Pneumatic actuators are driven by air pressure to open and close or adjust the valve actuators, commonly known as pneumatic head. Pneumatic actuators can be divided into diaphragm type, piston type and pinion and rack type.
1. Diaphragm actuator:
Diaphragm actuator refers to the use of the elastic diaphragm will be the input pressure into the thrust rod, through the push rod to make the valve center corresponding displacement, change the valve opening. Pneumatic piston actuator to the piston in the cylinder output thrust. Because the cylinder allows higher pressure, can obtain a greater thrust. And easy to make the long stroke of the actuator. It can use as a general control valve pushing device, the composition of pneumatic diaphragm actuator.
The signal pressure P of pneumatic diaphragm actuator ACTS on the diaphragm to make it deform, drive the push rod on the diaphragm to move. And make the valve core produce displacement, thus changing the opening of the valve. It is simple in structure, cheap in price, convenient in maintenance and widely used.
Pneumatic diaphragm actuator has two forms of positive action and reaction.
When the signal pressure from the controller or valve positioner increases, the stem downward action is call the positive action actuator.
When the signal pressure increases, the stem upward action is call the reaction actuator.
The signal pressure of the positive acting actuator is the diahragm gas chamber above the corrugated diaphragm.
The signal pressure of the counteracting actuator is the thin film gas chamber under the corrugated diaphragm.
By changing individual parts, the two can modify each other.
2. Rack and pinion actuator:
Pinion rack (double piston rack type) pneumatic actuator, with compact structure, beautiful appearance, quick response, stable operation, long service life and other characteristics.
All accessories are equip with the most advanced anti-corrosion treatment technology, which can adapt to various harsh working conditions. Its high and low temperature and various special travel actuators have good performance in various applications.
3. Piston actuator:
Pneumatic piston actuators make the piston move in the cylinder to produce thrust. Therefore, the film type is suitable for small output, high precision occasions. Piston type is suitable for large output force occasions, such as large diameter, high pressure drop control or butterfly valve pushing device.
In addition to the membrane type and piston type, there is a long stroke actuator. Which as a long stroke and a large torque, and is suitable for the occasions of output angular displacement and large torque.