Operational risk assessment of ballasting and de-ballasting on-board tanker ship under FMECA extended Evidential Reasoning (ER) and Rule-based Bayesian Network (RBN) approach

Ballasting and de-ballasting operations play a critical role in maintaining stability and safety onboard tanker vessels. The process involves considerable risks to human health, the marine environment and property since the failures during the operation may lead to loss of equipment, serious balance defection and related safety problems, and harm to the coastal ecosystems. In this context, this paper aims to fill the gap concerning this problem by analyzing the operational risks of ballasting and de-ballasting performed on tanker ships. It is utilized a robust methodological approach, Failure Mode Effects and Criticality Analysis (FMECA) to provide a detailed insight into operational hazards, and Evidential Reasoning (ER) and Rule-based Bayesian Network (RBN) to tackle with limitations of FMECA by evaluating the hazards' importance degrees. The highest-ranked risks are found as "unsynchronized cargo and ballast operation" with a crisp risk value of 50.59 and "excessive list during cargo operation" with 47.08 crisp risk value, while the least crisp risk valued (21.94) failure is "undetected blockage of air vents". Besides its robust theoretical background, the paper provides valuable insights to tanker officers, shipowners, safety and technical inspectors to minimize risks and enhance safety at the operational level onboard tanker vessels.