Views: 219 Author: Site Editor Publish Time: 2021-05-05 Origin: Site
Some special valves require emergency opening or closing under special circumstances. The fail safe electric valve actuators can prevent the danger from spreading further and minimize the loss of the factory. For some high-pressure large-diameter valves, the required actuator output torque is very large. At this time, the required actuator must improve the mechanical efficiency and use a high-output motor, so that the large-diameter valve can be operated smoothly. For some small torque valves, small electric valves are also used, which have the advantages of lighter weight, compact structure, and complete functions compared with ordinary types.
Rotary valves include seacock valves, mini ball valves, triple offset butterfly valves, and dampers or baffles. This type of valve requires an actuator that has the required torque to perform a 90-degree rotation operation.
Multi-turn valves can be non-rotating poppet stems or rotating non-lifting stems, or they require multiple rotations to drive the valve to the open or closed position. Such valves include in line ball valve (stop valve), gate valve, knife gate valve, etc. As an option, a hydraulic pneumatic cylinder or membrane actuator with linear output is also used to drive the above valves.
1. The fault phenomenon is that after powering on the electric actuator, it is found that the power indicator does not light up, the servo board has no feedback, and the signal does not act.
The fault judgment and maintenance process is as follows. Because the power indicator does not light up, first check whether the fuse is open. After checking that the fuse is intact and the fault phenomenon is comprehensive, it can be inferred that the fault may occur in the power supply part of the servo board. Then check the power indicator, use a multimeter to detect that the indicator is open, replace the indicator and troubleshoot.
An open circuit of the power indicator will cause the entire servo board to not work.
1. Another fault phenomenon is that after the actuator of the electric actuator is energized, the signal can be turned on, but it will not work. There are two types of electric actuators, part-turn electric valve actuator and multi-turn electric valve actuator.
The fault judgment and maintenance process is as follows. First check the feedback circuit carefully to confirm that the feedback signal is not faulty. The on indicator light is on when the on signal is given, indicating that the on is normal. The off indicator does not light up when the off signal is given, indicating that there is a problem with the off SCR part. First check the off indicator, use a multimeter to detect that the off indicator is open, replace it and eliminate the fault.
The thyristor does not work when the off and on indicator lights are off (open circuit).
1. After the electric actuator is energized, a signal is given. For example, the actuator will open to the end and then return to the designated position.
First of all, it is necessary to judge which of the servo board and the actuator has a problem.
When encountering the above failure phenomena, first determine which part of the failure occurred, and finally determine the root cause.
2. After the actuator is energized, give the closing signal (4mA) the actuator fully open and then fully closed.
First remove the servo amplifier board, directly power on the actuator and find that the original fault still exists. Check the resistance, the resistance value is normal, indicating that the resistance is OK. Check the motor windings and find that the resistance is normal and the motor is no problem. It is inferred from the fault that the capacitor may be bad, replace the capacitor again and eliminate the fault.
When this problem occurs, first suspect the resistance and capacitance.
1. The direction of action of the motor operated valve actuator is not controlled by the servo board.
First, let the user use a multimeter to detect the two current-limiting resistors and the phase-shifting capacitor and the winding resistance of the motor. The three factors that affect the steering of the actuator are the windings of the motor itself, the current-limiting resistor and the phase-shifting capacitor.
2. As long as the AC220V power supply is supplied on site, the protection switch will act immediately (trip), and the actuator fuse has been burned.
The final solution is to replace the new brake and motor, install the fuse of the servo board, re-debug and resume normal operation.
3. The movement direction of the actuator is not controlled by the input signal.
First check that the two current-limiting resistors and phase shifting capacitors are not abnormal. Check the winding resistance of the motor with a multimeter. It is found that the resistance value of the motor is 1.45MΩ (and changes from time to time), indicating that the motor windings are wrong. The final solution is to replace this motor.
