Stochastic Reliability and Economic Performance of a Rotary Kiln: A Semi-Markov and Regenerative-Point Case Study

This paper presents a stochastic reliability, availability, maintainability and economic analysis of a Rotary Kiln used in cement manufacturing. The model is based on 170 event records observed over 3,666 h from July to November 2025. The kiln is represented as a repairable multi-state system with normal, degraded, partial-failure, complete-failure, inspection and preventive-shutdown conditions. Estimated degradation, partial-failure and complete-failure intensities are 0.014150, 0.012920 and 0.005537 h-1, respectively. The semi-Markov and regenerative-point model gives a mean time to system failure of 233.734 h, reliability of 0.9030 at 24 h and 0.6635 at 96 h, and steady-state operational availability of 0.905892. Major repairs are the main maintainability constraint: repair completion within two hours is 0.3387 for major repair compared with 0.9019 for minor repair. Complete failures generate 42.96% of event-related cost. A coordinated improvement scenario reduces failure intensities, accelerates repair, increases inspection moderately and reduces unnecessary preventive shutdowns, it raises 96-h reliability to 0.7284, availability to 0.928343 and long-run profit from INR 125,238.84 to INR 134,217.84 per hour. The results support condition-based intervention, major-repair readiness and PLC-supported early detection.

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