Using a gas Y for Tig purge line

[worntorn]

I watched a recent video from Jody Collier about welding stainless, backpurging or using a heat sink. In the video I noticed that Jody mentioned the only way to get a purge line set up on a single tank is to purchase an expensive double regulator. Normally Jody's info is spot on but I knew this bit was wrong as I have a y with control valves ($12 Ebay, about $30 new) that works just fine for back purging. I thought everyone did it this way, but apparently not.

I sent a photo of it and explanation to Jody and he was very excited to get the info. He said he would like to post it on his site. For someone as talented as he is, he is completely devoid of EGO, which is refreshing.

Here is the text of the email I sent to him:

"Hi again Jody. I found a picture of the y.

I was thinking about the procedure for setting the flow and realized it is pretty easy.

for example, if you want 2 litres per hr for the purge and 5 for the torch then leave the valve to the torch wide open (always) and set the regulator so that it goes to 7 when you step on the pedal briefly. After the torch postflow stops and the flow gauge has dropped back to zero, open the purge valve until you get 2 on the flow gauge. When welding starts this will jump up to a regulated 7, 5 for the torch and 2 for the purge.

In this way pretty well any settings you want can be achieved."

Glen

[performance]

I actually use that valve for the 3 in one units, but turn it around the other way (it will work though the flow arrow is backwards) for changing gases without coupling and decoupling the lines constantly. I have recommended it to several for this. Western makes it I believe.

[worntorn]

It would work well for the machine connections! Yep, this one is a Western.

I did the same by purchasing some fittings and a couple of gate valves. I guess the possible advantages of the gate valve for this application is that you can see which is on and which is off, plus it only takes a quarter turn to be fully on or off.

The western Y might look neater on there though.

With either one, quick couplers can be used to feed the Y so the machine can still be quickly disconnected and reconnected when a move is required.

[DiabolicZ]

I just purchased a Tee fitting that allows two regulators to be used on one bottle. It cost me $26 dollars shipped, and I had a spare regulator laying around.

I followed this advice from user farmall on WeldingWeb. "You can just buy a valved Y-connection from Western Enterprises and split your argon output, but a better way is to get a CGA-580 tee and put a regulator on each output. That way the purge isn't competing with your rig.

I don't buy "dual" regulators because if one breaks then both are down. With a tee you can just swap out the bad reg. The tee is also cheaper than the Y.

The Y is Western #411, the Tee is a 312-T-92 Manifold Male CGA-580 Coupler Tee."

[worntorn]

After using the y for some time now, I would say that the purge competing with your rig is a not a concern at all, it works perfectly for both if set as I mentioned below. For someone who doesn't have a second regulator on hand cost for a Y setup is much lower.

I inherited a seond regulator a little while ago and mounted it on a second tank of argon I had here for awhile. I thought I would see if using this set for a purge instead of my Y would benefit the torch flow in anyway. As near as I could tell it made zero difference to shielding and weld quality.

I suppose if you were trying to run a really huge flow thru the purge it could have some effect, but I never seem to do that. Once the main vessel is purged (before welding) it is generally only a small purge flow that is needed.

Before getting the Y I tried to get a tee to set up two regulators like you have, but the Linde rep informed me that there was no way to install two regulators on a single tank. It seems he was wrong!

[angular]

I just purchased a Tee fitting that allows two regulators to be used on one bottle.

Same here: T-92 TEE CGA580 M/F/F 698944050191 (WESTERN ENTERPRISES)

About $17 for the tee. $26 for a second regulator. I pefer the two regulator approach since there's no guesswork or assuming that 2 + 2 = 4 and you're indeed getting the flow you calculated if you're running one regulator and a Y adapter.

[worntorn]

Wow that's reasonable for a regulator. The ones I was looking at were about $130 as I recall. But then I was looking at name brand stuff since a Welding Equipment Importer from Ontario told me a horror story about one of his Argon regs that blew up first time it got turned on. It seriously wounded the purchaser. He (the importer) was no longer sending his units out with that type of regulator, instead he found some more expensive ones that were thought to be better or at least more safe.

After hearing that story I did look at the Everlast regulator very carefully before first using it, but then I thought this is a company that has sold a ton of these things and if there was a problem with them it would have occurred by now and been dealt with.
I imagine that the 2500 psi Argon tank and regulator are probably the most potentially dangerous parts of the welding rig!

[angular]

Yikes... that's pretty scary. I ordered the tee from weldingsupply.com and I got the extra regulator from HTP (one of their eBay listings) who has a pretty decent reputation for welding supplies & consumables. However I have to say that the quality of the Everlast regulator is a lot better than I expected it to be just looking at pictures of it online prior to delivery. The tank pressure gauge is larger & easier to read than the HTP regulator.

[AussieChris]

If you have the bubble type flow meters you don’t really need two regulators, just two flow meters. I had a regulator/flowmeter from a previous welder. I didn’t like the regulator as the contents gauge was installed opposite the cylinder connection (suitable ok for cylinder valves pointing up). The Everlast regulator suits the sideways valve outlet much better.

So I removed the flow meter off my old regulator and, with the addition of a ¼” Tee and hex nipple, I grafted it onto the Everlast regulator. Now I can set the flow to my purge line without upsetting the torch flow.

Having said that, I really like Glen’s solution and wish I’d seen it earlier!


In the photos, the blue hoses go to the welder via the three-way valve so I can connect air for the plasma (it’s a multifunction PP205).

Chris
Brisbane Australia.

[DaveO]

Is there something about the chemistry of stainless steel that requires purging like this? Why do other metals not require this?

And a follow-on: does stainless require purging for butt welds only, or could you avoid it with a lap weld?

Thanks,
Dave O

[jakeru]

Yes DaveO, stainless steel has the property of good corrosion resistance (the iron in it will not readily oxidize, like steel), but that can be adversely affected if you allow "carbide precipitation" to occur. "Carbide" in this context refers to chromium carbide, a combination of Chromium, Carbon, and Oxygen that forms when all three elements are heated up and combined. By keeping atmosphere away from a hot stainless steel weld, oxygen is kept away and prevent carbide precipitation from occurring.

Another adverse effect of stainless steel oxidation is it can rapidly form and entrap large "bubbles" inside it as it forms, making a solidified "frothy/foamy" structure. As you can imagine, the porous structure won't give much strength and ductility so if you have it where you really need to have continuously welded metal, its could lead to a failure of the weld joint. The brittle oxide structure also can't be easily removed by additional welding (such as by applying additional heat with the TIG arc), but generally needs to be physically removed (IE: sawing or grinding it out) to remove it. The oxides of stainless steel impedes the flow of the molten metal weld joint, unlike steel oxides, which generally stay molten while welding and tend to harmlessly float to the surface.

Other metals oxidize more or less readily at varying temperatures, with varying objectionable effects. Some metals warrant the extra time and cost of back purging or applying additional shielding (Titanium comes to mind) while others generally do not (steel comes to mind.)

On some (aluminum and magnesium) the oxides form so readily, that back purging alone isn't sufficient to prevent the oxide formation, and flux or arc cleaning action (electrode positive operation) is necessary to keep oxides on the surfaces "blasted" or "chemically dissolved" clean.

So different metals call for different welding methods and procedures.

PS - yes on some weld joints the argon coming out of the TIG torch cup can keep all the hot metal shielded from oxidation. In some lap joints, this can be true. But I think an edge weld joint is an even better example. (welding two edges together laying flat against each other.) Sometimes you can clamp a block of metal ("backing block" or "chiller block") on the back side of the weld joint, it can help make a trough for argon to collet, and/or it can draw sufficient heat out of the back side to prevent or reduce the backside of the metal from getting to oxidation temperature.

[DaveO]

Thanks, jakeru, for such an informed response- that will be my metallurgy lesson for the day. This thread got me to reading up on purging in general; I read some interesting stuff about people using bladders to take up space and reduce the amount of shielding gas, etc., required.

Can I ask- what is your background? You've done this before!

[worntorn]

Is there something about the chemistry of stainless steel that requires purging like this? Why do other metals not require this?

And a follow-on: does stainless require purging for butt welds only, or could you avoid it with a lap weld?

Thanks,
Dave O

What Jakeru said