Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
IMPROVED COUPLING ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2016/016640
Kind Code:
A1
Abstract:
A coupling comprising a first part (310) having a fluid passageway (311), a second part (320) having a fluid passageway (321) and such that when the two parts are coupled, fluid can flow between the passageways (311, 321), and a cage (330), wherein one of the parts is coupled to the cage (330) by relative movement in a coupling direction, the cage (330) including a socket against which the part is sealed to retain fluid within the passageways (311, 321); wherein,the part includes a seal that is angled to the coupling direction and a direction perpendicular to the coupling direction, wherein the cage includes a breaking surface and the part includes a corresponding reaction surface and the surfaces are arranged parallel to the coupling direction such that they abut to resist relative movement of the cage (330) and part in the perpendicular direction.

Inventors:
READMAN, Matt (Self Energising Coupling Company Limited, Swan HouseNew Cheshire Business Park,Wincham Lane, Wincham Northwich Cheshire CW9 6GG, GB)
Application Number:
GB2015/052184
Publication Date:
February 04, 2016
Filing Date:
July 28, 2015
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SELF ENERGISING COUPLING COMPANY LIMITED (Swan House, New Cheshire Business ParkWincham Lane,Wincham, Northwich Cheshire CW9 6GG, GB)
International Classes:
F16L29/04; F16L37/30; F16L55/10
Domestic Patent References:
WO2007017677A12007-02-15
WO2008087457A12008-07-24
Foreign References:
US20120103450A12012-05-03
DE102007041170B32009-01-15
US5165439A1992-11-24
US6269836B12001-08-07
Attorney, Agent or Firm:
APPLEYARD LEES (15 Clare Road, Halifax, Yorkshire HX1 2HY, GB)
Download PDF:
Claims:
Claims

1 . A coupling comprising a first part having a fluid passageway, a second part having a fluid passageway and such that when the two parts are coupled, fluid can flow between the passageways, and a cage, wherein one of the parts is coupled to the cage by relative movement in a coupling direction, the cage including a socket against which the part is sealed to retain fluid within the passageways; wherein,

the part includes a seal that is angled to the coupling direction and a direction perpendicular to the coupling direction, wherein the cage includes a breaking surface and the part includes a corresponding reaction surface and the surfaces are arranged parallel to the coupling direction such that they abut to resist relative movement of the cage and part in the perpendicular direction.

2. The coupling of claim 1 , wherein the breaking surface and reaction surface are adapted to generate a frictional component that balances the separation force created by fluid pressure in the decoupling direction.

3. The coupling of claim 1 or 2, wherein the coupling includes a tension component, wherein the tension component prevents decoupling of the part and cage, the tension component being arranged to fracture at a predetermined tensile load.

4. The coupling of any of claims 1 to 3, wherein the second part is integral to the cage. 5. The coupling of any of claims 1 to 3, wherein the second part is separate to the cage.

6. The coupling of any proceeding claim, wherein one or both parts include a valve, wherein the valve has a plug that intersects a fluid passageway in a body at an angle thereto, the plug having an aperture that extends from one portion of a circumferential face to another portion, the plug being arranged within a socket and sealed to the socket to retain fluid within the fluid passageway; and wherein:

in one angular rotation arrangement, the aperture through the plug is aligned with the fluid passageway allowing fluid to flow through the valve; and

in another angular rotation arrangement, the plug closes the fluid passageway.

7. The coupling of claim 6, wherein the plug and socket are tapered and wherein the plug is caused to move linearly towards the tapered socket to seal the valve.

8. The coupling of claim 7, including an activation mechanism to rotate and move the plug simultaneously.

9. The coupling of Claim 8, wherein the activation mechanism biases the plug to the closed and sealed position.

10. The coupling of Claim 7 or 8, wherein the coupling includes restraining means to hold the activation mechanism in an open position when the two parts are coupled, wherein the activation mechanism is biased to close and seal the plug when the restraining means is removed.

1 1 . The coupling of Claim 10, wherein the restraining means is arranged to be automatically removed, when the first and second parts decouple.

12. A valve having a plug that intersects a fluid passageway in a body at an angle thereto, the plug having an aperture that extends from one portion of a circumferential face to another portion, the plug being arranged within a socket and sealed to the socket to retain fluid within the fluid passageway; and wherein:

in one angular rotation arrangement, the aperture through the plug is aligned with the fluid passageway allowing fluid to flow through the valve; and

in another angular rotation arrangement, the plug closes the fluid passageway. 13. The valve of claim 12, wherein the plug and socket are tapered and wherein the plug is caused to move linearly towards the tapered socket to seal the valve.

14. The valve of claim 13, including an activation mechanism to rotate and move the plug simultaneously.

15. The valve of Claim 14, wherein the activation mechanism biases the plug to the closed and sealed position.

16. A coupling including a first part and a second part, wherein one of the parts includes the valve of any of claim 12 to 15.

17. The coupling of Claim 16, wherein the coupling includes restraining means to hold an activation mechanism in an open position when the two parts are coupled, wherein the activation mechanism is biased to close and seal the plug when the restraining means is removed.

18. The coupling of Claim 17, wherein the restraining means is arranged to be automatically removed, when the first and second parts decouple.

19. The coupling of any of claims 16 to 17, wherein the first and second parts are coupled by relative movement in a coupling direction, and the coupling includes a cage that restricts relative movement of the two parts in a direction perpendicular to the coupling direction.

20. The coupling of Claim 19, wherein the seals retaining fluid within the fluid passageways are angled with respect to the coupling direction and perpendicular direction. 21 . The coupling of claim 19 or 20, wherein the cage is arranged to have a breaking surface parallel to the coupling direction and adapted such that the breaking surface abuts the part to cause a frictional force between the cage and part that resists decoupling.

22. The coupling of any of claims 6 to 1 1 , wherein the coupling includes a tension component that pins the two parts together, wherein the tension component is arranged to be broken under a tension component acting across the first and second parts before the first and second parts can move relative to each other in the decoupling direction.

23. The coupling of any of claims 9 to 12, wherein the cage is separate to both parts such that both parts can be coupled and decoupled to the cage by relative movement.

24. The coupling of any of claims 9 to 13, wherein the cage is integral to one of the parts. 25. The coupling of any of claims 17 to 24, wherein both parts includes a valve as claimed in claims 12 to 15.

26. The coupling of claim 25, wherein the coupling includes retaining means to retain each plug in the open position whilst the parts are coupled.

Description:
Improved Coupling Assembly

The present invention relates to an improved coupling and in particular, although not exclusively, to an improved coupling for use in fluid pipelines such as oil pipelines.

Fuse couplings are known for use in oil pipelines. The fuse couplings are used to couple pipelines for instance when coupling pipelines to tankers. Here, one end of the pipeline is often fixed, for instance, to a relatively fixed anchor such as a moored vessel. Due to unexpected movement of the tanker, the fuse coupling is used to automatically separate when a breakout force is exerted on the pipeline in order to prevent damage to sensitive equipment. For instance, should the tanker move unexpectedly whilst filling, a breakout force is applied across a fuse coupling which breaks apart and separates. Known valves are prone to false disconnects wherein pressure within the system causes the coupling valve to disconnect. That is, as the pressure within the valve creates a net force acting to push the coupling apart, the coupling can break out at lower than anticipated breakout forces applied as a tension component along the pipeline. False disconnects are also a source of delay and cost in the pipeline operation.

Often, the fuse couplings are designed to automatically shut off the pipeline to prevent oil escaping when the pipeline pulls apart. For instance, it is known to use a ball valve on either side of a full-bore coupling to act as a coupling valve. However, in order to seal the ball valves, a seal is required to be in constant contact between two surfaces to achieve the seal. The seal creates friction between the two surfaces as they move relative to each other to open and close the ball valve. Consequently, the ball valves generate a high friction component making them difficult to activate. Also, it is not easy to reliably close the ball valves on breakout of the coupling. Iris valves where a plurality of petal type components open and close are also known. However, a more reliable seal is beneficial.

There are also specific issues relating to certain types of fluid. For instance, LPG pipelines require metal-to-metal seals. Thus, valves that rely on other types of seal, for instance o-ring seals, cannot be used.

It is an aim of the present invention to attempt to overcome at least one of the above or other disadvantages. It is a further aim to provide an improved coupling that is able to compensate for the internal pressures caused by fluid pressure to provide a more reliable external breakout load. It is a further aim to provide a valved coupling having metal-to-metal seal when closed. It is a further aim to provide an improved coupling valve providing a full bore coupling that automatically shuts off when decoupled even under pressure. According to the present invention there is provided a coupling assembly and a coupling assembly including a valve as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows. According to exemplary embodiments, there is provided a valve having a plug that intersects a fluid passageway in a body at an angle thereto. The plug has an aperture that extends from one portion of a circumferential face to another portion, wherein in one angular rotation arrangement, the aperture through the plug is aligned with the fluid passageway allowing fluid to flow through the valve. In another angular rotation arrangement, the plug closes the fluid passageway. For instance annular seals either side of the aperture through the plug prevent fluid from exiting the fluid passageway. Advantageously, because the plug is angled to the fluid passageway and because the plug is moved between an open and closed arrangement by rotation, minimal force is required to activate the valve. It will be appreciated that in the exemplary embodiments the body includes a socket for receiving the plug. Fluid is retained in the valve by seals between the plug and socket.

Typically, the open and closed arrangements are at 180° of angular rotation to each other. However, dependent on the relative sizes of the plug, aperture and fluid passageway, other extents of angular rotation may be achieved between the open and closed positions. Advantageously, the movement to achieve the degree of angular rotation can be easily adapted to allow remote operation. For instance, in the exemplary embodiments a lever is secured to the end of the plug to the outside of the valve, wherein the lever allows activation of the valve by a degree of angular rotation.

Although the plug may be substantially a constant diameter across the active are of the plug, wherein the active area includes the two opposing annular seal areas either side of the aperture through the plug, and preferably also the area between the two opposing annular seals, in one exemplary embodiment, the plug is tapered. Here, the plug is tapered towards the end of the valve that is closed. In this embodiment, the socket is correspondingly tapered. Advantageously, as the plug is rotated between open and closed positions, the plug is also arranged to be moved linearly along the plug's axis. This linear movement of the tapered plug towards the tapered socket causes a seal to be formed between the plug and socket. Consequently, as well as an improved seal mechanism, it is possible to achieve a metal-to metal seal. Although it is typically envisaged that the plug and socket will have a constant taper between the two opposed annular seals, indeed, it is preferable as the seal is improved, it is only required that the seal area of the plug intended to seal between the plug and socket at the closed end moves towards a narrower section of the socket. In the exemplary embodiments including a tapered plug, the valve advantageously includes an activation mechanism that causes the plug to move rotationally to close the fluid passageway and also linearly to seal the passageway. Although the mechanism may be arranged to sequentially rotate and move the plug, in the exemplary embodiments, the mechanism is arranged to simultaneously rotate and move the plug. Here the mechanism may be cooperating threads formed on the plug and body respectively. Thus, as the thread of the plug is caused to rotate, it is also caused to move linearly.

Consequently, according to the exemplary embodiments, there is provided a valve having a plug as herein described. A first part and a second part of the valve are mated in use to form a coupling having a fluid passageway there through. At least one of the parts includes a plug. The fluid passageway is opened and closed by operating the plug.

In the exemplary embodiments, the plug is biased towards the closed position. Suitably, the bias is a biasing means such as a torsion spring. Here, the valve includes restraining means for preventing the plug from closing whilst the first and second parts are coupled. As the first and second parts are decoupled, for instance because a tension component is applied across the coupling that exceeds the breakout strength of the coupling, the restraining means is removed allowing the biased plug to move towards the closed position. The restraining means may be pins in the other of the parts opposed to the part having the plug, wherein the pins provide a positive abutment against the plug preventing movement towards the closed position only when the two parts are coupled. Consequently there is provided an automatic shut of coupling wherein at least one end of the pipeline is automatically closed upon breakout. The coupling can be re-joined by reconnecting the two parts and causing the plug to return to its open position.

It will be appreciated that the coupling can be arranged to close both parts by providing a plug in both parts. Here each part of the coupling includes a body having a fluid passageway there through and a plug angled thereto. To prevent fluid leakage when the parts are broken and closed by the plugs, the two parts may be angled at the distal ends. The angle is typically parallel to the angle of the plug so that a minimum extend of the body extends past the plug. The two parts meet at their distal ends. It will be appreciated that fluid is retained within the fluid passageways across the join by seals known in the art. As such, fluid pressure within the fluid passageway acts to force the parts apart. As the fluid pressure increases, the force urging the two parts apart also increases. This means that the tensile force applied across the coupling to breakout the coupling is dependent on the pressure within the fluid passageway. In exemplary embodiments including two parts each having a plug as herein described, the valve includes a cage restraining movement of the two parts relative to each other in a direction perpendicular to the fluid passageways. Here, the two parts are coupled by movement along a coupling axis and the cage prevents relative movement perpendicular to the coupling axis. Suitably, one or both of the parts slide relative to the cage. Here, because the plugs are angled across the fluid passageways, the effective area generated by the pressure within the fluid passageways generates a component acting perpendicular to the fluid passageway as well as parallel along the coupling direction. Moreover, the effective area is larger in the perpendicular direction due to the angled plug. Consequently, the fluid pressure generates a force urging the two parts to separate, which is carried by the cage. In the exemplary embodiments, the friction between the cage and parts acts to restrict sliding movement of the parts relative to the cage. This means that as the pressure in the fluid passageway increases, thereby increasing the force urging the two parts to slide apart within the constraint of the cage, the frictional force between the cage and parts also increases. In the exemplary embodiments, the cage includes brake pads at the abutment with the parts and by correct selection of the brake pad material, the frictional force can be selected to balance the breakout force generated by the pressure within the system. Consequently it is possible to provide a coupling wherein the breakout force required to be exerted by external factors can be substantially the same independent of the fluid pressure within the passageway. The two parts can be coupled together using tension pins as is known in the art to provide a fixed breakout force required to be overcome before the parts decouple.

In an exemplary embodiment according to a further aspect, there is provided a coupling comprising first and second parts that are held together by a cage. The cage allows movement of the first and second parts along a coupling and decoupling direction but prevents relative movement in other directions. The first and second parts include fluid passageways that when coupled provide a fluid passageway through the coupling. The first and second parts are arranged to have an angled end face. The fluid passageway in each part has an exit aperture on the angled end face. The cage includes a first and second opposed braking surface. The breaking surfaces are arranged in a plane parallel to the coupling direction. The first and second breaking surfaces are preferably spaced from each other. Each of the first and second parts includes a corresponding reaction surface. Angled seals are provided between each part and the cage to retain fluid within the passageways. The angled seals are angled with respect to both the coupling direction and the perpendicular direction to generate a separation force in both directions. In use, as pressurised fluid travels within the passageway, separation forces are generated. Because the seals are angled to the coupling direction, separation forces are created in the coupling direction as well as a direction perpendicular thereto. The friction between each pair of breaking and reaction surfaces can be designed to balance the separation force generated in the coupling direction so that the two parts are retained from separating. Moreover, the two parts require the same external axial load to separate independent of the fluid pressure within the coupling.

The breaking surfaces and corresponding reaction surfaces are suitably planar and arranged to oppose each other. The breaking and reaction surfaces may be similar to the previous aspect. That is, in this aspect, the coupling may be similar to the valve of the first aspect without the plug. Furthermore, as mentioned above, one or both parts may be moveable relative to the cage. That is, whilst the exemplary embodiments show both parts separating from the cage, it is envisaged that the cage could also be integral to one part. Here, only one part is moveable relative to the cage and only one set of corresponding breaking and reaction surfaces are required.

Although the exemplary embodiments are described in relation to fluid pipelines for oil, the coupling and valve technology described herein is applicable to other types of fluid pipeline. The technology is also suitable to larger and smaller sizes as well as different materials such as plastic valves.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figures 1 and 2 show perspective views of a valve according to a first embodiment in open and closed arrangements; Figures 3 and 4 show partial cut away views of the valve in the open and closed arrangements;

Figure 5 is a perspective view of a coupling according to a second embodiment; Figures 6 and 7 are perspective views showing the coupling of Figure 5 with buoyancy removed to reveal mated first and second parts;

Figure 8 is a close up perspective view of an area of Figure 7; Figure 9 is a partial cut away perspective view of the mated coupling; and

Figures 10 to 12 are sectional views showing the decoupling sequence respectively. Figures 13 and 14 are cutaway perspective views of a coupling according to a further embodiment showing the parts in coupled and uncoupled arrangements respectively.

Referring to Figures 1 and 2 a valve 100 comprises a body 1 10 having a fluid passageway 1 12 there through. A plug 120 is arranged within the body 1 10. The plug is housed within the body so as to be able to rotate between an open (figure 1) and a closed (figure 2) arrangements. As shown a lever 122 is attached to the plug 120 and accessible externally to the valve. It will be appreciated that actuation of the lever enables the plug to be rotated.

As shown in the figures, the fluid passageway is substantially straight and has a central axis. Usually, the fluid passageway has a constant and circular cross-section. The valve 100 is termed full bore because the cross-sectional area of the valve does not substantially changed across the valve. Furthermore, the fluid passageway remains substantially straight across the valve meaning reduced turbulence is applied to the fluid passing through the passageway. The plug is arranged at an angle to the fluid passageway. That is, the plug is formed to be substantially symmetrical about a central axis and the central axis of the plug is angled with respect to the axis of the fluid passageway. In the exemplary embodiments, the angle is shown to be around 30°. However, the angle may be arranged to within the range of less than 60° or less than 45° or less than 35° and more than 15° or more than 25°.

The plug 120 includes an aperture 124 that extends through the plug. The aperture suitably corresponds in size and shape to the fluid passageway of the body. Here, the aperture has a substantially straight central axis and has a substantially constant circular cross-section. The central axis is angled to the axis of the plug the same degree as the angle between the fluid passageway and plug. Thus, when the plug is rotated with respect to the body, at a set angle, the fluid passageway in the body and the aperture through the plug are aligned. The aperture 124 through the plug extends from one portion of the circumferential face of the plug to another. Thus, by creating an annular seal 126 between the plug and body at a distal end of the plug 120, the fluid passageway can be closed by rotation of the plug. For instance, the annular seal 126 at the distal end of the plug 120 forms a constant seal about the fluid passageway. When the plug is rotated so that the aperture on the circumferential face is arranged on the inside of the seal, a fluid passageway is created through the valve. When the plug is rotated so the aperture on the circumferential face is outside the annular seal, fluid is prevented from passing through the fluid passageway.

It will be appreciated that the plug is housed within the body so as to be able to be rotated relative thereto. In the exemplary embodiments a socket 130 is formed within which the plug is assembled. The socket is suitably sized so as to match the probe's size and shape and so as to therefore provide the support to allow the plug to rotate within the body. Suitable seals between the plug and socket are provided to prevent fluid from escaping the passageway to the outside of the valve in any rotational arrangement. The body is shown in the figures as substantially enclosing the plug wherein only the activation mechanism 122 extends to the outside of the valve. However, as described herein, dependant on the application, covers can also be supplied over the lever 122 to protect against the external environment. The body 1 10 may be a single piece, or as shown in Figure 3, may be formed from two parts sealed together as is known in the art. Here bolts 1 14 are shown.

Figure 4 shows the plug rotated to the closed position wherein the aperture through the plug is not arranged to exit the plug between the distal seal 126. As described a seal is made between the distal end of the plug and the socket. Although the seal maybe an annular seal such as an o-ring seal as is known in the art and sealed at all rotational angles of the plug, the plug in the exemplary embodiments includes a taper so that one point along the axis of the plug has a cross-sectional radius which is greater than another part. The socket has a corresponding area. Here, the plug is arranged to move towards the small cross-sectional point so that the taper of the plug engages the taper of the socket. This allows a surface seal to be achieved and, if the two parts are metallic forms a metal-to-metal seal. PTFE of other coatings can be applied to one or both parts to give softness to the sealing surfaces to promote good sealing as is known in the art.

In the exemplary embodiments, the plug is arranged to move laterally in the direction of the plug's axis. The taper may be arranged so that the plug moves towards the smaller cross- sectional area of the taper in either a positive direction into the valve or a negative direction moving out of the valve. Whilst the plug might rotate to close and then move laterally to seal, in the exemplary embodiments, the plug is moved laterally and rotated simultaneously. Here, a mechanism is used that links the lateral movement of the plug to rotational movement or vice-versa. In the Figures the mechanism is shown as cooperating threads on the plug 120 and body 1 10. That is, the plug is shown to have a threaded shank and the body a threaded aperture. Thus as the plug is actuated to move laterally or to rotate, the cooperating threads also create the simultaneous rotation or lateral movement.

The valve 100 may be used to create a 'fuse' in a pipeline. Fuses are used to provide predetermined breaking points in the pipeline should external factors provide a tension on the pipeline that would otherwise risk damaging more sensitive or costly equipment. Here, the fuse is designed to have a specific breakout strength so that the valve separates into two parts if the tension is exceeded. For instance the pins1 14 may be tension pins designed to fracture at a given load. When doing so the two parts of the body 1 10 would separate into two to relive the tension on the pipeline. It is preferable here for the fluid passageways to be automatically shut off so that if the valve separates whilst fluid is flowing, fluid loss to the environment is reduced. In the exemplary embodiments, the plug is therefore biased to automatically close should the two parts separate. As described in more detail herein, one part of the valve body 1 10 houses the plug and the other part includes abutments that restrict the rotation or lateral movement of the plug when the two parts are coupled. When the abutment is removed, for instance because the parts have decoupled, the plug is free to move or rotate and therefore automatically moves to the closed arrangement.

In the exemplary embodiments the plug is therefore biased to rotate or move laterally to the closed position. For instance a torsion spring is applied to bias the plug to move towards the closed position. Thus when the force restricting movement of the plug is removed, the torsion spring causes the plug to move or rotate towards the closed and sealed position. A fused valve that automatically shuts off one end of the fractured pipeline is therefore provided. According to a further exemplary embodiment there is provided a coupling 200. The coupling 200 is shown in Figure 5 for use in an oil pipeline wherein the coupling is intended to be floated on the top of water. Here, a buoyancy jacket 202 is arranged to surround the coupling. When the coupling is decoupled, the buoyancy jacket 212 must also be removed. Typically, the buoyancy jacket is arranged to separate along an axial separation line. However, for reasons that will become apparent, in the exemplary embodiments, the buoyancy jacket is arranged to separate along an axial separation line 203

As shown in Figure 7, the coupling 200comprises a first valve 100a and a second valve 100b. Each valve is substantially as herein described. The two valves form a coupling by being assembled together. Here the two parts are brought together along a coupling direction which substantially corresponds to the axial direction of the fluid passageways. When coupled the fluid passageway in the first valve is arranged to be substantially coincident with the fluid passageway in the second valve. A tension pin 210, shown in more detail in Figure 8 pins the two valves together. It will be appreciated by those in the art that the tension pin is arranged to fracture at a predetermined tensile load across the coupling. Once fractured, the two valves would be free to separate in the reverse direction to the coupling direction. The two valves are sealed together to prevent fluid loss to the outside. The seals are arranged at an angle to the coupling direction and also a direction perpendicular thereto. The seals may be any suitable seal for the given application such as an elastomeric seal or a metal to metal gland seal

A cage 230a and 230b is arranged on either side of the coupling to tie the two valves together in a direction perpendicular to the coupling direction. Thus the two valves are restricted from moving relative to each other except in the coupling and decoupling directions. As shown in Figure 8, the cages are a substantially 'c'-shaped structure that clamps against shoulders 218 of the valves.

As shown in Figure 9, when fluid is pressurised within the coupling, the fluid pressure creates separation forces on the coupling equivalent to the fluid pressure multiplied by the projected area of the seals. Thus, in the decoupling direction the projected area is shown by areas 251 and 252 and is the cross-sectional area of the fluid passageways. Because the plugs are sealed across and angle to the fluid passageway, separation forces are also created perpendicular to the fluid passageway. The projected area of these separation forces are depicted by areas 253 and 254 and the areas are elliptical between the seals of the plug. Geometry dictates that the areas 253, 254 are larger than the areas 251 , 252. The separation forces in the direction perpendicular to the fluid passageway are carried by the cage.

It will be appreciated that as the separation forces urge the two valves apart, the shoulders 218 are urged towards the cage 230. To separate, the valves must slide apart with one or both of the valves sliding relative to the cage. To separate, the separation forces created by the internal pressure of the fluid and the external tension must overcome the friction generated between the shoulders and cage. As the frictional forces are dependent on the fluid pressure, the friction can be used to balance the separation forces applied by the internal fluid pressure. In the exemplary embodiments shoulders or cage include brake pads 270 having a high coefficient of friction. The coefficient of friction can be selected to allow the forces to be balanced. Moreover, tensioning means 260 can be used to adjust the un-pressurised frictional resistance by adjusting the clamping force applied by the cage. In Figure 8, the tensioning means is shown as a series of bolts that are used to move the brake pad towards or away from the shoulder 218. The brake pad may be arranged to act on one or both shoulders.

Figures 10 to 12 show a decoupling process. When coupled, the plugs in the first and second valves are held in their open positions by retaining means shown as abutments or pins that extend from the other valve body to abut the plug and therefore prevent movement to the closed position when the two valves are coupled. In figure 10, the abutments are shown as pins 280. When a breakout force applied across the coupling exceeds the limit of the tension pin, the tension pin fractures allowing the two valves to separate along the decoupling direction. Advantageously, because to separate the breakout force must overcome the friction applied between the cage and valves, the separation forces in the decoupling direction exerted by the fluid pressure can be substantially cancelled out allowing the tension pin to fracture at a determined external load independent of the fluid pressure. As the two valves move apart the abutments are removed from restraining the respective plugs. Thus because the plugs are biased towards the closed position, they move and rotate to close and seal the respective ends of the valve. Consequently, when separated, see Figure 12, the two ends of the pipeline have been automatically sealed and closed preventing fluid loss even when broken under pressure.

To reconnect the coupling the valves are reconnected, and the abutment means reinstalled to hold the plugs in the open position.

Figures 13 and 14 show a further exemplary embodiment. Here, a coupling 300 is provided. The coupling 300 is in effect the valve of the previous embodiments without the valve aspect. That is, without the plug. A further description is given below, however, it will be appreciated that the parts common between the embodiments are interchangeable and the description given of each, may equally apply to the other.

Referring to Figure 14, the coupling 300 comprises a first part 310, a second part 320 and a cage 330. The cage is arranged to allow relative movement of the first and second parts in a coupling direction but to restrain relative movement of each part and the cage in a second, perpendicular direction. Each of the first and second parts 310, 320 has a fluid passageway 31 1 , 321 extending there through. The fluid passageways may have any path or shape but are suitably shown as being straight bores, coincidental with the coupling direction. The first and second parts include angled seals 312, 322 to retain fluid within the passageways when mated. The angled seals seal against the cage 330. The angled seals are angled with respect to the coupling direction. The angled seals are also angled with respect to the perpendicular direction. Here, the angled seals may therefore be arranged at an angle of more than 10° or an angle of more than 15 0 or an angle of more than 20° to each direction. Because the seals are angled to each direction, they have an effective area in both directions. Thus, when the coupling is pressurised to have fluid running through the passageways, a separation force is generated in both directions. As explained further below, the separation force generated in the perpendicular direction can be used to brake the system to provide a resistance to separation of the parts from the cage in the de coupling direction. In the figures the first and second parts are shown as having angled end faces 313, 323.

The angled end faces correspond to the angled seals.

The cage 330 provides a socket for the first and second parts. The socket provides the surface against which the angled seals contact. The cage 330 further provides a breaking surface for each part. The breaking surfaces 332, 334 are arranged parallel to the coupling direction so that as the parts decouple, the parts move parallel to the breaking surfaces. As will be appreciated, the breaking surfaces can be adapted to have a desired frictional coefficient and properties to suit the application. In particular the breaking surfaces may be adapted to have frictional properties to balance the separation forces. In the figures the breaking surface is shown as internal surface of the cage. However, the breaking surfaces may also be arranged elsewhere. The parts include corresponding reaction surfaces. Here, the corresponding reaction surfaces are also arranged parallel to the coupling direction so they slide parallel to the breaking surfaces when the parts are decoupled. It will be appreciated that the friction generated between the breaking surface and reaction surface controls the force required to separate the parts from the cage in the decoupling direction.

Although preferred embodiment(s) of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made without departing from the scope of the invention as defined in the claims.