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  • 350 gpm TFT

    Question? Can you really get 350 gpm out of the TFT fog nozzle on an 1.75 line?

  • #2
    Yes, but with caveats:

    -- Using the traditional friction loss for 1.75" rubber lined hose, and assuming 150' of 1.75" and a 100psi nozzle pressure, you need 385psi on the pump.

    -- Better, newer designed hose like Angus HiCombat or Ponn Conquest will drop the pump pressure down to the 280psi range (using the manufacturer's stated friction loss).

    -- Remember the pressure-volume curve on a Class A single stage fire pump -- 50% of nominal capacity @ 250psi. For a 1000gpm pump, that means it'll put out 500gpm @ 250psi. So it will be able to flow 350gpm @ 280psi if you're using new hose. Not sure what the exact pump curve is -- I don't think a 1000gpm could do 350gpm @ 385psi. I think, not positive, a 1500gpm pump can do 350gpm @ 385psi.

    Now, hose makes an important difference. Want to move 350gpm, not have unusually high pressures, and not use 2.5"? Check the manufacturer's friction loss on 2". Angus Red Chief 2" will deliver 350gpm @ 100psi nozzle pressure through 150' of 2" with a pump discharge pressure of 175psi.

    Matt

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    • #3
      Matt, remember the curve you are talking about is with a net engine pressure. When hooked to a hydrant alot more is capable

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      • #4
        When hooked to a hydrant alot more is capable

        Not our hydrants! But a good point, since we all get prejudiced by what we're used to, which in my area is long hose lines and/or low-pressure hydrants (we get good volume of 1500gpm, but only 10 or so psi residual pressure...the jail birds at the end of the 3 mile long main do get annoyed when they can't take showers though!)

        I indeed forgot about the "net" part. It's a rare event for us to have more than 20psi incoming on the pump, so unless I'm calculating a long hose relay I tend to disregard it.

        Centrifigual fire pumps are rated for their volume delivered at a particular pressure, at draft.

        A 1500gpm single stage pump delivers that volume at 150psi...

        HOWEVER, if you have positive incoming pressure (not at draft) you achieve the volume at 150psi PLUS incoming pressure. So say you're receiving water at 20psi, you achieve 1500gpm volume at 170psi. Got a 100psi coming in? You get 1500gpm @ 250psi.

        Same principle as a Two-Stage centrifigual pump. Take a 1000gpm 2stage pump. In volume there is 2 500gpm impellers pumping in "parrallel" to produce 1000gpm @ 150psi. Switch to "series" and one 500gpm impeller pumps into the next -- 150psi + 150psi = 500gpm @ 300psi. (A single stage 1000gpm pump would produce 500gpm @ 250psi).

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        • #5
          Can anyone tell me what the formula is for pump capacity. I know 100% @ 150 psi, 70% @ 200 psi, and 50% @ 250 psi, but I want to figure what % at 350 psi I can flow. I've looked in my IFSTA pumping apparatus manual (7th edition) and i can't find it.Because if indeed we get 350psi out of our tft's( if pumped at the correct pressure) I would like to know if we can support a second line off that truck. You've been a big help Dalmation thanks.

          [This message has been edited by OFDLUIT33 (edited 05-07-2001).]

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          • #6
            Your best bet is to get to get the model #, etc on the pump and call the manufacturer. (There may be a pump curve in the original documents if your lucky!)

            Looking up in the NFPA handbook (and the one at my home is old -- like 1980 or so) the performance curve is different dependent on some design features.

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            • #7
              I would avoid pumping lines at over 250 psi. Most of us only test our hose at 250 psi, that much pressure puts a great stress on the hose

              Some departments, like FDNY, have hose for high pressure operations, like pumping into a highrise's standpipe. From what I have read the lines are only used for that and are hooked up opposite the panel and away from the engineer, for safety.

              With products like the Vindicator or just a 2.5" line I would personally look for another way to flow large amounts of water. Also with the high pressure the TFT's nozzle reaction probably negates any advantage by using the smaller line.

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