5, the choice of caliber valve
The choice of valve diameter and the main basis for determining the flow capacity of valve that is Cv. In a variety of engineering design and selection of instruments, the valve must be calculated Cv and provide manual control valve design. Cv from the regulating valve to the valve diameter calculated to determine the general subject to the following steps:
1) determine the flow calculation. The existing production capacity, equipment and medium load conditions, decided to calculate flow Qmax and Qmin.
2) the determination of differential pressure valve before and after.
Valve has been chosen in accordance with the flow characteristics and system characteristics of the selected S (drag coefficient), and then calculating the pressure difference to determine.
3) calculation of Cv. According to the regulation of the media choose the right formula and charts to obtain Cmax and Cmin.
4) choice of Cv. According to Cmax, in the standard series of products to choose select> Cmax level and its nearest C.
5) check valve opening. General requirements for calculation of the flow at the time of the largest opening ≯ 90%, the smallest at the time of calculation of the flow opening ≮ 10%.
6) regulating valve of the check than the actual adjustable. Generally require more than the actual adjustable ≮ 10.
7) valve seat diameter and the determination of nominal diameter. The right to verify, in accordance with C determined.
6 Conclusion
The choice of valve is very meticulous work, we not only need a solid theoretical knowledge of the profession, but also have rich practical experience. Choice is not only conducive to good-conditioning control loop tuning of PID parameters so that the parameters were adjusted to get a better control effect, but also the life of valve increase greatly. Select regulating valve in line with local conditions, not static, it is necessary to the process in practice and innovation, constantly sum up, in particular with the mechanical-electrical integration technologies, computers and digital information technology, the structure and function regulating valve to get better, more comprehensive, for the selection of control valve provides a great convenience.
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