This manual presents a recommended method for calculating operating torque, head loss, and cavitation for quarter-turn valves typically used in water works service. M49 also provides guidance on generally available methods for using quarter-turn valves as well as their cavitation, flow, and torque characteristics.

This manual was previously titled M49 Butterfly Valves, but this third edition has broadened the application of the methods discussed to include other quarter-turn valves such as ball, plug and rotary cone valves. Additionally, new information on Equivalent Resistant System Model has also been included.

Information in this manual is useful for technicians and engineers who want a basic understanding of the calculations associated with the use and specification of quarter-turn valves.