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  • Solid bore tip restrictions.

    Sorry guys / gals. Racking my brain here trying to remember the rules of thumb regarding hose size versus tip size. We don't use them much in my areas so the knowledge is stale. Anyone got any material on it at hand? Anyone got a standard for 2.5 and 3"?


    Thanks.
    Ian "Eno" McLeod
    Senior Firefighter /EMT-A, A Shift
    HESD / OFD
    "To me, the charm of an encyclopedia is that it knows and I needn't."

  • #2
    Old rule of thumb for solid bore nozzles was that the nozzle size shouldn't be more than 1/2 of the hose size.

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    • #3
      Originally posted by jlcooke3 View Post
      Old rule of thumb for solid bore nozzles was that the nozzle size shouldn't be more than 1/2 of the hose size.
      thats the one I know.

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      • #4
        Originally posted by jlcooke3 View Post
        Old rule of thumb for solid bore nozzles was that the nozzle size shouldn't be more than 1/2 of the hose size.
        We were taught that one in training.

        I don't think there is a limit of tip size. I would be more concerned about GPM, reaction force, and friction loss.

        Maximize the GPM by using increasingly larger tips until either the nozzleman can't handle it effectively, or the pump pressure gets much over 150 psi.

        We used a 15/16" tip on a 1¾" line successfully. The GPM @ 50 psi is 185. With a 200' preconnect, the discharge pressure was 155, about the same for a 125 GPM Fog.

        You could give a house fire a swift kick in the nads with that line.
        The American people will never knowingly adopt Socialism. But under the name of 'liberalism' they will adopt every fragment of the Socialist program, until one day America will be a Socialist nation, without knowing how it happened. --Norman Mattoon Thomas, 6 time presidential candidate for the Socialist Party of America

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        • #5
          Thanks for the confirmation!
          Ian "Eno" McLeod
          Senior Firefighter /EMT-A, A Shift
          HESD / OFD
          "To me, the charm of an encyclopedia is that it knows and I needn't."

          Comment


          • #6
            My volly FD uses 1 1/4 inch slug tips on our 2 inch hose. We flow around 300 gpm at 40 psi at the tip.

            As has been stated the nozzle no greater than half the size of the hose was the old rule of thumb. But I guess like many other rules this one may have been made to be broken.
            Crazy, but that's how it goes
            Millions of people living as foes
            Maybe it's not too late
            To learn how to love, and forget how to hate

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            • #7
              Originally posted by firefuss
              they still make 2"
              I am not sure the point of this part of your post. Whether you are asking a question, making a statement, or being sarcastic...

              Yes, indeed they still make 2 inch and in my opinion, in our particular situation it is the perfect answer to our situation. We are a bedroom community with few resources during the day. Many times the first rig will roll out with 3 or 4 on board and that is all we will have for 5 to 10 minutes, even if we call mutual aid. We can't make the mistake of pulling the wrong size line and hope someone will cover us by pulling the 2 1/2. The two inch hose we use with the nozzle we use, a 200 gpm at 75 psi combination tip with the 1 1/4 slug behind it allows us to underpump to start and flow around 160 gpm at 55 nozzle pressure. If that isn't doing it we can go to 200 at 75, or dump the combo tip and go to almost 300 at 40 with the slug. Flow range from a 1 3/4 inch line all the way up to a hard hitting 2 1/2 with the same hose line. And YES, we move it with 2 guys on the line without any difficulties. So YES, they still make 2 inch and if more FD's would look at being progressive instead of set in their ways they might take a closer look at 2 inch hose.
              Crazy, but that's how it goes
              Millions of people living as foes
              Maybe it's not too late
              To learn how to love, and forget how to hate

              Comment


              • #8
                Nozzle diameter - vs - hose size

                When making flow calculations for SS nozzles, the nozzle diameter needs to be 1/2 or less than the hose diameter. That is the 29.87 X d squared X Sq. Rt. of Nozzle Pressure will give an incorrect flow calculation as the size of the nozzle is increased above 1/2 the hose size. As covered in some texts, the water is being accelerated at the nozzle by the nozzle pressure. With a hose size exactly the same as the nozzle, there would be very little pressure at the nozzle base, and the velocity of the water exiting the tip would be nearly the same as the velocity through the hose line. Poor reach or patterns will be the result. This does not mean that you can't exceed the recommended 1/2 ratio, it just means that you probably won't get the stream shape or performance that you expect. You definitely won't get the reach, but the reaction force should be slightly less. A good estimator for reach is Np/2 + 45 ft for SS nozzles in the 50 to 80 psi range on proper size hose lines.
                Last edited by KuhShise; 07-21-2008, 10:00 AM.

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                • #9
                  Originally posted by KuhShise View Post
                  When making flow calculations for SS nozzles, the nozzle diameter needs to be 1/2 or less than the hose diameter. That is the 29.87 X d squared X Sq. Rt. of Nozzle Pressure will give an incorrect flow calculation as the size of the nozzle is increased above 1/2 the hose size. As covered in some texts, the water is being accelerated at the nozzle by the nozzle pressure. With a hose size exactly the same as the nozzle, there would be very little pressure at the nozzle base, and the velocity of the water exiting the tip would be nearly the same as the velocity through the hose line. Poor reach or patterns will be the result. This does not mean that you can't exceed the recommended 1/2 ratio, it just means that you probably won't get the stream shape or performance that you expect. You definitely won't get the reach, but the reaction force should be slightly less. A good estimator for reach is Np/2 + 45 ft for SS nozzles in the 50 to 80 psi range on proper size hose lines.
                  I understand the science that you quote, But we have been using the 1 1/4 inch tip on our 2 inch lines for years and frankly it works for us. Yes, the stream may not be as pretty but when you are inside of a building how much range do you really need? 20, 30, 50 feet? Even outside we get a good reach of about 70 feet before the stream breaks up substantially.

                  I guess it may not be for everyone, but it works well for us.
                  Crazy, but that's how it goes
                  Millions of people living as foes
                  Maybe it's not too late
                  To learn how to love, and forget how to hate

                  Comment


                  • #10
                    My point illustrated exactly!

                    Fyred up, you just confirmed my statement. You said in your posts above that you were using 40 psi nozzle pressure and flowed about 300 gpm. The 300 gpm comes from the stated formula, but I just said that the calculation will be incorrect when the nozzle diameter begins to exceed 1/2 the hose diameter. You can't have it both ways. Now please tell me that your standard engine pressure on that 200 ft. of 2" line is about 190 psi or we will prove again that you are mixing apples and oranges and coming up with non-existant bushels. The friction loss in 2" at 300 gpm is around 72 psi per 100 ft. or at best using Ponn Supreme is 66 psi per 100 ft.
                    Second, I never said that it wouldn't work. What I did say was that improperly selecting nozzle diameter or effective diameter in excess of 1/2 the hose diameter will adversely affect the operational characteristic of the nozzle discharge in pattern and reach.
                    Kuh Shise just an old German B.S.er

                    Comment


                    • #11
                      Originally posted by KuhShise View Post
                      Fyred up, you just confirmed my statement. You said in your posts above that you were using 40 psi nozzle pressure and flowed about 300 gpm. The 300 gpm comes from the stated formula, but I just said that the calculation will be incorrect when the nozzle diameter begins to exceed 1/2 the hose diameter. You can't have it both ways. Now please tell me that your standard engine pressure on that 200 ft. of 2" line is about 190 psi or we will prove again that you are mixing apples and oranges and coming up with non-existant bushels. The friction loss in 2" at 300 gpm is around 72 psi per 100 ft. or at best using Ponn Supreme is 66 psi per 100 ft.
                      Second, I never said that it wouldn't work. What I did say was that improperly selecting nozzle diameter or effective diameter in excess of 1/2 the hose diameter will adversely affect the operational characteristic of the nozzle discharge in pattern and reach.
                      Kuh Shise just an old German B.S.er
                      We used a calibrated flow meter and an inline pressure gauge located behind the nozzle to set the flow and APPROXIMATE nozzle pressure. The flow was what we cared about, not the nozzle pressure.

                      As for the exact engine pressue I would have to stop at the FD today and look at the markings by the discharge to see what the engine pressure is. The friction loss is solely dependent on the type of hose and not on some formula that is a catch all rule of thumb place to start. It is IMPOSSIBLE for that formula to be accurate across the board because of the different types of hose, rubber lined double jacketed, thermoplastic lined double jacket, and nitrile rubber hose. The formulas have always been linked to the double jacket rubber lined hose which frankly we haven't used in years.

                      As I said you can do whatever you please, as will we. I will take our flow meter and pressure gauge tests over your claculations anyday of the week. The fact that we actually do this and it isn't just theory makes it 100% believable to us.
                      Crazy, but that's how it goes
                      Millions of people living as foes
                      Maybe it's not too late
                      To learn how to love, and forget how to hate

                      Comment


                      • #12
                        Originally posted by KuhShise View Post
                        The friction loss in 2" at 300 gpm is around 72 psi per 100 ft. or at best using Ponn Supreme is 66 psi per 100 ft.
                        Our Ponn Conquest is markedly better than our Ponn Supreme when it comes to FL.

                        I think the point is clear that you cannot use the values for gpm with the standard formula when the orifice is greater than half the hose diameter and get the accurate results you get when the orifice is smaller than half the diameter. The FL formulas are not absolutes due the number of variables, but flow through an orifice is.
                        Last edited by RFDACM02; 07-24-2008, 10:43 AM.

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