Which statement about a centrifugal cargo pump is true?

A centrifugal cargo pump relies on kinetic energy to move fluids, and therefore, it requires a positive pressure at the suction inlet to function effectively. This is due to the nature of centrifugal pumps, which use a rotating impeller to add velocity to the fluid. If a centrifugal pump does not have positive suction (meaning the pressure is below atmospheric pressure), it will not be able to draw fluid into the pump efficiently, leading to cavitation, which can damage the pump and impair its performance.

Positive displacement pumps, on the other hand, work differently by capturing a specific volume of fluid and moving it mechanically. Thus, saying that a centrifugal pump is a positive displacement pump is incorrect, as they operate on different principles.

Regarding rotation speed and discharge pressure, increasing the rotation speed of a centrifugal pump typically increases the discharge pressure, not decreases it. As the impeller spins faster, it imparts more energy to the liquid, increasing both its velocity and pressure at discharge.

Since the only accurate statement regarding a centrifugal cargo pump is that it must have positive suction, this is the correct choice.