CO2 and Nitrogen as MIG Cover Gas

[M_George]

I was given a bottle of 25% CO2 - 75% nitrogen. Can this be used as a cover gas for my MIG welder. I've ben using flux core for two years and finally have a bottle, and it is filled with this mixture. Might as well use it up before re-filling. If this makes sense.

 

[sberry]

No, that is basically air.

 

[lakeroadster]

I was given a bottle of 25% CO2 - 75% nitrogen. Can this be used as a cover gas for my MIG welder. I've ben using flux core for two years and finally have a bottle, and it is filled with this mixture. Might as well use it up before re-filling. If this makes sense.

Also known as Guinness Gas.. used for carbonating dark beer.

Said to produce a Guinness type pour.

 

[M_George]

It was used as a purge gas for AC, but making beer... Hummm sounds interesting, I can handle that. I guess its either that or filling tires... LOL

 

[M_George]

If it's filled with CO and mostly nitrogen now, should I expect the gas dealer to refill it with welding gas?

 

[strength_and_power]

The smaller molecule size of the nitrogen gives a different "mouth feel" vs straight CO2 when used for beer. Good chance the fitting is different and your welding regulator won't match up. Providing the tank is still in date, most welding gas suppliers will swap you for the correct bottle and only charge for the "refill"


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[dscheidt]

The smaller molecule size of the nitrogen gives a different "mouth feel" vs straight CO2 when used for beer. Good chance the fitting is different and your welding regulator won't match up. Providing the tank is still in date, most welding gas suppliers will swap you for the correct bottle and only charge for the "refill"

Beer gas (75% N2/25% CO2) is used for beer because nitrogen is largely insoluble in beer, so it comes out of solution as the beer leaves the tap. Guinness and similar beers are dispensed from a faucet with a restrictor plate, which is makes little bubbles. Regular beer is sometimes dispensed with beer gas, because you can turn the pressure up higher, while keeping the partial pressure of CO2 correct. That means you can push the beer further or higher (handy if your bar is on the third floor, but the kegs are in the basement), without it turning into foam.

 

[M_George]

The smaller molecule size of the nitrogen gives a different "mouth feel" vs straight CO2 when used for beer. Good chance the fitting is different and your welding regulator won't match up. Providing the tank is still in date, most welding gas suppliers will swap you for the correct bottle and only charge for the "refill"


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It mounted right up with the regulator on my Hobart 140. So all the fittings are correct, so that shouldn't be an issue. Is there any other differences I should be aware of?

 

[Git]

If it's filled with CO and mostly nitrogen now, should I expect the gas dealer to refill it with welding gas?

Look at the male fitting of the regulator that screws into the tank - your looking for something like "CGA-580" stamped on it by the threads. That should give you an idea what the tank threads are and then you can look it up on this chart and see what you got

CGA-580 is pretty common for an Argon Regulator (Argon/Co2 mix)

https://www.concoa.com/cgachart.html

 

[laser3kw]

CO2 has been a cover gas in mig applications for decades. Nitrogen on the other hand is avoided in welding. Nitrogen will break down in the weld arc and will dissolved into the metal. If it is not dispersed from the weld, it will cause porosity.
As far as refilling it with a good mig gas mix, ^^^^ what Git said.

 

[Jbullfrog]

The bottle will work fine, just not the right gas blend. Your distributor might trade you for a bottle of 75/25 Co Argon.

 

[Lelandwelds]

The bottle will work fine, just not the right gas blend. Your distributor might trade you for a bottle of 75/25 Co Argon.

Just peel the UN label off, ask for weld gas refill, and keep your mouth shut.

The "given a bottle" part worries me. How much does this bottle weigh? 50lbs? 125 lbs? Beer gas is somewhat uncommon in most markets in "sold" sizes.

 

[Lelandwelds]

Beer gas (75% N2/25% CO2) is used for beer because nitrogen is largely insoluble in beer, so it comes out of solution as the beer leaves the tap. Guinness and similar beers are dispensed from a faucet with a restrictor plate, which is makes little bubbles. Regular beer is sometimes dispensed with beer gas, because you can turn the pressure up higher, while keeping the partial pressure of CO2 correct. That means you can push the beer further or higher (handy if your bar is on the third floor, but the kegs are in the basement), without it turning into foam.

Still of topic but . . .

Best reason to use beer gas is $$profit $$. Higher pressure equals more beers per hour. Nitrogen means (less "foam =wasted beer"). We printed up a little flyer with the math spelled out and used it as a bill stuffer to bars and restaurants. We pumped our beer gas into CGA 320 cylinders to make the switch easy.

 

[M_George]

Just peel the UN label off, ask for weld gas refill, and keep your mouth shut.

The "given a bottle" part worries me. How much does this bottle weigh? 50lbs? 125 lbs? Beer gas is somewhat uncommon in most markets in "sold" sizes.

My brother recently retired from the HVAC business. It is about a 60cf cylinder that he used to purge air from the system before filling it with refrigerant. If I get it filled with welding gas, does it matter that it had nitrogen in it?

 

[lakeroadster]

It mounted right up with the regulator on my Hobart 140. So all the fittings are correct, so that shouldn't be an issue. Is there any other differences I should be aware of?

You shouldn't use it as a shielding gas... the mixture is incorrect. The shielding gas can change the strength / brittleness of the weld if the gas type is wrong. And it can also create porosity in the weld.

My brother recently retired from the HVAC business. It is about a 60cf cylinder that he used to purge air from the system before filling it with refrigerant. If I get it filled with welding gas, does it matter that it had nitrogen in it?

Depending on the size of the place you get your welding gas... typically they will give you a different bottle.. not refill the old one.

It's different than getting your gas grill bottle re-filled at the local RV place.

At least that's been my experience.

 

[M_George]

I've heard horror stories here on GJ of people who exchanged tanks then had the gas company send them a rental bill. I'm ok with exchanging the cylinder, but want it to remain my cylinder. Is there anything I should watch out for when making the exchange?

 

[American Locomotive]

I've heard horror stories here on GJ of people who exchanged tanks then had the gas company send them a rental bill. I'm ok with exchanging the cylinder, but want it to remain my cylinder. Is there anything I should watch out for when making the exchange?

It doesn't work like that. If you do an exchange, they take the bottle you have, and give you another one. You don't get the bottle back. Most places only exchange rented cylinders.

If the bottle has a company name stamped on the ring at the top, it is likely a rented bottle. The only exception I know of is AirGas, who often stamps their name on owned bottles, and will swap out owned bottles.

My local welding store only sells/fills 80 cu.ft tanks. Anything bigger is rented and exchanged.

 

[Lelandwelds]

My brother recently retired from the HVAC business. It is about a 60cf cylinder that he used to purge air from the system before filling it with refrigerant. If I get it filled with welding gas, does it matter that it had nitrogen in it?

I've heard horror stories here on GJ of people who exchanged tanks then had the gas company send them a rental bill. I'm ok with exchanging the cylinder, but want it to remain my cylinder. Is there anything I should watch out for when making the exchange?

The pumper will blow it down and pull a vacuum before filling. Maybe, if he suspects a contaminate pump to 100 psi, blow down, and vacuum again. Nitrogen won't hurt. Oxygen or water are the killers. They will swap it anyway. They will fill 20 or so at a time.

Anything smaller than a 150 is customer owned in the USA. Stand your ground and laugh at them if they tell you different. Don't stamp or grind ANYTHING on a cylinder.

 

[M_George]

The pumper will blow it down and pull a vacuum before filling. Maybe, if he suspects a contaminate pump to 100 psi, blow down, and vacuum again. Nitrogen won't hurt. Oxygen or water are the killers. They will swap it anyway. They will fill 20 or so at a time.

Anything smaller than a 150 is customer owned in the USA. Stand your ground and laugh at them if they tell you different. Don't stamp or grind ANYTHING on a cylinder.

Thanks Lelandwelds, that's the kind of info I need walking into a gas dealer as a newbe.