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  1. #1

    leak search in large refrigeration pipe system

    Good evening and greetings to everyone. Thank you for allowing me in your forum. I`m a new user, just out of technical college, with almost a year of working experience. I hope I can eventually add something to the wisdom and knowledge contained in this site, but right now I can only seek to benefit from your superior experience, skills and intellect.
    I´ve been contracted for the leak inspection of several sets of large refrigeration pipes being installed in a supermarket. The diameters of the pipes are 2-5/8 and 3 inches. The length of the sets are between 90 to 120 feet. I´ve used nitrogen for similar jobs in much smaller systems, but never before tried to tackle such a large system.
    In the same building, there is a compressed air system used for pneumatic packaging machines. I see that the compressed air goes through a mechanically refrigerated drier and several stages of filtration. As the copper pipes, after being installed, are containing ambient air anyway, would it be possible to use dried/filtered air for leak testing ? Thank you for any comments.

  2. #2
    Join Date
    Mar 2010
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    Morgan Hill Ca.
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    1,224
    Quote Originally Posted by coldseeker2013 View Post
    Good evening and greetings to everyone. Thank you for allowing me in your forum. I`m a new user, just out of technical college, with almost a year of working experience. I hope I can eventually add something to the wisdom and knowledge contained in this site, but right now I can only seek to benefit from your superior experience, skills and intellect.
    I´ve been contracted for the leak inspection of several sets of large refrigeration pipes being installed in a supermarket. The diameters of the pipes are 2-5/8 and 3 inches. The length of the sets are between 90 to 120 feet. I´ve used nitrogen for similar jobs in much smaller systems, but never before tried to tackle such a large system.
    In the same building, there is a compressed air system used for pneumatic packaging machines. I see that the compressed air goes through a mechanically refrigerated drier and several stages of filtration. As the copper pipes, after being installed, are containing ambient air anyway, would it be possible to use dried/filtered air for leak testing ? Thank you for any comments.

    Possible, but don't recommend it at all. Dry nitrogen or helium (helium would be expensive as hell).
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

  3. #3
    Join Date
    Jul 2011
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    Lehigh Valley, PA
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    471
    Go to Airgas or similar gas supply house & get about (4)--250 cf cylinders. For really big pressure test jobs you can always get an (1)-LG45 liquid cylinder = to 22 cylinders. Helium is for really critical jobs flowing gases (such as hydrogen) with really small molecules but is the best pressure gas test and can always be used. Nitrogen is lighter than air too so is a good leak test gas for just bout everything. Both are obviously inert. Never use any gas with a moisture content.

  4. #4
    Join Date
    Jul 2011
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    Lehigh Valley, PA
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    What will you use for leak detection once pressurized? How long are you being asked to keep the system under pressure?

  5. #5
    Join Date
    Jul 2012
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    Western KY
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    I would not do that. Ya it has a drier but that's only gonna get the air dryish. You will only add a lot of time to your evacuation trying to get the additional moisture out. Nitro is best bet, IMHO. Push it up and let it sit a few hrs and check for fall. If none start your evacuation. Get it down to 500 microns. If it will hold below 1000 microns for an hour you've got a tight dry system. Good luck.

  6. #6
    Join Date
    Oct 2005
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    B.C. Canada
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    Quote Originally Posted by Tommy knocker View Post
    I would not do that. Ya it has a drier but that's only gonna get the air dryish. You will only add a lot of time to your evacuation trying to get the additional moisture out. Nitro is best bet, IMHO. Push it up and let it sit a few hrs and check for fall. If none start your evacuation. Get it down to 500 microns. If it will hold below 1000 microns for an hour you've got a tight dry system. Good luck.
    I would think more than a few hours standing test...100feet of 3inch pipe might take some time to see a drop. I would say 24hours, but thats just me

  7. #7
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    Jul 2012
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    Western KY
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    Quote Originally Posted by coolerik View Post
    I would think more than a few hours standing test...100feet of 3inch pipe might take some time to see a drop. I would say 24hours, but thats just me
    Agreed

  8. #8
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    Oct 2005
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    B.C. Canada
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    904

  9. #9
    Good evening and thank you all for your replies. In a few words:
    1. Forget about dried/filtered pressurized air.
    2. Use only nitrogen + refrigerant mixture up to maybe 150 psig (10 kg/cm2). The system is to be operated with R-404A. Is this Nitro/R404A the easiest detectable mix?
    3. Check with electronic leak detector around joints for obvious leaks.
    3. 24 hour pressure holding test time.
    Am I missing something?

  10. #10
    Join Date
    Jul 2012
    Location
    Western KY
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    1,221
    Quote Originally Posted by coldseeker2013 View Post
    Good evening and thank you all for your replies. In a few words:
    1. Forget about dried/filtered pressurized air.
    2. Use only nitrogen + refrigerant mixture up to maybe 150 psig (10 kg/cm2). The system is to be operated with R-404A. Is this Nitro/R404A the easiest detectable mix?
    3. Check with electronic leak detector around joints for obvious leaks.
    3. 24 hour pressure holding test time.
    Am I missing something?
    A good micron guage.

  11. #11
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
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    471
    I'd pressurize with all nitrogen to 150psi. Using accurate pressure gauge securely tapped into the system, allow to hold for 24hrs. Take note of ambient temps as temps could change pressure. If pressure drops after 24hrs, using soap & water, test all joints. Make repairs as necessary. We used Ivory liquid & water for years before leak check soaps were used. Using your fingers wet with the soapy solution, wrap your hands around the joints, this is a good way to discover leaks.

    I agree with T. Knocker, for the evacuation stage of your project.

  12. #12
    I suspect that your preference for all nitrogen (instead of nitro+refrigerant) and soap and water (instead of electronic leak detector) might be related to something I have heard from other techs but never really got to know if it is myth or fact: that the chemistry of the components the Armaflex type insulation is made of, interferes with the electronic detector´s sensor sensitivity. I already cut open and removed a length of about 1 feet of the insulation at all joints. Does the sensitivity of the detector still be compromised?

  13. #13
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    471
    I don't see the need of electronic leak detection for large tubing runs. If you have good installation practices with trained installers, why should there be leaks in the first place? If you are sweating/brazing 2" & 3" copper, with sil fas, using a n2 purge, why would you need an electronic leak detector? You typically should not have leaks with a copper tubing installation. You could visually inspect the sweat joints too. The armerflex should be installed after the piping system has be approved, shouldn't it? Leak detectors are most valuable when used tracking down leaks on systems with many connections, valves, components, etc. already in service. Right?

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