A Hybrid Fuzzy Probabilistic Risk Assessment Framework with Expert Based Simulator Feasibility Assessment for Chemical Tanker Cargo Operations

This study proposes a sequential hybrid framework integrating the Fuzzy Delphi Method (FDM), Fuzzy DEMATEL, and Fault Tree Analysis (FTA), complemented by an expert-based simulator scenario feasibility assessment for chemical tanker cargo operations. Its contribution lies in the traceable integration of uncertainty-based risk screening, causal interaction analysis, explicit accident pathway modelling, and operational scenario representability. A two-round FDM involving twelve maritime professionals with seagoing experience as ship masters or watchkeeping officers and current maritime sector involvement identified twenty critical risk factors. Fuzzy DEMATEL characterised their directional influence relationships and informed an expert reviewed FTA structure, with logical gates assigned according to operational failure mechanisms. Self-reactive cargo thermal runaway (C2.5), inadequate tank segregation (C2.4), and cargo tank radar and sensor failures (C3.4) had the highest expert-estimated relative occurrence likelihoods. The FTA yielded a model-based relative top event likelihood of 0.7353, a semi-quantitative indicator rather than an empirical accident probability. Local sensitivity analysis identified C2.5 as the most influential of the selected basic events. Three experts independently assessed scenario representability, operator response measures, and recovery criteria in the TRANSAS LCHS 2000 Chemical/Product Tanker simulator. Cargo monitoring, atmosphere control, and overfilling scenarios were supported, whereas cargo transfer feasibility depended on simulator configuration. Temperature escalation was retained only as a conditional precursor representation because detailed chemical reaction behaviour could not be consistently reproduced. The framework supports risk informed safety prioritisation and future simulator scenario design.