High pressure packless metal diaphragm valve

Abstract

A valve body has a chamber with a lower portion provided with inlet and outlet openings and an upper portion that includes a diaphragm seat having a surface with a presclected degree of roughness. An assembly of individual flexible metallic diaphragms is positioned in a stacked arrangement a graphite gasket positioned on the roughened diaphragm seat. A bonnet bolted to the valve body applies a downward bearing force upon the outer annular edge of the diaphragm assembly to secure the diaphragm assembly and gasket in sealing relation with the valve body to seal the chamber upper portion from the chamber lower portion. A yoke member is secured to the valve body in surrounding, spaced relation with the bonnet. A valve member has a disc portion arranged to move into and out of abutting relation with a valve seat of the valve body to control the flow of fluid under substantial pressure through the chamber. The upper end of the valve member abuts the lower surface of the diaphragm assembly, and the end of a valve stem abuts the top surface of the diaphragm assembly oppositely of the valve member. An upper end of the valve stem is nonrotatably connected to a bushing which is axially fixed for rotation within the yoke member and is removably connected by an adapter to an actuator that transmits rotation to the bushing. Rotation of the bushing axially advances the valve stem without rotation in the yoke member and the bonnet to raise and lower the valve stem and the valve member to open and close the valve. Upward thrust exerted upon the valve stem when the valve is closed under full line pressure is transmitted from the valve stem through the yoke member to the valve body so that the upward thrust is not applied to the bonnet and the bearing force exerted by the bonnet upon the diaphragm assembly is not reduced, thus preventing leakage around the diaphragm assembly.