The present invention relates to a rod locking apparatus, and in particular to a rod locking apparatus suitable for use in locking the actuators in ram-type blow out preventers.
The present invention relates to a rod locking device for locking reciprocating piston type fluid actuators in a preferred position. Actuators of this type are particularly suited for positioning the rams of ram-type blow out preventers. It is advantageous and desirable to mechanically lock the rods of these actuators to provide that the blow out preventer rams will be maintained in a preferred position should hydraulic pressure be lost.
Relevant prior art systems include U.S. Pat. No. 4,969,390 which describes a ram locking apparatus for blowout preventer rams which allows the rams to be locked in the closed position. A tapered end of a rod and a wedge surface of a piston have serrated surfaces to increase friction between the wedging surfaces and to provide a self-locking engagement in a small, compact apparatus.
Other related prior art includes U.S. Pat. No. 2,632,425, U.S. Pat. No. 3,050,943, U.S. Pat. No. 3,242,826, U.S. Pat. No. 3,918,478, U.S. Pat. No. 3,941,141, U.S. Pat. No. 4,188,860, U.S. Pat. No. 4,290,577, U.S. Pat. No. 4,305,565, U.S. Pat. No. 4,519,571, U.S. Pat. No. 4,601,232, U.S. Pat. No. 4,840,346, U.S. Pat. No. 4,969,627, U.S. Pat. No. 5,025,708, and U.S. Pat. No. 5,056,418.
In an embodiment, the present invention provides a rod locking apparatus which includes a housing comprising a first tubular passage and a second tubular passage which are arranged to intersect with each other, the first tubular passage comprising a serrated locking surface, and a wedge piston slidably arranged in the first tubular passage. The wedge piston comprises a front side which comprises a wedge surface which is configured to engage an end surface of a rod to be locked, and a serrated rear side which is configured to engage with the serrated locking surface.
The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:
In an embodiment, the present invention provides a rod locking apparatus comprising:
Providing the rear side of the wedge piston with serrations which engage with the serrated locking surface means that the area of contact between the two serrated surfaces can be larger than in the arrangement described in U.S. Pat. No. 4,969,390. This provides a higher frictional locking force, and therefore provides more secure locking and/or allows a larger wedge angle to be used. A larger wedge angle allows for a shorter stroke length, and thus a shorter and more compact locking device.
The serrated locking surface may be integral with the remainder of the housing, or may be provided on a separate support part which is fixed relative to the housing.
The wedge piston is movable between a closed position in which it substantially blocks the second tubular passage, and an open position in which the second tubular passage is open.
The wedge piston may be provided with a through passage which extends from the front side to the rear side of the wedge piston generally parallel to the second tubular passage so that, when the wedge piston is in the open position, the through passage is generally coaxial with the second tubular passage, and when the wedge piston is in the closed position, the through passage is not aligned with the second tubular passage.
The rear side of the wedge piston may be inclined at an angle of between 10 and 20° to the wedge surface. In an embodiment, the rear side of the wedge piston can, for example, be inclined at an angle of around 12° to the wedge surface.
The first tubular passage may extend at an angle of between 100 and 110° to the second tubular passage. In an embodiment, the first tubular passage can, for example, extend at an angle of 102° to the second tubular passage.
The wedge piston may further be provided with two end surfaces which extend generally perpendicular to the rear side of the wedge piston.
A first one of the two end surfaces may provide a first piston face on which pressurized fluid introduced into a first end of the first tubular passage acts to push the wedge piston along the first tubular passage towards a second end thereof.
A second one of the two end surfaces may provide a second piston face on which pressurized fluid introduced into the second end of the first tubular passage acts to push the wedge piston along the first tubular passage towards the first end thereof.
Movement of the wedge piston from the open position to the closed position may comprise movement of the wedge piston from the second end of the first tubular passage towards the first end of the first tubular passage, and vice versa.
The surface area of the first piston face may be greater than the surface area of the second piston face.
The rod locking apparatus is further provided with a seal which extends between the housing and the wedge piston to substantially prevent a flow of fluid along the first tubular passage past the seal, while allowing the wedge piston to slide along the first tubular passage. The seal is advantageously mounted on the wedge piston. In an embodiment, the seal can, for example, comprise an O-ring mounted in a groove in the wedge piston.
The housing may further be provided with a first end cap which closes the first tubular passage at a first end thereof. The first end cap may be provided with an aperture and a pressurized fluid supply device which supplies a pressurized fluid into the first end of the first tubular passage via the aperture in the first end cap.
The housing may further be provided with a second end cap which closes the first tubular passage at a second end thereof. The second end cap may be provided with an aperture and a pressurized fluid supply device which supplies a pressurized fluid into the second end of the first tubular passage via the aperture in the end cap.
The housing may be provided with a supply tube which extends from the aperture in the second end cap into a bore in the wedge piston, there being a seal between the supply tube and the wedge piston which provides a substantially fluid tight seal between an interior surface of the wedge piston surrounding the bore and an exterior surface of the supply tube. In this case, an end portion of the bore is the second piston face.
In an embodiment, the present invention provides an assembly of a rod locking apparatus having a rod located in the second tubular passage, the rod having a first end which is located in the second tubular passage and a second end which extends out of the second tubular passage.
The surface area of the serrated locking surface is advantageously greater than the surface area of the first end of the rod.
In an embodiment, the present invention provides a rod locking apparatus comprising:
This advantageously allows for a reliable unlocking due to the higher force from the larger piston. A rod locking apparatus having a large interacting locking area may in particular have a large frictional locking force, and may thus need higher force to unlock.
The rod locking apparatus according to this embodiment may have any of the features or any combination of features of the rod locking apparatus according to the previously described embodiments.
In an embodiment, the present invention provides a new and improved subsea ram type blowout preventer which is a hydraulically actuated mechanical ram locking device. The device may be actuated as part of the single, overall rams closing function, or as a separate ram locking only function. The ram locking device is mounted as an integral sub-assembly to the pressure containing and controlling ram BOP bonnet assembly, whereby the bonnet assembly is mounted to the ram type BOP main pressure controlling and containing body member.
Blowout preventers were developed to cope with extreme erratic pressures and uncontrolled flow emanating from a well reservoir during drilling. Known as a “kick”, this flow of pressure can lead to a potentially catastrophic event called a “blowout”. In addition to controlling the downhole well pressure and the flow of oil and gas, blowout preventers are intended to prevent tubular goods used in well drilling, such as, drill pipe, casing, collars, tools and drilling fluid, from being blown out of the wellbore when a kick or blowout threatens. Blowout preventers are critical to the safety of the crew, the drilling rig, the environment, and to the monitoring and maintenance of well integrity; blowout preventers are thus intended to provide an additional and fail-safe barrier to the systems that include them.
Ram-type blowout preventers are part of an overall pressure control system used in oil and gas operations commonly used as pressure containment and unexpected wellbore pressure spikes and well pressure control events. A conventional ram-type BOP is similar in operation to a gate valve, but uses a pair of opposing steel plungers or rams. The rams extend toward the center of the wellbore to restrict flow or retract open in order to permit flow. The inner and top faces of the rams are fitted with composite steel and elastomeric packers that press against each other, against the wellbore, and around well tubular members running through the wellbore. Outlets at the sides of the BOP housing (body) are used for connection to choke and kill lines or valves.
Rams, or ram blocks, are generally of five common types: pipe, variable bore pipe, blind, shear, and blind shear. The ram type blow out preventer is further usually integrated with additional well containment and control devices that inclusively make up a subsea blowout preventer stack.
A wedge piston 12 is slidably provided in the main housing 1. The wedge piston 12 has a front side with a wedge surface 11 which engages a back end surface 13a of a tail rod 13 of a blowout preventer actuator. The wedge piston 12 also has a serrated rear side which engages with the serrated locking surface 4a.
The tail rod 13 is coupled to a hydraulic, ram operating piston 14 provided in the BOP bonnet 20 (see
In this embodiment, the wedge piston 12 has a transverse bore forming a through passage 17 which extends from the front side to the rear side of the wedge piston 12 generally parallel to the second tubular passage 23 and, when the wedge piston 12 is in the open position, is aligned with the second tubular passage 23 so that the tail rod 13 may extend along the second tubular passage 23, as shown in
The wedge piston 12 incorporates a spline shaped serrated rear side 16 which utilize a series of ridges, or teeth, that mesh with grooves in the serrated locking surface 4a (see
The serrated rear side 16 of the wedge piston 12 is inclined at an angle of between 10 and 20° to the wedge surface 11. In this embodiment, the serrated rear side 16 of the wedge piston 12 is inclined at an angle of around 12° to the wedge surface 11. The first tubular passage 22 extends at an angle of between 100 and 110° to the second tubular passage 23. In this embodiment, the first tubular passage 22 extends at an angle of 102° to the second tubular passage 23. Designing the first tubular passage 22 to extend at an angle to the second tubular passage 23 which corresponds to the angle of inclination between the serrated rear side 16 of the wedge piston 12 and the wedge surface 11 permits the back end surface 13a of the tail rod 13 to extend perpendicularly to the rod longitudinal axis. Other combinations of inclination angle and angle between the first tubular passage 22 and the second tubular passage 23 are, however, possible.
The wedge piston 12 is further provided with two end surfaces 9, 24 which extend generally perpendicular to the serrated rear side 16 of the wedge piston 12. A first end surface 9 of the two end surfaces 9, 24 provides a first piston face on which pressurized fluid introduced into a first end 27a of the first tubular passage 22 acts to push the wedge piston 12 along the first tubular passage 22 towards a second end 27b thereof. A second end surface 24 of the two end surfaces 9, 24 provides a second piston face on which pressurized fluid introduced into the second end 27b of the first tubular passage 22 acts to push the wedge piston along the first tubular passage 22 towards the first end 27a thereof.
In this embodiment, movement of the wedge piston 12 from the open position to the closed position comprises a translational movement of the wedge piston 12 in a direction extending from the second end 27b of the first tubular passage 22 towards the first end 27a of the first tubular passage 22, and vice versa.
A first end cap 8a and a second end cap 8b close the first tubular passage 22 at the first end 27a and second end 27b, respectively. Apertures in the form of channels 21a and 21b are provided through the first end cap 8a and the second end cap 8b along with a device for supplying pressurized fluid therethrough and into the first tubular passage 22. The rod locking device 100 is provided with a seal 26 which extends between the main housing 1 and the wedge piston 12 to substantially prevent the flow of fluid along the first tubular passage 22 past the seal 26, while allowing the wedge piston 12 to slide along the first tubular passage 22. In this embodiment, the seal 26 is provided in the form of an O-ring mounted in a groove on the wedge piston 12, to seal against the inner surface of the first tubular passage 22 and delimit a cavity 15. Providing pressurized fluid through channel 21a and into cavity 15 produces a pressure force on the first end surface 9 of the wedge piston 12 and acts to push the wedge piston 12 along the first tubular passage 22 in a direction away from the first end 27a. This moves the wedge piston 12 into the open, or unlocked, position of the rod locking device 100 and BOP ram.
In this embodiment, from the second end cap 8b, a supply tube 2 extends into the first tubular passage 22 and into a wedge piston bore 10 provided in the wedge piston 12. The supply tube 2 has an internal bore permitting hydraulic fluid communication from a hydraulic fluid supply (not shown in the drawings) through aperture/channel 21b in the second end cap 8b and into wedge piston bore 10. The supply tube 2 is sealed against wedge piston bore 10, for example, by O-rings 25 (see
As a result of using a wedge piston bore 10 and supply tube 2, it will be appreciated that, in this embodiment of the present invention, the surface area of the first piston face 9 is greater than the surface area of the second piston face 24. This means that, for a given fluid pressure, the force moving the wedge piston 12 to the open position is greater than the force moving the wedge piston 12 to the closed position. This may have the advantage of allowing a reliable unlocking of the rod locking device 100 and consequent opening of the BOP.
This need not be the case, however, and in an alternative embodiment of the present invention, the second piston face 24 may be provided on the end of the wedge piston 12 facing the second end 27b of the first tubular passage 22, the second piston face 24 of the wedge piston 12 being sealed against the inner surface of the first tubular passage 22, in a similar way to the arrangement provided by first piston face 9. Referring now to
To open the rod locking device 100, fluid pressure is provided through channel 21a to act on first piston surface 9 as described above. Advantageously, as first piston surface 9 is provided with a larger area than second piston face 24′ (see
Advantageously, the serrated rear side 16 is provided along substantially the full length of the wedge piston 12. The area of the serrated locking surface 4a may be adapted for a particular use or operating requirements, thus providing freedom to, for example, use a large locking surface in applications with high safety requirements.
The rod locking device according to the present invention thus provides a simple, robust, and more reliable, hydraulically actuated, mechanical assembly that provides a way to lock the rams of a ram-type blowout preventer in the closed and sealed position, even if hydraulic pressure is lost or removed, and only allows the rams to open when hydraulic pressure is intentionally applied to the BOP and locking mechanism's operating system for the expressed purpose of opening the blowout preventer's ram assemblies.
The rod locking device according to the present invention is suitable to lock any type of ram (pipe, variable bore pipe, shear, blind, shearing blind) in an infinite range of closed positions, providing a ridged mechanical locking mechanism for rams that will not allow them to open, or retreat from their closed position, even if no closing pressure is applied, or maintained. The rod locking device is equally suited for use with wellbore control devices utilizing gates, including such gates having shearing capability.
When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the present invention in diverse forms thereof.
The present invention is not limited to embodiments described herein; reference should be had to the appended claims.
Number | Date | Country | Kind |
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1514762.2 | Aug 2015 | GB | national |
This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/NO2016/050167, filed on Aug. 15, 2016 and which claims benefit to Great Britain Patent Application No. 1514762.2, filed on Aug. 19, 2015. The International Application was published in English on Feb. 23, 2017 as WO 2017/030444 A1 under PCT Article 21(2).
Filing Document | Filing Date | Country | Kind |
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PCT/NO2016/050167 | 8/15/2016 | WO | 00 |