Announcement

Collapse
No announcement yet.

Help with pipe angle fab

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Help with pipe angle 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
    If it is only a seven inch offset on a thirty two inch pipe, could you just cut a notch in the pipe and weld in a patch?

    Comment


    • #3
      You need one of these-

      https://www.discountbooksale.com/sto...rck=1038713935

      It has everything you need to layout an offset,or elbow or tee.Barnes and Noble usually stocks them here locally.

      There are several tube miter programs on the net,but I've never found one for anything bigger than 12" pipe.
      I just need one more tool,just one!

      Comment


      • #4
        Getting the "Bends"

        This is really just basic "Solid geometry" and "Development".

        But there are two variations of a common method that works.

        For a 30* bend, set the pipe up to tilt 15* from vertical on the shop slab floor. Use a tape measure and mark a line parallel to the floor. Also mark the "high" and "low" points on both sides of the marked-out line. Cut at that "tilted" line. Rotate one part 180* with respect to the other and butt up both parts together. You will now have a 30* "bend". Now prepare the cut faces for welding and weld it up.

        This also works for a 90* bend. It works too for a multiple-section "lobster-back" bend as well.

        There will very little "waste".

        I'd suggest trying it out on some scrap first though!!

        The other method is a variation on the "cut and shut" process.

        Set the pipe up and mark it for 15* as before. Now tilt it 15* the other way. Mark out again with the "near" parts of the lines touching. Mark the "high" and low points on the pipe as before.

        You now have a 30* "Vee" marked out. Cut out the "Vee" and remove it and bring both sides of the "Vee-cut" edges together. Do NOT rotate the pipes with respect to each other. Prepare them for welding. You will now have a 30* bend but the pipe will be shortened because of the lost/removed "Vee" section.

        Again - try it on scrap first - just in case!!

        Comment


        • #5
          Do you mean something like this ... mitering the pipe?



          -SD:
          Last edited by Smokedaddy; 08-06-2009, 02:56 AM.

          Comment


          • #6
            Is it possible to put a jog in the obstruction to clear the pipe?

            I recently had a project where a piece of 2" square structural tube was in the way a pipe I was installing. I cut part way through the square tube at each end of the piece to be removed, welded the new piece alongside, then finished the two cuts to remove the offending section. That maintained the alignment of the original square tube, and avoided having to make a torch cut near the new piece.

            Roger
            Any products mentioned in my posts have been endorsed by their manufacturer.

            Comment


            • #7
              Quick Change, not sure how much you need ? Hope this helps...



              As to marking up the cut, Tiffie's method is good for short lengths, but if the pipe is inconveniently long and or heavy the following may be easier:-

              Mark a line round the circumference at length of the outside of the bend (square to the pipe).

              Mark this line at the outermost point of the bend as '0'

              Measure the circumference of the pipe = C, and mark the pipe at 0, C/12, 2*C/12, 3*C/12, 4*C/12, ... 11*C/12 around the circumference. (These 12 marks are then at 360/12 = 30 degree intervals.)

              Where L = the difference in length between the 'long side' and the 'short side' at the cut (7.55 in diagram above):

              Calculate 6 offsets:-
              s1 = L/2*(1-cos(30)) = 0.067 * L (= 0.506)
              s2 = L/2*(1-cos(60)) = 0.250 * L (= 1.888)
              s3 = L/2*(1-cos(90)) = 0.500 * L (= 3.775)
              s4 = L/2*(1-cos(120))= 0.750 * L (= 5.663)
              s5 = L/2*(1-cos(150))= 0.933 * L (= 7.044)
              s6 = L/2*(1-cos(180))= 1.000 * L (= 7.550)

              Starting at the outside of the bend '0',
              mark the offset back along the pipe from the original line at the 12 positions:-

              0, s1, s2, s3, s4, s5, s6, s5, s4, s3, s2, s1


              Fill in between marks by eye.

              For very large diameters more steps may be required.

              Cheers
              .

              Comment


              • #8
                its all getting complicated, get a roll of brown paper [have used christmas wrap], look up lobster back bend, get a big compass, learn to divide a circle into 12, soon you will be able to get the development of just about any curve, its really easy [must be if i can do it!], template paper is really thick craft paper, develop it, draw it, cut it out, stick it with masking tape to test.
                once happy with profile use a punch to dot the outline.
                ideally the developed segments need rolling on a pyramid roll or wrap the developments round the pipe to get the miter shape, its not a straight line it a curve.

                Comment


                • #9
                  Don't forget, the OP has a 32" diameter pipe...

                  I can't help feeling a couple of minutes with a tape measure and a pocket calculator is much less complicated than messing about with big compass and an 9 foot long paper template !

                  Trigonometry is your friend...

                  Cheers
                  .

                  Comment


                  • #10
                    A roll of drywall tape is cheaper than a calculator, wrap around the pipe, mark the circumferential intersection and divide into appropriate segments by folding halves, quarters, etc. Transfer the folds back to the pipe. Drywall tape won't have the squaring ability like a Wrap-A-Round, but neither will be effective squaring that diameter.
                    I don't have anything against calculators, but you still have to get marks on the pipe unless you have mitre saws of appropriate size.

                    Comment


                    • #11
                      Originally posted by Barrington
                      Don't forget, the OP has a 32" diameter pipe...

                      I can't help feeling a couple of minutes with a tape measure and a pocket calculator is much less complicated than messing about with big compass and an 9 foot long paper template !

                      Trigonometry is your friend...

                      Cheers
                      .
                      sorry but same applies, i learnt how to do i before calculaors [ i did have a set of trig tables, log, sin, arcsin etc] but to be honest a template is better by a mile, you get to try it, if its big flooring template card is good.
                      ever tried calculating the segment [true lengths] of a 8 foot truncated hopper, or getting a 6 foot spiral lobsterback bend in 1/4 plate to fit with a calculator, works fine in the design office, dont see many in a fab shop [except for working out overtime!]
                      but i do agree, Trig is your friend,scale drawin works too
                      best wishes
                      mark

                      Comment


                      • #12
                        Getting a case of the "bends".

                        Originally posted by boslab
                        sorry but same applies, i learnt how to do i before calculaors [ i did have a set of trig tables, log, sin, arcsin etc] but to be honest a template is better by a mile, you get to try it, if its big flooring template card is good.
                        ever tried calculating the segment [true lengths] of a 8 foot truncated hopper, or getting a 6 foot spiral lobsterback bend in 1/4 plate to fit with a calculator, works fine in the design office, dont see many in a fab shop [except for working out overtime!]
                        but i do agree, Trig is your friend,scale drawin works too
                        best wishes
                        mark

                        Mark and Barrington.

                        You both pretty well have the answer, but it has to be reduced to what the Boiler-maker or the Sheet-Metal Worker can use on the shop-floor or "on-site".

                        I will sketch the answer later, but it is a mix of both your solutions.

                        The angular cut when "developed" (rolled out flat on the floor - as for a template) is essentially a sine-wave spread over the circumference of the pipe in say 12 equal spaces.

                        But it is quite easy to construct the template on the pipe so that pieces of pipe can be used instead of having to use flat plate and have it rolled.

                        Later.

                        Comment


                        • #13
                          Think about some alternatives:

                          Laser line projector and a flat frame around the pipe so you could project the line in the same plane as you worked your way around the pipe.

                          Sheet of plywood (attached to a frame to keep it flat) with a slightly oversized oblong hole in it. Position it around the pipe at the required angle, and use a long chalk marker to trace the cut(s).

                          Roger
                          Any products mentioned in my posts have been endorsed by their manufacturer.

                          Comment

                          Working...
                          X