changing shielding gas in tanks?

[Leeknivek]

I've got a bottle for my mig welder - 75/25 argon/co2. For the little bit I use the mig welder, I usually just use fluxcore. I want to teach myself tig, and my tig regulator fits onto this tank - but I have read that tig likes 100% argon. I have also read argon/helium mixes are good for both mig and tig. 

When one gets a tank refilled, can the tank be refilled differently than what it was previously? Can I use this 75/25 tank for straight argon? What's a price I can expect to pay?

[ThomasPowers]

What did your local welding supply place tell you?  They might be willing to trade bottles which would save you the flush charge.  Getting friendly with a good welding supply is worth a lot of money.  I once needed to do a lot of cutting and my local shop was willing to lend me the big O2 bottles with just a credit card number in case I didn't return them.

[HWooldridge]

I seriously doubt any supplier will put a different gas in a labeled cylinder but as Thomas said, they might swap it out for 100% argon.

[Leeknivek]

Haven't been ... yet. I got the tank through craigslist when buying my MIG welder. It's been empty so I just run fluxcore. The only one I have around here was Abco - but I think that's Airgas now? I'll have to check them out next time I'm in that area. 

I also found that my tig welder is not actually a standalone piece but a HF arc stabilizer - something I'll have to plug into my stick welder. Know anything on these? 

[Dodge]

Bottles are generally color coded for the gas or gas mix they contain. Some bottles such as acetylene, by design, can only contain that gas.

Edited June 17, 2015 by Dodge

[j.w.s.]

Bottles are generally color coded for the gas or gas mix they contain. Some bottles such as acetylene, by design, can only contain that gas.

Ironically it's the exact same threading for acetylene and propane, CGA-510 or CGA-300 depending on the tanks used, but they're completely interchangeable. I think CGA-510 is also the old bbq grill threading. But as to what the original poster asked, my local AirGas has exchanged cylinders when I wanted to switch gasses and yours should too, as long as it's in date. Which btw is a good way to keep your tanks inspected.

J

[jmccustomknives]

Most of the time these cylinders aren't filled on site anyway.  Usually the supplier will trade with you.  I really depends on the supplier and how cantankerous they want to be.  I will usually trade out unless there is a problem with the cylinder.

[Dodge]

Ironically it's the exact same threading for acetylene and propane, CGA-510 or CGA-300 depending on the tanks used, but they're completely interchangeable. I think CGA-510 is also the old bbq grill threading. But as to what the original poster asked, my local AirGas has exchanged cylinders when I wanted to switch gasses and yours should too, as long as it's in date. Which btw is a good way to keep your tanks inspected.

J

Agreed on the threads, J. What I meant about gas specific, was the porous material (cork?) that fills acetylene bottles to maintain its stability. And yup, my supplier will trade bottles for whatever you want. Also agree about keeping bottles up to date. Unfortunately, Its been so long since I got refills, I surely will be paying inspection fees next time

[Frosty]

This really isn't the place to be asking, a phone call to the local welding supply will tell a person what they need to know. Rules change place to place so log as they need code. What the local outfit will do has nothing to do with what one even 12 miles down the road.

Frosty The Lucky.

[DSW]

Chances are high you can get yourself 100% argon. As mentioned, my place will swap similar sized cylinders for other gasses no problem. I regularly swap mig gas for argon, Nitrogen for O2, or what ever, depending what I may need an extra cylinder for.

It's also possible to have them vacuum and purge the cylinder, so you can use the same cylinder for a different gas ( within reason if they take the same CGA valve). It's what most places do anyways when they swap cylinders at the refill center. Smaller operations  that fill themselves though charge extra for this.

 

As far as your HF box, what's your question? You really don't need an HF box to do basic scratch start tig with any DC stick welder. You'll need an air cooled tig torch with gas valve, plus torch consumables (tungsten, collet, collet body, cup or gas lens parts. All these are usually based on tungsten size with the exception of the cup), a power block and a gas hose and flow meter to hook up your argon, and obviously 100% argon gas. Infinitely adjustable DC stick machines work better than those with fixed taps as it allows you to better fine tune your amps for what you are doing. With any of these set up, you will not have remote amp control, even if your HF box has a pedal. If it does, all that does is turn on/off the power and HF, not make amp adjustments like it does on a dedicated tig machine. The pedal on an HF box does make starting/stopping a bead easier than simply doing basic scratch start, but it's not required.

If you have an AC only stick machine, you are sort of out of luck. AC tig is used for alum and for that you would need continuous high frequency to maintain an arc. However a dead basic Ac stick machine is tough to do alum tig with as you have no amp control. I've seen it done, but you have to have a lot of skill to pull off good results. HF boxes are often used with engine drives that have both AC output as well as a pin connector that allows remote amp control ( the older Ac capable Miller Trailblazers are a good example)

 

If you want to rig up your stick machine for tig, let me know. I'll need picts and good descriptions of what parts you already have, and I can tell you what will or will not work, and what you may need.

[Charlotte]

Since I worked in the industry I can answer this accurately.  The paint codes on cylinders are decided by the manufacturer.   Argon/Helium/Nitrogen are inert gases and so filled in cylinders with a fitting for inert gases.  Mixtures of those gases that  are inert follow the same formula and use a connection Called CGA (compressed gas association) 580.  If you own the cylinder they are able, legally,  to fill it with any of those three gases no matter what the color of the cylinder is.  This does not mean that the specific distributor  or its corporate connection will not add additional handling charges.   Most mixtures used in welding will also have a CGA connection of 580.  The only problem comes when there is Carbon monoxide/Hydrogen/  in the mixture which may require different Cylinder valve connections and also change the retest cycle limit of the cylinders.  Mixtures containing Oxygen may or may not have a 580 valve depending on the concentration.   Cylinders of pure oxygen have a CGA connection of 540.   Most Gas suppliers have little pocket books  with a load of useful information, applications and cylinder labeling for their product line.

Gas cylinders are not "flushed"  They are blown down and vacuumed.  Purging a cylinder only happens when you return a cylinder with no residual pressure. Gas mixtures are usually filled by pressure using a formula worked through engineering data and experience with the particular  equipment. For a gas mixture this means starting at a vacuum. You and your supplier will both get along better if you return the cylinder with 150 psig. remaining.

  

[Charlotte]

By the way  pure carbon dioxide  has a cga connection of 320.  

[Jaspal Singh]

Hi i bought new cylinder in April 2020. I put c35 gas.still cylinder is full not use. Can I refill  this cylinder from mig gas to pure organ gas for tig welding and can i use tig gas for mig welding hard wire 0.45,035

Thanks

jaspal singh welder

[Steve Sells]

a cylinder is used for ONE type of gas only, they are never interchanged.  As already stated here, you change out tanks if you need a different gas mix

[JoeM]

Hi!  I'm dealing with this situation right now myself.  I have an 80cuft tank with C25, and want to change the contents to 100% argon.  My supplier said that it would be fine for them to go from argon to C25, because there's argon in both cases, but going from C25 to argon requires a "green clean" process (whatever that is) because any residual CO2 will contaminate the gas if you are wanting to use it for TIG welding. He said they send the tanks out for that, and it takes a week or two for turnaround, and there's some additional cost.

I'm trying to find out what this process is, whether it's really just purging the tank and evacuating it to a reasonably high vacuum to remove as much of the previous gas as possible, or if there's more to it than that. Heck, I can probably do that here at home; I have a small vacuum pump which can pull 25in of vacuum, and afterwards I can transfer a bit of argon from my other tank into it.  Do this a couple of times, and I'm thinking that there will be essentially zero CO2 left inside.

However, in the interest of safety and a quality result, it's better to let them do it.  It's just a few bucks, and I'd hate XXXX XXXX to end up with a tank of bad gas that just causes a ton of grief when trying to get a good weld.

-- Joe M.

Edited July 20, 2021 by Mod30
Language

[Steve Sells]

so you are saying you want to intentionally contaminate a CO2 tank? Assuming you found someone to do that for you how would you feel in trusting them when you buy a tank from them, as to what is really in it if they will cheat like that?

[Frosty]

I asked the same question when I bought my Hobart 120 GMAW. Neither of the welding gas companies available would do it at all. They said cleaning a bottle properly cost more than buying one. My current supplier has no problem exchanging argon for my 75/25 bottle and switching back. 

I stopped having my original bottle refilled years ago, exchanging is faster and less expensive. Today I roll up to the dock, a yard hand asks what I want and swaps tanks. I park pull up to the storefront and pay, maybe do a little shopping they give me a discount when I buy a tank of gas. 

Just exchange your mix gas for what you want to use.

Frosty The Lucky.

[Chris Mamros]

I would like to ask Mr. Sells a question if i may? Is it acceptable to use a cylinder for a different gas at all? There will almost always be some level of contamination, correct. I understand the unique nature of something like acetylene, but can a cylinder legally be used to fill with a gas it was not intended to contain?

[Frosty]

Welcome aboard Chris, glad to have you. If you put your general location in the header you'll have a much better chance of meeting up with members living within visiting distance.

Some gasses can be mixed safely allowing one cylinder to be loaded with another gas. Check with your local welding gas dealer, there's no way a guy in Alaska or Illinois can say with any certainty. ESPECIALLY if we don't know where you are. Regs in Anchorage are a little different than here in Wasilla, about 50 miles.

Frosty The Lucky.

[Steve Sells]

Frosty covered it.  Just change out tanks.

[Chris Mamros]

My apologies John for not giving a geographical location because I really don’t have one!

actually, I’m a safety and environmental professional, and I work for an organization that does analytical work and relies on lab grade, chemicals and compressed gases of all types. I was trying to get a feel for whether it’s common practice to use a gas cylinder for different gases on every cycle of refilling by a supplier…

I mean, there are the obvious cylinders that can’t be mixed up like acetylene. 
 

But what do you think it would just be common sense that cylinders with other types of gases never go to laboratories, hospitals, R&D facilities, etc.

I read all of the regs and the compressed gas association materials, and it indicates about purging and to basically remove contaminants. 

Just trying to learn a little bit about how it’s handled from the average supplier.

What better way to learn, then to ask people that are accomplished professionals

[swedefiddle]

Good Morning Chris,

Do not try to put something else into a compressed bottle of whatever you have. One bottle of co2 stays as co2. One bottle of mixed gas for Mig, stays a mixed bottle for Mig. The same with all the different gases. Fuel, Acetylene or Propane are ALWAYS left-hand thread. This way, someone who doesn't know better, can't mix up the Fuel and Oxygen or Inert Gas.

Neil

[Chris Mamros]

I guess that’s kind of what I was looking for.