API 609 – Butterfly Valves: Double Flanged, Lug- and Wafer-Type

This standard covers design, materials, face-to-face dimensions; pressure-temperature ratings; and examination, inspection, and test requirments for gray iron, ductile iron, bronze, steel, nickel-base alloy, or special alloy butterfly valves that provide tight shutoff in the closed position and are suitable for flow regulation.

Valve configurations include double flanged, lug and wafer types with facings that permit installation between ASME and MSS flanges.