Pump Curves - 6 Types of head vs flow rate curves

1. Flat curve

Shows little variation of head at all flows between design point & shut-off. When a system consists of mostly Static Head or Static Pressure difference, it is termed a flat system curve.

Head vs Flow Flat curve

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2. Unstable curve

The same head is developed at more than

one flow rates.

Head vs Flow
Unstable curve

3. Stable curve

Only one flow rate at any one head.It is called stable if it exhibits a continuously negative slope (negative differential quotient from head and flow with regard to the Q axis.

Head Vs Flow
Stable curve

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4. Steep curve

Large increase in head developed at shut-off from B.E.P. When a system consists of mostly frictional resistance it is termed a steep system curve. With a steep curve, we can notice a steeper arch, resulting in a larger head (pressure) increase as the flow decreases, compared to the Steadily rising Curve.

Head Vs Flow
Steep curve

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5. Steadily rising curve

Head rises continuously from design point to shut-off. The head (pressure) increases continually as capacity is decreased, and you move to zero flow.

Head Vs Flow
Steadily rising curve

6. Drooping curve

Head developed at shut-off is less than head developed at some flow between B.E.P & shut-off. This curve shape is unstable in the area where there are two flows where the head (pressure) can be the same, in the low flow portion of the pump curve.

Head Vs Flow
Drooping curve

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