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  1. #1
    Join Date
    May 2009
    Posts
    308

    a tale of 2 micron gauges

    I have the field piece sman3 which I really like. It has a micron gauge and I use the vg200 from VPS on the middle port with a good isolation valve behind it. They disagree by 50-250 microns on any given day. If micron gauges are so great and necessary, why are they so unreliable?

  2. #2
    Join Date
    Oct 2003
    Location
    las vegas
    Posts
    1,505
    if you want reliability get the blu vac & mount it as far from the pump as u can. there have been reveral discussions on here regarding this.

  3. #3
    Join Date
    Jul 2011
    Location
    Salt Lake City, Utah
    Posts
    34
    I had a VG64 micron gauge, but recently bought an sman3. I could never get a vacuum under 500u from my robinair 15434 4cfm vacuum pump, and sometimes it wouldn't go under 1000u. I thought the vg64 gauge was messed up and cleaned it with alcohol but no difference.

    So I got the sman3 partly because it had the micron gauge built in. The sman3 and vg64 were within 10% and often closer, but still no low vacuum. So I bought another vacuum pump DV-142n and it works great, pumped down to 30 micron.

    So I'm playing around with the new vacuum pump for most of the day pulling a vacuum on my 30lb recovery tank, trying different hoses, different blank off methods, both micron gauges, etc, and by chance I took the top off of the robinair vacuum tree. It was a 5/16 m/m union with a 5/16 male plug in the end, not the factory 5/16 cap. I put my finger over the top and the robinair and it pulled right down to 40 micron. The home made cap had white plumbers tape on it as well, I never figured that it would be leaking. Very Stupid!!

  4. #4
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    so we pull a vacume from a charging and diagnostic manifold, with 3 hoses that permeate and also = 6 leak points. Interesting.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  5. #5
    Join Date
    Jul 2011
    Location
    Salt Lake City, Utah
    Posts
    34
    Yes, the long hoses permeate, very obvious when I was playing around with it. To get a good vacuum I connect the 12" blankoff hose right between the pump and the gauge, Vg64 or the sman3, or even put the gauge right on the pump. I have a J/B DV-29 Micron Gauge Blankoff kit with the hose and ball valves.

    If I use a 3' long rubber manifold line it won't hold a vacuum, I can't get it much below 200 micron to start with, and then it rises to 700 or so after it is blanked off with a ball valve (hehe at least now that the vacuum pump problem is resolved).

    The point was that I thought the vg64 micron gauge was wrong and I bought the sman3 and a new vacuum pump before I figured out what the problem was. I like the new tools and wanted them anyway, so no loss there. I thought it may help someone else think through and diagnose an equipment problem.

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