Which part is NOT typically found in a double suction centrifugal pump?

A double suction centrifugal pump features an impeller that is designed to draw fluid from both sides, effectively enhancing efficiency and flow while minimizing axial thrust. This design element is crucial because it allows the pump to handle larger volumes of fluid with reduced vibrations and operational stress.

In this context, specific components are integral to the design and functionality of double suction pumps. The volute casing is essential as it helps direct the fluid flow efficiently from the pump outlet after passing through the impeller. Thrust bearings are also critical, as they manage the axial loads on the rotor created during operation, helping to stabilize the pump components. Grease seals serve the important purpose of preventing contamination of the pump's internals while maintaining lubrication for moving parts.

In contrast, a single inlet impeller, which draws fluid from only one side, is not characteristic of double suction designs, hence its absence in this type of pump setup. Therefore, the correct answer highlights that this specific part does not align with the operational principles of a double suction centrifugal pump, distinguishing it from its features.