Innovative actuator solution

The order included spring-return pneumatic actuators to operate 30" and 36" Class 1500 ball valves. It was stipulated tthat aximum actuator output torque at a design pressure of 9.4 bar should not be in excess of 90% of the valves’ maximum allowable stem torque (MAST).

Faced with this challenge Rotork added a second pneumatic cylinder, mounted between the GP scotch yoke centre body and the spring-return cylinder. Both cylinders are pressurised in the same direction at the same time, so one delivers torque for valve movement, satisfying the valve MAST requirement, whilst the other independently applies the torque to compress the spring.