Root Cause Analysis and Reliability Improvement of Steel Car Wheel Derailment in LD1 Steelmaking Operations

Root Cause Analysis and Reliability Improvement of Steel Car Wheel Derailment in LD1 Steelmaking Operations Soumyajyoti Majumder, Himangshu S. Mandal Tata Steel Limited, Jamshedpur-831001, India Soumyajyoti Majumder : [email protected] Himangshu S. Mandal : [email protected] Abstract This paper presents a detailed root cause failure analysis (RCFA) of a derailment incident involving a Vessel-2 steel car at LD1 steelmaking operations. The derailment resulted in significant production loss and operational delay. Through systematic investigation involving mechanical inspection, dimensional analysis, metallurgical evaluation, and design comparison, the study identifies wheel collar damage induced by skewness, inadequate heat treatment, rail hardness mismatch, and legacy design limitations as primary contributors. Corrective, preventive, and long-term reliability improvement measures are proposed to enhance steel car performance and operational safety. Keywords Steel car derailment, wheel collar failure, skewness, rail-wheel interaction, RCFA, steel plant logistics 1. Introduction Steel cars play a critical role in steelmaking logistics by transporting molten steel from vessels to ladle furnaces and crane handling zones. Reliability of these cars is essential to avoid production disruptions. Despite standard maintenance practices, LD1 steel cars have historically exhibited shorter wheel life compared to LD2 and LD3. This paper documents a derailment incident and presents a technical analysis aimed at identifying failure mechanisms and improving system reliability. 2. Incident Description On 25 November 2024, the South-East and North-East wheels of Vessel-2 steel car at LD1 derailed, causing more than 24 hours of operational delay and loss of 31 heats. CCTV footage indicated no abnormal operational behavior. Initial inspection revealed severe dust accumulation on the track and significant wheel collar damage. 3. Observations and Data Collection Key observations included intact wheel bearings, cracked and worn wheel collars, severe track contamination, and damaged rail segments. Dimensional measurements taken prior to failure indicated higher deformation in the wheels that subsequently derailed. Wheel center distance measurements revealed a 13 mm mismatch, indicating skewness in the wheel assembly. 4. Failure Analysis 4.1 Mechanical Factors Skewed wheel alignment caused frequent contact between wheel collars and rails, accelerating collar wear. Damaged rail tracks further intensified impact loading. 4.2 Metallurgical Factors Chemical composition of the wheels met drawing requirements; however, surface hardening was absent. Inhomogeneous microstructure indicated improper heat treatment, leading to reduced fatigue strength. 4.3 Rail-Wheel Compatibility LD1 uses MRS 192 rails with higher hardness compared to previously used A150 rails. The hardness mismatch between wheel and rail accelerated wheel wear. 4.4 Design Limitations LD1 steel cars employ an older axle box guide and spring suspension design prone to wearinduced skewness. In contrast, LD2 and LD3 cars use improved designs with average wheel life of 3–5 years, whereas LD1 wheels last only 3–6 months. 5. Root Causes The derailment was primarily caused by wheel collar failure due to skewness. This was aggravated by poor wheel heat treatment, excessive rail hardness, damaged track condition, and an inherently skew-prone legacy steel car design. 6. Recommendations Corrective actions include replacement of axle box guides with proper alignment and rail replacement in damaged areas. Preventive measures include enhanced SAP PM inspections, in-situ hardness checks, improved wheel discard criteria, supplier quality feedback, and track cleaning solutions. Long-term recommendations include upgrading LD1 steel cars to newer designs and exploring AI-based derailment detection systems. 7. Conclusion This study highlights the importance of holistic analysis encompassing mechanical alignment, material quality, rail compatibility, and design robustness. Implementing the recommended actions is expected to significantly improve wheel life, reduce derailment risk, and enhance operational reliability at LD1. Acknowledgements The authors acknowledge the contributions of LD1 Mechanical Maintenance, Scientific Services, and Shared Services Technology Group for their support during investigation and analysis. References Internal Investigation Report: TSL/OSSTG-TSJ/INV/2759/25, Tata Steel Limited, 2025.