This standard establishes minimum requirements for rubber-seated butterfly valves, 3 in. (75 mm) through 72 in. (1,800 mm) in diameter, with various body and end types, for raw water, potable water, wastewater, and reclaimed water having a pH range from 6–12 and a temperature range from 33°–125°F (0.6°–52°C). This standard covers rubber-seated butterfly valves suitable for a maximum steady-state fluid working pressure of up to 250 psig (1,723 kPa), a maximum steady-state differential pressure of up to 250 psi (1,723 kPa), and a maximum full open fluid velocity of up to 16 ft/sec (4.9 m/sec) based on nominal valve size.

• 1.1.1 Body types, classes, and sizes. Valves described in this standard are provided in four body types and in classes as follows:
• 1.1.1.1 Wafer valves. Class 150B, in sizes 3–20 in. (75–500 mm).
• 1.1.1.2 Short-body and long-body flanged valves. Class 25A, Class 25B, Class 75A, Class 75B, Class 150A, and Class 150B and Class 250B, in sizes 3 in.–72 in. (75 mm–1,800 mm).
• 1.1.1.3 Mechanical-joint-end valves. Class 150B and Class 250B, in sizes 3 in.–24 in. (75 mm 600 mm), and Class 25A, Class 25B, Class 75A, Class 75B, Class 150A, Class 150B, and Class 250B, in sizes 30 in.–48 in. (750 mm–1,200 mm).
• 1.1.2 Definition of classification. In each case, the numeric designation represents the pressure rating (the maximum steady-state fluid working pressure, in pounds-per-square-inch gauge) and also the maximum steady-state differential pressure, in pounds per square inch, for which the valve is designed.
• 1.1.2.1 A and B designations. The designations A and B define the flow-rate capabilities with the valve in the fully open position. Valves designated A are rated for a maximum velocity of 8 ft/sec (2.4 m/sec), and B valves are rated for a maximum velocity of 16 ft/sec (4.9 m/sec) in the piping section upstream of the valve.

This standard can be referenced in purchase documents for rubber-seated butterfly valves that are described by the scope as defined above.