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  1. #1
    Fire This!! revrenhex's Avatar
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    Default DIY Foam or CAFS

    Hello,

    I have been trying to help a local volunteer fire department design a very low cost foam system to be used on brush/grass fires. Right now we currently use dawn dish soap in our water tank. I have been toying with an idea using an SCBA tank and regulator to inject air into the water after the pump. It has a moderate level of sucess, producing a decent soap foam. What I am needing is some reading on the science behind CAFS and foam in general. Any reading or any input would be appreciated!

    Thanks,

    Cliff Harris


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    Being new to the world of CAFS (we're going to get our first one next year), I don't have a lot of technical expertise. I know that Hale is or was marketing a system using a much larger, permanently mounted air cylinder. I had spoken with Waterous about it; they expressed several concerns. I don't know what Darley might be doing in that regard. If you could find one of the Hales maybe you could learn from it how to control and inject the air into the mix (preferably without infringing any patents). But I can't believe that an air pack cylinder would give you a whole lot of time. Maybe enough for an Indian tank or two.

    Stay safe out there, everyone goes home!

  3. #3
    Fire This!! revrenhex's Avatar
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    Default Sorry for the long delay

    Thanks for your post. With my current setup, I can produce a 4-6 inch moderately dry foam out of dawn dish soap, a 2216psi SCBA tank, a home made aspirating nozzle. The only thing, is to empty our 325gallon brush water tank, would need 4 SCBA tanks. So I mounted 2 Cascade bottles on the truck Giving us ALOT of air for our "foam" system, and a side bennifit of being able to refill a few SCBA's if we need to, ive got it plumbed for both. Our water pump and plumbing is homemade, and Ive built with with a few check valves so that pressurized air cannot back up into the pump. The only problem im having now, is regulating the water/air mixture. We are batch mixing 1/2 gallon of Dawn soap in 325gallons of water. Its very labor intensive, as one person is spraying while i stand at the truck and CONTSANTLY tweak the water/air to get a good foam.

    Any more ideas or comments would be greatly appreciated!

    Thanks again - Cliff H.

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    Default

    Search on CAFS over at the main Firefighters Forum

    A very good discussion on what you're working on some time back. An old guy from down in Texas (as I recall) contributed a wealth of info on CAFS tech and knowledge. If you need a cheap/free proportioner the US Navy regularily has available surplus (your state forester can track down and get for you thru FEPP if they will make the effort).

    Model is an FP-180 I don't have an NSN right now.
    http://www.tpub.com/content/combat/1.../10572_100.htm

  5. #5
    dazed and confused Resq14's Avatar
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    Default

    Quote Originally Posted by revrenhex
    The only problem im having now, is regulating the water/air mixture.
    A balancing valve solves this problem.
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    Default small line

    if you are lookinf for cheap "wet foam" and run hoses off your brush truck between 5/8" and 1", you could use a liquid fertilizer proportioner. its just a bucket that screws into a top that has a nozzle and hose threads. put your concentrate in the bucket and spray.

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    I will state the obvious and ask, you are using a fog nozzle right? We don't use CAFS around here, and we do lots of grass and brush fires. The fog nozzle whips up enough foam to get the job done.

    We also carry aspirators that whip up even more foam but I don't know if I'd want them to actively fight fire with. More likely to provide exposure protection but to be honest I've never used any of them on a real fire. KK Bubble Cup is probably the most well known, TFT also makes a clamp on aspirator that goes on the end of their nozzle.

    None of these solutions require you to carry air on the truck, just use what's in the atmosphere. But in reality I use foam basically just for its wetting ability, and any foaming that may be incidental.

    A local volunteer department had a large stored compressed air system like you describe on their quick attack but it was an albatross and they eventually ripped the POS out.

    Besides that fact they never used it anyway. We use full size Type 3 engines around here.

    Birken

  8. #8
    Forum Member Fire304's Avatar
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    Default

    I've been running CAFS since early 2001 and have read a bit on the subject, I love it and want to learn more.

    The problem you are describing, the air to water balancing, in one of the biggest hurdles that had to be over come in early CAFS research and development. "Back in the day" early units had to be hand balanced just as you describe.

    The simplest solution is a fixed pressure discharge with a metering valve and a pressure regulator. Decide how many PSI you want and adjust the injector regulator (you will need a standard SCBA to "shop air" pressure regulator) to match. Then adjust the metering valve (a valve between the regulator and the check valve, but not a ball valve) to give the desired water to air ratio when flowing (typically 1gal:1cfm for wildland application). It will not be as perfect as using a balancing valve, you may notice a little too much or too little air when you start the flow, but once flowing this tends to work well (Snuffer uses this system on their smaller CAFS skid units). Since there is no friction loss with CAFS, and the ideal discharge pressure if 80-100psi its pretty easy to set up. You will also need to recalcuate your air supply needs. By my calculations, you'll need eight 30 min bottles to make 1:1 CAFS in 325gal of water.

    For injecting the "foam concentrate" you can look into commercial pool chemical injectors. They are hydraulicly powered units which are fully self contained, simply plumb it in line (again, Snuffer uses this). I've often thought about using commercial Lemon Joy as a cheap training foam. Since Class A really is for the most part just super concentrated soap, it should work well.

    I was initially confused as I read your post. You mention using an aspirated nozzle. To take advantage of CAFS you must use a smooth bore nozzle, any other type of nozzle will break down your bubble structure and greatly diminish the effectiveness of the CAFS, to the point where you'd be better off with plain Class A foam. Most CAFS nozzles on 1 3/4" lines will be in the 3/4" to 1" range, usually stack tips with a 1 1/4" or 1 1/2" option for dry foam (great for exposure protection). You will need a minimum of 200 feet of hose to insure the air and water mix correctly, smaller hose will need less length. The size of the tip has less to do with volume (that's determined by your discharge valve), more with wetness/dryness and how far you can loft the foam.

    Frankly, given the technical difficulties of getting the air to water balance right, I'd get either one of the previously mentioned Bubble Cup nozzles or a small Vindicator nozzle and just run your soapy water through that. I've heard the Vindicator makes near CAFS quality foam, and I've used a Bubble Cup, it too makes great foam. I think Hale makes an add-on CAFS unit with is a gas powered compressor with all the required metering that you simply put on the discharge of an existing pump to get CAFS.

    Good luck, keep us posted with your progress.
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  9. #9
    Fire This!! revrenhex's Avatar
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    Alrighty, I replumbed the entire thing on Saturday. Here is how it is setup now (pics in the next few days)

    2 2015psi 230cfm "breathing air" cylinders.
    regulator to regulate air down too 65psi
    1/4 air line to water plumbing
    2" pipe off of water pump, splits at a T
    one side of the T has a 1" ball valve
    The other side of the T has a ball valve, gate valve, (for water metering), T
    Both of the above mentioned reconnect at a 1" T and go to the booster line.

    The second T has another ball and gate valve combo for air metering.

    I know it sounds confusing, but after alot of testing and tweeking, ive gotten it to where You just turn on the air tank, fire up the pump, turn on the "foam" side of the plumbing, and out comes a nice think simi-dry dawn soap foam. I was able to put down a simi-wet 6" foam blanket.

    Tomorrow I will try and get by there and get some pictures of the setup, and pictures of the foam application. The only two things I wish I could add to it (but dont have the funds to) are a venturi eductor for soap mixing, and a compressor for the air. Dream and wish!

    Thanks for all the input thus far, its really turning out to be an effective system!

    -Cliff H.

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    Fire This!! revrenhex's Avatar
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    Well, not only did I get a chance to demonstrate the DIY CAFS system, as im demo'ing it for the other guys at the station, we got a call for a structure fire following an explosion. Once on scene we had a fully envolved house and the beginings of a good grass fire. We even had a unknown source of magnesium/sodium (water reactive metal) that was burning.

    CAFS worked VERY well, not only extinguishing it, but totaly supressing it, not even smoldering. And with healthy doses of it, smothered the burning metal.

    Here are some action shots and setup shots of the system. All with an air tank and dawn dish soap.

    Pleasant Grove Volunteer Fire CAFS system

    Later!

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    Question

    Did you try using it with a smoothbore? I'm wondering if you need the air-aspirating nozzle or not? If you do, then you probably have too much water still in the line? If this is the case, from my limited knowledge, you're not seeing all the benfits of a CAFs line such as a lighter line and simpler nozzle.

    Lastly, why bother to reinvent a system thats being used and sold all over? If you're trying to build a system on the cheap, I'd be careful of moving into a interior attack mode with a unit made at home. Not that you can't do it as well as any manufacturer, but how about insurance? If something happens and the system fails and someone is hurt? Pretty damn expensive! Hell just a line bursting "could" be blamed on you for running a system that wasn't engineered or third party tested. Sorry to sound like a naysayer, you've defineately done some great work to this point, I just question the reality.

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    RFDACM, I see your point 100%, but I, like you, am in the Northeastern part of the country, where there is plenty of $$ to go around. Ever traveled down South or to the Midwest?? There are Depts there that are hurting for any eqpt out there. I applaud thier efforts to get the job done. I know from experience that that sometimes, "you just have to do what you have to do to get it done". Not always the right thinking, but it usually pays off. I'm sure that revrenhex checked it over a few times, and its possible with a little more tweaking, it could be better than a "professional" type, because its hand-made, with 100% safety in mind, instead of the $$ the big companies look at. Just my $0.02, that's all.

  13. #13
    Fire This!! revrenhex's Avatar
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    Just so we are all clear, I never designed it to be used as an offensive interior attack line. It was designed to be used on Brush/wildland/forrest fires, which make up 85% of our runs. I did however design it with total safety in mind. The entire system is built to only 30% of its capacity. All the plumbing, valving and hoses are rated to over 3 times my working pressures. And as far as the money goes, its absolutly hard to come by down here. We operate off of 100% donations and $115 a month from the county. That has to cover our fuel, equipment, utilities at the station and any other needs that arise. Im at a crossroads with the foam quality because of my limited air supply. Where I have it set now, a sloppy wet foam, we run though one of those tanks of air every tank of water, wich works out to 1cfm air / 1.41g water. I had it down to a 1-1 ratio, which produced a great dry foam, but I ran out of air before the tank was empty. And there will be almost no exposure protection to think about so I figured a little wetter would be better for the grassy stuff.

    I still have a question on the nozzle though. Do I need to refine my air nozzle, ditch it for a smooth bore, use a standard mulit-gpm straight/fog nozzle. Thats where Im still needing any input I can get. Ive never had the privlage of witnessing a "real" working CAFS system in action, not even the paid cities around here use them. So Im trying to design this thing flying blind.

    Thanks - Cliff H.

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    All the research and users I've seen use a smoothbore nozzle for CAFS. As was stated by someone previously, any other type nozzle actaully strips the bubbles from the stream.

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    Good going revrenhex, CAFS is soapy water and air being mixed by the friction of the hose and the bubbles in the middle of the hose move much faster than the bubbles rubbing the sides of the hose. This all causes the foam to compress in the hose and when the bubbles reach the discharge end of the hose they expand and regain velocity for a longer throw distance. If you use a reducing tip or adjustable nozzle it will accellerate the foam to a faster velocity but it may breakup the bubbles into a soapy spray. So try running the CAFS without anything on the end of the hose first, to see what the discharge looks like without disturbance or added accelleration. It should be the best quality cAFS foam possible for any particular CAFS set up. Then try it with your various nozzles and tips to see what they do to the CAFS quality of foam.

    I recommend the full flow smooth bore shut-off valve with nothing on the tip, and I use my fingers to shape the stream into a fan pattern for close up work.

    If you use soft hose try to prevent any kinks especially near the discharge, you might try a short section of hard hose for the firefighters to hold onto, it helps prevent the kinks while maneuvering the hose in close quarters.

    The best foam pressure is 90 to 120 psi, you should be getting around 100 feet throw.

    Hope this helps.
    Mark Cummins

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    Forgot to mention that the amount of foaming agent (or soap) in the water increases or decreases the durability of the foam, more soap makes the foam tuffer and the foam can withstand more disruption by tips, nozzles or or accelleration. and A jumping or kicking fire hose ALWAYS means there is not enough soap in the water.
    Mark Cummins

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    Fire This!! revrenhex's Avatar
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    Thank you so much for the helpfull information. Unfortunately the water pump we have can only push 70psi max. so Im having to do this whole thing on a smaller scale. Ive also replaced the gate valves with 2 Schrader Bellows flow control valves, which give me a much more precise control. I wish we could get a eductor for the soap (like the farm one mentioned above), but at $156 we are over budget on this project (sad huh.....). I am still looking to the farmers land we cover to see if I can get an eductor. The entire system is down at the moment (till saturday when I redo the air injection part of the CAFS.) I am going to try the smooth bore nozzle. Thank you so much for all of the information so far and keep it coming!!

  18. #18
    Fire This!! revrenhex's Avatar
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    Update:

    I have removed the two gate valves, and replaced them with Shrader Bellows flow control valves. I can now product a varied foam with the twist of a knob, from sloppy wet for grass fires to dry as shaving cream, that you can literaly stick to the ceiling, all from Dawn dish soap. I also took ya'lls advice and ditched the nozzle for a smooth bore one, and it was a good decision. I'll post some pictures this afternoon. Thanks again for the help and input everybody has provided.

    -Cliff H.

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    I know I'm reviving a long dead thread, but I would love to see some pictures of this setup.

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    Default revenhex and dawn

    hey rev - you probably have a good idea but I would NOT use dawn - it is a degreaser, meaning it is alcohol based. My suggestion is to use Ivory liquid -

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