Safety valve for high pressure hydraulic or pneumatic system - has annular piston acted on by downstream pressure which opposes spring to hold valve open

摘要

The safety valve for high pressure hydraulic or pneumatic supply line has a cylindrical body (4) with an inlet pipe (1). The outlet fitting (10) is retained in the body by a spring ring (36) and supports an annular piston (28). The valve head (37) is fixed to the boss (33) which is attached by radial ribs to the piston (28). The annular piston is exposed to the downstream pressure through the orifice (40) so that when the downstream pressure fails, the upstream pressure overcomes the force of the spring (26) and pushes the valve head (37) onto the seat (21). A small groove (39) in the valve head permits a small leak to allow the valve to re-open when the cause of the failure is rectified.