Test methods for pneumatic actuators
Pneumatic valve is more and more widely used 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 the types are becoming more and more. Several inspection methods of pneumatic actuators are introduced:
1. Fix the pneumatic actuator on the calibration table and connect the air source respectively. Control air source and displacement detection connecting rod; Accurately adjust the calibration table;
2. Mechanical zero calibration: input 4mA current signal (0%).02mpa, at this time, the cylinder piston stroke should be zero; If it is not zero, the zero can be adjusted by adjusting the nut on the zero screw (the zero is higher than the tight nut); The zero point and range need to be adjusted repeatedly; Zero error ≤1%;
3. Mechanical full-scale calibration: input 20mA current signal (100%).10mpa, at this time, the cylinder piston stroke should be the upper limit; If it is not the upper limit, adjust the range by adjusting the tightness of the range spring (small range, large range); The zero point and range need to be adjusted repeatedly; Full range error ≤1%;
4, range point positioning: zero and range after tuning, input 12mA current signal (50%, 0.06mpa), adjust the position of the transmitter connecting rod, so that it should be kept perpendicular to the horizontal plane at this point;
5. Full stroke deviation calibration: The input control gas signal is 0.02mpa(0%).036mpa(20%).0.052mpa(20%).0.068mpa(60%).0.084mpa(80%).0.1mpa(100%), so that the piston goes the complete stroke, the deviation of each point is necessary ≤1.5%;
6. Nonlinear deviation test: Input control air signal 0.02mpa(0%), and then gradually increase the input signal until 0.10mpa(100%), and then reduce the signal to 0.02mpa(0%), so that the actuator goes through the complete stroke, and record the stroke value corresponding to the increase or decrease of 0.008mpa signal pressure. The nonlinear deviation between the actual pressure ━ stroke relation and the theoretical value should be less than 1%; does
7 forward and reverse stroke variation test: the same as the nonlinear deviation test method, the actual forward and reverse pressure ━ in the stroke relationship, the cylinder piston in the same pressure value of the larger difference should be less than 1% of the larger difference between the cylinder piston;
8. Sensitivity test: the signal pressure is 0.03.0.06.0.09mpa in the stroke, increase and decrease the pressure, test in the cylinder piston rod began to move 0.1mm signal pressure change value of the larger change needs to be less than 0.2%;
9. Piston cylinder seal test: connect the pressure of 00.5mpa to any air chamber of the cylinder, then cut off the air source. Within 10 minutes, the pressure in the cylinder shall not exceed 0.01mpa; does
10. Position transmitter electrical zero detection: open the position cover, connect the wire; Input 12mA current signal (0.06mpa), at this time, adjust the circular eccentric wheel in the transmitter, so that the black line on the circuit board and the white line alignment; Then input 4mA current (0.02mpa), at this time, the transmitter internal adjustment of zero potentiometer, the output current is 4MA; Electrical zero error should be ≤1%;
11. Position transmitter electrical full scale detection: input 20mA current signal (0.1mpa), at this time, can adjust the transmitter in the adjusting range potentiometer, so that the output current is 20MA; Electrical full range error should be ≤1%;
12. Position feedback current entire stroke deviation calibration: input 4mA current (0%), and then gradually increase the input signal 8MA current (25%). 12mA current (50%). 16MA current (75%). Current (100%) is 0%.50%.100% feedback current error ≤1%, 25%.75% feedback current error ≤2%;
13 position feedback current positive and negative stroke difference test: and the cylinder positive and negative stroke difference test method is the same, the actual positive and negative stroke feedback current ━ in the stroke relationship, the cylinder piston in the same feedback current value of the larger difference ≤1%;
14. Make the verification record, fill in the verification record form item by item carefully, and the inspector must sign;
15. After the above test is qualified, the terminal of the position transmitter should be inserted, tighten the back cover, and then plug the air source inlet of the valve positioner with a plug;
