RadekSkylark

Hallo everyone, as I soon will need to weld my first real application SS tubes, wanted to get clear on few things about back purging, also tought that this topic will be informative and hope to gather good information here.

So, here are few questions:

1) Gas inlet should be located lower then gas outlet, right? Why is that important (I have an idea why, but want to be sure if someone can explain)?
2) If I use aluminium foil for end "cap", how many holes should I poke in it?
3) The idea is to fill up that pipe/tube with argon, and let it slowly move through those holes in the end also letting more argon in, like getting slow flow?
4) You need to start welding from first joint on gas inlet side, right?
5) Should I put silver duct tape on all the other joints?
6) Gas outlet should be the same size as inlet or bigger, right?

Hope guys who definetly know how this is done can chime in and get these things straight

Thanks

RadekSkylark

bump? please...

SovXietday

1) Yes. Argon is heavier than air, and therefor will sink in the tubes. It will still work if you start from down low, you will just need to make a better seal and wait longer for the argon to purge the pipe.

2) Depends on how you do it, if you ball it up and shove it in the end of the tube you won't really need to worry about holes. It doesn't seal that well.

3) The holes serve two functions. The first is to purge out the old air that has oxygen. The second is so that you don't have the argon build pressure in the tubing. If this happens it will blow out your last weld.

4) Best to start from the low point of the tubing, where the argon will collect first. If you purge the pipe well you can start wherever you want.

5) If the argon can flow to it, yes.

6) Just needs to be big enough to keep the thing from pressurizing with argon.

Honestly, give it a try. You're going to need to try a few different things to get the look that you want.

SovXietday

1) Yes. Argon is heavier than air, and therefor will sink in the tubes. It will still work if you start from down low, you will just need to make a better seal and wait longer for the argon to purge the pipe.

2) Depends on how you do it, if you ball it up and shove it in the end of the tube you won't really need to worry about holes. It doesn't seal that well.

3) The holes serve two functions. The first is to purge out the old air that has oxygen. The second is so that you don't have the argon build pressure in the tubing. If this happens it will blow out your last weld.

4) Best to start from the low point of the tubing, where the argon will collect first. If you purge the pipe well you can start wherever you want.

5) If the argon can flow to it, yes.

6) Just needs to be big enough to keep the thing from pressurizing with argon.

Honestly, give it a try. You're going to need to try a few different things to get the look that you want. You're just buiding a header so if it isn't perfect it's not a huge deal.

RadekSkylark

Thanks for replaying You could've just done it one time, I would've got it :D

Hope that the information you stated is correct.

P.S. I have tryied and before welding will try once more... just wanted to get straight with theory.

ToxicFabrication

Practice, see what works for you. On all my fixtures and jigs I have -4 stainless fittings welded on so I can easily plug lines in to certain runners.

RadekSkylark

Oh, yeah, forgot to ask about this....

When I'm using that mild steel block, I should drill a hole in front of each port of runner, and then one hole from side to meet that hole from port of the runner, and then I should add an argon line there, to back purge when welding flange to runner, right?

Thanks