page_title: Valve actuator
section_title: Hydraulic
hierarchical_section_title: Valve actuator / Types / Hydraulic
caption_attribution_description: English: Valve actuator in a process system
context_page_description: A valve actuator is the mechanism for opening and closing a valve. Manually operated valves require someone in attendance to adjust them using a direct or geared mechanism attached to the valve stem. Power-operated actuators, using gas pressure, hydraulic pressure or electricity, allow a valve to be adjusted remotely, or allow rapid operation of large valves. Power-operated valve actuators may be the final elements of an automatic control loop which automatically regulates some flow, level or other process. Actuators may be only to open and close the valve, or may allow intermediate positioning; some valve actuators include switches or other ways to remotely indicate the position of the valve.
  Used for the automation of industrial valves, actuators can be found in all kinds of process plants. They are used in waste water treatment plants, power plants, refineries, mining and nuclear processes, food factories, and pipelines. Valve actuators play a major part in automating process control. The valves to be automated vary both in design and dimension. The diameters of the valves range from one-tenth of an inch to several feet.
context_section_description: Hydraulic actuators convert fluid pressure into motion. Similar to pneumatic actuators, they are used on linear or quarter-turn valves. Fluid pressure acting on a piston provides linear thrust for gate or globe valves. A quarter-turn actuator produces torque to provide rotary motion to operate a quarter-turn valve. Most types of hydraulic actuators can be supplied with fail-safe features to close or open a valve under emergency circumstances.  Hydraulic pressure can be supplied by a self-contained hydraulic pressure pump.  In some applications, such as water pumping stations, the process fluid can provide hydraulic pressure, although the actuators must use materials compatible with the fluid.
caption: Electric valve actuator mounted on a pressure reducing needle valve.
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