This Standard Practice applies to valves for gen-eral liquid and gas service that effect valve closure by means of a resilient diaphragm sealing against a weir or a diaphragm acting in conjunction with a separate or integral disk-member sealing against a seat, having equal sealing capability in either flow direction, and having diaphragms being essentially made of elastomeric or plastic material or combinations thereof.

This Standard Practice defines the following categories of valves:

a) Class 125 or 150 Valves;

b) Standard Valves;

c) Valves for Special (Low Pressure) Applications.

The purchaser, when referencing the Standard, shall also specify the appropriate category as listed above.

This Standard Practice covers the following:

a) Pressure-Temperature Ratings and Design requirements;

b) Commonly Used Diaphragm Pressure Limitations;

c) Body, Bonnet, and Bolting Materials;

d) Commonly Used Face-to-Face Dimensions for Flanged Valves;

e) Body End Connections and Wall Thicknesses;

f) Actuator Application Requirements;

g) Tests;

h) Marking.