2014-12-05_WI-PFX-GRP-0001

Doc. N°: WI-PFX-GRP-0001

WORK INSTRUCTION

Rev.: 00

Date: 07/08/13

STRESS ANALYSIS OF GRP LINES Page: 1/22

WORK INSTRUCTION

STRESS ANALYSIS OF GRP LINES

WI-PFX-GRP-0001

07/08/13

00

Internal Use

BLO

Date

Revision

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Prepared by

Checked by

Approved by

Only the electronic version is updated, before any use the current version of this document shall be verified on the INTRANET network

This document is the property of the Company who will safeguard its rights according to the civil and penal provisions of the law. Model Ref. No. FORM-SSA-DSSM-001-E_5 Linked with GP-SSA-DSSM-001-E


WORK INSTRUCTION

Rev.: 00

Date: 07/08/13


INDEX INDEX..............................................................................................................................................................2 1.

SCOPE AND PURPOSE .........................................................................................................................3

2.

REFERENCE DOCUMENTS ...................................................................................................................3

3.

DEFINITIONS ..........................................................................................................................................3

4.

INTRODUCTION TO ISO 14692 ..............................................................................................................4

5.

GRP - GENERAL INFORMATION ...........................................................................................................5

6.

7.

5.1

JOINING SYSTEMS ............................................................................................................................5

5.2

FAILURES.........................................................................................................................................7 When, where and why do failures occur ............................................................................7

5.2.2

Some failures occur at fittings ............................................................................................7

5.2.3

Most failures occur at joints ...............................................................................................8

5.2.4

Why do joints fail? .............................................................................................................8

5.2.5

Steps to avoid failures .......................................................................................................8

DESIGN DATA ........................................................................................................................................9 6.1

MATERIAL PROPERTIES ....................................................................................................................9

6.2

PIPING DATA ..................................................................................................................................10

SUPPORTS ...........................................................................................................................................11 7.1

8.

5.2.1

SUPPORTS SPACING .......................................................................................................................11

STRESS ANALYSIS ..............................................................................................................................12 8.1

GENERAL .......................................................................................................................................12

8.2

STRESS ANALYSIS RESULTS ...........................................................................................................12

8.3

PRELIMINARY STRESS CALCULATION ................................................................................................12

8.4

CAESAR II ...................................................................................................................................15

8.5

8.4.1

Caesar II Configuration ....................................................................................................15

8.4.2

Special Execution Parameters .........................................................................................16

8.4.3

Piping input ......................................................................................................................17

8.4.4

Load Case options ...........................................................................................................21

MAXIMUM STRESSES ......................................................................................................................22



WORK INSTRUCTION

Rev.: 00

Date: 07/08/13


1. SCOPE AND PURPOSE The purpose of this work instruction is to define the general principles and the reference Codes and Standards that are applicable to the stress analysis verification of Glass Reinforced Plastic (GRP) piping. It provides information for the design, stress calculation and installation of GRP piping systems. 2. REFERENCE DOCUMENTS

Petroleum and natural gas industries – Glass-reinforced plastics (GRP) piping

ISO 14692

3. DEFINITIONS Anisotropic

Showing different properties when tested along axes in different directions.

Epoxy

Compound containing at least two epoxy or oxirane rings. Chemically, an epoxy ring is a three-membered ring containing two carbon atoms and one oxygen atom.

Failure

Condition caused by collapse, break, or bending, so that a structure or structural element can no longer fulfill its propose; in case of piping is the transmissions of fluid throughout the wall of a component or via a joint.

Fiber

Filamentary material with a finite length that at least is 100 times its diameter. Normally, filaments are not used individually and are assembled as twisted (yarn) or untwisted (tow) bundles composing hundreds of filaments.

FRP

Fiberglass Reinforced Plastic pipe - Term general for a plastic-based composite that is reinforced with any type of fiber, not necessarily glass.

GRE

Glass Reinforced Epoxy pipe - Epoxy resin-based composite that is reinforced with glass fibers.

GRP

Glass Reinforced Plastic - A thermosetting plastic based composite that is reinforced with glass fibers.

Liner

In a filament-wound component, the continuous resin rich coating on the inside surface, used to protect the laminate from chemical attack or to prevent leakage under stress.

LTHS

Long-Term Hydrostatic Strength

Mechanical joint

A joint between GRP piping components which has rubber gasket seals and does not require any bonding or lamination.

PTFE

Polytetrafluoroethylene

Topcoat

Equivalent to liner on the outer side



WORK INSTRUCTION

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Date: 07/08/13


4. INTRODUCTION TO ISO 14692 ISO 14692 is an international standard dealing with the qualification of fittings, joints and pipes. It describes how to qualify and manufacture GRP pipe and fittings and it gives guidelines for fabrication, installation and operation. The ISO 14692 consists of four parts: 

Part 1 : Vocabulary, symbols, applications and materials

This part gives the terms, definitions and symbols used. 

Part 2 : Qualification and manufacture

This part gives requirements for the qualification and manufacture of GRP piping and fittings. 

Part 3 : System design

This part gives the design guidelines. 

Part 4 : Fabrication, installation and operation

This part gives requirements and recommendations for fabrication, installation and operation of GRP pipe systems.



WORK INSTRUCTION

Rev.: 00

Date: 07/08/13


5. GRP - GENERAL INFORMATION 5.1

JOINING SYSTEMS

a) Conical-Cylindrical bonded joint This type of adhesive bonded joint consists of a slightly conical socket and a cylindrical spigot. This joint allows for an accurate assembly length with narrow tolerance and may be used for above- and underground pipe systems.

b) Taper/taper bonded joint The joint consists of a conical socket and a conical spigot. The adhesive is a two component epoxy resin system, packed in separate containers.



WORK INSTRUCTION

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Date: 07/08/13


c) Mechanical O-Ring Lock Joint The mechanical O-ring lock joint is a tensile resistant type of joint. This restrained type of joint can be used in unrestrained environments, e.g. aboveground.

d) Laminated joint The laminate joint is used to join plain-ended pipe sections. After preparation of the pipe surfaces, a specific thickness of resin impregnated glass reinforcement is wrapped over a certain length around the pipes to be joined; the thickness and the length of the laminate are related to diameter and pressure.



WORK INSTRUCTION

Rev.: 00

Date: 07/08/13


e) Flanged joint To enable connections with steel piping and to allow for easy assembling and disassembling of process lines. Glass fiber reinforced epoxy flanges are always flat faced and in view of this, matching flanges should also be flat faced. The flanged joint is completed by using a gasket.







5.2

FAILURES

5.2.1

When, where and why do failures occur

When o

Small part of the failures occurs during installation or operation

o

Most of the failures occur during hydro-testing (pressure testing)

Where o

Joints (most of the location)

o

Fittings : bends, tees, reducers

o

Plane pipe

Why o

Due to material defects

o

Defective installation (poor application of cement during installation)

o

Overloading of material due to shortcomings in design

5.2.2 

Some failures occur at fittings

Bends o

Molded bends (failures occur next to the bend)

o

Mitered bends (failures at the miter joints)



Tees (failures of the intersection)



Reducers



WORK INSTRUCTION

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Date: 07/08/13


5.2.3 

Most failures occur at joints

Types of joints o

Cemented joints

o

Laminated joints

o

Mechanical joints

5.2.4



Flanged joints



Lock joints

Why do joints fail?



Only small part of the joint failures are the result of material defection



Most joints failures are duo to:



o

Defective installation

o

Excessive loads (damages due to waterhammer, overloaded flanged joint due to external moments…)

Critical items in design o

Underestimation of load (proper prediction of loads)

o

Overestimate of joint capabilities (e.g. flanged joints)

o

Overestimate of system flexibility (prediction of flexibility)

5.2.5

Steps to avoid failures



Identification and assessment of specific critical items in GRP systems



Implement performance based codes



o

Design by analysis

o

Proper integration of material properties

o

Assessment of joint capabilities

Installation o

Verification of installation: as built conform design

o

Prior to Hydro-test



WORK INSTRUCTION

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Date: 07/08/13


6. DESIGN DATA MATERIAL PROPERTIES

6.1

Complicated mechanical properties of GRP pipe 

Orthotropic material o





Typical stiffness values o

Ec = 20 000 MPa (200 000 MPa for Carbon Steel)

o

Ea = 10 000 MPa

o

G = 9 000 MPa

High thermal expansion coefficient. o





Stiffness & strength properties in axial & circumferential direction are different

20 * 10E-06 mm/mm/°C (10 for Carbon Steel)

Typical design strength values o

Scircumferential = 70 MPa

o

Saxial = 35 MPa

SIF’s for fittings are different from metal



WORK INSTRUCTION

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Date: 07/08/13


6.2

PIPING DATA

The external diameter and minimum structural wall thickness shall be applied during GRP pipe stress analysis. Here below a typical sheet to be sent to the supplier at the beginning of the project and which has to be completed by him in order to have all information to perform final stress analysis. The template file is available here: Z:\PIPING_STRESS_PIP_PFX\TECHNIQUE\GRE\Work Instruction\GRE ISO14692 necessary DATA-rev1.xlsx GRE MATERIAL DATA SUMMARY FOR STRESS ANALYSIS CALCULATIONS USING CAESAR II SOFTWARE IN ACCORDANCE WITH CODE ISO 14692

Date

(A LL CELLS IN GREY SHA LL B E FILLED B Y SUP P LIER)

Supplier Material Type or Designation Product Commercial Designation Pipe Data Density Coefficient of Expansion Design Strain

Kg/m3 mm/m/°C %

Laminate Type

Axial modulus of elasticity Shear Modulus/Elasticity Modulus Shear modulus Ea/Eh*Vh/a Poisson's ratio Axial/Hoop Poisson's ratio Hoop/Axial Part factor f1 Part factor f2

Part factor f3 (Total) Long term hydrostatic strength Allowable design stress r (bi-axiale stress ratio) Short term axial strength at the 0 :1 condition Short term axial strength at the 2 :1 condition Long term axial strength at the 0:1 condition Long term axial strength at the 2:1 condition

Temp Ea Eh G

20

60

90

20

60

90

f1 f2 (sust.) f2 (therm) f2 (occ) f3 LTHS Sh r Sas (0:1) Sas (2:1) Sa (0:1) Sa (2:1)

Units 120 °C Mpa Mpa Mpa Mpa Mpa Mpa Mpa Mpa Mpa

Fittings Data: Laminate Type

r (bi-axiale stress ratio) (elbows & tees) Elasticity modulus Hoop and Axial Allowable design stress elbows Allowable design stress tees

Temp r Eh/Ea S elbow S tee

Units 120 °C Mpa Mpa



WORK INSTRUCTION

Rev.: 00

Date: 07/08/13


7. SUPPORTS 7.1

SUPPORTS SPACING

The supports shall be spaced to limit sag (< 6 mm). The span support is different from metallic piping systems. The maximum span lengths suggested for simply supported GRP pipes and full of water will be provided by Supplier. Heavy valves have to be supported independently from the pipe to avoid overloading in both horizontal and vertical directions and so reduce bending stresses on adjacent pipe.



WORK INSTRUCTION

Rev.: 00

Date: 07/08/13


8. STRESS ANALYSIS

8.1

GENERAL 

GRE/ GRP pipe expands due to pressure & temperature different from steel



Pipe/ Fitting dimensions and properties different from metal



GRE/ GRP pipe is orthotropic, axial and circumferential stiffness are different



GRE/ GRP systems require dedicated supporting

A stress analysis is required for systems listed below: 

Pipes > 6”



Pipes subject pressure surge, slug and two phase flow conditions



Pipes connected to sensitive equipment

8.2

STRESS ANALYSIS RESULTS

In the cases where the flexibility of the piping system under examination is found to be insufficient to absorb the imposed thermal expansion, the here below listed provisions shall be adopted, in the following order of preference: 

Changes in piping layout



Reinforcement of fittings (elbows / tees)



Installation of expansion joints

In case of underground GRE system, special care has to be taken with small branch connections. Sometimes, foam needs to be installed around small tees and part of the branch pipe to allow displacement.

8.3

PRELIMINARY STRESS CALCULATION

The information required for stress analysis, such as pipe wall thickness and external diameter, are provided by supplier. Nevertheless with no information at the beginning of a project, preliminary input data can be taken as a first approach. Thickness of GRE fittings can be estimated by taking 1.5 * pipe thickness. For GRP preliminary stress calculations, input data listed below shall be considered:

Material properties: Material selection in Caesar Corrosion Density

(20) FRP 0 mm 1.85 kg/dm3



WORK INSTRUCTION

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Date: 07/08/13


Pipe Data: Temperature (°C)

20

65

90

100

Axial modulus of elasticity : Ea (MPa)

10500

8950

8000

7550

Shear modulus : Eh (MPa)

20500

18100

16200

15375

Ea/Eh*Vh/a

0.33

0.32

0.32

0.32

Long term hydrostatic strength LTHS (MPa)

200

146

117

105

Allowable design stress Sh (MPa)

125

125

110

102

r: bi-axiale stress ratio

0.52

0.52

0.52

0.52

Short term axial strength at the 0:1 condition σas(0:1) (MPa)

65

Short term axial strength at the 2:1 condition σas(2:1) (MPa)

125

Long term axial strength at the 0:1 condition σal(0:1) (MPa)

32.5

32.5

28.6

26.5

Long term axial strength at the 2:1 condition σal(2:1) (MPa)

63

63

55

51

Temperature (°C)

20

65

90

100

r (elbows & tees)

1

1

1

1

Elasticity modulus Hoop and Axial : E (MPa)

20000

18000

16000

15000

Allowable design stress elbow Selbow (MPa)

80

80

70

65

Allowable design stress Tees Stee (MPa)

64

64

56

52

Fittings Data:

For other temperatures, the mechanical properties are calculated by interpolation.



WORK INSTRUCTION

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Date: 07/08/13


Stress envelop:

σal(0:1)) σal(1:1) σal(2:1)

Base

f2

32.5 63 63

0.67 0.83 0.89

SUS 0.67 22 42 42

OPE 0.83 27 52 52

OCC 0.89 29 56 56

σal(1:1) σal(2:1)

σal(0:1)

σhl(2:1)



WORK INSTRUCTION

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Date: 07/08/13


8.4

CAESAR II

The thicknesses used for stress analysis are mechanical thicknesses, it means that the liner and the top coat are not included. 8.4.1

Caesar II Configuration

The material properties are all overridden by Kaux – Special execution parameters or Caesar Input data. BS 7159 Pressure Stiffening: keep “Design Strain” as per Code. Exclude F2 From UKOOA bending stress: TRUE as per ISO 14692 (automatically TRUE if ISO 14692) Use FRP Flexibilities: Useful only in you have FRP with non-FRP-code calculation. (automatically TRUE if ISO 14692) Use FRP Sif: Useful only in you have FRP with non-FRP-code calculation. (automatically TRUE if ISO 14692)



WORK INSTRUCTION

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Date: 07/08/13


8.4.2

Special Execution Parameters



Enter the thermal expansion of the GRP pipe as per supplier pipe data.



Enter the FRP ratio Eh/Ea (as per supplier pipe data)



The FRP laminate type has to be filled in the Kaux or in the “bend type” input Textbox. For ISO 14692, the only choice is “3-CSM & Multi Filament”. WARNING: Empty value ≠ 3-CSM & Multi-Filament



WORK INSTRUCTION

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Date: 07/08/13


8.4.3

Piping input

σal(0:1) : Long Term Axial Stress at 0:1 Stress Ratio – Hoop stress is 0 at this point. σal(1:1) : Long Term Axial Stress at 1:1 Stress Ratio – σhl(1:1) = σal(1:1) σhl(1:1) : Long Term Hoop Stress at 1:1 Stress Ratio σal(2:1) : Long Term Axial Stress at 2:1 Stress Ratio - σhl(2:1) = 2 * σal(2:1) σhl(2:1) : Long Term Hoop Stress at 2:1 Stress Ratio Qs : Qualified Stress for Joints, Bends and Tees r : Bi-Axial Stress Ratio for Bends, Tees and Joints

A1 : Partial Factor for Temperature. As per ISO 14692-3 (§7.4.2), if the operating This document is the property of the Company who will safeguard its rights according to the civil and penal provisions of the law. Model Ref. No. FORM-SSA-DSSM-001-E_5 Linked with GP-SSA-DSSM-001-E


WORK INSTRUCTION

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Date: 07/08/13


temperature is less than or equal to 65°C, then A1 = 1. A2 : Partial Factor for Chemical Resistance. As per IOS 14692-3 (§7.4.3), if the normal service fluid is water, then A2 = 1. A3 : Partial Factor for Cyclic Service. Refer to ISO 14692-3 (§7.4.4) System design factor : The System Design Factor (SDF) is multiplied by the Occasional Load Factor (k) to generate the value of f2 (f2 = SDF * k), the Part Factor for Loading. By default the SDF is 0.67.

Loading Type

Load Duration

System Design Factor (SDF)

Occasional Load Factor (k)

Part Factor For Loading (f2)

Example of loading type

Occasional

Short-term

0.67

1.33

0.89

Hydrotest

Sustained Including Thermal Loads

Long-term

0.67

1.24

0.83

Operating

Sustained Excluding Thermal Loads

Long-term

0.67

1.00

0.67

Sustain

k : Thermal Factor. In the absence of further information, the thermal factor k should be taken as 0.85 for liquids and 0.8 for gasses



WORK INSTRUCTION

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Date: 07/08/13


Fittings - Bends

Different external diameter and thickness shall be specified for the bends (provided by the supplier). The laminate type affects the calculation of flexibility factors and stress intensification factors (only for BS 7159 and UKOOA codes). For ISO 14692 only type 3 filament wound laminate is considered.



WORK INSTRUCTION

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Date: 07/08/13


Fittings - Tees

Different external diameter and thickness shall be specified for the tees (provided by the supplier). Three types of tee are available in Caesar input (Tee, Qualified Tee, Joint). As per ISO 14692-3 (§D.2.3.4), if the tee is fabricated according to ISO, then specify “Qualified Tee” as type of tee (pressure stress multiplier will be equal to 1).



WORK INSTRUCTION

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Date: 07/08/13


8.4.4

Load Case options

Occasional load factor shall be noted. If they are equal to zero, the allowable loads will not be indicated in the output results files and will be equal to zero. By this way, CAESAR will put the occasional load factor to default values corresponding to the code, for example here with ISO 14692: 

1 * 0.67



1.24 * 0.67 = 0.83 for Operating Case



1.33 * 0.67 = 0.89 for Occasional Case

= 0.67 for Sustained Case

Note: If the GRE CAESAR file has been generated from a metallic pipe network CAESAR file, then the occasional load factors may be equal to zero, then no allowable stress will be calculated in the outputs. A way to avoid this, is to delete the file._J, then to rerun the CAESAR file and so a new file._J will be created with correct occasional load factor values.



WORK INSTRUCTION

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Date: 07/08/13


8.5

MAXIMUM STRESSES

LOAD CASES

Case N°

SUSTAINED (PIPE FULL) – WEIGHT+ DESIGN PRESSURE W+P1(+H)

7

WEIGHT (no contents) WNC+H

8

OPERATING At Tdesign max with Hull Deflection W+T1+D3+P1+H

2

OPERATING At Tdesign min with Hull Deflection W+T2-0.5D3+P1+H

3

OPERATING At Tdesign max W+T1+P1+H OPERATING At Tdesign min W+T2+P1+H OPERATING At Tmaxi ope W+T3+P1+H HYDROTEST (PIPE FULL) WEIGHT+HYDROTEST WIND X

WW+HP(+H)

11

U2

12

U3

13

D3

14

STRUCTURAL DEFL. DUE TO ACC. X D4

15

STRUCTURAL DEFL. DUE TO ACC. X D5

16

ACCELERATION Z HULL DEFLECTION (Sagging)

CONCENTRATED FORCE F1 ACCELERATIONS

17

U = √([U1] +[U2] +[U3] )

18

STRUCTURAL DEFLECTIONS 2 2 D = √([D4] +[D5] )

19

2

2

2

SUSTAINED + WIND X (W+P1(+H))+WIN 1

20

SUSTAINED + WIND Y (W+P1(+H))+WIN 2

21

SUSTAINED + OCC FORCE (W+P1(+H))+F1

22

SUSTAINED + ACCELERATION (W+P1(+H))+U

23

SUSTAINED + MAX DISPL. (W+P1(+H))+D

SOCC MPa

1

10

ACCELERATION Y

SSUS SOPE MPa MPa

6

WIN 2 U1

Allowable stresses

5

9

ACCELERATION X

Calculated stresses MPa

4

WIN 1 WIND Y

Node

24


Stress ratio

2014-12-05_WI-PFX-GRP-0001

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