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THMG092 – Metal Fires

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In this episode, we learn about the relatively unknown science behind metal fires.

Complete Show Notes

7:05 National Fire Protection Agency (NFPA) 6.3.3.5

  • The following agents shall not be used as extinguishing agents on combustible metal fires because of adverse reactions or ineffectiveness, unless they are compatible with the metal and are effective agents:
    • Water
    • Foams
    • Halon
    • Carbon dioxide
    • Nitrogen
    • Halocarbon clean agents
    • ABC dry chemicals

9:45 NFPA 6.3.3.9.2

  • An incipient fire occurring while the metal powder is in slurry form shall be permitted to be fought using listed Class B extinguishing agents, except that halogenated extinguishing agents shall not be used

10:30 NFPA 6.3.3.10.3

  • The use of pressurized extinguishing agents shall not be permitted on a combustible metal powder fire or chip fire, unless applied carefully as not to disturb or spread the combustible metal powder or chip fire

11:15 NFPA 6.3.4.4

  • Once the fire is extinguished and a crust is formed, the crust shall not be disturbed until the residue has cooled to room temperature

12:25 NFPA 6.4.1

  • The following information shall be provided to the emergency responder for the safe handling of combustible metal fires:
    • Perform a size-up, evaluation, and identification of metals involved in the fire
    • Ensure control of utilities to the affected area (water, gasses, power, etc.)
    • Review safety data sheets for the involved products and, if available, contact those familiar with the products and hazards
    • Evaluate whether the fire can be isolated safely and allowed to burn out
    • Determine whether uninvolved product and exposures (other than alkali metals) can be protected by hose streams after an adequate review has been complete
    • Water shall not be applied to alkali metals in either a fire or non-fire situation
    • Use an inert blanket like argon, helium, or nitrogen if the fire is burning in a closed container, such as a dust collection system to control the fire where an adequate delivery system is available and personnel safety is considered
    • Evaluate the potential for explosions
    • Use extreme caution with fires involving combustible metal powders, dusts, and fines because of the possibility of explosions, especially if the products become airborne and there is an available ignition source
    • Evaluate the control and shutdown of both domestic and fire protection water systems to prevent unintended contact of water with burning or molten combustible metal
    • Use extinguishing agents that are compatible with the hazards present
    • Use extreme caution with fires involving large quantities of product with structures
    • Most fires involving combustible metals cannot be extinguished in a manner other than by providing an inert atmosphere of argon or helium (or nitrogen for alkali metals or ions) if the product is dry
    • Most fires can be controlled by the application of argon or helium (or nitrogen for alkali metals or ions) or by the development of an oxide crust
    • The temperature of the metals involved in the fire can remain extremely high and the fire can flare up again if the product is disturbed prior to complete oxidation of the products or self-extinguishment
    • Water in contact with molten combustible metals will result in a violent steam explosion and can cause hydrogen explosions and reactions
    • Isolate the metal as much as possible and remember that large fires might be impossible to extinguish
    • Evaluate whether there is adequate drainage to prevent the contact of water with burning metal that’s not compatible for protecting exposures
    • Evaluate the fire to determine whether the fire can burn itself out naturally to minimize hazards to personnel and lose exposure

26:05 NFPA 6.5.2.1

  • Requires than an incident action plan (IAP) be available on-site to emergency responders – must contain specific actions in the event of a combustible metal fire and shall be coordinated with the facility management and emergency responders
  • The plan shall address locations for remote shutoff of supply systems when any of the following are present:
    • Water
    • Electrical materials
    • Flammable liquids
    • Toxic materials
    • Other hazmats
  • Plan also contains instructions for safe handling of combustible metal fires
  • When we add water to a metal fire, it usually increases the burning intensity and chances for an explosion
  • Applying water to alkali metals that aren’t involved in the fire will result in hazardous decomposition, ignition, or explosions
  • Carbon dioxide will intensity the burning – in fact, most combustible metals will burn in a 100% CO2 atmosphere
  • Dry chemical agents will react with alkali metals and intensify the fire, but you might have to use them on the non-metal part of the fire that’s extended to something else
  • Halogenated compounds like extinguishing agents have a two-fold problem because they produce some really nasty byproducts
  • Metals like titanium and zirconium have the potential to produce temperatures in excess of 700-850 degrees Fahrenheit – their dust can explode in temperatures as low as 68 degrees Fahrenheit
  • On the other hand, heavy bars, ingots, and thick plates are virtually impossible to ignite
  • Metals will extract moisture from concrete

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