A safety valve has a valve body, a piston contained in the valve body, a soluble alloy filled between said piston and said valve body, and a spring inserted between the piston and the valve body.Safety Valves The piston includes a path connecting both ends thereof, and has a first gas pressure receiving surface and a second gas pressure receiving surface at both ends.Needle Valves The first and second gas pressure receiving surfaces have the same area; the piston works as a balanced piston where the gas pressure in the fuel tank functions in reverse directions. GLOBE VALVEAs a result, no gas pressure is applied to the soluble alloy but only the energizing force of the spring is applied. Therefore, the pressure applied to the soluble alloy can be kept constant without regard to the increase of the gas pressure. A blow-down safety valve having means for directing the fluids exiting therefrom along a flow path which assists the valve member to open and seat quickly without excessive bleeding. The valve member includes a flat seating portion and an annular lip extending perpendicularly thereto to change the direction of the exiting fluid flow and direct it downwardly along the exterior wall of the valve inlet conduit, and a blow-down ring is provided to form an annular huddling chamber for receiving and collecting such downwardly directed fluid. The annular huddling chamber includes a bottom wall beneath the valve member annular lip and a side wall extending upwardly from the bottom wall toward and beyond the annular lip and in spaced relation thereto for directing fluid flow from the annular huddling chamber along a path substantially opposite to the direction of fluid flow into the huddling chamber.

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