Actuator assembly with a fail safe mechanism

Abstract

The invention relates to an actuator assembly (200, 300, 600, 700) for connection to an apparatus (101) comprising a body and a central passageway (202, 302, 602, 702) extending along a longitudinal axis of the body, wherein the actuator assembly comprises: - a sliding stem (207, 307, 607, 707), - an obstructing member (201, 301, 601, 701), fixedly attached to the sliding stem (207, 307, 607), - a first compartment (403, 403', 603, 703, 703'), a second compartment (404, 404', 604, 704, 704') and a third compartment (513, 513', 611, 711) having varying volumes depending on the position of the sliding stem (207, 307, 607, 707), wherein the volume of the first compartment (403, 403', 603, 703, 703') increases and the volume of the second compartment (404, 404', 604, 704, 704') decreases when the sliding stem (207, 307, 607, 707) slides in one direction, and the volume of the first compartment (403, 403', 603, 703, 703') decreases and the volume of the second compartment (404, 404', 604, 704, 704') increases when the sliding stem (207, 307, 607, 707) slides in another opposite direction.

Description

Technical field

[0001] The present invention relates to the field of oil or gas production wells and injection wells, and more specifically to an actuator assembly with a permanent or separately removable fail safe module for connection to an apparatus comprised in an oil or gas production well or an injection well. The invention also relates to an apparatus comprising the actuator assembly and a process of operating the actuator assembly in the apparatus. The actuator(s) of the invention can be fail safe open or closed. The actuator(s) of the invention can be adapted for subsea equipment or surface equipment and for any process.Technical background

[0002] Production and injection wells generally comprise apparatuses wherein a hydraulic actuator is meant to open or close a valve over a central passageway extending along an axis of the body of the apparatus. Examples of such apparatuses include Xmas trees, manifolds and other similar devices. In case the hydraulic actuator fails to open or close the valve, the actuator assembly can comprise a fail safe mechanism intended to safely close the valve. This fail safe mechanism typically comprises a spring in a stressed state that, when the valve needs to be closed (or needs to be opened), releases some or all of the stored energy, thereby effecting closure (or opening) of the valve. The valve needs to be closed (or opened) by this fail safe mechanism in particular when there is a loss of hydraulic pressure in the hydraulic actuator.

[0003] The main problem of this known fail safe mechanism is that the spring needs to be large enough to exert the force necessary to close (or open) the valve safely and quickly and provide sufficient displacement to fully stroke the valve to final position. The spring thus significantly drives up the size of the overall actuator assembly. This can be especially disadvantageous in a subsea environment.

[0004] Within this context there is a need for an improved actuator assembly comprising a (preferably ROV removable / installable) fail safe mechanism, which in particular is compact and reliable.Summary of the invention

[0005] According to a first aspect, the invention relates to the following items.

[0006] Item 1. An actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, wherein the actuator assembly comprises: a sliding stem, an obstructing member fixedly attached to the sliding stem, a first compartment, a second compartment and a third compartment having varying volumes depending on the position of the sliding stem, wherein the volume of the first compartment increases and the volume of the second compartment decreases when the sliding stem slides in one direction, and the volume of the first compartment decreases and the volume of the second compartment increases when the sliding stem slides in another opposite direction, wherein the actuator assembly is configured so that: the obstructing member has, when the actuator assembly is connected to the apparatus: an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed; and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed; at least one of the first compartment and second compartment is sealed and the other of the first compartment and second compartment is pressure equilibrated with the environment, so that, when the actuator assembly is connected to the apparatus, the obstructing member is biased towards one of the obstructing configuration and of the non-obstructing configuration; the third compartment is feedable with hydraulic fluid and the bias of the obstructing member towards one of the obstructing configuration and of the non-obstructing configuration may be overcome by applying sufficient hydraulic fluid pressure in the third compartment.

[0007] Item 2. The actuator assembly of item 1, wherein the other of the first compartment and second compartment is open to the environment.

[0008] Item 3. The actuator assembly of any one of items 1 to 2, wherein the first compartment is sealed and contains a pressurised gas and the second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0009] Item 4. The actuator assembly of any one of items 1 to 2, wherein the first compartment is pressure equilibrated with the environment, preferably is open to the environment and the second compartment is sealed and contains a gas.

[0010] Item 5. The actuator assembly of any one of items 1 to 4, wherein the actuator assembly is configured for use underwater and one of the first compartment and second compartment is open to the environment and is configured to be filled with water, preferably with seawater.

[0011] Item 6. The actuator assembly of any one of items 1 to 5, wherein the obstructing member comprises a ball valve and a scotch yoke configured to translate a linear motion of the sliding stem into a rotational movement of the ball valve.

[0012] Item 7. The actuator assembly of any one of items 1 to 6, wherein the obstructing member comprises or is a shear blade.

[0013] Item 8. The actuator assembly of any one of items 1 to 7, wherein the obstructing member comprises or is a gate valve.

[0014] Item 9. The actuator assembly of any one of items 1 to 8, wherein the actuator assembly comprises: at least one hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber, said piston dividing said chamber into the third compartment and a fourth compartment; a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber, said piston dividing said chamber into the first compartment and the second compartment, wherein the piston of the at least one hydraulic actuator and the piston of the fail safe module are fixedly attached to the sliding stem.

[0015] Item 10. The actuator assembly of item 9, wherein the first compartment is closest to the piston of the at least one hydraulic actuator and the second compartment is farthest from the piston of the at least one hydraulic actuator.

[0016] Item 11. The actuator assembly of items 9 or 10, wherein the chamber of the at least one hydraulic actuator and the chamber of the fail safe module are configured to be fixedly attached to the body of the apparatus.

[0017] Item 12. The actuator assembly of any one of items 9 to 11, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration.

[0018] Item 13. The actuator assembly of any one of items 9 to 12, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0019] Item 14. The actuator assembly of any one of items 9 to 13, wherein, when the at least one hydraulic actuator is not hydraulically actuated, the fail safe module is configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0020] Item 15. The actuator assembly of any one of items 9 to 14, wherein the piston of the at least one hydraulic actuator moves away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the piston of the at least one hydraulic actuator moves towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0021] Item 16. The actuator assembly of item 15, wherein, when the at least one hydraulic actuator is not hydraulically actuated, the pressure in the first compartment is greater than the pressure in the second compartment, so that the piston of the fail safe module pulls the piston of the at least one hydraulic actuator towards the fail safe module.

[0022] Item 17. The actuator assembly of any one of items 9 to 16, wherein the actuator assembly comprises a single hydraulic actuator, wherein the piston of the hydraulic actuator is axially aligned with the piston of the fail safe module.

[0023] Item 18. The actuator assembly of any one of items 9 to 16, wherein the actuator assembly comprises at least two parallel hydraulic actuators.

[0024] Item 19. The actuator assembly of item 18, wherein the actuator assembly further comprises: a bonnet having a central bore; a yoke connecting the pistons of the at least two parallel hydraulic actuators; and wherein the sliding stem is a central stem extending through the central bore of the bonnet, having a first end fixed to the yoke and a second end fixed to the obstructing member.

[0025] Item 20. The actuator assembly of item 19, wherein the bonnet is configured to be fixedly attached to the body of the apparatus, and the pistons of the hydraulic actuators are configured to drive the central stem through the central bore of the bonnet, thereby transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration.

[0026] Item 21. The actuator assembly of any one of items 1 to 8, wherein the actuator assembly comprises: an outer housing; an inner member fixed within the outer housing; a sleeve fixedly attached to the sliding stem, wherein the sleeve has a flange and is slidable within the outer housing and over the inner member; wherein the first compartment is delimited by the outer housing and the sleeve, the second compartment comprises an inner chamber within the inner member and is further delimited by the sleeve, and the third compartment is delimited by the outer housing, the inner member and the flange of the sleeve.

[0027] Item 22. The actuator assembly of any one of items 1 to 8, wherein the actuator assembly comprises: an outer housing; an active chamber within the outer housing; at least one, preferably two passive chambers within the outer housing; a piston connected to a piston rod slidable within the active chamber, wherein the third compartment is delimited within the active chamber by said piston; a respective piston connected to a piston rod slidable within each passive chamber, wherein the first compartment and the second compartment are located within each passive chamber on opposite sides of said piston; wherein the piston rod of the active chamber and the piston rods of the passive chambers are fixedly connected to the sliding stem.

[0028] Item 23. An assembly, comprising one or more actuator assemblies according to any one of items 1 to 22 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the third compartment, and preferably to at least one hydraulic actuator of each actuator assembly, if present.

[0029] Item 24. An apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, comprising the actuator assembly of any one of items 1 to 22 connected thereto.

[0030] Item 25. The apparatus of item 24, wherein the apparatus is a topside apparatus.

[0031] Item 26. The apparatus of item 25, wherein the topside apparatus is one of a blowout preventer (BOP), a surface flow tree (SFT), a tension frame (TF), a rig, or a workover control system (WOCS).

[0032] Item 27. The apparatus of item 24, wherein the apparatus is a subsea apparatus.

[0033] Item 28. The apparatus of item 27, wherein the subsea apparatus is one of a blowout preventer (BOP), a well control package (WCP), an emergency disconnect package (EDP), a lower riser package (LRP), an in-line tee (ILT), a high integrity pressure protection system (HIPPS), a manifold, a vertical Xmas tree (VXT), or a horizontal Xmas tree (HXT).

[0034] Item 29. A process of operating the actuator assembly in the apparatus of any one of items 24 to 28, comprising one or more of: applying hydraulic fluid pressure to the third compartment, so as to cause the obstructing member to transition from one of the obstructing configuration and the non-obstructing configuration, to the other of the obstructing configuration and the non-obstructing configuration; causing the obstructing member to transition from one of the non-obstructing configuration and the obstructing configuration to the other of the non-obstructing configuration and the obstructing configuration by ceasing to apply hydraulic fluid pressure in the actuator assembly.

[0035] Item 30. The process of item 29, wherein the actuator assembly is according to any one of items 9 to 20, comprising one or more of: hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration, thereby closing off the central passageway of the apparatus; causing the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus, owing to the fail safe module, without hydraulically actuating the at least one hydraulic actuator.

[0036] Item 31. The process of item 29, wherein the actuator assembly is according to any one of items 21 to 22, comprising one or more of: increasing hydraulic fluid pressure in the third compartment, so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; decreasing hydraulic fluid pressure in the third compartment, so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus.

[0037] Still according to the first aspect, the invention also relates to the following items.

[0038] Item 32. An actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, wherein the actuator assembly comprises: at least one hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber; a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber, the piston dividing the chamber into a first compartment closest to the piston of the at least one hydraulic actuator and a second compartment farthest to the piston of the at least one hydraulic actuator, wherein the piston of the at least one hydraulic actuator is fixed to the piston of the fail safe module; an obstructing member connected to the piston of the at least one hydraulic actuator and having, when the actuator assembly is connected to the apparatus, and depending on the position of the piston of the at least one hydraulic actuator: an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed; and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0039] Item 33. The actuator assembly of item 32, wherein at least one of the first compartment and second compartment of the fail safe module is sealed and the other of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0040] Item 34. The actuator assembly of item 32 or item 33, wherein the chamber of the at least one hydraulic actuator and the chamber of the fail safe module are configured to be fixedly attached to the body of the apparatus.

[0041] Item 35. The actuator assembly of any one of items 32 to 34, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration.

[0042] Item 36. The actuator assembly of any one of items 32 to 35, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0043] Item 37. The actuator assembly of any one of items 32 to 36, wherein when the at least one hydraulic actuator is not hydraulically actuated, the fail safe module is configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0044] Item 38. The actuator assembly of any one of items 32 to 37, wherein the piston of the at least one hydraulic actuator moves away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the piston of the at least one hydraulic actuator moves towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0045] Item 39. The actuator assembly of any one of items 32 to 38, wherein when the at least one hydraulic actuator is not hydraulically actuated, the pressure in the first compartment is greater than the pressure in the second compartment, so that the piston of the fail safe module pulls the piston of the at least one hydraulic actuator towards the fail safe module.

[0046] Item 40. The actuator assembly of any one of items 32 to 39, wherein the first compartment is sealed and contains a pressurised gas, preferably at a pressure greater than 150 bars, and the second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0047] Item 41. The actuator assembly of any one of items 32 to 39, wherein the first compartment is pressure equilibrated with the environment, preferably is open to the environment and the second compartment is sealed and contains a gas, preferably at a pressure less than 150 bars.

[0048] Item 42. The actuator assembly of any one of items 32 to 41, wherein the actuator assembly is configured for use underwater and one of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment and is configured to be filled with water, preferably with seawater.

[0049] Item 43. The actuator assembly of any one of items 32 to 42, wherein the obstructing member comprises a ball valve and a scotch yoke configured to translate a linear motion of the piston of the at least one hydraulic actuator into a rotational movement of the ball valve.

[0050] Item 44. The actuator assembly of any one of items 32 to 43, wherein the obstructing member comprises or is a shear blade.

[0051] Item 45. The actuator assembly of any one of items 32 to 42, wherein the obstructing member comprises or is a gate valve.

[0052] Item 46. The actuator assembly of any one of items 32 to 45, wherein the actuator assembly comprises a single hydraulic actuator, wherein the piston of the hydraulic actuator is axially aligned with the piston of the fail safe module.

[0053] Item 47. The actuator assembly of any one of items 32 to 45, wherein the actuator assembly comprises at least two parallel hydraulic actuators.

[0054] Item 48. The actuator assembly of item 47, wherein the actuator assembly further comprises: a bonnet having a central bore; a yoke connecting the pistons of the at least two parallel hydraulic actuators; a central stem extending through the central bore of the bonnet, having a first end fixed to the yoke and a second end fixed to the obstructing member.

[0055] Item 49. The actuator assembly of item 48, wherein the bonnet is configured to be fixedly attached to the body of the apparatus, and the pistons of the hydraulic actuators are configured to drive the central stem through the central bore of the bonnet, thereby transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration.

[0056] Item 50. An assembly, comprising one or more actuator assemblies according to any one or any combination of items 32 to 49 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the at least one hydraulic actuator of each actuator assembly.

[0057] Item 51. An apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, comprising the actuator assembly according any of items 32 to 49 connected thereto.

[0058] Item 52. The apparatus of item 51, wherein the apparatus is a topside apparatus.

[0059] Item 53. The apparatus of item 52, wherein the topside apparatus is one of a blowout preventer (BOP), a surface flow tree (SFT), a tension frame (TF), a rig, or a workover control system (WOCS).

[0060] Item 54. The apparatus of item 51, wherein the apparatus is a subsea apparatus.

[0061] Item 55. The apparatus of item 54, wherein the subsea apparatus is one of a blowout preventer (BOP), a well control package (WCP), an emergency disconnect package (EDP), a lower riser package (LRP), an in-line tee (ILT), a high integrity pressure protection system (HIPPS), a manifold, a vertical Xmas tree (VXT), or a horizontal Xmas tree (HXT).

[0062] Item 56. A process of operating the actuator assembly of any one of items 32 to 49, comprising one or more of: hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration, thereby closing off the central passageway of the apparatus; causing the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus, owing to the fail safe module, without hydraulically actuating the at least one hydraulic actuator.

[0063] According to a second aspect, the invention relates to the following items.

[0064] Item 57. An actuator assembly for an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, wherein the actuator assembly comprises: two parallel hydraulic actuators, each hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber; a bonnet having a central bore; a yoke connecting the pistons of the hydraulic actuators; an obstructing member having, when the actuator assembly is connected to the apparatus, and depending on the position of the piston of the two hydraulic actuators: an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed, and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed; a central stem extending through the central bore of the bonnet, having a first end fixed to the yoke and a second end fixed to the obstructing member; wherein: the bonnet and the chambers of the hydraulic actuators are configured to be fixedly attached to the body of the apparatus; the pistons of the hydraulic actuators are configured to drive the central stem through the central bore of the bonnet, thereby transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration.

[0065] Item 58. The actuator assembly of item 57, which comprises a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber, the piston of the fail safe module being fixed to the yoke.

[0066] Item 59. The actuator assembly of item 57 or 58, wherein the piston of the fail safe module divides the chamber into a first compartment closest to the yoke and a second compartment farthest to the yoke, wherein at least one of the first compartment and second compartment is sealed and the other of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0067] Item 60. The actuator assembly of any one of items 57 to 59, wherein the chambers of the hydraulic actuators and the chamber of the fail safe module are configured to be fixedly attached to the body of the apparatus.

[0068] Item 61. The actuator assembly of any one of items 57 to 60, wherein the hydraulic actuators are configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration.

[0069] Item 62. The actuator assembly of any one of items 57 to 61, wherein the hydraulic actuators are configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0070] Item 63. The actuator assembly of any one of items 57 to 62, wherein, when the hydraulic actuators are not hydraulically actuated, the fail safe module is configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0071] Item 64. The actuator assembly of any one of items 57 to 63, wherein the central stem moves away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the central stem moves towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0072] Item 65. The actuator assembly of item 64, wherein, when the hydraulic actuators are not hydraulically actuated, the pressure in the first compartment is greater than the pressure in the second compartment, so that the piston of the fail safe module pulls the yoke towards the fail safe module.

[0073] Item 66. The actuator assembly of any one of items 57 to 65, wherein the first compartment is sealed and contains a pressurised gas, preferably at a pressure greater than 150 bars, and the second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0074] Item 67. The actuator assembly of any one of items 57 to 65, wherein the first compartment is pressure equilibrated with the environment, preferably is open to the environment and the second compartment is sealed and contains a gas, preferably at a pressure less than 150 bars.

[0075] Item 68. The actuator assembly of any one of items 57 to 67, wherein the actuator assembly is configured for use underwater and one of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment and is configured to be filled with water, preferably with seawater.

[0076] Item 69. The actuator assembly of any one of items 57 to 68, wherein the obstructing member comprises a ball valve and a scotch yoke configured to translate a linear motion of the central stem into a rotational movement of the ball valve.

[0077] Item 70. The actuator assembly of any one of items 57 to 69, wherein the obstructing member comprises or is a shear blade.

[0078] Item 71. The actuator assembly of any one of items 57 to 70, wherein the obstructing member comprises or is a gate valve.

[0079] Item 72. An assembly comprising one or more actuator assemblies according to any one of items 57 to 71 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the hydraulic actuators of each actuator assembly.

[0080] Item 73. An apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, comprising the actuator assembly according to any one of items 57 to 71 connected thereto.

[0081] Item 74. The apparatus of item 73, wherein the apparatus is a topside apparatus.

[0082] Item 75. The apparatus of item 74, wherein the topside apparatus is one of a blowout preventer (BOP), a surface flow tree (SFT), a tension frame (TF), a rig, or a workover control system (WOCS).

[0083] Item 76. The apparatus of item 73, wherein the apparatus is a subsea apparatus.

[0084] Item 77. The apparatus of item 76, wherein the subsea apparatus is one of a blowout preventer (BOP), a well control package (WCP), an emergency disconnect package (EDP), a lower riser package (LRP), an in-line tee (ILT), a high integrity pressure protection system (HIPPS), a manifold, a vertical Xmas tree (VXT), or a horizontal Xmas tree (HXT).

[0085] Item 78. A process of operating the actuator assembly in the apparatus of any one of items 73 to 77, comprising one or more of: hydraulically actuating the hydraulic actuators so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; hydraulically actuating the hydraulic actuators so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration, thereby closing off the central passageway of the apparatus; causing the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus, owing to the fail safe module, without hydraulically actuating the hydraulic actuators.

[0086] According to the first aspect, the invention provides a new and different arrangement for actuators comprising a fail safe mechanism. The invention provides a more compact actuator assembly thanks to a fail safe mechanism allowing the actuator assembly to automatically and safely close the central passageway in case of a failure of the one or more hydraulic actuators. The invention obviates the need for a sizeable spring in the fail safe mechanism. Also, the invention makes it possible to use existing reliable actuators and associated devices so that there is no need to requalify existing field proven technology.

[0087] According to the second aspect, the invention provides two parallel hydraulic actuators, which makes the actuator assembly more compact than an in-line hydraulic actuator classical configuration. This configuration reduces the footprint of the apparatus and allows closer valves in the apparatus.

[0088] The invention further makes it possible to remove the need for hydraulic accumulators on temporary equipment which also drives the overall size. Owing to reduced equipment size, air freightable intervention packages may be achieved. It may be easier, quicker and less costly to install and remove packages onto / from rigs, vessels equipped with an actuator assembly according to the invention.Brief description of the drawings

[0089] FIG. 1A-1B show a perspective view of an example of an apparatus comprising multiple actuator assemblies according to the invention, with and without fail safe modules. FIG. 2A-2B show a cross-sectional perspective view of an example of an actuator assembly according to the invention, in a closed configuration and an open configuration. FIG. 3 shows a cross-sectional perspective view of another actuator assembly according to the invention. FIG. 4A-4B schematically show a cross-section of an example of a fail safe module in two different configurations. FIG. 5A-5B schematically show a cross-section of another example of a fail safe module in two different configurations. FIG. 6 schematically shows an example of actuator assembly according to the invention including a hydraulic circuit, in two different configurations. FIG. 7A-7B show a perspective view of another example of an actuator assembly according to the invention, in a closed configuration and an open configuration. FIG. 8A-8B schematically show a partial cross-sectional view of this actuator assembly in two different configurations. FIG. 9A-9B show a perspective view of another example of an actuator assembly according to the invention, in a closed configuration and an open configuration. FIG. 10A-10B schematically show a partial cross-sectional view of this actuator assembly in two different configurations. FIG. 11 schematically shows this actuator assembly together with the hydraulic circuit, in two different configurations. Detailed description

[0090] The invention will now be described in more detail without limitation in the following description.

[0091] An object of the present invention is an actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body.

[0092] The actuator assembly may comprise a sliding stem, an obstructing member fixedly attached to the sliding stem and at least three compartments, namely a first compartment, a second compartment and a third compartment, which have varying volumes depending on the position of the sliding stem.

[0093] When the actuator assembly is connected to the apparatus, the obstructing member may have an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0094] The volume of the first compartment may increase and the volume of the second compartment may decrease when the sliding stem slides in one direction, and the volume of the first compartment may decrease and the volume of the second compartment may increase when the sliding stem slides in another opposite direction. The directions along which the sliding stem slides may be perpendicular to the longitudinal axis of the body.

[0095] Each of the first and second compartments may contain a fluid at a certain pressure. The first compartment may be sealed and the second compartment may be pressure equilibrated with the environment (or the other way around). The pressure in the compartment which is sealed varies as a function of the volume of this compartment, whereas the pressure in the compartment which is pressure equilibrated with the environment is substantially independent from the volume of this compartment (this pressure is substantially equal to the environment pressure).

[0096] Each compartment may be defined by non-deformable walls only. At least one of the non-deformable walls may be movable (slidable), so that the volume in the compartment may vary. For the sake of completeness, as will be described in more detail below, the compartment which is pressure equilibrated with the environment may be in fluid communication with a bladder having a deformable (flexible) wall.

[0097] As a result of one compartment being sealed and the other compartment being pressure equilibrated with the environment, when the actuator assembly is connected to the apparatus, the obstructing member may be biased towards one of the obstructing configuration and of the non-obstructing configuration, preferably towards the obstructing configuration. This bias towards one configuration is due to the existence of a pressure differential between the first compartment and the second compartment if the obstructing member is in the other configuration.

[0098] The third compartment may be feedable with hydraulic fluid and the bias of the obstructing member towards one of the obstructing configuration and of the non-obstructing configuration may be overcome by applying sufficient hydraulic fluid pressure in the third compartment.

[0099] In some embodiments, the third compartment may belong to a hydraulic actuator, while the first and second compartments may belong to a fail safe module which is separate from the hydraulic actuator.

[0100] In this case, the actuator assembly may comprise at least one hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber. The piston may divide the chamber into the third compartment defined above, and a fourth compartment (different from the first, second and third compartments). The actuator assembly may further comprise a fail safe module which may comprise a chamber and a piston configured to slide back and forth within the chamber. The piston of the fail safe module may divide the chamber of the fail safe module into the first compartment defined above (preferably closest to the piston of the at least one hydraulic actuator) and the second compartment defined above (preferably farthest from the piston of the at least one hydraulic actuator). The piston of the at least one hydraulic actuator and the piston of the fail safe module may be fixedly attached to the sliding stem.

[0101] In other embodiments, the hydraulic actuator and the fail safe mechanism may be integrated into a single component. This single component may comprise an outer housing, an inner member fixed within the outer housing, a sleeve fixedly attached to the sliding stem, wherein the sleeve has a flange and is slidable within the outer housing and over the inner member. The first compartment may be delimited by the outer housing and the sleeve; the second compartment may comprise an inner chamber within the inner member and may be further delimited by the sleeve; the third compartment may be delimited by the outer housing, the inner member and the flange of the sleeve. The first compartment and the third compartment may be located on opposite sides of the flange.

[0102] An "apparatus" as disclosed herein refers to an assembly of mechanical parts comprising a collection of smaller mechanical components. Preferably, the apparatus is part of an installation of oil and gas production from a subterranean formation or of an installation for the injection of fluid into a subterranean formation. The subterranean formation may be onshore or offshore, preferably offshore.

[0103] An example of an apparatus is a Vertical Xmas Tree (VXT) 101 as can be seen in FIG. 1A and FIG. 1B.

[0104] The apparatus may be a topside apparatus. "Topside" refers to an apparatus located above the waterline.

[0105] In some embodiments, the topside apparatus can be a blowout preventer (BOP). A BOP is an apparatus configured to monitor oil or gas wells to prevent blowouts.

[0106] In some embodiments, the topside apparatus can be a surface flow tree (SFT). A SFT is an apparatus that provides well control. The SFT is used as an access point to run objects into the well. These objects can be for example cables, wires, etc.

[0107] In some embodiments, the topside apparatus can be a tension frame (TF). A TF is an apparatus that connects the riser to the rig tension system. The riser is a conduit having multiple uses. For example, the riser can be used for tool deployment that is running tools to well, fluid transfer or pressure control.

[0108] In some embodiments, the topside apparatus can be a rig. A rig is a massive apparatus configured to explore for and extract oil or gas from the ground or the ocean floor.

[0109] In some embodiments, the topside apparatus can be a workover control system (WOCS). A WOCS is an apparatus for monitoring and control of subsea installation. The WOCS enables safe and efficient control of installation, intervention, and completion work on subsea wells. It provides hydraulic control of subsea trees.

[0110] The apparatus may be a subsea apparatus. "Subsea" refers to an apparatus located below the waterline. For example, the apparatus may be installed at a water depth from 0 to 1000 m, or from 1000 to 2000 m, or from 2000 to 3000 m, or at a water depth of more than 3000 m.

[0111] In some embodiments, the subsea apparatus can be a blowout preventer (BOP). As previously discussed, the BOP prevents blowouts.

[0112] In some embodiments, the subsea apparatus can be a well control package (WCP). A WCP is a critical apparatus used for well control purposes. For example, during well control incidents, the WCP plays a crucial role in preventing blowouts, managing pressure, and ensuring safety.

[0113] In some embodiments, the subsea apparatus can be an emergency disconnect package (EDP). An EDP is an apparatus that provides disconnect function. The EDP is designed for emergency situations when another apparatus needs to be quickly disconnected from the well. Examples of when this might be necessary include extreme weather conditions that exceed the other apparatus' capability to maintain its position. For example, the EDP is necessary to quickly disconnect a rig that starts to drift. Indeed, it is not wanted that such a rig may pull on the well, so the EDP will release the rig if the latter is drifting, to prevent a spill to sea.

[0114] In some embodiments, the subsea apparatus can be a lower riser package (LRP). A LRP is an apparatus stacked on top of the tree that provides well control function, that is the LRP allows to shut and secure the well. A LRP is very similar to a WCP. For example, if mechanical work is needed in the well, the LRP can secure the well. The LRP can also serve as a mini BOP to protect the well.

[0115] In some embodiments, the subsea apparatus can be an in-line tee (ILT). An ILT is an apparatus package that creates a branched line tie-in point along a pipeline. For example, an ILT is a tee point to connect other tree or manifold on a pipeline. ILT is like a size reduced manifold.

[0116] In some embodiments, the subsea apparatus can be a high integrity pressure protection system (HIPPS). A HIPPS is an apparatus used to prevent another apparatus or part of the well from exceeding its rated pressure level. It acts as a barrier separating the high-pressure section of an apparatus or part from downstream apparatus. For example, the HIPPS can prevent over pressurisation of a pipeline or of the riser. The HIPPS does so by measuring the pressure on either side of the central passageway that is to be obstructed by the obstructing member. If there is any over pressure, the obstructing member will transition to the obstructing configuration so as to close the central passageway to protect the pipeline from suffering any damage from high pressure. Typically, the HIPPS is located between the well and the pipeline, on the seabed.

[0117] In some embodiments, the subsea apparatus can be a manifold. A manifold is an apparatus composed of headers and branched piping used to gather or distribute fluids as needed. Typically, manifolds include valves for controlling fluid flow on or off, and they may also incorporate other flow control devices (such as chokes) if these are not mounted directly on individual subsea trees. The manifold is used to gather production or distribute injection. The manifold is typically located at the bottom of the sea.

[0118] In some embodiments, the subsea apparatus can be a Xmas tree. A Xmas tree is an apparatus comprising an assembly of valves, spools, and fittings used to control the flow of oil or gas from a well. It sits atop the wellhead casing system and represents the interface between the well and the production facility. The Xmas tree regulates pressure, controls flow, and allows access to the wellbore for further completion work when needed. The Xmas tree makes it possible to isolate production or injection in the well, and allows to control the well. Therefore, a Xmas tree is used for production or injection. In offshore and subsea wells, the Xmas tree is often referred to as a subsea tree when positioned on the ocean floor.

[0119] In some embodiments, the subsea apparatus can be a vertical Xmas tree (VXT), i.e. a Xmas tree which is disposed vertically. The advantage is that this kind of orientation requires only one BOP deployment and connection to wellhead during installation but if workover operations like tubing changes are required, the VXT must be removed to install a BOP on top of the well.

[0120] In some embodiments, the subsea apparatus can be a horizontal Xmas tree (HXT). A HXT is a horizontally disposed Xmas tree. The advantage is that the total tree height is lowered but its replacement is more time-consuming and costly. A HXT can thus be preferred when tree replacement is unlikely.

[0121] By "connection to an apparatus" is meant that the actuator assembly can be mounted onto the apparatus. When mounted, the actuator assembly may provide an opening and closing function in the central passageway of the apparatus.

[0122] A "central passageway" refers to an elongated conduit, through which fluid (for example oil or gas) can travel and / or along which an elongated object such as a cable or wire may extend.

[0123] A "hydraulic actuator" refers to a component that is configured to actuate, an element (in this case, an obstructing member) to cause it to transition from one configuration to another configuration, depending on the pressure of a hydraulic fluid in the actuator. Hydraulic actuators are known to have advantages such as high actuating forces, high stroking velocities and high stability. The counterpart is that there is a risk of leakage of the hydraulic fluid making the hydraulic actuator fail to actuate. In some examples, a hydraulic actuator may open or close a valve.

[0124] A "fail safe mechanism" refers to a mechanism which causes the actuator assembly to return to a safe condition in the event of a breakdown or malfunction (such as in the event of a leak of hydraulic fluid). When the obstructing element is a valve, the fail safe mechanism may ensure that the valve is open, or (preferably) may ensure that the valve is closed, in case of failure. In some cases the fail safe mechanism is not integrated in the at least one hydraulic actuator, i.e., there is a fail safe module is comprised within the actuator assembly but separated from the at least one hydraulic actuator. In other cases, the hydraulic actuator and the fail safe mechanism may be integrated into a single component, as mentioned above. As will be further apparent below, the fail safe mechanism may have further functions and in particular may contribute to the normal mode of operation of the actuator assembly in the absence of failure.

[0125] An "obstructing member" refers to any mechanical part that can at least partly close the central passageway of the apparatus, depending on its position or configuration.

[0126] As can be seen in FIG. 1A and 1B, the apparatus may have multiple actuator assemblies mounted thereon. FIG. 1A illustrates a VXT comprising three actuator assemblies, without a fail safe module for the sake of clarity. FIG. 1B illustrates the same apparatus having two fail safe modules (106, 106') attached.

[0127] Several actuator assemblies may be associated with the same central passageway. Alternatively, or additionally, an apparatus may comprise two or more different central passageways (possibly having different longitudinal axes), wherein one or more actuator assemblies are arranged associated with each central passageway.Hydraulic actuator

[0128] The present description of the hydraulic actuator primarily applies to the embodiments wherein the hydraulic actuator is distinct and separate from the fail safe module.

[0129] The actuator assembly comprises at least one hydraulic actuator (at least two hydraulic actuators in the second aspect of the invention). Each hydraulic actuator may comprise a chamber and a piston configured to slide back and forth within the chamber. The chamber of each hydraulic actuator may be divided by the piston into two compartments, having variable volumes. At least one of these compartments corresponds to the third compartment mentioned above. The other compartment may be designated as a fourth compartment. Hydraulic fluid may be present in the third compartment and optionally also present in the fourth compartment. Hydraulic fluid may be more particularly hydraulic liquid, such as water or more preferably oil.

[0130] The chamber of the at least one hydraulic actuator may be configured to be fixedly attached to the body of the apparatus (i.e. so that the chamber is not movable relative to the body of the apparatus).

[0131] The at least one hydraulic actuator may be configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration. Transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration means clearing the central passageway of the apparatus that was originally at least partially obstructed by the obstructing element. By "hydraulically actuating", is meant feeding high pressure hydraulic fluid to a compartment of the chamber of the hydraulic actuator to move the piston and cause the volume of this compartment to increase.

[0132] The at least one hydraulic actuator may be configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration. Transitioning the obstructing member from the non-obstructing configuration to the obstructing configuration means partially or fully closing the central passageway of the apparatus that was originally cleared.

[0133] When the at least one hydraulic actuator is not hydraulically actuated, the fail safe module may be configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration. The fail safe module may take over the at least one hydraulic actuator to safely close the central passageway of the apparatus.

[0134] The piston of the at least one hydraulic actuator may move away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the piston of the at least one hydraulic actuator may move towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0135] When the at least one hydraulic actuator is not hydraulically actuated, the pressure in the first compartment of the fail safe module may be greater than the pressure in the second compartment of the fail safe module, so that the piston of the fail safe module pulls the piston of the at least one hydraulic actuator towards the fail safe module.

[0136] The direction of movement of the piston may be along an actuator axis. The actuator axis may be perpendicular to the longitudinal axis of the body.

[0137] The actuator assembly may comprise a single hydraulic actuator, wherein the piston of the hydraulic actuator is axially aligned with the piston of the fail safe module. This arrangement will be further referred to as the in-line arrangement.

[0138] An example of this in-line arrangement will now be described in more detail with reference to FIG. 3, which shows the actuator assembly connected to an apparatus 101. The actuator assembly comprises a hydraulic actuator 303 comprising a piston 305 configured to slide back and forth in a chamber 304. A piston rod 308 may be fixed to (preferably integral with) the piston 305 and also slide back and forth. The piston rod 308 may be positioned partially within the chamber 304 and partially out of the chamber 304. The piston rod 308 may extend along the actuator axis.

[0139] A central stem 307 (which is an embodiment of the sliding stem mentioned above) may be connected at a first end to the piston 305 of the hydraulic actuator 303 and may be configured to extend through the central bore of a bonnet 306. The central stem 307 may extend along the actuator axis. The central stem 307 may be connected at a second end (opposite the first end) to an obstructing member 301. The hydraulic actuator 303 may have a retracted position (piston 305 closest to the passageway 302 of the apparatus 101, as can be seen on FIG. 3, the piston rod 308 being at a position of zero or minimum extension outside of the chamber 304) and an extended position (piston 305 farthest from the passageway 302 of the apparatus 101, the piston rod 308 being at a position of maximum extension outside of the chamber). The obstructing member 301 may be in the non-obstructing configuration and therefore the central passageway 302 of the apparatus 101 may be clear (open) when the hydraulic actuator 303 is in the retracted position (as shown on FIG. 3), and the obstructing member 301 may be in the obstructing configuration and therefore the central passageway 302 of the apparatus 101 may be partially or fully closed when the hydraulic actuator 303 is in the extended position. However, the opposite orientation is also possible (obstructing configuration in the retracted position and non-obstructing configuration in the extended position).

[0140] The fail safe module may comprise a piston rod fixed to (preferably integral with) the piston as will be described in more detail below. The actuator assembly may comprise a connecting member 310 fixed on the one hand to an end of the piston rod 308 of the hydraulic actuator 303 (which is opposite the piston 305 of the hydraulic actuator 303); and fixed on the other hand to an end of the piston rod of the fail safe module (which is opposite the piston of the fail safe module); in such a way that the piston of the fail safe module is attached to the piston 305 of the hydraulic actuator 303 via the piston rod of the fail safe module, the connecting member 310 and the piston rod 308 of the hydraulic actuator 303.

[0141] The actuator assembly may be mounted on the apparatus 101 for example by screwing the bonnet 306 onto the body of the apparatus 101 by way of screws 309, 309'. The chamber 304 of the hydraulic actuator 303 may itself be fixed to the bonnet 306. The chamber of the fail safe module (not shown) may be fixed to the bonnet 306 or preferably to the chamber 304 of the hydraulic actuator 303, for example via a locking mechanism 311 present on the outside surface of the chamber 304 of the hydraulic actuator 303. Therefore, the bonnet 306, the chamber 304 of the hydraulic actuator 303 and the chamber of the fail safe module (not shown) may be fixedly attached to the body of the apparatus 101.

[0142] On the other hand, the central stem 307, the piston 305 and piston rod 308 of the hydraulic actuator 303, the connecting member 310 and the piston of the fail safe module (not shown) may be fixed together and may slide along a sliding direction relative to the body of the apparatus 101: the central stem 307 may slide within the central bore of the bonnet 306, the piston 305 and piston rod 308 of the hydraulic actuator 303 may slide within the chamber 304 of the hydraulic actuator 303, and the piston and piston rod of the fail safe module may slide within the chamber of the fail safe module. The sliding direction may be perpendicular to the longitudinal axis of the body of the apparatus 101. The sliding direction may be along the actuator axis. The obstructing member 301 may be in a fixed position relative to the central stem 307 so that this obstructing member 301 also slides together with the central stem 307, but other implementations of the obstructing member are possible, as will appear based on the further description below.

[0143] The central stem 307 may be aligned with the piston rod 308 of the hydraulic actuator 303. The piston rod of the fail safe module may be aligned with the piston rod 308 of the hydraulic actuator 303. The central stem 307, piston rod 308 of the hydraulic actuator 303 and piston rod of the fail safe module may all be aligned together.

[0144] Alternatively, the actuator assembly may comprise at least two hydraulic actuators, preferably at least two parallel hydraulic actuators. In this embodiment, the at least two hydraulic actuators may be simultaneously actuated to move the obstructing member. This arrangement will be further referred to as the parallel arrangement.

[0145] An example of this parallel arrangement will now be described in more detail with reference to FIG. 2A and FIG. 2B. FIG. 2A shows the actuator assembly in the non-obstructing configuration and FIG. 2B shows the actuator assembly in the obstructing configuration.

[0146] The apparatus 101 comprises an actuator assembly connected thereto. The actuator assembly may comprise a first hydraulic actuator 203 comprising a piston 205 configured to slide back and forth in a chamber 204, and a second hydraulic actuator 203' comprising a piston 205' configured to slide back and forth in a chamber 204'. A piston rod 209, 209' may be fixed to (preferably integral with) each respective piston 205, 205' and also slide back and forth. Each piston rod 209, 209' may be positioned partially within the respective chamber 204, 204' and partially out of the respective chamber 204, 204'.

[0147] The two pistons 205, 205' of the hydraulic actuators 203, 203' may be connected to a yoke 102 (via the extremities of the piston rods 209, 209' opposite the pistons 205, 205'). A central stem 207 (which is an embodiment of the sliding stem mentioned above) may be connected at a first end to the yoke 102 and may be configured to extend through the central bore of a bonnet 206. The central stem 207 may be connected at a second end to an obstructing member 201. The central stem 207 may extend along an actuator axis.

[0148] The hydraulic actuators 203, 203' may have a retracted position (piston 205, 205' closest to the passageway 202 of the apparatus 101, as can be seen on FIG. 2B, the piston rods 209, 209' being at a position of zero or minimum extension outside of the respective chambers 204, 204') and an extended position (piston 205, 205' farthest from the passageway 202 of the apparatus 101, as can be seen on FIG. 2A, the piston rods 209, 209' being at a position of maximum extension outside of the respective chambers 204, 204').

[0149] When the hydraulic actuators 203, 203' are in the retracted position as can be seen on FIG. 2B, the obstructing member 201 may be in the non-obstructing configuration and therefore the central passageway 202 of the apparatus 101 may be open. When the hydraulic actuators 203, 203' are in the extended position as can be seen on FIG. 2A, the obstructing member 201 may be in the obstructing configuration and therefore the central passageway 202 of the apparatus 101 may be partially or fully closed. However, the opposite orientation is also possible (obstructing configuration in the retracted position and non-obstructing configuration in the extended position).

[0150] The fail safe module may comprise a piston rod fixed to (preferably integral with) the piston as will be described in more detail below. The actuator assembly may further comprises a cradle 104 adapted for fixing the chamber of the fail safe module (not shown in the drawings) in such a way that the piston of the fail safe module is attached to the yoke 102 of the hydraulic actuators 203, 203', via the piston rod of the fail safe module. The cradle 104 may be fixed to the bonnet 206 by rods 208, 208'. The rods 208, 208' may extend through respective holes in the yoke 102.

[0151] The actuator assembly may be mounted on the apparatus 101 for example by attaching the bonnet 206 onto the body of the apparatus 101. The chambers 204, 204' of the hydraulic actuators 203, 203' may also be directly attached to the body of the apparatus 101 or may be attached to the bonnet 206. The chamber of the fail safe module (not shown) may be fixed to the cradle 104. Therefore, the bonnet 206, the chambers 204, 204' of the hydraulic actuators 203, 203' and the chamber of the fail safe module (not shown) may be fixedly attached to the body of the apparatus 101.

[0152] On the other hand, the central stem 207, the pistons 205, 205' (and piston rods 209, 209') of the hydraulic actuators 203, 203', the yoke 102 and the piston and piston rod of the fail safe module (not shown) may be fixed together and may slide along parallel sliding directions relative to the body of the apparatus 101: the central stem 207 may slide within the central bore of the bonnet 206, the piston 205, 205' (and piston rods 209, 209') of each hydraulic actuator 203, 203' may slide within the respective chamber 204, 204' of the hydraulic actuator 203, 203', the yoke 102 may slide onto the rods 208, 208' and the piston and piston rod of the fail safe module may slide within the chamber of the fail safe module. All of these elements may slide according to parallel sliding directions which may be perpendicular to the longitudinal axis of the body of the apparatus 101 (and along or parallel to the actuator axis). The obstructing member 201 may be in a fixed position relative to the central stem 207 so that this obstructing member 201 also slides together with the central stem 207, but other implementations of the obstructing member are possible, as will appear based on the further description below.

[0153] The central stem 207 may be aligned with the piston rod of the fail safe module along the actuator axis. The central stem 207 and the pistons rods 209, 209' of the hydraulic actuators 203, 203' (and optionally the rods 208, 208') may be arranged in parallel. The central stem 207 may be positioned between the piston rods 209, 209' of the hydraulic actuators 203, 203'. The central stem 207 may be positioned between the rods 208, 208'.

[0154] This parallel arrangement saves additional space compared to the in-line arrangement. Moreover, the at least two parallel hydraulic actuators may be smaller and lighter than a hydraulic actuator in the in-line arrangement. Indeed, as there are at least two hydraulic actuators combined, less force is required from each, and they can thus be reduced in size.

[0155] Referring back to FIG. 1A and 1B, an apparatus 101 is shown, which comprises three different actuator assemblies according to FIG. 2A and 2B. Each of these actuators assemblies comprises a yoke 102, 102' and 102" and a fixed cradle 104, 104' and 104".

[0156] On each fixed cradle 104, 104' and 104", a fail safe module 106, 106' is attached. One part of the fail safe module 106, 106' (namely the chamber) is connected to the fixed cradle 104, 104', and another part of the fail safe module 106, 106' (namely the piston rod) is connected to the yoke 102, 102'.Fail safe module

[0157] The present description of the fail safe module primarily applies to the embodiments wherein the hydraulic actuator is distinct and separate from the fail safe module.

[0158] As already mentioned above, the actuator assembly may comprise a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber. A piston rod may be fixed to (preferably integral with) this piston and also slide back and forth within the chamber. The piston of the fail safe module may divide the chamber of the fail safe module into a first compartment (preferably closest to the piston of the at least one hydraulic actuator) and a second compartment (preferably farthest from the piston of the at least one hydraulic actuator), having variable volumes, as defined above. A piston rod may be fixed to (preferably integral with) the piston. The piston rod may be positioned partially within the chamber and partially out of the chamber of the fail safe module. The volumes of the first and second compartments vary depending on the position of the piston in the chamber. The piston rod may extend in the first compartment of the fail safe module.

[0159] The fail safe module may be a passive device, i.e. it does not contain hydraulic fluid and is not fluidically connected to a hydraulic circuit.

[0160] Preferably, the fail safe module does not comprise any compressive spring.

[0161] At least one of the first compartment and second compartment of the fail safe module may be sealed and the other of the first compartment and second compartment of the fail safe module may be open to the environment. The environment may be the air, the ground, or the sea. "Open to the environment' means that there are one or more holes in the chamber allowing fluid to enter or exit one of the first compartment and second compartment of the fail safe module from or to the environment, so that pressure in said first compartment or second compartment may be equilibrated with the environment pressure. The other compartment may be "sealed", i.e. may not allow exchange of fluid and thus pressure equilibration with the environment.

[0162] The environment may be the sea, so that the compartment open to the environment may be filled with seawater. In this case the fail safe module may comprise a filter across the one or more holes, to protect the chamber of the fail safe module from any ingress of solids.

[0163] As an alternative to having one compartment of the two compartments open to the environment, it is also possible to enable an indirect pressure equilibration between this compartment and the environment. For example, a bladder may be positioned on the outside of the fail safe module so that the compartment is in fluidic communication with the bladder. Control fluid may be present in the bladder and in the compartment. The bladder may comprise one or more flexible walls, so that the environment pressure (for example hydrostatic pressure if the module is underwater) equilibrates with the pressure within the compartment. The other compartment may be sealed and unequilibrated with the environment pressure.

[0164] The fail safe module may be configured to transition between two positions. The first one may be a retracted position. In this configuration, the second compartment has a minimum volume (and the first compartment has a maximum volume), in other words, the piston of the fail safe module is in the position farthest from the chamber of the at least one hydraulic actuator and the piston rod is at a position of zero or minimum extension outside of the chamber of the fail safe module. The second one may be an extended position. In this configuration, the first compartment has a minimum volume (and the second compartment has a maximum volume), in other words, the piston of the fail safe module is in the position closest to the chamber of the at least one hydraulic actuator and the piston rod is at a position of maximum extension outside of the chamber of the fail safe module. Preferably, when the fail safe module is in the extended position, the at least one hydraulic actuator is in the retracted position; and when the fail safe module is in the retracted position, the at least one hydraulic actuator is in the extended position. Preferably, when the fail safe module is in the extended position, the obstructing member is in the non-obstructing configuration; and when the fail safe module is in the retracted position, the obstructing member is in the obstructing configuration. However, the opposite orientation is also possible.

[0165] Preferably, the pressure in the first compartment and the pressure in the second compartment may be such that the piston of the fail safe module may be biased towards the retracted position. But the piston may be drawn to the extended position if the at least one hydraulic actuator exerts a force which overcomes the pressure differential between the first and second compartments, as will be described in more detail below.

[0166] In a first variation, the first compartment of the fail safe module may be sealed and contain a pressurised gas, which is preferably at a pressure greater than a pressure threshold when the fail safe module is in the retracted position. The pressure threshold may be for example from 100 to 250 bars, such as from 150 to 200 bars,. The second compartment of the fail safe module may be open to the environment (e.g. the atmosphere, or seawater). The pressurised gas may be nitrogen or air. The pressure of the pressurised gas in the first compartment may be adjusted before deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, the piston diameters and the piston surface areas. This implementation is particularly useful for a topside apparatus, or for an underwater apparatus which lies in relatively shallow water (for example at a depth from 0 to 1500 m). The second compartment is then at hydrostatic pressure. When substantially no force is exerted by the hydraulic actuator(s), the pressure in the first compartment may be higher than the pressure in the second compartment, thereby pulling the piston in the retracted position.

[0167] Alternatively, in a second variation, the first compartment of the fail safe module may be open to the environment (e.g., seawater) and the second compartment of the fail safe module may be sealed and contain a gas (for example nitrogen or air), pressurised or not, and which is preferably at a pressure less than a pressure threshold, for example less than 150 bars such as from 1 bar to 150 bars, more preferably at a pressure of approximately 1 bar when the fail safe module is in the retracted position. The pressure of the gas in the second compartment may be adjusted prior to deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, the piston diameters and the piston surface areas. This implementation is particularly useful for a subsea apparatus which lies in relatively deep water (for example at a depth at least 1500 m, such as from 1500 to 3000 m). The first compartment is then at hydrostatic pressure. Again, when substantially no force is exerted by the hydraulic actuator(s), the pressure in the first compartment may be higher than the pressure in the second compartment, thereby pulling the piston in the retracted position.

[0168] The first variation is now disclosed in more detailed by referring to FIG. 4A and 4B. The fail safe module 106 may comprise a piston 401 connected to (such as integral with) a piston rod 402, as described above. The fail safe module 106 may further comprise a chamber divided by the piston into a first compartment 403 and a second compartment 404. The second compartment 404 may be open to the environment 408. A filter 406 may protect the second compartment 404 from any ingress of solids. As an alternative, the second compartment may be isolated from the environment by a bladder to enable equilibration with the environment pressure, as mentioned above. The fail safe module 106 may further comprise a compressed gas port 405 communicating with the first compartment 403, which may be used for loading the first compartment 403 with compressed gas, such as compressed nitrogen or air, before sealing the first compartment 403. FIG. 4A shows the piston 401 in the extended position. FIG. 4B shows the piston 401 in the retracted position. The transition from the retracted to extended position may be caused by actuating the one or more hydraulic actuators (not shown). The transition from the extended to retracted position may be caused, in the absence of actuation of the one or more hydraulic actuators, by the pressure in the first compartment 403 being greater than the pressure in the second compartment 404, causing the piston 401 to move so as to reduce the volume of the second compartment 404 and increase the volume of the first compartment 403. The volume of the second compartment 404 may then reach a minimum, non-zero value when the pressure in the first compartment 403 is equal to the pressure of the environment 408 (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartment 404 may reach a minimum value without reducing the pressure differential between the compartments to zero if the movement of the piston 401 is stopped by a mechanical stop in the chamber. Preferably, the obstructing member may be in an obstructing configuration when the fail safe module 106 is in the retracted position. The fail safe module 106 may further comprise a pressure gauge 407 configured to measure the pressure in the first compartment 403.

[0169] The second variation is now disclosed in more detailed by referring to FIG. 5A and 5B. The fail safe module 106 may comprise a piston 401' connected to (such as integral with) a piston rod 402', as described above. The fail safe module 106 may further comprise a chamber divided by the piston into a first compartment 403' and a second compartment 404'. The first compartment 403' may be open to the environment 408'. A filter 406' may protect the first compartment 403' from any ingress of solids. As an alternative, the first compartment may be isolated from the environment by a bladder to enable equilibration with the environment pressure, as mentioned above. The fail safe module 106 may further comprise a compressed gas port 405' communicating with the second compartment 404', which may be used for loading the second compartment 404' with compressed gas, such as compressed nitrogen or air, before sealing the second compartment 404'. Alternatively, the fail safe module 106 may be devoid of such compressed gas port 405', especially in case a gas at atmospheric pressure is present in the second compartment 404'. FIG. 5A shows the piston 401' in the extended position. FIG. 5B shows the piston 401' in the retracted position. The transition from the retracted to extended position may be caused by actuating the one or more hydraulic actuators (not shown). The transition from the extended to retracted position may be caused, in the absence of actuation of the one or more hydraulic actuators, by the pressure in the first compartment 403' being greater than the pressure in the second compartment 404', causing the piston 401' to move so as to reduce the volume of the second compartment 404' and increase the volume of the first compartment 403'. The volume of the second compartment 404' may then reach a minimum, non-zero value when the pressure in the second compartment 404' is equal to the pressure of the environment (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartment 404' may reach a minimum value without reducing the pressure differential between the compartments to zero if the movement of the piston 401' is stopped by a mechanical stop in the chamber. Preferably, the obstructing member may be in an obstructing configuration when the fail safe module 106 is in the retracted position. The fail safe module 106 may further comprise a pressure gauge 407' configured to measure the pressure in the second compartment 404'.

[0170] When the apparatus is subsea, the fail safe module may be connected in situ to the actuator assembly already partly mounted to the apparatus, by a remotely operated underwater vehicle (ROV). An ROV is a specialized robotic system designed to perform tasks in deep water, where human divers cannot safely operate. The fail safe module may also be ROV recoverable and ROV replaceable. This allows to only replace the fail safe module in case it no longer works properly instead of replacing the overall actuator assembly or the entire apparatus.Fail safe mechanism integrated with a hydraulic actuator as a single component

[0171] Making reference to FIG. 7A, 7B, 8A and 8B, the actuator assembly 600 may comprise an outer housing 609 and an inner member 614 fixed within the outer housing 609. The outer housing 609 and inner member 614 may extend along an actuator axis. The actuator axis may be perpendicular to the longitudinal axis of the body of the apparatus.

[0172] An inner space such as a substantially cylindrical inner space may be present in the outer housing 609 and the inner member 614 may be placed within this space. The inner member 614 may comprise an end wall 615 and a tubular extension 616. The end wall 615 of the inner member 614 may be fixed at one extremity of the outer housing 609 along the actuator axis, and the tubular extension 616 may extend within the inner space of the outer housing 609, along the actuator axis and towards the opposite end of the outer housing. The end wall 615 may project radially outwardly from the tubular extension 616. The end wall 615 may close off the extremity of the outer housing 609.

[0173] The outer periphery of the tubular extension 616 may be at a distance from the inner wall of the outer housing 609.

[0174] A sleeve 618 may be slidable (back and forth) within the outer housing 609 and over the inner member 614. More precisely, the sleeve 618 may be slidable over the tubular extension 616. The sleeve 618 may comprise a flange 620, a tubular portion 621 and an end wall 617. The tubular portion 621 may extend along the actuator axis. At least the flange 620 and part or all of the tubular portion 621 may be placed within the outer housing. The sleeve 618 may partly protrude from the outer housing 609, more precisely from an extremity of the outer housing 609 which is opposite the extremity at which the end wall 615 of the inner member 614 is fixed. The end wall 617 may be located out of the outer housing 609. The flange 620 may remain at all times within the outer housing 609. The extent to which the tubular portion 621 is outside of the outer housing 609 may depend on the position of the sleeve 618 along the actuator axis.

[0175] The sleeve 618 may cooperate with the outer housing 609 and the inner member 614 so as to define the three abovementioned compartments. These three compartments are isolated from each other and have variable volumes.

[0176] The first compartment 603 may be delimited by the outer housing 603 and the sleeve 618 (more precisely, the flange 620 and possibly the outer periphery of the tubular portion 603).

[0177] The first compartment 603 may be pressure equilibrated with the environment 608 (for example seawater). For example, it may be open to the environment. To this end, at least one opening 622 in the outer housing 609 may be provided to allow the exchange of fluid with the environment 608. The entire description concerning pressure equilibration contained in the above section "Fail safe module" applies similarly. In particular, a filter may be provided, or indirect pressure equilibration using a bladder may be used.

[0178] The second compartment 604 may be formed by an inner chamber 619 within the inner member 614, together with an inner space 610 within the sleeve 618. More precisely, the inner chamber 619 of the inner member 614 may extend along the tubular extension 616. The inner space 610 within the sleeve 618 may extend along and within the tubular portion 621. The size of the inner space 610 within the sleeve 618 varies as the sleeve 618 slides over the inner member 614, thereby ensuring that the volume of the second compartment 604 is variable.

[0179] The second compartment 604 may be sealed, as defined above. The second compartment 604 may contain a gas (for example nitrogen or gas), pressurised or not, and which is preferably at a pressure less than a pressure threshold, for example less than 150 bars such as from 1 bar to 150 bars, more preferably at a pressure of approximately 1 bar when sleeve 618 is in the extended position. The pressure of the gas in the second compartment may be adjusted prior to deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, and the dimensions of the actuator assembly. This implementation is particularly useful for a subsea apparatus which lies in relatively deep water (for example at a depth at least 1500 m, such as from 1500 to 3000 m), wherein the first compartment is at hydrostatic pressure.

[0180] A compressed gas port 605 may be present in the inner member 614, preferably on the end wall 615 of the inner member 614, which may be used for loading the second compartment 604 with compressed gas, such as compressed nitrogen or air, before sealing the second compartment 604. Alternatively, the actuator assembly may be devoid of such compressed gas port 605, especially in case a gas at atmospheric pressure is present in the second compartment 604. A pressure gauge may be connected to a pressure gauge port 623, preferably also on the end wall 615 of the inner member 614 and may be configured to measure the pressure in the second compartment 604.

[0181] Of course, the opposite can also be implemented, i.e. the first compartment may be sealed and the second compartment may be pressure equilibrated with the environment.

[0182] The third compartment 611 may be delimited by the outer housing 609, the inner member 614 and the flange 620 of the sleeve 618. The third compartment 611 may contain hydraulic fluid and may be fluidically connected to a hydraulic circuit.

[0183] The sleeve 621 may be fixed to the sliding stem 607 (which is itself connected to the obstructing member 601 as described elsewhere). The sliding stem 607 may extend along the actuator axis, away from the outer housing 609 and sleeve 621.

[0184] The outer housing 609 may be fixedly attached to the body of the apparatus, for example via a bonnet 606. The sliding stem 607 may slide within a bore in the bonnet 606.

[0185] Preferably, the actuator assembly does not comprise any compressive spring.

[0186] The actuator assembly may be configured to transition between two positions.

[0187] The first one may be a retracted position, as shown in FIG. 7B and 8B. In this configuration, the second compartment 604 has a minimum volume, the third compartment 611 has a minimum volume, and the first compartment 603 has a maximum volume; the sleeve 618 is in the position farthest from the central passageway 602 of the apparatus and the sleeve 618 is at a position of zero or minimum extension outside of the outer housing 609.

[0188] The second one may be an extended position, as shown in FIG. 7A and 8A. In this configuration, the first compartment 603 has a minimum (or zero) volume, the second compartment 604 has a maximum volume and the third compartment 611 has a maximum volume; the sleeve 618 is in the position closest to the central passageway 602 of the apparatus and the sleeve 618 is at a position of maximum extension outside of the outer housing 609.

[0189] Preferably, when the actuator assembly is in the extended position, the obstructing member 601 is in the non-obstructing configuration; and when the actuator assembly is in the retracted position, the obstructing member 601 is in the obstructing configuration. However, the opposite is also possible.

[0190] Preferably, the pressure in the first compartment 603 and the pressure in the second compartment 604 may be such that the sleeve 621 is biased towards the retracted position. But the sleeve 621 may be drawn to the extended position if the hydraulic fluid pressure in the third compartment 611 is sufficient to overcome the pressure differential between the first and second compartments 603, 604.

[0191] A hydraulic fluid port 612 may be present in the outer housing 609 and / or in the inner member 614, preferably on the end wall 615 of the inner member 614 as illustrated. The hydraulic fluid port 612 may be configured to fluidically connect the third compartment 611 to a hydraulic fluid circuit and thus to feed hydraulic fluid to the third compartment 611 or collect hydraulic fluid from the third compartment 611, thereby adjusting hydraulic fluid pressure within the third compartment 611.

[0192] A pressure gauge may be connected to a pressure gauge port 613, preferably also on the end wall 615 of the inner member 614 and may be configured to measure the pressure in the third compartment 611.

[0193] The transition from the retracted to extended position may be caused by feeding hydraulic fluid to the third compartment 611, thereby increasing hydraulic fluid pressure within this third compartment 611. The hydraulic fluid presses against the flange 620 of the sleeve 618, causing the sleeve 618 to slide away from the end wall 615 of the inner member 614. The flange 620 therefore acts as a piston in the hydraulic actuator. The flange 620 may abut against a stopping element of the outer housing 609 in the extended position, so that the sleeve 618 may not completely dislodge from the outer housing 609.

[0194] The transition from the extended to retracted position may be caused by releasing the hydraulic fluid pressure in the third compartment 611. As a result of the pressure in the first compartment 603 being greater than the pressure in the second compartment 604, the sleeve 618 is caused to move so as to reduce the volume of the second compartment 604 and third compartment 611 (hydraulic fluid may be withdrawn from the third compartment 611 as a result) and so as to increase the volume of the first compartment 603. The volume of the second compartment 604 may reach a minimum, non-zero value when the pressure in the second compartment 604 is equal to the pressure of the environment (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartment 604 may reach a minimum value without reducing the pressure differential between the first and second compartments to zero, if the movement of the sleeve 621 is stopped by a mechanical stop (such as the end wall 617 of the sleeve 618 abutting against the inner member 614 or the flange 620 of the sleeve 618 abutting against a stopping element of the outer housing 609.

[0195] When the apparatus is subsea, the actuator assembly may be connected in situ to the apparatus, by a ROV. The actuator assembly may also be ROV recoverable and ROV replaceable.

[0196] The ROV may also connect a hydraulic fluid line to the hydraulic fluid port 612. The hydraulic fluid line may be fluidically connected to a hydraulic circuit, for example a hydraulic circuit present in the apparatus itself.

[0197] Making reference to FIG. 9A, 9B, 10A and 10B, in another variation of the fail safe mechanism being integrated with the hydraulic actuator as a single component, the actuator assembly 700 may comprise an outer housing 709, within which are arranged at least a first chamber referred to as an active chamber 710 and at least a second chamber referred to as a passive chamber 714. In each chamber, a respective piston connected to (such as integral with) a piston rod is present, wherein the piston divides the chamber in respective compartments.

[0198] All piston rods may be arranged in parallel, parallel to an actuator axis. The actuator axis may be perpendicular to the longitudinal axis of the body of the apparatus.

[0199] There can be a single active chamber and a single passive chamber. Alternatively, there can be a single active chamber and two or more passive chambers. In the illustrated embodiment, there is a single active chamber 710 and two passive chambers 714, 714'. The passive chambers 714, 714' may extend on opposite sides of the active chamber 710.

[0200] A respective piston 715, 715' connected to (such as integral with) a piston rod 716, 716' may slide within each passive chamber 714, 714' along the actuator axis.

[0201] A piston 717 connected to (such as integral with) a piston rod 718 may slide within the active chamber 710 along the actuator axis.

[0202] The first compartment 703, 703' as defined above may be located in the or each passive chamber 714, 714' and extend on one side of the respective piston 715, 715', such as between said piston 715, 715' and the sliding stem 707 (or the obstructing member 701). When there are two (or more) passive chambers 714, 714', there are therefore two (or more) respective first compartments 703, 703' as defined above.

[0203] The or each first compartment 703, 703' may be pressure equilibrated with the environment 708 (for example seawater). For example, it may be open to the environment. To this end, at least one opening in the outer housing 709 may be provided to allow the exchange of fluid with the environment 708. The entire description concerning pressure equilibration contained in the above section "Fail safe module" applies similarly. In particular, a filter may be provided, or indirect pressure equilibration using a bladder may be used. It is possible for the first compartments 703, 703' to fluidically communicate together. For example, a single opening in the outer housing 709 may be provided to allow the exchange of fluid between the environment 708 and all of these compartments.

[0204] The second compartment 704, 704' as defined above may be located in the or each passive chamber 714, 714' and extend on one side of the respective piston 715, 715', opposite the first compartment 703, 703'. When there are two (or more) passive chambers 714, 714', there are therefore two (or more) second compartments 704, 704' as defined above.

[0205] The or each second compartment 704, 704' may be sealed, as defined above. The or each second compartment 704, 704' may contain a gas (for example nitrogen or gas), pressurised or not, and which is preferably at a pressure less than a pressure threshold, for example less than 150 bars such as from 1 bar to 150 bars, more preferably at a pressure of approximately 1 bar when the actuator in the extended position. The pressure of the gas in the or each second compartment may be adjusted prior to deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, and the dimensions of the actuator assembly. This implementation is particularly useful for a subsea apparatus which lies in relatively deep water (for example at a depth at least 1500 m, such as from 1500 to 3000 m), wherein the first compartment is at hydrostatic pressure.

[0206] A compressed gas port 705, 705' may be present on the outer housing 709, preferably on an end wall facing away from the sliding stem 707 and obstructing member 701, which may be used for loading the or each respective second compartment 704, 704' with compressed gas, such as compressed nitrogen or air, before sealing the second compartment 704, 704'. Alternatively, the actuator assembly may be devoid of such compressed gas port 705, 705', especially in case gas at atmospheric pressure is present in the or each second compartment 704, 704'.

[0207] Of course, the opposite can also be implemented, i.e. the first compartment(s) may be sealed and the second compartment(s) may be pressure equilibrated with the environment.

[0208] The third compartment 711 may be located in the active chamber 710 (or a third compartment may be located in each active chamber, in case there are several), and extend on one side of the associated piston 717, more preferably on the side which is not between said piston 717 and the sliding stem 707 and obstructing member 701

[0209] The third compartment 711 may contain hydraulic fluid and may be fluidically connected to a hydraulic circuit.

[0210] The compartment in the active chamber 710 which lies on the opposite side of the piston 717 (relative to the third compartment 711) may be sealed, or may be also fluidically connected to the hydraulic circuit, or may be open to the environment. It case it is open to the environment, it is possible for this compartment and for the or each first compartment 703, 703' to fluidically communicate together. For example, a single opening in the outer housing 709 may be provided to allow the exchange of fluid between the environment 708 and all of these compartments.

[0211] The outer housing 709 may be fixedly attached to the body of the apparatus, for example via a bonnet 706.

[0212] The sliding stem 707 may slide within a bore in the bonnet 706.

[0213] Preferably, the actuator assembly does not comprise any compressive spring.

[0214] The piston rods 716, 716', 718 associated with the passive chambers 714, 714' and active chamber 710 may be fixedly connected to the sliding stem 707, preferably via a transversal connector 713 located outside of the outer housing 709. As a result, all corresponding pistons 715, 715', 717 may concurrently slide back and forth in their respective chambers.

[0215] The actuator assembly may be configured to transition between two positions.

[0216] The first one may be a retracted position, as shown in FIG. 9B and 10B. In this configuration, the or each second compartment 704, 704' has a minimum volume, the third compartment 711 has a minimum volume, and the or each first compartment 703, 703' has a maximum volume; all pistons 715, 715', 717 are in a position farthest from the central passageway 702 of the apparatus and the piston rods 716, 716', 718 are at a position of zero or minimum extension outside of the outer housing 709.

[0217] The second one may be an extended position, as shown in FIG. 9A and 10A. In this configuration, the or each first compartment 703, 703' has a minimum (or zero) volume, the or each second compartment 704, 704' has a maximum volume and the third compartment 711 has a maximum volume; all pistons 715, 715', 717 are in a position closest to the central passageway 702 of the apparatus and the sleeve piston rods 716, 716', 718 are at a position of maximum extension outside of the outer housing 709.

[0218] Preferably, when the actuator assembly is in the extended position, the obstructing member 701 is in the non-obstructing configuration; and when the actuator assembly is in the retracted position, the obstructing member 701 is in the obstructing configuration. However, the opposite is also possible.

[0219] Preferably, the pressure in the first compartments 703, 703' and the pressure in the second compartments 704, 704' may be such that the sliding stem 707 is biased towards the retracted position. But the sliding stem 707 may be drawn to the extended position if the hydraulic fluid pressure in the third compartment 711 is sufficient to overcome the pressure differential between the first and second compartments.

[0220] A hydraulic fluid port 712 may be present in the outer housing 709 and may be configured to fluidically connect the third compartment 711 to a hydraulic fluid circuit and thus to feed hydraulic fluid to the third compartment 711 or collect hydraulic fluid from the third compartment 711, thereby adjusting hydraulic fluid pressure within the third compartment 711.

[0221] A pressure gauge may be connected to a pressure gauge port and may be configured to measure the pressure in the third compartment.

[0222] The transition from the retracted to extended position may be caused by feeding hydraulic fluid to the third compartment 711, thereby increasing hydraulic fluid pressure within this third compartment 711, so that the hydraulic fluid presses against the piston 717.

[0223] The transition from the extended to retracted position may be caused by releasing the hydraulic fluid pressure in the third compartment 711. As a result of the pressure in the first compartments 703, 703' being greater than the pressure in the second compartments 704, 704', the sliding stem 707 together with all rods 716, 716', 718 are caused to move so as to reduce the volume of the second compartments 704, 704' and third compartment 711 (hydraulic fluid may be withdrawn from the third compartment 711 as a result) and so as to increase the volume of the first compartments 703, 703'. The volume of the second compartment 704, 704' may reach a minimum, non-zero value when the pressure in the second compartments 704, 704' is equal to the pressure of the environment (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartments 704, 704' may reach a minimum value without reducing the pressure differential between the first and second compartments to zero, if the movement is stopped by a mechanical stop (such as the pistons 715, 715' abutting against an inner wall of the respective chambers).

[0224] When the apparatus is subsea, the actuator assembly may be connected in situ to the apparatus, by a ROV. The actuator assembly may also be ROV recoverable and ROV replaceable.

[0225] The ROV may also connect a hydraulic fluid line to the hydraulic fluid port 712. The hydraulic fluid line may be fluidically connected to a hydraulic circuit, for example a hydraulic circuit present in the apparatus itself.

[0226] The benefit of this arrangement is that the sealed compartments are only subjected to hydrostatic pressure and not subjected to the sum of hydrostatic pressure and hydraulic pressure.Obstructing member

[0227] The actuator assembly further comprises an obstructing member connected to the sliding stem.

[0228] In some embodiments, the obstructing member is connected to the piston of the at least one hydraulic actuator, by way of the central stem in the in-line arrangement, and by way of the piston rods, yoke and central stem in the parallel arrangement. The obstructing member has, when the actuator assembly is connected to the apparatus, and depending on the position of the sliding stem, an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed; and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0229] In the non-obstructing configuration, fluid (and / or objects) may move along the central passageway.

[0230] Preferably, in the obstructing configuration, the central passageway is fully obstructed, which means that the passage of fluid along the central passageway is fully blocked. Alternatively, it is also possible for the obstructing element to only partially obstruct the central passageway in the obstructing configuration. In this case, fluid (and / or) objects may still move along the central passageway, but the opening available for this movement within the central passageway has a reduced size relative to the non-obstructing configuration.

[0231] The obstructing member may comprise a ball valve and a scotch yoke configured to translate a linear motion of the sliding stem (and thus for example a linear motion of the piston of the at least one hydraulic actuator) into a rotational movement of the ball valve. For example, an ILT or a manifold can typically comprise such a ball valve.

[0232] The obstructing member may comprise or may be a shear blade. The shear blade acts as a guillotine in order to cut a wire, a cable, coiled tubing or any other object positioned through the central passageway of the apparatus. The cutting may be effected by transitioning the shear blade from the non-obstructing configuration to the obstructing configuration. For example, a WCP, a LRP, a EDP or a BOP can typically comprise a shear blade to cut what is located in the well. The shear blade may cooperate with a support member which is fixedly attached to the body of the apparatus, such that high shear is generated between the support member and the shear blade when the shear blade moves from the non-obstructing configuration to the obstructing configuration.

[0233] The obstructing member may comprise or be a gate valve or a ram. By gate valve, it is meant a member which may move linearly across the central passageway (preferably in a direction perpendicular to the longitudinal axis of the body). The gate valve may cooperate with a support member fixedly attached to the body of the apparatus. For example, the gate valve may be in the shape of a plate comprising a hole. In the non-obstructing configuration, the hole may be located in the central passageway, while in the obstructing configuration the hole may be located out of the central passageway, so that the plate obstructs the central passageway. This is what is illustrated in FIG. 2A, 2B and 3.

[0234] Preferably, the fail safe mechanism may be configured to force the obstructing member into the non-obstructing position (for example, to stroke open a hydraulic connector for an emergency disconnection).

[0235] Alternatively, the fail safe mechanism may be configured to force the obstructing member into the obstructing position (for example to stroke a valve closed, again for example for an emergency disconnection).

[0236] The fail safe module, or the entire actuator assembly (especially for the integrated embodiments) can be 3D printed from different materials depending the size of the gate valve. For example, for 2" and 5" sized gate valves, the fail safe module or the entire actuator assembly can be 3D printed from nickel alloy. For example, for 7" sized gate valve, the fail safe module or the entire actuator assembly can be 3D printed from titanium. This may reduce the manufacturing time as well as the cost of the actuator assembly. This may also improve the reliability of the actuator assembly. This may finally lower the overall weight of the actuator assembly. Preferably, the weight of the fail safe module or of the entire actuator assembly may be less than 60 kg, preferably less than 50 kg.Hydraulic circuit and operating process

[0237] The actuator assembly may be associated with a hydraulic circuit configured to feed pressurized hydraulic fluid to the at least one hydraulic actuator. The hydraulic circuit may be part of the apparatus, external to the apparatus, or may be partially included in the apparatus and partially external to the apparatus.

[0238] The hydraulic circuit may be a closed loop circuit so that there is no need to have a hydraulic umbilical cable to feed hydraulic fluid to the hydraulic circuit. This may allow to reduce the equipment required on a rig or vessel. In some examples, this hydraulic circuit may be used for an electric riser less well intervention (eRLWI).

[0239] The hydraulic circuit may comprise one or more flowmeters. The one or more flowmeters can be configured to monitor the circulation of hydraulic fluid in the hydraulic circuit. Information from the one or more flowmeters and / or information from one or more pressure sensors may be fed back to a control unit which may be configured to control the hydraulic circuit, and in particular the operation of the pump and / or valve which will be described in more detail below.

[0240] Now referring to FIG. 6, a closed loop hydraulic circuit is presented, in conjunction with an actuator assembly comprising a fail safe module and at least one hydraulic actuator distinct and separate from the fail safe module, as described above. The closed loop hydraulic circuit may be hydraulically connected to a single actuator assembly (i.e. each actuator assembly may be associated with a dedicated hydraulic circuit). Alternatively, as illustrated on the drawing, a closed loop hydraulic circuit may be hydraulically connected to two or more actuator assemblies. The or each actuator assembly may be as described according to all options and variations above. In the illustration, each actuator assembly comprises two hydraulic actuators, but the present description is also applicable to actuator assemblies comprising a single hydraulic actuator or more than two hydraulic actuators.

[0241] The hydraulic circuit may comprise a high pressurised hydraulic portion 517 and a low pressurised hydraulic portion 518. These portions are fluidically connected to a hydraulic fluid supply 508. In the high pressurised hydraulic portion 517, a pump 507, a flowmeter 506 and a pressure transmitter 505 (to measure pressure) may be present. The pump 507 may be configured to feed pressurized hydraulic fluid to the actuator assemblies. Control of the pump 507 may make it possible to control the pressure in the high pressurised hydraulic portion 517. This pressure may reach, by way of example, a maximum value from 200 to 500 bar, such as approximately 350 bar.

[0242] As described above, each actuator assembly may further comprise a fail safe module 501 comprising a piston 502 and piston rod configured to slide back and forth in a chamber divided by the piston 502 into a first compartment 503 and a second compartment 504, 504'. The first compartment 503 may be closest to the piston 511 of the hydraulic actuators 510 (and closest to the central passageway 515), and the second compartment 504, 504' may be farthest from the piston 511 of the hydraulic actuators 510 (and farthest from the central passageway 515). The piston rod of the fail safe module 501 may extend in the first compartment 503 of the fail safe module 501 and also extend out of the chamber of the fail safe module 501. As illustrated, in the parallel arrangement, the piston rod of the fail safe module 501 may be fixedly attached to a yoke 509.

[0243] As described above, each hydraulic actuator 510 in each actuator assembly may comprise a piston 511 fixed to a piston rod and configured to slide back and forth in a chamber divided by the piston 511 into a third compartment 513, 513' and a fourth compartment 512, 512'. The fourth compartment 512, 512' may be farthest from the piston 502 of the fail safe module 501 and the third compartment 513, 513' may be closest to the piston 502 of the fail safe module 501. The piston rod of each hydraulic actuator 510 may extend in the third compartment 513, 513' and also extend out of the chamber of the hydraulic actuator 510. The yoke 509 may be fixedly attached to the piston rods of the hydraulic actuators 510.

[0244] The yoke may also be fixedly attached to a central stem 514. This central stem 514 may be connected to an obstructing member 516 configured to transition between an obstructing configuration and a non-obstructing configuration to obstruct or clear a central passageway 515. As described above, alternatively, in the case of in-line arrangement, the central stem 514 may be directly connected to the piston 511 of the hydraulic actuator 510.

[0245] More generally, in each actuator assembly, the piston 502 and piston rod of the fail safe module 501, the piston 511 and piston rod of the hydraulic actuator(s) 510 and the central stem 514 may be fixed together and assume a linear movement.

[0246] The third compartment 513, 513' of each hydraulic actuator 510 may be fluidically connected to the high pressurised hydraulic portion 517. The fourth compartment 512, 512' of each hydraulic actuator 510 may be fluidically connected to the low pressurised hydraulic portion 518.

[0247] The hydraulic circuit may further comprise a valve, such as an electrically actuated directional control valve (DCV) 519. In case more than one actuator assemblies are connected to the same hydraulic circuit, there may be one such valve per actuator assembly. This valve may have a first position in which hydraulic fluid communication between the high pressurised hydraulic portion 517 and the third compartment 513 is open, and hydraulic fluid communication between the low pressurised hydraulic portion 518 and the third compartment 513 is closed; and a second position in which hydraulic fluid communication between the high pressurised hydraulic portion 517 and the third compartment 513' is closed, and hydraulic fluid communication between the low pressurised hydraulic portion 518 and the third compartment 513' is open. The fourth compartment 512, 512' may be in hydraulic fluid communication with the low pressurised hydraulic portion 518 in both positions on the valve. When the valve is in the first position, owing to the pump 507, the hydraulic pressure within the third compartment 513 of each hydraulic actuator 510 may increase and the piston 511 of the hydraulic actuator 510 may be biased towards the retracted position. When the valve is in the second position, the piston 502 of the fail safe module may drive the piston 511 of the or each hydraulic actuator 510 towards the extended position.

[0248] On the left hand side of FIG. 6 is presented a first configuration of the hydraulic circuit wherein the valve associated with one actuator assembly is in the first position. The pump 507 applies hydraulic pressure (by way of example, from 200 to 500 bar, such as approximately 350 bar) in the third compartment 513 of the or each hydraulic actuator 510 of the actuator assembly. This applied hydraulic pressure may be sufficient to overcome both the hydraulic pressure in the first compartment 512, and the pressure differential between the first compartment 503 and second compartment 504 of the fail safe module 501. As a result, the piston 511 of the or each hydraulic actuator 510 moves towards or is maintained in the retracted position, and the piston 502 of the fail safe module 501 is driven by the piston 511 of the or each hydraulic actuator 510 and moves towards or is maintained in the extended position. This may preferably correspond to a transition or maintenance of the obstructing member 516 to or in the non-obstructing configuration.

[0249] On the right hand side of FIG. 6 is presented a second configuration of the hydraulic circuit wherein the valve associated with another actuator assembly is in the second position. In this case, the pump 507 does not apply hydraulic pressure in the third compartment 513' of the or each hydraulic actuator 510 of the actuator assembly. The pressure differential between the first compartment 503 and the second compartment 504 of the fail safe module 501 is thus sufficient to drive the piston 502 of the fail safe module 501 towards the retracted position, so that the piston 511 of the or each hydraulic actuator 510 moves towards or is maintained in the extended position. This may preferably correspond to a transition or maintenance of the obstructing member 516 to or in the obstructing configuration.

[0250] The fail safe module can therefore be configured to cause the obstructing member to transition to a safe configuration (preferably to the obstructing configuration) in case of a malfunction of the hydraulic circuit, e.g. due to leakage of hydraulic fluid and loss of hydraulic pressure. Indeed, as explained above, in such a case, the fail safe module may bias the hydraulic actuators towards a position, for example the extended position, owing to the pressure differential between the compartments of the chamber of the fail safe module.

[0251] The fail safe module can also be configured to cause the obstructing member to transition from one configuration to another configuration as part of the normal operation of the actuator assembly, i.e. in the absence of malfunction. Indeed, as explained above, pressurized hydraulic fluid may be fed to only one compartment of the chamber of each hydraulic actuator, to cause the transition in one direction. By relaxing hydraulic pressurization in this compartment, and by simply relying on the pressure differential between the compartments of the chamber of the fail safe module, transition to the other direction may be achieved.

[0252] Alternatively (and different from what is depicted in FIG. 6), it is also possible for the hydraulic circuit to feed pressurized hydraulic fluid to both compartments of each chamber of a hydraulic actuator. In this case, the fail safe module can typically be used only as a safety feature.

[0253] Making reference to FIG. 11, a closed loop hydraulic circuit is presented, in conjunction with an actuator assembly comprising a fail safe mechanism and hydraulic actuator integrated into a single component, as described above in connection with FIG. 7A-7B and 8A-8B. In this context, unless otherwise specified, the description made above in connection with FIG. 6 remains applicable. Besides, the present description is also applicable in a similar manner to a fail safe mechanism and hydraulic actuator integrated into a single component, as described above in connection with FIG. 9A-9B and 10A-10B, the only difference being the arrangement of the compartments.

[0254] The closed loop hydraulic circuit may be hydraulically connected to a single actuator assembly (i.e. each actuator assembly may be associated with a dedicated hydraulic circuit). Alternatively, as illustrated on the drawing, a closed loop hydraulic circuit may be hydraulically connected to two or more actuator assemblies.

[0255] The hydraulic circuit may comprise a high pressurised hydraulic portion 817 and a low pressurised hydraulic portion 818. These portions are fluidically connected to a hydraulic fluid supply 808. In the high pressurised hydraulic portion 817, a pump 807, a flowmeter 806 and a pressure transmitter 805 (to measure pressure) may be present. The pump 807 may be configured to feed pressurized hydraulic fluid to the actuator assemblies. Control of the pump 807 may make it possible to control the pressure in the high pressurised hydraulic portion 817. This pressure may reach, by way of example, a maximum value of from 200 to 500 bar, such as approximately 350 bar.

[0256] As described above, each actuator assembly 801 may further comprise a sleeve 802 configured to slide back and forth in an outer housing 809. The actuator assembly 801 may comprise a first compartment 803 within the outer housing 809 and external to the inner member, closer to the central passageway 815; a third compartment 811 within the outer housing 809 and external to the inner member, further from the central passageway 815; and a second compartment 804 within the inner member and the sleeve 802. The sleeve 802 may extend out of the outer housing 809 and may be fixedly attached to the sliding stem 814.

[0257] The sliding stem 814 may be connected to an obstructing member 816 configured to transition between an obstructing configuration and a non-obstructing configuration to obstruct or clear the central passageway 815.

[0258] In each actuator assembly, the sleeve 802 and central stem 814 may be fixed together and assume a linear movement.

[0259] The third compartment 811 may be alternately fluidically connected (via a hydraulic fluid line 810 which may be a flexible line) to the high pressurised hydraulic portion 817 and to the low pressurised hydraulic portion 818, depending on the position of a valve 819 on the circuit, which may be a DCV as described above. In case more than one actuator assemblies are connected to the same hydraulic circuit, there may be one such valve per actuator assembly.

[0260] When the valve is in a first position, owing to the pump 807, the hydraulic pressure within the third compartment 811 of the actuator assembly 801 may increase and the sleeve 802 may be driven towards the extended position (left hand side of the drawing). The pump 807 may apply hydraulic pressure (by way of example, from 200 to 500 bar, such as approximately 350 bar) in the third compartment 811. This applied hydraulic pressure may be sufficient to overcome the pressure differential between the first compartment 803 and second compartment 804. As a result, the sleeve 802 moves towards or is maintained in the extended position. This may preferably correspond to a transition or maintenance of the obstructing member 816 to or in the non-obstructing configuration.

[0261] When the valve is in a second position (right hand side of the drawing), the pump 807 does not apply hydraulic pressure in the third compartment 811. The pressure differential between the first compartment 803 and the second compartment 804 is thus sufficient to drive the sleeve 802 towards the retracted position. This may preferably correspond to a transition or maintenance of the obstructing member 816 to or in the obstructing configuration.

[0262] The actuator assembly can therefore be configured to cause the obstructing member to transition to a safe configuration (preferably to the obstructing configuration) in case of a malfunction of the hydraulic circuit, e.g. due to leakage of hydraulic fluid and loss of hydraulic pressure. The actuator assembly can be configured to cause the obstructing member to transition from one configuration to another configuration as part of the normal operation of the actuator assembly, i.e. in the absence of malfunction.

Examples

Embodiment Construction

[0090]The invention will now be described in more detail without limitation in the following description.

[0091]An object of the present invention is an actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body.

[0092]The actuator assembly may comprise a sliding stem, an obstructing member fixedly attached to the sliding stem and at least three compartments, namely a first compartment, a second compartment and a third compartment, which have varying volumes depending on the position of the sliding stem.

[0093]When the actuator assembly is connected to the apparatus, the obstructing member may have an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0094]The volume of the first compartment may increase and the volume of the second compartment may decr...

Technical field

[0001] The present invention relates to the field of oil or gas production wells and injection wells, and more specifically to an actuator assembly with a permanent or separately removable fail safe module for connection to an apparatus comprised in an oil or gas production well or an injection well. The invention also relates to an apparatus comprising the actuator assembly and a process of operating the actuator assembly in the apparatus. The actuator(s) of the invention can be fail safe open or closed. The actuator(s) of the invention can be adapted for subsea equipment or surface equipment and for any process.Technical background

[0002] Production and injection wells generally comprise apparatuses wherein a hydraulic actuator is meant to open or close a valve over a central passageway extending along an axis of the body of the apparatus. Examples of such apparatuses include Xmas trees, manifolds and other similar devices. In case the hydraulic actuator fails to open or close the valve, the actuator assembly can comprise a fail safe mechanism intended to safely close the valve. This fail safe mechanism typically comprises a spring in a stressed state that, when the valve needs to be closed (or needs to be opened), releases some or all of the stored energy, thereby effecting closure (or opening) of the valve. The valve needs to be closed (or opened) by this fail safe mechanism in particular when there is a loss of hydraulic pressure in the hydraulic actuator.

[0003] The main problem of this known fail safe mechanism is that the spring needs to be large enough to exert the force necessary to close (or open) the valve safely and quickly and provide sufficient displacement to fully stroke the valve to final position. The spring thus significantly drives up the size of the overall actuator assembly. This can be especially disadvantageous in a subsea environment.

[0004] Within this context there is a need for an improved actuator assembly comprising a (preferably ROV removable / installable) fail safe mechanism, which in particular is compact and reliable.Summary of the invention

[0005] According to a first aspect, the invention relates to the following items.

[0006] Item 1. An actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, wherein the actuator assembly comprises: a sliding stem, an obstructing member fixedly attached to the sliding stem, a first compartment, a second compartment and a third compartment having varying volumes depending on the position of the sliding stem, wherein the volume of the first compartment increases and the volume of the second compartment decreases when the sliding stem slides in one direction, and the volume of the first compartment decreases and the volume of the second compartment increases when the sliding stem slides in another opposite direction, wherein the actuator assembly is configured so that: the obstructing member has, when the actuator assembly is connected to the apparatus: an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed; and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed; at least one of the first compartment and second compartment is sealed and the other of the first compartment and second compartment is pressure equilibrated with the environment, so that, when the actuator assembly is connected to the apparatus, the obstructing member is biased towards one of the obstructing configuration and of the non-obstructing configuration; the third compartment is feedable with hydraulic fluid and the bias of the obstructing member towards one of the obstructing configuration and of the non-obstructing configuration may be overcome by applying sufficient hydraulic fluid pressure in the third compartment.

[0007] Item 2. The actuator assembly of item 1, wherein the other of the first compartment and second compartment is open to the environment.

[0008] Item 3. The actuator assembly of any one of items 1 to 2, wherein the first compartment is sealed and contains a pressurised gas and the second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0009] Item 4. The actuator assembly of any one of items 1 to 2, wherein the first compartment is pressure equilibrated with the environment, preferably is open to the environment and the second compartment is sealed and contains a gas.

[0010] Item 5. The actuator assembly of any one of items 1 to 4, wherein the actuator assembly is configured for use underwater and one of the first compartment and second compartment is open to the environment and is configured to be filled with water, preferably with seawater.

[0011] Item 6. The actuator assembly of any one of items 1 to 5, wherein the obstructing member comprises a ball valve and a scotch yoke configured to translate a linear motion of the sliding stem into a rotational movement of the ball valve.

[0012] Item 7. The actuator assembly of any one of items 1 to 6, wherein the obstructing member comprises or is a shear blade.

[0013] Item 8. The actuator assembly of any one of items 1 to 7, wherein the obstructing member comprises or is a gate valve.

[0014] Item 9. The actuator assembly of any one of items 1 to 8, wherein the actuator assembly comprises: at least one hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber, said piston dividing said chamber into the third compartment and a fourth compartment; a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber, said piston dividing said chamber into the first compartment and the second compartment, wherein the piston of the at least one hydraulic actuator and the piston of the fail safe module are fixedly attached to the sliding stem.

[0015] Item 10. The actuator assembly of item 9, wherein the first compartment is closest to the piston of the at least one hydraulic actuator and the second compartment is farthest from the piston of the at least one hydraulic actuator.

[0016] Item 11. The actuator assembly of items 9 or 10, wherein the chamber of the at least one hydraulic actuator and the chamber of the fail safe module are configured to be fixedly attached to the body of the apparatus.

[0017] Item 12. The actuator assembly of any one of items 9 to 11, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration.

[0018] Item 13. The actuator assembly of any one of items 9 to 12, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0019] Item 14. The actuator assembly of any one of items 9 to 13, wherein, when the at least one hydraulic actuator is not hydraulically actuated, the fail safe module is configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0020] Item 15. The actuator assembly of any one of items 9 to 14, wherein the piston of the at least one hydraulic actuator moves away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the piston of the at least one hydraulic actuator moves towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0021] Item 16. The actuator assembly of item 15, wherein, when the at least one hydraulic actuator is not hydraulically actuated, the pressure in the first compartment is greater than the pressure in the second compartment, so that the piston of the fail safe module pulls the piston of the at least one hydraulic actuator towards the fail safe module.

[0022] Item 17. The actuator assembly of any one of items 9 to 16, wherein the actuator assembly comprises a single hydraulic actuator, wherein the piston of the hydraulic actuator is axially aligned with the piston of the fail safe module.

[0023] Item 18. The actuator assembly of any one of items 9 to 16, wherein the actuator assembly comprises at least two parallel hydraulic actuators.

[0024] Item 19. The actuator assembly of item 18, wherein the actuator assembly further comprises: a bonnet having a central bore; a yoke connecting the pistons of the at least two parallel hydraulic actuators; and wherein the sliding stem is a central stem extending through the central bore of the bonnet, having a first end fixed to the yoke and a second end fixed to the obstructing member.

[0025] Item 20. The actuator assembly of item 19, wherein the bonnet is configured to be fixedly attached to the body of the apparatus, and the pistons of the hydraulic actuators are configured to drive the central stem through the central bore of the bonnet, thereby transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration.

[0026] Item 21. The actuator assembly of any one of items 1 to 8, wherein the actuator assembly comprises: an outer housing; an inner member fixed within the outer housing; a sleeve fixedly attached to the sliding stem, wherein the sleeve has a flange and is slidable within the outer housing and over the inner member; wherein the first compartment is delimited by the outer housing and the sleeve, the second compartment comprises an inner chamber within the inner member and is further delimited by the sleeve, and the third compartment is delimited by the outer housing, the inner member and the flange of the sleeve.

[0027] Item 22. The actuator assembly of any one of items 1 to 8, wherein the actuator assembly comprises: an outer housing; an active chamber within the outer housing; at least one, preferably two passive chambers within the outer housing; a piston connected to a piston rod slidable within the active chamber, wherein the third compartment is delimited within the active chamber by said piston; a respective piston connected to a piston rod slidable within each passive chamber, wherein the first compartment and the second compartment are located within each passive chamber on opposite sides of said piston; wherein the piston rod of the active chamber and the piston rods of the passive chambers are fixedly connected to the sliding stem.

[0028] Item 23. An assembly, comprising one or more actuator assemblies according to any one of items 1 to 22 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the third compartment, and preferably to at least one hydraulic actuator of each actuator assembly, if present.

[0029] Item 24. An apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, comprising the actuator assembly of any one of items 1 to 22 connected thereto.

[0030] Item 25. The apparatus of item 24, wherein the apparatus is a topside apparatus.

[0031] Item 26. The apparatus of item 25, wherein the topside apparatus is one of a blowout preventer (BOP), a surface flow tree (SFT), a tension frame (TF), a rig, or a workover control system (WOCS).

[0032] Item 27. The apparatus of item 24, wherein the apparatus is a subsea apparatus.

[0033] Item 28. The apparatus of item 27, wherein the subsea apparatus is one of a blowout preventer (BOP), a well control package (WCP), an emergency disconnect package (EDP), a lower riser package (LRP), an in-line tee (ILT), a high integrity pressure protection system (HIPPS), a manifold, a vertical Xmas tree (VXT), or a horizontal Xmas tree (HXT).

[0034] Item 29. A process of operating the actuator assembly in the apparatus of any one of items 24 to 28, comprising one or more of: applying hydraulic fluid pressure to the third compartment, so as to cause the obstructing member to transition from one of the obstructing configuration and the non-obstructing configuration, to the other of the obstructing configuration and the non-obstructing configuration; causing the obstructing member to transition from one of the non-obstructing configuration and the obstructing configuration to the other of the non-obstructing configuration and the obstructing configuration by ceasing to apply hydraulic fluid pressure in the actuator assembly.

[0035] Item 30. The process of item 29, wherein the actuator assembly is according to any one of items 9 to 20, comprising one or more of: hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration, thereby closing off the central passageway of the apparatus; causing the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus, owing to the fail safe module, without hydraulically actuating the at least one hydraulic actuator.

[0036] Item 31. The process of item 29, wherein the actuator assembly is according to any one of items 21 to 22, comprising one or more of: increasing hydraulic fluid pressure in the third compartment, so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; decreasing hydraulic fluid pressure in the third compartment, so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus.

[0037] Still according to the first aspect, the invention also relates to the following items.

[0038] Item 32. An actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, wherein the actuator assembly comprises: at least one hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber; a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber, the piston dividing the chamber into a first compartment closest to the piston of the at least one hydraulic actuator and a second compartment farthest to the piston of the at least one hydraulic actuator, wherein the piston of the at least one hydraulic actuator is fixed to the piston of the fail safe module; an obstructing member connected to the piston of the at least one hydraulic actuator and having, when the actuator assembly is connected to the apparatus, and depending on the position of the piston of the at least one hydraulic actuator: an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed; and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0039] Item 33. The actuator assembly of item 32, wherein at least one of the first compartment and second compartment of the fail safe module is sealed and the other of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0040] Item 34. The actuator assembly of item 32 or item 33, wherein the chamber of the at least one hydraulic actuator and the chamber of the fail safe module are configured to be fixedly attached to the body of the apparatus.

[0041] Item 35. The actuator assembly of any one of items 32 to 34, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration.

[0042] Item 36. The actuator assembly of any one of items 32 to 35, wherein the at least one hydraulic actuator is configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0043] Item 37. The actuator assembly of any one of items 32 to 36, wherein when the at least one hydraulic actuator is not hydraulically actuated, the fail safe module is configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0044] Item 38. The actuator assembly of any one of items 32 to 37, wherein the piston of the at least one hydraulic actuator moves away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the piston of the at least one hydraulic actuator moves towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0045] Item 39. The actuator assembly of any one of items 32 to 38, wherein when the at least one hydraulic actuator is not hydraulically actuated, the pressure in the first compartment is greater than the pressure in the second compartment, so that the piston of the fail safe module pulls the piston of the at least one hydraulic actuator towards the fail safe module.

[0046] Item 40. The actuator assembly of any one of items 32 to 39, wherein the first compartment is sealed and contains a pressurised gas, preferably at a pressure greater than 150 bars, and the second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0047] Item 41. The actuator assembly of any one of items 32 to 39, wherein the first compartment is pressure equilibrated with the environment, preferably is open to the environment and the second compartment is sealed and contains a gas, preferably at a pressure less than 150 bars.

[0048] Item 42. The actuator assembly of any one of items 32 to 41, wherein the actuator assembly is configured for use underwater and one of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment and is configured to be filled with water, preferably with seawater.

[0049] Item 43. The actuator assembly of any one of items 32 to 42, wherein the obstructing member comprises a ball valve and a scotch yoke configured to translate a linear motion of the piston of the at least one hydraulic actuator into a rotational movement of the ball valve.

[0050] Item 44. The actuator assembly of any one of items 32 to 43, wherein the obstructing member comprises or is a shear blade.

[0051] Item 45. The actuator assembly of any one of items 32 to 42, wherein the obstructing member comprises or is a gate valve.

[0052] Item 46. The actuator assembly of any one of items 32 to 45, wherein the actuator assembly comprises a single hydraulic actuator, wherein the piston of the hydraulic actuator is axially aligned with the piston of the fail safe module.

[0053] Item 47. The actuator assembly of any one of items 32 to 45, wherein the actuator assembly comprises at least two parallel hydraulic actuators.

[0054] Item 48. The actuator assembly of item 47, wherein the actuator assembly further comprises: a bonnet having a central bore; a yoke connecting the pistons of the at least two parallel hydraulic actuators; a central stem extending through the central bore of the bonnet, having a first end fixed to the yoke and a second end fixed to the obstructing member.

[0055] Item 49. The actuator assembly of item 48, wherein the bonnet is configured to be fixedly attached to the body of the apparatus, and the pistons of the hydraulic actuators are configured to drive the central stem through the central bore of the bonnet, thereby transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration.

[0056] Item 50. An assembly, comprising one or more actuator assemblies according to any one or any combination of items 32 to 49 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the at least one hydraulic actuator of each actuator assembly.

[0057] Item 51. An apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, comprising the actuator assembly according any of items 32 to 49 connected thereto.

[0058] Item 52. The apparatus of item 51, wherein the apparatus is a topside apparatus.

[0059] Item 53. The apparatus of item 52, wherein the topside apparatus is one of a blowout preventer (BOP), a surface flow tree (SFT), a tension frame (TF), a rig, or a workover control system (WOCS).

[0060] Item 54. The apparatus of item 51, wherein the apparatus is a subsea apparatus.

[0061] Item 55. The apparatus of item 54, wherein the subsea apparatus is one of a blowout preventer (BOP), a well control package (WCP), an emergency disconnect package (EDP), a lower riser package (LRP), an in-line tee (ILT), a high integrity pressure protection system (HIPPS), a manifold, a vertical Xmas tree (VXT), or a horizontal Xmas tree (HXT).

[0062] Item 56. A process of operating the actuator assembly of any one of items 32 to 49, comprising one or more of: hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; hydraulically actuating the at least one hydraulic actuator so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration, thereby closing off the central passageway of the apparatus; causing the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus, owing to the fail safe module, without hydraulically actuating the at least one hydraulic actuator.

[0063] According to a second aspect, the invention relates to the following items.

[0064] Item 57. An actuator assembly for an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, wherein the actuator assembly comprises: two parallel hydraulic actuators, each hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber; a bonnet having a central bore; a yoke connecting the pistons of the hydraulic actuators; an obstructing member having, when the actuator assembly is connected to the apparatus, and depending on the position of the piston of the two hydraulic actuators: an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed, and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed; a central stem extending through the central bore of the bonnet, having a first end fixed to the yoke and a second end fixed to the obstructing member; wherein: the bonnet and the chambers of the hydraulic actuators are configured to be fixedly attached to the body of the apparatus; the pistons of the hydraulic actuators are configured to drive the central stem through the central bore of the bonnet, thereby transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration.

[0065] Item 58. The actuator assembly of item 57, which comprises a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber, the piston of the fail safe module being fixed to the yoke.

[0066] Item 59. The actuator assembly of item 57 or 58, wherein the piston of the fail safe module divides the chamber into a first compartment closest to the yoke and a second compartment farthest to the yoke, wherein at least one of the first compartment and second compartment is sealed and the other of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0067] Item 60. The actuator assembly of any one of items 57 to 59, wherein the chambers of the hydraulic actuators and the chamber of the fail safe module are configured to be fixedly attached to the body of the apparatus.

[0068] Item 61. The actuator assembly of any one of items 57 to 60, wherein the hydraulic actuators are configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration.

[0069] Item 62. The actuator assembly of any one of items 57 to 61, wherein the hydraulic actuators are configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0070] Item 63. The actuator assembly of any one of items 57 to 62, wherein, when the hydraulic actuators are not hydraulically actuated, the fail safe module is configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration.

[0071] Item 64. The actuator assembly of any one of items 57 to 63, wherein the central stem moves away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the central stem moves towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0072] Item 65. The actuator assembly of item 64, wherein, when the hydraulic actuators are not hydraulically actuated, the pressure in the first compartment is greater than the pressure in the second compartment, so that the piston of the fail safe module pulls the yoke towards the fail safe module.

[0073] Item 66. The actuator assembly of any one of items 57 to 65, wherein the first compartment is sealed and contains a pressurised gas, preferably at a pressure greater than 150 bars, and the second compartment is pressure equilibrated with the environment, preferably is open to the environment.

[0074] Item 67. The actuator assembly of any one of items 57 to 65, wherein the first compartment is pressure equilibrated with the environment, preferably is open to the environment and the second compartment is sealed and contains a gas, preferably at a pressure less than 150 bars.

[0075] Item 68. The actuator assembly of any one of items 57 to 67, wherein the actuator assembly is configured for use underwater and one of the first compartment and second compartment is pressure equilibrated with the environment, preferably is open to the environment and is configured to be filled with water, preferably with seawater.

[0076] Item 69. The actuator assembly of any one of items 57 to 68, wherein the obstructing member comprises a ball valve and a scotch yoke configured to translate a linear motion of the central stem into a rotational movement of the ball valve.

[0077] Item 70. The actuator assembly of any one of items 57 to 69, wherein the obstructing member comprises or is a shear blade.

[0078] Item 71. The actuator assembly of any one of items 57 to 70, wherein the obstructing member comprises or is a gate valve.

[0079] Item 72. An assembly comprising one or more actuator assemblies according to any one of items 57 to 71 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the hydraulic actuators of each actuator assembly.

[0080] Item 73. An apparatus comprising a body and a central passageway extending along a longitudinal axis of the body, comprising the actuator assembly according to any one of items 57 to 71 connected thereto.

[0081] Item 74. The apparatus of item 73, wherein the apparatus is a topside apparatus.

[0082] Item 75. The apparatus of item 74, wherein the topside apparatus is one of a blowout preventer (BOP), a surface flow tree (SFT), a tension frame (TF), a rig, or a workover control system (WOCS).

[0083] Item 76. The apparatus of item 73, wherein the apparatus is a subsea apparatus.

[0084] Item 77. The apparatus of item 76, wherein the subsea apparatus is one of a blowout preventer (BOP), a well control package (WCP), an emergency disconnect package (EDP), a lower riser package (LRP), an in-line tee (ILT), a high integrity pressure protection system (HIPPS), a manifold, a vertical Xmas tree (VXT), or a horizontal Xmas tree (HXT).

[0085] Item 78. A process of operating the actuator assembly in the apparatus of any one of items 73 to 77, comprising one or more of: hydraulically actuating the hydraulic actuators so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration, thereby clearing the central passageway of the apparatus; hydraulically actuating the hydraulic actuators so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration, thereby closing off the central passageway of the apparatus; causing the obstructing member to transition from the non-obstructing configuration to the obstructing configuration thereby closing off the central passageway of the apparatus, owing to the fail safe module, without hydraulically actuating the hydraulic actuators.

[0086] According to the first aspect, the invention provides a new and different arrangement for actuators comprising a fail safe mechanism. The invention provides a more compact actuator assembly thanks to a fail safe mechanism allowing the actuator assembly to automatically and safely close the central passageway in case of a failure of the one or more hydraulic actuators. The invention obviates the need for a sizeable spring in the fail safe mechanism. Also, the invention makes it possible to use existing reliable actuators and associated devices so that there is no need to requalify existing field proven technology.

[0087] According to the second aspect, the invention provides two parallel hydraulic actuators, which makes the actuator assembly more compact than an in-line hydraulic actuator classical configuration. This configuration reduces the footprint of the apparatus and allows closer valves in the apparatus.

[0088] The invention further makes it possible to remove the need for hydraulic accumulators on temporary equipment which also drives the overall size. Owing to reduced equipment size, air freightable intervention packages may be achieved. It may be easier, quicker and less costly to install and remove packages onto / from rigs, vessels equipped with an actuator assembly according to the invention.Brief description of the drawings

[0089] FIG. 1A-1B show a perspective view of an example of an apparatus comprising multiple actuator assemblies according to the invention, with and without fail safe modules. FIG. 2A-2B show a cross-sectional perspective view of an example of an actuator assembly according to the invention, in a closed configuration and an open configuration. FIG. 3 shows a cross-sectional perspective view of another actuator assembly according to the invention. FIG. 4A-4B schematically show a cross-section of an example of a fail safe module in two different configurations. FIG. 5A-5B schematically show a cross-section of another example of a fail safe module in two different configurations. FIG. 6 schematically shows an example of actuator assembly according to the invention including a hydraulic circuit, in two different configurations. FIG. 7A-7B show a perspective view of another example of an actuator assembly according to the invention, in a closed configuration and an open configuration. FIG. 8A-8B schematically show a partial cross-sectional view of this actuator assembly in two different configurations. FIG. 9A-9B show a perspective view of another example of an actuator assembly according to the invention, in a closed configuration and an open configuration. FIG. 10A-10B schematically show a partial cross-sectional view of this actuator assembly in two different configurations. FIG. 11 schematically shows this actuator assembly together with the hydraulic circuit, in two different configurations. Detailed description

[0090] The invention will now be described in more detail without limitation in the following description.

[0091] An object of the present invention is an actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body.

[0092] The actuator assembly may comprise a sliding stem, an obstructing member fixedly attached to the sliding stem and at least three compartments, namely a first compartment, a second compartment and a third compartment, which have varying volumes depending on the position of the sliding stem.

[0093] When the actuator assembly is connected to the apparatus, the obstructing member may have an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0094] The volume of the first compartment may increase and the volume of the second compartment may decrease when the sliding stem slides in one direction, and the volume of the first compartment may decrease and the volume of the second compartment may increase when the sliding stem slides in another opposite direction. The directions along which the sliding stem slides may be perpendicular to the longitudinal axis of the body.

[0095] Each of the first and second compartments may contain a fluid at a certain pressure. The first compartment may be sealed and the second compartment may be pressure equilibrated with the environment (or the other way around). The pressure in the compartment which is sealed varies as a function of the volume of this compartment, whereas the pressure in the compartment which is pressure equilibrated with the environment is substantially independent from the volume of this compartment (this pressure is substantially equal to the environment pressure).

[0096] Each compartment may be defined by non-deformable walls only. At least one of the non-deformable walls may be movable (slidable), so that the volume in the compartment may vary. For the sake of completeness, as will be described in more detail below, the compartment which is pressure equilibrated with the environment may be in fluid communication with a bladder having a deformable (flexible) wall.

[0097] As a result of one compartment being sealed and the other compartment being pressure equilibrated with the environment, when the actuator assembly is connected to the apparatus, the obstructing member may be biased towards one of the obstructing configuration and of the non-obstructing configuration, preferably towards the obstructing configuration. This bias towards one configuration is due to the existence of a pressure differential between the first compartment and the second compartment if the obstructing member is in the other configuration.

[0098] The third compartment may be feedable with hydraulic fluid and the bias of the obstructing member towards one of the obstructing configuration and of the non-obstructing configuration may be overcome by applying sufficient hydraulic fluid pressure in the third compartment.

[0099] In some embodiments, the third compartment may belong to a hydraulic actuator, while the first and second compartments may belong to a fail safe module which is separate from the hydraulic actuator.

[0100] In this case, the actuator assembly may comprise at least one hydraulic actuator comprising a chamber and a piston configured to slide back and forth within the chamber. The piston may divide the chamber into the third compartment defined above, and a fourth compartment (different from the first, second and third compartments). The actuator assembly may further comprise a fail safe module which may comprise a chamber and a piston configured to slide back and forth within the chamber. The piston of the fail safe module may divide the chamber of the fail safe module into the first compartment defined above (preferably closest to the piston of the at least one hydraulic actuator) and the second compartment defined above (preferably farthest from the piston of the at least one hydraulic actuator). The piston of the at least one hydraulic actuator and the piston of the fail safe module may be fixedly attached to the sliding stem.

[0101] In other embodiments, the hydraulic actuator and the fail safe mechanism may be integrated into a single component. This single component may comprise an outer housing, an inner member fixed within the outer housing, a sleeve fixedly attached to the sliding stem, wherein the sleeve has a flange and is slidable within the outer housing and over the inner member. The first compartment may be delimited by the outer housing and the sleeve; the second compartment may comprise an inner chamber within the inner member and may be further delimited by the sleeve; the third compartment may be delimited by the outer housing, the inner member and the flange of the sleeve. The first compartment and the third compartment may be located on opposite sides of the flange.

[0102] An "apparatus" as disclosed herein refers to an assembly of mechanical parts comprising a collection of smaller mechanical components. Preferably, the apparatus is part of an installation of oil and gas production from a subterranean formation or of an installation for the injection of fluid into a subterranean formation. The subterranean formation may be onshore or offshore, preferably offshore.

[0103] An example of an apparatus is a Vertical Xmas Tree (VXT) 101 as can be seen in FIG. 1A and FIG. 1B.

[0104] The apparatus may be a topside apparatus. "Topside" refers to an apparatus located above the waterline.

[0105] In some embodiments, the topside apparatus can be a blowout preventer (BOP). A BOP is an apparatus configured to monitor oil or gas wells to prevent blowouts.

[0106] In some embodiments, the topside apparatus can be a surface flow tree (SFT). A SFT is an apparatus that provides well control. The SFT is used as an access point to run objects into the well. These objects can be for example cables, wires, etc.

[0107] In some embodiments, the topside apparatus can be a tension frame (TF). A TF is an apparatus that connects the riser to the rig tension system. The riser is a conduit having multiple uses. For example, the riser can be used for tool deployment that is running tools to well, fluid transfer or pressure control.

[0108] In some embodiments, the topside apparatus can be a rig. A rig is a massive apparatus configured to explore for and extract oil or gas from the ground or the ocean floor.

[0109] In some embodiments, the topside apparatus can be a workover control system (WOCS). A WOCS is an apparatus for monitoring and control of subsea installation. The WOCS enables safe and efficient control of installation, intervention, and completion work on subsea wells. It provides hydraulic control of subsea trees.

[0110] The apparatus may be a subsea apparatus. "Subsea" refers to an apparatus located below the waterline. For example, the apparatus may be installed at a water depth from 0 to 1000 m, or from 1000 to 2000 m, or from 2000 to 3000 m, or at a water depth of more than 3000 m.

[0111] In some embodiments, the subsea apparatus can be a blowout preventer (BOP). As previously discussed, the BOP prevents blowouts.

[0112] In some embodiments, the subsea apparatus can be a well control package (WCP). A WCP is a critical apparatus used for well control purposes. For example, during well control incidents, the WCP plays a crucial role in preventing blowouts, managing pressure, and ensuring safety.

[0113] In some embodiments, the subsea apparatus can be an emergency disconnect package (EDP). An EDP is an apparatus that provides disconnect function. The EDP is designed for emergency situations when another apparatus needs to be quickly disconnected from the well. Examples of when this might be necessary include extreme weather conditions that exceed the other apparatus' capability to maintain its position. For example, the EDP is necessary to quickly disconnect a rig that starts to drift. Indeed, it is not wanted that such a rig may pull on the well, so the EDP will release the rig if the latter is drifting, to prevent a spill to sea.

[0114] In some embodiments, the subsea apparatus can be a lower riser package (LRP). A LRP is an apparatus stacked on top of the tree that provides well control function, that is the LRP allows to shut and secure the well. A LRP is very similar to a WCP. For example, if mechanical work is needed in the well, the LRP can secure the well. The LRP can also serve as a mini BOP to protect the well.

[0115] In some embodiments, the subsea apparatus can be an in-line tee (ILT). An ILT is an apparatus package that creates a branched line tie-in point along a pipeline. For example, an ILT is a tee point to connect other tree or manifold on a pipeline. ILT is like a size reduced manifold.

[0116] In some embodiments, the subsea apparatus can be a high integrity pressure protection system (HIPPS). A HIPPS is an apparatus used to prevent another apparatus or part of the well from exceeding its rated pressure level. It acts as a barrier separating the high-pressure section of an apparatus or part from downstream apparatus. For example, the HIPPS can prevent over pressurisation of a pipeline or of the riser. The HIPPS does so by measuring the pressure on either side of the central passageway that is to be obstructed by the obstructing member. If there is any over pressure, the obstructing member will transition to the obstructing configuration so as to close the central passageway to protect the pipeline from suffering any damage from high pressure. Typically, the HIPPS is located between the well and the pipeline, on the seabed.

[0117] In some embodiments, the subsea apparatus can be a manifold. A manifold is an apparatus composed of headers and branched piping used to gather or distribute fluids as needed. Typically, manifolds include valves for controlling fluid flow on or off, and they may also incorporate other flow control devices (such as chokes) if these are not mounted directly on individual subsea trees. The manifold is used to gather production or distribute injection. The manifold is typically located at the bottom of the sea.

[0118] In some embodiments, the subsea apparatus can be a Xmas tree. A Xmas tree is an apparatus comprising an assembly of valves, spools, and fittings used to control the flow of oil or gas from a well. It sits atop the wellhead casing system and represents the interface between the well and the production facility. The Xmas tree regulates pressure, controls flow, and allows access to the wellbore for further completion work when needed. The Xmas tree makes it possible to isolate production or injection in the well, and allows to control the well. Therefore, a Xmas tree is used for production or injection. In offshore and subsea wells, the Xmas tree is often referred to as a subsea tree when positioned on the ocean floor.

[0119] In some embodiments, the subsea apparatus can be a vertical Xmas tree (VXT), i.e. a Xmas tree which is disposed vertically. The advantage is that this kind of orientation requires only one BOP deployment and connection to wellhead during installation but if workover operations like tubing changes are required, the VXT must be removed to install a BOP on top of the well.

[0120] In some embodiments, the subsea apparatus can be a horizontal Xmas tree (HXT). A HXT is a horizontally disposed Xmas tree. The advantage is that the total tree height is lowered but its replacement is more time-consuming and costly. A HXT can thus be preferred when tree replacement is unlikely.

[0121] By "connection to an apparatus" is meant that the actuator assembly can be mounted onto the apparatus. When mounted, the actuator assembly may provide an opening and closing function in the central passageway of the apparatus.

[0122] A "central passageway" refers to an elongated conduit, through which fluid (for example oil or gas) can travel and / or along which an elongated object such as a cable or wire may extend.

[0123] A "hydraulic actuator" refers to a component that is configured to actuate, an element (in this case, an obstructing member) to cause it to transition from one configuration to another configuration, depending on the pressure of a hydraulic fluid in the actuator. Hydraulic actuators are known to have advantages such as high actuating forces, high stroking velocities and high stability. The counterpart is that there is a risk of leakage of the hydraulic fluid making the hydraulic actuator fail to actuate. In some examples, a hydraulic actuator may open or close a valve.

[0124] A "fail safe mechanism" refers to a mechanism which causes the actuator assembly to return to a safe condition in the event of a breakdown or malfunction (such as in the event of a leak of hydraulic fluid). When the obstructing element is a valve, the fail safe mechanism may ensure that the valve is open, or (preferably) may ensure that the valve is closed, in case of failure. In some cases the fail safe mechanism is not integrated in the at least one hydraulic actuator, i.e., there is a fail safe module is comprised within the actuator assembly but separated from the at least one hydraulic actuator. In other cases, the hydraulic actuator and the fail safe mechanism may be integrated into a single component, as mentioned above. As will be further apparent below, the fail safe mechanism may have further functions and in particular may contribute to the normal mode of operation of the actuator assembly in the absence of failure.

[0125] An "obstructing member" refers to any mechanical part that can at least partly close the central passageway of the apparatus, depending on its position or configuration.

[0126] As can be seen in FIG. 1A and 1B, the apparatus may have multiple actuator assemblies mounted thereon. FIG. 1A illustrates a VXT comprising three actuator assemblies, without a fail safe module for the sake of clarity. FIG. 1B illustrates the same apparatus having two fail safe modules (106, 106') attached.

[0127] Several actuator assemblies may be associated with the same central passageway. Alternatively, or additionally, an apparatus may comprise two or more different central passageways (possibly having different longitudinal axes), wherein one or more actuator assemblies are arranged associated with each central passageway.Hydraulic actuator

[0128] The present description of the hydraulic actuator primarily applies to the embodiments wherein the hydraulic actuator is distinct and separate from the fail safe module.

[0129] The actuator assembly comprises at least one hydraulic actuator (at least two hydraulic actuators in the second aspect of the invention). Each hydraulic actuator may comprise a chamber and a piston configured to slide back and forth within the chamber. The chamber of each hydraulic actuator may be divided by the piston into two compartments, having variable volumes. At least one of these compartments corresponds to the third compartment mentioned above. The other compartment may be designated as a fourth compartment. Hydraulic fluid may be present in the third compartment and optionally also present in the fourth compartment. Hydraulic fluid may be more particularly hydraulic liquid, such as water or more preferably oil.

[0130] The chamber of the at least one hydraulic actuator may be configured to be fixedly attached to the body of the apparatus (i.e. so that the chamber is not movable relative to the body of the apparatus).

[0131] The at least one hydraulic actuator may be configured to be hydraulically actuated so as to cause the obstructing member to transition from the obstructing configuration to the non-obstructing configuration. Transitioning the obstructing member from the obstructing configuration to the non-obstructing configuration means clearing the central passageway of the apparatus that was originally at least partially obstructed by the obstructing element. By "hydraulically actuating", is meant feeding high pressure hydraulic fluid to a compartment of the chamber of the hydraulic actuator to move the piston and cause the volume of this compartment to increase.

[0132] The at least one hydraulic actuator may be configured to be hydraulically actuated so as to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration. Transitioning the obstructing member from the non-obstructing configuration to the obstructing configuration means partially or fully closing the central passageway of the apparatus that was originally cleared.

[0133] When the at least one hydraulic actuator is not hydraulically actuated, the fail safe module may be configured to cause the obstructing member to transition from the non-obstructing configuration to the obstructing configuration. The fail safe module may take over the at least one hydraulic actuator to safely close the central passageway of the apparatus.

[0134] The piston of the at least one hydraulic actuator may move away from the fail safe module when the obstructing member transitions from the obstructing configuration to the non-obstructing configuration; and the piston of the at least one hydraulic actuator may move towards the fail safe module when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration.

[0135] When the at least one hydraulic actuator is not hydraulically actuated, the pressure in the first compartment of the fail safe module may be greater than the pressure in the second compartment of the fail safe module, so that the piston of the fail safe module pulls the piston of the at least one hydraulic actuator towards the fail safe module.

[0136] The direction of movement of the piston may be along an actuator axis. The actuator axis may be perpendicular to the longitudinal axis of the body.

[0137] The actuator assembly may comprise a single hydraulic actuator, wherein the piston of the hydraulic actuator is axially aligned with the piston of the fail safe module. This arrangement will be further referred to as the in-line arrangement.

[0138] An example of this in-line arrangement will now be described in more detail with reference to FIG. 3, which shows the actuator assembly connected to an apparatus 101. The actuator assembly comprises a hydraulic actuator 303 comprising a piston 305 configured to slide back and forth in a chamber 304. A piston rod 308 may be fixed to (preferably integral with) the piston 305 and also slide back and forth. The piston rod 308 may be positioned partially within the chamber 304 and partially out of the chamber 304. The piston rod 308 may extend along the actuator axis.

[0139] A central stem 307 (which is an embodiment of the sliding stem mentioned above) may be connected at a first end to the piston 305 of the hydraulic actuator 303 and may be configured to extend through the central bore of a bonnet 306. The central stem 307 may extend along the actuator axis. The central stem 307 may be connected at a second end (opposite the first end) to an obstructing member 301. The hydraulic actuator 303 may have a retracted position (piston 305 closest to the passageway 302 of the apparatus 101, as can be seen on FIG. 3, the piston rod 308 being at a position of zero or minimum extension outside of the chamber 304) and an extended position (piston 305 farthest from the passageway 302 of the apparatus 101, the piston rod 308 being at a position of maximum extension outside of the chamber). The obstructing member 301 may be in the non-obstructing configuration and therefore the central passageway 302 of the apparatus 101 may be clear (open) when the hydraulic actuator 303 is in the retracted position (as shown on FIG. 3), and the obstructing member 301 may be in the obstructing configuration and therefore the central passageway 302 of the apparatus 101 may be partially or fully closed when the hydraulic actuator 303 is in the extended position. However, the opposite orientation is also possible (obstructing configuration in the retracted position and non-obstructing configuration in the extended position).

[0140] The fail safe module may comprise a piston rod fixed to (preferably integral with) the piston as will be described in more detail below. The actuator assembly may comprise a connecting member 310 fixed on the one hand to an end of the piston rod 308 of the hydraulic actuator 303 (which is opposite the piston 305 of the hydraulic actuator 303); and fixed on the other hand to an end of the piston rod of the fail safe module (which is opposite the piston of the fail safe module); in such a way that the piston of the fail safe module is attached to the piston 305 of the hydraulic actuator 303 via the piston rod of the fail safe module, the connecting member 310 and the piston rod 308 of the hydraulic actuator 303.

[0141] The actuator assembly may be mounted on the apparatus 101 for example by screwing the bonnet 306 onto the body of the apparatus 101 by way of screws 309, 309'. The chamber 304 of the hydraulic actuator 303 may itself be fixed to the bonnet 306. The chamber of the fail safe module (not shown) may be fixed to the bonnet 306 or preferably to the chamber 304 of the hydraulic actuator 303, for example via a locking mechanism 311 present on the outside surface of the chamber 304 of the hydraulic actuator 303. Therefore, the bonnet 306, the chamber 304 of the hydraulic actuator 303 and the chamber of the fail safe module (not shown) may be fixedly attached to the body of the apparatus 101.

[0142] On the other hand, the central stem 307, the piston 305 and piston rod 308 of the hydraulic actuator 303, the connecting member 310 and the piston of the fail safe module (not shown) may be fixed together and may slide along a sliding direction relative to the body of the apparatus 101: the central stem 307 may slide within the central bore of the bonnet 306, the piston 305 and piston rod 308 of the hydraulic actuator 303 may slide within the chamber 304 of the hydraulic actuator 303, and the piston and piston rod of the fail safe module may slide within the chamber of the fail safe module. The sliding direction may be perpendicular to the longitudinal axis of the body of the apparatus 101. The sliding direction may be along the actuator axis. The obstructing member 301 may be in a fixed position relative to the central stem 307 so that this obstructing member 301 also slides together with the central stem 307, but other implementations of the obstructing member are possible, as will appear based on the further description below.

[0143] The central stem 307 may be aligned with the piston rod 308 of the hydraulic actuator 303. The piston rod of the fail safe module may be aligned with the piston rod 308 of the hydraulic actuator 303. The central stem 307, piston rod 308 of the hydraulic actuator 303 and piston rod of the fail safe module may all be aligned together.

[0144] Alternatively, the actuator assembly may comprise at least two hydraulic actuators, preferably at least two parallel hydraulic actuators. In this embodiment, the at least two hydraulic actuators may be simultaneously actuated to move the obstructing member. This arrangement will be further referred to as the parallel arrangement.

[0145] An example of this parallel arrangement will now be described in more detail with reference to FIG. 2A and FIG. 2B. FIG. 2A shows the actuator assembly in the non-obstructing configuration and FIG. 2B shows the actuator assembly in the obstructing configuration.

[0146] The apparatus 101 comprises an actuator assembly connected thereto. The actuator assembly may comprise a first hydraulic actuator 203 comprising a piston 205 configured to slide back and forth in a chamber 204, and a second hydraulic actuator 203' comprising a piston 205' configured to slide back and forth in a chamber 204'. A piston rod 209, 209' may be fixed to (preferably integral with) each respective piston 205, 205' and also slide back and forth. Each piston rod 209, 209' may be positioned partially within the respective chamber 204, 204' and partially out of the respective chamber 204, 204'.

[0147] The two pistons 205, 205' of the hydraulic actuators 203, 203' may be connected to a yoke 102 (via the extremities of the piston rods 209, 209' opposite the pistons 205, 205'). A central stem 207 (which is an embodiment of the sliding stem mentioned above) may be connected at a first end to the yoke 102 and may be configured to extend through the central bore of a bonnet 206. The central stem 207 may be connected at a second end to an obstructing member 201. The central stem 207 may extend along an actuator axis.

[0148] The hydraulic actuators 203, 203' may have a retracted position (piston 205, 205' closest to the passageway 202 of the apparatus 101, as can be seen on FIG. 2B, the piston rods 209, 209' being at a position of zero or minimum extension outside of the respective chambers 204, 204') and an extended position (piston 205, 205' farthest from the passageway 202 of the apparatus 101, as can be seen on FIG. 2A, the piston rods 209, 209' being at a position of maximum extension outside of the respective chambers 204, 204').

[0149] When the hydraulic actuators 203, 203' are in the retracted position as can be seen on FIG. 2B, the obstructing member 201 may be in the non-obstructing configuration and therefore the central passageway 202 of the apparatus 101 may be open. When the hydraulic actuators 203, 203' are in the extended position as can be seen on FIG. 2A, the obstructing member 201 may be in the obstructing configuration and therefore the central passageway 202 of the apparatus 101 may be partially or fully closed. However, the opposite orientation is also possible (obstructing configuration in the retracted position and non-obstructing configuration in the extended position).

[0150] The fail safe module may comprise a piston rod fixed to (preferably integral with) the piston as will be described in more detail below. The actuator assembly may further comprises a cradle 104 adapted for fixing the chamber of the fail safe module (not shown in the drawings) in such a way that the piston of the fail safe module is attached to the yoke 102 of the hydraulic actuators 203, 203', via the piston rod of the fail safe module. The cradle 104 may be fixed to the bonnet 206 by rods 208, 208'. The rods 208, 208' may extend through respective holes in the yoke 102.

[0151] The actuator assembly may be mounted on the apparatus 101 for example by attaching the bonnet 206 onto the body of the apparatus 101. The chambers 204, 204' of the hydraulic actuators 203, 203' may also be directly attached to the body of the apparatus 101 or may be attached to the bonnet 206. The chamber of the fail safe module (not shown) may be fixed to the cradle 104. Therefore, the bonnet 206, the chambers 204, 204' of the hydraulic actuators 203, 203' and the chamber of the fail safe module (not shown) may be fixedly attached to the body of the apparatus 101.

[0152] On the other hand, the central stem 207, the pistons 205, 205' (and piston rods 209, 209') of the hydraulic actuators 203, 203', the yoke 102 and the piston and piston rod of the fail safe module (not shown) may be fixed together and may slide along parallel sliding directions relative to the body of the apparatus 101: the central stem 207 may slide within the central bore of the bonnet 206, the piston 205, 205' (and piston rods 209, 209') of each hydraulic actuator 203, 203' may slide within the respective chamber 204, 204' of the hydraulic actuator 203, 203', the yoke 102 may slide onto the rods 208, 208' and the piston and piston rod of the fail safe module may slide within the chamber of the fail safe module. All of these elements may slide according to parallel sliding directions which may be perpendicular to the longitudinal axis of the body of the apparatus 101 (and along or parallel to the actuator axis). The obstructing member 201 may be in a fixed position relative to the central stem 207 so that this obstructing member 201 also slides together with the central stem 207, but other implementations of the obstructing member are possible, as will appear based on the further description below.

[0153] The central stem 207 may be aligned with the piston rod of the fail safe module along the actuator axis. The central stem 207 and the pistons rods 209, 209' of the hydraulic actuators 203, 203' (and optionally the rods 208, 208') may be arranged in parallel. The central stem 207 may be positioned between the piston rods 209, 209' of the hydraulic actuators 203, 203'. The central stem 207 may be positioned between the rods 208, 208'.

[0154] This parallel arrangement saves additional space compared to the in-line arrangement. Moreover, the at least two parallel hydraulic actuators may be smaller and lighter than a hydraulic actuator in the in-line arrangement. Indeed, as there are at least two hydraulic actuators combined, less force is required from each, and they can thus be reduced in size.

[0155] Referring back to FIG. 1A and 1B, an apparatus 101 is shown, which comprises three different actuator assemblies according to FIG. 2A and 2B. Each of these actuators assemblies comprises a yoke 102, 102' and 102" and a fixed cradle 104, 104' and 104".

[0156] On each fixed cradle 104, 104' and 104", a fail safe module 106, 106' is attached. One part of the fail safe module 106, 106' (namely the chamber) is connected to the fixed cradle 104, 104', and another part of the fail safe module 106, 106' (namely the piston rod) is connected to the yoke 102, 102'.Fail safe module

[0157] The present description of the fail safe module primarily applies to the embodiments wherein the hydraulic actuator is distinct and separate from the fail safe module.

[0158] As already mentioned above, the actuator assembly may comprise a fail safe module comprising a chamber and a piston configured to slide back and forth within the chamber. A piston rod may be fixed to (preferably integral with) this piston and also slide back and forth within the chamber. The piston of the fail safe module may divide the chamber of the fail safe module into a first compartment (preferably closest to the piston of the at least one hydraulic actuator) and a second compartment (preferably farthest from the piston of the at least one hydraulic actuator), having variable volumes, as defined above. A piston rod may be fixed to (preferably integral with) the piston. The piston rod may be positioned partially within the chamber and partially out of the chamber of the fail safe module. The volumes of the first and second compartments vary depending on the position of the piston in the chamber. The piston rod may extend in the first compartment of the fail safe module.

[0159] The fail safe module may be a passive device, i.e. it does not contain hydraulic fluid and is not fluidically connected to a hydraulic circuit.

[0160] Preferably, the fail safe module does not comprise any compressive spring.

[0161] At least one of the first compartment and second compartment of the fail safe module may be sealed and the other of the first compartment and second compartment of the fail safe module may be open to the environment. The environment may be the air, the ground, or the sea. "Open to the environment' means that there are one or more holes in the chamber allowing fluid to enter or exit one of the first compartment and second compartment of the fail safe module from or to the environment, so that pressure in said first compartment or second compartment may be equilibrated with the environment pressure. The other compartment may be "sealed", i.e. may not allow exchange of fluid and thus pressure equilibration with the environment.

[0162] The environment may be the sea, so that the compartment open to the environment may be filled with seawater. In this case the fail safe module may comprise a filter across the one or more holes, to protect the chamber of the fail safe module from any ingress of solids.

[0163] As an alternative to having one compartment of the two compartments open to the environment, it is also possible to enable an indirect pressure equilibration between this compartment and the environment. For example, a bladder may be positioned on the outside of the fail safe module so that the compartment is in fluidic communication with the bladder. Control fluid may be present in the bladder and in the compartment. The bladder may comprise one or more flexible walls, so that the environment pressure (for example hydrostatic pressure if the module is underwater) equilibrates with the pressure within the compartment. The other compartment may be sealed and unequilibrated with the environment pressure.

[0164] The fail safe module may be configured to transition between two positions. The first one may be a retracted position. In this configuration, the second compartment has a minimum volume (and the first compartment has a maximum volume), in other words, the piston of the fail safe module is in the position farthest from the chamber of the at least one hydraulic actuator and the piston rod is at a position of zero or minimum extension outside of the chamber of the fail safe module. The second one may be an extended position. In this configuration, the first compartment has a minimum volume (and the second compartment has a maximum volume), in other words, the piston of the fail safe module is in the position closest to the chamber of the at least one hydraulic actuator and the piston rod is at a position of maximum extension outside of the chamber of the fail safe module. Preferably, when the fail safe module is in the extended position, the at least one hydraulic actuator is in the retracted position; and when the fail safe module is in the retracted position, the at least one hydraulic actuator is in the extended position. Preferably, when the fail safe module is in the extended position, the obstructing member is in the non-obstructing configuration; and when the fail safe module is in the retracted position, the obstructing member is in the obstructing configuration. However, the opposite orientation is also possible.

[0165] Preferably, the pressure in the first compartment and the pressure in the second compartment may be such that the piston of the fail safe module may be biased towards the retracted position. But the piston may be drawn to the extended position if the at least one hydraulic actuator exerts a force which overcomes the pressure differential between the first and second compartments, as will be described in more detail below.

[0166] In a first variation, the first compartment of the fail safe module may be sealed and contain a pressurised gas, which is preferably at a pressure greater than a pressure threshold when the fail safe module is in the retracted position. The pressure threshold may be for example from 100 to 250 bars, such as from 150 to 200 bars,. The second compartment of the fail safe module may be open to the environment (e.g. the atmosphere, or seawater). The pressurised gas may be nitrogen or air. The pressure of the pressurised gas in the first compartment may be adjusted before deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, the piston diameters and the piston surface areas. This implementation is particularly useful for a topside apparatus, or for an underwater apparatus which lies in relatively shallow water (for example at a depth from 0 to 1500 m). The second compartment is then at hydrostatic pressure. When substantially no force is exerted by the hydraulic actuator(s), the pressure in the first compartment may be higher than the pressure in the second compartment, thereby pulling the piston in the retracted position.

[0167] Alternatively, in a second variation, the first compartment of the fail safe module may be open to the environment (e.g., seawater) and the second compartment of the fail safe module may be sealed and contain a gas (for example nitrogen or air), pressurised or not, and which is preferably at a pressure less than a pressure threshold, for example less than 150 bars such as from 1 bar to 150 bars, more preferably at a pressure of approximately 1 bar when the fail safe module is in the retracted position. The pressure of the gas in the second compartment may be adjusted prior to deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, the piston diameters and the piston surface areas. This implementation is particularly useful for a subsea apparatus which lies in relatively deep water (for example at a depth at least 1500 m, such as from 1500 to 3000 m). The first compartment is then at hydrostatic pressure. Again, when substantially no force is exerted by the hydraulic actuator(s), the pressure in the first compartment may be higher than the pressure in the second compartment, thereby pulling the piston in the retracted position.

[0168] The first variation is now disclosed in more detailed by referring to FIG. 4A and 4B. The fail safe module 106 may comprise a piston 401 connected to (such as integral with) a piston rod 402, as described above. The fail safe module 106 may further comprise a chamber divided by the piston into a first compartment 403 and a second compartment 404. The second compartment 404 may be open to the environment 408. A filter 406 may protect the second compartment 404 from any ingress of solids. As an alternative, the second compartment may be isolated from the environment by a bladder to enable equilibration with the environment pressure, as mentioned above. The fail safe module 106 may further comprise a compressed gas port 405 communicating with the first compartment 403, which may be used for loading the first compartment 403 with compressed gas, such as compressed nitrogen or air, before sealing the first compartment 403. FIG. 4A shows the piston 401 in the extended position. FIG. 4B shows the piston 401 in the retracted position. The transition from the retracted to extended position may be caused by actuating the one or more hydraulic actuators (not shown). The transition from the extended to retracted position may be caused, in the absence of actuation of the one or more hydraulic actuators, by the pressure in the first compartment 403 being greater than the pressure in the second compartment 404, causing the piston 401 to move so as to reduce the volume of the second compartment 404 and increase the volume of the first compartment 403. The volume of the second compartment 404 may then reach a minimum, non-zero value when the pressure in the first compartment 403 is equal to the pressure of the environment 408 (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartment 404 may reach a minimum value without reducing the pressure differential between the compartments to zero if the movement of the piston 401 is stopped by a mechanical stop in the chamber. Preferably, the obstructing member may be in an obstructing configuration when the fail safe module 106 is in the retracted position. The fail safe module 106 may further comprise a pressure gauge 407 configured to measure the pressure in the first compartment 403.

[0169] The second variation is now disclosed in more detailed by referring to FIG. 5A and 5B. The fail safe module 106 may comprise a piston 401' connected to (such as integral with) a piston rod 402', as described above. The fail safe module 106 may further comprise a chamber divided by the piston into a first compartment 403' and a second compartment 404'. The first compartment 403' may be open to the environment 408'. A filter 406' may protect the first compartment 403' from any ingress of solids. As an alternative, the first compartment may be isolated from the environment by a bladder to enable equilibration with the environment pressure, as mentioned above. The fail safe module 106 may further comprise a compressed gas port 405' communicating with the second compartment 404', which may be used for loading the second compartment 404' with compressed gas, such as compressed nitrogen or air, before sealing the second compartment 404'. Alternatively, the fail safe module 106 may be devoid of such compressed gas port 405', especially in case a gas at atmospheric pressure is present in the second compartment 404'. FIG. 5A shows the piston 401' in the extended position. FIG. 5B shows the piston 401' in the retracted position. The transition from the retracted to extended position may be caused by actuating the one or more hydraulic actuators (not shown). The transition from the extended to retracted position may be caused, in the absence of actuation of the one or more hydraulic actuators, by the pressure in the first compartment 403' being greater than the pressure in the second compartment 404', causing the piston 401' to move so as to reduce the volume of the second compartment 404' and increase the volume of the first compartment 403'. The volume of the second compartment 404' may then reach a minimum, non-zero value when the pressure in the second compartment 404' is equal to the pressure of the environment (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartment 404' may reach a minimum value without reducing the pressure differential between the compartments to zero if the movement of the piston 401' is stopped by a mechanical stop in the chamber. Preferably, the obstructing member may be in an obstructing configuration when the fail safe module 106 is in the retracted position. The fail safe module 106 may further comprise a pressure gauge 407' configured to measure the pressure in the second compartment 404'.

[0170] When the apparatus is subsea, the fail safe module may be connected in situ to the actuator assembly already partly mounted to the apparatus, by a remotely operated underwater vehicle (ROV). An ROV is a specialized robotic system designed to perform tasks in deep water, where human divers cannot safely operate. The fail safe module may also be ROV recoverable and ROV replaceable. This allows to only replace the fail safe module in case it no longer works properly instead of replacing the overall actuator assembly or the entire apparatus.Fail safe mechanism integrated with a hydraulic actuator as a single component

[0171] Making reference to FIG. 7A, 7B, 8A and 8B, the actuator assembly 600 may comprise an outer housing 609 and an inner member 614 fixed within the outer housing 609. The outer housing 609 and inner member 614 may extend along an actuator axis. The actuator axis may be perpendicular to the longitudinal axis of the body of the apparatus.

[0172] An inner space such as a substantially cylindrical inner space may be present in the outer housing 609 and the inner member 614 may be placed within this space. The inner member 614 may comprise an end wall 615 and a tubular extension 616. The end wall 615 of the inner member 614 may be fixed at one extremity of the outer housing 609 along the actuator axis, and the tubular extension 616 may extend within the inner space of the outer housing 609, along the actuator axis and towards the opposite end of the outer housing. The end wall 615 may project radially outwardly from the tubular extension 616. The end wall 615 may close off the extremity of the outer housing 609.

[0173] The outer periphery of the tubular extension 616 may be at a distance from the inner wall of the outer housing 609.

[0174] A sleeve 618 may be slidable (back and forth) within the outer housing 609 and over the inner member 614. More precisely, the sleeve 618 may be slidable over the tubular extension 616. The sleeve 618 may comprise a flange 620, a tubular portion 621 and an end wall 617. The tubular portion 621 may extend along the actuator axis. At least the flange 620 and part or all of the tubular portion 621 may be placed within the outer housing. The sleeve 618 may partly protrude from the outer housing 609, more precisely from an extremity of the outer housing 609 which is opposite the extremity at which the end wall 615 of the inner member 614 is fixed. The end wall 617 may be located out of the outer housing 609. The flange 620 may remain at all times within the outer housing 609. The extent to which the tubular portion 621 is outside of the outer housing 609 may depend on the position of the sleeve 618 along the actuator axis.

[0175] The sleeve 618 may cooperate with the outer housing 609 and the inner member 614 so as to define the three abovementioned compartments. These three compartments are isolated from each other and have variable volumes.

[0176] The first compartment 603 may be delimited by the outer housing 603 and the sleeve 618 (more precisely, the flange 620 and possibly the outer periphery of the tubular portion 603).

[0177] The first compartment 603 may be pressure equilibrated with the environment 608 (for example seawater). For example, it may be open to the environment. To this end, at least one opening 622 in the outer housing 609 may be provided to allow the exchange of fluid with the environment 608. The entire description concerning pressure equilibration contained in the above section "Fail safe module" applies similarly. In particular, a filter may be provided, or indirect pressure equilibration using a bladder may be used.

[0178] The second compartment 604 may be formed by an inner chamber 619 within the inner member 614, together with an inner space 610 within the sleeve 618. More precisely, the inner chamber 619 of the inner member 614 may extend along the tubular extension 616. The inner space 610 within the sleeve 618 may extend along and within the tubular portion 621. The size of the inner space 610 within the sleeve 618 varies as the sleeve 618 slides over the inner member 614, thereby ensuring that the volume of the second compartment 604 is variable.

[0179] The second compartment 604 may be sealed, as defined above. The second compartment 604 may contain a gas (for example nitrogen or gas), pressurised or not, and which is preferably at a pressure less than a pressure threshold, for example less than 150 bars such as from 1 bar to 150 bars, more preferably at a pressure of approximately 1 bar when sleeve 618 is in the extended position. The pressure of the gas in the second compartment may be adjusted prior to deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, and the dimensions of the actuator assembly. This implementation is particularly useful for a subsea apparatus which lies in relatively deep water (for example at a depth at least 1500 m, such as from 1500 to 3000 m), wherein the first compartment is at hydrostatic pressure.

[0180] A compressed gas port 605 may be present in the inner member 614, preferably on the end wall 615 of the inner member 614, which may be used for loading the second compartment 604 with compressed gas, such as compressed nitrogen or air, before sealing the second compartment 604. Alternatively, the actuator assembly may be devoid of such compressed gas port 605, especially in case a gas at atmospheric pressure is present in the second compartment 604. A pressure gauge may be connected to a pressure gauge port 623, preferably also on the end wall 615 of the inner member 614 and may be configured to measure the pressure in the second compartment 604.

[0181] Of course, the opposite can also be implemented, i.e. the first compartment may be sealed and the second compartment may be pressure equilibrated with the environment.

[0182] The third compartment 611 may be delimited by the outer housing 609, the inner member 614 and the flange 620 of the sleeve 618. The third compartment 611 may contain hydraulic fluid and may be fluidically connected to a hydraulic circuit.

[0183] The sleeve 621 may be fixed to the sliding stem 607 (which is itself connected to the obstructing member 601 as described elsewhere). The sliding stem 607 may extend along the actuator axis, away from the outer housing 609 and sleeve 621.

[0184] The outer housing 609 may be fixedly attached to the body of the apparatus, for example via a bonnet 606. The sliding stem 607 may slide within a bore in the bonnet 606.

[0185] Preferably, the actuator assembly does not comprise any compressive spring.

[0186] The actuator assembly may be configured to transition between two positions.

[0187] The first one may be a retracted position, as shown in FIG. 7B and 8B. In this configuration, the second compartment 604 has a minimum volume, the third compartment 611 has a minimum volume, and the first compartment 603 has a maximum volume; the sleeve 618 is in the position farthest from the central passageway 602 of the apparatus and the sleeve 618 is at a position of zero or minimum extension outside of the outer housing 609.

[0188] The second one may be an extended position, as shown in FIG. 7A and 8A. In this configuration, the first compartment 603 has a minimum (or zero) volume, the second compartment 604 has a maximum volume and the third compartment 611 has a maximum volume; the sleeve 618 is in the position closest to the central passageway 602 of the apparatus and the sleeve 618 is at a position of maximum extension outside of the outer housing 609.

[0189] Preferably, when the actuator assembly is in the extended position, the obstructing member 601 is in the non-obstructing configuration; and when the actuator assembly is in the retracted position, the obstructing member 601 is in the obstructing configuration. However, the opposite is also possible.

[0190] Preferably, the pressure in the first compartment 603 and the pressure in the second compartment 604 may be such that the sleeve 621 is biased towards the retracted position. But the sleeve 621 may be drawn to the extended position if the hydraulic fluid pressure in the third compartment 611 is sufficient to overcome the pressure differential between the first and second compartments 603, 604.

[0191] A hydraulic fluid port 612 may be present in the outer housing 609 and / or in the inner member 614, preferably on the end wall 615 of the inner member 614 as illustrated. The hydraulic fluid port 612 may be configured to fluidically connect the third compartment 611 to a hydraulic fluid circuit and thus to feed hydraulic fluid to the third compartment 611 or collect hydraulic fluid from the third compartment 611, thereby adjusting hydraulic fluid pressure within the third compartment 611.

[0192] A pressure gauge may be connected to a pressure gauge port 613, preferably also on the end wall 615 of the inner member 614 and may be configured to measure the pressure in the third compartment 611.

[0193] The transition from the retracted to extended position may be caused by feeding hydraulic fluid to the third compartment 611, thereby increasing hydraulic fluid pressure within this third compartment 611. The hydraulic fluid presses against the flange 620 of the sleeve 618, causing the sleeve 618 to slide away from the end wall 615 of the inner member 614. The flange 620 therefore acts as a piston in the hydraulic actuator. The flange 620 may abut against a stopping element of the outer housing 609 in the extended position, so that the sleeve 618 may not completely dislodge from the outer housing 609.

[0194] The transition from the extended to retracted position may be caused by releasing the hydraulic fluid pressure in the third compartment 611. As a result of the pressure in the first compartment 603 being greater than the pressure in the second compartment 604, the sleeve 618 is caused to move so as to reduce the volume of the second compartment 604 and third compartment 611 (hydraulic fluid may be withdrawn from the third compartment 611 as a result) and so as to increase the volume of the first compartment 603. The volume of the second compartment 604 may reach a minimum, non-zero value when the pressure in the second compartment 604 is equal to the pressure of the environment (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartment 604 may reach a minimum value without reducing the pressure differential between the first and second compartments to zero, if the movement of the sleeve 621 is stopped by a mechanical stop (such as the end wall 617 of the sleeve 618 abutting against the inner member 614 or the flange 620 of the sleeve 618 abutting against a stopping element of the outer housing 609.

[0195] When the apparatus is subsea, the actuator assembly may be connected in situ to the apparatus, by a ROV. The actuator assembly may also be ROV recoverable and ROV replaceable.

[0196] The ROV may also connect a hydraulic fluid line to the hydraulic fluid port 612. The hydraulic fluid line may be fluidically connected to a hydraulic circuit, for example a hydraulic circuit present in the apparatus itself.

[0197] Making reference to FIG. 9A, 9B, 10A and 10B, in another variation of the fail safe mechanism being integrated with the hydraulic actuator as a single component, the actuator assembly 700 may comprise an outer housing 709, within which are arranged at least a first chamber referred to as an active chamber 710 and at least a second chamber referred to as a passive chamber 714. In each chamber, a respective piston connected to (such as integral with) a piston rod is present, wherein the piston divides the chamber in respective compartments.

[0198] All piston rods may be arranged in parallel, parallel to an actuator axis. The actuator axis may be perpendicular to the longitudinal axis of the body of the apparatus.

[0199] There can be a single active chamber and a single passive chamber. Alternatively, there can be a single active chamber and two or more passive chambers. In the illustrated embodiment, there is a single active chamber 710 and two passive chambers 714, 714'. The passive chambers 714, 714' may extend on opposite sides of the active chamber 710.

[0200] A respective piston 715, 715' connected to (such as integral with) a piston rod 716, 716' may slide within each passive chamber 714, 714' along the actuator axis.

[0201] A piston 717 connected to (such as integral with) a piston rod 718 may slide within the active chamber 710 along the actuator axis.

[0202] The first compartment 703, 703' as defined above may be located in the or each passive chamber 714, 714' and extend on one side of the respective piston 715, 715', such as between said piston 715, 715' and the sliding stem 707 (or the obstructing member 701). When there are two (or more) passive chambers 714, 714', there are therefore two (or more) respective first compartments 703, 703' as defined above.

[0203] The or each first compartment 703, 703' may be pressure equilibrated with the environment 708 (for example seawater). For example, it may be open to the environment. To this end, at least one opening in the outer housing 709 may be provided to allow the exchange of fluid with the environment 708. The entire description concerning pressure equilibration contained in the above section "Fail safe module" applies similarly. In particular, a filter may be provided, or indirect pressure equilibration using a bladder may be used. It is possible for the first compartments 703, 703' to fluidically communicate together. For example, a single opening in the outer housing 709 may be provided to allow the exchange of fluid between the environment 708 and all of these compartments.

[0204] The second compartment 704, 704' as defined above may be located in the or each passive chamber 714, 714' and extend on one side of the respective piston 715, 715', opposite the first compartment 703, 703'. When there are two (or more) passive chambers 714, 714', there are therefore two (or more) second compartments 704, 704' as defined above.

[0205] The or each second compartment 704, 704' may be sealed, as defined above. The or each second compartment 704, 704' may contain a gas (for example nitrogen or gas), pressurised or not, and which is preferably at a pressure less than a pressure threshold, for example less than 150 bars such as from 1 bar to 150 bars, more preferably at a pressure of approximately 1 bar when the actuator in the extended position. The pressure of the gas in the or each second compartment may be adjusted prior to deployment. The pressure threshold may be a function of the surrounding water depth which is expected when the actuator assembly is positioned underwater, the well pressure, and the dimensions of the actuator assembly. This implementation is particularly useful for a subsea apparatus which lies in relatively deep water (for example at a depth at least 1500 m, such as from 1500 to 3000 m), wherein the first compartment is at hydrostatic pressure.

[0206] A compressed gas port 705, 705' may be present on the outer housing 709, preferably on an end wall facing away from the sliding stem 707 and obstructing member 701, which may be used for loading the or each respective second compartment 704, 704' with compressed gas, such as compressed nitrogen or air, before sealing the second compartment 704, 704'. Alternatively, the actuator assembly may be devoid of such compressed gas port 705, 705', especially in case gas at atmospheric pressure is present in the or each second compartment 704, 704'.

[0207] Of course, the opposite can also be implemented, i.e. the first compartment(s) may be sealed and the second compartment(s) may be pressure equilibrated with the environment.

[0208] The third compartment 711 may be located in the active chamber 710 (or a third compartment may be located in each active chamber, in case there are several), and extend on one side of the associated piston 717, more preferably on the side which is not between said piston 717 and the sliding stem 707 and obstructing member 701

[0209] The third compartment 711 may contain hydraulic fluid and may be fluidically connected to a hydraulic circuit.

[0210] The compartment in the active chamber 710 which lies on the opposite side of the piston 717 (relative to the third compartment 711) may be sealed, or may be also fluidically connected to the hydraulic circuit, or may be open to the environment. It case it is open to the environment, it is possible for this compartment and for the or each first compartment 703, 703' to fluidically communicate together. For example, a single opening in the outer housing 709 may be provided to allow the exchange of fluid between the environment 708 and all of these compartments.

[0211] The outer housing 709 may be fixedly attached to the body of the apparatus, for example via a bonnet 706.

[0212] The sliding stem 707 may slide within a bore in the bonnet 706.

[0213] Preferably, the actuator assembly does not comprise any compressive spring.

[0214] The piston rods 716, 716', 718 associated with the passive chambers 714, 714' and active chamber 710 may be fixedly connected to the sliding stem 707, preferably via a transversal connector 713 located outside of the outer housing 709. As a result, all corresponding pistons 715, 715', 717 may concurrently slide back and forth in their respective chambers.

[0215] The actuator assembly may be configured to transition between two positions.

[0216] The first one may be a retracted position, as shown in FIG. 9B and 10B. In this configuration, the or each second compartment 704, 704' has a minimum volume, the third compartment 711 has a minimum volume, and the or each first compartment 703, 703' has a maximum volume; all pistons 715, 715', 717 are in a position farthest from the central passageway 702 of the apparatus and the piston rods 716, 716', 718 are at a position of zero or minimum extension outside of the outer housing 709.

[0217] The second one may be an extended position, as shown in FIG. 9A and 10A. In this configuration, the or each first compartment 703, 703' has a minimum (or zero) volume, the or each second compartment 704, 704' has a maximum volume and the third compartment 711 has a maximum volume; all pistons 715, 715', 717 are in a position closest to the central passageway 702 of the apparatus and the sleeve piston rods 716, 716', 718 are at a position of maximum extension outside of the outer housing 709.

[0218] Preferably, when the actuator assembly is in the extended position, the obstructing member 701 is in the non-obstructing configuration; and when the actuator assembly is in the retracted position, the obstructing member 701 is in the obstructing configuration. However, the opposite is also possible.

[0219] Preferably, the pressure in the first compartments 703, 703' and the pressure in the second compartments 704, 704' may be such that the sliding stem 707 is biased towards the retracted position. But the sliding stem 707 may be drawn to the extended position if the hydraulic fluid pressure in the third compartment 711 is sufficient to overcome the pressure differential between the first and second compartments.

[0220] A hydraulic fluid port 712 may be present in the outer housing 709 and may be configured to fluidically connect the third compartment 711 to a hydraulic fluid circuit and thus to feed hydraulic fluid to the third compartment 711 or collect hydraulic fluid from the third compartment 711, thereby adjusting hydraulic fluid pressure within the third compartment 711.

[0221] A pressure gauge may be connected to a pressure gauge port and may be configured to measure the pressure in the third compartment.

[0222] The transition from the retracted to extended position may be caused by feeding hydraulic fluid to the third compartment 711, thereby increasing hydraulic fluid pressure within this third compartment 711, so that the hydraulic fluid presses against the piston 717.

[0223] The transition from the extended to retracted position may be caused by releasing the hydraulic fluid pressure in the third compartment 711. As a result of the pressure in the first compartments 703, 703' being greater than the pressure in the second compartments 704, 704', the sliding stem 707 together with all rods 716, 716', 718 are caused to move so as to reduce the volume of the second compartments 704, 704' and third compartment 711 (hydraulic fluid may be withdrawn from the third compartment 711 as a result) and so as to increase the volume of the first compartments 703, 703'. The volume of the second compartment 704, 704' may reach a minimum, non-zero value when the pressure in the second compartments 704, 704' is equal to the pressure of the environment (e.g. hydrostatic pressure underwater). Alternatively, the volume of the second compartments 704, 704' may reach a minimum value without reducing the pressure differential between the first and second compartments to zero, if the movement is stopped by a mechanical stop (such as the pistons 715, 715' abutting against an inner wall of the respective chambers).

[0224] When the apparatus is subsea, the actuator assembly may be connected in situ to the apparatus, by a ROV. The actuator assembly may also be ROV recoverable and ROV replaceable.

[0225] The ROV may also connect a hydraulic fluid line to the hydraulic fluid port 712. The hydraulic fluid line may be fluidically connected to a hydraulic circuit, for example a hydraulic circuit present in the apparatus itself.

[0226] The benefit of this arrangement is that the sealed compartments are only subjected to hydrostatic pressure and not subjected to the sum of hydrostatic pressure and hydraulic pressure.Obstructing member

[0227] The actuator assembly further comprises an obstructing member connected to the sliding stem.

[0228] In some embodiments, the obstructing member is connected to the piston of the at least one hydraulic actuator, by way of the central stem in the in-line arrangement, and by way of the piston rods, yoke and central stem in the parallel arrangement. The obstructing member has, when the actuator assembly is connected to the apparatus, and depending on the position of the sliding stem, an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed; and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0229] In the non-obstructing configuration, fluid (and / or objects) may move along the central passageway.

[0230] Preferably, in the obstructing configuration, the central passageway is fully obstructed, which means that the passage of fluid along the central passageway is fully blocked. Alternatively, it is also possible for the obstructing element to only partially obstruct the central passageway in the obstructing configuration. In this case, fluid (and / or) objects may still move along the central passageway, but the opening available for this movement within the central passageway has a reduced size relative to the non-obstructing configuration.

[0231] The obstructing member may comprise a ball valve and a scotch yoke configured to translate a linear motion of the sliding stem (and thus for example a linear motion of the piston of the at least one hydraulic actuator) into a rotational movement of the ball valve. For example, an ILT or a manifold can typically comprise such a ball valve.

[0232] The obstructing member may comprise or may be a shear blade. The shear blade acts as a guillotine in order to cut a wire, a cable, coiled tubing or any other object positioned through the central passageway of the apparatus. The cutting may be effected by transitioning the shear blade from the non-obstructing configuration to the obstructing configuration. For example, a WCP, a LRP, a EDP or a BOP can typically comprise a shear blade to cut what is located in the well. The shear blade may cooperate with a support member which is fixedly attached to the body of the apparatus, such that high shear is generated between the support member and the shear blade when the shear blade moves from the non-obstructing configuration to the obstructing configuration.

[0233] The obstructing member may comprise or be a gate valve or a ram. By gate valve, it is meant a member which may move linearly across the central passageway (preferably in a direction perpendicular to the longitudinal axis of the body). The gate valve may cooperate with a support member fixedly attached to the body of the apparatus. For example, the gate valve may be in the shape of a plate comprising a hole. In the non-obstructing configuration, the hole may be located in the central passageway, while in the obstructing configuration the hole may be located out of the central passageway, so that the plate obstructs the central passageway. This is what is illustrated in FIG. 2A, 2B and 3.

[0234] Preferably, the fail safe mechanism may be configured to force the obstructing member into the non-obstructing position (for example, to stroke open a hydraulic connector for an emergency disconnection).

[0235] Alternatively, the fail safe mechanism may be configured to force the obstructing member into the obstructing position (for example to stroke a valve closed, again for example for an emergency disconnection).

[0236] The fail safe module, or the entire actuator assembly (especially for the integrated embodiments) can be 3D printed from different materials depending the size of the gate valve. For example, for 2" and 5" sized gate valves, the fail safe module or the entire actuator assembly can be 3D printed from nickel alloy. For example, for 7" sized gate valve, the fail safe module or the entire actuator assembly can be 3D printed from titanium. This may reduce the manufacturing time as well as the cost of the actuator assembly. This may also improve the reliability of the actuator assembly. This may finally lower the overall weight of the actuator assembly. Preferably, the weight of the fail safe module or of the entire actuator assembly may be less than 60 kg, preferably less than 50 kg.Hydraulic circuit and operating process

[0237] The actuator assembly may be associated with a hydraulic circuit configured to feed pressurized hydraulic fluid to the at least one hydraulic actuator. The hydraulic circuit may be part of the apparatus, external to the apparatus, or may be partially included in the apparatus and partially external to the apparatus.

[0238] The hydraulic circuit may be a closed loop circuit so that there is no need to have a hydraulic umbilical cable to feed hydraulic fluid to the hydraulic circuit. This may allow to reduce the equipment required on a rig or vessel. In some examples, this hydraulic circuit may be used for an electric riser less well intervention (eRLWI).

[0239] The hydraulic circuit may comprise one or more flowmeters. The one or more flowmeters can be configured to monitor the circulation of hydraulic fluid in the hydraulic circuit. Information from the one or more flowmeters and / or information from one or more pressure sensors may be fed back to a control unit which may be configured to control the hydraulic circuit, and in particular the operation of the pump and / or valve which will be described in more detail below.

[0240] Now referring to FIG. 6, a closed loop hydraulic circuit is presented, in conjunction with an actuator assembly comprising a fail safe module and at least one hydraulic actuator distinct and separate from the fail safe module, as described above. The closed loop hydraulic circuit may be hydraulically connected to a single actuator assembly (i.e. each actuator assembly may be associated with a dedicated hydraulic circuit). Alternatively, as illustrated on the drawing, a closed loop hydraulic circuit may be hydraulically connected to two or more actuator assemblies. The or each actuator assembly may be as described according to all options and variations above. In the illustration, each actuator assembly comprises two hydraulic actuators, but the present description is also applicable to actuator assemblies comprising a single hydraulic actuator or more than two hydraulic actuators.

[0241] The hydraulic circuit may comprise a high pressurised hydraulic portion 517 and a low pressurised hydraulic portion 518. These portions are fluidically connected to a hydraulic fluid supply 508. In the high pressurised hydraulic portion 517, a pump 507, a flowmeter 506 and a pressure transmitter 505 (to measure pressure) may be present. The pump 507 may be configured to feed pressurized hydraulic fluid to the actuator assemblies. Control of the pump 507 may make it possible to control the pressure in the high pressurised hydraulic portion 517. This pressure may reach, by way of example, a maximum value from 200 to 500 bar, such as approximately 350 bar.

[0242] As described above, each actuator assembly may further comprise a fail safe module 501 comprising a piston 502 and piston rod configured to slide back and forth in a chamber divided by the piston 502 into a first compartment 503 and a second compartment 504, 504'. The first compartment 503 may be closest to the piston 511 of the hydraulic actuators 510 (and closest to the central passageway 515), and the second compartment 504, 504' may be farthest from the piston 511 of the hydraulic actuators 510 (and farthest from the central passageway 515). The piston rod of the fail safe module 501 may extend in the first compartment 503 of the fail safe module 501 and also extend out of the chamber of the fail safe module 501. As illustrated, in the parallel arrangement, the piston rod of the fail safe module 501 may be fixedly attached to a yoke 509.

[0243] As described above, each hydraulic actuator 510 in each actuator assembly may comprise a piston 511 fixed to a piston rod and configured to slide back and forth in a chamber divided by the piston 511 into a third compartment 513, 513' and a fourth compartment 512, 512'. The fourth compartment 512, 512' may be farthest from the piston 502 of the fail safe module 501 and the third compartment 513, 513' may be closest to the piston 502 of the fail safe module 501. The piston rod of each hydraulic actuator 510 may extend in the third compartment 513, 513' and also extend out of the chamber of the hydraulic actuator 510. The yoke 509 may be fixedly attached to the piston rods of the hydraulic actuators 510.

[0244] The yoke may also be fixedly attached to a central stem 514. This central stem 514 may be connected to an obstructing member 516 configured to transition between an obstructing configuration and a non-obstructing configuration to obstruct or clear a central passageway 515. As described above, alternatively, in the case of in-line arrangement, the central stem 514 may be directly connected to the piston 511 of the hydraulic actuator 510.

[0245] More generally, in each actuator assembly, the piston 502 and piston rod of the fail safe module 501, the piston 511 and piston rod of the hydraulic actuator(s) 510 and the central stem 514 may be fixed together and assume a linear movement.

[0246] The third compartment 513, 513' of each hydraulic actuator 510 may be fluidically connected to the high pressurised hydraulic portion 517. The fourth compartment 512, 512' of each hydraulic actuator 510 may be fluidically connected to the low pressurised hydraulic portion 518.

[0247] The hydraulic circuit may further comprise a valve, such as an electrically actuated directional control valve (DCV) 519. In case more than one actuator assemblies are connected to the same hydraulic circuit, there may be one such valve per actuator assembly. This valve may have a first position in which hydraulic fluid communication between the high pressurised hydraulic portion 517 and the third compartment 513 is open, and hydraulic fluid communication between the low pressurised hydraulic portion 518 and the third compartment 513 is closed; and a second position in which hydraulic fluid communication between the high pressurised hydraulic portion 517 and the third compartment 513' is closed, and hydraulic fluid communication between the low pressurised hydraulic portion 518 and the third compartment 513' is open. The fourth compartment 512, 512' may be in hydraulic fluid communication with the low pressurised hydraulic portion 518 in both positions on the valve. When the valve is in the first position, owing to the pump 507, the hydraulic pressure within the third compartment 513 of each hydraulic actuator 510 may increase and the piston 511 of the hydraulic actuator 510 may be biased towards the retracted position. When the valve is in the second position, the piston 502 of the fail safe module may drive the piston 511 of the or each hydraulic actuator 510 towards the extended position.

[0248] On the left hand side of FIG. 6 is presented a first configuration of the hydraulic circuit wherein the valve associated with one actuator assembly is in the first position. The pump 507 applies hydraulic pressure (by way of example, from 200 to 500 bar, such as approximately 350 bar) in the third compartment 513 of the or each hydraulic actuator 510 of the actuator assembly. This applied hydraulic pressure may be sufficient to overcome both the hydraulic pressure in the first compartment 512, and the pressure differential between the first compartment 503 and second compartment 504 of the fail safe module 501. As a result, the piston 511 of the or each hydraulic actuator 510 moves towards or is maintained in the retracted position, and the piston 502 of the fail safe module 501 is driven by the piston 511 of the or each hydraulic actuator 510 and moves towards or is maintained in the extended position. This may preferably correspond to a transition or maintenance of the obstructing member 516 to or in the non-obstructing configuration.

[0249] On the right hand side of FIG. 6 is presented a second configuration of the hydraulic circuit wherein the valve associated with another actuator assembly is in the second position. In this case, the pump 507 does not apply hydraulic pressure in the third compartment 513' of the or each hydraulic actuator 510 of the actuator assembly. The pressure differential between the first compartment 503 and the second compartment 504 of the fail safe module 501 is thus sufficient to drive the piston 502 of the fail safe module 501 towards the retracted position, so that the piston 511 of the or each hydraulic actuator 510 moves towards or is maintained in the extended position. This may preferably correspond to a transition or maintenance of the obstructing member 516 to or in the obstructing configuration.

[0250] The fail safe module can therefore be configured to cause the obstructing member to transition to a safe configuration (preferably to the obstructing configuration) in case of a malfunction of the hydraulic circuit, e.g. due to leakage of hydraulic fluid and loss of hydraulic pressure. Indeed, as explained above, in such a case, the fail safe module may bias the hydraulic actuators towards a position, for example the extended position, owing to the pressure differential between the compartments of the chamber of the fail safe module.

[0251] The fail safe module can also be configured to cause the obstructing member to transition from one configuration to another configuration as part of the normal operation of the actuator assembly, i.e. in the absence of malfunction. Indeed, as explained above, pressurized hydraulic fluid may be fed to only one compartment of the chamber of each hydraulic actuator, to cause the transition in one direction. By relaxing hydraulic pressurization in this compartment, and by simply relying on the pressure differential between the compartments of the chamber of the fail safe module, transition to the other direction may be achieved.

[0252] Alternatively (and different from what is depicted in FIG. 6), it is also possible for the hydraulic circuit to feed pressurized hydraulic fluid to both compartments of each chamber of a hydraulic actuator. In this case, the fail safe module can typically be used only as a safety feature.

[0253] Making reference to FIG. 11, a closed loop hydraulic circuit is presented, in conjunction with an actuator assembly comprising a fail safe mechanism and hydraulic actuator integrated into a single component, as described above in connection with FIG. 7A-7B and 8A-8B. In this context, unless otherwise specified, the description made above in connection with FIG. 6 remains applicable. Besides, the present description is also applicable in a similar manner to a fail safe mechanism and hydraulic actuator integrated into a single component, as described above in connection with FIG. 9A-9B and 10A-10B, the only difference being the arrangement of the compartments.

[0254] The closed loop hydraulic circuit may be hydraulically connected to a single actuator assembly (i.e. each actuator assembly may be associated with a dedicated hydraulic circuit). Alternatively, as illustrated on the drawing, a closed loop hydraulic circuit may be hydraulically connected to two or more actuator assemblies.

[0255] The hydraulic circuit may comprise a high pressurised hydraulic portion 817 and a low pressurised hydraulic portion 818. These portions are fluidically connected to a hydraulic fluid supply 808. In the high pressurised hydraulic portion 817, a pump 807, a flowmeter 806 and a pressure transmitter 805 (to measure pressure) may be present. The pump 807 may be configured to feed pressurized hydraulic fluid to the actuator assemblies. Control of the pump 807 may make it possible to control the pressure in the high pressurised hydraulic portion 817. This pressure may reach, by way of example, a maximum value of from 200 to 500 bar, such as approximately 350 bar.

[0256] As described above, each actuator assembly 801 may further comprise a sleeve 802 configured to slide back and forth in an outer housing 809. The actuator assembly 801 may comprise a first compartment 803 within the outer housing 809 and external to the inner member, closer to the central passageway 815; a third compartment 811 within the outer housing 809 and external to the inner member, further from the central passageway 815; and a second compartment 804 within the inner member and the sleeve 802. The sleeve 802 may extend out of the outer housing 809 and may be fixedly attached to the sliding stem 814.

[0257] The sliding stem 814 may be connected to an obstructing member 816 configured to transition between an obstructing configuration and a non-obstructing configuration to obstruct or clear the central passageway 815.

[0258] In each actuator assembly, the sleeve 802 and central stem 814 may be fixed together and assume a linear movement.

[0259] The third compartment 811 may be alternately fluidically connected (via a hydraulic fluid line 810 which may be a flexible line) to the high pressurised hydraulic portion 817 and to the low pressurised hydraulic portion 818, depending on the position of a valve 819 on the circuit, which may be a DCV as described above. In case more than one actuator assemblies are connected to the same hydraulic circuit, there may be one such valve per actuator assembly.

[0260] When the valve is in a first position, owing to the pump 807, the hydraulic pressure within the third compartment 811 of the actuator assembly 801 may increase and the sleeve 802 may be driven towards the extended position (left hand side of the drawing). The pump 807 may apply hydraulic pressure (by way of example, from 200 to 500 bar, such as approximately 350 bar) in the third compartment 811. This applied hydraulic pressure may be sufficient to overcome the pressure differential between the first compartment 803 and second compartment 804. As a result, the sleeve 802 moves towards or is maintained in the extended position. This may preferably correspond to a transition or maintenance of the obstructing member 816 to or in the non-obstructing configuration.

[0261] When the valve is in a second position (right hand side of the drawing), the pump 807 does not apply hydraulic pressure in the third compartment 811. The pressure differential between the first compartment 803 and the second compartment 804 is thus sufficient to drive the sleeve 802 towards the retracted position. This may preferably correspond to a transition or maintenance of the obstructing member 816 to or in the obstructing configuration.

[0262] The actuator assembly can therefore be configured to cause the obstructing member to transition to a safe configuration (preferably to the obstructing configuration) in case of a malfunction of the hydraulic circuit, e.g. due to leakage of hydraulic fluid and loss of hydraulic pressure. The actuator assembly can be configured to cause the obstructing member to transition from one configuration to another configuration as part of the normal operation of the actuator assembly, i.e. in the absence of malfunction.

Examples

Embodiment Construction

[0090]The invention will now be described in more detail without limitation in the following description.

[0091]An object of the present invention is an actuator assembly for connection to an apparatus comprising a body and a central passageway extending along a longitudinal axis of the body.

[0092]The actuator assembly may comprise a sliding stem, an obstructing member fixedly attached to the sliding stem and at least three compartments, namely a first compartment, a second compartment and a third compartment, which have varying volumes depending on the position of the sliding stem.

[0093]When the actuator assembly is connected to the apparatus, the obstructing member may have an obstructing configuration wherein the central passageway of the apparatus is at least partly obstructed and a non-obstructing configuration wherein the central passageway of the apparatus is not obstructed.

[0094]The volume of the first compartment may increase and the volume of the second compartment may decr...

Claims

1. An actuator assembly (200, 300, 600, 700) for connection to an apparatus (101) comprising a body and a central passageway (202, 302, 602, 702) extending along a longitudinal axis of the body, wherein the actuator assembly comprises: - a sliding stem (207, 307, 607, 707), - an obstructing member (201, 301, 601, 701), fixedly attached to the sliding stem (207, 307, 607, 707), - a first compartment (403, 403', 603, 703, 703'), a second compartment (404, 404', 604, 704, 704') and a third compartment (513, 513', 611, 711) having varying volumes depending on the position of the sliding stem (207, 307, 607, 707), wherein the volume of the first compartment (403, 403', 603, 703, 703') increases and the volume of the second compartment (404, 404', 604, 704, 704') decreases when the sliding stem (207, 307, 607, 707) slides in one direction, and the volume of the first compartment (403, 403', 603, 703, 703') decreases and the volume of the second compartment (404, 404', 604, 704, 704') increases when the sliding stem (207, 307, 607, 707) slides in another opposite direction, wherein the actuator assembly is configured so that: - the obstructing member (201, 301, 601, 701) has, when the actuator assembly is connected to the apparatus (101): • an obstructing configuration wherein the central passageway (202, 302, 602, 702) of the apparatus (101) is at least partly obstructed; and • a non-obstructing configuration wherein the central passageway (202, 302, 602, 702) of the apparatus (101) is not obstructed; - at least one of the first compartment (403, 403', 603, 703, 703') and second compartment (404, 404', 604, 704, 704') is sealed and the other of the first compartment (403, 403', 603, 703, 703') and second compartment (404, 404', 604, 704, 704') is pressure equilibrated with the environment, so that, when the actuator assembly is connected to the apparatus (101), the obstructing member is biased towards one of the obstructing configuration and of the non-obstructing configuration; - the third compartment (513, 513', 611, 711) is feedable with hydraulic fluid and the bias of the obstructing member towards one of the obstructing configuration and of the non-obstructing configuration may be overcome by applying sufficient hydraulic fluid pressure in the third compartment (513, 513', 611, 711).

2. The actuator assembly of claim 1, wherein the first compartment (403, 403', 603, 703, 703') is sealed and contains a pressurised gas and the second compartment (404, 404', 604, 704, 704') is pressure equilibrated with the environment, preferably is open to the environment; or wherein the first compartment (403, 403', 603, 703, 703') is pressure equilibrated with the environment, preferably is open to the environment and the second compartment (404, 404', 604, 704, 704') is sealed and contains a gas.

3. The actuator assembly of any one of claims 1-2, which is configured for use underwater and wherein one of the first compartment (403, 403', 603, 703, 703') and second compartment (404, 404', 604, 704, 704') is open to the environment and is configured to be filled with water, preferably with seawater.

4. The actuator assembly of any one of claims 1-3, wherein the actuator assembly comprises: - at least one hydraulic actuator (203, 203', 303) comprising a chamber (204, 204', 304) and a piston (205, 205', 305) configured to slide back and forth within the chamber (204, 204', 304), said piston (205, 205', 305) dividing said chamber (204, 204', 304) into the third compartment and a fourth compartment; - a fail safe module (106, 106') comprising a chamber and a piston (401, 401') configured to slide back and forth within the chamber, said piston (401, 401') dividing said chamber into the first compartment (403, 403') and the second compartment (404, 404'), wherein the piston (205, 205', 305) of the at least one hydraulic actuator (203, 203', 303) and the piston (401, 401') of the fail safe module (106, 106') are fixedly attached to the sliding stem.

5. The actuator assembly of claim 4, wherein the first compartment (403, 403') is closest to the piston (205, 205', 305) of the at least one hydraulic actuator (203, 203', 303) and the second compartment (404, 404') is farthest from the piston (205, 205', 305) of the at least one hydraulic actuator (203, 203', 303).

6. The actuator assembly of claim 4 or 5, wherein the chamber (204, 204', 304) of the at least one hydraulic actuator (203, 203', 303) and the chamber of the fail safe module (106, 106') are configured to be fixedly attached to the body of the apparatus (101).

7. The actuator assembly of any one of claims 4-6, wherein: - the at least one hydraulic actuator (203, 203', 303) is configured to be hydraulically actuated so as to cause the obstructing member (201, 301) to transition from the obstructing configuration to the non-obstructing configuration; and / or - the at least one hydraulic actuator (203, 203', 303) is configured to be hydraulically actuated so as to cause the obstructing member (201, 301) to transition from the non-obstructing configuration to the obstructing configuration; and / or - when the at least one hydraulic actuator (203, 203', 303) is not hydraulically actuated, the fail safe module (106, 106') is configured to cause the obstructing member (201, 301) to transition from the non-obstructing configuration to the obstructing configuration.

8. The actuator assembly of any one of claims 4-7, wherein the piston (204, 204', 304) of the at least one hydraulic actuator (203, 203', 303) moves away from the fail safe module (106, 106') when the obstructing member (201, 301) transitions from the obstructing configuration to the non-obstructing configuration; and the piston (203, 203', 303) of the at least one hydraulic actuator (203, 203', 303) moves towards the fail safe module (106, 106') when the obstructing member transitions from the non-obstructing configuration to the obstructing configuration; and preferably wherein, when the at least one hydraulic actuator (203, 203', 303) is not hydraulically actuated, the pressure in the first compartment (403, 403') is greater than the pressure in the second compartment (404, 404'), so that the piston (401, 401') of the fail safe module (106, 106') pulls the piston (205, 205', 305) of the at least one hydraulic actuator (203, 203', 303) towards the fail safe module (106, 106').

9. The actuator assembly of any one of claims 4-7, comprising a single hydraulic actuator (303), wherein the piston (305) of the hydraulic actuator (303) is axially aligned with the piston (401, 401') of the fail safe module (106, 106').

10. The actuator assembly of any one of claims 4-9, comprising at least two parallel hydraulic actuators (203, 203').

11. The actuator assembly of claim 10, further comprising: - a bonnet (206) having a central bore; - a yoke (102, 102', 102") connecting the pistons (205, 205') of the at least two parallel hydraulic actuators (203, 203'); and wherein the sliding stem is a central stem (207) extending through the central bore of the bonnet (206), having a first end fixed to the yoke (102, 102', 102") and a second end fixed to the obstructing member (201); and further preferably wherein the bonnet (206) is configured to be fixedly attached to the body of the apparatus (101), and the pistons (205, 205') of the hydraulic actuators (203, 203') are configured to drive the central stem (207) through the central bore of the bonnet (206), thereby transitioning the obstructing member (201) from the obstructing configuration to the non-obstructing configuration.

12. The actuator assembly of any of claims 1-3, which comprises: - an outer housing (609); - an inner member (614) fixed within the outer housing (609); - a sleeve (618) fixedly attached to the sliding stem (607), wherein the sleeve (618) has a flange (620) and is slidable within the outer housing (609) and over the inner member (614); wherein the first compartment (603) is delimited by the outer housing (609) and the sleeve (618), the second compartment (604) comprises an inner chamber (619) within the inner member (614) and is further delimited by the sleeve (618), and the third compartment (611) is delimited by the outer housing (609), the inner member (614) and the flange (620) of the sleeve (618); or which comprises: - an outer housing (709); - an active chamber (710) within the outer housing (709); - at least one, preferably two passive chambers (714, 714') within the outer housing (709); - a piston (717) connected to a piston rod (718) slidable within the active chamber (710), wherein the third compartment (711) is delimited within the active chamber (710) by said piston (717); - a respective piston (715, 715') connected to a piston rod (716, 716') slidable within each passive chamber (714, 714'), wherein the first compartment (703, 703') and the second compartment (704, 704') are located within each passive chamber (714, 714') on opposite sides of said piston (715, 715'); wherein the piston rod (718) of the active chamber and the piston rods (716, 716') of the passive chambers are fixedly connected to the sliding stem (707).

13. An assembly, comprising one or more actuator assemblies according to any one of claims 1-12 and further comprising a hydraulic circuit configured to feed pressurized hydraulic fluid to the third compartment, and preferably to at least one hydraulic actuator (203, 203', 303) of each actuator assembly, if present.

14. An apparatus (101) comprising a body and a central passageway (202) extending along a longitudinal axis of the body, comprising the actuator assembly of any one of claims 1-12 connected thereto.

15. A process of operating the actuator assembly in the apparatus (101) of claim 14, comprising one or more of: - applying hydraulic fluid pressure to the third compartment (513, 513', 611, 711), so as to cause the obstructing member (201, 301, 601, 701) to transition from one of the obstructing configuration and the non-obstructing configuration, to the other of the obstructing configuration and the non-obstructing configuration; - causing the obstructing member to transition from one of the non-obstructing configuration and the obstructing configuration to the other of the non-obstructing configuration and the obstructing configuration by ceasing to apply hydraulic fluid pressure in the actuator assembly.

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