Risk evaluation of ship-to-ship transfer of cargo operations by applying PFMEA and FIS

The ship-to-ship (STS) transfer of cargo operations are increasingly safe procedures, nevertheless they remain difficult and complex operations. The adverse effects of a potential accident demands a detailed and thorough work on risk and safety analysis for the transfer operations. In the light of the above, the Process Failure Mode and Effects Analysis (PFMEA) which is a branch of the traditional Failure Mode an d Effects Analysis (FMEA), is applied in combination with a Fuzzy Inference System (FIS) methodology to evaluate different risk scenarios of STS transfer of cargo operations. Although PFMEA is currently applied mainly to manufacturing processes, the aim of the paper is to implement this methodology to the ship-to-ship transfer of cargo. A significant advantage of the PFMEA is the analytical review of the STS operations. Nevertheless, serious drawbacks such as the fact that different combinations of the three implemented risk constituents may lead to the same Risk Priority Number (RPN) or the determination of the relative importance among the three risk factors of the PFMEA namely the likelihood of occurrence (O), the severity of a failure (S), and the ability to detect the potential failure (D), make the PFMEA weak and ineffective. To deal with the aforementioned weaknesses a fuzzy inference system (FIS) based on Mamdani's methodology, is applied as a remedy. The objective of this paper is to assess and evaluate different hazardous scenarios in an STS transfer operation implementing the PFMEA in combination with a FIS. To do so, a team of experts with relative experience with respect to STS transfer operations evaluated certain hazardous scenarios that have derived by the study of several guidelines and recommendations regarding these operations. The paper concludes with interesting insights emerged by the aforementioned tasks.