Abstract: A valve plug in which excess metal has been removed, leaving only the necessary surfaces for providing sealing and a flow passage. The invention abandons the truncated cone shape of the prior art for a non-conical shape; the only portions of the plug which extend toward the surface of the valve body are those necessary to provide sealing contact. The plug uses a pipe-shaped flow conduit having a cross-sectional dimension to match the size of the valve body seat around the flow ports in the valve body. The flow conduit has walls of substantially uniform thickness, such that the exterior surface of the conduit is spaced from the interior surface of the valve body, except at the ends of the conduit. In two embodiments, arcuate plates extend laterally from the sides of the flow conduit; the plates prevent the passage of fluid through the valve body when rotated into position adjacent the flow ports. A cavity is defined between the plates and the exterior surface of the flow conduit.

Abstract: A safety valve for relief of overpressure from a relatively low pressure high temperature fluid system with which the valve is intended to be operative. System pressure is communicated via a body inlet leading to the underside of a displaceable closure disc that cooperates with an annular seat for opening and closing the valve to fluid flow. A predetermined loading force is applied against the topside of the disc urging it toward closed position in opposition to fluid pressure thereat. To minimize or eliminate adverse temperature effects on the disc loading force at the set point operation of the valve, the closure force imposed against the disc is divided between a coaxially supported mass of predetermined weight and a compressed coil spring operative in series relation therewith.