Pneumatic actuator

Pneumatic actuator is an actuator that uses pneumatic pressure to drive the open and close or adjust the valve, also known as pneumatic actuator or pneumatic device, but commonly known as pneumatic head. Sometimes pneumatic actuators are equipped with certain auxiliary devices. Commonly used valve positioner and hand wheel mechanism. The function of the valve positioner is to improve the performance of the actuator by using the feedback principle, so that the actuator can achieve accurate positioning according to the control signal of the controller. The function of handwheel mechanism is to operate the control valve directly to maintain the normal production when the control system is power-off, gas stop, controller has no output or actuator fails.

When the compressed air enters the pneumatic actuator from the a pipe nozzle, the gas pushes the double pistons to move in a straight line 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 is opened. At this time, the gas at both ends of the pneumatic actuator valve is discharged with the B nozzle. On the contrary, when the compressed air enters the two ends of the pneumatic actuator from the B nozzle, the gas pushes the double plug to move in a straight line in the middle, and the rack on the piston drives the gear on the rotating shaft to rotate 90 degrees clockwise, and the valve is closed. At this time, the gas in the middle of the pneumatic actuator is discharged with a nozzle. The above is the transmission principle of standard type. According to the user's requirements, the pneumatic actuator can be installed with the transmission principle opposite 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 type) pneumatic actuator a nozzle is the air inlet, B nozzle is the exhaust port (b nozzle should be equipped with muffler). The inlet of nozzle a is an open valve, and the valve is closed by spring force when the air is cut off.

The types and structures of regulating mechanisms of pneumatic actuators are almost the same, mainly due to different actuators. Therefore, the introduction of pneumatic actuator is divided into two parts: actuator and control valve. Pneumatic actuator is composed of actuator and control valve. According to the size of the control signal, the corresponding thrust is generated to push the control valve to act. The regulating valve is the regulating part of the pneumatic actuator. Under the thrust of the actuator, the regulating valve produces a certain displacement or angle to directly regulate the flow of fluid.

1. The pneumatic device is mainly composed of cylinder, piston, gear shaft, end cover, seal and screw; The complete set of pneumatic device should also include opening indication, travel limit, solenoid valve, positioner, pneumatic components, manual mechanism, signal feedback and other components.

2. The connection dimension between pneumatic device and valve shall comply with the provisions of ISO5211 (bottom), GB / t12222 and GB / t12223.

3. When the air source is interrupted, the pneumatic device with manual mechanism shall be able to use its manual mechanism to open and close the Pneumatic ball valve. When facing the hand wheel, the hand wheel or handle shall rotate counterclockwise to open the valve and clockwise to close the valve.

4. When the end of piston rod is internal or external thread, there should be a suitable wrench port for standard wrench.

5. The sealing ring of piston shall be easy to replace and repair.

Pneumatic device

Pneumatic device

6. For the pneumatic device with buffer mechanism, the stroke length of buffer mechanism can refer to table 1.

7. The pneumatic device with adjustable buffer mechanism shall have a mechanism for adjusting its buffer effect outside the cylinder block.

8. The thread size of cylinder inlet and outlet shall meet the requirements of manur norm sypv, GB / t7306.1, GB / t7306.2 and GB / t7307.