Abstract

Like most metals, fine forms of titanium metal, such as powders and metal shavings, pose a significant fire hazard and, when heated in air, an explosion hazard. While large titanium metal pieces are difficult to ignite, these pieces will become ignitable under certain circumstances, such as dry chlorine, red fuming nitric acid and oxygen-rich environments. Any titanium fires and/or explosions occurring outside these well known conditions are considered unusual and unique.

An unexpected explosion occurred in the vent line connecting at the top of a titanium reactor that was used to make a fire-retardant fabric. The fabric was made by mixing 1,2,4,5-tetramethylbenzene (durene) and nitric acid in the presence of plentiful water at 1380C (2800 F). The line consisted initially of a short section of 6-inch titanium pipe and fitting before connecting to stainless vent line. Titanium seemed to be compatible with reactor conditions. There was no knowledge or expectation that these conditions could pose fire or an explosion hazard in titanium. That is, it was not feasible to create red fuming nitric acid or other known incompatible chemicals under reactor conditions.

Nevertheless, explosions occurred in the vent line but not in the reactor after 3 ½ years of operation. In this presentation, the cause for this accident will be discussed based on the findings in examining samples from the vent line and the results of high-temperature tests.

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