Precautions for installation of electric valves

The operating force distance of the electric valve is larger than that of ordinary valves. The switching speed of the electric valve can be adjusted. It has a simple structure and is easy to maintain. It can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. During the operation of traditional pneumatic valves, due to the buffering characteristics of the gas itself, they are not easily damaged by getting stuck, but they must have a gas source, and their control system is more complicated than that of electric valves.

The electric device of the electric valve is one of the devices used to operate the valve and connected to the valve. The device is driven by electricity, and its movement process can be controlled by stroke, torque or axial thrust. The working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specifications of the device and the position of the valve on the pipeline or equipment. Therefore, it is important to master the correct selection of valve electric devices and consider preventing overload (working torque higher than control torque) from occurring.

The correct selection of electric devices should be based on

1. Operating torque: 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 the maximum operating torque of the valve.
2. Operating thrust: There are two main structures of the valve electric device. One is without a thrust plate, in which case the torque is output directly; the other is with a thrust plate, in which the output torque is converted into output thrust through the stem nut in the thrust plate.
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 valve stem pitch, and the number of thread heads, and is calculated according to M=H/ZS (where: M is the total number of rotations that the electric device should satisfy; 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 rising stem valves, if the large 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 larger than the outer diameter of the valve stem of the rising stem valve. For partial-turn valves and concealed-stem valves in multi-turn valves, although the passage of the valve stem diameter does not need to be considered, the valve stem diameter and keyway size should also be fully considered when selecting and matching, so that they can work normally after assembly.
5. Output speed: The valve opens and closes very quickly and is prone to water hammer. Therefore, the appropriate opening and closing speed 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 methods are: thrust plate; valve stem passing (rising stem multi-turn valve); concealed stem multi-turn; no thrust plate; valve stem does not pass; partial-turn electric devices are widely used and are indispensable equipment for realizing valve program control, automatic control and remote control. They are mainly used on closed-circuit valves. But the special requirements of the valve electric device cannot be ignored - it must be able to limit the torque or axial force. Usually valve electric devices use couplings that limit torque.