Abstract: A gas flow isolation device includes a gas flow isolation valve movable from an opened condition to a closed condition. The module isolation valve in one embodiment includes a rupture disk in flow communication with a flow of gas when the module isolation valve is in an opened condition. The rupture disk ruptures when a predetermined pressure differential occurs across it causing the isolation valve to close. In one embodiment the valve is mechanically linked to the rupture disk to maintain the valve in an opened condition when the rupture disk is intact, and which permits the valve to move into a closed condition when the rupture disk ruptures. In another embodiment a crushable member maintains the valve in an open condition, and the flow of gas passed the valve upon rupturing of the rupture disk compresses the crushable member to close the isolation valve.

Abstract: A composite seal is disclosed having first and second metal layers overlying one another in spaced relation. A mineral layer is positioned between the metal layers. The metal and mineral layers have inner and outer perimeters, the inner perimeters overlapping to define an aperture. The metal layers are joined at a perimeter, preferably the outer perimeter, by welding. The metal layers are preferably precious metal or high temperature alloy foil and the mineral layer may be formed of mica, vermiculite, or modifications of vermiculite.