Electric actuator is an indispensable device to realize valve program control, automatic control and remote control. Its motion process can be controlled by stroke, torque or axial thrust. Because the working characteristics and utilization rate of electric actuators depend on the type of valve, the device working specifications and the position of the valve on the pipeline or equipment, the correct selection of electric actuators can prevent overloading (the working torque is higher than the control Torque) is critical.

     In general, the basis for the correct choice of electric actuator is as follows:

1.   Operating torque

Operating torque is the most important parameter for selecting the electric actuator. The output torque of the electric device should be 1.2 to 1.5 times the maximum torque of the valve operation.

2.   Operating thrust

There are two main structures of the electric actuator: one is to directly output torque without a thrust disk; the other is to configure a thrust disk, and the output torque is converted to output thrust through the stem nut in the thrust disk.

3.    Output shaft rotation

The number of rotations 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 must be calculated according to M = H / ZS (M is the total number of rotations that the electric device should meet, and H is the valve Opening height, S is the thread pitch of the valve stem transmission thread, and Z is the number of valve stem thread heads).     

4.   Stem diameters

For multi-turn type 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 bright stem valve. For the part of the rotary valve and the multi-turn valve of the dark-stem valve, although the passage of the stem diameter need not be considered, when selecting and matching, the diameter of the stem and the size of the keyway should be fully considered to ensure normal operation after assembly.

5.   Output speed

If the output speed of valve is too fast, water hammer will easily occur. Therefore, the appropriate opening and closing speed should be selected according to different use conditions.