In general, the basis for the correct selection of valve electric actuators is as follows:
1. Operating torque: The operating torque is the most important parameter for selecting the electric device of the valve. The output torque of the electric actuator should be 1.2 to 1.5 times the maximum torque of the valve operation.
2. There are two mainframe structures for operating the thrust valve electric device: one is to directly output torque without a thrust disk; the other is to configure a thrust disk, and the output torque is converted into output thrust by the stem nut in the thrust disk.
3. The number of rotations of the output shaft: the number of rotations of the output shaft of the valve electric device is related to the nominal diameter of the valve, the thread pitch of the valve stem, and the number of thread heads, which should be calculated according to M = H / ZS The total number of rotations, H is the opening height of the valve, S is the thread pitch of the stem drive thread, and Z is the number of thread heads of the stem).
4. Valve stem diameter For multi-turn type open stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass the valve 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 greater than the outer diameter of the stem of the open stem valve. For part-turn valves and concealed-rod valves in multi-turn valves, although there is no need to consider the passage of the stem diameter, the stem diameter and keyway size 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, it is easy to produce water hammer. Therefore, the appropriate opening and closing speed should be selected according to different use conditions.
6. Valve electric actuators have their special requirements, that is, they must be able to limit torque or axial force. Valve electric devices usually use couplings that limit torque. When the specifications of the electric device are determined, its control torque is also determined. Generally run within a predetermined time, the motor will not be overloaded.