Investigating the structural integrity, fitness-for-service (FFS) and the remaining lifetime of a corroded storage tank, subjected to structural buckling under fluid loading at various fill heights

This study presents a comprehensive Level 3 Fitness-For-Service (FFS) assessment of a 12.803-m-high aboveground storage tank affected by localized wall thinning and structural buckling. A finite element framework was developed to explicitly capture the synergistic effects of corrosion-induced thickness loss and geometric instability under realistic operating loads. The analysis was conducted for two representative fluid fill heights (8 and 10 m) to evaluate the structural stability and functionality limits of the tank. The results demonstrate that neglecting the interaction between corrosion and buckling can lead to non-conservative integrity assessments. While the tank exhibited loss of stability and inability to sustain the applied loading at a 10 m fill height, stable behavior and acceptable structural performance can be achieved at an 8 m fill height, indicating a safe operational limit under current conditions. In addition, the remaining service life of the tank was estimated using inspection-based corrosion data, corresponding to an average corrosion rate of 0.25 mm/year. Based on the allowable minimum wall thickness criterion, the remaining lifetime was estimated to be approximately 4 years. The proposed methodology provides a practical and robust decision-making framework for evaluating degraded storage tanks, enabling risk-informed operational limits, preventive maintenance planning, and life-extension strategies in industrial applications.