1. Fix the pneumatic actuator on the test table and connect the air source, control air source and displacement detection connecting rod respectively; Calibrate the instrument on the test bench accurately;
2. Zero point calibration of machinery.
Input 4mA current signal, control gas signal should be 0.02mpa, then the piston stroke of the cylinder should be zero; If not, zero can be adjusted by adjusting the nut on the zeroing screw.
3. Mechanical full range calibration.
Input 20mA current signal (100%), control gas signal should be 0.10mpa, then the cylinder piston stroke should be the upper limit; If it is not the upper limit value, the range can be adjusted by adjusting the tightness of the range tension spring.
4. Mid-point positioning of mechanical range.
After adjusting the zero point and the range, input 12mA current signal and adjust the position of the connecting rod of the position transmitter to keep it perpendicular to the horizontal plane at this point;
5. Full stroke deviation calibration.
Input control gas signal 0.02mpa (0%), and gradually increase the input signal 0.036mpa (20%), 0.052mpa (20%), 0.068mpa (60%), 0.084mpa (80%) and 0.1mpa (100%) to make the cylinder piston go through complete stroke, with each point deviation ≤1.5%;
6. Nonlinear deviation test.
Input control gas signal 0.02mpa (0%), and then gradually increase the input signal to 0.10mpa (100%), and then reduce the signal to 0.02mpa (0%), 0.008mpa to make the actuator complete travel, and record the travel value corresponding to each increase or decrease of signal pressure. The nonlinear deviation between the actual pressure ━ travel relation and the theoretical value should be ≤1%;
7. Positive and negative travel variation test.
The same as the nonlinear deviation test method, in the actual relationship between positive and negative ━ stroke of the cylinder piston under the same pressure value, the maximum difference of the positive and negative stroke value of the cylinder piston should be ≤1%;
8. Sensitivity test.
Increase and decrease the air pressure at the stroke of 0.03, 0.06 and 0.09mpa respectively. Test the change value of signal pressure required when the cylinder piston rod begins to move 0.1mm, and the maximum change should be ≤0.2%.
9. Sealing test of piston cylinder.
Connect 0.5mpa pressure into any air chamber of the cylinder, and then cut off the air source. Within 10 minutes, the decrease value of the pressure in the cylinder shall not exceed 0.01mpa;
10. Electric zero detection of position transmitter.
Open the upper cover of the position transmitter and connect the wires. Input 12mA current signal (0.06mpa), then adjust the circular eccentric wheel inside the transmitter to align the black line on it with the white line on the circuit board.
11. Electric full range detection of position transmitter.
Input 20mA current signal (0.1mpa), then adjust the internal range potentiometer of the transmitter to make the output current 20mA; Electric full range error should be less than 1%;
12. Position feedback current full stroke deviation calibration.
Input 4mA current (0%), and then gradually increase the input signal 8mA current (25%), 12mA current (50%), 16mA current (75%). And 20mA current (100%). Considering the nonlinear error of linear displacement converted into Angle change. Feedback current errors at 0%, 50%, 100% points should be ≤1%. And feedback current errors at 25% and 75% points should be ≤2%.
13. Position feedback current positive and negative travel variation test.
Same as the test method of the reverse stroke variation of the cylinder piston, in the actual positive and negative position feedback current ━ stroke relation. The maximum difference of the positive and negative stroke value of the cylinder piston under the same feedback current value should be ≤1%;
14. Make calibration records, fill them out item by item according to the calibration record table, and the inspectors must sign;
15. After the above tests are qualified, the internal wiring terminals of the position transmitter shall be inserted well, the back cover shall be tightened, and then the air source inlet of the valve positioner shall be sealed with a plastic plug.