H20Calc (Retired)

Pump Characteristic Curve from Innovyze H2OCalc

Pump Characteristic Curve

Pump Characteristic Curve

Pump characteristic curves are usually presented graphically describing the relationship between pump head, hp, and the flow rate, Q using either an exponential equation or 3-point quadratic form. The exponential pump characteristic curve is given as

where hc = the pump cutoff head associated with the zero flow condition (m, ft)

Kp = resistance coefficient

b = flow exponent

nR = pump speed ratio (the ratio of the actual pump speed to the rated pump

speed); for constant speed pump operation, nR is equal to 1.

Given three hp-Q points [hc, (hp,1, Q1), (hp,2, Q2)], the pump curve can be calculated as

If a single rated capacity (hrated, Qrated) is given, two more points can be added to the curve by assuming a shutoff head at zero flow equal to 133% of the design head and a maximum flow at zero head equal to twice the design flow. Then, the curve can be treated as a three-point curve.

The 3-point quadratic type of pump characteristic curve is

where ap, bp, cp are the coefficients of the quadratic curve.

The coefficients are calculated as

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