Part-turn actuators transmit torque to the valve for a rotation of one revolution or less. They do not have to be capable of withstanding axial thrust. Part-turn valves - such as butterfly valves and ball valves - are often designed in multi-turn version. SA part-turn actuators with direct actuation capabilities uses planetary gear mechanism to achieve part-turn operation.
Part-turn actuation can also be achieved by combining SA range multi-turn actuators with part-turn flange mounted (GS) and foot mounted (GF) worm gearboxes.
OPEN-CLOSE or modulating duty
Class A: OPEN-CLOSE duty. The actuator is required to drive the valve through its entire travel from the fully open position to the fully closed position or vice versa.
Class B: Inching/positioning or positioning duty. The actuator is required to occasionally drive the valve to any position (fully open, intermediate and fully closed).
Class C: Modulation or modulating duty. The actuator is required to frequently drive the valve to any position between fully open and fully closed.