Module 2 ยท Centrifugal Pumps
Pump Curves
A shows how a pump is expected to perform at different flows.
The main curve usually relates flow and head at a stated speed and impeller size. Other lines may show efficiency, power, and the minimum suction condition needed. The shows how the piping system resists flow.
The is where the pump curve and system curve meet. The Hydraulic Institute's preferred operating region for most centrifugal pumps is about 70 to 120 percent of the best efficiency point (BEP) flow. Changing speed, impeller size, or system resistance moves that point. A throttled valve raises system resistance. A changes pump speed.
Use the correct curve for the actual pump. A curve from a similar model can mislead. Operators do not need to design the system, but they should understand why a pump may produce less flow when discharge pressure rises.
Exam Need to Know
- Operating point = where pump curve meets system curve.
- Throttling raises system resistance; a VFD changes pump speed.
- Rising discharge pressure can mean less flow from a centrifugal pump.
Exam area: Equipment