The selection and determination of the caliber are mainly based on the flow capacity of the valve, i.e. cv. In the instrument design and selection of various projects, CV calculation shall be carried out for the regulating valve, and the design specification of the regulating valve shall be provided. From the CV calculation of the electric control valve to the determination of the valve diameter, the following steps are generally required:

1 Determination of calculation flow. The existing production capacity, equipment load and medium condition determine the Qmax and qmin of the calculated flow.

2. Determination of the pressure difference between the front and back of the electric control valve. Select s (resistance coefficient) according to the selected valve flow characteristics and system characteristics, and then determine the calculated pressure difference.

3 calculate Cv. According to the adjusted medium, choose the appropriate calculation formula and chart to obtain Cmax and Cmin.

4) Choose cv. According to Cmax, select the closest level C > Cmax in the selected product standard series.

5) Check the opening of electric control valve. Generally, it is required that the opening at the maximum flow rate shall be no more than 90%, and the opening at the minimum flow rate shall be no more than 10%.

6) Check calculation of the actual adjustable ratio of the electric control valve. Generally, the actual adjustable ratio is ≮ 10.

7) Determination of valve seat diameter and nominal diameter. After verification, confirm according to C.

The selection of electric control valve is a very meticulous work, which requires not only solid professional theoretical knowledge, but also rich practical experience. Good selection is not only conducive to the adjustment of PID parameters of the control loop, so that the adjusted parameters get better control effect, but also greatly increase the service life of the control valve. The selection of control valve should be adapted to local conditions, not unchangeable, and should be summarized and innovated in the process of practice. Especially with the application of mechatronics technology, computer and digital information technology, the structure and function of electric control valve become better and more comprehensive, which provides great convenience for the selection of electric control valve.