A RETRIEVABLE SUBSEA APPARATUS WITH A PRESSURE AND VOLUME COMPENSATING SYSTEM

Abstract

A retrievable subsea apparatus (1) with a pressure and volume compensating system, the apparatus comprising: a housing (1′) having in its interior a control system (9) located in a first section (3) thereof and an operating unit (6) located in a second section (4) thereof. The apparatus further comprises a penetrator (2) which constitutes an interface between the first section (3) and the second section (4), wherein the first section (3) has a substantially constant first pressure. An external pressure compensator (5, 5′) is associated with the second section (4) having a second pressure. The operating unit (6) comprises at least a first sub-unit (6′) and at least a second sub-unit (6″). The second section (4) is subdivided into at least a first sub-section (4′) and at least a second sub-section (4″) which is sealed off from the first 1,1 section (4′) and being associated with respective sub-unit (6′, 6″).

Claims

1. A retrievable subsea apparatus with a pressure and volume compensating system, the apparatus comprising: a housing having in its interior a control system located in a first section thereof and an operating unit located in a second section thereof, wherein a penetrator constitutes an interface between the first section and the second section, wherein the first section has a substantially constant first pressure, that an external pressure compensator is associated with the second section having a second pressure, that at least a first sub-unit and at least a second sub-unit constitute the operating unit, that at least a first sub-section and at least a second sub-section constitute the second section, that a first liquid is located in the first sub-section, and a second liquid is located in the second sub-section, that the second sub-section is sealed off from the first sub-.section, that the external compensator is in communication with the first sub-section, that the first sub-unit is at least partly associated with the first sub-section and the second sub-unit is associated with the second sub-section, and that an internal pressure compensator is configured to adjust for any pressure differences between the first and second sub-sections and is in contact with the first liquid in the first sub-section and with the second liquid in the second sub-section.

2. The apparatus of claim 1, wherein the first liquid has a first set of properties, and wherein the second liquid has a second set of properties.

3. The apparatus of claim 2, wherein the first and second properties are at least one of viscosity, dielectric property, lubrication and materials compatibility.

4. The apparatus of claim 1, wherein the first sub-unit comprises an electric motor, and wherein the second sub-unit comprises a gear assembly.

5. The apparatus of claim 1, wherein the first pressure in the first section is substantially at sea surface level atmospheric pressure.

6. The apparatus of claim 1, wherein the second pressure is equal to or above subsea pressure surrounding the apparatus housing.

7. The apparatus of claim 1, wherein the external pressure compensator is pre-tensioned to one side to yield a pressure in the second section above an external pressure, e.g. a subsea pressure.

8. The apparatus of claim 1, wherein the external compensator is linked to or communicates with a compensator movement sensor.

9. The apparatus of claim 8, wherein the external pressure compensator is configured to effect a volumetric displacement of the first liquid in the first sub-section to cause the internal pressure compensator to yield a corresponding volumetric change in the second sub-section.

10. The apparatus of claim 1, wherein the external pressure compensator is a first bellow open at one end and closed at the other end, the inside of the first bellow to be in communication with sea water, and wherein the outside and closed end of the first bellow being surrounded by the first liquid.

11. The apparatus of claim 1, wherein the external pressure compensator is made from at least one of or a composition of at least two of: a metal, a metal alloy, a rubber-type material and a plastics material.

12. The apparatus of claim 1, wherein the external pressure compensator is linked to or communicates with a movement sensor.

13. The apparatus of claim 10, wherein the closed end of the first bellow is linked to or communicates with a bellow movement sensor.

14. The apparatus of claim 12, wherein the sensor is a linear movement sensor of inductive, capacitive or resistive type.

15. The apparatus of claim 1, wherein the control system communicates with external power and communication equipment via the penetrator and the first sub-section.

16. The apparatus of claim 1, wherein the control system communicates with the first sub-unit, e.g. a motor, and a movement sensor of the external pressure compensator.

17. The apparatus of claim 1, wherein the internal pressure compensator is located in or associated with a wall or component which divides the first sub-section and the second sub-section.

18. The apparatus of claim 17, wherein the wall between the first and second sub-sections is integral with or is in a sealed engagement with a housing of the first sub-unit.

19. The apparatus of claim 1, wherein the internal pressure compensator is a piston movable in a cylindrical hole in the wall, and wherein a first end face of the piston contacts the first liquid, and a second end face of the piston contacts the second fluid.

20. The apparatus of claim 1, wherein the internal pressure compensator is a diaphragm membrane located transversely of a hole in the wall, and wherein a first face of the membrane contacts the first liquid, and a second end face of the membrane contacts the second fluid.

21. The apparatus of claim 20, wherein the membrane is located at one axial end of the hole.

22. The apparatus of claim 20, wherein a perforated member is located at the other axial end of the hole and being integral with the wall.

23. The apparatus of claim 1, wherein the wall has a circle shaped opening radially inwards of its circumference and extending axially through the wall, wherein the internal pressure compensator is a diaphragm membrane which is located transversely of the opening at one axial end thereof, wherein a first face of the membrane contacts the first liquid, and wherein a second face of the membrane contacts the second fluid.

24. The apparatus of claim 23, wherein a perforated member is located at the other axial end of the opening integrally with the wall.

25. The apparatus of any one of claims claim 1, wherein the internal pressure compensator is a bladder or a second bellow of rubber material being substantially located in the first sub-section and having an outlet which communicates with an axially extending hole through the wall, an interior of said the bladder or second bellow being in communication with the second liquid present in the second sub-section.

26. The apparatus of claim 1, wherein the internal pressure compensator is a circular continuous hose of rubber material being substantially located in the first sub-section, wherein the hose has at least one branched-off outlet which engages a hole through the wall, an interior of the outlet and hose being in communication with the second liquid present in the second sub-section.

27. The apparatus of claim 26, wherein the hose resides with a part of its body in a recess of a face of the wall in the first sub-section.

28. The apparatus of claim 1, wherein at least one of the first and second liquids is a mineral oil, a synthetic or semi-synthetic oil or a silicone oil.

29. The apparatus of claim 1, wherein the first section is a dry chamber filled with air or gas.

30. The apparatus of claim 1, wherein a first dynamic seal is present between the first sub-unit and the second sub-unit, and wherein a second dynamic seal is present at a downstream region of the second sub-unit.

31. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 shows a first embodiment of the retrievable subsea apparatus of the present invention.

[0031] FIG. 2 shows a second embodiment of the retrievable subsea apparatus of the present invention.

[0032] FIG. 3 shows a third embodiment of the retrievable subsea apparatus of the present invention.

[0033] FIG. 4 shows a fourth embodiment of the retrievable subsea apparatus of the present invention.

[0034] FIG. 5 shows a fifth embodiment of the retrievable subsea apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The five embodiments, which are illustrated, are non-limiting examples of the invention. The embodiment of FIG. 5 is currently the preferred mode of the invention.

[0036] In the description to follow, in a series arrangement, the compensator which interfaces the external environment, and controls the first oil-filled sub-section or chamber, is named the “external compensator” 5.

[0037] Further, in a series arrangement, in this description, we deal with two oil filled sub-sections or chambers. This does not however limit the scope of this invention to the use of only two sub-sections or chambers. In the description to follow, the compensator which controls this second oil filled sub-section or chamber is named the “internal compensator”.

[0038] It will be appreciated that “at least one first sub-section” and “at least one second sub-section” should be interpreted as implying that more than one of the first and/or second sub-sections could be provided.

[0039] Further, the terms “at least one first sub-unit” and “at least one second sub-unit” constituted by the operating unit should be interpreted to imply that more than one of the first and/or second sub-units could be present.

[0040] A loss of oil in the first or second sub-section or chamber may be caused by leakages through static or dynamic seals into the environment, or internally between the different sub-sections. The invention enables through the use of the compensators of the apparatus to compensate for such leakages to a certain extent. If the leakages are excessive, the apparatus may require replacement. If the oil volume in a sub-section becomes so low that the operation of the compensator will no longer be sufficient for compensation of leakage. However, the embodiment of FIG. 4 and more so the embodiment of FIG. 5 is able to compensate for a larger loss of oil in the second sub-section than the other embodiments.

[0041] In the shown embodiments of the retrievable subsea apparatus 1 they all have a housing 1′ and a penetrator 2, which constitutes an interface between a first section 3 and a second section 4. The first section 3 is sealed off by the penetrator 2 and has a substantially constant first pressure, suitably atmospheric pressure, e.g. sea surface level atmospheric pressure. The first section 2 is a dry chamber filled with air or gas.

[0042] The external pressure compensator 5 is associated with the second section 4, which has a second pressure. The second pressure may be equal to or suitably be above subsea pressure surrounding the apparatus housing. Suitably, the external compensator 5 can be pre-tensioned to one side thereof to cause such over-pressure in the second section 4.

[0043] The external pressure compensator 5 is of a type configured to be able to compensate for a volumetric displacement of a first liquid 7 in a sub-section 4′ of the second section 4 to yield a corresponding volumetric change in a second sub-section 4″ of the second section 4 via the action by an internal pressure compensator which is in contact with said first liquid 7 and a second liquid 8 in the second sub-section 4″. Thereby, any pressure difference temporarily arising between the pressures in sub-section 4′ and sub-section 4″ will be automatically adjusted in order to retain a pressure balance between these two sub-sections.

[0044] Specific preferred embodiments of the internal pressure compensator will be explained in more detail below with reference to the drawing FIGS. 1-5, respectively.

[0045] The external pressure compensator 5 is configured with one side thereof to be in contact with seawater and with the other side thereof to be in contact with or surrounded by the first liquid 7. The external pressure compensator 5 should be of a material or a composition of materials, which will not deteriorate in contact with seawater and in contact with a selected type of the first liquid 7. Such material is selectable suitably from a metal, a metal alloy, a rubber-type material and a plastics material, and any combination of two or more of these materials could constitute said composition. In a preferred, although non-limiting embodiment of the apparatus, the external pressure compensator 5 is a first bellow open at one end and closed at the other end.

[0046] Other types of materials than those mentioned and having similar properties may be used as technical alternatives.

[0047] Although the use of a bellow 5 is contemplated in the currently preferred embodiment of the external pressure compensator, other types of pressure compensators with capability of volumetric liquid displacement could be used.

[0048] The inside of the first bellow 5 is in communication with seawater via a perforated wall member 14. The outside and closed end of the first bellow 5 is surrounded by the first liquid 7. The closed end 5′ of the first bellow is linked to or communicates with a bellow movement sensor 15. The sensor 15 is suitably a linear movement sensor, which may be of inductive, capacitive or resistive type.

[0049] The control system 9 communicates with the first sub-unit 6′, e.g. an electric motor, via lines 16, and the movement sensor 15 of the external pressure compensator 5, i.e. the first bellow, via lines 17.

[0050] At least one first sub-unit 6′ and at least one second sub-unit 6″ constitute an operating unit 6. In a specific embodiment, the first sub-unit 6′ comprises an electric motor, and the second sub-unit 6″ comprises a gear assembly. The second section 4 is subdivided into at least one first sub-section 4′ and at least one second sub-section 4″ which is sealed off from the first section 4′. As seen from the drawings, the first bellow 5 is associated with the first sub-section 4′, the first sub-unit 6′ is at least partly associated with the first sub-section 4′, and the second sub-unit 6″ is associated with the second sub-section 4″. As seen from FIGS. 1-5, the first sub-unit 6′ could also at least partly extend with its housing into the second sub-section 4″ to be at least partly surrounded a second liquid 8 which is located in the second sub-section 4″.

[0051] The first liquid 7, which is located in the first sub-section 4′, has a first set of properties and a second liquid 8, which is located in the second sub-section 4″, has a second set of properties. The first properties are compatible with a structure and operation of the first sub-unit 6′ and the second properties are compatible with a structure and operation of the second sub-unit 6″. The first and second properties are suitably at least one of viscosity, dielectric property, lubrication and materials compatibility. In a currently preferred, although not limiting embodiment, the first liquid 7 has low viscosity and high dielectric properties and could be, as indicated above, e.g. a silicone oil, and the second liquid 8 has suitably a high viscosity and lubrication properties and could e.g. be a mineral oil or a synthetic or semi-synthetic oil.

[0052] The first section 3 contains a control system 9 in communication with external power and communication equipment 10 via said penetrator 2 and cable 11 through the first sub-section 4′ and a watertight connector 12.

[0053] The internal pressure compensator mentioned above is configured to adjust for any pressure differences between said first sub-section 4′ and the second sub-section 4″. The internal pressure compensator is located in or associated with a wall 18 or structural component, which divides or makes an interface wall between the first sub-section 4′ and the second sub-section 4″. The wall 18 is suitably integral with or is in a sealed engagement with a housing of the first sub-unit 6′.

[0054] The exemplifying various embodiments of the internal pressure compensator are now to be explained in further detail.

[0055] The embodiment of FIG. 1 shows an internal pressure compensator 19, which is a piston movable in a cylindrical hole in the wall 18. It is seen that a first end face of the piston 19 contacts the first liquid 7, and a second end face of the piston 19 contacts the second fluid 8.

[0056] The embodiment of FIG. 2 shows an internal pressure compensator 20 which is a diaphragm membrane located transversely of a hole 21 in the wall 18. A first face of the membrane 20 contacts the first liquid 7, and a second face of the membrane 20 contacts the second fluid 8. It is noted that the membrane 20 is located at one axial end of the hole 21. Optionally, a perforated member 22 may be located at the other axial end of the hole and being integral with the wall 18.

[0057] The embodiment of FIG. 3 shows that the wall 18 has a circular opening 23 radially inwards of its circumference and extending axially through the wall 18. The internal pressure compensator 24 is a diaphragm membrane located transversely of the opening 23 at one axial end thereof. Optionally, a perforated circle-shaped member 25 may be located at the other axial end of the opening 24 integrally with the wall 18. A first face of the membrane 24 contacts the first liquid 7, and a second face of the membrane 24 contacts the second fluid 8.

[0058] The embodiment of FIG. 4 shows an internal pressure compensator 26, which is a bladder or a second bellow of rubber material being. It is noted that the compensator 26 is substantially located in the first sub-section 4′ and has an outlet 26′ which communicates with an axially extending hole 27 through the wall 18. An interior of the bladder or second bellow 26 is in communication with the second liquid 8 present in the second sub-section 4″. In any case, compared with the embodiments of FIGS. 1-3, the compensator 26 which has liquid 8 inside provides for extra supply of oil 8 to the sub-section 4″ in case of oil leakage from the sub-section 4″ or via the sub-unit 6″ by virtue of the bladder or bellows 26 being compressed due to volumetric displacement of the liquid 7 in the sub-section 4′ caused by the bladder 5. Thereby a pressure drop in section 4″ is effectively compensated to yield a substantially same pressure in both sub-section 4′, 4″.

[0059] Oil leakage of oil 7 from the first sub-section 4′ could be via a first dynamic seal 28, which is present between the first sub-unit 6′ and the second sub-unit 6″. Further, oil leakage of oil 8 could be via a second dynamic seal 29 being present at a downstream region of the second sub-unit 6″.

[0060] The embodiment of FIG. 5 shows an internal pressure compensator 30 which is a circular continuous hose of rubber material being substantially located in the first sub-section 4′. The hose 30 has at least one branched-off outlet 31 which engages a hole 32 through the wall 18. An interior of said outlet 31 and hose 30 is in communication with the second liquid 8 present in the second sub-section 4″. The volume of the hose 30 implies that there is an extra supply of oil 8 available in case of excessive oil leakage of oil 8 to the outside of the apparatus 1. However, it will be appreciated that the oil which can be pressed out of the hose is very much dependent on the volume of oil 7 which the bellow 5 is able to cause a corresponding volume compression onto the hose 30 to yield a corresponding volume of oil 8 to leave the inside of the hose 30 and into the second sub-section, thereby providing for the required pressure compensation. Suitably, the hose 30 resides with a part of its body in a recess of a face of the wall 18 in the first sub-section 4′.

[0061] As indicated above, an exemplifying use of the inventive apparatus 1 could be to operate or adjust the state of a subsea installation 33 by letting a movable connector 34 at a downstream region of the second sub-unit 6″ engage a moveable mating connector 35 on the subsea installation, see FIG. 1.

[0062] Although the first and second sub-units 6′; 6″ could be an electric motor and a gear assembly, respectively, such a choice should not be considered to limit the present invention, as other choices could be made.