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<p>A discharge pulley shaft used in pellet plant failed prematurely within one month of service, despite an increase in shaft diameter from 250 to 320&#xa0;mm intended to enhance load-carrying capacity. The failure consistently initiated at the keyway region under normal operating conditions. A systematic failure investigation was conducted using visual examination, chemical analysis, microstructural characterization, ASTM E45-based inclusion assessment, hardness testing, and SEM-based fractographic and EDS analyses. The failed EN8 steel shaft was compared with an identical reference shaft supplied by the original equipment manufacturer that demonstrated satisfactory long-term performance. The failed shaft exhibited elevated sulfur content and a low Mn/S ratio (~21), resulting in inferior steel cleanliness and higher inclusion ratings, particularly sulfide and oxide–sulfide inclusions. Both shafts displayed a normalized ferrite–pearlite microstructure; however, the failed shaft showed a lower pearlite fraction and reduced hardness (~191 BHN) compared to the reference shaft (~213 BHN), indicating diminished fatigue resistance. Fractographic examination confirmed fatigue as the dominant failure mechanism, with crack initiation at the keyway edge promoted by cyclic impact and fretting due to improper key–shaft fit. SEM–EDS analysis revealed a higher concentration of complex oxide-rich surface deposits near the crack initiation region, acting as preferential sites for fatigue crack nucleation. The study concludes that the premature failure was primarily caused by geometric stress concentration and cyclic impact at the keyway due to improper key–shaft fit, while inferior metallurgical quality and elevated inclusion content acted as secondary factors that accelerated fatigue crack initiation. The findings emphasize that geometric modification alone is insufficient to ensure reliability and that strict control of steel chemistry, cleanliness, heat treatment condition, and keyway design is essential for fatigue-critical rotating components.</p>

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Failure Analysis of a Conveyor Discharge Pulley Shaft in Pellet Plant

  • 期刊论文

  • 发表日期：

    2026年3月28日

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  • Dhanraj Patil,
  • J. N. Mohapatra,
  • Ramakanth Pujar,
  • D. Satish Kumar

摘要

A discharge pulley shaft used in pellet plant failed prematurely within one month of service, despite an increase in shaft diameter from 250 to 320 mm intended to enhance load-carrying capacity. The failure consistently initiated at the keyway region under normal operating conditions. A systematic failure investigation was conducted using visual examination, chemical analysis, microstructural characterization, ASTM E45-based inclusion assessment, hardness testing, and SEM-based fractographic and EDS analyses. The failed EN8 steel shaft was compared with an identical reference shaft supplied by the original equipment manufacturer that demonstrated satisfactory long-term performance. The failed shaft exhibited elevated sulfur content and a low Mn/S ratio (~21), resulting in inferior steel cleanliness and higher inclusion ratings, particularly sulfide and oxide–sulfide inclusions. Both shafts displayed a normalized ferrite–pearlite microstructure; however, the failed shaft showed a lower pearlite fraction and reduced hardness (~191 BHN) compared to the reference shaft (~213 BHN), indicating diminished fatigue resistance. Fractographic examination confirmed fatigue as the dominant failure mechanism, with crack initiation at the keyway edge promoted by cyclic impact and fretting due to improper key–shaft fit. SEM–EDS analysis revealed a higher concentration of complex oxide-rich surface deposits near the crack initiation region, acting as preferential sites for fatigue crack nucleation. The study concludes that the premature failure was primarily caused by geometric stress concentration and cyclic impact at the keyway due to improper key–shaft fit, while inferior metallurgical quality and elevated inclusion content acted as secondary factors that accelerated fatigue crack initiation. The findings emphasize that geometric modification alone is insufficient to ensure reliability and that strict control of steel chemistry, cleanliness, heat treatment condition, and keyway design is essential for fatigue-critical rotating components.