What are pneumatic open and pneumatic closed actuators?

2025-03-17 13:20:06 58

Pneumatic actuators can be divided into two types: pneumatic on and pneumatic off. Pneumatic actuator with pneumatic opening, which means the valve opens when there is signal pressure and closes when there is no signal pressure; Pneumatic actuator with air closing function, which means the valve closes when there is signal pressure and opens when there is no signal pressure.

The selection of gas on and gas off is mainly considered for production safety. When the signal pressure is interrupted, it is necessary to avoid damaging the equipment and injuring the operators. If the boiler feedwater valve is in the open position with low hazard, an air tight pneumatic actuator should be selected. When controlling the entry of flammable gases into equipment, in order to prevent explosions, pneumatic actuators with gas opening should be selected.

For electric actuators, the terms "electric on" and "electric off" cannot be used to refer to pneumatic actuators. Because the working principle, driving mechanism, and driving energy of pneumatic actuators and electric actuators are different. The former uses compressed air pressure to drive, while the latter uses AC power to drive the motor to rotate. For pneumatic actuators, taking the diaphragm actuator as an example, when the signal pressure is interrupted, it relies on the reaction force of the compression spring to push the diaphragm and move the push rod component to close or open the valve. That's why there are two types: gas on and gas off. But once the electric actuator loses power, there is no driving power, so the valve can only stop at the position when the power is cut off, and it cannot be closed or opened.