The working principle of pneumatic actuator valve is to use the pressure energy of compressed air into mechanical energy, so as to drive the valve to open, close or regulate the action. The following is its specific working process:
Double-acting pneumatic actuator
Opening process: when the air source pressure from the port (2) into the cylinder between the two pistons in the middle chamber, so that the two pistons separated to the cylinder ends of the direction of movement, the two ends of the air cavity through the air port (4) discharged at the same time so that the two piston rack synchronously drive the output shaft (gears) rotating in the counterclockwise direction, thus driving the valve to open.
Closing process: On the contrary, when the pressure of air source enters into the air cavity 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 cavity is discharged through the air port (2), and at the same time, the rack and pinion of the two pistons synchronously drive the output shaft (gear) to rotate in the clockwise direction, so as to achieve the closure of the valve.
Single-acting pneumatic actuator
Opening process: when the pressure of air source enters the middle chamber between two pistons of the cylinder through the air port (2), the two pistons move separately towards the two ends of the cylinder, forcing the springs at both ends to be compressed, and the air in the air chamber at the two ends is discharged through the air port (4), and at the same time, the racks of the two pistons synchronously drive the output shaft (gears) to rotate in the counterclockwise direction to achieve the opening of the valve.
Closing process: After the pressure of the air source is reversed by the solenoid valve, the two pistons of the cylinder move to the middle direction under the elasticity of the spring, and the air in the middle air chamber is discharged through the air port (2), and at the same time, the rack of the two pistons synchronously drives the output shaft (gear) to rotate in the clockwise direction, and the valve is closed.
Pneumatic thin-film actuator
Positive acting: When the signal pressure from the controller or valve positioner increases, the valve stem moves downward. Signal pressure is passed into the membrane air chamber above the corrugated diaphragm, and air pressure enters the shell, exerting pressure on the diaphragm. As the air pressure on the diaphragm increases, the force exerted on the spring increases, which leads to the movement of the actuator, causing the valve spool to be displaced, thus changing the opening of the valve.
Reaction: When the signal pressure increases, the valve stem moves upwards. Signal pressure is passed into the membrane air chamber below the corrugated diaphragm, and air pressure enters the housing, exerting pressure on the diaphragm. As the air pressure on the diaphragm increases, the force exerted on the spring also increases, which leads to the movement of the push rod, causing the spool to be displaced, thus changing the opening of the valve.