At a brewery, the base plate-to-shell weld seam of a 90-m3 vertical cylindrical steel tank failed catastrophically. The 4-ton tank “took off” like a rocket leaving its contents behind, and landed on a van, crushing it. The top of the tank reached a height of 98′. The internal overpressure responsible for the failure was an estimated 8.7 psi. A rupture disc rated at 7.2 psi provided overpressure protection and thus prevented the tank from being covered by the European Pressure Equipment Directive. This safeguard failed and it was later discovered that the rupture disc had been installed upside down. The organizational root cause of this incident may be a fundamental lack of appreciation of the hazards of large volumes of low-pressure compressed air or gas. A contributing factor may be that the standard piping and instrumentation diagram (P&ID) symbol for a rupture disc may confuse and lead to incorrect installation. Compressed air systems are ubiquitous. The medium is not toxic or flammable. Such systems, however, when operated at “slight overpressure” can store a great deal of energy and thus constitute a hazard that ought to be addressed by safety managers.
Shortly before the tank failure, two refrigeration technicians employed by an external contractor arrived to service a large ammonia-cooling unit on the roof of the adjacent building. They parked their van next to the outdoor yeast storage tank, entered the building, and climbed the stairs to the roof. Immediately after passing through a doorway in a 3-m high noise protection wall on the roof, they heard a sudden dull “poof”. They turned around and saw the storage tank rising vertically in the air. The base of the tank clearly rose above the roof of the adjacent tall green building, and then fell back to the ground and landed on their van.
Testing revealed that the spring-operated pressure valve on the tank opened at 3.0 psi, as it was designed to do. However, the capacity was limited because of the small-bore 0.33″ connecting pipework. The rupture disc was intact. It was a reverse buckling type device that had been installed upside down (i.e., with the dome facing away from the tank). The vendor stated that the rupture disc likely could withstand an overpressure of at least three (3) times the pressure marked on the rating plate (i.e., ≥ 22 psi) before bursting if it were installed upside down.
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Source: Hedlund FH, et al., Large Steel Tank Fails and Rockets to Height of 30 meters Rupture Disc Installed Incorrectly, Safety and Health at Work (2016), http://dx.doi.org/10.1016/j.shaw.2015.11.004
