+ Reply to Thread
Results 1 to 6 of 6

Thread: Updated Tubing Size CFM Guidelines

  1. #1
    Join Date
    Feb 2012
    Location
    Northern Vermont
    Posts
    23

    Default Updated Tubing Size CFM Guidelines

    Does anyone know if there is any renewed research ongoing for updating the Cornell Mainline sizing guidelines? These CFM tables were conducted way back when the level of vacuum achieved was only 15"Hg. Would be curious how the modern high vacuum levels, and the increase in air flow friction change these sizing guidelines? Wonder if a correction offset could be applied per additional inch of Hg, if there is linear correlation.

    My actual end of mainline CFM measurements with our borrowed Lapierre CFM tester was way lower (60-70%) of what is published at 26.5"Hg at the end of the mainline. (Dry pipe/no sap, end of season with all drops capped back on their tee's). These guidelines don't account for mainline saddles protruding into the pipe which cause CFM restrictions, but this can't account for the 60-70% reduction.

    Would be a great research/grant project to update

  2. #2
    Join Date
    Jun 2009
    Location
    Verona, NY
    Posts
    375

    Default

    would part of the difference be the pump itself? most pumps are rated for cfm's based off 15" of vacuum, but i will say i have been using that as a guide and then increasing to the next size and the impact has been incredible, but also i run a lot of flat ground so i generally need a larger pipe to do the same work.
    I agree it never hurts to update or re-study, but i wonder if it would make more sense to develop an online calculator for people to use for sizing mainlines/wet dry's.
    4000 taps on vacuum, just trying to get a little better every year.

  3. #3
    Join Date
    May 2009
    Location
    UVM Proctor Maple Research Center, Underhill Ctr, VT
    Posts
    5,618

    Default

    Quote Originally Posted by corrowbasin View Post
    Would be a great research/grant project to update
    The problem is that there is no shortage of great projects to do, more the limited number of researchers and a limited amount of money to do the work.
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  4. #4
    Join Date
    Mar 2013
    Location
    Wisconsin
    Posts
    23

    Default

    Might be a dumb question but I have to ask. The CFM frictional loss in a dry line from a vacuum pump to a releaser are the same today at 15" as it was when all of the original research was done correct? New vacuum pumps from today(@15") still succumb to the friction loss in a pipe as a dairy pump(@ 15")? Both pumps would have the same CFM for comparison.

  5. #5
    Join Date
    May 2009
    Location
    UVM Proctor Maple Research Center, Underhill Ctr, VT
    Posts
    5,618

    Default

    Quote Originally Posted by One tap short View Post
    The CFM frictional loss in a dry line from a vacuum pump to a releaser are the same today at 15" as it was when all of the original research was done correct?
    Correct. If the pipe composition hasn't changed a lot, then the frictional loss would be the same. Differences in required CFM might arise from how tight the system can be made. There have been some small improvements in that realm (fittings are better, no parting lines, etc.), but probably not enough to make a huge difference. Others might be in how the system is installed (turns, bends, sags, etc.), the number and type of fittings (restrictions) used, and the level of gas production by the trees (not a factor likely to change from one system to the next, but could be different from site-site, especially with a warming climate).
    Dr. Tim Perkins
    UVM Proctor Maple Research Ctr
    http://www.uvm.edu/~pmrc
    https://mapleresearch.org
    Timothy.Perkins@uvm.edu

  6. #6
    Join Date
    Mar 2013
    Location
    Wisconsin
    Posts
    23

    Default

    Quote Originally Posted by DrTimPerkins View Post
    Correct. If the pipe composition hasn't changed a lot, then the frictional loss would be the same.
    Just as I thought it should be. The reason I asked is because a local dealer rep stated that those numbers are outdated when asked about the CFM's available at the end of a vacuum line to a remote section of woods. Not only was one section of 2" line not enough but the system would need a total of three at this distance. You'd think the person helping to lay out your woods would know a little more about running the numbers and where to find this information.

+ Reply to Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts