Pump systems rely on several characteristic curves to describe how flowrate and pressure behave.
- Pump curve shows the head that a pump can produce at differnet flowrates.
- System curve represents the head that the system requireds as flow variation, combining static head and friction losses.
- Friction curve is the head loss that only due to piping resistance.
- Control curve shows how the operating point shifts as a control device, such as a control vale, or speed adjustment (VSD), modifieds system resistance. This to ensure that the largest pressure drop (at the index terminal unit) have enough pressure for system to properly work.
The intersection of the pump curve and any system curve defines the operating pont – the single point where the pump and system are balanced.
Related notes:
Centrifugal pump characteristic curve – HQ curve
Understanding the pressure profile in open-loop water system
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