Patent Application
20140284506
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 to one another to restrict flow of fluid through the blowout preventer. Many rams include main bodies (or ram blocks) that receive sealing elements (or ram packers) that press together when a pair of opposing rams close against one another. Often, the rams are driven into and out of a main bore of a blowout preventer by operating pistons coupled to the rams by connecting rods (or ram shafts).
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 ram actuation assemblies for blowout preventers. In some embodiments, a ram actuation assembly includes a ram shaft and a removable piston connected to the ram shaft via intermediate mounting members. The mounting members, which may be segments of a split mounting ring in one embodiment, are positioned radially about the ram shaft, such as within an external groove of the shaft. The piston is fastened to the mounting members to retain the piston on the ram shaft.
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.
The ram actuation assembly of the present disclosure can be used in various blowout preventers, and such blowout preventers can be used in a variety of systems. By way of example, a drilling system 10 including a blowout preventer is illustrated in
The drilling rig 14 also includes a mast 20 and a hoisting system (here generally shown as including a traveling block 22, a crown block 24, and drawworks 26) to enable a top drive 28 to be raised and lowered with respect to a drill floor 30. The drill string 16 is suspended from the top drive 28, and extends through a hole in the drill floor 30 and through wellhead equipment 32 (e.g., a blowout preventer installed on a wellhead). The drill string 16 can be rotated by the top drive 28 and can be raised and lowered with the top drive 28 (via the traveling block 22) to facilitate drilling operations. Although the drilling system 10 is depicted as including the top drive 28, some other embodiments do not include a top drive, such as embodiments using a kelly and a rotary table for rotating the drill string 16.
One example of a blowout preventer 34 of the wellhead equipment 32 is generally depicted in
Bonnet assemblies 42 secured to the main body 36 include various components that facilitate control of rams 48 disposed in the blowout preventer 34. More specifically, in the depicted embodiment, ram actuation assemblies 50 are disposed in housings between bonnets 44 and end caps 46 of the bonnet assemblies 42. The ram actuation assemblies 50 include pistons 52 coupled to ram shafts 54. In operation, a force (e.g., from hydraulic pressure) may be applied to the pistons 52 to drive the rams 48, via the ram shafts 54, into the bore 38 of the blowout preventer 34. The rams 48 can be pipe rams (as depicted in
Various ram actuation assemblies can be used to control movement of rams in a blowout preventer. In one previous instance, ram actuation assemblies included a separable ram shaft with two shaft portions that could be coupled together via a threaded connection to retain (e.g., pin) a piston between the two shaft portions. But a threaded connection between the two shaft portions increases manufacturing expense (e.g., from machining the threads) and can be susceptible to galling. Further, if the two shaft portions are made of a soft material, like stainless steel, care must be taken by an assembler to properly align and connect the two shaft portions. Otherwise, the threaded surfaces of the two shaft portions could be scarred, and the actuation assembly could be misaligned (e.g., out-of-round) when connected. Another previous instance includes a ram actuation assembly in which the piston is formed integrally with the ram shaft. While this arrangement may avoid certain alignment issues, manufacturing costs may be undesirably high from increased machining time and material expense (e.g., by removing material from stainless steel bar stock, sized to accommodate the larger-diameter piston, to form the smaller-diameter shaft).
In some embodiments of the present technique, however, the ram actuation assemblies 50 include separate pistons 52 that can be installed on ram shafts 54 without threaded surfaces. Additional details of such ram actuation assemblies 50 may be better understood through reference to
As depicted in the present figures, the ram shaft 54 is formed from a single piece of material (such as metal), although the shaft could be formed with multiple pieces. More specifically, in at least some embodiments the ram shaft 54 is made from stainless steel bar stock (e.g., type 304 or type 316 stainless steel). And in accordance with certain embodiments, the depicted ram shaft 54 does not have threaded surfaces. Compared to certain previous arrangements, the omission of threaded connections on the ram shaft 54 in some embodiments allows the ram shaft 54 to reduce or avoid the problems of alignment, scarring, and galling discussed above. And by avoiding the need to cut threads on the shaft, such ram shafts 54 may also be less expensive to manufacture.
The ram actuation assembly 50 also includes one or more mounting members 60 for coupling the piston 52 to the ram shaft 54. In
The piston 52 and the mounting members 60 can be made from the same material as the ram shaft 54 (e.g., stainless steel). But in at least some embodiments the piston 52 and the mounting members 60 are made from different material than the ram shaft 54. For instance, in certain embodiments the ram shaft 54 is made from stainless steel and the piston 52 and the mounting members 60 are made from non-stainless steel, such as a chromoly steel (e.g., type 4130 steel) or a carbon steel. Because the piston 52 and mounting members 60 are separate from the ram shaft 54, they can be made from less expensive materials than the ram shaft 54, thereby reducing manufacturing expense compared to arrangements with ram shafts having integral pistons. Maintenance costs may also be lower, as the separate components could be individually replaced as needed.
To assemble the piston 52 and the mounting members 60 on the ram shaft 54, the mounting members 60 are first positioned about the ram shaft 54 as generally depicted in
The piston 52 includes an aperture 80 that allows the piston 52 to be slipped over an end of the ram shaft 54. Once the mounting members 60 are positioned about the ram shaft 54, the piston 52 may be moved along the ram shaft 54 to engage the mounting members 60. In this position, the piston 52 abuts a seal 70 within a seal groove 68 of the ram shaft 54. And like the seal 64, the seal 70 inhibits fluid from passing between interior portions of the bonnet assembly 42 separated by the piston 52. In at least some embodiments, the ram actuation assemblies 50 are constructed to use the same seals 64 and 70 as certain previous ram actuation assemblies. This enables a blowout preventer to be retrofit with ram actuation assemblies 50 that use the same seals as the previous ram actuation assemblies.
In the depicted embodiment, the piston 52 includes a recess 82 that allows the piston 52 to receive the mounting members 60 within the recess 82 such that the piston 52 circumscribes or otherwise encompasses the outer edges 78 of the mounting members 60. The piston 52 includes a shoulder 84 having threaded mounting recesses 86. In the depicted embodiment, after the mounting members 60 are received in the recess 82, the piston 52 can then be coupled to the mounting members 60 by threading the fasteners 62 into mounting recesses 86 through the holes 76, as generally depicted in
The recess 82 generally facilitates assembly of the piston 52 on the ram shaft 54 by allowing the piston 52 to encircle the split mounting ring segments or other mounting members 60 and hold them in place about the ram shaft 54 while the fasteners 62 are installed. But in other embodiments, the recess 82 could be omitted. For example, the piston 52 could have a flat transverse surface, rather than a recessed surface, that abuts the mounting members 60.
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.
