VALVE APPARATUS

Abstract

A valve apparatus (10) comprises a housing (12) defining a flow path (14), a valve seat (42) located within the housing (12) around a periphery of the flow path (14), a carriage member (16) located within the housing (12), a cutting arrangement (28) mounted on the carriage member (16), and a valve member (32) mounted on the carriage member (16) via a connection assembly (34) which permits relative movement between the valve member (32) and the carriage member (16). The carriage member (16) is moveable from a first position towards a second position to drive the cutting arrangement (28) across the flow path (14) and to move the valve member (32) into a position in which relative movement between the valve member (32) and the carriage member (16) permits the valve member (32) to sealingly engage and disengage the valve seat (42) to control flow along the flow path (14).

Claims

1. A valve apparatus, comprising: a housing defining a flow path; a valve seat located within the housing around a periphery of the flow path; a carriage member located within the housing; a cutting arrangement mounted on the carriage member; and a valve member mounted on the carriage member via a connection assembly which permits relative movement between the valve member and the carriage member, wherein the carriage member is moveable from a first position towards a second position to drive the cutting arrangement across the flow path and to move the valve member into a position in which relative movement between the valve member and the carriage member permits the valve member to sealingly engage and disengage the valve seat to control flow along the flow path.

2. The valve apparatus of claim 1, comprising a pocket for receiving or accommodating the valve member when the carriage member is located within its first position.

3.-5. (canceled)

6. The valve apparatus of claim 1, comprising a valve seat cutting arrangement mounted on or otherwise associated with the valve seat, wherein the valve seat cutting arrangement cooperates with the cutting arrangement mounted on the carriage member to establish a transverse shear stress in an object located within the flow path during movement of the carriage member from its first position towards its second position.

7. (canceled)

8. (canceled)

9. The valve apparatus of claim 6, wherein the valve seat cutting arrangement and the cutting arrangement mounted on the carriage member are spatially arranged relative to each other to define a shear plane or plane of cut.

10. (canceled)

11. The valve apparatus according to claim 1, comprising a cutting pocket for receiving at least a portion of a cut object.

12. The valve apparatus according to claim 1, wherein the valve member comprises a valve member sealing arrangement for sealing engagement with the valve seat.

13. The valve apparatus according to claim 12, wherein the valve member sealing arrangement comprises a sealing surface.

14. The valve apparatus according to claim 13, wherein the valve member sealing arrangement comprises one or more seal members, wherein at least one seal member is mounted on or within the sealing surface of the valve member.

15. The valve apparatus according to claim 13, wherein when the carriage member is located within its first position the valve member is positioned such that the sealing surface of the valve member is at least partially isolated from the flow path.

16. The valve apparatus according to claim 1, wherein the valve seat comprises a seat sealing arrangement for sealing engagement with the valve member.

17. The valve apparatus according to claim 16, wherein the seat sealing arrangement comprises a sealing surface.

18. The valve apparatus according to claim 17, wherein the seat sealing arrangement comprises one or more seal members, wherein at least one seal member is mounted on or within the sealing surface of the valve seat.

19. The valve apparatus according to claim 1, comprising a wiper arrangement for use in wiping one or both of the valve seat and the valve member during movement of the carriage member between its first and second positions.

20. The valve apparatus according to claim 19, wherein a valve seat wiper arrangement is mounted on the carriage member for wiping a sealing surface of the valve seat during movement of the carriage member.

21. The valve apparatus according to claim 20, wherein the valve seat wiper establishes compressive interference engagement with the sealing surface of the valve member.

22. The valve apparatus according to claim 1, wherein the cutting arrangement is moved along a cutting path during movement of the carriage member between its first and second positions, wherein a clearance gap is provided between the cutting path of the cutting arrangement and a sealing surface of the valve seat.

23. The valve apparatus according to claim 1, wherein, when the carriage member is in its second position, the valve member is moveable to engage the valve seat when a pressure differential is applied in a first direction, and is moveable to disengage the valve seat when a pressure differential is applied in a second direction, wherein the second direction is opposite the first direction.

24. The valve apparatus according to claim 1, wherein the valve member comprises at least one of a flapper, a ball, a portion of a ball, a poppet and a pin.

25. The valve apparatus according to claim 1, wherein the connection assembly providing connection between the valve member and the carriage member provides at least one degree of freedom of motion therebetween, wherein the at least one degree of freedom of motion comprises one or more of rotational motion, linear motion and motion along a curved path.

26. The valve apparatus according to claim 1, wherein the connection assembly comprises a pivot connection between the carriage member and the valve member.

27. The valve apparatus according to claim 1, comprising a biasing arrangement operable between the carriage member and the valve member, wherein the biasing arrangement biases the valve member to move relative the carriage member in one direction.

28. The valve apparatus according to claim 27, wherein the biasing arrangement biases the valve member in a direction to engage the valve seat when the carriage member is located within its second position.

29. The valve apparatus according to claim 1, comprising a valve member guide arrangement operable to guide the valve member during movement of the carriage member from its first position to its second position.

30. The valve apparatus according to claim 29, wherein the valve member guide arrangement comprises a track and follower arrangement.

31. The valve apparatus according to claim 1, comprising a track fixed relative to the housing and a follower member mounted on the valve member, wherein the follower member is received within said track such that movement of the valve member is controlled during movement of the carriage member.

32. The valve apparatus according to claim 1, comprising a stop arrangement for preventing or restricting movement of the carriage member beyond its first and/or second positions.

33. The valve apparatus according to claim 1, wherein the carriage member is rotatably mounted within the housing, such that the carriage member is rotatable to move between its first and second positions.

34. The valve apparatus according to claim 1, wherein the carriage member is mounted within the housing to be moved along a linear path between its first and second positions.

35. The valve apparatus according to claim 1, wherein the carriage member is mounted within the housing to be moved along an arcuate path between its first and second positions.

36. The valve apparatus according to claim 1, comprising an actuator for moving the carriage member between its first and second positions.

37. The valve apparatus according to claim 36, wherein the actuator comprises a rotary actuator for rotating the carriage member.

38. The valve apparatus according to claim 37, wherein the rotary actuator is mounted externally of the housing, with a rotatable drive shaft extending through a wall of the housing to providing driving engagement between the actuator and the carriage member.

39.-41. (canceled)

42. A method for controlling flow along a flow path, comprising: providing a carriage member carrying a cutting arrangement and a valve member; moving the carriage member from a first position towards a second position to drive the cutting arrangement across the flow path and to generally align the valve member with a valve seat; and moving the valve member relative to the carriage member to engage and/or disengage the valve seat to control flow along the flow path.

43.-44. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0124] These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0125] FIG. 1 is a partial sectional view of a valve apparatus in accordance with an embodiment of the present invention;

[0126] FIG. 2 is a longitudinal cross-sectional view of the valve apparatus of FIG. 1, with a carriage member shown in a fully open position;

[0127] FIG. 3 is a longitudinal cross-sectional view of the valve apparatus of FIG. 1 with a cutting edge of the carriage member initially engaging a section of coiled tubing extending through the valve apparatus;

[0128] FIG. 4 is a longitudinal cross-sectional view of the valve apparatus of FIG. 1, with the cutting edge of the carriage member cutting through coiled tubing;

[0129] FIG. 5A is a longitudinal cross-sectional view of the valve apparatus of FIG. 1, with the carriage member approaching a fully closed position;

[0130] FIG. 5B is an enlarged view of FIG. 5A in the region of the carriage member, showing a wiper component wiping a valve seat sealing surface during movement of the carriage member towards its closed position;

[0131] FIG. 5C provides an enlarged view of the valve assembly 10 of FIG. 1 in the region of a cutting insert on the carriage member, shown at the point of initial alignment with a cutting insert of the valve seat;

[0132] FIG. 5D provides a further enlarged view in the region of the cutting insert during alignment with a sealing surface of the valve seat;

[0133] FIG. 6A is a longitudinal cross-sectional view of the valve apparatus of FIG. 1 with the carriage member in a closed position, and with a valve member mounted on the carriage shown disengaged from a valve seat;

[0134] FIG. 6B is an enlarged view of FIG. 6A in the a region of the valve member and the valve seat;

[0135] FIG. 7A is a longitudinal cross-sectional view of the valve apparatus of FIG. 1 with the carriage member in a closed position, and with the valve member engaged with the valve seat;

[0136] FIG. 7B is an enlarged view of FIG. 6A in the a region of the valve member and the valve seat;

[0137] FIGS. 8A, 8B and 8C provide various views of a valve apparatus in accordance with an alternative embodiment of the present invention;

[0138] FIG. 9 is an enlarged view of a carriage member and valve member of a valve apparatus in accordance with an alternative embodiment of the present invention;

[0139] FIG. 10 is a partial sectional view of a valve apparatus in accordance with another embodiment of the present invention;

[0140] FIGS. 11, 12 and 13 are cross sectional diagrammatic illustrations of the valve apparatus of FIG. 10, showing stages in a closing operation;

[0141] FIG. 14 is a sectional view of a valve apparatus in accordance with another embodiment of the present invention, with the valve apparatus shown in an open configuration;

[0142] FIG. 15 is a sectional view of the valve apparatus of FIG. 14, shown in a closed configuration;

[0143] FIG. 16 is an enlarged view of a cutting arrangement of the valve apparatus of FIG. 14;

[0144] FIG. 17 is an enlarged view of a sealing arrangement of the valve apparatus of FIG. 14;

[0145] FIG. 18 is a perspective view of a subsea test tree (SSTT) in accordance with an embodiment of the present invention;

[0146] FIG. 19 is an exploded view of a rotary actuator for use in operating a valve apparatus;

[0147] FIGS. 20 and 21 illustrate the rotary actuator of FIG. 19 in different actuation configurations; and

[0148] FIG. 22 is a diagrammatic illustration of a landing string in accordance with an embodiment of the present invention, wherein the landing string is shown in use within a riser and BOP.

DETAILED DESCRIPTION OF THE DRAWINGS

[0149] A valve apparatus, generally identified by reference numeral 10, in accordance with an embodiment of the present invention is shown in partial cross-section in FIG. 1. The apparatus 10 may be used in any valve application where flow control is required. As described in more detail below, the valve apparatus 10 may be used within a subsea test tree (SSTT).

[0150] The apparatus 10 comprises a housing 12 which defines an internal flow path 14 for facilitating flow and objects to extend therethrough. Although not illustrated, the housing 12 may include connectors, such as flange connectors, on opposing ends to permit the apparatus 10 to be coupled within a flow system (not shown). Further, although the housing 12 is illustrated in FIG. 1 as a unitary component, the housing may be formed by multiple components.

[0151] A carriage member in the form of a saddle 16 is rotatably mounted within the housing via boss or shaft members 18 (only one visible in FIG. 1). The saddle 16 is shown in a first or open position in FIG. 1. The saddle 16 includes opposing rotary plates 20 (only one visible in FIG. 1) which are connected to the respective shaft members 18, with a cross member 22 extending between the rotary plates 20. Each shaft member 18 extends through a wall of the housing 12, sealed using dynamic seals 24, and secured to an actuator assembly 25, specifically a pair of rotary actuators 26 (only one visible in FIG. 1). The rotary actuators 26 may be any suitable actuator which can apply torque to the shaft members 18, and in the present embodiment is generally illustrated as a crank arm. Such a crank arm may be operated by a piston arrangement, for example.

[0152] A cutting insert 28 which includes a profiled cutting edge 30 is mounted on the saddle 16, specifically on the cross member 22 of the saddle 16, at a leading edge thereof. As will be described in further detail below, the cutting insert 28 is operable to cut through an object located within the flow path 14 during rotation of the saddle 16 from its first position of FIG. 1, to a second or closed configuration, described later.

[0153] A valve member in the form of a flapper 32 is pivotally mounted on the saddle 16, specifically on the cross member 22, via a pivot pin 34. The flapper 32 defines a peripheral sealing face 36 which carries a sealing member 38, which in some embodiments includes a non-elastomeric sealing member. In other embodiments no sealing member may be present, or more than one may be utilised. When the saddle 16 is positioned in its first position of FIG. 1 the flapper 32 is located within a recess 40, specifically an annular recess, formed in the housing 12. Accordingly, when the saddle 16 is positioned in the illustrated first position, the flapper 32 is oriented such that the sealing face 36 is generally outwardly facing, away from the flow path 14, and also generally positioned within the annular recess 40. Thus, the sealing face 36 may be protected to assist to minimise damage from flow and/or objects passing through or along the flow path 14. Although not illustrated, in some embodiments a protection seat profile may be formed or provided within the housing against which protection seat the flapper 32 engages when in its first position.

[0154] A valve seat 42 is mounted within the housing 12, around a periphery of the flow path 14. The valve seat 42 is generally annular in form and is sealed relative to the housing 12 via a seal member such as an O-ring 44. Although not shown, the valve seat 42 may be mounted on a biasing member, such as a spring, to bias the seat member 42 in a desired direction relative to the housing 12. The valve seat 42 defines a sealing surface 46 which is arranged to cooperate with the sealing surface 36 of the flapper 32 when the saddle 16 is located in a second position, as described below. Such engagement between the sealing surfaces 36, 46 facilitates closure of the flow path 14.

[0155] A seat cutting insert 48 is mounted on the valve seat 42, and as will be described below cooperates with the cutting insert 28 of the saddle 16 to cut an object within the flow path 14.

[0156] A wiper element 50 formed of a thermoplastic material such as PEEK, for example, is mounted on the saddle 16, specifically on the cross member 22 rearwardly of the cutting insert 28. As will be described in detail below, the wiper element 50 functions to wipe the sealing surface 46 of the valve seat 42, at least in the general region of cutting an object.

[0157] Reference is additionally made to FIG. 2 in which a longitudinal cross-sectional view of the apparatus 10 is shown, with the saddle 16 in its first or fully open position. In this position, as noted above, the flapper 32 is located within the recess 40 and thus largely protected from flow and any objects passing along the flow path 14. Further, when in this position the flow path 14 is largely unrestricted, thus minimising any bore restrictions which might otherwise create pressure/energy losses in a flow, provide a snagging point for objects or the like.

[0158] A closing sequence of the saddle 16 will now be described with reference to FIGS. 3 to 7. Referring first to FIG. 3, the saddle 16 is shown rotated until the cutting insert 28 engages an object, in this case coiled tubing 52, pushing the tubing 52 into engagement with the cutting insert 48 of the valve seat 42. In this respect, as the saddle 16 rotates, the cutting insert 28 is translated along a cutting path 54, illustrated in broken outline. Further rotation of the saddle 14, as illustrated in FIG. 4, crushes the tubing 52, with the cutting inserts 28, 48 establishing a shear stress in the tubing 52 largely along the direction of the cutting path 54 to cause this to be cut.

[0159] Once the tubing 52 is cut the saddle 16 continues to rotate and move the cutting insert 28 along the cutting path 54, as illustrated in FIG. 5A (the tubing 52 has been removed for clarity in FIG. 5A), with the lower cut tubing being pushed into the recess 40, thus minimising interference with the valve member 32. An enlarged view in the region of the cutting insert 28 is provided in FIG. 5B, reference to which is additionally made, and illustrates, in broken outline, a sealing plane 56 of the sealing surface 46 or the valve seat 42. A clearance gap 58 is provided between the cutting path 54 and the sealing plane 56. It should be noted that the clearance gap has been exaggerated in FIG. 5A for illustration purposes.

[0160] The feature of the clearance gap 58 is further illustrated with reference to FIGS. 5C and 5D. FIG. 5C provides an enlarged view in the region of the cutting insert 28, shown at the point of initial alignment with the cutting insert 48 of the valve seat 42. In this arrangement a very close relationship is achieved between the respective inserts 28, 48. FIG. 5D provides an enlarged view in the region of the cutting insert 28 during alignment with the sealing surface 46 of the valve seat 42. In this respect a separation is present between the cutting insert 28 and the sealing surface 46, which provides the clearance gap 58.

[0161] The provision of this clearance gap 58 minimises the risk of the cutting insert 28, which may have been damaged/deformed during cutting, from scoring the sealing surface 46 of the valve seat 42, which may otherwise prevent a full seal with the valve member 32 from being achieved.

[0162] Referring again to FIG. 5B, as the saddle 16 rotates, the wiper element 50 functions to wipe the sealing surface 46 of the valve seat, removing particles and other contaminates, preparing the surface 46 for a robust sealing engagement with the flapper 32.

[0163] Complete rotation of the saddle 16 to a second position is illustrated in FIG. 6A. Although not shown, the apparatus 10 includes an end stop which prevents the saddle 16 from rotating beyond this second position, ensuring proper alignment of the valve member 32. In the configuration shown in FIG. 6A the flapper 32 is shown positioned relative to the saddle 16 such that sealing engagement with the valve seat 42 is not yet achieved, still permitting flow along the flow path 14. An enlarged view in the region of the pivoting side of the flapper 32 is shown in FIG. 6B, which illustrates the presence of clearance between the sealing surface 36 of the flapper 32 and the sealing surface 46 of the valve seat 42.

[0164] FIG. 7A illustrates the flapper 32 fully pivoted about its pivot pin 34 such that the sealing surface 36 of the flapper 32 is engaged with the sealing surface 46 of the valve seat 42, thus preventing flow along the flow path 14. In the present embodiment the flapper 32 is passively mounted on the saddle 16, and as such is caused to pivot about its pivot pin 34 to provide sealing with the valve seat 42 by action of fluid flow and/or pressure within the flow path 14. For example, where the fluid pressure below the flapper 32 exceeds the pressure above, the flapper 32 will be moved and held in its closed position. Conversely, where the pressure above the flapper 32 exceeds the pressure below, the flapper 32 will be lifted from the valve seat 42, again allowing flow along the flow path. Such an arrangement permits the apparatus 10 to provide a pump-through capability, without altering the position of the saddle 16.

[0165] FIG. 7B is an enlarged view of the closed apparatus 10 in the region of the pivoting side of the flapper 32, illustrating the sealing engagement of the respective sealing faces 36, 46, and the sealing member 38. As most clearly illustrated in FIG. 7B, the flapper 32 includes a recessed region 60 which accommodates the cutting insert 48 on the valve seat 42 when the flapper 32 is closed.

[0166] An enlarged sectional view of a portion of a valve apparatus, generally identified by reference numeral 610, in accordance with an alternative embodiment of the present invention will now be described with reference to FIGS. 8A, 8B and 8C. The valve apparatus 610 is similar to the apparatus 10 first shown in FIG. 1 in both structure and operation, and as such like features share like reference numerals, incremented by 600. Referring initially to FIG. 8A, the apparatus 610 is shown in an open position and includes a housing 612 defining a flow path 614, with a saddle 616 rotatably mounted in the housing 612. The saddle 616 carries a cutting insert 628 which, in use, cooperates with a cutting insert 648 in a valve seat 642 to cut an object within the flow path 614. A flapper 632 is pivotally mounted on the saddle 616 via pivot pin 634, wherein the flapper 632 includes a sealing surface 636 and sealing members 638.

[0167] In the present embodiment the flapper 632 is operatively connected relative to the housing 612 via a track and follower arrangement. In this respect, the valve apparatus 610 includes a housing insert 90 which includes a track 91, and the flapper 632 includes a follower 92 (shown in broken outline in FIG. 8A) which is received within the track 91. FIG. 8B provides a perspective view of the housing insert 90 and flapper 632, in isolation, which illustrates the follower 92 received within the slot 91. Further, FIG. 8B illustrates a second follower 92a on an opposing side of the flapper 632 which is engaged with a respective opposing slot (not shown).

[0168] During rotation of the saddle 616 the pivoting movement of the flapper 632 relative to the saddle 616 is controlled by the profile of the track 91, and as illustrated in FIG. 8C, when the saddle 616 is fully rotated the flapper 632 is pivoted relative to the saddle 616 to engage the flapper 632 with the valve seat 642.

[0169] An enlarged sectional view of a portion of a valve apparatus, generally identified by reference numeral 110, in accordance with an alternative embodiment of the present invention is shown in FIG. 9. The valve apparatus 110 of FIG. 9 is similar to the apparatus 10 first shown in FIG. 1 in both structure and operation, and as such like features share like reference numerals, incremented by 100. Thus, the apparatus 110 includes a housing 112 defining a flow path 114, with a saddle 116 rotatably mounted in the housing 112. The saddle 116 carries a cutting insert 128 which, in use, cooperates with a cutting insert 148 in a valve seat 142 to cut an object within the flow path 114. A flapper 132 is pivotally mounted on the saddle 116 via pivot pin 134, wherein the flapper includes a sealing surface 136 and sealing member 138. In the present embodiment the flapper 132 is actively mounted on the saddle by the presence of a biasing arrangement in the form of a spring 62 which biases the flapper 132 to pivot outwardly relative to the saddle 116. Accordingly, when the saddle 116 is rotated into a second position, in a similar manner to saddle 16 of the first described embodiment, the flapper 132 may be positively moved by the spring 62 to engage the sealing surface 136 of the flapper 132 with the valve seat 142.

[0170] Although the spring 62 provides, to a certain degree, an active operation of the flapper 132, a pump through capability is still present by application of a positive pressure differential from above the flapper 132. In such a case the pressure applied above the flapper 132 would need to be larger than the pressure below, and be sufficient to exceed the extra closing force applied by the spring 62.

[0171] A partial cross-sectional view of a valve apparatus, generally identified by reference numeral 210, in accordance with an alternative embodiment of the present invention is shown in FIG. 10. The valve apparatus 210 of FIG. 10 is largely similar to the apparatus 10 first shown in FIG. 1 and as such like features share like reference numerals incremented by 200.

[0172] The apparatus 210 includes a housing 212 defining a flow path 214 and accommodates a carriage member in the form of a gate 216 which is arranged to move linearly within a pocket 64 formed in the housing 212. The gate 216 defines a cutting edge 230 which may be directly formed on the gate 216 or alternatively provided via an insert. A flapper 232 is pivotally mounted on the gate 216 via pivot connection 234, wherein the flapper 232 includes a peripheral sealing surface 236. A valve seat 242 is mounted in the housing 212, wherein the seat 242 defines a sealing surface 246 and a cutting region 248, which may be provided via a separate insert. As will be described below, in use sealing surface 246 cooperates with the sealing surface 236 of the flapper 232 to establish a seal therebetween, and the cutting edge 230 of the gate 216 cooperates with the cutting region 248 of the seat 242 to cut any object within the flow path 214.

[0173] The gate 216 is illustrated in FIG. 10 being located within a first position, in which the flow path 214 is completely open, with the flapper 232 being located within a recess 240. As in the apparatus 10 of FIG. 1, when the flapper 232 is positioned within the recess 240 said flapper 232 may be appropriately protected, minimising damage from flow and/or objects passing along the flow path 214.

[0174] The apparatus 210 further comprises an actuator arrangement 225 which includes a pair of lead-screws 218 which threadedly cooperate with threaded bores 66 on either side of the gate 216. One end of each lead-screw 218 is connected to a bush member 67, and an opposite end of each lead-screw 218 is connected to a rotary actuator 226. The actuators 226 operate to rotate the lead-screws and drive the gate 216 linearly within the pocket 64 across the flow path 214.

[0175] A closing sequence of the valve apparatus 210 will now be described with reference to FIGS. 11 to 13. The apparatus 210 is shown in a fully open position in FIG. 11, with the gate 216 located in a first position and the flapper 232 located within the pocket 240.

[0176] The gate 216 is then translated to move across the flow path 214 by operation of the lead-screws 218, as illustrated in FIG. 12. Any object which may be positioned within the flow path 214 will be cut by action of the respective cutting edges 230, 248. As the gate 216 is moved the flapper 232 is caused to pivot upwardly, for example by action of a camming arrangement and/or engagement with a portion of the housing 212.

[0177] As illustrated in FIG. 13, when the gate 216 is fully moved to a second position, the flapper 232 is positioned such that pivoting motion relative to gate 216 permits the sealing surface 236 of the flapper 232 to engage the sealing surface 246 of the valve seat 242, thus sealing the flow path 214. As in the apparatus 10 first shown in FIG. 1, the flapper 232 may facilitate a pump through capability.

[0178] FIG. 14 provides a cross-sectional illustration of a valve apparatus, generally identified by reference numeral 310, in accordance with a further alternative embodiment of the present invention. The apparatus 310 is similar in many respects to the apparatus 10 first shown in FIG. 1, and as such like features share like reference numerals, incremented by 300.

[0179] The apparatus 310 includes a housing 312 defining a flow path 314 and accommodates a carriage member in the form of a gate 316 which is arranged to move linearly within a pocket 70 formed in the housing 312. The gate 316 carries a first or upper cutting insert 328a, and a second or lower cutting insert 328b. A flapper 332 is moveably mounted on the gate 316 via a pinned link arm connection 334, wherein the flapper 232 includes a peripheral sealing surface 336 which is generally concave in profile. A first or upper valve seat 342a is mounted in the housing 312, wherein the first seat 342a defines a sealing surface 346 for sealing engagement with the sealing surface 336 of the flapper 316.

[0180] The upper valve seat 342a includes a first or upper cutting insert 348a which, in use, cooperates with the upper cutting insert 328a of the gate 316 to cut any object within the flow path 214. The apparatus 310 further includes a second or lower non-sealing valve seat 342a mounted in the housing 312 which includes a second or lower cutting insert 348b which, in use, cooperates with the lower cutting insert 328b of the gate 316 to cut any object within the flow path 314. During use, the upper and lower respective cutting inserts 328a, 328b, 348a, 348b will function to cut a slug from an object located within the flow path 314.

[0181] The gate 316 is illustrated in FIG. 14 being located within a first position, in which the flow path 314 is completely open, with the flapper 332 being located within a recess 340. As in the apparatus 10 of FIG. 1, when the flapper 332 is positioned within the recess 340 said flapper 332 may be appropriately protected, minimising damage from flow and/or objects passing along the flow path 314.

[0182] FIG. 15 illustrates the apparatus 310 in a fully closed position, with the gate 316 fully drawn across the flow path 314, aligning the flapper 332 with the upper valve seat 342 to permit sealing engagement between the respective sealing surfaces 336, 246.

[0183] An enlarged view in the region of the upper valve seat 342a is provided in FIG. 16, with the gate 316 in a position in which the upper cutting insert 328a is approaching the upper cutting insert 348a of the upper valve seat 342a. The sealing surface 346 of the upper valve seat 342a includes a plurality (three in the embodiment shown) of sealing members 72, such as non-elastomeric sealing members. Further, the cutting plane 74 (shown in broken outline) defined by movement of the gate 316 is such that clearance with the sealing surface 346 is provided, thus minimising the risk of the upper cutting insert 328a of the gate 316 from damaging the sealing surface 346, or its associated sealing members 72.

[0184] FIG. 17 provides an enlarged view in the region of the upper valve seat 342a, with the flapper 332 sealingly engaged with the upper valve seat 342a.

[0185] Embodiments of the present invention may be used in any suitable flow control application. In one exemplary use, embodiments of a valve apparatus of the present invention may be used within or as part of a subsea test tree (SSTT) 400, as illustrated in FIG. 18. The SSTT 400 includes a first or upper valve apparatus 410a (shown in broken outline) and a second or lower valve apparatus 410b (also shown in broken outline). Each valve apparatus 410a, 410b may be provided in accordance with any valve apparatus described herein, such as valve apparatus 10 first shown in FIG. 1, and as such no further description will be provided, except to say that a housing 412 of the SSTT 400 defines a common housing of both valve apparatus 410a, 410b. The SSTT 400 is shown in FIG. 18 connected to a slick joint 401 via a flange connector 402.

[0186] Each valve apparatus 410a, 410b is operated by respective rotary actuators 420. In some embodiments, a pair of diametrically opposed rotary actuators 420 may be provided for each valve apparatus 410a, 410b.

[0187] FIG. 19 shows an exploded view of an actuator 420. The actuator 420 includes an actuator body defined by the housing 412 of the SSTT 400. A drive shaft 418 which is connected to a rotary carriage member such as a saddle (not shown) extends through an aperture 75 in the housing 412 and is coupled, via a spline portion 76, to a vane piston 77. The vane piston 77 includes a hub 78, having splines 79 around an inside of an aperture through the hub 78, to enable the vane piston 77 to be coupled to the spline portion 76 of the drive shaft 418.

[0188] The vane piston 77 also includes vanes 80, extending from diametrically opposite sides of the hub 78. The vanes 80 taper from tips 81 to a root portion 82. Each vane 80 is both wider (around the rotation axis A) and thicker (along the rotation axis A) at the root 82 than at the tip 81. The increased width of each vane 80, such that the vane 80 is general trigonal as viewed along the rotation axis A, improves the mechanical strength of the vane piston 77.

[0189] The actuator body defines a cavity 83 sized to receive the vane piston 77. An actuator cover 84 is bolted (by bolts 85) over the cavity 83, so that the actuator cover and the actuator body together define an internal chamber. In use, the vane piston 77 is operable to rotate around the axis A within the internal chamber, as described below.

[0190] Fluid passages 86 extend through the housing 412 to the cavity 83 (and thus the internal chamber). The actuator 420 is also provided with a fluid control arrangement, for regulating the flow of hydraulic fluid to/from the internal chamber. Fluid flow conduits 87, which extend to the fluid control arrangement facilitate fluid transfer relative to the internal chamber.

[0191] An assembled and sectional view of the actuator 420 is shown in FIG. 20. The internal chamber is divided by the vane piston 77 into four piston chambers 88a-d. In the configuration shown in FIG. 20 chambers 88a and 88c are shown fully expanded, and chambers 88b and 88d are shown fully closed. Each piston chamber 88a-d is defined in part by the housing 412, by the vane piston 77 and by the actuator cover 84 (FIG. 19). Each piston chamber 88a-d communicates with a fluid passage 86, through which the flow of working hydraulic fluid is controlled via conduits 87 connected to the fluid control arrangement.

[0192] The actuator 420 is provided with inflatable bladders 89a-d disposed within each piston chamber 88a-d. In the configuration shown in FIG. 20 bladders 89a and 89c are shown fully inflated, and bladders 89b, 89d are fully deflated. The insides of the bladders 89a-d communicate with the passages and conduits 86, 87. Accordingly, the piston chambers 88a-d themselves are required only to contain the bladders 89a-d, and not to seal against a pressure differential, providing significant advantages. Moreover, the various internal surfaces of the actuator are not directly exposed to the working fluid.

[0193] The vane piston 77 is shown in FIG. 20 in a fully stroked position in the anti-clockwise direction. In order to move the vane piston 77 clockwise, as illustrated in FIG. 21 and reconfigure the associated valve apparatus, high pressure working fluid is caused to enter the bladders 89b and 89d in the piston chambers 88b and 88d, respectively, with fluid vented from the bladders 89a and 89c in respective piston chambers 88a and 88c.

[0194] The actuator 420 is provided with a vane piston 77 having diametrically opposed vanes 80. This ensures that the forces applied around the rotation axis are equal; i.e. that only rotational forces are applied to the drive shaft 418, and there is no net force applied normal to the rotation axis A. This arrangement mitigates against binding between the drive shaft and the housing 412.

[0195] An exemplary use of the SSTT 400 is diagrammatically illustrated in FIG. 22, which provides the SSTT 400 and slick joint 401 as part of a landing string 500. The landing string 500 may be used in multiple applications, such as in supporting wellbore intervention operations.

[0196] The landing string 500 is deployed through a marine riser 501 which is coupled to a blow-out preventer (BOP) 502 via a flex joint 503, wherein the BOP 502 is mounted on a wellhead 504. A flow path extends through the riser 501, the landing string 500 and its component parts, and in use provides access to a well for fluids, tools (run on wireline or tubing) or other apparatus/materials as required in an intervention.

[0197] The SSTT 400 sits in the landing string 500 above a tubing hanger 505, which is adapted to couple the landing string to the wellhead 504. A tubing hanger running tool 506 may also be provided to run the landing string to the wellhead 504 through the marine riser 501 and couple the tubing hanger 505 to the wellhead 504, as shown in FIG. 22.

[0198] The slick joint 401 is aligned with lower pipe rams 510 of the BOP 502 which may be closed against the slick joint 401 to form a seal in case of emergency.

[0199] In addition to the double barrier system within the SSTT 400, further valves may also be provided which sit above the BOP 502 when the landing string has been deployed, such as a retainer valve 507. The retainer valve 507 may be provided by a valve apparatus in accordance with an embodiment of the present invention.

[0200] The landing string 500 further includes a shear joint 508 which is aligned with shear rams 509 of the BOP 502.

[0201] All of the components of the landing string 500 are constrained to fit within the diameter of the riser 501. The components below the shear joint 508 must also fit within the BOP 502.

[0202] It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.