Failure mode and effects analysis method for subsea manifold leakage based on IVSFSs and AROMAN

Failure mode and effects analysis (FMEA) is widely applied for failure risk assessment in complex systems, yet traditional methods suffer from rigid risk priority number calculation, subjective weighting, and inadequate unce rtainty handling. This study proposes a novel FMEA framework that integrates interval-valued spherical fuzzy sets (IVSFSs) with the Alternative Ranking Order Method Accounting for Two-step Normalization (AROMAN) to evaluate leakage risks in subsea manifold systems. Compared with existing approaches, the proposed method enhances uncertainty modeling, enables more balanced expert opinion aggregation through interval-valued spherical weighted arithmetic mean operator, and improves risk discrimination by combining linear and vector normalization. A hybrid weighting scheme is adopted, incorporating subjective weights from the Simplified Best-Worst Method and objective weights from the Logarithmic Deviation-based Entropy and Criteria Impact method. Seven representative leakage failure modes are evaluated using a structure–mechanism–manifestation mapping model. Results show that valve dynamic seal wear and weld fatigue crack are the most critical modes. Sensitivity and comparative analyses substantiate the reliability and robustness of the proposed approach. This work offers a more interpretable and precise decision-support tool for subsea failure risk prioritization under high uncertainty.