welding gas cylinder questions.

[Pro-Painter]

I picked up a used Lincoln Pro-mig 175 a couple of weeks ago and I need to get a gas cylinder for it. I want to use a 75/25 mix of co2/argon as it fits my needs best. (75% co2/25% argon)

Harbor freight has (20cf )USA made argon cylinders on sale this week for $84.99 - 20% off = $67.99.

Can you use a dedicated argon cylinder for a argon/co2 mix? Or do you need a dedicated co2 cylinder?

I called around welding shops, and without an exchange, a 14cf cylinder would cost around $150. To fill a 20cf cylinder with a 75/25 mix it would be $25. SO buying the HF cylinder would save me quite a bit of money, and I would have my own USA made cylinder.

 

[WhoWhatNow]

Are you sure you want 75% CO2? I think The standard MIG gas is 75% argon/25% CO2.

Regardless, I would suggest pricing out larger tanks. I got a 60CF tank for about $150. The places around me will not fill small tanks, just exchange them. I wish I had got a 80 or 120cf tank instead. The cost to exchange/fill is much less as you increase tank size. Unless you need to be mobile there is not much reason to get a small tank.

 

[rlitman]

Can you use a dedicated argon cylinder for a argon/co2 mix?

All that matters is that the cylinder has a CGA-580 valve (it will).
That style valve is reserved for non-flammable, non-oxidizing gases such as Argon, Helium, Krypton, Neon, Nitrogen, Tetra Fluoro Methane, Xenon, and mixes of such gases. It isn't used for a cylinder filled with pure CO2, but would be used with any CO2 mix with argon.

Your welding gas supplier should apply the proper sticker to the cylinder's shoulder to identify what exact gas the cylinder is filled with.

 

[chris142]

Keep this in mind.

When you take your new bottle in they will swap you for one of theres. They don't fill bottles on site so your chances of getting your new bottle back is slim to none. But they will credit you with an exchange bottle.

The problem now is moisture in the exchange bottle. Often when JoeSmo runs a bottle out he leaves the valve open and this allows air and moisture into the bottle. If they refill the bottle without baking it or vacuuming it to remove the moisture your welds will have lots of splatter.

We were fighting the splatter problem for a couple of years untill we changed suppliers. The new supplier explained the moisture thing to me and since they vacuum and bake the bottles often we have not had any more trouble.

 

[Dan in Pasadena]

I need to do the exact same thing and got a quote of I think it was $189 for a large (don't remember HOW large) from my local Airgas place. I'm gonna be using it only for sheet metal repair so I don't have a real feel for how big a cylinder I need? Will the gas in the bottle, in my garage, last essentially forever?

 

[chris142]

Will the gas in the bottle, in my garage, last essentially forever?

If it sits too long the gasses will seperate. Simply remove the cylinder and roll it across the floor to mix them back together.

 

[Coldspot]

Hate to say this but your gas usage depends on how much you weld. You could weld all day or maybe an hour a day. I am garage manager for a local car club where we rent out 5 to 6 stalls over winter for guys to work on their vehicles. We switched to the smaller 60 cubic ft tanks because we were not using enough gas to justify the contract costs associated with the larger tanks. Hope this helps.
Gord

 

[Jack Olsen]

20 cf is too small. Get at least an 80 cf bottle. Look on Craigslist before you look to HF or anyone else that sells 'new bottles.' Just make sure the hydro on whatever you buy is current.

Better still to get a 125 cf. The cost difference might not look sensible upfront -- but to give it some perspective, the cost of refilling a 125 is only $4 more than an 80. You'll go broke refilling a 20, and you'll always run out on a Sunday when you're right in the middle of a job.

 

[Provincial]

If it sits too long the gasses will seperate. Simply remove the cylinder and roll it across the floor to mix them back together.

How long does it take for the gases to separate? In other words, if I haven't used the bottle in x moths (or weeks) should I remix the gases?

 

[FunkyfullWidth]

I have an 80 that i use for occasional home welding. sometimes I'll use it a few times a week, sometimes i'll go 6 months before needing a refill. I've never had an issue. When I first got a tank, I bought it off ebay. It was like 60 bucks cheaper then a supply place and had free shipping.. I've been running an exchange at the gas place and when I got into doing more welding I upgraded to the 80 and just paid the difference in cost.

 

[welder4956]

If it sits too long the gasses will seperate. Simply remove the cylinder and roll it across the floor to mix them back together.

 

[tdkkart]

I haven't checked for awhile, but when I bought my first tank the price was the same to fill a 40cf and a 125cf.
I've got a 125cf of 75/25 on my mig welder, a 300 of 100% Argon on my TIG. TIG welding uses alot of gas, enough that I'll buy a 2nd tank the next time I have a big project.

 

[loranger]

My dad had an old 125cf co2 cylinder he picked up at a yard sale that he gave me. I took it to Airgas and they let me "downgrade" to a 80cf 75/25 and only charged me the price for a hydro ($30). I have had it over a year now and its still almost full! I don't do much welding though.

 

[WWIIjeep]

How long does it take for the gases to separate? In other words, if I haven't used the bottle in x moths (or weeks) should I remix the gases?

It depends on the cylinder. Most cylinders intended for argon-CO2 mixed gas (AKA: 75/25, C-25, Stargold and several other names) have a mixing tube inside so that the heavier CO2 gas still gets mixed with the argon even when it's at the bottom of the cylinder. Some older cylinders have only a short mixing tube, which doesn't work as well, or even no tube at all, hence the recommendation for rolling the cylinder on the floor to mix the gases.

I see that welder4956 laughed at that suggestion from chris142, but that's what the welding gas suppliers used to suggest for older 75/25 cylinders that had been sitting unused for a while. Obviously, when you do that, you remove the regulator and put the safety cap back on before rolling.

Generally, the larger the cylinder, the less per cubic foot you'll pay for the gas, but there's really little point in having a cylinder of any sort that's going to sit around for years and years before getting used up.

A very common 75/25 cylinder size for home or small shop use is the "Q" size, nominally an 80 CF cylinder, but usually filled to 95 CF for 75/25 gas. The small "R" size typically used with "safecracker" welding kits is too small, and the S, K, and T sizes are generally too large for home shop use--especially the K and T--unless you're doing a fair amount of welding almost every day.

 

[chris142]

Just repeating what I learned last week from our new supplier. I had never heard of it till then.

 

[welder4956]

A mixture of 2 gases that exists in vapor form cannot seperate or one of them settle to the bottom of the cylinder as long as they are in vapor form. Air is a mixture of oxygen, nitrogen, argon, helium and other gases. Using this idea, the air in my air compressor should seperate the argon (which is heavier than air) to the bottom and helium to the top. This does not happen. To dissociate vapors, one of the gases must be reduced in temperature to below it's boiling point. Boiling point for argon is -302.3° F. Boiling point for CO2 is -70.6° F. So to seperate the argon vapor from the C02, the mixture temperature must be reduced to less than -70.6° F.

More reading for those interested:

http://www.co2captureproject.org/pdfs/3_basic_methods_gas_separation.pdf

 

[sometoyotaguy]

I have a small bottle that's about 3' tall. I'm not sure what size it is. It'll last awhile, but not nearly as long as I'd like for the $50 they charge to fill it. If you can deal with a larger tank it might be worthwhile, but you can always keep a smaller one as a spare later.

 

[Jim Johnstone]

If it sits too long the gasses will seperate. Simply remove the cylinder and roll it across the floor to mix them back together.

I guess I better "re mix" all my scuba tanks in the garage before I go diving, or else I'll end up breathing the nitrogen portion and just plain die.

 

[koditten]

If it sits too long the gasses will seperate. Simply remove the cylinder and roll it across the floor to mix them back together.

You're thinking of cetaline (spelling). I have argon/co2 cans that are 5 years old that have no issue with seperation. I have to call bull **** on this one.

Yes you are correct that cetaline can seperate form the acitone that is used in the can. This usually happens when the can has been sitting on its side for extended piriods.

KO

 

[welder4956]

Acetylene cylinders are filled with a porous material (calcium silicate) which are filled about 40% with liquid acetone. The acetone is absorbed by the porous material and then the acetylene is pumped in. The acetone absorbs the acetylene to keep the cylinder stable. If the cylinder is stored or transported on its side, the acetone will settle to that side and can be discharged through the regulator and torch if not allowed to stand upright long enough prior to use. The burning of the acetone is not really a problem, however the loss from the cylinder is, since it is used to keep the acetylene stable. There are varying opinions on how long the cylinder must be left upright before use, but generally 24 hours is the accepted practice.

 

[koditten]

Thank you, weldern4956, I didn't have the details at ready.

KO

 

[O_M_Jeep]

with a 20 I wouldnt worry about COO or anything like that, most welding supply places will just exchange the cylinder anyway, make sure the exchange has a recent hydro stamp date and is not a 1940s cylinder, you would be surprised how old most cylinders in steady use are. make sure you take your reciept with you when you exchange it, fedral law says you have to prove ownership when you exchange a bottle. For better info call any of your local welding supply places, or any Norco store.

 

[koditten]

Since we are still on the topic, any welding gas supply store that has a steady turn over is not going to have a problem with inpurities in the gas. Cylinders are purged before they are filled.

The only time you need to worry about "stale" gas is if you are welding in critical environments, for example, nuke plants or nuke shipbuilding. Every step of the build process is documented in detail.

Us, "Joe Builders" aren't going to have any issues with off the shelf cans of welding gas.

KO

 

[koditten]

Going back to the start, one of the questions was how long a can will last. I build between 18 and 22 trailers like in my avitar per year. I can go 8- 10 months on a can of gas. If I have a many odd jobs in between, this number will vary slightly. I just figure 1 can of argon/co2 per year to make the math easy.

As for contact tips, I honestly can't remember when I changed the tip last. Has to be going on 3 years.

ko

 

[lametec]

make sure the exchange has a recent hydro stamp date and is not a 1940s cylinder

What's wrong with a 1940's cylinder?

 

[78Bird]

nothing, if it's kept up on it's certs.

alot of places charge if you bring in an out-of-cert one.

 

[5mall5nail5]

If it sits too long the gasses will seperate. Simply remove the cylinder and roll it across the floor to mix them back together.

 

[bubinga]

It depends on the cylinder. Most cylinders intended for argon-CO2 mixed gas (AKA: 75/25, C-25, Stargold and several other names) have a mixing tube inside so that the heavier CO2 gas still gets mixed with the argon even when it's at the bottom of the cylinder. Some older cylinders have only a short mixing tube, which doesn't work as well, or even no tube at all, hence the recommendation for rolling the cylinder on the floor to mix the gases.

I see that welder4956 laughed at that suggestion from chris142, but that's what the welding gas suppliers used to suggest for older 75/25 cylinders that had been sitting unused for a while. Obviously, when you do that, you remove the regulator and put the safety cap back on before rolling.

Generally, the larger the cylinder, the less per cubic foot you'll pay for the gas, but there's really little point in having a cylinder of any sort that's going to sit around for years and years before getting used up.

A very common 75/25 cylinder size for home or small shop use is the "Q" size, nominally an 80 CF cylinder, but usually filled to 95 CF for 75/25 gas. The small "R" size typically used with "safecracker" welding kits is too small, and the S, K, and T sizes are generally too large for home shop use--especially the K and T--unless you're doing a fair amount of welding almost every day.

Okay I know this is this threat is 13 years old or whatever please don't jump my ****. I laugh too when I read it not because I thought it was wrong but it just struck me as funny I don't know why rolling it across the floor hope that makes sense.
I'mma also wanted to reopen this thread because I'm going to have some questions on Argon tanks myself.
Thanks guys!

 

[GeoBruin]

Okay I know this is this threat is 13 years old or whatever please don't jump my ****. I laugh too when I read it not because I thought it was wrong but it just struck me as funny I don't know why rolling it across the floor hope that makes sense.
I'mma also wanted to reopen this thread because I'm going to have some questions on Argon tanks myself.
Thanks guys!

So you re-opened the thread to tell us that you plan on reopening the thread?

 

[bubinga]

No I replied to the reply about it being funny where the first person that said it the person that replied to it he thought the poster thought it was wrong I thought it was funny too.