Piston-type thermally or pressure activated relief device

A bidirectional valve for controlling the flow of a compressed gas to and from a pressurized vessel comprising:

• a) a valve body including a first gas flow passage extending through said valve body and having first and second ends, said first end of said gas flow passage communicating with the interior of said pressurized vessel and said second end of said gas flow passage communicating with an outlet port on said valve body;
• b) a valve seat in said flow passage;
• c) a solenoid valve including a plunger slidable in said gas flow passage, said plunger including a head for sealing against said valve seat to close said gas flow passage;
• and
• d) a second gas flow passage communicating with the interior of said pressurized vessel and a gas vent port on said valve body, and a thermally or pressure activated pressure relief device blocking said second gas flow passage, said pressure relief device comprising a fluid escape passage in said valve body having a member therein which is porous to gases and liquids but not to solids, a plug of a fusible material which melts at a predetermined temperature adjacent to said member, a first piston positioned in said second gas flow passage, said first piston having first and second ends and being normally biased into a sealing relationship with said inlet, and a second piston positioned in said second fluid escape passage, said second piston being normally biased against and applying a compressive force on said plug.

In combination, a pressurized vessel having an opening therein and a thermally or pressure activated relief device mounted in said opening for releasing gas from said pressurized vessel when the temperature adjacent said vessel exceeds a predetermined threshold or when the pressure in the vessel exceeds a predetermined threshold, said thermally or pressure activated relief device comprising:

• a body having an inlet, an outlet, and a fluid flow passage communicating with said inlet and outlet;
• said body further including a fluid escape passage having a member therein which is porous to gases and liquids but not to solids;
• a plug of a fusible material which melts at a predetermined temperature adjacent to said member;
• a first piston positioned in said fluid flow passage, said first piston having first and second ends and being normally biased into a sealing relationship with said inlet;
• and
• a second piston positioned in said fluid escape passage, said second piston being normally biased against and applying a compressive force on said plug.