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that had a black line down the middle slighty in the metal on the suc line.
installer didnt clean off well soft solder silver on a heatpump charge left too soon cust PO
10 + years ago


  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Brazing and Soft Soldering

    I just taught my new students the ins and outs of soft soldering and brazing.

    As always, when learning these very important skills, I have my students cut open each and every joint so they can determine if they used too much filler material or too little; too much heat or too little.

    When they cut open the joint they can see the portions of the mating sections that are indeed joined with the filler material.

    When brazing, my guys learned to push 1 or 2 psig of nitrogen through the lines to prevent oxidation. They braze both with and without the nitropgen so they can see the difference.

    My questions for you guys are:

    1. When you learned to solder, did you actually cut open some soldered sections to make certain you were doing it right?

    2. When you were taught to braze, did you ever use nitrogen to keep all of that nasty flaking ot of your piping circuits?

    3. What soldering/brazing disaster stories do you have for my guys to motvate them to continuously strive for perfection in the world of soldering and brazing?
  • hr
    hr Member Posts: 6,106
    When I took my plumbing test

    in Montana, the pratical included building two offsets inside a wooden templete.

    The graded the layout bmath, copper prep and assembly, including reamed tube! Rarely done these day from what I observe :)

    Then the cut and pounded the joints apart to check the flux and solder.

    Tougher than you think to make 8 perfect joints.

    For soft solder prep work is critical. Sand and use a fitting brush even on brand new fittings.

    Over fluxing is the other big mistake. Just a thin film please.

    Water soluable flux takes more skill with a low burn temperature.

    The correct torch tip makes a world of difference.

    hot rod

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  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    Thanks for the words of wisdome, Hot Rod. Always a pleasure to hear from you...
  • Brad White_126
    Brad White_126 Member Posts: 12
    That Montana Plumbing Test

    raised my already high opinion of that great state.

    Our brazing specification has a nitrogen purge statement in there for the good reasons you state, Eugene. I am taking notes on how to improve that specification without micromanaging the means and methods.

    Thanks Hot Rod and Eugene!

  • don_182
    don_182 Member Posts: 69
    I always

    thought nitrogen were for guys like me that always were in a
    hurry and used hotter flames.

    I herd over the years that most flakes if we can call it that will travel around the system in settle in the bottom of the compressor.With really no harm done.

    If you're going to braze then nitro purge is a must.If you want to keep the flakes down then the soft stuff is the better way to go.

    I once went to apartment complex to do startup on 30 units.
    Every one had clogged orfices.Low head and no suction.
    This was track home where lines were left open after rough in.No ends were tape while running them in a crawl and up the side of the buildings.Leaks in the walls from no pressure check.evacuration took over 8 hours and then some.

    After about 6 weeks I finally got them all up and running only to turn around and give the owner myu two weeks notice.

    As they say...the service man not anygood unless the installer was good.I stunk.

  • Plumdog_2
    Plumdog_2 Member Posts: 873
    Colo. Plumbers

    used to test as Hot Rod describes. No Longer. We had to cut the sections in half longitudinally on a bandsaw and then pull apart the joints and measure the percentage of voids. Also, if the assembly didn't fit in the jig, you flunked. It was a three-dimensional series of fittings and nipples w/brazing and 95/5. Bring your own parts.
  • bob_50
    bob_50 Member Posts: 306
    BCuP and BAg

    Make sure you tell the student the difference. Never use any material containing phospherous on steel. It looks good but it's brittle and won't hold. I had a hot gas line blow right out of a compressor. I made a spark plug wrench foy my enduro bike out of steel and Sil-fosed it instead of BAg. Out in the middle of nowhere I fouled a plug! You guessed it. As for nitrogen I have done a lot of medical gas piping and you HAVE to purge. I think 2 to 3 psig is a little high. I like to put a piece of masking tape over the end of the run and poke a hole in it with a pencil. Turn the purge on so you get just enough nitrogen out of the hole to snuff out a match. All the large commercial refrigeration contractors I have worked for do not purge. If you ask the superintendant on the job if you should purge he'll say hell no, why do you think we have a service department! If you are running a lot of pipe it does take a lot longer to purge. I built a system once with a half dozen solenoid valves, 24 volt transformers, and jumper cables. While you were up on a platform lift brazing say 20 line sets on 10' wide trapeez hangers I would use the pipe as conductors and with the jumper cables I could control which set was being purged. It still takes too long.
  • mtfallsmikey
    mtfallsmikey Member Posts: 765
    I know I'm getting old when..

    I had to do a lead joint when I took my Master's test!
  • Techman
    Techman Member Posts: 2,144
    Brazing to steel -bob

    Hi bob Hi professor.In reference to brazing between copper/brass/bronze to steel ,it is my understanding that the phosphor is not the problem for brittle joints.Phos in the braze rod is a form of flux. The problem is in the percent of silver in the brazing rod . The highest sil-phos rod is 15% silver, so ,to make a good joint ,a 45% silver rod should be used. Flux (phos) must be used also .Watch for the higher silver bearing rods that have CADMIUM in them . Its DEADLY,!!!!!!!!!!!Enjoy your day!
  • bob_50
    bob_50 Member Posts: 306

    My understanding is the phospherous in sill fos is the flux and it is suitable for copper to copper only. If you use sil fos for copper to brass you need additional flux, borax based. Copper or brass to steel you need 45% silver or better plus borax based flux. The same for steel to steel. The American Welding Society gives the designations BCuP or BAg. Don't use BCuP with steel.
  • Sbergerson
    Sbergerson Member Posts: 7
    Pull the plugs

    I was doing a large refrigeration install and brazing in 20' lengths of tubing. The tube was dry and charged from the factory with nitrogen. As I was brazing one of the joints, something 20' away caught my eye. It was BLACK SMOKE coming from the end of the tube. It didn't take long to figure out that I forgot to remove the rubber plug from the 20' section I was brazing.

    I hate to think of the troubleshooting NIGHTMARE I would have had if I didn't notice the smoke!
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Can you say....


    I hate when that happens.
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