What loads are applied to a pump's shaft?

• A. Weight of rotating pump parts
• B. Starting and running torque
• C. Hydraulic forces
• D. All of the above

Answer: (D)

The loads on a pump shaft come from three main sources: the weight of the rotating parts, the torque needed to start and run the pump, and the hydraulic forces created by the fluid being pumped. The weight of the rotor and impeller is a vertical load that the bearings must support, contributing to static bearing loading. Starting and running torque are transverse loads transmitted along the shaft as the drive motor provides the power to accelerate and maintain rotation, which also places torsional and bending demands on the shaft and bearings. Hydraulic forces arise from the interaction with the fluid: impeller action generates axial thrust and radial forces, which push on the shaft and bearings as the fluid is accelerated and discharged. Since all of these factors place loads on the shaft, the total loading is the combination of weight, torque, and hydraulic forces.