by Bob Moffatt
Hey everyone, we hope you are having a marvelous day. Today we are discussing a couple different methods of welding in the root on pipe using GTAW. The first thing we are going to do is put in our tack welds, now in the 5G position, Bob prefers to put his tacks in at the 12 o'clock,
10 o'clock and 2 o'clock positions. Note, there are only 3 tacks and they are at the top section of the pipe. Typically what you'll see is 4 tacks spaced evenly at the 3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock. However with the backfeed technique, the bottom tack at 6 o'clock will get in the way and just isn't necessary with this method.
We are still going to start at the 6 o'clock position, we just wont have the tack there. Now what you want to do is drop the filler wire in from the top and rest it against the outer tack located at the 2 o'clock position. This will help stabilize the filler and keep it in place as you maneuver your torch hand up the root of the pipe. As you make progress, the filler will become shorter as it is melted and deposited into the weld joint, as this occurs, you only need to tilt the filler rod toward the outside opening and it will continue to flow into the root. From the 6 o'clock to the 8 o'clock position, you will most likely be better off placing your finger tip on the outside of the pipe to hold a good distance from the tip of the tungsten to the end of the filler metal. Once you hit the 8 o'clock position, you can rest the cup against the groove opening and wiggle the cup side to side as you progress up the outside of the pipe toward the top. You will have a nice opening along the root to look inside and ensue you are getting good reinforcement on the inside of the pipe.
Once the first side is done, drop back down and feather the start and work from the bottom to top again. Once both sides are done you can now focus on the top third section of the pipe and tie it all together. One more tip, make sure you clean your material on the inside, the weld will go much smoother if the metal is clean. Aside from that, just keep practicing. As always, thanks for the support.