Butterfly valves are named for the wing-like action of the flow-controlling disc, which operates at right angles to the flow. The disc has about the same diameter as the connecting pipe, and the flow is straight through, with a low pressure drop. Maintenance is easy due to the small number of moving parts. The butterfly valve can be used either as an on/off or modulating type of valve. Asahi/America has recently developed the advanced Type 57 valve, which has no metal to media or environment contact whatsoever. These valves may be operated manually, electrically, or pneumatically.
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