This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is extracted. These wellhead assemblies may include a wide variety of components, such as various casings, valves, fluid conduits, and the like, that control drilling or extraction operations.
More particularly, wellhead assemblies often include a blowout preventer, such as a ram-type blowout preventer that uses one or more pairs of opposing rams that press against one another to restrict flow of fluid through the blowout preventer. The rams typically include sealing elements (also referred to as ram packers) that press together when two opposing rams close against one another. In some instances, locking devices are used to lock the rams in their closed positions. But changes in pressure within the blowout preventer can increase axial loading on the locking devices. And in some instances this loading can cause difficulties in unlocking the rams.
Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
Embodiments of the present disclosure generally relate to locking devices. The locking devices of at least some embodiments include linear clutches that maintain axial loading on the locking devices within a designed loading range. In one embodiment, such locking devices are provided in a blowout preventer for locking rams in their closed positions. When the axial loading on the locking devices exceeds the designed loading range, the linear clutches allow the rams to move to release potential energy and to reduce axial loading on the locking devices. A locking sleeve of one embodiment includes a segmented end with one or more grooves to engage a complementary surface of an actuation assembly of a ram. When the locking sleeve is engaged in this manner, the ram and the actuation assembly are locked in place while still allowing discrete movement by these components to reduce axial loading on the locking device.
Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.
These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components.
Turning now to the drawings, a blowout preventer 10 is illustrated in
Bonnet assemblies 20 of the blowout preventer 10 include bonnets 22 secured to the main body 12. The bonnet assemblies 20 include cylinders that house various components that facilitate control of rams 30 (
As illustrated in the cross-sections of
In operation, a force (e.g., from hydraulic pressure provided by control fluid from accumulator bottles) may be applied to the operating pistons 34 to drive the rams 30, via the connecting rods 36, into the bore 14 of the blowout preventer 10. The connecting rods 36 extend through the bonnets 22 and enable forces on the pistons 34 to be transmitted to the rams 30. Various seals may be provided between the connecting rods 36 and the bonnets 22 to inhibit leaking while enabling axial movement of the connecting rods through the bonnets. Although the rams 30 are illustrated as hydraulically actuated rams in the presently depicted embodiment, it is noted that the rams 30 could be actuated in any other suitable manner as well.
In the embodiment shown in
Again with reference to
But potential energy is stored in the ram packers 38 when the rams 30 are closed. Particularly, wellbore pressure on the closed rams 30 can cause significant compression of elastomeric ram packers 38. And once the locking assemblies 40 are moved into locked positions and the pressure on the rams 30 or on the actuation assemblies 32 is reduced (such as by removing the wellbore pressure from the rams), the potential energy of the ram packers 38 cause the rams 30 to load against the locking assemblies 40. Left unchecked, such loading would increase the force needed to unlock the locking assemblies 40 from the rams 30. More specifically, a load on an actuation assembly 32 from the ram 30 would be transmitted to the locking assembly 40. If the transmitted load were sufficiently high, the motor 24 would have insufficient torque to disengage the locking assembly 40. In such an instance, hydraulic pressure could be applied to the operating piston 34 to provide a contrary force that reduces the net force on the locking assembly 40 to a level at which the motor 24 could then disengage the locking assembly 40. But such a solution would require additional time and would rely on the capability to supply enough hydraulic pressure to the operating piston 34 to sufficiently counter the load from the compressed ram packers 38.
Consequently, in the presently depicted embodiment the locking assemblies 40 include linear clutches in the form of locking sleeves 44 that cooperate with the actuation assemblies 32 to reduce axial loading on the locking assemblies 40 from the compressed ram packers 38. The locking sleeves 44 are constructed to resist movement of the actuation assemblies 32 when the sleeves 44 are moved into locked positions. But the sleeves 44 also permit small amounts of movement of the assemblies 32 with respect to the sleeves 44 when compressive axial loading from the energy stored in the ram packers 38 exceeds an upper threshold of a designed load range of the system. These small movements cause partial decompression of the ram packers 38, which reduces both the potential energy they store and the axial loading on the locking sleeves 44.
One example of such a locking sleeve 44 is depicted in
Additional elements of a locking assembly 40 in accordance with one embodiment are illustrated in
Operation of the locking assembly 40 in accordance with this embodiment may also be better understood with reference to
As generally depicted in
A detail view of the engagement of the locking sleeve 44 with the piston 34 when the locking sleeve 44 is extended into its locked position is provided in
More specifically, the locking sleeve 44 may be driven into the locked position to create a positive lock against the piston 34, such as depicted in
By way of example, if the axial loading on the locking sleeve 44 is sufficiently high, the interaction of the abutting teeth of grooves 50 and grooves 68 (i.e., the leftmost tooth of the grooves 50 and the rightmost tooth of the grooves 68 in
The locking sleeve 44 is designed to maintain axial loading from the piston 34 (caused by the ram packer 38) on the sleeve 44 within a desired range while in the locked position. That is, the system is constructed to maintain sufficient axial loading on the sleeve 44 to assure sealing of the locked ram 30 while reducing excess axial loading that would have to be overcome in order to return the sleeve 44 to the unlocked position. It is noted that the resistance provided by the sleeve 44 to axial loading from the piston 34 depends on the construction of the sleeve 44. For example, the material (e.g., steel) from which the sleeve 44 is formed impacts its elasticity and the force required to radially compress the segmented end 46. The configuration of the grooves 50 also impacts the amount of resistance provided by the sleeve 44 against the axial loading from the piston 34. Particularly, locking angles of the grooves 50 control the amount of radially directed force applied to the segmented end 46 from the piston 34.
Two examples of different groove configurations on locking sleeves 44 are depicted in
In the embodiment depicted in
From the above description, it will be appreciated that the presently disclosed locking assembly is a spring-loaded and load-limiting locking device that, when engaged, maintains a ram in a locked position and within a specific load range that ensures sealing while limiting force needed to unlock the device. Additional loading on the locking device (e.g., as a result of a reduction in hydraulic pressure on the ram) can be reduced through operation of the linear clutch, thereby reducing the amount of force needed to overcome such loading and unlock the device. It is further noted that while the locking sleeve 44 is described above as having exterior grooves 50 that engage interior grooves 68 of the piston 34, other embodiments may have different configurations while still providing a linear clutch that reduces axial loading on the locking sleeve 44. For instance, in one embodiment the piston 34 could have a protrusion with external grooves that cooperate with internal grooves on the locking sleeve 44 (i.e., the protrusion on the piston 34 could be inserted into the sleeve 44 rather than the sleeve 44 being inserted into recess 60 of the piston 34). And in other embodiments, the linear clutch could include other components that enable the reduction of axial loading from sealed rams 30. Still further, it is noted that the linear clutches described above are not limited to use in a blowout preventer, and they may be used to reduce loading in other systems in full accordance with the present techniques.
While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
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Entry |
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Cameron International Corporation, “EVO Product Line” brochure, dated Nov. 2011. |
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Number | Date | Country | |
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20140084192 A1 | Mar 2014 | US |