Bidirectional valve seal

摘要

A valve seal for a butterfly valve comprises a U-shaped annular seating member disposed in an annular slot in the valve body and a retaining ring for holding the seating member in place. The seating member cross-section comprises two legs and a bight portion connecting them. A first one of the legs is captured between the retaining ring and valve body to hold the seating member in the slot and enable limited rotational movement of the seating member. A radially inwardly projecting extension on the bight terminates in an annular sealing surface that cooperates with the valve disc. The seating member divides the slot into first and second axial sides in fluid pressure communication with the valve chamber. The seal also comprises an annular open-helical back-up member disposed in an annular cavity formed in the slot by the legs and bight portion of the seating member. The annular cavity is in fluid pressure communication with the second axial side of the slot. The back-up member resists cross-sectional compression and creates an expansive reaction force in a direction perpendicular to a cross-sectional compressive force. This arrangement provides effective sealing for system pressure from either side of the seal. The retaining ring is held to the valve body by attachment means comprising a plurality of radially extending threaded holes through the valve body and a plurality of conical blind holes in the retaining ring, each aligned with a threaded hole. A screw with a conical end is accepted in each threaded hole and cooperates with the blind holes to urge the retaining ring axially toward the valve body.