Different valves in the industrial sector are categorised by pressure class, size, industry, type, and other considerations. A valve actuator is a device with an input, output, and circuitry required for the valve’s operation. While a valve’s quality depends on its mechanical design, the machining, and metallurgy, actuators determine its performance in the control loop. Hence, it plays a significant role in determining the valve’s overall performance, and its choice must be made with thorough consideration of various factors. Following is some crucial information to help you make a sound decision while choosing an appropriate actuator:
There is a wide range of control valves available. When a valve actuator is chosen, you need to assess the type of valve operation. The two important types of valve operations are:
- Rotary operation: Rotary or quarter-turn operation includes a ball, butterfly, and plug valves. Quarter turn dampers also fit into this category. These valves are easier to fit with an actuator as the operation requires 90-degree rotation at the correct torque.
- Multi-turn operation: The valves in this group have either non-rising rotating or rising non-rotating stems. These valves need multiple turns to move the valve closure element from open to closed. Some valves in this group are knife gates, globe valves, sluice gates, and gate valves.
Valve actuator types
There are different valve actuators, most of which fall into specific categories depending on the required movement and applied power.
Hydraulic and pneumatic actuator (fluid power)- multi-turn: When a multi-turn output is needed to operate a linear-type of valve-like globe valve or gate valve, a fluid power actuator is the best solution. Usually, an electric actuator is ideal for these types of valves. Moreover, a hydraulic or pneumatic actuator could be viable for applications where electricity is not readily available.
Hydraulic and pneumatic actuator (fluid power)- quarter-turn: This type of actuator is highly versatile for applications that prioritise reliability and simplicity or where electric power is not readily available. It has various capabilities, including delivering a few inch-pound torques to a million-inch pound or more. A hydraulic and pneumatic actuator using a cylinder with some mechanism converts the cylinder’s linear motion to the quarter-turn motion needed for valve operation.
Electric actuator-quarter-turn: The positioning of the final element in this type of actuator is in one quadrant enabling 90-degree rotation. It is compact, uses small valves due to low power requirements, and can be configured with emergency power supplies.
Electric actuator-multi-turn: This kind of actuator is used in the most common type of valves. It is powered by a three-phased or single-motor driving a combination of spurs and level gears. These spurs and gears drive a stem nut engaging the valve’s stem to close and open.
Manual actuator: A motor actuator requires wheels, levers, or gears to facilitate movement. A manual actuator cannot be used for many valves because the application requires valves in remote pipelines or is unable to deliver the force needed for the operation. Moreover, such an actuator is inappropriate for valves in a hostile or toxic environment. It is also not as functional in applications that require safety precautions of permitting immediate shutdown.
The choice of a valve actuator primarily depends on valve operation and the type of power applied to achieve the specific movement. Hence, to gain more productivity and efficiency in the process industry, assess your valve operation and choose the proper actuator. Remember, selecting the wrong actuator would fail to operate a valve adequately and may cause severe damage to the valve and the valve system.