This is called System Head Curve. Pump curve supplied by the manufacturer indicates the increase in total head that takes place between the suction and delivery nozzles of a pump expressed in m.
However a pump operates in some systems where it has to overcome pipeline and pipe fittings resistance measured in meters. It is also known as pipeline characteristic.
Total head consists of there components at a defined discharge.
1) Static Head or static pressure dereference in m.
2) Friction losses in m (pipe and fittings losses).
3) Discharge (exit) velocity head in m (Vd2/2g).
The summation of these components constitute total head, H in m.
Pipeline Losses
Here we will consider point 2 in depth as it is a varying component related to the flow rate. The component is also called System Head (S.H). This plays an important role in determining total head H of the site under consideration.
When friction head is plotted against the discharge, a parabolic curve is obtained. Its because friction head varies as the square of the discharge. This curve is called System Resistance Curve (S.R). But popularly known as System Head Curve (S.H). This curve represents the relation between the pipe friction and flow rate. Reference plan for SH is taken as static head. Please refer fig. With increase in flow, resistance in the pipeline also increases. Hence a parabolic curve starts from the reference line i.e. static head.
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