Building a boom sprayer

Discussion in 'Pesticide & Herbicide Application' started by LawnsharkMB, Jun 20, 2013.

  1. LawnsharkMB

    LawnsharkMB LawnSite Senior Member
    Posts: 545

    I'm working on mounting a boom sprayer on the front my mower. The sprayer from tractor supply came with a 2.1 gpm pump. Should I upgrade to a 3.8 gpm or more?
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  2. Ric

    Ric LawnSite Fanatic
    Posts: 11,946

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    First thing you do is the Math. How many gallons do you want to apply per thousand sq ft is the first question you must answer. Next is your Ground speed and then your boom width to find the size pump you need.

    Important point is Pump rating. That 2.1 GPM pump is rated at Open Flow or zero PSI. As the PSI increases the GPM decreases.

    Good luck you need it.

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  3. LawnsharkMB

    LawnsharkMB LawnSite Senior Member
    Posts: 545

    I want to be able to spray up to 2 gallons per 1000sq ft. The z sprays have 4.1 gpm pumps. I just thought I would need a better pump if I wanted to spray higher volumes.
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  4. Ric

    Ric LawnSite Fanatic
    Posts: 11,946

    Until you do the math you don't know what you need. If you go slow enough you can put down a 6 inch wide strip with a Trigger sprayer and get 2 gallons per thousand calibration.

    How fast or slow does your Mower travel??

    How wide is the desired length of the Boom??

    Then that will tell you the size pump you need.


    My Walker travels 4 MPH or 88 ft X 4 = 352 ft per minute

    My Boom is 42 inches or 3.5 ft wide.

    352 ft X 3.5 ft = 1232 sq ft per minute. By using the correct size nozzles and adjusting the PSI, I spray approx one gallon per thousand sq ft with a 2.1 GPM Open flow 12 V pump. When I increase my PSI to 40 to get atomization of my spray, My GPM decrease to 1.25 GPM.

    Hopefully my example will get you thinking correctly. Building and Calibrating a boom sprayer takes a little Knowledge and a lot of Common Sense. If you don't have either, don't jump in the water.

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  5. LawnsharkMB

    LawnsharkMB LawnSite Senior Member
    Posts: 545

    I know how to calibrate and have the information you're asking.

    The pressure drops from 60 psi to 30 with the bypass valve all the way closed when you open the boom. I was just wondering if a stronger pump would make a big difference because 30 psi is the highest I can spray and I don't want to have to ride 1 mph to get the desired volume.
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  6. LawnsharkMB

    LawnsharkMB LawnSite Senior Member
    Posts: 545

    The highest volume I can spray going as fast as I want to go which is 2.5 mph is .75gal/K.

    I want to be able to spray up to 2 gallons per/k while going the same speed.
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  7. Ric

    Ric LawnSite Fanatic
    Posts: 11,946



    I can't seem to get my point across so I am done here. Maybe someone else can hit your level of understanding.

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  8. RigglePLC

    RigglePLC LawnSite Fanatic
    Posts: 11,774

    You don't need that much water. Ric is right. Boom sprayers apply less water and more chemical. Why not go with about a third of a gallon per thousand--like a Z-spray?

    If you insist on 2 gal per thousand--easy choice--go slow--use only 3 nozzles--or get a bigger pump.
    Naturally your tank will run out quicker--and you will spend a lot of time driving back to the truck, refilling the tank and mixing new chemicals.
    Suit your speed to the situation. Herbicides and insecticides 4 mph. Some odd product that requires four times as much water per thousand--just go 1 mph.
     
    Last edited: Jun 20, 2013
  9. Ric

    Ric LawnSite Fanatic
    Posts: 11,946

    Apparently I am not able to make my point. First I personally don't believe in applying anything less than a Gallon per Thousand. Fact is I have a 150 gallon rebuild Toro Ride on sprayer from a Golf Course that sprays 5 gallon per thousand at 4 MPH. Only after plumbing it with big hoses as well as proper pump size was I able to get that calibration. Therefore 2 gallon per thousand isn't wrong in my book.

    BUT MY POINT WAS NOT ABOUT A BIGGER PUMP, BUT WHAT SIZE PUMP IS NEEDED TO DELIVER 2 GALLONS PER THOUSAND. I was trying explain WHY/HOW math is used to engineer and Design a boom sprayer. I am not able to get my point across because # 1 I might not be a Good Teacher or # 2 I don't have students able to understand the Ideas I present to them.

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  10. lilmarvin4064

    lilmarvin4064 LawnSite Senior Member
    Posts: 757

    The original poster never said what type of product they we planning to spray. There are a bunch of products I wouldn't consider spraying less than 2 gal /1000.

    I have a small tank with a "2.2 GPM" pump on it. With the bypass turned off, I can't get more than 1 GPM out at the nozzle, but I used a skinny hose.
     

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