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Thread: TIG Welds

  1. #1
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    TIG Welds

    Too cold?

    Here a few examples of my TIG welds on 3 inch, schedule 10 stainless pipe. I get a variety of shiny colors on top. The inside of the pipe has no burn through and a blue, sometimes dark purple color. Do these welds look too cold? Shouldn't they lay a little more flat and be darker in color? They get tested for leaks at 300 PSI. That is the only test they will receive. But I want them to be as strong as possible and to last a life time.

    Hope the pic quality isn't too bad. I have to snap pictures sneakily at work

    Thanks in advance



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  2. #2
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    Re: TIG Welds

    1-Apparently there's no sand/grind prep to either piece, not even taking the skin off?

    2-No pics of the root, but what's shown is a lay rod cover pass over the bevel with
    very incomplete root fusion.

    3-Is there any spec. conformance required?

    ......or just a one time hydro and it's all 'Gud 2 Go'?

    I'd be more concerned about the lack of root fusion than the colors.
    Blackbird

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    Re: TIG Welds

    In addition to above comments, I'm confused by the width of the weld.
    Why is it so wide compared to the bevel?
    Dave J.

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    Re: TIG Welds

    Each piece gets a small 45 degree bevel. They butt right up to each other with no gap. I used a 3/32 rod and I spread probably 1/8 of an inch on either side of the bevel. Is this a bit much? This is my first welding job and nobody really explains much. Just learning as I go

  5. #5
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    Re: TIG Welds

    Is that really 3" sch.10 with threads? Nice cap, but like others have said, it's the consistent penetration that counts. Any discrepancies can allow cracks to start. Forever is a long time.

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    Re: TIG Welds

    Quote Originally Posted by PipeStand View Post
    Each piece gets a small 45 degree bevel. They butt right up to each other with no gap. I used a 3/32 rod and I spread probably 1/8 of an inch on either side of the bevel. Is this a bit much? This is my first welding job and nobody really explains much. Just learning as I go
    "Spreading on" the filler material is not correct for any welding I'm familiar with.

    Spreading filler material outside of the bevel is wasted filler and not doing anything structural for the weld.

    Did you get complete joint penetration (CJP) so that your pipe is fully fused all the way to the inside?
    (that inner corner will be melted and a little metal on the inside of the pipe if the answer is yes)

    Somewhere between figure 1 and figure 3
    (figure 2 is likely the weld you have now)

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    Disclaimer: I'm not a pipe welder, this is just general welding 101 type stuff I'm referring to.
    Last edited by MinnesotaDave; 07-10-2014 at 12:47 PM.
    Dave J.

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  7. #7
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    Re: TIG Welds

    From what I see if there is no gap then 300 PSI should not be any problem at all but are these going to be installed where there is NO vibration?


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    Re: TIG Welds

    pipes; that appears to be a sound weld. on the outside. it's what's on the inside that count's just as much. what's that look like?
    i.u.o.e. # 15
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    Re: TIG Welds

    I'll try to snag some pics of the inside weld tomorrow at work.

    MinnesotaDave, I do believe that weld is similar to figure 2. The strange thing is, they do not purge pipe where I work, and they frown upon sugar on the inside of the pipe (since fuel flows through it). Therefore, I can't really get 100% penetration, more like 95%. Is it possible to get 100% penetration with no purge and no burn through?

    There are probably vibrations, but not many. Here is an example of what I build...

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    That big aluminum vessel is a filter and fuel travels through the pipe. They are airplane re-fuellers.

  10. #10
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    Re: TIG Welds

    This is my first welding job, and I just hope its not going to set me up for failure in the future. I'd prefer learning correct methods now with good penetration to better myself.

    But, hey, I guess every weld shop has different ways of doing things

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    Re: TIG Welds

    Off topic from my TIG welding dilemma, but here is some fluxcore welding I did on pipe.... I believe penetration is much better with the MIG.

    On the inside, it doesn't look like sugar, but an even seam all the way around with dark lines on either side.

    Work requires me to knock off the stop/start with a file. That's what the scuff is you see on that one weld. Makes it look better when painted.

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    Re: TIG Welds

    Quote Originally Posted by PipeStand View Post
    This is my first welding job, and I just hope its not going to set me up for failure in the future. I'd prefer learning correct methods now with good penetration to better myself.

    But, hey, I guess every weld shop has different ways of doing things


    You are following their engineer's procedure, and that is what counts. It must be sufficient, so no sense overdoing it then. Do you sign off on any of this stuff? Or do they performance test?
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: TIG Welds

    Caps look good

  14. #14
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    Re: TIG Welds

    pipes; you doing ok for your first welding job! did you learn in school or by doing? the only direction you can go from here is up!
    i.u.o.e. # 15
    queens, ny and sunny fla

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    Re: TIG Welds

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    Baffled by this thread. That looks like some pretty serious equipment you're putting together. Is there that much difference between shop and field installations? I've only worked the latter and around here there would be a strict criteria as to who welds on a project like that. At the very least, there would be a procedure test required which would answer all the questions about complete penetration. Then there would probably be at least 10% x-ray requirement. Definitely purged. Another test before mig would be allowed. There was another thread going around where an inspector was concerned about signing off on structural welds without doing a visual. Seems this is a lot bigger deal considering you can only see the cap. Root tie-ins are probably the most critical part of the weld.
    Last edited by OldSparks; 07-12-2014 at 11:08 AM.

  16. #16
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    Re: TIG Welds

    I'm confused as hell as well.

    No disrespect meant, but you're learning "as you go" on pipe that carries pressurized fuel to airplanes?

    Your tig outwardly better than anything I can do, but why would you not purge? Doesn't look like cheap equipment.

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