Great topic. On water tower operations it is not standard nor often even discussed to flow CAFS. Though having 3 CAFS engines bordering around us, the topic came up and we gave it a shot. It is hard to qualify "good" CAFS but we were being supplied by a CAFS Engine, had the aerial about 90' out and around a 70 degree angle with a smoothbore nozzle which I believe was 2" diameter, and the percentage was .03%
We were flowing into trees, and brush, and it looked pretty good I guess.
A couple of key points is that typically you don't calculate Friction Loss for CAFS lines, but with elevation gain, you have to give in and ramp up the pump.
Try not to exceed a total of 300' of CAFS hose travel. - this includes Engine to Truck and Truck up to aerial nozzle. You will begin to break down and scrub off your bubbles.
Make sure to use a smooth bore nozzle or you will only be discharging "solution" if you use a fog nozzle - again, scrubbing off your bubbles.
If you are operating this aerial via a quint and being supplied from a CAFS Engine company, don't plan on boosting the pressure with your quint's pump, after being supplied with the CAFS. Pumps do not like to be supplied with CAFS - Air in the pump is not fun.
I bought 75 foot Pirsh and will be experimenting with a high volume CAFS I built for coal mine fire fighting applications.
I plan to flow about 6,000 gpm of expanded foam through the 2.5 inch smooth bore tube I'm using for a nozzle.
This unit is needed to apply lots of durable foam overhead and into oil seperation tanks that get hit by lightning here in the Barnett Shale Gas Fields around the Fort Worth Texas area.
I will use a 900 cfm compressor and flow about 100 gpm water with a 1% solution of ChemGuards new Mine Foam formula, it's got new polymers added for durability, and I have some left over from a recent coalmine fire where we pumped more than 700 million gallons of CAFS foam into a 5 square mile gob area about 3,000 under the ground. It worked well and the mine is back into full production.
I will try to add pictures when I get the Aerial hooked up to the CAFS.
HaHa, Not to fear, I've been doin this kinda stuff with CAFs for the past twentyfive years or so.
The fire service has yet to see a fraction of what foam can do to make our job safer,easier and much more affective.
Just a suggestion, CAFS is created by the friction inside of the hose so it generally helps to use a longer section rather than a shorter section to create the best quality of foam. An interesting fact about the friction loss is the bubbles that are shearing at the hose surface act like slick little ball bearings and allow the inner core to flow without much friction. It's easy to pump foam a thousand feet above the pump with no pressure loss. As the compressed foam reaches the discharge end of the pipe or hose it starts to decompress and expand its volume, this causes the foam to excellerate its volocity and increases throw distance. This is why you need more concentrat in the water to make it more durable and to prevent the volocity from blowing the foam appart.
Hope this helps quell the fear a little, ha.
Thanks for the great input Chad, keep up the good work.
We have CAFS prepiped on our 75ft aerial waterway. We did this for two reasons one it allowed us to use CAFS if needed in a master stream operation and second we wanted the ability to be able to have a CAFS discharge off of the tip for fires where a line would be streched off of the tip. We have used the CAFS out of the master stream only once on a large barn farm it and it seemed to work very well although it did produce a large foam blanket so we quickly shut it down. We have used the discharge also on a fire in a stip mall to hit some fire that was on the edge of the roof line and this worked out very well. With the barn fire a large volume of foam was produce very quickly which I think was very effective in stoping the fire from spreading as well as extinguishment.
Can you tell how much air cfm, water and solution gpm you were using?
The manufacturers seem to want us to use way too much water flow to stay closer to the NFPA volumes recommended for water applications. I've found this to be counter productive with CAFS and realworld foam applications. I believe it's the bubbles that do the work to present the thin films of water that make the bubble structure and the fact that the bubbles nearly explode into positive pressure steam when they come in contact with a lot of heat. Then the excess bubbles release water with deep penetrating surfactants to soak into the water repelant carbon soot to cool the source of the pyrolitic gases. I can't believe I said all that. Have you tried the Aerial CAFS to control SMOKE exposure to downwind public? The foam sticks to the particulate matter and scrubbs the air, there are experiments going on now with CAFS that are capturing the toxic carbon in flu gasses (CO, CO2 etc.) with the ions in the foam. It seems I learn something more about CAFS every day.
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