Abstract:
A gate valve for use in oil field applications having a seal assembly made up of an elastomeric case and a spring in the case having a V-shaped cross section. The spring has legs that depend from one another, and free ends of the legs that are contoured towards one another to define a rounded surface on outer surfaces of the legs. The rounded surface reduces stress contact between the spring and the case, thereby prolonging seal assembly life. The seal assembly can be placed between a stem in the valve and a gland packing. Other seal assembly locations include between a seat ring and counterbore in the valve body.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present disclosure relates to hardware for the production of hydrocarbons, and in particular to a seal element for use in valves used in hydrocarbon production. 
         [0003]    2. Brief Description of Related Art 
         [0004]    Typical gate valves used in connection with oil and gas operations have a valve body with a flow passageway that extends therethrough. The flow passageway intersects a central cavity in which a gate is typically reciprocated. The gate has an opening, and moves between open and closed positions. When in the open position, the opening is aligned with the fluid path so that fluid can flow therethrough. Conversely, when the gate is in the closed position, the gate blocks the flow passageway. Annular valve seats are usually provided in the valve body on opposing sides of the gate, the valve seats circumscribe the passage and seal against the valve to prevent cross flow between the flow passageway and central cavity. Valve gates typically attached to a stem, which controls the position of the gate between the open and closed positions and inserts through an axial bore in the valve body. A gland packing is usually installed in an annular space between the stem and axial bore. Seal elements are often installed with the valve seats and gland packing that seal between the valve body, elements of the gland packing, and valve body. 
       SUMMARY OF THE INVENTION 
       [0005]    Disclosed herein are examples of a valve assembly. In an example the valve assembly includes a valve body, where the valve body has a flow passageway, a cavity that is intersected by the flow passageway, and an axial bore in communication with the cavity. Also included with the valve assembly is a stem that inserts into the axial bore and a seal assembly disposed in the valve body. In this embodiment the seal assembly is made up of an annular elastomeric casing and an annular spring having a V-shaped cross section disposed in a recess in the casing and that has legs with free ends that are contoured towards one another so that a rounded surface is formed on inner and outer curved surfaces of the spring. The seal assembly can be disposed between the stem and a gland packing that is inserted in the axial bore and circumscribes the stem, and wherein the seal assembly defines a seal on the stem. The valve assembly can further have a plurality of seal assemblies in sealing contact around the stem, and wherein the gland packing has annular members that couple together in the annular space between the stem and the axial bore. Counterbores can be formed in the flow passageway and annular seat rings can be inserted into the counterbores, wherein a seal assembly is disposed in each of the counterbores, and the seat rings have a face that contacts opposing surfaces of a gate that is attached to the stem. Further included in this example are primary seal assemblies in annular spaces between the seat rings and the counterbores, wherein the seal assemblies are secondary seal assemblies, and wherein the primary seal assemblies are between the secondary seal assemblies and the faces. The valve body is optionally connected to a wellhead assembly that is used for producing hydrocarbons from a subterranean formation. In an example, the free ends angle from the legs of the spring at a value of from about 5° to about 25°. 
         [0006]    In another example the valve assembly includes a valve body, where the valve body has a flow passageway, a cavity that is intersected by the flow passageway, and an axial bore in communication with the cavity a stem that inserts into the axial bore, a gland packing in the axial bore and that circumscribes the stem, an annular seal assembly that circumscribes and seals around the stem, and that comprises an annular elastomeric casing and an annular spring having a V-shaped cross section disposed in a recess in the casing and that has legs with free ends that are contoured towards one another at an angle from the legs so that a rounded surface is formed on inner and outer curved surfaces of the spring. The seal assembly may be a gland seal assembly and where the valve assembly further includes a valve seat seal assembly that is disposed between a seat ring and a counterbore in the valve body. This example can further include primary seal assemblies in annular spaces between the seat rings and the counterbores, wherein the seal assemblies are secondary seal assemblies, and wherein the primary seal assemblies are between the secondary seal assemblies and the faces. The angle can range from 5° to 25°. Optionally, the valve body couples to a wellhead assembly used for producing hydrocarbons. A lip can be included on the elastomeric case that depends radially inward and over a one of the free ends of the spring. 
         [0007]    Another example of a valve assembly disclosed herein includes a valve body having a flow passageway, a cavity that is intersected by the flow passageway, and an axial bore in communication with the cavity. A counterbore is included in the valve body that circumscribes the passage and a seat ring in the counterbore. An annular seal assembly is between the counterbore and seat ring, and that is made up of an annular elastomeric casing and an annular spring having a V-shaped cross section disposed in a recess in the casing and that has legs with free ends that are contoured towards one another at an angle from the legs so that a rounded surface is formed on inner and outer curved surfaces of the spring. The valve assembly can further include a stem that inserts into the axial bore, and a gland packing around the stem, and wherein the seal assembly is a seat ring seal. A gland packing seal can be disposed between the gland packing and the stem and that defines a seal around the stem. The valve body can connect to a wellhead assembly that produces hydrocarbons. Optionally, the free ends depend from the legs at an angle of at least around 5°. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present technology will be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawings, in which: 
           [0009]      FIG. 1  is side cross-sectional view of a gate valve assembly having an example of a seat seal assembly in accordance with the present technology. 
           [0010]      FIG. 2  is an enlarged side cross-sectional view of a portion of the gate valve assembly corresponding to area  2  in  FIG. 1  and in accordance with the present technology. 
           [0011]      FIG. 3  is a sectional view of an example of the seat seal assembly of  FIG. 1  and in accordance with the present technology. 
           [0012]      FIG. 4  is an enlarged side cross-sectional view of a portion of the gate valve assembly corresponding to area  4  in  FIG. 1  and in accordance with the present technology. 
       
    
    
       [0013]    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 
       [0014]    The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be 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 its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term about includes +/−5% of the cited magnitude. 
         [0015]    It is to be further understood that the scope of the present disclosure 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 and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
         [0016]      FIG. 1  shows a side cross-sectional view of a gate valve assembly  10  according to an embodiment of the present technology, including examples of a gland packing assembly  12  and valve seat assembly  14 . The gate valve assembly  10  includes a gate  16  with an opening  18 . The gate  16  is attached to a stem  20 , and moves in a central cavity  22  of a valve body  30 . The central cavity  22  is perpendicular to and intersects a flow passageway  24  through which fluid can flow. In an example, gate valve assembly  10  is coupled to a wellhead assembly  25  that is used for producing hydrocarbons from a subterranean formation (not shown). 
         [0017]    The gate  16  and stem  20  are selectively moved between an open position and a closed position. To illustrate this functionality, in  FIG. 1  the gate  16  and stem  20  are shown in a split configuration, with their respective portions that are to the left of a centerline  26  an open position. Similarly, respective portions of the gate  16  and  20  to the right of centerline  26  are illustrated in a closed position. As can be seen, when the gate  16  is in its open position, the opening  18  is aligned with the flow passageway  24  so that fluid in the flow passageway  24  can pass through the opening  18 . In its open position, the gate  16  may be received into a recess  28  in the valve body  30 . Conversely, when the gate  16  is in its closed position, the gate  16  blocks the flow passageway  24 . In the closed position, the opening  18  is moved upward and out of registration with the flow passageway  24 ; and the gate  16  moves into the flow passageway  24 , thereby obstructing the flow of fluid through the flow passageway  24 . 
         [0018]    Movement of the gate  16  between an open and a closed position may be accomplished by any appropriate means. For example, the embodiment of  FIG. 1  shows a rising stem  20 , which opens and closes the gate  16  by moving the stem  20  upward and downward relative to the flow passageway  24 . Alternate embodiments may include non-rising stems that employ other means, such as threads, to raise and lower the gate  16  without raising and lowering the stem  20  itself. The example of the gate valve assembly  10  shown further includes a bonnet  29  mounted to the valve body  30 , and seat rings  32  between the valve body  30  and opposing sides of the gate  16 . The seat rings  32  are mounted in counterbores  34  that circumscribe the portions of the passageway  24  adjacent the central cavity  22 . Each seat ring  32  is mounted in one of the counterbores  34 , and has limited axial movement. The gland packing assembly  12  helps provide a seal between the stem  20  and the bonnet  29 . The valve seat assembly  14  seals between each seat ring  32  and the valve body  30 . Each seat ring  32  also has a face  35  positioned adjacent to the gate  16  to guide the gate  16 . 
         [0019]    An example of the gland packing assembly  12  from area  2  of  FIG. 1  is shown in an enlarged view in  FIG. 2 . In the illustrated example, the gland packing assembly  12  includes a primary stem seal  36 , a secondary stem seal  38 , and a tertiary stem seal  40 . The primary stem seal  36  includes a sealing portion  42  and an extended portion  44  that extends away from the flow passageway  24  substantially parallel to the stem  20 . The primary, secondary, and tertiary stem seals  36 ,  38 , and  40  are carried by a proximal cartridge body  48 . As shown in  FIG. 2 , the extended portion  44  of the primary stem seal  36  may engage the proximal cartridge body  48  at a threaded interface  50 . The proximal cartridge body  48  may include a secondary bonnet seal  52  configured to seal against a surface of the bonnet  29 . 
         [0020]    Referring back to  FIG. 1 , the stem  20  may include an optional stem protrusion  54  that engages a surface  56  of the bonnet  29  when the gate is in the open position, as shown in  FIG. 1 . In such embodiments, the engagement between the stem protrusion  54  and the surface  56  of the bonnet  29  creates a backseat seal that is closer to the flow passageway  24  than the gland packing assembly  12 . The stem protrusion  54  may be made of metal, so that it is resistant to corrosion, and has structural rigidity. The inclusion of such a backseat seal adds redundancy to the system, thereby further decreasing the risk of leaks between the stem  20  and the bonnet  29 . 
         [0021]    Referring back to  FIG. 2 , an annular cartridge body  58  is shown threaded to an inner surface of bonnet  29 . Upper and lower seals  60 ,  62  seal between cartridge body  58  and are provided in recesses in an inner circumference of cartridge body  58 . In the embodiment shown, the proximal cartridge body  48  couples to cartridge body  58  along a cartridge interface  64 , with the cartridge body  58  partially surrounding a portion of the proximal cartridge body  48 . In the illustrated example, the cartridge bodies  48 ,  58  are held together by axially applied compression loads acting on the gland packing assembly  12 . In some embodiments, however, the cartridge bodies  48 ,  58  may be integral with one another, and form a single cartridge body. In addition, the distal cartridge body  41  may be threadedly engaged with the bonnet  29  at an interface  65 . 
         [0022]    An annular spacer  66 , positioned between the secondary stem seal  38  and the tertiary stem seal  40 , and extending into a cavity behind the tertiary stem seal  40 . The annular spacer  66  has a lower end  68  that fits into the annular space between the extended portion  44  of the primary stem seal  36  and the stem  20 . One purpose of the annular spacer  66  is to restrain axial movement of the secondary stem seal  38  by providing a barrier to movement of the secondary stem seal  38  toward the tertiary stem seal  40 . In alternate embodiments, the annular spacer  66  could be replaced with any mechanism capable of helping to maintain relative movement of the secondary stem seal  38  and the tertiary stem seal  40 . For example, the annular spacer  66  could be replaced with a snap ring (not shown). 
         [0023]    The gland packing assembly  12  is designed to provide a multi-fault system for retaining pressurized fluids below the gland packing assembly  12 , and to prevent such fluids from passing between the stem seal gland packing assembly  12  and the stem  20 . Each of the primary, secondary, and tertiary stem seals  36 ,  38 ,  40  has a different structure, as described in detail below, and each provides a secure seal against the stem  20  of the gate valve assembly  10 . Each seal is structurally independent of the other seals, and is capable of sealing the space between the stem seal gland packing assembly  12  and the stem  20  independent of the other seals. Moreover, together these seals provide a redundancy that maintains the integrity of the interface between the gland packing assembly  12  and the stem  20 , even if one or two of the seals fail. 
         [0024]    Referring now to  FIG. 3 , shown is a valve seat assembly  14  according to an exemplary embodiment of the present technology. Shown set between the seat rings  32  and counterbores  34  are a primary seat seal  70  and secondary seat seal  72 , wherein the primary seat seal  70  is adjacent the secondary seat seal  72  and on a side proximate the face  35 . Optional sand excluders  74  are further illustrated and set in annular recesses  76  on an inner circumference of each seat ring  32 . As is known the primary and secondary seat seals  70 ,  72 , define a flow barrier between the seat rings  32  and counterbores  34 . 
         [0025]    As shown in side sectional view  FIG. 4  is a seal assembly  78  that represents an example design for one or more of the secondary stem seal  38 , check line seal  46 , upper seal  60 , lower seal  62 , and secondary seat seal  72 . Seal assembly  78  includes an annular elastomeric casing  80 , with a cross section that is generally V-shaped. As shown in cross section, the casing  80  has legs  82  that project from a base  84  and are spaced away from one another to define an opening  86  between the legs  82 . An annular metal spring element  88  with a V-shaped cross section is shown set in the opening  86 , that also has legs  90  that project away from a base  92 . Free ends  94  of the legs  90  are contoured towards one another and away from the walls of the recess  86  which defines a rounded surface  96  on the inner and outer curved surfaces of the spring element  88 . 
         [0026]    By contouring the free ends  94  of the legs  90  so that the rounded surface  96  contacts the elastomeric casing  80  lowers stresses between the spring element  88  and casing  80 . This in turn reduces damaging forces applied by the spring element  88  against the casing  80  and prolongs the useful life of the casing  80  and thus the seal assembly  78 . To retain the spring element  88  in the recess  86 , an optional lip  98  is provided on the casing  80  proximate the opening to the recess  86  and on an inner surface and terminal end of one of the legs  82 . In an example, the free ends  94  contour at an angle θ from the legs  90  that ranges from about 5° to about 25°. 
         [0027]    An advantage to utilizing the embodiments disclosed herein is that a seal made in accordance with the present disclosure seals better after many thermal and/or pressure cycles. Due to the different in thermal expansion of different materials in the seal assembly, the edge end of the spring protrudes into the seal jacket and has a ratcheting effect when the spring and jacket expand at different rate. The result is the jacket will be stretched and flattened after many thermal and pressure cycles until it can no longer seal. 
         [0028]    The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. For example, instead of elastomeric, the subject material can be a polymeric material, a polymeric/elastomeric material, and combinations thereof. This and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.