Patent Publication Number: US-6341624-B1

Title: Valve for cryogenic fluid

Description:
This application is a divisional of application Ser. No. 08/978,470, filed Nov. 26, 1997, entitled VALVE FOR CRYOGENIC VALVE, and now U.S. Pat. No. 5,934,327. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a valve and, more particularly, a valve for controlling the flow of cryogenic fluid. 
     2. Discussion of the Related Art 
     Cryogenic fluids, such as liquid nitrogen, liquid oxygen or the like, are often stored on-site at a facility for use in various applications. For example, a hospital may store liquid oxygen on-site for medical uses, or a company may store liquid nitrogen at its facility for manufacturing processes. Conventionally, a cryogenic fluid is held in a storage tank at a temperature and pressure that maintains the fluid in a liquid state for future usage in a gaseous state. 
     Cryogenic fluids are conventionally delivered to a facility in a transportable supply tank from which the fluid can be pumped through a fluid delivery system into the storage tank. The fluid delivery system often includes a complex arrangement of valves and piping for controlling the flow of fluid to the storage tank, as well as for preventing fluid leakage from the tank. The cryogenic fluid typically is pumped to both the top and the bottom of the storage tank requiring that the piping be split into two feed lines which are connected to the top and bottom of the storage tank. 
     Under some circumstances, cryogenic fluid may inadvertently flow out of the storage tank and either back through the fluid delivery system into the supply tank or escape into the atmosphere. For example, when transferring fluid to the storage tank, the pressure in the storage tank may exceed the capacity of the fluid delivery pump resulting in reverse flow from the storage tank into the supply tank. As another example, an individual may fail to close one or more valves resulting in fluid leakage onto the ground or into the atmosphere from the storage tank when the supply tank is disconnected from the storage tank. 
     Valves have been proposed that utilize a poppet check valve to prevent inadvertent reverse flow through the valve housing. Poppet check valves, however, are typically complex mechanisms that utilize preloaded springs for actuating the poppet valve in response to a predetermined pressure differential across the check valve. 
     Valves for use at cryogenic temperatures face an increased possibility of leakage through relatively small openings or seams due to shrinkage of the valve components when subjected to cryogenic temperatures. Thus, cryogenic valves require precisely fabricated valve components to ensure fluid tight shell and seat performance. The introduction of foreign matter or debris into the valve can interfere with the valve components, particularly the valve seat seals, resulting in fluid seepage through the valve. Additionally, unfiltered debris, particularly large scale debris, that pass through the fluid delivery system can potentially interfere with the operation of process equipment or other systems within the facility. 
     In view of the foregoing, it is an object of the present invention to provide an improved valve, particularly a valve for use with cryogenic fluids, that reduces the possibility of inadvertent reverse flow through the valve and limits the introduction of foreign matter. 
     SUMMARY OF THE INVENTION 
     The present invention is a valve for controlling the flow of cryogenic fluid from an inlet to a pair of outlets using a pair of valve actuators. The valve prevents fluid from inadvertently leaking or flowing back through the valve inlet using a relatively simple swing-type check valve. The valve may also filter undesirable debris from the fluid as it passes through the valve. 
     In one illustrative embodiment, the valve comprises a valve housing that includes an inlet, a first outlet and a second outlet, and has an inlet chamber, a first outlet chamber and a second outlet chamber that are adapted to receive fluid from the inlet and deliver the fluid to the first and second outlets. The inlet chamber and the first outlet chamber are fluidly coupled by a first valve aperture defined by a first valve seat, and the inlet chamber and the second outlet chamber are fluidly coupled by a second valve aperture defined by a second valve seat. First and second valve actuators cooperate with the first and second valve seats to seal the inlet chamber from the first and second outlet chambers. A check valve is pivotally mounted in the valve housing to prevent fluid flow from the valve housing through the inlet. 
     In another illustrative embodiment, the valve comprises a valve housing that includes an inlet, a first outlet and a second outlet, and has an inlet chamber, a first outlet chamber and a second outlet chamber that are adapted to receive fluid from the inlet and deliver the fluid to the first and second outlets. The inlet chamber and the first outlet chamber are fluidly coupled by a first valve aperture defined by a first valve seat, and the inlet chamber and the second outlet chamber are fluidly coupled by a second valve aperture defined by a second valve seat. First and second valve actuators cooperate with the first and second valve seats to seal the inlet chamber from the first and second outlet chambers. A filter is disposed in the housing between the inlet and the first and second outlets to remove debris from the fluid. 
     In a further illustrative embodiment, the valve comprises a valve housing that includes an inlet and an outlet, and has an inlet chamber and an outlet chamber that are adapted to receive fluid from the inlet and deliver the fluid to the outlet. The inlet chamber and the outlet chamber are fluidly coupled by a valve aperture defined by a valve seat. A valve actuator cooperates with the valve seat to seal the inlet chamber from the outlet chamber. A check valve is pivotally mounted in the valve housing to prevent fluid flow from the valve housing through the inlet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     It should be understood that the drawings are provided for the purpose of illustration only and are not intended to define the limits of the invention. The foregoing and other objects and advantages of the present invention will become apparent with reference to the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of one embodiment of a valve of the present invention schematically illustrating the valve coupled to a supply tank and a storage tank; 
     FIG. 2 is a cross-sectional end view of the valve taken along section line  2 — 2  in FIG. 1 illustrating one valve actuator in a closed position and the other valve actuator in an open position; 
     FIG. 3 is a cross-sectional view of the valve stem taken along section line  3 — 3  in FIG. 1; 
     FIG. 4 is a cross-sectional plan view of the valve taken along section line  4 — 4  in FIG. 2; 
     FIG. 5 is a cross-sectional side view of the valve taken along section line  5 — 5  in FIG. 2 illustrating the check valve in a closed position in solid lines and in an open position in phantom lines; 
     FIG. 6 is a fragmented cross-sectional side view similar to FIG. 5 illustrating an alternate embodiment of a stop for limiting the travel of the check valve; 
     FIG. 7 is a front view of another embodiment of a valve that includes parallel aligned valve actuators; and 
     FIG. 8 is a side view of the valve of FIG.  7 . 
    
    
     DETAILED DESCRIPTION 
     A valve  20  for controlling fluid flow, particularly cryogenic fluid, may be fluidly coupled between a supply tank  22  and a storage tank  24 , as illustrated in FIG. 1, as part of a fluid delivery system that transfers fluid from the supply tank  22  to the storage tank  24 . The supply tank  22  is coupled to a single valve inlet  26  and the storage tank  24  is coupled to a pair of valve outlets  28 ,  30 . The valve  20  advantageously divides the incoming fluid into separate feed lines  32 ,  34  to the storage tank, thereby reducing the complexity and increasing the reliability of the fluid delivery system. Additionally, the valve  20  may prevent fluid in the storage tank  24  from inadvertently flowing back through the valve either into the supply tank  22  or out to the atmosphere. The valve  20  may also filter undesirable debris from the fluid as it passes through the valve to reduce the risk of interfering with the operation of the valve itself or other equipment located downstream from the valve. 
     In one embodiment illustrated in FIGS. 1-4, the valve  20  includes a housing  36 , a pair of globe valve actuators  38 ,  39  for controlling fluid flow to the valve outlets  28 ,  30 , a check valve  40  for preventing reverse flow through the valve, and a filter  42  for restricting the size of debris that can pass through the valve. The valve actuators  38 ,  39  are independently controllable so that the fluid flow to the valve outlets  28 ,  30  can be selectively adjusted. Although globe valve actuators are described herein, it should be understood that the present invention may be used with other valve types as would be apparent to one of skill in the art. Additionally, since the valve actuators are identical in the illustrative embodiment, like parts are given like reference characters. 
     The housing includes a single valve inlet  26  and a pair of valve outlets  28 ,  30  which are fluidly coupled to the valve inlet  26  via internal valve chambers that divide the incoming fluid into separate feed lines. In one illustrative embodiment, the housing  36  has an inlet chamber  44  and a pair of outlet chambers  46 ,  48  that are fluidly coupled to the inlet chamber  44  via apertures  50 ,  52  disposed through an internal partition wall  54  that separates the chambers from each other. In particular, the inlet chamber  44  is fluidly coupled to the first outlet chamber  46  via a first aperture  50  that is defined by an annular first outlet valve seat  56 . Similarly, the inlet chamber  44  is fluidly coupled to the second outlet chamber  48  via a second aperture  52  that is defined by an annular second outlet valve seat  58 . The first and second outlet chambers  44 ,  46  may be coupled to outlet conduits  60 ,  62  which can be connected to the first and second valve outlets  28 ,  30 . The inlet chamber  44  itself is separated into a lower inlet chamber  64  and an upper inlet chamber  66  which are coupled to each other via a third aperture  68  in the partition wall  54 . The lower inlet chamber  64  is coupled to the valve inlet  26 , which can be connected to an inlet conduit  70 , via an inlet aperture  72  defined by an annular inlet valve seat  74 . 
     Fluid that is delivered to the valve through the valve inlet  26  enters the lower inlet chamber  64  and flows into the upper valve chamber  66  through the third aperture  68 . From the upper valve chamber  66 , the fluid then flows to one or both of the outlet chambers  46 ,  48  as controlled by the positions of the valve actuators  38  relative to the outlet valve seats  56 ,  58 . For example, as shown in FIG. 2, fluid will flow only from the upper inlet chamber  66  to the second outlet chamber  48  because the first outlet chamber  46  is sealed from the inlet chamber by the first valve actuator  38  which is closed against the first outlet valve seat  56 . 
     The housing  36  is preferably a unitary structure that advantageously reduces the number of joints, which in turn reduces the potential sources of leaks as well as the cost of the valve. The housing preferably is a bronze casting that may be subsequently joined to stainless steel or copper piping with conventional Sil-brazed joints  76 . As illustrated in FIGS. 1 and 2, the housing  36  may include mounting bosses  78  that can be used to mount the valve on a support structure. 
     In one illustrative embodiment as shown in FIGS. 1-2, the valve outlets  28 ,  30  are disposed on the housing  36  along parallel vertical axes and the valve actuators  38 ,  39  are each disposed on the housing at an angle A relative to the axes of the outlets to reduce the overall size of the housing. The valve actuators  38 ,  39  are removably mounted to an upper portion of the housing  36  so that the valve actuators can be easily inserted into and removed from the housing through relatively large openings to perform maintenance on the valve. In one embodiment, the angle A of each valve actuator  38 ,  39  is approximately 15°. However, it should be understood that the angle A of the actuators  38 ,  39  can vary, for example, from 0° to approximately 45°. 
     In one embodiment shown in FIGS. 1-3, each globe valve actuator  38 ,  39  generally includes a bonnet  80 , an extension tube  82 , a valve stem  84  and a valve seal  86  that can be seated against an outlet valve seat  56 ,  58  to seal the inlet chamber  44  from the corresponding outlet chamber  46 ,  48 . The bonnet  78  includes a flange portion  88  and an upwardly extending cylindrical neck  90  to which is secured the extension tube  82 , preferably using a heat fusion process (e.g., welding, brazing or the like) to create a leak-free joint. The bonnet  80  is mounted to the upper portion of the housing using suitable fasteners  92  (e.g., bolts or the like). A bonnet gasket  94  is disposed between the flange portion  88  and the housing  36  to prevent fluid leakage from the housing at the bonnet interface. The gasket is preferably formed from a plastic material, such as polytetrafluoroethylene (PTFE), although other suitable materials may be used. 
     The valve stem  84  is an elongated member, preferably cylindrical, that extends through the extension tube  82  and bonnet  80  into the interior of the valve housing to support the valve seal  86  in the housing. The lower portion of the valve stem includes external threads  96  which cooperate with corresponding internal threads in the bonnet  80  so that rotation of the stem  84  is translated into axial movement of the stem to raise and lower the valve seal  86 . The upper end of the valve stem  84  extends from the upper end of the extension tube  86  and supports a conventional knob or handle  98  that can be actuated to adjust the position of the valve seal  86 . 
     As shown in FIG. 2, the valve seal  86  is supported on the lower end of the valve stem  84  within the housing so that it can be raised and lowered relative to the outlet valve seat  56 ,  58 . In one embodiment, the valve seal  86  includes a disc holder  100  and a valve disc  102  that is secured to the disc holder using suitable fasteners, such as a disc washer  104  and a nut. The disc washer  104  may have a generally conical surface to provide a throttling effect between the valve seal  86  and the valve seat  56 ,  58  for enhanced control of the flow through the valve. The valve disc  102  is preferably formed from a plastic material, such as KEL-F or PTFE, or other suitable material apparent to one of skill, and has a solid, continuous lower surface that extends outwardly beyond the annular surface of the valve seat  56 ,  58 . 
     The stem  84  is supported in spaced relation to the extension tube  82  to form an annulus  106  therebetween so that the stem can rotate and move axially relative to the extension tube to raise and lower the valve seal  86 . A stem packing seal  108  is provided at the upper end of the extension tube  82  to prevent leakage from the valve along the valve stem  84 . In one illustrative embodiment shown in FIG. 3, the stem packing seal  108  includes a series of stacked rings  110  sandwiched between a lower adapter  112  and a packing sleeve follower  114  that are compressed with a packing nut  116  to seal the valve stem  84 . A conically-shaped bearing  118  may be disposed between the packing sleeve follower  114  and the packing nut  116  to laterally support the valve stem  84 . Preferably, the rings  110  include a series of alternating metal (e.g., brass) and plastic (e.g., PTFE) rings as disclosed in U.S. Pat. No. 4,844,411 issued to Donald R. Nelson, which is incorporated herein by reference. It should be understood that other suitable stem packing arrangements and materials may be used to prevent leakage of fluid along the valve stem as would be apparent to one of skill. 
     Cryogenic fluid present in the upper inlet chamber  66  may seep past the stem threads  96  and into the annulus  106  between the stem  84  and extension tube  82  toward the upper end of the stem, thereby lowering the temperature at the stem packing seals  108 . By reducing the size of the annulus  106  and increasing the length of both the stem  84  and the extension tube  82 , heat gain along the length of the extension tube causes the liquid to vaporize with a resulting pressure increase in the annulus that prevents additional liquid cryogen from seeping into the annulus. Thus, the vaporization of the liquid cryogen, controlled in part by the length of the stem  84  and extension tube  82 , operates to prevent the stem packing seals  108  from freezing by substantially reducing the amount of liquid cryogen present in the annulus  106  and maintaining that liquid a sufficient distance from the stem packing seals. 
     As indicated above, the valve  20  includes a check valve  40  for preventing a reverse flow of fluid through the valve inlet. In an illustrative embodiment shown in FIGS. 2,  4  and  5 , the check valve  40  is a swing-type check valve that is supported in the lower inlet chamber  64  of the valve housing adjacent the inlet valve seat  74 . In particular, the check valve  40  is pivotally mounted to a support arm  120  that extends downwardly from a cover plate  122  and into the inlet chamber through a relatively large opening in the housing  36  between the valve actuators  38 ,  39 . The cover plate  122  is removably secured to the housing using fasteners  124  (e.g., bolts or the like) so that the check valve  40  can be easily removed from the housing  36  to perform maintenance on the check valve itself or other internal components of the valve. A gasket  126  is disposed between the cover plate  122  and the valve housing  36  to prevent leakage of fluid from the housing. The location of the cover plate  122  between the valve actuators  38 ,  39  at the upper portion of the housing is a significant advantage because it provides easy access to the inlet chamber  44  without the need to first remove the valve housing from the fluid delivery system. Preferably, the gasket  126  is formed from a plastic material, such as PTFE, although other suitable materials may be used. 
     The check valve  40  includes a swing member  128 , a disc holder  130  and an annular disc  132  supported by the disc holder. The disc  132  can be secured to the disc holder with suitable fasteners, such as a disc washer and nut, that mate with a threaded stud extending from the disc holder through the disc. The disc holder  130  can be secured to the swing member with suitable fasteners, such as a washer and nut, that engage a threaded stud extending from the disc holder through the swing member  128 . As shown in FIG. 2, the swing member  128  includes a pair of extensions  134  that are disposed on opposite sides of the support arm  120  to hingedly support the check valve on the support arm with a pin  136  or other suitable fastener. Preferably, the disc  132  is formed from a plastic material, such as KEL-F or PTFE, although other suitable materials may be used as would be apparent to one of skill in the art. 
     As illustrated in FIG. 5, when fluid is pumped through the valve inlet  26 , the pressure of the fluid causes the check valve  40  to swing upwardly (shown in phantom) away from the inlet valve seat  74  so that the fluid can enter the lower inlet chamber  64  for subsequent distribution through the valve outlets  28 ,  30 . When fluid is no longer pumped through the valve or the pressure at the valve inlet is no longer sufficient to sustain fluid flow through the valve, the check valve  40  swings downwardly under the influence of gravity against the inlet valve seat  74 . The check valve  40  is forced tightly against the inlet valve seat  74  by back pressure within the valve housing to seal the valve inlet  26  against reverse flow. The sealing effectiveness of the check valve  40  may be further enhanced by positioning the valve inlet  26  so that it extends away from the housing  36  at a downward angle B relative to a horizontal plane with the inlet valve seat  74  being similarly angled relative to a vertical plane. In one embodiment, the inlet  26  is disposed at an angle B of approximately 6° and is perpendicular to the inlet valve seat. 
     The check valve may include a stop to limit its rotation as it opens to admit fluid flow through the valve housing. In one embodiment shown in FIGS. 2 and 5, the check valve  40  includes a stop  138  disposed on the swing member  128  which engages a portion of the housing wall to limit the rotation of the check valve. This advantageously reduces the amount of momentum that the check valve  40  can acquire and transmit to the valve housing  36  in the form of an impact force upon being opened. It also reduces the distance that the check valve  40  must rotate to seal the valve inlet  26  against reverse flow. 
     In another embodiment illustrated in FIG. 6, the valve housing  36  includes a boss  140  or other suitable protrusion disposed on the housing wall to further limit the rotation of the check valve  40  and reduce the impact force on the wall. The length of the stop  138  and/or the boss  140  can be varied to adjust the amount of check valve rotation within the valve. 
     The valve  20  also includes a filter  42  for limiting the size of debris that can pass through the valve. In one embodiment illustrated in FIGS.  2  and  4 - 6 , the filter  42  encloses the third aperture  68  between the lower and upper inlet chambers  64 ,  66  to prevent debris of particular size from passing into the upper inlet chamber  66  from which it could potentially damage the valve actuators  38 ,  39  and valve seats  56 ,  58  as well as be carried through the valve and into the fluid delivery system. The filter  42  is positioned along a lip  142  in the partition wall  54  and the upper portion of the housing about the access opening. The filter  42  may be a flexible sheet of material with spring-like characteristics (e.g., a perforated metal sheet, a screen or the like) that is rolled into a generally circular shape to produce a radially outward force that helps retain the filter in position within the lip  142 . The size of the apertures in the filter may be selected based on the filtering requirements for a particular application. As should be appreciated, the filter can readily be exchanged with other filters having different size apertures to adjust the filtering characteristics of the valve. 
     The location of the filter  42  in the upper inlet chamber  66  about the third aperture  68  has several advantages. For example, the filter  42  is highly accessible, so that it can be cleaned or replaced, by removing the cover plate  122  and check valve  40  from the upper portion of the housing. Once exposed, the filter  42  can easily be grasped and removed from the valve housing. Additionally, debris that is trapped by the filter  42  generally will fall downwardly due to gravity, particularly when fluid flow through the valve ceases, and collect in the bottom of the lower inlet chamber  64  for subsequent removal from the valve. 
     The valve  20  may include a purge system  144  that can be used to remove collected debris from the inlet chamber. Additionally, the purge system  144  may be used to purge the fluid delivery system of atmospheric air immediately prior to the fluid transfer process to avoid contaminating the cryogenic fluid valve. In one illustrative embodiment shown in FIGS. 1,  4  and  5 , the purge system  144  includes a purge valve  146  that is disposed at one end of a conduit  148  extending downwardly from the lower portion of the valve housing  36 . The conduit  148  is fluidly coupled to the lower inlet chamber  64  of the housing via a purge port  150  that extends through the lower wall of the housing. The purge valve  146  is readily actuated by a stem and handle assembly  152 . 
     The valve  20  may also include a thermal relief device  154  for releasing excessive internal pressure from the valve that may result from fluid vaporization due to an increase in temperature. In one embodiment as illustrated in FIG. 1, the thermal relief device  154  includes an inverted generally U-shaped conduit  156  and a spring loaded, pressure sensitive valve  158  that is disposed at the outlet of the conduit. The opposite end of the conduit  156  is attached to the cover plate  122  (FIG. 5) and is fluidly coupled to the upper inlet chamber  66  through a relief hole  160  in the cover plate. As illustrated, the outlet of the relief device is downwardly directed so that foreign matter, such as dirt and precipitation, does not obstruct the outlet. 
     In another illustrative embodiment as shown in FIGS. 7 and 8, the valve  20  includes a pair of parallel valve actuators  38 ,  39  that are axially aligned with a corresponding pair of parallel valve outlets  28 ,  30 . This arrangement uses a valve housing  162  that can be produced using a less complex fabrication process. The housing  162  may include mounting bosses  164  disposed on its side opposite the valve inlet  26  so that the valve can be mounted to a support structure  166 . The operational features of the valve are substantially identical to those illustrated in FIGS. 1-6 and as described above. 
     Having described several embodiments of the invention in detail, various modifications and improvements will readily occur to those skilled in the art. Such modifications and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined by the following claims and the equivalents thereto.