How should a pump handle air when dealing with centrifugal versus positive displacement?

In the context of centrifugal and positive displacement pumps, it is important to understand the mechanics of how each type of pump operates, particularly concerning their ability to handle air.

Positive displacement pumps are fundamentally designed to move a specific volume of fluid with each cycle or stroke. This means that they can effectively handle varying viscosities and can even progress air in certain configurations, such as in diaphragm or gear pumps. This unique functionality arises from their mechanism, which traps a volume of fluid (or gas) and forces it downstream. Therefore, they can be effective for situations where air may be present in the fluid, as they can compress air and move it through the system.

In contrast, centrifugal pumps rely on the kinetic energy derived from a rotating impeller to move the fluid. Air can cause significant issues for centrifugal pumps because they are not designed to compress fluids or gases. When air enters a centrifugal pump, it can lead to cavitation, which is the formation of vapor bubbles that can greatly reduce pump efficiency and even damage the pump. Consequently, while centrifugal pumps are not typically designed to pump air, they can handle minor air entrapment provided it's not excessive.

The answer stating that only positive displacement pumps can effectively handle air captures the essential difference between the two types