What is an important requirement for a centrifugal pump to prevent operational failure?

Priming a centrifugal pump is critical because these pumps cannot effectively move fluid until they are filled with the liquid they are intended to pump. Priming involves removing air from the pump casing and filling it with fluid to create a solid column of liquid, allowing the pump to generate the necessary suction for operation. If the pump is not properly primed before starting, it can lead to cavitation, air locking, and eventual operational failure. This is because the presence of air in the system can prevent the impeller from generating sufficient pressure and flow, causing damage and inefficiency.

The other options do not address the specific operational requirements necessary for a centrifugal pump. Regular lubricating oil checks are important for the motor bearings and other machinery, but they do not directly affect the pump's ability to start and operate effectively. The use of distilled water is not a requirement for all applications; most pumps can handle various types of fluids. Operating under atmospheric pressure can be relevant, but it’s not a strict operational requirement that impacts the start-up of a centrifugal pump. Proper priming is the definitive step needed to ensure that the pump functions correctly and efficiently.