This Standard Practice covers dimensions, design, testing, and marking requirements for butterfly valves. Further reference should be made to the MSS SP-68.

This Standard Practice covers two types of butterfly valves:

Type I – Valves for tight shut-off

Type II– Valves permitting seat leakage

This Standard Practice covers flangeless (wafer-type), single flange (lugtype), and flanged end valves in size NPS 1½ through NPS 72, along with grooved end valves, and shouldered end valves, with pressure ratings in accordance with the requirements of Sections 3 and 4.