Engine Failure Assessment Using Economic Risk Priority Number (ERPN) Approach

Heavy equipment in aluminum smelters operates under harsh thermal and mechanical conditions, leading to increased risks of vehicle failure and unplanned downtime. This study proposes an Economic Risk Priority Number (ERPN) approach to overcome the limitations of the conventional Risk Priority Number (RPN) used in Failure Mode and Effects Analysis (FMEA). A five-year maintenance dataset (2019–2024), comprising 2,303 corrective work orders across 58 units, was analyzed. The classical RPN is approach prioritized failure modes primarily based on frequency, identifying wheels and hydraulic systems as the most critical subsystems. However, the proposed ERPN model incorporates economic impact, including maintenance cost, labor cost, and production loss, leading to a reprioritization of the engine subsystem as the highest-risk component. The most severe engine failure resulted in a financial loss of approximately USD 1.92 million due to extended downtime and repair costs. Root cause analysis identified coolant loss, low oil pressure, and excessive vibration as primary contributors to failure, supported by diagnostic data and repeated alarm patterns. Statistical validation using the Kruskal–Wallis test confirmed significant differences among subsystem risk rankings for both RPN (χ² = 846.07, df = 4, p < 0.0001) and ERPN (χ² = 131.69, df = 4, p < 0.0001). The results demonstrate that ERPN provides a more realistic and economically aligned framework for maintenance prioritization in heavy industrial operations. The proposed approach enhances decision-making by integrating reliability analysis with economic impact, offering a practical tool for improving maintenance strategies and reducing operational risk in aluminum smelter fleets.