Butterfly Valve Design Standard: API 609, ASME B16.34
Face to Face: ASME B16.10
End Connection: ASME B16.5, ASME B16.25, ASME 16.47
Inspection and Test: API 598
Visual Inspection Standard: API 6D
Butterfly valves are generally favored because they cost less than other valve designs and are lighter weight, so they need less support. The disc is positioned in the center of the pipe. A rod passes through the disc to an actuator on the outside of the valve.
A butterfly valve is fully open or closed when the disc is rotated a quarter turn. The "butterfly" is a metal disc mounted on a rod and completely blocks off the passageway.
Butterfly valve is mainly used to restrict the flow of fluid on the pipeline, that is partially or filly open or close.
Butterfly valves could be used in different temperature and pressure depending on the process condition and could be used for a variety of different fluid depending on the valve material.