1. #1
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    Default CAFS & Tank fill operations

    Hello all, We are speccing our pumper with CAFS; we have been told that it onlly operates from the tank supply; and not a positive pressure water source; ( tanker/tender supply,supply hoselines, hydrant etc) Is this true, and if so,the tank to pump flows being 500-600 gpm or so.Why spend the money on a 1500 gpm pump for an attack engine when you will never use it?

    Any body want to help out an old time mpo>>>>>>>>>>>>

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    We just recieved a CAFS engine a couple of months ago, Waterous pump and CAFS system, KME engine.

    We have had tremendous success with this. One of the things that KME is doing, is ANY CAFS system includes a training class, at your department, from the system manufacturer. Waterous sent a guy down to our department, and after 30 years in emergency services, I think I learned more from this weekend class than any weekend class I have ever been to.

    With that said, I would URGE you - whoever you buy from, get this kind of training. Not from your local dealer, not from the manufacturer, but from the CAFS system manufacturer.

    Our foam is injected on the outlet side of the pump, so if your water is coming through the pump, even if the pump is idled, the CAFS system does not care. In our system, you DO need to have the PTO running to run the air compressor, but other systems will allow you to run off 12VDC, or even stored air bottles. The system does not care if the water came from the tank, suction inlet from hydrant, tanker, etc.

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    Here is an idea based on no practical experience of mine whatsoever, just what I have read.

    The article I have read indicates that w/ hydrant pressure and only running a single line or so, the engine does not have to throttle up much to supply the line. Since the compressor runs off the engine as well, the compressor is not driven fast enough to generate the cfm's needed for CAFS.

    On tank water or draft, the engine is throttled up higher and then so is the compressor which then supplies enough compressed air to the CAFS system.

    Sounded sort of logical, but wouldn't the manufacture account for this and build the system accordingly?

    Again, I read this. I have no experience with CAFS.

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    Default Logic

    I want a simple system to operate, and we will put in the training....You would think it would work under all conditions....... Why not put the compressor drive to operate under the fast idel mode .....or 75-80 psi pump pressure.

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    DFDMaxx has it right, you need some engine speed to turn the CAFS air compressor. Unless your hydrant pressures are pretty low, you will want to be operating from tank. That way you need to bring on some engine RPM to make hand line pressure. At the same time you get enough compressor speed to make air. On our newest engine, in order to make sure that we wouldn't run the tank dry, we had an automatic tank fill plumbed ahead of an MIV.

    The logic for retaining the 1500 GPM (or whatever size) pump is that there probably will be times when you just need to flow large volumes of straight water, no foam.

    Stay safe out there, everyone goes home!

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    I say again though - NOT ALL CAFS COMPRESSORS RUN OFF THE PTO!

    Some are 12 Volt - such as the one Pierce offers, and Waterous makes a
    stored air system, no compressor.

    (I am sure Pierce offers others - but the one they offered us was 12VDC.

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    We took delivery of a CFAS engine in March.

    It is great, Simple(relitivly) and work the same on tank,hydrant or from the porta tank.

    Watrous 1250 pump and Cafs, foam pump is foam pro.
    Compressor runs off PTO, We also run Hydraulice genset off another pto port.
    International 7400 chassis.

    You do need to train often with what ever you get.

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    We have a CAFS system on our 2004 engine. It has a Waterous 2000 GPM pump and CAFS system. We have not had any problems operating. Our typical structure fire if that is the first engine in it is supplied by the tanker until the drop tanks are set up, then drafting operations are started. Our response area has no pressure hydrants.

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    Hi: All,
    There are several things to look at when running a CAFS
    Most systems on the market are either driven from the main fire pump or PTO driven
    In simple terms with any compressor system CFM is a function of RPM (the faster the compressor turns the more air it will produce)
    That being said
    The fire pump to some point is the same impeller RPM produces volume (GPM) and PSI
    On a normal pump if connected to a hydrant or external source we only throttle up to SOP pressures
    simple Now let,s look at CAFS
    CAFS is run at lower pressures than water
    Usually 100-120 PSI
    If the system is connected to a hydrant or external source (inlet) and pressure is higher than 100-120 PSI than the pump just ideling will boost about 20-25 PSI pressure usually about 125-150 PSI
    If the maximum PSI a CAFS runs at is 150 the system will still work
    However we would like to be around 100-120 PSI
    If inlet pressure is higher then issue becomes more difficult must get pressure lower there are ways to do this
    One direct tank fill or an inlet pressure reducing valve or gate the inlet
    If inlet pressure is lower then not such an issue
    The systems on the market work fine at fairly low engine RPM
    But I do see many operators when connected to a hydrant think they must throttle up
    Look at the pump pressure it may not be necessary
    Now the Compressor
    The systems that are capable of producing around 200 CFM will usually produce about 80-90 CFM at engine idle
    Depending on what flows you are wanting to do this will supply usually 1 or 2 hand lines not a problem
    Now some questions need to be delt with to determine what will work best for your truck in your area
    If you have hydrants what is the highest PSI what is the Lowest PSI
    I have seen hydrants as low as 60 PSI and as high as 170+
    Usually hydrant PSI below 90 PSI works fairly well above this look at a way to reduce pump inlet pressure
    But there is no one answer for all
    I would suggest talk to the manufactures ask questions but have answers or get answers to their questions talk to them
    All will be happy and safe
    Thank you
    Ray

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    Hi All,

    Engine305, the reason stated by chiefengineer11 are correct. However, another more important reason is safety for the nozzleman. Keep in mind that any handline operated at a greater main pump discharge pressure than 100psi will be very, very difficult to handle. That being said, if your intake pressure is greater than 80psi, then at an engine idle, with a 1500 gpm pump, the main pump discharge pressure will most likely be well above 100psi. Will it make CAFS? YES, but it will be a difficult line to handle. Also the maximum main pump discharge pressure during any CAFS operation is 145psi. You would only use this for unmanned lines, deckgun, ground monitor etc...That is why it has been stated that CAFS works best from a static source such as a booster tank or drafting.

    chiefengineer11 solution is a very simple and doable solution to this problem.

    My department utilizes a direct tank "Auto-Fill" setup similar to what chiefengineer11 has. Our booster tank asks as a "buffer" between water supply and pump. If we are supplying or relaying we can easily have the water go directly into the pump by opening a valve.

    Training is the key and Waterous does include training with most of their CAFSystems. Take a look at their web site for more information regarding CAFS and training. Another good web site for CAFS information. http://www.compressedairfoam.com/com...irfoam.com.htm

    Hope this helps,

    Captain Lou

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    Default Tank fill

    Thanks guys.. a few companies are specing a regular manual tank fill, Pierce put in an auto tank fill at the rear connected to the tank level gage..

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    Default Yes There Is An "Auto Tank Fill" Feature

    I've just done 13 new Waterous Eclipse CAFS Engines for Vancouver and a number of other FD's as well as some Hale Cafspro and you can get a "Auto Tank Fill" feature that is integrated into either or both of the 6" Steamer Ports and a Rear Inlet (if spec'd)

    This control uses a Tank Sensor that opens and closes a line between the inlet and the tank to keep the tank constantly filled and is ideal to avoid the issues of operating from the tank only and then having to run a refill line back into the tank through the 2-1/2" Auxiliary Inlet.

    Any apparatus builder should be able to do it and I wouldn't spec a CAFS without it as it makes it a lot easier and less cumbersome for the Pump Operator.

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    Quote Originally Posted by Engine305 View Post
    Thanks guys.. a few companies are specing a regular manual tank fill, Pierce put in an auto tank fill at the rear connected to the tank level gage..
    Are you talking about the Foam tank? I have the tank fill that you use for the
    foam, where you just set the bucket of foam on the ground, stick the pickup tube into it, and push a button.

    Lots better than lifting those buckets up ontothe engine.

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    Default cafs

    Eng305
    I looked up CAFS in NFPA1901-2003. Section 22.9.1.1 requires the water pump to flow 2 gpm of water for each 1 cfm of compressor flow as a minimum requirement. So with a typical 200 cfm compressor the pump has to flow 400 gpm. So a typical CAFS system would never supply enough air to use the full 1,500 gpm for CAFS operation.
    More like 200 to 600 gpm. depending on how dry you want the foam.

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    You are correct on the NFPA requirment of minimum 2 GPM for every 1 SCFM
    witha 200 SCFM system a minimum of 400 GPM is required
    If running 2-1 you can run a 3-1 this would be 600 GPM and 200 SCFM
    You could go up to a 4-1 but the CAFS gets to wet around there
    As for why a 1500 GPM pump it could be a requirment for an ISO rating as many departments do this
    If this is not the case
    How much water can your hydrant system flow and what are the pressures
    Minimum and maximum
    Or just go with a direct automatic tank fill with a 2.5" connection
    Stay Safe
    Thanks
    Ray

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    CAFS is a relatively low-flow operation (usually about 90gpm per 1 3/4 line), so you don't really need a lot of water coming into the truck. The purpose of the (in our case)2000gpm pump is for big water evolutions, relay pumping, feeding an elevated stream. Also, if the fire you're fighting with CAFS turns out to be too much for CAFS you have ample reserve to feed those thirsty smooth bore nozzles should you switch to straight Class A or H2O.

    I've been an engineer on a large CAFS Rescue Pumper for 7 years now and can testify to the need to keep RPM's up, you still get CAFS at lower RPM's but the quality is much better if the engine is running at least 1000rpm. It took us a few years to really understand this.

    The next CAFS pumper we spec I'm going to push for the auto-fill. At least on Hale pumps, if you get a Hale MIV you can place an auto-fill on one of the unused intake relief valve ports on the side of the truck you normally hook up your pressurized water supply to. It will keep your tank topped off while still keeping you tapped into the big plug should you need lots of water.

    I recommend against making it SOP to hook into a direct tank fill and not your steamer, as if the fire goes down hill you'll not be able to take advantage of incoming pressure to flow big water.
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    Quote Originally Posted by Engine305 View Post
    Thanks guys.. a few companies are specing a regular manual tank fill, Pierce put in an auto tank fill at the rear connected to the tank level gage..
    the auto fill is the way to go. they are on our trucks now and as well as our Pierce that is on order. The only thing I dont like about it, is not knowing your residual.

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    Default ...

    From what I have been told - the reason to run your CAFS system off of the tank rather than from a pressurized water source is to maintain an even / steady flow of water so that the CAFS compressor can easily match the pump pressure.

    When running CAFS - there is USUALLY an air compressor switch on the pump panel that allows the compressor to run in "AUTO" or "FIXED" mode. FIXED mode would be used for running auxilliary equipment off the compressor (ie. air chisel, lifting bags etc.) AUTO mode is used when pumping CAFS. In order for the foam to have a consistent texture - the compressor trys its best to match the pump discharge pressure. If you run from a pressurized water source, inlet pressure tends to fluctuate, which results in increases and decreases in engine RPM - resulting in increases and decreases in pump pressure - which further results in compressor cfm's increasing and decreasing. All this increasing and decreasing means the nozzle man will get bucked around by the hose, and will have crappy foam at the tip.

    Anyone agree or disagree?

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    Quote Originally Posted by canuck1 View Post
    If you run from a pressurized water source, inlet pressure tends to fluctuate, which results in increases and decreases in engine RPM - resulting in increases and decreases in pump pressure - which further results in compressor cfm's increasing and decreasing.
    While on the surface this may sound correct, in reality modern CAFS systems are very well regulated in that regard (it was true with older systems like WEPS). There is a pretty complicated auto balance system (which you over ride in "Fixed" mode) which, if correctly adjusted, should keep your air pressure within 5psi of the water. CFM rate is set by gating the air valve, usually left wide open on most of the setups I've seen of late.

    If you see a system beating the nozzleman up it is usually a result of insufficient foam concentrate being injected into the water stream, the results are called "Slug Flow" and it is dangerous. Almost every time I've seen this it was because the foam tank ran dry or the operator turned off the (or failed to turn on) the foam system. Other possible causes are too low a concentrate % level, and too short of a hose on the discharge (insufficient mixing of the air and foam results in both cases).

    The root of the problem with pressurized water supplies, as I see it, is the engine RPM is too low to turn the compressor fast enough to generate the volume of air needed for CAFS operation. The results are a very wet foam and heavy lines.
    Last edited by Fire304; 09-28-2007 at 01:39 PM.
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    Quote Originally Posted by Fire304 View Post
    While on the surface this may sound correct, in reality modern CAFS systems are very well regulated in that regard (it was true with older systems like WEPS). There is a pretty complicated auto balance system (which you over ride in "Fixed" mode) which, if correctly adjusted, should keep your air pressure within 5psi of the water. CFM rate is set by gating the air valve, usually left wide open on most of the setups I've seen of late.

    If you see a system beating the nozzleman up it is usually a result of insufficient foam concentrate being injected into the water stream, the results are called "Slug Flow" and it is dangerous. Almost every time I've seen this it was because the foam tank ran dry or the operator turned off the (or failed to turn on) the foam system. Other possible causes are too low a concentrate % level, and too short of a hose on the discharge (insufficient mixing of the air and foam results in both cases).

    The root of the problem with pressurized water supplies, as I see it, is the engine RPM is too low to turn the compressor fast enough to generate the volume of air needed for CAFS operation. The results are a very wet foam and heavy lines.
    I think that means he agrees with you canuck.

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    I would say he kind of agrees
    To a point both are correct with the exception of the actual reason for idealy running a CAFsystem from a tank rather than the hydrant is
    The compressor needs RPM to produce air SCFM
    In other words CFM is a function of RPM
    the modern systems used today are very simmilar to the older systems with the exception of the air control circuit now usually called AUTO
    For the most part the systems on the market now are about 140-200 SCFM
    depending on the gearing driving the specific compressor the systems will produce the specified SCFM at about 1300 to 1500 engine RPM
    Some systems are at lower RPM some are at Higher RPM but about
    Now
    If connected to Hydrant at lets say 80 PSI witha 1500 GPM pump Truck Idle about 800 RPM (Lets say for Arguments sake) This is an avarage truck
    At idle the pump will usually produce about 20-25 PSI so now our pressure is at 100 to 105 PSI water pressure
    The average 200 SCFM compressor system is capable of producing about 80SCFM at idle
    So a single hand line attack could feasably be used
    depending on the flow could possibly use 2 handlines
    1.5/1.75" with 15/16" or 1" tip water flow about 80-90 GPM and air flow 30-40 SCFM
    But the average pump operator for some reason feels the need to throttle up
    and then the system pressure gets out of hand system pressures out of wack why it does not take much engine RPM to raise pressure from hydrant inlet pressure
    But a direct tank connection does make easier for the operator
    But a good operator can work with their equipment and manage the inlet water pressure it just takes some practice
    Stay Safe
    Ray

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    Quote Originally Posted by RFREY1 View Post
    But the average pump operator for some reason feels the need to throttle up ...

    But a good operator can work with their equipment and manage the inlet water pressure it just takes some practice
    "for some reason" after about 2 years of operating a 200cfm pneumax system on a 2000gpm Hale pump I realized that in CAFS made with hydrant pressure alone (and the resulting low RPM) the quality was crap, that every time I ran off of tank water (and roughly 1200rpm) the loft of the foam was much better and more consistant. I am at a loss to explain it, all the numbers say hydrant pressure and a single 15/16th tip should make the same quality foam as that from tank water, but it does not. I have since gain proficiency at balancing the MIV to keep the residual pressure below 20psi, which allows me to fill my tank and keep RPM up. If the hose is shut down the pressure goes up and the RPM's drop to idle, when CAFS is flowing I get my RPM's back. If time permits I'll also run a 2.5" hose to the aux inlet which is easier to gate, but I maintain the LDH in case I need big water fast.

    I've also notice that in communities from my area CAFS comes in two flavors; 200CFM and 80. Many are retrofitting or specing small 80 CFM units (usualy 2 1.5" preconnects and one 2.5" discharge), as they are much less expensive and do not ballon up the size of the pump house like the bigger units. Beside, if you need more than 2 handlines you're probably beyond the CAFS capability any way.
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    Quote Originally Posted by Fire304 View Post
    "for some reason" after about 2 years of operating a 200cfm pneumax system on a 2000gpm Hale pump I realized that in CAFS made with hydrant pressure alone (and the resulting low RPM) the quality was crap,
    I've also notice that in communities from my area CAFS comes in two flavors; 200CFM and 80. Many are retrofitting or specing small 80 CFM units (usualy 2 1.5" preconnects and one 2.5" discharge), as they are much less expensive and do not ballon up the size of the pump house like the bigger units. Beside, if you need more than 2 handlines you're probably beyond the CAFS capability any way.
    Have you ever seen a high volume CAFS on a LARGE WORKING FIRE? I have to grin when I read some of the experts talking about their CAFS and using tiny little nozzles like the 15/16 tips, and then they must be joking when they say to use 40 to 80 cfm and 2 gallons to 1 cfm expansion ratios. They don't even understand how adjusting the concentrate settings higher than .3 or .5, and what that does to the foam. No it does not make it dryer or wetter.

    My suggestion is to keep an open mind about CAFS until you see what a good operating, unrestricted CAFS can actually do when you let the bubbles do the work instead of trying to use the same ol water fire flow as before. Or maybe the pump manufacturers would like us to keep buying the big, expensive water pumps. If you throttle a CAFS down to a booster size discharge, you are defeating what a CAFS can do for you, and you would be better off not wasting your time or money.

    The real CAFS users are a special kind of fire fighters, keep up the good work.
    Mark Cummins

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    This is an older thread but what no one has mentioned here is the need to have a GPM flow meter to compare to the SCFM. You need to be able to compare the two. A 2:1 ratio (2 parts water to 1 part air) is considered wet foam. It's not a whole lot different than foam and water. It works for direct fire attack, but defeats the purpose of CAF. 1:1 is considered medium foam. It's still ok for direct fire attack. 1:2 is the clasic "shaving cream" CAF. It should just be used for exposure protection. It doesn't have enough water content for interior fire attack. The auto tank fill is a great option and I wish we had it. Bottom line though, if you can't compare your GPM to your SCFM, you can't say for certainn what ratio of foam you are making.
    Last edited by TVFR9923; 04-03-2008 at 11:58 PM.

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