On July 23, 1984, an explosion followed by a fire took place at a Union Oil petroleum refinery in Romeoville, Illinois, outside Chicago, killing 17 people and causing major property damage. This vessel was an amine absorber tower used to strip hydrogen sulfide from a process stream of propane and butane. The vessel was 18.8 metres (62 ft) tall, 2.6 metres (8.5 ft) in diameter, and made from 25 millimetres (0.98 in) thick plates of type ASTM A516 Grade 70 steel.The explosive force had been able to propel the upper 14 metres (46 ft) of the vessel a distance of 1 kilometre (0.62 mi) from its original location, while the base remained at the center of the fire that followed after the explosion.Testing of the vessel segments began with non-destructive testing methods.