API 609 Butterfly Valve Guide
API 609 butterfly valves can use concentric, double-offset, high-performance or triple-offset constructions depending on pressure, temperature, shutoff and service conditions.
Body style, seat system, disc and shaft materials, pressure class, shutoff direction and actuator torque need to be reviewed as one package rather than as separate catalogue options.
A complete inquiry should identify line size, class, wafer/lug/flanged interface, material, seat, fluid, temperature, leakage requirement and actuator or gearbox expectations.