What function does the shaft sleeve serve in a centrifugal pump?

The shaft sleeve plays a crucial role in preventing wear at the stuffing box by acting as a protective barrier between the shaft and the packing material. As the pump operates, the shaft rotates within the stuffing box, where packing material is used to create a seal to prevent leaks. Over time, the constant friction and movement can cause the shaft itself to wear down. By using a shaft sleeve, the surface that experiences this friction is replaceable and less critical than the shaft itself. This design protects the integrity of the shaft and extends the life of the packing by minimizing wear and potential leaks.

In the context of the other choices, the shaft sleeve does not connect the impeller to the motor, nor does it directly circulate water or protect the impeller from damage. Its specific purpose is centered on the protection of the shaft in the stuffing box area.