Pneumatic actuator is an actuator that uses air pressure to drive the opening and closing or regulating valve. It is also called
pneumatic actuator or pneumatic device, but it is generally called pneumatic head. The actuating mechanism and adjusting mechanism of pneumatic actuator are a unified whole, and its actuating mechanism includes membrane type, piston type, fork type and rack and pinion type.
The piston type has a long stroke, which is suitable for occasions requiring large thrust; The film type has a small stroke, which can only directly drive the valve rod. 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; It is often used on valves with large torque. The rack and pinion
pneumatic actuator has the advantages of simple structure, stable and reliable action, and safe explosion-proof. It is widely used in power plants, chemical industry, oil refining and other production processes with high safety requirements.
Working principle of
pneumatic actuator
1. Working principle diagram of double acting
pneumatic actuator
When the air source pressure enters the middle chamber between the two pistons of the cylinder from the air port (2), the two pistons will separate and move towards both ends of the cylinder, and the air in the air chambers at both ends will be discharged through the air port (4). At the same time, the two piston racks will synchronously drive the output shaft (gear) to rotate counterclockwise. On the contrary, when the air source pressure enters the air chambers at both ends of the cylinder from the air port (4), the two pistons move towards the middle of the cylinder, and the air in the middle air chamber is discharged through the air port (2). At the same time, the two piston racks synchronously drive the output shaft (gear) to rotate clockwise. (if the piston is installed in the opposite direction, the output shaft will rotate in the opposite direction.)
2. Working principle diagram of single acting
pneumatic actuator
When the air source pressure enters the middle chamber between the two pistons of the cylinder from the air port (2), the two pistons will separate and move towards the two ends of the cylinder, forcing the springs at both ends to compress, and the air in the air chambers at both ends will be discharged through the air port (4). At the same time, the two piston racks will synchronously drive the output shaft (gear) to rotate counterclockwise. When the air source pressure is reversed through the solenoid valve, the two pistons of the pneumatic actuator cylinder move towards the middle direction under the spring force, and the air in the middle air chamber is discharged from the air port (2). At the same time, the two piston racks synchronously drive the output shaft (gear) to rotate clockwise. (if the piston is installed in the opposite direction, the output shaft will rotate in the opposite direction when the spring returns).
