How to solve the fault of electric valve positioner? Advantages and disadvantages of electric valve and pneumatic valve

How to solve the fault of electric valve positioner? Advantages and disadvantages of electric valve and pneumatic valve

Electric valve positioner, also known as pneumatic valve positioner, is the main accessories of the regulator, usually used with the pneumatic regulator, it accepts the output signal of the regulator, and then with its output signal to control the pneumatic regulator, when the regulator action, the displacement of the valve stem and through the mechanical device feedback to the valve positioner, valve position through the electrical signal to the upper system. Through more than 20 years of experience accumulation, and technical engineers and electric valve positioner rational analysis combined with a large number of field repair experience, the electric valve positioner fault classification, analysis of the cause of the fault and find out the troubleshooting method, I hope to give the instrument workers in the installation and debugging of the actuator or daily maintenance of electric valve positioner to help.

1. Air source pressure fluctuation of electric valve positioner

Check the air filter pressure reducer, bottom of the water and dirt.

2, the electric valve positioner has an input signal but the output is small or not

Due to excessive adjustment of the trip trimmer screw of the positioner, the coil of the torque motor is unwelded, and the lead can be welded.

Torque motor coil internal wire break or burn out because of overcurrent; Use a multimeter to measure the coil resistance. Normally, it should be about 250. If the deviation from 250 L is too large, replace the coil.

Signal cable contact is poor; Check the wiring terminals to remove loosening.

Signal cable connection is reversed: Check whether the (+)(-) terminal connection is reversed.

Nozzle baffle position is not correct: readjust the parallelism, see the output change.

Loose nozzle fixing screw: tighten the nozzle fixing screw to meet the travel requirements.

The amplifier is faulty; Check whether the amplifier is faulty or replace it.

Pneumatic blockage: Use 0.12 to pass dirt.

Vent blockage: the bottom seat of the locator, there is a nozzle vent, if you do not pay attention to the blockage, the locator will stop working.

Baffle lever connection spring deformation or broken; Open the locator cover and replace it.

Change the pole of the permanent magnet and check whether the valve works.

Feedback lever falls off; Readjust the parallelism and see how the valve works.

Feedback lever range fixed pin skew: Adjust the pin to meet the travel requirements.

The regulating valve with hand wheel is not hit to the middle position; Check the handwheel position safety valve and adjust it to the middle position.

Loose CAM or improper position; Tighten the CAM or readjust the CAM position.

Hydraulic control valve flapper lever spring stiffness is not enough: change (+)(-) polarity wiring, adjust the distance between the flapper and nozzle, meet the travel requirements (then need to change the mode of regulator).

3, electric valve positioner output pressure oscillation

Dirt in an amplifier: Dirt in an amplifier.

Output pipeline or film head leakage: eliminate leakage phenomenon, make the valve smooth operation.

Film head diaphragm aging: replace the aging diaphragm can be.

Permanent magnet diverging error: readjust the parallelism of permanent magnet to eliminate magnetic circuit instability.

Loose screw fixing feedback lever: filter tightening fixing screw to eliminate valve vibration.

Large AC component of input signal: eliminate AC component or parallel a capacitor at the input end. Filter out AC interference.

Back pressure air road has dirt: eliminate dirt, troubleshooting.

Valve rod radial loosening: check the regulating valve.

4, electric valve positioner has no input and output

Backpressure block: Block dirt.

If the position of the automatic and manual switch is incorrect, the automatic and manual switch will be rotated clockwise to the position of the automatic check valve.

5. The accuracy of electric valve positioner is not good

Nozzle, stop plate adjustment is not good: adjust the parallelism or nozzle fixing screw, meet the accuracy requirements.

Gate valve back pressure air leakage; Eliminate air leakage.

The radial displacement of the regulating valve is large: check the regulating valve.

Improper adjustment of the zeroed screw: Adjust the zeroed screw to meet the accuracy requirements.

Feedback lever and fixed pin position discrepancy error: Reset pin position according to travel requirements.

The advantages and disadvantages of the pneumatic valve action distance is larger than the electric valve, the pneumatic valve switch action speed can be adjusted, simple structure, easy to maintain, in the process of action because of the buffer characteristics of the gas itself, not easy to be damaged by jamming, but must have the air source, and its control system is more complex than the electric valve.
Pneumatic valve response is quick, safe and reliable, many factories with high control requirements are designed for pneumatic instrument control elements set up compressed air station. Electric means electric.