because Displacement sensor Generally, there are two, so when one is found to be broken, the aviation plug of the broken one can be pulled out, and the maintenance can be carried out when the machine stops. If both are broken, they must be replaced online. For general hydraulic motor, the following operation steps are carried out:
1. DEH makes the valve position command of the hydraulic servo motor zero.
2. Tighten the stop valve of the hydraulic servo motor, and the valve will close accordingly.
3. Put the straight line Displacement sensor Pull out the aviation plug, loosen the screw fixing the sensor and the nut on the pull rod, replace with a new displacement sensor, and fix the sensor again, and plug in the aviation plug. Note: the fixing screw must be tightened.
4. Connect the pull rod and align the scale on the pull rod with the end face of the sensor. This is the initial zero position.
5. Open the stop valve, give a signal to the servo valve to make the valve fully open, and adjust the initial value and maximum value of VCC card in DEH device.
Note: in this process, the power circuit should be considered according to the actual situation.
6. After the VCC card is adjusted, it can be closed-loop to check whether the valve position jitters. If there is jitter, you need to pull out the VCC card and use the extension board to adjust the oscillator frequency in the VCC card. See the replacement and adjustment section of VCC card for details.
7. For main steam valve, medium pressure main steam valve or medium pressure control valve of 300 MW unit, these valves are normally fully open. When replacing the linear displacement sensor, keep the valve (hydraulic servo motor) fully open.
8. Fix the aluminum tube of the new displacement sensor, pull the sensor by hand, and roughly adjust the LVDT zero position and full degree in VCC according to the original fully open and fully closed position of hydraulic servo motor to meet the indication requirements. After adjustment, fix the sensor rod to put the sensor into closed loop.