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Thread: Cafs

  1. #1
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    Default Cafs

    We have a 2002 Darley AUTO CAFS pumper which has the trash line, both crosslays, and all 3 rear hosebed discharges, and deck gun plumbed with foam and CAFS. I wanted to run my CAFS knoweldge through the board here to make sure I'm understanding it correctly.

    From what I have read on here and other sites, a 2:1 or 3:1 ratio of GPMS to CFMS is ideal for attacking fires. Our air presets at 60 cfm (halfway open on the quarter turn valves, this is factory preset). I also understand that if "shaving cream" foam is wanted, one would run a ratio of 2:1, or 2 parts air and one part water.
    Using the above numbers my flows would be something like this:
    Wet CAFS 60 CFM air with 120-180 gpm water
    Dry CAFS 60 CFM air with 30 gpm water.

    I understand that when attacking the fire we still want the ideal target flow of water, and using CAFS doesn't change that. I was wondering, since the truck air compressor is only 230 or 250 cfm, and there are multiple CAFS discharges, if I could choke the air back to say 30 or 40 cfm, and maintain the same ratios mentioned in the above paragraph, if that is acceptable. Is there any circumstance or time I would want to change the ratios or air flows around?

    I also understand that CAFS is a pneumatic calculation, and not a hydraulic calculation. From a previous post on here, I remember that a handline has no noticeable friction loss for up to 2000 feet of hose. However, a point was made about master streams having friction loss. Our truck has a preplumbed CAFS deck gun. What formulas or equations would I use to figure out CAFS for the deck gun?

    I understand that CAFS is finished foam product, and should be applied using the appropriate nozzle. Most of our CAFS lines use 1 1/4 smooth bore tips. Is this an ideal size for the setup mentioned? I had read somewhere that 15/16 or 1" tips were more ideal. Is the larger tip we're using affecting the stream?

    I had fun figuring stuff out on the last post with everyone's help. Thanks in advance for any replies.


  2. #2
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    Fordrules, I have worked extensively with CAFS on one truck previously, part of the spec committee, and was with the department for quite awhile before relocating due to job necessities. As we researched the purchase and planned the training to place it in service these were our main goals. 1.75" CAFS attack line minimum of 100gpm water, 2.5" CAFS line 225 gpm water. The truck was a 06 Pierce 1750 Hale Qmax/Husky Foam/Hercules CAFS 240 cfm compressor. From the research we looked at back then Darley was the only one that I can remember which had valves for the air flow. Therefore wet/dry foam was controlled by changing the water valve position only. In order to make things simple for you, I would seriously consider leaving the air valves where they are, and realize the limitations of the truck for CAFS, and make your additional lines water or foam depending on how the truck is plumbed. Because if you choke back the air flow and maintain the same ratios you will also drop your water flow, Your 120 gpm @ 60cfm goes to 60gpm @ 30cfm that is not the same line and this may have some deleterious effects to your operation.
    As far as the deck gun I have no idea for calculations to help you. The best I would say is maybe pick a flow like 400 gpm water at a 3:1 water to air and see what you get, realize that you will use over half your compressor capacity to make that deck gun work at that flow.
    As far as the nozzle you use, it depends on your theory of CAFS, for us when we put our CAFS engine into service we wanted to be able to have a good line if the compressor went down or we just switched to foam solution or water for the line. Therefore we ran 15/16" smoothbores. This gave us a good line for with appropriate back pressure when not in CAFS.

    Sorry about the lengthy response, you asked alot of questions.

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    Thanks for the reply. Some of my questions were more hypothetical, as only the 2 of the six lines have smoothbores on them. The rest have TFT autos. I do like your logic behind the 15/16 tips. I figure winter is a good time to brush op on theory...

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    Default Darley Contacts

    As you have a Darley AutoCAFS unit have you spoken with any of their folks in regards to your setup ? We have a Darley AutoCAFS Engine on order and they are great folks to work with and can answer any of your questions. Contact either Neal Brooks or Troy Carothers at Darley with any questions you have, they are both extremely well versed in CAFS operations.

    http://www.cafsinfo.com/

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    That site is nothing more then an advertisement for Darley. Too bad, because it contains a lot of information. Their "how to spec a cafs rig" is pretty obviously a Darley-only spec
    Quote Originally Posted by ThNozzleMan
    Why? Because we are firemen. We are decent human beings. We would be compelled by the overwhelming impulse to save an innocent child from a tragic, painful death because in the end, we are MEN.

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    Honorary Disclaimer: While I am a manufacturer representative, I am not here to sell my product. Any advice or knowledge shared is for informational purposes only. I do not use Firehouse.Com for promotional purposes.

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    Quote Originally Posted by Res343cue View Post
    That site is nothing more then an advertisement for Darley. Too bad, because it contains a lot of information. Their "how to spec a cafs rig" is pretty obviously a Darley-only spec
    In his initial post fordrules indicated that he has a "Darley" AutoCAFS pumper that is the reason for referring him to the website. Neal Brooks is the National Sales Manager of Darley's Apparatus Division and is extremely knowledgeable in CAFS and his website does contain a lot of good information on CAFS. Either Mr. Brooks or Troy Carothers also from Darley would be able to assist him with any questions regarding his Darley AuotCAFS system.

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    Thanks for the link

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