1. #1
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    Default CAFS in Standpipes

    Does anyone know if it is possible to pump CAFS or any other type of foam through a standpipe?

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    Default cafs in standpipe

    I read an article a year or so ago about a department (don't remember which) did some training on this very issue. I did work, and with minimal friction loss on higher floors. If I can find the article I'll try to post it.

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    Default cafs in standpipe

    Do a google search "Montgomery county, Maryland cafs standpipe" you will find an article by Paul Grimwood on this very exercise.

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    Possibly, you need to check the manufacturer's spec sheet. The system may need to be flushed and/or drained to prevent freezing and/or corrosion.

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    Default Air Standpipe

    Pumping foam into the system would be questionable.
    I know something SF has talked about is requiring all new highrises to have a standpipe system for air supply. That way air cylinders can be refilled on a staging floor rather than run them up and down stairs.
    Jason S. - SFFD
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    MARYLAND RESEARCH I am very interested in this topic and welcome any information. I note the Maryland tests only went to five storeys but they did appear to present some effective results in using CAFS through the six inch standpipe.

    A colleague of mine who works with CAFS suggests that 'In theory, CAFS should be capable of being pumped far higher than water for a given pressure. The height depends on the density of the CAFS being applied, as this varies with foam type (Wet or Dry). I have some theoretical values that I have calculated, and would suggest that 1 bar will lift wet CAFS (3:1) approx 22m height and medium CAFS (7:1) approx 70m. I know that CAFS systems have been used to supply water CAFS to an aerial platform,successfully, however this would have been through relatively small bore pipe work. The issue is what will happen to the CAFS media when in a stationary 150mm dia column say 30m high? Will the water start to separate out of the bubbles and fall back to the bottom of the riser? I have to say that I don't know'.

    The thought is that if the CAFS flow becomes static in the standpipe for any period, the water will separate from the air bubbles and fall back down the riser .... as the bubbles pop .... leaving air at the top and water at the bottom.

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    I find this all VERY interesting. We dont have CAFS, but a standard class A/B foam system. I never thought of pumping a standpipe with class A, but I can see the benifits, if its possible.
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    Quote Originally Posted by PaulGRIMWOOD
    The thought is that if the CAFS flow becomes static in the standpipe for any period, the water will separate from the air bubbles and fall back down the riser .... as the bubbles pop .... leaving air at the top and water at the bottom.
    I am only familiar with a few demos of CAFS, so I would like to know if this is a problem when using cafs in a conventional horizontal handline? If so, what is the foam's average decay time?

    I could see this being more of an issue in a proprietary standpipe than a combination riser. The sprinkler system would maintain a certain minimum flow until the open head was capped, which should prevent any separation problems. A dedicated standpipe however would certainly flow much less, and with a lot more intermittence.

    Perhaps a bleed valve on the connection or nozzle would allow the FF to ensure he was primed to the tip with quality foam before making his attack?


    On a related note, how about CAFS on the sprinkler? It would have to work like a dry system, with a remote source of foam, but I would imagine it would result in a lot less water damage, with similar knockdown effectiveness as regular CAFS.

    Although the unlimited flow could either run out prematurely, or leave you with quite the room full of bubbles.
    Never argue with an Idiot. They drag you down to their level, and then beat you with experience!

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    I have tested CAFS in a 5 story standpipe(4-5 in piping) and in an aerial at about 90 ft. Both results were very promising. Excellent foam and almost no friction loss. We need to test in somthing more substantial. Any ideas what we need to try and look for guys?

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    My major concern of using CAFS in standpipes is that compressed air is a store of energy.

    Even the mighty Dal doesn't know what the heck the calculations & other engineering considerations are to begin to understand if it's a reasonable risk.

    But I do know a 6" riser has about 15 times the volume, and thus 15x as much stored energy, per foot as an 1.5" line.

    If something fails, there is a hell of a lot more energy in that system then when you're pump water.

    Remember, when pumping if you close the discharge, rev down the pump, whatever you almost instantly remove the bulk of the energy from the riser if something goes wrong.

    With CAFS, you don't have that control -- all the energy in the riser will continue to expel.

    I know we're only dealing with 100psi.

    Maybe it's much ado about nothing, but I'd sure like some people with "PE" coming after their names to take a look at it before it is adopted as a standard practice!

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    There was an article in Fire Engineering maybe 4-5 years ago from the chief of an industrial fire department on using Class B foam through standpipes and even sprinklers. Contrary to popular belief, according to the article, special sprinkler heads are not needed to use the foam effectivly. I'm currently out of town right now, but when I get home I'll try and find that article.
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    Mcaldwell, one of the canadian safety boards (the name escapes me)had published results of cafs through sprinklers. I believe it had something to do with fuel fires at aircraft hangars. If I get time and remember who and where I'll get some info up here. If I'm remembering right it worked very well.

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    Contrary to popular belief, according to the article, special sprinkler heads are not needed to use the foam effectivly.

    Film forming foams should work fine -- since they largely use their ability to form a film to seal the fuel.

    However, film forming works best with minimal protrusions in the film -- they're great for an airport tarmack or tank where there are large, uninterrupted areas of fuel.

    Get off into rough areas, lots of debris poking through the fuel, etc they're not as effective because the film has many breaks in it.

    In those circumstance you need to generate bubbles to form a mechanical seal instead of film seal. Film forming in these roles does have some advantages over mechanical (flouroprotein & Class A) foams, as it will form a film as it drains. As stated, when there are lots of breaks in the surface of the fuel, the film is weak around each. But at least it's a bit more sealing than the mechanical foams which lose all seal as the foam breaks down.

    Sprinkler heads & regular nozzles won't produce a good mechanical foam, since you need the agitation to produce the bubbles.

    Class B, either film forming or not, will act as a wetting agent when delivered through sprinklers against primarily Class A fuels. So will Class A, with less environmental impact. Of course if you have sprinklers, I'm not sure why you'd bother with wetting foams since you there is an assumption you have essentially unlimited water supply and you're not trying to tweak the last drop out of a handline. The P.E. who signed off on the design should have an adequate system to control a fire with plain water alone.

    CAFS can make a very good mechanical foam to control Class B fuels. You do not have the residual film-forming capabilities (except for a few departments that do use film-forming Class B foam for their CAFS...for expense and environmental reasons, I question that logic, but it is an idea not to rule completely out).

    At any rate, for the advantages of Class A & Class A CAFS in normal structure fire attack lines IMHO that is all most departments should carry. Almost no one has sufficient Class B foam supplies both in delivery rate & duration to handle anything more than a small Class B fire that a couple of CAFS equipped pumpers could handle with a mechanical foam just as well.

    Of course, CAFS doesn't require special nozzles...a smoothbore works nicely to deliver the mechanical blanket.

    CAFS for standpipes is intriguing -- CAFS has several things going on simultaneously that are an advantage over plain liquid. First and foremost is the compressed air which can release it's energy to make up for losses in the system due to "friction" and elevation. Friction is probably significantly less due to the effect of the bubbles rolling by themselves (basically, they're a lot slipperier than plain water), and from what I understand you probably find the bubbles tend to like to congregate along the liner to further improve the performance (that's speculation told to me by a hydraulic engineer speaking about bubbles in a hydraulic system in general).

    (As an aside, contrast the the "rolling bubbles" to the old fast water systems from the 1970s -- plain water small H2O molecules mechanically tumble a lot, and this causes turbulence. Fast (or was it Quick?) Water was Polyethylene Oxide (or a handful of similiar polymers). These long polymers reduced the turbulence by help to guide those short H2O molecules (long polymers can't tumble as much). Kind of think a highway full of crotch rocket motorcycles weaving in and out amongst themselves, then start injecting a bunch of tractor trailers -- traffic smooths out because the small motorcycles can't weave in and out as easily. Class A improvements in friction is due to the same effect. CAFS, with the bubbles, essentially makes mechanically larger structures that roll easily to reduce the effects of turbulence (as perceived as friction loss)

    CAFS into a standpipe is intriguing to me, but like I said in my first post, I'd just use caution and speak with engineers on it. My gut says the standpipes should be able to handle the 100psi air pressure, but what if they don't or if we're forgetting some engineering principle?

    That's a heck of a lot of energy stored in the system. We know what an SCBA bottle can do when it blows. Ok, sure we're only dealing with 1/40th the pressure, but we're dealing with hundreds of times the volume. Without doing the math, my guess is a 10 story 6" riser probably would store the energy stored in 2 or 3 30 minute high pressure bottles.


    =======================
    Now, whoever figures out how to make a system to efficiently strip water out of CAFS will become if not rich, well at least famous and financially comfortable. For one reason: Rural water supply. You could probably reduce long lays to 3" lines since your friction loss is essentially nill and deliver 1000gpm volumes for a mile or more. Can't use air alone (you need the foam to keep it entrained in the water, otherwise it rapidly seperates).

    Hose is always cheaper in overall cost dollar, manpower, and time wise than tankers for each gallon delivered. Make it practical with smaller diameters and for much greater distances, you have a tanker shuttle killer for many areas.

    You'd also want to develop some sort of "flow restrictor" that if there is a sudden surge in flow (such as a line just burst) it would shut down or restrict the flow until the pressure re-equalizes. These would be the safeties on potentially multi-mile lays to protect the public from the stored energy shoudl there be a hose burst. Maybe place them every 200' or so between couplings.

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    Default cafs

    what a god send for the fire service !!!!!!! we used it on a major structior fire at a walmart super center two weeks ago it worked just fine for us as for high rises we dont have anythang over 4stories but we use cafs on every thing on this pretickuler fire we use appx 75gal of class a and80class b we think it was the best investment money could buy.

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    Who/where is the old CAFS guru from the SE/Texas area? Interesting concept.

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    Default CAFS in standpipes

    CAFS can indeed work well in standpipe systems. In fact, the long runs of pipe can actually aid in the mixing times and provide a great foam.

    As far as water hammer and burst, that shouldn't be much of a concern for properly engineered and installed systems. The weakest past of the system will be the hoses, supply or attack, with a 3x safety factor compaired to the pipes 10x factor.

    CAFS through sprinklers is a different story. Reduced orfices such as residential heads will degrade the air/solution mix and result in a watery foam.

    FYI, not all class A foams are suitable for CAFS. A good CAFS/A foam should make a dry foam at .01%. Many class A's won't make dry foams at 1%.

    AFFF's also work well in some sprinkler heads, but expect little to no mechanical aspiration to result in good foam quality. There are foam heads built specifically for high quality foam results.

    As an FYI, check the UL directory to see if your foam is listed with sprinkler heads. Most quality class B foams are. Class A's are not.

    http://database.ul.com/cgi-bin/XYV/c...E/srchres.html

    The question mentioning "decay time" is actually a term measured as "quarter drain time".

    Aspirated class A foams of low expansion are designed to drain quickly to aid in extinguishment. Quarter drain time is the time it takes for 25% of the water to drain out of the aspirated foam mixture. These times run 3-10 minutes for low to mid-expansion foams. CAFS foams can take as long as 1 hour in tests we have done.

    As a note, every CAFS system we have tested is different as far as quality, so YMMV.

    Joe Stonecypher
    Kidde Fire Fighting
    National Foam
    Angus Foam/Hose
    Last edited by jtstoney; 02-20-2006 at 02:39 AM. Reason: Typo correction

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    Quote Originally Posted by jtstoney
    CAFS can indeed work well in standpipe systems. In fact, the long runs of pipe can actually aid in the mixing times and provide a great foam.

    As far as water hammer and burst, that shouldn't be much of a concern for properly engineered and installed systems. The weakest past of the system will be the hoses, supply or attack, with a 3x safety factor compaired to the pipes 10x factor.


    Joe Stonecypher
    Kidde Fire Fighting
    National Foam
    Angus Foam/Hose
    Joe thanks for this valuable input. However, it is always necessary to support such clear statements with 'the evidence'. Could you kindly point me/us in the direction of valid research reports that enable you to be so sure of these issues above.

    Thanks.

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    As far as water hammer and burst, that shouldn't be much of a concern for properly engineered and installed systems.

    I'd hope not as CAFS inherent to the compressibility of air (the "CA") isn't subject to water hammer (which is due to the momentum of effectively incommpressible water).

    I suppose many of these sprinkler systems are tested using air, and certainly there are dry-pipe systems that depend on pressurized pipes.

    Still, given the amount of energy that could be stored in these suckers, and knowing we've had bad experience in the past with the fire service and engineers taking different views of how things should work I'd like to see people with Professional Engineer stamps who design sprinkler systems sign off on the principle of using CAFS in standpipes lessen the chance we're forgetting something.

    One thing I just thought of is with PRVs -- how would a pressure reducing valve react to CAFS? One Meridian Plaza had PRVs set to maintain 60psi downstream of them, regardless of the pressure upstream. That's pretty easy to do with incompressible water -- but how would these suckers react to compressed air flowing through them? It's these types of "Oh, we forgot about that" types of situations we can avoid by working with sprinkler system designers.

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