Requirements for explosion-proof electric actuators:
1. When the actuator performs manual operation, in order to provide the regulator with automatic tracking basis (tracking is the need for non-disturbance switching), there should be a valve position tracking signal on the actuator. This is not only the need for position feedback of the actuator itself, but also the need for valve position indication.
2. There should be enough torque for the actuator whose output is transfer, and enough force for the actuator whose output is linear displacement, so as to overcome the resistance of the load. Especially for high-temperature and high-pressure valves, the sealing and packing pressure is relatively tight. After a long time of closing, it often takes more force to open than normal. As for the action speed, it is not necessarily high, because the flow adjustment and control do not need to be too fast. In order to increase the output torque or force, the output shaft of the motor has a reducer. If the motor itself is low-speed, the reducer can be simpler.
3. In order to protect the valve and transmission mechanism from being damaged due to excessive operating force, there should be a limit device and a force or torque limit device on the actuator.
4. The transmission system of the reducer or motor should have self-locking characteristics. When the motor does not rotate, the unbalanced force of the load (such as the weight of the gate valve) cannot cause changes in the rotation angle or displacement. Therefore, a worm gear mechanism or an electromagnetic brake is often used. With such measures, in the event of an unexpected power failure, the valve position can be maintained at the position before the power failure.
5. In the event of a power failure or a regulator failure, it should be possible to manually operate the actuator in order to take emergency measures. To do this, a clutch and handwheel are required.
In addition to the above basic requirements, in order to facilitate coordination with various valve characteristics, it is best to have optional nonlinear characteristics on the actuator. In order to cooperate with the computer, it is best to directly input digital signals. In recent years, there are also actuators with PID operation function, which are the so-called "digital actuators" and "intelligent actuators".
