The correct selection of valve electric devices should be based on:

1. Operating torque: Operating torque is the most important parameter for selecting valve electric devices. The output torque of the electric device should be 1.2-1.5 times the maximum torque for valve operation.

2. Operating thrust: There are two types of main structures for valve electric devices. One type does not have a thrust disc and directly outputs torque; Another type is equipped with a thrust disc, where the output torque is converted into output thrust through the valve stem nut in the thrust disc.

3. Number of turns of output shaft: The number of turns of the output shaft of the valve electric device is related to the nominal diameter, valve stem pitch, and number of thread heads of the valve. It is calculated according to M=H/ZS (where M is the total number of turns that the electric device should meet); H is the opening height of the valve, mm; S is the pitch of the valve stem transmission thread, mm; Z is the number of valve stem thread heads. ）

4. Valve stem diameter: For multi turn open stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through the valve stem of the matched valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the valve stem of the rising stem valve. For some rotary valves and concealed stem valves in multi rotary valves, although the issue of valve stem diameter passing does not need to be considered, the size of the valve stem diameter and keyway should also be fully considered when selecting, so that they can work normally after assembly.

5. Output speed: The opening and closing speed of the valve is fast, which can easily cause water hammer phenomenon. Therefore, appropriate opening and closing speeds should be selected according to different usage conditions.

6. Installation and connection methods: The installation methods of electric devices include vertical installation, horizontal installation, and floor installation; The connection method is: thrust disc; Valve stem passing through (open stem multi turn valve); Multiple rotations of the hidden pole; No thrust disc; The valve stem does not pass through; Partial rotary electric devices have a wide range of applications and are essential equipment for achieving valve program control, self-control, and remote control. They are mainly used in closed-circuit valves. But the special requirements of valve electric devices cannot be ignored - they must be able to limit torque or axial force. Usually, valve electric devices use couplings that limit torque.