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Thread: Pipe offset fab

  1. #1

    Default Pipe offset fab

    I need to make a section of irrigation pipe that will offset the line around an obstruction by 7". The pipe is 32" diameter and made of 11ga steel (about 1/8"). The 7" offset needs to take place over a distance of 14". Does anyone know how to layout pieces for this job or where I might find directions/calculations for doing it? I think it will need to be welded up from cut pieces but maybe it's a rolling job???

  2. #2
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    That kind of an offsett seems real close to tin bashers stuff. Check out sheet metal layouts for how to layout a flat sheet to mate with an angled cut. I know there's a in my old drafting text, but I haven't laid hands on it in years...

    have a look around on this tinbashers' site, or join and ask...

    http://www.thesheetmetalshop.com/PNp...orum-f-20.html
    Last edited by camdigger; 08-05-2009 at 06:23 PM.

  3. #3
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    the pipe fitter's and pipe welder's handbook. by thomas w. frankland.

  4. #4
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    That's a 30 for each bend in the offset, but a thin slices and lots of welding for 32" pipe.

    Bob

  5. #5
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    If you don't want to get into math, you can down n' dirty a layout at half scale on a piece of plywood, shop floor, workbench,etc. Make a plan view and draw your pipe's lines plus the obstruction. All pretty easy to see and measure. Multiply twice for the work, barring the intersecting angle.

    How many segments in the turn would depend on pressure and friction loss.
    Sure, the turn could be rolled.
    At that size, backwelding would be a piece of cake if you're a bit off with the cuts.

    BTW, if you do this regularly, the Frankland book is highly recommended.

  6. #6
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    My advice is to buy, beg, borrow or steal a pipe fitters handbook as was mentioned to learn how to make pipe layout templates.
    They aren't all that hard to make but the effort is well worth the time saved in trying to weld up a poor fitting joint.
    Here's a brief explanation how they work...
    http://www.weldinginspectionsvcs.com...latesample.htm
    Yup...lay it out on the shop floor or whatever and you'll get the angles etc that you need to work with.
    Russ
    Last edited by torker; 08-06-2009 at 08:57 AM.
    I have tools I don't even know I own...

  7. #7
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    Quote Originally Posted by torker
    Here's a brief explanation how they work...
    http://www.weldinginspectionsvcs.com...latesample.htm
    Yup...lay it out on the shop floor or whatever and you'll get the angles etc that you need to work with.
    Russ
    Looks like the same graphical method in my drafting text.....

  8. #8
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    Do you mean something like this ... mitering the pipe?



    -SD:

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  10. #10
    igotalathe Guest

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    Quote Originally Posted by Quick Change
    I need to make a section of irrigation pipe that will offset the line around an obstruction by 7". The pipe is 32" diameter and made of 11ga steel (about 1/8"). The 7" offset needs to take place over a distance of 14". Does anyone know how to layout pieces for this job or where I might find directions/calculations for doing it? I think it will need to be welded up from cut pieces but maybe it's a rolling job???
    Your dimensions will not work out. They will be close, but not dead on. The main piece of info that is missing is the dimensions of the obstacle. But, no matter. Here's how. Ten feet from the end of the pipe use a wrap-a-round to draw a line around the pipe. If you want the bend to veer right then your next mark will be on the left side of the pipe. This mark will be 13 1/4 inches closer to the end of the pipe. Your first cut will be from the wrap-around line to the 13 1/4 inch mark. That will be a 22 1/2 degree, diagonal cut. Rotate the pipe 180 degrees and weld it back together. Your pipe should now head off to the right at a 45 degree angle. From the weld, advance 13 1/4 inch on the left side and 32 inches on the right side. This cut will be 45 degrees. Rotate the pipe and weld it together. Now your pipe should head off to the left at a 45 degree angle. From the weld, advance 13 1/4 left side & 32 right side, cut, rotate & reweld. That gives an offset of 9 3/8 inches over a distance of 18 3/4 inches. Three cuts...three welds. Done. Good luck.
    Last edited by igotalathe; 08-18-2009 at 12:01 PM.

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