Gate valve with improved secondary body to bushing seals

Abstract

The gate valve includes a body having a valve member or gate chamber, passages communicating through the body into the chamber, a recess in the body surrounding the opening of each passage into the chamber, a bushing positioned in each of the recesses, a gate positioned within the chamber, means for moving the gate within the chamber between positions communicating flow between the passages and closing flow between the passages, inner and outer unidirectional seals positioned between the surface of each of the recesses facing the gate and the opposing surface of the bushing in the recess, each of the seals include a U-shaped lip sealing element and a U-shaped spring positioned within the lip sealing element and urging the legs of the element apart into sealing engagement between the bushing and the body, the inner seal, which is positioned closest to the passage has the open end of its sealing element facing the passage and the outer seal, which is farther from the passage than the inner seal, has the open end of its sealing facing away from the passage, each of the seals being positioned within a recess in one of the bushing and the body which has a depth less than the height of the seal while it is still in an effective sealing condition, the seals being compressible in height so that their bushings engage the body recess in a metal-to-metal seal when they are loaded and recoverable from such compressed position to provide a tight seal when said loading is relieved. It is preferred that the seals utilize an aromatic polymer such as polyetheretherketone or polyethersulfone for the lip sealing elements and an Elgiloy or nonferrous metal spring material for the spring.