HOIS Good Practice Guide on In-Service Inspection of Offshore Composite Components

HOIS GP1 Issue 2

A Report prepared for HOIS

M Wall, RJ Lee, ESR Technology

martin.wall@esrtechnology.com

May 2012

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Authorisation Sheet

Report Title: HOIS good practice guide on in-service inspection of offshore composite components

Customer Reference: HOIS

Project Reference: UC000138-01-01-12

Report Number: HOIS GP1

Issue: Issue 2 Updated

Distribution List: Open Publication

Author: Dr Martin Wall

16/4/2012

Reviewed: Richard Lee

16/4/2012

Authorised: Dr Stephen Burch

2 May 2012

COPYRIGHT ESR Technology Ltd This report is the Copyright of ESR Technology Ltd and has been prepared by ESR Technology Ltd under contract to HOIS. Subject to the terms of the contract the contents of this report may not be reproduced in whole or in part, nor passed to any organisation or person without the specific prior written permission of the Commercial Manager, ESR Technology Ltd. ESR Technology Ltd accepts no liability whatsoever to any third party for any loss or damage arising from any interpretation or use of the information contained in this report, or reliance on any views expressed therein. Cover photo: UT inspection of offshore GRP joint, courtesy Petrobras

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Executive Summary This updated good practice guide covers the inspection and non-destructive evaluation (NDE) of offshore composite components in-service and includes lessons learnt from several inspection trials on HOIS FRP samples including the glass reinforced flow loop pipe sample supplied by Petrobras. Specifically this guide excludes manufacturing quality control, quality assurance or inspection, for which the reader is referred to ISO 14692. All components that form part of a GRP piping system (e.g. pipe, branches, bends, tees, tapers, flanges, fittings and joints) are covered. This includes piping, from 50 mm (2) to over 1 m (40) diameter, and fittings. Specific guidance is provided on composite connections including adhesively bonded joints, laminated joints and flanged connections. Fittings include T-joints, bends, branches and flanged connections and may typically be manually overwound or laminated giving a wide range of wall thickness, 2 mm to 50 mm. The guide encompasses the recommendations regarding NDE of composites in available standards including ISO 14692, NORSOK M-622, preceding NORSOK and UKOOA studies, and relevant API and ASTM standards. Good practice has been included from individual oil companies design and engineering specifications, HOIS members inputs, and ESR experience in composite inspection. Relevant published studies and initiatives in the UK funded by the Department for Business, Innovation & Skills (formerly the Department of Trade & Industry) and the Technology Strategy Board, TSB have been cited. In addition, a watching brief of technologies employed in the USA on inspection and monitoring of composites have also been assessed. We have restricted consideration to defect types that may occur in-service or be present after installation. It is assumed that an appropriate inspection and quality control plan has been in place during manufacture including monitoring the state of cure in line with that in ISO 14692. Composite vessels and tanks are not specifically included as there is limited use of these offshore. The recommendations regarding process pipework inspection will however generally be applicable to vessels and accessibility is often better. Secondary structures such as ladders, walkways, gratings, and equipment housings are not included. The major issue here is removal of the protective gel coat in marine environments, exposing fibres. Visual inspection and painting or refurbishment of the gel coat is usually adequate here. The inspection methods considered for pipework applications may also be relevant to these applications if the application is safety critical. Although this guide refers to offshore components, it is equally relevant to onshore applications and in several cases the techniques used would be similar. Inspection of GRP piping is generally more difficult to carry out compared to metal pipes for a number of reasons. This includes general unfamiliarity by inspectors of inspecting composites and the anisotropic and heterogeneous nature of these materials causing signal noise and attenuation. Porosity and the laminated nature of the microstructure account for some of these effects. This guide has been updated to take account of lessons learnt from a series of inspection trials conducted under the auspices of the FPSO and Flexible Risers Working Group on a 6 GRE spool piece (flow loop) prepared by Petrobras. The flow loop contained a number of intentional bondline defects including paper inserts, incorrect application of adhesive and incorrect surface preparation. The 3 metre flow loop contains two 90-degree elbows and a

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centre bell and spigot bonded joint with five separate adhesive joints. Some of these joints had manufacturing or adhesion defects introduced in the assembly process. Differences in joint fabrication practice have also been used in the joints. Data obtained using manual ultrasonics were somewhat variable but were generally able to detect the back wall echo but not necessarily the deliberately introduced defects. Automated ultrasonics using either twin probes or phased arrays produced reasonable B-scan images showing the layered nature of the material and in some cases reflections from the introduced defects. Interpretation of reflected signal waveforms was more complex than would be expected for steel components as the GRP structure is elastically anisotropic and heterogeneous with signal attenuation due to voids/porosity and the scattering nature of the laminated structure. It was sometimes difficult to get a consistent back wall echo with some variability in response between joints. The inspection operators will need to familiarise themselves with particular glass reinforced epoxy components and choose optimum probe type. Ultrasonic B-scan images are the preferred acquisition mode as they can give a clearer delineation of bond line defects and back wall echo. Generally the lower frequency probes ( MHz - 2 MHz) gave better sample penetration than 5 MHz probes but with reduced resolution. Phased array wheel probes were relatively quick to scan the pipe surfaces but had some positional difficulties around elbows and fittings due to roller sliding. Of the various non contact inspection methods trialled, i.e. laser shearography, microwave inspection and radiography, the latter technique produced the best images using the XRS-3 portable pulsed X-ray source used in conjunction with a GEIT DXR250P digital detector array. In this case some details of the joints were revealed including bondline defects such as porosity (however there was no evidence of the paper inserts) and good images of the pipe wall and fittings. After the inspection trials were completed the flow loop was cut open and macro-photographs were taken of joint sections to reveal the location and extent of the defects. In many cases the joint defects were lack of adhesive and porosity. The quality of the elbow end fittings was also assessed and showed evidence of poorly wetted out fibres which was detected during several ultrasonic trials. A section of the centre bell and spigot joint was prised open, as recommended by a consultant from the pipe manufacturer, to reveal the quality of the bond. In summary, each of the inspection trials had practical challenges and most techniques were able to detect some of the defects. Ultrasonic inspection was able to detect loss of back wall echo, bondline features and end fitting irregularities. Radiographic examination using digital detectors together with image enhancement filters was able to reveal pipe wall and end fitting details, bondline porosity and quality of adhesive fillet but not gaps in the adhesive bond.

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Contents

1.0 SCOPE ........................................................................................................... 1

2.0 REASONS FOR INSPECTION ....................................................................... 3

3.0 BACKGROUND .............................................................................................. 4 3.1 Introduction ................................................................................................. 4

3.2 Requirements for Non-Destructive Evaluation (NDE) .................................. 4

3.3 Factors affecting inspection ......................................................................... 5

3.4 Materials ..................................................................................................... 6

3.5 Applications................................................................................................. 6

3.6 Fabrication methods .................................................................................... 7

3.7 Issues during installation ............................................................................. 7

3.8 Issues in-service ......................................................................................... 7

3.9 Life prediction .............................................................................................. 9

3.10 Painting ....................................................................................................... 9

3.11 Lined vessels and pipework ........................................................................ 9

4.0 REFERENCES ............................................................................................... 9 4.1 GRP Design, Qualification and Integrity Standards ..................................... 9

4.2 NDE Codes and Standards ....................................................................... 10

4.3 NDT Procedures ....................................................................................... 10

4.4 HSE good practice guides ......................................................................... 11

5.0 DEFINITIONS ............................................................................................... 11

6.0 PERSONNEL QUALIFICATIONS ................................................................ 13 6.1 Installer requirements ................................................................................ 13

6.2 NDT personnel .......................................................................................... 13

7.0 EQUIPMENT ................................................................................................ 13

8.0 HEALTH AND SAFETY ............................................................................... 13 8.1 Inspection ................................................................................................. 14

8.2 Dust hazards ............................................................................................. 14

9.0 DAMAGE MECHANISMS ............................................................................ 14 9.1 Overview ................................................................................................... 14

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9.2 Manufacturing defects ............................................................................... 15

9.3 Defects following handling and installation ................................................ 15

9.4 In-service defects ...................................................................................... 15

10.0 INSPECTION STRATEGY ........................................................................... 16 10.1 Manufacturing inspection .......................................................................... 17

10.2 Documentation required ............................................................................ 17

10.3 Handling and delivery ................................................................................ 18

10.4 Inspection after installation ........................................................................ 18

10.5 In-service inspection ................................................................................. 21

10.6 HSE good practice guides ......................................................................... 22

10.7 DNV guidance for operation and in-service inspections ............................ 23

10.8 Inspection strategy for life extension and ageing ....................................... 23

10.9 When to Inspect ........................................................................................ 26

11.0 SELECTION OF NDE METHODS ................................................................ 26 11.1 Manufacturing inspection .......................................................................... 33

11.2 After installation ........................................................................................ 33

11.3 In-service .................................................................................................. 33

12.0 INSPECTION PRACTICE BY COMPONENT............................................... 33 12.1 Pipework ................................................................................................... 36

12.2 Fittings ...................................................................................................... 38

12.3 Supports ................................................................................................... 38

12.4 Joints ........................................................................................................ 39

12.5 Adhesively bonded joints........................................................................... 40

12.6 Laminated joints ........................................................................................ 42

12.7 Flange connections (fixed and loose ring designs) .................................... 44

12.8 Repairs ..................................................................................................... 45

13.0 INSPECTION GUIDANCE BY DEFECT TYPE ............................................ 45 13.1 Delaminations ........................................................................................... 45

13.2 Erosion or loss of wall thickness ................................................................ 47

13.3 Impact damage ......................................................................................... 48

13.4 Matrix cracking .......................................................................................... 49

13.5 Significant cracks ...................................................................................... 51

13.6 Materials degradation ................................................................................ 52

13.7 Environmental ingress and weepage (matrix cracking and delamination) .. 53

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14.0 NDE METHODS ........................................................................................... 53 14.1 Validation and calibration samples ............................................................ 53

14.2 Visual inspection ....................................................................................... 55

14.3 Pressure testing ........................................................................................ 56

14.4 Ultrasonics ................................................................................................ 57

14.5 Radiography.............................................................................................. 62

14.6 Tap testing ................................................................................................ 65

14.7 Thermography ........................................................................................... 67

14.8 Shearography ........................................................................................... 69

14.9 Acoustic emission ..................................................................................... 71

14.10 Acousto-Ultrasonics .................................................................................. 72

14.11 Microwave inspection ................................................................................ 73

14.12 Differential Scanning Calorimetry (DSC) and hardness tests (e.g. Barcol or Shore) ....................................................................................................... 76

15.0 MONITORING METHODS ............................................................................ 76

16.0 DEVELOPING NDE METHODS ................................................................... 77

17.0 EVALUATION AND ASSESSMENT ............................................................ 78

18.0 FAILURE PREVENTION .............................................................................. 80

19.0 ACKNOWLEDGEMENTS ............................................................................ 80 Appendices

APPENDIX A GRP CODES AND STANDARDS................................................ A-82

APPENDIX B INSPECTION GUIDANCE FROM ISO 14692 .............................. B-85

APPENDIX C DAMAGE MECHANISMS IN COMPOSITES .............................. C-97

APPENDIX D EXAMPLES OF IN-SERVICE DEGRADATION OF COMPOSITE COMPONENTS ......................................................................... D-110

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1.0 Scope

This good practice guide covers the inspection of offshore composite components in-service and after installation. The focus is on inspection of low to medium pressure process pipework (~10-50 bar), the primary application of composites offshore. This good practice guide specifies additional and optional requirements to ISO 14692 (all parts). All components that form part of a GRP piping system (e.g. pipe, branches, bends, tees, flanges, and joints) are covered. The good practice is directed towards piping systems in GRP materials used on offshore production platforms, but may also be used for similar onshore systems dependent on the location and fabrication method. Composite materials in the context of this good practice guide are defined as, and limited to, fibre reinforced thermosetting matrix (or resin) systems. These have several features that make them attractive for use in the Oil and Gas industry, namely ease of installation, light weight and good corrosion resistance. Glass fibres are the most common reinforcement and epoxy resins are primarily used as the matrix material. Other types of resins can be used depending on the application and in many cases corrosion resistant liners are used which may affect the inspection results obtained. Conventional inspection strategy and practice is described. In addition, this document provides guidance on selection and how to apply non-destructive examination (NDE) and testing (NDT) methods; an area where very limited guidance is available in existing standards such as ISO 14692. Newer NDE methods such as microwave inspection, acousto-ultrasonics, tap-testing, ultrasonic B-Scan and laser shearography are also included in addition to those found in the main industry standards ISO 14692, NORSOK M622 and the ASME Boiler and Pressure Vessel Code Section V. Such methods are widely used elsewhere for inspection of composites and are starting to find application in the Oil and Gas sector. All components that form part of a GRP piping system (e.g. pipe, branches, bends, tees, tapers, flanges, fittings and joints) are covered. This includes piping, from 50mm (2) to over 1m (40) diameter, and fittings. Specific guidance is provided on composite connections including adhesively bonded joints, laminated joints and flanged connections. The guidance is applicable both to high quality filament wound pipework, and to piping systems that have been manufactured by manual overwinding or hand laminated giving variability in thickness and surface quality. Wall thicknesses ranging from 2mm to 50mm are considered. Higher wall thicknesses are generally associated with fittings or connections. Inspection of GRP piping is generally more difficult to carry out compared to metal pipes for a number of reasons. This includes general unfamiliarity by inspectors of inspecting composites and the anisotropic and heterogeneous nature of these materials causing signal noise and attenuation. Porosity and the laminated nature of the microstructure account for some of these effects. This document is directed towards GRP piping and components used topside on offshore production platforms, but may also be used for similar onshore systems. The same technologies have applicability to subsea, downhole and pipeline applications of composites, though there will be issues in terms of access and marinisation if carried out in-situ. The following generic component types have been considered in the development of the NDE recommended practice:

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Process pipework and fittings Filament wound piping 2 to 40 diameter, 2mm to 50mm wall thickness; Tapered, laminated or moulded fittings, t-joints (5mm to 50 mm wall thickness). Connections Adhesively bonded joints; Laminated joints; Flange connections (fixed and loose ring designs). These encompass most currently relevant topside components offshore. This good practice guide does not specifically cover composite vessels and tanks as there is limited use of these offshore. The recommendations regarding process pipework inspection will however, generally be applicable to vessels and accessibility is often better. Established practice has developed for inspection of lined and unlined GRP vessels and tanks in refineries using ultrasonic B-scanning and TOFD in addition to visual inspection. The guide encompasses the recommendations regarding NDE of composites in available standards including ISO14692, NORSOK M-622, preceding NORSOK and UKOOA studies and relevant US standards such as API, ASME and ASTM. Elements of good practice have also been included from individual oil companies design and engineering specifications together with inputs from various HOIS members and ESR general experience in composite inspection. Relevant published studies and initiatives in the UK funded by the UK Government such as the former DTI and the Technology Strategy Board; in the USA on inspection and monitoring of composites; and aerospace, defence, military and space standards have also been assessed. We have restricted consideration to defect types that may occur on installation or in-service. It is assumed that an appropriate inspection and quality control plan has been in place during manufacture including monitoring the state of cure in line with that in ISO 14692. The NDE technology discussed could also be applied to structural beams, pultruded sections and secondary structures such as ladders, walkways, gratings, and equipment housings. The major issue here is removal of the protective gelcoat in marine environments, exposing fibres. Visual inspection and painting or refurbishment of the gelcoat is usually adequate here. The inspection methods considered for pipework applications may also be relevant to these applications if the application is safety critical. For structural components such as beams an appropriate life management strategy should be put in place in line with ISO 14692 and relevant ASTM standards. Thermoplastic polymers and reinforced thermoplastics (RTPs) are outside the scope of this guide, although the same NDE methods are likely to be applicable. Resins commonly used in RTP include polyethylene (PE), polypropylene (PP), and polyamide (PA-Rilsan) and polyvinyldifluoride (PVDF). In many cases visual inspection is the only method used for composite components after they enter service and provided the system design accounts for all anticipated loadings (including thermal and axial loads, pressure and surge forces, etc.) and they are installed correctly can provide many years of service often in severe corrosive environments.

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2.0 Reasons for inspection

Integrity management of composite materials is less developed than for metallic materials. This tends to be application specific and relies on engineering judgement. Problems are most likely to be encountered during or after installation. If properly installed, composite components are normally very tolerant of service conditions and few problems are likely to occur during the design life (typically 20-25 years). Hence, it is usual to apply just visual inspection and routine pressure testing after installation. Non destructive evaluation (NDE) methods may be applied in the following circumstances:

For safety critical components;

For quality assurance reasons;

Following installation;

Where problems have been encountered in service;

For re-qualification following any repairs;

To assess quality of adhesive joints;

To establish current condition of the component and ageing encountered;

To assess in-service damage;

To assist in assessment of remnant life;

For plant life extension;

If required for health and safety reasons or to satisfy legal or regulatory requirements;

To establish condition of the lining in lined vessels;

To determine condition relevant parameters such as glass transition temperature tg, Barcol hardness or coupon testing;

To verify that the component is performing in accordance with its design intent;

As part of an integrity management strategy;

Identify deviations from specifications or functional requirements as early as possible and form a basis for corrective action.

The role of inspection is to assure technical integrity during operations and form a basis for maintenance evaluation/planning. It may also serve to provide a fitness-for-purpose evaluation and contribute to the improvement of current and future designs and inspection strategy. Composites are becoming used in an increasing range of structural and process applications, and at higher pressures and more severe environments. For this reason NDE in-service is becoming more common.

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3.0 Background

3.1 Introduction

Fibre reinforced plastic (FRP) composite materials are seeing increased use in the Oil and Gas industry. Composite materials have been used in chemical, processing and refinery applications for over 40 years primarily in containment applications. The first application in the North Sea was in the early 1980s1

. Corrosion resistance, light weight and in some cases design flexibility and continuous manufacture are the primary business drivers, which when used to advantage in design, can lead to either reduced life-cycle costs or improved safety. There are also advantages in ease of fabrication, mechanical and chemical properties and cost.

Composites are fundamentally different to metallic materials, and provided the correct resin and fibre types have been selected and the components are properly installed and qualified, few issues are normally encountered in service. Particular problems may be encountered with adhesive joints especially those made in the field. Material selection in corrosive environments is a specialist area and end users are reliant on service experience and advice and ratings supplied by the main composite suppliers.

3.2 Requirements for Non-Destructive Evaluation (NDE)

The application of non-destructive evaluation (NDE) methods on composites is primarily undertaken on manufacture. Currently, very little in-service NDE inspection is performed on composites on offshore installations. Composites are traditionally conservatively designed to allow for in-service damage and based on previous experience. Reliance is placed on proof testing following installation with visual inspection and dimensional checks. Whether this is the best approach in the longer term remains to be established. NDE in-service is often more difficult and less widely done.

Installation of composite components is not always straightforward and service difficulties can often be traced back to incorrect installation. There is also an increased use of composites in more structural applications and in more severe environments. For these reasons, it is becoming more important to understand the degradation that may occur in material properties in service and to confirm that installation has been effective.

Composites offer particular advantages in weight and corrosion resistance for floating installations such as floating production storage and offloading vessels (FPSOs). Minimising topside weight is a key issue for floating installations. Applications of composites in FPSOs include water treatment, firewater mains and secondary structures.

FPSOs can also offer a more challenging environment due to hull motion and movement of the vessel under wave loading. This can lead to a specific requirement for in-service NDE of composites due to issues that have arisen in offshore service. This includes the fatigue of longer pipe sections under wave loading of the vessel in FPSOs, cracking of pipe flanges following installation, and failure of adhesively bonded connections.

The lack of detailed procedures and qualification of NDE methods for offshore may limit the uptake of composites in more challenging process applications offshore.

1 HSE research Report RR039 Cost Effective use of composites offshore; Part B: Summary of the Joint industry - industry programme on the cost effective use of fibre reinforced composites offshore. UK Health & Safety Executive HSE; HSE Reports, 2003 http://www.hse.gov.uk/RESEARCH/rrhtm/rr039.htm

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3.3 Factors affecting inspection

The main factors affecting inspection of composites offshore are access, surface finish, material quality, complex geometry and thickness. These and other factors such as unfamiliarity with composites may limit the applicability of traditional NDE methods such as ultrasonics and favour composite or polymer specific methods such as microwave inspection, thermography, acoustoultrasonics or radiography for complex geometries and thick sections. An advantage is the fact that composites generally have good defect tolerance and fatigue properties. The way in which NDE methods are applied is similar to metallic materials though the types of defects that may be present are different. Delamination and disbonding are the most important defects compared to cracking in metallic materials. Composites are damage tolerant and can support a significant amount of damage compared to steel where an individual fatigue crack can become critical and lead to failure. Composite materials by their construction and diverse methods of fabrication pose some physical challenges and benefits to inspection as some are transparent or translucent. Their mechanical properties are generally anisotropic (in many cases they are orthogonally anisotropic, i.e. orthotropic) due to the methods of lay-up and the different properties of polymer and reinforcement. Surface roughness is generally higher than would be expected for a metallic pipe and hence there may be difficulties in probe coupling. Composite materials are usually more highly attenuating than steel and lower frequencies are used when inspecting using ultrasonics. There are differences associated with individual NDE methods. Visual inspection can show up a wider range of defects in composites. With suitable illumination it is possible to look through some composite components to see internal defects. Ultrasound is more highly attenuated by composites due to the many internal interfaces and porosity so it is normally necessary to use lower frequencies. The surface finish can also pose difficulties in coupling. Common electromagnetic methods such as eddy current and magnetic particle inspection, MPI, are not applicable to glass-fibre reinforced epoxy (GRE) composites as the materials are non-conducting. Composites are less absorbing of X- or gamma- rays so it is necessary to use lower energy sources or less penetrating isotopes. Thermal diffusion is slower than in metals which simplify thermography inspection. Long wavelength methods such as microwaves which would cause reflection on metal surfaces are well suited to polymers and composites because of their dielectric properties and better match of wavelengths to microstructural differences. Similarly surface strain measurements such as laser shearography are easier because of the lower stiffness and the ease of distortion of composites compared to metals. Composite components are often painted for cosmetic or protective reasons. This may be for pipe identification and also provide some additional protection against ultra-violet rays (UV) or from the external environment. A consequence is that it is no longer possible to inspect the component visually using internal illumination, a standard method. In this case detection and monitoring of service damage may be more difficult.

On FPSOs process equipment can be more closely packed than on conventional platforms making access for NDE difficult.

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3.4 Materials

The composite materials used in the offshore industry are primarily glass fibre reinforced plastic (GRP) which can be used in tanks, vessels or piping systems. A variety of glass fibre types and resins may be used dependent on environment and conditions. The primary fibre used is glass, although carbon and aramid are used in limited applications. The primary resin system (thermosetting) used is epoxy or polyester, although vinyl esters, polyurethanes and furanes are also used to a limited extent. The method of manufacture is predominantly filament winding implying continuous fibre composites, although some components are pultruded, resin transfer moulded or made by hand lay-up.

3.5 Applications

Composites are used in an increasing range of applications, Figure 1. Off-shore applications are diverse and include pipework, e.g. fire water mains systems, water injection systems, and access structures. Generally speaking, the major use of composite components offshore is in pipework and containment applications. The most commonly used composite structure is filament wound glass fibre reinforced thermosetting plastic matrix (GRP) pipe, often epoxy, polyester or vinyl ester. Typically, these GRE pipes range in diameter from 50 to 4000 mm. Pressure ratings range from 5 to 120 bar, the higher pressure ratings only applicable to smaller pipe diameters. The primary applications of composites within the Oil and Gas industry include:

piping systems; process equipment; access equipment (stairs, gratings); beams; modules and secondary structures; tubing and casings; tanks and vessels; lifeboats; risers; pipelines; mudmats; protective covers.

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Figure 1 Example of GRP pipework offshore. Left, water treatment and firewater mains

GRP components, Petrobras P50 FPSO (Courtesy Petrobras); right, GRP firewater mains.

3.6 Fabrication methods

Commercial grade composites in these industries are normally produced by filament winding, with increased use of moulding processes such as resin transfer moulding (RTM). Manual overlay, lamination or moulding is used on filament wound pipe in the tapered regions associated with nozzles, flanges, manifolds and attachments.

3.7 Issues during installation

Correct handling and installation is important for composite components. There is a risk of surface or impact damage. Adequate supports are required for pipework, in accordance with the guidance in ISO 14692. Care is needed in preparation of adhesive and laminated joints to ensure good alignment, clean surfaces and adequate distribution and curing of adhesive. A common issue for flanged joints is over-tightening leading to overstressing of joints and flange cracking. The integrity and leak tightness of piping systems is usually verified by pressure testing. Composite pipework is normally subjected to thorough inspection and acceptance criteria at the manufacturing stage in accordance with ISO 14692. There is the likelihood that some manufacturing flaws, usually benign, may carry through to service in the nature of the fabrication methods used.

3.8 Issues in-service

Composites do not corrode in the conventional sense but can be subject to a number of degradation mechanisms in-service, including: physical ageing, mechanical ageing and chemical ageing. The consequence of these can be a reduction of 20 - 40% or greater in the strength characteristics of the polymer during the lifetime of the component and introduction of damage including matrix cracking and delaminations. This is handled in design codes by use of regression curves based on short term and longer term (typically 1,000h and 10,000h) tests to determine the qualification pressure for the component and the allowed operating pressure over the design life. There is concern about whether such methods of life assessment are sufficiently robust, given the increasing diversity of applications in which composites are applied. In contrast to steel vessels or pipework, where non-destructive methods such as ultrasonics, electromagnetics and radiography are widely applied, very little inspection other than visual

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inspection or pressure testing is currently undertaken on composite components in the offshore, chemical, process and petrochemical industries. Limited guidance on in-service NDE methods for composites is included in offshore GRP standards notably ISO 14692 (currently under revision) and NORSOK M-622. These provide general guidance on NDE methods that may be applicable but limited information on the practical application of the methods. Moreover there has been significant development of newer NDE methods in other industries, such as aerospace and marine, which do not feature in these current standards. There is a need to assess the potential benefits of these methods in offshore applications and to provide a more rigorous recommended practice to guide their application.

There are limitations in the testing methods used in ISO 14692 and ASTM standards to estimate the regression curve or degradation that may occur with ageing in service. Most studies are in water rather than organic solvents or the other fluids that are seen in service. Tests are also expensive to run (ASTM D2992 asks for data up to 2 years) thus the lack of widespread usage of these tests in environments aside from water. Recent developments have been to use 1,000h tests as a shorter term alternative to confirm long term properties. Immersion testing rather than single-sided exposure mechanisms may cause mass gain as well as loss; so single-point data is of limited use in prediction of longer term degradation. Service components suffer environmental degradation from the surfaces; hence the degradation seen in immersion tests may be worse than seen in practice2. Most ageing studies accelerate ageing by testing for a shorter time (~1,000h) at a more elevated temperature. Small temperature increases above the service temperature but below the resin glass transition temperature (Tg) can offer useful indications of long term behaviour3

. However, if the mechanisms encountered over the longer term differ to those in the accelerated tests the degradation curves and predictions of remnant life obtained may be unrepresentative.

A diversity of environments can be encountered in the oil, gas and process industries. These can cause damage to both matrix and the fibres. It is important that the resin and fibre types are correctly selected for the application to maximize the resistance in service. In Oil industry applications a corrosion resistant layer (or veil) containing more resistant fibres and gel coat is commonly applied to the surface. Similar practice may be used in chemical applications. Such layers are effective at preventing environmental damage but are relatively thin (~200um). It is important to confirm on visual inspections that excessive grazing of the gel coat has not occurred and that damage has not occurred to these protective layers. Areas of pipe bends, variations in wall thickness, support or change in geometry are particularly susceptible to damage or degradation in composite systems. These may encounter local stress concentrations and care is needed in design to ensure these can adequately support the operating pressures of the piping or vessel and that the allowance made in regression curves for ageing is sufficient. Composites are more susceptible to impact damage than conventional materials, but also exhibit a good tolerance. In most cases this is benign and repairable, though may affect residual life. Significant impact damage can produce immediate weepage and partial loss of containment. It is important that impact damage is identified and repaired if necessary. For all these reasons, more application of NDE methods in-service would be beneficial. 2 Ageing of composites in oil and gas applications, S Frost; Ageing of Composites, Ed. Rod Martin, Chapter 14 p 375-395, Woodhead publishing, ISBN 978-1-84569-352-7, 2008 3 ISO/TS 24817 Petroleum, petrochemical and natural gas industries- Composite Repairs for pipework-Qualification and design, installation, testing and inspection; 2006

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3.9 Life prediction

In the onshore and offshore Oil and Gas industries a more robust approach is developing2 to life prediction and extension, based on materials characterisation and non destructive evaluation of the actual damage in service components. This offers to improve the accuracy of life prediction and reduce the risk of premature failure. There would be benefits in extending such good practice more widely in the offshore and onshore industries.

3.10 Painting

External painting is not required since GRP is not subject to atmospheric corrosion. If painting is necessary for other reasons, the surface should be lightly blast-cleaned before the paint system is applied and painting should be carried out after inspection and test of the component. Painting is detrimental to inspection as it impedes visual inspection methods particularly where internal illumination is used.

3.11 Lined vessels and pipework

In chemical and onshore processing applications, pressure vessels and piping are often lined with polyethylene or other resistant polymers. Most GRP pipework offshore is unlined. There are particular issues for lined or painted GRE vessels or pipework. If a lining is used then a compromise may be made on the resin and fibres used in the GRE vessel. These may not be as resistant as would be used if the GRE was exposed to the environment. It is important in this case to monitor the lining condition since lining failure could lead to degradation and failure of the GRE vessel in a shorter timescale than might typically occur for an unlined vessel exposed to the same environment.

4.0 References

The following codes and standards have been considered and have been referred to in this good practice guide. The latest issue of the references shall be used unless otherwise agreed. Other recognized standards may be used provided it can be shown that they meet or exceed the requirements of the standards referenced below.

4.1 GRP Design, Qualification and Integrity Standards

ISO 14692-1, Petroleum and natural gas industries Glass-reinforced plastics (GRP) piping BS EN ISO Part 1: Vocabulary, symbols, applications and materials.

ISO 14692-2, Petroleum and natural gas industries Glass-reinforced plastics (GRP) piping BS EN ISO Part 2: Qualification and manufacture.

ISO 14692-3, Petroleum and natural gas industries Glass-reinforced plastics (GRP) piping BS EN ISO Part 3: System design.

ISO 14692-4, Petroleum and natural gas industries Glass-reinforced plastics (GRP) piping BS EN ISO Part 4: Fabrication, installation and operation.

Det Norske Veritas Offshore Standard; DNV-OS-C501, Composite components, January 2003.

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NORSOK STANDARD M-622 Fabrication and installation of GRP piping systems Rev. 1, April 2005 (Replaces M-621 and M-622 (1999), based upon ISO 14692 (all parts), but extended with sections on quality control and NDT).

ASME BPVC Section X Fibre-reinforced plastic pressure vessels, The American Society of Mechanical Engineers.

4.2 NDE Codes and Standards

ASTM D2563 Standard Practice for Classifying Visual Defects in Glass-Reinforced Plastic Laminate Parts.

EN 473 Non-destructive testing Qualification and certification of NDT personnel General principles.

ASTM E1067 Standard Practice for Acoustic Emission Examination of Fiberglass Reinforced Plastic Resin (FRP) Tanks/Vessels.

ASTM E1495 02 Standard Guide for Acousto-Ultrasonic Assessment of

Composites, Laminates, and Bonded Joints.

ASTM E2191 - 08 Standard Practice for Examination of Gas-Filled Filament-Wound Composite Pressure Vessels Using Acoustic Emission.

ASTM E2832 Standard Practice for Active Thermography of Composite

Panels in Aerospace Applications.

ASTM E2582 - 07 Standard Practice for Infrared Flash Thermography of Composite Panels and Repair Patches Used in Aerospace Applications.

ASTM D 2563 Standard Practice for Classifying Visual Defects in Glass-Reinforced Plastic Laminate Parts.

ASTM WK 12737 Standard Practice for Shearography of Flat Panel Sandwich Core Materials Used in Aerospace Applications.

4.3 NDT Procedures

The following procedures have also been developed but have not reached full standards recognition:

DRA/NPL Working Draft Standard v05, Fibre Reinforced Plastics Ultrasonic C-scan inspection of composite structures: Parts 1-6, National Physical Laboratory & QinetiQ Ltd.

Aker Recommended Practice on radiography of GRP offshore.

Offshore generic ultrasonic procedure (ESR, DTI CPD4D).

Ultrasonic A-scan and B-scan procedures (ESR, DTI CPD4D).

Ultrasonic C-scan procedure (ESR, DTI CPD4D).

Active thermography procedure (ESR, DTI CPD4D).

Laser shearography procedure (ESR, DTI CPD4D).

Ultrasonic TOFD practice GRP vessels (ESR, Sonomatic).

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Escape craft NDT procedures (Amerada Hess and others).

4.4 HSE good practice guides

Concise good practice guides have recently been produced by HSE on FRP pipe and composite overwrap repairs. Designed for HSE inspectors, these provide simple summaries on what can go wrong, damage mechanisms and normal inspection practice (based on ISO 14692). Photographs are included showing damage mechanisms. The latter included advice from members of the Association of Composite Repair Suppliers AcoRes originally formed by ESR Technology.

HSE GRP pipe fact sheet, Health and Safety Laboratories HSL; Final draft Revision 1, 2009.

FRP composite repair fact sheet, Health and Safety Laboratories HSL; Draft Final, 2009.

5.0 Definitions

For the purposes of this practice document, the following terms, definitions and abbreviations apply in addition to those in ISO 14692 Part 1.

E-glass Glass fibre normally used to reinforce GRP pipes, consisting mainly of SiO2, Al2O3 and MgO.

ECR or C-glass Glass fibre or synthetic veil having a better chemical resistance against acids than E-glass, used primarily as reinforcement for the resin-rich internal liner.

Fittings Pressure-tight fluid containing components with geometry different from straight pipe (e.g. flanges, tees, elbows, reducers etc.).

Hand lay-up A process for fabricating a composite structure in which discontinuous reinforcements (woven mats, chopped strand mats) are impregnated with a matrix material and are manually applied on a mandrel.

In-field hydrostatic test Short term hydrotest after installation, used as a leak test. Defined as 1.5 times the system design pressure.

Mill hydrostatic test Short term hydrotest at the mill (or factory), used as a quality control check. Defined as 1.5 times the nominal pressure rating.

Phenolic A class of polymer resins made from phenol and formaldehyde, and cured by air drying or heat baking. Chemical resistance can be further increased via heat and catalyst treatment.

Pipeline system Pipe with components subject to the same design conditions and typically used to transport fluids between wells and field facilities, field facilities and processing plants, processing plants and storage facilities.

Piping components Mechanical elements suitable for joining or assembly into pressure-tight fluid containing pipeline or piping systems. Components include bends, reducers, tees, flanges, gaskets, bolting, valves, and devices such as expansion joints, flexible

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joints, pressure hoses, liquid traps, strainers and in-line separators.

Piping system Pipe with components subject to the same design conditions and typically used within a processing facility. The piping system also includes pipe supports, but does not include support structures.

Regression curve Decay curve based on short and long term testing at the design stage to show the predicted degradation in materials properties and safe operating pressure during the design life of the GRP component (See ISO 14692 for use and derivation).

R-Glass Glass fibre having a better chemical stability than E-glass in high pH environments.

S-Glass Glass fibre having a higher strength than E-glass and considerably more expensive than E-glass.

The following abbreviations are used:

DN Nominal diameter

DSC Differential scanning calorimetry

DWSI Double wall single image

ECR Glass fibre grade with good chemical resistance in acidic environment

EX Classification of explosion hazards

FRP Fibre reinforced plastic

GRE Glass-fibre reinforced epoxy

GRP Glass-fibre reinforced polyester

GRVE Glass-fibre reinforced vinylester

HSE Health and Safety Executive (U.K.)

MAWP Maximum Allowable Working Pressure

MW Microwave

NDE Non-destructive evaluation

NDT Non-destructive testing

NPD Norwegian Petroleum Directorate

PE Pulse echo

PED Pressure Equipment Directive

RT Radiographic testing

UT Ultrasonic testing

TT Transient thermography

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6.0 Personnel qualifications

6.1 Installer requirements

All pipe, fittings and related items shall be installed by qualified GRP pipe fitters and thereafter approved by a qualified GRP piping inspector. GRP pipe fitters and GRP piping inspectors shall be qualified according to the minimum requirements detailed in Annex D of ISO 14692 Pt 4. As an alternative, the pipe fitters, supervisors and inspectors maybe qualified in accordance with another internationally recognised certification scheme based on acceptance by the company.

6.2 NDT personnel

NDT Personnel should be qualified in accordance with a recognised international code and standard such as EN 473. It is recommended that all personnel carrying out visual or NDE inspection of GRP components have appropriate certification (ASTM, CSWIP etc) for the NDE method and specific experience in the inspection of GRP components. Routine inspections may be carried out by a Level I inspector with Level II supervision. More sophisticated NDE methods such as transient thermography or shearography should be undertaken by a specialist practitioner in the NDE method, preferably with at least Level II certification. NORSOK M622 recommends that ultrasonic inspectors shall be qualified according to EN 473, Level 2 or equivalent. Additionally, they shall also have had specific training for GRP pipe joints in the ultrasonic test method to be used. Within Europe, NDT inspectors of joints in piping systems falling into category III and IV (equipment/vessels) according to PED, shall be approved by a 3rd party organisation recognised by an European Union (EU) member state.

7.0 Equipment

The NDE equipment to be used for the inspection shall be portable and rugged enough for the intended service. Equipment intended for laboratory use will normally not be suitable for field use. In particular moisture is detrimental. If outdoor testing is performed, the necessary precautions shall be taken to protect the equipment from rain, wind etc. Most offshore platforms have EX 1 zones in which no electric equipment that can produce sparks is allowed. The operator of the NDE equipment shall ensure that the equipment to be used fulfils the EX requirements, or obtain special permission from the safety department on board to execute the inspection in special zones, in shutdown periods, etc.

8.0 Health and Safety

In general, all safety precautions set forth by the manufacturer of pipes and fittings, chemicals, etc., shall be adopted. Materials safety data sheets should always be read before

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commencing work. The installer shall follow the health and safety guidance given in Annex F of ISO 14692 Part 4.

8.1 Inspection

In general, all safety precautions relevant to the NDE method being deployed should be followed as in the test procedure. Individual NDE methods such as radiography, shearography, thermography or microwave inspection will have their own specific safety requirements.

8.2 Dust hazards

During machining of GRP, a dust mask and adequate work clothing should be worn in order to prevent inhalation of, or skin irritation by, the glass-fibre dust produced. Machining should be done in a well-ventilated room or in the open air in order to minimize contact with dust. In the workshop a portable dust extraction unit should be used with the point of extraction as close as possible to the work.

9.0 Damage mechanisms

9.1 Overview

Composite components are subject to ageing by a number of processes which can reduce the strength and properties of the pipework. This includes physical ageing, mechanical ageing and chemical ageing. These are normally allowed for in design through regression curves, encompassed in relevant design standards such as ISO 14692. A detailed overview of damage mechanisms in composites can be found in Appendix C. Physical ageing processes include moisture ingress, swelling and plasticization common with other polymeric components. These processes are referred to as static fatigue. Mechanical ageing refers to the development of defects during service including matrix cracking, delaminations and impact damage. Chemical ageing refers to environmental processes that change the chemical structure or bonding within the component and therefore degrade its physical properties; this includes hydrolysis, and modification of bonding or cross linking. These ageing processes apply equally to adhesive as well as the composite resin and result in a change in the glass transition temperature tg and properties. In its broadest definition ageing can be defined as the reduction in performance of a component as a function of the applied conditions. The three primary causes of ageing for composite components in the Oil and Gas industry are through chemical species ingress, elevated operating temperature and length of time of load application. Service experience in the Oil and Gas sector is that damage to the composites from ingress of the environment (internal or external) is minimal and does not significantly affect materials properties. Progressive damage may occur under service loadings by matrix cracking, the normal response of composite materials to loading. For process pipework the main service risk is weepage of the process fluid eventually leading to failure of component. The other failure mode of concern is fibre failure. Generally, this occurs at the ultimate load-bearing capacity of the composite component and results in gross failure. The ageing process accelerates the failure process, be it increasing the density of micro-cracks, affecting the glass transition temperature Tg, changing the physical properties of the matrix, or reducing the strength of fibres.

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Offshore GRP components in-service are designed so that the loading is insufficient to cause fatigue or stress corrosion cracking. Fatigue can be relevant in aged components or in new designs due to inadequacies in the design or variations in loading beyond that allowed for. There is experience of fatigue cracking of GRP piping in FPSOs where longer pipe lengths have been used than normal. Defects can occur in either the GRP material or in the mechanical and/or adhesive-bonded joints that make up the piping system. Joint defects, including defects in prefabricated pipe spools, are more likely to occur than defects in the GRP material, provided QA procedures are followed during manufacture, handling and delivery. Care is needed in the preparation and assembly of adhesive joints as well as recognition of the degradation and ageing of the adhesive bond that will occur in service. Other relevant mechanisms include impact damage, disbonding, flange cracking, erosion, cavitation and environmental ingress.

9.2 Manufacturing defects

The possible causes of manufacturing flaws, and an overview of NDE techniques suitable for detecting these defects, are summarized in the Tables in ISO 14692 and NORSOK M-622 together with acceptance criteria. These tables are included in Appendix B. Manufacturing and handling defects are outside the scope of this guide except insofar as they carry over into the service component and affect service life or the properties in service.

9.3 Defects following handling and installation

Defects that can potentially occur during handling and installation are summarised in ISO 14692 Pt. 4, Table 4, (see Appendix B). The main issues of concern to operators are impact damage and problems with adhesive joints. Defect types include the following:

Impact wear or abrasive damage;

Barely visible impact damage (BVID);

Incorrect curing of adhesively bonded or laminated joint;

Misaligned joints;

Defects in adhesive bond (disbond, kissing bonds, lack of adhesive, excess adhesive);

Flange cracks and leaks;

Residual manufacturing flaws.

9.4 In-service defects

The relevant in-service defects for which NDE inspection is considered in offshore vessels, tanks, process pipework and fittings are as follows:

Ageing, materials degradation;

Matrix cracking;

Delamination;

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Disbonding;

Weepage (matrix cracking and delamination);

Impact damage;

Fatigue;

Fibre failure;

Erosion or wall loss;

Cavitation;

Significant cracks;

In lined pipework or vessels the possibility of liner damage or disbonding should also be considered.

10.0 Inspection Strategy

The operator shall define an inspection strategy for the GRP systems and components to identify system criticality and the requirements for inspection. This shall cover:

manufacturing control and following installation;

detection of in-service damage;

detection of damage due to accidental loads or overloads at all stages;

detection of damage due to unexpected high degradation of long term properties.

Inspection shall be linked to possible failure modes and mechanisms identified in the design or experienced on installation or in-service. The strategy shall at least contain:

the items to be inspected, arranged according to their order of importance;

the parameters to look for and or measure, e.g. cracks, delaminations, impact damages, overheating (or damages from local burning), visible overloading (bending, unintended use), discoloration;

methods of inspection to be applied for each item;

inspection frequency;

acceptance criteria;

reporting routines. Guidance on the development of an inspection strategy for GRP components can be found in ISO 14692 Part 2 Annex H, which groups components for inspection in terms of criticality, probability of failure and consequences. This is referred to below and the relevant Tables are reproduced in Appendix B. NORSOK M-622 includes additional and optional requirements beyond that provided in ISO 14692 as well as a specific and different grouping for pre-fabricated pipe spools and adhesive joints. The Operator should specify which grouping method is being followed. Specific guidance on inspection for other reasons, such as life extension, defect detection or due to service reasons is provided later in this Section.

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In projects where more than one set of Regulatory Authorities' rules apply or several contractors are involved, only one inspection strategy and one common inspection programme shall apply for the GRP piping system.

10.1 Manufacturing inspection

The possible causes of manufacturing flaws, and an overview of NDE techniques suitable for detecting these defects, are summarized in the Tables in ISO 14692 and NORSOK M-622 together with acceptance criteria (See Appendix B). Manufacturing processes used to produce fittings are typically more complicated and less automated than those used to manufacture pipes. The manufacturing problems which may occur tend, therefore, to be more prevalent in the fittings, and NDE of fittings should be prioritised. Manufacturing and handling defects are outside the scope of this guide except insofar as they carry over into the service component and affect service life or the properties in service.

10.2 Documentation required

All relevant as-built drawings and records shall be available and maintained. It is recommended that as a minimum these include the following details:

pipe nominal diameters and pipe wall thicknesses; key layout dimensions; location of supports/restraints; fire classification and location of fire-rated pipe, if applicable; conductivity classification, location of conductive pipe, location of earth-grounding

points, earth continuity requirements, frequency and method of inspection. The supplier shall provide the installer with the following information, which shall include but not be limited to: a) Operating and Design parameters:

design pressure; design temperature; Tg of the resin used in component manufacture; Tg of the adhesive used in component manufacture (if appropriate); qualified pressure of each component and minimum qualified pressure in each

piping system; mean and maximum velocity conditions in each piping system; chemical resistance limitations, if applicable; procedures to eliminate or control water hammer and cavitation, if applicable; fire classification and location of fire-rated pipe, if applicable; conductivity classification, location of conductive pipe, earth linkage/grounding

requirements and location of earthing points; criticality.

b) System drawings and support requirements for heavy equipment;

c) Preferred locations for connection of final joint in pipe loops, if appropriate;

d) System criticality and minimum requirements for inspection during installation.

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The dimensions of the components and spools shall be available for the installer and operator. The quantity, qualified pressure, nominal dimensions, and relevant special requirements of all piping components and prefabricated spools shall be verified for compliance with the purchase order. Shipments of piping components not complying with the purchase order shall be reported to responsible personnel and to the pipe producer for corrective actions.

10.3 Handling and delivery

The installation of composite structures shall be carefully planned. It shall be part of the design analysis. Handling composite structures like metal structures may introduce severe damage. Any aspects of handling that deviates from typically practice with metal structures should be identified. Procedures should be in place to describe special handling requirements for composites. Handling of composite structures requires special care. Handling instructions should follow each component. Point loads should be avoided. Scraping, wear and tear should be avoided. Bending the structure into place should be avoided. Lifting shall only be done at specially indicated spots that were designed to take such loads. Inspection requirements after installation are covered in Sections 5.1 and 5.2 of ISO 14692. This part of ISO 14692 assumes that the fittings and pipes have been correctly manufactured and inspected according to the criteria given in ISO 14692-2. The handling of the GRP components shall follow the guidelines given in Annex B of ISO 14692 Part 4 and the requirements of the pipe manufacturer. All piping components shall be visually inspected in accordance with Table A.1 of ISO 14692 Pt. 4 for damage that may have occurred during storage and shipment. Rejected components shall be replaced. If doubts concerning the extent of defects occur during inspection, a specialist approved by the operator shall perform a second inspection of the delivered items. Upon arrival at site the packaging shall be checked visually for possible transport damage. Vessels should be handled and stored in the original packing for as long as possible to avoid possible damage. The vessel shall be inspected after unpacking. External surface cracks (e.g. caused by the hydrostatic pressure test, transport or storage) shall not exceed Level III of ASTM D2563. All piping components shall as far as possible be installed so that they are stress-free. Therefore:

bending of pipes to achieve changes in direction, or forcing misaligned flanges together by over-torquing bolts is not permitted;

the manufacturers recommendations for bolt-torquing sequence, torque increments and maximum bolt torque shall be followed.

All installation activities shall be verified independently for high safety class components. Whether the verification shall be done by the manufacturer himself, by the customer, or by a third party should be decided by the project.

10.4 Inspection after installation

Traditionally, most GRP piping applications have been inspected visually and the quality assessed by pressure testing prior to commissioning. Once commissioned no further inspection has been performed.

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This approach has generally functioned well and it is anticipated it will remain. Some difficulties with this approach have been noted when GRP has been applied offshore. Current limitations associated with inspection of GRP pipe and piping systems include:

over-reliance on system pressure testing, occasionally contributing to inadequate quality control of the system during various stages of manufacture, material receipt on site and installation;

visual inspection criteria being overly subjective (i.e. photographic standards for piping applications have not been readily available);

pressure testing occurring at a late stage in construction which may limit access and make any necessary repairs difficult and costly.

The following routine quality assurance/control measures are intended to help in ensuring that GRP piping systems are installed without problems. A suggested inspection strategy for GRP piping systems after installation, which considers system criticality and availability/ accessibility, is illustrated in Figure 2 taken from NORSOK M-622 (1999). This should be used as the basis for developing an appropriate specific strategy for a particular installation. The limitations noted above are addressed by:

Highlighting key quality control activities;

Emphasising visual inspection in accordance with NORSOK M-622 Annex A;

Identifying the (limited) circumstances when system design pressure testing may be replaced with various combinations of additional NDT and functional testing at operating pressure.

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Figure 2 Inspection Strategy for manufacture and installation of GRP piping and tank

systems based on flowchart in NORSOK M622

Piping or Tank system to be

inspected

QC to Standard by Supplier (1), Pre-

Fabricator (2), Installer (2)

Is system critical?

(3)

Are QC findings acceptable

(9)?

Visual Inspection (5)

Functional Test (8)

Visual Inspection (5)

Pressure test per Standard

(6)

System Acceptance

Visual Inspection (5)

Additional NDT (7)

Inspection Findings

Acceptable? (10)

Functional Test (8)

Is system available/ testable?

(4)

No

Yes

Yes

Yes

No

No

Yes

Fail, Replace, Redesign

Fail, Replace, Redesign

No

Pass

Pass Fail

Fail

Pass

Fail

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Notes to Figure 2 1. Includes 100% hydrostatic pressure testing at a frequency to be defined. 100% visual

inspection should be performed.

2. Certified personnel shall be appointed for fabrication and installation. 100% visual inspection recommended.

3. System is critical if failure can result in: Injury to personnel; operational shutdown with unacceptable economic consequences (Examples: fire water delivery system, some cooling water systems). System is non-critical if System is non-critical if: acceptable functionality is maintained even if most likely failure modes occur; operating pressure is much lower than system design pressure (examples: open drains, some cooling water systems).

4. System is ready available for testing if it is: physically accessible; not prohibitively expensive to prepare for pressure testing (i.e. blinding off joints, blocking deluge nozzles, etc.)

5. Visual inspection shall be done on 100% of system in accordance with Annex A.

6. Full system hydrotest in accordance with ISO 14692.

7. Other NDT methods applied as appropriate (see ISO 14692 Pt. 4 or Appendix B). NDT to be performed on at least: 10% of joints 250 mm diameter, 25% of joints > = 250 mm diameter; and all field joints.

8. Pressure testing per ISO 14692 to be replaced by a leak test at operating pressure.

9. Supplier and prefabrication testing frequencies may be reduced for non-critical systems, however at least 10% of all testable components shall be tested. QC findings are acceptable if there is no risk that system safety or function will be compromised.

10. Inspection QC findings are acceptable if there is no risk that system safety or function will be compromised.

10.5 In-service inspection

The objective of this section is to provide guidance on development of an inspection strategy and the requirements for operation and in-service inspections. In case of findings at the inspections, a plan should be worked out listing suggested actions to be taken, depending on the type of findings. The plan may be included in the inspection strategy. GRP piping systems shall be inspected at regular intervals, in accordance with the inspection strategy, to ensure that the piping system is in a satisfactory state consistent with its continued operation. This strategy shall be documented and communicated to the qualified inspectors and NDT personnel responsible for the equipment and system. The selection of an inspection programme should be based on a thorough evaluation of the consequences of failure. Assessment of the likelihood and severity of failure should be based on parameters such as previous experience, material properties, design of process units, operating process conditions, etc. Guidance on the development of an in-service inspection strategy is given in the flow charts in Figure 3 and Figure 4. Figure 3 shows the development of an inspection strategy in accordance with Annex H of ISO 14692 Pt. 4. Figure 4 gives guidance on development of an inspection strategy where inspection is carried out for other reasons; for example where damage has occurred in service, for defect detection, or for life extension.

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A system is non-critical if:

Failure will not result in injury to personnel; Failure will not result in unacceptable economic consequences; Acceptable functionality is maintained even if the most likely failure modes

occur; The operating pressure is significantly less than nominal design pressure,

e.g. the system includes open drains, cooling-water systems. A system is considered ready and available for pressure testing if it is: physically accessible; and not prohibitively expensive to prepare for pressure testing (i.e. blinding off joints, blocking deluge nozzles, etc.). In projects where more than one set of Regulatory Authorities' rules apply or several contractors are involved, only one inspection strategy and one common inspection programme shall apply for the GRP piping system. Unless there are other specific reasons for carrying out NDE inspection, it is recommended the in-service inspection strategy for the GRP components shall be developed in accordance with the guidance given in ISO 14692 Pt. 3 Annex H and Tables H.1. and H.2. (see Appendix C). Table H.1 gives suggested inspection programmes based on the likelihood of defects or degradation occurring and the criticality of the system. The interactions between materials and process conditions should be considered when selecting condition-monitoring methods. This entails a comprehensive materials engineering evaluation that considers the most probable failure/degradation mechanisms and defects. Equipment shall be classified into Inspection Groups (A-D) given in Annex H of ISO 14692 Pt. 3 based on equipment classification (or criticality), probability of failure, and severity (consequence) of failure. The selection of NDT methods and inspection intervals shall take account of the recommendations for the Inspection Group given in Table H.2. Suggested inspection intervals are given in Table H.2. It is recommended that an initial selection of NDE methods for use in detecting defects which are most likely to occur during operation of GRP piping systems is made using the Tables in ISO 14692 Pt.4 Table 4 along with the recommended acceptance criteria. Possible causes and recommended corrective actions are also included. Relevant non-destructive testing (NDT) methods should be selected if possible, bearing in mind the possibilities and limitations of each method. A combination of several methods may be required in order to achieve safe and cost-effective utilization of the equipment/ system. Since ISO 14692 was issued a number of new NDE methods have become established. More detailed guidance on Selection of NDE methods encompassing these new methods is given below in Section 11.0.

10.6 HSE good practice guides

Concise good practice guides4,5

on inspection of GRP pipe and FRP composite overwrap repairs have been produced by HSE. The latter includes advice from members of the Association of Composite Repair Suppliers AcoRes, originally formed by ESR Technology.

4 HSE GRP pipe fact sheet, Health and Safety Laboratories HSL; Final draft Revision 1, 2009 5 FRP composite repair fact sheet, Health and Safety Laboratories HSL; Draft Final, 2009

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In each case, the fact sheet provides guidance to inspectors on what can go wrong, the types of damage to look for in offshore pipework and the inspection methods that are recommended in ISO 14692. This includes a useful 1 page Summary of issues at the end for inspectors conducting site inspections, with photographs of relevant damage mechanisms. Relevant advice is also given on joints and fittings. Photographs are included showing damage mechanisms.

10.7 DNV guidance for operation and in-service inspections

DNV Standard DNV-OS-C501 provides general guidance on structural integrity assessment of composite components to demonstrate fitness for purpose in cases where deviations from the originally intended design appear during operations. In Section 12 of DNV-OS-C501 an inspection philosophy for integrity assessment of composite components is developed which defines the requirements for operation and in-service inspections. It is noted that, once the component is commissioned, an inspection philosophy for the component should be established and the philosophy shall at least contain:

Items to be inspected, arranged according to their order of importance (criticality rating);

Parameters to look for and or measure, e.g. cracks, delamination, impact damage, overheating (or damage from local burning), visible overloading (bending, unintended use), discoloration, etc.;

Methods of inspection to be applied for each item; Inspection frequency; Acceptance criteria; Reporting routines.

It is also noted that in the case of inspection indications, which may be false calls or genuine defects, a plan should be executed listing suggested actions to be taken depending on the type of findings. The plan may be included in the inspection philosophy. Inspection procedures shall be defined for:

Manufacturing control; Detection of damage due to accidental loads or overloads; Detection of damage due to unexpected high degradation of long term properties.

Inspection shall be linked to possible failure modes and mechanisms identified in the design.

10.8 Inspection strategy for life extension and ageing

The inspection programmes in Table H.2 of ISO 14692 Pt 3 include the use of destructive testing of material samples to characterize long-term material degradation under the most aggressive operating conditions, and as a justified means to extend GRP equipment past its rated life. Such material samples should be representative of the equipment in-service, i.e. by testing a pipe sample removed from service, or by testing coupons which have been exposed to the same media and stress levels that are seen in service. If the initial materials engineering evaluation indicates that destructive tests are required, the same test methods as those used to pre-qualify the material should be used. More guidance on the assessment of ageing is given in Section 13.6 below. The Tables from ISO 14692 referred to above are reproduced in Appendix B.

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Figure 3 Inspection Strategy for in-service inspection of GRP piping and tank systems

taking account of guidance in Annex H and Tables H.1. and H.2. of ISO 14692 Pt 3.

Piping System, Vessel or Tank system to be

inspected

Classify System by Criticality, Probability of Failure and Severity according to Table

H.1 of ISO 14692 Pt/ 3

Inspection Group in ISO 14692 Table

H.1.?

Visual Inspection internal/ external at

intervals of 0.3 x service life. First

inspection after 1-2 years

Inspect according to the relevant Group A, B or C

in Table H.2 of ISO 14692 Pt/ 3

System assumed OK for continued service

No

A-C

Inspect as Group D in Table H.2 of ISO

14692 Pt/ 33

Destructive testing of relevant components

or NDE to assess current condition and

potential for life extension

Defects Found?

D

Service life beyond original

estimated service life?

Visual inspection internal/ external

Identify degradation

mechanisms and suitable NDE

NDE Inspection

Yes

Assess defects. Replace, Repair

Define next inspection interval

Modify or change inspection group. See ISO 14692 pt. 3 Table H2?

Yes

No

Define new operating life and /or

safe operating pressure

Reason for inspection?

To satisfy ISO 14692

Follow Flow Chart in Table for non

ISO 14692 Inspections

Other

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Figure 4 Inspection Strategy for in-service inspection of GRP piping and tank systems for

life extension, damage detection or other reasons (Non ISO 14692 Pt. 3 inspections).

Piping System, Vessel or Tank system to be

inspected

Identify relevant damage mechanisms

Select suitable NDE methods

System assumed OK for continued service

Defects Found?

Visual inspection internal/ external

NDE Inspection

Assess defects. Replace, Repair

Define next inspection interval

Modify or change inspection group.

See ISO 14692 pt. 3 Table H2?

Yes

No

Compare with initial regression curve (ISO 14692)

Reason for inspection?

To satisfy ISO 14692

Follow Flow Chart in Table for ISO 14692

Inspections

Defect detection, Other

Remove selected components for

destructive testing or carry out NDE

Life Extension

Assess and define new operating life

and /or safe operating pressure

(ISO 14692)

Accessible for inspection?

Yes

No

Estimate actual regression in

condition

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10.9 When to Inspect

GRP piping systems are often used in systems that are not safety-critical and which may be classified as ANSI/ASME B 31.3 Category D systems requiring no inspection. However, these systems can be crucial in maintaining uninterrupted production. Therefore, the choice of when to inspect is largely an economic question. Unless there are specific reasons to inspect more frequently, it is recommended that the guidance in ISO 14692 Pt 3, Annex H referred to above is used to define inspection frequency. This will be dependent on the group (A-D) defined in Annex H for the component. The probability and consequences of system failure must warrant the added cost of inspection. For prefabricated pipe spools or adhesive joints the guidance on inspection timing and grouping of components according to criticality in Table 3 of NORSOK M622 (2005) may be followed as an alternative. The specific guidance in NORSOK M622 (2005) is as follows: The GRP piping systems shall be inspected within the first year (group 2 and group 3 systems) and within the second year (group 1) after start of service. The inspection interval thereafter shall be 1 year to 2 years for group 2 systems and group 3 system and 3 years for group 1 systems. The inspection intervals shall be adjusted, i.e. reduced or increased depending on observed severe degradation or gained confidence in materials and construction. An increase of inspection intervals can be considered after 5 years of service. Destructive testing is required if the service life is extended beyond the originally estimated service life. Economic and risk considerations will not only determine whether a GRP system is inspected at all, but also whether it should be periodically inspected while in service. A suggested, reasonable balance between costs and benefits of inspections is that both non-critical and critical piping systems should at least be visually inspected within 1-2 years after start of service. Following this the frequency of inspection should be according to the developed strategy. To ensure satisfactory operation of GRP pipework and vessels over a period of years, periodic inspections shall be performed to check that the GRP material is sound. This inspection shall include connections and branches to the wall, bottom corner, supports and the inner liner, if present. Although visual inspection is the most common method of inspection, other non-destructive techniques such as ultrasonics and radiography are being developed with increasingly reliable results. During inspection, damage to surfaces should be avoided by suitably covering footwear and ladders. Cleaning processes shall be checked to ensure that the internal or external protective surfaces will not be damaged or destroyed by incorrect application.

11.0 Selection of NDE methods

The choice of NDE method which is practically applicable to a given component will depend on a number of factors including the access, wall thickness and surface conditions. Available inspection methods may not detect all critical failure mechanisms. However, the methods may detect preceding failure mechanisms. A link between detectable failure mechanisms and critical failure mechanisms shall be established. The reliability and functionality of all inspection methods should be documented.

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In many cases a complete inspection programme cannot be developed due to the limited capabilities of available NDE equipment. In that case the following alternatives taken from the DNV OS 501 guidance may be used:

Inspection of components during or right after manufacturing may be replaced by well documented production control.

Inspection to detect damage due to accidental loads or overloads may be compensated for by monitoring the loads and comparing them to the design loads.

Effect of higher degradation than expected can be compensated for by using the failure type brittle in the long term analysis. If this method is used the component must be replaced or re-evaluated after all overloads or other events exceeding the design requirements. This approach shall be agreed in advance.

If the failure mechanisms are not fully understood, or competing failure mechanisms are present and one is uncertain about their sequence, inspection is required.

Since ISO 14692 was issued in 2002 a number of new NDE methods have become established for inspection of composites such as microwaves, shearography and acousto-ultrasonics. The guidance in Tables 4 and 5 of ISO 14692 Pt. 4 forms a basis for the initial selection of NDE methods. However, the recommendations on NDE are general, do not define the specific NDE method to be used (for example stating ultrasonics), and do not encompass more recent developments. For this reason it is recommended that Table 1 and Table 2 below are used for selection of suitable NDE methods. In these Tables the advice in ISO 14692 Pt 4 has been updated to take account of other potential NDE methods that are now available. For specific defect types Table 12 of ISO 14692 Pt. 2 should also be considered (see Appendix C). This Table refers to manufacturing inspection, but the recommendations are still relevant in-service and following installation provided access is sufficient. More detailed guidance on the selection of NDE methods and NDE practice for specific components and defect types is given in Sections 12.0 and 13.0 below. Section 14.0 gives advice on how to practically apply individual NDE methods as well as the current status in regard to application offshore. Relevant non-destructive testing (NDT) methods should be selected if possible, bearing in mind the possibilities and limita