An improved FMEA approach based on interval-valued spherical fuzzy sets and CODAS method for LNG tank safety analysis

The demand for liquefied natural gas (LNG) as an efficient energy source is increasing. Still, its poor pressure resistance makes it prone to hazardous accidents and requires suitable risk assessment methods to identify storage leakage risk. Failure mode and effects analysis (FMEA) is used as an important risk analysis tool to assess the failure modes of tank systems, but the traditional method has the potential to lead to inaccurate evaluation results. This paper proposes an improved FMEA approach based on the interval-valued spherical fuzzy set (IVSFS) and combinative distance-based assessment (CODAS) method for assessing storage safety. The CODAS method determines the risk prioritization, and expert linguistic evaluations are expressed by IVSFSs, which reduces the ambiguity of the evaluation information. The subjective and objective weights of risk factors are obtained by the extended level-based weight assessment (LBWA) and removal effects of criteria (MEREC) methods with IVSFS, respectively, which aggregate into synthetic weights. A new score function for IVSFS is proposed to improve discriminative power and simplify the calculation process. To clearly describe the specific implementation, the method was applied to assess the leakage risk of storage tanks at an LNG receiving terminal in China. The result illustrates that the highest level of risk is the appurtenant pipeline rupture, while the design defect is the lowest level of risk. The sensitivity analyses validated the flexibility of managing uncertain and complex expert assessments. Kendall's rank correlation coefficients and comparative analysis validated the feasibility and high discriminatory power of this approach.