The selection and determination of the caliber is mainly based on the flow capacity of the valve, namely Cv. In the instrument design and selection of various projects, the Cv calculation of the regulating valve must be carried out, and the regulating valve design specification should be provided. From the calculation of the Cv of the electric control valve to the determination of the valve diameter, the following steps are generally required:
1 Calculate the determination of the flow rate. The existing production capacity, equipment load and medium conditions determine the Qmax and Qmin of the calculated flow.
2 Determine the pressure difference before and after the electric control valve. Select S (resistance coefficient) according to the selected valve flow characteristics and system characteristics, and then determine and calculate the pressure difference.
3Calculate Cv. Choose appropriate calculation formulas and charts according to the adjusted medium to obtain Cmax and Cmin.
4) Choose Cv. According to Cmax, select the first level C> Cmax and the closest to it from the selected product standard series.
5) Check the opening of the electric control valve. Generally, it is required that the opening at the maximum calculation flow is ≯90%, and the opening at the minimum calculation flow is ≮10%.
6) Checking calculation of actual adjustable ratio of electric control valve. Generally, the actual adjustable ratio is required to be ≮10.
7) Determination of valve seat diameter and nominal diameter. After verification is appropriate, determine according to C.
The selection of electric control valves is a very meticulous work, which requires not only solid professional theoretical knowledge, but also rich practical experience. A good choice is not only conducive to the adjustment of the PID parameters of the control loop, so that the adjusted parameters get better control effects, but also greatly increases the service life of the control valve. The choice of regulating valve should be tailored to local conditions, not static. It should be continuously 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 regulating valve become better and more comprehensive , It provides great convenience for choosing electric control valve.