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How to select an electric control valve?

Issuing time:2023-06-08 23:40

The selection of electric control valves can be considered from the following aspects:

1、 From the medium aspect of the control process, (1) the shape and structure of the valve core are mainly considered based on factors such as the selected flow characteristics and unbalanced forces. (2) Due to the corrosiveness of the medium, it is recommended to choose valves with a simple structure as much as possible while meeting the regulatory function. (3) When the temperature and pressure of the medium are high and have significant changes, valves with valve cores and valve seats that are subject to small temperature and pressure changes should be selected. (4) Wear resistance: When the fluid medium is a suspension containing high concentration of abrasive particles, the valve core and valve seat joint surface will experience severe friction every time they close. Therefore, the flow path of the valve should be smooth, and the internal material of the valve should be hard. (5) Prevent flash evaporation and cavitation. Flash evaporation and cavitation only occur in liquid media. In the actual production process, flashing and cavitation not only affect the calculation of flow coefficient, but also form vibration and noise, which shortens the service life of the valve. Therefore, when selecting a valve, flashing and cavitation should be prevented.

2、 From the perspective of output force, in order to ensure the normal operation of the regulating valve, the actuator used should be able to generate sufficient output force to overcome various resistance, ensure high sealing and valve opening. For double acting pneumatic, hydraulic, and electric actuators, there is generally no return spring. The magnitude of the force is independent of its operating direction, therefore, the key to selecting an actuator is to understand the output force and the rotational torque of the motor. For single acting pneumatic actuators, the output force is related to the opening of the valve, and the force appearing on the regulating valve will also affect the motion characteristics. Therefore, it is required to establish force balance throughout the entire opening range of the regulating valve.

3、 Considering the characteristics of the regulating valve, the flow characteristics of the regulating valve refer to the relationship between the relative flow rate of the medium flowing through the valve and the displacement (relative opening of the valve). The ideal flow characteristics mainly include four types: straight line, equal percentage (logarithmic), parabola, and fast opening. The commonly used ideal flow characteristics are only straight line, equal percentage (logarithmic), and fast opening. The parabolic flow characteristic is between a straight line and an equal percentage, and can generally be replaced by an equal percentage characteristic. The quick opening characteristic is mainly used in binary regulation and program control, so the selection of regulating valve characteristics is actually the selection of straight line and equal percentage flow characteristics. 5、 The selection and determination of the regulating valve diameter are mainly based on the valve's flow capacity, i.e. Cv, when considering the diameter of the regulating valve. When designing and selecting instruments in various engineering projects, it is necessary to calculate the Cv of the regulating valve and provide a design manual for the regulating valve.

4、 Select the diameter and material of the electric control valve based on pressure, medium, and flow rate

5、 Select voltage

6、 Choose whether the electric actuator is explosion-proof or not, or its explosion-proof level and protection level

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