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Thread: High vacuum in gravity tubing research

  1. #1
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    Default High vacuum in gravity tubing research

    There is a recent article by Tim Wilmont, UV Proctor Maple Research Center in the Maple Syrup Digest. It explains in detail their findings for using 3/16" tubing for gravity systems. The performance looks to be excellent. Sap gallons per tap hole were equivalent with a vacuum pump system. A decent amount of fall is needed for this to work. There is also information as to where to find the fittings and tubing.

    I have about 40 sugars I hang buckets on, just over a hill. I don't want to try hook them into my vacuum system because of cost and how far they are away. If I add the reds around them I will be at 75 taps. I can put a tank at the bottom of the hill and I should have about 30' of fall for many of the taps. I already drive to the bottom of the hill with my BAT mobile to collect the buckets. A little more road improvement and I should be good. I wasn't going to do any expansion this year but this could be a fun little project
    136 on high vacuum for 2013
    60 taps on 3/16" gravity tubing
    A&A 2X8, raised flue evaporator
    hood, parallel flow pre heater and air over fire
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    I read this also and found it to be very interesting. I'm glad your going to try it. Please let us know how it works for you. Just 8-9 months to go.

    Spud

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    There was plenty of research done on this years ago (70's-80's maybe). And there is plenty to be said for it. We ran thousands of taps this way. the plus side is if you have a good run, this system will gain yo more sap. But, if you have a year with weeping runs, it will impede your yield because you don't get enough sap in the lines to get them moving and they vaporlock. This was my experience from many years of trying. Pumped vacuum is where it is at. Not saying not to try it, just saying don't think it is going to be like pumped vacuum.
    shrunken producer, from 8,000 taps to 4,000 vac 250 gravity
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    Quote Originally Posted by lew View Post
    There was plenty of research done on this years ago (70's-80's maybe). And there is plenty to be said for it. We ran thousands of taps this way. the plus side is if you have a good run, this system will gain yo more sap. But, if you have a year with weeping runs, it will impede your yield because you don't get enough sap in the lines to get them moving and they vaporlock. This was my experience from many years of trying. Pumped vacuum is where it is at. Not saying not to try it, just saying don't think it is going to be like pumped vacuum.
    You used 3/16" tubing and fittings?
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  5. #5
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    Not 3/16, but the tubing diameter we use today, 5/16. the principle is the same. Cram so much sap into a pipe that the weight of the sap going down the pipe starts to "pull" of the upper end of the tubing. this pull is your vacuum. We would have as many as 120 taps on a single 5/16 line. There were times when we were tapping and the sap was running that you could hear the vacuum on an open spile over the sound of a running tanaka tapper. this type of tubing does work. Just not well on weepy or slow runs.
    shrunken producer, from 8,000 taps to 4,000 vac 250 gravity
    5x10 Max Flue pan on its own arch 3x7 D&G finishing rig All oil fired
    CDL 2400 RO
    filterpress
    Atlantic Fluidics A-20 vac pump with a Bernard mechanical Double Releaser
    sp-11, bb2 vac pumps

  6. #6
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    Quote Originally Posted by lew View Post
    Not 3/16, but the tubing diameter we use today, 5/16. the principle is the same. Cram so much sap into a pipe that the weight of the sap going down the pipe starts to "pull" of the upper end of the tubing. this pull is your vacuum. We would have as many as 120 taps on a single 5/16 line. There were times when we were tapping and the sap was running that you could hear the vacuum on an open spile over the sound of a running tanaka tapper. this type of tubing does work. Just not well on weepy or slow runs.

    The point of Tim's research was that 3/16" ID tubing has about 1/3 of the interior volume per unit length than the 5/16". Therefore, you don't need to cram as many taps on a single line to produce enough enough sap to fill the water column, thereby establishing the natural vacuum. In Tim's research, even mediocre days with slow, weepy runs produced high vacuum levels (>20 inHg) in 3/16" tubing. The keys to this setup are leak-free lines, tight lines (no sags), and a good bit of head below the last tap, say 20 feet at least. Many of us don't have the necessary slope, but for those that do have sloped, remote bushes with no power this seems like it would be worth a try.

    It will be interesting to see if the suppliers start making 3/16 fittings in the next few years. It seems like all they need to change is the hose-barb portion of their designs, right?
    Last edited by jrgagne99; 06-08-2012 at 07:22 AM.
    Boulder Trail Sugaring
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  7. #7
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    When I read the study, I was impressed with the vac. numbers they were getting. A vac. system though will get the trees to run on marginal days, which this type of gravity system will not do. On a season like the one we had, this will get you a lot more sap. In a normal season though, I wonder what the production differences are.
    Josh

    2009 - 370 on vacuum and 16 buckets
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  8. #8
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    The production numbers are in the study. One of the 3/16 gravity bushes actually out produced one of their sugar bushes that was on a Busch vacuum pump. It produced more sap per tap over about a month. Another gravity bush almost matched the vacuum system, but another came in at half as much. It sounds like they are going to continue research on this.

    Maybe Dr. Perkins could provide a link on here. It would give many others access to the study. Or, everyone can join their Maple Association and receive the Maple Digest.

    I look at the economics of this, especially for the small producer. It wouldn't be cost effective for me to run power or a dry line and have a releaser for 75 taps. But, by tubing it as in the study, I might get three times the amount of sap per tap than my buckets.
    136 on high vacuum for 2013
    60 taps on 3/16" gravity tubing
    A&A 2X8, raised flue evaporator
    hood, parallel flow pre heater and air over fire
    BAT mobile back in action
    12X28 sugar shack

  9. #9
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    Quote Originally Posted by Gary R View Post

    Maybe Dr. Perkins could provide a link on here. It would give many others access to the study. Or, everyone can join their Maple Association and receive the Maple Digest.
    Just FYI, anyone can receive Maple Digest without necessarily joining their Maple Association. When I inquired, this is the note I got from the publisher:

    The cost is $6.00 per year in the U.S. and $8.00 per year in Canada. There are 4 issues a year (Feb., June, Oct. and Dec.) The publication is 5 1/2 " x 9" and there are 40 pages. If you join your state maple association - the Digest is included in your dues (exceptions are VT and Ontario).

    Send check to:
    Maple Syrup Digest
    PO Box 240
    Canterbury, NH 03224
    Boulder Trail Sugaring
    140 Taps on Vacuum, 20 Buckets
    Homemade Releaser
    Homemade 20"x40" Hybrid Pan - 10 gph
    Homemade Steamaway - 5 gph
    Homemade RO - 10 gph

  10. #10
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    My wife and I put up the 3/16" lines last weekend. I only have three runs about 600' long. They will have about 20 taps each and about 50' of fall for most of the taps. I assembled the drop lines last night. I found a way to use my tubing tools with the 3/16" tubing. I took a piece of very soft tubing that was 1/2"OD x 1/4"ID, cut it 1 1/2" long and then cut it length ways in half. I put one piece in each lower jaw of the tubing tool. I originally was going to glue them in place, but they embedded them selves into the threads of the clamps. Everything went together well. I'll cut the drops in this weekend. I already have CDL clear seasonal spouts on the drops. I'm putting end caps on them until I tap.

    Here's the link for the research. http://www.uvm.edu/~pmrc/
    136 on high vacuum for 2013
    60 taps on 3/16" gravity tubing
    A&A 2X8, raised flue evaporator
    hood, parallel flow pre heater and air over fire
    BAT mobile back in action
    12X28 sugar shack

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