Pneumatic actuator with top mounted handwheel company introduces the inspection method of pneumatic actuator
Pneumatic valves are used more and more widely in various industries, and the technology of pneumatic actuators is getting better and better. The gap between domestic pneumatic actuators and imported pneumatic actuators is getting smaller and smaller, and there are more and more types. Several inspection methods for pneumatic actuators are introduced:
1. Fix the pneumatic actuator on the calibration bench, and connect the air source, control air source and displacement detection connecting rod respectively; Accurately adjust the calibration table;
2. Mechanical zero calibration: input 4 ma current signal (0%) 02 mpa, at this time, the stroke of the cylinder piston should be zero; If it is not zero, the zero point can be adjusted by adjusting the nut on the zero screw (the zero point is higher than the nut); The zero point and range need to be adjusted repeatedly; Zero error ≤ 1%;
3. Mechanical full scale calibration: the current signal (100%) of the input 20ma control gas signal is 00% 10mpa, at this time, the stroke of the cylinder piston should be the upper limit; If it is not the upper limit, the range (small spring, large spring) can be adjusted by adjusting the spring tightness; The zero point and range need to be adjusted repeatedly; The full range error shall be ≤ 1%;
4. Range midpoint positioning: after adjusting the zero point and range, input a 12 ma current signal (50%, 0.06 mpa), and adjust the position of the connecting rod of the position transmitter to make it perpendicular to the horizontal plane;
5. Full stroke deviation calibration: input the control gas signal of 0.02 mpa (0%), then gradually increase the input signals of 0.036 mpa (20%), 0.052 mpa (20%), 0.068 mpa (60%), 0.084 mpa (80%), 0.1 mpa (100%) to make the piston travel fully, and the deviation at each point shall be ≤ 1.5%;
6. Nonlinear deviation test: input the control gas signal of 0.02 mpa (0%). 10 mpa (100%). 02 mpa (0%) to make the actuator complete the stroke, and record the increase and decrease every 0 times For the stroke value corresponding to the 008mpa signal pressure, the nonlinear deviation between the actual pressure stroke relationship and the theoretical value should be ≤ 1%; ※
7. Positive and negative stroke variation test: the same as the nonlinear deviation test method, the actual positive and negative pressure - in the stroke relationship, the difference value of the cylinder piston under the same pressure value should be ≤ 1% of the difference value of the cylinder piston;
8. Sensitivity test: when the signal pressure is 0.03.0.06.0.09 mpa, increase and decrease the air pressure in the stroke respectively, and test the large change of the signal pressure change value that starts to move 0.1 mm in the cylinder piston rod, which needs to be ≤ 0.2%;
9. Sealing test of piston cylinder: connect the pressure of 0.5mpa into any air chamber of the cylinder, and then cut off the air source. Within 10 minutes, the pressure drop in the cylinder shall not exceed 0.01 mpa; ※
10. Electrical zero point detection of position transmitter: open the position cover and connect wires; Input 12ma current signal (0.06mpa), at this time, adjust the round eccentric wheel in the transmitter to align the black line with the white line on the circuit board; Then input 4 ma current (0.02 mpa), at this time, adjust the zero potentiometer inside the transmitter, and the output current is 4 ma; The electrical zero error should be ≤ 1%;
11. Electrical full range detection of position transmitter: input 20ma current signal (0.1mpa), at this time, adjust the adjustment range potentiometer in the transmitter to make the output current 20ma; The electrical full range error shall be ≤ 1%;
12. Calibration of the whole stroke deviation of position feedback current: input 4 ma current (0%), and then gradually increase the input signal 8 ma current (25%). 12 ma current (50%). 16 ma current (75%). 20 ma current (100%) is 0%. 50%. 100% feedback current error ≤ 1%, 25%. 75% feedback current error ≤ 2%, taking into account the nonlinear error of linear displacement conversion into angle change;
13. Position feedback current positive and negative stroke difference test: the test method is the same as that of cylinder positive and negative stroke difference test. The actual positive and negative stroke feedback current - in the stroke relationship, the large difference of cylinder piston under the same feedback current value ≤ 1%;
14. Make verification records, carefully fill in the verification record form item by item, and the inspectors must sign;
15. After the above tests are qualified, insert the wiring terminal of the position transmitter, tighten the back cover, and then block the air supply inlet of the valve positioner with a plug.
