The present invention relates to a torque tool, and in particular, but not exclusively, to a torque tool which is used to actuate a rotary subsea valve.
A typical valve has a valve member which is mounted in a valve body or a housing, the valve member being movable relative to the housing between a closed position in which it impedes a flow of a fluid along a flow passage, and an open position in which it does not significantly impede the flow of the fluid along the flow passage. The valve member is mounted on a stem, which extends through an aperture in the housing, there being a seal assembly provided between the housing and the valve stem which allows for movement of the valve stem in the aperture while substantially preventing a leakage of the fluid from the valve housing via the aperture.
The valve member could be moved between its open and closed positions by rotation of the valve stem about its longitudinal axis, as in a ball valve, or by a translational movement parallel to its longitudinal axis, as in a gate valve.
To operate the valve, there is also provided a drive apparatus, such as an electric motor, which is connected to the stem, potentially via a driveline including a gearing system. The drive system is operable to move the valve stem and to drive a movement of the valve member between its open and closed positions. The drive apparatus may be provided in a retrievable torque tool if the valve member is moved between its open and closed positions by rotation of the valve stem. This may comprise an electric motor which is connected to a valve stem interface part via a gearbox so that operation of the motor drives rotation of the valve stem interface part. The valve stem interface part provides a mechanical coupling to the valve stem so that the rotation of the valve stem interface part is carried through to the rotation of the valve stem.
The motor, gearbox, and valve stem interface are typically mounted in a fluid filled housing, which fluid filled housing has an opening via which the valve stem can be engaged with the valve stem interface. The interior of the housing is connected to a compensator, and seals are provided between the housing and the valve stem interface so as to contain the fluid in the housing while allowing the valve stem interface to rotate relative to the housing. The present invention relates to a new configuration of such seals.
An aspect of the present invention is to provide for a new configuration of the above-described seals.
In an embodiment, the present invention provides a torque tool which includes a valve stem interface part having an exterior surface and a longitudinal axis which is parallel to the exterior surface, a torque tool housing having an aperture, an exterior, and an interior which comprises a volume of a fluid, a motor which is connected to the valve stem interface part so that an operation of the motor causes the valve stem interface part to rotate about the longitudinal axis, a first seal, and a second seal. The aperture of the torque tool housing is configured so that the valve stem interface part is accessible from the exterior of the torque tool housing. The first seal is arranged between the torque tool housing and the exterior surface of the valve stem interface part. The first seal comprises a seal body which comprises a first ring and a second ring. The first ring and the second ring each comprise a generally circular first portion having a free edge, and a second portion. The second portion of each of the first ring and the second ring of the first seal are connected together. The second seal is arranged between the torque tool housing and the exterior surface of the valve stem interface part. The second seal comprises a seal body which comprises a first ring and a second ring. The first ring and the second ring each comprise a generally circular first portion having a free edge, and a second portion. The second portion of each of the first ring and the second ring of the second seal are connected together. The first seal and the second seal are each configured to be axially displaceable relative to one another. The first seal and the second seal are configured to together provide a substantially fluid tight seal between the exterior surface of the valve stem interface part and the torque tool housing so as to substantially prevent the fluid in the torque tool housing from leaking out of the torque tool housing via the aperture. The first seal forms a first barrier to a leakage of the fluid along the aperture, and the second seal forms a second barrier to the leakage of the fluid along the aperture.
The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:
A first aspect of the present invention provides a torque tool comprising a housing having an exterior and an interior in which is located a volume of fluid, a motor, and an interface part having an exterior surface and a longitudinal axis which is parallel to the exterior surface, the motor being connected to the interface part so that operation of the motor causes the interface part to rotate about its longitudinal axis, the housing having an aperture via which the interface part may be accessed from the exterior of the housing, the torque tool further comprising first and second seals provided between the housing and the exterior surface of the interface part, the seals being axially displaced relative to one another and together providing a substantially fluid tight seal between the exterior surface of the interface part and the housing to substantially prevent fluid in the housing from leaking out of the housing via the aperture, the first seal forming a first barrier to leakage of fluid along the aperture and the second seal forming a second barrier to leakage of fluid along the aperture, the seals each having a seal body which comprises a first ring and a second ring, the rings each having a generally circular first portion having a free edge and a second portion, the second portions of the rings being connected together, wherein the seals are arranged so that, for each seal, the second portions of both rings are closer to the fluid than the first portions of the rings, and the first portion of the first ring is in contact with the housing and the first portion of the second ring is in contact with the exterior surface of the interface part.
The first portion of the first ring may be in sealing engagement with the housing, and the first portion of the second ring is in sealing engagement with the exterior surface of the interface part.
The seals may have a generally V-shaped or U-shaped cross-section.
Each seal is advantageously provided with a spring which is arranged to urge the first portions of the rings apart, the spring urging the first ring into contact with the housing, and the second ring into contact with the exterior surface of the interface part.
Each spring may be a compression spring which is located in the space between the two rings of the seal body.
The spring of the second seal advantageously urges the first portions of the rings apart with a greater force than the spring of the first seal so that if the fluid is pressurized up to a threshold level, fluid may leak along the aperture past the first seal, but would be prevented from passing the second seal.
The motor may comprise an electric motor.
The motor may be connected to the interface part via a gearing system.
The torque tool may further be provided with a compensator which is connected to the interior of the housing and which acts to equalize the pressure of the fluid in the housing with the pressure of the environmental fluid at the exterior of the housing.
The interface part may comprise a socket.
These and other characteristics will become clear from the following description of illustrative embodiments, which are given as non-restrictive examples, with reference to the attached drawings.
The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, “upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings which are associated with a normal use of the present invention. The terms are used for the reader's convenience only and shall not be limiting.
The valve 10 is also provided with a valve stem 16 having an exterior surface and a longitudinal axis A which is parallel to the exterior surface and which extends through an aperture in the housing 11. A first end of the valve stem 16 is secured to the valve member 12 and is located inside the housing 11, and a second, free, end of the valve stem 16 is located outside of the housing 11. As, in this embodiment, the valve member 12 is rotated between its open position and closed position by rotating the valve stem 16 about its longitudinal axis A, at least a central portion of the valve stem 16 is cylindrical, and the exterior surface of the central portion is curved.
The valve 10 further comprises first and second annular seals 18, 20 which are provided between the housing 11 and the exterior surface of the central portion of the valve stem 16, the first and second annular seals 18, 20 being axially displaced relative to one another and together providing a substantially fluid tight seal between the exterior surface of the valve stem 16 and the housing 11 to substantially prevent a working fluid in the housing 11 from leaking out of the housing 11 via the aperture. The first annular seal 18 forms the first barrier to a leakage of working fluid along the aperture, and the second annular seal 20 forms the second barrier to the leakage of working fluid along the aperture. In other words, the first annular seal 18 is closest to the interior of the housing 11, and the second annular seal 20 is closest to the exterior of the housing 11. The first and second annular seals 18, 20 may be O-rings, lip seals, or any other form of suitable seal as are known to persons skilled in the art.
It should be appreciated, however, that the present invention is not restricted to use with a ball valve. The present invention could be applied to any configuration of valve which comprises a rotatable shaft which is mounted in an aperture in the valve housing.
Also shown in
The torque tool 22 comprises a motor 24 which is connected to a valve stem interface part 26 via a gearbox 28 so that operation of the motor 24 causes a rotation of the valve stem interface part 26. In one embodiment, the motor 24 is an electric motor, but it will be appreciated that any other device which, when powered, can produce a rotational movement could instead be used (for example, a hydraulic motor).
The valve stem interface part 26 provides a releasably mechanical coupling to the valve stem 16 so that the rotation of the valve stem interface part 26 is carried through to rotation of the valve stem 16.
The valve stem interface part 26 may, for example, comprise a socket into which the free end of the valve stem 16 can be inserted. The free end of the valve stem 16 has in this case a non-circular transverse cross-section (for example, hexagonal), with the socket of the valve stem interface part 26 having a corresponding shape.
The motor 24, gearbox 28, and valve stem interface part 26 are mounted in a torque tool housing 30, which has an opening via which the valve stem 16 can be engaged with the valve stem interface part 26. The interior of the torque tool housing 30 is filled with a fluid (e.g., oil) and is connected to a compensator 36, with seals 32, 34 being provided between the torque tool housing 30 and the valve stem interface part 26 so as to contain the fluid in the torque tool housing 30 while allowing the valve stem interface part 26 to rotate relative to the housing.
A first seal 32 forms the first barrier to leakage of housing fluid and a second seal 34 forms the second barrier to leakage of housing fluid. In other words, the first seal 32 is closest to the interior of the torque tool housing 30, and the second seal 34 is closest to the exterior of the torque tool housing 30. The seals 32, 34 also prevent an ingress of fluid from the environment (environmental fluid) surrounding the torque tool housing 30 (sea water if the valve is actuated subsea) into the torque tool housing 30, the second seal 34 forming a first barrier to the ingress of environmental fluid into the torque tool housing 30, and the first seal 32 providing a second barrier to the ingress of environmental fluid into the torque tool housing 30.
The seals 32, 34 are lip seals and are illustrated in detail in
The seal body is advantageously made from a flexible and resilient polymer such as rubber or PTFE.
The seals 32, 34 are arranged so that the second portions of the rings 32a, 32b, 34a, 34b of both seals 32, 34 (i.e., the base of the V/U) are closer to the fluid in the torque tool housing 30 than the first portions of the rings 32a, 32b, 34a, 34b of both seals 32, 34.
The seals 32, 34 are each provided with a spring 38, 40 which is arranged between the two rings 32a, 32b, 34a, 34b of each seal 32, 34 to urge the first portions of the rings 32a, 32b, 34a, 34b apart. In this embodiment, the spring 38, 40 urges the first ring 32a, 34a into contact with the torque tool housing 30 and the second ring 32b, 34b into contact with the valve stem interface part 26.
In this embodiment, the springs 38, 40 are compression springs, which in this embodiment are annular and have a generally V-shaped cross-section, and are made from a metal such as a spring steel. The springs 38, 40 are compressed to bring their free edges together for insertion into the space between the two rings 32a, 32b, 34a, 34b of each seal body, and then released so that each of the free edges engages with one of the rings 32a, 32b, 34a, 34b of the seal body. It will be appreciated by a skilled person that other configurations of spring could equally be used. The spring could, for example, have a U-shaped cross-section, or be toroidal in shape. The spring could be metallic (i.e., made from a spring steel) or be made from an elastomeric material. Each spring 38, 40 could moreover, in fact, comprise a plurality of springs.
The compensator 36 provides that the fluid in the torque tool housing 30 is pressure balanced with the fluid pressure at the exterior of the housing 11 (the environmental fluid pressure). When the torque tool 22 is assembled, the fluid pressure in the torque tool housing 30 will therefore be at atmospheric pressure, or perhaps at a pressure which is slightly higher than atmospheric pressure, but if the torque tool 22 is used subsea, the compensator 36 will provide that the pressure of the fluid inside the torque tool housing 30 increases to match the water pressure at the depth to which the torque tool 22 is lowered.
There is, however, a small volume of trapped fluid 42 in the space between the seals 32, 34, and this trapped fluid 42 will be at atmospheric pressure and is not pressure balanced with the environmental fluid pressure. As such, if the two seals 32, 34 provide a perfect seal between the torque tool housing 30 and the valve interface part 26, the pressure of this trapped fluid 42 will stay at atmospheric pressure even when the torque tool 22 is used subsea and is exposed to an environmental fluid pressure which is substantially greater than atmospheric pressure. This would create a pressure differential across the seals 32, 34, each seal 32, 34 being exposed to fluid at the subsea fluid pressure on one side, and atmospheric pressure on the other side. When the torque tool 22 is used at significant depths, this pressure differential can be high, for example, around 400 Bar (40,000 kPa) when the valve 19 is used at a depth of 4,000 m.
In some embodiments, the fluid in the torque tool housing 30 may be pressurized to a pressure which is slightly above atmospheric pressure when the torque tool 22 is assembled. The trapped fluid 42 will in this case be at a pressure which is slightly above atmospheric pressure. Nevertheless, if only a slight over-pressure is applied, there may still be a significant pressure differential across the seals 32, 34 when the torque tool 22 is used at depth.
This pressure differential can cause frictional drag between the seals 32, 34 and the valve interface part 26 which impedes the rotational movement of the valve stem interface part 26 which is required to rotate the valve stem 16 and actuate the valve 10. There can consequently be a significant variation in the torque required to rotate the valve stem 16 depending on the depth at which the valve 10 is located. This can make accurate control of the valve movement tricky, as the torque applied by the motor 24 to the valve stem interface part 26 is known, but what this translates to in terms of the torque applied to the valve member 12 is not known. Moreover, to provide a motor 24 which is capable of overcoming the frictional drag on the valve stem interface part 26 when the valve 10 is used at great depths, it will be necessary to provide a significantly more powerful (and therefore larger) motor 24 than would be required to operate the valve 10 at lower depths.
This problem may be alleviated by using the arrangement of the seals 32, 34 described above.
Considering the second seal 34, it will be appreciated that the pressurized environmental fluid would act with the spring 40 to force the first portions of the rings 34a, 34b apart against the torque tool housing 30 or the valve stem interface part 26 respectively, thus increasing the effectiveness of the seal and reducing the chances of environmental fluid passing the seal 34.
In contrast, considering the first seal 32, the pressurized fluid inside the torque tool housing 30 will act against the spring 38 to urge the first portions of the rings 32a, 32b together and out of sealing engagement with the torque tool housing 30 and the valve stem interface part 26, thus reducing the effectiveness of the seal. There may thus be some leakage of fluid in the torque tool housing 30 past the first seal 32 into the space between the seals 32, 34, thus increasing the pressure of the trapped fluid 42. This would reduce the pressure differential across the seals 32, 34 and reduce the frictional drag on the valve stem interface part 26.
The spring 40 of the second seal 34 is advantageously more powerful than the spring 38 of the first seal 34, and therefore urges the first portions of the rings 34a, 34b apart with a greater force than the spring 38 of the first seal 32. This means that if the fluid in the torque tool housing 30 is pressurized up to a threshold level, fluid may leak past the first seal 32 into the volume of trapped fluid 42, but be prevented from passing the second seal 32.
It will be appreciated that, by virtue of this arrangement, the pressure of the fluid between the seals 32, 34 is elevated to match or be close to the environmental pressure at depth. When the torque tool 22 is brought back to the surface from use at depth, the fluid between the seals 32, 34 could be higher than atmospheric pressure. However, when the pressure differential across the second seal 34 is high enough, the pressurized fluid trapped between the seals 32, 34 will act against the spring 40 to urge the first portions of the rings 34a, 34b together and out of sealing engagement with the housing 30 and valve stem interface part 26, thereby reducing the effectiveness of the second seal 34. There may thus be some leakage of fluid from the volume between the seals 32, 34 past the second seal 34 to the exterior of the torque tool housing 30, thus reducing the pressure of the trapped fluid 42.
It should be appreciated that while the present invention is described above in relation to a torque tool for use in actuating a subsea valve, this need not be the case, and may be applied to a torque tool used in other applications which requires the rotation of a part. It could, for example, be applied to a torque tool used for securing a bolt in a flanged coupling of a subsea pipeline. As before, the torque tool could be permanently or semi-permanently mounted on the part in question, and operated exclusively to rotate that particular part, being removed or replaced only when faulty or when rotation is no longer required. It could alternatively be a tool which is moved from part to part, by a human operator or by an ROV, to rotate different parts in succession.
The present invention is not limited by the embodiments described above; reference should also be had to the appended claims.
Number | Date | Country | Kind |
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2115449.7 | Oct 2021 | GB | national |
This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/NO2022/050247, filed on Oct. 27, 2022 and which claims benefit to Great Britain Patent Application No. 2115449.7, filed on Oct. 27, 2021. The International Application was published in English on May 4, 2023 as WO 2023/075608 A1 under PCT Article 21 (2).
Filing Document | Filing Date | Country | Kind |
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PCT/NO2022/050247 | 10/27/2022 | WO |