Pneumatic actuator is an actuator that relies on air source to drive the valve to open and close. Its actuator and drive mechanism are integral, so the structure is simple and the volume is small. It is widely used in power plants and other occasions with high safety requirements. No matter what equipment it is, it will encounter problems after a long period of use, and pneumatic actuators are no exception.
Common faults and maintenance methods of pneumatic actuators:
Fault 1. After the power is turned on, the voltage indicator light does not light, the servo release board has no feedback, and there is no action for the signal.
Maintenance method: It is necessary to check whether the fuse is open. If it is in good condition, check whether the power supply of the servo release board is in good contact. If it is normal, check the power indicator light. If the indicator light is open, it means that the indicator light is faulty.
Fault 2. After the actuator is energized during operation and debugging, a signal is provided, and the valve can be opened but does not act when it is closed.
Maintenance method: First check the feedback circuit. If there is no fault, the indicator light is on when the signal is turned on, indicating that it is normal. When the signal is turned off, the indicator light does not light, indicating that there is a problem with the thyristor off. Check the indicator light, use a multimeter to check the off indicator light, open circuit, and return to normal after replacing the thyristor.
In general, the selection of pneumatic actuators needs to consider multiple factors, such as the operating conditions of the valve, operating temperature, operating frequency, management and pressure difference, conveying medium (lubrication, drying, mud), etc., in the selection of pneumatic actuators In the process, the main points are as follows.
1. Operating thrust: There are two main structures of the valve electric device: one is not equipped with a thrust plate, and the torque is directly output; the other is equipped with a thrust plate, and the output torque is converted into the output thrust through the valve stem nut in the thrust plate.
2. Operating torque: Select the main parameters of the valve electric device, and the output torque of the pneumatic actuator should be 1.2 to 1.5 times the maximum operating torque of the valve. The moving speed of the pneumatic actuator is quite large. In many cases, when the load increases, the speed of the pneumatic actuator will become very slow, but its output pressure has nothing to do with the operating pressure. A good separation for pneumatic actuators.
3. Stem diameter versus multi-turn rising stem valve: If the large valve stem diameter allowed by the electric device cannot pass through the valve stem of the equipped valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device needs to be larger than the outer diameter of the valve stem of the rising stem valve. For part-turn valves and dark-stem valves in multi-turn valves, although the passage of the diameter of the valve stem does not need to be considered, the diameter of the valve stem and the size of the keyway should also be fully considered when selecting, so that the valve can work normally after assembly.
