Publish Time: 2021-07-28 Origin: Site
Valve electric actuator is an indispensable device for realizing valve program control, automatic control and remote control. Its movement process can be controlled by stroke, torque or axial thrust. The correct selection of valve electric devices is essential to prevent overload (working torque is higher than control torque). What are the basis for the correct selection of valve electric actuators?
The basis for correct selection of valve electric actuator
1. Operating torque: The operating torque is the most important parameter for selecting the valve electric device. The output torque of the electric actuator should be 1.2 to 1.5 times the maximum valve operating torque.
2. There are two main structures for operating the thrust valve electric device: one is not equipped with a thrust plate, and the torque is directly output; the other is with a thrust plate, and the output torque is converted into output thrust through the stem nut in the thrust plate.
3. The number of turns of the output shaft: the number of turns of the output shaft of the valve electric device is related to the nominal diameter of the valve, the pitch of the valve stem, and the number of thread heads. It should be calculated as M=H/ZS (M is what the electric device should meet the total number of turns, H is the opening height of the valve, S is the thread pitch of the valve stem, and Z is the number of stem threads).
4. If the maximum stem diameter allowed by the electric device cannot pass through the 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 must be larger than the outer diameter of the stem of the rising stem valve. For part-turn valves and dark-stem valves in multi-turn valves, although the passage of the stem diameter does not need to be considered, the stem diameter and the size of the keyway should also be fully considered when selecting, so that it can work normally after assembly.
5. Output speed: If the opening and closing speed of the valve is too fast, water hammer will easily occur. Therefore, the appropriate opening and closing speed should be selected according to different conditions of use.
6. Electric valve actuators have their special requirements, that is, they must be able to limit torque or axial force. Usually the valve electric device uses a torque limiting coupling. When the specifications of the electric device are determined, the control torque is also determined. Generally run within a predetermined time, the motor will not be overloaded.
7. When the power supply voltage is low, the required torque cannot be obtained, and overload occurs, we should use a thermostat for the overload protection of the motor continuous operation or jog operation; for the protection of the motor stall, use a thermal relay ; For short-circuit accidents, use fuses or overcurrent relays.
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