Aluminum scuba cylinders in oxygen-enriched and oxygen service – what happens to an aluminum scuba tank in an oxygen-fed fire?
- First, an ignition source of some sort—a flame or spark, excessive or prolonged heat, impact, etc.—ignites a contaminant, which serves as the initial fuel for the fire. Please remember: many materials that might not ignite and burn in standard air under normal atmospheric pressure will ignite and burn, often furiously, in a high-pressure, oxygen-rich environment.
- The initial fire begins melting the metal of the cylinder and/or the scuba valve, at which point the molten metal itself becomes fuel and starts to burn. The melt temperature for aluminum is 1,220 degrees F (660 degrees C), which gives you some idea of how hot an oxygen-fed fire can become—and it usually reaches these elevated temperatures in less than one second. All the time that the metal is burning, oxygen is being consumed and the fire is intensifying.
- The action of the fire rapidly increases the pressure inside the cylinder, and all the while more and more aluminum is melting and starting to burn, fueling the fire and weakening the cylinder to the point that it can no longer hold the growing pressure. All this occurs so quickly that the pressure-relief device on the valve does not have time to activate.
- By the time the pressure-relief device is ready to activate, either the valve is forcefully ejected at high velocity or the cylinder ruptures—or both.
- Afterwards, it is very difficult, if not impossible, to determine the nature of the original contaminant, because the contaminant has been completely consumed or driven off by the extremely hot fire. At that point, a thorough examination of the total oxygen system, cleanliness records, cleaning methods, system use, care and maintenance records, filling procedures and other relevant data may reveal possible sources of contamination.
Posted by Luxfer