A fluid control valve utilizes a rotatable plug valve member mounted in a fluid passage to control the flow of fluids.BALL VALVES Two segments are placed on each side of the plug valve member within a recess located between the plug valve member and the body of the fluid passage. The outer surface of the segments includes an elastomeric seal and metal annular boss,Plug Valves which acts as a stop to limit deformation of the seal when the valve is closed and under pressure. A fluid control valve comprising: a body having a flow passage therethrough and a transverse opening therein;Ball Valves a rotatable plug valve member mounted in the transverse opening for rotation about an axis, the rotatable plug valve member having a port therethrough and being capable of movement between a closed position in which the rotatable plug valve member prevents fluid flow through the flow passage and an opened position in which the port of the rotatable plug valve member aligns with the flow passage; a pair of recesses, each located in the flow passage between the rotatable plug valve member and the body; two partially cylindrical segments, each located within one of the recesses and having an inner wall surface in contact with the rotatable plug valve member and an outer wall surface adjacent a base of the recess, each segment having a hole whose axis aligns with the flow passage; a channel located on the outer wall surface of each segment, the channel having two sides and a bottom and surrounding the hole of the segment on which it is located; a metal annular boss adjacent to the channel, protruding from the outer wall surface of each of the segments towards the base of the recess and surrounding one of the holes, each of the bosses having a face spaced from contact with the base of one of the recesses when the plug valve member is in the opened position; an elastomeric seal located in the channel on the outer wall surface of each of the segments, each elastomeric seal being located a greater distance from an axis of the hole than the boss and in sealing engagement with the base of one of the recesses; and the protrusion of each boss being selected such that when under a selected fluid pressure acting on the plug valve member while in the closed position, a downstream one of the elastomeric seals deforms further into its channel and the face of a downstream one of the bosses contacts the base of the recess to limit the deformation of the downstream one of the elastomeric seals. A method of controlling the flow of fluid through a conduit, the method comprising the steps of: (a) connecting a plug valve into the conduit, the valve comprising a rotatable plug valve member located within a transverse cavity of a body, a downstream segment having an inner wall surface in contact with the rotatable plug valve member, a hole therethrough and an outer wall surface, an elastomeric seal deformed within a channel made up of a bottom and two sides located on the outer wall surface surrounding the hole, the elastomeric seal being in sealing engagement between the outer wall surface and a portion of the body, and a boss located on the outer wall surface of the segments adjacent to the channel; (b) applying fluid pressure to the plug valve and moving the plug valve member to a closed position, causing a downstream directed force due to the fluid pressure to push the downstream segment in a downstream direction, further deforming the elastomeric seal against the body and causing the boss to contact the body to stop movement of the downstream segment; then, (c) opening the plug valve member, thereby causing the elastomeric seal to push the downstream segment in an upstream direction and moving the boss from contact with the body.

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