Co2 Tanks

[ACK]

I'm new to welding and want to hook up the Hobart 140 to gas. My local Craig's List has Co2 tanks for paintball guns and beer, others with no description at all, some are steel and others aluminum. Are there tanks that can and can't be used with a welder? Does the valve threading vary by intended use? What do you look for when purchasing a used tank ... or just go to the local welding supply store and bite the bullet?

Would a tank like this be appropriate for welding ... http://philadelphia.craigslist.org/tls/5244429865.html

[biketopia]

that would work, but if you are welding mild steel it's better to use a mix of argon/co2 pure co2 is best for welding aluminum. You could call your local supply place and see if they will take it in on trade.

[Bigdav160]

Cut and paste from an article on welding gasses:

Carbon Dioxide (CO2) is the most common of the reactive gases used in MIG welding and the only one that can be used in its pure form without the addition of an inert gas. CO2 is also the least expensive of the common shielding gases, making an attractive choice when material costs are the main priority. Pure CO2 provides very deep weld penetration, which is useful for welding thick material; however, it also produces a less stable arc and more spatter than when it is mixed with other gases. It is also limited to only the short circuit process. For many companies, including those that place an emphasis on weld quality, appearance and reducing post-weld clean up, a mixture of between 75 – 95 percent Argon and 5 – 25 percent CO2 will provide a more desirable combination of arc stability, puddle control and reduced spatter than pure CO2.. ..........If you’re welding a non-ferrous metal — aluminum, magnesium or titanium — you’ll need to use 100 percent Argon.

[_Ogre]

buy the biggest tank you can afford or you will be filling it all the time
or running out on the weekend when the lws is closed

when buying used tanks make sure it's not a rental tank or your lws may not fill it
also tanks need to be pressure tested and inspected every 7 yrs, figure that in when buying an used tank

[ACK]

So typically the local supply house doesn't care if I walk in with an empty Co2 or Acetylene tank and ask for C25, as long as I'm trading in an equal size tank that's inspected and not leased? Also, how do they know if a tank is leased? I know these are rookie questions, 50 years on this earth and I still don't know it all.

[BR3W CITY]

They won't fill a Fuel (left hand) tank with a Shielding/inter gas (normal thread). Thats a no-no.

Tanks are stamped with serial numbers like a VIN up on the neck and sometimes under the bottle. Most of the large gas companies will have thier names stamped along with those numbers. If you take it to a commercial welding supply, they can see if the tank is under lease (but if it is, they may create a problem for you).

Smaller places might still allow you to refill a tank, but usually they'll let you trade in a tank of "dubious history" in exchange for a new tank from them, sans any of the credit checks or deposits etc. I've bought them from contractor sales and flea markets before. Very few places will actually just fill your tank outright, since its much harder for them to ascertain that you've properly maintained and transported the tank.

[Bigdav160]

Where I'm from, any bottles under ~150 cu/ft are "owners bottles". Anything larger are leased.

There are several welding stores nearby. Sometimes they fill my bottles, sometimes they exchange.

You have to be careful because sometimes they give you a bottle close to it's expiration date.

[ERASER5]

"Owner" bottles no matter the size do not have a collar with names formed into them. If the tank has a collar, a gas company owns it.

The smaller bottles are usually owned and you simply trade the empty for a full one just like it. The 100# bottles can be owned, but you will likely lose it to a trade because you need it now. Then later the gas guy forgets all about it and charges you rent. It's practically impossible to fight and win.

So rule of thumb, own the small bottles, rent the big bottles.

[Bigdav160]

Eraser, you made me look. My oxygen and acetylene tanks were given to me by a neighbor that was moving. the rest i purchased.

C25- no name. I had refilled at a local store recently
Acetylene - no name
CO2 - no name
Oxygen - Airgas. This bottle I did exchange at an Airgas store
Argon - Airgas. The local store has been filling my bottle but just recently changed to Praxair. They exchanged it just the other day for this bottle.