Chiksan® Swivel Joints - Topco Oilsite Products Ltd.

Weco ® Actuator Sizing InformationActuator Sizing InformationRequired Operating Torques:There are three torques to be considered when selectingthe proper actuator for a butterfly valve:(1) Seating Torque - The torque required todisplace a resilient seat and effect shutoff(2) Bearing Torque - The torque required toovercome friction forces on the valve shaftbearing surfaces(3) Dynamic Torque - Torque due to fluid forceswhich tend to close the valve.The torques for resilient seated valves tabulated in thissection are the sum of (1) and (2) above for various shutoffpressures. These tabulated values include a safetyfactor large enough to insure proper valve operation inmost general butterfly valve applications. Where unusualservice conditions exist (such as likelihood of seat swelling,or low and high temperature seat hardening), anadditional safety factor may be applicable.Dynamic TorqueDynamic torque is torque on the valve shaft due to thefluid forces on the valve disc. This torque is a function ofvalve diameter, pressure drop, and a torque coefficient(Ct) which varies with angle opening. Torque is calculatedby the equation:T = C tD 3 ∆PWhere: T = Dynamic torque (in-lb)D = Valve Dia. (in.)C t= Dynamic torque coefficient(see table below)C t vs. Angle OpenAngle Open 0 10 20 30 40 50 60 70 80 90C t 0 .007 .014 .022 .033 .050 .087 .143 .215 0BV8A