Pressure relief valve

摘要

A pressure relief valve 11 has a housing 13 fluidly connected to a pressurized system line 19 carrying a system fluid. The housing 13 carries a moveable piston 45 and a valve member 25 that both move between closed and open positions. The piston defines an upper chamber 47 and a lower chamber 49 within the housing. A pressurized fluid is supplied to the upper chamber 47 to bias the piston toward the closed position. After the relief valve opens from excessive system pressure, the pressurized fluid is injected into the lower chamber 49 via injector stab 57 to delay the return of the piston 45 to the closed position. Initially, the fluid in the lower chamber 49 flows through a check valve 53 while the piston 45 returns to the closed position. Then the fluid vent 75 in the lower chamber vents from the lower chamber 49 as the piston 45 and valve member 25 approach the closed position.