1. #1
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    Post nozzle reaction, straight stream VS solid stream

    Correct me if I am wrong but it's my understanding that nozzle reaction is nozzle reaction. It does not matter if the reaction is produced from a fog nozzle straight stream or a smooth bore solid stream. With this being said read the following statistics. A 350 gpm straight stream from an automatic nozzle produces a nozzle reaction of 177 lbs. An 1-3/8" tip at 59.5 nozzle pressure delivers 433 gpm with the identical 177 lbs. nozzle reaction. IFSTA says that the above mentioned smooth bore is going against their rules because the nozzle pressure is higher than 50 and the flow is higher than 350 gpm. They say the reasoning behind their rules is the fact that these higher flows and pressures create an unsafe handline. Yet, they allow for the 350 gpm from the automatic nozzle with the identical nozzle reaction. I'm confused! Are there any thoughts on this?

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    Perhaps because they consider the automatic nozzle safer? You ARE able to gate the line down, thereby reducing the reaction, whereas you cant do that on a smoothbore....that's a LOT of water on a handline anyway!...just a thought...

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    First, nozzle reaction is a small part of an example of the fact that "........for ever action in nature there is an EQUAL and OPPOSITE reaction.<br />Usually (until droplet delivering nozzles that equates to hundreds of openings instead of one smoothe jet (open nozzle vs. fog (automatic) nozzles.<br />So if the Velocity of the water is in a single direction from a single opening at a given Nozzle Pressure (open nozzle - smooth bore) Then the Nozzle reaction is in the same direction for the entire quantity of delivery. <br />NOW - If the Quantity is 'broken" into different pathways at the tip of the fog nozzle you have hundreds of jets (streams) in different directions and in most cases colliding with each other with the effect of mathematically reducing and cancelling the NR which is now the sum of the parts. <br />That is why there is less reaction from the NOT SMOOTH BORE nozzle at the same Nozzle Pressure and why you must increase Nozzle Pressure in those nozzles (2 X) to get the same water with the same size hose diameter as you do with the smooth bore controlling nozzle.<br />The relationship in the values within formulae in hydraulics is simple but today's fire service is "digitized" and the relationship with all the parts of supplying water (or more important) not supplying water is LOST.<br />But then again all the wizards of the old days left the 'book' on the kitchen table and worked formulas from the pumps by "stepping on the line every now and then" LOL

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    I agree with 111truck. There is a big difference in nozzle reaction based on the type of nozzle in use. As was stated earlier it is a simple case of applying Newton's third law of motion- every action has an equal and opposite reaction. The greater the nozzle discharge pressure, the greater the nozzle reaction.
    "Never trust a smiling dog"
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    So Larry where do you think the books got there information from. When I calculated the original facts for this thread I used the formulas the IFSTA book provided. Its my opinion that alot of this stuff is several years old and has not been updated with the changing times. I know they do a revision every so often. At least they add new photos.

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    You guys are correct, that it doesn't matter what nozzle you are using, NR will be the same with the same flow and pressure. Unfortunately, most auto nozzles (TFT) are pumped at 50 psi more than smooth bore nozzles, which thereby increases their total nozzle reaction. TFT even admits to as much in the literature on their website. The only difference is that if the nozzle reaction is too great, you can gate the TFT down. A smoothbore at 50 psi pumps approx. the same flow as most TFTs at 100. Word?

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    [quote]Originally posted by CIFD88:<br />[QBUnfortunately, most auto nozzles (TFT) are pumped at 50 psi more than smooth bore nozzles, which thereby increases their total nozzle reaction. TFT even admits to as much in the literature on their website. The only difference is that if the nozzle reaction is too great, you can gate the TFT down. A smoothbore at 50 psi pumps approx. the same flow as most TFTs at 100. Word?[/QB]<hr></blockquote>

    CIFD88,<br /> It's not unfortunate, it's a fact. All fog nozzles require 100psi at the tip for a good stream. The exception to this of course, would be low pressure fog nozzles. The key issue here is Nozzle reaction-which is a direct result of the Gpm flowing. The required tip pressure of the fog nozzle or the smooth bore nozzle are only a piece of the total equation causing the nozzle reaction. You stated that a smoothbore nozzle at 50psi and a fog at 100psi will flow the same. The tip pressures are only a piece of the puzzle, so to speak, so this is an incomplete statment. If I want to deliver 160gpm's to a fire you would set your pump discharge pressure to compensate for length of line ,type of line and what nozzle you're using. Two hoselines being equal, the one with the fog nozzle wil require higher PDP to flow the same GPM as the smooth bore. The nozzle reaction of the smooth bore however will be greater. Gating down the line flowing would be a mistake. You would reduce your GPM delivery to the fire placing the crew in jeopardy and ultimatly letting the BTU's beat the gpms. Thus,you lose. <br /> Stay low and stay safe---

    [ 01-26-2002: Message edited by: Smokeetr4 ]</p>
    "Never trust a smiling dog"
    Delaware F.O.O.L. FTM-PTB-EGH

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    Smokeetr4 "Two hoselines being equal, the one with the fog nozzle wil require higher PDP to flow the same GPM as the smooth bore. The nozzle reaction of the smooth bore however will be greater. "

    If you're flowing the same amount of GPMs on both an automatic and a smoothbore, the reaction will always be greater on the auto than the smooth.

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    BuLL 1000 gpm from a fog tip and 1000 gpm from a SB at the same NP have the same NR.
    Last edited by fcvfd; 01-28-2002 at 02:33 AM.

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    fcvfd

    This is Larry Stevens, former Editor of a rag magazine who was run off. Larry has many issues and one of them is an intense jealousy of other departments. You see, Larry is a volunteer who is known for his hot temper and cool intellectual ability.

    Lets ask Larry some questions.

    1. Larry, do you want to tell people why Fire-Rescue ran you off?
    2. Would you rather I do it?
    3. Why is is that the Fallon guys despise you so much.
    4. Why don't you come to the EXPO and meet everyone.
    5. How is that girl Larry?

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    ....Would you rather I do it?

    Yes!

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    Whoa....The same amount of GPM and the same NP will result in the same NR, like you said Mr Stevens, but when was the last time you flowed a fog nozzle at 50psi, where you would be flowing a smooth bore?

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    Read the initial statement that formed this post.

    ...but when was the last time you flowed a fog nozzle at 50psi,

    We have low pressure Automatics 45 psi NP. So the answer would be everyday to your question. And a smooth bore always looks better at higher NPs.

    ...where you would be flowing a smooth bore?

    Every fire, we have nozzles that are both mooth bore and fogs.

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