WO2024013502A1

WO2024013502A1 - Valve assembly

Info

Publication number: WO2024013502A1
Application number: PCT/GB2023/051837
Authority: WO
Inventors: John Thompson
Original assignee: Site and Field Services Limited
Priority date: 2022-07-14
Filing date: 2023-07-13
Publication date: 2024-01-18
Also published as: GB202210350D0; GB2620618A

Abstract

Disclosed herein is a subsea valve assembly for protecting a hose when connected to a subsea pipeline from depressurisation leading to hose collapse. The valve assembly comprises a valve body comprising a valve inlet fluidly connected by a fluid path to a valve outlet for conveying fluid from a hose to a pipeline, and a valve member, said valve member configured such that in a first position the valve member occludes the fluid path inhibiting fluid flow between the valve inlet and valve outlet, and in a second position the valve member permits fluid flow between the valve inlet and valve outlet. The valve member is arranged with respect to the valve body such that at least a portion of the valve member is exposed to ambient fluid pressure external to the valve which gives rise to a force that urges the valve member towards the first position, and such that fluid pressure at the valve inlet gives rise to a force that urges the valve member towards the second position. The valve assembly further comprises a biasing means configured to apply a biasing force on the valve member urging the valve member towards the second position such that said valve member moves to the first position when the force arising from said ambient fluid pressure exceeds a combination of the force arising from the fluid pressure at the valve inlet and the biasing force, and moves to the second position when a combination of the force arising from the fluid pressure at the valve inlet and the biasing force exceeds the force arising from the ambient fluid pressure.

Description

VALVE ASSEMBLY

Technical Field

The present invention relates to valve assemblies for protecting hoses connecting subsea pipelines from hose collapse.

Subsea pipelines for conveying extracted hydrocarbons are typically pressurised at atmospheric pressure resulting in an often-substantial pressure difference between internal pipeline pressure and the ambient hydrostatic pressure of the surrounding water. The greater the subsea depth of the pipeline, the greater this pressure difference.

When connecting lines and hoses to such pipelines, for example for servicing and maintenance operations such as flushing, cleaning and pigging, this pressure difference poses particular problems. For example, when lowering a hose to a pipeline from a surface vessel, the fluid in the hose must be appropriately pressurised as it descends to prevent its collapse as it is exposed to increasing sub-sea pressure. However, once the hose is connected to a pipeline pressurised at atmospheric pressure, the higher-pressure fluid in the hose will rapidly discharge into the pipeline. This rapid discharge of fluid leads to a corresponding rapid depressurising of the hose which, without mitigating measures, will typically lead to hose collapse.

To address this, service interfaces for connecting hoses and lines to pipelines are typically protected by a check valve assembly. A check valve is configured to only permit forward flow of fluid from the hose above a set pressure. This is known as the “cracking pressure”. With an appropriately set cracking pressure, a check valve prevents rapid fluid discharge and depressurisation of a connecting hose or line thereby reducing the risk of hose or line collapse.

Different check valve assemblies are available. Some check valves are mechanically configured to provide a pre-set cracking pressure. This is normally achieved by a valve member being biased closed with a biasing arrangement (e.g., a spring) with a compression rate selected so that the bias is only overcome (and thus the valve opened) by pressures greater than the desired cracking pressure.

Such check valve assemblies have a fixed cracking pressure irrespective of the depth at which they are deployed. However, the cracking pressure required to reduce the likelihood of hose collapse varies in dependence on the depth at which the hose connects to the pipeline. Accordingly, check valves in which the cracking pressure is mechanically set can typically only be used in a narrow range of subsea depths.

Improvements to such arrangements include self-regulating check valves in which the cracking pressure varies in dependence on the hydrostatic pressure at the depth at which the check valve is deployed. As described for example in UK patent GB2509077, such check valve assemblies include a valve member which is biased closed by a mechanical biasing arrangement (in keeping with check valves with pre-set cracking pressures). However, one or more apertures are provided in the valve assembly which expose the side of the valve member on which the biasing forces act to ambient hydrostatic pressure. The total force biasing the valve member closed is the sum of the force of the mechanical biasing and the force exerted by the ambient hydrostatic pressure. In this way, the cracking pressure varies in dependence on the ambient hydrostatic pressure and, usefully, such check valves can be used at a range of subsea depths.

However, even if a hose is protected by either a pre-set or self-regulating check valve, it has been found that hoses are still vulnerable to collapse, particularly at greater subsea depths. In particular, as a hose descends towards the pipeline, fluctuations in the pressurisation of the hose (which is pressurised by pumps on the service vessel) or simply the higher hydrostatic pressures at deeper depths can still give rise to hose collapse.

Summary of the Invention

In accordance with a first aspect of the invention there is provided a subsea valve assembly for protecting a hose when connected to a subsea pipeline from depressurisation leading to hose collapse. The valve assembly comprises a valve body comprising a valve inlet fluidly connected by a fluid path to a valve outlet for conveying fluid from a hose to a pipeline, and a valve member, said valve member configured such that in a first position the valve member occludes the fluid path inhibiting fluid flow between the valve inlet and valve outlet, and in a second position the valve member permits fluid flow between the valve inlet and valve outlet. The valve member is arranged with respect to the valve body such that at least a portion of the valve member is exposed to ambient fluid pressure external to the valve which gives rise to a force that urges the valve member towards the first position, and such that fluid pressure at the valve inlet gives rise to a force that urges the valve member towards the second position. The valve assembly further comprises a biasing means configured to apply a biasing force on the valve member urging the valve member towards the second position such that said valve member moves to the first position when the force arising from said ambient fluid pressure exceeds a combination of the force arising from the fluid pressure at the valve inlet and the biasing force, and moves to the second position when a combination of the force arising from the fluid pressure at the valve inlet and the biasing force exceeds the force arising from the ambient fluid pressure.

Optionally, the valve member has a first surface and a second surface, said second surface fluidly isolated within the valve assembly from the first surface, wherein the valve member is arranged with respect to the valve body such that the fluid pressure at the valve inlet acts on the first surface and the ambient fluid pressure acts on the second surface.

Optionally, the valve member is located within a chamber, said ambient fluid pressure is transferred into said chamber via pressure transfer means and thereby acts on said second surface.

Optionally, the pressure transfer means comprises one or more apertures providing a fluid opening to fluid external to the valve assembly.

Optionally, the biasing force is of a magnitude such that in combination with friction forces acting on the valve member, movement of the valve member due to the force of gravity acting on the valve member is inhibited. Optionally, the biasing force substantially does not exceed a magnitude such that in combination with friction forces acting on the valve member, movement of the valve member due to the force of gravity acting on the valve member is inhibited.

Optionally, the valve member is located within the valve assembly.

Optionally, the valve outlet comprises a plurality of individual outlet apertures.

Optionally, the biasing means comprises a spring.

Optionally, the spring is a tension spring.

In accordance with a second aspect of the invention there is provided a subsea stab connector comprising an inlet hose connection and an outlet, wherein said subsea stab connector has incorporated therein a subsea valve assembly in accordance with the first aspect, said subsea valve assembly operable to control fluid from the inlet hose connection to the outlet.

Optionally, the subsea valve assembly is located at a distal end of the subsea stab connector.

In accordance with certain embodiments of the invention a valve assembly is provided which can usefully be incorporated in stab connectors for connecting hoses to subsea pipelines. In contrast to certain conventional techniques, the valve assembly is arranged such that as long as pressure on a fluid inlet side (typically from fluid pressure from within a hose) is balanced with, or greater than, ambient hydrostatic pressure, then the valve member is biased open. This means, assuming a suitable surface side connection to atmospheric pressure, as the valve assembly descends, the internal pressure along the entire length of the hose is balanced with the ambient hydrostatic water pressure. This means as the hose descends, it is protected from collapse. However, on connection to a pipeline, any pressure differential between the fluid inlet side and the ambient hydrostatic pressure acts to urge the valve closed thereby protecting the hose from hose collapse.

Various aspects and features of the invention are defined in the claims. Brief Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings where like parts are provided with corresponding reference numerals and in which:

Figure 1 provides an external view of a subsea stab connector for use in subsea hose connecting operations;

Figures 2a and 2b provide simplified schematic diagrams depicting a cross-section of a subsea stab connector incorporating a hose-collapse protection valve assembly in accordance with certain embodiments;

Figure 3 provides a simplified schematic diagram depicting pressures to which a subsea stab connector incorporating a valve assembly in accordance with certain embodiments of the invention is exposed;

Figure 4 provides a diagram showing in simplified form the balanced internal pressure and hydrostatic pressure at all points along the length of a hose being lowered to a pipeline for connection in which the hose is connected to a subsea stab connector incorporating a valve assembly in accordance with certain embodiments of the invention;

Figure 5a provides a simplified schematic diagram depicting the pressures associated with initial connection of a subsea stab connector incorporating a valve assembly in accordance with certain embodiments of the invention and a female subsea stab connector;

Figure 5b provides a simplified schematic diagram depicting the pressures associated with fluid flow from a subsea stab connector incorporating a valve assembly in accordance with certain embodiments of the invention to pipeline via a female subsea stab connector;

Figures 5c and 5d provide simplified schematic diagrams depicting the pressures associated with a reduction in hose pressure in a subsea stab connector incorporating a valve assembly in accordance with certain embodiments of the invention which may lead to hose collapse, and

Figure 6a, 6b and 6c provide simplified schematic diagrams depicting a valve in accordance with certain embodiments of the invention. Detailed Description

Figure 1 provides an external view of a subsea stab connector 101 for use in subsea hose connecting operations. Incorporated in the subsea stab connector 101 is a valve assembly for protecting a hose to which the subsea stab connector 101 is connected against hose collapse.

In keeping with conventional subsea stab connectors, the subsea stab connector 101 comprises a main body 102, a threaded hose connector 103 via which a hose is connected, and an arm 104 which is manipulated by a Remotely Operated Vehicle (ROV) and used to insert the subsea stab connector 101 into an annular female connector. Such an annular female connector is located at a service interface and provides the means by which the subsea stab connector 101 and the hose to which it is attached are connected to a pipeline. Towards the distal end of the subsea stab connector 101 are first and second external seals 105. The first and second external seals 105 provide a seal with the interior of the annular female connector when the subsea stab connector 101 is inserted. A plurality of fluid outlets 106 are located between the first and second external seals 105. The interior of the annular female connector comprises a corresponding plurality of fluid inlets. In use, once the subsea stab connector 101 is inserted in the annular female connector and a seal formed by the first and second external seals 105, the subsea stab connector 101 is rotated by the ROV manipulating the arm 104 which aligns the fluid outlets 106 of the subsea stab connector 101 with the corresponding fluid inlets of the annular female connector. An interface valve connecting the annular female connector and the interior of the pipeline is then opened and a fluid connection is formed between the hose connected to the subsea stab connector 101 and the pipeline connected to the annular female connector.

Figures 2a and 2b provide simplified schematic diagrams depicting a cross-section of the subsea stab connector 101 and in particular show the incorporation a hose-collapse protection valve assembly 202 configured in accordance with certain embodiments of the invention. The valve assembly 202 has a valve body formed by the distal end 203 of the subsea stab connector 101.

The valve assembly 202 comprises a valve member 204 and a fluid inlet 205. The fluid outlets 106 of the subsea stab connector 101 form the valve outlet of the valve assembly 202. The valve member 204 is seated in a chamber 207 at the distal tip of the subsea stab connector 101 such that the valve member 204 can slidably move back and forth between a first position and second position. The valve member 204 is provided with a seal 208 which fluidly isolates a non-fluid flow facing side of the valve member 204 from the fluid flow facing side of the valve member 204 (it will be understood that “fluid flow” in this context refers to fluid flowing through the valve assembly from the hose). With the valve member 204 seated within the chamber 207, the chamber 207 is enclosed except for a plurality of apertures 209 which provide an opening fluidly connecting the interior of the chamber 207 with fluid surrounding the subsea stab connector 101. An external view of these apertures 209 is shown in Figure 1.

The valve member 204 is configured to move relative to the rest of the valve body between an open position (shown in Figure 2a) in which a fluid path between the fluid inlet 205 and fluid outlets 106 is open permitting fluid to flow through the fluid path, and a closed position (shown in Figure 2b) in which the fluid path between the fluid inlet 205 and fluid outlets 106 is occluded.

More specifically, the valve member 204 includes a sealing surface 210 which faces towards a corresponding sealing surface 211 of the fluid inlet 205.

When the sealing surface 210 of the valve member 204 is urged against the sealing surface 211 of the fluid inlet 205, a seal is formed and fluid flow between the fluid inlet 205 and the fluid outlets 106 is inhibited.

The valve assembly 202 further comprises biasing means in the form a tension spring 212. The tension spring 212 is connected at one end at a fixing connecting it to the interior of the chamber 207, and at the other end to a further fixing, connecting it to the valve member 204.

The tension spring 212 thus arranged gives rise to a bias force that urges the valve member 204 towards the open position shown in Figure 2a. Friction forces also act to inhibit movement of the valve member 204 within the chamber 207.

Preferably, the tension spring 212 is selected so that it gives rise to a bias force which, in combination with the friction forces acting to inhibit movement of the valve member within the chamber, is at least sufficient to hold the valve member 204 in the open position against the force of gravity acting on the mass of the valve member 204. This means that even if the full mass of the valve member 204 was to provide a force urging the valve member to the closed position (for example, as would be the case if the orientation of the subsea stab connector 101 as shown in Figures 2a and 2b was rotated 90 degrees clockwise), then the combination of the bias force and the friction forces would still be sufficient to hold the valve member in the open position.

Preferably still, in certain embodiments, the tension spring 212 is selected so that it gives rise to a bias force which, in combination with the friction forces acting to inhibit movement of the valve member within the chamber, is sufficient to hold the valve member 204 in the open position against the force of gravity acting on the mass of the valve member 204 but substantially no greater than this. In other words, a combination of the bias force and the friction forces are only just sufficient to overcome the force of gravity on the mass of the valve member 204. This means that the valve member 204 will remain in the open position against the force of gravity but any forces acting to urge the valve member 204 to the closed position that exceed this, will move the valve member 204 to the closed position.

Forces acting on the fluid-flow facing surface 213 of the valve member 204 in a distal direction urge the valve member 204 in a distal direction towards the open position, whereas forces acting on the non-fluid-flow facing surface 214 of the valve member 204 in a proximal direction (which as can be seen from Figures 2a and 2b generally extends around the interior facing surface of the valve member 204) urge the valve member 204 in a proximal direction towards the closed position.

Whether the valve member 204 moves from the open position to the closed position, or vice versa, depends on the balance of forces acting on the valve member 204.

Specifically, (disregarding any gravitational effect on the valve member 204 due to its orientation), if the forces acting on the non-fluid-flow facing surface 214 of the valve member 204 in a proximal direction are greater than the sum of the bias force of the tension spring 212, the forces acting on the fluid-flow facing surface 213 of the valve member 204 in a distal direction, and the friction force that acts to inhibit slidable movement of the valve member 204, then the valve member 204 will remain in or move to the closed position.

Conversely, starting from the closed position (disregarding any gravitational effect on the valve member 204 due to its orientation), if the sum of the bias force of the tension spring 212 and the forces acting on the fluid-flow facing surface 213 of the valve member 204 in a distal direction are greater than the forces acting on the non-fluid-flow facing surface 214 of the valve member 204 in a proximal direction ,and the friction force that acts to inhibit slidable movement of the valve member 204, then the valve member 204 will remain in or move to the open position.

By virtue of the arrangement of the valve member 204 in the chamber 207 and the provision of the apertures 209, ambient fluid pressure of the fluid surrounding the subsea stab connector 101 gives rise to a force on the non-fluid-flow facing surface 214 of the valve member 204 that acts in a distal direction urging the valve member 204 towards the closed position. Correspondingly, pressure at the fluid inlet 205 gives rise to a force on the fluid-flow facing surface 213 of the valve member 204 that acts in a distal direction urging the valve member 204 towards the open position.

Typically, the surface areas of the non-fluid-flow facing surface 214 and the fluid-flow facing surface 213 of the valve member 204 are shaped and sized so that when the fluid pressure acting on the non-fluid-flow facing surface 214 and fluid pressure acting on the fluid-flow facing surface are substantially balanced, the distal-direction-acting force and the proximal-direction- acting force are substantially balanced.

Consequently, when the ambient fluid pressure of the fluid surrounding the subsea stab connector 101 is balanced with the pressure at the fluid inlet 205, the tension force provided by the tension spring 212 means that the valve member 204 is in the open position. However, if the pressure at the fluid inlet 205 drops below the ambient fluid pressure and this pressure differential is sufficient to overcome the bias force of the tension spring 212, the valve member 204 moves to the closed position.

As explained in more detail below, advantageously, this configuration permits a mode of subsea hose connection that provides improved hose-collapse protection.

As described above, in use the subsea stab connector 101 is connected to a hose at proximal end 215 via the threaded hose connector 103 and the other end of the hose is typically connected to a pump system on a surface vessel. When being deployed, the subsea stab connector 101 is lowered from the surface vessel to a pipeline service interface, typically guided by a ROV.

The pressures that the subsea stab connector 101 and a hose 301 are exposed to during this lowering operation are explained further with reference to Figure 3.

On the surface vessel, the valve member 204 is set in the open position and held there due to biasing force of the tension spring 212 and friction forces acting on the valve member 204. Accordingly, when the subsea stab connector 101 enters the water and assuming the surfaceside end of the hose is open to atmospheric pressure or equivalent (for example by connecting the surface-side end of the hose to a tank that is open to atmospheric pressure or pumping fluid into the hose at a rate that means it is filled as it descends) the interior of the subsea stab connector 101 and the hose 301 flood with water. Similarly, by virtue of the apertures 209, the chamber 207 floods with water. Consequently, as the subsea stab connector 101 descends, at any given depth, the chamber 207, the interior of the subsea stab connector 101 and the interior of the hose 301 have an internal fluid pressure which is not less than the external ambient hydrostatic pressure fluid (pambient pressure).

As the fluid pressure in the chamber 207 is balanced with the fluid pressure at the fluid inlet 205, (disregarding any gravitational effect on the valve member 204 due to its orientation) the only force acting on the valve member 204 is the bias force provided by the tension spring 212 and friction forces acting to inhibit valve member movement 204. Therefore, even as the ambient hydrostatic pressure (pambient pressure) increases as the subsea stab connector 101 descends, the valve member 204 is held in the open position. As a result of this, advantageously, at all points along the length of the hose between the subsea stab connector 101 and the surface vessel, the hydrostatic pressure within the hose 301 balances with the ambient hydrostatic in the immediate vicinity of the hose 301 , therefore there is no risk of hose collapse. This is depicted in simplified form in Figure 4.

When the subsea stab connector 101 reaches the pipeline service interface, it is guided into a female connector part and fluidly connected with the pipeline. This is explained further with reference to Figures 5a to 5d.

Figure 5a provides a cross-sectional view of the subsea stab connector 101 when initially inserted in a female connector part 502 which provides an interface with a pipeline 503. An interface valve 504 seals the interior of the pipeline 503 from the interior of the female connector part 502. Before the subsea stab connector 101 is inserted in the female connector part 502, and initially after the subsea stab connector 101 is inserted in the female connector part 502, the interface valve 504 is in a closed position.

As described above and as shown in Figure 5a, the pipeline 503 is typically pressurised at atmospheric pressure (Patmospheric pressure). As can be seen in Figure 5a, when initially inserted in the female connector part 502, the internal pressure in the interior of the subsea stab connector 101 and the chamber 207 are at the ambient hydrostatic pressure at the depth of the pipeline (pambient pressure at pipeline) -

Once the subsea stab connector 101 is fully inserted in the female connector part 502 as shown in Figure 5a, the pump on the service vessel is typically activated which pressurises the fluid in the hose 301 and the interior of the subsea stab connector 101. The normal operating pump pressure (p_pum_{P P}ressure>ambient _Pressure at _PiPeiine) is greater than the ambient hydrostatic pressure at the depth of the pipeline (p_ambient _Pressure at _PiPeline) ■

As shown in Figure 5b, the interface valve 504 is then then opened (typically by an ROV actuating an external lever).

This operation exposes the interior of the subsea stab connector 101 to the interior of the pipeline 503. The pressure difference between the interior of the pipeline 503 (p_atmos_Pheric _Pressure) and the interior of the subsea stab connector 101 (p_Pum_{P P}ressure>ambient _Pressure at _PiPeiine) results in fluid from the hose 301 flowing into the pipeline 503 from the fluid inlet 205 via the fluid outlets 106 into the pipeline 503 via the Interface valve 504.

In this configuration, (disregarding any gravitational effect on the valve member 204 due to its orientation), the sum of the forces urging the valve member 204 into the open position (the normal operating pump pressure (p_{pump pre}ssure>ambient pressure at pipeline) acting on the fluid-flow facing surface 213 of the valve member 204, the bias force of the tension spring 212 and friction force acting to inhibit movement of the valve member 204) are greater than the forces urging the valve member 204 into the closed position (the ambient hydrostatic pressure at the depth of the pipeline (pambient _Pressure at _PiPeiine) acting on the non-fluid-flow-facing surface), so the valve member 204 remains in the open position.

Should the fluid pressure in the hose drop below the ambient hydrostatic pressure at the depth of the pipeline (pambient _Pressure at pipeline) , it will become vulnerable to hose collapse in regions of the hose where the external ambient hydrostatic pressure is greater than the internal hose fluid pressure. The greater this pressure differential, the more vulnerable the hose is to collapse as a greater length of the hose extending up to the surface vessel will be exposed to external ambient hydrostatic pressures greater than the internal hose fluid pressure. Figure 5c depicts operation of the subsea stab connector 101 in such a failure mode.

In the event that the pipeline pressure reduces to a pressure (p<_ambient pressure at pipeline) Which is at least less than the ambient hydrostatic pressure at the depth of the pipeline (pambient pressure at pipeline) , the balance of ferees acting on the valve member 204 change. Specifically, if the force on the valve member 204 due to the ambient hydrostatic pressure at the depth of the pipeline (Pambient pressure at pipeline) is greater than the sum of the force on the valve member 204 due to the reduced pipeline pressure (p<_ambient pressure at pipeline) , the bias force of the tension spring 212 and the friction forces inhibiting movement of the valve member 204, the valve member 204 moves to the closed position. As described above, preferably the tension spring 212 is configured to provide a bias force which in combination with friction forces, is only just sufficient to overcome the force of gravity on the mass of the valve member 204. At typical subsea pressures, even small pressure differentials between the pressure in the hose and the ambient hydrostatic pressure at the depth of the pipeline (p_ambient pressure at pipeline) will be much greater than a combination of such a bias force and friction forces. Accordingly, in typical sub-sea settings, as soon as the pressure in the hose drops below the ambient hydrostatic pressure at the depth of the pipeline (pambient pressure at pipeline), the valve member 204 moves to the closed position and the hose is protected from collapse.

In alternative embodiments, a biasing member providing a greater biasing force could be used. The effect of this would be to increase the required pressure differential between the ambient hydrostatic pressure and the pressure in the hose necessary to cause the valve member to move to the closed position. This may be desirable in certain applications, for example where hose pressure fluctuation is expected and where the hose has a degree of structural resistance to collapse and/or where there are additional hose collapse mitigating measures in place. A biasing member providing a lower biasing force could be used although the effect of this would be increasing the sensitivity of the valve to the pressure differential between the ambient hydrostatic pressure and the pressure in the hose, but the valve element may be more likely to close if the orientation of the valve assembly changed. This may be appropriate in applications where such changes in orientation are unlikely, and it is important for the valve to be very sensitive to pressure differentials between the ambient hydrostatic pressure and the pressure in the hose.

In another failure mode, the connection to atmospheric pressure may be disrupted at the surface vessel as the subsea stab connector 101 descends towards the pipeline service interface. In this event, and unless equalised by the exposure to the ambient fluid pressure via the fluid outlets 106, the fluid pressure in the subsea stab connector 101 may be inhibited from equalising with the ambient hydrostatic pressure and drop below the ambient hydrostatic pressure as the subsea stab connector 101 descends below the point at which the failure occurred leaving the hose vulnerable to collapse.

Operation of the subsea stab connector 101 in this failure mode is described further with reference to Figure 5d. As the subsea stab connector 101 descends below depth D, in the event that the hose pressure at the subsea stab connector 101 fails to increase to at least the ambient hydrostatic pressure at a depth D (p_ambient pressure at depth D), then the force acting on the non-fluid-flow facing surface 214 (due to the ambient hydrostatic pressure at a depth D (ambient pressure at depth D)) exceeds the force acting on the fluid-flow facing surface 213 (the sum of the force of the interior pressure of the subsea stab connector 101 (p<ambient pressure at depth D), the bias force and the friction force), and thus the valve member 204 moves to the closed position protecting the hose from collapse.

In the embodiments described above, the valve assembly is incorporated in a subsea stab connector. However, hose-collapse protection valves in accordance with other embodiments of the invention can be alternatively located. An example of such an embodiment is described with reference to Figure 6a.

Figure 6a provides a simplified schematic diagram depicting a cross-section of a hosecollapse protection valve 601 arranged in accordance with certain embodiments of the invention. The configuration of the hose-collapse protection valve 601 and its operation are substantially in keeping with the valve assembly described above except that it is configured to be incorporated within a pipeline service interface for connecting a hose with a pipeline.

The hose-collapse protection valve 601 comprises an inlet 602 for receiving fluid from a hose. The inlet 602 is connected via a fluid path 603 formed in a valve body of the hose-collapse protection valve 601 to an outlet 604 from which fluid flows into the pipeline. The hose-collapse protection valve 601 further comprises a valve member 605 which is seated in a chamber 606 so that the valve member 605 can slidably move back and forth between an open position (shown in Figure 6a) in which the fluid path 603 is uninterrupted and a closed position where the valve member 605 occludes the fluid path 603 inhibiting fluid flow from the inlet 602 to the outlet 604.

With the valve member 605 seated within the chamber 606, the chamber 606 is enclosed except for an external opening 607 which opens the chamber 606 to fluid outside the hosecollapse protection valve 601 and thus the ambient hydrostatic pressure at the depth of the hose-collapse protection valve 601 . The valve member 605 is provided with a seal 609 which fluidly isolates a non-fluid flow facing side of the valve member 605 from the fluid flow facing side of the valve member 605.

The hose-collapse protection valve 601 further comprises biasing means in the form a tension spring 608. The tension spring 608 is connected at one end at a fixing connecting it to the interior of the chamber 606, and at the other end to a further fixing, connecting it to the valve member 605 thus giving rise to a bias force that biases the valve member valve member 605 towards the open position shown in Figure 6a. Preferably, the bias force provided by the tension spring 608 is selected so that it is sufficient to hold the valve member 605 in the open position against the force of gravity acting on the mass of the valve member 204 but no more.

In use, assuming the hose-collapse protection valve 601 is connected to a pipeline pressurised at atmospheric pressure (p_atmos_Pheric pressure), the fluid pressure at the outlet 604 is the atmospheric pressure in the pipeline. Meanwhile, the pressure in the chamber 606 is the ambient hydrostatic pressure (p_ambient pressure at pipeline) at the depth of the pipeline connection. Assuming the hose is successfully pressurised for pumping operations, the fluid pressure at the inlet 602 will be a pump pressure (p_pump _Pressure>ambient pressure at pipeline) which is greater than the ambient hydrostatic pressure (pambient pressure at pipeline). In this situation, as shown in Figure 6b, the forces urging the valve member 605 into the open position (the bias force of the tension spring 608 and the force exerted by the pump pressure (p_pump pressure>ambient pressure at pipeline) on the fluid-flow-side of the tension spring 608) will overcome the forces urging the valve member 605 into the closed position (i.e. the force exerted by the ambient hydrostatic pressure (pambient pressure at pipeline) on the non-fluid-flow-side of the valve member 605). Consequently, the valve member 605 will remain in the open position.

On the other hand, if the hose depressurises for some reason to a pressure below the ambient hydrostatic pressure (pambient pressure at pipeline) at the depth of the pipeline connection, then, as shown in Figure 6c, the forces urging the valve member 605 into the open position (the bias force of the tension spring 608 and the force exerted by the reduced pump pressure (p<_ambient pressure at pipeline) on the fluid-flow-side of the tension spring 608) and friction forces acting to inhibit movement of the valve element 605 will be overcome by the force urging the valve member 605 into the closed position (i.e. the force exerted by the ambient hydrostatic pressure (pambient pressure at pipeline) on the non-fluid-flow-side of the valve member 605). Consequently, the valve member 605 will move to the closed position, and the hose will be protected from collapse.

Use of the hose-collapse protection valve 601 described above means that the hose can descend to the pipeline with its distal end open and thereby exposed to ambient hydrostatic pressure (in keeping with the pressure distribution shown in Figure 4) thus protecting the hose from collapse.

The skilled person will understand that embodiments of the invention may be manifested in many alternative configurations using equivalent features and components. For example, the biasing means can be provided by any suitable means for providing a biasing force in a subsea environment and could, in alternative arrangements be a compression spring which urges the valve member into the open position by resisting spring compression rather than resisting spring extension. In the examples described above, ambient hydrostatic pressure acts on the valve member by being transferred into a chamber within which the valve member is located via one or more apertures fluidly connecting to fluid external to the valve. In alternative embodiments, alternative pressure transfer means can be used, for example deformable elements (e.g., diaphragms) or moveable pistons or similar exposed on one side to the fluid external to the valve. In the embodiments described above, the valve member is located entirely within the valve body and generally moves between the open position to the closed position by reciprocating motion due to its slidable location within the chamber. However, in alternative configurations, the valve member may be located substantially outside of the valve body and only extend partially into the valve body to the extent necessary to occlude the path connecting the valve inlet and outlet. Further, in alternative embodiments, a valve assembly could be provided with multiple individual valve elements each configured and operable as described above.

The embodiments described above have been described in terms of a pipeline where the internal pressure is atmospheric pressure. However, it will be understood that embodiments of the invention will work to protect a hose from hose collapse if the interior of the pipeline is at other pressures that are lower than the internal pressure of the hose, for example pressures that are less than atmospheric pressure and more than atmospheric pressure.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations).

It will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope being indicated by the following claims.

Claims

1 . A subsea valve assembly for protecting a hose when connected to a subsea pipeline from depressurisation leading to hose collapse, said valve assembly comprising a valve body comprising a valve inlet fluidly connected by a fluid path to a valve outlet for conveying fluid from a hose to a pipeline, and a valve member, said valve member configured such that in a first position the valve member occludes the fluid path inhibiting fluid flow between the valve inlet and valve outlet, and in a second position the valve member permits fluid flow between the valve inlet and valve outlet, wherein the valve member is arranged with respect to the valve body such that at least a portion of the valve member is exposed to ambient fluid pressure external to the valve which gives rise to a force that urges the valve member towards the first position, and such that fluid pressure at the valve inlet gives rise to a force that urges the valve member towards the second position, and wherein said valve assembly further comprises a biasing means configured to apply a biasing force on the valve member urging the valve member towards the second position such that said valve member moves to the first position when the force arising from said ambient fluid pressure exceeds a combination of the force arising from the fluid pressure at the valve inlet and the biasing force, and moves to the second position when a combination of the force arising from the fluid pressure at the valve inlet and the biasing force exceeds the force arising from the ambient fluid pressure.

2. A subsea valve assembly according to claim 1 , wherein the valve member has a first surface and a second surface, said second surface fluidly isolated within the valve assembly from the first surface, wherein the valve member is arranged with respect to the valve body such that the fluid pressure at the valve inlet acts on the first surface and the ambient fluid pressure acts on the second surface.

3. A subsea valve assembly according to claim 2, wherein the valve member is located within a chamber, said ambient fluid pressure is transferred into said chamber via pressure transfer means and thereby acts on said second surface.

4. A subsea valve assembly according to claim 3, wherein the pressure transfer means comprises one or more apertures providing a fluid opening to fluid external to the valve assembly.

5. A subsea valve assembly according to any previous claim, wherein the biasing force is of a magnitude such that in combination with friction forces acting on the valve member, movement of the valve member due to the force of gravity acting on the valve member is inhibited.

6. A subsea valve assembly according to claim 5, wherein the biasing force substantially does not exceed a magnitude such that in combination with friction forces acting on the valve member, movement of the valve member due to the force of gravity acting on the valve member is inhibited.

7. A subsea valve assembly according to any previous claim, wherein the valve member is located within the valve assembly.

8. A subsea valve assembly according to any previous claim, wherein the valve outlet comprises a plurality of individual outlet apertures.

9. A subsea valve assembly according to any previous claim, wherein the biasing means comprises a spring.

10. A subsea valve assembly according to claim 9, wherein the spring is a tension spring.

11. A subsea stab connector comprising an inlet hose connection and an outlet, wherein said subsea stab connector has incorporated therein a subsea valve assembly according to any of claims 1 to 10, said subsea valve assembly operable to control fluid from the inlet hose connection to the outlet.

12. A subsea stab connector according to claim 11 , wherein the subsea valve assembly is located at a distal end of the subsea stab connector.