Abstract:
A fluid control device comprises a valve body, a valve plug, a valve cage, and a sealing ring. At least a portion of the sealing ring is disposed within a gap between the valve plug and the valve cage to provide a seal therebetween when the valve plug is in the closed position. The sealing ring includes an L-shaped cross-section that provides an effective seal regardless of the port diameter of the fluid control device, and thus, reduces the number of types of seals required to be stored in inventory for various applications.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to control valves for controlling fluid flow, and more particularly, control valves including a valve plug movably disposed within a valve cage. 
       BACKGROUND 
       [0002]    Typical fluid process control systems comprise various components for controlling various process parameters. For example, a fluid process control system may include a plurality of control valves for controlling flow rate, temperature, and/or pressure of a medium flowing through the system. The end product is dependent on the accuracy of the control of these parameters, which is, in turn, dependent on the geometry and characteristics of the control valves. For example, control valves are specifically designed and selected to provide for particular flow capacities and pressure changes. If and when these characteristics are compromised, the quality of the end product may be affected. One way such characteristics may be compromised is by inadvertent leakage of the process. 
       SUMMARY 
       [0003]    One embodiment of the present invention includes a fluid control device comprising a valve body, a valve seat, a valve plug, a valve cage, and a sealing ring. The valve body includes an inlet port and an outlet port. The valve seat is disposed within the valve body and defines an opening fluidly communicating between the inlet port and the outlet port. The valve plug includes an external surface and is movable between a closed position and an open position. In the closed position, the valve plug engages the valve seat and forms a primary seal. In the open position, the valve plug is displaced from the valve seat. The valve cage is disposed within the valve body and includes an internal surface sized to receive the valve plug such that a gap between the valve cage and the valve plug defines a leak path. The sealing ring of the disclosed embodiment has a generally L-shaped cross-section. At least a portion of the sealing ring is disposed within the gap to provide a secondary seal sealing the leak path when the valve plug is in the closed position. 
         [0004]    In at least one embodiment, the sealing ring comprises a flange portion and a resilient sealing band portion. The flange portion is secured to one of the valve cage and the valve plug. The resilient sealing band portion sealingly engages the internal surface of the valve cage and an external surface of the valve plug to provide the secondary seal when the valve plug is in the closed position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a cross-sectional side view of a fluid control device constructed in accordance with one embodiment of the present disclosure; 
           [0006]      FIG. 2  is a partial cross-sectional side view of the fluid control device of  FIG. 1  taken from circle II of  FIG. 1 ; and 
           [0007]      FIG. 3  is a detailed partial cross-sectional side view of the fluid control device of  FIG. 2 , taken from circle III of  FIG. 2  and illustrating the flexible nature of a sealing ring of the device during operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]      FIG. 1  depicts one embodiment of a control valve  10  constructed in accordance with the principles of the present invention. The control valve  10  generally comprises a valve body  12 , a bonnet  30 , a cage retainer  18 , a cage  20 , a sealing ring  21  (shown in  FIG. 2 ), a valve plug  16  and a valve seat  14 . The valve body  12  defines an inlet port  22 , an outlet port  24 , and a fluid flow path  26  extending between the inlet port  22  and the outlet port  24 . The valve plug  16  is coupled to the end of a valve stem  28 , which extends through the bonnet  30  and is adapted to be coupled to an actuator (not shown). The actuator controls the displacement of the valve plug  16  between a closed position (shown in  FIG. 1 ) in engagement with the valve seat  14  to define a primary seal and an open position (not shown) displaced from the valve seat  14 . The sealing ring  21  provides a secondary seal between the cage retainer  18  and the cage  20 . In the disclosed embodiment, the sealing ring  21  comprises a body having a generally L-shaped cross-section, as depicted in  FIGS. 2 and 3  and described in more detail below. 
         [0009]    With continued reference to  FIG. 1 , the valve seat  14  is carried within a throat portion  32  of the valve body  12  and defines an opening  34  in fluid communication with the fluid flow path  26 . The cage retainer  18  is clamped into the valve body  12  by the bonnet  30 , which is fixed to the valve body  12  with a plurality of fasteners  36 . So configured, the cage retainer  18  clamps the cage  20  and valve seat  14  into the throat portion  32  of the valve body  12 . 
         [0010]    The cage  20  comprises a generally cylindrical member defining a plurality of windows  42  in fluid communication with the fluid flow path  26 . Additionally, as illustrated in  FIG. 2 , the cage  20  includes a lower shoulder  44  seated against the valve seat  14  and an upper recess  46  receiving a portion of the sealing ring  21  and the cage retainer  18 . Specifically, the upper recess  46  of the cage  20  receives a lower shoulder  48  of the cage retainer  18 , which secures the sealing ring  21  to the cage  18 . So disposed, the internal surface  37  of the cage retainer  18  defines an annular channel  50 . In the disclosed embodiment, the annular channel  50  is disposed between the cage retainer  18  and the cage  20  and accommodates a portion of the sealing ring  21 . In alternative embodiments, however, the annular channel  50  can be defined by either the cage retainer  18 , the cage  20 , or both. 
         [0011]    As depicted in  FIG. 3 , the upper recess  46  of the cage  20  includes a bottom surface  52  and a side surface  54  disposed generally perpendicular to the bottom surface  52 . The lower shoulder  48  of the cage retainer  18  defines a bottom surface  56 , an external side surface  58 , and an internal side surface  60 . The external and internal side surfaces  58 ,  60  are disposed generally perpendicular to the bottom surface  56 . The internal side surface  60  defines an external boundary of the annular channel  50 . Additionally, the lower shoulder  48  of the cage retainer  18  comprises a bull-nosed corner  62  between the bottom surface  56  and the internal side surface  60 , and a chamfered corner  64  between the bottom surface  56  and the external side surface  58 . 
         [0012]    As shown in  FIG. 1 , for example, the valve plug  16  of the disclosed embodiment comprises a balanced valve plug having an external surface  66  and a pair of through-bores  68 . The through-bores  68  are in fluid communication with the fluid flow path  26  and a cavity  70  defined by the interior of the cage retainer  18 . Accordingly, the pressure in the valve body  12  is balanced on both sides of the valve plug  16 , even when the valve plug is in the closed position (shown in  FIG. 1 ). As shown in  FIG. 3 , the external surface  66  of the valve plug  16  comprises a multi-contoured surface including a first perimeter surface  66   a , a second perimeter surface  66   b , and a transition surface  66   c  disposed between and connecting the first and second perimeter surfaces  66   a ,  66   b.    
         [0013]    As illustrated in  FIG. 2 , the first transition surface  66   a  includes a first diameter D 1 , and the second perimeter surface  66   b  includes a second diameter D 2 . The second diameter D 2  is smaller than the first diameter D 1 . The transition surface  66   c  includes a generally frustoconical surface that converges from the first perimeter surface  66   a  to the second perimeter surface  66   b . The transition surface  66   c  is disposed at an angle σ relative to the second perimeter surface  66   b . The angle σ can be in the range of approximately ten degrees (10°) to approximately eighty degrees (80°), and in one embodiment, approximately thirty degrees (30°). 
         [0014]    In one alternative embodiment, however, the transition surface  66   c  can include a rounded bull-nose type surface. In another alternative embodiment, the transition surface  66   c  can include a surface that is perpendicular to the first and second perimeter surfaces  66   a ,  66   b . Such a configuration may not interfere with the movement of the valve plug  16  because the legs  80   a ,  80   b  of the sealing band portion  78  are disposed at angles, as described. As such, when the valve plug  16  moves from an open position to the closed position, for example, the sharp corner of the valve plug  16  that is located between the first perimeter surface  66   a  and the transition surface  66   c  would engage the second leg  80   b  of the sealing band portion  78 . Further movement of the valve plug  16  in the downward direction would therefore compress the sealing band portion  78  until the first perimeter surface  66   a  became engaged with the peak  84 . 
         [0015]    Referring back to  FIG. 1  and as mentioned above, the valve plug  16  is disposed within the cage retainer  18  and adapted for displacement between the closed position and one or more open positions. Accordingly, the internal surface  37  of the cage retainer  18  is sized and configured so as not to interfere with the movement of the valve plug  16 . For example, as depicted in  FIGS. 2 and 3 , the internal surface  37  of the cage retainer  18  includes a diameter D 3  that is larger than the diameters D 1 , D 2  of the first and second perimeter surfaces  66   a ,  66   b  of the external surface  66  of the valve plug  16 . So configured, a gap  74  exists between the cage retainer  18  and the valve plug  16 , through which fluid in the flow path  26  and the cavity  70  of the cage retainer  18  can leak, especially from the cavity  70  to the windows  42  of the cage  20  when the valve plug  16  is in the closed position. 
         [0016]    Therefore, the control valve  10  constructed in accordance with the principles of the present invention comprises the sealing ring  21  to seal the gap  74  and prevent leakage. As illustrated in  FIG. 3 , the sealing ring  21  comprises a one-piece member including a flange portion  76  and a resilient sealing band portion  78  disposed generally orthogonal to each other such that the sealing ring  30  has a generally L-shaped cross-section. In the disclosed embodiment of the sealing ring  21 , the flange portion  76  extends generally radially outwardly from the sealing band portion  76 . As shown in  FIG. 3 , the flange portion  76  is clamped between the bottom surface  52  of the upper recess  46  in the cage  20  and the bottom surface  56  of the lower shoulder  48  of eth cage retainer  18 . Additionally, as shown, the sealing band portion  78  is accommodated within the annular channel  50  in the cage  18 . 
         [0017]    The flange portion  76  comprises a generally flat annular disk. The sealing band portion  78  comprises first and second opposing legs  80   a ,  80   b  and a foot  82 . The legs  80   a ,  80   b  meet at a peak  84  and include respective bases  86   a ,  86   b  disposed opposite the peak  84 . Accordingly, the legs  80   a ,  80   b  define a generally V-shaped cross-sectional portion of the sealing band portion  78  of the sealing ring  21 . The base  86   a  of the first leg  80   a  connects to the flange portion  76  of the sealing ring  21  at a flexible shoulder portion  88 . The base  86   b  of the second leg  80   b  connects to the foot  82  at a flexible shoulder portion  90 . So configured, the sealing band portion  78  of the sealing ring  21  is resilient and can be deformed between a relaxed state and a compressed state during operation of the control valve  10 . 
         [0018]    For example, when the valve plug  16  is in an open position (not shown), the valve plug  16  is displaced upward from the closed position such that the second perimeter surface  66   b  is disposed proximate to the sealing band portion  78  of the sealing ring  21 . The second perimeter surface  66   b  is smaller in diameter than the first perimeter surface  66   a , and therefore, spaced further from the internal side surface  60  of the lower shoulder  48  of the cage retainer  18 , which defines the annular channel  50 . The annular channel  50  thus has a larger radial dimension when the valve plug  16  is in an open position, which allows the sealing band portion  78  to assume the relaxed state, which is depicted by dashed lines in  FIG. 3 . 
         [0019]    In the relaxed state, the sealing band portion  78  can be completely relaxed or can be slightly compressed due to engagement with the second perimeter surface  66   b . However, the sealing band portion  78  is configured to exert no force, or a very small amount of force, against the second perimeter surface  66   b . Accordingly, there is no friction, or only a very small amount of friction, between the peak  84  of the sealing band portion  78  of the sealing ring  21  and the second perimeter surface  66   b . This lack of friction enables the valve plug  16  to easily move from between various open positions, each including the second perimeter surface  66   b  in close proximity to the sealing band portion  78 . Additionally, this lack of friction increases the useful life of the sealing ring  21  by eliminating unnecessary wear on the peak  84  thereof when the valve plug  16  moves merely between open positions within the cage retainer  18  that do not require the gap  74  to be sealed, for example. 
         [0020]    Still referring to  FIG. 3 , when the sealing band portion  78  is in the relaxed state, the first leg  80   a  is separated from the flange portion  76  of the sealing ring  21  by an angle α, the legs  80   a ,  80   b  are separated by an angle β, and the second leg  80   b  is separated from the foot  82  by an angle γ. The angle α can be in the range of approximately one-hundred and five degrees (105°) to approximately one-hundred and twenty-five degrees (125°), and at least in one embodiment, approximately one-hundred and fifteen degrees (115°). The angle β can be in the range of approximately one-hundred and ten degrees (110°) to approximately one-hundred and fifty degrees (150°), and at least in one embodiment, approximately one-hundred and thirty degrees (130°). The angle γ can be in the range of approximately one-hundred and forty-five degrees (145°) to approximately one-hundred and sixty-five degrees (165°), and at least in one embodiment, approximately one hundred and fifty-five degrees (155°). 
         [0021]    During operation, the valve plug  16  moves toward the closed position (shown in  FIGS. 1-3 ), wherein the valve plug  16  seals against the valve seat  14  and the first perimeter surface  66   a  is disposed proximate to the sealing band portion  78  of the sealing ring  21 . As the valve plug  16  displaces downward, relative to the orientation of  FIG. 3 , the transition portion  66   c  of the external surface  66  of the valve plug  16  slides over the peak  84  of the sealing band portion  78  and begins to compress the sealing band portion  78  toward the compressed state. The compressed state is indicated with solid lines in  FIG. 3  and is realized upon engagement of the peak  84  with the first perimeter surface  66   a . The angled, frustoconical configuration of the transition surface  66   c  helps to smoothly transition the peak  84  of the sealing band portion  78  between the second perimeter surface  66   b  and the first perimeter surface  66   a . As described above, the diameter D 1  of the first perimeter surface  66   a  is larger than the diameter D 2  of the second perimeter surface  66   b . Therefore, when the valve plug  16  is in the closed position, the radial dimension of the annular channel is smaller than when the valve plug  16  is in an open position, as described above. Accordingly, the sealing band portion  78  of the sealing ring  21  assumes the compressed state. 
         [0022]    In the compressed state, the bases  86   a ,  86   b  of the respective legs  80   a ,  80   b , as well as the foot  82 , sealingly engage the internal side surface  60  of the lower shoulder  48  of the cage retainer  18 , which defines the annular channel  50 . Additionally, the peak  84  of the sealing band portion  78  sealingly engages the first perimeter surface  66   a  of the external surface  66  of the valve plug  16 . So configured, the sealing band portion  78  seals the gap  74  between the valve plug  16  and the cage retainer  18  and prevents leakage of fluid therethrough. Preferably, in the compressed state, the sealing band portion  78  applies a force to the first perimeter surface  66   a  of the valve plug  16  and the internal side surface  60  of the cage retainer  18  that is sufficient to prevent the pressurized fluid in the valve body  12  and the cavity  70  of the cage retainer  18  from leaking through the gap  74 , even under high temperatures, e.g., greater than or equal to approximately 450° F. (232.22° C.). 
         [0023]    In one embodiment, the sealing ring  21  can be constructed of metal such as Inconel X750 (Industry Designation N07750), 718 metal (Industry Designation N07718), or any other suitable material capable of withstanding relatively high temperatures, e.g., greater than or equal to approximately 450° F. (232.22° C.). 
         [0024]    As illustrated, when the sealing band portion  78  is in the compressed state, the entire V-shaped cross-sectional portion deforms, i.e., flattens, such that first leg  80   a  is separated from the flange portion  76  by an angle α′, the legs  80   a ,  80   b  are separated by an angle β′, and the second leg  80   b  is separated from the foot  82  by an angle γ′. The angle α′ can be in the range of approximately ninety-five degrees (95°) to approximately one-hundred and fifteen degrees (115°), and at least in one embodiment, approximately one-hundred and five degrees (105°). The angle β′ can be in the range of approximately one-hundred and thirty degrees (130°) to approximately one-hundred and seventy degrees (170°), and at least in one embodiment, approximately one-hundred and fifty degrees (150°). The angle γ′ can be in the range of approximately one-hundred and fifty-five degrees (155°) to approximately one-hundred and seventy-five degrees (175°), and at least in one embodiment, approximately one hundred and sixty-five degrees (165°). 
         [0025]    During further operation of the control valve  10 , as the valve plug  16  moves back into an open position, the valve plug  16  unseats from the valve seat  14  and moves upward, relative to the orientation of the valve body  12  in  FIGS. 1-3 . The peak  84  of the sealing banc portion  78  of the sealing ring  21  slides along the first perimeter surface  66   a , then over the transition surface  66   c . In one embodiment wherein the peak  84  maintains a slightly compressed state when the valve plug  16  is in an open position, the peak  84  finally slides along the second perimeter surface  66   b . In alternative embodiments, however, where the sealing band portion  78  assumes a fully relaxed state when the valve plug  16  is in an open position, the peak  84  may not contact the second perimeter surface  66   b  at all. 
         [0026]    In light of the foregoing, it should be appreciated that a control valve  10  and sealing ring  21  constructed in accordance with the embodiment described herein provides a robust fluid tight seal between a moving valve component, i.e., the valve plug  16  of the disclosed control valve  10 , and a stationary valve component, i.e., the cage retainer  18  of the disclosed control valve  10 , at least when the moving valve component is in a closed position. Moreover, the disclosed embodiment of the multi-contoured surface of the valve plug  16  constructed in accordance with the embodiment described herein may provide the advantage of prolonging the useful life of the sealing ring  21  by reducing and/or eliminating wear when the control valve  10  is open by reducing and/or eliminating friction between the sealing band portion  78  and the second perimeter surface of the valve plug  16 . 
         [0027]    While the sealing ring  21  has been depicted and described herein as being secured to the cage retainer  18  and the valve plug  16  has been described herein as carrying the multi-contoured surface, an alternative embodiment can include the sealing ring  21  secured to the valve plug  16 , while the internal surface  37  of the cage retainer  18  can define the multi-contoured surface, similar to that which is disclosed in commonly owned U.S. Pat. No. 6,851,658, issued Feb. 8, 2005 and entitled “Control Valve Trim and Bore Seal,” the entire contents of which are hereby expressly incorporated herein by reference. So configured, the sealing ring  21  would be arranged such that the flange portion  76  extends radially inwardly from the sealing band portion  78 , as opposed to radially outwardly, as disclosed above. Moreover, the valve plug  16  may define an annular channel, similar to the channel  50  disclosed herein, for accommodating the sealing band portion  78  of the sealing ring  21 . Further still, the valve plug  16  may be equipped with a retainer ring, or some other fastening means, that would be disposed in the annular channel, for example, for securing the flange portion to the valve plug  16 . 
         [0028]    Moreover, while the cage retainer  18  has been disclosed herein as including a two-piece clamped valve cage, the present invention is not limited to such two-piece construction. Rather, the sealing ring  21  disclosed herein can alternatively be incorporated within a control valve having a one-piece clamped valve cage, for example. With such a one-piece valve cage, the annular channel  50  could be simply formed in the internal surface  37 . Additionally, such a one-piece valve cage could include a ring retainer or some other fastening means, for securing the flange portion  76  of the disclosed sealing ring  21  to the cage retainer  18 . 
         [0029]    Finally, while the generally L-shaped sealing ring  21  has been described herein as including a sealing band portion  78  with a generally V-shaped cross-section, alternative embodiments can include alternative configurations. For example, in one alternative embodiment, the sealing band portion  78  of the sealing ring  21  can include a generally linear upstanding wall with an annular bead formed on a surface thereof. The bead would be adapted to sealingly engage the external surface  66  of the valve cage  16  of the embodiment depicted herein, or alternatively, the internal surface  37  of the cage retainer  18  of the alternative embodiment described above, wherein the sealing ring  21  is secured to the valve plug  16 . 
         [0030]    Accordingly, in light of the foregoing, it should be appreciated that the control valve  10  and sealing ring  21  of the present invention is not limited to the embodiments and examples described herein, but rather, are intended to be defined by the spirit and scope of the attached claims, and any equivalents thereof.