Abstract:
An SPM valve for use in a subsea environment includes a spool selectively movable between first and second positions to thereby arrange the valve in respective armed and disarmed configurations. The particular arrangement of a supply port and discharge port with respect to the spool permits a pressurized working fluid supplied to the supply port to bias the spool to both the first and second positions once an external force is applied to the spool to initially set the spool in either the first or second position.

Description:
RELATED APPLICATION 
     This application is a non-provisional of and claims the benefit of and priority to U.S. Provisional Patent Application No. 61/695,208 titled “Stabilized Valve” filed Aug. 30, 2012, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of Invention 
     The present invention relates generally valves which are operable to control the flow of pressurized fluids to a blowout preventer in offshore oil or gas wells. In particular, the invention relates to a sub plate mounted (SPM) valve that is selectively movable between an armed configuration and a disarmed configuration, and is adapted for maintaining operable stability in both the armed and disarmed configuration. 
     2. Description of Related Art 
     Valves used in hydrocarbon recovery operations include SPM valves for controlling the flow of pressurized fluid to a blowout preventer. Although these valves are typically referred to as sub plate mounted valves, the particular mounting position for these valves may vary between applications. 
     Various types of SPM valves have been developed including 2-way and 3-way valves. One common design for SPM valves includes a valve housing with an open interior defining a longitudinal axis. The open interior is fluidly communicable with a supply port, a discharge port, and often with a vent port as well. A spool is selectively movable through the open interior, along the longitudinal axis, to control fluid flow between the supply port and the discharge port. The spool can be moved to a first position within the open interior wherein fluid is permitted to flow between the supply port and the discharge port thereby arranging the valve in an “armed” configuration. The spool can also be moved to a second position within the open interior where fluid is prevented from flowing between the supply port and the discharge port thereby arranging the valve in a “disarmed configuration.” Thus the valve is operable to arm and disarm hydraulic circuits, which may include additional valves for operating the ram of a blowout preventer. 
     Many of the valves of this type include springs to bias the spool to one of the first and second positions. The spool is generally movable to the other of the first and second positions by providing a pilot pressure to a pilot port of the valve. Other valves are double-piloted and require a pilot pressure to be maintained at one of two pilot ports to maintain the spool in a particular position within the open interior. Fluid flowing through the spool of these valves often serves to counteract the spring bias or the pilot pressure, and thus, the spool can be unstable and shift to an unintended position. 
     SUMMARY OF EMBODIMENTS OF THE INVENTION 
     A valve is described that employs a working fluid to maintain the valve in a particular configuration, e.g., either armed or disarmed, once the valve has been moved to the particular configuration. A supply port of the valve is arranged to provide a pressurized working fluid such that a spool of the valve is biased by the working fluid to a first position when the valve is moved to an armed configuration and such that the spool biased by the working fluid to a second position when the valve is moved to the disarmed configuration. 
     In accordance with an embodiment of the present disclosure, a valve for use as an sub plate mounted valve in a subsea environment includes a valve body having an upper end, a lower end and an interior cavity therein. The interior cavity defines a longitudinal axis. A supply port extends laterally through the valve body and is fluidly communicable with the interior cavity. An upper valve seat is disposed within the interior cavity, and a lower valve seat is disposed within the interior cavity. A discharge port extends axially through the lower end of the valve body and the lower valve seat. The discharge port is fluidly communicable with the interior cavity. A spool is disposed within the interior cavity and is selectively movable between a first position wherein the spool is engaged with the upper valve seat to permit fluid flow between the supply port and the discharge port and a second position wherein the spool is engaged with the lower valve seat to prohibit fluid flow between the supply port and the discharge port. 
     In some embodiments, the spool includes an upward facing shoulder on an external side thereof such that fluid pressure applied to the upward facing shoulder biases the spool toward the second position. In some embodiments, the valve further includes an arming pilot port and a disarming pilot port, wherein fluid pressure applied to the arming pilot urges the spool toward the first position and wherein fluid pressure applied to the disarming pilot port urges the spool toward the second position. In some embodiments, the valve further includes a valve stein coupled to spool, and the valve stem includes a head having a downward facing surface in fluid communication with the arming pilot port and an upward facing surface in fluid communication with the disarming pilot port. In some embodiments, the valve stem extends into an interior of the spool, such that fluid pressure within the spool biases the valve stem toward the upper valve seat. 
     In some embodiments, the valve further includes a vent port extending laterally through the valve body, wherein the vent port is in fluid communication with the discharge port through the spool when the spool is in the second position and wherein the vent port is fluidly isolated from the discharge port when the spool is in the first position. In some embodiments, the valve further includes a spool seal disposed radially about the spool and axially between the supply port and the vent port, wherein the spool seal is operable to prevent fluid flow around an outer diameter surface of the spool between the vent port and the supply port. In some embodiments, the supply port is fluidly coupled to a supply of a pressurized working fluid, and the discharge port is fluidly coupled to a trigger valve that is operable to control fluid pressure to a ram of a blowout preventer. In some embodiments, the discharge port is fluidly coupled directly to the ram of a blowout preventer to control operation of the blowout preventer. In some embodiments, the spool defines an upper sealing face for engagement with the upper valve seat, and the upper sealing face includes an outward and upward facing surface, and the spool defines a lower sealing face for engagement with the lower valve seat, and the lower sealing face includes an inward and downward facing surface. 
     A method of controlling fluid flow in subsea environment includes the steps of supplying a pressurized working fluid to the supply port, applying a fluid pressure to the arming pilot port to induce movement of the spool to the first position such that a flow of working fluid between the supply port and the discharge port is established; and relieving the fluid pressure from the arming pilot port such that the flow of the working fluid maintains the spool in the first position. 
     In some embodiments, the method further includes the steps of applying a fluid pressure to the disarming pilot port to induce movement of the spool to the second position such that the flow of working fluid between the supply port and the discharge port is interrupted, and relieving the fluid pressure from the disarming port such that the working fluid applies a three to an exterior of the spool to maintain the spool in the second position. 
     In accordance with another embodiment of the present disclosure, a valve for use in a subsea environment includes a valve body defining an interior cavity therein and a longitudinal axis. A first valve seat is disposed at a discharge end of the interior cavity, and a second valve seat is disposed at a pilot end of the interior cavity opposite the discharge end of the interior cavity. A supply port extends laterally through the valve body and is fluidly communicable with the interior cavity. A discharge port extends axially through the first valve seat, and a spool is disposed within the interior cavity. The spool is selectively movable between a first position wherein the spool is axially spaced from the first valve seat such that a fluid flow path is defined between the supply port and the discharge port extending along an exterior of the spool and a second position wherein the spool is axially engaged with the first valve seat, and wherein a sealing face of the spool circumscribes the discharge port such that the flow path is obstructed by the spool. 
     In some embodiments, the spool includes an upward facing shoulder on an external side thereof, such that fluid pressure applied to the upward facing shoulder biases the spool toward the second position. In some embodiments, the valve further includes a spool seal disposed radially about the spool and axially between the upward facing shoulder and the second valve seat. The spool seal is operable to contain a pressurized fluid in an annular region around the upward facing shoulder when the spool is in the second position. In some embodiments, the supply port is fluidly isolated from an interior of the spool when the spool is in the second position. 
     In some embodiments, the valve farther includes a vent port extending laterally through the valve body, wherein the vent port is in fluid communication with the interior of the spool when the spool is in the second position. In some embodiments, the vent port is exposed to a fluid at an ambient pressure, and the supply port is exposed to a working fluid at a higher pressure than the ambient pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained, and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings that form a part of this specification. It is to be noted, however, that the drawings illustrate only preferred embodiments of the invention and are therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
         FIG. 1  is a cross-sectional side view of a stabilized valve arranged in an armed configuration and including a spool movable between first and second positions in accordance with an example embodiment of the present disclosure; 
         FIG. 2  is a schematic view of the stabilized valve of  FIG. 1  illustrating forces applied to the spool by a working fluid when the valve is arranged in a disarmed configuration. 
         FIG. 3  is a schematic view of the of the stabilized valve of  FIG. 1  illustrating forces applied to the spool by the working fluid when the valve is arranged in the armed configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. 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, and the prime notation, if used, indicates similar elements in alternative embodiments. 
     In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. Additionally, for the most part, details concerning well drilling, running operations, and the like have been omitted inasmuch as such details are not considered necessary to obtain a complete understanding of the present invention, and are considered to be within the skills of persons skilled in the relevant art. 
     Referring to  FIG. 1 , valve  10  is a stabilized SPM valve that employs a working fluid “F” to maintain a configuration of valve  10 . Valve  10  does not rely on springs or a pilot pressure to maintain either armed or disarmed configurations once valve  10  is properly arranged in the particular configuration. For purposes of this description, valve  10  is described as including a lower end  12  (a discharge end) and an upper end  14  (a pilot end). The use of “lower” and “upper” herein is to aid in understanding of the invention and does not indicate any specific orientation or position. 
     Valve  10  includes a valve body  16  defining an interior cavity  18  with longitudinal axis  20  defined therethrough. Supply port  22 , discharge port  24  and vent port  26  are each defined through valve body  16  and are fluidly communicable with the interior cavity  18 . Supply port  22  is fluidly connected to supply of pressurized working fluid “F,” and extends laterally through valve body  16  to a lower end of interior cavity  18 . Discharge port  24  is fluidly coupled to trigger valve “T,” and extends from the lower end of interior cavity  18  axially through valve body  16 . One skilled in the art will appreciate that that trigger valve “T” can be provided as part of a hydraulic circuit for controlling fluid pressure to a ram of a blowout preventer (not shown), and that valve  10  is thus employable to arm and disarm the hydraulic circuit. Alternatively, discharge port  24  of valve  10  can be directly coupled to the ram of a blowout preventer to control operation of the blowout preventer. Vent port  26  extends from an upper end of interior cavity  18  laterally through valve body  16 , and in many applications is opened to the subsea environment defining an ambient pressure. Vent port  26  is an optional feature of valve  10  and is eliminated in some embodiments without departing from the concepts of the present invention. A pressure of the working fluid “F” is higher pressure than the ambient pressure. 
     Spool  34  is constructed as an elongated, annular member and is provided within interior cavity  18 . Spool  34  is axially movable within interior cavity  18  to control a flow of working fluid “F” to and from various ports  22 ,  24 ,  26 . Spool  34  is movable to a first position at an upper end of interior cavity  18 , as illustrated  FIG. 1 , to arrange valve  10  in the “armed” configuration. When valve  10  is arranged in the armed configuration, working fluid “F” is permitted to flow from supply port  22 , through interior cavity  18  of valve body  16 , and exit valve  10  through discharge port  24 . The flow of working fluid “F” through an open upper end of spool  34  is prevented by engagement of upper sealing face  34   a  of spool  34  with upper valve seat  36 . Spool seal  38  is provided radially between spool  34  and valve body  16  and axially between supply port  22  and vent port  26  to prevent working fluid “F” from flowing around an outer diameter surface of spool  34  between vent port  26  and supply port  22 . Spool seal  38  is configured as an annular “t-seal” circumscribing spool  34 , and is operable to maintain sealing engagement with spool  34  throughout axial movements of spool  34  within interior cavity  18 . 
     Spool  34  is movable to a second position at a lower end of interior cavity  18  to arrange valve  10  in the “disarmed” configuration (see  FIG. 2 ). When valve  10  is arranged in the disarmed configuration, the flow working fluid “F” between supply port  22  and discharge port  24  is prevented by sealing engagement a lower sealing face  34   b  of spool  34  with lower valve seat  42 . To engage the lower end of spool  34  with lower valve seat  42 , spool  34  is moved axially away from upper valve seat  36 . Thus, when valve  10  is in the disarmed configuration, fluid within spool  34  or discharge port  24  is permitted to flow over the upper end of spool  34  and exit valve  10  through vent port  26 . 
     Valve stem  46  is provided to facilitate axial movement of spool  34 . A lower end of valve stem  46  is coupled to spool  34  by radial fins  48  extending to an inner diameter surface of spool  34 . Interstitial spaces defined between radial fins  48  permit the passage of fluids axially through spool  34 . A head  50  defined at an upper end of valve stem  46  slidingly engages stem housing  54 . Disarming pilot port  56  is in fluid communication with an upward facing surface  50   a  of bead  50  and arming pilot port  58  is in fluid communication with a downward facing surface  50   b  of head  50 . A pilot pressure applied to disarming pilot port  56  urges head  50  in a downward direction toward lower end  12  of valve  10 , and thus urges spool  34  into the second position in sealing engagement with lower valve seat  42 . Conversely, a pilot pressure applied to arming pilot port  58  urges head  50  in a direction toward the upper end of valve  10 , and thus urges spool  34  into sealing engagement with upper valve seat  36 . Thus, by applying pilot pressure at the appropriate pilot port  56 ,  58 , valve stem  46  can be manipulated to move spool  34  between the first and second positions and toggle valve  10  between the armed and disarmed configurations. In embodiments, no pilot pressure is required to be maintained at either pilot port  56 ,  58  to maintain valve  10  in either of the armed or disarmed configurations. Thus, once a pilot pressure is applied to one of the pilot ports  56 ,  58 , to move spool  34  to one of the first and second positions, the pilot pressure may be relieved, and the particular armed or disarmed configuration of the valve achieved is maintained. 
     Shoulder  60  is provided the lower end of spool  34 . An outer diameter OD 1  of shoulder  60  is greater than an outer diameter OD 2  of a body  62  of spool  34 . Spool  34  tapers between OD 1  and OD 2  along outward and upward facing shoulder  64 , which defines a transition between shoulder  60  and body  62 . In alternate embodiments (not shown), a flat shoulder can be provided at lower end of spool  34 . 
     Referring to  FIG. 2 , valve  10  is illustrated schematically in the disarmed configuration wherein lower sealing face  34   b  of spool  34  is sealingly engaged with lower valve seat  42 . A relatively high surface area on an exterior of spool  34  is in contact with working fluid “F” since a greater axial length of spool  34  is disposed beneath spool seal  38 . Lower sealing face  34   b  includes a sealing face taper  68 , which is an inward and downward facing tapered surface. When valve  10  is in the disarmed configuration, the pressurized working fluid “F” applies a force on the exterior of spool  34 , which includes upward facing shoulder  64 . Spool seal  38  contains working fluid “F” in an annular region around upward facing shoulder  64  when spool  34  is in the second position. In this manner, the high pressure of the working fluid “F” presses lower sealing face  35   b  downward into lower valve seat  42 . The working fluid “F” is isolated from the interior of spool  34 , and thus, the high pressure does not act upon the sealing face taper  68  of the lower sealing face  34   b  when valve  10  is arranged in the disarmed configuration. The interior of spool  34  may be exposed to the relatively low pressure of the subsea environment through vent port  26 . Thus, the working fluid “F” generates a pressure differential between the interior and exterior of spool  34 , and thereby serves to urge spool  34  in the direction of lower valve seat  42  to maintain valve  10  the disarmed position. 
     Referring to  FIG. 3 , valve  10  is illustrated schematically in the armed configuration wherein upper sealing face  34   a  of spool  34  sealingly engages upper valve seat  36 . Upper sealing face  34   a  includes an upper sealing face taper  70 , which is an outward and upward facing tapered surface. When valve  10  is arranged in the armed configuration, the working fluid “F” is permitted to flow into the interior of spool  34 , and thus the relatively high pressure of the working fluid “F” acts on the interior of spool  34  to press upper sealing face  34   a  upward into upper valve seat  36 . Fins  48 , valve stem  46 , sealing face taper  68  are all exposed to the relatively high pressure of the working fluid “F.” The pressure of the working fluid acting on these elements serves to bias spool  34  toward the upper valve seat  36 . The working fluid “F” is isolated from the exterior of spool  34  at the upper sealing face  34   a , and thus the relatively high pressure of the working fluid. “F” does not act upon the upper sealing face taper  70  of the upper sealing face  34   a  when valve  10  is in the armed configuration. The working fluid “F” again generates a pressure differential, and thereby serves to urge spool  34  in the direction of upper valve seat  36  to maintain valve  10  the armed configuration. 
     As illustrated in  FIG. 3 , supply port  22  is arranged with respect to discharge port  24  and spool  34  such that spool  34  can be axially spaced from lower valve  42  when valve  10  is arranged in the armed configuration. Since discharge port  24  extends axially through lower valve seat  42 , working fluid “F” is communicable between supply port  22  and discharge port  24  along a fluid flow path extending between spool  34  and lower valve seat  42  as indicated by arrows  72 . The fluid flow path is defined exclusively on an exterior of spool  34 , and thus, it is not necessary for working fluid “F” to flow axially through spool  34  when valve  10  is arranged in the armed configuration. 
     It is understood that the present invention may take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or scope of the invention. Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.