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

WORK INSTRUCTION

STRESS ANALYSIS OF GRP LINES

Doc. N: WI-PFX-GRP-0001

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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

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WI-PFX-GRP-0001

07/08/13 00 Internal Use BLO

Date Revision Description of Revision 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

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INDEX

INDEX .............................................................................................................................................................. 21. SCOPE AND PURPOSE ......................................................................................................................... 32. REFERENCE DOCUMENTS ................................................................................................................... 33. DEFINITIONS .......................................................................................................................................... 34. INTRODUCTION TO ISO 14692 .............................................................................................................. 45. GRP - GENERAL INFORMATION ........................................................................................................... 5

5.1 JOINING SYSTEMS ............................................................................................................................ 55.2 FAILURES......................................................................................................................................... 7

5.2.1 When, where and why do failures occur ............................................................................ 75.2.2 Some failures occur at fittings ............................................................................................ 75.2.3 Most failures occur at joints ............................................................................................... 85.2.4 Why do joints fail? ............................................................................................................. 85.2.5 Steps to avoid failures ....................................................................................................... 8

6. DESIGN DATA ........................................................................................................................................ 96.1 MATERIAL PROPERTIES .................................................................................................................... 96.2 PIPING DATA .................................................................................................................................. 10

7. SUPPORTS ........................................................................................................................................... 117.1 SUPPORTS SPACING ....................................................................................................................... 11

8. STRESS ANALYSIS .............................................................................................................................. 128.1 GENERAL ....................................................................................................................................... 128.2 STRESS ANALYSIS RESULTS ........................................................................................................... 128.3 PRELIMINARY STRESS CALCULATION ................................................................................................ 128.4 CAESAR II ................................................................................................................................... 15

8.4.1 Caesar II Configuration .................................................................................................... 158.4.2 Special Execution Parameters ......................................................................................... 168.4.3 Piping input ...................................................................................................................... 178.4.4 Load Case options ........................................................................................................... 21

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

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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

ISO 14692 Petroleum and natural gas industries Glass-reinforced plastics (GRP) piping

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

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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.

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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.

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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.

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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

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5.2.3 Most failures occur at joints

Types of joints o Cemented joints o Laminated joints o Mechanical joints

Flanged joints Lock joints

5.2.4 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

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6. DESIGN DATA

6.1 MATERIAL PROPERTIES

Complicated mechanical properties of GRP pipe

Orthotropic material o Stiffness & strength properties in axial & circumferential direction are different

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

Typical design strength values o Scircumferential = 70 MPa o Saxial = 35 MPa

SIFs for fittings are different from metal

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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 SOFTWAREIN ACCORDANCE WITH CODE ISO 14692(ALL CELLS IN GREY SHALL BE FILLED BY SUPPLIER) Date

SupplierMaterial Type or DesignationProduct Commercial Designation

Pipe Data

Density Kg/m3Coefficient of Expansion mm/m/CDesign Strain %

Laminate TypeUnits

Temp 20 60 90 120 CAxial modulus of elasticity Ea MpaShear Modulus/Elasticity Modulus Eh MpaShear modulus G MpaEa/Eh*Vh/a -Poisson's ratio Axial/Hoop -Poisson's ratio Hoop/Axial -Part factor f1 f1 -Part factor f2 f2 (sust.) -

f2 (therm) -f2 (occ) -

Part factor f3 (Total) f3 -Long term hydrostatic strength LTHS MpaAllowable design stress Sh Mpar (bi-axiale stress ratio) r -Short term axial strength at the 0 :1 condition Sas (0:1) MpaShort term axial strength at the 2 :1 condition Sas (2:1) MpaLong term axial strength at the 0:1 condition Sa (0:1) MpaLong term axial strength at the 2:1 condition Sa (2:1) Mpa

Fittings Data:

Laminate TypeUnits

Temp 20 60 90 120 Cr (bi-axiale stress ratio) (elbows & tees) r -Elasticity modulus Hoop and Axial Eh/Ea -Allowable design stress elbows S elbow MpaAllowable design stress tees S tee Mpa

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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.

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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 (20) FRP

Corrosion 0 mm

Density 1.85 kg/dm3

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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 as(0:1) (MPa) 65 Short term axial strength at the 2:1 condition as(2:1) (MPa) 125 Long term axial strength at the 0:1 condition al(0:1) (MPa) 32.5 32.5 28.6 26.5 Long term axial strength at the 2:1 condition al(2:1) (MPa) 63 63 55 51

Fittings Data:

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

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

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Stress envelop:

Base f2 SUS 0.67 OPE 0.83

OCC 0.89

al(0:1)) 32.5 0.67 22 27 29 al(1:1) 63 0.83 42 52 56 al(2:1) 63 0.89 42 52 56

al(0:1)

al(1:1) al(2:1)

hl(2:1)

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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)

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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

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8.4.3 Piping input

al(0:1) : Long Term Axial Stress at 0:1 Stress Ratio Hoop stress is 0 at this point. al(1:1) : Long Term Axial Stress at 1:1 Stress Ratio hl(1:1) = al(1:1) hl(1:1) : Long Term Hoop Stress at 1:1 Stress Ratio al(2:1) : Long Term Axial Stress at 2:1 Stress Ratio - hl(2:1) = 2 * al(2:1) hl(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

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temperature is less than or equal to 65C, 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 DurationSystem

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

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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.

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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).

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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 = 0.67 for Sustained Case 1.24 * 0.67 = 0.83 for Operating Case 1.33 * 0.67 = 0.89 for Occasional 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.

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8.5 MAXIMUM STRESSES

LOAD CASES Case N Node Calculated stresses

MPa

Allowable stresses Stress ratio SSUS

MPa SOPE MPa

SOCC MPa

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

4

OPERATING At Tdesign min W+T2+P1+H

5

OPERATING At Tmaxi ope W+T3+P1+H

6

HYDROTEST (PIPE FULL) WEIGHT+HYDROTEST WW+HP(+H)

1

WIND X WIN 1 9

WIND Y WIN 2 10

ACCELERATION X U 1 11

ACCELERATION Y U 2 12

ACCELERATION Z U 3 13

HULL DEFLECTION (Sagging) D 3 14

STRUCTURAL DEFL. DUE TO ACC. X D 4 15

STRUCTURAL DEFL. DUE TO ACC. X D 5 16

CONCENTRATED FORCE F 1 17

ACCELERATIONS U = ([U1]2+[U2]2+[U3]2) 18

STRUCTURAL DEFLECTIONS D = ([D4]2+[D5]2) 19

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 24

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

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