Please anyone who know suggest me with below information ;1. What is the difference meaning between the pressure drop and differential pressure of control valve?2. When making a hydraulic calculation example for transfer liquid with pump,how can we know the suitable pressure drop of control valve to gain the good control? I mean it should be estimated first and included in the pressure loss in pipe or it can be calculated from different pressure of performance curve and system curve of pump at rated flow rate. 3. The suitable pressure drop of control valve mentioned in 2, is it come from rated flow, maximum flow or ?4. When sizing of control valve, shall we use pressure drop or differential pressure?1.Differential pressure is the same as pressure drop. P1 (inlet) -P2 (outlet = DP2. A guideline is for the valve to take 1/3 of the system pressure drop in its wide-open position. If the pump puts out 100 psi, and the system pressure must be 40 psi, then the system pressure drop is 60, and the valve should drop at least 20. 3. Max flow. At min flow the system drop goes away (proportional to Q^2) so essentially ALL the DP is taken by the valve. 4. Sometimes.DP and Pressure drop are the same but they are not the ONLY motive force to consider. For flow at greater than critical pressure drop (also known as choked flow) the sizing is done on the choke drop. This, by definition will be less than the actual drop, but the flowrate becomes independent of downstream pressure when the DP exceeds critical. The term "Choked Flow" tends to scare people. It's just a point where you use a different equation. Open the valve more and you get more flow. Increase inlet pressure and you get more flow. You just won't get any more flow by lowering the outlet (downstream) pressure.

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