Abstract: A valve assembly configured to maintain a seal during thermal cycling includes a valve body defining a flow passage, and a fluid control member disposed in the flow passage for controlling the flow of fluid. An actuating shaft is interconnected with the fluid control member for moving the fluid control member. A housing including an internal wall defining a shaft bore is connected to the valve body, and the actuating shaft extends through the shaft bore with the internal wall of the housing radially spaced from the actuating shaft to define a sealing cavity. A seal is located within the sealing cavity for inhibiting fluid flow between the actuating shaft and the housing. The seal includes a plurality of first surfaces and the housing defines a plurality of opposed surfaces such that sealing contact of the seal with the actuating shaft and the housing is maintained during thermal cycling.

Abstract: A valve has an actuating shaft packing assembly for located in a valve enclosure cover for preventing leakage of process fluid into the space between the actuating shaft and the cylindrical sidewall of a bore in the cover. The assembly includes an annular lip located at the axial end of the bore proximal to the fluid control member. The lip extends axially away from the fluid control member. An annular sealing ring is positioned between the lip and the cylindrical sidewall of the bore and formed of a material having a greater coefficient of thermal expansion than the valve body or actuating shaft. The annular ring shrinks when cooled and increases the sealing effectiveness between the sealing ring and the lip for enhanced suppression of fluid flow between the sealing assembly and the cylindrical sidewall.