1. #1
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    Default Largest Effective SB Tip for 1¾

    Brothers:

    Nozzle reaction aside, what is the largest diameter smooth bore tip that can be effectively used for 1¾” hose? The old rule of thumb was that the diameter could be no greater than ½ of the hose’s diameter (e.g., 1¼”tip for 2½ hose, 15/16”tip for 1¾” hose).

    Does this still apply in your opinion?
    Last edited by BScott; 08-17-2007 at 10:17 AM. Reason: typo

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    Quote Originally Posted by BScott View Post
    Does this still apply in your opinion?
    Unless somebody has rewritten the rules governing hydraulics when I wasn't looking, yes, it's a good a rule of thumb now as it ever was.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    My volly FD uses 2 inch hose and we use a 1 1/4 inch slug to flow 300 gpm at just over 40 psi a t the tip. There is some stream degradation but we have put a regular 1 1/4 inch tip on this set up and it works fine.

    As for your set up using 1 3/4 inch hose, I know several FD's that use 1 inch tips on 1 3/4 inch hose successfully.

    My suggestion get the tip you want to try and see how it works.

    Good luck.

    FyredUp

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    The largest tip you can use is based solely on how well you think it works and within the limits of the hose.

    1" is usually the largest common tip for 1 3/4" but you can get away with up to 1 1/8" too, depending on your distance.

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    I would suggest to try a bunch of them, I know you can do the 1 1/4" but the hose likes to kink alot behind the nozzle... FL-wise, go as high as you can w/o going above the 250 psi discharge pressure mark. You can do the big flows with small hose, if anyone wants to contest that, fine, but try it and see. I'd put this to outside expose use.


    the best interior tip is the 15/16th IMHO

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    I would stay with the 15/16. Friction loss becomes a problem as the tip size / flow increases. BTW 7/8 is one half of 1 3/4, but the 15/16 seems to work ok.

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    Quote Originally Posted by BScott View Post
    Brothers:

    Nozzle reaction aside, what is the largest diameter smooth bore tip that can be effectively used for 1¾” hose? The old rule of thumb was that the diameter could be no greater than ½ of the hose’s diameter (e.g., 1¼”tip for 2½ hose, 15/16”tip for 1¾” hose).

    Does this still apply in your opinion?
    Yes, stick with the rule. it is science. I guess would ask what you are trying to achieve with a bigger tip besides more water? There is some truth behind putting more pressure to the handline, but that only will work to a certain extent. It's like the old 5 lb. bucket with 10 lbs. of "stuff" to put into it. With adding more pressure, you can actually reduce the gpm's due to turbulance and the velocity of the water moving through the hoseline. so you will actually have the oppisite result and just beat the attack team up with excessive pressure. Unfortunately you must consider nozzle reaction. If it is an issue of more water, add another or a bigger line.

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    I don't get it. For some reason you can't put a 1 inch smoothbore on a 1 3/4 line and flow 209 gpm, but you can put a TFT automatic on that same line and flow in excess of 250gpm?

    Please...get real, the 1 inch tip is perfectly acceptable and a number of FD's in my area do this.

    182 gpm = approximately 50 pounds per 100 feet (by formula)

    200 gpm = approximately 62 pounds per 100 feet (by formula)

    For a 200 foot preconnect you are talking 150 pounds for the 15/16" and 174pounds for the 1 inch. Both pressures are well within the capabilities of a modern pumper. Even if you go to 300 feet you are still only talking 200 and 236 pounds. Once again these are theoretical numbers and yours will surely be less due to modern hose construction.

    It will work, trust me. Although, I honestly think the best set-up would be a smaller tip such as a 7/8 stacked on top of the 1 inch.

    FyredUp
    Last edited by FyredUp; 08-21-2007 at 08:36 PM.

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    FyredUp is correct-

    My dept actually tests our nozzles when we get them just to see what kind of GPM we are working with. Our setup for 1.75" is a TFT Midforce/VIT. This can be run as an automatic in standard fog or low-pressure fog. You can also unscrew the fog and have a VIT- SB. (We use a 15/16" tip most of the time.)

    Here's the numbers my dept got for the TFT Midforce/VIT after running several tests. This is on level ground with 200' of 1.75" (our elevation is over 5280' above sea level).

    - TFT midforce fog (standard): PDP 150, NP 100, GPM 125 (FL/100' 25)
    - TFT midforce fog (low-pressure): PDP 150, NP 50, GPM 175 (FL/100' 50)
    - TFT in VIT (15/16" solid tip): PDP 150, NP 50, GPM 185 (FL/100' 50)

    FL and GPM were rounded to the nearest 5 psi. The test was setup to get the correct NP (50 or 100). We measured NP and GPM, and the PDP just happened to equal out.

    Another note: we also tested with minor kinks in the lines to see the reduction in gpm. Even minor kinks in the line with the low-pressure or SB greatly reduced GPM and the shape of the stream.
    "...there isn't a firefighter in the free world who is forced to join this profession." -John Norman

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    I have known of the diameter VS hose size rule for years and have never known why the rule is the rule. The true fact is that 1-3/4" hose can flow alot of water with tup sizes up to 1-1/4". I would recomend a NP of at least 50 psi minimum for whatever size tip is used. As far as a maximum NP there is nothing wrong with a NP of 100 psi and greater used with smooth bores as long as the water is there and the proper nozzle handling techniques are used. A 300 GPM 1-3/4" blitz line with a 100 psi Np using a 1" tip is sweet and one dude can handle it.

    The mind is like a parachute,it works best when it is open.

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    Quote Originally Posted by flyntstone View Post
    I guess would ask what you are trying to achieve with a bigger tip besides more water?
    What else is there?

    Quote Originally Posted by flyntstone View Post
    If it is an issue of more water, add another or a bigger line.
    So adding a few psi with a larger tip isn't easier that adding a second line or using a 2.5"? Why not use the maximum amount of water you can safely flow through each size hose you operate?

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    I agree but what if that is not an option. First in with two or three with a big fire . A lightweight line at a higher pressure can work.

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