Abstract:
A high temperature ball valve seal is disclosed that achieves Class IV shutoff for operating temperatures above 550 degrees F. The ball valve seal includes a C-seal positioned between a main seal and a seal housing to prevent fluid from flowing through a secondary flowpath when the ball valve is in a closed position.

Description:
FIELD OF THE INVENTION 
     The disclosure relates to fluid valves and, more particularly, to high-temperature ball-type fluid valves. 
     BACKGROUND OF THE DISCLOSURE 
     Ball valves are used in a wide number of process control system applications to control some parameter of a process fluid (this may be a liquid, gas, slurry, etc.). While the process control system may use a control valve to ultimately control the pressure, level, pH or other desired parameter of a fluid, the control valve basically controls the rate of fluid flow. 
     Typically, a ball valve may include a fluid inlet and a fluid outlet separated by a ball element which, by rotating about a fixed axis and abutting a seal assembly, controls the amount of fluid flow therethrough. During operation, the process control system, or an operator controlling the control valve manually, rotates the ball element against, or away from a surface of the seal assembly, thereby exposing a flow passage, to provide a desired fluid flow through the inlet and outlet and, therefore, the ball valve. 
     Ball valve components, including the ball element and the seal assembly, are typically constructed of metal; this stands especially true when used in high pressure and/or high temperature applications. However, the ball element and seal assembly suffer wear due to the repeated extensive engagement of the ball element and seal assembly during opening and closing of the valve. The problems resulting from the wear include, but are not limited to, diminished life span of the valve components, increased frictional forces between the ball element and the seal assembly, and undesirable leakage between the ball element and the seal assembly. Similarly, because the frictional forces tend to increase as the components become more worn, the dynamic performance and control characteristics within the valve are worsened, resulting in inefficiencies and inaccuracies in the valve. 
     In the past attempts have been made to incorporate a biased main seal into the seal assembly to correct the above mentioned problems. Some heavy duty designs have incorporated to a Teflon® radial seal to enhance sealing performance under high-temperature operations. Ball valves having Teflon® radial seals are able to achieve Class IV shutoffs up to operating temperatures of approximately 550 deg F. Above 550 deg. F, a graphite piston ring is currently used because Teflon® deteriorates above approximately 550 deg. F. Graphite piston rings, while able to withstand higher temperatures, are only capable of achieving Class III shutoffs. As a result, ball valves having a Class IV shutoff capability above approximately 550 deg. F are not currently available. 
     Therefore, there remains a need for a high-temperature ball valve having a Class IV shutoff capability for systems operating above approximately 550 deg. F. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the disclosure, a ball valve is provided having a fluid inlet and a fluid outlet. A seal element includes a biased main seal and a C-seal disposed between the main seal and a seal housing, enabling the ball valve to achieve Class IV shutoff capability at high-temperatures. 
     In accordance with another aspect of the disclosure, a method of operation for a ball valve, having an inlet and an outlet, is provided. The method includes, orienting a C-seal between a seal housing and a main seal to achieve Class IV shutoff capability at high operating temperatures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a ball valve constructed in accordance with the teachings of the disclosure; 
         FIG. 2  is a cross-sectional view of the ball valve of  FIG. 1 , taken along line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the ball valve of  FIG. 1 , taken along line  3 - 3  of  FIG. 1 , and with the location of the ball element when the valve is in the open position being shown in phantom; 
         FIG. 4  is an enlarged, fragmentary sectional view of a portion of  FIG. 3 , depicting the ball valve in the closed position, including a main seal, a C-seal, a spring member and a seal housing; and 
         FIG. 4A  is a enlarged, fragmentary sectional view of a portion of  FIG. 3 , depicting the ball valve in the closed position including a main seal, two C-seals, a spring member and a seal housing. 
     
    
    
     While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the disclosure to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Referring now to the drawings, and with specific reference to  FIGS. 1-3 , a ball valve constructed in accordance with the teachings of the disclosure is generally depicted by reference numeral  20 . As shown therein, the ball valve  20  includes a housing  30  having a primary flowpath  33  between an inlet  31  and an outlet  32 , a seal assembly  50  attached to the housing  30  and a ball element  80  mounted on rotatable shafts  90  and  91  is disposed within the housing  30 . 
     The housing  30 , having a generally cylindrical shape, defines the primary flowpath  33  for a fluid traveling therethrough. At the bottom of the housing  30 , as oriented in  FIG. 2 , is the outlet  32 , of the primary flowpath  33 , the outlet  32  being surrounded by an outlet flange  38 . In a middle portion of the housing  30 , a thru hole  40  penetrates the right wall of the housing  30 , and a blind hole  41  opens to the interior of the housing  30 , both holes  40  and  41  being concentric to each other and adapted to receive the shafts  90  and  91 , respectively. Disposed between the drive shaft  90  and the outer right wall or “drive end” of the housing  30 , is a packing follower  42 , a set of packing rings  44 , and a bearing  43   a . Located on the drive end of housing  30 , and engaging with fasteners  35 , is an actuator mounting flange  34 . Now turning to the top of the housing  30 , still as oriented in  FIG. 2 , is a counterbore  39 , creating the inlet  31  of the primary flowpath  33  and, receiving the seal assembly  50 . Surrounding the inlet  31  is an inlet flange  36 , the inlet flange  36  fastens the valve  20  to an incoming pipe (not shown). It should be noted at this point, that the inlet flange  36  and the outlet flange  38  may be wholly or partially removed, and that the connections between the inlet  31  and the outlet  32  may be made in various ways. 
     The seal assembly  50 , as shown best in  FIGS. 4-4A , includes a first sealing body, preferably a main seal  64 , and a second sealing body, preferably a seal housing  52 . As mentioned above, the seal assembly  50  is disposed within the counterbore  39  of the housing  30 , and more specifically, an exterior surface  54  of the seal housing  52  is fixedly attached within the counterbore  39 . On an interior surface  53  of the seal housing  52 , is a pair of annular shoulders  55   a  &amp;  55   b  which receive a C-seal  60  and a resilient member, such as a wave spring  70 , respectively. The C-seal  60  and the resilient member  70  connect the main seal  64  to the seal housing  52 . The resilient member  70  is disposed between the main seal  64  and the seal housing  52 , creating a bias on the main seal  64  toward the ball element  80 , by the addition of which a secondary flowpath  77  between the main seal  64  and the seal housing  52  is created. The C-seal creates a flow restriction of the fluid through the secondary flowpath  77 . The C-seal is trapped between an annular shoulder  74  on the main seal and an annular shelf  76  on the seal housing  52 . An opening of the C-seal  63  faces away from the ball  80  and toward the incoming fluid. 
     Abutting the main seal  64 , when the valve  20  is in the closed position, is the ball element  80  ( FIG. 4 ). The ball element  80  includes a spherical surface  82  that engages the main seal  64  when the valve is in the closed position. Attached to the ball element  80 , through thru holes  84   a  &amp;  84   b  are the follower shaft  91  and the drive shaft  90 , respectively. 
     As mentioned previously, aiding the shafts  90  and  91  in alignment and rotation, are bearings  43   a  &amp;  43   b , disposed between the housing  30  and the shafts  90  and  91 , respectively. Once again, as oriented in  FIG. 2 , the follower shaft  91  is disposed in the blind hole  41  of the follower end of housing  30 . Engaging the follower shaft  91  and disposed between the follower end of housing  30  and the ball element  80  is the bearing  43   b , and disposed between the drive end of the housing  30  and the ball element  80  is the bearing  43   a . The drive shaft  90  then penetrates through the drive end of housing  30  via the thru hole  40 , and engages the packing rings  44  and the packing follower  42  before protruding outside of the housing  30 . At a outside end  92  of the shaft  90 , the shaft  90  may be adapted to engage with an opening and closing mechanism. 
     In  FIG. 4 , the ball element  80  is rotated to abut the main seal  64 , thereby creating a flow restriction of the primary flowpath  33  at a contact point  66 . Preferably, as shown in  FIG. 4 , when the ball element  80  presses against the main seal  64 , the main seal  64  may be displaced into the seal housing  52  by compressing the resilient member  70 . To ensure proper movement and operation of the main seal  64 , relative to the ball element  80  and the seal housing  52 , a predetermined or calculated gap  71  created between the main seal  64  and the seal housing  52  may be carefully set. The gap  71  may be carefully set to ensure that the main seal  64  contacts the ball element  80 , when the valve  20  is in the closed position. Working in combination with the gap  71  to ensure proper movement and operation of the valve  20 , is a gap  73  created between the main seal  64  and the housing  30 . The gap  73  ensures that the main seal  64  comes into direct contact with the housing  30 , at the proper time, when the valve  20  is opening and closing. For example, if the gap  73  were too large, the main seal  64  may stay in contact with the ball element for an extended period of time during opening and closing of the valve  20 , thereby resulting in an unwanted and avoidable amount of friction and wear between the main seal  64  and ball element  80 . Similarly, if the gap  73  were too small the main seal  64  may contact the housing during the opening and closing of the valve  20  too soon, effectively preventing the main seal  64  from contacting the ball element  80 , thereby creating a leak in the valve  20 . 
     As the ball element  80  rotates toward the closed position, the ball element  80  contacts the main seal  64 , thereby causing the gap  71  to become smaller as the ball element  80  rotates further into the fully closed position. 
     Also shown in  FIG. 4  is the secondary flowpath  77 , created between the main seal  64  and the seal housing  52  for accommodation of the resilient member  70 . To prevent seepage through the secondary flowpath  77 , preferably a C-seal is disposed between the main seal  64  and the seal housing  52 , and more specifically is disposed between the annular shoulder  55   a  on the inner surface  53  of the seal housing  52  and the main seal  64 . The C-seal  60  has an opening  63  that receives fluid through the secondary flow path  77  and thereby biases ends of the C-seal outward to seal the secondary flowpath  77 . Multiple C-seals  60   a  and  60   b  may also be positioned in series to prevent the flow of fluid through the secondary flowpath  77  when the valve  20  is pressurized from either the inlet or the outlet ( FIG. 4A ). It should be realized, however, that two C-seals placed in series, is one of many ways to restrict the flow of fluid through the secondary flowpath  77  bi-directionally. Among other solutions, for example, the C-seals could be placed in parallel. Furthermore, because the C-seal  60  is disposed between the seal housing  52  and the main seal  64 , the main seal  64  is enabled to properly align with the ball element  80 . The C-seal  60  is elastic and is able to expand and contract. 
     The C-seal  60  also aids in the alignment of the ball element  80  to the main seal  64 . This is accomplished during the closing of the valve  20 , when the ball element  80  contacts the main seal  64  at the contact point  66 . The ball element  80 , at that time, places forces on the main seal  64  and attempts to displace the main seal  64  relative to the inner surface  53  of the seal housing  52 . The C-seal  60  allows the main seal  64  to be displaced axially and radially, allthewhile keeping the ball element  80  and main seal  64  aligned thereby creating a flow restriction of the primary flowpath  33 . 
     When the ball valve  20  is in the closed position, high pressure forces are created at the inlet  31 . The increase of pressure may force the process fluid to bypass the primary flowpath restriction and be forced through the secondary flowpath  77 . Preventing the fluid from penetrating through the secondary flowpath  77  is the C-seal  60 , positioned such that the opening  63  faces toward the incoming fluid. Similarly, the increase of pressure may begin to deform or flex shafts  90  and  91  toward the direction of flow. As shafts  90  and  91  flex, the ball element  80  may begin to be displaced in a normal direction relative to the seal assembly  50 . Preventing a leak between the displaced ball element  80  and the main seal  64 , is the resilient member  70 , by biasing the main  64  seal toward the ball element  80  as the ball element  80  is displaced. As the pressure increases, the shaft  90  and  91  may further flex, thereby further increasing the displacement of the ball element  80 . The main seal  64  will continue to be biased against the ball element  80 , until the main seal  64  is stopped, or the resilient member  70  is fully decompressed. As noted earlier, however, the high pressure may be created at the outlet  32 , depending on the direction of the fluid flow through the primary flowpath  33 . If the primary flowpath  33  would be reversed, the fluid would penetrate from the other side of the secondary flowpath  77 , around the resilient member  70 , and be restricted from further penetration by the C-seal  60   b  ( FIG. 4A ), also positioned such that the openings are facing toward incoming fluid. Similarly, the high pressure fluid may deform or flex the shafts  90  and  91 , thereby displacing the ball element  80  toward the seal assembly and main seal  64 . Preventing the leak of fluid between the ball element  80  and the main seal  64 , once again, may be the resilient member  70  by biasing the ball element  80  against the main seal  64 . As the pressure increases, thereby further flexing the ball element  80  toward the seal assembly  50 , the main seal  64  may eventually bottom out on the seal housing  52 , thereby substantially eliminating the gap  71 . 
     The C-seal may be formed from any temperature resistant, flexible material such as, N07718. 
     The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.