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Abstract The purpose of this study is to investigate crankcase explosion in two-stroke marine diesel engine systematically by using fault tree analysis method in fuzzy environment for system reliability and shipping sustainability. Maritime accidents might cause deadly and costly results in both human lives, commodities, environmental and financial aspects. Crankcase explosion is one of the most dangerous causalities that might possibly damage both ship structure and crew members. In this study, we determine all root causes of crankcase explosion, and calculate the probabilities in a stepwise manner by implementing field expert consultations. As a result, we find that the occurrence probability of the crankcase explosion is 1.249428E-007 which is close to real case. Bearing originated hot spots and personnel failures are also found as the most risky events. Highlights • Root causes and structure of crankcase explosion are investigated in this study. • Fuzzy fault tree analysis method is firstly applied to analyze crankcase explosion. • The probability of crankcase explosion is found as 1.25E-07. • The riskiest event chain is determined as MCS1 (BE11, UE and BE4). • Underlying reasons of crankcase explosion are explained, and suggestions are given. [ABSTRACT FROM AUTHOR]

• Maintenance risks in a two-stroke marine diesel engine were investigated. • FAHP method was used to rank maintenance risks. • Critical maintenances and physical dimensions resulted in higher risk rankings. Maintenance activities in ship machineries are of vital importance due to economical and operational requirements. Most of ships in commercial activities have two-stroke marine diesel engines (MDEs) in the propulsion systems. Durability of the commercial activities depends on the stable operation of the main engine in the ship propulsion system. This phenomenon shows the importance of maintenance activities in the two-stroke MDEs. In this study, 46 identified maintenance activities in the two-stroke MDEs were investigated via fuzzy analytical hierarchy process (FAHP) method considering risk magnitudes. The results revealed that critical maintenance activities and physical dimensions of the parts have higher risk rankings. It was also achieved from the research that top and lowest risky maintenances are the overhaul of the turbocharger (T1) and dismantling and mounting of safety valve (C5), respectively. [ABSTRACT FROM AUTHOR]