LOW PRESSURE STEM GAS SEAL

摘要

A backup stem seal for a gate valve retains pressure in the body when the valve is in the closed position. The backup seal is secondary to the main stem seal assembly (20) in the bonnet (12). It features metal-to-metal contact between surfaces (22, 24) that are radially oriented or sloping and further can contain a retaining groove (26) for a seal ring (32) in one or both the opposed metal-to-metal surfaces (22, 24). The groove (26) can be formed to better retain the ring (32) from damage from flowing fluids when the valve is open. A passage through the bonnet (34) may be used to test for leakage past such seal. The backup seal allows maintenance of the main stem seal (20) without removing the valve from service.