Analysis of boiler efficiency using the direct method and an integrated FMEA–fishbone approach: A case study at an automotive manufacturing plant

Abstract

Frequent boiler failures interrupt the steam supply to the paint-shop pretreatment line of an automotive plant and degrade its energy performance. This study evaluated the efficiency of the most critical boiler at an automotive manufacturing plant and identified the failure modes and root causes behind its decline. A descriptive quantitative case study was carried out on five water-tube boilers from July to August 2024. Boiler No. 1, which accounted for 43.5% of the total downtime (990 min), was selected as the critical unit. Its daily efficiency over 28 operating days was calculated with the direct (input–output) method from log sheet data, steam-table enthalpies, and a natural-gas heating value of 39,120.46 kJ/m³. Failure risks were prioritized with Failure Mode and Effect Analysis (FMEA) using ratings from eight boiler personnel, and the dominant failure was traced with a fishbone diagram. Daily efficiency ranged from 63.3% to 98.4% (mean 87.6%); six days fell below 75%, four of which coincided with misfire interventions. Misfire had the highest risk priority number (RPN = 245), followed by boiler tube leakage and brittle strainer filters (RPN = 96 each). Its causes were distributed across man, method, machine, environment, and system factors. An integrated preventive, corrective, and predictive maintenance strategy is proposed, focusing on gas flushing, air–fuel ratio control, sensor calibration, combustion monitoring, and condition-based maintenance.