Results 1 to 6 of 6

Thread: Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

  1. #1
    Join Date
    Mar 2012
    Location
    Australia
    Posts
    810
    Post Thanks / Like

    Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

    So this is a little job i've just finished up that I thought might be interesting, especially since this is a 100% xray pipe job that is welded in a way that's not usual.

    This is for Munkel a little bit as he was asking a while back about running solid wire pulse uphill, Normally I would do this job with a Fronius TPS 2700 but that machine is out of action at the moment so I'm subbing in a Lincoln V-350 PRO running the .035 argon blend pulse program and an LN25 feeder instead, it doesnt do as good of a job as the fronius, but it does show that pulse can make vertical spray arc welding work pretty well.

    I've been fabricating and welding lobster back elbows made out of 762mm (or 30" in banana's) spiral seam pipe for a fire fighting water supply line in a coal mine.

    The job starts with a length of pipe with a centerline snapped 180 apart to get the centers for the patterns.



    The patterns are done on a computer and printed up on A0 sheets that are taped together.



    The pattern is wrapped around the pipe and the lines transferred through to the pipe with a center punch, the punch marks are then joined up with a paint marker to make the cut lines.



    Once the length is marked out we take it outside and cut it up with a 9 inch grinder.



    Jumping forward a bit just because I didnt take pics in order, this shows the basic setup to put an elbow together, get the bottom section level and square and weld it to the flood rails, then set each section on top and use a digital level to get them to the right angle.



    the only problem is that being spiral seam pipe, it isn't flat, straight, square, level or round, so the sections are never cut exactly as they should be and the pipe is never round, this one isn't to bad, but sometimes the sections can be out of round by up to an inch.





    I personally just use a lever tacked to the pipe to get it lined up, sometimes if it's way out a dog and wedge is needed bu this is much faster and does the job 95% of the time, the smallfox wedge inn the prep is to get the angle just right.



    The other fun part of being spiral seam pipe is even with good patterning the preps never line up, if it's only about by 1/4 inch your doing well, so once the angle is right you tack it together and knife the prep with a 9 inch hard disk to get the prep consistant all the way around.



    Last edited by ttoks; 10-13-2021 at 07:19 AM.

  2. Likes Shootr, whtbaron, robocow, farmersammm liked this post
  3. #2
    Join Date
    Mar 2012
    Location
    Australia
    Posts
    810
    Post Thanks / Like

    Re: Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

    once I have a consistent gap with the right angle I bring the gap down to around 1/8", tack it on the outside of the pipe and put a small 1/8 bevel on the inside of the pipe.

    The root is welded from the inside vertical down running a lincoln V350PRO with .035 Hyundai SM-70 ER70S-6 wire on the .035 pulse program with an LN25 suitcase with 18% Co2, 3% O2 79% argon gas, the V-350 pro pulse program is not a synergic pulse program so wire feed, and pulse gross and trim are all set independently.

    the root setting I use is 500 IPM with the machine set to 550 (which the the machines estimate for a given wire feed, I often like it set higher than the actual wire feed setting) with a 1/4 stick out and the trim at the max which increases the pulse frequency and narrows the weld pool on the V-350 , this ends up being around 31.5 volts and 190 amps, this ends up not quite being a spray pulse setting, but it punched through the pipe fairly well even though i'm running the root downhill.

    Downhand part of the root



    And the overhead/downhill part of the root.



    And this is how much in punches through the pipe, around 2/3 of the way through all the way around as long as the 1/8 bevel and 1/8 gap is consistent.



    And the root on all 3 joints for this elbow done.



    Then I back grind the outside of the pipe again with a 9 inch grinder with a hard disk to get to clean metal.



    I swap out my gas shroud for the cap as I run ALOT of stick out for the cap, going from the tip just inside the shroud.



    To recessed in about 1/2 an inch.

    .

  4. Likes Shootr, farmersammm liked this post
  5. #3
    Join Date
    Mar 2012
    Location
    Australia
    Posts
    810
    Post Thanks / Like

    Re: Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

    My stick out for the cap ends up at around the 30mm, or 1 1/4" mark.



    And the setting are turned down, 400 IPM, with the machine set to 410, this end up being around 120 amp's at 28ish volts for the cap, this gives a true pulsed spray arc for vertical up, I run alot of stick out to get the overall heat out of the weld pool to make it easier to control going vertical up, but the pulse allows the .035 to spray even with the huge stick out and much lower amperage than would usually be needed for spray transfer, again I'd usually run a fronius TPS 2700 in pulse for this and that machine gives a mucher nice final weld appearance than I can get with the V-350.



    Vertical section of the fill/cap on the inside of the elbow.







    and vert section on the outside.



    Running from 9-12 o'clock in one go.




    And all done ready to go be painted and sent to site.

    Last edited by ttoks; 10-13-2021 at 07:24 AM.

  6. #4
    Join Date
    Dec 2010
    Location
    Wenatchee Washington
    Posts
    353
    Post Thanks / Like

    Re: Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

    Thank you for taking the time to document this work with photos and a detailed explanation. Fascinating.

    Would plasma work for cutting the pipe, rather than a 9" grinder. That grinder looks like a killer!
    Lincoln Precision TIG 185.
    Flex-Loc 150 torch.
    Super-Flex hose.
    Lincoln MIG 180.
    Victor Oxy/Act torch set.
    DeWalt Bandsaw with SWAG stand

  7. Likes ttoks liked this post
  8. #5
    Join Date
    Jul 2008
    Posts
    3,146
    Post Thanks / Like

    Re: Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

    Quote Originally Posted by ttoks View Post

    And this is how much in punches through the pipe, around 2/3 of the way through all the way around as long as the 1/8 bevel and 1/8 gap is consistent.

    Interesting stuff, thanks for posting up!

    Question: On the inside of the pipe, do you leave the weld joints non-flush with the material? In other words, is there a depression at the weld joints on the inside? I'm not a pipe welder (just a hobbyist) but I'm surprised they wouldn't want that joint to be filled flush if not reinforced a bit...

    Or is it actually flush on the inside? (I can't quite tell in this pic)

    Quote Originally Posted by ttoks View Post
    Last edited by Kelvin; 10-13-2021 at 10:09 AM.

  9. Likes ttoks liked this post
  10. #6
    Join Date
    Mar 2012
    Location
    Australia
    Posts
    810
    Post Thanks / Like

    Re: Fabricating 30" lobster back pipe elbows and welding with Pulsed MIG.

    Quote Originally Posted by WenValley View Post
    Thank you for taking the time to document this work with photos and a detailed explanation. Fascinating.

    Would plasma work for cutting the pipe, rather than a 9" grinder. That grinder looks like a killer!
    Plasma or oxy would work, but it's a lot easier to get a straight cut with the grinder on pipe.

    Quote Originally Posted by Kelvin View Post
    Interesting stuff, thanks for posting up!

    Question: On the inside of the pipe, do you leave the weld joints non-flush with the material? In other words, is there a depression at the weld joints on the inside? I'm not a pipe welder (just a hobbyist) but I'm surprised they wouldn't want that joint to be filled flush if not reinforced a bit...

    Or is it actually flush on the inside? (I can't quite tell in this pic)
    I'm not sure If i explained it properly or not, but the root it welded from inside, not outside the pipe, it's just above flush, although in the pic I think it looks a littler lower than flush because of the paint on the inside which is is 1/16 thick.

  11. Likes WenValley, Broccoli1, Kelvin, 12V71 liked this post

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Page generated in 1,638,549,198.25443 seconds with 12 queries