[AT] OT - AFFF Fire Foam Unit

[Steve W.]

Richard Walker wrote:
> There used to be a few firefighters following ATIS, and I'm hoping 
> for some help with an equipment question.
> 
> I recently bought a skid-mounted fire control unit ridiculously cheap 
> at a municipal surplus auction.  It consists of a Halon portion and 
> an AFFF (Aqueous Film Forming Foams) portion using CAF (Compressed 
> Air Foam) technology.  I am only interested in the AFFF portion, 
> since we live in a high fire danger area backed up to the San Gabriel 
> Mountains in Southern CA.  If a wildfire heads our way, foaming down 
> the house and surrounding vegetation beforehand can increase our 
> chances of coming through OK.
> 
> The AFFF system is actuated from a large cylinder of high-pressure 
> nitrogen.  A fixed regulator reduces this high pressure to a constant 
> lower pressure.  I'm thinking about getting away from this dependency 
> and converting to compressed air.  The air supply hoses leading to 
> the pressurized foam solution tank are 200 PSI working pressure and 
> 1/2" in size.  So based on this, my wild guess is that the needed 
> working pressure might be around 100 PSI and the air volume from 20 
> to 50 CFM, assuming the hoses were roughly sized to the air requirements.
> 
> Would anyone with experience have a more precise answer as to 
> pressure and air volume?
> 
> Whatever, that will take one BIG compressor.
> 
> Photo of the unit:
> 
> http://www.walkerpublications.com/tractors/FireFoam02.jpg
> 
> Thanks.
> 
> 
> Richard

That one looks like an OLD rig.
The gas system on that does two things, one the gas itself provides the
pressure to operate the system and it also is used to help the foam
expand. Basically it is a LOT like the old chemical rigs except it uses
the gas to pressurize the tank instead of the contents self generating
the pressure. Replacing the gas cylinder with a compressor isn't a bad
idea BUT you will need a large compressor. Figure 100 PSI and over 40
CFM to do the same thing the gas cylinder does.

http://www.firecombat.com/cafs.htm
is a current version of your unit using a built in tank to supply the
pressure.

Also keep in mind that you will want different foam than what is
normally used for fighting fires. You want the stuff that lasts a long
time (talk to a local fire dept. about this as the stuff is NOT cheap
and has an expiration date).

-- 
Steve W.