[AT] OT - AFFF Fire Foam Unit

[Dan Folske]

We have a CAF unit on one of our small trucks that sucks foam concentrate 
from a 5 gallon bucket and injects it into the water stream along with 
compressed air from a small engine driven compressor. Our main pumper 
carries a siphon unit which can be put into a 1 1/2 inch line to suck 
concentrate from a bucket and then you put a foam nozzle on the end of the 
attack hose. The foam nozzle has vents which pull air into the water foam 
mix creating the foam bubbles. The CAF unit adds a greater volume of air and 
seems to provide a more uniform bubble size. Each additional trapped air 
bubble is another layer of insulation. I don't recall offhand what we're 
running for air pressure or volume but it is not extreme. I'll look tomorrow 
if I get the chance.

None of the small departments around here use nitrogen. I would suspect that 
the nitrogen might be better in some circumstances with volatile fuels and 
confined spaces but for our use plain compressed air or natural aspiration 
works fine.

Dan Folske
Assistant Fire Chief
Bowbells Volunteer Fire Department

There maybe a professional firefighter on the list that can provide you with 
more details.


----- Original Message ----- 
From: "charliehill" <charliehill at embarqmail.com>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Wednesday, July 29, 2009 7:14 PM
Subject: Re: [AT] OT - AFFF Fire Foam Unit


> Richard I'm not one of the firefighters but let me add some fuel to the 
> fire
> (pun intended).  Nitrogen will not oxidize a fire but air, being mostly
> nitrogen but about 19% oxygen will.  Is that going to affect the fire
> protective characteristics of the foam?   Just wondering.
>
> Charlie Hill
> ----- Original Message ----- 
> From: "Richard Walker" <richardwalker at pobox.com>
> To: <at at lists.antique-tractor.com>
> Sent: Wednesday, July 29, 2009 7:29 PM
> Subject: [AT] OT - AFFF Fire Foam Unit
>
>
>> 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
>>
>> _______________________________________________
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>> http://www.antique-tractor.com/mailman/listinfo/at
>
> _______________________________________________
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