Control valve pressure drop at other flow conditions

3 Control valve pressure drop at other flow conditions [4,5  

Flow through each control valve usually has three difierent capacities maximum, normal, and miniinuin. Hydraulic study is usually either based on maximum flow or normal How. From hydraulic study (without pump or compressor available pressure drop of the control valve at cither condition (case 0) is calculated. The available control valve pressure drop at other two flow conditions (case 1 or 2) can be estimated by following equation  

Once control valve pressure drop at maximum, normal, and minimum flow cases are known. Required valve sizing coefTicient at each flow cases can be calculated. 

Control valve inlet pressure drop of ease 1 or 2 can be calculated using Eq. (18u) or Eq. (18d) below. Eq. (1 c) is used for system without pump or compressor, while Eq. (1 Sd) ts used for systiemi has pump or compiessor. dpiO in Eq. (18c) or Eq. (18d) is the system pressure drop upstream of control valve for case 0. Use calculated dpi to adjust the case 0 control valve inlet pressure for iIk other two cases. 

---