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Engineered Composite Repairs: End User Good Practice Guide
Version 1
A deliverable of the HSE Shared Research Project on Engineered Composite Repairs
Authors:
David Johnson
HSE Science Division
Matthew Blackburn
HSE Energy Division
Report Number:
EM/19/53
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Engineered Composite Repairs: End User Good Practice Guide
Version 1
A deliverable of the HSE Shared Research Project on Engineered Composite Repairs
Report authorised by:
Report approved by:
Date of Issue:
Authors:
End User/Customer:
Technical Reviewer:
Editorial Reviewer:
Project number:
Access control marking:
Distribution list:
Prof Andrew Curran BSc PhD FRSB FCMI Hon FFOM
John Allen BSc PhD CChem MRSC
31st August 2020
David Johnson BEng MSc(Eng) MSc CEng MIMMM
Matthew Blackburn MA CEng MIMechE
SRP: Engineered Composite Repair Sponsor Group
Adam Bannister BMet CEng FIMMM
Paul McCann BEng CEng MIMechE
PH15252
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Engineered Composite Repair Sponsor Group
SRP: Engineered Composite Repair Sponsor Group
Disclaimer:
This report and the work it describes were co-funded by the Health and Safety Executive (HSE) and
the sponsors of the HSE Shared Research Project on Engineered Composite Repairs. Its contents,
including any opinions and/or conclusions expressed, are those of the authors alone and do not
necessarily reflect HSE policy.
© Crown copyright 2020
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ACKNOWLEDGEMENTS
This document was produced under the auspices of the HSE Shared Research Project on Engineered
Composite Repairs.
The project was sponsored by the following organisations. Their support is duly acknowledged:
Shell U.K. Ltd
Spirit Energy Ltd
Sellafield Ltd
EDF Energy Ltd
TAQA Bratani Ltd
Belzona Polymerics Ltd
Henkel Ltd
Rockrose Energy Plc
Centrica Storage Ltd
National Grid Plc
Chrysaor Ltd
TEAM Industrial Services
Metalyte Pipeworks Ltd
BSEE
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CNOOC U.K. Ltd
Total U.K. Ltd
SGN Ltd
Apache North Sea Ltd
ICR Integrity Ltd
Clockspring|NRI
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CONTENTS
ACKNOWLEDGEMENTS ............................................................................................. 2
GLOSSARY, ACRONYMS AND DEFINITIONS ................................................................ 5
1
2
3
4
5
6
INTRODUCTION ................................................................................................. 7
1.1
Background ............................................................................................................................. 7
1.2
Scope ....................................................................................................................................... 7
1.3
Purpose ................................................................................................................................... 7
1.4
Relevant Legal Requirements ................................................................................................. 8
SUMMARY OF KEY CONSIDERATIONS................................................................. 9
2.1
General.................................................................................................................................... 9
2.2
Key Considerations.................................................................................................................. 9
PHASE 1: DECISION MAKING PROCESS ............................................................. 14
3.1
General.................................................................................................................................. 14
3.2
Anomaly Identification and Characterisation ....................................................................... 14
3.3
Corrective Action .................................................................................................................. 14
3.4
Repair .................................................................................................................................... 15
PHASE 2: PRE-INSTALLATION ACTIVITIES .......................................................... 18
4.1
General.................................................................................................................................. 18
4.2
Assigning Roles and Responsibilities for Composite Repair Application .............................. 18
4.3
Supply of Input Data and Review of Repair Design .............................................................. 18
4.4
On-site Preparation and Organisation .................................................................................. 20
PHASE 3: INSTALLATION .................................................................................. 22
5.1
General.................................................................................................................................. 22
5.2
Repair Location Site Preparation .......................................................................................... 22
5.3
Repair Installation ................................................................................................................. 23
5.4
Inspection/Quality Assurance ............................................................................................... 24
5.5
Post Installation Tasks/Requirements .................................................................................. 24
5.6
Repair Completion Documentation ...................................................................................... 28
PHASE 4: ONGOING INTEGRITY MANAGEMENT ................................................ 29
6.1
General.................................................................................................................................. 29
6.2
Records.................................................................................................................................. 29
6.3
In-Service Inspection ............................................................................................................. 31
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7
6.4
Ongoing Validity of Input Data.............................................................................................. 34
6.5
Life Extension/Life Reduction ............................................................................................... 34
6.6
Decommissioning and Removal ............................................................................................ 36
REFERENCES .................................................................................................... 37
APPENDIX A - ENGINEERED COMPOSITE REPAIRS: KEY CONSIDERATIONS................ 39
A1
General.................................................................................................................................. 39
A2
Surface Preparation .............................................................................................................. 39
A3
Defect / Leak Sealing ............................................................................................................. 44
A4
Cure ....................................................................................................................................... 45
A5
In-service Inspection ............................................................................................................. 46
A6
Training and Competency ..................................................................................................... 47
A7
Applications........................................................................................................................... 48
APPENDIX B – VISUAL INSPECTION CHECKLIST ........................................................ 51
APPENDIX C – NDT TECHNIQUE SELECTION CHART (PART A) ................................... 52
APPENDIX D – NDT TECHNIQUE SELECTION CHART (PART B) ................................... 53
APPENDIX E - NDT TECHNIQUE SELECTION CHART (PART C) .................................... 54
APPENDIX F – HOLD POINTS AND MANUFACTURING CONSIDERATIONS .................. 55
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GLOSSARY, ACRONYMS AND DEFINITIONS
KEY TERMS
Defined life
The actual repair service lifetime. This is defined by the end user and
is often informed by the shutdown or maintenance cycle of the
repaired system. The defined life is less than or equal to the design
life of the repair.
Design life
Maximum application lifetime of the repair.
Job Responsible Coordinator
An individual appointed by the operator to oversee the repair
process.
Pressure testing
After repair application, pressure testing may be required. This
could be to confirm the integrity of the repair, or, if a shutdown was
required, to bring plant back into service. If a pressure test is
required after a shutdown, it is paramount that the test pressure is
communicated with the repair supplier and the repair is designed for
the test pressure.
Substrate
The surface to which the repair is applied.
Interface
The bond between the laminate and the substrate.
Laminate
Part of a repair system that is the composite.
Surface preparation
Preparation of substrate prior to applying composite repair.
Safety Critical
Failure(s) that could cause or contribute substantially to a major
accident; or a purpose of which is to prevent, or limit the effect of, a
major accident.
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ACRONYMS
DLR
Defined life repair
DRS
Dynamic response spectroscopy
HSE
Health and Safety Executive
JRC
Job Responsible Coordinator
NDT
Non-destructive testing
PEC
Pulsed eddy current (inspection technique)
RBI
Risk based inspection
MIC
Microbially induced corrosion
P&ID
Piping and instrumentation diagram
QR
Quick response – as in, QR code.
RFID
Radio frequency identification
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1
1.1
INTRODUCTION
Background
Over recent years there has been an increasing trend towards the use of composite repairs on
impaired containment equipment. This has brought benefits in terms of improved integrity and
reduced downtime. However, the risks associated with the application of such repairs have not
always been correctly evaluated. Whilst the majority of repairs have been successful, there have
also been failures. These have been attributable to a range of factors including poor installation
practices, deficient design, inadequate specification and use in unsuitable applications.
In 2017 a Shared Research Project sponsored by HSE, operators and repair suppliers was established
to improve the collective knowledge and understanding of composite repairs. The project focussed
on a number of key areas, such as: quality assurance and integrity management; inspection; inservice performance; and human factors.
A key deliverable of the project was to identify and document agreed good practice to promote
improved management of composite repairs throughout their lifecycle. As such, this document
incorporates key learnings, insights and lessons learned identified as part of the project.
1.2
Scope
There are two recognised standards for the design and installation of engineered composite repairs,
ASME PCC-2 [1] and the standard that underpins this guide, BS EN ISO 24817 [2]. The scope of this
document is primarily concerned with the external application of composite repairs to impaired
pipework used in the petroleum, petrochemical and natural gas industries. However, with
appropriate consideration the principles are relevant to a wide range of industries and containment
applications. Given their ubiquity, wet laid/hand laminated repairs are the focus, although many of
the principles outlined are equally valid for other types of composite repair, such as pre-cured
systems.
Given its prevalence in plant applications, the repair of carbon steel substrates forms the basis of
this guide. However, many of the key principles and considerations are equally valid for other
substrates provided they form part of a qualified repair system.
1.3
Purpose
BS EN ISO 24817 details the qualification and design, installation, testing and inspection aspects of
composite repairs. This document should be used in conjunction with the Standard, and serves as a
practical guide for end users. It provides additional information pertinent to the upfront decision
making process in selecting a composite repair, factors to be considered in the design and
application of the repair, and broader integrity management considerations. The intention is that
end users take account of the good practice highlighted by this document in developing their own inhouse procedures.
The guide is set out in four separate but inherently linked phases: Phase 1: Decision Making
Process; Phase 2: Pre-Installation Activities; Phase 3: Installation; Phase 4: Ongoing Integrity
Management. Preceding the section on the decision making process (Phase 1), there is a summary
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of key considerations, specific to engineered composite repairs. The purpose of the information in
this section is to underpin and inform the decision making process.
1.4
Relevant Legal Requirements
Applicable regulations in the United Kingdom (UK) include:
1. The Control of Major Accident Hazards (COMAH) Regulations, 2015 [3] (Onshore only)
2. Health and Safety at Work etc Act, 1974 [4]
3. The Offshore Installations (Offshore Safety Directive) (Safety Case etc) Regulations 2015
(SCR2015) [5] (offshore only)
4. The Pipeline Safety Regulations (PSR), 1996 [6]
5. The Pressure Systems Safety Regulations (PSSR), 2000 [7] (Onshore only)
6. The Offshore Installations (Prevention of Fire & Explosion and Emergency Response)
Regulations, 1995 [8] (Offshore only)
7. The Management of Health and Safety at Work Regulations, 1999 [9]
8. The Offshore Installations and Wells (Design and Construction, etc) Regulations, 1996 [10]
(Offshore only)
9. The Provision and Use of Work Equipment Regulations (PUWER), 1998 [11]
End users should take account of the good practice highlighted by this document with respect to the
specific legal and regulatory frameworks pertinent to their industrial sector and operations.
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2
2.1
SUMMARY OF KEY CONSIDERATIONS
General
The successful specification, installation and through-life management of engineered composite
repairs relies on a number of key factors. Fundamental, is a robust and informed decision making
process, establishing whether a composite repair is the most appropriate course of action,
establishing whether it is technically viable and, particularly for safety critical repairs, whether its
integrity can be assured for its entire lifecycle. Thus, for the process to be effective, it needs to be
underpinned with an appropriate level of knowledge and a general awareness of the key
considerations.
This Section summarises key considerations to inform the decision making process outlined in
Section 3. It is, in part, an abridged version of Appendix A, which can be consulted for more detailed
information1.
2.2
Key Considerations
2.2.1 Causes of Failure
 The top three critical installation steps associated with the ultimate failure of a composite repair
have been identified as:
i.
Surface Preparation;
ii.
Curing;
iii.
Defect/Leak Sealing.
 It is also noteworthy that a number of repair failures have been attributed to incomplete or
inaccurate information being supplied to the repair supplier by the client. This serves to reaffirm
the importance of this particular pre-installation task.
2.2.2 Training and Competency
 All end user personnel involved in the specification, application and management of engineered
composite repairs should have had sufficient training and be deemed competent. Some
roles/responsibilities for key members of staff are listed below:
Technical Authority (or equivalent)
i.
ii.
iii.
1
Review of repair supplier design proposals and verifying that they are fit for
purpose.
Aware of the general capabilities and limitations of composite repair technology
and non-destructive testing (NDT) techniques. This will inform the decision making
process as to whether a composite repair is feasible/appropriate.
Reviewing repair close out documentation and establishing that the repair reflects
what was proposed and is fit for purpose.
Appendix A also provides detailed references to underpin the points outlined in this section.
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On-site field engineers (or equivalent)
i.
ii.
Aware of the key hold points as well as pre/post installation quality assurance
checks.
Sign-off following post-installation inspection and reviewing any associated
documentation/paperwork.
On-site inspection engineers (or equivalent)
i.
ii.

Aware of the key areas to inspect and allowable limits for defects.
Reviewing inspection data (visual and/or more sophisticated forms of NDT) and
highlighting anomalies for further investigation.
End user confirmation at key hold points should be undertaken for all safety critical repairs.
2.2.3 Applications
 The highest in-service failure rate to date on pipework systems has been on reducers and tees.
 Vessels require special consideration, with over one in ten repairs applied subsequently failing in
service. This failure rate is significantly higher than for all other repair applications.
 For novel repairs, perhaps infrequently applied, or repairs with specific considerations (e.g.
restricted access), consideration should be given to undertaking full-scale feasibility trials.
2.2.4 Defect/Leak Sealing
 Repairs to defects that have gone through-wall and are leaking are possible but require special
consideration.
 Requires confirmation that any leak sealing device/technology has isolated the leak and will do
so for the duration of the repair installation, including curing.
 The presence of any leak sealing device should be considered at the design stage in defining the
defect size and geometry used for the design.
 Inadequate or ineffective leak sealing measures at the time of repair installation have resulted in
several repair failures on safety critical equipment.
2.2.5 Surface Preparation
 Surface preparation of the substrate is critical to achieving satisfactory adhesion between the
repair laminate and repair surface. It is the single most important step for ensuring a
successful repair.
 It is imperative that the surface preparation procedure (and subsequent repair) is managed.
Time delays can lead to oxidation (and further contamination) of the prepared surface which
affects the initial strength, integrity and, in particular, durability of the adhesive bond. To
maximise surface preparation quality, exposure times between process steps should be kept
to an absolute minimum.
 Contaminants can significantly affect bond performance and need to be removed/reduced to
acceptable levels.
 In terms of bond durability: Grit blast cleaning to Sa 2.5 > Hand or Power tool cleaning to St 3 >>
Hand or Power tool cleaning to St 22.
2
It should be noted that both cleanliness and roughness are important. As such, the surface preparation method, tool(s) used,
preparation grade stipulated etc should also be accompanied by a surface profile requirement.
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



The surface preparation method leading to the most durable repairs is via abrasive blastcleaning using grit, resulting in an angular surface profile in the range 75-115µm and a
preparation grade of Sa 2.5. This should be the default choice for all safety critical repairs3.
It has been demonstrated that a specialised rotary bristle tool4 is the most effective power tool;
leading to more durable repairs than those made on surfaces prepared using other power tools.
Hand or power tool cleaning (to a surface preparation grade of St 2 and St 3) using a wire brush
and a rotating abrasive belt have been demonstrated to be ineffective.
There is a limited evidence base for medium/long term integrity using current practices. This is
particularly relevant to safety critical applications where the repair affords primary containment.
2.2.6 Cure
 The cure schedule should be managed to give the same level of cure (or glass transition
temperature) during the installation of the repair as was qualified and assumed in the design.
 Where, based on qualification testing, the supplier can demonstrate that the required glass
transition temperature is achieved by ambient cure alone, then heat treatment may be omitted.
In all other cases the supplier shall provide a heat treatment procedure (temperature profiles
and hold times) which has been demonstrated to achieve the required glass transition
temperature during qualification.
 Any heat applied to cure must be controlled and known. Taking credit for heat treatment due to
heating from the process fluid is not permitted.
 Post curing should only be undertaken once the resin has hardened and on equipment that is
depressurised and drained.
 Pressure cannot be brought back to normal operating conditions until an acceptable level of
cure has been achieved. Not doing so has been identified as a principal cause of repair failure.
 Consideration needs to be afforded to the total number of layers that make up the repair
laminate, the number of layers that can be cured at one time, and the cumulative time this will
take.
2.2.7 In-service Inspection
 The three candidate areas for inspection are: (1) the repair laminate; (2) the substrate; (3) the
bond between the repair laminate and the substrate.
 When determining the extent and periodicity of inspection, consideration should be given to the
degradation mechanism(s) of the substrate, its location (internal or external), as well as
consequences of failure.
 A risk based inspection (RBI) [or suitable equivalent] approach should be adopted.
 The application of a composite repair prevents subsequent substrate inspection using: standard
ultrasonic testing, including phased array; surface NDT methods; visual examination; and
magnetic particle inspection.
 There remains no validated inspection technique to establish the integrity of the bond,
emphasising the importance of appropriate surface preparation and adherence to qualified
procedures.
3
The inclusion of a silane treatment step in the surface preparation procedure can lead to improved bond durability between the repair
laminate and the substrate.
4
See Appendix A for full details.
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




For non-safety critical applications, it is likely that any inspection schedule will be limited to a
periodic visual examination only. (See Appendix B)
For safety critical applications, the viability of effectively deploying proposed NDT techniques
should be established – this may require practical trials prior to repair application.
For safety critical applications, a baseline inspection should be conducted pre and post repair
installation.
For safety critical applications - in addition to visual inspection, inspections using available NDT
equipment should be used to confirm the condition of the substrate throughout the repair
lifetime.
For safety critical applications:
External Defects
i.
ii.
iii.
A maintenance strategy should be in place to ensure that the repair laminate
remains intact, with no evidence of edge lifting or corrosion at the edges of the
repair.
Periodicity of any inspection should be such that the integrity of the line remains
assured.
The potential for internal corrosion must be considered throughout the life of the
repair. If internal corrosion is determined as active, then a suitable strategy to
mitigate the threat should be determined (e.g. change in process conditions, use of
inhibitors or reduced life of repair, etc).
Internal Defects or Through-Wall Defects
i.

Further deterioration or growth of the defect may continue despite application of
the repair, unless other measures are taken and are verified to be effective.
ii.
In addition to the requirements of the external corrosion case, the maintenance
strategy should ensure that the internal defect does not grow to a size greater than
that assumed in the design or that the repair laminate does not disbond from the
substrate.
iii.
Awareness of limitations of NDT techniques for identifying and characterising pit-like
features, particularly microbial induced corrosion (MIC).
iv.
It is important to be aware of, and take account of, the increased risk profile when a
defect is through-wall and the repair is acting as the primary means of containment.
This may have been due to an external and/or internal mechanism. The integrity of
the repair must be ensured throughout its lifecycle.
Appendices C-E provides a summary of the inspection techniques along with their capabilities
and limitations. Pulsed eddy current (PEC), radiography and dynamic response spectroscopy
(DRS) are the most established techniques for the inspection of composite repairs but still have a
range of limitations. DRS, in particular, can be used as a quality assurance tool immediately post
repair application.
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2.2.8 Repair Lifetime
Design Life




The design life is the maximum application lifetime of the repair. It is defined by the owner and
used by the repair supplier for the purposes of design. It may transpire that the owner defined
design life is not feasible given the defect type and service conditions. It should be agreed
between the repair supplier and the client.
The minimum design lifetime of the composite repair shall be two years.
It is important that the client ensures that any information/data used for the purposes of design
by the repair supplier is robust and accurate.
Through-life considerations – findings from inspection data/changes in process conditions may
mean that the initial inputs are no longer valid. These have implications for repair integrity and
safety.
Defined Life




The defined life is the actual application or intended service lifetime of the repair. It defines the
time after which the repair needs to be re-validated or its removal scheduled.
The defined life is set by the end-user with due consideration of the risks associated with each
repair. For safety critical applications the defined life should be set by the risk assessment on a
case by case basis.
For safety critical applications, if the repair is intended to provide the primary means of
containment (either immediately after application or at any time during the life of the repair)
it should be considered for short-term use only5.
Special consideration should be afforded to scenarios where there is an active internal
degradation mechanism where damage has not yet broken through-wall but could do so during
the life of the repair. In this case, the ability of the repair to provide primary containment must
be demonstrated for the largest defect that is considered may develop. Initial, successful
performance of the repair, shall not be considered to provide any indication of future reliability
because of the changes expected in the defect.
5
Consideration should be given to bringing shutdowns forward if the risk profile warrants such action – the integrity of the repair must be
ensured throughout its lifecycle.
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3
3.1
PHASE 1: DECISION MAKING PROCESS
General
During the lifetime of engineering plant and offshore installations it is probable that fixed equipment
(such as piping on process and utility systems) will suffer from degradation necessitating the need
for remedial action. These anomalies represent a deviation from what is considered standard,
normal or expected and a process should be in place that captures each key step from identification
right through to successful close-out. The process is likely to include a range of personnel and all
roles and responsibilities should be clearly defined. This helps ensure that the process works at a
system level with reduced propensity for errors or oversight.
This section details the key elements of the decision making process. In particular, it covers repair
versus replacement considerations as well as repair selection.
3.2
Anomaly Identification and Characterisation
When identified, a survey should be undertaken to fully characterise the anomaly as well as to
establish the condition of the surrounding substrate. Documentation should include the following:

Location of the anomaly (asset; component

Detail of the damage found - degradation
mechanism(s) and extent of the defect.
type; component or line identification number;
physical location; access requirements; P&ID.)

Component leaking/not leaking

Safety critical/non-safety critical




Service
Material type
Corrosion allowance
Component insulated/not insulated




Corrosion circuit
Nominal wall thickness
Piping class
Design and operating temperature and
pressure
The level of detail should permit a comprehensive and robust assessment to be made. Given that an
anomaly likely constitutes a failure in the integrity management system, any possible mitigating
actions should be identified in order to prevent reoccurrence.
3.3
Corrective Action
In the case where an anomalous item means that a component will have limited or no remaining
redundancy and cannot tolerate any further deterioration, an engineering assessment should be
undertaken for continued service and corrective action. An assessment of the anomaly should be
made and remedial options considered. Possible options include:
1. Replacement of the defective item;
2. Isolation and/or removal of the defective item or modification to the system control
parameters to limit temperature/pressure exposure, e.g. reduce system trip pressures;
3. Implementation of a routine inspection / monitoring regime;
4. Undertaking a detailed engineering study to identify possible solutions or tolerability, e.g.
fitness for service assessment;
5. Defined life repair.
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It should be noted that more than one mitigation option may be required – i.e. the application of a
defined life repair may also require an interim inspection / monitoring task prior to the repair being
installed.
Where replacement or repair are the options being considered, guidance for safety critical pipework
is provided in HSE Offshore Safety Notice 04/2005 – Weldless Repair of Safety Critical Piping, July
2005 [31]. The philosophy described which is directly transferrable to other industry sectors is6, in
order of preference:
1. Replace like for like7;
2. Temporary repair until replacement can be carried out;
3. Permanent repair only where replacement is not practical.
Whilst the focus of the Safety Notice relates to safety critical pipework, this philosophy is valid for all
containment equipment. Indeed, adopting this approach is in line with the principles of prevention
and acts to control risks at source rather than taking palliative measures.
To inform the top level repair or replace decision making process, a number of aspects should be
considered, including:
3.4

Why repair rather than replace?

What additional safety and business risk will
this bring if safety critical?

How tolerant of the safety/business risks are
we/should we be? Corporate view?

Can we manage the long-term integrity
challenges this will bring?

What operational changes could make a
repair unsuitable – are these controlled?

Lifecycle cost – resource etc.

Viability – particularly access and ability to
perform processes to required standard, e.g.
surface preparation.

On-going
integrity
management
considerations, e.g. inspection.
Repair
3.4.1 Defined Life Repairs
Repairs to safety critical equipment should only be considered when all reasonable measures to
enact a replacement in the first instance have proven unsuccessful. Repairs should be assessed with
respect to their risk and the conclusion reached that there is no practicable means of replacement in
the short term. This may be due to operational constraints, part availability, lead times or hot work
constraints. If this is the case, a defined life repair could be considered. These generally take the
form of engineered clamps or engineered composite repairs.
For safety critical repairs offshore there should be ongoing dialogue with Verification Bodies.
6
The hierarchy of risk control and inherent safety are detailed in COMAH guidance (with respect to Reg 5) and ‘Reducing Risks, Protecting
People’ (R2P2).
7
In this context, like for like means replacing the component to the original design basis. It does not preclude improving the component
design/specification.
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For non-safety critical applications the same philosophy should apply, accepting that the reduced
risk posed by the fluid media or service function means that defined life repairs may be tolerated to
a greater extent.
3.4.2 Repair Selection
The selection of an appropriate repair technique or product can only be made when the cause and
extent of the defect, existing design /operating criteria, work site access and operational constraints
are established and understood. Each repair technique has its own limitations (service, pressure,
temperature, material, geometry, size, specialist vendor requirements, cost and delivery, etc.) and it
is critical that the repair selected is fit for purpose taking into account the nature of the defect
throughout the lifecycle.
All proposed defined life repairs should undergo an engineering assessment to ensure suitability.
The engineering assessment should not only establish whether a repair type is technically viable, but
also whether it is the correct course of action. Therefore, the level of assessment should be tailored
to the defined life repair’s intended service and consequences of failure. For safety critical repairs
this essentially takes the form of a risk assessment. In certain cases the suitability of a repair may
require a formal management of change procedure to be carried out. Some of the main elements to
be considered are:

Can the repair be installed whilst the
component is operational or what level of
isolation/purge is required?
Safety
considerations – live blasting etc.

What is the nature and location of the
defect? Estimation of the rate of and extent
of any further deterioration that would
further compromise the pipe condition or
any installed repair.

What are the design and operating
conditions of the defective component?

Is the component subject to any upset
conditions? Including start-up/shut down.

Is the repair required to be suitable during or
after a major incident such as a mechanical
impact, jet or pool fire or explosion?

Type of component and geometry being
repaired (pipe/vessel, simple/complex).

What hazards are associated with system
service? (Fluid, Pressure, Temperature)

What are the previous delivery times for this
type of repair?

What is the availability of personnel with the
competency to apply the repair?

Can the required level of surface preparation
be achieved safely? Extent and specification.

What operational measures, including (if
relevant) permits, gas testing and fire
protection requirements are required to
ensure safety near the repair area?

Consideration of the ability to inspect
beneath clamps, wraps and connectors once
fitted to determine the condition of the
pipework. Determining access and suitability
for future inspection to monitor further
degradation in service.

What are the anticipated failure modes of
the component?

What are the anticipated failure modes of
the repair?

What is the anticipated life span of the
repair?

Are any further operational controls
required, in addition to the temporary
repair, to ensure ongoing integrity?
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
Remaining life of pipework to which the
joint/repair is to be carried out.

Determining
access,
complexity
suitability for installation of the repair.

Compatibility of the repair clamp/wrap with
the internal/external environment.

Determining whether additional supports are
required to support the repair due to extra
loading on the pipework.

Does the application of the repair render any
equipment inoperable (such as an
encapsulated valve)?
What are the
implications?

Is there the potential for a change in process
conditions over the lifetime of the repair that
could lead to new types of degradation?

Cumulative risk – multiple repairs on one
line. Is there a risk of any interaction
between multiple repairs?

Inspection resource requirements.

Does the owner have the necessary
expertise on site to manage the installation
of the repair?

Does the site have the necessary expertise to
manage through-life?

Likelihood of over pressurisation e.g.
pressure testing of the repaired system. Can
this additional loading be accounted for in
the design of the repair?

Availability of data to inform
design/specification of the repair.

Likelihood of success – perhaps based on
previous experience or industry good
practice.

The effect of the operating cycle on the
integrity of the repair, effects of load cycling
(if this is a feature of plant operation – how
can it affect the integrity of the repair?)

Will installation of the repair ‘move’ the
failure mode to elsewhere? (vibration,
pressure, heat etc.)
and
the
Special attention should be afforded to situations where widespread deterioration of a system
exists, perhaps multiple repairs on a single line. In these situations the risk assessment must
consider the cumulative risk; this may be impaired fire performance, excessive weight, the potential
for multiple leak sites etc. Special attention should also be afforded to situations where there is an
active internal degradation mechanism. This is particularly the case for microbiologically induced
corrosion (MIC).
The evaluation should be undertaken by competent persons. It is important to still be mindful of the
replacement option when undertaking this exercise.
This is especially true where
data/information/circumstances may make a repair difficult. The replacement/repair decision may
have to be revisited.
During the screening exercise the viability of applying an engineered composite repair will have been
evaluated. BS EN ISO 24817 calls for a repair feasibility assessment8 to be undertaken by the owner
and repair supplier. A curtailed number of factors from Section 3.4.2 are considered.
8
BS EN ISO 24817:2017, Section 7.1
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4
4.1
PHASE 2: PRE-INSTALLATION ACTIVITIES
General
If the output of the repair decision making process (Phase 1) is that an engineered composite repair
is to be installed then there are a number of key pre-installation activities that need to take place.
The repair process should be coordinated by a competent owner representative. This section
discusses roles and responsibilities, assessment of the repair design and key on-site preparation and
organisation considerations. If a pre-installation baseline inspection has been specified this should
be conducted.
4.2
Assigning Roles and Responsibilities for Composite Repair Application
An operator representative (herein referred to as a ‘Job Responsible Coordinator’) should be
assigned to manage the key elements of the process, engaging with internal and external parties to
install a repair within prescribed timescales and to the agreed standard.
It is particularly important that the ‘Job Responsible Coordinator’ identifies a focal point at the repair
application site (independent of operations) thereby ensuring that the environment/facilities are as
agreed with the repair supplier. This ‘on-site field engineer’ (or equivalent) should coordinate the
repair installation and ensure that tasks are carried out to the appropriate standard and within
specified timescales. The level of supervision and quality assurance should be proportional to the
consequences of failure, with greater emphasis placed on repairs to safety critical equipment.
In order to facilitate communications, the contact information for the ‘Job Responsible Coordinator’
should be supplied in the assessment. To ensure correct repair installation it is important that all
lines of communication are clear, with the ‘Job Responsible Coordinator’ communicating with the
repair supplier and, in offshore applications, the operations teams both on and offshore.
Depending on the nature and complexity of the repair, application could be undertaken either by the
repair supplier or alternatively support personnel including core crew, maintenance and inspection
contractor personnel. In the case of non-repair supplier personnel, they shall have undertaken
formal training via the product vendor and have been deemed competent. This guide assumes the
former (i.e. repair supplier applied) but the key principles are common. Repairs to safety critical
equipment should only be installed by the vendor or a vendor approved supplier.
4.3
Supply of Input Data and Review of Repair Design
The ‘Job Responsible Coordinator’ will ensure that the repair supplier has all information required to
appropriately design the repair. An overview of the information required is provided in BS EN ISO
24817, Annex A9. Each repair supplier may have their own internal forms and requirements;
Annex A should be used as the minimum level of detail in these cases. The data inputs include: pipe
details; repair class and lifetime; loading; defect and projected size; anticipated conditions during
installation of the repair; facilities to be provided by the client and details of the defect area. The
detail level to which these requirements are fulfilled will have been determined by the output of the
repair feasibility assessment (Section 3.4.2). In practice, all data may have been supplied to the
9
BS EN ISO 24817:2017, Section 7.4, also provides further information.
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repair supplier at the enquiry stage and therefore no further information may need to be provided.
Photographs of the defective part to be repaired, along with locational information and drawings
will aid the design and installation of the repair, Figure 4.1.
Figure 4.1
Photo of the spool to be repaired along with isometrics, plot plans and P&IDs.
The repair supplier will provide a number of documents prior to repair application. These include a
method statement, risk assessment and a work pack that should provide drawings of the repair
along with the design calculations.
The proposed design, including calculations, should be subject to an internal review by the ‘Technical
Authority’ (or equivalent) to verify their applicability and accuracy. In particular, the inputs used for
design purposes should be checked. Where appropriate, Independent Verification Bodies should be
consulted.
The work pack should also include the repair supplier’s training certifications and relevant details of
their competence to complete the repair as designed. Elements that need to be checked/verified
include:

The repair lifetime/replacement date are as
expected.

The design risk assessment is sufficient for
the repair under consideration, and suitably
mitigates all foreseeable incidents.

That any preferred system de-pressurisation
is acceptable and realistic - or the design, as
submitted, shall be re-worked accordingly to

The repair system method statement,
including details of the surface preparation,
the quality of application, the interface
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alter and/or eliminate the system depressurisation.
between the repair and existing finishes and
the repair acceptance criteria.

The repair drawing is specific and
appropriate
to
the
repair
under
consideration.

Details of the interface protection system (if
applicable) between the repair and the
existing pipe/plant.

The defect size and geometry used in the
design calculations are
10
representative/correct.

Have any stop gap leak sealing techniques
been installed? Have these been considered
in the design? Confirm the size of the stopgap used is less than or equal to the size of
the defect used in the design.

The curing time for the repair, providing
limitations on what can and cannot be done
to the repair until curing is complete.

The design has suitably addressed the
required fire performance and has mitigated
the potential for cathodic disbondment
associated with pipe/plant that is
cathodically protected (if appropriate).

If deemed required by the design, the
pressure testing regime is appropriate and
can be undertaken safely. Confirm repair
designed for test pressure.

That the composite repair supplier’s
‘installers’ are qualified to the requirements
of BS EN ISO 24817, Annex I, that their
qualifications are within date and the
composite repair supplier is registered on
the owner’s approved repair supplier list.

That the composite repair supplier has
provided a declaration that the repair shall
be designed, installed and finished in
accordance with BS EN ISO 24817.

Inspection requirements are included and
are achievable in term of technique(s) and
periodicity.
It is notable that a number of repair failures have been attributed to incomplete or inaccurate
information being supplied to the repair supplier by the client [12]. Indeed, this has been identified
as one of the principal reasons for repair failure.
4.4
On-site Preparation and Organisation
The ‘Job Responsible Coordinator’ should confirm and agree any on-site requirements with the
repair supplier and communicate these to the ‘on-site field engineer’, as appropriate. The ‘on-site
field engineer’ should be accountable for ensuring that the repair location and any other
requirements are in place prior to the arrival of the repair supplier. Requirements are likely to
include access to storage and a working area for laying out materials and wetting out the
reinforcement fabric. A covered table is normally required for wetting out the fabric and to reduce
the risk of contamination.
10
The selection of the generic through-wall defect and size for design, i.e. the selection of the correct dimension, may not simply be the
size of the actual defect but rather may be either the dimension of the unprepared surface area neighbouring the defect or if filler is used
over the defect, the dimension of the defect is the surface area of filler.
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The repair location should be accessible by the repair supplier’s representatives and any other
interested parties. It should be noted that in some instances this may require scaffolding to be
erected or the use of specialist equipment. In order to create an environment that permits the
repair to be installed (within prescribed limits) a habitat may need to be erected. Approval (via
permits or equivalent) may be required for any heat sources, lighting and photographic apparatus.
If line isolation is required this should be discussed with all parties to establish how this is to be
achieved and implemented. Further, if pressure testing is required post repair application this also
needs to be organised. Pressure testing is discussed further in Section 5.5.4. Work orders relating to
any post-installation requirements such as paint coatings (particularly at the ends of the repair) need
to be placed.
The repair supplier should be able to advise on the storage requirements for resins, it is important
that any recommendations are followed. Generally speaking, all constituent materials should be
kept dry and at moderate temperatures as temperature extremes can lead to defective/damaged
constituent materials and/or make them difficult to work with. Shelf life of constituents/materials
should be monitored/checked.
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5
5.1
PHASE 3: INSTALLATION
General
Successful installation is directly related to the workmanship of the technicians who undertake the
repair. It is an entirely manual process, with often difficult working conditions and time pressures.
This section details the hold points during installation of a repair system, quality assurance checks
prior to the commencement of the repair, the installation, and post installation inspection and
quality assurance considerations. It also details post installation tasks and requirements.
5.2
Repair Location Site Preparation
5.2.1 General
As detailed in Section 4.4, the ‘on-site field engineer’ is accountable for ensuring that the repair site
and any requirements are as agreed with the repair supplier. A site briefing and risk assessment
should be completed prior to the commencement of any work. Given that the risk assessment will
have been prepared in advance, its relevance to the actual location/conditions should be verified.
The repair supplier should verify that the repair site is that detailed in the repair work pack.
5.2.2 Hold Points During Installation of a Repair System
BS EN ISO 2481711 specifies a number of hold points during the installation of a composite repair.
These cover: the method statement; environmental conditions; surface preparation; filler profile;
stage check on reinforcement fibre or cloth orientation; tests of repair laminate; QA records;
pressure testing. For safety critical applications the ‘on-site field engineer’ should witness the
process and corroborate information/activities either at these designated hold points or at other
times. An overview of a wet lay-up composite manufacturing process and some suggested hold
points can be found in Appendix F.
5.2.3 Surface Preparation
Surface preparation is most commonly undertaken by an owner nominated representative (e.g. onsite fabric maintenance team) and less frequently by the repair supplier. In the case of the former, it
is particularly important that dialogue has taken place between the repair supplier and ‘on-site field
engineer’ to ensure that the required equipment and materials are available to enable the qualified
surface preparation procedure to be replicated on site.
The surface preparation procedure on-site should be the same as that qualified by the repair
supplier and used in the design. This includes not only the extent12 of the surface preparation but
also the preparation grade, the surface profile, the method and tool(s) used and the time the
prepared surface is exposed before repair application. Time between surface preparation steps
should be kept to an absolute minimum. Wherever possible the surface should be prepared
immediately prior to repair application.
For safety critical repairs, non-conformances are a cause for rejection and the (correct) surface
preparation procedure should be repeated until the desired specification(s) are achieved.
11
12
BS EN ISO 24817:2017, Section 8, Table 14
Overall extent as well as confirming any surface neighbouring defect has also been prepared, if assumed in the design.
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Importantly, if the surface preparation on-site is not to specification and cannot be achieved in
practice then a re-design by the repair supplier would be required and could subsequently mean
that qualification data is not available and the repair proposed is not suitable and should not be
applied.
The impact of any change should be evaluated in the context of the original decision making process
(Section 3), particularly the risk assessment.
5.2.4 Quality Assurance Checks Prior to Application of the Repair
BS EN ISO 2481713 details quality assurance checks for the substrate prior to application of the repair
to ensure the condition of the site is as per the design.
This includes, as a minimum, the geometry, material and dimensions of the substrate, surface
preparation, surface temperature and the location/size/nature of the defect.
In addition to the substrate checks described above, if a leak sealing clamp (or other device) is
present, it should be confirmed that it is not leaking.
For safety critical repairs the ‘on-site field engineer’ (or another person deemed competent) should
verify the pre-application checks.
The pre-application hold points (Section 5.2.2) and quality checks are deemed particularly important
as it has been established that, collectively, non-conformances account for the largest number of
repair failures [12]. Specific issues relate to defect size (larger than assumed in the design),
incorrect/inferior surface preparation, incorrect surface preparation extent, lack of leaking sealing or
leaking clamps during installation, environmental conditions not suitable for repair application.
5.3
Repair Installation
The installation of the composite repair should be carried out in accordance with the approved
method statement and by the repair supplier’s qualified installers. A photographic record of the key
installation steps and hold points should be taken by the repair supplier, and for lower risk repairs it
is likely that this record will suffice in preference to witnessing each stage.
If the pipe has been isolated/depressurised/undergone pressure reduction in order to apply the
repair, the repaired substrate may be returned to service only after the specified cure schedule has
been achieved. The required cure time, and cycle, before re-pressurisation of the pipework is
specified by the repair supplier and must be followed as accurately as possible. Additional heat
sources such as heating blankets may be required.
Repair failures attributed to non-conformances at this stage have been as a result of [12]: (1)
incorrect type/amount of primer being applied; (2) incorrect number of layers applied; (3) poor cloth
wet out; (4) high levels of voidage; (5) poor consolidation due to access restrictions; (6) lack of
compression; (7) curing protocol not being fulfilled; (8) insufficient curing time; (9) environmental
conditions (too cold).
13
BS EN ISO 24817:2017, Section 9.2, Table 15
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5.4
Inspection/Quality Assurance
5.4.1 Inspection of the repair after installation
Post application, the repair supplier’s technicians shall inspect the repair and compare to the
acceptable limits detailed in BS EN ISO 2481714. The inspection will focus on the interface between
the pipe and the ends of the repair, the surface resin rich layer and the repair laminate. Dimensional
checks of the repair should be completed to confirm the axial extent, taper length and repair
thickness are as per the design. Hardness testing should be conducted and cure schedules reviewed
to infer degree of cure.
When deemed acceptable, the repair supplier's technicians shall ensure that they adequately record
the repair by means of photographs, and shall complete and sign all paperwork, certificates and
documentation associated with the repair. If the ‘on-site field engineer’ has witnessed the repair
process they may wish to undertake a further inspection along with reviewing any documentation
and signing off the repair.
At this time, if a post-installation baseline inspection (using more sophisticated NDT techniques) has
been specified this should now be conducted (or at the earliest opportunity) and documented in a
manner that permits comparison with future repeat inspections.
5.5
Post Installation Tasks/Requirements
5.5.1 Corrosion Protection Reinstatement
Post repair application there will be prepared metal surfaces at the ends of the repair. For
substrates susceptible to corrosion it is important that measures are taken to reinstate the original
coating or a suitable alternative as soon as possible. Failure to protect the edges of the repair can
lead to localised corrosion of the substrate.
Figure 5.1
14
Corrosion at edges of repair due to lack of corrosion protection applied post
repair.
BS EN ISO 24817:2017, Section 9.2, Table 16
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If this is not remedied within a suitable timeframe, the corrosion can become progressively worse.
This can lead to two issues: (1) The corrosion can progress under the tapered regions of the repair,
Figure 5.1, leading to wall-thinning and local disbondment; (2) if (1) occurs the interface acts as a
repository for moisture which is known to be especially deleterious to adhesive bonds [27].
With appropriate planning and the correct materials this situation can be easily avoided. Painting
the bare metal regions should be undertaken after the visual QA inspection of the repair has been
completed, Figure 5.2. This should be completed as soon as possible after repair application;
preferably at the time of manufacture. Clarifying from the outset who will reinstate the corrosion
barrier is important. Usually the corrosion barrier is reinstated by the owner, and requires specific
skills and attention. The paint can extend from the substrate over the landing areas or taper regions
of the repair15. If a coating is applied over the tapered regions these should be clearly marked to
help minimise the risk of damage during maintenance16.
If for some reason reinstatement of the corrosion protection cannot take place at the time of repair
manufacture the ‘Job Responsible Coordinator’ should ensure that the ongoing inspection and
maintenance of the repair is considered until such time as the corrosion barrier can be reinstated.
The repair should not be considered as complete from an operator perspective until this task is
completed.
Figure 5.2
Paint coating to mitigate corrosion of substrate at edges of repair.
5.5.2 Paint Coating
In addition to coating the bare metal at the edges of the repair, consideration should be given to
extending this coating over the entire repair. Doing so can act to highlight the presence of the repair
as well as offering some UV protection, Figure 5.3.
15
Check with the repair supplier that the paint coating is compatible with the composite repair if extending paint onto repair.
For carbon repairs a glass layer may be used to isolate the substrate from the carbon reinforcement. This glass layer may extend beyond
the taper region of the repair. As such, the axial length of the isolation layer needs to be documented and identified after recoating.
16
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Figure 5.3
Repair painted orange to promote awareness amongst on-site operatives17
However, application of the paint can hinder visual examination of the repair laminate. Accordingly,
the propensity for UV damage should be discussed with the repair supplier at the design stage to
establish whether it is a realistic proposition based on location and design life. Prior to any paint
application, the repair supplier should be consulted to confirm that the paint coating is compatible
with the repair.
5.5.3 Additional Precautions
It is important to protect the repair from damage in service, perhaps incurred via uncoordinated and
ill-informed fabric maintenance activities or accidental damage from dropped objects or chemical
exposure. In part this risk can be reduced by having appropriately updated engineering drawings to
indicate the presence and criticality of any repairs.
In addition, the presence of the composite repair on the pipe on site should be identified with
suitable markings. For locations where it is appropriate to do so, a warning sign should also be
fitted, Figure 5.4. A high visibility paint coating can aid identification and define the boundaries of
the repair (Section 5.5.2).
17
Note prepared section of substrate to right of repair that has not been coated – considerations outlined in Section 5.5.1 apply.
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Figure 5.4
(l-r) Tapered region damaged by fabric maintenance activities; warning sign to
warn site operatives of presence of composite repair.
If through the risk assessment process it was deemed that protective covers were required to
protect the repair from impact damage these should now be installed (Figure 5.5). Consideration
will need to have been given to the ease with which the cover(s) can be removed to facilitate
inspection activities.
Figure 5.5
(l-r) Composite repair; with impact protection cover in place.
5.5.4 Pressure Testing
Pressure testing can be undertaken once the repair has been applied and has fully cured. This
should have been specified by the owner (with due consideration to the risk assessment), if
required, or as recommended by the relevant design standard for the substrate.
The primary candidate for pressure testing is likely to be a safety critical repair to a through-wall
defect. In this case, a pressure test can be used to highlight major installation shortcomings – e.g.
insufficient surface preparation.
If the line required isolation, or production needed to be stopped during repair application it may
become necessary to perform a pressure test when the line is reintroduced to service. If this is the
case, the repair must have been designed to accommodate the pressure test conditions. Therefore,
if a pressure test is required on the system on start-up then the pressure reached during this test
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must be accounted for as part of the design process. Discussions early on in the repair design
process will allow for the design to take pressure testing into account; a more substantial repair may
be required due to the increased demand of the pressure test. A guidance note [32] is available on
the safety requirements for pressure testing.
5.6
Repair Completion Documentation
The following documentation shall be provided by the repair supplier to the owner on completion of
the repair.

Repair details and unique reference.

Repair design, comprising details of laminate
lay-up.

Material records and batch numbers.

Repair application.

Quality control records.

Competency certificates of installer and
supervisor.

Independent inspection (if carried out),
comprising test report.

Service inspection, comprising details of service
inspection intervals and repair condition.

Details of the curing cycle.

Details of pressure test (if carried out).

Operating and system conditions during
manufacture.

Any deviations from agreed method or design.

Photographic record.
Post installation, a closeout report should be prepared by the repair supplier and provided to the
client. This acts as a formal record of the repair installation and documents the above information.
This information should be retained for future reference, see Section 6.2.
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6
6.1
PHASE 4: ONGOING INTEGRITY MANAGEMENT
General
The effort afforded to the ongoing integrity management of installed engineered composite repairs
should be based on their criticality and the consequences of failure. The focus should be on repairs
to safety critical equipment, which will include implementing the in-service inspection strategy
defined at the decision making stage.
This section covers the important task of updating records, in particular adding the repair to the
defined life repair register and updating engineering documentation. It also covers in-service
inspection, life extension/reduction and decommissioning.
6.2
Records
6.2.1 Defined Life Repair Register
BS EN ISO 2481718 details owner responsibilities which includes setting up a defined life repair
register. The defined life repair register (also known as a temporary repair register or composite
repair management system) is an essential requirement for managing the lifecycle of the repair.
The ‘Job Responsible Coordinator’ should ensure that a close out report is received from the repair
supplier and that the repair is added to the register and is subsequently signed off by the ‘Technical
Authority’ (or equivalent). The register should include the following items:
18

Unique repair number

Date identified / notified

Line number

P & ID number

Piping isometric drawing number

Location (module / level)

Service

Hydrocarbon (Yes / No)

Safety critical system (Yes/No)

Applicable performance standard

Date of repair application

Operational conditions at time of repair

Repair type

Expiry date

Inspection plan / Routine number

Inspection frequency

Planned replacement date

Shutdown required for replacement (Yes/No)

Repair status (live / closed).

Anomaly report / MCDR

Repair completion documentation

Process conditions before and after repair
application

Photographs of defect/repair process etc.

Inspection technique(s)

Defect type – active/inactive

Design life and defined life

Coating reinstated (substrate at edges of
repair)

Process fluid
BS EN ISO 24817:2017, Annex L
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6.2.2 Identification
Each repair should be allocated a unique reference ID from the register. The unique reference
number should be stencilled or otherwise permanently marked on the repaired section to facilitate
subsequent inspection and reporting, Figure 6.1. The use of quick response (QR) codes and Radiofrequency identification (RFID) can also aid in the identification of repairs.19
Figure 6.1
Identification approaches – defined life repair (DLR) tag; sticker affixed to repair
and stencilled ID reference.20
6.2.3 Updating Engineering Documentation
Relevant engineering documentation (e.g. P&IDs/Isometrics/Plot Plans) should be updated such that
there is no ambiguity as to where the repairs are located and their criticality, Figure 6.2. A
photograph of the repair’s location and condition should also be included.
19
When engineered composite repairs are used for underground applications GPS coordinates should be recorded and logged for future
reference.
20
Note prepared sections of substrate that have not been coated – considerations outlined in Section 5.5.1 apply.
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Figure 6.2
6.3
Updated engineering documentation – photos, Isometrics, plot plans and P&IDs.
In-Service Inspection
6.3.1 General
An inspection strategy should have been developed with inputs from the repair supplier and
specialist inspection companies. An RBI approach is suggested with details documented in the DLR
register.
A review of in-service failures [13] suggests that the vast majority of repairs that fail do so within a
relatively short period (within weeks) post-installation. This is generally attributable to installation
related issues and, in particular, sub-standard surface preparation. Whilst this failure data may
reflect that in the vast majority of instances composite repairs have been used on a short term basis
only (and as such failure data pertaining to medium/long term applications is not available), it does
demonstrate that verifying initial integrity should form an important part of the overall inspection
strategy.
6.3.2 Inspection Strategy
The inspection strategy should have been defined at the decision making stage and will specify the
periodicity of the inspection as well as indicating whether the inspection should cover one or more
of the following: (1) repair laminate; (2) substrate; (3) bond.
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For non-safety critical repairs the inspection will likely take the form of a visual examination of the
repair and the adjacent substrate. BS EN ISO 2481721 provides guidance on defects and allowable
limits for the resin rich layer, repair laminate and interface between the substrate and repair at the
edges.
An informed visual examination performed well can not only identify whether the repair has failed,
but also some signs of deterioration. To aid the visual examination it is recommended that an
inspection template is produced along the same lines as that in Appendix B. It is suggested that
photographic records be taken at each inspection to monitor condition over time. It is particularly
important to examine the tapered regions of the repair for any evidence of the laminate lifting away
from the substrate. Feeler gauges can be helpful in establishing the extent of any lifting in the
tapered region. Leaks or weeps often manifest themselves at the edges of the repair but sometimes
can also be seen coming through the body of the repair, Figure 6.3. These leaks indicate that the
composite repair has failed.
Figure 6.3
(l-r) Leak at edge of repair22; through main body of composite repair.
Safety critical repairs are likely to be subjected to the same visual examination as non-safety critical
repairs, albeit on a more frequent basis. In addition, as detailed in Section 2.2.7, inspection of the
substrate should have been considered. For external substrate defects, the periodicity will have
been set such that the integrity of the line remains assured. For internal mechanisms, an inspection
strategy will have been derived that permits evaluation of the footprint, and/or depth, of any
defects to verify that they are within tolerable limits with respect to the repair design. For safety
critical gas systems, gas detection equipment should also be considered.
A key element at this stage is the verification/validation of the assumptions made at the decision
making stage. In other words, establishing whether the inspection strategy defined at the decision
making stage provides the required data to ensure integrity. Issues related to coverage and/or
resolution may necessitate revisiting the inspection strategy (informed by Appendices C-E) and in
some cases may require a re-evaluation as to whether an engineered composite repair is
appropriate (Section 3.3).
21
22
BS EN ISO 24817:2017, Section 9.2, Table 16
Note prepared section of substrate that has not been coated – considerations outlined in Section 5.5.1 apply.
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6.3.3 Key Inspection Techniques – Ongoing Integrity Considerations
Section 2.2.7 detailed that dynamic response spectroscopy (DRS), pulsed eddy current (PEC)23 and
radiographic techniques (or a combination thereof) are the most established techniques for the
inspection of composite repairs.
If an inspection was conducted directly after repair installation (Section 5.4.1) this can act as a
baseline for all future inspection activities.
If the inspection strategy was to use solely DRS to detect defects in the laminate, bondline and
substrate a review of baseline data would indicate whether this is still an acceptable approach.
Using DRS, any flaws in the laminate and/or bondline precludes substrate thickness measurements
in those areas. A review of the baseline data would provide an indication of the likely successful
coverage for wall thickness measurement and whether a further technique would be required,
perhaps using DRS solely to identify/monitor defects in the laminate/bondline. Comparison with
baseline inspection data would be particularly useful for detecting new defects in the laminate or
bondline, despite the exact (through-thickness) position of the flaw not being indicated. It would
not be expected that flaws would develop in the laminate or interface post installation. In such
cases the operator should liaise with the repair supplier.
If the inspection strategy was to monitor general external corrosion using PEC, a key consideration
will be to verify that there is also no threat from any internal corrosion mechanism. If a baseline
inspection has been performed this provides an opportunity to monitor for any changes. This can be
enhanced by interrogating the inspection data. For a repair applied for general external corrosion
any changes in wall thickness measurement are likely to indicate the presence of an internal
mechanism. If it is a localised mechanism it is unlikely to be detected.
In line with DRS and PEC, for radiographic techniques a baseline inspection provides an opportunity
to monitor change. The main focus should be consideration to any future threats and accessibility to
enable the number of required exposures and from the appropriate angles.
6.3.4 Key Considerations
Section 6.3.2 highlighted the importance of confirming/validating that the inspection strategy
defined at the decision making stage yields the required data to ensure integrity. For safety critical
repairs this is something that needs to be considered throughout the life of the repair.
For repairs to substrates suffering from external corrosion, consideration should be given to any
changes to process conditions that may result in the substrate being exposed to a different
degradation mechanism than was envisaged when the repair was designed and installed. For any
planned changes to process conditions it is expected that an appropriate risk assessment is
conducted (See Section 6.4).
If the repair is considered to be safety critical, significant corrosion at the edges of the repair
(potentially coupled with lifting of the repair laminate) should result in a reassessment of the design
requirement and potentially, repair of the original repair or replacement.
23
Substrate only.
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6.3.5 Remedial Action
If defects in the interface, resin rich layer, and repair laminate are outwith the limits specified within
BS EN ISO 2481724 then there are three options:



Removal of the repair (this should be undertaken if the repair has failed).
Repair of the repair laminate.
Localised repair of the damaged region.
Under certain circumstances, if defects are identified in the repair laminate, the repair can be
treated as a defect and a new composite repair can be applied over the compromised one.
However, careful consideration needs to be given before this approach is employed as it can lead to
excessively large repairs25.
If inspection of the substrate indicates that the size of the defect is found to be approaching or
exceeding that used in the design, advice should be sought from the repair supplier. In the case of
the former, this is particularly important where the periodicity of inspections is such that the defect
size may exceed that used in the design prior to the next planned inspection.
If additional defects in the substrate are identified during inspection that were not accounted for at
the design stage, advice should be sought from the repair supplier as part of a broader risk
assessment. In particular, it should be established whether an engineered composite repair remains
the appropriate corrective action given the additional defects (see Section 3.3).
6.4
Ongoing Validity of Input Data
As detailed in Section 2.2.8, the repair design is informed by the input data supplied by the client.
These inputs represent only a small part of the broader considerations as to whether the use of an
engineered composite repair is the most appropriate course of action (Section 3.3).
For safety critical repairs it is important that the accuracy and validity of the original design
inputs/assumptions remain valid and that the broader considerations detailed in Section 3.3 are
reviewed on a periodic basis.
Prior to any planned change it is expected that an appropriate risk assessment is conducted that
gives due consideration to features such as the repair. This should include consulting the repair
supplier to identify any compatibility issues and broader fitness for service considerations. In the
event of an unplanned change in process conditions the owner should seek the advice of the repair
supplier. Consideration of the process conditions and the potential effect on the composite repair
should be made throughout its lifetime.
6.5
Life Extension/Life Reduction
6.5.1 Extension
The decision to extend the repair design life should be documented. All supporting records to
underpin any decisions should also be kept for future reference.
24
25
BS EN ISO 24817:2017, Section 9.2, Table 16
This may also impact the efficacy of NDT techniques given additional repair thickness.
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For non-safety critical repairs it is suggested that the owner should discuss an extension to the
design lifetime with the repair supplier taking into account operating history. The repair shall
undergo a visual inspection. Provided it is assessed that failure of the repair would present no
significant risk to personnel safety or damage to the environment this close visual inspection will
suffice and a life extension may be granted provided the repair remains in good condition with no
signs of deterioration.
For safety critical repairs the design and installation details must be available (these shall include
records of the surface preparation of the substrate and that the design and cure of the repair met
the original specifications) and the installation records must be sufficient to demonstrate the repair
was installed in full compliance with the repair supplier’s qualified procedures. In particular, the
surface preparation achieved (in terms of preparation grade, surface profile, method and tool(s)
used) at the time of installation shall be considered with respect to performance, long-term
durability and approval of any life extension. In addition, the substrate should be inspected to
inform the decision making process. Factors to be considered in determining if the design life of a
safety critical repair may be extended include:

Inspection for degradation of repair.

NDT of repair and substrate, if possible.

Substrate
degradation
(corrosion)
mechanism(s) (internal/external).

The surface preparation procedure when
installed.

Additional threats since installed or over
additional lifetime (e.g. different/additional
degradation mechanism(s)).

Review of installation documentation.

Service conditions and operational history
with respect to repair design conditions.

Review of calculations.

Limiting factor for design life initially and
whether this still stands or can be overcome.

Evidence of the system being able to extend
beyond its current life.

Validity/applicability
assessment.

Repair is acting or could act as primary
means of containment.
of
original
risk
Special consideration should be afforded to the design life extension of safety critical repairs
where the repair is acting or could act as the primary means of containment. As detailed in
Section 2.2.8, such repairs are for short term use only.
Re-validation of the repair design lifetime is performed by re-designing the repair based on the
required lifetime and the most up to date inspection data on the defect of concern26.
6.5.2 Reduction
As detailed in Section 6.3, changes to process conditions and other threats can occur. If the review
of the broader considerations detailed in Section 3.3 concludes that an engineered composite repair
is still appropriate, the implications of these changes on the original design basis will need to be
considered.
26
Note that any redesign may also impact on the efficacy of NDT techniques.
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The repair supplier should be approached and requested to re-evaluate the design based on the new
information. The outcome of this assessment may be: (1) an engineered composite repair is no
longer viable; (2) Remedial action; (3) In the absence of any (possible) remedial action, a reduction in
the design life of the repair.
The operator should also re-consider the defined life of the repair to establish whether it is still
suitable in light of the new information. The defined life repair register and any other appropriate
documentation should be revised to reflect any changes.
6.6
Decommissioning and Removal
6.6.1 Decommissioning
Adequate systems of work and documentation should be maintained (in particular a repair register)
such that it is clearly apparent when the defined lives of repair systems are approaching and action
is required. Reference should be made to the original risk assessment prior to decommissioning of a
repair system. If necessary, a revised risk assessment should be carried out.
6.6.2 Repair removal
The removal of repair material may be achieved by mechanical means (e.g. grit blasting and highpressure water jetting). This activity should be informed by an appropriate risk assessment.
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7
REFERENCES
1. ASME PCC-2, Repair of Pressure Equipment and Piping, 2018
2. BS EN ISO 24817:2017, Petroleum, petrochemical and natural gas industries – Composite repairs
for pipework – Qualification and design, installation, testing and inspection (ISO 24817:2017),
2017.
3. Control of Major Accident Hazards (COMAH) Regulations, 2015
4. Health and Safety at Work etc Act, UK Public General Acts, 1974
5. The Offshore Installations (Offshore Safety Directive) (Safety Case etc) Regulations 2015
(SCR2015)
6. The Pipeline Safety Regulations (PSR), UK Statutory Instruments, 1996
7. The Pressure Systems Safety Regulations (PSSR), UK Statutory Instruments, 2000 (Onshore only)
8. The Offshore Installations (Prevention of Fire & Explosion and Emergency Response)
Regulations, UK Statutory Instruments, 1995 (Offshore only)
9. The Management of Health and Safety at Work Regulations, UK Statutory Instruments, 1999
10. The Offshore Installations and Wells (Design and Construction, etc) Regulations, UK Statutory
Instruments, 1996 (Offshore only)
11. The Provision and Use of Work Equipment Regulations (PUWER), UK Statutory Instruments, 1998
12. Yeomans, E.Y., Human Factors associated with installation of an Engineered Composite Repair –
Task and human failure analysis, ERG/18/29, HSE, 2018
13. Harris, W., Review of In-service Failures, ES/2018/33, HSE, 2018
14. BS EN ISO 8501 – Visual assessment of surface cleanliness, Part 1 – Part 4
15. BS EN ISO 8502 – Tests for the assessment of surface cleanliness, Part 2 – Part 12
16. BS EN ISO 8503 – Surface roughness characteristics of blast-cleaned steel substrates, Part 1 –
Part 5
17. BS EN ISO 8504 – Surface preparation methods, Part 1 – Part 3
18. Guidance Notes on Composite Repairs of Steel Structures and Piping, American Bureau of
Shipping (ABS), September 2019
19. Davis, M., Review of Adhesive Bonding Aspects of BS EN ISO 24817, Adhesion Associates Pty.
Ltd., 2019
20. BS EN ISO 8502-5, Preparation of steel substrates before application of paints and related
products — Tests for the assessment of surface cleanliness — Part 5: Measurement of chloride
on steel surfaces prepared for painting (ion detection tube method), 1998
21. Recommended Practice, DNV-RP-C301, Design, fabrication, operation and qualification of
bonded repair of steel structures, July 2015
22. BS EN ISO 8504-1, Preparation of steel substrates before application of paints and related
products — Surface preparation methods — Part 1: General principles, 2019
23. BS EN ISO 8504-2, Preparation of steel substrates before application of paints and related
products — Surface preparation methods — Part 2: Abrasive blast-cleaning, 2019
24. BS EN ISO 8504-3, Preparation of steel substrates before application of paints and related
products — Surface preparation methods — Part 3: Hand- and power-tool cleaning, 2018
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25. BS EN ISO 8501-1, reparation of steel substrates before application of paints and related
products — Visual assessment of surface cleanliness — Part 1: Rust grades and preparation
grades of uncoated steel substrates and of steel substrates after overall removal of previous
coatings, 2007
26. BS EN ISO 8503-5, Preparation of steel substrates before application of paints and related
products — Surface roughness characteristics of blast-cleaned steel substrates — Part 5: Replica
tape method for the determination of the surface profile, 2017
27. Broughton, J., 'Wedge Test Benchmarking Trials', A report prepared by Oxford Brookes
University for the Health and Safety Executive, Health and Safety Executive, EM/20/19, 2020
28. Bannister, A.C., Nemcova, A., Inspection Techniques for Composite Wrapped Pipes:
Lookup Charts for Technique Selection, EM/19/51, HSE, 2019
29. Bannister, A.C., Nemcova, A., Inspection Techniques for Composite Wrapped Pipes: Selection,
Capabilities and Limitations, EM/19/47, HSE, 2019
30. Yeomans, E.Y., Engineered Composite Repairs – addressing human factors issues associated with
installation – training and qualification, HF/19/17, HSE, 2019
31. HSE Safety Notice 04/2005 – Weldless Repair of Safety Critical Piping, HSE, 2005
32. Safety Requirements for Pressure Testing, Guidance Note GS4 (Fourth Edition), Health and
Safety Executive, 2012
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APPENDIX A - ENGINEERED COMPOSITE REPAIRS: KEY CONSIDERATIONS
A1
General
The successful specification, design, installation and through-life management of engineered
composite repairs depends on a number of factors.
This section provides an overview of some key considerations. In part, these have been selected
based on reviews of in-service failures [12, 13]. The top three [12] critical installation steps
associated with the ultimate failure of a composite repair have been identified as: (1) Surface
Preparation; (2) Curing; (3) Defect/Leak Sealing.
Training and experience was also identified [12] as a key topic where improvement could lead to a
greater number of compliant installations with fewer failures. The effect of component
type/geometry is also considered [13]. Inspection has been included given its importance for
ongoing integrity management, as have design/defined life considerations based on the implications
of the above.
The intention is that the information in this section should be used to supplement and inform the
decision making process outlined in Section 3.
A2
Surface Preparation
A2.1 General
Surface preparation of the substrate is critical to achieving satisfactory adhesion27 between the
repair laminate and repair surface. It is the single most important step for ensuring a successful
repair. Surface preparation generally involves removing contaminants from the substrate by
degreasing, exposing a fresh chemically active surface and in some cases modifying the surface by a
chemical process to enhance bond durability. Thus, surface treatment of steel produces a rough
surface, free from contamination and enhances the formation of chemical bonds between steel and
the adhesive.
Effective surface preparation is necessary to achieve initial strength and particularly long-term
durability in the service environment. Failure to adequately prepare a bonding surface may result in
bond failure and/or corrosion of the bond region. The fact that the results of the bonding process
cannot be fully verified by subsequent inspection and testing acts to reaffirm the essential need for
good process control and adhering to qualified procedures.
The four standards below address the preparation of steel substrates:
1.
2.
3.
4.
BS EN ISO 8501 – Visual assessment of surface cleanliness [14]
BS EN ISO 8502 – Tests for the assessment of surface cleanliness [15]
BS EN ISO 8503 – Surface roughness characteristics of blast-cleaned steel substrates [16]
BS EN ISO 8504 – Surface preparation methods [17]
27
In this case it is the adhesion (i.e. the interfacial interactions) that is the consideration - how the environment is attacking the interface
and how well the interface resists this is a function of surface preparation. Bulk changes and chemical compatibility are also important
and need to be considered.
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These standards were originally conceived for the corrosion protection of steel structures by
painting, but have since been used for preparing steel surfaces for repair using bonded repair
technology.
It is important to note that BS EN ISO 24817 is a performance based standard. As such, the surface
preparation processes and procedures should be qualified by testing. An overview of the key steps
is provided in the following sections.
A2.2 On-site Conditions
Guidance [18] suggests the steel temperature and air humidity should be monitored for possible
condensation on the steel during surface preparation and fabrication/installation. It is stated that
the steel temperature should be at least 3°C higher than the air dew point and that the relative
humidity should not be greater than 80%.
BS EN ISO 24817 states that for installation of the repair the surface of the pipe shall be dry and at a
temperature above the dew point or otherwise in compliance with the conditions validated by repair
qualification testing28. BS EN ISO 2481729 suggests that repairs should not be applied when the
temperature of the surface is less than 3°C above the dew point of the surrounding air or when the
relative humidity of the air is greater than 85%, unless local conditions dictate otherwise.
Verifying the environmental conditions are acceptable is a key hold point during the installation of a
repair system30.
A2.3 Removal of Contaminants
Contaminants are well known to adversely affect bond performance. Contaminants can include:
slag, rust, laminated rust scale, mill scale, oil, grease, salts including chlorides and sulphates,
moisture etc.
Prior to mechanical abrasion using the selected method (see A2.4), an initial treatment should be
performed that removes any surface contaminants. This is often achieved via water/solvent based
cleaners. Performing the mechanical abrasion step prior to the removal of contamination will force
the contaminants to be embedded in the surface deleteriously affecting bond performance [19].
Where salt contamination is plausible (e.g. coastal locations/offshore), a salt test should be
performed. BS EN ISO 8502-5 [20] describes a field test for the measurement of chloride ions.
Chloride salts left on a surface before mechanical treatment can have a deleterious effect on
performance. Acceptance levels of 80 mg/m2 [21] and 50 mg/m2 [18] are quoted in existing
guidance.
For severely contaminated surfaces an additional step is required. Heavy, firmly adhering rust and
scale should firstly be removed via hand/power tool cleaning or water jetting, as appropriate. The
initial treatment should then be conducted prior to the main mechanical abrasion step using the
selected method [19].
28
29
30
BS EN ISO 24817:2017, Section 6
BS EN ISO 24817:2017, Section J3
BS EN ISO 24817: 2017, Section 8.3, Table 14
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A2.4 Surface Cleaning31 (Mechanical Abrasion)
BS EN ISO 8504-1 [22] covers surface preparation methods with the most relevant described in BS
EN ISO 8504-2 [23] (Abrasive blast cleaning) and BS EN ISO 8504-3 [24] (Hand- and power-tool
cleaning).
Abrasive blast-cleaning is achieved via the impingement of abrasive onto the surface to be prepared.
The abrasive used takes the form of grit which is angular and has fractured faces. Hand-tool cleaning
involves preparing the steel substrate by the use of hand tools, without power assistance. This
usually takes the form of scrapers, hand wire brushes etc. Power-tool cleaning involves preparing
the steel substrate by the use of power-assisted hand tools.
It is important to note that this step does not remove oils, grease etc, hence the importance of the
stage detailed in Section A2.3.
Once complete, all loose material should be removed. At this stage some surface preparation
procedures incorporate an additional degreasing step. In all cases, once completed it should be
ensured that the surface is dry and all debris has been removed.
A2.5 Assessment
A2.5.1 General
BS EN ISO 24817 details the surface preparation hold points32. These encompass visual assessment
of the surface cleanliness, assessment of the surface profile and wettability.
A2.5.1 Visual assessment of surface cleanliness
BS EN ISO 8501-1:2007 [25] specifies a number of preparation grades33, indicating the method of
surface preparation and the degree of cleaning. The most common preparation grades are Sa 2.534,
St 2 35 and St 336. It is paramount that the surface preparation grade achieved on-site is the same
[including the method/tool(s)/procedures used] as those used to qualify the repair system and for
the purposes of design.
A2.5.2 Assessment of the roughness of cleaned surfaces
BS EN ISO 8503 [16] defines tests for the assessment of the roughness of abrasive blast-cleaned
surfaces. BS EN ISO 8503-5 [26] is most relevant, describing a replica tape method for the
determination of the surface profile. Existing guidance states that the surface profile should range
from 75 to 115µm [18, 21].
31
The use of the word ‘cleaning’ for this step in standards can lead to confusion. A clean surface is an essential requirement for adhesion.
However, a clean surface is not a sufficient condition for adhesion. The surface must also be chemically active to enable reactions to occur
at the interface. This step usually involves abrasion to remove existing weak oxide layers, leaving the surface to develop a fresh chemically
active and stable surface that is suitable for adhesion.
32
BS EN ISO 24817: 2017, Section 8.3, Table 14
33
Sa, St or FI indicates the type of cleaning method used. The number indicates the degree of cleaning from mill scale, rust and previous
coatings. Surface preparation by blast-cleaning is designated by the letters ‘Sa’, surface preparation by hand and power tool cleaning,
such as scraping, wire-brushing and grinding is designated by the letters ‘St’, whilst surface preparation by flame cleaning is designated by
the letter ‘FI’.
34
Sa 2.5: When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from mill scale, rust, paint
coatings and foreign matter. Any remaining traces of contamination shall show only as slight stains in the form of spots or stripes.
35
St 2: Thorough hand and power tool cleaning: When viewed without magnification, the surface shall be free from visible oil, grease and
dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.
36
St 3: Very thorough hand and power tool cleaning: As for St 2, but the surface shall be treated much more thoroughly to give a metallic
sheen arising from the metallic substrate.
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In practice, the replica tape method is often also used on surfaces prepared using other methods in
an attempt to establish a minimum surface profile.
A2.5.3 Assessment of Surface Wettability
Adhesive bonding involves a liquid ‘wetting’ a solid surface. This implies the formation of a thin film
of liquid spreading uniformly in contrast to one that readily breaks into bead-like droplets. The
formation of bead-like droplets implies that the surface is contaminated. A continuous film indicates
good wettability whilst the formation of distinct droplets indicates poor wettability. A stipple test is
defined in BS EN ISO 2481737.
A2.5.4 Non-conformance
If after conducting the assessment stage it transpires that the required grade/specification has not
been achieved the surface preparation procedure and any subsequent assessment should be
repeated.
It should be noted that a surface that was originally deemed to be compliant and to specification
may subsequently be deemed to be non-compliant if oxidation occurs. In this case, as above, the
surface preparation procedure and any subsequent assessment should be repeated.
A2.6
Corrosion Inhibitors and Chemical Treatment
A2.6.1 Corrosion Inhibitors
Specifically formulated corrosion inhibitors (i.e. not grease) work by delaying the onset of corrosion
of the prepared surface. If such corrosion inhibitors are considered to be part of the surface
preparation procedure it is essential that their use has been qualified by testing. In particular, any
effect on the initial strength, integrity or durability of the bond needs to be established. In the
absence of such data, the focus should be to minimise exposure times between process steps and to
repeat the surface preparation procedure if oxidation occurs (Section A2.5.4).
In some cases corrosion inhibitors may also include coupling agents that take the form of silanes (see
Section A2.6.2).
If a qualified corrosion inhibitor is applied as part of the surface preparation procedure and there is
going to be a subsequent delay in the lamination step, it is important to protect the surface of the
pipe from contamination post application of the corrosion inhibitor.
A2.6.2 Chemical Treatment
BS EN ISO 2481738 states that a chemical treatment may (or may not) be used. A chemical
treatment can be applied to a prepared surface to prevent hydration, thereby enhancing bond
longevity [19]. One effective method is the use of silanes. Silanes can be used in three ways: (1) As
a surface preparation treatment applied directly to the active surface prior to bonding; (2)
Incorporated into a primer that must be applied directly to the active surface prior to bonding; (3)
Incorporated as an additive in the adhesive/resin system that must be applied directly to the active
surface during the bonding process.
37
BS EN ISO 24817:2017, Table 14
BS EN ISO 24817: 2017, Section J.2
38
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Whilst the inclusion of a silane treatment step can lead to improved durability, their effectiveness is
dependent on a range of factors including the surface condition of the metal. As such this needs to
be well controlled via the use of an effective surface preparation procedure prior to application. If a
chemical treatment step is considered to be part of the surface preparation procedure it is essential
that their use has been qualified by testing. In particular, any effect on the initial strength, integrity
or durability of the bond needs to be established.
A2.7 Surface Drying
It is important that post application of any primers etc and prior to commencement of the
lamination procedure that there is no evidence of any surface liquid remaining.
A2.8 Surface Exposure Times
BS EN ISO 2481739 states that the time period between completion of the surface preparation stage
and the application of the repair laminate should be as short as possible but no longer than four
hours. No guidance is provided on the times between actual process steps.
It has been demonstrated [27] that a time delay of four hours between surface cleaning (the
process described in Section A2.5) and lamination can dramatically reduce bond performance and
in-service durability. To maximise surface preparation quality, exposure times between process
steps are to be kept to a minimum. All bonding processes must be performed as rapidly as possible,
with breaks in the steps kept to an absolute minimum. No foreign matter is to contact the surface.
During any breaks in processes, surfaces are to be protected. However, it should be noted that
whilst covering the prepared area may prevent further contamination it will not stop weak oxide
growth.
Given the high potential for contamination during field repairs, the coordination and management of
schedules for implementation of repairs should be considered, especially where repair tasks are
potentially disrupted by changes of shift teams or where task responsibilities are shared between
different contractors [19].
A2.9 In-service Performance and Durability Considerations
BS EN ISO 8504-3 [24] states that hand- and power-tool cleaning generally provide a surface
cleanliness which is inferior to that achieved by abrasive blast-cleaning. Given this type of abrasion
is dependent on repeated contact over the surface, any contaminants can be widely distributed by
the process. As detailed in Section A2.5.1, hand- and power-tool cleaning is usually undertaken to
achieve a preparation grade of St 2 or St 3.
In practice, hand cleaning and power-tool cleaning are often synonymous with preparation grades St
2 and St 3 respectively. Abrasive blast-cleaning is typically undertaken to a preparation grade of Sa
2.5. BS EN ISO 8504-2 [23] considers abrasive blast cleaning to be the most effective method for
mechanical surface preparation. Experience in other sectors also suggests that this method is the
most effective and has the most reproducible results [19].
It has been demonstrated experimentally [27] that the different cleaning methods lead to
contrasting surface topographies and variability in their ability to remove corrosion deposits. Hand
39
BS EN ISO 24817, Section J.2
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cleaning with a wire brush to a preparation grade of St 2 and power-tool cleaning with a rotating
abrasive belt to St 3 have been shown to produce inconsistent surface topographies with clear
identifiable regions of oxides still visible. In contrast, the use of a specialised rotary bristle tool40 or
grit blasting to Sa 2.5 results in considerably more uniform surface topographies, with little to no
visible oxides.
In terms of durability, it has been demonstrated that grit blasting to a preparation grade of Sa 2.5
leads to superior results compared to a preparation grade of St 3 (achieved using a rotating abrasive
belt power tool in [27]) and significantly improved results over a preparation grade of St 2 (achieved
manually using a wire brush in [27]). The latter, in particular, led to very poor durability
characteristics. It was demonstrated that the specialised rotary bristle tool can lead to results
comparable41 to those achieved via grit blasting to Sa 2.5. As such, hand or power tool cleaning (to a
surface preparation grade of St 2 and St 3) using a wire brush and a rotating abrasive belt have been
demonstrated to be ineffective.
The difference in performance between a rotating abrasive belt and the specialised rotary bristle
tool highlights the importance of power tool selection. Preparation grade is simply a way of
classifying visual surface cleanliness, the broader requirements for adhesion already outlined in
Section A2.1 apply.
It was found that the addition of a chemical treatment step (silane) to a grit blasted surface to a
preparation grade of Sa 2.5 (as per Section A2.6.2) improved durability still further.
An overall observation was that despite a clear hierarchy being established, there remains some
doubt over current practice and its ability to guarantee optimum durability. Further, it was
highlighted that water and therefore water-based fluids are particularly deleterious to adhesive
bonds.
A number of the above observations are corroborated by a review of in-service failures [13] where it
was found that more failures were ultimately attributed to ‘bonding issues’ when a substrate had
been prepared to St 2, as compared to St 3 and particularly Sa 2.5. However, overall, the study
found that the failure rate was very low. It was also noted that the data suggested that the majority
of failures occurred instantaneously. However, in both cases this may be a reflection that in the vast
majority of instances composite repairs have been used on a short term basis only – typically to
coincide with the expected cycles of shutdowns or maintenance schedule.
A3
Defect / Leak Sealing
Repairs to defects that have gone through-wall and are leaking are possible but require special
consideration. It is particularly important to verify that any leak sealing device/technology has
isolated the leak and will do so for the duration of the repair installation, including curing. There
have been several repair failures on safety critical equipment where it was established that the
40
In these tests a Monti Bristle Blaster® was used. The Bristle Blaster® is a type of rotary bristle power tool and has the potential to result
in a surface cleanliness that exceeds St 3 as per BS EN ISO 8501-1. Visually, without magnification, it has the potential to produce a bare
metal appearance that is similar to Sa 2.5.
41
It is important to note that consistent with other power tools, the potential for cross-contamination of the surface remains. Results are
based on flat plate trials only.
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approach to leak sealing was inadequate at the time of repair installation [12]. The presence of any
leak sealing device should be considered at the design stage and the size/geometry of defect
selected to encompass the device and any filler used.
A4
Cure
A4.1 General
It is important that the same level of cure (or glass transition temperature) is achieved during the
manufacture of the repair as was qualified and used in the design. Cure duration and any post cure
requirements should be considered in the repair assessment to ensure a suitable repair system is
applied.
A4.2 Cure Schedule
The cure schedule describes the temperature time/ profile. It should have been established that the
cure schedule is suitable to achieve the necessary Tg value. Where, based on qualification testing,
the supplier can demonstrate that the required glass transition temperature is achieved by ambient
cure alone, then heat treatment may be omitted. In all other cases the supplier shall provide a heat
treatment procedure (temperature profiles and hold times) which has been demonstrated to
achieve the required glass transition temperature during qualification.
Post curing should only be undertaken once the resin has hardened and on equipment that is
depressurised and drained. Any heat applied to cure must be controlled and known. Taking credit
for heat treatment due to heating from process fluid is not permitted.
The operator should be aware of the time required for cure and the requirement that the repair is to
be cured to an acceptable level (see A4.3) before the pressure is brought back to normal operating
conditions. Not doing so has been identified as the principal reason for repair failure during this
phase of the repair installation [12].
Consideration needs to be afforded to the total number of layers that make up the repair laminate,
the number of layers that can cured at one time, and the cumulative time this will take.
A4.3 Quality Assurance Checks
Hardness testing (Shore or Barcol) is not a direct measurement of cure but can provide an indication
that the repair system has cured to an acceptable level. When measured, the hardness should not
be less than 90% of the minimum value obtained from repair system qualification42.
Hardness testing alone should not be relied upon to infer an acceptable level of cure. Temperature
profiles and hold times should also be scrutinised.
A4.4 Special Considerations
Design temperature should be carefully considered. If a line has a high design temperature but
operates at a lower temperature, the use of a high temperature resin system may result in under
curing of the laminate leading to a failed repair - unless the repair is post-cured before being put in
service.
42
BS EN ISO 24817: 2017, Section 7.5.3
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A5
In-service Inspection
A5.1 General
Inspection requirements are a key input at the decision making stage when evaluating options for
remedial action. The three candidate areas for inspection are: (1) the repair laminate; (2) the
substrate; (3) the bond between the repair laminate and the substrate. A range of inspection
techniques are available with different capabilities and limitations. Depending on defect type,
consequences of failure, extent of the inspection and data requirements, it is possible that more
than one technique will be required
A5.2 Extent and Periodicity
When determining the extent and periodicity of inspection, consideration should be given to the
degradation mechanism(s) of the substrate as well as consequences of failure. A risk based
inspection (RBI) type approach (or suitable equivalent) is advised. The accuracy of the defect report
is important as it informs the appropriate selection of NDT techniques.
For non-safety critical applications it is likely that any inspection schedule will be limited to a
periodic visual examination only. Appendix B provides an overview of some possible defects. These
are limited to the external surface of the repair and substrate.
For safety critical applications, in addition to visual inspection, inspections should employ available
non-destructive testing (NDT) equipment to confirm the condition of the substrate.
For external substrate defects that are not through-wall, the maintenance strategy should consider
the condition of the repaired substrate as well as the repair. Along with ensuring that the repair
laminate remains intact, there should be no evidence of damage to the laminate, edge
lifting/disbonding, or corrosion at the edges of the repair. The periodicity of any inspection should
be such that the integrity of the line remains assured. The threat of internal corrosion must be
considered throughout the life of the repair. If internal corrosion is determined as active, then the
end user should discuss implications with the repair supplier; particularly the suitability of the
installed repair in the context of this additional threat. In some cases a suitable strategy to mitigate
the threat may be determined (e.g. change in process conditions, use of inhibitors or reduced life of
repair, etc.).
For internal or through-wall defects further deterioration or growth of the defect may continue
despite application of the repair, unless other measures are taken and are verified to be effective. In
addition to the requirements of the external corrosion case, the maintenance strategy should ensure
that the internal defect does not grow to a size greater than that assumed in the design or that the
repair laminate does not disbond from the substrate. It is important to be aware of, and take
account of, the increased risk profile when a defect is through-wall and the repair is acting as the
primary means of containment. This may have been due to an external and/or internal mechanism.
The integrity of the repair must be ensured throughout its lifecycle.
A5.3 Capabilities and Limitations
A range of NDT techniques are available each with their own capabilities and limitations.
Appendices C-E provides a summary with respect to the key areas to inspect [28]. These summaries
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should be used as a basic guide, identifying candidate techniques for subsequent detailed
discussions with inspection companies, as appropriate. It is notable that for a number of NDT
techniques, whilst their capability to detect absolute values is restricted, they can be used to identify
change. i.e. comparing before and after.
Whilst some NDT techniques can identify and size bondline defects, there remains no validated
inspection technique to establish the integrity of the bond, emphasising the importance of
appropriate surface preparation and adherence to qualified procedures.
It has been found [29] that whilst there are a range of techniques available, pulsed eddy current
(PEC), radiography and dynamic response spectroscopy (DRS) are the most established techniques
for the inspection of composite repairs, despite each technique having its own limitations.
Depending on a range of factors, both radiography and DRS have the potential to identify both
laminate and bondline defects. This is a particular strength of the DRS technique and, as such, it has
been used as a quality assurance tool post installation.
The application of a composite repair prevents the subsequent use of some NDT techniques to
establish the condition of the substrate. This includes standard ultrasonic testing, including phased
array, as well as surface NDT methods such as dye penetrant testing, visual examination and
magnetic particle inspection.
Further details on in-service inspection is provided in Section 6.3.
A5.4 Practical Considerations
In addition to the points raised in Section A5.3, the viability of successfully deploying any NDT
techniques should be considered at the decision making stage.
Consideration should be given to conducting an inspection to confirm that the selected inspection
techniques are viable from a capability and practical standpoint.
A5.5 Baseline Inspection
For safety critical repairs, a baseline inspection should be conducted pre43 and post repair
installation. The post installation inspection serves two purposes. Firstly, for some techniques it
affords an opportunity to establish the quality of the repair installation. Secondly, it permits a
comparison of future inspection data to ‘as installed’. This is particularly applicable for techniques
that can be used to identify change over time.
A6
Training and Competency
A6.1 General
All end user employees involved in the specification, application and management of engineered
composite repairs should have had sufficient training and experience to be deemed competent [30].
Composite repair technology is a specialised field, potentially employing a range of materials and
processes that are unfamiliar to many. A review [30] has recommended the following training:
43
This depends on how comprehensive/time since the anomaly report was prepared and whether sufficient data was acquired during the
viability inspection to preclude this additional step.
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1. Training for operator/client personnel involved in engineered composite repair installation
to give them the knowledge of the systems and awareness of the potential issues and
increased likelihood of failure if the repair is not prepared, installed and cured as specified.
2. Training for installers, supervisors and client personnel in human factors aspects surrounding
the management, installation and inspection of engineered composite repairs may help with
the understanding of the nature and type of human errors and the factors that may make
errors and short cuts more likely.
A6.2 Applicability
Candidates for (tailored) training programmes are:
1. Technical Authority (or equivalent)
2. On-site field engineers (or equivalent)
3. On-site inspection engineers (or equivalent)
The ‘Technical Authority’ (or equivalent) should have a sufficient level of competency to review
repair supplier design proposals and verify that they are fit for purpose. Further, they should be
aware of the general capabilities and limitations of composite repair technology and NDT
techniques. This will inform the decision making process as to whether a composite repair is
feasible/appropriate. In addition, when the repair has been installed and added to the repair
register, the ‘Technical Authority’ should be able to review the repair close out documentation and
establish that the repair reflects what was proposed and is fit for purpose.
For safety critical repairs, an end user representative should be at the repair site to verify hold points
and act as a further level of quality assurance/control. With this in mind, ‘on-site field engineers’ (or
equivalent) should have an awareness of the key hold points as well as the pre/post installation
quality assurance checks. They should have the necessary competence to sign-off the repair
following inspection and reviewing any associated documentation/paperwork.
On-site inspection engineers (or equivalent) should have a sound appreciation of composite repair
technology. Specifically, they should be aware of the key areas to inspect and allowable limits for
defects. They should be competent in reviewing inspection data (visual and/or more sophisticated
forms of NDT) and highlighting anomalies for further investigation.
A6.3 Training
Competence can be developed through training and/or operational experience. The most effective
is likely to be a combination of the two. A number of repair suppliers now offer composite repair
awareness training courses which present an ideal opportunity to learn about the technology. The
courses often take the form of theoretical and practical sessions. In many cases, bespoke courses
can be provided, catering for the direct needs of the client.
A7
Applications
A7.1 General
BS EN ISO 24817 covers the qualification and design, installation, testing and inspection procedures
for composite repair systems involving damage commonly encountered in oil, gas, utility pipework
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systems and vessels. For pipework systems, this can mean repairing a range of geometries including:
straights, tees, bends, reducers and flanges.
A7.2 Performance and Reliability
A review of in-service failures [13] suggests that for pipework systems the rate of failure is highest
for repairs to reducers and tees.
Vessels require special consideration, with over one in ten repairs subsequently failing in service
[13]. This failure rate is significantly higher than for all other repair types. A large number of these
failures were attributed to difficulties in consolidating the repair onto the side of the vessel. Such
repairs often take the form of a patch rather than a circumferential wrap and can be more
challenging to apply successfully.
A7.3 Special Considerations
For novel repairs, perhaps infrequently applied, or repairs with specific considerations (e.g.
restricted access), consideration should be given to undertaking full-scale feasibility trials [30]. Such
trials can prove informative for both the repair supplier and the client. They can help establish
whether a composite repair is viable, as well as informing and optimising any procedures which may
take place at the repair site.
The time and effort afforded to such an activity is likely to only be warranted for safety and
potentially business critical repairs.
A8
Repair Lifetime
A8.1 General
All engineered composite repairs should have a design life and a defined life. These should be
clearly stipulated in all relevant documentation, including the defined life repair register.
A8.2 Design Life
The design life is the maximum application lifetime of the repair. It is defined by the owner and used
by the repair supplier for the purposes of design. It may transpire that the owner defined design life
is not feasible given the defect type and service conditions. Ultimately, it should be agreed between
the repair supplier and the client. It is important that the client ensures that any information/data
used for the purposes of design by the repair supplier is robust and accurate.
Each engineered repair shall have a design life which may be the same, but shall never be less than
the defined life of the repair. Composite repairs shall have a specified minimum design life of two
years44.
As the repair design is based on the (initial) input data provided by the client, for safety critical
repairs it is important that any potential deviations (through-life) are discussed with the repair
supplier. This may be informed by, for example, inspection data or a change in process conditions.
The revised input data may mean that an engineered composite repair is no longer an appropriate
solution or result in the design life being reduced unless some form of remediation is undertaken.
44
BS EN ISO 24817:2017, Section 7.3
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Once a repair has exceeded its design life it shall be removed or re-evaluated. Section 6.4 provides a
more comprehensive overview of design life reduction and extension.
A8.3 Defined Life
The defined life is the actual application or intended service lifetime of the repair. The defined life is
set by the end-user with due consideration of the risks associated with each repair and defines the
time after which the repair needs to be re-validated or its removal scheduled. Defined life extension
does not generally require repair supplier input, rather re-consideration of the risks associated with
the repair.
For safety critical applications the defined life should be set by the risk assessment on a case by case
basis.
For safety critical applications, if the repair is intended to provide the primary means of containment
(either immediately after application or at any time during the life of the repair) it should be
considered for short-term use only45.
Special consideration should be afforded to scenarios where there is an active internal degradation
mechanism where damage has not yet broken through wall but could do so during the life of the
repair. In this case, the ability of the repair to provide primary containment must be demonstrated
for the largest defect that is considered may develop. Initial, successful performance of the repair,
shall not be considered to provide any indication of future reliability because of the changes
expected in the defect.
It should be noted that the risk profile associated with each repair can change over time, for
example, this may be influenced by changes in process conditions, inspection findings etc. As such,
for safety critical repairs the defined life should be subject to periodic review to confirm that the
design basis is still appropriate and valid.
45
Consideration should be given to bringing shutdowns forward if the risk profile warrants such action – the integrity of the repair must
be ensured throughout its lifecycle.
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APPENDIX B – VISUAL INSPECTION CHECKLIST
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APPENDIX C – NDT TECHNIQUE SELECTION CHART (PART A) [29]
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APPENDIX D – NDT TECHNIQUE SELECTION CHART (PART B) [29]
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APPENDIX E - NDT TECHNIQUE SELECTION CHART (PART C) [29]
Aspect
Large pipe diameters

Thick walled pipe



Thin walled pipe

Substrate magnetic
properties
Repair material(s)

Small pipe diameters



Wrap thickness


Wrap surface quality




Liquid within pipe


Presence of welded
features, attachments or
component edges
Extent of wrap coverage



Principal effects on inspection techniques
Radiography: May limit application for tangential radiography,
typical upper limit 8” for Schedule 40 pipes, increasing to 14”
for thinnest walls; exact limit depends on pipe wall thickness
and radiation source being used
PEC: Probe contact limitations, Typical lower limit 1”
DRS: Probe contact limitations, Typical lower limit 4”
Radiography: May limit application depending on radiation
source being used in the case of tangential radiography
PEC and DRS: Typically 3 mm lower wall thickness, limit
increases with wrap thickness for DRS
PEC: Requires magnetic material such as C-steel; cannot be
used on austenitic, duplex or super-duplex steels
Microwave: cannot be used on carbon fibre wraps (Material
must be non-conducting)
Visual: Less effective on carbon fibre wraps or painted wraps
due to reduced contrast
DRS: Putty/filler used for repair of external defects can
potentially prevent WT measurements in those areas
PEC: Wrap thickness increases lift-off and therefore
exacerbates wall thickness averaging effect
DRS: Limited to 12 mm wrap thickness in most cases, up to
19 mm by exception
Radiography: Thick wraps can decrease image resolution
Laser Shearography: Limited to ~10 mm thick
Laser Shearography: Surface scratches or gouges can affect
image quality
DRS: Poor surface quality such as wrinkles limits applicability of
method
Radiography: Presence of oil or water reduces image
resolution and increases required exposure time
GWU: Length range of inspection is reduced by presence of
high viscosity fluids
PEC: Reduced resolution at locations nearer to an edge or
attachment than one probe footprint diameter
GWU: Welded attachments and flanges can affect results
GWU: Requires access to a bare pipe surface on at least one
side of the wrap
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APPENDIX F – HOLD POINTS AND MANUFACTURING CONSIDERATIONS
Method statement (and supporting design information)
 Check cure requirements are appropriate and achievable.
 Confirm defect details and location.
 Confirm substrate geometry and material.
 Confirm surface preparation requirements and that the
repair supplier has undertaken qualification testing using
the methods to be employed on-site.
 Confirm verification activities have taken place, if required.
 Confirm assumptions are valid and realistic.
 Verify worksite requirements.
 Confirm who is responsible for what and liaise with all
parties, as appropriate.
Materials Preparation
 Check all materials to be used for repair:
o Fibre reinforcement
o Resin
o Filler
o Hardener
o Batch numbers
o Dates etc.
Environmental conditions
 Verify environmental conditions repair:
o Relative humidity
o Dew point
o Substrate surface temperature

If required, confirm the following has been provided:
o Access
o Lighting
o Shelter
o Work area/table for material preparation
Surface preparation
 Confirm that exposure times between steps has been kept
to an absolute minimum.
 Verify that the substrate is free from contamination - water,
service fluids, oils etc.
 Undertake salt test, if required.
 Confirm that the preparation grade achieved on-site is the
same as assumed in the design/method statement –
including extent of surface preparation.
 Confirm that surface preparation method/tool used on site
is the same as that assumed in the design/method
statement.
 Ensure that the correct number of surface profile
measurements are taken. Confirm within limits.
 Confirm acceptable stipple test result.
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Filler Profile
 Check correct filler used, as appropriate, so that there is a
smooth profile prior to application of the laminate.
Installation
 Ensure that the correct materials are used / are in date etc.
 Ensure all mixing is done correctly.
 Ensure that the lamination process occurs as soon as
possible after surface preparation activities are completed.
 Ensure that the correct number of layers are applied.
 Ensure that each consecutive layer of reinforcing fabric is
wetted out with resin and is appropriately consolidated.
 Ensure the fibre direction is as per the design.
 Ensure the layers of the repair are free from foreign matter
and contamination
Tests on repair laminate
 Ensure that the curing cycle has been completed in
accordance with the requirements.
 Ensure hardness check completed and recorded. Verify
within limits. Review temperature profiles and hold times.
 Verify repair thickness.
 Verify axial length and taper length of the repair.
 Verify inspection has been completed and the results
recorded. Check within limits.
 Verify that a photographic record has been taken.
 Verify the corrosion barrier been reinstated.
 Verify that baseline NDT has been carried out (if required).
 Verify the repair been identified and tagged.
QA Records
 Ensure the repair process (as undertaken on site) is fully
documented in a close out report, to include:
o Repair reference number
o Visual inspection report
o Thickness measurement
o Repair axial extent measurement
o Curing Details
o Personnel who applied repair
o Hardness measurement (if undertaken)
o DSC measurement (if undertaken)
o Bond strength measurements (if undertaken)
o Inspection and NDT results (if undertaken)
Pressure Testing
 Undertaken if required.
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HSE’s Buxton operations are certified to:
ISO 9001 OHSAS 18001
Health and Safety Executive
Science Division
Harpur Hill
Buxton
Derbyshire
SK17 9JN
UK
www.hsl.gov.uk
www.hse.gov.uk/research
1.2 Redgrave Court
Merton Road
Bootle
L20 7HS
T: +44 (0)20 3028 2000
E: hslinfo@hsl.gsi.gov.uk
help employers reduce injuries, accidents, and ill health
amongst their workforce, increasing productivity
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the wide range of analytical services, HSL social
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scientists can help customers identify ways to