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CAFS and CLASS B

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  • CAFS and CLASS B

    ok - anyone have any info on the effectiveness of Class B foam concentrate used in conjunction with CAFS?

    Does it work? I have only ever seen CAFS used with Class A foam concentrate.

    Thanx in advance.....

  • #2
    we use B foam with our CAFS system alot. works great!!!!

    Comment


    • #3
      Can anyone direct me to a study or field test of class A used in cafs with flammable liquids. Reason I ask is that I have heard alot of municipalities have been only specing class A systems and no B systems on pumpers due to the large need for B is in a liquid spill, justifying that there wouldn't be enough even with multiple pumpers o/s and they'd rather just use A foams
      Originally Posted by madden01
      "and everyone is encouraged to use Plain, Spelled Out English. I thought this was covered in NIMS training."

      Comment


      • #4
        I believe the Nikiski Alaska fire dept. did a large scale test with LNG and other flammable liquids. I think the gents name I spoke with there was Captain Jim Alleman. They have a LNG plant and several refinery chemical plants in their coverage area and have done a lot of testing on suppression methods

        Comment


        • #5
          Hi All,

          Class B and CAFS.

          Let me start by stating CAFS manufactures strong, very tiny, uniformed bubbles that will "seal" and suppress vapors, which is what is burning in a B type fire.

          Lets forget the type of foam concentrate for now. One of the ingredients key to any succesful CAFS operation is the foam concentrate. Whatever type of concentrate that is used must be able to make bubbles and hold its bubbles structure after being manufactured.

          So most B foam concentrates will work very well with CAFS. You may not use as much concentrate compared to an aspirating application due to the small, uniform bubble structure of the CAFS bubble. What you have to remember is B foam concentrates are very viscous, thick like molasses. Most foam proportioners utilized with a CAFSytem are small or around 5 gpm and/or have a difficult time pumping the thicker B concentrates. But if you spec a bigger foam pump to do the B foam you may not be able to pump at the lower injection rates, .2 or .3 which are common for A foam operations.

          That is one on the reasons I don't suggest or recommend a dual tank system. The other reason is the cross contamination of the A and B concentrates. Remember A and B foam concentrates do NOT like each other. When they mix together a chemical reaction occurs that will become your worst nightmare. The departments that I know, mine included that have a dual tank system have experienced this problem to one degree or another.

          Will an A foam that is applied with CAFS extinguish and suppress vapors? I have to say "yes" based on my own experience on the fireground. My department, while at our local county training academy a few months ago had them light off some 4 x 8 tubs of water with diesel fuel and gasoline. The local "foam" instructor was very confident that when we applied our A foam with our CAFSytem it would not work. We flowed approximately 45 gpm of water and injected Class A foam at .7%. The A concentrate that we used was Phos-Chek WD881. We applied it using one 1 3/4" handline with an open 1 3/8" ball valve as the nozzle. The finished foam that was applied was of a shaving cream type consistency. We did have a backup line in place, just in case.

          We lit off the fuel, about 15 gallons total, 5 gas and 10 diesel, let it get going and started to apply the foam. It went out in about 1 minute, 35 seconds. There was a very visible foam blanket on the water. The "foam" instructor still was not convinced that the A foam worked on the B fire. He went on to say that we did not have vapor suppression. I told him to go and try and light it off with the propane pole torch. He tried and it would not light off until we wash the foam blanket away. I know this was not a "scientific" study, but it worked. And we did it 5 more times with the sane results. The "foam" instructor was still not convinced, but my department and I were.

          Hope this helps,

          Captain Lou
          "Got Foam?"
          Last edited by CaptLou; 03-01-2007, 07:55 AM.

          Comment


          • #6
            I've heard they did or are doing some studies of using A foam on B fires.They say you might have to coat it twice with the A but it still does the job. The reason I guess is knock it with A then coat it with B. As we all know B foam is very expensive!! And the big companies will save some $$ this way.

            Comment


            • #7
              I would think that once the fire is knocked down the vapor suppression is solely dependant on the staying power of the foam blanket. Captlou, can you give us some relative times for the time it takes for a class A foam blanket to break down? One would think a study similar to the non-scientific one you conducted that put an ignition source above the faom blanket would allow you to see how long before enough vapor was released to re-ignite?

              Good topic, we've had B foam systems on our pumpers for a long time and generally the foam needs to be dumped (training) due to age vs. the number of times we use it. Of course the potential is always there. We've proposed a regional B foam trailer in hopes that depts. could save a few bucks and still have a more realistic foam capability present.

              Comment


              • #8
                RFDACM02,

                We didn't monitor the time or wait and see how long it took for the foam blanket to finally break down. This being a "lets see if" training session.

                Like I said in my post we injected the concentrate at .7% to make a thicker bubble that would last longer to increase drain time. I could try .9 or 1% the next time and compare drain times.

                Phos-Chek WD881 has consistently made great bubbles for us since 1998. I had read in one of their adds in a fire magizine that WD881 would work on B type fires. And it did. It would be nice if Phos-Chek would conduct a test and see how their foam concentrate performs on B fires or spills in a CAFS application, since CAFS does make strong, small, uniform bubbles.

                The next time my department is at the academy I'll do more non-scientific testing.

                Be Safe,

                Capt Lou
                "Got Foam?"

                Comment


                • #9
                  We have been using class A CAFS for about 6 years now and in exposure protection we have put shaving cream consistency on a vinyl sided house 15 ft. from a fully involved car fire that extended into the garage next to the house and had no damage to the vinyl siding on the house.
                  If you dry the cafs out it will stick and last for over 12 hours if the wind stays down and doesn't dry the mixture out and break down the bubble structure. A blanket of dry CAFS foam will stay on top of a porta tank overnight with no problem thats as long as we have tested it.

                  Comment


                  • #10
                    If you want a thicker or dryer finished foam, increase the ratio of compressed air to foam solution. Remember, compressed air takes up only 30% of your hose. If you change the proportioning ratio of foam concentrate to water, you might need to change your nozzle. Anything higher than .8 or .9%, your loosing the benifet of cafs. Cafs with class b ratios should be the same (0.3-0.5%) with the right size tip. AR-AFFF is recomended for cafs.
                    Last edited by oledriver; 03-01-2007, 10:05 PM.

                    Comment


                    • #11
                      Originally posted by oledriver View Post
                      If you want a thicker or dryer finished foam, increase the ratio of compressed air to foam solution. Remember, compressed air takes up only 30% of your hose. If you change the proportioning ratio of foam concentrate to water, you might need to change your nozzle. Anything higher than .8 or .9%, your loosing the benifet of cafs. Cafs with class b ratios should be the same (0.3-0.5%) with the right size tip. AR-AFFF is recomended for cafs.
                      We were told anything over .5 with A is wasting it.

                      Comment


                      • #12
                        Hi All,

                        We seem to have stimulated some good discussions regarding dryer or wetter foam.

                        To make the foam dryer in a CAFS operation you are correct less water, more air. But to make a "thicker" bubble, that will have a longer drain time, you add more concentrate.

                        Now for CAFS operations, .3% is the stating point for setting a proportioner for a fire attack operation. Most concentrates, depending on the quality, will work great at .3%. I do know with Phos-Chek WD881, I can make good bubbles at .2%, because WD881 is a good, quality concentrate. There are other concentrates on the market that I have tried and to get the same or similar results as the WD881, I have to go as high as .6 or .8%. As I have said before in order for any CAFSystem to work the concentrate has to be able to make bubbles.

                        It is also a fact that Class A foam injected above 1% will make such a thick bubble that it will impede the release of water. Therefore, extinguishment will not occur as fast compared to a lesser amount of concentrate being injected.

                        My comments about .7% was for B type of fires. The reason for injecting more concentrate is because you want to slow down the breakdown of the Class A foam bubbles. Remember, Class A foam is carbon loving and a surfactant. Diesel and gasoline are carbon based. So to slow the breakdown of the Class A foam blanket you make a thicker bubble. You are basically asking the Class A foam to do something that it was not really designed to do. But because of the efficiency of a CAFSystem to make strong, small uniformed bubbles, Class A foam when applied with a CAFSystem works on B type fire or spills.

                        Something I didn't mention in my prior post while trying extinguish the B fire at the academy was that when I tried to "dry" the foam out with less water while injecting concentrate at both .5% and .7%, it appeared that the heat from the fire was evaporating what little water I was flowing (30-35gpm) before it could settle onto the fire. When I increased the gpm to around 45 gpm the "foam flakes" stopped rising up and the blanket was able to fall into the pan and start to smother and extinguish the fire and vapors. The .7% injection rate just made it harder for the blanket to breakdown as the bubble was thicker. The water was only making the foam a little wetter.

                        Hope this helps,

                        Capt Lou
                        "GotFoam?"
                        Last edited by CaptLou; 03-02-2007, 11:30 AM.

                        Comment


                        • #13
                          hey, Lou (or any others out there) have you heard of any foam that is both A and B type. Is it useful?

                          My chief wants it but I cannot find too much on something out there. On the next bid spec, I wanted to know if we could go for that type or if just to go with A only or 2 different tanks again.

                          All re: welcomed for this one...
                          Originally Posted by madden01
                          "and everyone is encouraged to use Plain, Spelled Out English. I thought this was covered in NIMS training."

                          Comment


                          • #14
                            Hi ffmedcbk1,

                            I have seen some of the so called A/B foams. Not impressed. I find it hard to believe that you can make a concentrate that is carbon loving for A fires and non carbon loving for B fires. Think about what each foam is supposed to do.

                            I would recommend that you stay away from A/B type concentrates. Install a single tank system for A foam only and spec a CAFSystem. Dual tank foam system setups work, but every department I know that has one, mine included, has had cross contamination issues that have caused major operational and $$$$ problems with the foam system. And most were caused by a firefighter doing something wrong. I don't recommend a dual tank setup.

                            If you want something for that B incident, think about a county foam trailer with inductors and matching nozzles.

                            Like I said before a CAF'd, quality class A foam concentrate will extinguish a B type fire.

                            Hope this helps,

                            Capt Lou
                            "GotFoam?"

                            Comment


                            • #15
                              This is great. Very good thread. We are getting our first CAFS pumper, and can't wait to use this knowledge.

                              Insofar as class B fires, I was pretty much thinking (Uninformed) that the class A would do fine through the CAFS system, but my backup plan is to use a foam eductor and the old pickup line into the bucket for class B foam.

                              We only speced a foam cell for A.

                              Comment

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