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  1. #1
    Join Date
    Feb 2004
    Posts
    6

    Frown

    Guys,
    Some input please.
    I have fought with micron levels while bench testing a new micron guage. I need another brain, mine is exhausted.
    Should I forsake the micron idea and just focus on standing pressure and vacuum tests? Books say it works. I've even done it many many times. Now it won't work. Makes no sense to me. I'm out of time to keep bench testing this high- tech, battery operated,micron detecting expensive junk. The old-timers weren't so bad huh!
    Somebody throw me a line! I'm not a new comer to this field. I've been here a long time.
    Help!
    Thanks to you all!


    I have the following symptoms. Test includes #1 vacuum pump, one new refrigeration hose connected to the pump, and new digital micron guage #1.
    1. micron level down to 400 microns,valved pump #1 off.
    2. Pump turned off.Levels of microns climb rapidly to unacceptable levels.
    3.Installed 2nd isolation valve to seal before hose connection at pump.Same results.Microns climb just as fast.
    4. Same test,new refrigeration hose.(I mean a new one!)
    same results.
    5. Buy new micron guage.Performed all the same tests as above with new micron guage.Hmmph!The exact same symptoms.
    6.Pulled out my "Not so old" analog micron guage,same equipment above.Performed same test.Same results.Microns climb just as fast as always.I even used a second valve a second time to isolate the pump.Nothing bettered.

    Fittings good shape,not scratched or pitted.Every concievable idea I have thought of I have done.Still,no worky.
    Trash all of this equiment? It is new! I know not of another culprit that it could be. I could condemn the new digital micron guages as a bad design,but the same symptom exists with my analog guage I've had all along. It's not the guages. It's not the hoses. It appears the micron target just cannot be maintained once the pump is isolated. Why? I don't know. Do any of you?
    I even used copper tubing instead of a hose! Same symptom.

  2. #2
    Join Date
    Jun 2003
    Location
    in a tree looking in your window
    Posts
    1,175
    I have never been a fan of these new fangled digital micron gauges, I think all they really read is temperature and try and convert it some vacuum level, I believe ambient temps and batteries give you different readings. All I use is a mercury manometer and it has never failed me yet.

    Dude

  3. #3
    Join Date
    May 2004
    Location
    Toronto
    Posts
    276
    From what you have told me i would say that there is a problem somewhere in connections being that you obtain the same readings with both gauges.
    Some questions I have:
    -what type of hoses are you using?
    -how long did you pull a vacuum?
    -where are you connecting your micron gauge?

  4. #4
    Join Date
    Oct 2003
    Location
    Vancouver, British Columbia
    Posts
    230

    Yellow Jacket?

    Apparently the sensing element in this unit is made of high purity components which make it ultra-sensitive. The use of standard rubber coated hoses can be a problem. Outgassing of the hoses can occur meaning that molecules from the hose material can affect the vacuum reading. Also refrigerant oil trapped in guage "o" rings and throughout the manifold can also be an issue. Thus it is recommended to use stainless hoses to prevent outgassing and trapping of molecules on inner hose walls. Keep hose lengths to a minimum. For best results, change vacuum pump oil prior to each operation. If it is determined that you have oil in guage manifolds then a degassing procedure may be required. Despite our best efforts to prevent this, air can come into contact with guage and hose internal surfaces allowing for the presence of moisture. During use of the vacuum guage, the element must be set upright (connection end down) to prevent refrigeration oil from getting into the sensor which can cause errant readings and improper operation. I have achieved a 250 micron vac by following the above procedures. If you decide to use rubber hoses, it is recommended to go with 3/8" hoses for best results.
    If a day went by without a problem - there'ld be a problem.

  5. #5
    Join Date
    Apr 2002
    Location
    most of the time in the Philippines
    Posts
    1,211
    I use gauges and metal hoses and pump made by JB Industries and consistently achieve micron levels at 250 to 500. I change the pump oil with each use. I blanked off a job one time and then was called away to take care of an immediate problem. 4 hours later, I still had 275 microns. I use separate guages. [separate from my regular charging/testing manifold and hoses] I took the fittings and gauges out of them and resealed with locktite thread sealant. Hooking up the rig can be a PIA, but when you do a 1 hour blankoff test that holds at 400 microns, you know there are no leaks, no moisture and no non condensables. For me, it's worth the trouble.

  6. #6
    Join Date
    Feb 2004
    Posts
    6
    Thanks guys,
    This crazy meter does describe how it converts some type of reading to a direct and proportional micron reading. Using its ability,it adjusts the current at the sensing element constantly,thereby providing a steady temperature..bla bla bla.....Hey!, I wonder...How far do you think I could throw it? LOL
    I would think it might be hoses, but I went to only 1/4" copper on vacuum pump(Short line) straight to this micron meter. Still loses ground rapidly.
    I'll be watching this post a little while. If someone can give me a theory why , even with copper line, I get the same results.

    ET

  7. #7
    Join Date
    Apr 2002
    Location
    most of the time in the Philippines
    Posts
    1,211
    Tell us more about the micron meter. Like what brand is it? With just a short copper line straight in, it's the meter, the pump or a leak. I found we had a leak on the pump. I took all the fittings out and resealed them with a locktite thread sealant.

  8. #8
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,819
    Alternative would be to connect a compound gauge directly to you inlet port of your vacuum pump through one of those short gauge connectors (about $7.00 or less) and do the same test. If the gauge reachs atmosphere you have a problem with your vacuum pump.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  9. #9
    Join Date
    Jan 2004
    Location
    mass
    Posts
    539
    i believe moonman is right i have had similar response,and after changing gauge manifold and hoses that has solved the problem.so like jhd i now use i gauge set for vacuum only.

  10. #10
    Join Date
    Feb 2004
    Posts
    6

    Vacuum problems

    Guys,
    See if this sounds correct. I've done some homework. I believe I have an understanding now...here goes.
    Acceptable levels of vacuum reached as long as pump running,but lose my target of 400 microns (small systems) or 700 microns (Large systems). After pump isolation levels rise.
    Some information I came across stated that (after pump isolation) , levels must stay below 2000 microns in the system for a considerable time period, to assure a clean and dry system. Sounds like an increase is to be expected! I was shooting for my 400 to 700 targets to be maintained after pump isolation and to be my final readings. DUH! Am I wrong or what? I just observed my manifold vacuum guage stay nearly 30" for full duration of test, but the digital micron guage rose to a peak of 1549 microns and finally stop. That is below 2000! Vacuum guage still at 30". This scenerio is working. It looks correct to me too. Do any of you know my latest findings to be wrong?
    Thanks for your help!
    ET

  11. #11
    Join Date
    Feb 2004
    Location
    Madison, WI
    Posts
    295
    I don't really know if this will help but I did a similar experiment some years ago and had the same issure with rapidly rising readings after blanking off the vac pump. I think one problem with bench testing a micron gauge like that is you have no reservoir for the vaccum. What I mean by that is when you have a micron gauge hooked up to an entire system you have a large area to pull a vacuum on so tiny leakage is not noticeable, but when you hook up a micron gauge to a hose and blank it off the volume of this "system" is so small that tiny leaks that normally would not be an issue now are. By tiny I mean very tiny like that amount that could come through the stem of the shut off valves etc. which would not be considered significant enough for a leak detector to pick up. If you try that same test but with a recovery cylinder in the system for added volume you might find your readings don't rise to unacceptable levels.

  12. #12
    Join Date
    Oct 2003
    Location
    Vancouver, British Columbia
    Posts
    230

    Re: Vacuum problems

    Originally posted by et
    Guys,
    See if this sounds correct. I've done some homework. I believe I have an understanding now...here goes.
    Acceptable levels of vacuum reached as long as pump running,but lose my target of 400 microns (small systems) or 700 microns (Large systems). After pump isolation levels rise.
    Some information I came across stated that (after pump isolation) , levels must stay below 2000 microns in the system for a considerable time period, to assure a clean and dry system. Sounds like an increase is to be expected! I was shooting for my 400 to 700 targets to be maintained after pump isolation and to be my final readings. DUH! Am I wrong or what? I just observed my manifold vacuum guage stay nearly 30" for full duration of test, but the digital micron guage rose to a peak of 1549 microns and finally stop. That is below 2000! Vacuum guage still at 30". This scenerio is working. It looks correct to me too. Do any of you know my latest findings to be wrong?
    Thanks for your help!
    ET
    Micron readings will rise if moisture or non-condensibles are present in the system. The difference between the tiniest of leaks and moisture presence is that the micron reading will continue to climb w/o stopping if a leak is present as opposed to a micron climb and level out with presence of moisture or non-condensibles. Rate of climb in a leaking system of course depends on the size of the Leak(s). The type of vacuum you want to achieve is dependant on the type of system you are working on. Low temp. applications have less tolerance for moisture presence in the system thus 50 to 100 microns initially with a rise to 300 microns within 3 minutes is o.k. maxing out at 500 microns. For any other types of system, achieving and maintaining 500 microns is very good. However, if the level rises to 2000 microns within 2 hours you MAY have a leak. (ASHRAE's standard is 1000 microns) Flush system with dry nitrogen and revacuum. It is recommended to install a ball valve between the system service port and the vacuum guage sensing element. Your compound guage will not budge fromm 29.9+ "hg until the micron level rises above 2000 microns. And of course on top of all this good work a new drier will ensure the integrity of the refrigerant after dehydration and charging has been completed.
    If a day went by without a problem - there'ld be a problem.

  13. #13
    Join Date
    Dec 2003
    Location
    Nevada
    Posts
    1,815
    Where is the gauge installed in relation to the pump?
    Quote
    “Engineers like to solve problems. If there are no problems handily available, they will create their own." Scott Adams

    "We can't solve problems by using the same kind of thinking we used when we created them."
    Albert Einstein

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