be provided that is always greater than the plunger o ring friction regardless of pressure differential a cap 3 is threadedly attached not shown to the body member 1 the releasing mechanism comprises a meltable or fusible plug or pin member 7 contained inside a heat conducting cylinder 19 of anodized aluminum or the like a heater coil 20 of turns of resistance wire 21 is wound about the cylinder 19 and connected to electrical power wires 15 which provide electrical current thereto a partition 22 a separates a void space 23 in cylinder 19 from the meltable or fusible plug 7 the heater wide 21 coil straddles the partition 22 a in cylinder 19 a hole 22 in the partition 22 a provides fluid communication into void space 23 which has its opposite end open thus when the fusible or meltable plug member 7 is rendered liquid or otherwise pliable it can flow under the pressure of opening forces described above into void space 23 and into bore 24 inside cap 3 allowing lateral motion of plunger 2 into the u201c open u201d position the fusible or meltable plug member may comprise a suitable tin lead alloy or bismuth alloy or antimony alloy chosen to provide mechanical compressive strength but having a relatively low 500 u00b0 f to 1000 u00b0 f melting point and high creep resistance at high temperature preferably up to its melting point in operation the valve enters the operating environment in the closed position as shown seals 10 11 and 12 prevent fluid passage and pressure communication from input port 16 to output port.