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.
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| Head vs Flow Flat curve |
2. Unstable curve
The same head is developed at more than
one flow rates.
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| 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.
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| Head Vs Flow Stable curve |
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.
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| Head Vs Flow Steep curve |
How to calculate suction head in pump ?
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.
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| 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.
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| Head Vs Flow Drooping curve |
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