate number of specimens is obtained from each welder’s segment of the pipe. Table 3 shows sample locations for welder qualification welds. This table is very similar to and should not be confused with Table 2, which shows sample locations for procedure qualification welds. If the pipe diameter is less than 2.375 in (60.3 mm), two test welds must be made to obtain the required number test specimens.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities If the pipe diameter is less than 1.315 in (33.4 mm), a tensile test of one full pipe section specimen may be substituted for the root-bend and nick-break specimens. If the tensile test specimen breaks in the weld, it is also evaluated as if it is a nick-break test specimen. G6.5.2 Tensile-strength, Nick-break, and Bend-test Procedures for Butt Welds See guidance pertaining to tensile strength, nickbreak, and bend testing provided in G5.6. For welder qualification, it is not necessary to measure tensile strength since a welder qualification test is intended to evaluate welder skill, not the suitability of the welding procedure. At the option of the user, the specimens designated for tensile testing may be subjected to the nick-break test instead. G6.5.3 Tensile-strength Test Requirements for Butt Welds It is permissible for the tensile strength test specimen to break in the weld. If the specimen breaks in the weld, it is evaluated as if it is a nickbreak test specimen. G6.5.4 Nick-break Test Requirements for Butt Welds See guidance provided in G5.6.3.3. G6.5.5 Bend Test Requirements for Butt Welds See guidance provided in G5.6.4.3. However, for a welder qualification test, it is permissible for bend test specimen for welds in high-test (i.e., high tensile strength) materials to break in the weld before they bend into a full U shape. If the specimen breaks in the weld, it is evaluated as if it is a nick-break test specimen. See guidance provided in G5.6.3.3. The statement in 6.5.5 pertaining to bend test specimens that do not bend to a full U shape does not imply that specimens do not have to be tested to the full extent of the jig. Retesting of one bend test specimen is allowed during welder qualification if, in the opinion of the company, the imperfection observed is not representative of the weld. Retesting is allowed only once.

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G6.5.6 Sampling of Test Fillet Welds The phrase “segments of pipe nipples” refers to the qualification of two welders on a single pipe nipple using the “brother-in-law” technique. For fillet welds made on pipe in the horizontal fixed position, one full circumferential weld completed by two welders is sufficient to test both welders. For fillet welds made on pipe in the 6F position (inclined at 45 degrees), each welder must complete one half of the up hill fillet weld and one half of the downhill fillet weld in order to provide test specimens representing all of the fillet weld orientations for each welder. G6.5.7 Test Method and Requirements for Fillet Welds See guidance provided in G5.8. G6.6 RADIOGRAPHY-BUTT WELDS ONLY G6.6.1 General For butt welds, the company may elect to use radiography for evaluation of welder qualification welds instead of destructive testing. However, some regulatory codes require that welders be qualified by destructive testing when they are to make production welds in certain locations, (e.g., welders who weld compressor station piping to meet the requirements of 49 CFR Part 192). Since radiography is the only nondestructive test method mentioned as an alternative to destructive testing, the use of other test methods, such as automated ultrasonic testing, is not currently allowed. G6.6.2 Inspection Requirements See guidance pertaining to acceptance standards in G9.3. The use of radiography results to choose good or bad portions of the weld for subsequent destructive testing for the purpose of qualifying or disqualifying a welder is prohibited. G6.7 RETESTING If a welder fails a qualification test because of unavoidable conditions or conditions beyond the control of the welder, that welder may be given a second opportunity to qualify. If that welder fails the second time, acceptable proof of additional welder


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities training must be submitted before taking the test again. G6.8 RECORDS Records of detailed test results for each welder must be maintained. The level of detail required is not specified and is left to the discretion of the user. Figure 2 is a sample welder qualification test record (WQTR), which can also be used as a procedure qualification record (PQR). The use of Figure 2 is not mandatory, although a form similar to this should be used. It is common, but not mandatory, to include a space for a revision number, which may be required eventually. A list of welders and the procedures for which they are qualified must also be maintained. API 1104 does not address time intervals over which a welder qualification is valid. Required welder requalification intervals are left to the discretion of the user and are addressed in a variety of other codes and regulations. At the discretion of the company, a welder may be required to re-qualify if the competence of that welder comes into question.

G7 Design and Preparation of a Joint for Production Welding Section 7 gives guidance on the use of qualified welding procedures during production welding. Much of this section simply indicates that the qualified welding procedure specification (WPS) must be followed (i.e., welders must follow the qualified welding procedure). Changes to a qualified welding procedure are allowed provided that an essential variable is not violated. Changes to welding variables that are not essential variables are allowed by simply revising the WPS without the need for requalification, although sound engineering judgment should be used. A revised WPS should be identified by a revision number. Revisions to a qualified welding procedure must be authorized by the company. Welders are not permitted to weld outside of the ranges specified in the qualified welding procedure even if an essential variable is not violated. There are many instances of the word “should” in Section 7 of API 1104. The word “should” indicates a recommended practice, whereas the word “shall” indicates a mandatory requirement. G7.1 GENERAL Documentation of a qualified welder usually consists of a welder qualification test record

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(WQTR). Documentation of a qualified welding procedure consists of a WPS and a procedure qualification record (PQR). API 1104 also refers to the latter as a coupon test report. A PQR ‘supports’ a WPS. A WPS can be supported by more than one PQR. It is common, but not mandatory to list the PQRs that support a particular WPS. It is good practice to ensure that copies of welder and welding procedure documentation are available in the field during production welding. For pipe that meets the requirements of more than one pipe grade (i.e., pipe that is ‘multi-graded’ or ‘dual or triple stenciled’), it is not necessary to use a welding procedure that is qualified for the highest grade to which the pipe is certified. It is only necessary to use a welding procedure qualified for use on the grade for which the material will be used. For example, for pipe certified to both API 5L X42 and X52, a welding procedure qualified for use on X42 is acceptable provided that the material is being used as X42. However, for some applications (e.g., high longitudinal strains), it is good practice to at least match the actual yield strength of the pipe. The use of filler metal with yield strength that matches or overmatches the actual yield strength of the pipe material prevents longitudinal strains from accumulating in the weld region, which is more likely to contain imperfections than the pipe material. Since there is no requirement in API 1104 to designate the position of the pipe material during procedure qualification (e.g., horizontal, vertical, or some position in between), there are no limits on the use of a qualified welding procedure in applications where the axis of the pipe is displaced significantly from that which was used during procedure qualification. Sound engineering judgment should be used when determining the applicability of a qualified welding procedure when the axis of the pipe is displaced significantly from that which was used during procedure qualification. For a welder who has a single qualification to 6.2, however, there are welder qualification limits for position. See guidance provided in G6.2.2f. G7.2 ALIGNMENT When lining up for girth welding, API 1104 allows for some degree of offset between adjoining edges of the pipe. Since the word should is used to describe the 1/8 in. (3 mm) maximum offset specified, this is a recommended practice and not a requirement. Offsets larger than this are allowed provided that they are the result of pipe end dimensional variations that are within the limits of Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities the specification to which the pipe was purchased and that the offset has been distributed uniformly around the circumference. Pipe end dimensional variations that can result in offset include pipe diameter tolerances, out-of-roundness tolerances, and wall thickness tolerances. It is recommended that offsets larger than 1/8 in. (3 mm) that are due simply to misalignment not be allowed. Acceptable end preparations for butt welds between pipe having unequal wall thickness, unequal yield strength, or both are provided in a variety of other codes and standards. API 1104 does not address the placement of longitudinal seams or the separation of longitudinal seams on adjacent pipes during girth welding. However, it is common practice to place the longitudinal seams in the top half of the pipeline and to stagger the longitudinal seams on adjacent pipes. G7.3 USE OF LINEUP CLAMP FOR BUTT WELDS If allowed by the WPS, the lineup clamp can be removed prior to the completion of the root bead provided that the completed part of the bead is in approximately equal segments and is spaced approximately equally around the circumference. When using an internal lineup clamp, if preventing pipe movement will be difficult or if the weld will be unduly stressed, the clamp must be left in place until the root bead is complete. When using an external lineup clamp, root-bead segments should be uniformly spaced around the circumference and the root bead should be at least 50% complete before the clamp is removed. The word should in the previous sentence denotes a recommended practice and not a requirement. For highly-stressed welds (e.g., tie-in welds), it is preferable that as much of the root bead be completed as possible before the clamp is removed.

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oxygen cutting. The word should indicates a preference for machining or machine oxygen cutting. The use of manual methods requires company authorization. The design and dimensions of field bevels must conform to the qualified WPS. G7.5 WEATHER CONDITIONS Inclement weather conditions that can have an adverse affect of weld quality include low temperatures, moisture in the air (e.g., precipitation, high humidity, etc.), high winds, etc. Preheating is often specified in a WPS when the ambient temperature is lower than a specified value. When the surface temperature is below the ambient dew point, moisture will condense on the pipe surface, which, if welded over, will contribute to increased weld hydrogen levels. The use of preheating will eliminate moisture and other contaminants (e.g., coating residue) prior to welding. High winds can disrupt the shielding of the molten weld metal, which can lead to porosity. Low temperatures can cause increased weld cooling rates, which can lead to the development of crack-susceptible weld microstructures and can cause hydrogen to become trapped in the weld. Preheating can also slow weld cooling rates somewhat and allow hydrogen diffusion following welding. During inclement weather, temporary shelters can be used to protect the weld and its immediate surroundings. Responsibility for determining how and when to conduct welding operations in inclement weather conditions lies with the company. G7.6 CLEARANCE When welding above ground or in a trench, adequate clearance should be provided for the welder so that movement around the pipe is not obstructed. Since the word should is used to describe the 16 in. (400 mm) minimum clearance specified, this is a recommended practice and not a requirement.

G7.4 BEVEL G7.7 CLEANING BETWEEN BEADS G7.4.1 Mill Bevel The design and dimensions of mill bevels must conform to the qualified WPS G7.4.2 Field Bevel Pipe ends for butt welding may be beveled in the field by any convenient machine method. Machining or machine oxygen cutting produces a higher quality bevel that manual methods such as grinding and hand

Cleaning of the weld groove prior to welding and between beads must be carried out as specified in the qualified WPS. Hand or power tools may be specified. Between pass grinding is specifically required to remove surface imperfections when using semiautomatic or mechanized welding. When silicon in the weld puddle forms heavy glass deposits (primarily when using the GMAW process), these must be removed between passes when requested by the company.



G7.8 POSITION WELDING In position welding, the pipe or assembly is stationary (i.e., not rotating) while the weld metal is being deposited. Welding while the pipe is stationary, rolling the pipe, and then welding again (sometimes referred to as quarter welding) is also position welding (not roll welding). G7.8.1 Procedure During position welding, adequate support and clearance must be provided. A change in position from position welding to roll welding, or vice versa, constitutes an essential variable for procedure qualification. G7.8.2 Filler and Finish Beads The thickness of weld passes on the top and bottom of a stationary pipe tend to be greater than for the sides. Therefore, stripper beads may be required to even out the weld cross-sectional thickness prior to depositing the cap pass. Stripper passes, commonly required in the 2 to 4 o’clock positions, are typically deposited using welding parameters for fill passes.

from roll welding to position welding, or vice versa, constitutes an essential variable for procedure qualification. G7.9.2 Filler and Finish Beads While not prohibited, stripper passes are generally not required for roll welds. Since the word shall is used to describe the minimum height of the weld crown (at least flush with the parent metal), this is a requirement. The word should is used to describe the 1/16 in. (1.6 mm) maximum cap height and the weld width of at least 1/8 in. (3 mm) wider than the original groove, however, making these recommended practices and not requirements. While not required for roll welds, the start/stop location for a subsequent bead should not coincide with the start/stop location of a previous bead to reduce the chance of accumulating start/stop imperfections in a particular location.. It is not permissible to leave slag deposits on completed welds, as this interferes with visual inspection.

Since the word shall is used to describe the minimum height of the weld crown (at least flush with the parent metal), this is a requirement. The word should is used to describe the 1/16 in. (1.6 mm) maximum cap height and the weld width of at least 1/8 in. (3 mm) wider than the original groove, however, making these recommended practices and not requirements.

G7.10 IDENTIFICATION OF WELDS

The start/stop location for a subsequent bead should not coincide with the start/stop location of a previous bead. It is not permissible to leave slag deposits on completed welds, as this interferes with visual inspection.

G7.11 PRE- AND POST-HEAT TREATMENT

G7.9 ROLL WELDING Roll welding refers to rolling the pipe while the weld metal is being deposited. Welding while the pipe is stationary, rolling the pipe, and then welding again (sometimes referred to as quarter welding) is position welding (not roll welding). G7.9.1 Alignment The ability to use roll welding is left to the discretion of the company, although adequate support must be provided. However, a change in position

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The method by which each welder must identify his (or her) work is left to the discretion of the company. This typically involves the use of a system of paint marker markings. If die stamping is specified, low-stress type dies (e.g., dot style or round face) should be used.

Material conditions that may necessitate the use of pre- or post-heating include heavy wall thickness and/or high carbon equivalent values. Weather conditions that may necessitate the use of pre- or post-heating include low temperatures and/or moisture in the air (e.g., precipitation, high humidity, etc.). Pre- and/or post- heating must be carried out as prescribed in the WPS. Preheating carbon steel to a precise temperature is generally not required. It is usually acceptable to exceed the minimum-required preheat temperature by approximately 100°F (56°C). However, maximumallowable interpass temperature requirements should not be violated. Common methods used to preheat pipelines prior to welding include gas torches and quartz lamps (radiation methods), electric resistance


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities heaters (conduction methods), and induction heaters (induction methods). Preheating should be applied in a manner that ensures that the full material volume surrounding the joint is thoroughly heated to above the specified minimum temperature. General preheating guidance suggests that the material should be thoroughly heated for a distance equal to the thickness of the material being welded, but not less than 3 in. (75 mm) in all directions from the point of welding. When possible, heat should be applied to the side opposite of that which is to be welded, and measurements should be made on the surface adjacent to the joint (i.e., the temperature should be measured on the opposite side of that which is heated). Where this is impractical, time should be allowed for the temperature to equalize after removal of the heat source before the temperature is measured. For girth welds in large diameter pipe, the preheat temperature could fall to below the minimum-required temperature before an individual weld pass is completed, If this occurs, welding should be interrupted and preheat should be reapplied. It may be useful to think of preheat temperature as the “arc start temperature,” or the temperature of the weld zone during welding of any weld bead (i.e., not just the first weld bead). Temperature measurement methods commonly used include contact thermometers (digital or analog), non-contact infrared pyrometers, and temperature indicating crayons (e.g., Tempilsticks™). The minimum-required preheat temperature should be maintained throughout the welding operation. Once welding begins, this temperature is generally referred to as the interpass temperature. If the welding operation is interrupted, preheating should be reapplied until the minimum-required preheat temperature is reestablished. The minimumrequired interpass temperature should be equal to the minimum-required preheat temperature unless otherwise indicated. For many welding applications, the heat from the welding operation is sufficient to maintain the desired temperature without the continuous external application of heat. If preheating is specified in the welding procedure, it should also be applied when tack welding. Cracks that develop in tack welds that are not completely consumed by the final weld can initiate cracks in the final weld.

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When using post-heating (or post-weld preheat maintenance) to minimize the risk of cracking (i.e., to allow hydrogen diffusion), the post-weld heating must be applied prior to the onset of cracking. Parameters for post-weld heat treatment (PWHT) for stress relief often include a temperature to which the joint can be heated without controlling the heating rate, a maximum-allowable heating rate from this temperature to the PWHT temperature range, the hold time at PWHT temperature range (usually expressed in hours per unit of wall thickness), and the maximum-allowable cooling rate from this temperature.

G8 Inspection and Testing of Production Welds G8.1 RIGHTS OF INSPECTION The company may dictate what type of inspection will occur, and when and how often it will occur. Other codes, standards, and regulations may set minimum requirements for inspection. Inspection during welding may include visual inspection or nondestructive testing. G8.2 METHODS OF INSPECTION Production welds may be inspected using nondestructive testing (e.g., radiography or other methods specified by the company) provided that the method can produce indications of imperfections that can be accurately interpreted and evaluated. Production welds can also be sampled (i.e., cut out) for destructive testing. Acceptance criteria for imperfections discovered by nondestructive testing are those contained in Section 9 (or Appendix A). Acceptance criteria for imperfections discovered by destructive testing are those contained in 6.5. It should be noted that some acceptance criteria in 6.5 are more stringent than those in Section 9. The use of Appendix A is for girth welds only and requires extensive analysis and testing prior to use. See guidance provided for Appendix A. Trepanning involves removing and destructively testing a portion of the weld (e.g., removed using a hole saw). This results in the need to repair the area from which the sample was taken, which makes it impractical for pipeline girth welding applications.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities The company may require that inspectors demonstrate the effectiveness of the inspection procedures being used, and their ability to use those procedures. G8.3 QUALIFICATION OF INSPECTION PERSONNEL The level of education, experience, and training required for welding inspection personnel is left to the discretion of the company. No specific examination is required. However, the company must keep records pertaining to qualification of welding inspection personnel. Requirements for nondestructive personnel are contained in 8.4.

testing

G8.4 CERTIFICATION OF NONDESTRUCTIVE TESTING PERSONNEL G8.4.1 Procedures Certification of nondestructive testing personnel is covered in American Society for Nondestructive Testing (ASNT) Recommended Practice No. SNTTC-1A and the ASNT Central Certification Program. Other nationally recognized programs for certification may also be used with company approval. ASNT requires inspectors to have specified levels of education and training, experience, and performance on qualification exams. G8.4.2 Record The company must keep detailed records pertaining to certification of nondestructive testing personnel.

G9 Acceptance Standards for Nondestructive Testing Nondestructive testing detects imperfections in a component or structure. All components and structures contain imperfections, which are interruptions or irregularities in an otherwise uniform structure. An imperfection is not considered a defect until it has been compared to an acceptance standard and found to be non-conforming. In other words, all defects are imperfections but not all imperfections are necessarily defects. When performing a nondestructive examination, the inspector may find imperfections that may or may

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not require rejection. To determine the disposition of a particular imperfection, the inspector must compare the attributes of that imperfection (e.g., size, shape, location, orientation, etc.) to the acceptance standards in Section 9. Acceptance standards are given in terms of absolute length, aggregate length within any continuous 12 in. (300 mm) of weld length, and for pipe with an outside diameter less than 3.5 in. (88.9 mm), aggregate length expressed as a percentage of the total weld length. Where multiple standards are given for a specific imperfection, the imperfection is considered a defect should any one of the listed conditions exist. G9.1 GENERAL Section 9 presents acceptance standards for imperfections detected by radiographic, magnetic particle, liquid penetrant, and ultrasonic testing methods. Each has a source of probing energy or a medium that, upon encountering an imperfection in weld (or base material), changes in some detectable way. For a given imperfection type, it is not necessary or advisable to consider or apply acceptance standards for different nondestructive test methods (except for visual inspection as described below). For example, the definition of linear indication for magnetic particle and liquid penetrant testing (length more than three times the width) should not be applied to porosity indications in radiographic applications. The acceptance standards in Section 9 also apply to imperfections detected by visual inspection. Visual inspection involves examining materials, with or without magnification or remote examination devices such as mirrors or fiber optics. Visual inspection can be performed before, during, and after welding operations. For detection of imperfections that would be cause for rejection according to the acceptance standards contained in Section 9, or for rejection on other grounds (e.g., welding procedure was not followed), visual inspection generally precedes other inspection methods. If a weld is rejected on the basis of visual inspection, the expense of more costly nondestructive test methods can be avoided. When qualifying welders in accordance with 6.5, it is not acceptable to select specific welds for destructive testing based on nondestructive testing results.



G9.2 RIGHTS OF REJECTION A weld that passes nondestructive testing may still be rejected by the company if in their opinion the imperfection can be detrimental to the weld. Only the depth of an imperfection is mentioned in 9.2, but it would seem reasonable that other attributes of the imperfection (e.g., length) could be included as well. G9.3 RADIOGRAPHIC TESTING Radiographic testing (RT) is based on the distinction between transmission and absorption of xray and gamma radiation, producing images captured on film or other media. Areas where material is thinner or less dense will transmit more radiation to the film, producing darker images; areas where material is thicker or denser will transmit less radiation to the film, producing lighter image. Imperfections cause patterns of lightness or darkness, which radiographic inspectors are trained to interpret and evaluate. Radiographic films produce negative images. Material that is thinner or less dense will produce a darker image. A dark image on a radiograph is described as being more dense than a light image. Conversely, material that is thicker or more dense will produce a lighter image. A light image on a radiograph is described as being less dense than a dark image. When considering density, be aware of the difference between density of the radiographic image and density of the material. Detectability of imperfections is significantly affected by the shape and orientation of the imperfection when subjected to radiographic RT. Volumetric imperfections, such as porosity and slag inclusions may be easily detected by radiography while some planar (i.e., crack-like) imperfections may be more difficult to detect if not oriented parallel to the path of the penetrating radiation. For example, a crack oriented in the through-wall direction may be detected much more easily than a mid-wall lamination of similar size. For the sake of convenience, the acceptance standards for RT contained in 9.3 are summarized in Table G2. G9.3.1 Inadequate Penetration without Highlow High-low refers to misalignment of adjoining pipe sections. Inadequate penetration, also called

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incomplete joint penetration, can occur with or without high-low. IP and IPD are joint root conditions where the weld metal does not extend entirely through the thickness of a groove weld joint and one or both of the root faces of the weld bevel are not completely consumed. Causes of IP include improper technique, improper joint configuration, or improper fit-up. Radiographic images of IP and IPD typically appear as a dark area with well defined straight edges that follow the root face down the center of the weld. G9.3.2 Inadequate Penetration Due to Highlow See guidance provided in G9.3.1. The acceptance standards for IPD are generally less stringent than for IP. G9.3.3 Inadequate Cross Penetration Inadequate cross penetration occurs when welding is being performed from both sides of the joint and the two beads do not meet within the joint. Causes of ICP include improper technique and improper joint configuration. The radiographic image of ICP typically appears as a dark straight line in the center of the weld, reflecting lower density. G9.3.4 Incomplete Fusion Incomplete fusion is a weld imperfection in which fusion does not occur between weld metal and fusion faces or adjoining weld beads. API 1104 differentiates between IF (incomplete fusion open to the surface) and IFD (incomplete fusion below the surface). In both cases, the most common causes included improper manipulation of electrode by the welder and improper joint configuration. Radiographic images of IF and IFD typically appear as a dark line or lines oriented in the direction of the weld. G9.3.5 Incomplete Fusion Due to Cold Lap See guidance provided in G9.3.4. The acceptance standards for IFD are generally less stringent than for IF. G9.3.6 Internal Concavity Internal concavity (also called suck-back) is a root surface condition in which the weld bead surface is somewhat below the inside surface of the pipe


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities wall. Causes of IC include improper technique, and excessive heating and melting of the root pass during the welding of the second pass. The radiographic image of IC typically appears as a darker area with irregular edges and is quite wide in the center of the image. G9.3.7 Burn-through Not to be confused with “burning through” during welding onto an in-service pipeline where the welding arc causes the pipe wall to be breached and allows the contents to escape. G9.3.7.1 A burn-through is a localized collapse of the molten pool leaving a depression or crater type imperfection in the root area of the weld. Causes of BT include improper technique, excessive amperage, and improper joint configuration. The radiographic image of BT typically appears as dark spots often surrounded by light areas. G9.3.7.2 No guidance material required. G9.3.7.3 Only one acceptable BT is allowed for pipe with an outside diameter less than 2.375 in. (60.3 mm).

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radiograph but often appears as dark, round or irregular spots or specks appearing singularly, in clusters, or in rows. Porosity can be elongated and may have the appearance of having a tail. Section 9.3.9 distinguishes between individual or scattered porosity (P), cluster porosity (CP), and hollow bead porosity (HB). Causes of porosity include contaminants or moisture in the weld zone, improper shielding of the welding arc, and improper travel speed. G9.3.9.2 Acceptance or rejection of porosity is based on two factors; size of the individual pores (9.3.9.2 a and b) and amount (9.3.9.2 c). In judging the amount, reference is made to Figures 19 and 20, which provide schematic representations of porosity that are used for comparison purposes. G9.3.9.3 If cluster porosity cannot be proven to be in the finish pass, the criteria in 9.3.9.2 apply. If part c of 9.3.9.2 applies, then Figures 19 and 20 must be used even if the indication on the radiograph has been identified as cluster porosity. G9.3.9.4 Any elongated porosity indication in the root pass should be considered to be hollow bead. G9.3.10 Cracks

G9.3.8 Slag Inclusions G9.3.8.1 A slag inclusion is an entrapment of nonmetallic solid in the weld metal or between the weld metal the parent material. Two kinds of slag inclusion are recognized in 9.3.8; elongated (ESI) and isolated (ISI). Causes of SI include improper technique, improper manipulation of the electrode, insufficient current, and insufficient cleaning of weld beads. The radiographic image of SI typically appears as dark jagged asymmetrical shapes within the weld or along the weld joint areas. G9.3.8.2 Wagon tracks typically occur in pairs and are treated as a single indication unless the width of either ‘track’ exceeds 1/32 in. (0.8 mm). G9.3.8.3 See guidance provided in G9.3.8.2, For pipe with an outside diameter less than 2.375 in. (60.3 mm), acceptable length for ESI, and acceptable length and width of ISI, depends on wall thickness. G9.3.9 Porosity G9.3.9.1 Porosity is the result of gas entrapment in the solidifying metal. It takes many shapes on a

A crack, either longitudinal or transverse, is a linear imperfection with sharp end conditions. Cracks are the most critical imperfection because of their tendency to grow and propagate under stress. Cracks are characterized by their location within the weld (heat-affected zone or weld metal), and whether they develop during welding (hot cracks) or after cooling (cold cracks). In API 1104, the only cracks that may be acceptable without repair are shallow star or crater cracks, which appear at the end of a weld bead. While other defect types depend on the skill of the welder, cracks tend to occur if the necessary conditions are met regardless of welder skill. Provided that the welding procedure is followed, the formation of cracks in general is usually indicative of a deficiency in the welding procedure for the particular materials being welded and the particular conditions under which the procedure is being used. The radiographic image of a crack typically appears as jagged and often faint irregular lines. The detectability of cracks is strongly influenced by their orientation relative to the path between the radiation source and the film (or detector). Cracks parallel to the radiation path are more likely to be detected than cracks oriented at a sharp angle to the radiation path.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities G9.3.11 Undercutting Undercutting is a groove melted into the base metal during welding. Internal or root undercut occurs in the base metal adjacent to the root of the weld. In the radiograph, it will appear as a dark irregular line offset from the centerline of the weld. Undercut is not as straight as lack of penetration because it does not follow a ground or prepared edge. External undercut occurs in the base metal adjacent to the face of the weld and is also readily detectable by visual examination. In the radiograph, it appears as a dark irregular line along the outside edge of the weld. Causes of undercutting include improper manipulation of the electrode by the welder, excessive amperage, and improper travel speed. External undercut is normally detected visually prior to radiographic testing. The length criteria in 9.3.11 should be used in conjunction with the visual acceptance standards for undercutting in 9.7 to determine whether an instance of undercutting is acceptable or rejectable. When both methods are used, mechanical measurements made in conjunction with visual inspection govern. G9.3.12 Accumulation of Imperfections When considering accumulation of imperfections within a given weld length, the length of undercutting and incomplete penetration due to high low are not included. These are considered separately in Paragraphs 9.3.2 and 9.3.11. G9.3.13 Pipe or Fitting Imperfections If radiography discloses defects in pipe or fittings, they must be reported to the company. G9.4 MAGNETIC PARTICLE TESTING Magnetic particle testing (MT) employs magnetizing current and iron powder to locate imperfections in ferromagnetic materials. When a magnetic field encounters an obstruction, such as an imperfection or defect, the magnetic field ‘leaks’ into the atmosphere. This leakage attracts the particles of iron powder. Sound materials that do not contain defects or imperfections and do not leak magnetic current do not attract iron powder. MT only detects imperfections that are at or very close to the surface being inspected. DC current may be capable of finding subsurface imperfections close to the surface, while AC current typically finds only surface imperfections. Various forms of MT have been developed to improve detectability of imperfections.

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Generally, the more sensitive methods use magnetic particles suspended in a carrier liquid, which improves the mobility of the particles and allows them to be more easily attracted to small imperfections. Examples include wet fluorescent MT and the use of colored (usually black) particles in a liquid suspension applied to a surface that is first sprayed with a thin layer of white contrast paint. In MT, the inspector identifies locations where particles accumulate. Depending on their nature and size, the imperfections may cause the item to be rejected or explored further. For the sake of convenience, the acceptance standards for MT contained in 9.4 are summarized in Table G3. G9.4.1 Classification of Indications G9.4.1.1 When using MT, the inspector should be careful to distinguish between relevant accumulations of particles due to defects and irrelevant accumulations due to inherent characteristics of the weld. For example, in some cases, metallurgical differences between weld metal and heat-affected zones may cause perturbations in the magnetic field that result in accumulations of particles at or near the fusion line. Generally, those accumulations are somewhat less distinct than accumulations resulting from the presence of imperfections. Geometric irregularities, such as abrupt changes in thickness at the toe of girth weld caps or the toe of a lumpy fillet weld can also result in particle accumulations. Dressing the toe of a weld by grinding or similar mechanical means can improve inspectability. G9.4.1.2 If the inspector is not sure what an indication is, the surface should be conditioned (e.g., by dressing the toe of a weld by grinding) and reexamined. G9.4.1.3 The inspector must ascertain which relevant imperfections are linear and which are rounded, because linear indications are more prone to propagation. G9.4.2 Acceptance Standards If MT gives ambiguous results, other nondestructive testing methods may be used to determine the disposition of the weld.



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G9.4.3 Pipe or Fitting Imperfections

G9.5.3 Pipe or Fitting Imperfections

If magnetic particle testing discloses defects in pipe or fittings, they must be reported to the company.

If PT discloses defects in pipe or fittings, they must be reported to the company. G9.6 ULTRASONIC TESTING

G9.5 LIQUID PENETRANT TESTING Liquid penetrant testing (PT) relies on the ability of certain types of liquids to enter into surface voids and crevices by capillary action, and remain there when the surface liquid is removed. Then a contrast medium (developer) reveals the penetrant remaining in the voids and crevices. The contrast medium may be a powder in liquid suspension or ultraviolet light. For the sake of convenience, the acceptance standards for PT contained in 9.5 are summarized in Table G3 at the end of this section.

Ultrasonic testing (UT) involves the propagation of sound waves through materials, and capture of the reflected echo from density changes in the material being inspected. These changes appear on a display screen as peaks and valleys. The inspector compares them to a reference standard to determine acceptability. For the sake of convenience, the acceptance standards for UT contained in 9.6 are summarized in Table G4. G9.6.1 Classification of Indications

G9.5.1 Classification of Indications G9.5.1.1 When using PT, the inspector should be careful to distinguish between relevant indication due to imperfections or defects and irrelevant indications due to characteristics of the weld. Anomalous or uncertain results can be obtained if excess penetrant is not thoroughly cleaned from the surface prior to the application of the developer. However, excessive cleaning can inadvertently remove penetrant from the actual imperfections, thus preventing detection. Failure to appropriately clean the surface to be inspected before the application of the penetrant can also interfere with the ability to subsequently remove excessive penetrant before the developer is applied. However, power wire brushing and some other mechanical methods of cleaning can smear metal over the surface opening of small imperfections and interfere with penetrant absorption. G9.5.1.2 If the inspector is not sure what an indication is, the surface must be conditioned and reexamined. G9.5.1.3 The inspector must ascertain which relevant imperfections are linear and which are rounded, because linear indications are more prone to propagation. G9.5.2 Acceptance Standards

The inspector must distinguish between linear, transverse, and volumetric indications, because linear indications are the most prone to propagation. G9.6.1.1 When using UT, the inspector should be careful to distinguish between relevant indications due to imperfections or defects and irrelevant indications due to the geometry of the weld. G9.6.1.2 See guidance provided for imperfection types and causes in G9.3.

various

G9.6.1.3 See guidance provided for imperfection types and causes in G9.3.

various

G9.6.1.4 See guidance provided for imperfection types and causes in G9.3.

various

G9.6.1.5 If ultrasonic testing gives ambiguous results, other nondestructive methods may be used to determine the disposition of the weld. G9.6.2 Acceptance Standards The inspector must distinguish between linear, transverse, and volumetric indications, because linear indications are the most prone to propagation. G9.6.2.1 No guidance material required.

If PT gives ambiguous results, other nondestructive testing methods may be used to determine the disposition of the weld.



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Table G2 – Summary of Radiographic Testing Acceptance Standards SYMBOL

Inadequate Penetration without High-Low [9.3.1]

IP

Length shall not exceed 1 in. (25 mm).

Aggregate length shall not exceed 1 in. (25 mm) in any continuous 12 in. length of weld. Any weld less than 12 in. (300 mm) in length, aggregate length shall not exceed 8% of the weld length.

Inadequate Penetration Due to High-Low [9.3.2]

IPD


Aggregate length shall not exceed 3 in. (75 mm).

Inadequate Cross Penetration [9.3.3]

ICP


Aggregate length shall not exceed 2 in. (50 mm).

IF


Aggregate length shall not exceed 1 in. (25 mm). Any weld less than 12 in. (300 mm) in length, aggregate length shall not exceed 8% of the weld length.

IFD


Aggregate length shall not exceed 2 in. (50 mm) in any continuous 12 in. length of weld, or aggregate length shall not exceed 8% of the weld length.

Incomplete Fusion [9.3.4]

Incomplete Fusion Due to Cold Lap [9.3.5]

INDIVIDUAL INDICATION SIZE

TOTAL INDICATION SIZE

INDICATION TYPE

Internal Concavity [9.3.6]

IC

Any length is acceptable provided the density of the radiographic image of the IC does not exceed that of thinnest adjacent parent material. For areas that exceed the density of the thinnest adjacent parent material, the criteria for burn-through are applicable.

Burn-through – Pipe OD ≥ 2.375 in. (60.3 mm) [9.3.7.1]

BT

Maximum dimension shall not exceed 1/4 in. (6 mm) or the thinner of the nominal wall thicknesses joined, and the density in any portion of the BTs image exceeds that of the thinnest adjacent parent material.

Sum of the maximum dimensions of separate BTs exceeds that of the thinnest adjacent parent material shall not exceed 1/2 in. (13 mm) in any continuous 12 in. length of weld or the total weld length, whichever is less.

Burn-through – Pipe OD < 2.375 in. (60.3 mm) [9.3.7.1]

BT

Maximum dimension shall not exceed 1/4 in. (6 mm) or the thinner of the nominal wall thicknesses joined, and the density in any portion of the BTs image exceeds that of the thinnest adjacent parent material.

More than one BT of any size is present and the density in any portion of the BTs image exceeds that of the thinnest adjacent parent material.



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Table G2 – Summary of Radiographic Testing Acceptance Standards INDICATION TYPE

SYMBOL



Elongated Slag Inclusion – Pipe OD ≥ 2.375 in. (60.3 mm) [9.3.8.1]

ESI

Width shall not exceed 2 in. (50 mm) in length or 1/16 in. (1.6 mm).

Aggregate length shall not exceed 2 in. (50 mm) or width exceed 1/16 in. (1.6 mm). Aggregate length of ESI and ISI shall not exceed 8% of the weld length.

Elongated Slag Inclusion – Pipe OD < 2.375 in. (60.3 mm) [9.3.8.1]

ESI

Length shall not exceed 3 times the thinner of the nominal wall thicknesses joined or width exceed 1/16 in. (1.6 mm).

Aggregate length of ESI and ISI shall not exceed 8% of the weld length.

Isolated Slag Inclusion – Pipe OD ≥ 2.375 in. (60.3 mm) [9.3.8.1]

ISI

Maximum width shall not exceed 1/8 in. (3 mm).

Aggregate length shall not exceed 1/2 in. (13 mm) or more than four ISI indications with the maximum width of 1/8 in. (3 mm) in any continuous 12 in. (300 mm) length of weld. Aggregate length of ESI and ISI shall not exceed 8% of the weld length.

Isolated Slag Inclusion – Pipe OD < 2.375 in. (60.3 mm) [9.3.8.1]

ISI

Porosity (Individual or scattered, including cluster porosity in any pass except the finish pass) [9.3.9.1]

P

Maximum dimension of individual pore shall not exceed 1/8 in. (3 mm) or 25% of the thinner of the nominal wall thicknesses joined. Maximum distribution of scattered porosity shall not exceed concentration shown in Figures 19 or 20.

Cluster Porosity (Finish pass only). [9.3.9.3]

CP

Diameter of cluster shall not exceed 1/2 in. (13 mm).

Aggregate length shall not exceed 2 times the thinner of the nominal wall thicknesses joined and maximum width shall not exceed one-half the thinner of the nominal wall thicknesses joined. Aggregate length of ESI and ISI shall not exceed 8% of the weld length.

Aggregate length shall not exceed 1/2 in. (13 mm) in any continuous 12 in. (300 mm) length of weld.

All Rights Reserved



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Table G2 – Summary of Radiographic Testing Acceptance Standards INDICATION TYPE Hollow Bead [9.3.9.4]

Cracks [9.3.10] Undercutting (Internal External) [9.3.11]

SYMBOL



HB

Individual indication shall not exceed 1/2 in. (13 mm) in length. Individual HB indications, each greater than 1/4 in. (6 mm) in length, shall be separated by less than 2 in. (50 mm).

Aggregate length shall not exceed 2 in. (50 mm) in any continuous 12 in. (300 mm) length of weld, or the aggregate length of all HB indications shall not exceed 8% of the weld length.

C or

Accumulation of Imperfections [9.3.12]

IU or EU

AI

None permitted of any size or location in the weld, except a shallow crater crack or star crack with a length 5/32 in. or less (4 mm) is permitted. Aggregate length of EU and IU, in any combination, shall not exceed 2 in. (50 mm) in any continuous 12 in. (300 mm) length of weld, or exceed one-sixth of the weld length. Aggregate length, excluding IPD and EU or IU, shall not exceed 2 in. (50 mm) in any continuous 12 in. (300 mm) length of weld, or exceed 8% of the weld length.

Note: 1. All densities referred to in 9.3.1 through 9.3.13 are based on negative images. 2. Parallel ESI indications separated by approximately the width of the root bead (wagon tracks) shall be considered a single indication unless the width of either of them exceeds 1/32 in. (0.8 mm). In that event, they shall be considered separate indications.



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Table G3 – Summary of Magnetic Particle and Liquid Penetrant Testing Acceptance Standards RELEVANT INDICATION TYPE

SYMBOL

Crater Cracks or Star Cracks


Length shall not exceed 5/32 in. (4 mm).

Cracks

C

Incomplete Fusion

IF

Rounded Indications


None permitted of any size or location in weld, except a shallow crater crack or star crack. Total length shall not exceed 1 in. (25 mm) in a continuous 12 in. (300 mm) length of weld or 8% of the weld length. Maximum dimension of individual pore shall not exceed 1/8 in. (3 mm) or 25% of the thinner of the nominal wall thicknesses joined. Maximum distribution of scattered porosity shall not exceed concentration shown in Figures 19 or 20. Diameter of cluster porosity shall not exceed 1/2 in. (13 mm).

Aggregate length of cluster porosity shall not exceed 1/2 in. (13 mm) in any continuous 12 in. (300 mm) length of weld.

Notes: 1. Any indication with a maximum dimension of 1/16 in. (1.6 mm) or less shall be classified as nonrelevant. 2. For evaluation purposes, the maximum dimension of a rounded indication shall be considered its size. 3. When doubt exists about the type of imperfection being disclosed by an indication, verification may be obtained by using other nondestructive testing methods.

©



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Table G4 – Summary of Ultrasonic Testing Acceptance Standards RELEVANT INDICATION TYPE Cracks

SYMBOL


C

None permitted of any size or location in weld.

Indications

Vertical height (through-wall) dimension shall not exceed one quarter of the wall thickness.


Multiple indications at the same circumferential location with a summed vertical height (through-wall) dimension exceeding one half the wall thickness.

Linear Surface cracks)

(other

than

LS

Aggregate length shall not exceed 1 in. (25 mm) in any continuous 12 in. (300 mm) length of weld or exceed 8% of the weld length.

Linear Buried cracks)

(other

than

LB

Aggregate length shall not exceed 2 in. (50 mm) in any continuous 12 in. (300 mm) length of weld or exceed 8% of the weld length.

Transverse (other than cracks)

T

Evaluate using the criteria for volumetric indications

Volumetric Cluster

VC

Maximum dimension shall not exceed 1/2 in. (13 mm).

Volumetric Individual

VI

Maximum dimension shall not exceed 1/8 in. (3 mm).

Volumetric Root (open to the ID surface)

VR

Maximum dimension shall not exceed 1/4 in. (6 mm) or the nominal wall thickness, whichever is less.

Accumulation of Indications (above level)

AR

Relevant evaluation

Total length shall not exceed 1/2 in. (13 mm) in any continuous 12 in. (300 mm) length. Aggregate length shall not exceed 2 in. (50 mm) in any 12 in. (300 mm) length of weld, or exceed 8% of the weld length.

Notes: 1. Linear surface indications are interpreted to be open to the ID and OD surface. 2. Linear buried indications are interpreted to be subsurface with in the weld and not ID or OD surface-connected. 3. When doubt exists about the type of imperfection being disclosed by an indication, verification may be obtained by using other nondestructive testing methods.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities G9.6.2.2 No guidance material required. G9.6.2.3 The acceptance standards for buried indications are generally less stringent than for surface breaking indications. Surface breaking imperfections are more prone to propagation than buried imperfections. G9.6.2.4 No guidance material required. G9.6.2.5 No guidance material required. G9.6.2.6 No guidance material required. G9.6.2.7 No guidance material required. G9.6.2.8 No guidance material required. G9.6.3 Pipe or Fitting Imperfections If ultrasonic testing discloses defects in pipe or fittings, they must be reported to the company. G9.7 VISUAL ACCEPTANCE STANDARDS FOR UNDERCUTTING Visual inspection involves examining materials, with or without magnification or remote examination devices such as mirrors or fiber optics.

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by the company, and an approved and qualified repair welding procedure is used. Provided that the original welding procedure was followed during production welding, the formation of cracks in general is usually indicative of a deficiency in the welding procedure for the particular materials being welded and the particular conditions under which the procedure is being used. When repairing a crack, the deficiencies of the procedure used to make the original weld should be rectified. This often involves the use of low-hydrogen electrodes and/or preheat and interpass temperatures that are higher than those used to make the original weld. G10.1.2 Defects Other Than Cracks The company must authorize repair of defects in the root and filler beads, but need not authorize repair of cover pass defects. Two conditions are noted that require the use of a qualified repair welding procedure for defects other than cracks: when the repair employs a welding process different from that of the original weld, and when a previously repaired area is repaired again. For other repairs, the original welding procedure is sufficient. G10.2 REPAIR PROCEDURE

G9.7.1 General Visual examination requirements for welder qualification welds are contained in 6.4. G9.7.2 Acceptance Standards As noted here and in G9.3.11, whenever mechanical measurements are made in conjunction with visual inspection, the acceptance standards based on mechanical measurements given in Table 4 supersede those in 9.3.11.

G10 Repair and Removal of Defects G10.1 AUTHORIZATION FOR REPAIR

Repair welds are often made under more challenging conditions than production welds. Factors that make repair welds more challenging to make include excavation geometries (produced by hand grinding), particularly for the root region of through-wall repairs, restraint provided by surrounding weld metal (higher levels of residual stress), and thermal severity (faster weld cooling rates) caused by surrounding weld metal. As a result, repair welds tend to be susceptible to hydrogen cracking. For repair welding procedures, consideration should be given to the use of lowhydrogen electrodes and/or increased preheat and interpass temperatures.

The only cracks that may be acceptable after further evaluation and repair are shallow star or crater cracks that do not exceed 5/32 in. (4 mm).

A qualified repair procedure must include the minimum requirements listed in 10.2.1 through 10.2.6. Destructive testing is necessary to demonstrate that the procedure is adequate. The extent of testing is left to the discretion of the company.

Cracks other than shallow star or crater cracks may be repaired if the total length of the crack is less than 8% of the weld length, the repair is authorized

For procedures that will only be used for repair welding, it is common for segments of weld repairs to be made on a full circumference weld and to

G10.1.1 Cracks


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities extract and test specimens from the repaired locations. At the discretion of the company, procedures can be developed for backwelding (see guidance provided in G5.3.2.5 and G5.4.2.3), partial-wall repairs, through-wall repairs, and multiple repairs. A qualified welding procedure consists of a welding procedure specification (WPS) and a procedure qualification record (PQR). API 1104 also refers to the latter as a coupon test report. A PQR ‘supports’ a WPS. A WPS can be supported by more than one PQR. It is common, but not mandatory to list the PQRs that support a particular WPS. G10.2.1 Examples of methods of exploration include carbon arc gouging, grinding, etc. G10.2.2 Examples of methods for defect removal include carbon arc gouging, grinding, etc. G10.2.3 Examples of methods to confirm complete removal of the defect include visual inspection and nondestructive examination (e.g., magnetic particle testing). If liquid penetrant testing is used, all residue should be removed prior to repair welding. G10.2.4 The use of sufficiently-high preheat and interpass temperatures is particularly important considering that repair welds tend to be more highly restrained than the original weld. G10.2.5 See guidance provided in G5.3.2. G10.2.6 Examples of interpass nondestructive testing methods include visual inspection and nondestructive examination (e.g., magnetic particle testing). If liquid penetrant testing is used, all residue should be removed prior to resuming welding. G10.3 ACCEPTANCE CRITERIA G10.3.1 Once a weld is repaired, it must be inspected in the same manner as the original weld and meet the acceptance criteria contained in Section 9. At the discretion of the company, only the repaired area can be inspected or the entire weld can be re-inspected. It is common for mechanized welds originally inspected using automated ultrasonic testing (AUT) and evaluated using alternative acceptance criteria developed using Appendix A to be repaired and inspected using RT and evaluated using the workmanship-based acceptance criteria in Section 9.

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G10.4 SUPERVISION G10.4.1 No guidance material required. G10.5 WELDER G10.5.1 No guidance material required.

G11 Procedures for Nondestructive Testing Just as welding requires the use of a written procedure, so does nondestructive testing. G11.1 RADIOGRAPHIC TEST METHODS Radiographic testing (RT) is based on the distinction between transmission and absorption of xray and gamma radiation, producing images captured on film or other imaging media. Areas where material is thinner or less dense will transmit more radiation to the film, producing darker images; areas where material is thicker or denser will transmit less radiation to the film, producing lighter images. Imperfections cause patterns of lightness or darkness, which RT inspectors are trained to interpret and evaluate. Radiographic films produce negative images. Material that is thinner or less dense will produce a darker image. A dark image on a radiograph is described as being more dense than a light image. Conversely, material that is thicker or more dense will produce a lighter image. A light image on a radiograph is described as being less dense than a dark image. When considering density, be aware of the difference between density of the radiographic image and density of the material. Detectability of imperfections is significantly affected by the shape and orientation of the imperfection when subjected to RT. Volumetric imperfections, such as porosity and slag inclusions, may be easily detected by radiography while some planar (i.e., crack-like) imperfections may be more difficult to detect if not oriented parallel to the path of the penetrating radiation. For example, a crack oriented in the through-wall direction may be detected much more easily than a mid-wall lamination of similar size. The subsections listed under 11.1 describe how to produce radiographic images using low-energy nonparticulate radiation (x-rays or gamma radiation).


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities API 1104 Standard does not specify the conditions under which x-ray or gamma radiography should be used. The resulting images are what determine the acceptability of the method chosen. Single-wall exposure for single-wall viewing (SWE/SWV) is the preferred method over doublewall exposure for single-wall viewing (DWE/SWV) or double-wall exposure for double-wall viewing (DWE/DWV) when the inside of the pipe is accessible. The x-ray technique offers better radiographic sensitivity (sharper image and higher contrast for better detection of planar imperfections) compared to the gamma radiation technique. Also, finer grain Class I radiographic film offers better resolution than higher-speed, coarser-grain Class II film. G11.1.1 General The subsections listed under 11.1 describe how to produce radiographic images using either x-rays or gamma rays. API 1104 does not specify the conditions under which x-ray or gamma radiography should be used. The resulting image quality is what determines the acceptability of the method chosen. The phrase “prior to the performance of production radiography” has no specific time limit. It is only necessary that the radiographic procedure or procedures to be used be established and qualified sometime prior to the start of production radiography. G11.1.2 Details of Procedure G11.1.2.1 General Only the details that are applicable to the method that will be used (i.e., film radiography or radiography using other imaging media) need to be recorded. G11.1.2.2 Film Radiography All of the applicable details described in 11.1.2.2 for film radiography must be recorded in the radiographic procedure. G11.1.2.3 Other Imaging Media All of the applicable details described in 11.1.2.3 for radiography using other imaging media must be recorded in the radiographic procedure.

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G11.1.3 Exposure Geometry Exposure geometry is the relationship between the radiation source, the weld being inspected, and the film (or other imaging media). G11.1.3.1 Film Radiography No guidance material required. G11.1.3.2 Other Imaging Media No guidance material required. G11.1.4 Type of Image Quality Indicators (IQI) An image quality indicator (IQI) is a device used to measure the quality of radiographic images. It is placed on the weld prior to radiography and various attributes must be visible when viewing the resulting film. IQIs were previously referred to as penetrameters in API 1104. The company has the option to choose between either ASTM or ISO type IQIs. The use of hole-type penetrameters is no longer allowed. G11.1.5 Selection of Image Quality Indicators (IQI) IQIs are chosen for a particular application based on the thickness of the weld, plus any weld reinforcement (internal plus external combined). Knowing the weld thickness and the required IQI type, the inspector can use Tables 5 and 6 to determine the essential wire diameter for the application. The essential wire diameter indicates which of the wires on the IQI must appear clearly across the entire area of interest. The essential wire cannot be obscured by lead letters or numbers, artifacts, water stains, etc. G11.1.6 Placement of Image Quality Indicators (IQI) Three different IQI placement options exist. The first, and most common, is to place the IQI across the weld, spaced equally around the pipe on the source side or film side of the pipe. When placing the IQI across the weld is impractical due to weld reinforcement or profile, a separate block of similar material (also called a shim) is used to elevate the IQI to a height equal to the top of the weld reinforcement. The third location option, placing the IQI on a heat shield, is used primarily to radiograph hot materials.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities G11.1.6.1 Film No guidance material required. G11.1.6.2 Other Imaging Media

G11.1.10.1 Film Density No guidance material required. G11.1.10.2 Film Viewing Equipment

No guidance material required.


G11.1.7 Production Radiography

G11.1.10.3 Film Viewing Facilities

Technicians interpreting radiographic images must be certified to Level II or Level III according to the requirements of the ASNT Recommended Practice SNT-TC-1A or equivalent. Unless the company requests reporting of all imperfections, the inspector must report only imperfections that are rejectable (i.e., that are determined to be defects) according to 9.6. G11.1.8 Identification of Images Lead letters or numbers must be placed on the weld being inspected to identify the image. This is particularly important when a single weld is represented by multiple radiographs because the identification markers will distinguish between the end of one radiograph and the start of the next. G11.1.9 Storage of Film and Other Imaging Media G11.1.9.1 Film Improper storage can damage unexposed film. The requirements for film storage and the recognizable characteristics of film damaged due to improper storage are provided in this section.

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No guidance material required. G11.1.11 Image Processing The company may request that the film be readily viewable for at least three years. Radiographic film can be photographed if images are to be maintained for very long times, however, the images should include a scale for size reference and, if possible, include the radiographic image of the IQI. Radiographic film can also be digitized and the electronic files can be maintained indefinitely. G11.1.12 Image Processing Area All of the RT equipment and the area where image processing occurs must be kept clean. G11.1.13 Radiation Protection The radiographer is responsible for all aspects of radiation safety. Because the gamma ray and x-ray radiation used in RT is nonparticulate electromagnetic radiation unaffected by gravity, effective shielding requires distance, lead, or a significant thickness of concrete or steel. RT work areas must be properly posted and cleared of all nonessential personnel.

G11.1.9.2 Other Imaging Media No guidance material required. G11.1.10 Film Density The light area representing the image of a weld on a film must provide enough contrast from the dark area representing the image of the base metal. The requirements for determining that adequate density exists to ensure proper viewing of the film’s image are provided in the subsections listed under 11.1.10. The best way to view radiographic film is with equipment that transmits light through the film to help the inspector see the image of the weld being inspected. The characteristics of suitable film viewing facilities are also described.

G11.2 MAGNETIC PARTICLE TEST METHOD Magnetic particle testing (MT) employs magnetizing current and iron powder to locate imperfections in ferromagnetic materials. When a magnetic field encounters an obstruction, such as an imperfection or defect, the magnetic field ‘leaks’ into the atmosphere. This leakage attracts the particles of iron powder. Sound materials that do not contain imperfections or defects and do not leak magnetic current do not attract iron powder. MT only detects imperfections that are at or very close to the surface being inspected. DC current may be capable of finding subsurface imperfections close to the surface, while AC current typically finds only surface imperfections. Various forms of MT have been developed to improve detectability of imperfections.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities Generally, the more sensitive methods use magnetic particles suspended in a carrier liquid which improves the mobility of the particles and allows them to be more easily attracted to small imperfections. Examples include wet fluorescent MT and the use of colored (usually black) particles in a liquid suspension applied to a surface that is first sprayed with a thin layer of white contrast paint. In MT, the inspector identifies locations where particles accumulate. Depending on their nature and size, the imperfections may cause the item to be rejected or explored further. A procedure for MT must be written, qualified by demonstration, and accepted by the company prior to use. The MT procedure must comply with ASTM E 709, Standard Guide for Magnetic Particle Examination, published by the American Society for Testing and Materials. ASTM E 709 is a tutorial that supports ASTM E 1444, Standard Practice for Magnetic Particle Testing. Although API 1104 does not mention the latter document, both are necessary for comprehensive guidance on the methods and quality control requirements for MT. G11.3 LIQUID PENETRANT TEST METHOD Liquid penetrant testing (PT) relies on the ability of certain types of liquids to enter into surface voids and crevices by capillary action, and remain there when the surface liquid is removed. Then a contrast medium (developer) reveals the penetrant remaining in the voids and crevices. The contrast medium may be a powder in liquid suspension or ultraviolet light. When using PT, the inspector should be careful to distinguish between relevant indication due to defects and irrelevant indications due to characteristics of the weld. Anomalous or uncertain results can be obtained if excess penetrant is not thoroughly cleaned from the surface prior to the application of the developer. However, excessive cleaning can inadvertently remove penetrant from the actual imperfections, thus preventing detection. Failure to appropriately clean the surface to be inspected before the application of the penetrant can also interfere with the ability to subsequently remove excessive penetrant before the developer is applied. However, power wire brushing and some other mechanical methods of cleaning can smear metal over the surface opening of small imperfections and interfere with penetrant absorption.

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A procedure for PT must be written, qualified by demonstration, and accepted by the company prior to use. The PT procedure must comply with ASTM E 165, Standard Test Method for Liquid Penetrant Examination, published by the American Society for Testing and Materials. ASTM E 165 is a tutorial that supports ASTM E 1417, Standard Practice for Liquid Penetrant Testing. Although API 1104 does not mention the latter document, both are necessary for comprehensive guidance on the methods and quality control requirements for PT. G11.4 ULTRASONIC TEST METHODS Ultrasonic testing (UT) involves the propagation of sound waves through materials, and capture of the reflected echo from density changes in the material being inspected. These changes appear on a display screen as peaks and valleys. The inspector compares them to a reference standard to determine acceptability. G11.4.1 General This section applies to both new and in-service circumferential butt welds (groove welds in a butt joint). A detailed procedure must be developed, qualified by demonstration, and agreed upon by the contractor and company. The pipe being inspected with UT must be uncoated and the inspector should be aware of surface conditions that can interfere with scanning. API 1104 does not specify the required inspection techniques to be used within automated ultrasonic testing (AUT) systems such as pulse-echo or time-of-flight diffraction (TOFD). Required mapping techniques or techniques for coupling control are not specified either. The choice of these is left to the discretion of the user. G11.4.2 Details of Procedure The required details of a written procedure for UT of welds are provided in the subsections listed under 11.4.2. G11.4.2.1 General The procedures furnished to the company should include all of the variables for UT and should include


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities sketches for such things as joint design, scanning patterns, and inspection results. G11.4.2.2 Ultrasonic Procedure All of the applicable details described in 11.4.2.2 for UT must be recorded in the UT procedure. Specific guidance for each item listed, as appropriate, is provided below. a. Types of welds include fillet, groove, etc. Types of joints include butt, lap, and tee. b. Base materials should be listed according to the requirements of Section 4. Materials should be identified by their ASTM or API specification number. c. During UT, the transducer must slide freely across the base material, so the surfaces of materials subject to UT must be free from such things as spatter or weld reinforcement. d. Welding and fabrication involves many steps where UT may be required. The procedure should clearly define the stage of the welding or fabricating operation at which examination is to be performed. e. The manufacturer of the UT equipment should be identified and the specifications for all instruments and accessories should be listed. Transducers for various types of materials and for different angles at which sound can be projected through the material are available from a variety of UT equipment manufactures. f. An indication of whether the UT process is to be applied manually (where the operator has full control of scanning) or automatically (where the operator applies no manual scanning techniques) must be specified. g. The manufacturer and product number of the couplant, the gel-like substance that lubricates the surface of the material to be scanned and provides an airtight bond between the transducer and the surface, should be specified. h. In the manual mode of UT, a weld may be scanned in many ways. The specific characteristics of the scanning process necessary to ensure scanning of the entire surface so the returning echo can be evaluated should be described. These characteristics include angle and frequency of sound waves, the temperature of the material, scanning patterns, the speed at which the weld is scanned, and reference points or markings identifying the geometric characteristics of the joint. i. Reference standards of similar material and geometry should be used to qualify techniques and calibrate the UT process. Sketches and crosssectional views of these standard blocks must be provided.

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j. Calibration of UT equipment is essential to verify that the UT equipment and procedures are working properly and to provide standard points of reference to compare echoes from actual inspections to those performed on reference standards during calibration. The UT procedure must specify when to calibrate, what calibration reference standards to use, sensitivity-level requirements to achieve, and the required steps involved with calibration. k. The amount of sensitivity (sound is measured in decibels) above what was used on the reference standard must be recorded. l. Acceptable and rejectable height levels for a return echo peak must be established and recorded. Sound waves projected into a weld will bounce back to their source from different portions of the weld at different times, and these return echoes depict geometric differences in the weld. The return echoes appear on the equipment screen as peaks, which will vary in screen height depending on their strength, differences within portions of a weld, and the sensitivity settings of the instrument. m. The method of recording the inspection results must be identified. n. A sample inspection reporting form must be provided. G11.4.3 Ultrasonic Testing Personnel Requirements Only Level III UT inspectors are qualified to develop application techniques and procedures, which must include qualification by demonstration. G11.4.4 Demonstration of the Testing Procedure Prior to a UT procedure being used, it must be demonstrated and accepted by the company. The demonstration involves creation of reference welds similar to production welds, using an approved welding procedure. These reference welds, specifically designed with defects and geometrical differences, such as joint configuration and repaired areas, are then used to demonstrate that the UT procedure will effectively find the conditions deliberately created in the reference weld, as detected using radiographic testing (RT). Destructive testing can be required by the company to resolve differences in detection results between UT and RT of demonstration welds. Where discrepancies exist between detection results from UT and RT, destructive testing results should govern.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities If destructive testing of the reference weld indicates that a particular imperfection (e.g., lack of fusion) is detectable by UT and not by RT, then it would seem reasonable to for the company to strongly prefer the use of UT over RT for the inspection of production welds. The principals of probability of detection (POD) can be used to determine the most appropriate nondestructive testing method for the welding process being used. Since vertical height (through-wall dimension) of an indication is part of the acceptance criteria listed in 9.6.2.1, consideration should be given to including indication height sizing in the list of required capabilities. G11.4.5 API Sensitivity Reference Standard The sensitivity reference standards for use in measuring the screen height of return echoes from known geometric conditions (the notches in the calibration block) must be made of materials similar to those in production applications. The peaks on the instrument screen that return echoes from these notches must be 80% of the screen height. For new construction applications, it is not mandatory to dynamically scan the reference standard containing the required calibration reflectors. Consideration should be given to dynamically scanning the calibration standard, which will eliminate the need for transfer and attenuation measurements. Flat bottom holes may also be used for calibration purpose in addition to the N10 notches at the ID and OD surface. No clear requirements are given regarding size of these flat bottom holes except that the diameter should be approximately equal to the thickness of one welding fill pass. While Figure 21A implies that notch depths of 10% of the actual WT can be used, the depth of N10 notches is generally limited to 1.0 mm (0.039 in.) in practice.

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of 1.25 times the longest surface skip distance can be difficult to achieve. In the case of interfering reflectors, no acceptance criteria are specified. G11.4.7 Scanning and Evaluation Level The subsections listed under 11.4.2 identify the scanning techniques and screen height requirements for manual compression wave testing of the parent material, and for manual and automated testing of welds. Inspection of the parent material and inspection of the weld must be performed and documented independently. G11.4.7.1 Parent Material Ultrasonic Testing No guidance material required. G11.4.7.2 Manual Ultrasonic Weld Testing No guidance material required. G11.4.7.3 Automated Ultrasonic Weld Testing Scanning and evaluation level requirements are the subject of some debate. In practice, it is not clear when and why the plus 4dB sensitivity needs to be applied in relation to the evaluation level screen height. As indicated in 3.2.18, “shall” is a term that indicates a mandatory requirement. The term “should” indicates a recommended practice. Since the calibration block must be made of materials similar to those in production applications, the measurement of attenuation and transfer would seem to be redundant. The use of techniques other than pulse-echo may be used if demonstrated to be adequate. G11.4.8 Production Ultrasonic Testing Unless the company requests reporting of all imperfections, the inspector must report only imperfections that are rejectable (i.e., that are determined to be defects) according to 9.6.

G11.4.6 Parent Material Ultrasonic Testing Before UT of a completed weld, the UT inspector must conduct a compression wave test on the parent metal adjacent to the weld to locate any reflectors in the parent material that may interfere with the weld metal inspection.

G11.4.9 Identification of Reported Indications No guidance material required.

For new construction applications, the requirement to scan the parent material with coverage



G12 Mechanized Welding with Filler Metal Additions Mechanized welding is a method of application where welding process parameters and torch guidance are controlled mechanically or electronically but may be manually varied during welding to maintain the specified welding conditions. This section combines the requirements for procedure qualification, equipment and operator qualification, inspection of production welds, acceptance standards, and repair for mechanized welding into a single section. For some of these topics, reference is also made to other sections of API 1104. G12.1 ACCEPTABLE PROCESSES Section 12 applies to the processes listed in 12.1 only if they are performed in a mechanized mode. Section 5 applies to these processes they are performed in a manual or semiautomatic mode. Some mechanized welding system employ a manual or semi-automatic root pass (or possibly a root and hot pass). For these systems, it would seem that Section 12 is more applicable than Section 5. G12.2 PROCEDURE QUALIFICATION The phrase “before production welding is started” has no specific time limit. It is only necessary that the welding procedure specification (WPS) to be used for production welding be established and qualified sometime prior to the start of production welding. Procedure qualification requirements in Section 12 for mechanized welding are similar to those in Section 5 for manual or semiautomatic welding. Section 12 requires both destructive and nondestructive testing whereas Section 5 requires only destructive testing. Section 12 refers to Section 5 for destructive testing requirements, except that nick-break testing is not required, and to Section 9 for nondestructive testing requirements. A WPS need not be established and qualified by the company itself. However, it is common practice for the company to approve each qualified WPS that will be used for production welding.

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G12.3 RECORD A qualified welding procedure consists of a WPS and a procedure qualification record (PQR). API 1104 also refers to the latter as a coupon test report. A PQR ‘supports’ a WPS. A WPS can be supported by more than one PQR. It is common, but not mandatory to list the PQRs that support a particular WPS. Figure 1 in API 1104 is a sample WPS. Figure 2 is a sample PQR, which can also be used as a welder qualification test record (WQTR). The use of Figures 1 and 2 is not mandatory, although forms similar to these should be used. It is common, but not mandatory, for both to include a space for a revision number, which may be required eventually. A welder who performs a test joint that qualifies a WPS becomes qualified to perform that procedure provided that all of the testing required for a welder qualification is performed and passed. Other welders then may qualify to perform the same welding procedure. See additional guidance provided in Section 5.2. G12.4 PROCEDURE SPECIFICATION G12.4.1 General Only the welding variables that are applicable to the welding process and welding method to be used need to be documented. All of the applicable welding variables described in 12.4.2 must be included in the WPS. Many of these variables are limited by the essential variable changes given in 12.5. Changes to welding variables that are not listed in 12.5 are allowed by simply revising the WPS without the need for requalification, although sound engineering judgment should be used. A revised WPS should be identified by a revision number. G12.4.2 Specification Information G12.4.2.1 Process Eight possible welding processes are listed in 1.1. The welding processes that are generally applicable to mechanized welding are shown in Table G1 in the guidance provided in G1.1 and include SAW, GTAW, GMAW, FCAW, and PAW. Examples of the ‘type of welding technology’ that may be utilized include GMAW with pulsed Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities current (GMAW-P) or advanced waveform power supplies (e.g., Lincoln Invertec STT II with STT Waveform Control and CSC MIG Weld Process Controller from Miller Electric’s Jetline division). A description of the equipment to be utilized could include the manufacturer and model number of the internal welder and external welding bugs, and the version number of the software control program. G12.4.2.2 Pipe and Fitting Materials It is common, but not mandatory, to specify the industry standard or specification to which the base material was manufactured, as well as the grade of the base material. The latter establishes the basis for the tensile strength requirements in 5.6.2.3 and the basis for selecting the welding consumables to be used. It is not clear what constitutes an “acceptable ASTM specification.” This presumably refers to ASTM specifications that are acceptable to the company. Base materials and base material groupings are addressed in 5.4.2.2. To qualify a WPS for an entire group, the test joint must be made using the material with the highest specified minimum yield strength (SMYS) in the group. For production welding that involves joining base materials from two different strength groups, a WPS for the higher strength material must be employed. For material with a SMYS higher than 56,000 psi (386 MPa), it is good practice but not mandatory to document the carbon equivalent for all base materials used in the procedure qualification. G12.4.2.3 Diameters Unlike Section 5, no suggested groupings for outside diameter are provided. The range of outside diameters over which the procedure is applicable is left to the user to define. Guidance can be found in a variety of other codes and standards. G12.4.2.4 Wall Thickness Group and Number and Sequence of Beads Unlike Section 5, no suggested groupings for wall thickness are provided. The range of wall thicknesses over which the procedure is applicable is left to the user to define. Guidance can be found in a variety of other codes and standards.

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If the welding procedure covers a range of wall thicknesses, it is appropriate to include a range for the number of beads required for each wall thickness. The WPS is not required to contain a sketch of the sequence of beads. However, the sequence of beads must somehow be designated. It is good practice but not mandatory to specify the welding technique that should be used – e.g., stringer beads, weave beads, or a combination of both. If the welding procedure covers a range of wall thicknesses and a combination of techniques, the weld width (or wall thickness) at which the transition from one technique to another should occur should also be specified. G12.4.2.5 Joint Design In addition to specifying the required bevel angle, it is common practice, but not mandatory, for the bevel angle tolerances to be specified. The required root opening may be expressed as an approximate value or a specific value with applicable tolerances. In addition to specifying the required size of the root face, it is common practice, but not mandatory, for the root face tolerances to be specified. Backup can be either consumable (e.g., consumable inserts) or non-consumable (e.g., copper backing shoes). G12.4.2.6 Filler Metal The filler metal to be used should be identified by size and its AWS (or other) specification and classification numbers. While not required, the trade name of the filler metal can also be listed for information purposes, if desired. However, it is insufficient to list trade name only. Filler metals with lower classified strength levels than the line pipe (e.g. ER70S-6 electrode on X80 line pipe) are commonly used with mechanized vertical-down GMAW. The welding parameters for a mechanized vertical-down narrow-groove GMAW pipeline girth weld are significantly different than those used for the AWS filler metal classification test plate weld. Using the same filler metal, higher strengths are typically observed on the mechanized low heat input vertical-down welds.



G12.4.2.7 Electrical Characteristics Current can be either alternating current (AC) or direct current (DC). For DC, polarity can be either electrode negative (straight polarity) or electrode positive (reverse polarity). If pulsed current is to be used, it is good practice to indicate this and to specify pulse parameters, etc.

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obtained (welding power source display, brand and type of meter used, etc.). G12.4.2.8 Position A definition for “roll welding” is provided in 3.2.15. Roll welding refers to rolling the pipe while the weld metal is being deposited.

An amperage and voltage range for each filler metal type and size must be specified. The specified range should reflect the minimum and maximum values that produce an acceptable weld (or a weld with desired toughness properties, if required). The limits of the range should be based on sound engineering judgment. Ranges for amperage and voltage specified by the electrode manufacturer can be used for guidance.

There is no requirement in API 1104 to designate the position of the pipe material (e.g., horizontal, vertical, or some position in between). API 1104 has traditionally been used for construction of cross country pipelines, which involves girth welding with the pipe in the horizontal position. If welding is to be performed with the pipe in a position other than horizontal, it would seem to be prudent to indicate that here.

The ranges specified should be wide enough so that the qualified welding procedure can be implemented in the field. The ranges should not be so wide that operating at the edges of the ranges produces an unacceptable weld. For example, the allowable range for amperage and voltage should be no larger than the median value +/- 20%.

G12.4.2.9 Direction of Welding

In addition to ranges for amperage, voltage, and travel speed, it is good practice, but not mandatory, to specify a heat input range for each welding pass. Heat input takes into account the collective effect of amperage, voltage, and travel speed on the thermal cycle of the weld. The specified range should reflect the minimum and maximum heat input values that produce an acceptable weld, not the calculated minimum and maximum values from the amperage, voltage, and travel speed range.

The primary intent of this requirement is to prevent the weld from experiencing hydrogen cracking prior to completion. Specifying a maximum-allowable time between passes does this by a) preventing the weld from cooling excessively between passes and b) providing less time for cracking to occur. The time between the completion of the root bead and the start of the second bead is most critical since the weld has less cross-sectional area at this stage.

Actual values for amperage and voltage used during the procedure qualification test need not be recorded in the WPS; only the ranges need to be specified. The actual values used during the procedure qualification test should be recorded in the PQR.

When determining what value to specify on a WPS for time between passes, the time-dependant nature of hydrogen cracking should be considered, as well as the probability of the weld to cracking. Shorter times decrease the chance that cracking can occur prior to the completion of the weld. Longer times can be justified when the probably of cracking is low (e.g., higher preheat/interpass temperatures, low-hydrogen welding process, etc.).

When using welding power sources generating waveform output (e.g. GMAW-P), the voltage and amperage measurements may vary significantly depending on the type and brand of meter used, meter settings, and sampling rate. Commercially available meters are generally not designed to measure fluctuating high-amperage welding outputs and the welding equipment meters are commonly used instead. When using waveform welding processes, in addition to the volts and amps, it is good practice to record where these values were

If welding is to be performed with the pipe in the vertical position, the direction of welding is horizontal. G12.4.2.10 Time between Passes

G12.4.2.11 Type of Lineup Clamp Information pertaining to the type and removal of a lineup clamp generally pertains to production welding. For mechanized welding however, it is common for the lineup clamp that will be used for production welding to be used during the procedure qualification test, also. Revision 1 – April 30, 2010


Requirements/recommendations for root bead completion prior to lineup clamp removal are given in 7.3. The information specified in the WPS should comply with the requirements/recommendations given in 7.3. See guidance in G7.3. G12.4.2.12 Cleaning The extent of cleaning required for the weld bevel prior to welding and between each weld pass must be described. G12.4.2.13 Pre-heat Treatment Preheat is the minimum specified temperature of the entire weld zone immediately prior to the start of welding. In a multipass weld, it is also the temperature immediately before the second and subsequent passes. This section requires the user to specify the width of the weld zone. It may be useful to think of preheat temperature as the “arc start temperature,” or the temperature of the weld zone during welding of any weld bead (i.e., not just the first weld bead). The primary reason for preheating is to prevent the weld from experiencing hydrogen cracking during welding or soon after completion. Preheating does this by driving off moisture and other contaminants prior to welding, slowing the weld cooling rate somewhat, which has a beneficial effect on the weld microstructures that develop, and allowing hydrogen to diffuse from the weld during welding and after completion. Common methods used to preheat pipelines prior to welding include gas torches and quartz lamps (radiation methods), electric resistance heaters (conduction methods), and induction heaters (induction methods). A minimum-required preheating temperature is normally specified. Once welding begins, this temperature is generally referred to as the interpass temperature. For some applications, it is also common to specify a maximum-allowable interpass temperature. For some applications, preheating is specified only when the ambient or pipe surface temperature is below a certain value. Additional information pertaining to the application of pre- and post-heating is provided in the guidance provided in G7.11.

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Common methods for temperature measurement include contact thermometers (digital or analog), non-contact infrared pyrometers, and temperature indicating crayons (e.g., Tempilsticks™). If used to expedite nondestructive testing (NDT) and/or joint coatings, the type of weld cooling after welding, such as air cooling or accelerated cooling with water, should be specified. The maximum metal temperature at which accelerated cooling is applied should also be specified. G12.4.2.14 Post-heat Treatment Post-heating and slow cooling can have a beneficial effect on welds by allowing hydrogen diffusion after welding. If carried out at high enough temperatures, post-weld heat treatment (PWHT) can also temper hard weld microstructures and relieve residual welding stresses. Modern microalloyed and control-rolled line pipe steels can be very sensitive to temperature above approximately 400ºF (200ºC). The benefits of PWHT must be weighed against the loss of desirable materials attributes when PWHT is applied. Common methods used for post-weld heat treatment of pipeline girth welds include electric resistance heaters, induction heaters, and quartz lamps. PWHT parameters for stress relief often include the width of the area to be heated, a temperature to which the joint can be heated without controlling the heating rate, a maximum-allowable heating rate from this temperature to the PWHT temperature range, the hold time at PWHT temperature range (usually expressed in hours per unit of wall thickness), and the maximum-allowable cooling rate from this temperature. This section also requires the user to specify the width of the zone to be heated. Temperature measurement and control during post-weld heat treatment is normally accomplished using welded thermocouples and dedicated control units. G12.4.2.15 Shielding Gas and Flow Rate AWS A5.32/A5.32M Specification for Welding Shielding Gases provides standard AWS classifications for common shielding gases and gas mixtures that can be used in preparation of procedure specifications. AWS A5.32/A5.32M also provides purity requirements for the listed gases and mixtures.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities The specified range should reflect the minimum and maximum values that produce an acceptable weld. G12.4.2.16 Shielding Flux Shielding flux type refers to submerged arc welding. The shielding flux should be identified by its AWS (or other) specification and classification numbers. The trade name or number of the shielding flux should also be listed. However, it is insufficient to list trade name only.

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testing another weld. These latter variables are referred to as essential variables. Procedures for mechanized welding are often qualified in accordance with this section but also in conjunction with Appendix A when alternative acceptance standards based on engineering critical assessment will be used. For these applications, the more stringent essential variable requirements in Appendix A supersede some of those listed in this section. G12.5.2 Changes Requiring Requalification

G12.4.2.17 Speed of Travel The travel speed range for each pass must be specified. The specified range should reflect the minimum and maximum values that produce an acceptable weld. Travel speed is measured in the direction of weld progression. Weave motion perpendicular to the direction of weld progression is not included in the travel speed measurement. The range specified should be wide enough so that the qualified welding procedure can be implemented in the field. The range should not be so wide that operating at the edges of the range produces an unacceptable weld. For example, the allowable range for travel speed should be no larger than the median value +/- 20%. G12.4.2.18 Other Factors The purpose of this section is to allow aspects of the specific process being used, which are not covered in the preceding sections, to be specified. Several examples are provided. If used to expedite NDE and joint coatings, the type of weld cooling after welding, such as air cooling or accelerated cooling with water, should be specified. The maximum metal temperature at which accelerated cooling is applied should also be specified. G12.5 ESSENTIAL VARIABLES G12.5.1 General API 1104 allows some degree of departure from the variables used to qualify a WPS. However, departures from variables that affect the mechanical properties or soundness of completed welds are not allowed without requalification by preparing and

Essential variables are those that require the procedure to be requalified, or a new procedure qualified, if the range specified in the WPS for any of those variables is exceeded. G12.5.2.1 Welding Process See guidance provided in G.4.2.1. G12.5.2.2 Pipe Material To qualify a welding procedure for an entire group, the procedure qualification must be carried out on the material with the highest specified minimum yield strength in the group. The strength level grouping listed in 12.5.2.2 should be based on nominal strength levels. The actual strength levels that are now specified in API Spec 5L (Forty-fourth Edition) as the result of normalization need not be considered (i.e., it is not necessary to consider that API 5L-X42 now has an actual specified minimum yield strength, expressed in US Customary units, of 42,100 psi). A procedure qualified using a combination of materials only qualifies the procedure for that combination of materials. Regarding the note provided in 12.5.2.2, sound engineering judgment should be used when determining the compatibility of the base materials. An example of a base material compatibility factor that might be considered within one of the groupings specified is carbon equivalent level. For a pipe material of a given grade, higher carbon equivalent materials generally have reduced weldability compared to lower carbon equivalent materials.



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G12.5.2.3 Joint Design API 1104 does not define what constitutes a minor change in joint design. For mechanized welding, it would seem reasonable to allow changes to the bevel angle of up to + 10%/-5% of the nominal value and changes to the root opening or land of up to +/- 20% of the nominal value without the need for requalification. G12.5.2.4 Wall Thickness See guidance provided in G12.4.2.4.

G12.5.2.10 Shielding Gas and Flow Rate A change from one shielding gas to another refers to nominal composition. API 1104 does not define what constitutes a major change in shielding gas flow rate. Even if a change in the shielding gas flow rate does not visually affect the weld (e.g., does not result in porosity), the weld properties (e.g., strength and toughness) may be adversely affected. It would seem reasonable to allow changes of up to +/- 20% of the nominal value without the need for requalification.

G12.5.2.5 Pipe Diameter See guidance provided in G12.4.2.3

G12.5.2.11 Shielding Flux No guidance material required.

G12.5.2.6 Filler Metal If a filler metal is not listed in one of the groups of Table 1 in API 1104, it requires separate qualification. See the note under Table 1. Regarding the note provided in 12.5.2.6, sound engineering judgment should be used when determining the compatibility of the filler metals within the groups specified in Table 1. G12.5.2.7 Size of Filler-metal Wire See guidance provided in G12.4.2.6. G12.5.2.8 Time between Passes The maximum time between the completion of the root bead and the start of the second bead is an essential variable for procedure qualification, whereas the maximum time between the completion of the second bead and the start of other beads is not.

G12.5.2.12 Speed of Travel See guidance provided in G12.4.2.17. G12.5.2.13 Pre- and Post-heat Treatment Requirements See guidance provided in G12.4.2.13 and G12.4.2.14. For preheating, a decrease in the specified minimum preheat temperature should constitute an essential variable. The addition of preheat or an increase in the specified minimum preheat temperature should not require the procedure to be requalified unless toughness properties, if specified, are thought to be affected. For PWHT, the addition of PWHT or a change from the ranges or values specified in the procedure should each constitute an essential variable.

Exceeding the maximum allowable time between the completion of the root bead and the start of the second bead during production welding is grounds for rejection of that weld. Consequently, one common practice during procedure qualification for mechanized GMAW is to delay welding of the hot pass for up to 48, or even 72 hours after completion of the root pass. This extended delay is to accommodate significant delays between passes during production welding that could be caused by equipment failure, etc.

G12.5.2.14 Electrical Characteristics

G12.5.2.9 Direction of Welding

The purpose of this section is to allow welding operators to demonstrate their ability to make acceptable welds using the qualified procedure and


See guidance provided in G12.4.2.7. G12.5.2.15 Orifice Diameter or Orifice Gas Composition No guidance material required. G12.6 QUALIFICATION OF WELDING EQUIPMENT AND OPERATORS


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities the equipment that will be used in production welding. Qualification requirements for welding operators in Section 12 are similar to those in Section 5 for welder qualification except that Section 12 does not require nick-break testing. In 6.5.2, substitution of nick-break tests for tensile strength tests is allowed. It is not appropriate to substitute nick-break tests for tensile strength tests and then to use the language in 12.6 to eliminate these nick-break tests. The substitution clause in 6.5.2 is intended only for manual and semi-automatic welding. For mechanized welding, the tensile strength tests should not be replaced by nick-break tests (as allowed in 6.5.2 for manual and semiautomatic welding) and thus omitted. This section allows for evaluation of the completed test weld by destructive methods, nondestructive methods, or both. It refers to Section 6.6 for evaluation by nondestructive methods. Section 6.6 specifically states that radiography can be used in lieu of destructive methods. While it would seem that the use of a qualified automated ultrasonic testing (AUT) system would not only be appropriate but preferred for evaluation of mechanized GMA welds, the use of AUT only would seem to be prohibited for the qualification of welding operator by this section. Since this section allows for evaluation of the completed test weld by destructive methods only, AUT could be used to supplement destructive testing at the option of the user. The phrase “Prior to the start of production welding” has no specific time limit. It is only necessary that the welding operators to be used for production welding be qualified sometime prior to the start of production welding. The essential variables for welding operators listed in 12.6.1 are different from the essential variables for procedure qualification in 12.5.2. G12.6.1 Scope While the title of this section is “Scope”, it contains a list of essential variables for welding operators, which require that the welding operator be requalified if changes beyond the limits listed are exceeded. Specific guidance for each item listed, as appropriate, is provided below. a. The essential variable is a change from one welding process to another process or combination of

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processes, a change in mode of transfer (e.g., short circuit transfer to spray transfer), or a change in polarity. b. See guidance provided in G12.4.2.9. c. A change from solid wire or metal cored wire to a flux cored wire is also a change of process. d. No guidance material required. e. Welding operator shall qualify on the heaviest nominal wall thickness of the ranges established in the applicable WPS. f. See guidance provided in G12.4.2.8. g. A welding bug is a mechanized device that provides movement of the welding torch around the pipe. h. No guidance material required. i. See guidance provided in G12.5.2.3. It would appear that the period after the word “established” is in error and that the word “For” should not be capitalized. j. This provision allows the company to qualify welding operators for specific weld passes without having that operator complete an entire weld. G12.7 RECORDS OF QUALIFIED OPERATORS The company must maintain records of test results for each welding operator. Figure 2 in API 1104 is a sample PQR, which can also be used as a WQTR. The use of Figure 2 is not mandatory, although a form similar to this should be used. It is common, but not mandatory, to include a space for a revision number, which may be required eventually. The company must also maintain a list of operators and the procedures for which they have qualified. G12.8 INSPECTION AND TESTING OF PRODUCTION WELDS See guidance provided in Section G8. The first sentence of 8.2 indicates that nondestructive testing may consist of radiographic testing (RT) or another method specified by the company. The preferred method of inspection for many mechanized welds is automated ultrasonic testing (AUT). Even though AUT is not mentioned in Section 8, this is not intended to preclude the use of AUT on mechanized pipeline girth welds. G12.9 ACCEPTANCE STANDARDS FOR NONDESTRUCTIVE TESTING See guidance provided in Section G9 or Appendix A, as appropriate.



G12.10 REPAIR AND REMOVAL OF DEFECTS See guidance provided in Section G10. G12.11 RADIOGRAPHIC TESTING For RT, see guidance provided in G11.1. UT is the preferred method for many mechanized welds and should be performed in accordance with 11.4 Even though UT is not mentioned in 12.11, this is not intended to preclude the use of UT on mechanized pipeline girth welds.

G13 Automatic Welding Without Filler- metal Additions G13.1 ACCEPTABLE PROCESSES This section applies only to the flash buttwelding process. This section combines the requirements for procedure qualification, equipment and operator qualification, quality assurance, acceptance standards, and repair for flash butt-welding into a single section. For some of these topics, reference is also made to other sections of API 1104. G13.2 PROCEDURE QUALIFICATION Procedure qualification requirements in Section 13 for flash butt-welding are similar to those in Section 5 for manual or semiautomatic welding and Section 12 for mechanized welding except that at least two test welds are required and destructive testing must be proceeded by radiographic testing (RT). The number of test specimens required for flash butt welding depends on the outside diameter of the pipe, with larger pipe diameters requiring more specimens. As in Section 5, nick-break testing is required, however the specimens for flash butt welding are wider and more specimens are required. G13.2.1 Procedure The phrase “before production welding is started” has no specific time limit. It is only necessary that the welding procedure specification (WPS) to be used for production welding be established and qualified sometime prior to the start of production welding.

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A WPS need not be established and qualified by the company itself. However, it is common practice for the company to approve each qualified WPS that will be used for production welding. G13.2.2 Radiography Prior to Mechanical Testing Mechanical testing must be preceded by RT. G13.2.3 Mechanical Testing of Butt-welded Joints G13.2.3.1 General No guidance material required. G13.2.3.2 Tensile-strength Tests G13.2.3.2.1 Preparation See guidance provided in G5.6.2.1. 13.2.3.2.2 Method See guidance provided in G5.6.2.1. G13.2.3.2.3 Requirements It is acceptable according to API 1104 for the measured tensile strength across the weld to be less than the actual tensile strength of the pipe material. However, some pipeline designs require matching or over-matching strength girth welds. Such requirements should be specified in the contract documents. If a tensile test specimen breaks in the weld, it is also evaluated as if it is a nick-break test specimen. G13.2.3.3 Nick-break Test G13.2.3.3.1 Preparation Figure 25 illustrates a nick-break test specimen for flash butt welding, which is wider than that described in Section 5, and includes instructions on how to prepare the nick. Macro-etching of nickbreak test specimen for flash butt welding is required to locate the fusion line. The nick-break test is a subjective test that judges the soundness of a weld by fracturing the specimen through the weld so the fracture surfaces can be examined for the presence of imperfections. The term “nick-break” refers to the saw-cut notch Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities that initiates fracture, making the specimen easier to break. While nicking the specimen with a hacksaw is preferred, it would seem to be appropriate to allow the specimen to be nicked with a narrow disk grinder as well. It is not appropriate to “nick” the specimens using an oxy-fuel torch.

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Many of these variables are limited by the essential variable changes given in 13.5. Changes to welding variables that are not listed in 13.5 are allowed by simply revising the WPS without the need for requalification, although sound engineering judgment should be used. A revised WPS should be identified by a revision number. G13.5 ESSENTIAL VARIABLES

G13.2.3.3.2 Method See guidance provided in G5.6.3.2. G13.2.3.3.3 Requirements No guidance material required. G13.2.3.4 Side-bend Test

G13.5.1 General API 1104 allows some degree of departure from the variables used to qualify a WPS. However, departures from variables that affect the mechanical properties or soundness of completed welds are not allowed without requalification by preparing and testing another weld. These latter variables are referred to as essential variables.

G13.2.3.4.1 Preparation See guidance provided in G5.6.5.1. G13.2.3.4.2 Method See guidance provided in G5.6.5.2. G13.2.3.4.3 Requirements See guidance provided in G5.6.5.3. G13.3 RECORD A qualified welding procedure consists of a WPS and a procedure qualification record (PQR). API 1104 also refers to the latter as a coupon test report. A PQR ‘supports’ a WPS. A WPS can be supported by more than one PQR. It is common, but not mandatory to list the PQRs that support a particular WPS. It is common, but not mandatory, for both to include a space for a revision number, which may be required eventually. A welder who performs a test joint that qualifies a WPS becomes qualified to perform that procedure provided that all of the testing required for a welder qualification is performed and passed. Other welders then may qualify to perform the same welding procedure. G13.4 PROCEDURE SPECIFICATION

G13.5.2 Changes Requiring Requalification Essential variables are those that require the procedure to be requalified, or a new procedure qualified, if the range specified in the WPS for any of those variables is exceeded. Since no range of acceptability is given in this section for the essential variables for flash butt welding, any change to these variables requires requalification of the procedure. G13.6 QUALIFICATION OF EQUIPMENT AND OPERATORS The purpose of this section is to allow welding operators to demonstrate their ability to make acceptable welds using the qualified procedure and the equipment that will be used in production welding. It calls for each welding unit (machine) and each operator to be qualified simultaneously through both radiography and destructive testing. This section does not specify any essential variables for qualification of welding operators. Since this section provides that both the equipment and the operator are qualified at the same time, the essential variables specified in Section 13.5 apply. While not specifically indicated, welding operators to be used for production welding should be qualified sometime prior to the start of production welding.

All of the applicable welding variables described in 13.4 must be included in the WPS.



G13.7 RECORDS OF QUALIFIED OPERATORS The company must maintain records of test results for each welding operator. Figure 2 in API 1104 is a sample PQR, which can also be used as a WQTR. The use of Figure 2 is not mandatory, although a form similar to this should be used. It is common, but not mandatory, to include a space for a revision number, which may be required eventually. The company must also maintain a list of operators and the procedures for which they have qualified. G13.8 QUALITY ASSURANCE OF PRODUCTION WELDS Quality assurance of production welds made using the flash butt-welding process is normally accomplished by removing and testing selected production welds, monitoring the welding sequence using a strip chart recorder, nondestructive testing, measurement of reinforcement height, and monitoring post-weld heat treatment using a strip chart recorder. G13.8.1 Rights of Inspection No guidance material required. G13.8.2 Rejection Based on Strip Chart No guidance material required. G13.8.3 Rejection Based on Nondestructive Testing No guidance material required.

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G13.8.5 Rejection Based on Post-heat Treatment No guidance material required. G13.9 ACCEPTANCE STANDARDS FOR NONDESTRUCTIVE TESTING For flash butt welds, acceptance criteria are provided only for isolated slag inclusions. Since no reference is made to acceptance criteria for other imperfections, these appear to be unacceptable regardless of their size. G13.9.1 General See guidance provided in G13.9.2. G13.9.2 Defects No guidance material required. G13.10 REPAIR AND REMOVAL OF DEFECTS G13.10.1 Repairs Permitted See guidance provided in Section G10. G13.10.2 Repairs Not Permitted Reference to 9.3.8.2 and 9.3.8.3, which contain acceptance criteria for slag inclusions detected by radiography, appears to be in error. Acceptance criteria for porosity, to which 13.10.2 pertains, are contained in 9.3.9.2 and 9.3.9.3. G13.11 RADIOGRAPHIC PROCEDURE

G13.8.4 Rejection Based On Reinforcement No guidance material required.

See guidance provided in G11.1.



APPENDIX A—ALTERNATIVE ACCEPTANCE STANDARDS FOR GIRTH WELDS5 GA.1 General Workmanship vs. Alternative Acceptance Criteria The basis of the workmanship acceptance criteria in Section 9 and the alternative acceptance criteria in Appendix A is quite different. The workmanship criteria were originally developed on the basis of achievable level of sound workmanship by skilled welders using properly maintained equipment and executing properly qualified welding procedures. Provided that the welding procedures are properly qualified, the workmanship criteria remain the same for all pipeline projects. The acceptance criteria are not altered by the weld properties and expected loads on the pipeline girth welds. In contrast the alternative acceptance criteria are based on the philosophy of fitness-for-service, i.e., the fitness of the particular welds for the intended purposes. Consequently the acceptance level in the alternative acceptance criteria is correlated to the weld properties and expected loads on the girth welds for a particular project of interest or a specific section of a pipeline. More rigorous testing is required to apply the alternative acceptance criteria. Although the allowable flaw length from the alternative acceptance criteria is frequently greater than that of the workmanship acceptance criteria for most onshore pipeline projects, this is not always the case. In certain offshore applications, the allowable flaw length from the alternative acceptance criteria may be smaller than that of the workmanship criteria. It is generally not possible to rigorously compare the relative conservatism between the workmanship and alternative acceptance criteria. The extent of material qualification tests is different for these two types of acceptance criteria. The level of field quality control may be different as well. Pipelines built to either acceptance criteria have shown excellent records of safety when these criteria are applied consistently. Minimum CTOD Toughness and its Significance In the previous versions of Appendix A, only the allowable flaw height was dependent on the 5 This guidance is specifically written for API 1104 Appendix A 20th Edition July 2007 Errata.

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measured crack tip opening displacement (CTOD) toughness. The allowable flaw length was a function of either pipe wall thickness or diameter. In the July 2007 Errata version of Appendix A, both flaw height and length are correlated to the measured CTOD toughness. This approach allows for more consistent levels of conservatism across the entire range of CTOD toughness. As the allowable flaw size is adjusted and correlated to measured CTOD toughness as a continuous function, the reduction in the minimum required CTOD toughness in this version of Appendix A does not imply a reduced conservatism in any way. It is important to recognize that the minimum required CTOD toughness in Appendix A is entirely different from the minimum toughness requirement a company may set in its material qualification. The minimum required CTOD in this appendix should not be used as a material qualification standard. The minimum required CTOD here only implies that the alternative defect acceptance criteria are suitable when this minimum value is achieved. Selection of Options For consistency the use of Option 1 or 2 is mandatory6 when the fatigue loading spectrum is within the limit defined in A.2.2.1 of Appendix A. More detailed background information on Options 1 and 2 may be found in a paper by Wang, et al.7 Selection of Appendix A vs. Workmanship A company has the option of selecting the workmanship acceptance criteria of Section 9 or the alternative acceptance criteria of Appendix A. When the use of Appendix A is selected, it is not advisable to switch to workmanship acceptance criteria when the welds are determined to not meet the standards of Appendix A. Examples of unexpected issues may include extremely low CTOD toughness and high fatigue flaw growth rates. These issues may indicate inadequate design or inappropriate selection of line pipe material and welding processes. The 6

The use of API 1104 Appendix A is at the option of the Company. The term “mandatory” here is applicable when the use of API 1104 Appendix A is selected. 7 Wang, Y.-Y., Liu, M., Horsley, D., and Bauman, G., “A Tiered Approach to Girth Weld Defect Acceptance Criteria for StressBased Design of Pipelines,” 6th International Pipeline Conference, Paper No. IPC2006-10491, September 25-29, 2006, Calgary, Alberta, Canada.


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities underlining causes for such issues should be investigated and rectified.

GA.2 Stress Analysis

Necessary Conditions for Using Appendix A

GA.2.1 AXIAL DESIGN STRESS

All of the prerequisite conditions outlined in the list at the end of Section A.1 must be met to apply Appendix A. The statistical distribution of material properties, such as the difference between the actual yield strength and the specified minimum yield strength (SMYS), can not be used to justify going beyond the limits set in Appendix A. Weld Quality Considerations in Implementing the Flaw Acceptance Criteria Depending on the CTOD toughness and the longitudinal stress/strain, the allowable flaw size produced by Appendix A may be quite large. Overly generous allowable flaw size may not be necessary. The flaw acceptance criteria should not be viewed as a substitute for sound welding quality control. At the option of the company, the allowable flaw size could be reduced so sound welding quality control is exercised. For heavy wall pipes, the maximum allowable flaw height of nearly 50% wall thickness could be quite large. In most instances of well-controlled weld processes, the allowable flaw height needs not be more than 2 to 3 times the weld bead height, except in cases of short flaw length under limited circumstances. Appendix A currently covers flaw acceptance criteria of individual flaws. Interacting flaws that are re-categorized as a single flaw are effectively treated as a single flaw. Appendix A does not presently cover flaw accumulation rules. These rules would have governed the total number or accumulative length of all flaws in a single girth weld. Sound engineering practice dictates that having appropriate flaw accumulation rules is a good engineering practice. It is advisable to establish the total number and the accumulative length of all non-interacting flaws in a single girth weld. Excessive number of repairs in any single girth weld may be indicative of welding quality control issues. Since repair welds generally have inferior quality than mechanized welds, it is advisable to limit the total number of repairs in any single girth weld.

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Purpose of the Stress Analysis The stress analysis serves two purposes: (1) determining the fatigue spectrum severity, hence appropriate analysis options that may be used for developing defect acceptance criteria, and (2) providing the maximum magnitude of longitudinal stress as an input for the determination of the allowable flaw size. Stresses on Pipeline Girth Welds The stresses affecting the integrity of pipeline girth welds may be broadly divided into static and cyclic (alternating) stresses. The cyclic stresses are usually induced by the temperature and pressure fluctuations of the pipelines. The static stresses may come from construction and service conditions, e.g., unsupported span for offshore pipelines. For onshore pipelines, the highest static stresses generally occur during construction. However, high static stresses may also occur in service when large displacement is imposed on the pipelines, such as in the case of washout or ground movement. Estimation of Static Stresses Under normal onshore construction conditions, the longitudinal stresses are predominantly controlled by the lift height of the pipe relative to the bottom of the trench. For offshore pipelines high static stress may occur in pipelay operation from pipelay tension and bending along the firing line and stinger. The stresses from horizontal directional drill (HDD) can be estimated from the curvature of the pipe path, pull force, and the interaction between the pipe and surrounding soil (including friction). More details of the stress analysis may be found in a paper by Liu, et al.8

8 Liu, M., Wang, Y.-Y., and Rogers, G., “Stress Analysis of Pipe Lowering-in Process during Construction,” Proceedings of the 7th International Pipeline Conference, Paper No. IPC2008-64630, September 29 – October 3, 2008, Calgary, Alberta, Canada.



GA.2.2 CYCLIC STRESS GA.2.2.1 Analysis Sources of Cyclic Stresses In a typical onshore pipeline operation, cyclic stresses in the longitudinal direction of pipelines may come from pressure and temperature fluctuations. The longitudinal cyclic stresses could cause the girth weld flaws to grow. The pressure fluctuation may be a part of normal operation or shutdown and startup. The change in the pipeline temperature can come from the changes of the fluid temperature, soil temperature, and the heat transfer between the fluid and the soil. Pressure fluctuations induce longitudinal stresses due to the Poisson’s effects. Temperature changes cause thermal contraction or expansion of the pipe, resulting in longitudinal stresses. Onshore pipeline installations usually do not impose significant cyclic stresses. Some special installation techniques may impose cyclic stresses on girth welds. One example is pneumatically assisted pull-back in HDD installations. The fatigue spectrum of the affected girth welds must be evaluated for such special circumstances. Offshore pipeline installations could impose significant cyclic stresses. The relative motion of the pipelay vessel and the pipe off the stinger could generate significant fatigue cycles, either during normal laying or in the event of work stoppage due to weather and other conditions. The stresses from these conditions must be evaluated accordingly. One of the most significant sources of fatigue for offshore pipelines is VIV from free span in ocean current. The fatigue cycles applied to the flaw acceptance criteria should be correlated to allowable span limits and remediation schedules during the operation of the pipelines. Cyclic Stresses from Temperature and Pressure Fluctuation In determining the overall temperature effect, it is necessary to assume a zero-stress temperature, i.e., temperature at which the pipeline is stress-free. The construction temperature is typically the zero-stress temperature. When the pipeline operating temperature is lower than the construction temperature, a tensile longitudinal stress is formed due to the thermal contraction of the pipeline.

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A fatigue analysis typically starts from the anticipated or postulated temperature and pressure histories. The longitudinal stress (σ) is related to the pressure (p) and temperature (T) through the following relation,

σ =ν p

D − Eα (T − T0 ) , 2t

(1)

where ν is Poisson’s ratio, α is the thermal expansion coefficient, E is Yong’s modulus, D is pipe diameter, t is pipe wall thickness, and T0 is the construction temperature (assumed stress-free temperature). The pressure and temperature variations effectively produce ∆σ i in Eq. A-1 of Appendix A. The pressure fluctuation in natural gas pipelines is generally small. Large pressure fluctuations may occur, such as in startup and shutdown conditions; the frequency of such fluctuation is small, i.e., there are few cycles. The stress range ∆σ i is therefore controlled mostly by thermal cycles. The pressure fluctuation in liquid pipelines can be greater than that in gas pipelines. The influence of the pressure fluctuation should be properly considered. Consideration of Residual Stresses It is generally not necessary to consider residual stress in computing the fatigue spectrum per Eq. A-1 in Appendix A. However the effects of residual stresses may be considered in Option 3. GA.2.2.2 Environmental Effects on Fatigue The use of Option 3 is recommended when the concentration of either CO2 or H2S exceeds typical historical levels experienced in non-corrosive pipelines. The appropriate fatigue growth curves must be used in the evaluation.9 GA.2.3 SUSTAINED-LOAD CRACKING No guidance material required. GA.2.4 DYNAMIC LOADING No guidance material required.

9 It is this author’s view that the limit on the use of Appendix A “when the concentration of either CO2 or H2S exceeds typical historical levels” is only applicable to Options 1 and 2. This interpretation is however inconsistent with the text of Appendix A.



GA.2.5 RESIDUAL STRESS No guidance material required.

GA.3 Welding Procedure GA.3.1 GENERAL Assumptions and Rationale of the Welding Procedure Qualification The use of the welding procedure qualification test data in the development of flaw acceptance criteria of field production welds assumes that the field welds will be produced in a similar manner thus having similar mechanical properties as the procedure qualification welds. A rigorous quality control program for the field welds is necessary to ensure such assumptions are met. The company must be vigilant about signs of field weld quality problems, such as excess repair rates, even though such repairs are allowed for the purpose of applying the flaw acceptance criteria. Objectives of Welding Procedure Qualification The primary objective of welding procedure qualification is to establish that a welding procedure can reliably produce welds with the necessary properties to meet or exceed the requirements set forth by relevant codes, standards, and/or company specifications. In a large pipeline construction project, line pipe materials from different manufacturers are welded with a variety of welding processes. Therefore it is necessary to establish the applicable range of a qualified procedure. The weld properties are expected to remain largely the same within the applicable range of the qualified procedures. Concept of Essential Variables To ensure a qualified procedure is applied within its applicable range, it is necessary to understand the essential variables. The essential variables are parameters that are known to affect the weld property. For the purpose of welding procedure qualification, these essential variables are known and controllable parameters. There could be other parameters that affect weld properties; but not yet known or controllable. The potential impact of these unknown and/or uncontrollable parameters is generally dealt with by applying a safety factor in design practice and weld acceptance criteria.

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Weld and HAZ Properties Line pipe steels and welds are made of polycrystalline grains. The characteristics of these grains and their relative arrangement determine the performance of these materials. From the viewpoint of structural integrity of a weld, the properties of the deposited weld metal and heat-affected zone (HAZ) are of importance. In comparison to the base line pipe material, these regions tend to have inferior properties. For the deposited weld metal, its properties are affected by the chemical composition of the welding consumable and the thermal history experienced by the weld metal. In addition to the “native” composition of the welding consumables, the composition of the deposited weld metal may be influenced by “dilution” and the application of shielding gas. The dilution generally refers to the transportation of elements between the weld metal and the base metal, either through the fluid stir of the molten weld pool or diffusion processes. The thermal history experienced by the weld metal can be affected by a large number of parameters, including reheating by subsequent welding passes. The properties of the HAZ are affected by the chemical composition of the base pipe material, the gain size and orientation prior to the application of weld thermal cycles, and the welding thermal cycles. Therefore a good “match” between the base materials and the weld processes is necessary to achieve satisfactory HAZ properties. Thermal history has a major impact on the properties of deposited weld metal and the HAZ through its effects on the phase transformation of steels. Any parameter that could potentially affect the thermal history may influence the weld properties. Significance of the Essential Variables in Appendix A The properties of welds are primarily affected by the initial state of the material (chemical composition, grain size, etc.) and the cooling rate. The significance of the essential variables listed in Appendix A is shown in reference to their influence on the initial state of the materials and cooling rate in Table G5.



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Table G5 – Essential Variables and Their Influence

Description

Section ID

Cooling Rate

Approximately Equivalent Essential Variables in Section 12

ID

a

Welding process, mode of arc transfer, or method of application

12.5.2.1

x

b

Pipe grade, manufacturing process of pipe material, chemical composition

12.5.2.2

Essential Variable in Appendix A

c

Joint Design

12.5.2.3

x

Welding position

Not listed

x

e

Pipe wall thickness

12.5.2.4

x

f

Size, type, and heat number of fill metal

g

Time between the completion of root bead and the start of the second bead

x

x x

12.5.2.8

x

Welding direction

12.5.2.9

x

l

Type of current

12.5.2.14

x

m

Pre-heat temperature

12.5.2.13

x

n

Interpass temperature

Not listed

x

p

Pipe diameter

12.5.2.5

x

Heat input

12.5.2.12

x

Note:

P1

12.5.2.6 & 12.5.2.7

h

1

Chemical Chemical Initial Grain Composition, Composition, Size, Base Deposited Base Pipe Pipe Material Weld Metal Material

x

d

q

Initial Microstructure Condition

P

P

Possible

Additional Notes on Essential Variables Essential Variable b When the same grade of pipe is sourced from different pipe manufacturers or the skelp is sourced from different plate/coil manufacturers for the same pipe mill, it is normally necessary to qualify each material individually. If (a) multiple pipe mills source the plate/coils from the same manufacturer, (b) the plates/coils are made to the same specification using the same process route and have the same basic chemical composition, and (c) the manufacturing processes of the pipe mills are substantially the same, it is sufficient to consider the pipes as one single material.

If (a) multiple plate/coils manufacturers supply the skelp to the same pipe mill, and (b) the plates/coils are made to different specifications, or using the different process routes, or having different basic chemical compositions among the plate/coils manufacturers, the pipes can be treated as different materials defined by their source, i.e., plate/coil manufacturers. In the case where multiple materials are used for the same project, for instance, Materials A, and B, it is necessary to conduct toughness tests of the deposited weld metal and each individual HAZ. For low-dilution welding processes (e.g., low heat input solid wire GMAW processes), the HAZ toughness may be obtained by placing notches into Side A and Side B of a joint A-B. It is not necessary to qualify joints A-A, B-B, and A-B individually. For high Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities dilution processes, such as submerged arc welding, it may be necessary to qualify welds in joints A-A, BB, and A-B individually. Essential Variable f For practical considerations, it is advisable to ensure that sufficient quantities of consumables of the same heat number are available for the intended number of welds when applying the qualified procedure of the same heat number. Essential Variable n The interpass temperature is intended to establish the maximum temperature of the material at the start of a welding pass. Essential Variable o Some modern microalloyed and control-rolled line pipe steels can be very sensitive to temperature above approximately 200ºC (392ºF). The benefits of PWHT must be weighed against the loss of desirable attributes of the materials when PWHT is applied. Essential Variable q The microstructure and the mechanical properties of welds (deposited weld metal and HAZ) are strongly affected by the thermal history experienced by the material. The welding heat input is a key essential variable.

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the thermal history experienced by the weld must be controlled and the correlation must be established between the procedure qualification welds and the field production welds. GA.3.2 MECHANICAL PROPERTY TESTING GA.3.2.1 Weld Tensile Properties GA.3.2.1.1 Specimen Preparation and Testing The cross-weld tensile specimens without a reduced gage section as those in Section 12 could sometimes fail near the test machine grips. The reported tensile strength could be affected when this failure location occurs. Appendix A therefore requires the tensile specimens with a reduced gage section. GA.3.2.1.2 Requirements Further information on the assessment of weld strength mismatch can be found in other publications.10,11,12 GA.3.2.2 Charpy Impact Energy GA.3.2.2.1 Specimen Preparation A total of 18 specimens, six at each o’clock position, are required.

If the heat input were to vary around the o’clock position of a weld, the 10% limit on the variation must be applied to the o’clock-position-specific nominal heat input of the qualified procedure.

For the HAZ notched specimens, the current notch location is intended to have the notch intersect the grain-coarsened HAZ in the middle one-third of the specimen thickness. The notch location is referenced to the fusion boundary for the easy location of the notch position.

New Welding Processes and Essential Variables

GA.3.2.2.2 Testing

The list of essential variables in Appendix A reflects the current consensus understanding from fundamental welding metallurgy and practical experience. New line pipe materials and welding processes are being introduced continuously to meet new pipeline requirements and to increase the costeffectiveness of new pipeline constructions. Some examples of new welding procedures are multi-wire GMAW and laser-GMAW hybrid processes. These processes produce different thermal history from the traditional single-wire GMAW process. The weld properties from these new materials and welding processes could be affected by additional parameters (such as electrode/torch spacing) not currently listed in Appendix A. All process parameters that affect


10

Wang, Y.-Y., Kirk, M. T., Gordon, J. R., and Pisarski, H. G., “Incorporating Weld Metal Mismatch into Structural Integrity Assessment,” in Pipeline Technology, Vol. 1, R. Denys, Eds., Elsevier Science B. V., 1995, pp. 475-486. 11 Wang, Y.-Y. and Kirk, M. T., “A Structural Assessment Procedure for Welded Structures with Weld Metal Strength Mismatch,” ASME PVP Conference, Montreal, July 22-26, 1996. 12 Warke, R. W, Wang, Y.-Y., Ferregut, C., Carrasco, C. J., and Horsley, D. J., “A FAD-Based Method for Probabilistic Flaw Assessment of Strength-Mismatched Girth Welds,” in Probabilistic and Environmental Aspects of Fracture and Fatigue, ASME PVP-Vol. 386, Edited by S. Rahman, 1999, pp. 89-99



GA.3.2.2.3 Requirements The determination of shear area is sometimes subjective and difficult for weld samples. The alternative is using the transition curve of the Charpy impact energy. The equivalent requirement of the shear area is that the temperature corresponding to the mid-point of the transition curve must be less than the minimum design temperature. Historically, the required minimum and average impact energy values in Appendix A were sufficient to ensure ductile behavior for lower grade welds (X52 and lower) made before the advent of microalloyed and control-rolled steels. For modern high strength welds, these required minimum and average impact energy values are quite low. Frequently these energy values would be on the lower transition part of the Charpy energy transition curves. The requirements for the Charpy shear area are meant to ensure ductile behavior. Modern GMAW welds frequently have much higher impact energy at the upper shelf of the transition curves than the minimum required values. Welds having difficulty meeting the minimum energy requirements could indicate quality issues that must be examined by qualified experts. GA.3.2.3 Fracture Toughness Testing GA.3.2.3.1 General No guidance material required.

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Cold weather construction may justify low temperature tests. The selection of this test temperature should be balanced by the consideration of the potential over-conservatisms of the traditional high-constraint CTOD test. CSA Z662-2007 Annex C provides procedures to derive more appropriate low-constraint CTOD toughness from standard highconstraint CTOD test results.13,14 An alternative approach is selecting low-constraint tests such as shallow-notched CTOD specimens or single edge notch tension (SENT) specimen. The application of the CSA procedures and the low-constraint tests should be advised by qualified fracture mechanics experts. These alternative approaches are not formally endorsed by Appendix A. Special permits may be required from appropriate regulatory authorities. GA.3.2.3.4 Re-Testing Previous versions of Appendix A allowed for retesting if the toughness were too low to meet the minimum toughness requirements. Given the natural variations in fracture toughness, this would have effectively allowed somewhat selective use of test data for the same welds. This version of Appendix A does not allow retesting for the sole purpose of hoping to generate higher toughness values. Due to the lowered minimum toughness requirement, most welds are expected to meet the minimum toughness requirements. The underlying cause of the low toughness should be examined if a weld fails to meet the minimum toughness requirements. GA.3.2.3.5 Requirements

GA.3.2.3.2 Specimen Preparation High-quality macros are often necessary to identify un-tempered grain coarsened HAZ. GA.3.2.3.3 CTOD Toughness Testing The minimum design temperature is often defined by pipeline design engineers. As CTOD toughness can have strong dependence on test temperature, the test temperature must be the lowest expected temperature for the postulated critical state at which the allowable flaw sizes would be the smallest. For onshore pipelines, the postulated critical state is often the pipe lowering-in processes when the girth welds are expected to experience the highest longitudinal stress/strain. The corresponding CTOD test temperature would be, in this case, the lowest expected pipe lowering-in temperature.

This requirement is different from pervious versions of Appendix A.

GA.4 Qualification of Welders No guidance material required.

13 Annex C, CSA Z662-2007, “Oil and Gas Pipeline Systems,” Canadian Standards Association, 2007. 14 Wang, Y.-Y., Liu, M., Horsley, D., and Zhou, J., “A Quantitative Approach to Tensile Strain Capacity of Pipelines,” 6th International Pipeline Conference, Paper No. IPC2006-10474, September 25-29, 2006, Calgary, Alberta, Canada.



GA.5 Inspection and Acceptable Limits GA.5.1 PLANAR IMPERFECTIONS GA.5.1.1 Structure of the Procedures to Determine the Maximum Acceptable Imperfection Size No guidance material required. GA.5.1.2 Determination of Acceptable Imperfection Size by Option 1

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GA.5.1.2.2 Example of Option 1 Application The imperfection allowance curve similar to that in Figure A-9 may be converted to an allowance table for a range of flaw height. The increment of the flaw height can be selected to best match the setup of NDT equipment. GA.5.1.3 Determination of Acceptable Imperfection Size by Option 2 GA.5.1.3.1 Background More information on the application of the failure assessment diagram may be found in a publication by Wang et al.4 and the references cited in the publication.

Girth weld high-low misalignment has shown to be detrimental to girth weld stress and strain capacity. The effects of high-low misalignment on the flaw acceptance criteria are not explicitly considered in Appendix A. Published work is available on the effects of misalignment on weld integrity15,16, , although this is a subject of great complexity. It is advisable to seek the assistance of fracture mechanics experts on the treatment of high-low misalignment..

GA.5.1.3.2 Determination of Critical Imperfection Size

A cross-weld tensile test used in a typical welding procedure qualification is not sufficient to verify the detrimental effects of misalignment for an actual full-scale pipe. Such a test with misalignment is non-conservative in predicting full-scale pipe behavior as the misaligned weld is easily re-aligned during the test of such small specimens. Such realignment cannot occur as easily in full-scale pipes when the remaining circumference would impose considerable restraint for such realignment. Welds without the benefits of realignment are expected to behave more poorly than welds that could be realigned during a test.

The solution of Fb was not intended to be used for very short flaws, i.e., 2c/t < 1.0. Appropriate KI solutions from other sources may be applied for such short flaws. The current formulation assumes the deepest point of a flaw is the most critical location. For very short and deep flaws, the KI values near the free surface could be higher than that of the deepest point when a small D/t pipe is under global bending. Such a scenario is not considered in Appendix A. The flaw acceptance criteria should not be developed per Appendix A for such flaws.

GA.5.1.2.1 Computation of the Load Level Pr

GA.5.1.4 Determination of Acceptable Imperfection Size by Option 3

The parameter Pr must be computed from specified minimum values. The use of actual strength is not permitted.

Option 3 is permitted only when the fatigue spectrum severity exceeds the limit set for Options 1 and 2.

No guidance material required. GA.5.1.3.3 Determination of the Key Components in the FAD Procedure

GA.5.1.4.1 General

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Wang, Y.-Y. and Liu, M., “The Role of Anisotropy, Toughness Transferability, and Weld Misalignment in the Strain Based Design of Pipelines,” Proceedings of the 17th International Offshore and Polar Engineering Conference (ISOPE 2007), Lisbon, Portugal, July 1-6, 2007. 16 Wang, Y.-Y. and Liu, M., “Weld Integrity from the Perspective of Strain-Based Design of Large Diameter and High Strength Pipelines,” Special Issue of the Proceedings of “Pipeline Technology Now and Then” at the 8th International Welding Symposium, 8WS, November 16-18, 2008, Kyoto, Japan.

Various available procedures may incorporate safety factors at different stages of the assessment process. When a qualified assessment procedure is selected, the procedure must be followed in its entity. GA.5.1.4.2 Fatigue Flaw Growth Appropriate fatigue growth curves must be selected based on the internal and external conditions Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities the pipe material is exposed to so any acceleration of fatigue growth from a normal benign environment is properly accounted for. All static failure models must be checked simultaneously when the flaw is allowed to grow from the cyclic loads. This is particularly important when the static peak load may occur before the expected end of the fatigue life. GA.5.1.4.3 Inspection Error and Safety Factor on Allowable Imperfect Size The treatment of inspection error should follow the selected assessment procedure. GA.5.1.5 Transverse Planar Imperfections The driver for any potential failures from transverse planar flaws is the hoop stress, not the longitudinal stress that drives the girth weld flaws being considered in all other parts of Appendix A. The assessment of the significance of transverse planar flaws can be a source of different opinions. Some may have the opinion that the occurrence of transverse planar flaws is the result of improperly executed welding procedures. Others may think that the discovery of transverse planar flaws is associated with statistical occurrence. Regardless of the causes of the transverse planar flaws, the significance of the flaws can be assessed using qualified fitness-forservice procedures. These procedures are not provided in Appendix A currently. Since the transverse planar flaws are of limited length, they become significant if the toughness or the ductility of the material is very low.

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GA.5.3 ARC BURNS No guidance material required. GA.5.4 IMPERFECTION INTERACTION Appropriate flaw sizing accuracy and probability of detection must be considered in applying the imperfection interaction rules.

GA.6 Record The development of the imperfect acceptance criteria involves a large amount of data, ranging from material properties and pipeline stresses under various construction and service conditions. The data can become a valuable source of information during the operation and maintenance of the pipeline. The records of both accepted and non-accepted flaws are useful in future quality control and construction cost estimation.

GA.7 Repairs Weld repair procedures must be established and qualified for realistic repair scenarios. The company should establish rules on minimum repair size, repair on repairs, and the total number of permissible repairs on any single girth weld.

GA.8 Nomenclature No guidance material required.

GA.5.2 ACCEPTABLE LIMITS OF VOLUMETRIC IMPERFECTIONS No guidance material required.



APPENDIX B—IN-SERVICE WELDING GB.1 General This section combines the requirements for procedure qualification, welder qualification, welding practices, inspection, acceptance standards, and repair for in-service welding into a single section. For some of these topics, reference is also made to other sections of API 1104. The background section prominently indicated that the requirements for fillet welds in the main body of API 1104 should be applied to in-service welds that contact the carrier pipe, except for the alternative/additional requirements that are specified in Appendix B. In other words, Appendix B is not a stand-alone document and must be used in conjunction with the main body of API 1104. As indicated in 3.2.18, “shall” is a term that indicates a mandatory requirement. The term “should” indicates a recommended practice. The term “shall” does not appear in Appendix B. Examples of appurtenances include branch fittings, fabricated branch connections, pressurecontaining tees, Type B full-encirclement repair sleeves, etc. For pipelines and piping systems that have been fully isolated and decommissioned, or have not been

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commissioned, the requirements in the main body of API 1104 should apply instead of those in Appendix B. For welds that do not contact the carrier pipe, such as longitudinal seam welds of full-encirclement fittings that include the use of backing strips or filletwelded overlapping side strips, it is not necessary to consider these to be in-service welds. The requirements in the main body of API 1104 should apply instead of those in Appendix B. In-service welds are defined as those that fuse directly into the wall of an in-service pipeline or piping system. A burnthrough, or blowout as it is sometimes referred, will occur when welding onto a pressurized pipe if the unmelted area beneath the weld pool has insufficient strength to contain the internal pressure of the pipe. An illustration of a typical burnthrough is shown in Figure G2. A burnthrough typically results in a small pin-hole in the bottom of what was the weld pool. The risk of burnthrough will increase as the pipe wall thickness decreases and the weld penetration increases. For welding onto thinner inservice pipelines (i.e., less than 0.250 in. [6.4 mm] thick), the use of a welding procedure that limits heat input may be necessary. API 1104 refers to burnthrough as “burning through” to distinguish it from a “burn-through” (excessive root penetration in a butt weld) described in 9.3.7.

Figure G2 – Typical Burnthrough on 0.125-in. (3.2-mm) Thick Pipe


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities A common first step toward avoiding hydrogen cracking in welds made onto in-service pipelines is to minimize the hydrogen level by using low-hydrogen electrodes or a low-hydrogen welding process. Lowhydrogen electrodes with the H4R supplemental designator (e.g., AWS E7018-H4R), packaged in small-quantity, hermetically sealed cans are ideally suited for in-service welding. However, Appendix B does not preclude the use of cellulosic-coated electrodes (e.g., AWS EXX10-type), as long as the welding procedures have been qualified in accordance with the requirements of this section and are used within the qualified range of essential variables. As added assurance against hydrogen cracking, welding procedures that minimize the formation of crack-susceptible microstructures should be developed and followed. Procedure options for minimizing the formation of crack susceptible microstructures include the use of a sufficiently-high heat input level, the use of preheating, the use of a temper bead deposition sequence, or some combination of these. Temper bead procedures are also useful for welding onto thin-wall in-service pipelines (i.e., less than 0.250 in. [6.4 mm] thick) where the use of a high heat input level represents a risk of burnthrough. While the use of thermal analysis models is not a substitute for procedure qualification, these models can be useful for determining starting parameters prior to procedure qualification and for interpolating between qualified thermal severity levels and material carbon equivalent levels. See guidance provided in GB.2.1.1.1. The primary benefit of preheating is to allow the weld to cool more slowly. While the effective use of preheating for this purpose during in-service welding is difficult for some pipeline operating conditions, preheating does tend to burn off moisture and other contaminants, the presence of which can increase weld hydrogen levels, prior to welding. Temper bead sequences rely on the heat from subsequent passes or layers to temper and refine the HAZ of previous passes or layers. The sequence in which welds are made for some appurtenances can affect stresses acting on the weld. Recommendations are provided in B.4.2. See guidance provided in GB.4.2. An example of a conflict between the main body of API 1104 and Appendix B is the essential variable

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for material groupings for procedure qualification. In the main body, the essential variable is strength level. In appendix B, the essential variable is carbon equivalent level. For in-service welds, procedures should be qualified in accordance with carbon equivalent levels as opposed to strength level groupings.

GB.2 Qualification of In-service Welding Procedures As noted above, Appendix B is not a stand-alone document. The requirements for fillet welds in Section 5 should be the basis on which procedures for in-service welding should be qualified. For inservice welds, Appendix B contains alternative requirements to those specified in Section 5 and additional requirements beyond those specified in Section 5. GB.2.1 PROCEDURE SPECIFICATION GB.2.1.1 Specification Information General requirements for developing a welding procedure specification (WPS) are provided in 5.4. See guidance provided in G5.4. The additional and/or alternative specification information for inservice welding are given in B.2.1.1. GB.2.1.1.1 Pipe and Fitting Materials Appendix B allows procedures for in-service fillet welding to be qualified in accordance with carbon equivalent level groupings as opposed to specified minimum yield strength groupings. This provision is included because hydrogen cracking susceptibility is more a function of carbon equivalent level than it is to specified minimum yield strength, and carbon equivalent level can vary widely depending on pipe manufacturer and vintage. For example, a modern API 5L-X52 material that has been thermo-mechanically processed may have a low carbon-equivalent value (and, therefore, a high resistance to hydrogen cracking); whereas, most 1950s-vintage X52 materials have a high carbonequivalent value. The specified minimum yield strength of the materials to which the procedure applies should also be specified in the WPS, although specified minimum yield strength is not an essential variable for in-service fillet welds. For in-service welds other than fillet welds, the strength of the completed weld should meet or exceed the specified minimum yield strength of the pipe and fitting material. The maximum-allowable carbon equivalent Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities of the materials to which the procedure applies should also be specified in the WPS. This applies to both the pipe material and the appurtenance material. The development of crack-susceptible weld microstructures depends on the chemical composition or carbon equivalent of the materials being welded and on weld cooling rates. Weld cooling rates depend on welding parameters and the thermal severity of the pipeline operating conditions. The provision for allowing a given welding procedure (i.e., a given set of welding parameters) to be used for higher carbon equivalent materials than the material used for procedure qualification is intended to allow the use of thermal analysis models to evaluate tradeoffs that can be made between the carbon equivalent of the materials and thermal severity levels. If, for example, a procedure will be used under less severe thermal conditions than those used for procedure qualification, it may be appropriate to allow that procedure to be used for higher carbon equivalent materials without an increase in the risk of hydrogen cracking. The use of thermal analysis models is permitted for interpolating between qualified thermal severity levels and material carbon equivalent levels provided no increase in the risk of hydrogen cracking results. For a given material chemical composition, an increase in the predicted HAZ hardness can be interpreted to represent an increase in hydrogen cracking risk. The IIW (International Institute of Welding) carbon equivalent formula is provided in the footnote, since it is generally appropriate for most older line pipe materials to which in-service welding is commonly applied. Other carbon equivalent formulas may be used provided that the same formula is used for procedure qualification and production welding. Chemical composition of an in-service pipeline can be determined by interrogating records from when the pipeline was built (e.g., mill test reports), by direct analysis using portable equipment (e.g., portable optical emission spectrometer), or by removal of samples (e.g., filings removed using a high-speed rotary file) for laboratory analysis. Guidance can be found in Appendix A of the PRCI Pipeline Repair Manual by Jaske, et al.17

17 Jaske, C. E., Hart, B. O., and Bruce, W. A., “Pipeline Repair Manual,” Final Report to Pipeline Research Council International, Inc., Arlington, Virginia, Contract PR-186-0324, August 8, 2006, DNV Columbus, Inc., Dublin, Ohio.

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GB.2.1.1.2 Pipeline Operating Conditions For in-service welds, the thermal severity (in terms of weld cooling rates that result) depends not only on wall thickness, but also on the pipeline operating conditions such as the thermal properties and temperature of the pipe contents, the flow rate, and if the pipe contents are a gas, also on the pressure (thermal conductivity of gasses change with pressure). For in-service welding, the procedure should document the condition under which the procedure was qualified and the actual conditions to which the procedure applies (e.g., ranges for wall thickness, pipe contents, temperature, flow rate, pressure, etc.). See guidance provided in GB.2.3. GB.2.1.1.3 Heat Input Range The most common procedures for in-service welding rely on the use of a sufficiently high heat input level to overcome the effect of the flowing contents. In addition to ranges for amperage, voltage, and travel speed, a heat input range for each welding pass should be specified for in-service welding procedures that rely on the use of a sufficiently high heat input level. Control of heat input level is an important aspect of assuring adequate tempering for procedures intended to overcome the effect of heat removal by the contents by using temper bead deposition sequence (temper bead procedures). Heat input takes into account the collective effect of amperage, voltage, and travel speed on the thermal cycle of the weld. The specified range should reflect the measured minimum and maximum heat input values that produce an acceptable weld, not the calculated minimum and maximum values from the amperage, voltage, and travel speed range. GB.2.1.1.4 Weld Deposition Sequence As an alternative to the use of a sufficiently high heat input level to overcome the effect of the flowing contents, procedures designed to make use of tempering from subsequent passes can be used to minimize the development of crack-susceptible weld microstructures. These procedures are generally referred to as temper bead procedures. Temper bead procedures typically involve depositing a first layer or "buttering" layer using stringer beads that are deposited within the acceptable heat input range for preventing burnthrough. Subsequent passes are deposited in such a way as to maximize the amount of grain refinement and tempering of the buttering layer. For in-service welding procedures that rely on Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities the use a temper bead deposition sequence, the required weld deposition sequence should be specified. The weld deposition sequence should include tolerances for bead spacing to assure proper tempering of the previous passes.

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thermal severity. This applies to the thickness of both the pipe material and the appurtenance material.

General requirements for essential variables are provided in 5.3.2. See guidance provided in G5.3.2. The additional and/or alternative essential variables for in-service welding are given in B.2.2.

Welds made onto thin-wall pipelines are made in close proximity to the flowing pipeline contents, which removes heat from the pipe wall. This effect becomes less prominent as pipe wall thickness exceeds some critical value, thought to be approximately 0.5 in. (12.7 mm) for typical applications, and reverts back to a conventional relationship due to the thermal mass of the pipe wall itself at greater thicknesses.

GB.2.2.1 Changes Requiring Requalification

GB.2.2.1.4 Weld Deposition Sequence

Essential variables are those that require the procedure to be requalified, or a new procedure qualified, if the range specified in the WPS for any of those variables is exceeded.

If the procedure relies on the use of a temper bead deposition sequence to minimize the development of crack-susceptible weld microstructures, that sequence should be followed during production welding. A change in the bead spacing beyond the limits in the procedure specification should be considered an essential variable.

GB.2.2 ESSENTIAL VARIABLES

GB.2.2.1.1 Pipe and Fitting Materials Appendix B allows procedures for in-service fillet welds to be qualified in accordance with carbon equivalent level groupings as opposed to specified minimum yield strength groupings. See guidance provided in GB.2.1.1.1. For in-service welds other than fillet welds, the strength of the completed weld should meet or exceed the specified minimum yield strength of the pipe and fitting material. While not explicitly stated in B2.2.1.1, carbon equivalent of the materials being welded should be considered an essential variable for in-service welding as opposed to specified minimum yield strength, except for the provision provided in B.2.1.1.1. GB.2.2.1.2 Pipeline Operating Conditions For in-service welds, the thermal severity (in terms of weld cooling rates) depends not only on wall thickness, but also on the pipeline operating conditions. For in-service welds, instead of pipe wall thickness, an increase in the thermal severity of the pipeline operating conditions above the group qualified constitutes an essential variable. See guidance provided in GB.2.1.1.2. GB.2.2.1.3 Pipe Wall Thickness For in-service welding, while it is not necessary to consider pipe wall thickness itself as an essential variable, wall thickness should be considered along with pipeline operating conditions as it affects

It is not necessary to consider the addition of buttering layer passes (e.g., to reduce gaps between a pipeline and a full-encirclement fitting) as an essential variable provided that the passes are deposited using parameters specified in the qualified welding procedure. However, the WPS should be revised to show the revised number of beads. GB.2.3 WELDING OF TEST JOINTS General requirements for welding of test joints for fillet welds are provided in 5.7. See guidance provided in G5.7. The additional and/or alternative requirements for in-service welding are given in B.2.3. When performing a procedure qualification for in-service welding, the user has the option to qualify a procedure for either a sleeve weld or a branch weld. To qualify a welding procedure for a branch connection, the testing requirements for both the groove and fillet portion of the weld are the same as those for a fillet weld. Without simulating the ability of the in-service pipeline to remove heat from the pipe wall, unrealistically slow weld cooling rates result, in addition to different solidification characteristics of the weld. The note provides guidance on how to easily simulate in-service conditions and indicates that procedures qualified with flowing water inside the pipe are suitable for most typical in-service applications (i.e., up to and including the most severe in-service welding applications). The note also Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities indicates that other media (e.g., motor oil) may be used to simulate less severe thermal conditions (e.g., low-pressure, thinner-wall natural gas pipelines operating at low flow rates). The use of this technique is illustrated in Figure G3. It should be noted that the pipe is not required to be aligned at approximately 45 degrees as indicated in Figure B-2. This test position qualifies the procedure for all positions. Tests may be performed in other positions, which will qualify the procedure for that position only. The use of procedures qualified with flowing water inside the pipe may represent a risk of burnthrough when applied to thin-wall (i.e., less than 0.250 in. [6.4 mm]) in-service pipelines operating at

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less severe thermal conditions. For these applications, the risk of burnthrough should be assessed independently (e.g., using thermal analysis models or by procedure qualification under less severe thermal conditions with pressure inside the pipe). For in-service welds made on very thick-wall pipe or fittings, the weld cooling rate can exceed the cooling rate of test welds made on water-filled pipe of moderate wall thickness. Thermal analysis modeling can be used to compare the estimated cooling rate of qualification welds with the estimated cooling rate of actual in-service conditions to verify that the test setup produced cooling rates that are representative of actual service conditions.

Figure G3 – Typical Setup for Welding Procedure Qualification under Simulated In-Service Conditions

GB.2.4 TESTING OF WELDED JOINTS It should be noted that some acceptance criteria for imperfections discovered during procedure qualification testing are more stringent than those for imperfections discovered by nondestructive testing of production welds. This is intended to account for the more-favorable conditions that generally exist where welding procedures are normally qualified (e.g., in an enclosed welding shop as opposed to on a pipeline right-of-way).

To qualify a welding procedure for a branch connection, the testing requirements for both the groove and fillet portion of the weld are the same as those for a fillet weld. GB.2.4.1 Preparation General requirements for testing of fillet welds are provided in 5.8. See guidance provided in G5.8. For in-service welding, the locations, minimum number of specimens, and the tests to which they are to be subjected are given in B.2.4.1. It is good Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities practice to allow the test weld to sit for some time (e.g., overnight) prior to removing specimens so that any cracking that is going to occur has time to do so. It should be noted that for qualification testing of branch welds, it may be difficult to obtain the required number of specimens when the branch is smaller than 8.625 in. (203 mm) diameter. GB.2.4.2 Longitudinal Seam Welds General requirements for testing of butt welds are provided in 5.6. See guidance provided in G5.6. Longitudinal seams that do not contact the carrier pipe (e.g., butt welds that include the use of a backing strip or fillet-welded overlapping side strips) are not considered in-service welds according to the definition in B.1. Recommendations for testing these welds, which are typically made in conjunction with the qualification of procedures for in-service welding of full-encirclement sleeves and fittings, are provided in Appendix B for convenience only. Longitudinal seams of full-encirclement sleeves or fittings that consist of butt welds should be tested in accordance with 5.6. While not explicitly stated in B.2.4.2, longitudinal seams that consist of filletwelded overlapping side strips should be tested in accordance with 5.8. See guidance provided in G5.6 and G5.8. GB.2.4.3 Branch and Sleeve Welds General requirements for testing of fillet welds are provided in 5.8. See guidance provided in G5.8. In addition to the nick-break test specified in 5.8, Appendix B also specifies the macro-section test and face-bend test for in-service branch and sleeve welds. For a branch connection, both the groove and fillet portion of the weld are treated as a fillet weld. GB.2.4.4 Macro-section Tests—Branch and Sleeve Welds The macro-section test involves cutting a welded test joint through its cross section, polishing the face of the weld and heat-affected zone, and examining the surface for imperfections. The macro-section test

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also allows hardness testing in the HAZ to be performed. GB.2.4.4.1 Preparation Machine cutting is preferred. If the specimen is cut using a thermal process (e.g., oxy-fuel cutting), the heat-affected area from the cut must be removed by a non-thermal process. The width of the heataffected area from the cut using a thermal process is typically 1/4 in. (6 mm) or less. The phrase “to at least a 600 grit finish” refers to the abrasiveness of the sandpaper that should be used. It is good practice to polish the specimen sufficiently so that the fusion line can be clearly distinguished. In addition to ammonium persulfate or dilute hydrochloric acid, dilute nitric acid in methanol (e.g., Nital) can be used. The etchant should be applied using a swab until the weld structure becomes clearly visible. GB.2.4.4.2 Visual Examination While not required, it is common for prepared macro-section specimens to be examined with a magnifying device. GB.2.4.4.3 Hardness Testing Hardness testing is often used as a performance indicator for welds, including assessment for the risk of hydrogen cracking. The preferred procedure involves making hardness measurements at the toe of the weld in the coarse-grained HAZ on the pipe material side of the joint. Five Vickers 10-kg indents are spaced 0.6 mm (0.024 in.) from each other and 0.2 mm (0.008 in.) from the fusion line. The results for these five measurements in the area of maximum hardness are then averaged. This technique is illustrated in Figure G4. The Vickers hardness testing method using a 10kg load is specified, as this commonly used for weld heat-affected zones (i.e., the indent produced is an appropriate size for weld heat-affected zones). It is not appropriate for the Rockwell, Brinell, or other large-scale hardness methods to be used and the results converted to the Vickers scale.



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Figure G4 – Suggested Procedure for HAZ Hardness Measurement HAZ hydrogen cracks tend to occur in areas where hard microstructures coincide with stress concentrations. For in-service welds, these areas tend to occur at the toe of the weld in the pipe material. If the weldability of the appurtenance material is less favorable than that of the pipe material (i.e., if the appurtenance material has a higher carbon equivalent than the pipe material), consideration should also be given to making hardness measurements in the coarse-grained HAZ on the appurtenance material side of the joint. In order to assess the overall hydrogen cracking susceptibility of in-service welds, averaging the results of the five measurements taken in the coarsegrained region of the HAZ near the weld toe has been found to be appropriate. Consideration can be given to excluding measurements that deviate significantly from the median value. The results are then reported as an average for this region of anticipated maximum hardness.

allows higher hardness to be tolerated. In addition, lower carbon content materials tend to crack at lower hardness levels and higher hardness can be tolerated when welding higher carbon content materials. Recommended hardness limits for materials in the 0.375-in. (9.5-mm) thickness range with a carbon content greater than 0.10% are provided in a paper by Bruce, et al.18 Limits that take the effect of material thickness into account have also been proposed.19 This work also showed that HAZ hardness is a lesseffective performance indicator for welds in modern microalloyed and control-rolled line pipe steels. GB.2.4.5 Face-bend Test—Branch and Sleeve Welds The primary purpose of the face-bend test is to expose any hydrogen cracks that may be present, particularly at the weld toe area.

GB.2.4.4.4 Requirements The widely-used limit of 350 HV is conservative for some applications (and may be non-conservative for others – e.g., where weld hydrogen levels are not controlled). Critical hardness level, or the hardness level below which hydrogen cracking is not expected, depends on the hydrogen level of the welding process being used and on the chemical composition (carbon content and carbon equivalent level) of the materials being welded. Closer control of hydrogen level

18 Bruce, W. A., Etheridge, B. C., and Carman, A., “Heat-Affected Zone Hardness Limits for In-Service Welding,” Proceedings of the 7th International Pipeline Conference, Paper No. IPC2008-64003, Calgary, Alberta, Canada, September 29-October 3, 2008, DNV Columbus, Inc., Dublin, Ohio. 19 Bruce, W. A., Etheridge, B. C., Arnett, V. R., Carman, A., and Nolan, D., "Development of Heat-Affected Zone Hardness Limits for In Service Welding," Final Report to U.S Department of Transportation, PHMSA Research and Development, Agreement #DTPH56-07-T-000004, Project #216, DNV Columbus, Inc., Dublin, Ohio, September 2009.



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GB.2.4.5.1 Preparation

GB.2.4.5.2 Method

Because of the geometry associated with branch and sleeve welds, preparation of face-bend test specimens is different than that for butt welds specified in 5.6.4.

Hydrogen cracking, which is also referred to as delayed cracking, can take some time to occur. Therefore, testing of face-bend test specimens should not occur immediately after welding. A time delay of at least 24 hours is specified. Time delay prior to inspection of production welds for hydrogen cracking is addressed in B.5.

Machine cutting is preferred. If the specimen is cut using a thermal process (e.g., oxy-fuel cutting), the heat-affected area from the cut must be removed by a non-thermal process. Where wall thickness is greater than 0.500 in. (12.7 mm), it may be reduced to 0.500 in. (12.7 mm) by machining the inside surface The weld reinforcement can be removed using a belt sander or by grinding, although care should be taken to ensure that sanding or grinding to below the surface of the specimen (e.g., to remove undercut) is avoided. Also, deep scratches or grinding marks that are parallel to the weld (i.e., perpendicular to the specimen) may cause an otherwise acceptable weld to fail. The note provided in B.2.4.5.1is intended to allow both the nick-break test and the face-bend test to be performed on the same specimen. If the nickbreak test can be performed without introducing a notch in the pipe material side of the specimen, this remaining portion can be used for the face-bend test.

Testing of face-bend test specimens taken from branch and sleeve welds is similar to that for butt welds specified in 5.6.4. See guidance provided in G5.6.4. GB.2.4.5.3 Requirement Causes of failure may include lack of ductility, cracks, incomplete fusion or penetration, porosity, and/or trapped slag. A typical hydrogen crack at the toe of a sleeve fillet weld in a face-bend test specimen is shown in Figure G5.

GB.3 In-service Welder Qualification General requirements for welder qualification (single qualification) are provided in 6.2. See guidance provided in G6.2. The additional and/or alternative requirements for in-service welder qualification are given in B.3.

Figure G5 – Typical Hydrogen Crack at Toe of Sleeve Fillet Weld in Face-Bend Test Specimen


Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities Longitudinal seams that do not contact the carrier pipe (e.g., butt welds that include the use of a backing strip or fillet-welded overlapping side strips) are not considered in-service welds according to the definition in B.1. Recommendations for testing these welds, which are typically made in conjunction with the qualification of welders for in-service welding, are provided in Appendix B for convenience only. The essential variables for pipe diameter for inservice welder qualification in B.3 are less restrictive than those in 6.2.2. For in-service welding, essential variables for pipe diameter for in-service welder qualification in B.3 should apply. The last sentence in B.3 is intended to allow for the multiple qualification of an in-service welder. Multiple qualification of an in-service welder is limited by the essential variables in 6.3 (multiple qualification) and B.3 (in-service qualification). A welder who has an existing multiple qualification to 6.3 using filler metals from Group 1 or 2 in Table 1 (e.g., AWS EXX10-type), and an in-service qualification to B.3 using filler metals from Group 3 (e.g., AWS EXX18-type), should not be considered an in-service welder for all positions, all diameters, and all wall thicknesses using filler metals from Group 3. For an in-service welder to be qualified for all positions, all diameters, and all wall thicknesses using filler metals from Group 3, the existing multiple qualification to 6.3 and the in-service qualification to B.3 must be for filler metals from Group 3. GB.3.1 WELDING OF TEST JOINT Without simulating the ability of the in-service pipeline to remove heat from the pipe wall, unrealistically slow weld cooling rates result, in addition to different solidification characteristics of the weld. The note provides guidance on how to easily simulate in-service conditions and indicates that welders qualified with flowing water inside the pipe are suitable for most typical in-service applications (i.e., up to and including the most severe in-service welding applications). The note also indicates that other media (e.g., motor oil) may be used to simulate less severe thermal conditions (e.g., low-pressure, thinner-wall natural gas pipelines operating at low flow rates). The phrase “to the satisfaction of the company” is intended to preclude the need to perform multiple welder qualification tests. If a welder is to be qualified for both heat input control and temper bead deposition procedures, that welder can perform a

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welder qualification test using one technique and demonstrate the other using another method (e.g., using plate material arranged for lap fillet welds) provided that the company considers this to be satisfactory. Similarly, the company can require that a welder perform a qualification test using heat inputs at the upper end of the anticipated range of specified heat inputs, and then demonstrate the ability to make welds at lower heat inputs using a second weld of some type using heat inputs at the lower end of the heat input range. The scope of testing of the second weld, if any, is at the discretion of the company. GB.3.2 TESTING OF WELDED JOINTS See guidance provided in G6.4 and G6.5. Longitudinal seams of full-encirclement sleeves or fittings that consist of butt welds should be tested in accordance Table B-2. While not explicitly stated in B.3.2, longitudinal seams that consist of filletwelded overlapping side strips should be tested in accordance with 5.8. See guidance provided in G5.8. GB.3.3 RECORDS See guidance provided in GB.3.1.

GB.4 Suggested In-service Welding Practices General requirements for production welding are provided in Section 7. See guidance provided in Section G7. Additional and/or alternative requirements for in-service welding are given in B.4. Additional guidance specific to in-service welding can also be found in Appendix A of the PRCI Pipeline Repair Manual by Jaske, et al.17 Prior to in-service welding, relevant parameters such as pipe material, pipe contents, operating pressure, flow conditions, and wall thickness at the location of the welding should be determined. The welding procedure that will be used should be appropriate for the specific application. Procedure selection for avoiding hydrogen cracking is often made based on the chemical composition (carbon equivalent) of the pipe material. Chemical composition of an in-service pipeline can be determined by interrogating records from when the pipeline was built (e.g., mill test reports), by direct analysis using portable equipment (e.g., portable optical emission spectrometer), or by removal of samples (e.g., filings removed using a Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities high-speed rotary file) for laboratory analysis. Guidance can be found in Appendix A of the PRCI Pipeline Repair Manual by Jaske, et al.13 Wall thickness should be determined using appropriate ultrasonic testing equipment to ensure that corrosion or erosion has not greatly affected the actual wall thickness from the nominal value. An ultrasonic wall thickness check can also be used to investigate for the presence of defects. Low-hydrogen electrodes should be properly stored and handled to ensure that low hydrogen levels result. Moisture can be absorbed by the electrode coating during storage and handling. Since different low-hydrogen electrodes behave differently with respect to moisture absorption, it is important to follow the specific electrode manufacturer’s recommendations for storage and handling. It should be noted that the performance of circumferential fillet welds deposited using lowhydrogen electrodes can be influenced by the use of cellulosic-coated electrodes for making the longitudinal seam welds of full-encirclement fittings. Cellulosic-coated electrodes should not be indiscriminately substituted for low hydrogen welding practices for the longitudinal seams, even though the longitudinal seams made with backing strips are not required to be qualified in accordance with Appendix B. The ability to accurately control heat input levels is an important aspect of being able to safely weld onto in-service pipelines. For welding onto inservice thin-wall pipelines, it may be necessary to maintain a heat input below a maximum-allowable value. For procedures that are intended to overcome the effect of the flowing contents by using a sufficiently high heat input, it may be necessary to maintain a heat input above a minimum-required value. For some applications, it may be necessary to maintain a heat input within a specified range (i.e., between a minimum-required and a maximumallowable value). Accurate measurement of heat input levels can be achieved using conventional equipment (amp tongs, voltmeter, stopwatch, etc.) or purpose-built arc monitoring equipment. The run-out ratio scheme can also be used to control heat input levels. Using this scheme, the length of weld deposited is specified as some percentage of the electrode length consumed. Regardless of the method chosen to control heat input levels, a test plate should be used by the welder prior to depositing welds on an in-service pipeline to

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ensure that the proper heat input level is being achieved. Appendix B does not address safety during welding aspects directly, but refers to API RP 2201 instead. GB.4.1 ALIGNMENT GB.4.1.1 Fit-up Care should be taken to ensure that full encirclement repair sleeves and fittings fit snugly around the pipe. This increases the effectiveness of the reinforcement provided by the repair sleeve or fitting and minimizes the complications associated with fillet welding in the presence of a gap. The most common method of facilitating proper fit up the use of chains and hydraulic jacks. Purpose-built clamps are also available for this purpose. While excessive gap is not defined, it is common to limit gaps to 1/16 to 1/8 in. (1.6 to 3.2 mm) maximum. Weld metal build-up (buttering layers) can be used when other methods are insufficient. It is not necessary to consider the addition of buttering layer passes as an essential variable provided that the passes are deposited using parameters specified in the qualified welding procedure. However, the WPS should be revised to show the revised number of beads. GB.4.1.2 Root Opening—Longitudinal Seam Welds For full-encirclement sleeves and fittings, the longitudinal seams should be fitted with a mild steel back-up strip or suitable tape to prevent penetration of the weld into the carrier pipe. Penetration of the longitudinal butt weld into the carrier pipe is undesirable since any crack that might develop is exposed to the hoop stress in the carrier pipe. GB.4.2 WELDING SEQUENCE For full-encirclement sleeves and fittings requiring circumferential fillet welds, the sequence in which welds are made can affect stresses acting on the welds because welds contract as they solidify and cool. The sequence described in B.4.2 (i.e., longitudinal seams first, and then one end before the other) should be used to minimize stresses. For Type A full-encirclement repair sleeves (reinforcement only) and for full-encirclement reinforcement of stub-on hot tap branch connections, Revision 1 – April 30, 2010

Guidance Material for API Standard 1104 – Welding of Pipelines and Related Facilities (Figures B-8, B-10, and B-11), it is not necessary to fillet weld the ends to the pipeline provided that the full-encirclement fits tightly around the pipeline. The longitudinal seam welds provide the necessary reinforcement. Some companies, however, weld the ends to prevent further corrosion, which can also be accomplished using an effective coating system. The sequence in which individual beads within a given weld are made can also affect the weld microstructures that result. The ability of a temper bead sequence to reduce hydrogen cracking risk is dependent upon proper placement of the weld beads. During execution of a temper bead procedure, the welder should be thoroughly familiar with the proper sequence. Between-pass inspection should be carried out to assure proper bead placement, particularly at the weld toes. For welds that contact the carrier pipe, even for non-temper-bead procedures, the beads should be deposited is such a way as to maximize tempering. To do this, the beads should be stacked away from the carrier pipe material. Bead sequence is not an essential variable provided that the passes are deposited using parameters specified in the qualified welding procedure. However, the WPS should be revised to show the revised bead sequence.

GB.5 Inspection and Testing of Inservice Welds General requirements for inspection and testing are provided in Section 8. See guidance provided in Section G8. The additional and/or alternative specification information for in-service welding is given in B.5. Since in-service welds that contact the carrier pipe can be particularly susceptible to hydrogen cracking, an inspection method that is capable of detecting these cracks, particularly at the carrier pipe weld toe, should be used. Magnetic particle testing (MT) has been shown to be more effective than liquid penetrant testing (PT) for detecting hydrogen cracks at the toe of sleeve-, saddle-, and branch-to-carrier pipe welds. MT has the ability to detect imperfections that are located slightly below the surface (if DC magnetization is used), whereas PT does not. The use of magnetic particles suspended in a carrier liquid is generally more sensitive than the use of dry powders. Both wet fluorescent MT and the use of colored (usually black) particles over a surface that is first sprayed with a

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thin layer of white contrast paint tend to perform equally well. Ultrasonic testing (UT) can be used to supplement MT results. The successful application of UT for the typical geometries associated with inservice welds has been shown to be highly dependent on operator skill. Hydrogen cracking, which is also referred to as delayed cracking, requires time to occur. The reason for this is that time is required for the hydrogen to diffuse to areas with crack susceptible microstructures. Prior to inspection for hydrogen cracking, a sufficient delay time should be allowed to elapse. When determining appropriate delay times prior to inspection, the time-dependant nature of hydrogen cracking should be considered, as well as the expected susceptibility of the weld to cracking. Longer delay times decrease the chance that cracking can occur after inspection has been completed. The probability of cracking, and thus the importance of determining an appropriate delay time, can be minimized by using more conservative welding procedures. For example, if the hydrogen in the weld is allowed to diffuse away after welding by the continuous application of preheating (i.e., preheating and post-heating), the probability of cracking is significantly reduced, and immediate inspection may be justified. A delay time of twelve hours would seem to be a reasonable time for the range of thicknesses that are encountered during most typical in-service welding applications. Longer times should be considered for thicker materials (e.g., pipe wall thickness greater than 12.7 mm [0.5 in.] and/or heavy-wall fittings) and/or for lower ambient temperatures.

GB.6 Standards of Acceptability: Nondestructive Testing (Including Visual) See guidance provided in Section G9.

GB.7 Repair and Removal of Defects General requirements for repair and removal of defects are provided in Section 10. See guidance provided in Section G10. Excavation of defects in in-service welds should be limited to grinding only. Care should always be taken when grinding on an in-service pipeline to prevent an area of reduced wall thickness that is larger than what is appropriate for the operating pressure in the pipeline from being produced. Revision 1 – April 30, 2010

Guidelines for Interpretation and Application of API 1104

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