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Thread: Sweetening the Pans - Continuous Flow

  1. #1
    Join Date
    Jan 2008
    Location
    Frankford, Ontario
    Posts
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    Default Sweetening the Pans - Continuous Flow

    The subject of Sweetening the Pans comes up regularly with new sugar makers looking to expand from a few taps and batching to more trees.

    A continuous flow arch is usually filled at the beginning of the season, then left full through the season (except for long cold or dry spells and cleaning). The first boil is used to "sweeten" or build a gradient in the pans from raw sap at the inlet to finished syrup at the outlet.

    For reference, I took some photos of my arch before and after sweetening that might help to illustrate the process. I usually run about 1" deep.


    Starting - Raw Sap.jpg
    Photo 1. Initial Fill
    Arch initially filled with sap. Flue pan on right, syrup pan on left. Sap enters in the bottom right, moves to the front, crosses to the middle, back to the back, then to the far side and out the front of the flue pan. You can see the valve that allows me to isolate the syrup pan from the flue pan. Once it enters the syrup pan, it again follows a serpentine path before exiting at the front left.

    Initial fill is 40litres or ~10 gals of sap.


    Flue Pan boiling.JPG
    Photo 2 - Flue pan boiling
    During boiling, there is violent mixing going in each section, so the concentration within each section is continually balanced. However, each section is being fed by the section before it, so as the sap moves through the evaporator, it gets more and more concentrated.


    Sweetened.jpg
    Photo 3. Gradient established
    I shut down after 300l or 80gals of sap and allowed it to cool to take some photos. You can see the gradient that has now been established. Bottom right is clear as that is where raw sap is entering. The front section is getting close to syrup. (took ~100 gals until the first draw)
    The gradiant in the evaporator will stay like this through the season, unless I drain it to prevent freezing damage or for a long dry spell. At the end of every day, I close the valve between the flue and syrup pans to prevent mixing back, and open it up again when the pans start to boil.

    At the end of the season when I am out of sap, I will close the isolation valve, drain the flue pan into a pail and add it to the syrup pan, then flood the flue pan with water to finish off the last batch.
    Big_Eddy
    Eastern Ontario (Quinte)
    20+ years on a 2x3 block arch,
    Homemade 20"x64" drop flue since 2011

    Build a Block Arch
    Build a Flat Pan
    Build a Flue Pan
    Sweetening the Pans
    Build a Bending Brake
    Using a Hydrotherm
    How much Sap to Sweeten?

  2. #2
    Join Date
    May 2010
    Location
    Savoy, MA
    Posts
    375

    Default

    Thanks Big Eddy. I am about to get started on my Mason 2x4 for the first time this year….just waiting for the sap to start flowing. I have been reading up on this. Can I ask a few follow up questions?

    My 3 section pan does not have isolation valves between the sections. So, I understand the concept of sweetening the pan and going through roughly 100 gallons to get that done. At the end of my day, with no ability to keep the gradient in the 3 sections of my pan, my sap will all flow back to a uniform concentration. Any way to tackle this problem? Is there a way to re-establish the gradient the next morning? Or will the simple process of firing up the evaporator and introducing fresh sap do the trick?

    Thanks in advance.
    16x24 Timber Frame Sugar House
    Mason 2x4 Evaporator
    90 trees on buckets

  3. #3
    Join Date
    Mar 2013
    Location
    Trenton Falls, NY
    Posts
    63

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    I have a question also - you mentioned freezing damage. I have about 10 gallons of sap in my evaporator now also. With the season being so crummy, I only get sap in small quantities in sputters - then it locks into deep freeze again. Am I ok leaving sweetened-but-not-yet-syrup in the pan for up to a week until I finally get more sap?

  4. #4
    Join Date
    Jan 2008
    Location
    Frankford, Ontario
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    Quote Originally Posted by bigschuss View Post
    My 3 section pan does not have isolation valves between the sections. So, I understand the concept of sweetening the pan and going through roughly 100 gallons to get that done. At the end of my day, with no ability to keep the gradient in the 3 sections of my pan, my sap will all flow back to a uniform concentration.
    At any given time, the sap is level in your pans. If you are running relatively shallow (1") in your pans and leave it at that depth when you shut down, there is nothing to make it "flow back". There will be some mixing at the margins, but unless you stir or mix it deliberately or pour in raw sap, your gradient should remain essentially in place. When you start back up, you want to get the boil going before you open the valves and start flooding in new sap. It may take a bit longer than usual to get your first draw as the gradient is reestablished, but should not be an issue.

    If you do want to isolate the sections, something as simple as a chunk of maple plopped in front of the opening will prevent enough mixing to maintain the gradient.
    Big_Eddy
    Eastern Ontario (Quinte)
    20+ years on a 2x3 block arch,
    Homemade 20"x64" drop flue since 2011

    Build a Block Arch
    Build a Flat Pan
    Build a Flue Pan
    Sweetening the Pans
    Build a Bending Brake
    Using a Hydrotherm
    How much Sap to Sweeten?

  5. #5
    Join Date
    Jan 2008
    Location
    Frankford, Ontario
    Posts
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    Default Sweetening the Pans - Continuous Flow

    Quote Originally Posted by TrentonMaple View Post
    I have a question also - you mentioned freezing damage. I have about 10 gallons of sap in my evaporator now also. With the season being so crummy, I only get sap in small quantities in sputters - then it locks into deep freeze again. Am I ok leaving sweetened-but-not-yet-syrup in the pan for up to a week until I finally get more sap?
    Depends on a number of factors. The risk is that sap freezes and splits the pan. Flue pans are more at risk than flat pans. Some folks take a chance, others leave a light or heater in the arch or light a small fire every few days. I usually watch the forecast to see how hard I think it will freeze. If I think it will freeze solid, I siphon out into a stainless pail, then pour it back in before the next boil. Concentrated sap will slush before it freezes hard, so -5C or higher, I usually leave it in.
    Last edited by Big_Eddy; 03-24-2014 at 06:25 PM.
    Big_Eddy
    Eastern Ontario (Quinte)
    20+ years on a 2x3 block arch,
    Homemade 20"x64" drop flue since 2011

    Build a Block Arch
    Build a Flat Pan
    Build a Flue Pan
    Sweetening the Pans
    Build a Bending Brake
    Using a Hydrotherm
    How much Sap to Sweeten?

  6. #6
    Join Date
    Mar 2009
    Location
    Lyman, NH
    Posts
    2,311

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    Great description of the continuous flow process and gradients which is a difficult concept to grasp!

    I leave sap in my pans all season except an occasional draining of the front pan for cleaning. I let my pans freeze solid as it is impractical to drain everything and bring it up to the house and keep it warm, but I do take the precaution of bringing the levels as low as I dare when I shut down before an anticipated freeze.

    Of course, this year I still haven't even bothered to finish tapping or set up the evaporator yet as it's too darn cold.
    2012: Probably 750 gravity taps and 50 buckets.

    600 gal stainless milk tank.
    2 - 100 gallon stock tanks
    one 30 gal barrel
    50 buckets

    3' x 10' Waterloo Raised Flue wood fired evaporator w/ open pans.

    12" x 20" Filter Canner

    Sawmill next to sugarhouse solves my sugarwood problem

    Gather with GMC 3500 2wd Pickup w/ 425 gallon Plastic Tank.

    Been tapping here in Lyman NH since 1989 but I've been sugaring since 8 years old in 1968.

  7. #7
    Join Date
    Mar 2011
    Location
    Haverhill, Ma
    Posts
    818

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    pic of my pan as of this morning after approx 100 gals boiled...

    IMG_0417B.JPG

    I'm perplexed as to root cause...fire not hot enough? not localized enough? I dunno
    2019 - New 12X12 boiling pavilion
    2018 - New Mason 2X3 Hobby XL and homemade RO
    2017 - 49 taps on gravity, 6 on buckets.
    2016 - 19 taps on new 3/16 tubing, 24 on buckets
    2015 - 51 taps, 26 buckets
    2014 - 50 taps, 14 buckets, steel railroad toolbox converted into arch, new 2X3 continuous flow Phaneuf from Homestead Maple
    2013 - 33 taps, 12 buckets, steel railroad toolbox converted into arch, steam table pans
    2012 - 26 taps, 10 buckets, steel railroad toolbox converted into arch, steam table pans

  8. #8
    Join Date
    Feb 2014
    Location
    Peru, IN
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    29

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    I have a question also. It looks like you don't reverse your flow in your pan. Do you have to clean it very often of sugar sand?

  9. #9
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    Jan 2008
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    Frankford, Ontario
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    Quote Originally Posted by feathercast View Post
    I have a question also. It looks like you don't reverse your flow in your pan. Do you have to clean it very often of sugar sand?
    I can rotate my front pan 180 but I never have. I remove it once or twice a season and give it a light cleaning. Do a thorough job at the end of the year.
    Big_Eddy
    Eastern Ontario (Quinte)
    20+ years on a 2x3 block arch,
    Homemade 20"x64" drop flue since 2011

    Build a Block Arch
    Build a Flat Pan
    Build a Flue Pan
    Sweetening the Pans
    Build a Bending Brake
    Using a Hydrotherm
    How much Sap to Sweeten?

  10. #10
    Join Date
    Jan 2008
    Location
    Frankford, Ontario
    Posts
    1,008

    Default

    Quote Originally Posted by eustis22 View Post
    pic of my pan as of this morning after approx 100 gals boiled...

    I'm perplexed as to root cause...fire not hot enough? not localized enough? I dunno
    Tell us more about your setup and how you are running it.
    • How deep is the sap? Was the level constant?
    • How are you adding sap - float valve, steady drip, a gallon at a time? Where?
    • What is your evaporation rate - about 6 gallons / hr?
    • Was the fire steady, or did you take a break for lunch, let the fire die down etc.?
    • Foaming - was there any, are you using defoamer?

    To establish a gradient, especially with a small number of sections, you need a steady process. Every time you allow the sap level to change in the pan, you are moving sap between sections and mixing. Sap finds its own level. If you are running 1 1/2" deep in your 2x3 pan, you have about 6 gallons in the pan. Add 2 gallons of raw sap, and you just pushed 1/2 the second section into the third, and most of the first into the second, mixing the syrup and messing with your gradient. Likewise, if you boil hard for a while and the sap level drops to 1" and you refill back to 1 1/2", you've done the same thing. Foaming in the last section does the opposite. The foaming causes the level in the last section to rise, pushing almost syrup back into the middle section and mixing it with the partially evaporated sap there.

    Establishing a visible gradient in a small pan is not easy. The higher the evaporation rate and the more sections in the pans, the easier it is to see the gradient develop and the more distinct the difference in concentration will be between sections. Regardless, if you keep adding sap at one end only, you will develop a gradient. If you can - test the concentration in each of your sections - I expect they will be different even if you can't see it visually.
    Big_Eddy
    Eastern Ontario (Quinte)
    20+ years on a 2x3 block arch,
    Homemade 20"x64" drop flue since 2011

    Build a Block Arch
    Build a Flat Pan
    Build a Flue Pan
    Sweetening the Pans
    Build a Bending Brake
    Using a Hydrotherm
    How much Sap to Sweeten?

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