Investigation of torsional fatigue failure of a centrifugal pump shaft

Shafts of centrifugal pumps are both load bearing and power transmitting component which are usually composed of martensitic stainless steel. In this paper, an attempt is made to manifest how minute deviations from the standard dimensions of the keyway of a shaft leads to the occurrence of premature torsional fatigue along the keyway seat. Microstructural characterization via optical microscope, SEM and EDS further revealed faulty heat treatment of the material that resulted in inferior mechanical properties which assisted in the accelerated crack propagation and ultimate failure of the shaft within 2.5 years of service leading to a shutdown of blast furnace for approximately 10 h. Comparative material analysis was carried out on samples of shaft from other pumps in service (which has not failed) to manifest that proper heat treatment of the shaft material can bring about desired mechanical properties of component and procrastinate the failure.