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 (lug-type), and flanged end valves in sizes 1 1/2 NPS thru 72 NPS, grooved end valves, and shouldered end valves with pressure ratings in accordance with the requirements of Sections 3 and 4.