Cartridge-type direct loaded safety and pressure-relief valve having flow path for preventing supersonic flow and minimizing valve hysteresis

摘要

A safety and pressure relief valve has a seat at the end of a nozzle, a disk which is axially movable from a closed seat-engaging position to an open position, and a sleeve which is telescopically slidable relative to the disk to define variable orifices downstream of the seat and disk. When the valve initially opens, a flow force characteristic having relatively large slope begins the lift movement of the disk. Immediately after opening, an internal pressure related movement of the diskholder relative to the disk occurs to thereby changes the flow path. The valve performs further opening, discharging and closing sequences with the shifted flowpath. Before reseating, the diskholder regains its initial position relative to the disk. In one embodiment, the disk, nozzle and sleeve are mounted in a cartridge assembly which is detachably connected to a valve bowl or body.