Slam shut thermally triggered valve

A dual diaphragm subassembly, comprising:

• an upper diaphragm and a lower diaphragm;
• a moveable piston;
• and
• a spacer that slidably accommodates the moveable piston;
• a replaceable thermal screw device connected to the spacer and comprising:
• (i) a threaded screw portion configured to removably secure the thermal screw device in a hole of the spacer;
• (ii) a replaceable thermal fuse removably located in the threaded screw portion configured to rupture above a predetermined temperature and as a function of sensed pressure on one side of the thermal fuse wherein the replaceable thermal fuse comprises at least one of:
• natural rubber;
• synthetic rubber;
• acrylonitrile butadiene styrene (ABS) plastic, low-density polyethylene (LDPE);
• and, (iii) a lock set screw that retains the replaceable thermal fuse in place in the threaded screw portion;
• wherein the moveable piston and spacer are configured to allow a sensing pressure to be introduced to one side of the thermal fuse, permitting the moveable piston to move freely while the thermal fuse, when intact, prevents the sensing pressure from leaking into an area beneath the upper diaphragm.