I asked one of our consultants to address your issue who recently helped another university lab. His response:
There are a number of issues involved in fire control/extinguishing and certainly the agents/methods-used are a key concern.
In my background, I have been involved with training, and on occasion, having to put out laboratory-scale fires involving "energetic" or pyrophoric or metallic materials. Most of my actual lab experiences were with alkyl aluminum compounds. I have not had any experience with large scale industrial fires with these materials.
I have had significant experience with large scale industrial fires but those were mostly flammable organic materials, mostly "solvents" and hydrogen - lots of hydrogen fires. In laboratories where such materials were present, we always had solid commercial extinguishers present.
There are several class D fire extinguisher agents available; some will handle multiple types of metals, others will not.
• Sodium chloride (Super-D, Met-L-X or METAL.FIRE.XTNGSHR) contains sodium chloride salt, which melts to form an oxygen-excluding crust over the metal. Useful on most alkali metals including sodium and potassium, and other metals including magnesium, titanium, aluminum, and zirconium.
• Copper based (Copper Powder Navy 125S) developed by the U.S. Navy in the 70s for hard-to-control lithium and lithium-alloy fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface. Lithium only.
• Graphite-based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR) contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well. Unlike sodium chloride powder extinguishers, the graphite powder fire extinguishers can be used on very hot burning metal fires such as lithium, but unlike copper powder extinguishers will not stick to and extinguish flowing or vertical lithium fires. Like copper extinguishers, the graphite powder acts as a heat sink as well as smothering the metal fire.
• Sodium carbonate-based (Na-X) used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. Limited use on other metals. Smothers and forms a crust.
• Some water based suppressants may be used on certain class D fires, such as burning titanium and magnesium. Examples include the Fire Blockade and FireAde brands of suppressant. Some metals, such as elemental Lithium, will react explosively with water, therefore water-based chemicals should never be used on such fires due to the possibility of a violent reaction.
Most class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel. There are a number of "complications" with Class D fires:
Hope this is helpful.
Experts at Finding Technical Experts™
I am looking into the advantages and disadvantages of using Met-L-X or Lith-X scoopable dry powder extinguishing agent versus outfitting labs with the extremely large dry powder extinguishers that this material traditionally comes in. I am hoping for a solution for the usual pyrophoric and reactive metal suspects; alkyllithiums, trimethyl aluminum, diethyl zinc, potassium, sodium, magnesium, etc.
If anyone has an experience with using or training with this extinguishing, I would appreciate any insight that you might have. I have already contacted Ansul and am awaiting their response.
Brandon S. Chance, M.S., CCHO
Program Manager, Chemical Safety
Environmental Health and Safety
262 Alexander Street
Princeton, NJ 08540
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