Pressure relief devices

Claim 1

In combination with a heat exchanger of the tube-in-shell type for operating so that water/steam flows in the tubes and liquid metal flow in the closed shell and over the tubes a safety expedient comprising a duct communicating with the shell at the lower end thereof, a storage vessel to which said duct leads and which is disposed at a lOwer level than that of said shell and a pressure relief device disposed in said duct and normally closing it, said pressure relief device comprising a closure membrane, means supporting and sealing the closure membrane in the duct, said closure membrane normally preventing flow of liquid metal in said duct and being of a material inert to liquid metal, and, on the downstream side of said closure membrane, a rigid backing member bearing against and supporting said closure membrane, said rigid backing member being pivotable from the position supporting said closure membrane to a position leaving the duct open on failure of the closure membrane, said rigid backing member being held in the position supporting the closure membrane by a shear pin designed to fail, together with said closure membrane, on a pressure rise in the heat exchanger shell such as would be caused by evolution of hydrogen from reaction between the liquid metal and water/steam on failure of a heat exchanger tube, thereby opening the duct on failure of the closure membrane and pivoting of the rigid backing member to allow flow of liquid metal from the heat exchanger shell through the duct into the storage vessel.