Generally, the basis for selecting the valve electric actuator is as follows: 

1. Operating torque: operating torque is the most important parameter for selecting the valve electric device, and the output torque of the electric actuator shall be 1.2-1.5 times of the maximum operating torque of the valve.

2. There are two main structures for operating the electric device of the thrust valve: one is to output the torque directly without the thrust disk; the other is to configure the thrust disk, and the output torque is converted into the output thrust through the stem nut of the thrust disk.

3. Number of turns of output shaft: the number of turns of the output shaft of the electric device of the valve is related to the nominal diameter of the valve, the valve stem pitch and the number of screw heads, which shall be calculated according to M = H / ZS (M is the total number of turns that the electric device shall meet, h is the valve opening height, s is the valve stem drive screw pitch, and Z is the valve stem screw head).

4. Stem diameter for multi turn open stem valves, if the maximum stem diameter allowed by the electric device cannot pass through the stem of the 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. Although it is not necessary to consider the passing of stem diameter for some rotary valves and concealed stem valves in multi rotary valves, it is also necessary to fully consider the stem diameter and the size of keyway when selecting and matching, so that they 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 proper opening and closing speed should be selected according to different conditions.

6. The electric actuator of the valve has its special requirements, that is, it must be able to limit the torque or axial force. In general, the valve electric device adopts coupling with limited torque. When the specification of the electric device is determined, its control torque is also determined. Generally, the motor will not be overloaded when it runs in a predetermined time.