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Electric valves are simply controlled by electric actuators to achieve the opening and closing of valves. It can be divided into two parts: the upper part is an electric actuator, and the lower part is a valve.
Electric valve device is an indispensable device for realizing valve programming, automatic control, and remote control. Its movement process can be controlled by the magnitude of stroke, torque, or axial thrust. Due to the fact that the operating characteristics and utilization of electric valve devices depend on the type of valve, the operating specifications of the device, and the position of the valve on the pipeline or equipment, the correct selection of electric valve devices is crucial to prevent overloading (working torque higher than control torque).
Generally, the basis for the correct selection of electric valve devices is as follows:
Operating torque Operating torque is the main parameter for selecting an electric valve device, and the output torque of the electric device should be 1.2 to 1.5 times the large operating torque of the valve.
There are two main structures for operating thrust electric valve devices: one is to directly output torque without configuring a thrust disc; The other is to configure a thrust disk, where the output torque is converted into output thrust through the valve stem nut in the thrust disk.
The number of turns of the output shaft of an electric valve device is related to the nominal diameter of the valve, the pitch of the valve stem, and the number of thread heads. It should be calculated as 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 thread pitch of the valve stem transmission thread, and Z is the number of thread heads of the valve stem).
If the opening and closing speed of the output speed valve is too fast, it is easy to generate water hammer phenomenon. Therefore, appropriate opening and closing speeds should be selected based on different usage conditions. Electric valve devices have special requirements that must be able to limit torque or axial force. Generally, electric valve devices use torque limiting couplings. When the specification of the electric device is determined, its control torque is also determined. Generally, the motor will not be overloaded when operating for a predetermined time. However, overload may occur if the following conditions occur:
One is that 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 so that it is greater than the stopping torque, resulting in continuous excessive torque generation, causing the motor to stop rotating;
The third is intermittent use, resulting in heat accumulation that exceeds the allowable temperature rise of the motor;
The fourth is that due to some reason, the circuit of the torque limiting mechanism malfunctions, resulting in excessive torque;
The fifth is that the operating ambient temperature is too high, which relatively reduces the thermal capacity of the motor.
