Failure pressure and fatigue analysis of the API 12F shop welded, flat bottom tanks

This study investigates the failure pressure on the API 12F shop welded steel tanks and performs a fatigue evaluation to estimate the permissible number of pressure cycles for these equipment. Four different analyses were carried out on more than 350 finite element models to determine various failure pressure modes of these storage tanks. An elastic analysis considering potential buckling modes was developed to determine the yielding pressure of the tanks. The redistribution of stresses due to inelastic deformations and plastic collapse were evaluated through an elastic-plastic stress analysis considering the plastic hardening of the material. A wind load analysis was performed to evaluate the stress levels at all regions of the tank and estimate the uplift deformations. Moreover, the increase of the design pressure was investigated regarding the stress levels and bottom uplift. Additionally, an elastic stress analysis following the ASME Boiler & Pressure Vessel Code Section VIII, Division 2, Design-by-Analysis rules was implemented to determine the fatigue life of the storage tanks. This research provides engineering calculations to evaluate the current design of the API 12F tanks and the design internal pressures guaranteeing a safe performance of the equipment