Risk Prioritization of LPG Fuel Use in Maritime Applications: An Experimental Data-Supported FMEA and Entropy-Weighted MCDM Framework

Studies on the use of LPG in maritime applications mostly evaluate emissions, engine performance, or system safety separately; approaches that integrate experimental findings with ship-level risks remain limited. This study aims to evaluate the trade-offs between the environmental advantages of LPG and energy performance and safety requirements within a common decision support framework. In the experimental phase, a single-cylinder gasoline–LPG spark-ignition engine was tested at five LPG mixture ratios and six load levels between 500–3000 W; specific fuel consumption, thermal efficiency, CO, CO₂, and HC were measured. Using legislation, the literature, and engineering evaluation, 38 failure types were identified from the experimental findings and prioritized using FMEA and entropy-weighted multi-criteria decision-making methods. The final ranking was obtained using the Borda method, and inter-method agreement and ranking stability were validated with sensitivity analyses. The results showed that increasing the LPG ratio reduced CO, CO₂, and HC emissions, but higher ratios increased fuel consumption and decreased thermal efficiency. Specific fuel consumption, gas detection error, and thermal efficiency were identified as the three most prioritized risks. The findings reveal that the emission benefits of LPG in maritime applications should be evaluated in conjunction with sensing, insulation, emergency stop reliability, and energy performance. This integrated approach provides a scientific basis for balanced and transparent fuel decisions.