The three-stage pneumatic actuator is an actuator that uses air pressure to drive the valve to open, close or adjust. It is also called a pneumatic actuator or a pneumatic device, but it is usually called a pneumatic head. Sometimes pneumatic actuators are equipped with some auxiliary devices. Commonly used valve positioners and handwheel mechanisms. The function of the valve positioner is to use the feedback principle to improve the performance of the actuator, so that the actuator can achieve precise positioning according to the control signal of the controller. The function of the handwheel mechanism is to directly operate the control valve to maintain normal production when the control system is powered off, the gas is stopped, the controller has no output or the actuator fails. Three-stage pneumatic actuator When the compressed air enters the pneumatic actuator from the nozzle of the a pipe, the gas pushes the double piston to move linearly to both ends (cylinder head end). The rack on the piston drives the gear on the rotating shaft to rotate 90 degrees counterclockwise, and the valve opens. At this time, the gas at both ends of the valve of the pneumatic actuator is discharged through the nozzle B. On the contrary, when compressed air enters both ends of the pneumatic actuator from nozzle B, the gas pushes the double plug to move linearly in the middle, the rack on the piston drives the gear on the rotating shaft to rotate clockwise 90 degrees, and the valve closes. At this time, the gas in the middle of the pneumatic actuator is discharged through the nozzle. The above is the standard transmission principle. According to the user's requirements, the installation of the pneumatic actuator can adopt the opposite transmission principle to the standard type, that is, select the right shaft to turn clockwise to open the valve, and turn counterclockwise to close the valve. Single-acting (spring return) pneumatic actuator nozzle a is the air inlet, nozzle B is the exhaust port (nozzle B should be equipped with a silencer). The inlet of nozzle a is an open valve. When the air is cut off, the valve is closed by spring force.
