CENTRIFUGAL PUMPSFluid FlowSystemCharacteristicCurveFigure 9 Typical System Head Loss CurveIn the chapter on head loss, it was determinedthat both frictional losses and minor losses inpiping systems were proportional to thesquare of the flow velocity. Since flowvelocity is directly proportional to thevolumetric flow rate, the system head lossmust be directly proportional to the square ofthe volumetric flow rate. From thisrelationship, it is possible to develop a curveof system head loss versus volumetric flowrate. The head loss curve for a typical pipingsystem is in the shape of a parabola as shownin Figure 9.SystemOperatingPointFigure 10 Operating Point for a Centrifugal PumpThe point at which a pumpoperates in a given piping systemdepends on the flow rate and headloss of that system. For a givensystem, volumetric flow rate iscompared to system head loss on asystem characteristic curve. Bygraphing a system characteristiccurve and the pump characteristiccurve on the same coordinatesystem, the point at which thepump must operate is identified.For example, in Figure 10, theoperating point for the centrifugalpump in the original system isdesignated by the intersection ofthe pump curve and the systemcurve (hLo).HT-03 Page 52 Rev. 0
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