Magnesium fires
Art Donahue
Chief
Glenville Hill Fire Department
Scotia, New York
The April 1995 issue contained three excellent articles on magnesium fires. The information provided on safety–what to do and what not to do–was quite educational. However, the list of extinguishing agents for reactive metals left out the material I have had the most success with.
A project I was once associated with utilized liquid lithium as a heat transfer medium. As luck would have it, the containment vessel failed during a test at a research lab. The molten metal ate its way, rather spectacularly, though most of the instrumentation, piping, and wiring. MET-L-X® [Ansul Fire Protection] was not effective on the flowing lithium.
What did work was copper powder shoveled on slowly and uniformly. The copper would melt and form a crust containing the liquid lithium and hastening cooling. As more lithium flowed, more copper powder would be added as needed. Water was never introduced, as your articles correctly stated. The whole idea was to contain the liquid to minimize the damage and let the molten metal cool and solidify. This technique also works well with lithium salts, and another benefit is that no hydrogen is generated. Published information on testing with copper powder states that it works with magnesium as well.
I would guess that very few fire departments will ever have to deal with this kind of fire. I`m writing so that others might learn from this rather unique experience.
John Sachen responds: Thanks for your case study of a difficult Class D metal fire. As the articles pointed out, it is critical to start with an approved or recommended agent. MET-L-X® is ineffective on all but the very smallest lithium fires and is not recommended for them.
Until very recently, the only agent for lithium was LITH-X®, from Ansul. LITH-X® is a form of graphite with various additives.
A new agent for lithium, NAVY 125S copper powder, has been developed in a joint venture between Ansul and the U.S. Navy. Copper powder forms a eutectic alloy with the lithium and is a very good agent.
The original listing for copper powder was for lithium. Within the past few months, Underwriters Laboratories has added magnesium to its 1995 listings for the agent.
One drawback to copper powder is its high cost–about three times the cost of MET-L-X®.
