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<br />I <br />~ <br /> <br />Failure OfRefrigeratitrank. <br />ED&T File Number: HST0786-22095 <br /> <br />e <br /> <br />Page 5 <br />April 20, 1999 <br /> <br />6.0 CONCLUSIONS <br /> <br />6.1 The refrigerant storage tank. failed at the weld between the shell and the head. <br />The weld quality and design of the tank. did not meet ASME code <br />specifications for pressure vessels. <br /> <br />6.2 The tank. did not have a nameplate as required of a coded vessel. The <br />manufacturer of the tank. could not be determined. <br /> <br />6.3 The tank. was regularly operated at pressures that exceeded the 150 psi <br />working pressure rating of the tank.. <br /> <br />6.4 The tank. was not adequately protected by a pressure relief device. The tank. <br />was probably equipped with a pressure relief valve set at 350 psi. The PRY <br />setting exceeded the 150 psi working pressure rating of the tank. and the 300 <br />psi test pressure. The tank. failed within the pressure range of 150-350 psi. <br /> <br />6.5 The pressure capacity of the tank. had probably deteriorated since being <br />pressure tested in 1995. Corrosion and cyclic fatigue contributed to reducing <br />the burst capacity. <br /> <br />6.6 Once the tank ruptured, the pressurized refrigerant rapidly vaporized and <br />expanded creating a boiling liquid, expanding vapor explosion (BLEVE). <br />The force of the BLEVE propelled the tank. out of the building and damaged <br />objects in its path. <br />