Valve Actuator
A valve actuator is a device that operates a valve by converting an energy source into linear or rotary motion, allowing remote, automatic or high-torque operation. Pneumatic actuators use compressed air acting on a diaphragm or piston, in spring-return (fail-safe) or double-acting configurations, and include rack-and-pinion and scotch-yoke designs for quarter-turn valves. Electric actuators use a motor and gearbox with limit and torque switches and may provide modulating control. Hydraulic and electro-hydraulic actuators deliver high forces for large valves and pipeline service. Manual gear operators reduce the input effort for handwheel operation. Selection requires the valve torque or thrust with a safety margin, operating time, fail-safe position, duty cycle, supply pressure or voltage, enclosure rating and hazardous area certification. Mounting interfaces for part-turn and multi-turn actuators are standardised in ISO 5211 and ISO 5210 respectively.
Examples
- Spring-return pneumatic actuator for an emergency shutdown valve
- Electric multi-turn actuator on a pipeline gate valve
- Gear operator on a large butterfly valve