Valve actuators automate valve operation in industrial process industries. Hydraulic actuators are commonly used for butterfly valves, while electric actuators are used for gate valves. Linear actuators are used for control valves. Handwheels allow for manual control.
Used in industrial process industries including water, oil and power plants, valve actuators provide automated operation of valves along a pipe system. The use of actuated valves allows engineers to remotely control an entire process system, limiting the need for direct human interaction. There are several types of actuators, determined by their operating mechanisms; these take the form of a pneumatic, electric, or hydraulic valve actuator.
Hydraulic actuators are most commonly used to operate butterfly valves that require less than 360 degrees of rotation within the pipe to provide fluid level control. The hydraulic valve actuator converts electrical signals into fluid pressure within the hydraulic cylinder to provide motion. If required, technicians can easily retrofit the hydraulic actuators to existing manually operated valve controls.
The primary format of a hydraulic valve actuator used in the process industry is the rack and pinion actuator. This type of actuator provides rotary motion by regulating the hydraulic pressure within the piston arm of the actuator. It can rotate the valve flange by extending the arm and returning it to its original position by retracting the arm. With this limited movement, hydraulic actuators are not used for multi-turn valve control.
Three different styles of valve actuators are available, each specific to different valve models. The first of these are multi-turn actuators, which control gate valves. These valves are capable of a full 360 degree rotation and are controlled by electric valve actuators due to the unrestricted one-way rotation required.
Part-turn actuators function similarly to multi-turn actuators, but only need to rotate through an angle of approximately 90 degrees. Butterfly valves are the most common type controlled by part turn actuators and can be controlled by an electric, pneumatic or hydraulic valve actuator. A key area where multi-turn and part-turn actuators differ is in their requirements to resist thrust. Since multi-turn valves are not limited in their rotation, the actuator must be able to resist the thrust force it experiences. Part-turn valves are supported by parts of the valve body and are therefore not required to resist thrust.
The third type of actuated valve control is the linear actuator. These linear actuators work by blocking the pipe and are therefore most commonly seen on control valves. This type of valve works by pressing a plug into the pipe and exerting a thrust-like level of force acting on the face of the valve. Most actuated valves are also fitted with handwheels to allow manual control if required.
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