A 20-year-old, 56-m³ cylindrical expansion tank (7 m high, 3-m diameter, 10-mm thick sheet metal), tested at 2.5 bar, exploded inside a refinery’s distillation unit. All connection tubes were torn off. The fully open tank shell, with its bottom and roof blown off over the entire circumference, was projected tens of metres, as was the hot diesel fuel contained therein. A tremendous shockwave was generated. The accident occurred during break time for personnel: most of the refinery’s 70 technicians normally present in the zone were offsite eating lunch. 7 workers were killed at a neighbouring site, of whom 6 were employed by a material handling firm. Nine other individuals were injured and required hospitalisation. The fire was brought under control in an hour by first responders.