Failure Analysis of the Luffing Cylinder Bracket in a Stacker Cum Reclaimer

This investigation report details the failure of a luffing cylinder bracket on a Stacker Cum Reclaimer (SCR) at Tata Steel's RMM facility on November 8th, 2024. The catastrophic failure resulted in partial SCR collapse. The investigation, conducted by the team, revealed a complete fracture of the bracket, initiating from a sharp edge lacking adequate support. Site observations and analysis of the fracture surface indicated crack propagation from the bottom of the bracket. While standard maintenance practices were followed and operational parameters remained within acceptable limits, a finite element analysis (FEA) revealed critical stress concentrations in the original design, particularly at the unsupported sharp edge of the top bracket cover. A subsequent, field-applied modification to the design—the addition of an external support plate—exacerbated the issue due to inadequate welding and a sharp edge, further increasing stress concentrations and leading to failure.

The root cause was determined to be inadequate design of the initial bracket, compounded by deficiencies in the field-applied modification. The FEA highlighted stress concentrations in the unsupported portion exceeding 202 MPa under operational loads. The investigation proposes corrective actions, including replacement of the damaged bracket and the addition of properly designed stiffeners to both brackets according to a modified design. This modified design, incorporating additional external support plates, reduced the maximum stress significantly, mitigating future risk. The report also recommends preventive measures, such as installing pressure transmitters and implementing a more rigorous inspection checklist, to enhance operational safety and prevent similar incidents. A detailed why-why analysis is provided to support these findings and recommendations.