WO2016001622A1

WO2016001622A1 - Methods of testing electrofusion fittings and testing apparatus

Info

Publication number: WO2016001622A1
Application number: PCT/GB2015/051712
Authority: WO
Inventors: Stephen Barnes
Original assignee: Pioneer Lining Technology Limited
Priority date: 2014-07-04
Filing date: 2015-06-10
Publication date: 2016-01-07
Also published as: GB2527841A; GB201411970D0

Abstract

Methods and apparatus (321) are provided that enable the integrity of a weld between an electrofusion fitting (301) and a pipe lining (305a, 305b) to be tested in the field. Circumferential seals are provided at either side of a gap or bevel between sections of lined pipe (303a, 303b) to be joined, defining a test region (315) between the electrofusion fitting (301), pipe linings (305a, 305b) and the seals to allow leak testing, pressure testing and/or vacuum testing to be performed. The methods and apparatus (321) may equally be employed to check the fit up between the electrofusion fitting (301) and the pipe lining (305a, 305b) prior to welding them together, and may also be used during the welding process to support the electrofusion fitting (301), maintain fit up and improve weld quality.

Description

Methods of Testing Electrofusion Fittings and Testing Apparatus The present invention relates to the field of electrofusion fittings such as employed to join sections of lined pipe. More specifically, the present invention concerns methods that enable the integrity of an interface or weld between an electrofusion fitting and a pipe lining to be tested in the field, and corresponding testing apparatus for performing the tests. Background to the invention It is known that the life and performance of new and existing pipelines can be extended and optimised by lining lengths of metal pipe with polymer liners. For example, the Applicant's Swagelining® pipe lining service allows existing pipelines to be remediated and new pipelines to be provided with corrosion resistance by installing a polymer liner that remains in tight contact with the inside of a host pipe. To join adjacent lined pipe lengths, it is known to provide an electrofusion fitting to connect the inner pipe linings prior to welding the metal pipe lengths together. The Applicant's earlier International Application Publication Number WO 2010/041016, Figure 1 of which is reproduced in part in Figure 1 of the present application, discloses an electrofusion fitting 101 and a method of forming a pipe joint between two lined metal pipe lengths 103a, 103b incorporating such a fitting 101. The electrofusion fitting 101 is a sleeve largely comprised of a thermoplastic material and includes heating coils 107a, 107b disposed at either end of the fitting 101. In use, the lining 105a is stripped back and the electrofusion fitting 101 inserted into the end of metal pipe length 103a. The heating coils 107a are then provided with electrical power which causes the fitting 101 and the lining 105a in the vicinity of the coils to melt and fuse together. The process is repeated to fuse the fitting 101 to the lining 105b of the other metal pipe length 103b, after which the metal pipe lengths themselves 103a, 103b are welded together at 109. The effect is such that a very effective weld is formed between the fitting 101 and the pipe linings 107a, 107b. However, if the weld is incomplete it is possible that fluid from within the pipe lining could leak through the weld and come into contact with the metal pipe causing corrosion and potentially ultimate failure, which defeats the purpose of having the metal pipe lined in the first place. To date, the applicant is aware of only two ways to test the integrity of such an electrofusion weld in the field, the first of which is ultrasonic testing which despite the advantage of being a non-destructive and arguably non-disruptive methodology is complex and difficult to perform reliably and repeatedly in the field.

Furthermore, the results can be difficult to interpret. The second is disclosed in the Applicant's earlier British Patent Number GB2500285, Figure 2 of which is reproduced in Figure 2 of the present application. The electrofusion fitting 201 in this case is provided with a channel 211 that extends from an aperture 213 towards the middle of the fitting 201 to a point between the heating coils 207a, thus providing a means of fluid communication between a point proximal the end of the pipe 203a and a test zone (or test region) 215a. After the heating coils 207a have been activated to weld the fitting 201 to the lining 205a, the integrity of the weld can be subjected to a hydrostatic test to determine if there is any pressure loss which would correspond to a leak in one or both of the welds. While this electrofusion fitting provides an integrated or self-contained way of testing the integrity of the electrofusion welds it may not be suitable for use in all applications or environments. Accordingly, it is an object of at least one aspect of the present invention to provide an alternative way of testing the integrity of such an electrofusion weld in the field. Embodiments of aspects of the present invention are intended to realise this object and to obviate or mitigate one or more further disadvantages of existing methods of testing and provide apparatus for performing the tests. Further aims and objects of the invention will become apparent from reading the following description.

Summary of the invention According to a first aspect of the invention, there is provided a method of testing the integrity of an interface between an electrofusion fitting and a pipe lining of a section of lined pipe, the method comprising creating a circumferential seal around the section of lined pipe so as to define a test region between the interface and the seal, and performing a leak test on the test region. There may be two lined pipe sections having respective pipe linings to be joined by the electrofusion fitting; the circumferential seal may be applied around one of the two lined pipe sections and another circumferential seal may be applied around the other of the two lined pipe sections; wherein the test region is defined between the circumferential seals and the interfaces between the electrofusion fitting and the pipe linings. An interface may comprise an electrofusion weld between the electrofusion fitting and a respective pipe lining. Alternatively, it may comprise at least a portion of a surface of the electrofusion fitting in contact with at least a portion of an opposing surface of a respective pipe lining prior to electrofusion welding. Accordingly, the test may be carried out before performing the electrofusion weld and/or after performing the electrofusion weld. Furthermore, performing the leak test may comprise providing fluid to the test region and monitoring pressure within the test region. This may comprise a pressure test.

Alternatively, performing the leak test may comprise at least partially evacuating the test region and monitoring pressure within the test region. This may comprise a vacuum test. Advantageously, the method comprises at least partially evacuating the test region while performing the electrofusion weld. This can be achieved by continually pumping fluid and/or other material out of the test region. This may remove air and/or by-products resulting from the electrofusion weld. Optionally, the method further comprises inserting at least one locking ring into a bore of the pipe lining to urge an outer surface of the pipe lining against an inner surface of the lined pipe section. Insertion of the at least one locking ring may further define the test region as being bounded by at least one inner circumferential seal between the pipe lining and the lined pipe section effected by the locking ring. Preferably, the method comprises testing the integrity of the interface before performing an electrofusion weld, performing the electrofusion weld, and testing the integrity of the interface after performing the electrofusion weld. Preferably, the method comprises repositioning the electrofusion fitting relative to the pipe lining responsive to a determination that there is a leak in the interface, before performing the electrofusion weld. Preferably, the integrity of the interface is tested again before performing the electrofusion weld. Optionally, the method comprises heating at least a portion of the electrofusion fitting to a first temperature lower than a melting point of the material of the electrofusion fitting before performing the electrofusion weld. This initial heating step or pre-heat can expand the electrofusion fitting to improve or ensure contact between the surface of the electrofusion fitting and the pipe lining, i.e. the fit-up. Preferably, the method comprises testing the integrity of the interface after pre-heating the electrofusion fitting and before performing the electrofusion weld. Again, the method may comprise repositioning the electrofusion fitting relative to the pipe lining responsive to a determination that there is a leak in the interface, before performing the pre-heat again. The integrity of the interface may be tested again before performing the electrofusion weld. Optionally, creating a circumferential seal may comprise applying an elastomeric sealing member around the section of lined pipe. Alternatively, creating a circumferential seal may comprise applying an inflatable member around the section of lined pipe. The inflatable member may be a bladder. The circumferential seal or seals may be applied by providing a pipe repair clamp around a gap between adjacent lined pipe sections whose respective pipe linings are to be joined by the electrofusion fitting. The pipe repair clamp may be provided with one or more interfaces to permit fluid communication between leak testing apparatus and the test region. According to a second aspect of the invention, there is provided a method of testing the integrity of interfaces between an electrofusion fitting and pipe linings of two sections of lined pipe to be joined together, the method comprising creating circumferential seals around the sections of lined pipe on either side of a gap between the lined pipe sections so as to define a test region between the interfaces and the seals, and performing a leak test on the test region. The method may comprise testing the integrity of the interface between the electrofusion fitting and one of the pipe linings by performing the leak test after performing an electrofusion weld on the other interface. The electrofusion weld on the other interface may have been performed prior to inserting the electrofusion fitting into the pipe lining. Embodiments of the second aspect of the invention may comprise features corresponding to the preferred or optional features of the first aspect of the invention or vice versa. According to a third aspect of the invention, there is provided an apparatus for testing the integrity of an interface between an electrofusion fitting and a pipe lining of a section of lined pipe, the apparatus comprising a sealing member adapted to apply a circumferential seal around the section of lined pipe to define a test region between the interface and the seal, and leak testing means operable to perform a leak test on the test region. The apparatus may comprise a pipe repair clamp comprising one or more interfaces to permit fluid communication between the leak testing means and the test region. Preferably, the leak testing means comprises pressure monitoring means. Optionally, the leak testing means further comprises fluid delivery means, which may comprise a pump configured to supply fluid to the test region. Alternatively, the leak testing means further comprises fluid extraction means, which may comprise a pump configured to remove fluid from the test region. Optionally, the apparatus comprises two spaced sealing members positioned on the apparatus to apply corresponding circumferential seals around, and on either side of a gap between, two lined pipe sections to be joined together. Optionally, the sealing members may comprise elastomer seals. Alternatively, the sealing members may comprise inflatable bladders. Embodiments of the third aspect of the invention may comprise features corresponding to the preferred or optional features of the first or second aspects of the invention or vice versa. According to a fourth aspect of the invention there is provided a method of constructing a pipeline comprising two or more sections of lined pipe, the method comprising testing the integrity of interfaces between an electrofusion fitting and pipe linings of two sections of lined pipe to be joined together in accordance with the first or the second aspect. The method may comprise pre-heating the electrofusion fitting to improve fit-up between the electrofusion fitting and the pipe linings. The integrity of the interfaces may be tested before, during and/or after performance of electrofusion welds between the electrofusion fitting and the pipe linings. The method may comprise welding the lined pipe sections together, responsive to a determination that there is no leak in either of the interfaces after the electrofusion welds have been performed. The method may be repeated to join subsequent sections of lined pipe to the pipeline until a desired length of pipeline is constructed. Embodiments of the fourth aspect of the invention may comprise features corresponding to the preferred or optional features of the first, second or third aspects of the invention or vice versa. According to a fifth aspect of the invention there is provided a method of laying a pipeline, the method comprising testing the integrity of interfaces between an electrofusion fitting and pipe linings of two sections of lined pipe to be joined together and welding the lined pipe sections together, in accordance with the fourth aspect. Optionally, the method comprises feeding the pipeline out from a pipe-laying vessel as it travels forward. The pipeline may preferable be fed out from the stern of the vessel, or from any other location on the vessel. Optionally, the method comprises constructing the pipeline length-by-length. Adjacent sections of lined pipe may be welded on board. Embodiments of the fifth aspect of the invention may comprise features corresponding to the preferred or optional features of the first to fourth aspects of the invention or vice versa. According to another aspect of the invention, there is provided a method of testing a weld between an electrofusion fitting and a pipe lining, a method of testing fit-up between an electrofusion fitting an a pipe lining prior to performing a weld, or a method of joining sections of lined pipe substantially as herein described with reference to Figures 3 and 4 of the appended drawings. According to a further aspect of the invention, there is provided an apparatus for testing a weld between an electrofusion fitting and a pipe lining, an apparatus for testing fit-up between an electrofusion fitting an a pipe lining prior to performing a weld, or an apparatus for joining sections of lined pipe substantially as herein described with reference to Figures 3 and 4 of the appended drawings.

Brief description of the drawings Aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following drawings (like reference numerals referring to like features) in which: Figure 1 is a partial reproduction of Figure 1 of the Applicant's earlier International Application Publication Number WO 2010/041016, showing a schematic sectional view of an electrofusion fitting according to the prior art; Figure 2 is a reproduction of Figure 2 of the Applicant's earlier British Patent Number GB2500285, showing a schematic sectional view of an electrofusion fitting having a channel extending to a test region according to the prior art; Figure 3 is a cross-sectional view of an electrofusion fitting located between two sections of lined pipe and a testing apparatus for testing the integrity of the interfaces between the electrofusion fitting and the linings according to aspects of the present invention; and Figure 4 is an enlarged view of the region marked "A" in Figure 3, specifically showing a test region created by the testing apparatus.

Detailed description of preferred embodiments As discussed in the background to the invention above, it is desirable to provide an alternative way to test the integrity of a weld formed between an electrofusion fitting and pipe linings in the field to those known from the prior art. An embodiment of the present invention will now be described with reference to Figures 3 and 4 which provides such an alternative and may obviate or mitigate one or more problems with prior art methods. An electrofusion fitting 301 is formed by a cylindrical sleeve of a thermoplastic material having pairs of heating coils 307a, 307b disposed toward either end of the fitting 301. The electrofusion fitting 301 is shaped and sized to be inserted into the end of a lined pipe section 303a/303b and received in a recess 306a/306b in the end of the pipe lining 305a/305b. The heating coils 307a/307b are embedded in the outer surface of the fitting 301 , so as to be adjacent to and facing an inner surface of the pipe lining 305a/305b, such that when provided with electrical power the thermoplastic material of the fitting 301 and of the lining 305a/305b in the vicinity of the coils melts and fuses together, thus creating circumferential or annular welds between the fitting 301 and the pipe lining 305a/305b. As previously acknowledged, it is important to validate that the welds created between the fitting 301 and the pipe lining 305a/305b are leak free, to ensure that the corrosion resistance provided by the polymer lining of the pipe is intact across the joint between subsequent lined pipe sections. This prevents ingress of fluids from the bore of the lined pipe to the annular space between the lining and the pipe itself when the pipe is filled and working under pressure. To this end, a testing apparatus 321 is disposed on and around the pipe sections

303a, 303b so as to encapsulate the gap 309 between the ends of the pipe sections 303a, 303b. Sealing members 323 provide circumferential seals around respective pipe sections. The sealing members 323 may for example comprise inflatable bladders to selectively or controllably apply the circumferential seals, however in this embodiment they comprise an elastomeric material which is compliant with the outer diameter of the pipe sections 303a, 303b. Structurally the testing apparatus 321 may resemble (physically and/or functionally) a pipeline repair clamp although the testing apparatus 321 is provided with an interface 324 for the connection of vacuum pumping equipment, fluid delivery equipment, pressure gauges and/or the like. A test region 315 is thereby provided between the testing apparatus 321 and the electrofusion fitting 301. The test region 315 is bounded by the sealing members

323a, 323b and the interface or seal between the electrofusion fitting 301 and the pipe linings 305a, 305b. This region can then be pressurised or evacuated to test the integrity of the interface or seal between the electrofusion fitting 301 and the pipe linings 305a, 305b by monitoring the pressure within the test region 315.. Note that the term "interface" relates to the surface areas of the electrofusion fitting and the pipe linings which are or should be in contact, and includes inter alia the situation where these surfaces are welded together (such as post-energising of the heating coils) and where these surfaces are merely in contact prior to energising the heating coils (so- called fit-up). Integrity therefore includes the effectiveness of the seal provided by the electrofusion welds and the continuity of the contact between the surfaces prior to being welded together. The test region 315 can be subjected to a low level of air pressure using a pump (not shown) in fluid communication with the test region 315 - for example by connection to the interface 324. The pressure can be monitored and any loss of pressure can be attributed to the existence of an escape path through one or both of the interfaces or seals between the electrofusion fitting 301 and the pipe linings 305a, 305b, that is, a leak. Alternatively, a vacuum pump (not shown) connected to the interface 324 or otherwise in fluid communication with the test region 315 can be used to draw air out of the test region 315. Similarly, if the vacuum is unstable, or if it is not possible to reach an expected vacuum pressure, this may be attributed to the existence of an escape path or leak in one or both of the interfaces or seals between the electrofusion fitting 301 and the pipe linings 305a,305b. While the test may be carried out after the electrofusion welds have been made between the fitting 301 and the pipe linings 305a, 305b, it is also envisaged and it is in fact advantageous to carry out the test before and/or during creation of the welds between the electrofusion fitting 301 and the pipe linings 305a, 305b. Accordingly, performance of the test at any or all stages of the process of joining sections of lined pipe (or indeed any combination in between) are within the scope of the present invention. By way of example, the Applicant has developed a method of creating a weld between a section of lined pipe and an electrofusion fitting in which the heating coils are supplied electrical current at a sufficiently low level such that the electrofusion fitting is heated to a first temperature lower than a melting point of the material of the electrofusion fitting prior to performing the actual electrofusion welding step. This is termed "pre-heat" by the Applicant. By virtue of the initial pre-heat step, the electrofusion fitting can expand to improve the fit-up between the surface of the fitting and the pipe lining. Accordingly, when the welding step is performed, reliability is much improved. The test region 315 can therefore be leak tested, pressurised or evacuated in accordance with the procedures described above to test the integrity of the fit-up between the electrofusion fitting 301 and the pipe linings 305a, 305b before the heating coils 307a, 307b are energised. If a leak is detected, the fit-up can be remade and re-tested before energising the heating coils to create the welds between the electrofusion fitting 301 and the pipe linings 305a, 305b. Of course depending on machining tolerances etc. it may not be necessary to perform the pre-heat step if the fit-up between the electrofusion fitting and the pipe linings is adequate or leak-free; accordingly the pre-heat step might only be performed responsive to a pressure or vacuum test indicating that there is a leak in the fit- up. It is particularly advantageous if, when using evacuation/vacuum techniques to test the integrity of the fit-up, the evacuation/vacuum is maintained while the heating coils

307a, 307b are energised to create the welds between the electrofusion fitting 301 and the pipe linings 305a, 305b. Any air or by-products created or released from the components during the electrofusion process may thereby be drawn away from the fusion zones and as a result reduce the risk of voiding - thus resulting in an improved weld. The vacuum will also act to keep the electrofusion fitting 301 compressed to the pipe linings 305a, 305b during the electrofusion process. This might remove the need for additional physical support. While the Applicant's Swagelining® pipe lining service installs a polymer liner that remains in tight contact with the inside of a host pipe, it is possible that such a liner, or a liner installed using alternative or competing methodologies, may be slightly spaced from the host pipe or there may exist discrete channels or gaps. In these situations, fluid may leak out of the test region through these channels or gaps when pressurised or leak tested, or fluid may leak into the test region through these channels or gaps if a vacuum is applied. Accordingly, it is advantageous to insert locking rings 325a/325b to tightly compress the pipe linings 305a/305b against the inside wall of the pipe sections 303a/303b. The locking rings 325a/325b thereby provide a seal which prevents fluid from crossing over the area of the compression and may also serve to anchor the pipe linings to prevent any movement due to residual strain which may be released when machining the recesses to receive the electrofusion fitting. When the locking rings 325a, 325b are in place, the test region 315 can be further defined as being bounded by corresponding compression areas - that is, the surfaces of the pipe linings 305a, 305b which are urged against the inside wall of the pipe sections 303a/303b. It is known that fluids can reside behind the liner in the annular space; when a large number of short pipe sections are joined there is a risk that these fluids accumulate along an extended annulus resulting from the joined sections which raises the risk of liner collapse - a particular concern in hydrocarbon applications. The locking rings 325a/325b prevent such accumulation occurring by effectively partitioning the annular space along a continuous lined pipe length. The locking rings 325a/325b may be inserted prior to machining recesses to receive the electrofusion fitting, or simply prior to receiving the electrofusion fitting in the recesses. Alternatively, the locking rings 325a/325b may be inserted when the pipe sections are lined, which might even be prior to transporting the lined pipe sections to a location where they are to be joined together. Once it has been determined that the electrofusion welds have been performed satisfactorily, the testing apparatus 321 can be removed and the pipe lengths 303a, 303b themselves can be welded together at gap 309. If the optional locking rings 325a/325b have been employed these are generally left in position to avoid transferring any residual strain in the pipe linings 305a, 305b to the welds and/or the electrofusion fitting which might cause damage to the former or cause the latter to move. Of course these can be removed if desired, but it is envisaged that in most applications the locking rings 325a/325b will remain in place. The locking rings 325a/325b may therefore be comprised of a corrosion resistant material, or for example carbon steel with a corrosion protective coating. It is particularly advantageous if the integrity test can be carried out as a leak test rather than as a pressure test, because this reduces complexity and means that the test can be performed in situations where pressure tests might be unsuitable (e.g. where there are explosion or ignition risks). Furthermore, rather than inserting the electrofusion fitting 301 into the pipe linings

303a, 303b and performing the welds at either end of the electrofusion fitting 301 simultaneously, the welds may be performed one at a time and the integrity of each weld can therefore be tested individually. Alternatively, the electrofusion fitting 301 may already be welded at one end to the lining 305b of pipe 303b (and the integrity of the weld tested using the methods of the invention or otherwise) for example, prior to bringing the pipe sections 303a, 303b together in which case the methods of the invention can be employed to test the integrity of the weld and/or fit-up between the electrofusion fitting 301 and pipe lining 305a. This allows at least one of the welds to be performed off the critical path, reducing operational complexity. It will of course be understood that while the present invention has been illustrated with reference to electrofusion fittings for joining lined pipe sections, the methods (and apparatus) may be applied to an electrofusion fitting employed to join standalone plastic pipes. Common techniques for laying pipe on the sea floor include s-lay pipeline installation and j-lay pipeline installation. In these methods, pipe is fed out from the stern of a pipe-laying vessel as it travels forward; s-lay refers to the "s" shape of the pipeline between the vessel and the seabed resulting from the substantially horizontal deployment direction, and j-lay refers to the "j" shape of the pipeline between the vessel and the seabed resulting from the substantially vertical deployment direction. In s-lay and j-lay operations, a pipeline can be constructed length-by-length in which case adjacent sections of pipe are welded on board (as contrasted with a reel-lay method in which case a continuous length of pipe is deployed from a reel). To date, no pipeline installed in an s-lay operation has been lined. This is due to the high cost and fabrication complexity associated with conventional methods of joining sections of lined pipe. The Applicant's electrofusion fittings provide a robust and rugged way of joining sections of lined pipe, and the method of testing the integrity of the electrofusion welds of the present invention permits these electrofusion fittings and the corresponding welded joints to be tested quickly and effectively in the field and provide confidence that will allow the many and varied benefits of lined pipe to be exploited in s-lay, and j-lay, applications. Accordingly, a pipeline consisting of several lined pipe sections can be constructed and the integrity of the welds between fittings and linings tested in situ as part of the pipeline fabrication process. In fact, even using reel-lay or tow-in pipeline installation methods, subsequent lengths of lined pipe (which may be one or several km long rather than, say, 12 m long as used in length-by-length on-deck fabrication methods) can be joined and the joint integrity tested - and of course the continuous pipe (deployed from reel or by tow-in) might itself consist of several lined pipe sections so joined and tested onshore. Very fast modern pipeline welding makes use of a closed bevel. However, to date it has not been possible to use a closed bevel approach in conjunction with electrofusion fittings, other than by employing the approach disclosed in the Applicant's earlier International Application Publication Number WO 2013/136062 in which access to leak test or pressure test the welds can be achieved by drilling one or more holes through the closed bevel. The holes drilled through the closed bevel allow access to the channel through the electrofusion fitting which extends to a test region. A probe can be inserted through the closed bevel and received in the channel and thereby supply leak test or pressure test fluid to the test region. However, the testing method of the present invention can be performed, and the testing apparatus employed, in closed bevel applications as readily as in open bevel applications - without the need to drill through the closed bevel. Whether "narrow gap" or "closed" fit up approaches are adopted, it is still possible to pressurise or evacuate the test region as described above by creating circumferential seals around the pipe sections at either side of the bevel. Note that subsequent to testing the integrity of the welds and removing the testing apparatus 321 , but prior to welding the pipe sections 303a, 303b together, an insulating material can be injected into the test region 315 (specifically the annular space

surrounding the electrofusion fitting 301 in the region of the gap 309. This will protect the electrofusion fitting 301 from heat damage while the ends of pipe sections 303a, 303b are welded together. Alternatively, the electrofusion fitting 301 may be provided with an insulating material, which may for example be integrally formed or applied as a coating, prior to use. The invention provides methods and apparatus that enable the integrity of a weld between an electrofusion fitting and a pipe lining to be tested in the field. Circumferential seals are provided at either side of a gap or bevel between sections of lined pipe to be joined, defining a test region between the electrofusion fitting, pipe linings and the seals to allow leak testing, pressure testing and/or vacuum testing to be performed. The methods and apparatus may equally be employed to check the fit up between the electrofusion fitting and the pipe lining prior to welding them together, and may also be used during the welding process to support the electrofusion fitting, maintain fit up and improve weld quality. Throughout the specification, unless the context demands otherwise, the terms 'comprise' or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.

Claims

Claims 1. A method of testing the integrity of interfaces between an electrofusion fitting and pipe linings of two sections of lined pipe to be joined together, the method comprising creating circumferential seals around outer surfaces of the sections of lined pipe on either side of a gap between the sections of lined pipe so as to define a test region between the interfaces and the seals on either side of the gap, and performing a leak test on the test region.

2. The method according to claim 1 , wherein the interface or interfaces comprise an electrofusion weld between the electrofusion fitting and a respective pipe lining.

3. The method according to claim 1 , wherein the interface or interfaces comprise at least a portion of a surface of the electrofusion fitting in contact with at least a portion of an opposing surface of a respective pipe lining prior to electrofusion welding.

4. The method according to any preceding claim, wherein the test is carried out before performing the electrofusion weld.

5. The method according to any preceding claim, wherein the test is carried out after performing the electrofusion weld.

6. The method according to any preceding claim, wherein performing the leak test comprises providing fluid to the test region and monitoring pressure within the test region.

7. The method according to any of claims 1 to 5, wherein performing the leak test comprises at least partially evacuating the test region and monitoring pressure within the test region.

8. The method according to any preceding claim, comprising at least partially

evacuating the test region while performing the electrofusion weld.

9. The method according to claim 8, wherein fluid and/or other material is continually pumped out of the test region.

10. The method according to claim 8 or claim 9, comprising removing air and/or by- products resulting from the electrofusion weld.

1 1. The method according to any preceding claim, comprising inserting at least one locking ring into a bore of the pipe lining to urge an outer surface of the pipe lining against an inner surface of the lined pipe section.

12. The method according to claim 11 , wherein insertion of the at least one locking ring further defines the test region as being bounded by at least one inner circumferential seal between the pipe lining and the lined pipe section effected by the locking ring.

13. The method according to any preceding claim, comprising testing the integrity of the interface before performing an electrofusion weld, performing the electrofusion weld, and testing the integrity of the interface after performing the electrofusion weld.

14. The method according to any preceding claim, comprising repositioning the

electrofusion fitting relative to the or each pipe lining responsive to a determination that there is a leak in the interface, before performing the electrofusion weld.

15. The method according to claim 14, wherein the integrity of the interface is tested again before performing the electrofusion weld.

16. The method according to any preceding claim, comprising heating at least a portion of the electrofusion fitting to a first temperature lower than a melting point of the material of the electrofusion fitting to pre-heat the electrofusion fitting before performing the electrofusion weld.

17. The method according to claim 16, comprising testing the integrity of the interface after pre-heating the electrofusion fitting and before performing the electrofusion weld.

18. The method according to claim 17, comprising repositioning the electrofusion fitting relative to the pipe lining responsive to a determination that there is a leak in the interface, before performing the pre-heat again.

19. The method according to claim 18, wherein the integrity of the interface is tested again before performing the electrofusion weld.

20. The method according to any preceding claim, wherein creating a circumferential seal comprises applying an elastomeric sealing member around the section of lined pipe.

21. The method according to any of claims 1 to 19, wherein creating a circumferential seal comprises applying an inflatable member around the section of lined pipe.

22. The method according to claim 21 , wherein the inflatable member is a bladder.

23. The method of any preceding claim, wherein the circumferential seals are applied by providing a pipe repair clamp around a gap between adjacent lined pipe sections whose respective pipe linings are to be joined by the electrofusion fitting.

24. The method of claim 23, wherein the pipe repair clamp is provided with one or more interfaces to permit fluid communication between leak testing apparatus and the test region.

25. An apparatus for testing the integrity of interfaces between an electrofusion fitting and pipe linings of sections of lined pipe to be joined together, the apparatus comprising sealing members adapted to apply circumferential seals around outer surfaces of the sections of lined pipe on either side of a gap between the sections of lined pipe to define a test region between the interfaces and the seals on either side of the gap, and leak testing means operable to perform a leak test on the test region.

26. The apparatus of claim 25, comprising a pipe repair clamp comprising one or more interfaces to permit fluid communication between the leak testing means and the test region.

27. The apparatus of claim 25 or claim 26, wherein the leak testing means comprises pressure monitoring means.

28. The apparatus of any of claims 25 to 27, wherein the leak testing means further comprises fluid delivery means.

29. The apparatus of claim 28, wherein the fluid delivery means comprises a pump

configured to supply fluid to the test region.

30. The apparatus of any of claims 25 to 27, wherein the leak testing means further comprises fluid extraction means.

31. The apparatus of claim 30, wherein the fluid extraction means comprises a pump configured to remove fluid from the test region.

32. The apparatus of any of claims 25 to 31 , wherein the apparatus comprises two

spaced sealing members positioned on the apparatus to apply corresponding circumferential seals around, and on either side of a gap between, two lined pipe sections to be joined together.

33. The apparatus of claim 32, wherein the sealing members comprise elastomer seals.

34. The apparatus of claim 32, wherein the sealing members comprise inflatable

bladders.

35. A method of constructing a pipeline comprising two or more sections of lined pipe, the method comprising testing the integrity of interfaces between an electrofusion fitting and pipe linings of two sections of lined pipe to be joined together in accordance with any of claims 1 to 24.

36. The method according to claim 35, comprising pre-heating the electrofusion fitting to improve fit-up between the electrofusion fitting and the pipe linings.

37. The method according to claim 35 or claim 36, wherein the integrity of the interfaces are tested before, during and/or after performance of electrofusion welds between the electrofusion fitting and the pipe linings.

38. The method according to any of claims 35 to 37, comprising welding the lined pipe sections together, responsive to a determination that there is no leak in either of the interfaces after the electrofusion welds have been performed.

39. The method according to any of claims 35 to 38, repeated to join subsequent

sections of lined pipe to the pipeline until a desired length of pipeline is constructed.

40. A method of laying a pipeline, the method comprising testing the integrity of interfaces between an electrofusion fitting and pipe linings of two sections of lined pipe to be joined together and welding the lined pipe sections together, in accordance with any of claims 35 to 39.

41. The method of claim 40, comprising feeding the pipeline out from a pipe-laying

vessel as it travels forward.

42. The method of claim 41 , wherein the pipeline is fed out from the stern of the vessel.

43. The method according to any of claims 40 to 42, comprising constructing the pipeline length-by-length.

44. The method according to any of claims 40 to 43, wherein adjacent sections of lined pipe are welded on board the vessel.

45. A method of testing a weld between an electrofusion fitting and a pipe lining, a

method of testing fit-up between an electrofusion fitting an a pipe lining prior to performing a weld, or a method of joining sections of lined pipe substantially as herein described with reference to Figures 3 and 4 of the appended drawings.

46. An apparatus for testing a weld between an electrofusion fitting and a pipe lining, an apparatus for testing fit-up between an electrofusion fitting an a pipe lining prior to performing a weld, or an apparatus for joining sections of lined pipe substantially as herein described with reference to Figures 3 and 4 of the appended drawings.