What Are the Difference between Single-acting and Double-acting Pneumatic Actuators?

Air powered actuator is an actuator that uses compressed air to drive valve switches or adjust media flow. Pneumatic actuators are generally used in conjunction with valves. Common valves mainly include air actuated butterfly valve, air actuated ball valve and pneumatic operated gate valve.

 

The double acting pneumatic actuator means that the pneumatic actuator starts to rotate to open the valve when it is ventilated. When the valve is to be closed, the other side can only be closed by ventilating. It is reset by the cylinder and can only remain in place when the air source is lost. The pneumatic actuator starts to turn to open the valve. When the valve is to be closed, the other side needs to be lifted to close.

 

In general, double acting pneumatic actuators are often used, and double acting pneumatic cylinders do not have springs. Therefore, the cost is lower than that of a single acting pneumatic actuator.

 

The single-acting pneumatic actuator opens the valve when the air is ventilated, and automatically closes when the air source is not ventilated. The single-acting pneumatic actuator automatically resets by the spring. It is generally used more in dangerous situations, such as conveying flammable gas or flammable liquid. When the air source is lost and an emergency occurs, the single acting actuator can automatically reset to minimize the risk, while the double acting actuator is generally not easy to reset.

 

Single-acting and Double-acting Pneumatic Actuators

 

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 of the rotating shaft to rotate 90 degrees counterclockwise, and the valve is turn on. At this time, the gas at both ends of the pneumatic actuator valve is discharged with the B pipe. Conversely, when compressed air enters the two ends of the pneumatic button 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 that can rotate 90 degrees clockwise. The valve is closed. At this time, the gas in the pneumatic linear slide actuator is discharged with nozzle A. The above is the standard transmission principle.

 

According to user needs, the high speed pneumatic actuator can be installed with a transmission principle opposite to the standard type. That is, the clockwise rotation of the collimate axis is selected to open the valve, and the counterclockwise rotation is to close the valve. Single-acting (spring return type) pneumatic actuator A nozzle is the air inlet, B nozzle is the exhaust hole (B nozzle should be equipped with a muffler). The inlet of nozzle A is to open the valve, and the valve is closed by spring force when the air is cut off.

 

The air source hole complies with NAMUR standard. The shaft assembly hole at the bottom of the pneumatic actuator (in accordance with ISO5211 standard) is a double square, which is convenient for linear or 45° angle installation of the valve with a square rod. The top and top holes of the output shaft comply with NAMUR standards. The adjustment screws at both ends can adjust the opening angle of the valve.