Abstract: Disclosed is a butterfly valve comprising sealing means for a movable valve member in the form of a resilient high temperature destructible sealing ring and a resilient high temperature indestructible seating ring, both of which are normally preloaded into radial sealing engagement with the movable valve member. The high temperature destructible seating ring is the primary seal and the high temperature indestructible seating ring being a backup seal in one direction of flow and the high temperature indestructible seating ring is the primary seal in the opposite direction of flow. Upon destruction of the high temperature destructible seating ring, the high temperature indestructible seating ring is so retained and configured to provide bidirectional seating.

Abstract: A bidirectional butterfly valve comprising sealing means for a movable valve member in the form of a seating ring and retaining means therefor cooperatively configured to maintain bidirectional axial sealing engagement with the retaining means and radial sealing engagement with the movable valve member at normally encountered or cryogenic temperatures.

Abstract: A conical compression spring having the characteristics of a cylindrical spring of much greater free length. The spring is characterized by wire whose diameter diminishes from base to apex end and by coils whose pitch diminishes from base to apex end such that the ratio of mean coil diameter to wire diameter is constant from coil to coil. Further, each coil diameter is preferably dimensioned to fit within the next larger coil permitting a spring to be designed which exhibits a small solid compressed height.