With the widespread use of scotch yoke pneumatic actuator, the technology of scotch yoke pneumatic actuator in China is getting better and better. Before using the pneumatic actuator of the fork, the correct inspection method can help us to make an effective judgment. Next, Beijing Ruitou, to talk with you about the inspection methods and standards of the scotch yoke pneumatic actuator.
1) Pneumatic actuator calibration preparation and appearance inspection
1. All test instruments should be electrified and preheated 30 minutes in advance.
2. The pressure of the test gas source should be 0.6+0.1Mpa,;
3. There is no obvious damage to the exterior of the actuator, no obvious flaw in the air-guide copper pipe and the assembly is firm.

4. The length of the connecting screw of the position transmitter must meet the technical requirements of the type of the actuator to be inspected; the plane formed by the connecting rod fastened on the transmitter shaft and the connecting screw should be perpendicular to the horizontal plane;

2) Inspection standards and methods for pneumatic actuators
1. Fix the pneumatic actuator mechanism on the calibration table, connect the air source, control the air source and displacement detection connecting rod respectively, and adjust the instrument on the calibration table accurately.
2. Mechanical zero point calibration: input 4mA current signal (0%) and control gas signal should be 0.02Mpa, at which time the stroke of cylinder piston should be zero; if not, zero point can be adjusted by adjusting the nut on the zero adjusting screw (zero point is higher than the tight nut); zero point and range need to be adjusted repeatedly; zero error should be less than 1%;
3. Full-range calibration of machinery: input 20 mA current signal (100%) and control gas signal should be 0.10 Mpa, at which time the stroke of cylinder piston should be the upper limit value; if not, the range can be adjusted by adjusting the elasticity of the range tension spring (the range is smaller, the range is larger, the tension spring); zero point and the range need to be adjusted repeatedly; the full-range error should be less than 1%;
4. Medium point positioning of mechanical range: after zero point and range adjustment, input 12 mA current signal (50%, 0.06 Mpa) to adjust the position of the connecting rod of the position transmitter so that it is perpendicular to the horizontal plane at this point;
5. Full-stroke deviation calibration: input control gas signal 0.02Mpa (0%) and then gradually increase input signal 0.036, Mpa (20%), 0.052, Mpa (20%), 0.068, Mpa (60%), 0.084, Mpa (80%), 0.1, Mpa (100%) to make the cylinder piston complete stroke, the deviation of each point is less than 1.5%.
6. Nonlinear deviation test: input control gas signal 0.02 Mpa (0%) and then gradually increase the input signal until 0.10 Mpa (100%) and then reduce the signal to 0.02 Mpa (0%) so that the actuator can complete the stroke. The non-linear deviation between the actual pressure-stroke relationship and the theoretical value should be less than 1%;
7. Measurement of positive and negative stroke variation: The maximum difference between positive and negative stroke values of cylinder piston under the same pressure value should be less than 1% in the relationship between positive and negative pressure and stroke, which is the same as that of non-linear deviation measurement.
8. Sensitivity test: Increase and decrease the pressure at the signal pressure of 0.03, 0.06 and 0.09 Mpa respectively, and test the change of signal pressure required when the cylinder piston rod begins to move 0.1 mm, the maximum change is less than 0.2%.
9. Sealing test of piston cylinder: Put 0.5 and Mpa pressure into any air chamber of the cylinder, then cut off the gas source. Within 10 minutes, the pressure drop in the cylinder should not exceed 0.01 and Mpa;
10. Electrical zero detection of position transmitter: open the upper cover of position transmitter and connect the wire; input 12 mA current signal (0.06, Mpa), then adjust the circular eccentric wheel in the transmitter to align the black line above the circuit board with the white line; then input 4 mA current (0.02, Mpa), then adjust the zero potential in the transmitter to make the output current 4 mA; The error should be less than 1%.
11. Full-range electrical detection of position transmitter: input 20 mA current signal (0.1, Mpa), then adjust the range potentiometer in the transmitter to make the output current 20 mA; the full-range electrical error should be less than 1%;
12. Full-range deviation calibration 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%) and 20 mA current (100%). Considering the non-linear error of linear displacement conversion to angle change, 0%, 50%, 100% feedback current error should be less than 1%, 25%, 75% feedback current error should be less than 2%.
13. Measurement of positive and negative stroke variation of position feedback current: The maximum difference of positive and negative stroke value of cylinder piston under the same feedback current value is less than 1% in the actual relationship between positive and negative position feedback current and stroke, which is the same as that of cylinder piston.
14. Make a good verification record and fill it in carefully one by one according to the contents of the verification record form. The inspector must sign it.
15. After the above tests are completed and qualified, the inner terminal of the position transmitter should be inserted, the back cover tightened, and then the gas source inlet of the valve positioner should be blocked with a plastic plug.
Above is a summary of some problems about the scotch yoke pneumatic actuator, which is met by Beijing Ruitou's editor according to the actual work of the merchants, for reference only.