Abstract:
The disclosure provides an efficient design for a pressure rated oil field gate valve that meets the challenges of providing a quality product with minimal increase in price due to the design. It minimizes weight increase in the valve body over valves not meeting strict pressure specifications, due to strengthening ribs at strategic places without having to increase the overall body size as in commonplace in the industry. It provides redundancy of seals with minimal costs and no change in seat pockets over valves not capable of meeting the higher standards. It provides multiple shear points along a valve stem that can still allow a user to operate the valve from external to the valve bonnet. It further provides for additional sealing of the valve bonnet to the valve body by using elasticity in metal over long lengths to maintain a compression seal between the bonnet and the body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Nos. 60/979,022 and 60/979,025, both filed Oct. 10, 2007, which are incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not applicable. 
       REFERENCE TO APPENDIX 
       [0004]    Not applicable. 
       BACKGROUND 
       [0005]    1. Field of the Invention 
         [0006]    The disclosure relates to oil field equipment, and particularly to oil field gate valves, such as those valves meeting pressurization specifications. 
         [0007]    2. Description of Related Art 
         [0008]    As in most realms, the oil field market is influenced by safety concerns balanced against cost and value for products and services. To control the minimum safety requirements, regulations and specifications are promulgated in the oil field industry, so that customers can purchase equipment necessary for projects with the expectation that the equipment will meet certain standards. Known and respected specifications for oil field equipment are promulgated by the American Petroleum Institute (“API”) that requires valves to meet rigorous tests. A significant focus is on valves and similar control devices, because of the dangers of oil field wells that are controlled by valves. One specific specification is API 6A PSL-2 PR2 for product specification level and performance requirements. A valve has to pass certain tests as virtually leak proof for an extended period of time for a gaseous medium at elevated pressures (that is, generally 5,000 psi and above) and elevated temperatures (generally 250° F. and above). The challenge is to design a valve that can meet such rigorous tests in the industry that is affordable to customers and competitive to the marketplace. 
         [0009]    Standard design engineering for such valves generally increases the overall cross-sectional diameters and thicknesses of the valve body to add mass to the valve for increased pressure requirements and performance. The valve acts as a pressure vessel and must withstand not only the pressure, but must be stiff enough to minimize the engineering strain at stress levels to maintain alignment of the valve components which must seal, connect, rotate, translate up and down, and otherwise function for their intended purpose all without leakage at critical junctures. Most valves in the market place reflect this standard practice of adding more mass to the overall size, even though a significant portion of the valve cost is directly related to simply the amount of material in the valve body. Another common practice is to increase larger cavities for larger seals, which in turn causes increased cross-sections of the valve body, which leads to the above referenced increase in material and costs. Another practice is to rely on metal-to-metal seals, because at PR2 pressures and temperatures, rubber and elastomeric seals may extrude and fail. However, as the valve ages, the surface finish of the mating surfaces deteriorates and the valves can leak, decreasing its useful life. The challenge is to include additional sealing while keeping costs to a minimum. 
         [0010]    These challenges have been met in various ways by the industry. Generally, the remedy is to meet the engineering tests such as the API 6A PSL-2 PR2 referenced above even at an additional cost of materials, attempt to negotiate competitive prices from suppliers of the additional components, increase manufacturing efficiency, contract offshore to other suppliers, and demand an incremental price increase. 
         [0011]    Therefore, there remains a need to provide an improved valve that can meet such specifications and tests that are still competitive in the marketplace. 
       BRIEF SUMMARY 
       [0012]    The disclosure provides an efficient design for a pressure rated oil field gate valve that meets the challenges of providing a quality product with minimal increase in price due to the design. It minimizes weight increase in the valve body over valves not meeting strict pressure specifications, due to strengthening ribs at strategic places without having to increase the overall body size as in commonplace in the industry. It provides redundancy of seals with minimal costs and no change in seat pockets over valves not capable of meeting the higher standards. It provides multiple shear points along a valve stem that can still allow a user to operate the valve from external to the valve bonnet. It further provides for additional sealing of the valve bonnet to the valve body by using elasticity in metal over long lengths to maintain a compression seal between the bonnet and the body. 
         [0013]    The disclosure provides a gate valve, comprising: a valve body having a flow passage from a first port to a second port with a gate cavity disposed between the first port and the second port, the gate cavity intersecting the flow passage; a valve bonnet coupled to the valve body with a bonnet opening; a gate slidably coupled to the valve body in the gate cavity, the gate adapted to slidably move at an angle to a centerline of the flow passage to block the flow when the gate is in a closed position to cover a cross-sectional area of the flow passage and allow flow when the gate is at least in a partially open position when the gate does not entirely cover the cross-sectional area of the flow passage; a stem rotatably coupled through the bonnet opening to the gate and adapted to move the gate reciprocally across the cross-sectional area of the flow passage between the closed and open positions; a seat pocket disposed on each side of the gate cavity in the valve body, the seat pocket having a bore that forms an outer perimeter of the seat pocket and a back face in the valve body distal from the gate cavity to create a stepped surface around the flow passage; and a seat disposed in each seat pocket and adapted to seal between the gate and the valve body. The seat comprises: a seat body having: a flow opening aligned with the flow passage; a gate face disposed toward the gate; a perimeter surface adapted to fit into the bore of the seat pocket; and a rear face disposed toward the back face of the seat pocket, the rear face comprising a first metal radial sealing surface having a shaped sealing surface and adapted to seal against the back face of the seat pocket in metal-to-metal contact. 
         [0014]    The disclosure also provides a gate valve, comprising: valve body having a flow passage from a first port to a second port with a gate cavity disposed between the first port and the second port, the gate cavity intersecting the flow passage, the valve body further comprising at least two ribs extending from a portion of the valve body distant from the valve bonnet to a portion of the valve body external to the flow passage, a first rib being disposed toward the first port and a second rib being disposed toward the second port; a valve bonnet coupled to the valve body with a bonnet opening; a gate slidably coupled to the valve body in the gate cavity, the gate adapted to slidably move at an angle to the centerline of the flow passage to block the flow when the gate is in a closed position to cover a cross-sectional area of the flow passage and allow flow when the gate is at least in a partially open position when the gate does not entirely cover the cross-sectional area of the flow passage; a stem rotatably coupled through the bonnet opening to the gate and adapted to move the gate reciprocally across the cross-sectional area of the flow passage between the closed and open positions; a seat pocket disposed on each side of the gate cavity in the valve body, the seat pocket having a bore that forms an outer perimeter of the seat pocket and a back face in the valve body distal from the gate cavity to create a stepped surface around the flow passage; and a seat disposed in each seat pocket and adapted to seal between the gate and the valve body. 
         [0015]    The disclosure further provides a gate valve, comprising: a valve body having a flow passage from a first port to a second port with a gate cavity disposed between the first port and the second port, the gate cavity intersecting the flow passage; a valve bonnet coupled to the valve body with a bonnet opening; a gate slidably coupled to the valve body in the gate cavity, the gate adapted to slidably move at an angle to a centerline of the flow passage to block the flow when the gate is in a closed position to cover a cross-sectional area of the flow passage and allow flow when the gate is at least in a partially open position when the gate does not entirely cover the cross-sectional area of the flow passage; a stem rotatably coupled through the bonnet opening to the gate and adapted to move the gate reciprocally across the cross-sectional area of the flow passage between the closed and open positions; a seat pocket disposed on each side of the gate cavity in the valve body, the seat pocket having a bore that forms an outer perimeter of the seat pocket and a back face in the valve body distal from the gate cavity to create a stepped surface around the flow passage; and a seat disposed in each seat pocket and adapted to seal between the gate and the valve body. The seat comprises: a seat body having: a flow opening aligned with the flow passage; a gate face disposed toward the gate; a perimeter surface adapted to fit into the bore of the seat pocket, the perimeter surface having a peripheral groove extending toward a centerline of the seat body; a rear face disposed toward the back face of the seat pocket; and a flexible castellated seal disposed in the peripheral groove of the seat body, the castellated seal having a series of castellations on a first face, the first face being disposed toward the gate face of the seat body of the seat. 
         [0016]    The disclosure still further provides a gate valve, comprising: a valve body having a flow passage from a first port to a second port with a gate cavity disposed between the first port and the second port, the gate cavity intersecting the flow passage, the valve body further comprising at least two ribs extending from a portion of the valve body distant from the valve bonnet to a portion of the valve body external to the flow passage, a first rib being disposed toward the first port and a second rib being disposed toward the second port, wherein the ribs form an angled surface from a central portion of the valve body toward the first port and the second port at an angle to a centerline through the first port and second port; a valve bonnet coupled to the valve body with a bonnet opening; a gate slidably coupled to the valve body in the gate cavity, the gate adapted to slidably move at an angle to the centerline of the flow passage to block the flow when the gate is in a closed position to cover a cross-sectional area of the flow passage and allow flow when the gate is at least in a partially open position when the gate does not entirely cover the cross-sectional area of the flow passage; a stem rotatably coupled through the bonnet opening to the gate and adapted to move the gate reciprocally across the cross-sectional area of the flow passage between the closed and open positions; a seat pocket disposed on each side of the gate cavity in the valve body, the seat pocket having a bore that forms an outer perimeter of the seat pocket and a back face in the valve body distal from the gate cavity to create a stepped surface around the flow passage; and a seat disposed in each seat pocket and adapted to seal between the gate and the valve body. The seat comprises: a seat body having: a flow opening aligned with the flow passage; a gate face disposed toward the gate; a perimeter surface adapted to fit into the bore of the seat pocket, the perimeter surface having a peripheral groove extending toward a centerline of the seat body; a rear face disposed toward the back face of the seat pocket, the rear face comprising a rear cylindrical groove and a first metal radial sealing surface formed on the rear face adjacent the rear cylindrical groove, the first metal radial sealing surface being adapted to seal against the back face in metal-to-metal contact as a first seal, and the rear face further comprising a second metal radial sealing surface formed on the rear face adjacent the rear cylindrical groove and distal from the first metal radial sealing surface relative to the rear cylindrical groove, the second metal radial sealing surface adapted to seal against the back face in metal-to-metal contact as a second seal, wherein at least one of the metal radial sealing surfaces comprises a shaped sealing surface; and a peripheral step formed in the perimeter surface adjacent the rear face; a rear flexible seal disposed in the cylindrical groove of the rear face and adapted to seal against the back face as a third seal; and a flexible castellated seal disposed in the peripheral groove of the seat body, the castellated seal having a series of castellations on a first face, the first face being disposed toward the gate face of the seat body of the seat, the flexible castellated seal forming a fourth seal. 
         [0017]    The disclosure provides a gate valve, comprising: a valve body having a flow passage from a first port to a second port with a gate cavity disposed between the first port and the second port, the gate cavity intersecting the flow passage; a valve bonnet coupled to the valve body with a bonnet opening; a gate slidably coupled to the valve body in the gate cavity, the gate adapted to slidably move at an angle to a centerline of the flow passage to block the flow when the gate is in a closed position to cover a cross-sectional area of the flow passage and allow flow when the gate is at least in a partially open position when the gate does not entirely cover the cross-sectional area of the flow passage; a stem rotatably coupled through the bonnet opening to the gate and adapted to move the gate reciprocally across the cross-sectional area of the flow passage between the closed and open positions; a seat pocket disposed on each side of the gate cavity in the valve body, the seat pocket having a bore that forms an outer perimeter of the seat pocket and a back face in the valve body distal from the gate cavity to create a stepped surface around the flow passage; and a seat disposed in each seat pocket and adapted to seal between the gate and the valve body. The seat comprises: a seat body having: a flow opening aligned with the flow passage; a gate face disposed toward the gate; a perimeter surface adapted to fit into the bore of the seat pocket; a rear face disposed toward the back face of the seat pocket; and a peripheral step formed in the perimeter surface adjacent the rear face; and a flexible peripheral seal disposed around the peripheral step formed in the perimeter surface. The flexible peripheral seal comprises: a jacket having a heel portion of flexible material of a longitudinal thickness and a groove formed in an outer periphery of the jacket, having at least two peripherally extending seal arms; and a peripheral spring disposed in the jacket groove, the peripherally extending seal arms being biased to a width, measured from an outside surface of one seal arm to an outside surface of the other seal arm, that is greater than the heel longitudinal thickness. 
         [0018]    The disclosure also provides a gate valve, comprising: a valve body having a flow passage from a first port to a second port with a gate cavity disposed between the first port and the second port, the gate cavity intersecting the flow passage, the valve body further comprising at least two ribs extending from a portion of the valve body distant from the valve bonnet to a portion of the valve body external to the flow passage, a first rib being disposed toward the first port and a second rib being disposed toward the second port, wherein the ribs form an angled from a central portion of the valve body toward the first port and the second port at an angle to a centerline through the first port and second port; a valve bonnet coupled to the valve body with a bonnet opening; a gate slidably coupled to the valve body in the gate cavity, the gate adapted to slidably move at an angle to the centerline of the flow passage to block the flow when the gate is in a closed position to cover a cross-sectional area of the flow passage and allow flow when the gate is at least in a partially open position when the gate does not entirely cover the cross-sectional area of the flow passage; a stem rotatably coupled through the bonnet opening to the gate and adapted to move the gate reciprocally across the cross-sectional area of the flow passage between the closed and open positions; a seat pocket disposed on each side of the gate cavity in the valve body, the seat pocket having a bore that forms an outer perimeter of the seat pocket and a back face in the valve body distal from the gate cavity to create a stepped surface around the flow passage; and a seat disposed in each seat pocket and adapted to seal between the gate and the valve body. The seat comprises: a seat body having: a flow opening aligned with the flow passage; a gate face disposed toward the gate; a perimeter surface adapted to fit into the bore of the seat pocket, the perimeter surface having a peripheral step formed in the perimeter surface adjacent the rear face; a rear face disposed toward the back face of the seat pocket, the rear face comprising a rear cylindrical groove and a first metal radial sealing surface formed on the rear face adjacent the rear cylindrical groove and adapted to seal against the back face in metal-to-metal contact as a first seal, and the rear face further comprising a second metal radial sealing surface formed on the rear face adjacent the rear cylindrical groove and distal from the first metal radial sealing surface relative to the rear cylindrical groove, the second metal radial sealing surface adapted to seal against the back face in metal-to-metal contact as a second seal, wherein at least one of the metal radial sealing surfaces comprises a shaped sealing surface; and a rear flexible seal disposed in the cylindrical groove of the rear face and adapted to seal against the back face as a third seal; and a flexible peripheral seal disposed around the peripheral step formed in the perimeter surface adjacent the rear surface, the flexible peripheral seal forming a fourth seal. The flexible peripheral seal comprises: a jacket having a heel portion of flexible material of a longitudinal thickness and a groove formed in an outer periphery of the jacket, having at least two peripherally extending seal arms; and a peripheral spring disposed in the jacket groove, the peripherally extending seal arms being biased to a width, measured from an outside surface of one seal arm to an outside surface of the other seal arm, that is greater than the heel longitudinal thickness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a schematic cross-sectional view of an exemplary embodiment of a gate valve described herein. 
           [0020]      FIG. 2  is a schematic cross-sectional view of a portion of a valve body of the gate valve of  FIG. 1  illustrating valve seat pockets. 
           [0021]      FIG. 3  is a schematic cross-sectional assembly view of an exemplary embodiment of a valve seat. 
           [0022]      FIG. 3A  is a schematic cross-section view of a portion of a seat body. 
           [0023]      FIG. 3B  is a schematic cross-section view of a portion of an alternative seat body. 
           [0024]      FIG. 4  is a schematic perspective view of the assembled valve seat. 
           [0025]      FIG. 5  is a schematic cross-sectional view of the valve body with the valve seats installed in the valve seat pockets. 
           [0026]      FIG. 6  is a schematic cross-sectional assembly view of another exemplary embodiment of a valve seat. 
           [0027]      FIG. 6A  is a schematic cross-sectional view of a portion of a flexible peripheral seal. 
           [0028]      FIG. 7  is a schematic perspective view of the assembled valve seat shown in  FIG. 6 . 
           [0029]      FIG. 8  is a schematic cross-sectional view of the valve body with the valve seats installed in the valve seat pockets. 
           [0030]      FIG. 9  is a schematic side view of the valve body illustrating ribs. 
           [0031]      FIG. 10  is a schematic partial cross-sectional view from an end illustrating the ribs. 
           [0032]      FIG. 11  is a schematic bottom perspective view of the valve body of  FIGS. 9 and 10 . 
           [0033]      FIG. 12  is a schematic cross-sectional view of the valve bonnet with a stem assembled therein. 
           [0034]      FIG. 13  is a schematic top perspective assembly view of the valve body and valve bonnet with extended bonnet bolts. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    The Figures described above and the written description of specific structures and functions below are not presented to limit the scope of what Applicants have invented or the scope of the appended claims. Rather, the Figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present inventions will require numerous implementation-specific decisions to achieve the developer&#39;s ultimate goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related, and other constraints, which may vary by specific implementation, location and from time to time. While a developer&#39;s efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of skill in this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. Lastly, the use of a singular term, such as, but not limited to, “a,” is not intended as limiting of the number of items. Also, the use of relational terms, such as, but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the like are used in the written description for clarity in specific reference to the Figures and are not intended to limit the scope of the invention or the appended claims. 
         [0036]      FIG. 1  is a schematic cross-sectional view of an exemplary embodiment of a gate valve described herein. The gate valve  2  generally includes a body  4  having a pair of flanges  6 ,  8  at each end of the body. A first port  10  is formed on one end of the body and a second port  12  is formed on another end. Generally, the ports are aligned and, in any case, form a flow passage  13  therebetween having a centerline  31 . The flanges include a seal surface  14  for placement of a flange seal (not shown) to enable sealing between an adjacent flange and connecting equipment. Other types of connections can be formed, although flanges are common for the pressure ratings of such valves. The valve body  4  includes a gate cavity  16  disposed between the first port and the second port, so that the gate cavity intersects the flow passage  13 . Generally, the gate cavity  16  is disposed perpendicular to the flow passage  13 , although other angles can be used. The gate cavity contains a gate  30  to be described below that blocks the flow passage and controls flow therethrough. To effectively block flow through the flow passage, a seat  20  is generally disposed on each side of the gate cavity and gate. A seat pocket  18  is formed in the flow passage  13  to contain the seat  20 . Generally, the seat  20  will have an opening size commensurate with the flow passage  13 . In the orientation of the exemplary embodiment shown in  FIG. 1 , a seat pocket  18 A is formed on a left side of the gate cavity  16  and a seat pocket  18 B is formed on a right side of the gate cavity, so that the gate can translate up and down in the gate cavity between the seats  20 A and  20 B, respectively, disposed therein. Further details of the seat and seat pocket will be described below. 
         [0037]    Relative to the orientation in  FIG. 1  of the valve, an upper portion of the valve is generally termed a bonnet  22 . The bonnet  22  is attached to the valve body  4  through a plurality of bonnet bolts  24 . A bonnet cavity  108  is created between the valve body and the internal portion of the bonnet that is fluidicly coupled to a gate cavity  16 . A bonnet opening  26  is formed in the bonnet  22  through which a stem  28  is assembled. The stem  28  can be rotated in the bonnet  22  and move the gate  30  up and down in the gate cavity  16 . The movement is caused by rotation of a threaded surface  32  formed between the gate and the stem such that rotation of the stem effectively moves the gate along the threaded surfaces in a translating motion. In the embodiment shown, the movement of a gate is at a perpendicular angle to the centerline  31  formed through the flow passage  13 , although the angle can vary if so designed. The stem can be rotated by an actuator  34 . Generally, an actuator can be a hand wheel, level, motor-driven gear, or other movable elements. A bonnet-to-body seal  36  is disposed between the bonnet  22  and the valve body  4  to generally eliminate leakage to the outside of the valve. A packing  38  is disposed around the stem  28  to generally eliminate leakage upward through the opening  26  in the bonnet  22 . A cap  40  is mounted over the stem with one or more other seals between the bonnet  22  and the stem  28 . A grease fitting  42  is generally included in the cap  40  to lubricate bearings, the stem, various contact surfaces, and the like. 
         [0038]    A shear pin  44  is inserted through an opening in the stem  28  and a bearing adjacent the stem. The shear pin  44  helps to protect the stem from breaking internal to the bonnet  22  when extraordinarily high stresses are placed on the stem. Generally, a smaller cross-sectional area of the stem is created in manufacturing the threaded engagement surface  32  on the stem due to a thread relief This smaller cross-section creates a weakened section in the stem from the manufacturing process. The shear pin  44  is designed to fail in shear to protect the stem  28  from breaking at the thread relief  46  internal to the bonnet  22 , where the shear pin can be more readily accessed through the cap  40  and replaced as necessary. The exemplary embodiment of the valve includes a further groove, herein a stem groove  48 , to further protect the stem from breakage, if the stem shear pin  44  does not break in accordance with its design load. More details are provided below. 
         [0039]    Further, the valve body  4  includes ribs  50 , described in more detail below, that help stiffen the valve body to maintain alignment of various valve components and structure under high stress loads. These ribs are provided in contrast to generally accepted teachings for valve design by not significantly increasing the overall mass of the valve body to create such stiffness. 
         [0040]      FIG. 2  is a schematic cross-sectional view of a portion of a valve body of the gate valve of  FIG. 1  illustrating valve seat pockets. The valve  2  and particularly the valve body  4 , includes the flow passage  13  with a centerline  31  formed therethrough. The seat pocket  18 , such as a first seat pocket  18 A and a second seat pocket  18 B, is formed along the flow passage in the valve body on both sides of the gate cavity  16 . For purposes herein, the seat pocket  18  includes a bore  52  with an outer perimeter and a back face  54 , where the term “rear” is intended to include a surface distal from the gate or gate cavity, and the term “forward” is intended to include a surface toward the gate or gate cavity. 
         [0041]      FIG. 3  is a schematic cross-sectional assembly view of an exemplary embodiment of a valve seat.  FIG. 3A  is a schematic cross-section view of a portion of a seat body.  FIG. 3B  is a schematic cross-section view of a portion of an alternative seat body. The figures will be described in conjunction with each other. The seat described can meet the API 6A tests for at least a 5,000 PSI rated pressure valve. The seat  20  generally includes a seat body and various seals assembled thereof In the orientation shown in  FIG. 3 , the seat  20  corresponds to the orientation of the seat  20 A described and shown in  FIG. 1 . The seat  20 B is generally a mirror image of the seat  20 A with the orientation reversed, so that corresponding surfaces face forward toward the gate to interact therewith. The seat  20  includes a seat body  60  of generally a cylindrical shape having an inner perimeter  61  forming a flow opening  62  approximately equal to the flow passage  13  along the centerline  31  shown and described in  FIG. 1 . The seat body generally includes a gate face  64  disposed toward the gate  30  described in  FIG. 1 . The seat body further includes a perimeter surface  66  that is disposed radially outward toward the outer perimeter of the bore  52  described in  FIG. 2 . The seat body  60  further includes a rear face  68  disposed toward the back face  54  of the seat pocket  18 , also shown in  FIG. 2 . 
         [0042]    More specifically, the gate face  64  includes a gate cylindrical groove  74  formed in the gate face. A gate flexible seal  76  is assembled and mounted to the gate face in the gate cylindrical groove  74 . The gate flexible seal  76  can be made of a variety of materials and generally of materials that reduce the slidable friction between the seat  20  and the gate  30 . One exemplary and non-limiting material is PTFE, also known as Teflon. An outer metal surface  78  disposed radially outward from the gate cylindrical  74  forms an axial stop to the movement of the seat to the gate along the centerline  31 . A portion  82  of the outer metal surface  78  can be tapered or formed with a radius to help guide the gate  30  as it translates up and down past the seat  20  in the orientation shown. An inner metal surface  80 , disposed radially inward toward the centerline  31  can be further to used to support the flexible seal  76  in a perimeter and provide a stop to the relative movement between the seat and the gate. 
         [0043]    The perimeter surface  66  of the seat body  60  includes a peripheral groove  70  formed in the perimeter surface and having walls on either side of the groove from the seat body. Further, a peripheral step  72  is formed toward the rear face  68  and intersects the rear face, so that the peripheral step has one wall of the seat body in the direction of the gate face. A groove  84  can also be formed in the peripheral surface of the seat body for maintenance purposes, mainly, to assist in disassembly of the seat  20  from the seat pocket  18 , shown in  FIG. 1 . 
         [0044]    The rear face  68  includes a rear cylindrical groove  86 , so that a rear flexible seal  88  can be disposed therein. The rear flexible seal  88  forms a flexible seal that can enable sealing even if the back face  54  of the seat pocket  18  should become rough from use and deterioration, or contaminants be disposed thereon. A metal radial sealing surface  90  is disposed radially around the rear face. Without limitation, the metal radial sealing surface  90  can be formed outward from the rear cylinder groove  86  away from the centerline  31 . The metal radial sealing surface  90  forms a metal seal by establishing metal-to-metal contact with the back face  54  of the seat pocket  18 . Similarly, a second metal radial sealing surface  92  can be similarly formed around the rear face. Without limitation, the metal radial sealing surface  92  can be formed inward from the rear cylinder groove  86  toward the centerline  31 . 
         [0045]    One or more of the metal radial sealing surfaces  90 ,  92  can be shaped to establish one or more shaped sealing surfaces  132 ,  134 , respectively. The shaped sealing surfaces can be formed with a radius R, as shown in  FIG. 3A , or tapered at an angle β, as shown in  FIG. 3B . For example and without limitation, the radius R can be 1″-2″ from a center point aligned with the middle of the rear cylindrical groove  86 , more advantageously 1.4″-1.6″, and an angle β can be 2°-10°, more advantageously 3°-5°, and any radius or angle therebetween inclusively. The resulting leading edges  148 ,  150  of the shaped sealing surfaces  132 ,  134  can first contact the back face  54  to establish a concentrated load and a more effective seal over a smaller cross-sectional area than without the shaped sealing surfaces. The contacting area of a shaped sealing surface that contacts the back face of the seat pocket can be self-adjusting by deforming the leading edge as necessary under high stress loads until the contacting surface area has deformed enough to support a sealing load caused by the contact force between the metal sealing surface and the back face to establish an equilibrium condition, and yet minimize the contacting area required to support the load to help maintain an effective seal. 
         [0046]    In  FIG. 3 , a flexible castellated seal  94  is sized to be disposed into the peripheral groove  70  formed in the perimeter surface  66  of the seat body. The castellated seal with castellations  102  having merlons  106  adjacent crenels  104  will be described in more detail in reference to  FIG. 4  and its function in  FIG. 5 . A wave spring  96  can be disposed in the peripheral step  72 . The wave spring  96  biases the seat  20  away from the back face  54  of the seat pocket  18  and toward the gate  30  disposed in the gate cavity  16 , shown in  FIGS. 1 and 2 . 
         [0047]      FIG. 4  is a schematic perspective view of the assembled valve seat. The seat body  60  and the assembled seals form the seat  20 . The gate face  64  is disposed toward the gate  30  in  FIG. 1  and provides a smooth surface for the gate to translate across the gate space. The perimeter surface  66  contains one or more seals, such as the flexible castellated seal  94 , and the rear face  68  generally includes one or more metal-to-metal seals through one or more metal radial sealing surfaces and the rear flexible seal  88  to further enhance sealing for deteriorated surfaces. 
         [0048]    The castellated seal  94  includes one or more castellations  102 . A castellation is formed by an axially extended portion known as a merlon  106  adjacent a crenel  104  and generally between two crenels. The castellations of the castellated seal are disposed on a forward facing surface  100  that is disposed toward the gate face  64  of the seat  20  and the gate  30  of  FIG. 1 . The rear surface  98  of the castellated seal  94  that is disposed toward the rear face  68  of the seat  20  generally includes a smooth seal that is noncastellated. As will be described in  FIG. 5 , the castellated seal effectively creates an inexpensive one-way seal that allows upstream leakage and downstream sealing for the gate valve. 
         [0049]      FIG. 5  is a schematic cross-sectional view of the valve body with the valve seats installed in the valve seat pockets.  FIG. 5  illustrates the relative flow with the sealing functions of the seats disposed on both sides of the gate  30 . As described above, the valve body  4  includes a gate  30  that translates across the flow passage  13  to control the flow through the flow passage  13 . To meet the required standards, such as the API 6A specifications referenced above, the seat  20  must seal between the seat pocket and the gate under rigorous conditions. While certain third party designs have offered various solutions, the solutions generally are an expensive arrangement. The present system is a simplified and inexpensive solution. 
         [0050]    In general, the seat  20 A is disposed in the seat pocket  18 A on the left side of the gate  30  and seat  20 B is disposed on the right side of the gate in the seat pocket  18 B, using the orientations for illustrative purposes shown in  FIG. 5 . With a gate in a downward position, so that it blocks the flow passage  13  and fluid  110  therethrough, a small amount of fluid at pressure P 1  leaks past the seat  20 A into the bonnet cavity  108 . This intentional leakage helps equalize the forces on both sides of the seat  20 A in the seat pocket  18 A and reduces a sealing force from the upstream seat to the gate  30 . The reduced sealing force on the upstream side of the gate at the higher pressure P 1  allows a lower force to open the gate as it slides across the face of the seat  20 A. Further, the pressure P 1  equalizes (with relatively minor pressure drops) with the pressure P 2  in the bonnet cavity  108 . The bonnet cavity  108  is fluidly coupled to the right side of the gate above the seat pocket  18 B, so that the pressure P 2  on the right side of the gate in  FIG. 2  is equal to the pressure P 2  on the left side. The mirror image orientation of the seat  20 B in the seat pocket  18 B and the reverse orientation of the seals compared to the seat  20 A creates a seal so that the fluid at pressure P 2  is prevented from leaking downstream of the seat  20 B into the downstream portion of the flow passage  13  at pressure P 3 . 
         [0051]    Thus, the upstream seat  20 A leaks intentionally and the downstream seat  20 B seals intentionally (in the orientations of the fluid flow shown). If the flow was reversed, so that seat  20 B became the upstream seat and seat  20 A became the downstream seat, the result would be the mirror image where the upstream seat  20 B would leak and the downstream seat  20 A would seal. The simplicity of this design and yet the ability to seal in such fashion is caused by astute orientation and selection of the various components described here. 
         [0052]    More specifically, the pressure P 1  in conjunction with the action of the wave spring  96  forces the seat  20 A toward the gate  30 . The metal-to-metal contact of the metal radial sealing surface  90  or the metal radial sealing surface  92  or both is not effectively engaged to seal against the back face  54 . Similarly, the rear flexible seal  88  is not effectively engaged to seal against the back face  54  and thus fluid at pressure P 1  leaks past the three seals. The fluid at pressure P 1  then encounters the flexible castellated seal  94 . However, with the orientation shown in  FIG. 4 , the rear surface  98  is pushed away from the adjacent wall of the peripheral groove  70  and does not seal in the groove  70 , and allows fluid at pressure P 1  (ignoring any losses in pressure along the way) to flow through the castellations  102 , specifically, the crenels  104 , of the castellated seal  94  and leak past the castellated seal  94 . The crenels  104  cannot seal because the merlons  106  keep the crenels  104  from sealing against adjacent wall of the peripheral groove  70 . Thus, the fluid at pressure P 1  leaks past the seat  20 A into the bonnet cavity  108  at substantially the same pressure to established pressure P 2  downstream of the seat  20 A. 
         [0053]    However, on the right side of  FIG. 5 , the downstream seat  20 B, effectively seals the fluid at pressure P 2  from flowing farther downstream into the remaining flow path. The fluid flows at pressure P 2  along the surfaces between the bore  52  and the perimeter surface  66  of the seat  20 B. However, this time due to the mirror image placement of the seals, the flow passes first through the crenels  104  of the castellations  102  and encounters the rear surface  98  of the castellated seal  94 . The pressure P 2  forces the rear surface  98  against the downstream wall of the peripheral groove  70  and effectuates a seal thereon. The flow is stopped. If any flow should inadvertently leak past the seal  94  on the rear surface  98 , the fluid will encounter a metal radial sealing surface  90  that is sealing in metal-to-metal contact against the back face  54  of the seat pocket  18 B. The metal-to-metal contact is enhanced by the pressure P 2  forcing the seat  20 B against the back face  54  of a seat pocket  18 B. Further, the rear flexible seal  88  is also being forced against the back face  54  for another sealing surface. Finally, the metal radial sealing surface  92  that is disposed radially inward from the seal  88  is also being forced against the back face  54  of the seat pocket  18 B. Thus, the seat  20 B in one embodiment includes four sealing surfaces to help prevent leakage of fluids downstream of the seat  20 B. 
         [0054]      FIG. 6  is a schematic cross-sectional assembly view of another exemplary embodiment of a valve seat.  FIG. 6A  is a schematic cross-sectional view of a portion of a flexible peripheral seal.  FIG. 7  is a schematic perspective view of the assembled valve seat shown in  FIG. 6 . The figures will be described in conjunction with each other. This embodiment of the valve seat  20  is designed for higher pressures than the seat shown in  FIGS. 3-5 . Because of the higher pressures, a different design can be utilized more efficiently. Higher pressures include 10,000 PSI and qualify for meeting the API  6 A test described above for a 10,000 PSI rated pressure valve. The seat body  60  includes an inner perimeter  61  that forms a flow opening  62  through the seat  20 . The seal body  60  includes a gate face  64 , perimeter surface  66 , and rear face  68 . The gate face  64  generally includes a metal surface that is disposed adjacent the gate  30  described above. The gate face  64  can include a tapered or radius portion  82  to assist in aligning the gate as the gate encounters the gate face  64  in its traversal. A groove  84  can be included for disassembly on the perimeter surface  66 . A peripheral step  72  can be formed in the perimeter surface  66  adjacent to the rear face  68 . In this seat body  60 , the peripheral step  72  can be used to efficiently support a peripheral seal  112  that can seal to the periphery of the seat pocket  18  and/or the back face  54  of the seat pocket. The seat body  60  can further include a rear cylinder groove  86  formed in the rear face  68 . A metal radial sealing surface  90  disposed radially outward from the rear cylindrical groove  86  can form a metal-to-metal seal against the back face  54  of the seat pocket  18  described above. Similarly, a metal radial sealing surface  92  can form a metal-to-metal seal against the back face  54  in additional to or in lieu of the metal radial sealing surface  90 . The seat shown in  FIG. 6  is aligned according to the orientation of the seat  20 A described above. A rear flexible seal  88  can be disposed in the rear cylindrical groove  86  to similarly seal as described above for the seat of  FIGS. 3-5 . 
         [0055]    The peripheral seal  112  generally includes a jacket  114  of flexible material. The jacket  114  includes an inner peripheral surface  116  that is sized to fit over the diameter of the peripheral step  72 . The jacket generally includes a cross-sectional shape that has a radial portion termed a “heel”  118 . The heel  118  has a longitudinal thickness “T” relative to the centerline  31 . A groove  120  is formed in the peripheral seal  112  radially outward from the heel  118 . The groove  120  can form a U-shaped cross-section so that a peripheral spring  126  that can be stretched and assembled thereto. The peripheral spring  126  can be a coil spring. The peripheral spring  126  can also be a spring with a cross-section generally in the shape of a “U”. Generally, the open portion of the “U” will be placed facing radially away from the centerline of the seal. The groove  120  formed in the peripheral seal  112  creates a first arm  122  and a second arm  124  with the spring disposed at least partially therebetween. The arms  122  and  124  peripherally extend radially outward from the heel  118 . The arms are biased to a width W that is greater than the thickness T of the heel, when the width is measured from an outside surface  128  of one arm to an outside surface  130  of the other arm  124 . The outward bias assists in biasing the seat  20  toward the gate  30  described above. 
         [0056]      FIG. 8  is a schematic cross-sectional view of the valve body with the valve seats of  FIG. 6  installed in the valve seat pockets. The flow in  FIG. 8  is similar to the flow described above for  FIG. 5  and has similar results in that the upstream seat is designed to bypass a certain amount of fluid under pressure to equalize the pressure between the gate  30  and the upstream seat  20 A, and yet restrict pressure from passing downstream of the downstream seat  20 B. More specifically, the valve body  4  includes a seat body  18 A into which a seat  20 A is disposed, and a seat pocket  18 B into which a seat  20 B is disposed. In the flow direction  110  illustrated in  FIG. 7  from left to right, the seat  20 A is the upstream seat and the seat  20 B is the downstream seat. The seats are mirror images of each other, so that the gate face of each as described above faces the gate from opposite directions. The pressure P 1  of a fluid upstream of the upstream seat  20 A exerts pressure against the seat  20 A and leaks past the rear flexible seal  88  and metal radial sealing surfaces  90 ,  92 , as described above in  FIG. 5 , encounters the peripheral seal  112 . The fluid flowing in this direction collapses the arms toward each other and leaks past the peripheral seal  112  and into the bonnet cavity  108  to stabilize the pressures that the pressure P 2  is approximately equal to the pressure P 1 . The left side of the bonnet cavity  108  illustrated in  FIG. 8  is fluidicly coupled to the right side of the bonnet cavity  108 , so that fluid at pressure P 2  encounters the downstream seat  20 B. As the fluid passes between an annulus created between the outer periphery of the seat  20 B and the bore  52  of the seat pocket, the fluid encounters the peripheral seal  1   12 . However, from this direction, the fluid at the pressure P 2  energizes the arms  122 ,  124  of the seal  112  by forcing them away from each other and forces the seat  20 B against the wall of the peripheral step  72  on one side and the back face  54  of the other side. The arms seal so that the fluid at pressure P 2  does not leak past the peripheral seal  112 . If any fluid leaks past the seal  112 , it encounters the metal radial sealing surface  90  which seals in a metal-to-metal fashion against the back face  54  by the fluid at pressure P 2 , forcing the seat against the back face  54 . Further, any fluid leaking past the metal-to-metal seal created by the metal radial sealing surface  90  further encounters the rear flexible seal  88 . The rear flexible seal  88  on the downstream seat  20 B is pressed against the back face  54  and seals against the back face  54 . Further, the other metal radial sealing surface  92  creates a seal against the back face  54 , as the seat  20 B is pressed against the back face  54 . Thus, the seat  20 B in one embodiment includes four sealing surfaces to help prevent leakage of fluids downstream of the seat  20 B. 
         [0057]    Thus, the system intentionally allows fluid to flow past an upstream seat (such as  20 A in the above example) and conversely seal when flowing past a downstream seat (such as  20 B in the above example). If the flow  110  was reversed, the seat  20 B would become the upstream seat and would allow pressures to stabilize by allowing fluid to seep past the seals in a downstream position, and the seat  20 A would be downstream and seal the fluid from leaking past the seat with its respective seals. 
         [0058]      FIG. 9  is a schematic side view of the valve body illustrating ribs.  FIG. 10  is a schematic partial cross-sectional view from an end illustrating the ribs.  FIG. 11  is a schematic bottom perspective view of the valve body of  FIGS. 9 and 10 . The figures will be described in conjunction with each other. The valve body  4  is generally a nonsymmetrical valve body between the upper portion and the lower portion relative to the centerline  31  of the flow passage  13 . The nonsymmetrical nature of the valve is generally due to the bonnet being coupled to the upper portion in which additional material is unnecessary and would otherwise add to the cost. Thus, the valve body portion  138  adjacent the bonnet has less material than the valve body portion  140  distal from the bonnet. Since the valve body portion  138  has less material, the valves and particularly the ends, flexes in a non-coplanar fashion when pressurized, so that the flanges  6 ,  8  bend at angles α 1  and α 2  relative to their orientation in a nonpressurized state. The nonsymmetrical portions of the valve cause the valves ends when the valve is under pressure to be deformed by being nonsymetrically stressed. Such movement (engineering “strain”) is calculable due to stress-strain curves at given stress levels for given metals. If the connections to other equipment are sufficiently rigid, the connections may reduce the deflection. However, the valve is in a strained condition. 
         [0059]    Typical valve engineering practices would dictate adding a significant amount of bulk material to the valve to be able to withstand the stress and strain. However, as discussed above, the additional bulk material adds significant cost as well. In contrast to the typical engineering practice, the inventors realize that selective positioning of relatively thin, minute amounts of material could make a significant difference in the overall stiffness and rigidity of the valve body. Thus, in contrast to standard engineering practice, the valve disclosed herein can add one or more ribs  50 A,  50 B (collectively, ribs  50 ) to the valve body to provide sufficient rigidity for the elevated pressures, and still retain a lower material cost than in standard engineering practice. More specifically, the valve having a valve body portion  142 A external to the flow passage  13  can have a rib  50 A coupled between the valve body portion  140  and the valve body portion  142 A. Similarly, the valve can have a rib  50 B disposed between the valve body portion  140  and the valve body portion  142 B external to the flow passage  13 . 
         [0060]    As shown in  FIG. 9 , the ribs  50  can have an angled surface  146  between the valve body portion  140  and the valve body portions  142 A,  142 B. The term “angled” is used broadly and includes sloped and curved surfaces. In some embodiments, the rib can have an opening formed therethrough to lessen the material and weight, depending on manufacturing. 
         [0061]    As shown in  FIG. 10 , the rib  50  can have a rib thickness T R . In the embodiment shown, the rib thickness can be a consistent thickness other than allowances for radii where the ribs join the valve body passage  142  or other transitions. In other embodiments, the rib thickness can vary, depending on manufacturing complexities and costs. 
         [0062]      FIG. 12  is a schematic cross-sectional view of the valve bonnet with a stem assembled therein. The bonnet  22  includes an opening  26  through which the stem  28  can be inserted. The stem  28  is threadably coupled to the gate  30  as described above for actuating the gate up and down in the gate cavity  16  by rotating the stem  28  by an actuator  34 . Under certain conditions, the stem  28  can be overstressed and fail, generally by excess torque from the actuator  34 , creating a shear failure. A shear pin  44  coupled from the stem  28  to a bearing  56  provides a protective mechanism to overstressing the stem and possibly breaking the stem at a less desirable location. However, sometimes, the shear pin can be replaced with an improperly rated shear pin and not shear, and the stem can be sheared at a weak point. One weak point is a thread relief  46  that is created in forming the threads  32  along the portion of the stem that engages the gate described above. If the stem fails at the thread relief  46 , the valve is generally taken offline and dissembled which could interrupt production flow and create a significant expenditure. Thus, the inventors have provided another safety device that supplements the shear pin  44 . Specifically, the stem  28  in at least one embodiment can provide a weakened point in the stem at a stem groove  48 . The stem groove  48  is formed external to the bonnet  22  and generally external to the cap  40  of the bonnet. If the stem fails to shear the shear pin when excess torque is applied, it can shear at the thread groove  48  instead of the thread relief  46 . If the stem shears at the stem groove  48 , there can still be sufficient length on the stem  28  external to the bonnet to be engaged by a pipe wrench or other device for rotating the valve, independent of the actuator  34 . In general, the diameter D G  of the stem groove  48  will be less than the diameter D T  of the thread relief  46 , so that the smaller and weaker cross-section will be the thread groove  48 . More specifically, the stem groove  48  establishes a smaller cross-sectional area in the stem  28  than a cross-sectional area at a thread relief  46  on the stem. In turn, the cross-sectional area of the stem groove  28  has a greater shear strength than a shear strength of the shear pin  44  inserted through the stem. Thus, the shear pin should fail first, then the stem groove  48 , and both fail before the thread relief  46  fails. 
         [0063]      FIG. 13  is a schematic top perspective assembly view of the valve body and valve bonnet with extended bonnet bolts. An additional feature of an embodiment of the valve disclosed herein is the use of significantly longer bonnet bolts to act as metal “springs” on the bonnet-to-body seal  36 . It is typical that a bonnet bolt will be a relatively short, stubby bolt. The inventors have realized as an added advantage to the design shown herein, that a much longer bonnet bolt can be used as a mechanical “spring” to maintain pressure under varying conditions on the bonnet-to-body seal  36 . Specifically, the length L of the bonnet bolt  24  can be multiples of length of a standard bonnet bolt. In at least one embodiment, the length L of the bonnet bolt  24  can be 2× to 6×, and more preferably 4×, of a standard length of bonnet bolt. The invention can use the modulus of elasticity (Young&#39;s Modulus) of a stress-strain curve for the particular metal to determine that under a given stress, the metal will be deformed a certain length (“strained”) and thus stretched to create a metal “spring” that can absorb varying stresses and still maintain a tight seal on the bonnet-to-body seal  36 . A longer bolt can accommodate a longer strain for a given stress and effectively operate more as a spring with a lower spring constant for increased flexibility in sealing to the bonnet-to-body seal  36 . 
         [0064]    The bolts are generally coupled to valve body bolt holes  154  in the valve body  4 . The bonnet  22  can be assembled with the stem  28  and other associated components, and inserted over the bonnet bolts  24 , so that the bolts travel through bonnet bolt holes  156 . The bonnet bolts are then pre-stressed to a certain torque using nuts and other fasteners, so that the bolts are strained (that is, stretched in tension) for a given stress in an elastic engineering mode without incurring plastic permanent deformation. The engineering strain creates a “spring” loaded force on the lower bonnet sealing surface  158 , also shown in cross-sectional view in  FIG. 1 . The lower bonnet sealing surface  158  engages the bonnet-to-body seal  36  that creates a tight seal between the bonnet  22  and the valve body  4  under varying stress loads. 
         [0065]    Other and further embodiments utilizing one or more aspects of the inventions described above can be devised without departing from the spirit of the invention. For example, the cables could be chains, the motive forces could be gears and sprockets, and other variations. Further, the various methods and embodiments of the translating movement that shifts the pile and launches the piles can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements can include plural elements and vice-versa. 
         [0066]    The order of steps can occur in a variety of sequences unless otherwise specifically limited. The various steps described herein can be combined with other steps, interlineated with the stated steps, and/or split into multiple steps. Similarly, elements have been described functionally and can be embodied as separate components or can be combined into components having multiple functions. 
         [0067]    Unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising,” should be understood to imply the inclusion of at least the stated element or step or group of elements or steps or equivalents thereof, and not the exclusion of a greater numerical quantity or any other element or step or group of elements or steps or equivalents thereof. The term “couple”, “coupled,” “coupling,” “coupler,” and like terms are used broadly herein and may include any method or device for securing, binding, bonding, fastening, attaching, joining, inserting therein, forming thereon or therein, communicating, or otherwise associating, for example, mechanically, magnetically, electrically, chemically, directly or indirectly with intermediate elements, one or more pieces of members together and may further include without limitation integrally forming one functional member with another in a unity fashion. The coupling may occur in any direction, including rotationally. 
         [0068]    The systems and methods herein have been described in the context of various embodiments and not every embodiment has been described. Apparent modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the concepts of the Applicants, but rather, in conformity with the patent laws, Applicants intend to protect all such modifications and improvements to the full extent that such falls within the scope or range of equivalent of the following claims. 
         [0069]    Further, any references mentioned in the application for this patent, as well as all references listed in the information disclosure originally filed with the application, are hereby incorporated by reference in their entirety to the extent such may be deemed essential to support the enabling of the concept. However, to the extent statements might be considered inconsistent with the patenting of the concept, such statements are expressly not meant to be considered as made by the Applicant(s).