Centrifugal Pumps in Parallel

As the inlet and the outlet of each pump shown in figure below are at similar points in the system, each pump must generate the same pump head. The sum flow rate in the system, though, is the sum of the separate flow rates for each pump.

Figure: Pump characteristic curve for two identical Centrifugal Pumps used in parallel

Whenever the system characteristic curve is consider with the curve for pumps in parallel, operating point at the intersection of the two curves symbolizes a higher volumetric flow rate than for a single pump and a greater system head loss. As shown in figure below, a greater system head loss takes place with the raised fluid velocity resultant from the raised volumetric flow rate. Since of the greater system head, the volumetric flow rate is really less than twice the flow rate attained by using a single pump.

Figure: Operating point for two parallel Centrifugal pumps