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View Poll Results: All variables constant, switching 15 deg to 25 deg nozzles reduces impact by almost?

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  • 0%

    0 0%
  • 10%

    31 16.06%
  • 25%

    12 6.22%
  • 40%

    102 52.85%
  • 50%

    43 22.28%
  • 60%

    5 2.59%
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Thread: Nozzle Trivia

  1. #1
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Question Nozzle Trivia

    NO prizes here!!

    After seeing so much damaged concrete pictures in the past few weeks and doing some damage myself, I ask you this (without looking it up).


    Question:



    With the same psi & gpm pump , temp, nozzle orifice size and distance from surface being cleaned, switching from 15 degs to 25 deg nozzles reduces the impact by almost .................. (what)?????.

  • #2
    BS Detector, Esquire 10,000 PLUS POSTER Tony Shelton's Avatar
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    I said 40% because I was thinking that a 15 puts the water in 40% more of an area than a 25. But now that I think about it I think impact is the same, the impact is just spread out over a larger area. ???????? What is the answer MAD SCIENTIST???????
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  • #3
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Not that MAD! Tony , just trying to understand the basic fluid mechanics of nozzles, to minimize property damage and maximize cleaning.

  • #4
    Member 2000 PLUS POSTER tomtucson's Avatar
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    Well, I just sprayed one foot with the 15 and the other with the 25 ....

    Without looking it up?? You're asking for a guess? 20%

    This type of thing is best dealt with totally empirically. To be exact, the distance to the point of impact is changing along with the impact angle, meaning bust out some calculus, but approximations should be reasonably accurate. That type of fluid flow is modeled with complex (imaginary number space) calculus, but it's best handled by 'try it and see'. I think a big factor with surface cleaner impact is how fast the bars are spinning - faster meaning less time on any one spot to grind in. Anyways, I use nothing but 40's ever.
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  • #5
    Member 2000 PLUS POSTER tomtucson's Avatar
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    Here's one for you Nigel. My #10 nozzle (15 deg) looks to be ~ 3/32 by 2/32 for an area of 3/512 in. The chart says 8.7 gpm @ 3000 psi. How fast - what speed - is the water leaving the nozzle?

    Does spinning the nozzles into or away from the spray affect the speed the water hits the cement significantly?
    Tom Cusick
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  • #6
    Member 5000 PLUS POSTER Larry Millette's Avatar
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    I'm naturally pretty lousy with nozzle sizes but I said only 10%.
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    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Quote Originally Posted by tomtucson View Post
    Well, I just sprayed one foot with the 15 and the other with the 25 ....

    Without looking it up?? You're asking for a guess? 20%

    This type of thing is best dealt with totally empirically. To be exact, the distance to the point of impact is changing along with the impact angle, meaning bust out some calculus, but approximations should be reasonably accurate. That type of fluid flow is modeled with complex (imaginary number space) calculus, but it's best handled by 'try it and see'. I think a big factor with surface cleaner impact is how fast the bars are spinning - faster meaning less time on any one spot to grind in. Anyways, I use nothing but 40's ever.


    When I say "Impact" its instantaneous impact for a given instantaneous increment of time.
    The impact is the same regardless of length of time in any particular spot.

    The more time in one spot, just means that the spot is subjected to the same impact over and over and hence may damage the surface or clean better.

  • #9
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Quote Originally Posted by tomtucson View Post
    Here's one for you Nigel. My #10 nozzle (15 deg) looks to be ~ 3/32 by 2/32 for an area of 3/512 in. The chart says 8.7 gpm @ 3000 psi. How fast - what speed - is the water leaving the nozzle?

    Does spinning the nozzles into or away from the spray affect the speed the water hits the cement significantly?
    No idea on the speed (velocity) the water is leaving the nozzle.

    Second questions answer, I think spinning the nozzle into or away from the surface to be cleaned does not significantly affect the velocity the water hits the cement for typical surface cleaner nozzle heights.

    The velocity is so high at 1 to 1.25 inches from the nozzle that it maybe insignificant.

    However as the height increases beyond 1 to 1.25 inches the spinning speed affects the velocity the water hits the surface exponentially.

  • #10
    Member 2000 PLUS POSTER tomtucson's Avatar
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    Just an interesting figure, by my calculations at 3000 psi, #10 nozzle, 8.7 gpm - the water is leaving the nozzle at 28,600 ft/sec!! or 5.4 MILES per sec! Isn't that like 28 times the speed of sound? Did I mess up a number in there, its pretty straight forward. Speed = volume water / area of nozzle. My #10 looks to be ~ 2/32" x 3/32" or 3/512 sq in , 1 cubic ft = 7.5 gallons so 8.7 gal = 2010 cubic in so 2010 divide by 3/512 and convert to feet....
    Tom Cusick
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    BS Detector, Esquire 10,000 PLUS POSTER Tony Shelton's Avatar
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    I found this avatar of Nigel on the mad scientist board. He's the administrator there.

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  • #12
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Quote Originally Posted by tomtucson View Post
    Just an interesting figure, by my calculations at 3000 psi, #10 nozzle, 8.7 gpm - the water is leaving the nozzle at 28,600 ft/sec!! or 5.4 MILES per sec! Isn't that like 28 times the speed of sound? Did I mess up a number in there, its pretty straight forward. Speed = volume water / area of nozzle. My #10 looks to be ~ 2/32" x 3/32" or 3/512 sq in , 1 cubic ft = 7.5 gallons so 8.7 gal = 2010 cubic in so 2010 divide by 3/512 and convert to feet....
    I think something is incorrect.

    Velocity at the nozzle orifice , simplified is:

    = (volume flow rate of water)/(cross-sectional area of the orifice)

    This only holds true for velocity at the orifice and for a very small distance past the orifice, but greater distances for a zero degree orifice nozzles




    Just working off of your basis Tom and assuming that your average of the size of the #10 nozzle is correct.

    Your math multiplication of the area is correct......> 3/512 sq.in

    To change (sq.in) to square feet .....> 1 square inches = 0.00694444444 square feet

    Then 3/512 sq.in = 3/512 sq.in x .00694' = .000040664 (square feet)


    Your math of volume flow rate is right on; but you dimensions (units) are off.

    (1 cubic ft)= ~7.5 gallons

    Your Pump output is 8.7 gallons/min

    Change (gallons per minute) to (cubic feet per minute)

    1 US gallon = 0.133680556 cubic feet

    Thus 8.7 gallons/min = 0.133680556 x 8.7 = 1.163 (cubic feet per minute)


    Velocity (feet per minute) = Volume flow rate (cubic feet per minute) / Area (feet squared)

    Thus velocity is = 1.163 / .000040664 = ~ 28,600 ft/min

    speed of sound at sea level = 66 986.2205 feet per minute

    Therefore ---> 28600/66986 = ~ 2/5 the speed of sound.

    MY BRAIN IS HURTING, ITS BEEN A LONG TIME TOM,

  • #13
    Member 3000 PLUS POSTER Paul Kassander's Avatar
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    Wow...I just adjust the height of my nozzle when I am spraying so I don't damage the surface...those ore some crazy calculations Nigel are you building a space shuttle or something?

  • #14
    Member 2000 PLUS POSTER tomtucson's Avatar
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    Nigel, just converted to feet at the end but put gallons per SEC instead of min.
    Tom Cusick
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  • #15
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Quote Originally Posted by Paul Kassander View Post
    Wow...I just adjust the height of my nozzle when I am spraying so I don't damage the surface...those ore some crazy calculations Nigel are you building a space shuttle or something?
    That was the true intent of this post to show how effective an adjustable height surface cleaner can be. Because when you change nozzles to the industry provided standard (15, 25, 40) the impact decreases exponentially, and you cannot fine tune surface cleaning. from 15 degs to 25 degs is a big drop in impact.

    I am not building anything, I will leave that to Envirospec, they build unique systems that always impress.

  • #16
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Quote Originally Posted by tomtucson View Post
    Nigel, just converted to feet at the end but put gallons per SEC instead of min.
    I left it all in gpm's Tom.

    You did all the leg work I just double checked your numbers.

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    Member Graduate Student welder's Avatar
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    So, what is the correct percentage.??? the answer to your question you asked.

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    Member Honorary Professor Dollarspa's Avatar
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    Quote Originally Posted by Paul Kassander View Post
    Wow...I just adjust the height of my nozzle when I am spraying so I don't damage the surface...those ore some crazy calculations Nigel are you building a space shuttle or something?

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  • #19
    Griffs Services PowerWash 2000 PLUS POSTER 810f250's Avatar
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    Quote Originally Posted by welder View Post
    So, what is the correct percentage.??? the answer to your question you asked.
    Just a little bit longer, wanted more members to see the question and vote, I will post it or someone else may know the chart and do the honors.

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    Member Graduate Student welder's Avatar
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    Quote Originally Posted by 810f250 View Post
    Just a little bit longer, wanted more members to see the question and vote, I will post it or someone else may know the chart and do the honors.
    ok...

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