How to Choose Valve Electric Device Correctly

Valve electric devices are indispensable equipment for achieving valve programming, automatic control, and remote control, and their movement process can be controlled by the magnitude of stroke, torque, or axial thrust. Due to the working characteristics and utilization rate of valve electric devices, they depend on the type of valve, the operating specifications of the device, and the position of the valve on the pipeline or equipment. Therefore, the correct selection of valve electric devices is crucial to prevent overloading (working torque higher than control torque).

How to Choose Valve Electric Device Correctly

1. Operating torque

The operating torque is the most important parameter for selecting the valve electric device, and the output torque of the electric device should be 1.2~1.5 times the maximum operating torque of the valve.

2. Operating thrust

There are two main structures for valve electric devices: one is to output torque directly without a thrust disc; Another option is to configure a thrust disc, where the output torque is converted into output thrust through the valve stem nut in the thrust disc.

3. Number of output shaft revolutions

The number of turns of the output shaft of the valve electric device is related to the nominal diameter, valve stem pitch, and number of thread heads of the valve, and should be calculated according to M=H/ZS (M is the total number of turns that the electric device should meet, H is the valve opening height, S is the valve stem transmission thread pitch, and Z is the number of valve stem thread heads).

4. Stem diameter

For multi turn open stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through 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 rising stem valve. For non rising stem valves in partial rotation valves and multi rotation valves, although the diameter of the valve stem does not need to be considered, the size of the valve stem diameter and keyway should also be fully considered during selection to ensure normal operation after assembly.

5. Output speed

If the opening and closing speed of the valve is too fast, it is prone to water hammer phenomenon. Therefore, the appropriate opening and closing speed should be selected based on different usage conditions.

Valve electric devices have special requirements, that is, they must be able to limit torque or axial force. Usually, valve electric devices use torque limiting couplings. After the specification of the electric device is determined, its control torque is also determined. Generally, it runs within a predetermined time and the motor will not overload. But if the following situations occur, it may lead to overload: firstly, the power supply voltage is low and the required torque cannot be obtained, causing the motor to stop rotating; The second is to mistakenly set the torque limiting mechanism to exceed the stopping torque, causing continuous excessive torque generation and causing the motor to stop rotating; The third is intermittent use, which generates heat accumulation that exceeds the allowable temperature rise of the motor; Fourthly, due to some reason, the circuit of the torque limiting mechanism malfunctions, resulting in excessive torque; Fifthly, the operating environment temperature is too high, which relatively reduces the Heat capacity of the motor.

In the past, the methods of protecting motors were to use fuses, overcurrent relays, thermal relays, thermostats, etc., but each of these methods had its own advantages and disadvantages. There is no absolutely reliable protection method for variable load equipment such as electric devices. Therefore, various combinations must be adopted to induce