What can cause poor performance in a centrifugal pump?

Poor performance in a centrifugal pump occurs when air enters the pump. When air is introduced into the system, it disrupts the liquid flow, leading to cavitation, reduced pressure, and ultimately a decrease in the pump's efficiency. The presence of air bubbles can cause the pump to lose its prime, resulting in intermittent operation or complete failure to move the fluid. This is because centrifugal pumps rely on a continuous column of liquid to create suction; air disrupts that column, preventing the pump from generating the necessary pressure to facilitate fluid movement.

In contrast, over-speeding can lead to inefficiencies and even damage to the pump, but it does not directly correlate with poor performance in terms of operation. The correct size impeller is crucial for optimal performance; using an incorrectly sized impeller can lead to operational issues, but that differs from the immediate impact of air entering the system. As for excessive seal water, while it could contribute to operational inefficiencies, it does not fundamentally disrupt the flow of the pump in the same way that air does. Hence, the introduction of air into the pump is a primary factor that consistently results in poor performance.