A DOT 3AA 1800 CO2 cylinder ruptured and exploded, causing property damage. The failed CO2 cylinder had been recently filled and was in a delivery truck in the process of being delivered. Reportedly, the frangible disk overpressure safety had been inadvertently overridden. A metallurgical failure analysis of the ruptured CO2 cylinder was requested. Visual examination revealed that the rupture was primarily longitudinal with the upper cylinder body on both sides of the valve exhibiting fracture. Macro and microscopic examination revealed distinct chevron markings pointing towards the fracture origin in the neck of the subject cylinder.
As a result of the forming process used to shape the cylinder neck during original manufacture, areas were created in the cylinder neck which were susceptible to cracking and/or localized, trench-like corrosion. Over pressurization to the point of rupture resulted from the warming of an overfilled cylinder.