NO20180337A1

NO20180337A1 - Rod locking appratus

Info

Publication number: NO20180337A1
Application number: NO20180337A
Authority: NO
Inventors: Thor Arne Håverstad; J Gilbert Nance; John L Alsup; Marion E Eagles; Iii Bolie C Williams; Erik Norbom
Original assignee: Electrical Subsea & Drilling As
Priority date: 2015-08-19
Filing date: 2018-03-07
Publication date: 2018-03-07
Also published as: AU2016307635A8; BR112018003204A2; GB2557777A; WO2017030444A1; GB201514762D0; US20180252060A1; GB201803686D0; AU2016307635A1

Abstract

A rod locking apparatus comprising a housing having a first and second intersecting tubular passages, the first tubular passage being provided with a serrated locking surface, a wedge piston slidably arranged in the first tubular passage, the wedge piston having a front side with a wedge surface adapted in use to engage an end surface of a rod to be locked, wherein the wedge piston has a serrated rear side which engages with the serrated locking surface.A rod locking apparatus comprising a housing having a first and second intersecting tubular passages, the first tubular passage being provided with a serrated locking surface, a wedge piston slidably arranged in the first tubular passage, the wedge piston having a front side with a wedge surface adapted in use to engage an end surface of a rod to be locked, where the wedge piston has a serrated rear side which engages with the serrated locking surface.

Description

ROD LOCKING APPARATUS

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.

Background

This 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 ensure that the blow out preventer rams will be maintained in a preferred position should hydraulic pressure be lost.

Relevant prior art systems include US patent document US 4,969,390 which discloses 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 provide a self-locking engagement and thereby provide a small, compact apparatus.

Other related prior art includes US patent documents US2632425, US3050943, US3242826, US3918478, US3941141, US4188860, US4290577, US4305565, US4519571, US4601232, US4840346, US4969627, US5025708, and US5056418.

Summary

According to an embodiment we provide a rod locking apparatus comprising: a housing having a first and second intersecting tubular passages, the first tubular passage being provided with a serrated locking surface,

a wedge piston slidably arranged in the first tubular passage,

the wedge piston having a front side with a wedge surface adapted in use to engage an end surface of a rod to be locked,

wherein the wedge piston has a serrated rear side which engages with the serrated locking surface.

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 illustrated in US 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 gives 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 such 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 one embodiment, the rear side of the wedge piston is 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 one embodiment, the first tubular passage extends 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 flow of fluid along the first tubular passage past the seal, whilst allowing the wedge piston to slide along the first tubular passage. Advantageously, the seal is mounted on the wedge piston. In a preferred embodiment, the seal comprises an 0-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 means for the supply of 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 means for the supply of pressurized fluid in to 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 one embodiment we provide 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 one embodiment we provide a rod locking apparatus comprising:

a housing having a first and second intersecting tubular passages,

a wedge piston slidably arranged in the first tubular passage,

the wedge piston having a front side with a wedge surface adapted in use to engage an end surface of a rod to be locked, and two end surfaces which extend generally perpendicular to the rear side of the wedge piston,

the wedge piston being 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,

a first one of the two end surfaces providing 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 to a second end thereof,

a second one of the two end surfaces providing 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 to the first end thereof,

movement of the wedge piston from the open position to the closed position comprising movement of the wedge piston from the second end of the first tubular passage to the first end of the first tubular passage, and vice versa,

wherein the surface area of the first piston face is greater than the surface area of the second piston face.

Advantageously, this allows reliable unlocking due to the higher force from the larger piston. In particular, a rod locking apparatus having a large interacting locking area may have a large frictional locking force and thus may 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.

Brief description of the drawings

FIGURE 1 is a perspective view of a cross-section through an assembly of a rod locking apparatus according to the invention and a tail rod of a blowout preventer actuator,

FIGURE 2 is a longitudinal cross-section through the assembly illustrated in Figure 1 in the open position,

FIGURE 3 is a longitudinal cross-section through the assembly illustrated in Figure 2 in the closed position,

FIGURE 4a is a perspective view of the wedge piston and serrated rear side of the rod locking apparatus illustrated in Figure 1,

FIGURE 4b is a perspective view of the serrated locking surface of the rod locking apparatus illustrated in Figure 1.

Detailed description

In one embodiment, the invention relates to a new and improved subsea ram type blowout preventer 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. As a general body, bonnet, and locking assembly these parts make up primary members of a subsea ram type blowout preventer.

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 crew, drilling rig, and environment, and to the monitoring and maintenance of well integrity; thus blowout preventers are 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.

Figure 1 illustrates one embodiment of a ram locking device 100 according to the present invention. The device 100 comprises a main housing 1 having a first tubular passage 22 and a second tubular passage 23. In this embodiment, the housing 1 is provided with a mounting attachment 5 to attach the ram locking device to the BOP bonnet 20, as illustrated in Figure 2. The first tubular passage is provided with a serrated locking surface 4a, which in this embodiment is provided on a support part 4 (illustrated in detail in Figure 4B), which is fixed relative to the housing 1 and described in further detail below. It should be appreciated, however, that the support part 4 may be integral with the housing.

A wedge piston 12 is slidably provided in the 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 blow out 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 Fig. 2), and extends into the second tubular passage 23. The wedge piston 12 is movable between a closed position in which it substantially blocks the second tubular passage 23 and an open position in which the second tubular passage 23 is open.

In this example, 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 21 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 Figure 2. When the wedge piston 12 is in the closed position, the through passage 17 is not aligned with the second tubular passage 23, as illustrated in Figure 1.

The wedge piston 12 incorporates a spline shaped rear side 16 which utilize a series of ridges, or teeth, that mesh with grooves in the serrated locking surface 4a (see Fig. 4B). The design of the serrations on the rear side 16 of the wedge piston 12 and the serrated locking surface 4a may be according to one of the alternatives described in US 4,969,390 or any other suitable design. This may include splines, grooves, ridges, or teeth, or a combination thereof, suitable for producing a mating motion and a friction-based locking effect between the rear side 16 of the wedge piston 12 and the serrated locking surface 4a.

The 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 example, the 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 23 passage. In this example, 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 rear side 16 of the wedge piston 12 and the wedge surface 11 permits the end surface 13a of the rod 13 to extend perpendicularly to the rod longitudinal axis. However, other combinations of inclination angle and angle between the first and second tubular passages are possible.

The wedge piston 12 is further provided with two end surfaces 9, 24 which extend generally perpendicular to the rear side 16 of the wedge piston 12. A first one 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 one 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 example, movement of the wedge piston 12 from the open position to the closed position comprises 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 of the first tubular passage, and vice versa.

A first end cap 8a and a second end cap 8b close the first tubular passage 22 at its outer ends 27a and 27b. Apertures in the form of channels 21 a and 21 b are provided through the end caps 8a and 8b along with means for supplying pressurized fluid therethrough and into the first tubular passage 22. The rod locking device is provided with a seal 26 which extends between the housing and the wedge piston to substantially prevent flow of fluid along the first tubular passage past the seal, whilst allowing the wedge piston to slide along the first tubular passage. In this example, the seal 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 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 locking device and BOP ram.

In this example, 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) through aperture/channel 21b in the second end cap 8b and into bore 10. The supply tube 2 is sealed against wedge piston bore 10, for example by means of O-rings 25 (see Figs 2 and 3). The second piston face is therefore formed by the end face of the wedge piston bore 10. Provision of hydraulic fluid pressure into wedge piston bore 10 through supply tube 2 generates a pressure force on the second piston face in the wedge piston bore 10 and urges the wedge piston 12 away from second end 27b along the first tubular passage 22 and to a locked position of the rod locking device and BOP ram.

As a result of using a wedge piston bore 10 and supply tube 2, it will be appreciated that, in this embodiment of the invention, the surface area of the first piston face is greater than the surface area of the second piston face.

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 reliable unlocking of the rod locking device and consequent opening of the BOP.

This need not be the case, however, and in an alternative embodiment of the 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 , the second end 24 of the wedge piston 12 being sealed against the inner surface of the first tubular passage, in a similar way to the arrangement provided by piston face 9. Referring now to Figure 2, a ram locking device is shown in an open, or unlocked, position. In this state the BOP ram is open. The ram locking device is fixed to a BOP bonnet 20 by mounting attachment 5. A ram operating piston 14 is provided in the BOP bonnet 20 to operate the ram. In this position the through passage 17 of the wedge piston 12 is aligned with the second tubular passage 23 and the tail rod 13 extends through the through passage 17.

Figure 3 shows the closed position of the ram locking device is shown. In this state, closing of the BOP ram has been performed by ram operating piston 14 and the tail rod 13 has been moved out of the through passage 17.

Subsequently, fluid pressure is provided through channel 21b and into wedge piston bore 10 to move the wedge piston 12 towards the first end 27a. As the wedge piston approaches its end position towards the first end 27a, the wedge surface 11 engages the end surface 13a of the tail rod 13. The rear side 16 of the wedge piston 12 is inclined by approximately 12° to the wedge surface 11 , thus moving the wedge piston towards the first end 27a produces a wedging force between the wedge piston 12 and the end surface 13a and support part 4. This produces a mating motion between the serrated rear side 16 of the wedge piston 12 and the serrated locking surface 4a (see Figure 4B), which provides a friction-based self-locking effect. Thus, even in the case of loss of fluid pressure in wedge piston bore 10 and a back force acting by the tail rod 13 on the wedge surface 11 , the friction between the serrated rear side 16 of the wedge piston 12 and the serrated locking surface 4a will keep the wedge piston 12 in the locked position.

To open the ram locking device, fluid pressure is provided through channel 21a to act on piston surface 9 as described above. Advantageously, as piston surface 9 is provided with a larger area than second piston surface 24' (see Figure 1), the locking device can be securely unlocked even in the case of a strong friction locking effect.

Figure 4A shows details of the wedge piston 12 with the serrated rear surface 16 and the through passage 17. Figure 4A further shows the support part 4. The support part 4 may have a throughbore 27 which is aligned with the second tubular passage 23 (see Fig. 1) to allow the rod 13 to extend through the throughbore 27 in the open position of the locking apparatus, as shown in Fig. 2. Figure 4B shows further details of a part of the support part 4, showing the serrated locking surface 4a which, in use, engages with the serrated rear side 16 of the wedge piston 12.

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 invention thus provides a simple, robust, and more reliable, hydraulically actuated, mechanical assembly that provides means 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 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 utilised for realising the invention in diverse forms thereof.

Claims

1. A rod locking apparatus comprising:

a housing having a first and second intersecting tubular passages, the first tubular passage being provided with a serrated locking surface,

a wedge piston slidably arranged in the first tubular passage,

2. A rod locking apparatus according to claim 1 wherein the serrated locking surface is integral with the remainder of the housing, or may be provided on a separate support part which is fixed relative to the housing.

3. A rod locking apparatus according to claim 1 or 2 wherein 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.

4. A rod locking apparatus according to any preceding claim wherein the wedge piston is 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 such 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.

5. A rod locking apparatus according to any preceding claim wherein the rear side of the wedge piston is inclined at an angle of between 10 and 20° to the wedge surface.

6. A rod locking apparatus according to any preceding claim wherein the rear side of the wedge piston is inclined at an angle of around 12° to the wedge surface.

7. A rod locking apparatus according to any preceding claim wherein the first tubular passage extends at an angle of between 100 and 110° to the second tubular passage.

8. A rod locking apparatus according to any preceding claim wherein the first tubular passage extends at an angle of 102° to the second tubular passage.

9. A rod locking apparatus according to any preceding claim wherein the wedge piston is further provided with two end surfaces which extend generally perpendicular to the rear side of the wedge piston.

10. A rod locking apparatus according to any preceding claim wherein a first one of the two end surfaces provides 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.

11. A rod locking apparatus according to claim 10 wherein a second one of the two end surfaces is provided with 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.

12. A rod locking apparatus according to claims 10 or 11 wherein movement of the wedge piston from the open position to the closed position comprises 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.

13. A rod locking apparatus according to any preceding claim wherein the surface area of the first piston face is greater than the surface area of the second piston face.

14. A rod locking apparatus according to any preceding claim wherein the rod locking apparatus is further provided with a seal which extends between the housing and the wedge piston to substantially prevent flow of fluid along the first tubular passage past the seal, whilst allowing the wedge piston to slide along the first tubular passage.

15. A rod locking apparatus according to claim 14 wherein the seal is mounted on the wedge piston.

16. A rod locking apparatus according to claim 15 wherein the seal comprises an O-ring mounted in a groove in the wedge piston.

17. A rod locking apparatus according to any preceding claim wherein the housing is further provided with a first end cap which closes the first tubular passage at a first end thereof.

18. A rod locking apparatus according to claim 17 wherein the first end cap is provided with an aperture and means for the supply of pressurized fluid into the first end of the first tubular passage via the aperture in the first end cap.

19. A rod locking apparatus according to claim 17 or 18 wherein the housing is further provided with a second end cap which closes the first tubular passage at a second end thereof.

20. A rod locking apparatus according to claim 19 wherein the second end cap is provided with an aperture and means for the supply of pressurized fluid in to the second end of the first tubular passage via the aperture in the end cap.

21. A rod locking apparatus according to claim 20 wherein the housing is 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.

22. An assembly of a rod locking apparatus according to any preceding claim, and 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.

23. An assembly according to claim 22 wherein the surface area of the serrated locking surface is greater than the surface area of the first end of the rod.

24. A rod locking apparatus comprising:

a housing having a first and second intersecting tubular passages,

a wedge piston slidably arranged in the first tubular passage,

25. A rod locking apparatus according to claim 24 having any of the features or any combination of features of the rod locking apparatus according to claims 1 to 21.

26. A rod locking apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

27. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.