WO2016151339A1

WO2016151339A1 - A pipeline breakaway coupling

Info

Publication number: WO2016151339A1
Application number: PCT/GB2016/050857
Authority: WO
Inventors: Richard Thomas
Original assignee: Klaw Products Limited
Priority date: 2015-03-26
Filing date: 2016-03-24
Publication date: 2016-09-29
Also published as: GB201505222D0; GB2536701B; GB2536701A

Abstract

A pipeline breakaway coupling (10) comprising a pair of shut-off valve housings (12) clamped to each other by means of a detachable collar (14). The shut-off valve housings (12) define a hollow bore (16) along which flowable material may flow and the collar (14) permits the shut-off valve housings (12) to separate from each other on operation of an actuation mechanism (18) operably engaged with the collar (14). A shut-off valve (20) is located within the hollow bore (16) of each shut-off valve housing (12). Each shut-off valve (20) includes a shut-off valve member (22) movable between a valve open position and a valve closed position in which the shut-off valve member (22) shuts off the flow of any flowable material through the hollow bore (16). Each shut-off valve member (22) is biased to move to its valve closed position on separation of the shut-off valve housings (12). The collar (14) includes a pair of collar members (26,28). Each of the collar members (26,28) is pivotably coupled to the other at or towards a first end (26a,28a) so as to allow pivotable movement of the collar members (26,28) relative to each other. The collar members (26,28) are secured to each other at or towards their other, second ends (26b, 28b), so as to clamp the collar members (26,28) about the shut-off valve housings (12), by means of a breakaway coupling mechanism (30). The actuation mechanism (18) includes an actuator (32) and a driving assembly (38) to drive the actuator (32) from an extended position to a retracted position on operation of the actuation mechanism (18). The actuator (32) breaks the breakaway coupling mechanism (30) on driving movement of the actuator (32) into its retracted position.

Description

A PIPELINE BREAKAWAY COUPLING

The invention relates to a pipeline breakaway coupling. Breakaway couplings are known and are often used in situations where a pipeline may be exposed to a tensile loading which, in the absence of a breakaway coupling, could cause the pipeline to fracture. Typically such a pipeline may be one used for carrying material between a ship and a dock. If such a fracture occurs, the material being conveyed along the pipeline flows freely out of the fractured ends of the pipeline. This can cause significant spillage that is expensive to clear and may be environmentally undesirable. The presence of a breakaway coupling enables the pipeline to facture at a specified location (i.e. at the coupling) and for spillage to be avoided by providing valves in the breakaway coupling which are actuated when the coupling breaks. According to an aspect of the invention there is provided a pipeline breakaway coupling comprising:

a pair of shut-off valve housings clamped to each other by means of a detachable collar, the shut-off valve housings defining a hollow bore along which flowable material may flow and the collar permitting the shut-off valve housings to separate from each other on operation of an actuation mechanism operably engaged with the collar; and

a shut-off valve located within the hollow bore of each shut-off valve housing, each shut-off valve including a valve member movable between a valve open position and a valve closed position in which the valve member shuts off the flow of an flowable material through the hollow bore, each valve member being biased to move to its valve closed position on separation of the shut-off valve housings,

wherein the collar includes a pair of collar members, each of the collar members being pivotably coupled to the other at or towards a first end so as to allow pivotable movement of the collar members relative to each other and the collar members being secured to each other at or towards their other, second ends, so as to clamp the collar members about the shut-off valve housings, by means of a breakaway coupling mechanism, and

the actuation mechanism includes an actuator and a driving assembly to drive the actuator from an extended position to a retracted position on operation of the actuation mechanism, the actuator breaking the breakaway coupling mechanism on driving movement of the actuator into its retracted position. The provision of an actuation mechanism that is operable to break the breakaway coupling and thereby allow the shut-off valve housings to separate from each other allows selective operation of the pipeline breakaway coupling in circumstances where it is desirable to break a pipeline.

The actuation mechanism could be operated to cause separation of the shut-off valve housings remotely from a ship or shore-based control room in circumstances where personnel or sensors determine that it is no longer safe or desirable to continue the flow of flowable material along the pipeline. The actuation mechanism could, for example, be operated in circumstances where sensors detect a tensile load applied to the pipeline that exceeds predetermined limits.

The provision of valves in the shut-off valve housings that are biased to move to their valve closed positions on separation of the shut-off valve housings ensure that the fractured ends of the pipeline are shut-off on operation of the actuation mechanism.

So as to reduce the undesirable effects of back pressure that could otherwise occur on closing of the shut-off valve located upstream from the juncture between the shut-off valve housings, on separation of the shut-off valve housings, the pipeline breakaway coupling may further include a choke or throttle valve assembly. In the context of this application, the terms "choke" and "throttle" are considered synonymous.

In such embodiments, the pipeline breakaway coupling may include a choke valve housing connected to one of the shut-off valve housings, the choke valve housing extending the hollow bore defined by the shut-off valve housings, and a choke valve located in the hollow bore of the choke valve housing, the choke valve including a choke valve member movable between a valve open position and a valve closed position in which the choke valve member restricts or otherwise chokes or throttles the flow of any flowable material through the hollow bore, the actuator driving movement of the choke valve member to the valve closed position on movement of the actuator from its extended position towards its retracted position thereby closing the choke valve during a first phase of movement of the actuator from the extended position before breaking the breakaway coupling during a second phase of movement of the actuator onward to the retracted position. The provision of a choke valve, which the skilled reader will appreciate is intended to be located upstream of the juncture between the shut-off valve housings, allows the flow of any flowable material through the hollow bore to be reduced before the breakaway coupling mechanism is broken to allow separation of the shut-off valve housings and closure of the shut-off valves.

This in turn reduces the risk of any unwanted effects of back pressure through the flowable material on closure of the shut-off valves.

Preferably the driving assembly is configured to drive movement of the actuator at a first speed during the first phase of movement and a second, faster speed during the second phase of movement.

Proceeding in this manner allows gradual movement of the choke valve member to the valve closed position so as to minimise any back pressure upstream of the pipeline breakaway coupling that might otherwise occur as a result of closing the choke valve. In particularly preferred embodiments, the actuator may be provided in the form of a hydraulic piston located within a hydraulic cylinder, and the pipeline breakaway coupling may further include a volume of oil stored under pressure and arranged to selectively flow into the cylinder in a first direction and drive movement of the piston from its extended position to its retracted position.

The use of a hydraulic cylinder and piston assembly facilitates remote operation of the actuation mechanism through wired or wireless communication with a control processor coupled to the hydraulic cylinder. In such embodiments, the oil may be delivered to the cylinder so as to facilitate driving movement of the piston via a flow control valve, the flow control valve being adjustable to control the first speed of movement of the piston during the first phase of movement.

A skilled reader will appreciate that the rate at which the oil flows into the cylinder will in turn effect the rate at which the oil drives movement of the piston within the cylinder.

In embodiments where it is desirable to accelerate movement of the piston once the choke valve is closed, the cylinder may include a bypass arrangement in the form of a bypass plunger. In such embodiments, the bypass plunger is depressible to divert the flow of oil into the cylinder and bypass the flow control valve, thereby allowing an unrestricted flow of oil into the cylinder in the first direction, the piston being configured to engage and depress the bypass plunger on completion of the first phase or movement so as to initiate the second phase of movement and accelerate movement of the piston to its retracted position.

So as to render the pipeline breakaway coupling suitable for use in cryogenic applications, such as the transfer of liquid natural gas, the actuation mechanism may include a heater to hear the volume of oil. In such embodiments the actuation mechanism may be configured to circulate heated oil in a second, opposite direction into the cylinder and through the piston so as to heat the cylinder and the piston without driving movement of the piston from its extended position to its retracted position.

Heating the cylinder and piston reduces the risk of ice forming on or in the actuation mechanism, and ensures smooth movement of the piston in the cylinder on operation of the actuation mechanism to break the breakaway coupling mechanism. In such embodiments, a jetted check valve may be provided in the pathway through the piston so as to allow a through flow of oil during heated oil circulation and prevent a through flow of oil in the opposite direction during driving movement of the piston from the extended position to the retracted position. The provision of a jetted check valve leads to the generation of additional heat in the oil passing there through, which is advantageous and helps to compensate for losses in heat through conduction during circulation of the heated oil.

It will be appreciated that in circumstances where the piston is in the retracted position, the flow of oil into the cylinder in the second direction will drive movement of the piston from the retracted position to the extended position. Such movement does not occur during normal operation of the breakaway pipeline coupling where the piston is located in the extended position. So as to secure the second ends of the collar members together so as to maintain the clamping action of the collar about the shut-off valve housings, the breakaway coupling mechanism preferably includes an actuation collar. The actuation collar has first and second clamp members configured to clamp about locking pins provided at or towards the second ends of the collar members so as to secure the collar members to each other at or towards their second ends. In such embodiments, the first and second clamp members are secured together by means by one or more frangible connectors and the actuation mechanism is configured to break the or each frangible connector on driving movement of the actuator to its retracted position.

The actuator may be arranged to move relative or otherwise in proximity to the actuation clamp during driving movement from its extended position to its retracted position. This allows the actuator to be configured to engage one of the first and second clamp members as it reaches its retracted position so as to apply a force to separate the first and second clamp members and thereby break the or each frangible connector, It will be appreciated that it is advantageous in such embodiments that the speed of movement of the actuator is increased during the second phase of movement so as to enable the actuator to apply a sufficiently large force to cause separation of the first and second clamp members and thereby break the or each frangible connector. In particularly preferred embodiments, the actuation clamp may include a removable slide pin protruding from the first or second clamp member, the actuator being configured to engage the slide pin as it reaches its retracted position so as to apply a force to separate the first and second clamp members and thereby break the or each frangible connector. The slide pin is removable so as to selectively allow retraction and extension of the actuator without engaging the respective clamp member and thus not causing separation of the first and second clamp members.

It will be appreciated that in embodiments of the invention the actuator could engage the respective clamp member, via the removable slide pin, through either a pushing or pulling action aimed at seeking to separate the first and second clamp members and break the or each frangible connector.

In embodiments where the actuation mechanism includes a hydraulic cylinder and piston arrangement, the actuation clamp may be coupled to the cylinder via one or more hoses to allow the circulation of heated oil through the actuation clamp.

This reduces the risk of ice building up on the actuation clamp when the breakaway pipeline connector is used in cryogenic applications, which could otherwise greatly increase the force required to separate the first and second clamp members and break the or each frangible connector. So as to couple the choke valve to the actuator, the pipeline breakaway coupling may include a yoke having a slot configured to engage a pin protruding from the actuator to translate movement of the actuator from its extended position towards its retracted position into movement of the choke valve member from the open valve position to the closed valve position.

Preferably in such embodiments the choke valve member is mounted on a shaft that is rotatable to move the choke valve member between the open valve position and the closed valve position, the shaft being coupled to the yoke to translate movement of the actuator into rotation of the shaft.

So as to facilitate operation of the choke valve and ensure an efficient coupling between the actuator and the rotatable shaft, the rotatable shaft may be arranged to extend diametrically across the hollow bore of the choke valve housing so that its axis is offset about the diameter of the hollow bore relative to the actuator.

In such embodiments, the axis of the shaft of the choke valve may be offset from an axis extending generally perpendicularly through the actuator by approximately 10°. In embodiments where the actuator is configured to follow a linear path during movement from the extended position to the retracted position, the yoke may include a slot having a curved or arcuate profile section to drive rotation of the shaft to move the choke valve member to the closed valve position during the first phase of movement of the actuator and a linear profile section to retain the choke valve member in the closed valve position during the second phase of movement of the actuator.

In embodiments where the actuation mechanism includes a hydraulic cylinder and piston arrangement, and the yoke is located within a yoke housing coupled to the hydraulic cylinder, the yoke housing may include a purge port for connection to a source of nitrogen gas for injection into the yoke housing and through the choke valve during purging and a plurality of exhaust openings to allow air and moisture to be expelled from the yoke housing during purging.

The provision of a purge port thereby render it possible to maintain the choke valve and ensure efficient operation as and when required. Similarly each shut off valve may include a purge port for connection to a source of nitrogen of gas for injection through each of the shut-off valves during purging to remove moisture from valve surfaces. It is also envisaged that the pipeline breakaway coupling may include a double body seal arranged between abutting surfaces of the shut-off valve housings to maintain a seal between the shut-off valve housings during closing of the shut-off valves.

This arrangement reduces the risk of the shut-off valve housings separating before movement of the shut-off valve members into their valve closed positions is complete.

Other advantageous features will be apparent from the following description in which a preferred embodiment will be described with reference to the accompanying drawings in which:

Figure 1 shows a pipeline breakaway coupling according to an embodiment of the invention;

Figure 2 shows an exploded view of the pipeline breakaway coupling shown in

Figure 1 ;

Figure 3 shows a side view of the pipeline breakaway coupling shown in Figure 1 ;

Figure 4 shows an elevational view from below of the pipeline breakaway coupling shown in Figure 1 ;

Figure 5 shows a first end view through a shut-off valve of the pipeline breakaway coupling shown in Figure 1 ;

Figure 6 shows a second end view through a choke valve of the pipeline breakaway coupling shown in Figure 1 ;

Figure 7 shows a cross-sectional view of the pipeline breakaway coupling along the line A-A of Figure 5;

Figure 8 shows a cross-sectional view of the pipeline breakaway coupling along the line D-D of Figure 5;

Figures 9a and 9b illustrate the relative position of the actuator of the pipeline breakaway coupling of Figure 1 in an extended position;

Figures 10a and 10b illustrate the relative position of the actuator of the pipeline breakaway coupling of Figure 1 following completion of a first phase of movement and closure of a choke valve and before a second phase of movement; Figures 1 1a and 11b illustrate the relative positon of the actuator of the breakaway pipeline coupling following completion of the second phase of movement and breakage of the breakaway coupling mechanism; and

Figures 12 and 13 illustrate the structure of a yoke provided to couple the actuator to a choke valve of the pipeline breakaway coupling shown in Figure 1.

A pipeline breakaway coupling 10 according to an embodiment of the invention is shown in Figure 1. The pipeline breakaway coupling 10 includes a pair of shut-off valve housings 12 clamped to each other by means of a detachable collar 14.

The shut-off valve housings 12 define a hollow bore 16 along which flowable material may flow and the collar 14 permits the shut-off valve housings 12 to separate from each other on operation of an actuation mechanism 18 operably engaged with the collar 14. A shut-off valve 20 (Figure 8) is located within the hollow bore 16 of each shut-off valve housing 12 and each shut-off valve 20 includes a shut-off valve member 22 movable between a valve open position (Figure 8) and a valve closed position (not shown). In the valve open position, the shut-off valve member 22 bisects the hollow bore 16 of the respective shut-off valve housing 12 (Figure 8). In the valve closed position (not shown) the shut-off valve member 22 sealingly engages against a valve seat defined about the circumference of the respective shut-off valve housing and shuts off the flow of a flowable material through the hollow bore 16.

Each shut-off valve member 22 is biased to move to its valve closed position on separation of the shut-off valve housings 12. In the embodiment shown in Figure 8, each shut-off valve member 22 is mounted on a pivot shaft and is biased to move to its valve closed position by means of a spring 24. The spring 24 preferably includes contra wound spring portions mounted on opposite ends of the pivot shaft and engaged with the shut-off valve members 22 so as to bias each of the shut-off valve members 22 towards the valve closed position.

The shut-off valves 20 are located in the shut-off valve housings 12 in opposed configurations such that, whilst the shut-off valve housings 12 remain clamped together, the opposing shut-off valve members 22 interleave with each other (Figure 7). This engagement allows each shut-off valve member 22 to oppose movement of the other shut- off valve member 22 until separation of the shut-off valve housings 12 moves the shut-off valve members 22 out of engagement with each other and the bias provided by springs 24 causes the shut-off valve members 22 to move to their valve closed positions.

Referring back to Figure 1 , the collar 14 includes a pair of collar members 26,28. Each of the collar members 26,28 is pivotably coupled to the other at or towards a first end 26a, 28a via a mounting bracket 29 secured to one of the shut-off valve housings 12 so as to allow pivotable movement of the collar members 26,28 relative to each other. So as to clamp the collar member 26,28 about the shut-off valve housings 12, the collar members 26,28 are secured to each other at or towards their other, second ends 26b, 28b by means of a breakaway coupling mechanism 30.

The breakaway coupling mechanism 30 includes an actuation clamp 40 having first and second clamp members 42,44 (Figure 2) configured to clamp about locking pins 46 provided at the second ends 26b,28b of the collar members 26,28 so as to secure the collar member 26,28 to each other.

The first and second clamp members 42,44 are secured together by means of a plurality of frangible connectors in the form of break studs 48. In the embodiment shown in Figure 1 , the pipeline breakaway coupling 10 includes a choke valve housing 34 connected to one of the shut-off valve housings 12. In the embodiment shown in Figure 1 , the choke valve housing 34 is formed integrally with the adjacent shut- off valve housing 12. It is envisaged that in other embodiments the two housings 34,12 could be formed separately and secured together by means of sealed joints between the two housings 34,12, or the choke valve housing 34 could be omitted entirely.

The choke valve housing 34 extends the hollow bore 16 defined by the shut-off valve housings 12 and includes a choke valve 36 (Figure 8) located in the hollow bore 16 to provide a flow restricted on operation of the actuation mechanism 18.

The choke valve 34 includes a choke valve member 36 mounted for rotation about a shaft 38 and, in the embodiment shown in Figure 8, is provided in the form of a butterfly valve arrangement. The choke valve member 36 is movable between a valve open position in which it bisects the hollow bore 16 of the choke valve housing 34 (Figure 8) and a valve closed position (not shown) in which the choke valve member 36 extends across the bore so as to restrict, choke or otherwise throttle the flow of any flowable material through the hollow bore 16.

In use, the pipeline breakaway coupling 10 is located in a pipeline so that the choke valve is located upstream of the juncture between the shut-off valve housings.

In the embodiment shown in Figure 1 , the pipeline breakaway coupling 10 includes an actuation mechanism 18 having an actuator in the form of a hydraulic piston 32 and a driving assembly in the form of a hydraulic cylinder 38 connected to a volume of oil stored under pressure (not shown) and arranged to selectively flow into the cylinder 38 to drive movement of the piston 32. Referring to Figure 8, the piston 32 is shown in an extended position relative to the cylinder 38 with a first end 32a received in a counter bore 50 formed in the first and second clamp members 42,44 of the actuation clamp 40.

At its other, second end 32b, the piston 32 is coupled to the rotatable shaft 38 of the choke valve by means of a yoke 52, the rotatable shaft 38 being secured within an aperture 60 formed through the yoke 52 (Figures 12 and 13).

The piston 32 is coupled to the yoke 52 by means of pins 54 protruding in opposite directions from the end of the piston 32 so as to engage within slots 56 formed in bifurcated sections 58 of the yoke 52 between which the piston 32 is received. The slots 56 formed in the bifurcated sections 58 of the yoke 52 are shaped so as to define an arcuate profile section 62 and a linear profile section 64.

The rotatable shaft 38 is mounted so as to extend diametrically across the hollow bore of the choke valve housing 34. However, so as to allow coupling of the piston 32 with the rotatable shaft 38 of the choke valve, the rotatable shaft 38 is offset about the diameter of the hollow bore 16 relative to the piston 32, as shown in Figure 6, by an angle Θ of approximately 10°. So as to reduce the risk of introducing turbulent fluid flow when flowable material flows through the hollow bore 16 when the choke valve member 36 and the shut-off valve members 22 are located in the valve open positions, the orientations of the shut-off valves 20 are arranged to align with the choke valve, as illustrated in Figure 5, which shows the shafts of the shut-off valves 20 also offset by an angle Θ of approximately 10°.

The actuation mechanism 18 is operable in use to break the breakaway coupling 30 and allow separation of the shut-off valve housings 12 and thereby cause closure of the shut- off valves 20 provided in the shut-off valve housings 12.

It is envisaged that the actuation mechanism could be operated to cause separation of the shut-off valve housings remotely from a ship or shore-based control room. The actuation mechanism could, for example, be operated to cause separation when personnel and/or sensors determine that it is no longer sage or desirable to continue the flow of flowable material along the pipeline.

Whilst such circumstances would very likely arise when sensors detect a tensile load applied to the pipeline that exceeds a predetermined limit, as is the case with convention pipeline breakaway couplings, it is envisaged that remote operation of the actuation mechanism could also allow the breakaway coupling to be broken in response to other non-tensile load related safety concerns and the usefulness of the pipeline breakaway coupling is not therefore limited solely to addressing problems associated with tensile loads in the pipeline.

Operation of the actuation mechanism will now be described with reference to Figures 9a, 9b, 10a, 10b, 11a and 11b. Referring to Figures 9a and 9b, the piston 32 commences in an extended position with the first end 32a received in the counter bore 50 formed in the first and second clamp members 42,44 of the actuation clamp 40.

The second end 32b is located between the bifurcated sections 58 of the yoke 52 so that pins 54 are centrally located within slots 56.

In order to facilitate movement of the piston 32 within the cylinder 38, the actuation mechanism includes a volume of oil stored under pressure and arranged to selectively flow into the cylinder.

On operation of the actuation mechanism 18, the oil is delivered to the cylinder 38 in a first direction via a flow control valve 64 (Figure 3) so as to drive movement of the piston 32 in the cylinder 38 from its extended position towards a retracted position. The flow control valve 64 is adjustable to control the speed at which the oil flows into the cylinder 38 and thereby controls the resultant speed of movement of the piston 32 during this first phase of movement.

Movement of the piston 32 from its extended position towards it retracted position draws the first end of the piston 32a out of the counter bore 50 formed in the actuation clamp 40, as shown in Figure 10a. It also causes longitudinal movement of the second end of the piston 32b relative to the yoke 52.

By virtue of the engagement of pins 54 within the arcuate profile sections of slots 56 provided in the yoke 52, longitudinal movement of the second end of the piston 32b drives rotation of the yoke 52, as illustrated in Figure 10a, which in turn causes rotation of shaft 38 of the choke valve. Accordingly, during this first phase of movement, the choke valve member 22 is moved to its valve closed position so as to restrict the flow of any flowable material through the hollow bore 16, as shown in Figure 10b.

The purpose of the choke valve is not to close the hollow bore because this would, in turn, cause an undesirable back pressure upstream within the pipeline. The purpose of the choke valve instead is to restrict or otherwise choke or throttle the flow of flowable material.

In addition, the speed of movement of the piston 32 is controlled through use of the control flow valve 64 so as to carefully control the speed at which the choke valve member 22 is moved to its closed position so as to choke or otherwise throttle the flow of material gradually and thereby minimise the risk of any back pressure building upstream in the pipeline.

Movement of the piston 32 so as to cause closing of the choke valve locates a shoulder 66 formed on the piston 32 against a bypass plunger 68, as shown in Figure 10b. Continued movement of the piston 32 towards its retracted position causes the shoulder 66 to depress the bypass plunger 68 and thereby initiate a second phase of movement of the piston 32.

On depression of the bypass plunger 68, the flow of oil into the cylinder 38 is diverted so as to bypass the flow control valve 64. This in turn results in an unrestricted flow of oil into the cylinder 38 which in turn applies an increased driving force to the piston 32 so as to accelerate movement of the piston 32 towards its retracted position. Movement of the piston 32 so as to cause closing of the choke valve also however locates the first end of the piston 32a against a slide pin 70 protruding from the first clamp member 42 into the counter bore 50 in the actuation clamp 40. This engagement prevents any further movement of the first end of the piston 32a relative to the first clamp member 42.

This means that, on depression of the bypass plunger 68, the acceleration of the flow of oil into the cylinder 38 causes the first end of the piston 32a to apply a stronger pulling force to the first clamp member 42 than would otherwise occur if the oil continued to flow via the flow control valve 64. The size of this pulling force in turn breaks the break studs 48 interconnecting the first and second clamp members 42,44 and causes separation of the first and second clamp members 42,44 as the piston 32 pulls the first clamp member 42 towards the cylinder housing, as shown in Figure 11 a. Movement of the piston 32 to its retracted position does not affect the choke valve by virtue of the location of pins 54 within the linear profile sections of slots 56 which allow the pins 54 to travel along the length thereof without applying any turning force to the yoke 52. Accordingly the choke valve member 22 is retained in its valve closed position, as shown in Figure 11 b.

Separation of the first and second clamp members 42,44 of the actuation clamp 40 releases locking pins 46 provided at the second ends 26b,28b of the collar members 26,28. This in turns allows collar members 26,28 to pivot about their pivotal connections with the mounting bracket 29 away from the shut-off valve housings 12 and allows separation of the shut-off valve housings 12.

The provision of mounting bracket 29 secured to one of the shut-off valve housings 12 prevents loss of the collar members 26,28. The provision of a chain 76 connected between each collar member 26,28 and the cylinder housing seeks to restrain movement of the collar members 26,28.

As described above, movement of the shut-off valve housings 12 away from each other disengages the opposing shut-off valve members 22 from each other, thereby allowing each of the shut-off valve members 22 to move to its valve closed position and shut off the flow of any flowable material from the fractured ends of the pipeline. The provision of a double seal arrangement 72 between abutting surfaces of the shut-off valve housings 12 maintains a seal between the shut-off valve housings 12 during closing of the shut-off valves 20. More specifically, the location of a rim of an inner shut-off valve housing 12a within the rim of an outer shut-off valve housing 12b together with the provision of two seals and a spigot 74 extending about the rim of the inner shut-off valve housing 12a, maintains a seal between the abutting surfaces as the rim of the inner shut-off valve housing 12a is withdrawn from the rim of the outer shut-off valve housing 12b.

The use of oil to drive movement of the piston 32 in the cylinder 38 provides a useful functionality during normal use of the breakaway pipeline coupling 10, i.e. during normal flow of flowable material through the hollow bore 16. In preferred embodiments, the actuation mechanism 18 may additionally include a heater (not shown) to heat the volume of oil that is otherwise stored under pressure to drive the piston in the event 32 of operation of the actuation mechanism 18 to break the breakaway coupling mechanism 30. Once heated, the heated oil may be circulated through the cylinder 38 and the piston 32 in an opposite direction to the direction in which oil flows into the cylinder 38 to drive the piston 32 from its extended position to its retracted position.

Circulating the heated oil in the opposite direction serves instead to drive the piston 32 towards its extended position and hence has no resultant effect on the position of the piston 32. The provision of galleries formed in the cylinder walls and through the piston 32 allows the heated oil to circulate and thereby heat the cylinder 38 and the piston 32.

This is particularly useful in circumstances where the pipeline breakaway coupling 10 is being used in a pipeline transferring a cryogenic material, such as liquid natural gas. Heating of the cylinder 38 and the piston 32 reduces the formation of any ice and maintains the component parts in a suitable condition for operation in the event it proves necessary to operate the actuation mechanism to separate the shut-off valve housings 12. The provision of a jetted check valve 80 in the piston 32 allows the flow of heated oil through the piston 32 during the step of circulating heated oil whilst preventing the flow of oil in the opposite direction through the piston 32 when oil flows into the cylinder 38 in the opposite direction in order to drive movement of the piston 32 from the extended position towards the retracted position. In addition, the inclusion of a jet in the jetted check valve 80 leads to the generation of additional heat in the oil, which helps to compensate for losses caused by conduction as the heated oil circulates through the rest of the actuation mechanism 18.

In the embodiment shown in Figure 1 , the pipeline breakaway coupling 10 additional includes hoses 78 extending from the housing of the cylinder 38 in order to transfer heated oil to the actuation clamp 40 and allow circulation of heated oil through galleries formed in the first and second clamp members 42,44 so as to heat these component parts also and reduce the formation of ice over the actuation clamp 40 which could otherwise render it impossible to separate the first and second clamp members 42,44 when required or at least require a significantly larger force applied to the piston 32 to break the break studs 48 and pull the first clamp member 42 away from the second clamp member 44.

The ability to control the flow of oil into the cylinder 38 in the opposite direction could also prove useful in circumstances where it is desirable to test cycle movement of the piston 32 between its extended and retracted positions so as to check operation of the piston 32 and also check operation of the choke valve.

In such circumstances, the slide pin 70 is removed from the first clamp member 42 so as to allow the piston 32 to be driven from its extended position to its retracted position, as described above and shown in Figures 10a, 10b, 11a, 11b, 12a and 12b. Once in its retracted position, directing the flow of oil into the cylinder 38 in the opposite direction to that required to drive the piston 32 from its extended position to its retracted position, i.e. in the same direction as described above for the purposes of circulating heated oil, will drive the piston 32 from its retracted position back to its extended position. The slide pin 70 may then be relocated so as to protrude from the first clamp member 42 into the counter bore 50 of the actuation clamp 40.

An additional feature of the breakaway pipeline coupling 10 shown in Figure 1 is illustrated in Figures 3 and 7. Figure 3 shows a purge valve and exhaust arrangement 82 formed in the housing 84 for the yoke 52. The purge valve includes a purge port for connection to a source of nitrogen gas for injection into the yoke housing 84 and is surrounded by a plurality of exhaust vents. The provision of this arrangement means that, on injecting nitrogen gas into the yoke housing 84, air and moisture is forced out of the yoke housing 84 via the exhaust vents.

Figure 7 shows a purge port 86 provided in each of the shut-off valves 20 for connection to a source of nitrogen gas for injection through each of the shut-off valves 20 so as to remove moisture from valve surfaces.

Removing moisture from valve surfaces renders it possible to maintain the valves and ensure efficient and effective operation as and when required.

Claims

1. A pipeline breakaway coupling comprising:

a shut-off valve located within the hollow bore of each shut-off valve housing, each shut-off valve including a shut-off valve member movable between a valve open position and a valve closed position in which the shut-off valve member shuts off the flow of any flowable material through the hollow bore, each shut-off valve member being biased to move to its valve closed position on separation of the shut-off valve housings,

the actuation mechanism includes an actuator and a driving assembly to drive the actuator from an extended position to a retracted position on operation of the actuation mechanism, the actuator breaking the breakaway coupling mechanism on driving movement of the actuator into its retracted position.

2. A pipeline breakaway coupling according to Claim 1 further including a choke valve housing connected to one of the shut-off valve housings, the choke valve housing extending the hollow bore defined by the shut-off valve housings, and a choke valve located in the hollow bore of the choke valve housing, the choke valve including a choke valve member movable between a valve open position and a valve closed position in which the choke valve restricts the flow of any flowable material through the hollow bore, the actuator driving movement of the choke valve member to the valve closed position on movement of the actuator from its extended position towards its retracted position thereby closing the choke valve during a first phase of movement of the actuator from the extended position before breaking the breakaway coupling during a second phase of movement of the actuator onward to the retracted position.

3. A pipeline breakaway coupling according to Claim 2 wherein the driving assembly is configured to drive movement of the actuator at a first speed during the first phase of movement and a second, faster speed during the second phase of movement. 4. A pipeline breakaway coupling according to any one of the preceding claims wherein the actuator is provided in the form of a hydraulic piston located within a hydraulic cylinder, and the pipeline breakaway coupling further includes a volume of oil stored under pressure and arranged to selectively flow into the cylinder in a first direction and drive movement of the piston from its extended position to its retracted position.

5. A pipeline breakaway coupling according to Claim 4 when dependent on Claim 3 wherein the oil is delivered to the cylinder via a flow control valve, the flow control valve being adjustable to control the first speed of movement of the piston during the first phase of movement.

6. A pipeline breakaway coupling according to Claim 5 wherein the cylinder includes a bypass plunger depressible to divert the flow of oil into the cylinder and bypass the flow control valve, thereby allowing an unrestricted flow of oil into the cylinder in the first direction, the piston being configured to engage and depress the bypass plunger on completion of the first phase of movement so as to initiate the second phase of movement and accelerate movement of the piston to its retracted position.

7. A pipeline breakaway coupling according to any one of Claims 4 to 6 wherein the actuation mechanism includes a heater to heat the volume of oil and is configured to circulate heated oil in a second, opposite direction into the cylinder and through the piston so as to heat the cylinder and the piston without driving movement of the piston from its extended position to its retracted position.

8. A pipeline breakaway coupling according to Claim 7 wherein the pathway through the piston includes a jetted check valve to allow a through flow of oil during heated oil circulation and prevent a through flow of oil in the opposition direction during driving movement of the piston from the extended position to the retracted position.

9. A pipeline breakaway coupling according to any one of the preceding claims wherein the breakaway coupling mechanism includes an actuation clamp having first and second clamp members configured to clamp about locking pins provided at or towards the second ends of the collar members so as to secure the collar members to each other at or towards their second ends, the first and second clamp members being secured together by means of one or more frangible connectors and the actuation mechanism being configured to break the or each frangible connector on driving movement of the actuator to its retracted position.

10. A pipeline breakaway coupling according to Claim 9 wherein the actuator is arranged to move relative to the actuation clamp during driving movement from its extended position to its retracted position, the actuator being configured to engage one of the first and second clamp members as it reaches its retracted position so as to apply a force to separate the first and second clamp members and thereby break the or each frangible connector.

11. A pipeline breakaway coupling according to Claim 9 wherein the actuation clamp includes a removable slide pin protruding from the first or second clamp member, the actuator being configured to engage the slide pin as it reaches its retracted position so as to apply a force to separate the first or second clamp members and thereby break the or each frangible connector, the slide pin being removable so as to selectively allow retraction and extension of the actuator without engaging the respective clamp member. 12. A pipeline breakaway coupling according to any one of Claims 9 to 11 when dependent on Claim 7 wherein the actuation clamp is coupled to the cylinder via one or more hoses to allow circulation of heated oil through the actuation clamp.

13. A pipeline breakaway coupling according to any one of Claims 3 to 12 when dependent on Claim 2 wherein the choke valve is coupled to the actuator via a yoke, the yoke including a slot configured to engage a pin protruding from the actuator to translate movement of the actuator from its extended position towards its retracted position into movement of the choke valve member from the open valve position to the closed valve position.

14. A pipeline breakaway coupling according to Claim 13 wherein the choke valve member is mounted on a shaft rotatable to move the choke valve member between the open valve position and the closed valve position, the shaft being coupled to the yoke to translate movement of the actuator into rotation of the shaft.

15. A pipeline breakaway coupling according to Claim 14 wherein the shaft extends diametrically across the hollow bore of the choke valve housing, the axis of the shaft being offset about the diameter of the hollow bore relative to the actuator so as to allow translation of the movement of the actuator into rotation of the shaft via the yoke.

16. A pipeline breakaway coupling according to Claim 14 or Claim 15 wherein the actuator is configured to follow a linear path and the yoke includes a slot having a curved profile section to drive rotation of the shaft to move the choke valve member to the closed valve position during the first phase of movement of the actuator and a linear profile section to retain the choke valve member in the closed valve position during the second phase of movement of the actuator.

17. A pipeline breakaway coupling according to Claim 13 when dependent on Claim 4 wherein the yoke is located within a yoke housing coupled to the cylinder, the yoke housing including a purge port for connection to a source of nitrogen gas for injection into the yoke housing during purging and a plurality of exhaust openings to allow air and moisture to be expelled from the yoke housing during purging. 8. A pipeline breakaway coupling according to any of the preceding claims further including a collar bracket fixed to one of the shut off valve housings, each of the collar members being pivotably mounted at or towards its first end on the collar bracket.

19. A pipeline breakaway coupling according to any one of the preceding claims wherein each shut-off valve includes a purge port for connection to a source of nitrogen of gas for injection through each of the shut-off valves during purging to remove moisture from valve surfaces.

20. A pipeline breakaway coupling according to any one of the preceding claims further including a double body seal arranged between abutting surfaces of the shut-off valve housings to maintain a seal between the shut-off valve housings during closing of the shut-off valves.