FIELD OF THE INVENTION

The invention relates to a composite pipe termination for use in the oil and gas industry, such as in subterranean and sub-sea locations, and a method of providing a composite pipe termination.

DESCRIPTION OF THE RELATED ART

Subsea oil and gas drilling and development employs pipes to transport liquid and/or gaseous hydrocarbons from the seabed to the sea surface and to transport injection fluids from the surface to the seabed. These pipes have typically been made from steel or from unbonded layers of materials, such as one or more layer(s) of steel wires combined with a plastic liner, which together form a flexible, unbonded steel pipe. Such unbonded, flexible pipes are covered by American Petroleum Institute standard API 17J.

Over time, the subsea depths at which hydrocarbons are extracted has tended to increase. This development has been accompanied by a need to operate under harsher conditions including one or more of conditions of increased salinity, higher acidity, higher internal and external pressures and higher temperatures. In order to address these challenges, the industry has turned to composite pipes, comprising fibre-reinforced thermoplastic polymer. Reference may be made to WO 2012/072993 A1 which discloses such composite pipes. These pipes may be manufactured by winding tapes of composite material onto a pipe liner and fusing them thereto, then winding further layers of tape on top and fusing each layer to the immediately preceding layer. The composite material typically comprises a thermoplastic matrix, such as polyether ether ketone, with fibres embedded therein and the liner is typically made of the same thermoplastic material as the matrix. These pipes are lighter and better able to withstand the more severe environments as well as the more complex dynamic loading conditions including tension, bending and intemal/external pressure found deep below the sea surface. DNV standard DNVGL-ST-F119 (August 2018) relates to thermoplastic composite pipes for offshore applications in the oil and gas industry.

An obstacle to the introduction of such composite pipes has been the ability to effectively terminate such pipes and to reliably connect them to non-composite, especially steel, piping and apparatus at both subsea and surface interfaces. Composite pipe terminations and connections must be able to provide a reliable transition from the composite pipe material to a standard steel pipe, which may typically incorporate a steel flange or hub connection. The different structural properties of the two materials on the one hand and the differences in thermal expansion on the other, may make it challenging to effect both a reliable structural and sealing connection. Reference may also be made to WO 2012/095633 A1 and WO 2017/163021 A1 , which disclose prior art terminations for a composite pipe.

The end cap load may be a significant source of axial tensile forces on a pipe end (broadly speaking, the end cap load or force is the product of the internal pressure and the internal cross-sectional area). In the subsea extraction of oil and gas, pipe ends near the sea bed may be subject to significant additional tensile axial forces as a result of the weight of the pipe extending above it. These tensile axial forces may make it more challenging to connect composite pipes to pipes made of other materials, such as steel.

There is a need to improve composite pipe terminations, such that they may reliably be connected to metal piping. In particular, there is a need to improve the seal achieved by the composite pipe termination and to improve its ability to resist tensile axial forces. In addition, it is desirable for the diameter of the pipe termination to be kept small so that it is not significantly larger than the diameter of the pipe.

For completeness, pipe terminations are also known from GB 2 439 146 A, EP 2 492 571 A2 and US 2014/0312612 A1. These documents relate to flexible steel, unbonded pipe of the type discussed above. Although such flexible pipes may comprise multiple layers including steel and polymer layers, the pipes are, at heart, steel pipes and not composite pipes as presently defined. As a result of these pipes being fundamentally steel pipes, the problems of providing a termination to a composite pipe do not arise. The end-fitting generally comprises a steel flange, which is attached to the underlying steel carcass of the flexible steel, unbonded pipe. This is a metal-to-metal connection, so the challenges which may arise when attaching a steel end-fitting to a composite pipe do not occur.

It is against this background that the present invention has been devised.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a composite pipe termination is provided comprising: a) a composite pipe formed of composite material and having an interior pipe surface, an exterior pipe surface and a pipe end, wherein composite material is a material comprising a polymer matrix and a plurality of reinforcing fibres embedded in the polymer matrix; b) a liner, wherein the interior pipe surface is fused to the liner; c) an annular element having an internal surface attached to a portion of the exterior pipe surface and an external surface, wherein the external surface comprises a bulge portion in which the annular element has its maximum radial thickness; d) an end-fitting which interfaces with the annular element; e) tensile tendons, each tensile tendon having a proximal end disposed closer to the end-fitting and a distal end disposed more remotely from the end-fitting, the tensile tendons being affixed to and extending axially across the external surface of the annular element including across the bulge portion, and wherein the tensile tendons extend beyond the annular element in the direction away from the end-fitting and the distal ends are affixed under tension directly or indirectly to the composite pipe in order to allow axial load transfer from the composite pipe termination to the composite pipe.

The first aspect of the invention permits distribution of tensile axial forces from the pipe end back to regions of the pipe located before the pipe end.

As used herein, the term “end-fitting” means a device intended to attach to another apparatus, such as a pipe, or an end cap, and may comprise a flange, hub or the like.

As used herein, the term “axial” refers to the axis of the composite pipe, which extends longitudinally along the composite pipe.

As used herein, the term “tendon” refers to a strip, a rod, or cord of material connecting two separate elements.

According to one embodiment of the first aspect, in order to effect indirect connection of the distal ends to the composite pipe, the composite pipe may additionally comprise a sheath disposed around and attached to a portion of the exterior pipe surface beyond the annular element in the direction away from the endfitting and the distal ends of the tensile tendons are affixed to the sheath. The sheath may be attached to a portion of the exterior pipe surface contiguous with the annular element.

According to one alternative of this embodiment, the sheath comprises and preferably consists of the same material as the polymer matrix. If the materials are the same, then they may be fused together to form a unitary material, such that there is no interfacial connection between the sheath and the composite pipe, which provides a stronger construction than in the case of different materials connected at an interface.

According to another alternative of this embodiment the tensile tendons comprise and preferably consist of composite material having a polymer matrix of the same material as the sheath. For the reasons just provided, this provides a stronger connection between the tensile tendons and the sheath than in the case of different materials connected at an interface.

According to further alternative of this embodiment the composite material of the tensile tendons is the same as the composite material of the composite pipe and, in addition, the sheath consists of the same material as the polymer matrix of both the composite material of the tensile tendons and the composite material of the composite pipe. For the reasons just provided, this provides a stronger connection between these three elements than in the case of different materials connected at interfaces.

According to another alternative of this embodiment, each tensile tendon contacts the sheath over a contact region extending from the tensile tendon’s distal end towards the end-fitting and each tensile tendon is affixed to the sheath over the entire contact region. Maximising the area to which the tensile tendons are connected tends to maximise the strength of the connection between the two elements.

According to another embodiment of the first aspect, the tensile tendons extend axially.

According to a further embodiment of the first aspect, the distal ends are affixed at a location which is disposed at a distance equivalent to from 2 to 25, preferably from 3 to 10, pipe external diameters from the pipe end.

According to another aspect of the first embodiment, the tensile tendons, together, are configured, dimensioned and sufficient in number, to withstand a load which is equivalent to from 1 to 4 times the end cap load of the composite pipe (the end cap load is the tensile axial force acting on the end of the composite pipe when under internal pressure). According to one embodiment, the liner comprises an extension portion which extends beyond the pipe end.

According to a further embodiment: a. the external surface of the annular element comprises a first tapered part which tapers from the bulge portion towards the composite pipe in a direction away from the end-fitting; b. an intermediate layer is provided which adheres to and covers the external surface of the annular element and the portions of the tensile tendons extending axially across the external surface of the annular element; c. the composite pipe termination additionally comprises an annular collar which encloses and mates with the intermediate layer to provide an interference fit which locks the annular collar to the intermediate layer; and d. wherein the annular collar matingly engages with the end-fitting to lock the end-fitting to the annular collar.

According to one alternative of this embodiment, the annular element comprises and preferably consists of thermoplastic polymer and more preferably the annular element consists of PEEK.

According to another alternative of this embodiment, the intermediate layer comprises and preferably consists of thermosetting polymer and more preferably the intermediate layer consists of epoxy resin.

According to a further alternative of this embodiment, the external surface of the annular element comprises a second tapered part which tapers from the bulge portion towards the composite pipe in a direction towards the end-fitting.

According to another alternative of this embodiment, the tensile tendons are affixed to the external surface of the annular element by fusion. According to a further alternative of this embodiment: a. the annular collar comprises a locking portion having an inner surface which is provided with a female thread; b. the end-fitting comprises an outer surface which is provided with a male thread; c. the male thread on the outer surface of the end-fitting engages with the female thread of the locking portion to provide the mating engagement which locks the end-fitting to the annular collar.

According to another alternative of this embodiment, the annular element comprises an extension region which extends beyond the pipe end and is spaced therefrom to define an annular cavity around the pipe end.

According to a further alternative of this embodiment the end-fitting defines a receiving cavity.

According to this alternative, the composite pipe termination may additionally comprise a hub, wherein the hub defines a first interface which mates with the annular cavity and a second interface which matingly engages with the receiving cavity to lock the hub to the end-fitting.

According to this alternative, the hub may comprise a tapered region which increases in radial thickness in a direction toward the first interface and wherein the composite pipe termination additionally comprises a wedge disposed between the hub and the extension region of the annular element, wherein the wedge provides an interference fit between the extension region of the annular element and the wedge and between the tapered region of the hub and the wedge to lock the hub into the annular cavity. The wedge may comprise and preferably consists of a thermoplastic polymer and more preferably the wedge consists of PEEK.

According to this alternative, the second interface may be provided with a male thread and the receiving cavity may be provided with a female thread, such that the male thread engages with the female thread to provide the mating engagement which locks the hub to the end-fitting.

According to this alternative, the composite pipe termination may additionally comprise sealing means which provide a seal between the pipe end, the extension portion and the hub and may additionally provide electrical insulation between the composite pipe and the hub, thereby preventing the flow of electric currents between these two elements. The sealing means may comprise and preferably consist of thermoplastic polymer and more preferably the sealing means consist of PEEK.

According to this alternative, the hub may comprise a receiving portion formed to receive a portion of the extension portion and form a lip seal, wherein, in use, the lip seal is pressed against the receiving portion by the pressure of fluid contained within the pipe termination to enhance the seal.

Instead of an arrangement in which the annular collar directly locks to the end fitting, the following alternative arrangement may be provided: a. the annular collar comprises a locking portion having an inner surface which is provided with a female thread; b. the end-fitting comprises a reduced diameter portion having an outer surface which is spaced from the inner surface of the annular collar to provide an annular locking space; c. a locking ring is provided having an outer surface provided with a male thread; d. the male thread of the locking ring engages with the female thread of the locking portion to lock the locking ring within the annular locking space and prevent the end-fitting from moving axially with respect to the annular collar.

According to a second embodiment of the first aspect of the invention, the annular element is made of steel and wherein the tensile tendons are affixed to the external surface of the annular element by means of two or more retaining belt(s).

According to one alternative of this embodiment the retaining belt(s) consist of the same composite material as the composite pipe. If the materials are the same, then they may be fused together to form a unitary material, such that that there is no interfacial connection between the retaining belt(s) and the tensile tendons, which provides a stronger construction than in the case of different materials connected at an interface.

According to another alternative of this embodiment the retaining belt(s) comprise and preferably consist of composite material and more preferably the polymer matrix consists of PEEK and the reinforcing fibres embedded therein consist of carbon fibres.

According to a further alternative of this embodiment, the external surface of the annular element comprises a first tapered part which tapers from the bulge portion towards the composite pipe in a direction away from the end-fitting.

According to another alternative of this embodiment, the external surface of the annular element comprises a second tapered part which tapers from the bulge portion towards the composite pipe in a direction towards the end-fitting.

According to a further alternative of this embodiment, the tensile tendons are coated with an electrically insulating material. It may be advantageous to electrically insulate the tensile tendons from the annular element to prevent electrical currents from circulating, especially in the case in which the reinforcing fibres comprised within composite materials are electrically conductive. According to this embodiment, the tensile tendons may be coated with PEEK.

According to another alternative of this embodiment the annular element defines a male connector which is disposed beyond the pipe end and the end-fitting defines a female connector which matingly engages with the male connector to lock the annular element to the end-fitting. According to this embodiment, the male connector may comprise a male thread and the female connector may comprises a female thread such that the male thread engages with the female thread to provide the mating engagement which locks the annular element to the end-fitting. According to a further alternative of this embodiment, the composite pipe termination additionally comprising sealing means which provide a seal between the pipe end, the extension portion and the annular element. The sealing means may comprise and preferably consist of thermoplastic polymer and more preferably the sealing means consist of PEEK.

According to another alternative of this embodiment, the annular element comprises a receiving portion formed to receive a portion of the extension portion and form a lip seal, wherein, in use, the lip seal is pressed against the receiving portion by the pressure of fluid contained within the pipe termination to enhance the seal.

According to one embodiment of the first aspect of the invention, wherein the endfitting is made of steel.

According to another embodiment of the first aspect, the end-fitting comprises a flange.

According to a further embodiment of the first aspect, the polymer matrix comprises and preferably consists of thermoplastic polymer and more preferably the polymer matrix consists of PEEK.

According to another embodiment of the first aspect, the reinforcing fibres comprise glass fibres, carbon fibres, or mixtures thereof, and preferably the reinforcing fibres consist of carbon fibres.

According to a further embodiment of the first aspect, the composite pipe comprises wound tapes of composite material which have been fused together and wherein the polymer matrix consists of thermoplastic polymer.

According to a further embodiment of the first aspect, the liner comprises and preferably consists of thermoplastic polymer and more preferably consists of PEEK. According to a second aspect of the invention, a method of providing a composite pipe termination is provided, the method comprising: a) providing a composite pipe formed of composite material and having an interior pipe surface, an exterior pipe surface and a pipe end, wherein composite material is a material comprising a polymer matrix and a plurality of reinforcing fibres embedded in the polymer matrix; and wherein the interior pipe surface is fused to a liner; b) providing an annular element having an internal surface and an external surface, wherein the external surface comprises a bulge portion in which the annular element has its maximum radial thickness; c) attaching the internal surface of the annular element to a portion of the exterior pipe surface; d) providing an end-fitting and disposing it to interface with the annular element; e) providing tensile tendons, each tensile tendon having a proximal end and a distal end; f) disposing the tensile tendons, such that the proximal end of each tensile tendon is disposed closer to the end-fitting and the distal end of each tensile tendon is disposed more remotely from the end-fitting, such that the tensile tendons are affixed to and extend axially across the external surface of the annular element including across the bulge portion and the tensile tendons extend beyond the annular element in the direction away from the end-fitting; g) affixing the tensile tendons the external surface of the annular element and affixing the distal ends under tension directly or indirectly to the composite pipe in order to allow axial load transfer from the composite pipe termination to the composite pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a side-elevation of a composite pipe termination according to a first embodiment of the invention.

Figure 2 shows expanded details of the composite pipe termination shown in Figure 1 from detail view A.

Figure 3 shows expanded details of the composite pipe termination shown in Figure 1 from detail view B.

Figure 4 shows expanded details of the composite pipe termination shown in Figure 1 from detail view C.

Figure 5 shows an exploded perspective view of the composite pipe termination shown in Figure 1.

Figure 6 shows a side-elevation of a composite pipe termination according to a second embodiment of the invention.

Figure 7 shows expanded details of the composite pipe termination shown in Figure 6 taken from detail view D.

Figure 8 shows expanded details of the composite pipe termination shown in Figure 6 taken from detail view E.

DETAILED DESCRIPTION A detailed description of the invention will now be provided with reference to the above figures. A given reference number is always used to denote the same feature in each of the accompanying drawings.

Figure 1 shows a side-elevation of a composite pipe termination according to a first embodiment of the invention. Specifically, it shows a composite pipe 1 having an interior pipe surface 1 a, an exterior pipe surface 1 b and a pipe end 1 c. A liner (shown in more detail in Figures 2 and 4) is fused to the interior pipe surface 1 a.

Typically, the composite pipe consists of wound tapes of composite material which have been fused together. The composite material typically consists of a PEEK matrix and a plurality of carbon fibres embedded therein. The tapes are typically wound onto a PEEK liner.

An end-fitting 5 is provided is provided comprising a flange for attachment to another apparatus, such as another pipe. End-fitting 5 is typically made of metal and is preferably made of steel.

The composite pipe termination comprises an annular element 2 attached to the exterior pipe surface 1 b. The annular element 2 comprises a bulge portion 2a at which the annular element 2 has its maximum radial thickness. Typically, the annular element is made of polyether ether ketone (PEEK). As can be seen, the annular element 2 interfaces with the end-fitting 5.

The external surface of the annular element 2 comprises a first tapered part 2b which tapers from the bulge portion 2a towards the composite pipe 1 in a direction away from the end-fitting 5. In addition, the external surface of the annular element 2 comprises a second tapered part 2c which tapers from the bulge portion 2a towards the composite pipe 1 in a direction towards the end-fitting 5.

Tensile tendons 3 are provided, each tensile tendon having a proximal end 3a disposed closer to the end-fitting and a distal end 3b disposed more remotely from the end-fitting. The tensile tendons 3 extend axially across the external surface of the annular element 2 including across the bulge portion 2a, first tapered part 2b and second tapered part 2c and beyond the annular element 2 in the direction away from the end-fitting. The distal ends 3b are affixed under tension directly to a sheath 4

Sheath 4 is disposed around and attached to a portion of the exterior pipe surface 1 b beyond the annular element 2 in the direction away from the end-fitting 5 and is contiguous with the end of the annular element 2 further from the end-fitting.

The sheath 4 is typically made of PEEK and is typically attached to the composite pipe 1 by fusing it to the pipe.

The tensile tendons 3 are typically made of the same composite material as the composite pipe and are typically coated with PEEK to electrically insulate the carbon fibres embedded in the composite and prevent an electrical current from flowing between the tensile tendons 3 and other metal parts, such as the end-fitting 5. Such a current may give rise to corrosion.

Each tensile tendon 3 is attached to the annular element 2 along the entire interface between the tendon 3 and the annular element and is typically attached by fusing it to the annular element 2. In addition, each tensile tendon 3 is attached to the sheath 4 along the entire interface between the tensile tendon 3 and the sheath 4 and is typically attached by fusing it to the sheath 4.

As can also be seen from Fig.1 , annular element 2 additionally comprises an extension region which extends beyond the pipe end 1c and is spaced therefrom to define an annular cavity around the pipe end 1c. In the embodiment shown in Fig.1 , the annular cavity also extends axially along the pipe 1 in the direction away from the end-fitting 5. Moreover, end-fitting 5 defines a receiving cavity.

The composite pipe termination additionally comprises a hub /, which is typically made of metal and is preferably made of steel. The hub 7 defines a first interface 7a which mates with the annular cavity. The first interface comprises steps in the radial direction and the annular cavity comprises corresponding steps which mate with the steps of the first interface. Without wishing to be bound by theory, the presence of such steps may serve to distribute stress at the interface better than a planar interface would, thereby avoiding undesirable stress concentrations.

The hub 7 also defines a second interface 7b which mates with the receiving cavity to lock the hub to the end-fitting 5. Mating engagement between the receiving cavity and the hub is achieved by threaded hub connection 8, achieved by a male thread on the outer surface of the hub 7 which engages with a female thread on an inner surface of the end-fitting 5 to provide the mating engagement which locks the hub 7 to the end-fitting 5.

In addition, the hub 7 comprises a tapered region which increases in radial thickness in a direction toward the first interface 7a. The composite pipe termination additionally comprises a wedge 9 disposed between the hub 7 and the extension region of the annular element 2. The wedge 9 provides an interference fit between the extension region of the annular element 2 and the wedge 9 on the one hand, and between the tapered region of the hub 7 and the wedge 9 on the other hand, to lock the hub into the annular cavity. The wedge is typically made of PEEK.

An intermediate layer 10 is provided which adheres to and covers the external surface of the annular element 2 and the portions of the tensile tendons 3 extending across the external surface of the annular element 2.

The composite pipe termination additionally comprises an annular collar 6 which encloses and mates with the intermediate layer 10 to provide an interference fit which locks the annular collar 6 to the intermediate layer 10. Typically, the intermediate layer 10 is made of epoxy resin. Moreover, the annular collar 6 matingly engages with the end-fitting 5 to lock the end-fitting 5 to the annular collar 6. In the embodiment shown, mating engagement is achieved via a threaded connection 11 achieved by a male thread on the outer surface of the end-fitting 5 which engages with a female thread on a locking portion of the annular collar 6 to provide the mating engagement which locks the end-fitting 5 to the annular collar 6.

The composite pipe termination show in Fig.1 additionally comprises sealing means

12 which provide a seal between the pipe end, the extension portion and the hub. The sealing means are typically made of PEEK.

In the embodiment of Fig.1 , a tensile tendon retaining collar 13 is provided, which is typically made of metal and preferably of steel. The tensile tendon retaining collar

13 provides an additional means to hold the tensile tendons 3 in place and acts against the tendency of the tensile tendons 3 to peel away under in-use conditions.

In the embodiment of Fig.1 , a steel end cap 14 is provided. The purpose and function of end cap 14 is described in more detail below in relation to the manufacturing of the composite pipe termination.

As explained above, Figure 2 shows expanded details of the end-fitting shown in Figure 1 from detail view A. Fig.2 shows the composite pipe 1 , the interior pipe surface 1a, the exterior pipe surface 1 b and the liner 1 d, fused to the interior pipe surface 1a. It also shows sheath 4, annular element 2 and a tensile tendon 3 extending across the surface of annular element 2 and sheath 4.

As explained above, Figure 3 shows expanded details of the end-fitting shown in Figure 1 from detail view B. Fig.3 shows the composite pipe 1 , onto which is fused annular element 2. In turn, tensile tendons 3 are fused onto the annular element 2 and additionally retained by tensile tendon retaining collar 13. Annular collar 6 is also shown as are intermediate layer 10, and end cap 14.

Figure 4 shows expanded details of the end-fitting shown in Figure 1 taken from detail view C. In this figure, liner 1d is shown to have an extension portion, which is a portion of the liner which extends beyond the pipe end (the pipe end is located on the far left, out of this figure). Hub 7 is shown in this figure to have a receiving portion 15 machined into it which receives part of the extension portion to form a lip seal. In use, the extension portion is pressed against the receiving portion 15 by the pressure of fluid flowing through the composite pipe termination to enhance the seal. Sealing means 12 can also be seen in this figure.

Figure 5 shows an exploded perspective view of some elements of the composite pipe termination of Figure 1 , showing (moving from bottom right to top left) end cap 14, annular collar 6, tensile tendon retaining collar 13, intermediate layer 10, sheath 4, tensile tendons 3, annular element 2, hub 7 , wedge 9 and end-fitting 5.

Typically, the composite pipe termination of the first embodiment is manufactured as follows:

The composite pipe end 1 a is machined to provide it with a chamfer and to remove a portion of pipe 1 in order to create an extension portion of liner which extends beyond the pipe end 1a. Sealing means 12 (typically made of PEEK tape) are then fused to the chamfered portion of the composite pipe. A sheath 4 is then made by overwrapping a length of pipe 1 and sealing means 12 with (typically PEEK) tape. After this, a pre-made annular element 2 is slid into place and attached to the pipe at a position which is contiguous with the end of the sheath 4 and such that the annular element 2 is adjacent to the pipe end 1a and the extension region extends beyond the pipe end 1a. Attachment may be by means of screws, such as “set” or “grub” screws, or by other suitable means.

Axially-aligned tensile tendons 3 are then attached by fusing them under tension to the external surface of the annular element 2 and to sheath 4. After this, steel tensile tendon retaining collar 13 is fitted around the tensile tendons 3 at the end of the first tapered part 2b further from the end-fitting.

Hub 7 is then fitted into the annular cavity formed between the pipe end 1c and the extension region of the annular element 2. Wedge 9 is then fitted to provide an interference fit locking the hub 7 into position the annular cavity.

End-fitting 5 is then attached to the other end of hub 7 by means of threaded hub connection 8.

Annular collar 6 is then placed around the annular element 2 such that there is an annular space between the annular collar and the annular element. The annular collar is locked to end-fitting 5 by means of threaded connection 11 . At the end of the annular collar further from the end-fitting 5, an end cap 14 is attached which serves as a preliminary attachment to hold the annular collar in a correctly aligned position prior and ensure the presence of the annular space prior to formation of the intermediate layer 10 which is intended to occupy the annular space. End cap 14 also prevents liquid, uncured epoxy from escaping during formation of intermediate layer 10.

Intermediate layer 10 is manufactured by pumping liquid, uncured (typically epoxy) resin into the annular space via ports (not shown). On curing, the epoxy solidifies to form the intermediate layer which mates with both the annular element 2 and the annular collar 6.

Figure 6 shows a side-elevation of a composite pipe termination according to a second embodiment of the invention. Specifically, it shows a composite pipe 1 having an interior pipe surface 1a, an exterior pipe surface 1 b and a pipe end 1c. A liner (shown in more detail in Figures 7 and 8) is fused to the interior pipe surface 1 a.

Typically, the composite pipe consists of wound tapes of composite material which have been fused together. The composite material typically consists of a PEEK matrix and a plurality of carbon fibres embedded therein. The tapes are typically wound onto a PEEK liner.

An end-fitting 5 is provided is provided comprising a flange for attachment to another apparatus, such as another pipe. End-fitting 5 is typically made of metal and is preferably made of steel.

The composite pipe termination comprises an annular element 2. The external surface of the annular element 2 comprises a bulge portion 2a at which the annular element 2 has its maximum radial thickness. Typically, the annular element is made of metal, preferably steel. The annular element 2 is typically attached to the pipe by means of an interference fit and screws, such as “set” or “grub” screws may be provided to enhance the strength of the connection.

The external surface of the annular element 2 comprises a first tapered part 2b which tapers from the bulge portion 2a towards the composite pipe 1 in a direction away from the end-fitting 5. In addition, the external surface of the annular element 2 comprises a second tapered part 2c which tapers from the bulge portion 2a towards the composite pipe 1 in a direction towards the end-fitting 5.

Tensile tendons 3 are provided, each tensile tendon having a proximal end 3a disposed closer to the end-fitting and a distal end 3b disposed more remotely from the end-fitting. The tensile tendons 3 extend axially across the external surface of the annular element 2 including across the bulge portion 2a, first tapered part 2b and second tapered part 2c and beyond the annular element 2 in the direction away from the end-fitting. The distal ends 3b are affixed under tension directly to a sheath 4.

Sheath 4 is disposed around and attached to a portion of the exterior pipe surface 1 b beyond the annular element 2 in the direction away from the end-fitting 5 and is spaced from the end of the annular element 2 further from the end-fitting. An annular spacer element 15 is placed around the composite pipe in the gap between the annular element 2 and the sheath 4.

The sheath 4 is typically made of PEEK and is typically attached to the composite pipe 1 by fusing it to the composite pipe 1. The annular spacer element 15 is typically made of PEEK, but is typically not attached to the composite pipe 1 .

The tensile tendons 3 are typically made of the same composite material as the composite pipe and are typically coated with PEEK to electrically insulate the carbon fibres embedded in the composite and prevent an electrical current from flowing between the tensile tendons 3 and other metal parts, such as the annular element 2 and the end-fitting 5. Such an electrical current may give rise to corrosion, which it is desirable to avoid.

The tensile tendons 3 are attached to the annular element 2 by means of two or retaining belts 16, one being located adjacent to the proximal end of the tensile tendons 3 and the other being located adjacent to the end of the annular element which is more distant from the end-fitting 5. The retaining belts are typically made of composite material consisting of a PEEK matrix in which are embedded carbon fibres.

In addition, each tensile tendon 3 is attached to the sheath 4 along the entire interface between the tensile tendon 3 and the sheath 4 and is typically attached by fusing it to the sheath 4. Furthermore, each tensile tendon 3 is attached to the annular spacer element 15 along the entire interface between the tensile tendon 3 and the annular spacer element 15 and is typically attached by fusing it to the annular spacer element 15.

The annular element 2 defines a male connector which extends beyond the pipe end and the end-fitting defines a female connector which matingly engages with the male connector to lock the annular element to the end-fitting. Mating engagement between the annular element 2 and the end-fitting 5 is achieved by threaded attachment 17, comprising a male thread on the outer surface of male connector which engages with a female thread on an inner surface of the female connector to provide the mating engagement which locks the annular element 2 to the end-fitting 5.

The composite pipe termination show in Fig.6 additionally comprises sealing means 18 which provide a seal between the pipe end, the extension portion and the hub. The sealing means are typically made of PEEK.

Figure 7 shows expanded details of the end-fitting shown in Figure 6 taken from detail view D. In this figure, composite pipe 1 and liner 1d can be seen. The annular element 2 and spacer element 15 are also shown over which a tensile tendon 3 extends. Tensile tendon 3 is coated with a non-conductive coating 3a, which is typically PEEK. Tensile tendon retaining belt 16 is also shown.

Figure 8 shows expanded details of the end-fitting shown in Figure 5 taken from detail view E. In this figure, liner 1 d is shown to have an extension portion, which is a portion of the liner which extends beyond the pipe end (the pipe end is located on the far left, out of this figure). Annular element 2 is shown in this figure to have a receiving portion 19 machined into it which receives part of the extension portion to form a lip seal. In use, the extension portion is pressed against the receiving portion 19 by the pressure of fluid flowing through the composite pipe termination to enhance the seal. Sealing means 18 can also be seen in this figure.

Typically, the composite pipe termination of the second embodiment is manufactured as follows:

The composite pipe end 1 a is machined to provide it with a chamfer and to remove a portion of pipe 1 in order to create an extension portion of liner which extends beyond the pipe end 1a. Sealing means 12 (typically made of PEEK tape) are then fused to the chamfered portion of the composite pipe. A sheath 4 is then made by overwrapping a length of pipe 1 with (typically PEEK) tape. An annular spacer element 15 is then placed around the pipe contiguous with the sheath 4.

After this, a pre-made annular element 2 is slid into position so that the end which is more remote from the end-fitting is contiguous with the annular spacer element 15. The annular element 2 forms an interference fit with the pipe 1 and may additionally be retained in place by “set” or “grub” screws, or by other suitable means.

Axially-aligned tensile tendons 3 are then attached under tension to the external surface of the annular element 2, to the spacer element 15 and to sheath 4. Tensile tendons 3 are retained around the form of the annular element by retaining belts 16. Connection to the annular element 2, to the spacer element 15 and to sheath 4 is by fusion of the tensile tendons 3 to the spacer element 15 and to sheath 4.

The annular element 2 is then attached to end-fitting 5 by means of threaded attachment 17.