Patent Application
20120304853
Pressure-controlled pistons are used to operate subsurface safety valves and other systems in the borehole drilling industry. Some systems include a piston to actuate a flow tube in order to open a closure mechanism, such as a flapper valve. Often, there is a length of the piston that is circumferentially unsupported, which can result in deflection of the piston due to the pressure necessary to keep the closure mechanism in an open position. Deflection is often exacerbated because a radial offset exists between an axis of the piston and an axial surface of the flow tube that engages a coupling on the piston, which results in a bending moment on the piston. Subsurface safety valves are important features in downhole systems and the industry is accordingly desirous of any improvements in the operation of such safety valves.
An actuation assembly including a sleeve member having a radially outwardly extending projection; and a piston having an axis, the piston operatively coupled to the projection of the sleeve member and arranged to exert an actuation force on the projection of the sleeve member for actuating the sleeve member, the actuation force positioned about radially aligned with the axis or radially outwardly from the axis.
An actuation assembly including a sleeve member; and a piston having an axis, the piston operatively coupled to the sleeve member and arranged to exert an actuation force on the sleeve member for actuating the sleeve member, the actuation force exerted at a non-planar contact surface.
A method of actuating a component including providing a piston having an axis; providing a sleeve member; coupling the piston to a radially outwardly extending projection of the sleeve member; and actuating the sleeve member by exerting an actuation force on the projection of the sleeve member via the piston, the actuation force positioned about radially aligned with the axis or radially outwardly from the axis.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
Referring now to the drawings,
The window 20 is provided, for example, to accommodate travel of a coupling 26 and a stabilizer 28 relative to the housing 16. The coupling 26 is arranged on the piston 12 and used by the piston 12 to transfer forces to a sleeve 30 via the stabilizer 28. The sleeve 30 is exemplified in the drawings as a flow tube, but it is to be appreciated that generally any sleeve, portion of a sleeve, etc. could be loaded by the piston 12 to control operation of a valve or other device. The valve or other device could be any type of device actuatable by a piston. The stabilizer 28 is fixedly secured to the sleeve, via, for example, bolts 32 in corresponding bores 34, welds, etc. In this way, the stabilizer 28 acts as a rigid radial extension of the sleeve 30 for receiving the forces exerted by the piston 12 via the coupling 26. Axial actuation of the sleeve 30 by the piston 12 (via the coupling 26 and the stabilizer 28) is arranged to cause a flapper valve, ball valve, or the like, to open according to known flow tube and/or safety valve systems.
From
Advantageously, the contact surface 38 is illustrated in the same plane 42 as the axis 18, so an actuation force FA exerted by the piston and a reaction force FR exerted by the stabilizer 28 are aligned with the axis 18 of the piston 12. The force FA is controllable, for example, by an external control line operatively connected to the piston 12 or a piston chamber for the piston 12 that can be supplied with a pressurized fluid or the like. There exists no radial offset between the forces FA and FR (since they are aligned with the axis 18), which results in essentially no bending moment exerted on the piston 12. Since there are two protrusions 36 located on opposite sides of the piston 12 from each other, it is to be noted that the resultant actuating and reaction forces are coaxially aligned with the axis 18, at the midpoint between the protrusions 36.
A purpose of the current invention is to maintain alignment of the actuation and reaction forces with the axis 18 of the piston 12. However, it is to be appreciated that perfect alignment is not always practical or even possible, due to manufacturing tolerances, errors, shifting of components under load, etc. It is to be appreciated in view of the description herein that projections that are curved, tapered, pointed, etc., are particularly well suited for alleviating any problems due to misalignment of components while maintaining the contact surface along a line substantially perpendicular to, and aligned in the same plane as, the axis 18. For example, the cross-sectional shape of each projection 36 could be triangular, ellipsoidal, spherical, etc. Providing protrusions that are tapered, curved, etc., such as protrusions 36, helps to ensure that even if the coupling 26 and/or stabilizer 28 rotate to some degree relative to each other (or are otherwise misaligned, such as due to manufacturing defects or tolerances), the contact surface 38 will nevertheless be located on the protrusion 36, and therefore very close to maintaining alignment with the axis 18.
Further, the contact surface does not need to be continuous, but could be formed from a plurality of point contacts (e.g., spherical protrusions) arranged along a line, for example. More broadly, it is to be appreciated that other non-planar contact surfaces could be formed by protrusions, and that arrangement along a line is just one embodiment that provides advantages over prior systems. By non-planar contact surface it is intended to mean that two flat, planar surfaces are not matingly engaged to form the contact surface, not that the contact surface can not be formed in a plane. For example, a plurality of point contact surfaces (e.g., from a plurality of spherical protrusions) could be arranged in a pattern (e.g., a grid) for forming a contact surface as a plurality of lines that are all located in a plane, but the surface formed by these point contacts is non-planar.
In view of the foregoing, it is to be understood that while it is stated herein that in some embodiments the actuation and/or reaction forces are “perpendicular to” or “aligned in the same plane as” the axis 18, this may not always be possible or practical and that at least some degree of misalignment is expected. As described below with respect to
The following refers generally to
As shown in the cross-sectional view of
The stabilizer 28 is shown in more detail in
An even greater reduction in deflection of the piston 12 can be accomplished by maintaining the piston 12 coaxially in the opening 60 of the stabilizer 28. The piston 12 should ideally be able to slide smoothly through the opening 60, so misalignment of the piston 12 with the opening 60 could result in increased friction and/or the piston 12 binding, bending, or otherwise becoming damaged. Since the stabilizer 28 is fixedly secured to the sleeve 30, more firmly setting a position of the sleeve 30 enables better alignment of the piston 12 with the opening 60. One example of an arrangement for maintaining a centered position of the sleeve 30 is shown in
Further details for some embodiments of the assembly 10 can be appreciated in view of
In order to prevent torque on the sleeve 30, it may also be advantageous to circumferentially align the piston 20 with a valve mechanism that is loaded by the sleeve 30 to open the valve. For example, assuming the flapper valve 76 is used, the flow tube would be subjected to higher torque if the piston 12 and the pin 78 for the flapper valve 76 were circumferentially misaligned. In order to ensure alignment of these components, threaded couplings between the piston housing and flapper housing could be clocked or timed so that the pin 78 and the piston 12 are substantially circumferentially aligned when the housings are secured together.
Several experimental tests were performed to quantify the impact of the various features described herein on deflection of a piston while actuating a flow tube in a subsurface safety valve system.
The above embodiments describe a piston that pushes a coupling into a stabilizer.
The hinges could be fully or at least partially articulated to enable some relative movement between the coupling 92 and the stabilizer 94 in order to account for defects, manufacturing tolerances, shifting or rotation due to loads, etc. In one embodiment, for example, the arm 98 of the stabilizer 94 includes a rotatable ball socket 104, through which the pin 102 extends, for enabling some misalignment between the coupling 92 and the stabilizer 94 in any direction. Alternatively, the pin 102 could be fixedly secured to the coupling 92, the stabilizer 94, or both.
An assembly 106 is shown in
To an astute reader, it may seem contradictory in view of the above disclosure to create a radial offset between the actuation and reaction forces FA and FR and the axis 18 of the piston 12, when it was previously stated such a radial offset was responsible for creating a moment that increased deflection of a piston. However, it is to be appreciated that the natural tendency of such sleeve actuation pistons is typically to buckle in a generally radially outward direction, due to, for example, the arrangement of the system. Thus, aligning the actuation and reaction forces FA and FR with the axis 18 of the piston 12 will virtually eliminate one source of bending moment on the piston, but will not account for bending from any other sources. As a result, in some situations positioning the actuation and reaction forces FA and FR radially outwardly from the axis 18 of the piston 12 may advantageously create an opposing bending moment to counteract other bending moments on the piston, for even further reducing deflection of the piston 12. Of course, creating too large of a radially outward offset may result in radially inward deflection, so the distance to offset the contact surface 38, 114 from the axis 18, if any, should be determined on a case by case basis. Upon identifying any such moments, an offset for the protrusions could be determined by setting the sum of the moments about the piston axis to zero and solving for the offset. For example, finite element analysis, experimental deflection tests, or other methods may be used to determine other moments and forces on pistons.
While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
