Sāfe'ty-vălve, n.

n. (Steam-eng.) (a.) A valve fitted to the boiler of a steam-engine, which opens and lets out the steam when the pressure within becomes too great for safety. (b.) A valve in a steam-boiler, opening inward, to admit the air and prevent the boiler from being crushed or injured by the pressure of the atmosphere as the steam cools.

Safety-valve. a, boiler; b, valve; c, fulcrum or support; d, steelyard lever; e, weight.