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  1. #53
    Join Date
    Apr 2009
    Location
    R.O.T.
    Posts
    301
    I put the ntrogen tank on the liquid line, start brazing at the closest joint to the nitrogen, then work my way toward the coil, then the suction side back out to the condenser. I'll tell yall somthin no one has mentioned yet. What about when you remove a cooling coil on a system that has been in service for a while? If it has been freezing up, there will be excess oil in the coil. When you braze it back in, it will flare, smoke, and burn like hell. Not if you use nitrogen. Nitrogen displaces the oxygen, therefore combustion cannot occur. I've always believed in putting driers as close to the TXV as possible. Plus if it is inside, it will never rust out. How many times have you guys found driers leaking that were outside at the condenser, layin on the dirt and grass. Not tryin to tell anyone how to do their job, just tryin to offer some of my thinkin.

  2. #54
    how much cooler does a constant low pressure flow of n2 keep the lines? enough to save a bulb on an txv while welding? (these bulbs from what i've seen have to be removed to prevent damage randomly, extreme care prevents this but the bulbs are far too sensitive to risk in my opinion)

  3. #55
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,911
    Twilli says whats nitrogen?
    No Heat No Cool You need Action Fast

  4. #56
    Join Date
    May 2009
    Location
    Central Florida
    Posts
    65
    Quote Originally Posted by twilli3967 View Post
    Twilli says whats nitrogen?
    It's what busy techs use to blow out drain lines and inflate flat tires on the service truck. Gotta run dispatch is hollerin.
    Last edited by ACworks; 05-16-2009 at 06:43 PM. Reason: spelling misteaks

  5. #57
    Join Date
    Sep 2002
    Location
    Warren, Michigan
    Posts
    84

    Talking

    Tiwilli,

    Quit clowing! You know very well what Nytrogin is but you gotta make sure the Potassiums, and Sil Phos has been removed. Seems like it's just basic fertilizer to me, but the real question is: how much do you pour in before you start brazin on the pipes?


    Toddfather
    Never argue with an idiot: They'll drag you down to their level, and beat you with experience!

  6. #58
    Join Date
    Nov 2003
    Location
    northern mass
    Posts
    411

    nitro flow

    I must admit that I have never flowed nitro when brazing. I feel like an ass saying that, but it's the truth. 19 years later and i've never had an issue....that I know of...as a result. And I will say, that i'm confident that I would find out.

    Anyway, it's not that I avoid doing things the right way....hell people get anoid with me 'cuz I make them do everything the right way and no shortcuts. But I have a rep that I want/need to uphold.
    Which is why I am surprised that I do not flow nitro. I guess I always was under the impression that 4 braze joints on a system doesn't create enough crap to amount to anything.
    But it feels like the "last piece of the puzzle" to me and I guess I should change my ways and start doing it. Most people tell me i'm being too anal, but if it's better......well then it's better.

    So I guess i'll ask this.........out of everyone out there who has been doing it for years and seen all it's aspects in practice........what is your general procedure for doing it and why?


    I can only assume that since most people don't do it, that everyone has their own method and practices of performing the task. And if I'm to start doing it.....then i'd like to do it right.
    I only try to be the best.....though i'm not......but in my efforts to be, I hope to learn and achieve more than most !!

  7. #59
    Join Date
    May 2007
    Posts
    735
    Hello, brian in mass. I have been using nitrogen purge for over 30 years, but I can't say I have ever seen a failure of any kind that could definitely be attributed to not using nitrogen. So I don't preach it as much as I used to, there are so many bigger fish to fry. But one of my personal goals has always been to do every reasonable thing possible to make a system last as long as possible. I wonder if a compressor that gives 15 years of service might have given 20 years of service if there had been no copper oxide in the crankcase, so I use nitrogen. As far as technique, it varies with the circumstances. But my general rules are: Make sure the nitrogen has a free path to atmosphere by removing shraders or hoses or even leaving a pipe disconnected at first. If smoke comes out the place that's open to atmosphere, there is still air in the system. It is easy to braze faster than the nitrogen can purge the air. So I will do an initial purge at 10 psi before changing to the lower purging pressure. I was doing nitrogen purge before anybody I know had heard of a low pressure regulator, and I still don't use one (though I should). I gently tweak the regulator with the hose disconnected from until I feel a very, very slight breeze coming from the hose. After connecting the hose to the system, I prove that nitrogen is leaving the system by seeing it blow out a small flame at the opening to atmosphere (cigarette lighter). There are times when you can't get flow through components without building up pressure, or you can't be sure of getting flow through every fitting; reversing valves are one example. Then I will apply nitrogen and let it blow out the fittings, then completely relieve pressure before brazing. Let nitrogen continue to flow until the brazes have cooled.
    I just remembered one of the reasons I have continued using nitrogen purge. When York introduced their new line of heat pumps in 1978, you could only use precharged line sets with them. The compressor failure rate was incredibly low; we had about one failure a year. A few years later, they began offering units where you could field supply the line sets, which we did. The compressor failure rate went up. Why? I was doing the startups and I was calculating and weighing in the extra charge, so that wasn't the reason. One thing that had changed was that the installers were running the line sets and they weren't using nitrogen purge. I can't say if that had anything to do with the increased failure rate (maybe the compressors themselves were different), but that was the only thing that I knew had changed.
    Last edited by fxb80; 05-17-2009 at 12:59 PM. Reason: Remembered one reason why I use nitrogen.

  8. #60
    Join Date
    Nov 2003
    Location
    northern mass
    Posts
    411
    i purged today for the first time after writing that the other day.....i noticed I had a leak after and I think it's 'cuz i had too much pressure. hahaha I was laughing because I really never have leaks. So, I guess I need to cut back on the pressure. And I guess I need to carry alot more nitro !
    I only try to be the best.....though i'm not......but in my efforts to be, I hope to learn and achieve more than most !!

  9. #61

    Brazing with nitro

    Purging with nitro should always be done to prevent oxidation inside the piping.The key is to use a low pressure bubble regulator.The question i have is can you braze joints while using a vacuum pump?

  10. #62
    Join Date
    Jul 2010
    Location
    Andalucia
    Posts
    3,230
    Quote Originally Posted by ac/joe View Post
    Purging with nitro should always be done to prevent oxidation inside the piping.The key is to use a low pressure bubble regulator.The question i have is can you braze joints while using a vacuum pump?
    I had to once because a solenoid was leaking by and not letting me seal the joint but you should not, and I can think of no reason to do it. You can pill solder etc into the system.

  11. #63
    Join Date
    Jul 2010
    Location
    Catoosa, OK
    Posts
    32
    Quote Originally Posted by re2ell View Post
    bruce, and then maybe your instructor meant that nitrogen was not used in class while brazing, that might be a possibility????

    when i was in brazing class, we didn't use nitrogen to purge the lines, not for the sake of learning the art.

    just a thought
    Ditto, we only used it for pressure testing but it was emphasized to use dry nitrogen when applicable for the reasons it's supposed to be used. Those oxides, like many of you said, just end up clogging up screens and causing more work down the road.

    When we practiced brazing, we only cut 3" pieces and brazed up, down, sideways, saddle joints...etc. Not worth wasting money on copper pieces that ended up in the recycle barrel.

  12. #64
    Join Date
    Mar 2003
    Posts
    7,326
    Purging nitrogen reduces or eliminates the oxides from brazing piping without flowing nitrogen. It is a requirement for med gas projects as those systems need to be uuber clean for obvious reasons. it is recommended for brazing refrigerant tubing by most manufacturers. it does do a better, cleaner job. my personaL recommendation is to use a low pressure regulator typically found in wleding supply stores as oposed to a standard reg. better control, less nitrogen used. my guys are pretty particular and use it everytime to the best of my knowledge. in fact, we were at a manufacturer last week, and while touring the plant, we noticed that they only brazed with nitrogen when doing things like tx valves or solenoid valves. they made their own coils, and did not use nitrogen purging when building the coils. I did ask, and it was like i was asking in another language. i have also seen this at other manufacturers with whom we do business. seems like this question will live on forever.

  13. #65
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,076
    Wow, who dug this thread out of the cellar? 05-18-2006
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

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