Piston-type thermally or pressure activated relief device

摘要

A relief device (50) which activates in response either to excess temperatures or pressures in or around a pressurized vessel and which resists extrusion related failures even at high pressures is provided. The relief device includes a body (52) having an inlet (54),. an outlet (54), and a fluid flow passage (42) communicating with the inlet and outlet. The body further includes a fluid escape passage (58) having a member (60) therein which is porous to gases and liquids but not to solids and a plug (60) of a fusible material which melts at a predetermined temperature positioned adjacent to the porous member. A first piston (66) is positioned in the fluid flow passage and is normally biased into a sealing relationship with the inlet. A second piston (68) is positioned in the fluid escape passage and is normally biased against and applies a compressive force on the plug of fusible material.