Structural verification of an oil-cutting tank affected by corrosion and differential settlements

Resumo

Crude oil cutter tanks are essential components in the hydrocarbon production process. In Argentina's
Patagonia region, these metal tanks sit over a concrete platform, which may be affected by differential settlements
caused by uneven compaction of the soil or damage by unexpected water flow. Additional damage can occur due
to corrosion originated by the emulsifying mixture stored in the tank. This work analyzes the structural behavior
of an oil cutter steel tank with evidence of damage due to localized corrosion and differential settlements and its
structural response under wind loads. The analysis is implemented by modeling the tank with a multipurpose finite
element code following three scenarios: tank without damage, tank damaged by corrosion measured by thickness
reduction and unevenness obtained by surveying work, and progress of deterioration. Simulation results are
compared with measurements carried out on a real tank using non-destructive tests. Results show that the
equilibrium paths are non-linear, with clear signs of instability. The presence of imperfections, such as reduced
thicknesses and vertical settlements, diverts the structure from the undamaged configuration and bifurcation
buckling for much lower load levels. Reduced wall thicknesses and differential settlements generate stress
concentrations that increase the deterioration of the structure.