what is best foam concentration to extinguished a methanol fire?
Most AR-AFFF foams work at the 3% and 6% concentration on polar solvents. Either concentration should be fine. However, depending on the manufacturer, the minimum required application density will vary. The advantage of 3% concentration foam is that it will require less concentrate, therefore a smaller concentrate tank.
Thanks for your reply. But does NFPA mentioned the best foam concentration for Methanol or it will depend on the type of the liquid?
For Methanol you would need an AR type of AFFF. The manufacturer (brand) would be a personal choice as would be either a 3% concentrate or a 6% concentrate. NFPA does not recommend a certain brand of foam concentrate but does state the application rate for extinguishment and vapor suppression.
These days, it doesn't make a lot of sense to use a 6% concentrate, since it doubles the size of the foam concentrate storage tank and thus adds that much more cost to the project. The application rates can vary between manufacturers, so the first thing to do is select the particular foam concentrate you want to use and then consult the data sheet or consult with the particular manufacturer for their recommended application rate. While some application rates are shown on the data sheet, those rates were typically determined during U.L. testing with relatively low fuel temperatures, so if you are in a warm climate where the fuel is "hot" consider increasing your application rate to account for those higher temperatures.
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