pumpeevnen

Pumpeevnen, or pumping capacity, describes the ability of a pump to move a fluid against the resistance of a connected piping system. It is most commonly expressed through the pump’s performance curve, which shows how the discharge flow rate Q varies with the head H that the pump develops at a given operating speed. In practice, engineers select a pump for a target flow at the required head, or specify the head the system must provide for a given flow.

Key features of the pump curve: as head increases, flow decreases; the curve starts at the shut-off head (maximum head at zero flow) and ends near zero head at maximum flow. Efficiency η is also plotted, and there is a region near the best efficiency point (BEP) where the pump operates most economically.

Performance curves are obtained under standardized test conditions and published by manufacturers; standards such as ISO 9906 are used in many cases. The actual operating point is the intersection of the system curve (head vs. flow in the piping network) with the pump curve.

Several factors influence pump capacity: pump type (centrifugal vs positive-displacement), impeller geometry and size, speed, and the liquid properties (density, viscosity, temperature). System resistance from pipes, fittings, valves, and static head determines the head that must be overcome. Cavitation can reduce effective head; adequate net-positive suction head (NPSH) is required.

Applications span water supply, heating and cooling, irrigation, and industrial processes. In design and operation, the pump is chosen to meet the required Q at the system head while operating near its BEP for efficiency. Oversizing or undersizing can lead to poor performance or energy waste.