Fuzzy and grey theories in failure mode and effect analysis for tanker equipment failure prediction

Failure Mode and Effects Analysis (FMEA) has been extensively used for examining potential failures in many industries. Unlike the traditional FMEA, the risk factors of occurrence (O), severity (S) and detection (D) of each failure mode are evaluated by linguistic terms and fuzzy ratings in this research, and their relative weights are considered, which make the results more useful and practical. Both grey theory and fuzzy theory are applied in FMEA, in which fuzzy set theory is used to calculate the fuzzy risk priority numbers (FRPNs), and grey theory is applied to calculate the grey relational coefficient. The rankings of the failure modes are both determined by FRPNs and the grey theory. An example of oil tanker equipment failure is provided, and the results show that the evaluation of failure modes by both fuzzy theory and grey theory are quite similar. The practical application of fuzzy and grey theories proposed in this paper helps to enhance the reliability of the prediction, and the predicted ranking of equipment failure can be used for better decision-making concerning inspection and maintenance, which in turn will make tanker shipping more safe and reliable.