pumpkurvor

Pump curves, or pumpkurvor, are graphical representations of a pump’s performance under a specific set of conditions. They show how key operating quantities, such as flow rate, head, efficiency, input power, and required net positive suction head (NPSH), relate to one another for a given speed and fluid.

The main curves include:

- Head (or pressure) versus flow rate: typically a decreasing curve for centrifugal pumps, indicating that the head the pump can generate drops as flow increases. The point where the curve intersects the system’s requirements determines the operating point.

- Efficiency versus flow: shows the efficiency of the pump at different flows, with a peak near the best efficiency point (BEP).

- Power input versus flow: indicates the electrical or mechanical power required at each flow, usually increasing with flow.

- NPSH required (NPSHr) versus flow: the minimum suction head needed to avoid cavitation at each flow.

Reading and interpretation:

- The horizontal axis usually represents flow rate (Q); the vertical axis can represent head (H), efficiency (η), or power (P).

- The shut-off head is the maximum head at zero flow, while the BEP is the flow where efficiency is highest.

- Curves shift with changes in speed or impeller size; higher speeds generally raise head and efficiency but also increase power consumption and NPSH needs.

Applications and use:

- Pump selection and system design rely on matching a pump curve to the system curve (the head required by the piping network at different flows) to determine the operating point.

- Pumps can be arranged in series to increase head or in parallel to increase flow, with combined curves derived from the individual curves.

- Curves are provided by manufacturers and are affected by fluid properties, viscosity, temperature, and wear; NPSH availability must be ensured to prevent cavitation.

Overall, pumpkurvor are essential tools for understanding, selecting, and operating pumping systems in a neutral, evidence-based manner.