Abstract: A valve assembly, including a valve body, at least one passage along which fluid can be selectively allowed to pass, and at least one ball located in the passage so as to be movable between a first position in which a channel in the ball forms part of the passage and a second position in which the ball prevents fluid passing and wherein at least one end of the body and depending inwardly towards one side of the at last one ball there is provided is retention assembly.

Abstract: A bellows energized seal assembly includes a seal body, a main seal that is axially slidable within the seal body, and a bellows connected to the seal body and the main seal. The bellows both biases the main seal and provides a seal between the seal body and the main seal.

Abstract: The invention relates to a valve assembly which includes at least one, but typically two, balls located along a passage and which balls can be moved between open and closed positions to selectively control the passage of fluid along the passage. The valve assembly includes at, at least one end thereof, a retaining assembly which allows the effective sealing against one surface of a ball and retention of the ball in position. A sealing assembly is also provided when two balls are provided, which allows effective sealing to be achieved and at least one of the two trunnions which allows each of the balls to be mounted within the valve body is located only internally of the valve body. The components of the valve assembly can in one embodiment all be inserted into and located within the valve body from one common end.

Abstract: A metal seated floating ball valve for in-line repair has a valve body, a ball mounted in the valve body, a stem connected to the ball, and a bonnet connected to the valve body. The floating ball valve further has a first seat and a second seat adjacent the ball mounted in the valve body, an energizing ring mounted in the valve body proximate the first seat and in series with the first seat and the second seat, and a valve seat bias mounted in the valve body proximate the energizing ring and in series with the energizing ring. The energizing ring may have a slot near the upper end and a wedge surface along the lower end.

Abstract: A seal used in a valve includes a ring-shaped cartridge. The cartridge has a first portion and a second portion. The first and second portions hold a sealing portion, and the first and second portions have respective first and second curved surfaces adjacent to a sealing surface of the sealing portion. Radii of curvature of the curved surfaces enable an initial point of contact between a flow control member and the cartridge to be on the sealing surface when the flow control member moves to a closed position.

Abstract: A seat block capable of maintaining a well-fitted state of a seat portion in a simple and reliable manner regardless of use conditions. A seat portion base body (43) is provided in a housing (67) provided with a valve passage (66) and allows a piston (28) for opening and closing a valve passage (66) to be pressed on the seat portion base body (43). A spring member (23) applies an elastic force to the seat portion base body (43) such that the elastic mechanism (23) cooperates with the housing (67) to retain the seat portion base body (43).

Abstract: A fluid flow control device includes a valve body, a bonnet, a control assembly, and a seal assembly. The valve body defines an inlet portion, an outlet portion, a bonnet opening, and a fluid flow path extending between the inlet portion and the outlet portion. The bonnet is disposed in the bonnet opening. The control assembly is at least partly supported by the bonnet, and includes a ball element disposed within the valve body and rotatable between an open position and a closed position. The valve body defines an internal recess at a location downstream from the inlet portion and adjacent the bonnet opening. The seal assembly is disposed within the internal recess and includes a movable sleeve seal, a retaining device, and one or more sealing elements for preventing leakage between the sleeve seal and the retaining device and/or the valve body.

Abstract: A gate valve includes: a valve box; a support body disposed inside a hollow portion; a valve plate including a fixed valving section, a movable valving section sliding in a direction in which a flow passage is extended, a first peripheral region; and a second peripheral region; a first biasing section disposed at the first peripheral region, allowing the movable valving section to move toward a first opening portion, allowing the movable valving section to come into contact with an inner surface, pressing the movable valving section onto the inner surface, and closing the flow passage; and a second biasing section disposed at the second peripheral region, allowing the movable valving section to move toward a second opening portion, and releasing the flow passage by separating the movable valving section from the inner surface.

Abstract: A seal assembly is provided for a rotary ball valve having a top-mounted bonnet, thereby allowing the seal assembly to be installed and removed without removing the valve from the pipeline. In an embodiment, the seal assembly may include a seal ring disposed within the valve interior and biased toward the ball element of the valve. A seal carrier may be disposed between the seal ring and the valve body, and the seal carrier may be removably secured to the valve body by a plurality of bolts disposed in the valve interior. A primary leak path may exists between the seal ring and the seal carrier and a secondary leak path may exists between the seal carrier and the valve body. A first and second auxiliary seal may prevent fluid flow through the primary and secondary leak path, respectively.

Abstract: A gate valve comprises a valve body having an internal working fluid passage and an internal gate chamber extending transverse to the working fluid passage. In addition, the gate valve comprises a gate disposed in the internal gate chamber and movable within the gate chamber between a closed position obstructing fluid flow through the working fluid passage and an open position allowing fluid flow through the working fluid passage. Further, the gate valve comprises an internal sealing arrangement coaxially disposed in the working fluid passage and extending between the valve body and the gate to form a barrier between the internal working fluid passage and the gate chamber. The internal sealing arrangement includes a frustoconical metal sealing surface adapted to sealingly engage an opposed mating frustoconical metal sealing surface on the valve body to form a first tapered metal-to-metal seal between the sealing arrangement and the valve body.

Abstract: A gate valve includes a floating gate valve seat that effects a seal between a gate of a gate valve and a gate valve body using a metal seal. The gate valve includes a floating gate valve seat interposed between a gate and a gate valve body. The gate valve seat has a spring member with a cylindrical portion secured to the gave valve seat. The spring member has a leg that exerts a spring force against the gate valve body to maintain a seal between the floating gate valve seat and the gate. A metal-to-metal seal seals between the cylindrical portion of the spring member and a cylindrical portion of the gate valve seat.

Abstract: A magnetic valve device includes a valve receiving device and a valve insert of a magnetic valve which is received in the valve receiving device. A high pressure resistance is obtained in one of the modes of embodiment. The magnetic valve device includes either a pressure mechanism configured to press the valve insert against the valve receiving element or a sealing element arranged in a notch in the valve insert or a sealing element arranged between an axial filter and the valve insert.

Abstract: A faucet includes an annular body (101), a throttle valve (102) constituting a seat and an annular metal gasket positioned therebetween while being accommodated in a recess, the movable sealing element being connected by a plate to a static sealing element gripped within the recess, the plate is flexible and there is play between the recess and the part of the main surfaces of the dynamic sealing element closest to the seat (102) when said element is remote from the seat (102).

Abstract: For pulsed injection of liquids into the ground, the tool has a rotating cylinder, having through-slots. The tool has an insert, which is pressed against the rotating cylinder. As the cylinder rotates, the slots in the rotor cover/uncover the slots in the insert, creating the required pulses. By suitably shaping the slots, the pulses can have a fast rise-time from closed to open. The insert is shaped to minimize flow interference.

Abstract: A seal assembly is provided for a rotary ball valve having a top-mounted bonnet, thereby allowing the seal assembly to be installed and removed without removing the valve from the pipeline. In an embodiment, the seal assembly may include a seal ring disposed within the valve interior and biased toward the ball element of the valve. A seal carrier may be disposed between the seal ring and the valve body, and the seal carrier may be removably secured to the valve body by a plurality of bolts disposed in the valve interior. A primary leak path may exist between the seal ring and the seal carrier and a secondary leak path may exist between the seal carrier and the valve body. A bellows seal may prevent fluid flow through the primary leak path, and an auxiliary seal may prevent fluid flow through the secondary leak path.

Abstract: A valve includes a valve body, a valve element to selectively control flow through the valve, and a seal member and seat member together providing a fluid-tight seal between a valve cavity and a fluid passage in the valve body. A live-loaded biasing member is adapted to apply a live-loaded sealing force to the seat member to bias the seat member toward sealing engagement with the valve element. When the pressure in the fluid passage exceeds the pressure in the valve cavity, an unbalanced passage pressure load biases the seat member toward sealing engagement with the valve element. When the pressure in the valve cavity exceeds the pressure in the fluid passage, an unbalanced cavity pressure load biases the seat member toward sealing engagement with the valve element. The live-loaded sealing force is in parallel with each of the unbalanced passage pressure load and the unbalanced cavity pressure load.

Abstract: A ball valve having an anti-rotational pressure plate that allows for a balanced pressure load on a valve member is provided. Additionally, the pressure plate can also fix the rotation of an adjacent flow disk, allowing for angular-orientation specific flow characterizing features to be used with the flow disk. By fixing the rotation of the flow disk, the ball valve can characterize flows using a greater variety of flow disk geometries, including angular-orientation dependent and angular-orientation independent flow disks. Further, the pressure plate could also be directly in the form of a flow disk that has anti-rotation features.

Abstract: The slide type valve of the present invention has a structure in which a movable flowpath forming member is pressed toward a slidable sealing member by use of a spring member and in which the load of the slidable sealing member received from the movable flowpath forming member becomes equal to a constant spring load determined by a spring force of the spring member. Additionally, an attachment member holding the movable flowpath forming member that is movable to the fixed flowpath forming member has a housing hole whose shape substantially coinciding with the shape of the movable flowpath forming member. The movable flowpath forming member is housed in the housing hole so as to be slidable in a direction perpendicular to the first end surface of the fixed flowpath forming member, and, accordingly, the load distribution is uniformed both in a first seal sliding surface and in a second seal sliding surface of the slidable sealing member.

Abstract: A gate valve seat for a gate valve includes a seat having a stepped outer wall surface, with a spring, spacer ring, front facing lip seal, and a rear facing lip seal disposed about the stepped outer surface of the seat. The spring may be releasably locked into a compressed configuration for installation of the gate of the gate valve.

Abstract: Seals, ball valve assemblies, and methods of operating ball valves assemblies are provided. The seal includes an annular jacket, a restrictor, and a spring energizer. The annular jacket includes a first annular pocket and a second annular pocket. The restrictor is disposed in the first annular pocket and is capable of restricting shrinkage of the first annular pocket to a predetermined diameter range, if the seal is exposed to a temperature within a predetermined temperature range. The spring energizer is disposed in the second annular pocket and is configured to supply a force against the annular jacket to maintain the seal against a contact surface.

Abstract: Flexible seals for process control valves are disclosed. An example disclosed seal includes a seal for use with a butterfly valve. The example seal includes a substantially flexible ring-shaped carrier configured to be fixed within the butterfly valve and to surround a flow control aperture therein. Additionally, the seal includes a ring-shaped cartridge coupled to an inner diameter of the ring-shaped carrier. The cartridge includes a first portion and a second portion coupled to the first portion to define a circumferential opening to hold a seal ring.

Abstract: The presented valve (1) is based on two axially adjustable sleeve-shaped valve seat rings (14, 36) that are associated with locking arrangements in the form of annular armature plates (22, 35) and associate holding coils (24, 36). The valve closure member (39) can be variably adjusted via a position adjustment drive. Said valve closure member has a double function. On the one hand, it acts to move the valve seat rings (14, 26) into locking position and, on the other hand, it acts to control the gas flow.

Abstract: A ball valve assembly for use as a control valve for controlling the flow of gas through a continuous stroke pneumatic tool. The valving element is generally spherical and non-magnetizable. The generally spherical valving element is loosely confined between two concave generally conical surfaces, which are provided on valve seat members. The concave generally conical surfaces are opposed to one another to define a valve chamber therebetween. Sufficient clearance is provided so the generally spherical valving element is free to roll and tumble as it moves in the valve chamber between the concave generally conical surfaces. This allows the ball valve assembly to be self purging of excess lubricant, dust, and the like. Wear is distributed over the entire generally spherical surface of the valving element. The loose confinement is also sufficient to provide a relatively large cross-section of gas passageway through the control valve assembly.

Abstract: A pressure balanced rotary valve can be made more compact if the ports on the stator within can be located on a port pitch circle of smaller diameter. In certain circumstances for rotary valves used in pressure swing adsorption devices, it is acceptable for the spacing between the ports to be made smaller than the ports themselves. In a rotary valve comprising variable loading means (e.g. pistons) and fixed loading means (e.g. springs), this can involve reducing the piston size and increasing the load provided by the springs.

Abstract: Embodiments and methods are disclosed herein that relate to a valve assembly. The valve assembly includes a housing having a passage formed therethrough, and a valve ball having a through hole and disposed in the housing, in which the valve ball is rotatable between an open position that has the through hole aligned with the passage and a closed position that has the through hole misaligned with the passage. The valve assembly further includes a first seat having a first sealing surface and disposed in the housing adjacent to the valve ball, and a second seat having a second sealing surface and disposed in the housing adjacent to the first seat such that the first sealing surface of the first seat is disposed adjacent to the second sealing surface of the second seat. At least one of the first sealing surface of the first seat and the second sealing surface of the second seat comprises an arcuate surface.

Abstract: Embodiments and methods are disclosed herein that relate to a valve assembly. The valve assembly includes a housing having a passage formed therethrough, and a valve ball having a through hole and disposed in the housing, in which the valve ball is rotatable between an open position that has the through hole aligned with the passage and a closed position that has the through hole misaligned with the passage. The valve assembly further includes a seat having a first tapered surface and disposed in the housing adjacent to the valve ball, wherein the seat is biased towards the valve ball, and a seat holder having a second tapered surface and disposed in the housing adjacent to the seat such that the first tapered surface of the seat is disposed adjacent to the second tapered surface of the seat holder.

Abstract: A flow through injection valve having a stationary member, a movable member, a surface of the stationary member interfacing with a surface of the movable member; and at least one pin isolation valve having a flow through internal conduit and movably positioned so that the internal conduit can interface with at least one flow through conduit in the movable member. The pin isolation valves are movably positioned so that the internal conduit is also capable of fluidically communicating with another flow through internal conduit in the movable member. The flow through injection valve can be combined with a similar flow through isolation valve to serve as a multiple valve and typically for replacing a conventional face seal valve of a high pressure liquid chromatography (HPLC) system. The multiple valve allows flow to be transferred through without need for switching or rotating under high pressure. Movement is by rotation or translation.

Abstract: A pressure control butterfly valve includes a valve disc rotatable in a vertical direction relative to a flow passage in a body, a seat ring reciprocating in a direction of the flow passage to allow a valve seat seal part to abut on and separate from the valve disc, and a valve opening/closing mechanism provided with an airflow path to which air is supplied in a direction of separating the seat ring from the valve disc and with a spring for biasing the seat ring toward the valve disc. The valve opening/closing mechanism is for nonslidably rotating the valve disc from which the seat ring has been separated by supply of air to the airflow path and for allowing the seat ring to abut on and separate from the valve disc by means of the supply of air to the airflow path and the biasing force of the spring when the valve disc has been rotated to a valve-closed state, thereby controlling pressure in the flow passage.

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

Abstract: A metallic seal for a 90° valve features a generally rectangular shape in section that defines a chamber open to internal pressure that can enlarge the chamber to enhance the sealing effect. Sealing occurs at discrete locations at portions of the seal that are preferably rounded in shape. Overlapping ends that define the entrance to the chamber also are positioned to minimize excessive deflection and resulting plastic deformation that could close off the entrance to the chamber.

Abstract: In a disclosed embodiment, a chemical process has a pair of beds, with each of said beds having at least one connection to receive a source of gas, and for delivering gas downstream. Each of the beds includes chemical treatment elements. The system includes a connection to a source of a gas to be treated, and a connection for receiving treated gas to be delivered to a downstream use, a connection to a source of a cleaning gas, and a connection to deliver the cleaning gas downstream. A rotary valve includes a rotary actuator for rotating a valve to selectively switch each of the beds between the several connections.

Abstract: A valve having high and low pressure seals. The valve has a housing in which is mounted a valve closing member having a sealing surface which faces an opening in the housing. A low pressure seal surrounds the opening and is biased into contact with the sealing surface. A high pressure seal also surrounds the opening. Pressure in the valve pushes the closing member against the low pressure seal, which moves toward the opening until the closing member contacts the high pressure seal.

Abstract: “A flow control valve for fluidized material comprises a valve housing having a valve chamber with a valve seat and a valve plug having a flow passage, the valve plug being arranged inside the valve chamber in front of the valve seat (30) so as to be rotatable about an axis of rotation for controlling a flow through the flow control valve. It further comprises spring means biasing the valve plug against the valve seat perpendicularly to the axis of rotation, for achieving a sealing contact between the valve seat and the valve plug. According to an important aspect of the invention, the spring means comprises at least one cantilever spring (40) arranged in a clearance space opposite to the valve seat (30) so as to bias the valve plug against the valve seat.

Abstract: A valve includes a valve body, a valve element to selectively control flow through the valve, and a seal member and seat member together providing a fluid-tight seal between a valve cavity and a fluid passage in the valve body. A live-loaded biasing member is adapted to apply a live-loaded sealing force to the seat member to bias the seat member toward sealing engagement with the valve element. When the pressure in the fluid passage exceeds the pressure in the valve cavity, an unbalanced passage pressure load biases the seat member toward sealing engagement with the valve element. When the pressure in the valve cavity exceeds the pressure in the fluid passage, an unbalanced cavity pressure load biases the seat member toward sealing engagement with the valve element. The live-loaded sealing force is in parallel with each of the unbalanced passage pressure load and the unbalanced cavity pressure load.

Abstract: A trunnion type ball valve having valve seats that are laterally moveable within seat recesses of the valve and establish sealing engagement with a valve ball member that is trunnion supported for rotational movement between open and closed positions. The valve seat members are self-centering for optimum sealing engagement with the spherical sealing surface of the ball member. The internal geometry of the seat assemblies are designed to permit optimum flow through the valve mechanism even under circumstances where the seat members are located in laterally off-center relation with respect to the centerline of the flow passages due to self-centering seat movement. The ball valve is readily adapted for fire-safe application via the use of heat resistant seals and metal-to-metal sealing of components to prevent or minimize leakage in the event of seal destruction or degradation by excess heat.

Abstract: A valve assembly is provided that includes a flowbody, a valve element movably disposed within the flowbody, and a flat beam spring-energized seal mechanism. The flat beam spring-energized seal mechanism includes a wiper seal carried by one of the flowbody and the valve element and movable between a retracted position and an extended position. The wiper seal includes a wave contour defining at least one seal wave. A flat beam spring is disposed in alignment with the at least one seal wave and configured to move the wiper seal toward the extended position when a force is exerted upon it by the at least one seal wave.

Abstract: A valve assembly comprising a housing and a valve member mounted within the housing rotatable about an axis and between at least a dispensing position and a further position, for instance a volume selection position during which a material can be withdrawn from a container, and, preferably, a seat for mounting and guiding the valve member within the housing, wherein at least one of said housing, valve member, and seat is made of a synthetic material and the assembly further comprises a spring, which urges at least two of said housing, valve member, and seat together.

Abstract: Ball valves that include a gland that is interposed between a spring and a seat. The ball valves include a valve body, a ball, a valve seat, and an annular spring. The spring urges the gland member toward the valve seat to urge the valve seat toward the ball.

Abstract: A double-disk slide valve (10), the shut-off plates (16, 17) of which are displaceable by means of an actuator rod (21) and which is provided with a bridging pipe (22) having two sealing rings (23, 24) that are in operative engagement with corresponding housing sealing seats (14, 15) of the slide valve housing (11) when the slide valve is in the open position. At least one of the two housing sealing seats (14, 15) rests, by the action of a resilient element (25), under predetermined pressure against the sealing ring(s) (23, 24) associated with the bridging pipe (22) when the slide valve is in the open position and against the peripheral edge of the shut-off plate(s) (16, 17) when the slide valve is in the closed position.

Abstract: A trunnion type ball valve having valve seats that are laterally moveable within seat recesses of the valve and establish sealing engagement with a valve ball member that is trunnion supported for rotational movement between open and closed positions. The valve seat members are self-centering for optimum sealing engagement with the spherical sealing surface of the ball member. The internal geometry of the seat assemblies are designed to permit optimum flow through the valve mechanism even under circumstances where the seat members are located in laterally off-center relation with respect to the centerline of the flow passages due to self-centering seat movement. The ball valve is readily adapted for fire-safe application via the use of heat resistant seals and metal-to-metal sealing of components to prevent or minimize leakage in the event of seal destruction or degradation by excess heat.

Abstract: A pressing means for pressing a slide plate against a fixed plate by uniform pressure has simple, strong construction and can be easily assembled. A slide gate valve unit includes a pair of pressing members 10 having a U-shaped cross section and capable of receiving protrusions 11 protruding from sides of a base frame secured to the lower surface of the bottom wall of a molten metal container and the lower surfaces of side parts of a slide case 4. Elastic members 12 are extended between upper parts 10a of the pressing members and the upper surfaces of the protrusions of the base frame. Side parts of the slide case 4 are supported on the upper surfaces of the lower parts 10b of the pressing members.

Abstract: A reduced component wear valve is comprised of a valve body having a passage therethrough and a disc attached to a rotatable shafts. The disc is utilized with a seal forming a gap between the disc and the seal proximate to the rotational axis of the disc. When the disc is in the open position, the seal major axis is greater then the disc diameter and they do not touch. As the disc rotates to near closure, the disc perimeter engages the minor axis of the seal (which is smaller than the disc diameter), and the disc stretches the seal in the minor axis direction thus decreasing the major axis such that the gap is closed. The seal can be preformed in an elliptical shape or it can be formed into an elliptical shape by a retaining mechanism. The seal may be a single-piece or a multi-piece assembly press-fit into the valve body. Zero or light disc to seal contact during the majority of the valve disc rotation minimizes valve seal wear and rotational friction.

Abstract: Valve assemblies and methods of designing valve assemblies having a valve ball, an upper seat, and a lower seat. When fluid pressure is applied to the valve ball, the valve ball will float in the axial direction between an upper position, a neutral position, and a lower position in response to fluid pressure. The valve assembly may be made suitable for internal blowout preventers.

Abstract: A foot pedal evacuates debris and fluid from the field of view of a camera during arthroscopic procedures. In a first embodiment, the foot pedal houses a ball check valve to control fluid flow, and includes a base and a foot support hingedly mounted to one another. The foot support includes a valve actuator that opens the ball check valve by distorting the shape of its valve seat. The ball check valve includes a pair of connectors at the ends of the valve adapted to accept irrigation tubing. The connectors are in axial alignment with one another in a first embodiment and in parallel relation to one another in a second embodiment. A third embodiment eliminates the ball check valve and a spring-loaded lever pinches a tube to prevent fluid flow. Depression of the foot support overcomes the bias of the spring so that liquid fluid flows through the tube.

Abstract: A pigging ball valve with a housing and ball core supported for rotation within the housing. The ball core sits on a valve seat, which is supported by a seat carrier. The valve seat carrier has three distinct diameters that locate the seat in the housing and thus provides an anti-cocking feature. A seat insert has a pressure sealing surface and wiper lip on the outer diameter of the pressure sealing surface. An internal seat deflector ring is provided inside of the pressure sealing surface. The seat carrier is spring loaded.

Abstract: A ball valve for refrigerating system includes a valve body, a valve seat that fits into the valve body by a screw thread, a valve ball accommodated within the valve body, two plastic sealing elements on both sides of the valve ball, a valve rod connected to the valve ball, and a valve cap on said valve rod. One of the two sealing elements is a first sealing element which is provided with a suitable spring assembly on its periphery. The spring assembly includes at least two springs with ladder-shaped longitudinal sections that are reverse-superimposed. The inside of first sealing element fits well with the surface of said valve ball, while its outside functions as a supporting surface and an acting surface for said spring assembly. The resulting configuration provides a ball valve with a desirable sealing effect.

Abstract: A plug valve assembly includes a plug and a segment seal assembly. The segment seal assembly is configured to reduce the differential pressure load across the segment seal assembly when the valve is closed. The segment seal includes an opening in fluid communication with a sealed vent region that is formed between the segment seal and the plug.

Abstract: A water faucet includes a valve body, two conducting members, a valve seat, two control valves, two control handles, and two control plates. Thus, the water faucet is available for an upright water outlet pipe and a horizontal water outlet pipe, so that the water faucet has different water output ways, thereby enhancing the versatility of the water faucet.

Abstract: A valve arrangement for a vacuum pump includes a valve head displaceable substantially perpendicular to a flow direction of a fluid through the valve arrangement, a valve seat, and a valve spring for biasing the valve head into a flat abutment engagement with the valve seat, with the valve spring being formed of at least one substantially hollow body made of an elastomeric material.

Abstract: A seat assembly extending about an inlet passage of a valve and engaging a valve member is disclosed. The seat assembly includes an annular seat carrier having an annular groove formed therein, and a seat positioned in and extending from the annular groove of the seat carrier. The seat has an inner side, an outer side, and a plurality of spaced apart, concentric seal rings extending from the inner side of the seat to the outer side thereof. The seal ring nearest the inner side of the seat is engageable with the valve member to provide an innermost seal when the seat assembly is acted upon by a pressure within a pressure range and the seal ring nearest the inner side of the seat is deflectable in a radially outward direction and out of sealing engagement with the valve member when the pressure exceeds the pressure range to cause the adjacent seal ring to provide the innermost seal.