[weldin mike 27]

Hi all.

First, let me make 2 things clear. 1. I have almost no practical experience with purging. And 2. This idea WILL NOT be for food grade, merely a way to weld ss tubes so as not to get sugaring.

My question is, if I had to weld some 3" light wall tube, say, like 1/16, like one might find on an turbo, snorkel or exhaust. Could I make a dam in one tube, a little way down the tube, tack up the tubes, then put the tig torch in with the argon flowing.
Fill the space inside the pipe then dam the other tube, with a little vent.

That is to say, dam enough argon in there to make a passable weld without having to have another flow meter and associated hardware.

Keeping in mind this is only very basic home jobs.

Hopefully this is not to confusing.

Mick.

[taz]

Personally I do not think it would work.
If you have a second tank buying a cheap regulator will only set you back 20-30$.
If you don't have a second tank then install a tee in your line to send argon to your torch and purge at the same time.
This makes it very difficult to regulate the flow though but it would be better than nothing and should suffice for the odd home project.

[Markus]

You will get colour for sure, but that's not the end of the world. Only corrosion resistance will be weakened. Will it prevent sugaring? Interesting.. maybe it will indeed, but how to make sure that you have enough argon at the end of the weld?

I would personally get that second flow meter. Perhaps you will you use it in future jobs too Also thin stainless is a lot easier to weld with purge inside.

Btw you can use nitrogen as well, if you do have it at your home. Grade was austenitic right?

[weldin mike 27]

Assuming austenitic grade. Might need to try one of these days.

[taz]

If you can get a good fit up, then autogenous welding without purging will be fine. Most exhausts are welded without purging anyway (not that I agree with that).

[Oscar]

If you're trying to "trap" argon between two dams inside the pipe without the argon continually flowing in the section that is blocked off, I'd venture to say no it won't work. The mean free speed of gaseous molecules is high enough that the argon will dissipate quickly regardless if it's initially denser than air. Would it be better to have residual argon in there instead of just air? Sure, but if the concentration goes down to 50/50 or less, then I'm not sure it would be worth the trouble for me.

You're obviously doing exhaust work, so there are two inexpensive logical choices: dual-flowmeter (HTP sells for $99) to purge if doing turbocharger ducting, or SolarFlux B if working on non-turbo stuff.

[Msumner]

Ya i would run a y with two flow regs for your torch and one for the purge off the same tank. I would then to save money just use tape as the dam and use tape on the other side with a few holes in it....last i would have tape around the bevel minus where i was welding so 3/4 of the pipe taped removing a 1/4 at a time. Hope this helps

[Otto Nobedder]

If you have access to "dry ice", you can rig a CO2 purge for a little bit of nothing. CO2 is "active", so not the ideal solution, but should prevent the sugaring.

Steve S

[Oscar]

Ya i would run a y with two flow regs for your torch and one for the purge off the same tank. I would then to save money just use tape as the dam and use tape on the other side with a few holes in it....last i would have tape around the bevel minus where i was welding so 3/4 of the pipe taped removing a 1/4 at a time. Hope this helps

This is much easier--note the argon bottle behind the TIG welder:

[Otto Nobedder]

That's the setup I have on 3 of four machines.

I built mine from two used Harris flowmeters, one 1/4" NPT close nipple, one 1/4" FNPT tee, and some teflon tape.

While I got all the flowmeters for free, if I'd bought them on e-bay I'd have less than $40 in the whole setup.

I'll find the picture I posted here.

[EDIT] Here's one view...
http://forum.weldingtipsandtricks.com/v ... ter#p15067

Steve S

[Msumner]

Now thats what i am talking about lol

[weldin mike 27]

Thanks for all the ideas folks. I'm going to do a bit of research into the zero dollar option because anything I do at home will be making zero dollars so not worth spending money on.

[Superiorwelding]

Mick,
My thoughts are this. I have wondered the same thing as you. I believe if you do not have the option at a given time you can purge the exhaust, or whatever the tubing is, pull your hose out leaving a very small hole for expansion and it will be better than nothing. I do not believe it will look like a real continuous purge but you don't need food grade welds there either. I have some small SS tubes and might give it a shot one day. One question I have though, is the joint to be welded autogenous or will there be a gap? If there is a gap I say it is probably not worth it.

I believe the cheapest option for you is a simple "T" fitting as pictured. This is a Westen brand I believe. I have 6 of these set up for various reasons and they work very well for what you want but keep in mind opening the second valve will cause pressure drop on your main side, which I am sure you already knew.
-Jonathan

[weldin mike 27]

Thanks Jon. I plan to try with no filler, no gap. I have never done this before. Also its hot and dry here so there is not much happening at the moment.