Pressure relief valve for low temperature gases - has piston which cuts off inlet channel if outlet channel is blocked by ice

摘要

The valve is fitted to a cylinder or system containing carbon dioxide or other liquefied gas at pressures in excess of 25 bar and at temperatures lower than minus 100 deg. C. Gas flows into the valve through the high pressure input channel (1), through a channel inside the control piston (4) and into an expansion chamber between the piston and the housing (3). The reduced pressure gas then flows out of the valve via reduced pressure output channel (2). If a blockage occurs in the expansion chamber or outlet channel (2), e.g. due to icing up, the piston is forced backwards against the spring (5), cutting off the inlet channel. If the piston continues to move back, the internal pressure is eventually released via the safety relief channel (9).