The selection and determination of valve diameter

The selection and determination of valve diameter are according to the flow capacity of the regulating valve, in short is CV. The design and selection of variety engineering instruments, should be calculated by CV, and provide regulating valve design instructions.

From the CV valve calculation to determine the caliber of the valve, the CV value and the opening are two conceptual problems, the abroad calls CV, the domestic uses to call KV. KV represents the valve flow capacity, which is defined as: When the regulating valve is fully open, the valve pressure difference at both ends ΔP is 100KPa, fluid gravity r is 1gf / cm3 (i.e. normal temperature water), the flow rate per hour through the regulating valve is calculated by m3/h or t/h dollars.

Generally as the following steps:

1) Calculation of the flow rate. The existing production capacity, equipment load and medium conditions, determine the calculation of flow Qmax and Qmin.

2) The determination of the front and back of valve. According to flow characteristics and system characteristics of the selected valve to determine S (resistance coefficient), and then calculate pressure difference.

3) Calculate CV. According to the adjustment of the medium to choose appropriate calculation formula and charts, and get Cmax and Cmin.

4) Select CV. According to Cmax, select >Cmax and the closest to level C in the selected product standard series.

5) Check the regulating valve opening.  When the opening is ≯90%,the calculation of flow is generally required the maximum, and when the opening ≮10%, the flow is required MIN.

6) Check the actual adjustment of the regulating valve. The general requirements of the actual adjustable is≮ 10.

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

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