Boring post but it may help a couple of you.
As mentioned in a previous post I am taking a 12 ” branch test. This is a common test out in the oilfield. It shows the ability to not only weld but also fit pipe. If you can do both well you are ahead of the game.
There is ZERO math in this. Simple layout and reference tables only. You can do any angle the same way in 1 degree increments. I still do the math on crazy takeoffs and offsets but this method works 95% of the time.
For this post I am using 8” coated line pipe .188 wall.This test is silly in that you could never fabricate a branch and put it in service on a pipeline. You have to use tee’s, crosses or elbows.
What I use-
Receipt Tape (ask a cashier he or she might give you a roll. That’s how I got mine.)
bungee or rubber band
oxyacetylene hand torch and beveler. Bevelers are not essential. If you are cutting stainless or aluminum you can use a plasma or cut off wheel.
Fishmouth pipe template measures by James A. Fucciani or The Pipe Fitters Blue Book by W.V. Graves. There are three blue books that I know of. You want the one that’s light blue. I will photo my books so you can see the ones I use.
Finally good music and lots of patience :)
Step 1- Cut a square piece of pipe. The green coating is god awful and I burn it off and then wire brush. Never grind except on bevels and waste pieces. A lot of this pipe is susceptible to stress risers because of heat treatment. Also never ever strike an arc outside of your weld bevel. You will get run off a job for that in the oilfield.
Step 2- Wrap your receipt tape around the pipe like you would a wrap around. Make sure the edges are aligned and then make a square cut across the tape.
Step 3- Fold into 16 segments. 4”-12” pipe is usually done like this. Larger pipe is done in 32 segments and below 4” is typically 8 segments.
Step 4- Cut the corners off the receipt tape.
Step 5- Wrap the bungee around the pipe.
Step 6- Wrap the receipt tape around pipe and line up the ends. Slide or roll the bungee over the tape to hold it in place.
Step 7- Mark the “valleys” in the tape with silver pencil or sharpie.
Step 8- Mark your longitudinal lines using a piece of angle iron as a square.
Step 9- Look in your book for the appropriate intersection or branch size. For this it is a 90 degree 8” on 8” branch or intersection. The pipe with the hole is the header and the pipe with the fishmouth is the branch. You will find the ordinates and listed from 1-5. Find the fifth ordinate which is 2.68 and add about 1/4”. Place your real wrap around on the pipe and move back from the end to about 2 15/16” and draw a line around the pipe. The finer the line the more accurate. This line will be your baseline and you will measure from here.
Step 10- Mark your ordinanate points on the longitudinal segment lines start with 1.(1 is baseline so its 0)( 2 is .28”)(3 is 1.05”)(4 is 2.06”) and (5 is 2.68”) you then go back down with 4…3…2…1…2…3…4…5…4…3…2…1 until you have gone around the pipe. Mark your points with sharpie or use a punch.
Step 11- Connect the dots with your wrap around and a SHARP soapstone. If you can visualize the cut then you can also freehand the dots.
Step 12- Cut! I always cut to the line. Take your time and get ready for a lot of grinding.
Feel free to add your two cents. I do this in the hopes that I may learn more.
Thanks for looking