Early on a Saturday morning, a two-inch pipe in an unoccupied building in a plant shut down for the weekend ruptured violently. There were no injuries because nobody was in the building at the time. Nearby piping was bent and ruptured by impact from the failed pipe, and there was other minor equipment damage. The released material did not ignite, and was contained by the building spill containment system. The initial investigation of the incident determined that the ruptured pipe had been liquid-filled, blocked in by closed valves, and overheated. The investigation could have stopped at that point, blaming the rupture on thermal expansion of the trapped liquid. However, a more detailed root cause investigation that yielded significant new knowledge of the thermal stability of the material was performed. This knowledge also resulted in redesign of the plant piping and the emergency relief systems on a number of plant vessels.