Simply put, the electric valve is to use an electric actuator to control the valve, so as to realize the opening and closing of the valve. It can be divided into upper and lower parts, the upper part is the electric actuator, and the lower part is the valve. It can also be called an air-conditioning valve.

Electric valve is a product of automatic control valve. It can not only realize the switching function, but also the regulating type electric valve can realize the function of valve position adjustment. The stroke of the electric actuator can be divided into two types: 90° angular stroke and straight stroke. Special requirements can also meet the full stroke of 180°, 270°, and 360°. The quarter-stroke electric actuator is used in conjunction with the quarter-stroke valve to realize the internal rotation of the valve within 90° to control the on-off of the pipeline fluid; the straight-stroke electric actuator is used with the straight-stroke valve to realize the up and down movement of the valve plate to control the on and off of the pipeline fluid. 

The following points should be paid attention to when choosing electric valve: 

1. The operating torque is the main parameter for selecting the valve electric device. The output torque of the electric device should be 1.2 to 1.5 times of the 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 according to M=H/ZS (M is the total amount that the electric device should meet The number of turns, H is the opening height of the valve, S is the thread pitch of the stem drive thread, and Z is the number of stem thread heads). 

4. Valve stem diameter For multi-turn rising stem valves, if the large 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 be fully considered when selecting and matching, so that it can work normally after assembly. 

5. If the opening and closing speed of the output speed 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. The valve electric device has its special requirements, that is, it must be able to limit the torque or axial force. Usually the valve electric device adopts a torque-limiting coupling. When the specifications of the electric device are determined, its control torque is also determined.