AWWA JAW34254

Quarter-turn types of valves are subject to stresses and torques produced by the flow forces in the valve and by the rotation of the valve disk with an actuator. This article discusses the different types of torque to which a valve can be exposed, focusing on the use of dynamic flow torque coefficients to predict and evaluate flow torque. The derivation of a torque coefficient that incorporates the variation of geometry for different sizes of a valve is presented. The coefficient also utilizes a correction factor for the loss coefficient and gas expansion. A method and a scaling factor to correct flow torque coefficients for different valve sizes and loss coefficients are described. Several examples and plots of torque coefficients are included for various valve types. Includes 6 references, figures.