Which fire pump has a clearance issue between the impeller hub and housing?

The clearance issue between the impeller hub and housing is characteristic of a centrifugal pump. In centrifugal pumps, the impeller rotates within the casing, and precise alignment is critical. If the clearance between the impeller hub and the housing is not properly maintained, it can lead to inefficiencies, increased wear, and operational issues. This is because any excessive clearance can cause a drop in performance due to the loss of efficiency in fluid transfer and potential cavitation.

Other types of pumps, such as piston pumps, rotary vane pumps, and rotary gear pumps, operate on different principles and typically do not exhibit the same clearance-related issues between a hub and a housing. For instance, piston pumps rely on a reciprocating action and typically have tight tolerances but do not have an impeller setup where clearance is a critical concern. Similarly, rotary vane pumps and rotary gear pumps have their own design mechanisms that minimize the impact of clearance between components, focusing instead on volumetric efficiency and pressure generation.