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 ?C Valves for tight shut-off Type II?C Valves permitting seat leakage This Standard Practice covers flangeless (wafer-type)@ single flange (lugtype)@ and flanged end valves in size NPS 1? 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.