Effect of mitigation on the catastrophic failure of storage tanks

Abstract

This work investigates the effect of incorporating mitigation techniques on the catastrophic collapse of above-ground storage tanks in terms of dynamic pressures and overtopping fractions using Computational Fluid Dynamics (CFD). Catastrophic Overtopping Alleviation of Storage Tanks (COAST) and Mitigation of Tank Instantaneous Failure (MOTIF) protection measures are implemented. COAST is a deflector fitted to the top of the bund wall that is a structure surrounding a storage tank and MOTIF is a baffle fitted inside the storage tank. An optimisation study has been conducted to select the optimum mitigation technique and the optimum inclination angle of COAST. Subsequently, the effect of incorporating mitigation techniques using different capacities and shapes of bund wall is investigated along with the effect of using various heights of the fluid within the tank. Results show that COAST alone is more effective than combining the two mitigation techniques and the optimum inclination angle giving the lowest dynamic pressures and overtopping fractions is 80°. COAST significantly reduces the overtopping fractions ranging between 93% and 98% for the various capacities investigated. The highest reduction corresponds to a bund wall capacity of 200% of the capacity of the tank. The effect of COAST in reducing the overtopping fractions is more significant for circular shapes than square, rectangular, and triangular walls. Regarding the height of the fluid, COAST is more effective for tall tanks compared to middle and squat tanks.