Eductor System

Discussion in 'Pesticide & Herbicide Application' started by vegomatic40, Feb 15, 2003.

  1. vegomatic40

    vegomatic40 LawnSite Senior Member
    from 6
    Posts: 406

    I spent several hours and mucho dinero on a chemical eductor system this winter and I am having problems making it work properly. When the local Trugreen branch that I worked at installed a new fill system several years ago, I managed to procure their old eductor bowl that had been dedicated to the Tree/Shrub fill side. I knew that relatively little Urea had been run through it and the venturi had a little corrosion on it but was in pretty good shape overall so I cleaned it up and gave it a shot. I plumbed a new 1" line coming off the backflow preventer down to the 1 1/4" inlet to the eductor and out to a 1 1/2" checkvalve on the "outgoing side." I also tested it going through my 1 1/2" hose before plumbing my trucks for with customary camlocks, checkvalves, ballvalves etc. I even ran a bag of 46-0-0 through it to time the flow and suction and came up with 30 gal/min and it sucked through 50 lb of urea in 55 secs. At these rates I predicted that I would have to have all my products and *hit together at the time of any fill but, should have time to get all my stuff in to the tank. I have tons of water volume and can fill my 500 gal tank in about 16-18 minutes. That has proven to be the case but the problem is the eductor sucks the products through the bowl so slowly that I cannot get all stuff in before I am "topped out" and I end of having to crawl up into the truck and topfill as before. I'm getting to be an old geezer and the less hopping up and down I do the better. I thought I might try elevating the eductor up 3-4' (above truck inlet-camlock) to see if the physics of gravity etc. might be a solution but haven't tried that yet. Any help/advice would be greatly appreciated.
     
  2. muddstopper

    muddstopper LawnSite Silver Member
    Posts: 2,342

    I am not sure how you have your eductor setup or how it is supposed to work. But I will give this a try. As I understand eductor jet setups I believe that as the fluid flows thru them that the velocity of the fluid creates a suction that picks up additional materials and forces it out the outlet in volumes up to four time the initial input but with less velocity than the initial input. This is only true if the material being sucked up has the same or close to the same flow rates. What you are mixing sounds like water as the initial ingredient and fertilizer or herbicides (Liquid or Granular?) as the material being sucked up. Now with that in mind the first thing that I am looking at is the initial flow going into the eductor. You have decreased the input line size down from 1¼ inch, which has an area of 1.227 in. to a line size of 1 in., which has an area of 0.7854 in. You have effectively cut the available flow in almost half although you have probably doubled the velocity by pumping thru a 1 in inlet. Now you are saying that you have an outlet size of 1½ in. That is an area of 1.7671 in. This is 2¼ times bigger than the inlet side and should flow 2¼ times as much as can be pumped into it by the 1 in inlet but at 2 ¼ less velocity.
    I am wondering why you used 1 in line for your inlet. The jet was obviously designed to use a 1¼ inlet. when the line size goes back from 1 in, to 1 1/4 in. you lose your velocity. My best guess with the limited information is that you have reduced the flow of water into the eductor jet by restricting the size of the inlet and that by returning to the 1¼ you should increase the amount of flow thru the enductor and thereby increase the amount of material sucked up and moved into your mixing tank.
    Hope this helps
     
  3. vegomatic40

    vegomatic40 LawnSite Senior Member
    from 6
    Posts: 406

    Thanks for your reply. The reason I used a 1" line reduced to the 1 1/4" input side is that is the maximum size that can be plumbed coming off the backflow preventer. To add a true 1 1/4" input line would involve a minimum $7000-8000 investment by tearing up the street and adding a new 2" system coming off the main with a entirely new backflow preventer, meter etc.
    I understand that reducing the inlet size increases velocity but I only have a "gut feeling" that it should not reduce the efficiency of the venturi/eductor. The outlet side (1 1/2") has stayed the same as the original and I am pretty sure that I cannot reduce it or the system would fail to work at all. I do use a combination of WP's, EC's etc. , and have used them in the past with good results when the system was installed before. I also installed a large, resettable water meter on the inlet side but it is unlikely to give any flow resistance. The only other variation from the original setup is the addition of a 1 1/2" checkvalve directly attached to the outlet side of the eductor bowl for added safety to reduce the possibility of contamination of the water source. Since I have also plumbed all my trucks with the same checkvalve it may be a case of overkill and I may try removing it from the eductor to see if helps to improve the vacuum of the venturi.
    What do you think of the idea of elevating the eductor bowl? Will this possibly increase flow or just make things tougher to dump in the bowl? Thanks again for your input.
     
  4. muddstopper

    muddstopper LawnSite Silver Member
    Posts: 2,342

    After reading your reply about having to tear up the streets and such I realized that we are talking about two intirely different systems. I was assuming that you where getting your water directly from a fire hydrant or pond with a pump and that the backflow preventor was located at the tank. And that you where using the pump setup on your tank to pump the water through the enductor. The reason I say this is because that is how my tank is set up for mixing. As I fill my tank with water I use my tank pump to recirculate the water thru three 1 1/4 in. inductor type jets back into the tank to mix the fetilizers. My pump will pump 380 gpm and is powered by a 20 hp Honda. I spray large areas with this setup and use granular and pellitized products.
    I dont really know what to tell you about how to fix your problem but I would check the inside of your check valves to see that the inside diameter is really 1 1/2 inches since most checks are not as big inside as the pipe size suggests. The seat and ball inside the check valve take up some of the area inside the valve so you may have to increase your check valve size to get a true 1 1/2 in. inside diameter. Or maybe eliminate it altogether since you already have other checks installed, which is probably the best bet.
    As for elevating the bowl, it might help but, if you have to climb up to put your chemicals in the bowl you will be back to where you where to start with as far as having to climb up on the truck and filling from the top.
    Best I can do, hope this helps.
     
  5. vegomatic40

    vegomatic40 LawnSite Senior Member
    from 6
    Posts: 406

    I eliminated the 1 1/2" checkvalve on the outlet side and things have improved dramatically. Still have to hussle a little and use minimum amounts of water for the slurry but seems to be working fine now. Thanks again for the input.
     

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