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  • FRICTION LOSS FORMULAS

    I am working on rewriting our dept's friction loss formulas. This entails testing & indexing a sample group of over 200 sections of 1-1/2, 1-3/4,2-1/2,3in,&5in hose. So far the "rule of thumb" method most closely resembles our friction loss profiles. The question is,how many of you are using 2Q formula, rule of thumb, or something else, and is it manageable,teachable and do you have the testing to back up your decision?

    [ 07-20-2001: Message edited by: BLACKSHEEP-1 ]

  • #2
    Do you use various brands of hose in each size or do you consistently buy the same brand?

    Reason I ask is I would get the FL numbers from the mfg if you wanted to revise formulas. Or, better yet, get a flow meter, test them like you're doing and screw the formulas, build a pump chart showing the preconnected flows and then how much to incresase for each section added to it and other configurations (wyed lines, piercing nozzles, foam eductors, etc...)

    Each company can do their own testing and that way any plumbing problems specific to that particular apparatus can be noted and accounted for in the pump chart.

    Another bonus - testing to back up your own procedures is already done.
    It's only my opinion. I do not speak for any group or organization I belong to or associate with or people I know - especially my employer. If you like it, we can share it, you don't have to give me credit. If you don't, we are allowed to disagree too (but be ready to be challenged, you may be on to something I'm not). That's what makes America great!

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    • #3
      I knew it wouldn't take long ol' buddy! We use low-bid whatever. By the way, we tested new 5in. Snap-tight hose/snap-tight couplings, and were blowing the couplings off on the acceptance tests, not all but quite a few(200psi).We took the old aluminum couplings and used them on the new hose w/good results. The questionable couplings have a black plastic insert that you can see when you look into the end of the hose.

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      • #4
        You can get the spec sheets for the snap tite here:
        http://www.snap-tite.com/divisions/s...ePDFfiles.html

        They have the FL info on them.

        Snap-tight hose/snap-tight couplings, and were blowing the couplings off...

        I've heard of this happening. There was a forum on it in the old forums, but since you can't search the new ones - or if you can I can't figure it out - I can't find it.

        We took the old aluminum couplings and used them on the new hose w/good results.

        How many? Did the vendor do it for you or did you have to do it?

        I feel bad for you if you did it, it sucks!
        It's only my opinion. I do not speak for any group or organization I belong to or associate with or people I know - especially my employer. If you like it, we can share it, you don't have to give me credit. If you don't, we are allowed to disagree too (but be ready to be challenged, you may be on to something I'm not). That's what makes America great!

        Comment


        • #5
          I offered to do the same thing for my Department after a Pump Operator class. We sat down and figured out what each handline SHOULD be pumped at. After all the math was done, we took a artist paint brush and marked the face of the corasponding (?) guage with what pressure to throttle up to. It has made things A LOT simpler for everyone. Now we set the brake, engage the pump, chock the wheel, check which line is in use, open the valve and thottle up. ALL DONE.

          If you are looking for formulas, e-mail me and I can send them to you.
          Rexcin

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          • #6
            Thanks for the info. Actually WE have been doing the recoupling. One of you out there tried to contact me with some friction loss tables via e-mail. When I went to retrieve it at work I lost it, would you mind resending it, -sorry.

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            • #7
              Some of the operators in my deparment (including myself) were taught a simple way to remember friction loss. 1 3/4" is 40 lbs. 2 1/2" is 15 lbs. 3" is 10 lbs. 5" is 7lbs. All of those are per 100'. Every time I need to pump at an incident, I find myself reciting these numbers...40,15,10,7. They aren't an exact science but, then again, when is firefighting an exact science. We haven't done any solid, concrete testing but in messing around with pressures during drills, we have found that they do come pretty close to the numbers that all the manufacturers put out on their charts. Good Luck, Stay Safe!

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              • #8
                Blacksheep - Oak Ridge NL FD (TN) had a coupling blow in testing a few years ago, it was mde by a 3rd party vendor for Snaptite.

                And if you're replacing the couplings and you didn't work a deal out with the vendor, you're getting ripped off. If this is the case, I would call the mfg rep.

                Scott
                www.gvfd.org

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                • #9
                  FD5017, we use the same rule of thumb up here in Canada only we convert to KPA (kilopascals Go figure eh!) and millimeters. 45mm is 150kpa loss per 45meters and so on.An instructer that tuaght me my Pump A course lectured us on the Q formula till the cows came home. He then asked us if we had it in our heads, we repleyed yes. He then said forget it cause you will never use it again. He then taugt us the rule of thumb, saying that it is what you will use in a hurry on the fire scene. He then went on to say that the best rule of thumb was if the entry team was standing at the door with their thumbs pointing up that meant more pressure, if they were coming out the door backwards with their thumbs down that meant less pressur Whatever you use to make it work is fine just make it easy to use.

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                  • #10
                    I guess he first thing to do would be to see if your department has standardized hose and nozzle loads. If you do then that should make your job much easier. My department has standard loads and nozzles. If you use he 2q2+q method, then figuring FL is easier, as it is all in the hose diameter and quantity of water you are flowing. All you have to do is make a cheat sheet by figuring Fl at various flows, add nozzle pressure, apliances and elevation and you have your Pump discharge pressure.

                    We have what we call a pump panel companion that has all of that information on it. It cross references type of nozzle, nozzle flow,
                    and friction loss for that flow. it also has figures for FL in appliances and the departments aerial apparatus.

                    It also has other various department specific info on it. I is very usefull to me at any rate. We have also dabbled i the CxQxL formula too. But that entails hose testing to determine your departments own coefficient of hose, wich becomes a pain in the behind. If you want any further info feel free to e-mail me.

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                    • #11
                      WE HAVE A CHEAT SHEET ON EACH ENGINE WITH DIFFERENT FLOW RATES THROUGH EACH PRECONNECTED LINE. SAVES TIME AND HEADACHE. BUT WHEN SOME OTHER ARRANGEMENT IS MADE UP FOR WHATEVER SITUATION, I ALWAYS GET THEM WATER FIRST, TAKING A "SWAG"(SCIENTIFIC WILD *** GUESS) THEN AFTER EVERYTHING IS SET TEMPORARILY I WILL FIGURE WHAT THE FL ACTUALLY IS WITH A GREASE PENCIL ON THE SIDE OF THE ENGINE. I HAVE ALWAYS USED THE FL=C*(Q2)*L FORMULA. BEFORE ANYONE SAYS IT IS TOO COMPLICATED, JUST REMEMBER ANY TOOL WILL RUST WHEN NOT USED, ESPECIALLY THOSE TOOLS IN OUR MINDS.
                      IT IS AS SIMPLE AS THE 40,15,10,7 RULE AS LONG AS YOU UNDERSTAND IT.
                      FL=C*(Q2)*L

                      C=COEFFICIENT
                      1.5"=24
                      1.75"=15.5
                      2.5"=2
                      3"=.8
                      5"=.08

                      Q=QUANTITY IN GPM
                      SIMPLY PUT GPM/100=Q EX:250GPM=2.5
                      MULTIPLY THAT NUMBER BY ITSELF
                      L=LENGTH
                      LENGTH IN FEET/100 EX:200FEET=2

                      MAYBE THIS WILL HELP YOU.

                      [ 08-31-2001: Message edited by: firemanred ]
                      Jeff Canada
                      Firefighter/EMT
                      Engine Co. 671
                      Sanger, Texas

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