Integrated Fuzzy MCDM Frameworks in Risk Prioritization of Failure Modes

Failure Modes and Effects and Criticality Analysis (FMECA) is a widely adopted proactive risk assessment and prioritization approach among the reliability and safety engineers. According to AS/NZS IEC 60812:2020, the associated risk of a failure mode is expressed in terms of a risk priority number (RPN)—a product of three risk factors. However, in case of unavailability and/or inability to obtain the field data, the risk factors are often subjectively assessed by a team of cross-functional experts, which are later translated into crisp values by employing predefined and customized scales on risk factors. These subjective and/or crisp evaluations contain some inherent uncertainties, that can negatively impact on proper risk ordering of failure modes. To overcome some of the limitations of the traditional approach, this chapter describes two novel integrated multi-criteria decision-making (MCDM) frameworks by employing the concepts of type-1 fuzzy sets/fuzzy sets and interval type-2 fuzzy sets (IT2FSs). The IT2F-decision-making trial and evaluation laboratory (IT2F-DEAMTEL) method is adopted to calculate the weights as well as causal dependencies among the risk factors. These weights are further utilized in two MCDM methods (viz., modified multi-attributive ideal real comparative analysis (fuzzy MAIRCA), and modified fuzzy measurement of alternatives and ranking according to compromise solution (fuzzy MARCOS)), which are solely aimed at risk ranking of failure modes. To validate the ranking abilities of the integrated frameworks, a FMECA case study on process plant gearbox is considered. Finally, the validations of the obtained ranking results are performed by comparing the outputs with other popular fuzzy MCDM methods and through detailed sensitivity analyses.