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Thread: Head pressure required to feed preheater

  1. #1
    Join Date
    May 2011
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    Parkman Maine
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    Default Head pressure required to feed preheater

    Just curious what people are running for elevation drop between their head/feed tank and preheater or even float box outlet. I'm in the process of building a platform for a 250 gal milk tank, my current roof allows for 6 inches of vertical drop before the rafters become an inconvenience.

    Thanks
    Smoky Lake 2x8 Raised Flue
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  2. #2
    Join Date
    Jan 2006
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    Oneida NY
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    I'm not sure what the minimum might be, but on mine the bottom of the tank is 14" above the inlet to the preheater and 9" above the outlet. Then my line goes to the float box. At the float box, I have a 14" drop straight down to an elbow that then feeds the float box. I put 4 vents in my preheater but have never needed to use any, gravity does it all.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  3. #3
    Join Date
    Mar 2006
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    Lanark, ON
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    We have about 4 feet of drop from the feed tank to the preheater. When the tank starts to get low it is noticeable that the sap comes through slower and the levels in the flue pan drop so you need to open up the float valve a bit more.
    4,600 Taps on vacuum
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  4. #4
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    Jan 2011
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    Southern Ohio
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    I'm not sure that a lot of drop is necessary to feed your float box, but if your preheater is restrictive in size then head pressure would be more critical. If You don't have the room for drop then over size your line down to the point of restriction and it should help. It's about weight on any given point, so there are ways to increase weight other than vertical drop, but vertical drop is the simplest.

  5. #5
    Join Date
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    Lake County Ohio
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    There's only about 8" from the bottom of my sap tank to the inlet for the preheater/flue pan float box. When the tank gets to about 40 gal, the sap level is below the highest part of the preheater, so I installed a bypass valve that allows me to re-direct sap to the flue pan float box, bypassing the preheater all together.
    I have a clear hose "sight glass" running up along the side of the tank to monitor levels....Works great as long as you're watching the level in the tank.
    John Allin

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  6. #6
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    May 2011
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    Parkman Maine
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    Quote Originally Posted by buckeye gold View Post
    I'm not sure that a lot of drop is necessary to feed your float box, but if your preheater is restrictive in size then head pressure would be more critical. If You don't have the room for drop then over size your line down to the point of restriction and it should help. It's about weight on any given point, so there are ways to increase weight other than vertical drop, but vertical drop is the simplest.
    Good point. I might have to experiment with some different sized supply lines this winter.
    Smoky Lake 2x8 Raised Flue
    Mason Arch

    5 Buckets
    300 Gravity
    120 High Shurflo vac

    7" Wes Fab Filter Press
    Mason Finisher
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  7. #7
    Join Date
    May 2011
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    Default

    Quote Originally Posted by johnallin View Post
    There's only about 8" from the bottom of my sap tank to the inlet for the preheater/flue pan float box. When the tank gets to about 40 gal, the sap level is below the highest part of the preheater, so I installed a bypass valve that allows me to re-direct sap to the flue pan float box, bypassing the preheater all together.
    I have a clear hose "sight glass" running up along the side of the tank to monitor levels....Works great as long as you're watching the level in the tank.
    I like this idea. After all I'm only planning on having the tank low during shutdown.
    Smoky Lake 2x8 Raised Flue
    Mason Arch

    5 Buckets
    300 Gravity
    120 High Shurflo vac

    7" Wes Fab Filter Press
    Mason Finisher
    Mason Water-Jacketed Canner

  8. #8
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    Apr 2005
    Location
    Washington, VT
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    138

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    Most of the preheaters we have dealt with required a small pump to keep the flow consistent and prevent vapor lock.
    3x8 Algier Evaporator. 600 gph Lapierre RO. 10" Filter press. We buy sap.

  9. #9
    Join Date
    Jan 2006
    Location
    Oneida NY
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    My pre-heater also has a by pass, but I only need to use it to drain the feed lines. Gravity works all the time, no pump needed.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  10. #10
    Join Date
    Mar 2012
    Location
    Walpole, NH
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    1,363

    Default

    Quote Originally Posted by hookhill View Post
    Most of the preheaters we have dealt with required a small pump to keep the flow consistent and prevent vapor lock.
    Prehearter should not need a pump, but having a vent line off from it to prevent vapor-lock is usually needed.
    Sugaring for 45+ years
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    2022 added a used RB25 RO Bucket
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