Experience refilling argon or 75/25 cylinders yourself?

[jwmorris]

I do it all the time. I use steel brake line with double flare on each end that is sort of adjustable if you can get them close. You don't get a full fill but it does save money.

 

[Sodo]

I do it all the time........You don't get a full fill but it does save money.

Great! Experience counts!

Are you refilling 75/25? What do you mean you dont get a full fill? I understand if the pressure simply equalizes but is there liquid in a full bottle of 75/25? Some of the guys here are saying only CO2 has liquid but 75/25 is just gas. If 75/25 is just gas then the big tank drops pressure until the little tank becomes equal.

 

[PANHAPP]

Welding shops can sell you a pigtail to fill from one bottle to another for most gasses. If you have an oxygen or other bottle that you can't get filled you can bring home a newly exchanged bottle and put half of it in the other one for reserve. Some LWS don't like to sell them though.

 

[Arc weld]

Another thing to worry about is if the small cylinder you own is in test date. If you were filling your own cylinder and something happened and the test date was past due, you could be in serious trouble.

 

[jwmorris]

This is what I use. The ziploc bags are to keep "stuff" out of the line. The sets we have at the farm, the ends are covered in foil.

By not "full fill" it is not like taking a gallon or water and filling a quart glass with it.

Instead it is like taking a large air tank and filling a smaller one. the PSI the small tank fills to depends on the size of the two tanks. If one was completely empty and the other at 100 psi, IF both tanks are the same size and you connect them you will wind up with only half in each.

 

[Sodo]

This is what I use. The ziploc bags are to keep "stuff" out of the line. The sets we have at the farm, the ends are covered in foil.

Perfect, thx for the pic!

Trying to find out if a 75/25 mix is just "gas" or is there liquid in a "full" cylinder? Because if there is liquid, you CAN "fill the quart from the gallon" -----> if you can transfer liquid. Understood, if its just air it equalizes pressure only.

If there is liquid: Have a full 100cf tank. You connect it to a 100CF empty tank. Pressure will equalize, and remain the same. The tank with the liquid weighs more (thus has more cf) than the tank with just gas. Even though the pressure is equal. Propane behaves like this if you don't up-turn the supply tank.

If there's no liquid: Have a full 100cf tank. You connect it to a 100cf empty tank. Pressure will equalize at 50% of original pressure. Tanks have equal amount of gas.

So, does anybody know for sure, if 75/25 is only gas? Or is there liquid in a full tank?

 

[Arc weld]

It's gas as has already been mentioned in this thread. You can buy high pressure braided lines which would be the best bet but you need to go to the welding/gas supply and tell them what you want to do and see if they will sell you what you need. You may have to sign a waiver that they are not responsible if you purchase your gas from them and then transfill other cylinders. Until you do that, nobody on here can help you. I think someone needs to explain it to you in person and also point out the potential problems with doing it.

 

[PANHAPP]

Sodo I guess for 75/25 you could turn the bottle upside down and crack the valve to check for liquid. Wear heavy gloves. let me know if you try it. The guy at the local Airgas told me there is no liquid for what that's worth. It seems like there would have to be liquid to me.
If there is liquid you should be able to lay both down (assuming they are the same size) and let the liquid equalize. You might want to let them lay there for awhile. have the valves open and have the outlets pointed parallel to the floor with no high spots in the pigtail.

For Argon just fill with the bottles standing up. You may need to support one if it's smaller. Open the valve on the bottle to be filled. Then open the full one slowly. You will get some heating from the gas being compressed in the empty tank.

I have not tried to fill a 75/25 bottle yet but plan to fill a small one. I have filled oxygen and nitrogen with no problems .

 

[CNC Dan]

FWIW
My LWS used to fill my 80cf tank from a bunch of other large tanks. Ten large tanks all connected to a manifold, and my empty tank. Each large tank valve was opened, then closed in turn. When the first large tank was low enough, he would swap in a new full tank, and each tank moved down one place in the valve opening. He used magnetic labels to keep track of the order. He also used a fan to keep my tank cool.

 

[Sodo]

Good info here thanks to all!

Dan, that makes sense,,,,,(sequence of introducing the new full tanks to the manifold and cycle out the partial tanks). Thanks very much for that mental picture! I guess a guy could do that in his shop too, then be able to fill his 'travel tanks' fuller.

ArcWeld, where did you see confirmation that theres no liquid in a full 75/25 bottle? YoMax 4 has some really good info here, but I'm still not sure. Thanks YoMax4 you really explained a lot and clearly too. FYI my new, full 80cf 75/25 bottle has about 2050psi (argon 75%, CO2 25%). ArcWeld says straight CO2 maxes out at 850psi (then goes into liquid).

I suppose the receiving cyl heats up about the same amount of 'heat units' that the supply cyl cools down. Is this correct? As the receiving cyl heats, then its pressure rises and thus won't accept as much gas in. Does it make sense then to set the supply valve for a slow flow to give receiving cyl time to get rid of its heat during the transfer? Makes sense that cooling the receiving cyl with a fan or otherwise would speed up the process (if necessary).