TIG Root Pass On Pipe: Tight Gap Welding !

Tight Gap TIG Welding

Most welders I tend to run across seem to prefer a wider gap when  putting in a tig( heliarc)root on pipe. Many like a 5/32 gap with up to a 1/8″ thick landing when making a jack stand weld that you can roll out. Never really understood why. I think most of them just have not took the time to explore welding with a tighter gap like a 3/32 or a 1/16 gap. Especially on a easy roll out weld.

Putting a tig root in with a tight gap

Warning: Try at your own risk! Only to be attempted with jack stand welds.

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  • When putting a root in with a tighter gap you must first start with the fit.
  • If you want to start out with a 3/32 gap you can bevel the pipe with 1/16 land.  If you chose to use the 1/16 gap you will need to have a knife sharp edge on your bevel. 3/32 gap would be a good starting point for some one that is not used running at a higher heat. It might be a good idea to try this on flange weld if this pipe is going to be possible x-ray shot. That way you can easy fix it if needed.
  • You will need to have a good consistent gap all the way around and very little high low. If you have some spots on the fit that are to tight you will need to take a 1/16  metabo blade and cut your gap in.
  • Grab some 3/32 tig wire.
  • Most wide gap welders feed the wire from the inside of the pipe. This is obviously not going to work now since the gap is at least the same size or smaller the same size as the wire.
  • I have noticed that welders who weld with wider gaps have to run colder thus making the completion of the weld taking much longer.  This is not good for you or your employer. The quicker you get done with the weld the more valuable you are to your employer as long as you produce quality code welds. Your gonna need to turn up heat. Don’t be scared. Just try it!
  • Try setting your machine around 100 amps to start on a 3/32 gap and 125amps with a 1/16 gap. You can gradually increase your heat when you start to feel a little more comfortable with the speed of everything.
  • If do not free hand tig weld you will probably find this to be a little harder walking the cup. I plan on discussing free handed welding technique at another time.
  • Welding with a tight gap with tig can speed up your weld time dramatically. It is great way cut down on time under the hood. It works way better on jack stand welds when fabricating pipe. Position welds in the field sometimes get to much high low, obstructions are in the way, etc….. High/Low is a tight gap killer. When welding on a higher heat it can gouge your inner bevel which leads to problems that will be discussed  later. There are a lot more variables to get a good fit in a field. Be careful when trying it on position welds in the field. I would strongly suggest to practice on the jack stands for some time before trying your hand at field position welds.
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