Abstract:
Fluid valves having an integral safety shut-off are described. An example valve assembly includes a body defining a flow path between an inlet and an outlet and opposing seating surfaces. The example valve assembly includes first valve trim including a first valve stem operatively coupled to a first closure member, the first closure member to engage one of the seating surfaces to control fluid flow between the inlet and the outlet during normal operation. The example valve assembly includes second valve trim including a second valve stem operatively coupled to a second closure member, the second closure member to engage the other one of the seating surfaces during a failure condition to restrict fluid flow between the inlet and the outlet. A surface of the second closure member to define a partial wall of the flow path during normal operation such that a profile of the flow path defined by the body and the second closure member is substantially continuous.

Description:
RELATED APPLICATION 
     This patent arises from a continuation of U.S. patent application Ser. No. 12/269,657, filed Nov. 12, 2008, now U.S. Pat. No. 8,033,274, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This patent relates generally to fluid valves and, more specifically, to fluid valves having an integral safety shut-off. 
     BACKGROUND 
     Control valves are commonly used in process plants to control the flow of a fluid (e.g., a gas, a liquid, etc.) or any other substance through pipes and/or vessels to which they are connected. A control valve is typically composed of one or more inlets and outlets, and includes a flow control element or member (e.g., a valve gate, a piston, a valve plug, a closure member, etc.) that operates to control fluid flow through apertures that fluidly couple the inlet(s) to the outlet(s). A closure member is typically coupled to a valve bonnet that is mechanically coupled (e.g., bolted, clamped, threaded into, etc.) to the valve body. Typically, the closure member is configured to engage a sealing structure (e.g., a seat ring) that encompasses a flow path through the valve. 
     In practice, some process plants, in addition to control valves, include a safety shut-off valve (e.g., an emergency shut-off valve) positioned upstream or downstream from each of the control valves to quickly stop the flow of fluid in response to, for example, a system failure. While these safety shut-off valves provide many benefits to a fluid control process in some instances, the additional space and system length (e.g., pipe run lengths) required to incorporate the safety shut-off valves pose some challenges in designing a process plant, particularly in cases where available space is very limited. 
     In the past, many fluid control processes were designed without safety shut-off valves. However, there is a demand to update these processes with safety shut-off valves (e.g., safety integrated system hardware (SIS)) to ensure that system failures are properly contained. To do so, existing piping may have to be cut and/or re-routed to accommodate the additional space required by the safety shut-off valves. Alternatively, when designing new fluid processes, designers may have limited space in which to implement the safety shut-off valves and, thus, to do so, it may be difficult or impossible to position these safety shut-off valves within the fluid control process. 
     SUMMARY 
     An example valve assembly includes a body defining a flow path between an inlet and an outlet and opposing seating surfaces. The example valve assembly includes first valve trim including a first valve stem operatively coupled to a first closure member, the first closure member to engage one of the seating surfaces to control fluid flow between the inlet and the outlet during normal operation. The example valve assembly includes second valve trim including a second valve stem operatively coupled to a second closure member, the second closure member to engage the other one of the seating surfaces during a failure condition to restrict fluid flow between the inlet and the outlet. A surface of the second closure member to define a partial wall of the flow path during normal operation such that a profile of the flow path defined by the body and the second closure member is substantially continuous. 
     An example valve assembly providing safety shut off functionality includes a body defining a flow path between an inlet port and an outlet port. The example valve assembly includes a control valve including a first bonnet and a first closure member to control fluid flow through the body during normal operation by sealingly engaging a first seating surface. The example valve assembly includes a safety shut off valve including a second bonnet. The first bonnet and the second bonnet are substantially coaxially opposed. The safety shut off valve includes a second closure member to restrict fluid flow through the body during a failure condition by sealingly engaging a second seating surface. The second closure member includes a compliant seal to be positioned in a bore defined by the body during normal operation to substantially prevent fluid flow through the body from affecting the compliant seal. 
     An example valve assembly providing safety shut off functionality. The valve assembly includes a body defining a flow path between an inlet port and an outlet port and a control valve to control fluid flow through the flow path during normal operation. The example valve assembly includes a safety shut off valve including a first closure member to sealingly engage a first seating surface during a failure condition. The first closure member includes a tapered portion and a compliant seal adjacent the tapered portion. During the failure condition, the tapered portion is to sealingly engage a tapered surface of the first seating surface and the compliant seal is to sealingly engage a surface adjacent the tapered surface of the first seating surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a known control valve. 
         FIG. 2  depicts an example control valve having an integral safety shut-off. 
         FIG. 3  depicts the example control valve of  FIG. 2  with the integral safety shut-off operative to block fluid flow through the valve. 
         FIG. 4  depicts another example control valve having an integral safety shut-off. 
         FIG. 5  depicts an example blank bonnet that may used to implement the example valves depicted  FIGS. 2-4 . 
     
    
    
     DETAILED DESCRIPTION 
     Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify the same or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and/or conciseness. Additionally, several examples have been described throughout this specification. Any features from any example may be included with, a replacement for, or otherwise combined with other features from other examples. 
     The example bonnet assemblies and example control valves described herein advantageously provide integral safety shut-off functionality in control valves, thereby eliminating the problems encountered with known valves and known safety shut-off valves, which are physically separated from their corresponding control valves. In particular, the example bonnet assemblies and example valves described herein provide an integral safety shut-off to enable valves to be installed that have the same face-to-face dimensions as known control valves while also including safety shut-off features and functionality. As a result, known fluid valves that are not provided with safety shut-off functionality can be relatively easily replaced with the example valves described herein. Specifically, because the example valves described herein have substantially the same face-to-face dimensions as known valves, existing piping does not have to be cut and/or re-routed, which significantly reduces installation time and costs. Additionally, in some examples, the example valves described herein may be provided with an example blank bonnet positioned opposite the first bonnet, which controls the flow of fluid through the valve during normal operation. The blank bonnet enables the example valves to be later retrofitted (e.g., in the field or while the valve remains installed in a process control system) with a second bonnet (as described in detail below) that provides safety shut-off functionality to the valve. 
       FIG. 1  depicts a known control valve  100  that has a valve body  102  having a fluid flow passage way  104  between an inlet  106  and an outlet  108 . A bonnet  110  is coupled to the valve body  102  via a plurality of fasteners  112 . The bonnet  110  includes a bore  116  along with a packing follower  118  that urges a valve packing  120  in a sealing engagement against a stem  114  to substantially prevent fluid from exiting the bonnet  110  between the stem  114  and the valve packing  120 . As shown, a packing flange  122  is coupled to the bonnet  110  via a plurality of fasteners  126  and the packing follower  118  is positioned between the packing flange  122  and the valve packing  120 . An end  128  of the stem  114  extends from a bonnet body  124  and is operatively coupled to an actuator (not shown). Additionally, an opposite end  130  of the stem  114  is coupled to a closure member  132  (e.g., a plug). 
     To control fluid flow through the valve body  102 , valve trim  133  is positioned between the inlet  106  and the outlet  108  to provide certain flow characteristics (e.g., to reduce noise and/or cavitation generated by the flow of fluid through the control valve  100 ). The valve trim  133  includes a cage  134 , the closure member  132  and the stem  114 . The closure member  132  has an outer surface  136  sized to slidingly engage an inner surface  138  of the cage  134 . Additionally, the closure member  132  has a seating surface  140  to engage a seat  142  (e.g., a seat ring) positioned at least partially within an aperture  144  to control the flow of fluid between the inlet  106  and the outlet  108 . In practice, the actuator moves the stem  114  between a closed position at which the seating surface  140  engages the seat  142  to prevent fluid from flowing through the control valve  100  and an open position at which the closure member  132  is spaced from the seat  142  to allow fluid to flow through the control valve  100 . 
       FIG. 2  depicts an example control valve  200  that has a body  202  having a fluid flow passage way  204  between an inlet  206  and an outlet  208 . While the example control valve  200  is depicted as a globe valve, the examples described herein can be implemented in any other type of valve such as, for example, other types of sliding stem valves. 
     A bonnet assembly  209  includes a first bonnet  210  and a second bonnet  216 . The first bonnet  210  is positioned adjacent to a first bore  211  and coupled to the body  202  via a plurality of fasteners  212  on a first side of a flow control aperture  214  that fluidly couples the inlet  206  and the outlet  208 . The second bonnet  216  (e.g., a field removable bonnet) is positioned adjacent to a second bore  217  and coupled to the body  202  via a plurality of fasteners  218  on a second side of the aperture  214  opposite the first bonnet  210 . The first bore  211  is substantially coaxial with the second bore  217 . 
     The first bonnet  210  receives a first stem or shaft  222 , via the first bore  224 , along with a first packing follower  226  that urges a first valve packing  228  in sealing engagement against the first stem  222  to substantially prevent fluid from exiting the first bonnet  210  between the first stem  222  and the first valve packing  228 . The first bore  224  and first valve packing  228  guide the first stem  222  relative to the first bonnet  210 . As shown, a first packing flange  230  is coupled to a first bonnet body  232  via a plurality of fasteners  234  and the first packing follower  226  is positioned between the first packing flange  230  and the first valve packing  228 . An end  235  of the first stem  222  extends from the first bonnet body  232  and is operatively coupled to a first actuator (not shown). Additionally, an opposite end  236  of the first stem  222  is coupled to a first closure member  238 . 
     Similarly, the second bonnet  216  receives a second stem or shaft  240 , via the second bore  242 , along with a second packing follower  244  that urges a second valve packing  246  in sealing engagement against the second stem  240  to substantially prevent fluid from exiting the second bonnet  216  between the second stem  240  and the second valve packing  246 . The second bore  242  and the second valve packing  246  guide the second stem  240  relative to the second bonnet  216 . As shown, a second packing flange  248  is coupled to a second bonnet body  250  via a plurality of fasteners  252  and the second packing follower  244  is positioned between the second packing flange  248  and the second valve packing  246 . An end  254  of the second stem  240  extends from the second bonnet body  250  and is operatively coupled to a second actuator (not shown). Additionally, an opposite end  247  of the second stem  240  is coupled to a second closure member  258 . It should be appreciated that the second stem  240  may be operatively coupled to any desired device to actuate the second closure member  258  between an open position and a closed position independent from the first closure member  238 . For example, the second stem  240  may be operatively coupled to a stored energy actuation mechanism such as, for example, a coil spring or a stack of disc springs along with a retaining mechanism and/or latching system (e.g., a mechanical or hydraulic restraint) that retains the second closure member  258  in the open position during normal operation, but releases the second closure member  258  after a predetermined condition occurs such as, for example, a system failure. 
     To control fluid flow through the body  202 , a first cage  260  is positioned between the inlet  206  and the outlet  208  to provide certain flow characteristics (e.g., quick opening, equal percentage, and/or to reduce noise and/or cavitation generated by the flow of fluid through the control valve  200 ). Generally, a first valve trim includes the first stem  222  and the first closure member  238 . The first closure member  238  has an outer surface  262  sized to slidingly engage an inner surface  264  of the first cage  260 . Additionally, the first closure member  238  has a first seating surface  266  to engage a first seat  268  of a seat ring  269  positioned at least partially within the aperture  214  to control the flow of fluid between the inlet  206  and the outlet  208 . In practice, the first actuator (not shown) moves the first stem  222  between a closed position at which the first seating surface  266  engages the first seat  268  to prevent fluid from flowing through the control valve  200  and an open position at which the first closure member  238  is spaced from the first seat  268  to allow fluid to flow through the control valve  200 . 
     Additionally, the control valve  200  may be provided with a second guide  270  that is positioned opposite the first cage  260  and adjacent the second bonnet  216 . Generally, a second valve trim includes the second stem  240  and the second closure member  258 . Although not shown, in some examples, the second guide  270  may be integrally coupled to or an integral part of the second bonnet  216 . The second closure member  258  has an outer surface  272  sized to slidingly engage an inner surface  274  of the second guide  270 . Additionally, as shown in  FIGS. 2 and 3 , the second closure member  258  has a second seating surface  276  to engage a second seat  278  that opposes the first seat  268  and which is positioned at least partially within the aperture  214  to control the flow of fluid between the inlet  206  and the outlet  208  during, for example, a system failure. In this example, the first seat  268  is a first surface of the seat ring  269  and the second seat  278  is a second surface of the seat ring  269  that is opposite the first surface. 
     If the second closure member  258  moves and engages the second seat  278  (as shown in  FIG. 3 ), the fluid flow through the control valve  200  substantially stops and the second closure member  258  remains seated against the second seat  278  until, for example, the second closure member  258  is manually moved back to the open position. Additionally, if the second bonnet  216  is implemented in a flow-up valve, such as the example control valve  200 , a pressure drop across the control valve  200  and/or a fluid force against the second closure member  258  each at least partially assist the second closure member  258  in sealingly engaging the second seat  278  and, thus, relatively less force may be needed (e.g., a smaller and/or lighter actuator may be utilized) to maintain the position of the second closure member  258  relative to the second seat  278 . However, in other examples, the examples described herein can be implemented in any other valve design such as, for example, a flow down valve. 
     In operation, the second bonnet  216  along with portions of the second valve trim provide safety shut-off functionality to the control valve  200  while enabling the example control valve  200  to maintain substantially the same face-to-face dimensions as the known control valve  100 . Specifically, in contrast to known fluid control processes that require a separate safety shut-off valve, extra space and/or re-routed piping, the example control valve  200  includes both the first closure member  238  that controls the fluid flow through the control valve  200  during normal operation and the second closure member  258  that provides safety shut-off functionality to substantially stop the flow of fluid through the control valve  200  during, for example, a system failure. During normal operation, the second closure member  258  is positioned such that a surface  280  of the second closure member  258  is substantially flush with an inner surface  282  of the control valve  200  to substantially prevent the second closure member  258  from affecting the flow of the fluid through the control valve  200  when the second closure member  258  is not in use. In practice, the second closure member  258  is not often utilized and, thus, the components of the second bonnet  216  and the second valve trim may be made of relatively less expensive and/or less wear and/or corrosion resistant material. However, in other examples, the second closure member  258  may be contoured to provide a predetermined flow characteristic. For example, the surface  280  may include a contour or a curved surface (not shown) to provide flow disruption to induce turbulence in the flow stream to substantially reduce recirculation flow. 
     To replace the second bonnet  216  on the control valve  200 , the fluid pressure is reduced (e.g., drained, blocked and/or the fluid may be re-routed around the control valve  200 ) from the pipe and/or vessel to which the control valve  200  is coupled and then the fasteners  218  are removed from the second bonnet body  250 . The second bonnet  216  is then removed from the control valve  200 . Next, a different second bonnet  216  may be positioned in the control valve  200  and the fasteners  218  may be retightened to ensure proper positioning of the second bonnet  216  relative to the body  202 . 
     Alternatively, to replace a spring  284  positioned within the second bore  242  and/or the second valve packing  246  of the second bonnet  216  while the second bonnet  216  is coupled to the body  202  of the control valve  200 , the fluid pressure is reduced from the pipe and/or vessel to which the control valve  200  is coupled and the fasteners  252  are removed from the second packing flange  248 . Next, the second packing follower  244 , the spring  284  and/or the second valve packing  246  are removed and replaced. The second packing flange  248  may then be repositioned relative to the second bonnet body  250  and the fasteners  252  are adjusted to compress the spring  284  to exert a force against the second valve packing  246  to create a fluid seal between the second stem  240  and the second valve packing  246 . 
       FIG. 4  depicts another example control valve  400  that includes a first bonnet  402  and a second bonnet  404 . The example control valve  400  is substantially similar to the example control valve  200  of  FIGS. 2 and 3 . However, in contrast to the example control valve  200 , the example control valve  400  has a valve body  406  that includes a second seat  408  that has a tapered surface  410  and a surface  412  adjacent the tapered surface  410  that correspond to a tapered portion  414  and a longitudinal portion  416  of a second closure member  418 , respectively. The longitudinal portion  416  has a groove  420  into which a seal  422  (e.g., an o-ring, a compliant seal, a quad ring, a molded disc, a lip seal, etc.) is positioned. During normal operation, the seal  422  is positioned within a bore  421  of a cage or guide  423  of the second bonnet  404  or the control valve  400  to substantially prevent a flow of fluid from affecting the seal  422 . Specifically, limiting exposure of the seal  422  to the flow of fluid may advantageously extend the useful life of the seal  422  and/or substantially prevent the flow of the fluid from unseating the seal  422  from within the groove  420 . Additionally, the tapered portion  414  of the second closure member  418  may minimize the effect that the second closure member  418  has on the flow of fluid through the control valve  400 . 
     When the second closure member  418  moves and engages the second seat  408 , the fluid flow through the control valve  200  substantially stops. Specifically, the seal  422  within the groove  420  engages the surface  412  and the tapered portion  414  engages the tapered surface  410 . In some examples, the interaction between the tapered surface  410  and the tapered portion  414  is a metal-to-metal engagement and/or seal that limits the flow of fluid through the control valve  400  even if the fluid seal between the seal  422  and the surface  412  fails. 
       FIG. 5  depicts an example blank bonnet  500  having a flange  502  that receives a plurality of fasteners  504  to couple the blank bonnet  500  to the example control valve  200  or  400 . Additionally, the blank bonnet  500  includes an elongated member or plug  506  that has a diameter that corresponds to a diameter of the second bore  217  or  428 . If the blank bonnet  500  is implemented on the control valve  200  or  400 , a surface  508  of the elongated member  506  is substantially flush with the inner surface  282  of the control valve  200  of  FIGS. 2 and 3  and/or an inner surface  430  of the control valve  400  of  FIG. 4  to substantially prevent the elongated member  506  from affecting the flow of the fluid through the control valve  200  or  400 . 
     In practice, some users may be interested in creating a versatile fluid control process that initially does not have safety shut-off features. However, these users may want the ability to update their fluid control process in the future without cutting and/or re-routing piping to create the necessary space to install known safety shut-off valves, as is necessary in fluid control processes that include valves such as, the known control valve  100 . To enable users to create such a fluid control process, the example control valve  200  or  400  may be initially implemented with the blank bonnet  500 . 
     To replace and/or field replace the blank bonnet  500  with the second bonnet  216  or  404 , the fluid pressure is reduced from the pipe and/or vessel to which the control valve  200  or  400  is coupled and then the fasteners  504  are removed from the flange  502 . The blank bonnet  500  is then removed from the control valve  200  or  400 . Next, the second bonnet  216  or  404  may be positioned in the control valve  200  or  400  and the fasteners  218  may be tightened to ensure proper positioning of the second bonnet  216  or  404  relative to the valve body  202  or  406 . 
     Alternatively, to temporarily replace the second bonnet  216  or  404  with the blank bonnet  500  to, for example, repair the second bonnet  216  or  404  and/or the second valve trim, the fluid pressure is reduced (e.g., fluid is drained) from the pipe and/or vessel to which the control valve  200  or  400  is coupled and then the fasteners  218  are removed from the control valve  200  or  400 . The second bonnet  216  or  404  is then removed from the control valve  200  or  400 . Next, the blank bonnet  500  may be positioned in the control valve  200  or  400  and the plurality of fasteners  504  may be tightened to ensure proper positioning of the blank bonnet  500  relative to the valve body  202  or  406 . 
     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.