Failure analysis and structural fatigue resistance design of multistage centrifugal pump shaft

•Fatigue failure mechanism was elucidated for multi-stage centrifugal pump shaft.•Specific technical measures to prevent pump shaft failure were proposed.•Fatigue resistance design is performed for pump shaft structure and coupling.•Feasibility of the new pump shaft system has been verified by experiment. In the operation of multistage centrifugal pump, the pump shaft of 304 stainless steel is subjected to a variety of alternating loads. It is one of the parts prone to failure. The fracture microscopic observation, chemical composition analysis and mechanical property measurement of the fractured pump shaft are carried out. Through the fracture analysis, it is found that the pump shaft failure is caused by fatigue mechanism with characteristic of multi-source crack initiation, and there are many cavities and inclusions at the fracture. From the numerical analysis, it is found that there is significant stress concentration at the fracture, which exceeds the fatigue limit of the material and eventually leads to the fatigue fracture. Besides, the appropriate fillet radius and elastic coupling are designed for the pump shaft, which can effectively reduce the stress concentration and improve the service life of the pump shaft. Finally, the fatigue life of the improved pump shaft was experimentally verified.