HSEHealth & SafetyExecutiveTemporary/permanent piperepair - GuidelinesPrepared by AEA Technology Consultingfor the Health and Safety ExecutiveOFFSHORE TECHNOLOGY REPORT2001/038

HSEHealth & SafetyExecutiveTemporary/permanent piperepair - GuidelinesAEA Technology ConsultingE1 CulhamAbingdonOxfordshireOX14 3EDUnited KingdomHSE BOOKS

Crown copyright 2001Applications for reproduction should be made in writing to:Copyright Unit, Her Majesty’s Stationery Office,St Clements House, 2-16 Colegate, Norwich NR3 1BQFirst published 2001ISBN 0 7176 2069 7All rights reserved. No part of this publication may bereproduced, stored in a retrieval system, or transmittedin any form or by any means (electronic, mechanical,photocopying, recording or otherwise) without the priorwritten permission of the copyright owner.This report is made available by the Health and SafetyExecutive as part of a series of reports of work which hasbeen supported by funds provided by the Executive.Neither the Executive, nor the contractors concernedassume any liability for the reports nor do theynecessarily reflect the views or policy of the Executive.ii

EXECUTIVE SUMMARYThis document provides guidance on the applicability of a range of pipe repair clampsand pipe connectors to a range of pipe repair scenarios. These repair scenarios cover themost common types of damage/deterioration to piping systems, such as internal andexternal corrosion, and also cover situations where the damage is extensive. Repairclamps are typically used where the damage is localised and pipe connectors are usedwhere the damage is more extensive. Examples of the different types ofdamage/deterioration are explained and the different types of clamps and connectors thatare commonly used are illustrated.The guidance provided in this document includes the limitations of the different types ofrepair components with respect to operating pressure, operating temperature, andlongevity (temporary or permanent repair). Classification of the repair in terms of being atemporary repair or a permanent repair is provided within the context of ‘fitness-forpurpose’ and special consideration is given to the repair of safety critical piping systems.This guidance document is primarily concerned with the use of metallic repaircomponents, however, as composite materials are finding increasing applications to piperepair situations, this document also provides a review of the use of composite repaircomponents.iii




1. INTRODUCTIONThis Guidance Document is aimed at providing information on the range of available pipe repaircomponents that are applicable to a range of repair scenarios. Piping systems and pipework canfail in a number of ways. The most commonly experienced failures, or threatened failures, areassociated with either internal or external corrosion of the pipe wall. Other failures may involveother metal loss mechanisms, such as erosion, fretting/chafing or gouging. Repairs may beeffected on-line using simple band-type clamps or patches or may involve the replacement of asection of pipe or pipework in conjunction with pipe couplings/connectors. There are a number ofproprietary repair components/systems in existence, involving both metallic and compositematerials, but these systems may have certain limitations regarding their applicability against arange of repair scenarios. This Guidance Document, therefore, is aimed at providing guidelineson the applicability of a range of these devices/systems against the different repair scenarios andservice/duty requirements, together with the requirements for the medium and long-terminspection/monitoring of the repair to ensure continuing ‘fitness for intended purpose’.1.1 SCOPE OF DOCUMENTThe scope of this document involves the use of pipe repair clamps and connectors. This documentalso provides a review of the use of composite materials for the repair of pipework. Thisdocument does not, therefore, provide guidelines on other pipe repair methods, such as by-passrepairs using hot-taps and stopples, ‘slip-lining’ repairs using plastic liners, and repairs usingweld overlays to re-instate the pipe wall.Pipe, piping, piping components, and pipework are all terms often used when describingpipework and piping systems. This guidance document is concerned with the repair of pipework –the term pipework referring to an arrangement of pipes and pipe fittings (e.g. elbows, bends, tees,reducers, flanges). This guidance document does not, therefore, cover the repair of non-pipeworkitems such as valves, filters etc.Pipelines are specific examples of pipework and piping systems used to convey fluids oversignificant distances. Although these guidelines have been specifically produced to address aboveground pipework and piping systems, they may equally be applicable to buried pipelines andsubmarine pipelines (buried or not). Some of the repair concepts discussed in these guidelinesrequire consideration of the restraint of axial loadings which, in the case of buried pipelines, maybe automatically accommodated (restraint afforded by pipe/soil friction etc.).These guidelines apply to the repair of carbon steel pipe and pipework only. Other metallicpipe/pipework, such as stainless steel, duplex stainless steel, copper nickel etc., may present otherfactors for consideration (e.g. weldability, surface treatment/preparation agents for compositematerials etc.), and are outwith the scope of this document.1.2 LAYOUT OF DOCUMENTThis document is primarily concerned with metallic mechanical clamps and connectors as usedfor the repair of damaged/deteriorated pipe components. As composite materials are findingincreasing applications to pipe repair situations, a review of their use is presented in section 6 ofthis document. All other sections of this document, including the section presenting the results ofthe literature searches, are primarily concerned with the use of metallic mechanical clamps andconnectors for the repair of damaged/deteriorated pipe components.1


2. LITERATURE REVIEWA number of sources of information have been accessed in order to glean information concerningthe state-of-the-art of pipework repair systems/components. These sources of information consistof, in the main, known databases that hold references of publications (articles etc.), but aresupplemented by other non-direct information sources, such as the Internet.Section 6 of this guidance document presents a review of the use of composite materials for therepair of pipework, and presents the work that is currently being carried out within the WorkingGroup on pipe repairs using composite materials. The literature review presented in this sectionof the document, therefore, concentrates on metallic mechanical repair sleeves, clamps, andcouplings/connectors, but also considers the use of un-reinforced composite materials (e.g. epoxyresin without any reinforcement material) used in conjunction with metallic repair components.2.1 DATABASE SEARCHESA number of database searches have been conducted in order to identify current and pastactivities relating to the use of pipework repair systems/components. The databases chosen werebased on knowledge of their popularity and coverage of the subject matter –Engineering, Energy,Science and Technology. The following databases have been accessed: The Energy Technology Data Exchange (ETDE) –this database is hosted by the UnitedState’s Department of Energy (USDOE) for the International Energy Agency (IEA) which isan international consortium that collects and exchanges research and technology informationthrough the ‘Energy Database’. The Energy Database covers all aspects of energy technologyand its environmental effects, covering all energy sources (including fossil fuels), energyconservation and energy policy. ‘COMPENDEX’ –this database is hosted by Energy Information Inc. (Ei). COMPENDEX isthe world’s most comprehensive Inter-disciplinary Engineering Database, offering over fivemillion summaries of journal articles, technical reports, conference papers, and proceedings.Ei recently acquired API EnCompass (the premier source of world-wide information for thedownstream petroleum, petrochemical, natural gas, and energy industries) thus adding one ofthe premier online databases for the oil and gas industries to their portfolio: APILIT - theTechnical Literature database. Ei’s internet address is ‘APILIT2’ –this is Ei’s Technical Literature database for non-subscribers. ‘TULSA2’ –this database is hosted by the University of Tulsa and contains references totechnical literature on the oil and gas exploration and production industry.Each of the above databases was searched for relevant references using suitable KEYWORDS.The KEYWORDS used were; PIPE, PIPING, REPAIR, CLAMP, CONNECTOR,COMPOSITE, WRAP, REVIEW, OVERVIEW, STATE ART (2 words) and SURVEY. Thedatabases are searched looking for these keywords, or combinations of the keywords, within theTITLE, ABSTRACT, and CONTROLLED TERM (CT) LISTING. Controlled Terms areKeywords, Indexing Terms (IT) or Subject Terms (ST) added by the database administrator.In order to set a realistic limit on the number of references revealed by the searches, the daterange for the searches was set at 1985 to present day –COMPENDEX holds records dating backto 1970. A large number of potentially relevant references was noted against the individualkeywords and the combination of the main keywords of PIPE/PIPING and REPAIR (4760references). By concentrating the searches on the Titles and Controlled Terms (i.e. ignoring theinformation contained within the Abstracts) this number was reduced to 763. Combining theseresults with the keywords of REVIEW, OVERVIEW, STATE ART (state-of-the-art), and3

SURVEY revealed a total of 86 references. This was particularly useful to check on the existenceof any previously published reviews of pipe/pipeline repairs. The basic details of these referencesare presented, for information, at Appendix 1 of this document.The Titles and associated Controlled Terms of the 763 and 86 references were studied to identifythe relevance of the references. Study of the Abstracts of 6 relevant references revealed 4 papersto be of particular relevance, and copies of these were obtained through the British Library’sDocument Supply Centre. The Abstracts of these 4 papers are presented at Appendix 2 of thisdocument.In addition to the above databases, AEA Technology’s National Non-Destructive TestingCentre’s database ‘QUALTIS’ was searched for technical literature pertaining to pipe/pipingrepair. Despite there being some 63,000 separate references in all, dating back to the 1960s, noneof the database entries were found to be relevant to the subject of pipe repair components.2.2 THE INTERNETAs a source of information on pipe repair clamps and connectors, the Internet’s information baseis vast. Various ‘search engines’ can be used which, when used with appropriate searchwords/phrases, guarantee that relevant information is captured. Review of the results of thevarious searches invariably identified individual companies that offer pipe repair products andservices. The information contained within the various individual company web sites is usually ofa general nature with little in the way of detailed technical information (e.g. pressure/temperaturelimitations of repair clamps). However, the individual company web sites invariably containedcontact details and these details were used to obtain further information concerning thecompany’s products and services.2.3 OTHER SOURCES OF INFORMATIONA number of additional articles have been found indirectly from AEA Technology’s library oftechnical periodicals (e.g. Offshore Engineer, Pipe Line & Gas Industry etc.), conferenceproceedings and through other connections. These articles tend to either supplement theinformation obtained through other sources, or tend to discuss specific applications of aparticular repair solution that may not be directly associated with piping or piping components.For example, 1 particular article describes a repair that involved the helium purging of a specialhabitat placed over a leaking sub-sea pipeline check valve and the subsequent epoxy-resininjection into a sleeve placed over the check valve.2.4 SUMMARY OF LITERATURE REVIEW RESULTSA large amount of relevant information has been sourced and reviewed during the production ofthis guidance document. The vast majority of the existing pipe repair products and services havebeen available for some time now and various repair components, such as heavy duty repairclamps, are available as standard items (e.g. PLIDCO clamps, Furmanite clamps, IPSCO’s splitsleeve repair clamps etc.). These proprietary items are typically designed to comply with, orexceed, the requirements of Industry Standards, such as API 6H: Specification on End Closures,Connectors and Swivels which covers pipeline closures, connections, couplings, misalignmentdevices (swivels) and split mechanical fittings. These proprietary items, and other repaircomponents, may also have obtained ‘type approvals’ from Certifying Authorities, such as DNVand Lloyd’s Register for use to perform pipe repairs or to perform pipe modifications/tie-ins etc.4

One particular repair solution that may be regarded as relatively new, and one which is regardedas being novel in its approach, is the epoxy-filled sleeve repair technique. This technique avoidsthe potential hazards of welding on an operational pipe/pipeline by using steel sleeves filled withepoxy grout (or resin). The technique, developed separately by a number of operators, such asBritish Gas1, Battelle2 in the USA and Gasunie3 in Holland, differ in their method of application,but all rely on the same principle –to provide a continuous radial load transfer between the epoxyresin and the steel sleeve. This repair technique is discussed further, based on British Gas’experiences, in section 4.2 of this document.5


3. PIPE REPAIR SCENARIOSThere are three main repair scenarios considered in this guidance document; pipe subject toexternal metal loss (caused by corrosion or mechanical damage), pipe subject to internal metalloss (caused by corrosion, erosion or erosion/corrosion), and piping components that are leaking.In addition to these main repair scenarios, the extent of the deterioration or damage (i.e. localisedor extensive) will also be considered when choosing the repair methods and repair components.These repair scenarios are described further in the following sections.3.1 PIPE SUBJECT TO EXTERNAL METAL LOSSMany pipework failures have been caused by external corrosion. External corrosion may bepresent in many forms including simple environmental corrosion (e.g. coating breakdown andsubsequent corrosion, corrosion under insulation etc.), crevice corrosion, and galvanic corrosion.Regardless of the actual corrosion mechanism that is active, the resulting damage is in the formof metal loss –loss of wall thickness. This metal loss may be localised (as in the case of corrosionunderneath a pipe support) or may be extensive (in the case of corrosion under insulation).Mechanical damage to pipework may, or may not, be accompanied by metal loss. For example,an indentation may have simply deformed the pipe locally without any associated gouging orthinning of the pipe wall. Plain dents up to six percent of the diameter of the pipe do not need tobe repaired. Deeper indentations may need to be repaired or may need to be removed if theirpresence could cause operational problems (e.g. interference with pigging). By virtue of theirprobable causes, dents are considered to be an example of localised damage.Cracking (not strictly speaking, damage involving metal loss) of weldments or of the parent pipeitself, but which has not resulted in leakage of the piping system requires special consideration.The repair of a cracked section of pipework would involve arresting any further propagation(providing that the crack itself is not threatening integrity) or removal/repair.Whatever the cause of the external metal loss, it is assumed that the prevention of furtherdeterioration will automatically be addressed by the combination of realising the presence of thedamage/deterioration (measures taken to prevent re-occurrence) and the repair action itself.3.2 PIPE SUBJECT TO INTERNAL METAL LOSSConveyed fluids within piping systems, especially in oil and gas and petrochemical applications,can present problems of internal corrosion, erosion, or a combination of corrosion and erosion.Dependent on the severity and extent of the internal damage/deterioration the pipework may beleaking or be in threat of leaking. The repair scenario considered here, however, is when internalmetal loss has not resulted in leakage –the next section deals with pipework leaks.Unlike external corrosion, it may not be possible to arrest the metal loss mechanism and furthertime-dependant damage/deterioration will continue. Unless it is possible to arrest the metal lossmechanism, the chosen repair components will need to accommodate the effects of the eventualfurther deterioration. In these cases the reinstatement of pipe integrity may only be considered tobe temporary, unless the design of the repair components specifically address the effects offurther deterioration, at least up to the remaining life of the piping system.Unlike external corrosion, internal corrosion, erosion or corrosion/erosion is more difficult toquantify, both in terms of the absolute metal loss and the extent of this metal loss. Inspection7

techniques are available, such as ultrasonics and radiography, to assist in this quantification.What is important is to gain as much information as possible on the damage/deterioration toenable the correct repair method to be chosen. It is particularly important to obtain informationregarding the ability of the sustained damage to accommodate the axial stresses which, incomplex pipe systems, can be significant. Also, further deterioration of existing internal metalloss may result in the pipe wall being unable to carry these axial loads.3.3 PIPE SUBJECT TO LEAKAGELeakage may be caused by internal or external metal loss (or, very rarely, a combination of thetwo). Leakage may also be caused by cracking of welded seams or joints or of the parent pipeitself. Depending on the extent of the discovered damage, repair may require the installation of arepair clamp (localised repair) or the replacement of a section of pipe utilising connectors orcouplings. In all cases where the pipe contents are leaking, it will be necessary to consider thesuitability of the repair component to not only accommodate the pressure containmentrequir