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Soldering - pipes going black

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  1. #1
    Apprentice (new member)
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    Default Soldering - pipes going black

    Hello,

    I'm trying to solder 2" and 1/4" copper pipes together - I drilled a hole in the side of the 2" pipe to thread the small pipe through as a heat exchanger (trying to make a simple cooling system for a computer).

    My problem is that the pipe is going black and the flame green before the pipe is hot enough for solder to be added. I have cleaned it as much as possible and used heaps of flux.

    Is it possible the flame isn't strong enough - so the heat is dissipating before it builds up in the joint? I'm using a 'bernzomatic' propane torch and the flux / solder that came with it.

  2. #2
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    the flame will turn green from a combo of the flux burning and solder, the little mapp gas might not be able to pump enough heat into the 2" pipe, though only trying to weld 1/4 inch should be able to be done.

    the pipe turning black is from not getting enough heat into it. be patient it'll take ages to try get the heat in. hold it in one spot for a couple of minutes trying not to move the flame at all.

    with the mapp bottles i prefer to solder with 5% rods, they dont need as much heat to run easier

  3. #3
    Soldiers Earned Your Right To Free Speech watson's Avatar
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    Are you using the bernzomatic MAPP gas or just the propane??

  4. #4
    GeoffW1
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    Quote Originally Posted by wozz View Post
    the flame will turn green from a combo of the flux burning and solder, the little mapp gas might not be able to pump enough heat into the 2" pipe,
    Hi,

    He mentioned propane, not MAPP gas. That won't get hot enough for a 5% silver solder joint, especially not with a big 2" pipe to carry away all the heat.

    Besides it is not needed.

    As it is not subjected to mains pressure like a domestic water service, I'd just use soft solder (tin/lead) for which a propane flame should be adequate. If the small pipe is a neat fit in the hole in the large pipe, that should form a mechanical support for the joint too.

    Cheers

  5. #5
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    true, i just read the bernzo, didnt even see the propane lol.

    what colour is the bottle you're using? the yellow, propylene, will burn 100 or so degrees hotter then the blue, propane fuel

  6. #6
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    Either way both will be hot enough to soft solder, if you get it too hot it will burn the flux turning it black amd the solder wont stick. Just an idea.
    Plumbers were around long before Jesus was a carpenter

  7. #7
    Old Chippy 6K
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    Araldite?
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

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