Securing polymer liners in pipes

Abstract

A method of manufacturing a polymer lined pipe joint comprises inserting a tubular polymer liner 30 into a carbon steel pipe joint 10, then overlapping an end portion of the liner with an overlay 14 o

Description

This invention relates to polymer-lined pipes and to polymer-lined pipelines made up of such pipes. The invention can be used when manufacturing lined pipe joints and when fabricating pipelines from a succession of lined pipe joints, for example when installing subsea pipelines in S-Lay and J-Lay operations. Corrosion-resistant polymer liners enable pipelines of carbon steel to convey corrosive fluids, such as sea water or ‘sour’ hydrocarbons with high sulphur content, and provide a less expensive alternative to corrosion resistant alloys (CRA). GB 2186340 discloses a method of lining a pipe with a polymer liner, that method being known in the art by the registered trade mark ‘Swagelining’. Initially, the external diameter of the liner is greater than the internal diameter of the pipe. The liner is pulled through a die that narrows the liner and then is pulled in that narrowed state into and through the pipe while being kept under tension. The liner is then expanded within the pipe in a process of reversion, where the tension is relaxed to allow the liner to expand against the interior of the pipe. When fabricating pipelines from a succession of polymer-lined pipes or ‘pipe joints’, it is necessary to weld together the pipe joints end-to-end without allowing the heat of welding to damage their liners. An example of such a method to connect lined pipe joints is described in GB 2298256 and is known in the art by the registered trade mark ‘Weldlink’. In the Weldlink method, a tubular fitting is welded to an end of a carbon steel pipe joint before the pipe is lined with a polymer liner, for example by the aforementioned Swagelining technique. The fitting can be made of corrosion-resistant steel or can be made of carbon steel with a corrosion-resistant cladding deposited on its interior. In either case, the corrosion-resistant inner face of the fitting has a corrugated or castellated profile defined by a longitudinal series of machined circumferential grooves spaced inboard of a free end of the fitting. An end portion of the liner overlaps the series of grooves. A stainless steel compression ring is forced axially or expanded into the fitting, within the end portion of the liner overlapping the grooves, to force that portion of the liner into engagement with the grooves. Thus secured to the pipe joint, the liner is cut back from the free end of the fitting, which can then serve as a butt-welding interface to another similarly-equipped pipe joint. The requirement to weld a fitting to the pipe joint is a disadvantage of the Weldlink method. Also, the step change in internal diameter between the liner and the section of the fitting adjoining the weld can hinder pigging operations and disrupt fluid flow. WO 2021 / 094734 addresses the latter problem by interposing a fit-up sleeve between the opposed liners of the conjoined pipe joints. The fit-up sleeve can also reduce exposure of the pipe joint to corrosive fluids, hence reducing or removing the need for corrosionresistant materials in or on the pipe wall proximate to the weld. However, there is still a need to weld a fitting to the end of a pipe joint, in addition to the need to install the fit-up sleeve. GB 2391597 discloses a method of connecting lined pipes using a corrosion-resistant tubular bridging sleeve that is sandwiched between the liner and the wall of each pipe to protect the liner from the heat of welding. An expanding ring located within the liner provides a seal between the liner and the bridging sleeve. The bridging sleeve has a castellated inner surface to improve the seal and to enhance the grip between the liner and the sleeve. Conversely, GB 2545183 discloses a fitting or sleeve with external castellations disposed within a liner, whereas GB 2407629 discloses crimping an internal sleeve against an internally-castellated liner. In EP 3850256, an end portion of the internal wall of a pipe is coated with a weld overlay of corrosion-resistant alloy steel. An internally castellated profile is machined into the overlay. A polymer liner is then placed within the pipe, for example by the Swagelining technique, and is cut back from the pipe end after a period of reversion. Next, a ring of corrosion-resisting steel alloy is inserted into the pipe end. The ring has an annular part with an externally castellated profile, which is inserted into an end portion of the liner aligned with the internally castellated profile of the overlay. A sleeve or other expandable, inflatable or deformable tool is then inserted into the pipe to crimp the castellated annular part of the ring against the liner that is sandwiched between the ring and the internally castellated section of the overlay. The ring also has a frusto-conical part that is welded to the internal wall of the pipe coated with the overlay, outboard of the end of the liner. These crimping and welding operations complicate manufacture of the lined pipe. In some arrangements such as that disclosed in GB2357325, external threaded couplings may be used. However, such arrangements are unsuitable for pipes that may need to be bent along their length or that need to be welded to ensure sufficient mechanical strength. Against this background, the invention resides in a method of manufacturing a polymer-lined pipe joint, the method comprising: inserting a tubular polymer liner into a carbon steel pipe joint; overlapping an end portion of the liner with an overlay of corrosionresistant material disposed within an end portion of the pipe joint and extending to an end edge of the pipe joint; and radially expanding the end portion of the liner into sealing engagement with a castellated inner profile of the overlay. The overlay may be disposed within a wall of the pipe joint that extends continuously along a full length of the pipe joint. The end portion of the liner may be expanded radially by forcing a tubular expander into the liner, for example by sliding the expander into the liner as an interference fit within the liner. The expander may be a compression ring contained within the end portion of the pipe joint or a sleeve protruding from the end portion of the pipe joint. In the latter case, the method may comprise welding the pipe joint to another polymer-lined pipe joint at a mutual interface defined by their abutting end edges, with the sleeve extending across the interface into radially-expanding engagement with the liners of the conjoined pipe joints. The sleeve can then maintain continuous corrosion resistance between the liners across the interface. The expander can be inserted into a circumferential recess in the liner at which a wall of the liner is of locally reduced thickness, the recess being aligned with the castellated profile of the overlay. The expander can be fitted into the recess substantially flush with an inner face of the liner. The liner, which is apt to be inserted into the pipe in a Swagelining operation, can be terminated inboard of the end edge of the pipe joint, in alignment with a portion of the overlay outboard of the castellated profile. The abovementioned method can be preceded by forming the overlay within the end portion of the pipe joint, which can be followed by machining the castellated profile in the overlay. Two or more pipe joints can be joined end-to-end by one or more butt welds, which may be carbon steel welds, and the liner can extend continuously between those pipe joints. Conversely, the pipe joint can be joined to a like polymer-lined pipe joint with a weld of corrosion-resistant alloy along a mutual interface defined by their abutting end edges. Correspondingly, the inventive concept embraces a pipe joint having a wall of carbon steel, the pipe joint comprising: an overlay of corrosion-resistant material disposed within an end portion of the pipe joint and extending to an end edge of the pipe joint; and a tubular polymer liner having an end portion overlapping with and expanded radially into sealing engagement with a castellated profile of the overlay. The pipe joint may further comprise a tubular expander disposed within the liner in alignment with the castellated profile, the expander forcing the liner radially outwardly into sealing engagement with the castellated profile. The expander can be an interference fit within the liner, and can have a non-castellated radially outer surface. Again, the expander may be a compression ring contained within the end portion of the pipe joint or a sleeve protruding from the end portion of the pipe joint. The sleeve may comprise an end portion in radially-expanding engagement with the liner and a central portion of increased diameter disposed longitudinally outboard of the liner. In combination, a pipe joint of the invention can be welded to another similar polymer-lined pipe joint at a mutual interface defined by their abutting end edges, with the sleeve extending across the interface in radially-expanding engagement with the liners of the conjoined pipe joints. The expander can be received in a circumferential recess in the liner where a wall of the liner is of locally reduced thickness, the recess being aligned with the castellated profile of the overlay. Thus, the expander can lie substantially flush with an inner face of the liner when the expander is in the recess. The inventive concept also extends to a pipeline comprising a succession of pipe joints of the invention or made by methods of the invention. Instead of having a CRA connector welded onto a pipe end as a discrete fitting, the invention allows a corrosion-resistant connector to be part of the pipe so that no additional welding is required. Using a process similar to manufacture of mechanically-lined pipe, where a liner connects to overlays on pipe ends, castellations can be machined into the overlay sections. Also the length of the overlay sections can be increased to allow for one or two weld cut outs. A corrosion-resistant compression ring or a corrosion-resistant sleeve is used to lock and terminate the liner. The liner can be machined locally to thin the liner in alignment with each compression ring or sleeve to reduce their impact on flow performance and on pigging. In addition to pipelines for conveying hydrocarbons, solutions of the invention may be competitive to shorter CRA-clad water injection lines. Embodiments of the invention implement a method to ensure continuity of internal lining within a steel pipeline, the method comprising: providing at least one polymer-lined pipe, wherein at least one end of the pipe comprises castellations overlapped by the corresponding end of the inner liner; inserting an inner sleeve inside the said end of the polymer-lined pipe; and pushing the inner sleeve in order to crush the inner liner inside the castellations. The castellations may, for example, be machined inside the pipe end. The method may comprise providing a carbon steel pipe, machining the castellations and lining the pipe with an internal polymer liner such that the liner covers the castellations. The method may also comprise providing two pipes to be connected to the same inner sleeve. The inner sleeve may be manufactured with a diameter that ensures, as far as possible, continuity of the diameter of the internal lining after fabrication. The polymer liner may comprise two or more layers, at least one of which is polymeric. The polymer liner may comprise a metallic layer, for example of aluminium, for impermeability to migration of gases through the liner into the annulus between the liner and the surrounding pipe wall. Thus, a polymer-lined pipe joint of the invention is made by: inserting a tubular polymer liner into a carbon steel pipe joint; overlapping an end portion of the liner with an overlay of corrosion-resistant material disposed within an end portion of the pipe joint, the overlay extending to an end edge of the pipe joint; and radially expanding the end portion of the liner into sealing engagement with a castellated profile of the overlay. The end portion of the liner can be radially expanded by forcing a tubular expander into the liner as an interference fit, the expander being a compression ring contained within the end portion of the pipe joint or a sleeve protruding from the end portion of the pipe joint. In order that the invention may be more readily understood, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a schematic side view in longitudinal section of castellations machined in a CRA-clad end of a pipe joint; Figure 2 is a schematic side view in longitudinal section of a double pipe joint with castellations like those of Figure 1 in each end; Figure 3 corresponds to Figure 2 but shows a polymer liner inserted into the pipe joint and a compression ring fitted into one end of the pipe joint to lock and terminate the liner; Figure 4 is a schematic side view in longitudinal section of pipe joints like that of Figure 1, each fitted with compression rings to lock and terminate their liners; Figure 5 corresponds to Figure 4 but shows the pipe joints abutting in end-to-end relation, ready to be welded together; Figure 6 is a schematic side view in longitudinal section of a sleeve inserted into a castellated end of a pipe joint like that of Figure 1; Figure 7 corresponds to Figure 6 but shows the sleeve also inserted into an additional pipe joint with the pipe joints abutting in end-to-end relation, ready to be welded together; Figures 8a and 8b are schematic side views in longitudinal section that show assembly of pipe joints fitted with compression rings in a variant of the arrangement shown in Figures 4 and 5; and Figures 9a and 9b are schematic side views in longitudinal section that show assembly of pipe joints fitted with a common sleeve in a variant of the arrangement shown in Figures 6 and 7. Figure 1 of the drawings shows an end of a length of pipe for use in fabricating a subsea pipeline, for example during a J-lay or S-lay operation performed aboard an installation vessel offshore. The pipe may be of any length, in this example being a pipe joint 10 with an industry-standard nominal length such as twelve metres, or a multiple of that nominal length. The pipe joint 10 has a pipe wall 12 of carbon steel along its full length but a tubular insert or overlay 14 of a corrosion-resistant alloy, such as a steel alloy, is deposited, for example by welding, to an inner face of the pipe wall 12 within at least one end of the pipe joint 10. The overlay is formed within the pipe wall 12 that extends continuously along the full length of the pipe joint 10, uninterrupted by an intermediate weld in contrast to the aforementioned Weldlink solution. The overlay 14 extends longitudinally inboard from the end edge 16 of the pipe joint 10 and is circumferentially and longitudinally continuous. An inboard portion 18 of the overlay 14 has a corrugated or castellated profile 20 that faces radially inwardly. The castellated profile 20 in defined by a longitudinal series of circumferential ridges 22 of a corrosion-resistant alloy. Conveniently, the ridges 22 may be defined by, and between, a longitudinal series of circumferential grooves 24 that are machined into the overlay 14 to a depth extending partially through the thickness of the overlay 14. However, the ridges 22 could instead be deposited onto, formed with or applied to the overlay 14 to stand proud of the overlay 14, with grooves 24 thereby defined between the ridges 22. An outboard portion 26 of the overlay 14 extending from the inboard portion 18 to the end edge 16 of the pipe joint 10 has a smooth surface of corrosion-resistant alloy that faces radially inwardly. The circumferential end edge 16 at the end of the pipe wall 12 is shown here as being bevelled in readiness for eventual butt-welding to another pipe joint 10 disposed end-to-end. However, bevelling of the end edge 16 could be performed at any later stage before welding takes place. A similar overlay 14 may be provided in mirror relation on the opposite end of the pipe joint 10. Alternatively, two or more pipe joints 10 can be welded together at their mutual interface as shown in Figure 2. In this example, a double pipe joint 10D comprises pipe joints 10 that have overlays 14 in their outer ends and that are joined together with a butt weld 28 at their abutting inner ends. A conventional carbon steel weld can be formed at that interface, which will be protected from corrosion by a polymer liner 30 as will now be explained. Figure 3 shows a tubular polymer liner 30 that may be inserted into and expanded against the pipe joint 10D of Figure 2. The liner 30 is shown here after reversion and with its ends cut back to positions inboard of the end edges 16 of the pipe joint 10, sufficiently removed from the end edges 16 as not to be damaged by the heat of welding during pipeline fabrication. More specifically, the ends of the liner 30 align with the outboard portions 26 of the overlays 14. Consequently, end portions of the liner 30 overlap the castellated inboard portions 18 of the overlays 14. On the left side of Figure 3, a compression ring 32 is shown having been forced longitudinally into an end of the pipe joint 10 on the radially inner side of the liner 30. Thus, the compression ring 32 is an interference fit within the liner 30. The compression ring 32 is advanced longitudinally into alignment with the castellated inboard portion 18 of the overlay 14. Consequently, radially outward force exerted by the compression ring 32 forces the liner 30 into sealing engagement and mechanical engagement with the castellated profile 20. Specifically, the liner 30 deforms to adopt a profile complementary to, and inter-engaged with, the castellated profile 20. When another compression ring 32 is similarly pressed into the opposite end of the pipe joint 10 shown to the right in Figure 3, the result is to create a continuous corrosionresistant barrier between the carbon steel pipe wall 12 and the lumen of the lined pipe joint 10. That barrier is defined to a major extent by the liner 30 and to a minor extent by the outboard portions 26 of the overlays 14 that are exposed to the lumen of the pipe joint 10 between the ends of the liner 30 and the end edges 16 of the pipe joint 10. Figures 4 and 5 show mutually-opposed ends of lined pipe joints 10, each fitted with compression rings 32 as described above to lock and terminate their liners 30. Figure 5 shows the pipe joints 10 abutting in end-to-end relation, ready fortheir bevelled end edges 16 to be welded together at their mutually abutting interface. The weld will be formed of a corrosion-resistant alloy in this instance, reflecting exposure of the weld to corrosive fluids that will be conveyed along a pipeline formed of the pipe joints 10. It will be apparent that the longitudinal inset of the ends of the liners 30 from the end edges 16 of the pipe joints 10 helps to protects the liners 30 from damage due to radiant and conductive heat produced during welding. However, additional cooling provisions may be employed to protect the liners 30 if needs be. The function of the compression rings 32 to force the liner 30 into engagement with the castellated profiles 20 of the overlays 14 can instead be performed by a tubular sleeve 34 as shown in Figures 6 and 7. Thus, the compression ring 32 and the sleeve 34 are examples of a tubular expander that acts on the liner 30. The sleeve 34 bridges the interface between abutting lined pipe joints 10 and so is in common between those pipe joints 10. Specifically, one end portion 36 of the sleeve 34 acts on the liner 30 of one pipe joint 10 and the other end portion 36 of the sleeve 34 acts on the liner 30 of the other pipe joint 10, those end portions 36 being aligned with the castellated profiles 20 of the respective overlays 14. The sleeve 34 can be inserted first into an end of one of the pipe joints 10 as shown in Figure 6 and subsequently into an end of the other pipe joint 10 as shown in Figure 7, as the pipe joints 10 are brought together. Alternatively, the pipe joints 10 could be brought together simultaneously around the sleeve 34. Once in place between the pipe joints 10, the sleeve 34 bridges continuously between the liners 30 of the pipe joints 10 to maintain continuous corrosion protection along the length of the pipeline thus being fabricated. Finally, Figures 8a, 8b, 9a and 9b show how compression rings 32 or a sleeve 34 can be accommodated in undercut circumferential recesses 38 machined into the radially inward side of the liner 30 in alignment with the castellated profiles 20 of the overlays 14. Reducing the local thickness of the liner 30 in this way reduces radially inward protrusion of the compression ring 32 or sleeve 34 into the lumen of a lined pipe joint 10. Indeed, if the depth of a recess 38 corresponds to the thickness of the compression ring 32 or the sleeve 34, the compression ring 32 or sleeve 34 will lie substantially flush to the adjoining inner surface of the liner 30, to the benefit of flow dynamics and pigging. The sleeves 34 shown in Figures 6, 7, 9a and 9b may be made of a corrosion-resistant alloy or may be coated with a corrosion-resistant material. The sleeves 34 have a central portion 40 of greater wall thickness than their end portions 36. Internally, the sleeves 34 have constant diameter along their length, meaning that the sleeves 34 step 5 up in external diameter from their end portions 36 to the central portion 40. Shoulders 42 thereby defined between the end portions 36 and the central portion 40 face the opposed ends of the liners 30. The central portion 40 is received between the ends of the liners 30 in alignment with the weld interface, and may be surrounded by a heat-resistant material to resist the heat of welding if needs be. 10 Other variations are possible within the inventive concept. For example, where a sleeve extends continuously between liners of adjoining pipe joints, corrosion-resistant outboard portions of the overlays could be omitted and a conventional carbon steel weld could be formed between the pipe joints. In this instance, the sleeve may shield 15 the weld and its environs from corrosive fluids in use.

Claims

1. A method of manufacturing a polymer-lined pipe joint, the method comprising:inserting a tubular polymer liner into a carbon steel pipe joint;overlapping an end portion of the liner with an overlay of corrosion-resistant material disposed within an end portion of the pipe joint and extending to an end edge of the pipe joint; andradially expanding the end portion of the liner into sealing engagement with a castellated profile of the overlay.

2. The method of Claim 1, comprising radially expanding the end portion of the liner by forcing a tubular expander into the liner.

3. The method of Claim 2, comprising sliding the expander into the liner as an interference fit within the liner.

4. The method of Claim 2 or Claim 3, wherein the expander is a compression ring contained within the end portion of the pipe joint.

5. The method of Claim 2 or Claim 3, wherein the expander is a sleeve protruding from the end portion of the pipe joint.

6. The method of Claim 5, comprising welding the pipe joint to another polymer-lined pipe joint at a mutual interface defined by their abutting end edges, with the sleeve extending across the interface into radially-expanding engagement with the liners of the conjoined pipe joints.

7. The method of Claim 6, wherein the sleeve maintains continuous corrosion resistance between the liners across the interface.

8. The method of any of Claims 2 to 7, comprising inserting the expander into a circumferential recess in the liner at which a wall of the liner is of locally reduced thickness, the recess being aligned with the castellated profile of the overlay.

9. The method of Claim 8, comprising fitting the expander into the recess substantially flush with an inner face of the liner.

10. The method of any preceding claim, comprising terminating the liner inboard of the end edge of the pipe joint, in alignment with a portion of the overlay outboard of the castellated profile.

11. The method of any preceding claim, preceded by forming the overlay within the end portion of the pipe joint.

12. The method of Claim 11, further comprising machining the castellated profile in the overlay.

13. The method of any preceding claim, wherein the overlay is disposed within a wall of the pipe joint extending continuously along a full length of the pipe joint.

14. The method of any preceding claim, wherein two or more pipe joints are joined end-to-end by one or more butt welds and the liner extends continuously between those pipe joints.

15. The method of Claim 14, wherein the or each of the butt welds is a carbon steel weld.

16. The method of any preceding claim, comprising joining the pipe joint to a like polymer-lined pipe joint with a weld of corrosion-resistant alloy along a mutual interface defined by their abutting end edges.

17. The method of any preceding claim, comprising inserting the liner into the pipe in a Swagelining operation.

18. A pipe joint having a wall of carbon steel, the pipe joint comprising:an overlay of corrosion-resistant material disposed within an end portion of the pipe joint and extending to an end edge of the pipe joint; anda tubular polymer liner having an end portion overlapping with and expanded radially into sealing engagement with a castellated profile of the overlay.

19. The pipe joint of Claim 18, further comprising a tubular expander disposed within the liner in alignment with the castellated profile, the expander forcing the liner radially outwardly into sealing engagement with the castellated profile.

20. The pipe joint of Claim 19, wherein the expander is an interference fit within the liner.

21. The pipe joint of Claim 19 or Claim 20, wherein the expander has a non-castellated radially outer surface.

22. The pipe joint of any of Claims 19 to 21, wherein the expander is a compression ring contained within the end portion of the pipe joint.

23. The pipe joint of any of Claims 19 to 21, wherein the expander is a sleeve protruding from the end portion of the pipe joint.

24. The pipe joint of Claim 23, wherein the sleeve comprises an end portion in radially-expanding engagement with the liner and a central portion of increased diameter disposed longitudinally outboard of the liner.

25. The pipe joint of any of Claims 19 to 24, wherein the expander is received in a circumferential recess in the liner where a wall of the liner is of locally reduced thickness, the recess being aligned with the castellated profile of the overlay.

26. The pipe joint of Claim 25, wherein the expander lies substantially flush with an inner face of the liner when the expander is in the recess.

27. The pipe joint of any of Claims 18 to 26, wherein the liner terminates inboard of the end edge of the pipe joint, in alignment with a portion of the overlay outboard of the castellated profile.

28. The pipe joint of any of Claims 18 to 27, wherein the overlay is disposed within a wall of the pipe joint extending continuously along a full length of the pipe joint.

29. Two or more pipe joints of any of Claims 18 to 28, joined end-to-end by one or more butt welds, wherein the liner extends continuously between the pipe joints.

30. Two or more pipe joints of any of Claims 18 to 28, joined end-to-end with a weld of corrosion-resistant alloy along a mutual interface defined by their abutting end edges.5 31. In combination, the pipe joint of Claim 23 or Claim 24 welded to another polymer-lined pipe joint at a mutual interface defined by their abutting end edges, with the sleeve extending across the interface in radially-expanding engagement with the liners of the conjoined pipe joints.10 32. The combination of Claim 31, wherein the sleeve maintains continuous corrosionresistance between the liners across the interface.

33. A pipeline comprising a succession of pipe joints of any of Claims 18 to 30 or combinations of Claim 31 or Claim 32 or made by the method of any of Claims 1 to 17.

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