Centrifugal pump operating point and flow adjustment

Centrifugal pump operating point and flow regulation First, the working point Centrifugal pump characteristic curve is the inherent characteristics of the pump itself, it has nothing to do with the outside world. However, once the pump is arranged to work in a given piping system, its actual operation depends not only on the characteristics of the centrifugal pump itself but also on the operating characteristics of the piping. Therefore, to select and make good use of centrifugal pumps, we must also take into account the characteristics of the pipeline. When liquid is delivered in a particular line, the pressure head He required for the line varies with the square of the flow rate Qe. The relationship drawn on the paper coordinates that is the corresponding pipeline characteristics curve. If the centrifugal pump characteristic curve and its pipeline characteristics plotted on the same coordinate paper, the intersection of two lines M is called the pump operating point. Select the pump, the required operating point corresponding to the flow and pressure head can meet the requirements of the piping system, but also happens to be provided by the centrifugal pump, that Q = Qe, H = He. Second, the flow control (1) to change the valve opening to change the centrifugal pump outlet pipeline valve switch, its essence is to change the pipeline characteristics curve. When the valve is closed, the local resistance of the pipeline increases, the pipeline characteristic curve becomes steeper, the working point moves from M to M1, and the flow rate decreases from QM to QM1. When the valve is open, the pipe resistance decreases, the pipeline characteristic curve becomes flat, the working point moves to M2 and the flow rate increases to QM2. With the valve to adjust the flow quickly and easily, and the flow can be continuous changes, suitable for chemical continuous production characteristics. Therefore, a wide range of applications. The disadvantage is the valve off hours, increased resistance loss, increased energy consumption, not very economical. (2) to change the pump speed to change the pump speed is essentially to change the pump characteristic curve. The original pump speed is n, the working point is M, if the pump speed is increased to n1, the pump characteristic curve H - Q moves upward, the working point moves from M to M1, and the flow rate increases from QM to QM1. If the speed of the pump is reduced to n2, the operating point is shifted to M2 and the flow rate drops to QM2. This method of adjustment requires variable speed devices or expensive variable speed prime mover, and difficult to achieve continuous adjustment of flow, it is rarely used in chemical production.