Views: 267 Author: Site Editor Publish Time: 2021-03-10 Origin: Site
Pneumatic actuators are actuators that use air pressure to drive open and close or adjust valves.
When compressed air enters the compact pneumatic actuator from nozzle A, the gas pushes the double pistons to move linearly to both ends (cylinder head end). The rack on the piston actuator drives the gear on 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 actuated ball valve or air actuated ball valve is discharged with the B nozzle.
Conversely, when compressed air enters the two ends of the pneumatic actuator from the B nozzle, the gas pushes the double plug to move linearly toward the middle. The rack on the piston actuator valve drives the gear on the rotating shaft to rotate 90 degrees clockwise, and the valve is closed.
Before we learned about the following selection factors of pneumatic actuators.
1. The operating torque of the valve plus the safety factor recommended by the manufacturer/according to the operating conditions.
2. Air pressure or power supply voltage of the actuator.
3. The type of actuator is double-acting or single-acting (spring return) and the output torque under a certain air supply or the output torque under the rated voltage. This factor mainly involves single acting pneumatic actuator, double acting pneumatic actuator and spring return pneumatic actuator.
4. The steering and failure modes of the actuator.
Pneumatic actuated valves are now more and more widely used in various industries, and the technology of pneumatic actuators is getting better and better.
1. Non-linear deviation test. The non-linear deviation between the actual pressure and stroke relationship and the theoretical value should be ≤1%.
2. Deterioration test of positive and negative stroke. Similar to the non-linear deviation test method, in the actual positive and negative pressure and stroke relationship, the maximum difference between the positive and negative stroke values of the cylinder piston under the same air pressure value should be ≤1%.
3. Sensitivity test. Increase and decrease the air pressure at the stroke of signal pressure 0.03, 0.06, 0.09Mpa respectively, and test the signal pressure change value required when the cylinder piston rod starts to move 0.1mm. The maximum change should be ≤0.2%.
4. Sealing test of piston cylinder. Connect the pressure of 0.5 Mpa to any air chamber of the cylinder, and then cut off the gas source. Within 10 minutes, the pressure drop in the cylinder should not exceed 0.01 Mpa.
5. Fix the pneumatic air actuator on the calibration platform, and connect the air source, control air source and displacement detection link respectively.
6. Mechanical zero point calibration. Input 4mA current signal (0%), the control gas signal should be 0.02Mpa, at this time the cylinder piston stroke should be zero. If it is not zero, you can adjust the zero point by adjusting the nut on the zero adjusting screw (the zero point is higher than the nut). The zero point and range need to be adjusted repeatedly; the zero point error should be ≤1%.
7. Mechanical full-scale calibration. Input 20mA current signal (100%), the control gas signal should be 0.10Mpa, at this time the cylinder piston stroke should be the upper limit. The zero point and span need to be adjusted repeatedly. The full scale error must be ≤1%.
8. Electrical full-scale detection of position transmitter. Input a 20mA current signal (0.1 Mpa), at this time you can adjust the range potentiometer in the transmitter to make the output current 20mA. The electrical full-scale error should be ≤1%.
In addition, there are the following detection methods, including position feedback current full stroke deviation calibration, position feedback current positive and negative stroke variation test, mechanical range midpoint positioning, full stroke deviation calibration and position transmitter electrical zero point detection.
