scope:

This Standard Practice covers dimension, design, testing and marking requirements for butterfly valves Further reference should be made to the MSS Standard Practice for high pressure, offset, butterfly valves, when published

This standard practice covers two types of butterfly valves:

Type I - Valves for tight shut of (tested per subsection 11.2.1).

Type II - Valves permitting seat leakage (see subsection 11.2.2).

This Standard Practice covers flangeless (wafer type), single flanged (lug type), flanged end and grooved end valves in sizes 11/2 thru 72 with pressure rating up to and including ANSI Class 150