Abstract: A pressure relief safety device useful for operation in a low pressure range. The device utilizes a non-metallic relatively thin air-impermeable membrane extending across a housing, the latter of which is in communication with a system operable under pressure. When the pressure in the system increases beyond a predetermined threshold pressure level, the membrane will expand and contact a rupturable member which will rupture the membrane. In this way relief for the excess pressure conditions is obtained. The rupturable member is adjustably located with respect to the membrane to thereby adjust and vary the predetermined threshold pressure level.

Abstract: A reverse buckling rupture disc safety device wherein there are associated cutting means, these cutting means releasably mounted in a sub-assembly, allowing ready replacement of the cutting means.