Abstract:
A wellhead assembly includes a valve with a valve actuator. The valve actuator linearly moves a valve stem and valve member assembly to selectively open and close the valve. The valve actuator moves the valve stem by reciprocatingly moving a piston that is attached to the valve stem. The piston is moved by applying pressurized hydraulic fluid to a piston surface. Piston direction is controlled by a selector valve that selectively diverts a hydraulic flow to either side of the piston. The actuator further includes a piston assembly for pressurizing a hydraulic flow, where the piston assembly reciprocates in response to engagement by a profiled rotating cam member.

Description:
BACKGROUND 
     1. Field of Invention 
     The device described herein relates generally to the production of oil and gas. More specifically, the present disclosure relates to a system and method of mechanically charging hydraulics and actuating a valve using the hydraulics. 
     2. Description of Related Art 
     Valves assemblies are typically provided within wellhead production trees of both surface and subsea wellheads. The valve assemblies are used to control the flow of oil or gas from a wellhead and/or for controlling circulating fluid flow in and out of a wellhead. Most valves include a valve body with an inlet and an outlet, a passage connecting the inlet and outlet, a valve member that slides in and out of the passage for controlling flow through the valve, and a valve stem for handling the valve member. A valve handle is generally coupled to the valve stem. Gate valves and other sliding stem-type valves have a valve member or disc and operate by selectively moving the stem to insert/remove the valve member into/from the flow of fluid to stop/allow the flow when desired. 
     Some larger valves, or valves having a large pressure differential across the valve member, may require an increased actuating force. These valves may require that a gear train may be included between the handle and the stem. Valve assemblies having a gear or gear train coupled with the valve stem may be powered by a rotating source, where the gear train converts the rotating force into a linear force for sliding the valve stem. Opening and closing wellhead valves can be performed manually by rotating a handwheel or handle, or with an actuator. Electrical actuators may include a motor to provide a rotating source whereas a hydraulic actuator typically includes a piston associated with a pressurized hydraulic fluid for actuating a valve. 
     SUMMARY OF INVENTION 
     Disclosed herein is a device and method of actuating a valve, the valve may be a part of a wellhead assembly. In one embodiment, a valve actuator for actuating a valve between an open and a closed position includes a housing, a main piston for coupling to the valve and axially movable within a bore of the housing. Moving the piston to a first location in the bore configures the valve in an open position and moving the piston to a second location in the bore configures the valve in a closed position. Also included in this embodiment is a rotatable camplate having a contoured surface and a piston assembly reciprocatable within a cylinder in the housing fillable with fluid. The piston assembly is engagable with the contoured surface, so that rotating the camplate reciprocates the piston assembly within the cylinder. A hydraulic fluid cylinder discharge is provided in the cylinder, so that moving the piston assembly in one direction pushes the fluid into the cylinder discharge. A hydraulic circuit in fluid communication with the cylinder discharge is provided that is in selective communication with the bore on opposing sides of the main piston. Selectively directing hydraulic flow to a side of the main piston moves the main piston between the first and second locations in the bore. 
     Optionally included is a second piston assembly with a second cylinder, the second piston assembly engagable with the contoured surface. The second cylinder is fillable with fluid and includes a hydraulic fluid cylinder discharge in fluid communication with the hydraulic circuit. A fluid reservoir in fluid communication with a fluid inlet in the cylinder may be included. The assembly may have a selector valve that includes an inlet in fluid communication with the cylinder discharge and an exit in selective fluid communication with one of the bore first location or the bore second location. The selector valve can further include a second inlet selectively in fluid communication with one of the bore first location or the bore second location. The valve actuator can also include a latch coupled between the main piston and the bore wall to selectively retain the piston in one of the positions. In an embodiment, the latch comprises a piston lock housed in a cavity formed on the main piston outer periphery, the piston lock being radially extendable from within the cavity into a recess provided on the bore wall. A lock retainer can be implemented that is moveable from a passage adjacent the cavity into a space between the piston lock and a cavity wall when the piston lock is extended from within the cavity. The valve actuator can further include a seal on the lock retainer in sealing contact with the passage wall, so that the lock retainer is returnable within the passage in response to pressurizing the cavity. 
     In another embodiment a valve actuator for actuating a valve between an open and a closed position, the valve actuator is described herein that includes a housing having a bore within a longitudinal axis, an axially moveable stem in the bore for coupling to a valve element, an annular main piston in the bore and connected to the stem for axially moving the stem, a rotatable cam plate concentrically mounted around the axis mounted rotatably to the housing, a fluid supply cylinder in the housing offset from the bore, a fluid supply piston having a cam follower in engagement as the camplate rotates with the camplate for stroking the supply piston, and passages leading from the fluid supply cylinder to the bore for delivering hydraulic fluid to the bore to stroke the main piston. The main piston can have a forward side and a rearward side and passages that lead to a bore at opposite ends of the cylinder to stroke the piston in a forward direction and a rearward direction. 
     Also described herein is a method of actuating a valve. In an embodiment the method includes rotating a crank member having a contoured surface, engaging the rotating contoured surface with a reciprocatable pressurizing element to thereby reciprocatingly drive the reciprocatable pressurizing element, contacting fluid with the reciprocating pressurizing element to form a pressurized hydraulic flow, and actuating the valve by selectively directing the pressurized hydraulic flow to a hydraulic system mechanically coupled to the valve, so that the pressurized hydraulic flow applies an actuating force on the valve through the hydraulic system. Alternatively, the method may include locking and unlocking the piston. Moreover, the actuator can be included on a subsea wellhead and manipulated by a remotely operated vehicle (ROV). 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side partial sectional schematical view of a surface wellhead assembly. 
         FIG. 2  is a side partial sectional schematical view of a subsea wellhead assembly. 
         FIGS. 3A and 3B  respectively are a side partial sectional view of an embodiment of a valve actuator in an open position and an associated valve member in a valve body. 
         FIG. 4  is a side view of an embodiment of a portion of the valve actuator of  FIG. 3 . 
         FIG. 5  is an overhead view of an embodiment of a portion of the valve actuator of  FIG. 3 . 
         FIG. 6  is a side partial sectional view of an embodiment of the valve actuator of  FIG. 3  in a closed position. 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
       FIG. 1  is a side partial sectional view illustrating a wellbore assembly  10  provided over a wellbore  12  that intersects a formation  14 . The wellbore assembly  10  includes a wellhead housing  16  mounted in the wellbore  12  and a production tree  18  affixed on the wellhead housing  16 . An axial bore  20  is formed through the wellhead assembly  10  allowing passage through the wellhead assembly  10  and into the wellbore  12 . A swab valve  22  is provided at the bore  20  upper end. Extending from the production tree  18  is a production line  24  with an inline production valve  26 . A passage  28 , shown in dashed outline, is provided within the production tree  18 . The passage  28  provides communication between the production line  24  and the bore  20 . 
     An optional bypass line  30  also extends from the production tree  18 ; the bypass line includes an inline bypass valve  32 . In the embodiment of  FIG. 1 , the production line  24  and bypass line  30  extend from opposite sides of the production tree  18 . The bypass line  30  registers with a passage  34  within the production tree  18 . The passage  34  provides fluid communication from the bypass line  30  to an annulus formed between co-axial tubulars (not shown) disposed within the wellbore  12 . 
       FIG. 2  illustrates a side partial section view of a subsea wellbore assembly  40  for use in producing fluids from a subsea wellbore  42 . The wellbore  42  intersects a subsea formation  44 . The subsea wellbore assembly  40  includes a wellhead housing  46  with an attached production tree  48 . A bore  50  extends through the wellbore assembly  40  providing access through the wellbore assembly  40  to the wellbore  42 . A swab valve  52  in the production tree  48  controls flow through the bore  50 . A production line  54  having an inline production valve  56  connects to a side of the production tree  48 . The production line  54  communicates with a passage  50  that extends through the production tree  48  into communication with the bore  50 . A bypass line  60  extends from a side of the production tree  48  opposite the production line  56 ; the bypass line  60  includes an inline bypass valve  62 . A bypass passage  63  within the wellhead assembly  40  registers with the bypass line  60  providing communication between the bypass line  60  and an annulus (not shown) between tubulars in the wellbore  42 . 
     A remotely operated vehicle (ROV)  64  is schematically depicted adjacent the wellhead assembly  40 . The ROV  64  is deployed on a tether  66  and includes a control arm  68  projecting outward from the ROV  64 . Referring now to  FIG. 1  and  FIG. 2 , a valve actuator  70  is schematically depicted coupled to each valve  22 ,  26 ,  32 ,  52 ,  56 ,  62 . The valve actuator may couple directly to the valve stem of each valve  22 ,  26 ,  32 ,  52 ,  56 ,  62  and apply an actuating force for adjusting flow through the valves  22 ,  26 ,  32 ,  52 ,  56 ,  62 . The valve actuator described herein can be powered manually or with the ROV  64 . 
     With reference now to  FIG. 3A , a side partial sectional view of an embodiment of a valve actuator assembly  70  is provided. In the embodiment of  FIG. 3A , the actuator assembly  70  includes a main body  72  having a reduced diameter thereby defining a transition  73 . An axial bore  74  is formed through the body  72 . The main body  72  includes a reduced diameter neck  75  shown along the bore  74  outer radius from the transition  73  and terminating to define the bore  74  upper terminal end. A main piston  76  is provided within the bore  74  and configured to reciprocate axially within the bore  74 . The piston  76  includes a cavity  77  shown formed along the piston  76  outer diameter and directed inward toward the bore axis Ax. A piston lock  78  is depicted disposed in the cavity  77 . Embodiments of a piston lock  78  include a C-ring pressed within the cavity  77  and biased outward against the bore  74  inner wall. Alternate embodiments include one or more segments provided within the cavity extending along a portion of the piston  76  outer circumference. The piston lock  78  includes a profiled detent  79  (discussed below in greater detail) on a lower surface and adjacent its outer radius. Engaging profiled detent  79  with a correspondingly profiled element draws the piston lock  78  from within the cavity  77  and into a locking engagement within the bore  74 . 
     A lock retainer  80  is shown in cross-section in the vertical portion of the cavity  77 . The lock retainer  80  includes a seal  81  on its outer periphery shown in sealing engagement with the cavity  77  wall. A spring  82  shown compressed between an end of the lock retainer  80  in the uppermost portion of the cavity  77 . An additional seal  83  is shown on the piston  76  outer periphery in sealing engagement with the bore  74 . 
     The piston  76  is anchored on a stem  84  having an upper end shown projecting upward outside of the housing  72 . An upper bonnet  88  is shown provided on the main body  72  upper end. The upper bonnet  88  circumscribes the stem  84  upper end and seals  89  also circumscribe the upper stem in sealing contact to provide a pressure barrier along the stem  84 . A gate  85  ( FIG. 3B ) is coupled to the stem  84  lower end. The gate is provided in a valve body  86 , where the valve body  86  includes a valve passage  87 . The gate  85  is selectively extendable in and out of the passage  87 . 
     An elongated hand crank  90  is provided and aligned substantially perpendicular with the bore axis A x . The hand crank  90  is attached to a planar camplate  91 . The camplate  91  coaxially circumscribes the extended neck  75  outer radius and rests on the main body  72  along the transition  73 . A thrust bearing  94 , also circumscribing the extended neck  75  outer diameter is disposed on the camplate  91  upper surface. 
     A top plate  96  on the extended neck  75  upper terminal end is shown secured thereto with a lock ring  100 . The lock ring  100  extends into corresponding registered recesses respectively provided on the top plate  96  inner radius in the extended neck  75  outer diameter. The top plate  96  is shown having a generally triangular cross section and includes a flange  97  inwardly depending from its upper portion towards the bore axis A x . The flange  97  is shown engaging a profile on the upper bonnet outer radius, thereby securing the upper bonnet  88  with the main body  72 . 
     A plurality of cylinders  102  are depicted in  FIG. 3A  shown aligned substantially parallel with and offset from the bore axis A x  projecting into the main body  72 . The cylinders&#39;  102  upper ends are open at the transition  73 . Piston assemblies  106  are shown disposed within the cylinders  102 . The piston assemblies  106  include piston rods  107  that are coupled with rollers  108  on their upper ends. The rollers include ridges  109  circumscribing their outer radii. Further included with the piston assemblies  106  are inner pistons  110  staged within outer pistons  111 . Springs  112  radially circumscribe the piston rods  107  spanning lengthwise between shoulders. Shoulders are respectively provided proximate the base of each piston rod  107  and the outer pistons  111 . The rollers  108 , which are shown contacting the camplate  91  lower surface, have their ridges  109  engaged within a correspondingly shaped V-notch  113  provided on the camplate  91  lower surface. 
     The cylinders  102  are attached to respective suction lines  126 , wherein each suction line  126  includes a check valve  128  that only allows flow in the suction lines  126  in a direction towards the cylinders  102 . The suction lines  126  each have an inlet connected with a fluid reservoir  133  (shown in dashed outline). Also attached to the cylinders  102  are discharge lines  134 , each discharge line having a discharge check valve  136  limiting flow through the discharge lines  134  in a direction away from the cylinders  102  to a selector valve  142 . A lower flow line  144  attaches to a second inlet into the selector valve  142 . The lower flow of the line  144  has an inlet connected to a port  146 , where the port  146  extends through the main body  72  into fluid communication with the bore  74 . Exiting the selector valve  142  is a return line  147  shown in partial dashed outline and terminating at the reservoir  133 . A second outlet from the selector valve  142  connects to an upper flow line  148  shown terminating at a port  150 . The port  150  is formed through the extended neck  75  and into the bore  74  above the piston  76 . A lower port  146  is formed through the body  72  and communicates with a lower portion within the bore  74 . 
     Interaction between the camplate  91  and the piston assemblies  106  is illustrated in a side partially exploded view in  FIG. 4 . Provided on the lower surface of the camplate  91  is a camring  151 . The camring  151  is shown with an undulating contoured profile formed along a substantially circular path on the camplate  91  lower surface. In the embodiment of  FIG. 4 , the piston assemblies  106  ride the camplate  91  along the camring  151  circular path. The corresponding ridges  109  and V-notch  113  maintain a desired alignment between the piston assemblies  106  and the camplate  91 . In one mode of operation, the camplate  91  is rotated about its axis, for example, by applying a lateral force to the hand crank  90 . The springs  112  provide a contacting force on the piston assemblies to maintain the rollers  108  in contact with the camring  151  undulating surface. Accordingly, rotating the camplate  91  while maintaining contact between the camring  151  and piston assemblies  106  causes the pistons to track the camring  151  surface moving the piston assemblies  106  in a reciprocating motion. 
     With reference again to  FIG. 3A , reciprocating the piston assemblies  106  within their respective cylinders  102  reduces pressure therein when they stroke upward. The reduced pressure in the cylinders  102  draws fluid from the reservoir  133  through the suction lines  126 , across the check valves  128 , and into the cylinders  102 . Continued camplate  91  rotation engages the piston assemblies  106  with a downwardly depending section of the camring  151  causing one of the piston assemblies  106  to a downward stroke. On the downward stroke, fluid in the cylinders  102  is blocked from flowing into the suction lines  126  by the check valves  128 . Instead, the discharge flow from the cylinders  102  is directed to the discharge lines  134 , across the check valves  136 , and to the selector valve  142 . In the embodiment of  FIG. 3A , the selector valve  142  directs the discharge flow from the cylinders  102  into the upper flow line  148 , which is connected on its other end to the port  150 , thereby directing flow into a portion of the bore  74  above the piston  76 . Continued pumping, by virtue of rotating the camplate  91  to operate its profiled surface on the piston assemblies  106 , continues additional hydraulic fluid flow into the portion of the bore  74  to move the piston  76  and therefore actuate a valve member  85  shown (in  FIG. 3B ) connected with the valve actuator  70 . As noted above, in the embodiment of  FIG. 3B , the valve member  85  is in the open position within the valve body  86 , allowing flow through the passage  87 . Continued operation of the valve actuator  70  ultimately moves the valve member  85  into the passage  87 , thereby blocking flow through the valve. 
       FIG. 5  illustrates in overhead view a partially exploded portion of the valve actuator  70 . Here, a cross-section of the valve body is illustrated from above, depicting the spatial relationship between the bore  74 , cylinders  102  and the reservoir  133 . Accordingly, in this embodiment, the cylinders  102  and reservoir  133  are formed in the main body portion residing below the transition  73 . 
     With reference now to  FIG. 6 , a side partial sectional view of the valve actuator  70  is illustrated wherein the associated valve member  85  has been moved within the valve body  86  into a closed position to block flow through the passage  87 . Actuating the valve member  85  into the closed position is shown as being accomplished by moving the piston  76  to a lower portion of the bore  74 . Optionally, when in the closed position, the piston may be locked in a closed position within the bore  74 . The piston lock  78  as shown in  FIG. 6  projects outward from the cavity  77 . A latch release  152  is shown mounted in the lower portion of the bore  74 , the latch release  152  is configured to launch the piston lock  78  from within the cavity  77 . The latch release  152  includes an annular peak  153  or ridge formed on the latch release  152  upper surface. The peak  153  is adapted for engagement with the profiled detent  79  on the piston lock  78  lower surface to launch the piston lock  78  from within the cavity  77 . Downward piston  76  movement to the bore  74  bottom contacts the detent  79  with the peak  153 . Opposingly formed angled surfaces on the peak  153  and the profiled detent  79  come into contact, resulting in a force on the piston lock  78  directed radially outward from the bore axis Ax. The bore wall  74  includes a recess  156  along its lower edge configured to receive the piston lock  78  therein. In embodiments where the piston lock  78  is a C-ring, inherent stress in the ring expands the ring outward so the profiled detent  79  is past the ridge  153 . Pushing the piston lock  78  radially outward from within the cavity  77  provides a space in the cavity  77  behind the piston lock  78 . The spring  82  can then push the lock retainer  80  into the space thereby securing the piston lock  78  into a locking configuration. Once engaged, the piston lock  78  can secure the piston  76  therein, even though no fluid is in the cylinder  74  to push the piston  76  downward. 
     In the embodiment of  FIG. 6 , the selector valve  142  has been manipulated to provide a flow path therethrough as indicated by its internal arrows to open the valve passage  87 . Thus, resetting the selector valve  142  as shown in  FIG. 6 , in combination with providing fluid flow through the selector valve as shown, releases the piston lock  78  and moves the piston  76  upwards within the bore  74 . Upward piston  76  movement pulls the valve member  85  into its open position allowing flow through the passage  87 . In the embodiment shown in  FIG. 6 , hydraulic fluid from the reservoir  133  is again drawn into the cylinders  102  by actuating the piston assemblies  106 , such as by rotating the camplate  91 . Fluid discharged from the cylinders  102  is directed to the selector valve  142  via the discharge lines  134 . In the selector valve  142  configuration of  FIG. 6 , however, the discharge fluid from the piston assemblies  106  through the selector valve  142  is directed to the lower flow line  144 ; instead of the upper flow line  148  as shown in the embodiment of  FIG. 3A . The fluid in the lower flow line  144  from the selector valve  142  is forced through the port  146  and into the bore  74  lower portion. The fluid circulating into the bore  74  lower portion flows into and pressurizes the cavity  77 . The seals  81  create a pressure barrier so an upward force is applied to the lock retainer  80  by the pressurized circulating fluid. The applied upward force urges the lock retainer  80  upward into the cavity  77  thereby leaving the space behind the piston lock  78 . The fluid pressure builds below the piston  76  seal  83  to push the piston  76  upward. Upward piston  76  movement engages the piston lock  78  with the recess  156  upper surface. Continued pressurized fluid flow into the bore  74  increases the upward force applied to the piston  76  and ultimately exceeds the force to press the piston lock  78  into the cavity  77 . The piston  76  is released when the piston lock  78  is pushed into the cavity  77  to allow the piston  76  to travel within the bore  74 . Accordingly, as long as a fluid pressurizing source is applied to the hydraulic circuit depicted herein, manipulating the selector switch  142  can dictate the direction of the piston  76  travel within the bore  74  and actuate motion of the valve member  85  in and out of the flow passage  87 . 
     Referring back to  FIG. 3A , shown illustrated is an optional embodiment of the piston assemblies  106 ; this includes a staged piston having the inner piston  110  and corresponding respective outer pistons  111 . The inner pistons  110  directly connect to the piston rods  107 . The outer pistons  111  circumscribe the inner pistons&#39;  110  outer diameter and under an applied force will disengage from the inner pistons  110 . Once disengaged, the outer pistons  111  will slide on the inner pistons&#39;  110  outer surface. Thus, in situations when a valve member  85  may require an excessive force for movement, the valve movement force is transferred into the hydraulic fluid being pumped by the piston assemblies  106 . When the force on the piston assemblies  106  transferred from the cylinders&#39;  102  fluid pressure exceeds the threshold sliding force, the inner pistons  110  will begin sliding with respect to the outer pistons  111 . Sliding the outer pistons  111  and only moving the inner pistons  110  reduces the piston assemblies&#39;  106  effective cross -sectional area. This area reduction correspondingly reduces the input force necessary to reciprocate the piston assemblies  106  within the cylinders  102 . As the force necessary to motivate the valve member is reduced, the inner and outer pistons will become re-engaged, thereby returning the effective piston assembly  106  area to its original area. 
     Although the valve actuator  70  is illustrated as having a pair of piston assemblies  106 , single piston valve actuator embodiments exist, as well as more than two piston assemblies. Further optionally, the valve actuator can be used with any slideable valve, it is not limited to applications of valves operating in conjunction with a wellhead assembly. Optionally, a shaft or other coupling can be affixed to the camplate  91 . The camplate  91  can thus optionally be rotated by a motor (or ROV  64 ) via the shaft or coupling. 
     It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.