Patent Publication Number: US-2023151898-A1

Title: Check valve

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and all benefit of U.S. Provisional Patent Application Ser. No. 63/280,346, filed on Nov. 17, 2021, for CHECK VALVE, the entire, disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Check valves are used to allow flow in one direction but then close off flow in the reverse direction to prevent undesirable backflow in piping systems. The valve element (e.g., poppet) of a check valve typically has two main forces acting upon it, the closing force that can be generated by a spring, magnet, or gravity and the opening force generated from the upstream fluid. Valve chatter can occur when the forces are balanced (i.e., offsetting) and there are instabilities in the flow of system media. It is often advantageous to have the force acting to open the poppet measurably greater than the force to close the valve; however, this is typically achieved with a tradeoff in the full stroke of the valve element and a reduction in overall flow capability. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with an embodiment of one or more of the inventions presented in this disclosure, a check valve includes a valve element and a valve body having a body housing, an annular valve seat insert, a bushing, and a biasing member. The body housing includes an outer circumferential wall extending between an inlet port and an outlet port to define a valve cavity therebetween. The valve seat insert is seated in a body seat surface surrounding the inlet port. The bushing is disposed in the valve cavity and defines a central bore, with the bushing including an outboard end surface axially engageable with the valve seat insert. The biasing member is disposed between a bearing portion of the body housing and an inboard end of the bushing to allow for axial movement of the bushing with respect to the body seat surface. The valve element extends through the bushing central bore and is movable between a closed position in which the valve element seals against the valve seat insert to prevent flow between the inlet port and the outlet port, and an open position in which fluid flow is permitted from the inlet port to the outlet port. 
     In accordance with another embodiment of one or more of the inventions presented in this disclosure, a check valve includes a valve element and a valve body having a body housing, an annular valve seat insert, and a bushing. The body housing includes an outer circumferential wall extending between an inlet port and an outlet port to define a valve cavity therebetween. The valve seat insert is seated in a body seat surface surrounding the inlet port. The bushing is disposed in the valve cavity and defines a central bore, with the bushing including an outboard end surface in axial engagement with the valve seat insert. The valve element extends through the bushing central bore and is movable between a closed position in which a head portion of the valve element seals against the valve seat insert to prevent flow between the inlet port and the outlet port and an open position in which fluid flow is permitted from the inlet port, into the bushing central bore, and through an internal flow passage in the valve element to the outlet port. The bushing further comprises a tapered flow guide surface opposite the outboard end surface and angled to substantially match an angled conical surface of the valve element head portion, to guide flow toward the valve element flow passage when the valve element is in the open position. 
     In accordance with another embodiment of one or more of the inventions presented in this disclosure, a check valve includes a valve element and a valve body having a body housing, an annular valve seat insert, and a bushing. The body housing includes an outer circumferential wall extending between an inlet port and an outlet port to define a valve cavity therebetween. The valve seat insert is seated in a body seat surface surrounding the inlet port. The bushing is disposed in the valve cavity and defines a central bore, with the bushing including an outboard end surface in axial engagement with the valve seat insert. The valve element extends through the bushing central bore and is movable between a closed position in which the valve element seals against the valve seat insert to prevent flow between the inlet port and the outlet port, and an open position in which fluid flow is permitted from the inlet port to the outlet port. The body seat surface includes a recessed surface sized to retain the valve seat insert and an annular inner wall portion extending axially inboard from the recessed surface, the annular inner wall portion being sized to limit compression of the valve seat insert by the valve element to a predetermined fraction of an uncompressed thickness of the valve seat insert. 
     In accordance with another embodiment of one or more of the inventions presented in this disclosure, a check valve includes a valve element and a valve body having a body housing, an annular valve seat insert, and a bushing. The body housing includes an outer circumferential wall extending between an inlet port and an outlet port to define a valve cavity therebetween. The valve seat insert is seated in a body seat surface surrounding the inlet port. The bushing is disposed in the valve cavity and defines a central bore, with the bushing including an outboard end surface in axial engagement with the valve seat insert. The valve element extends through the bushing central bore and is movable between a closed position in which the a head portion of the valve element seals against the valve seat insert to prevent flow between the inlet port and the outlet port, and an open position in which fluid flow is permitted from the inlet port to the outlet port. The body seat surface includes a secondary seal surface positioned to sealingly engage an outer peripheral sealing face of the valve element head portion, radially inward of the valve seat insert, when the valve element is exposed to a backpressure exceeding a threshold backpressure. 
     In accordance with another embodiment of one or more of the inventions presented in this disclosure, a check valve includes a valve element and a valve body having a body housing, an annular valve seat insert, and a bushing. The body housing includes a first body housing member including an inlet port, a body seat surface surrounding the inlet port, and an outer circumferential wall extending to a female threaded end portion, and a second body housing member including an outlet port and a male threaded end screw assembled with the female threaded end portion. The valve seat insert is seated in a body seat surface surrounding the inlet port. The bushing is disposed in the valve cavity and defines a central bore, with the bushing including an outboard end surface in axial engagement with the valve seat insert and an inboard end engaged by a bearing portion of the male threaded end screw to transmit an axial compressive force from the second body housing member to the valve seat insert. The valve element extends through the bushing central bore and is movable between a closed position in which the valve element seals against the valve seat insert to prevent flow between the inlet port and the outlet port, and an open position in which fluid flow is permitted from the inlet port to the outlet port. 
     In accordance with another embodiment of one or more of the inventions presented in this disclosure, a check valve includes a valve element and a valve body having a body housing, an annular valve seat insert, and a bushing. The body housing includes an outer circumferential wall extending between an inlet port and an outlet port to define a valve cavity therebetween. The valve seat insert is seated in a body seat surface surrounding the inlet port. The bushing is disposed in the valve cavity and defines a central bore, with the bushing including an outboard end surface in axial engagement with the valve seat insert. The valve element extends through the bushing central bore and movable between a closed position in which the valve element seals against the valve seat insert to prevent flow between the inlet port and the outlet port, and an open position in which fluid flow is permitted from the inlet port, into the bushing central bore, and through an internal flow passage in the valve element to the outlet port. The body seat surface and the bushing outboard end surface together define an annular seal cavity sized to retain the valve seat insert. The bushing further comprises at least one outer peripheral recess extending to the outboard end surface to intersect the annular seal cavity, with the at least one outer peripheral recess including a vent passage intersecting the bushing central bore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages and benefits will become apparent to those skilled in the art after considering the following description and appended claims in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a cross-sectional schematic view of a check valve in accordance with an exemplary embodiment of the present disclosure; 
         FIG.  2    is a cross-sectional view of a check valve in accordance with another exemplary embodiment of the present disclosure, shown with the poppet in the open position; 
         FIG.  3    is a cross-sectional view of the check valve of  FIG.  2   , shown with the poppet in the closed position; 
         FIG.  4    is an enlarged partial cross-sectional view of the poppet sealing portion of the check valve of  FIG.  2   , shown with the poppet in a closed, secondary sealing position; 
         FIG.  5    is a perspective view of the poppet of the check valve of  FIG.  2   ; 
         FIG.  6    is a perspective view of the bushing of the check valve of  FIG.  2   ; 
         FIG.  7    is an enlarged partial cross-sectional view of valve seal and venting arrangement of the check valve of  FIG.  2   ; 
         FIG.  8    is a cross-sectional view of a check valve in accordance with another exemplary embodiment of the present disclosure, shown with the poppet in the open position; 
         FIG.  8 A  is an enlarged partial cross-sectional view of the poppet and body sealing portions of the check valve of  FIG.  8   , shown with the poppet in the open position; 
         FIG.  9    is a cross-sectional side view of the check valve of  FIG.  8   , shown with the poppet in the closed position; 
         FIG.  9 A  is an enlarged partial cross-sectional view of the poppet and body sealing portions of the check valve of  FIG.  8   , shown with the poppet in the closed position; 
         FIG.  10    is a perspective view of the bushing of the check valve of  FIG.  8   ; 
         FIG.  11    is another cross-sectional side view of the check valve of  FIG.  8   , showing a bushing vent passage; 
         FIG.  11 A  is an enlarged partial cross-sectional view of the poppet and body sealing portions of the check valve of  FIG.  8   , showing the bushing vent passage; 
         FIG.  12    is a cross-sectional view of a check valve in accordance with another exemplary embodiment of the present disclosure; 
         FIG.  12 A  is an enlarged partial cross-sectional view of the poppet and body sealing portions of the check valve of  FIG.  12   , shown with the poppet in the closed position; 
         FIG.  12 B  is an enlarged partial cross-sectional view of poppet and body sealing portions of a check valve accordingly to another exemplary embodiment of the present disclosure, shown with the poppet in the closed position; 
         FIG.  12 C  is an enlarged partial cross-sectional view of poppet and body sealing portions of a check valve accordingly to another exemplary embodiment of the present disclosure, shown with the poppet in the closed position; 
         FIG.  13    is a cross-sectional view of a check valve in accordance with another exemplary embodiment of the present disclosure; 
         FIG.  13 A  is an enlarged partial cross-sectional view of the poppet and body sealing portions of the check valve of  FIG.  13   ; 
         FIG.  13 B  is a perspective view of the inlet end screw of the check valve of  FIG.  13   ; 
         FIG.  13 C  is a perspective view of the bushing of the check valve of  FIG.  13   ; 
         FIG.  14    is a cross-sectional view of a check valve in accordance with another exemplary embodiment of the present disclosure; and 
         FIG.  14 A  is an enlarged partial cross-sectional view of the poppet and body sealing portions of the check valve of  FIG.  15   . 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions—such as alternative materials, structures, configurations, methods, circuits, devices and components, software, hardware, control logic, alternatives as to form, fit and function, and so on—may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Parameters identified as “approximate” or “about” a specified value are intended to include both the specified value and values within 10% of the specified value, unless expressly stated otherwise. Further, it is to be understood that the drawings accompanying the present disclosure may, but need not, be to scale, and therefore may be understood as teaching various ratios and proportions evident in the drawings. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the inventions instead being set forth in the appended claims, as currently written or as amended or added in the future. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated. 
     In an exemplary embodiment of the present disclosure, as schematically shown in  FIG.  1   , a check valve  10  includes a valve body  11  defining inlet and outlet ports  21 ,  22 , an outer circumferential wall  23  and a valve seat  60  disposed in an annular seat surface  14  surrounding the inlet port  21 . A valve element or poppet  30  is retained in a cavity  15  in the valve body  11  and movable in an internal guide passage (e.g., defined by an internal bushing  40 , as described below) between a first, closed position in which a sealing forward end  31  of the valve element seals against the valve seat  60 , for example, to block backflow to the inlet port  21  or low pressure flow from the inlet port, and a second, open position in which fluid flow is permitted through one or more flow passages  33  in the poppet  30  between the inlet port  21  and the outlet port  22 . A biasing member  50  installed in the valve cavity  15  may apply a biasing force to the valve element  30  to bias the valve element towards the closed position. 
     The bushing  40  may include an outboard end surface  42  that extends opposite the seat surface  14  to further define an annular seat cavity  16  within the valve body  10 , for example, to further enclose and retain the valve seat  60  within the seat cavity. 
     According to an aspect of the present disclosure, the check valve  10  may include a valve seat formed from an annular valve seat insert  60  (e.g., elastomeric  0 -ring or gasket, or plastic gland) secured with a seat surface  14  of the valve body  11  by a sleeve or bushing  40  installed in the valve body  11 . In some such embodiments, the bushing  40  may be sized and positioned for controlled compressive engagement of the valve seat insert  60 , for example, to effect a seal with the valve element  30  at an inner diameter of the valve seat insert  60 , and a seal between the body seat surface  14  and the valve seat insert, while preventing over-compression of the valve seat insert. In other embodiments, the bushing may provide for seat insert containment without compressing or even contacting the seat insert at least under some conditions (e.g., in the valve&#39;s closed position). 
     As shown, the bushing  40  may additionally provide a guide passage for the valve element  30 , for example, to direct fluid flow past the sealing forward end  31  of the valve element into the central flow passage  33  within the valve element. 
     Other exemplary embodiments of a check valve having a poppet carrier that applies a compressive or retaining force to a seat seal element are described in co-pending PCT Application Publication No. WO2020/236853, the entire disclosure of which is incorporated herein by reference. 
     A variety of configurations may be utilized to provide a check valve with a compressed, retained valve seat insert and a valve element guide passage for a poppet having an internal flow passage. 
       FIGS.  2 - 7    illustrate an exemplary embodiment of a check valve  100  including a valve body  110 , a poppet  130 , a biasing spring  150 , and a valve seat insert  160 . The valve body  110  includes a first or inlet port  111 , a second or outlet port  112 , and an outer circumferential wall  113  extending between the inlet and outlet ports to define an interior valve cavity  115  in which the poppet  130  and biasing spring  150  are retained. The biasing spring  150  surrounds a tail portion  135  of the poppet  130 , and is compressed between a head portion  131  of the poppet and a bearing portion  126  of the body housing  120 . The valve seat insert  160  is carried by a body seat surface  124  (e.g., a recessed surface or counterbore) surrounding the inlet port  111 . The inlet and outlet ports  111 ,  112  may be provided with end connections  101 ,  102  (e.g., tube fitting connections) to assemble the check valve  100  in a fluid system. 
     The exemplary valve body  110  includes a body housing  120  including first and second body housing members  120 - 1 ,  120 - 2  assembled (e.g., threaded assembly) to define the interior valve cavity  115 , with the inlet port  111  disposed on the first body housing member  120 - 1  and the outlet port  112  disposed on the second body housing member  120 - 2 . The body seat surface  124  is disposed in (e.g., integrally formed in) the first body housing member  120 - 1 . While the body housing members may be provided in a variety of structural arrangements, in the illustrated embodiment, the first body housing member  120 - 1  includes a substantially tubular body or enclosure structure defining the outer circumferential wall  113  and the interior valve cavity  115 , and the second body housing member  120 - 2  includes an end screw structure having a male threaded inboard end  123  that is threadably assembled with a female threaded inboard end  128  of the first body housing member. 
     A body seal gasket  119  (e.g., with one or more backup rings  119   a,  as shown) may be provided in an annular groove in the second body housing member inboard end  123 , for example, to provide a body seal between the valve cavity  115  and the threaded engagement of the body housing members  120 - 1 ,  120 - 2 , thereby eliminating wetted threads. In other embodiments, as illustrated, for example, in the embodiment of  FIG.  14   , the check valve  400  may include a body seal gasket  419  that is axially compressed between a counterbore surface  421  of the inlet enclosure housing member  420 - 1  and a shoulder surface  422  of the outlet end screw housing member  420 - 2 , which can also isolate the mating threads from the wetted portions of the valve. In some embodiments, the body seal gasket  419  may be metal (e.g., stainless steel, nickel alloy, brass, bronze, aluminum), for example, to provide a leak tight seal across a greater range of temperatures (e.g., about −60° C. to about 300° C.). The body gasket seal may be coated or lubricated to enhance the seal. 
     A variety of valve seats and valve seat installation arrangements may be utilized, including, for example, plastic or elastomeric valve seats. In an exemplary embodiment, the valve seat may be provided as an annular elastomeric seal (e.g., O-ring or other such gasket), for example, for use in non-cryogenic (e.g., temperatures at or above −40° C.) systems requiring enhanced sealing capability. Exemplary elastomeric materials include, but are not limited to, fluoroelastomers (e.g., FKM), ethylene propylene diene monomer (EPDM), hydrogenated nitrile rubber (HNBR), and nitrile rubber. In the illustrated embodiment of  FIGS.  2 - 7   , the valve seat insert  160  includes a gasket seal, and the body seat surface  124  is provided as a counterbore formed (e.g., machined) in the first body housing member  120 - 1  surrounding the inlet port  111 , in which the gasket seal  160  is seated. The gasket seal  160  is positioned to radially align with a head portion  131  of the poppet  130 , for sealing engagement with the poppet head portion when the poppet is in the closed position. In the exemplary embodiment, an outer peripheral sealing edge  132  of the poppet head portion  131  engages an inner periphery  162  of the gasket seal  160 . The outer peripheral sealing edge  132  may be provided with a radiused surface sized to optimize contact pressure and stress within the gasket seal  160  while compressed under higher back pressure. In an exemplary embodiment, the outer peripheral sealing edge  132  is provided with a contact surface having a radius between about 10% and about 30% of the gasket seal cross-sectional thickness. In other embodiments, the poppet may be provided with a frustoconical tapered sealing surface, similar to the embodiments of  FIGS.  8 - 12 C , described in greater detail below. 
     The poppet  130  includes a central bore  133  and one or more intersecting side channels  134  defining a poppet flow path extending from the head portion  131 , inboard of the sealing edge, to an inboard tail portion  135  of the poppet. The poppet side channels  134  may extend at an angle (e.g., about 55° with respect to the valve central axis) selected to optimize flow from the inlet port  111  to the poppet central bore  133 . When the poppet  130  is in an open position (e.g., with the inlet fluid pressure sufficient to overcome the biasing force of the spring  150 ), fluid from the inlet port  111  passes between the gasket seal  160  and the poppet head portion  131 , and through the side channel(s)  134  and central bore  133  to the outlet port  112 . The poppet head portion  131  may be provided with a conical surface  136  angled (e.g., about 30° to 60°, or about 40° to 45°, or about 45°, with respect to the valve central axis) to direct flow past the gasket seal  160  and toward the ends of the poppet side channels  134 . As shown, the tail portion  135  of the poppet  130  is received in a counterbore  125  of the outlet port  112 , for example, to substantially isolate the biasing spring  150  (disposed radially between the poppet tail portion and the bushing  140 ) from the system fluid. The outlet port counterbore  125  may be located to limit the open position of the poppet  130 , by abutment with the poppet tail portion  135 , for example, to limit compression of the biasing spring  150  to a desired functional range. 
     In some embodiments, the minimum flow areas of the inlet and outlet ports  111 ,  112  may be equal to or less than a flow area through the side channels  134  and central bore  133  of the poppet  130 . In other embodiments, the flow area through the side channels  134  and central bore  133  of the poppet  130  may be configured to be less than the flow areas of the inlet and outlet ports  111 ,  112 , for example, to bias the poppet  130  in the open position with minimal oscillation as the differential pressure across the check valve equalizes. 
     To effect a consistent seal between the poppet head portion  131  and the gasket seal  160  and between the gasket seal and the body seat surface  124  in the closed position, an axial compressive force may be applied to the gasket seal. In the illustrated embodiment, the valve body  110  includes a tubular bushing  140  installed in the valve cavity  115 , around the poppet  130  and biasing spring  150  to apply a compressive force against the gasket seal  160 . The bushing  140  includes a central bore  141  in which the poppet  130  is closely received and guided between closed and open positions. An inboard end  143  of the bushing  140  is indirectly engaged by the valve body housing  120  (e.g., by an inboard end face or bearing portion  126  of the second body housing member  120 - 2 ), forcing an outboard end surface  142  of the bushing  140  into compressing and sealing engagement with a medial peripheral portion  163  of the valve seat insert  160 . In the illustrated embodiment, the outboard end surface  142  of the bushing  140  engages a shoulder portion  129  of the first body housing member  120 - 1  to limit compression of the gasket seal  160  (e.g., to prevent damage to the gasket seal). While any suitable materials may be used, in an exemplary embodiment, the bushing may be provided in a material (e.g., one of stainless steel, nickel alloy, brass, bronze, aluminum, and PEEK) dissimilar to the body housing material (e.g., a different one of stainless steel, nickel alloy, brass, bronze, aluminum, and PEEK), for example, to minimize wear or galling of the contacting surfaces, or to provide specific desired material properties for one or both of the bushing and the body housing. In other embodiments, the same material may be used for both the bushing and the body housing. 
     The valve seat gasket seal  160  may be radially retained with the body seat surface  124  by an annular inner wall portion  127  extending axially inboard from the recessed body seat surface, toward the bushing  140 . When pressurized fluid is applied to the inlet port  111 , the inner wall portion  127  shields the flow away from direct contact with the gasket seal inner periphery  162 , for example, to protect the relatively soft gasket seal  160  from abrasive high velocity flow. The recessed surface  124 , inner wall portion  127  and bushing end surface  142  together define an annular seal cavity  116  retaining the valve seat gasket seal  160  (e.g., in an inner peripheral portion of the seal cavity). The seal cavity  116  includes an inner peripheral gap  117  defined by the inner wall portion  127  and bushing end surface  142 , which exposes the inner peripheral sealing portion  162  of the valve seat gasket seal  160 , radially aligned with the outer peripheral sealing edge  132  of the poppet head portion  131  to provide a fluid tight seal when the poppet  130  is in the closed position. 
     In some applications, the body seat surface may include a secondary sealing surface that is engaged by the poppet head, for example, when the poppet is subjected to a substantial backpressure (e.g., greater than 25 psi, greater than 50 psi, or greater than 100 psi), for example, to limit or prevent damage to the gasket seal. In the illustrated embodiment, the inner wall portion  127  provides a secondary metal-to-metal sealing surface  127   a  engageable with an outer peripheral sealing face  137  of the poppet head portion  131 , radially inward of the gasket seal  160 , for example, when the poppet  130  is exposed to a backpressure exceeding a threshold backpressure, causing the poppet to compress the gasket seal inner periphery  162 . In such an arrangement, the height h of the inner wall portion  127  may be selected to prevent over-compression of the gasket seal. For example, the height h of the inner wall portion may be selected such that the distance d between the sealing face  137  and the body seat surface  124  (which may, but need not correspond to the height h) is limited to a predetermined fraction of the gasket seal cross-sectional thickness (e.g., about 35% to about 65%, or about 40% to about 55%) to limit compression of the gasket seal by a corresponding fraction of the gasket seal cross-sectional thickness (e.g., about 65% to about 35%, or about 60% to about 45%). 
     The thickness t of the inner wall portion  127  may be selected to provide sufficient strength to withstand bearing engagement by the poppet  130 , for example, under substantial backpressure loads, to provide a desired gasket seal inner diameter fit clearance, to provide a desired bore inner diameter to accommodate desired flow rates, and/or to provide a sufficient sealing surface for engagement with the outer peripheral sealing face  137  of the poppet head portion  131 . 
     The outboard end of the bushing  140  may be provided with a tapered flow guide surface  144  opposite the end surface  142 , disposed at an angle θ 1  (e.g., about 30° to 60°, or about 40° to 45°, or about 40° , with respect to the valve central axis) to complement or substantially match (e.g., within about 5° taper angle) an angle θ 2  of the conical surface  136  of the poppet head portion  131 , to guide flow toward the poppet side channels  134 , for example, to reduce turbulence and optimize flow performance. 
     In some applications, the gasket seal valve seat may expand in size or volume while the valve is in service, for example, due to chemical reactivity, or pressure or temperature changes within the valve. According to another aspect of the present disclosure, a biasing member may be provided between the bushing and the valve body housing to transmit an axially compressive force from the valve body housing to the bushing. In applications where the gasket seal expands, compressibility of the biasing member allows for axial movement of the bushing away from the body seat surface to avoid damage to the gasket seal. 
     In the illustrated embodiment, one or more Belleville washers  145  (or other suitable biasing member) are disposed between the inboard end  143  of the bushing  140  and the inboard end face or bearing portion  126  of the second body housing member  120 - 2 , to allow for axial movement of the bushing  140  with respect to the body seat surface  124 , for example, to accommodate changes in the size of the gasket seal  160  or other dimensional tolerances in the valve components. In the illustrated embodiment, a spring bearing  146  is provided between the biasing member  145  and the bushing  140 , for example, to provide a stable seating surface for the biasing member  145 . As shown, the spring bearing  146  may additionally provide a seating surface for the biasing spring  150 . In other embodiments (not shown), the bushing may be provided with a bearing portion integrally formed with the inboard end of the bushing, to provide bearing surfaces for the biasing member and/or biasing spring. 
     According to another aspect of the present application, the annular seal cavity  116  may be provided with one or more venting passages (e.g., intersecting an outer peripheral portion of the seal cavity) to provide seal-energizing fluid pressure against an outer peripheral surface of the valve seat gasket seal  160  when the poppet  130  is in the closed position, and to provide for venting of pressurized fluid from the seal cavity  116  when the poppet is in the open position. This venting when the valve  100  is opened may prevent the valve seat gasket seal  160  from being forced through the inner peripheral gap  117  due to a build-up of pressure in the seal cavity  116 . As illustrated in  FIGS.  6  and  7   , the outboard end portion  142  of the bushing  140  may be provided with one or more vent passages extending from the annular seal cavity  116  to the bushing central bore  141 . While many different vent passages may be provided, in the illustrated embodiment, the outboard end portion  142  includes one or more vent holes  147  extending from the bushing bore  141  to recessed (e.g., flatted) outer portions  148  of the outboard end portion  142 . When the valve  100  is opened (due to sufficient positive fluid pressure applied to the poppet head portion  131 , overcoming the forces of the biasing spring  150 ), pressure around the outer periphery of the seal cavity  116  is vented through the vent hole(s)  147  to the central bore flow path. When the valve  100  is closed (due to forces of the biasing spring  150  overcoming any upstream fluid pressure), pressurized downstream fluid passes through the vent hole(s)  147  into the outer periphery of the seal cavity  116  to pressurize or energize the valve seat gasket seal  160 , thereby facilitating sealing engagement between the inner periphery  162  of the gasket seal  160  and the poppet head portion  131 . 
     In other embodiments, according to another exemplary aspect of the present disclosure, a check valve may be provided with a body seat surface of a body housing and a bushing end surface together defining an undercut or dovetail groove shaped annular seal cavity sized and oriented to present an inner peripheral seal surface for a valve element (e.g., poppet) while retaining the gasket seal against extrusion through the inner peripheral gap in the dovetail groove. 
       FIGS.  8 - 11 A  illustrate another exemplary embodiment of a check valve  200 , which may be similar to the check valve  100  of  FIGS.  2 - 7    (with corresponding components numbered accordingly), having a valve body  210  including a body housing  220 , a valve seat insert or gasket seal  260 , and a bushing  240  having an end surface  242  that extends adjacent to a body seat surface  224  in the body housing (e.g., in first threaded body housing member  220 - 1 , as shown) to form a dovetail groove shaped annular seal cavity  216  sized to retain the gasket seal  260  and expose an inner peripheral sealing portion  262  of the gasket seal  260  for sealing engagement with the valve element or poppet  230 . As shown, the bushing end surface  242  may, but need not, be shaped to extend outboard beyond the bushing engaging shoulder portion  229  of the body housing  220 . 
     The body seat surface  224  and bushing end surface  242  may be provided with a variety of surface contours to form a variety of different undercut or dovetail groove shaped annular seal cavities  216 , with a rear seating surface  216 - 1  defined by a recessed surface or groove portion  225  of the body seat surface, an inner side surface  216 - 2  defined by an inner wall portion  227  of the body seat surface, and an outer side surface  216 - 3  defined by the bushing end surface  242 . In the illustrated example, the rear seating surface  216 - 1  of the groove  225  is inwardly tapered (e.g., an angle between about 40° and about 80°, or about 66° , with respect to the valve central axis), with the dovetail groove side surfaces  216 - 2 ,  216 - 3  angled with respect to the seating surface (e.g., forming an included angle α of about 40° to about 80° to form a conical dovetail groove having an inner peripheral gap or neck portion  217  (e.g., having a width of about 55% to about 85% of the nominal gasket seal cross-section), for example, for exposure of the inner peripheral sealing portion  262  of the gasket seal  260 . 
     While the side surfaces  216 - 2 ,  216 - 3  may be positioned to compress the gasket seal  260  against the rear seating surface  216 - 1  to effect a seal with the seating surface (similar to the check valve  100  of  FIGS.  2 - 7   ), in some embodiments, the side surfaces  216 - 2 ,  216 - 3  may be effective to merely hold the gasket seal  260  in the annular seal cavity  216  when the poppet  230  is in the open position, with the poppet head portion  231  compressing the gasket seal against the rear seating surface  216 - 1  when in the closed position to effect a seal with the seating surface. While the sides of the seal cavity are shown as flat surfaces, in some embodiments, the seal cavity surfaces may be contoured (e.g., concave) surfaces, for example, to more closely correspond with the geometry of the gasket seal cross-section. 
     In the illustrated embodiment, an outer stepped portion  249  of the bushing  240  engages a shoulder portion  229  of the first body housing member  220 - 1  to consistently position the bushing end surface  242  (and outer side surface  216 - 3 ) with respect to the rear seating surface  216 - 1  and inner side surface  216 - 2  of the annular cavity  216 . While any suitable materials may be used, in an exemplary embodiment, the bushing  240  may be provided in a material (e.g., one of stainless steel, nickel alloy, brass, bronze, and aluminum) dissimilar to (e.g., softer than) the body housing material (e.g., a different one of stainless steel, nickel alloy, brass, bronze, and aluminum), for example, to minimize wear or galling of the contacting surfaces, to limit wear to the less critical, less expensive, or more easily replaced component, or to provide specific desired material properties for one or both of the bushing and the body housing. 
     In the exemplary embodiment, an outer peripheral sealing edge  232  of the poppet head portion  231  engages the inner periphery  262  of the gasket seal  260 . The outer peripheral sealing edge  232  may be provided with a tapered (e.g., frustoconical) surface sized to optimize contact pressure and stress within the gasket seal  260  while compressed under higher back pressure. For example, the sealing edge surface may be sized to extend along a width of about 40% to about 80% of the nominal gasket seal cross-section. In an exemplary embodiment, the angle β 1  of the tapered sealing edge surface  232  may substantially match (e.g., within about 5° to within about 15°) the angle β 2  of the rear seating surface  216 - 1 , for example, for substantially uniform compression of the gasket seal  260  between the sealing edge surface and the rear seating surface when the poppet is in the closed position. In other embodiments, the tapered outer peripheral sealing edge may be replaced with a radiused sealing edge or shoulder portion, similar to the poppet  130  of  FIGS.  2 - 7   . 
     Similar to the check valve  100  of  FIGS.  2 - 7   , the inner wall portion  227  may provide a secondary metal-to-metal sealing surface  227   a  engageable with an outer peripheral sealing face  237  of the poppet head portion  231 , radially inward of the gasket seal  260 , for example, when the poppet  230  is exposed to a backpressure exceeding a threshold backpressure, causing the poppet to more greatly compress the gasket seal inner periphery  262  (e.g., as compared to gasket seal compression resulting from the closing forces of the biasing spring  250 ). In such an arrangement, the height h of the inner wall portion  227  may be selected to prevent over-compression of the gasket seal. For example, the height h of the inner wall portion may be selected such that the distance d between the sealing edge surface  232  and the opposed seating surface  216 - 1  is limited to a predetermined fraction of the gasket seal cross-sectional thickness (e.g., about 65% to about 95%) to limit compression of the gasket seal by a corresponding fraction of the gasket seal cross-sectional thickness (e.g., about 35% to about 5%). 
     The thickness t of the inner wall portion  227  may be selected to provide sufficient strength to withstand bearing engagement by the poppet  230 , for example, under substantial backpressure loads, to provide a desired gasket seal inner diameter fit clearance, to provide a desired bore inner diameter to accommodate desired flow rates, and/or to provide a sufficient sealing surface for engagement with the outer peripheral sealing face  237  of the poppet head portion  231 . 
     The outboard end of the bushing  240  may be provided with a tapered flow guide surface  244  opposite the end surface  242 , angled (e.g., about 35° to 65°, or about 40° to 45°, or about 40°, with respect to the valve central axis) to complement or substantially match (e.g., within about 15° or within about 5°) the angled conical surface  236  of the poppet head portion  231 , to guide flow toward the poppet side channels  234 , for example, to reduce turbulence and optimize flow performance. 
     Similar to the check valve  100  of  FIGS.  2 - 7   , one or more Belleville washers  245  (or other suitable biasing member) may be disposed between the inboard end  243  of the bushing  240  and the inboard end face or bearing portion  226  of the second body housing member  220 - 2 , to allow for axial movement of the bushing  240  with respect to the body seat surface  224 , for example, to accommodate changes in the size of the gasket seal  260  or other dimensional tolerances in the valve components. In the illustrated embodiment, a spring bearing  246  is provided between the biasing member  245  and the bushing  240 , for example, to provide a stable seating surface for the biasing member  245 . As shown, the spring bearing  246  may additionally provide a seating surface for the biasing spring  250 . In other embodiments (not shown), the bushing may be provided with a bearing portion integrally formed with the inboard end of the bushing, to provide bearing surfaces for the biasing member and/or biasing spring. 
     Similar to the check valve  100  of  FIGS.  2 - 7   , the annular seal cavity  216  may be provided with one or more venting passages (e.g., intersecting an outer peripheral portion of the seal cavity) to provide seal-energizing fluid pressure against an outer peripheral surface of the valve seat gasket seal  260  when the poppet  230  is in the closed position, and to provide for venting of pressurized fluid from the seal cavity  216  when the poppet is in the open position. This venting when the valve  200  is opened may prevent the valve seat gasket seal  260  from being forced through the inner peripheral gap or dovetail neck portion  217  due to a build-up of pressure in the seal cavity  216 . As illustrated in  FIGS.  10 ,  11 , and  11 A , the outboard end portion  242  of the bushing  240  may be provided with one or more vent passages extending from the annular seal cavity  216  to the bushing central bore  241 . While many different vent passages may be provided, in the illustrated embodiment, the outboard end portion  242  includes one or more vent holes  247  extending from the bushing bore  241  to recessed (e.g., chamfered) outer portions  248  of the outboard end portion  242 . When the valve  200  is opened (due to sufficient positive fluid pressure applied to the poppet head portion  231 , overcoming the forces of the biasing spring  250 ), pressure around the outer periphery of the seal cavity  216  is vented through the vent hole(s)  247  to the central bore flow path. When the valve  200  is closed (due to forces of the biasing spring  250  overcoming any upstream fluid pressure), pressurized downstream fluid passes through the vent hole(s)  247  into the outer periphery of the seal cavity  216  to pressurize or energize the valve seat gasket seal  260 , thereby facilitating sealing engagement between the inner periphery  262  of the gasket seal  260  and the poppet head portion  231 . 
     Other seat seal groove configurations may be utilized. In the exemplary embodiment of  FIGS.  12  and  12 A , the inner wall portion  227 ′ may be provided with a tapered outer surface  227   b ′ to provide a desired included angle a (with bushing end surface  242 ′), for example, about 40° to about 80°, for the dovetail groove cavity  216 ′, for example, to provide a desired retention of the gasket seal  260 . While the sides of the seal cavity are shown as flat surfaces, in some embodiments, the seal cavity surfaces may be contoured (e.g., concave) surfaces, for example, to more closely correspond with the geometry of the gasket seal cross-section. 
     In the exemplary embodiment of  FIG.  12 B , the annular seal cavity  216 ″ includes a tapered seat surface  224   a ″ opposite from and which may, but need not, be angled to substantially match (e.g., within about 15° or within about 5° an outer peripheral sealing edge  232 ″ of the poppet head portion  231 ″, and a radial seat surface  224   b ″, opposite from and which may, but need not, be substantially parallel to match (e.g., within about 15° or within about 5° the radial bushing end surface  242 ″. As shown, the inner wall portion  227 ″ may include an axially extending outer surface  227   b ″ that further defines the seal cavity  216 ″, resulting in a four-sided (e.g., trapezoid shaped) seal cavity for the gasket seal  260 ″. This configuration may, for example, be simpler to manufacture or machine than the dovetail groove configurations of  FIGS.  8 - 11  and  12 - 12 A . While the sides of the seal cavity are shown as flat surfaces, in some embodiments, the seal cavity surfaces may be contoured (e.g., concave) surfaces, for example, to more closely correspond with the geometry of the gasket seal cross-section. 
     In the exemplary embodiment of  FIG.  12 C , the annular seal cavity  216 ′″ includes a first tapered seat surface  224   a ′″ opposite from and which may, but need not, be angled to substantially match (e.g., within about 15° or within about 5°) an outer peripheral sealing edge  232 ′″ of the poppet head portion  231 ′″, and a second tapered seat surface  224   b ′″ opposite from and which may, but need not, be angled to substantially match (e.g., within about 15° or within about 5°) the tapered bushing end surface  242 ′. In some embodiments, the tapered surface of the sealing edge  232 ′ may be disposed at a greater angle β 1  than the angle β 2  of the first tapered seat surface  224   a ′″ (e.g., about 10° greater), for example, to reduce pinching of the gasket seal  260 ′″ by the closing poppet. As shown, an axially extending outer surface  227   b ′″ of the inner wall portion  227 ′″ and an axially extending inner peripheral surface  224   c ′ of the body seat recess  224 ′″ may, but need not, be provided to further define the seal cavity  216 ′, resulting in a six-sided seal cavity for the gasket seal  260 ′″. This configuration may, for example, be sized and shaped to more closely fit the geometry of the gasket seal  260 ′″, resulting in balanced strains and stresses on the captured gasket seal while under poppet load and/or fluid pressure. This design may utilize a lower initial squeeze of the gasket seal by the poppet head sealing edge  232 ′″ while utilizing pressure load to and deformation of the gasket seal  260 ′ to still produce a seal at high backpressure, similar to the other embodiments disclosed herein. The first and second tapered seat surfaces  224   a ′″,  224   b ′″ may be joined by a fully radiused surface or by one or more transitioning flat surfaces. While the sides of the seal cavity are shown as flat surfaces, in some embodiments, the seal cavity surfaces may be contoured (e.g., concave) surfaces, for example, to more closely correspond with the geometry of the gasket seal cross-section. 
     In the embodiments of  FIGS.  2 - 12 A , the check valve body housing is formed from a female threaded enclosure defining the inlet port, body seat surface, and outer circumferential wall defining the valve cavity, and a male threaded end screw defining the outlet port and the poppet counterbore, with an end portion of the end screw defining the biasing member bearing portion. In other embodiments, a check valve may be provided with a body housing formed from a male threaded end screw defining the inlet port, with an end portion of the end screw defining a body seat surface, and a female threaded enclosure defining the outlet port, the outer circumferential wall, and the poppet counterbore. Such an arrangement may facilitate machining of the body seat surface, for example, by providing the body seat surface on an endmost surface of a male threaded end screw, rather than in a recessed cavity within a tubular body housing member. 
       FIGS.  13  and  13 A  illustrate an exemplary embodiment of a check valve  300 , which may be similar to the check valves  100 ,  200  of  FIGS.  2 - 7  and  8 - 12 A  (with corresponding components numbered accordingly), and including any one or more of the features described above, having a valve body  310  including a body housing  320 , a valve seat insert or gasket seal  360 , and a bushing  340  having an end surface  342  that extends adjacent to a body seat surface  324  on the body housing (e.g., in first threaded body housing member  320 - 1 , as shown) to form an annular seal cavity  316  sized to retain the gasket seal  360  and expose an inner peripheral sealing portion  362  of the gasket seal  360  for sealing engagement with the valve element or poppet  330 . 
     The exemplary body housing  320  including first and second body housing members  320 - 1 ,  320 - 2  assembled (e.g., threaded assembly) to define the interior valve cavity  315 , with the inlet port  311  disposed on the first body housing member  320 - 1  and the outlet port  312  disposed on the second body housing member  320 - 2 . The body seat surface  324  is disposed on (e.g., integrally formed with) the first body housing member  320 - 1 . The first body housing member  320 - 1  includes an end screw structure having a male threaded inboard end  323  defining the body seat surface  324 . The second body housing member  320 - 2  includes a substantially tubular enclosure structure defining the outer circumferential wall  313  and the interior valve cavity  315 , with a female threaded portion  328  that is threadably assembled with the male threaded inboard end  323  of the first body housing member  320 - 1 . A body seal gasket  319  (e.g., with one or more backup rings  319   a,  as shown) may be provided in an annular groove in the first body housing member inboard end  323 , for example, to provide a body seal between the valve cavity  315  and the threaded engagement of the body housing members  320 - 1 ,  320 - 2 , thereby eliminating wetted threads. In other embodiments, the check valve may include a body seal gasket (e.g., a metal gasket) that is axially compressed between a counterbore surface of the outlet enclosure housing member and a shoulder surface of the inlet end screw housing member, similar to the embodiment of  FIG.  14    described herein. 
     The body seat surface  324  and bushing end surface  342  may be provided with a variety of surface features to form a variety of different annular seal cavities  316 . In the illustrated example, the body seat surface  324  includes a recessed surface defined by a flat, radially extending outer end face  324   a,  and an annular inner wall portion  327  extending axially inboard of the recessed surface, and the bushing end surface  342  includes a flat, radially extending inner end face  342   a,  and an annular outer wall portion  342   b  extending axially into engagement with the recessed surface of the body seat surface. In other embodiments, the end faces and annular wall portions may be contoured to provide differently shaped annular cavities (e.g., the dovetail groove cavities described herein). 
     The outboard end of the bushing  340  may be provided with a tapered flow guide surface  344  opposite the end surface  342 , angled (e.g., about 35° to 65°, or about 40° to 45°, or about 40°, with respect to the valve central axis) to complement or substantially match (e.g., within about 15°, or within about 5°) the angled conical surface  336  of the poppet head portion  331 , to guide flow toward the poppet side channels  334 , for example, to reduce turbulence and optimize flow performance. 
     Similar to the check valve  100  of  FIGS.  2 - 7   , one or more Belleville washers  345  (or other suitable biasing member) may be disposed between the inboard end  343  of the bushing  340  and the inboard end face or bearing portion  326  of the second body housing member  320 - 2 , to allow for axial movement of the bushing  340  with respect to the body seat surface  324 , for example, to accommodate changes in the size of the gasket seal  360  or other dimensional tolerances in the valve components. In the illustrated embodiment, a spring bearing  346  is provided between the biasing member  345  and the bushing  340 , for example, to provide a stable seating surface for the biasing member  345 . As shown, the spring bearing  346  may additionally provide a seating surface for the biasing spring  350 . In other embodiments (not shown), the bushing may be provided with a bearing portion integrally formed with the inboard end of the bushing, to provide bearing surfaces for the biasing member and/or biasing spring. 
     While any suitable materials may be used, in an exemplary embodiment, the bushing  340  may be provided in a material (e.g., one of stainless steel, nickel alloy, brass, bronze, and aluminum) dissimilar to (e.g., softer than) the body housing material (e.g., a different one of stainless steel, nickel alloy, brass, bronze, and aluminum), for example, to minimize wear or galling of the contacting surfaces, to limit wear to the less critical, less expensive, or more easily replaced component, or to provide specific desired material properties for one or both of the bushing and the body housing. 
     Similar to the check valves  100 ,  200 ,  200 ′ of  FIGS.  2 - 12 A , the annular seal cavity  316  may be provided with one or more venting passages (e.g., intersecting an outer peripheral portion of the seal cavity) to provide seal-energizing fluid pressure against an outer peripheral surface of the valve seat gasket seal  360  when the poppet  330  is in the closed position, and to provide for venting of pressurized fluid from the seal cavity  316  when the poppet is in the open position. This venting when the valve  300  is opened may prevent the valve seat gasket seal  360  from being forced through the inner peripheral gap due to a build-up of pressure in the seal cavity  316 . As illustrated in  FIG.  13 B , the outboard end portion  342  of the bushing  340  may be provided with one or more vent passages extending from the annular seal cavity  316  to the bushing central bore  341 . While many different vent passages may be provided, in the illustrated embodiment, the outboard end portion  342  includes one or more vent holes  347  and notched end portions  348  of the outboard end portion  342 . When the valve  300  is opened (due to sufficient positive fluid pressure applied to the poppet head portion  331 , overcoming the forces of the biasing spring  350 ), pressure around the outer periphery of the seal cavity  316  is vented through the vent hole(s)  347  to the central bore flow path. When the valve  300  is closed (due to forces of the biasing spring  350  overcoming any upstream fluid pressure), pressurized downstream fluid passes through the vent hole(s)  347  into the outer periphery of the seal cavity  316  to pressurize or energize the valve seat gasket seal  360 , thereby facilitating sealing engagement between the inner periphery of the gasket seal and the poppet head portion  331 . 
     In the embodiments of  FIGS.  2 - 13 A , the valve seat insert  160 ,  260 ,  260 ′,  360  is an elastomeric gasket seal seated in an annular groove or seal cavity  116 ,  216 ,  216 ′,  316  in the body housing  120 ,  220 ,  220 ′,  320 . In other embodiments, the valve seat insert may be provided as a plastic gland or ring installed in the body housing. In some applications, a plastic valve seat material may be selected based on chemical compatibility, temperature ratings, wear resistance, or other such factors. Exemplary plastic materials include, but are not limited to, polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), and ultra-high-molecular-weight polyethylene (UHMWPE). 
       FIGS.  14  and  14 A  illustrate an exemplary embodiment of a check valve  400 , which may be similar to the check valves of  FIGS.  2 - 13 A  (with corresponding components numbered accordingly), and including any one or more of the features described above, having a valve body  410  including a body housing  420  formed from an inlet enclosure  420 - 1  and outlet end screw  420 - 2  (e.g., similar to the body housing members  120 - 1 ,  120 - 2  of the check valve of  FIGS.  2 - 7   ), a valve seat insert (e.g., plastic gland)  460 , and a bushing  440  having an end surface  442  that extends adjacent to a body seat surface  424  on the body housing (e.g., in the inlet enclosure  420 - 1 , as shown) to form an annular seal cavity  416  sized to retain the valve seat insert  460  and expose an inner peripheral sealing portion  462  of the seat insert  460  for sealing engagement with the valve element or poppet  430 . 
     To effect a consistent seal between the poppet head portion  431  and the seat insert  460  and between the seat insert and the body seat surface  424  in the closed position, an axial compressive force may be applied to the seat insert. In the illustrated embodiment, the tubular bushing  440  installed in the valve cavity  415  is sized and positioned to apply a compressive force against the seat insert  460 . The bushing  440  includes a central bore  441  in which the poppet  430  is closely received and guided between closed and open positions. An inboard end  443  of the bushing  440  is indirectly engaged by the valve body housing  420  (e.g., by an inboard end face or bearing portion  426  of the second body housing member  420 - 2 ), forcing an outboard end surface  442  of the bushing  440  into compressing and sealing engagement with a medial portion  463  of the valve seat insert  460 . In the illustrated embodiment, the outboard end surface  442  of the bushing  440  engages a shoulder portion  429  of the first body housing member  420 - 1  to limit compression of the valve seat insert  460  (e.g., to prevent damage to the seat insert). The outboard end surface  442  of the bushing  440  may be contoured (e.g., tapered axially outward and radially inward) to provide a desired amount of compression of the seat insert  460  when the bushing abuts the shoulder portion  429 . 
     While any suitable materials may be used, in an exemplary embodiment, the bushing  440  may be provided in a material (e.g., one of stainless steel, nickel alloy, brass, bronze, aluminum, and PEEK) dissimilar to the body housing material (e.g., a different one of stainless steel, nickel alloy, brass, bronze, aluminum, and PEEK), for example, to minimize wear or galling of the contacting surfaces, or to provide specific desired material properties for one or both of the bushing and the body housing. In other embodiments, the same material may be used for both the bushing and the body housing. 
     The valve seat insert  460  may be radially protected or aligned with the body seat surface  424  by an annular inner wall portion  427  extending axially inboard from the recessed body seat surface, toward the bushing  440 . When pressurized fluid is applied to the inlet port  411 , the inner wall portion  427  shields the flow away from direct contact with the gasket seal inner periphery  462 , for example, to protect the seat insert  427  from abrasive high velocity flow. The recessed surface  424 , inner wall portion  427  and bushing end surface  442  together define an annular seal cavity  416  retaining the valve seat gasket seal  160  (e.g., in an inner peripheral portion of the seal cavity). The seal cavity  416  includes an inner peripheral gap  417  defined by the inner wall portion  427  and bushing end surface  442 , which exposes the inner peripheral sealing portion  462  of the valve seat insert  460 , radially aligned with the outer peripheral sealing edge  432  of the poppet head portion  431  to provide a fluid tight seal when the poppet  430  is in the closed position. 
     While the seat insert  460  may be loosely fit or press fit with the body seat surface  424 , in some embodiments, the inner wall portion  427  may be staked or crimped radially outward to secure the seat insert with the inlet enclosure  420 - 1  prior to assembly of the check valve body  420 . 
     In some applications, the inner wall portion  427  may provide a secondary metal-to-metal sealing surface engageable with an outer peripheral sealing face of the poppet head portion, as described in greater detail above with respect to the embodiments of  FIGS.  2 - 13 C . 
     The outboard end of the bushing  440  may be provided with a tapered flow guide surface  444  opposite the end surface  442 , angled (e.g., about 30° to 60°, or about 40° to 45°, or about 40°, with respect to the valve central axis) to complement or substantially match (e.g., within about 15°, or within about 5°) the angled conical surface  436  of the poppet head portion  431 , to guide flow toward the poppet side channels  434 , for example, to reduce turbulence and optimize flow performance. 
     In some applications, the valve seat insert may expand in size or volume while the valve is in service, for example, due to chemical reactivity, or pressure or temperature changes within the valve. According to another aspect of the present disclosure, a biasing member may be provided between the bushing and the valve body housing to transmit an axially compressive force from the valve body housing to the bushing. In applications where the gasket seal expands, compressibility of the biasing member allows for axial movement of the bushing away from the body seat surface to avoid damage to the gasket seal. 
     In the illustrated embodiment, one or more Belleville washers  445  (or other suitable biasing member) are disposed between the inboard end  443  of the bushing  440  and the inboard end face or bearing portion  426  of the second body housing member  420 - 2 , to allow for axial movement of the bushing  440  with respect to the body seat surface  424 , for example, to accommodate changes in the size of the gasket seal  460  or other dimensional tolerances in the valve components. In the illustrated embodiment, a spring bearing  446  is provided between the biasing member  445  and the bushing  440 , for example, to provide a stable seating surface for the biasing member  445 . As shown, the spring bearing  446  may additionally provide a seating surface for the biasing spring  450 . In other embodiments (not shown), the bushing may be provided with a bearing portion integrally formed with the inboard end of the bushing, to provide bearing surfaces for the biasing member and/or biasing spring. 
     According to another aspect of the present application, the annular seal cavity  416  may be provided with one or more venting passages (e.g., intersecting an outer peripheral portion of the seal cavity) to provide seal-energizing fluid pressure against an outer peripheral surface of the valve seat insert  460  when the poppet  430  is in the closed position, and to provide for venting of pressurized fluid from the seal cavity  416  when the poppet is in the open position. This venting when the valve  400  is opened may prevent the valve seat insert  460  from being forced through the inner peripheral gap  417  due to a build-up of pressure in the seal cavity  416 . While many different vent passages may be provided, in the illustrated embodiment, the outboard end portion  442  includes one or more vent holes  447  extending from the bushing bore  441  to recessed (e.g., flatted) outer portions  448  of the outboard end portion  442 . When the valve  400  is opened (due to sufficient positive fluid pressure applied to the poppet head portion  431 , overcoming the forces of the biasing spring  450 ), pressure around the outer periphery of the seal cavity  416  is vented through the vent hole(s)  447  to the central bore flow path. When the valve  400  is closed (due to forces of the biasing spring  450  overcoming any upstream fluid pressure), pressurized downstream fluid passes through the vent hole(s)  447  into the outer periphery of the seal cavity  416  to pressurize or energize the valve seat insert  460 , thereby facilitating sealing engagement between the inner periphery  462  of the valve seat insert and the poppet head portion  431 . 
     The inventive aspects have been described with reference to the exemplary embodiments. Modification and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.