Influence of different storage tank bunding configurations on the dispersion of flammable vapour cloud generated by an overfilling incident

The high risk associated with storage tanks is due to the high volumes of substances stored and their hazardous characteristics. Loss of containment events may result in severe consequences. For this reason the implementation of effective protective measures, such as bunding systems, are essential to mitigate potential damage. This work investigates how different bund configurations affect the dispersion of a flammable vapour cloud generated by a tank overfilling scenario. The analysis was performed using computational fluid dynamics (CFD), considering an overfilling event similar to the 2005 Buncefield accident. Unlike previous studies, both cascade and pool evaporation were modelled simultaneously using a wall-film approach. Results show that neglecting pool evaporation significantly underestimates vapour generation, with evaporated mass increasing from 11.8% to 66.6% when the pool contribution is included. An extensive parametric study of bund configurations was conducted varying the tank–wall distance, bund wall height, number of tanks, basin burial, anti-overtopping deflectors, and wind direction. Bund geometry was found to significantly affect both source term and damage distances. Increasing the bund wall height from 1.8 m to 3.6 m reduces LFL/2 damage distances by about 45%. Conversely, complete burial of the basin may increase damage distances by up to 9% due to reduced turbulence and mixing. Anti-overtopping deflectors reduce damage distances by roughly 20%, while frontal wind conditions increase them by more than 20%.