Blast-Induced Failure Analysis of Liquid Ammonia Storage Tank

Abstract Ammonium nitrate (AN) is a widely used compound in the agriculture and mining industries that, if improperly handled, poses a significant explosive hazard, as evidenced by the 2020 Port of Beirut explosion. In the wake of this event, the Australian government required failure analysis studies for all bulk AN storage. This paper details one such failure analysis study where bulk solid AN was stored at a mining facility that also featured a large, double-walled, refrigerated API 620 storage tank containing liquid ammonia. The goal of this study was to determine the quantity of solid AN that, if an explosion were to occur, could cause failure of the tank, potentially resulting in a significantly larger explosion. Nonlinear dynamic finite element analysis (FEA) was performed to simulate blast overpressure wave propagation and incidence upon the exterior tank wall and system response including contact between inner and outer tank walls. The tank was subjected to blast scenarios ranging from the equivalent of 77,000 lbsTNT up to 420,000 lbsTNT to study its behavior from essentially elastic response through effectively certain loss of containment. There is no industry standard or published code establishing failure criteria for a tank or pressure vessel subjected to an external explosion. Therefore, various sources were used to inform the criteria defining structural failure of the tank, including the United States Department of Defense Unified Facilities Criteria 3-340 (DOD UFC 3-340-02), ASME Boiler and Pressure Vessel Code Section VIII Division 3 (ASME VIII-3), and ASME VIII-2. Comparisons were made between these methods, and a range of AN quantities likely to cause failure of the tank is proposed. This study highlights the challenges of blast analysis, failure-level response simulation, and, ultimately, quantifying the consequence of cascading failure events.