FRP Pipe Failures & Lessons to be learnedPaulin Webinar April 2008

Scope of Webinar

Experience basis for present webinar

Part 1. Failures in GRP Pipe System a survey

Part 2. Measures to avoid failures.

The Role of system design & code compliance if any

Some details of System Design by Analysis

Nomenclature

Abbreviation

FRP

GRP

GRE

GRV

GRP

RTRP

Description

Fiber Reinforced Plastic pipe

Glass Reinforced Plastic pipe

Glass Reinforced Epoxy pipe

Glass Reinforced Vinyl Ester pipe

Glass Reinforced Polyester pipe

Reinforced Thermosetting Resin Pipe

50 Years Fiberglass pipe. A commodity?? Why Glass Reinforced Plastic - revisited

Corrosion Resistance (low maintenance costs)

Low weight (easy handling)

Low friction (low pressure loss)

Large flexibility (relatively low loads due to expansion)

Large variety in possible shapes

EXAMPLEGRP heat exchanger header box & pass partitionplates in corrosive conditions

Model Implementation

State of the art in Pressure-Diameter domain

Pressure-Diameter domain

0

10

20

30

40

50

60

70

80

90

100

0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000

Nominal Diameter [mm]

Des

ign

Pres

sure

[Bar

g]

.

Pipe wallload P*D=2700

2 examples of pressure pipes at the large bore side of the spectrum

3500mm cooling water 4000mm cooling water header

EXAMPLE

Variety of GRP pipes & fittings

Manufacturing process of pipe and fittingsHand Lay-up, contact moldedFilament wound

Winding angleCentrifugially castedWith and without filler (sand)

Resin systemsPolyesterVinyl esterEpoxy

Various curing agents

FRP pipe pressure versus diameter

Pipe type and Usage

0

10

20

30

40

50

60

70

80

0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000

Nominal Diameter [mm]

Des

ign

Pre

ssur

e [B

arg]

Epoxy U/G

Polyester, Vinylester &Epoxy, U/G & A/G

Polyester & Vinylester mostly U/G

Oil & Water long distance

Cooling Water

Fire water

Typical for GRP large variety of jointing systems

Tensile resistantFull pressure trust capability

Cement, lamination, mechanical lock joint, flangeApplication: U/G & A/G and in hybrid systems

Non-tensile resistantNo or only limited pressure trust capability

Double bell couplers, bell and spigot seal jointApplication: U/G & A/G in long straight pipe lines (with special supporting)

FRP pipe pressure versus diameter

Jointing systems

0

10

20

30

40

50

60

70

80

0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000

Nominal Diameter [mm]

Des

ign

Pre

ssur

e [B

arg]

Cemented & Laminated

Cemented, laminated, RSLJ, flanges, RSJ, double bell couplers

Double bell couplers & laminations

Drawback for still wider applications

Failures are blamed on the materialMetal pipe failures are blamed on (system) design, while fiberglass failures are blamed on the material

Confidence is shattered by failures

EXAMPLE

Complicated mechanical properties of GRE/GRP pipe

Orthotropic materialStiffness & strength properties in axial & circumferential direction are different

Typical stiffness valuesEc = 20.000 MPa (200.000 MPa for steel)Ea = 10.000 MPaG = 9.000 MPa

High thermal expansion coeff.20 * 10E-06 mm/mm/deg C (10 for C.S.)

Typical design strength valuesScircumferential = 70 MPaSaxial = 35 MPa

Stiffness bends (typical Kgrp = 5 * Ksteel

SIF’s for fittings are different from metal

Material PropertiesVariation for different suppliers (> 20%), Typical designs will be inaccurate

Lin. exp

Ecirc

Eaxial

Vax/circ

Vcirc/ax

Rho

Allowable

Parameter

20

20.500

11.500

0.65

0.38

1.85

43

Supplier 1 Supplier 2 Supplier 3 Supplier 4

18

25.000

11.000

0.56

0.37

1.85

26

22

17.000

8.000

0.69

0.39

1.55

34

25

20.000

11.000

0.35

0.20

1.85

28

Mm/mm/degC

MPa

MPa

1000 kg/cum

MPa

GRP-pipe systemsWhen, where and why do failures occur

WhenSmall part (<5%) of the failures occurs during installation or operationMost of the failures occur during hydro-testing (pressure testing)

WhereJoints (89%)Fittings (10%), bends, tees, reducersPlane pipe (1%)

WhyDue to material defects (<2%)Defective installation (49%)Overloading of material due to shortcomings in design (49%)

Plane pipe failures are rare

Flexible wall makes FRP sensitive to buckling due to vacuum

EXAMPLE

Some failures occur at fittingsTypes of fittings

BendsMolded bends (failures occur next to the bend)Mitered bends (failures at the miter joints)

Tees (failures of the intersection)Filament wound tees (typical d/D > 0.4)Contact moulded tees (typical d/D < 0.25)

Reducers

Typical failures adjacent to bend

Delaminated pipe

EXAMPLE

Tee failure during pressure testing

Pressure thrust (A/G)

EXAMPLE

Impact into pipe rack

Large elasticity of material results in large energy release during failure

Large tee failure during pressure testing EXAMPLE

EXAMPLEFailure of a contact molded tee during pressuretesting

Most failures occur at joints

Types of jointsCemented jointsLaminated jointsMechanical joints

Flanged jointsLock joints

Ideally no defective joints

Reality 0.1% (1 out of 1000) of installed joints show a defect as a result of manufacturing of the joint at site

Non destructive test methods are poorDefect only appear during hydro-test

EXAMPLECemented joint failure (defective joint)

EXAMPLEExcessive local compressive loads at a jointWall compressive crushing

EXAMPLECemented joint failurePoor application of cement during installation

EXAMPLEFlange failure immediately adjacent to bend

EXAMPLECemented Joint failure due to surge during testing

EXAMPLEMechanical joint (lock joint) failureDefective joint

EXAMPLEMechanical joint (lock joint) failure due to overloading

Why do joints fail?

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

Most joints failures are duo to:Defective installation (± 50%)Excessive loads (± 50%)

Almost always a result of shortcomings in design

Critical items in designUnderestimation of load (proper prediction of loads)Overestimate of joint capabilities (e.g. flanged joints)Overestimate of system flexibility (prediction of flexibility)

EXAMPLETypical example of failure due to unforeseenpressure thrustsubsea

EXAMPLEOverloaded joint failureWith large consequential damage due to waterhammer

EXAMPLENon tensile lock joint subject to part pressure thrustUnderground excessive lock load

EXAMPLEOverloaded flanged joint due to external moments

EXAMPLEOverloaded flanged manhole

EXAMPLEOverloaded laminated joint

Delaminated joint of water transportation system

EXAMPLEFailures due to errors in design

Failure due to undersized hold-down support

EXAMPLEHeader up-heave due to trench inundation

EXAMPLEFloating header due to insufficient soil cover

Steps to avoid failures – Subject of part 2 of the webinar

Identification and assessment of specific critical items in GRP systems

Implement performance based codesDesign by analysisProper integration of material propertiesAssessment of joint capabilities

InstallationVerification of installation: as built conform designPrior to Hydro-test