a butterfly valve
A Butterfly Valve is a circular disk pivoted along one diameter. In the fully open position, the disk is parallel to the direction of flow. The damper in a stovepipe or a warm-air heating system is of this type, which is also used in the intake passage to carburetors on gasoline engines. On hydraulic turbines such valves may be 20 feet or more in diameter.
Some valves operate automatically; check (or nonreturn) valves, for example, are self-acting and permit flow in one direction only. They are made in several types. If the movable element in the globe valve were kept on its seat by gravity or a spring, it would permit flow from left to right but not from right to left.
Safety valves, which are usually of the poppet type, open at a predetermined pressure. The movable element may be kept on its seat by a weighted lever or a spring strong enough to hold the valve closed until the pressure is reached at which safe operation requires opening.
More products of valves
