1. Operating torque The operating torque is the main parameter for selecting the valve electric device, and the output torque of the electric device should be 1.2 to 1.5 times the larger 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 diameter of the valve stem 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.
