Views: 271 Author: Site Editor Publish Time: 2021-02-20 Origin: Site
Pneumatic actuators are actuators that use pneumatic pressure to drive open and close or adjust valves. They are also called pneumatic cylinder actuators or pneumatic devices, but they are generally called pneumatic heads. The actuator and adjustment mechanism of the pneumatic actuator are a unified whole. The actuator has membrane type, piston type, fork type and rack and pinion type.
The pneumatic linear actuator has a long stroke and is suitable for occasions requiring greater thrust. The membrane type has a small stroke and can only directly drive the valve stem. The fork type pneumatic actuator has the characteristics of large torque, small space, and the torque curve is more in line with the torque curve of the valve. But it is not very beautiful, and it is often used on valves with high torque. Rack and pinion actuator has the advantages of simple structure, stable and reliable action, and safety and explosion-proof. It is widely used in power plants, chemical industry, oil refining and other production processes with high safety requirements.
Pneumatic actuators are mainly divided into single acting pneumatic actuator and double acting pneumatic actuator.
When compressed air enters the pneumatic actuator from the A nozzle, the gas pushes the double piston to move linearly to both ends (cylinder head end). The rack on the piston drives the gear on the rotating shaft to rotate 90 degrees counterclockwise, and the valve is opened. At this time, the gas at both ends of the air actuator valve is discharged with the B nozzle. Conversely, when compressed air enters the two ends of the pneumatic actuator from the B official nozzle, the gas pushes the double plug to move linearly in the middle, and the rack on the piston drives the gear on the rotating shaft to rotate 90 degrees clockwise, and the valve is closed. At this time, the gas in the middle of the pneumatic actuator is discharged with the A nozzle. The above is the standard transmission principle.
1. Membrane actuator
The membrane type actuator is the most commonly used, it can be used as a general control valve pushing device to form a pneumatic membrane type actuator. The signal pressure of the pneumatic diaphragm actuator acts on the diaphragm to deform it, and drives the push rod on the diaphragm to move, so that the valve core is displaced, thereby changing the valve opening. It has simple structure, low price, convenient maintenance and wide application.
2. Piston type actuator
The pneumatic piston actuator causes the piston to move in the cylinder to generate thrust. Obviously, the output power of the piston type is much greater than that of the film type. Therefore, the membrane type is suitable for occasions with low output and high precision. The piston type is suitable for occasions with large output force, such as large diameter, high pressure drop control or pneumatic butterfly valve pushing device.
3. Rack and pinion actuator
Pneumatic rack and pinion actuator has the characteristics of compact structure, beautiful appearance, quick response, stable operation and long service life. All accessories adopt the most advanced anti-corrosion treatment technology, which can adapt to various harsh working conditions. Its high and low temperature and various special stroke actuators have good performance in various application fields.
Before selecting a pneumatic actuator, please confirm the valve torque and add a safe value to the torque. Water vapor or non-lubricating liquid medium increases the safety value by 25%. The non-lubricating slurry liquid medium increases the safety value by 30%.
