Q: How are pump shafts and bearings designed and what impacts the reliability? The pump shaft transmits the torque from the driver and bearings and must carry the torsional, radial and axial loads. Figure 1 shows the normal loads that exist. The magnitude of the loads are dictate by the pump hydraulic design, and where the pump is operated relative to its best efficiency point. The design of the shaft and the bearings will be a function of the loads. For example, higher power pumps will have higher torque loads, and thicker shafts to accommodate, or if high radial loads are unavoidable, the shaft will be thicker, and or the overhang from the bearings will be reduced to limit the deflection that occurs. There are many different bearing designs, and the bearings selected will consider the speed of rotation, and radial and axial reaction forces. If thrust will occur in both directions and again additional design considerations apply.
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