In power plant, the actuator and valve create a single unit — the control valve. Actuators perform different motion sequences, including linear, pivoting and rotating motions, and they are powered by pneumatic, hydraulic or electrical energy. Actuators receive a control signal from automation systems and single board computer. The single board computer is converted into a motion so that the control element of the actuating element assumes a corresponding position. With control valves, this is a stroke motion. With flaps, ball cocks or rotary plug valves, this is a pivoting motion.
Power plants have traditionally used pneumatic actuators to drive the many control valves throughout their facilities. However, major improvements in embedded systems control-valve actuator technology are helping power providers achieve their most important objectives at a lower cost.
The new electric actuators can hold up to the demands of continuous movement.
refer to: http://www.power-eng.com/articles/print/volume-117/issue-8/features/opportunities-to-improve-efficiency.html
