Welding School

When tig welding certain alloys such as stainless, 9 chrome, inconel etc.. you will need to purge your pipe with argon before attempting to put a root in. This can be done very easy on a weld test or fabricating pipe on jack stands. Situations will arise that will be very difficult to achieve a good purge such as tie ends, tube welding and other field welds you will some time not have the full control over. I will discuss a few simple steps to get a good purge below. Example given is for a 6″ pipe.

• First step would be to use masking tape to seal up all holes
• After the pipe is sealed with masking tape you will need to poke some weep holes in one end. Simply use some 1/8 wire and poke 4 or 5 holes in the tape. This will allow the argon to push the oxygen out and over take the pipe.
• You will need to make sure you have a diffuser on the end of your argon hose. You can use a gas lens or some steel wool and tape one of them to your argon hose. I have seen welders try to purge with a open ended argon hose. This does not work to well.
• After you insert the diffuser in the pipe and tape back up you are ready to set your flow meter. Crank it up high for a minute or longer. If you have a bigger volume of pipe you can leave it on longer. After initial flush you can turn it down. On a 6″ pipe 10′ft long i would set it around 20-30 on your flow meter. You can check it with a cigarette lighter. Pull a few inches of tape back from the bevel and engage the lighter and put the flame in the gap. If it goes out usually your purge is good enough. You do need to make sure that the pressure of the argon is not blowing out the flame.
• Stay tuned for a video on this subject

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. WeldingSchoolOnline.com will not be liable for any busting of x-rays or getting fired.

Example is with a 6″ carbon pipe. Video is coming soon.

* 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.