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).

 

[PANHAPP]

Dan was that 75/25 that you were getting. Sodo you wont need to cool the receiving bottle, just crack the full one. It will only take a minute to get half of it into the other one.

 

[PANHAPP]

ON airgas site "25% Carbon Dioxide Balance Argon Industrial Shielding Gas Mix, Size 300 Cylinder, CGA580" So they are giving you 25% by weight or pressure? Then filling the cylinder up with argon. That means you aren't getting 50 pounds of liquid like a co2 bottle. I have left my 75/25 on the welder once that explains why it didn't last very long.

 

[CNC Dan]

Dan was that 75/25 that you were getting.

Yes. AKA C25

 

[Arc weld]

I get the feeling this thread could go on for the next 6 month's. :mur: That's why I suggested going and talking to the welding supply in person. You're looking for answers on a public forum and you're not really sure who, if anyone, knows what they're talking about. You might run into the same problem at the welding supply too, so see if you can talk to someone who actually does the mixing and filling. I responded to Yomax4's post asking why a specialized(non freezing) Co2 regulator only allows a max. 1500 PSI inlet pressure if Co2 is normally filled to 1800 PSI like he suggested. I have nothing against him and think he is very knowledgeable on most welding topics but I never did receive a response to my question. Another reason to talk to someone who fills cylinders.

To weld you need to have gas, not liquid. Anything coming out of the cylinder will be gas, so if you are trans-filling C-25 to a smaller cylinder, gas will come out, not liquid. Get a 3000 PSI braided stainless line and CGA 580 fittings for each end. If you can, get a high pressure 1/4 turn valve to T into the line. This gives you an easy way to relief the pressure before you loosen the fittings to disconnect the line from the 2 cylinders. If they won't sell you these parts for what you want to do, you're out of luck.

C-25 is not measured by weight or by pressure. C-25 means 25% Co2 and 75% argon by volume (cu. ft.). You don't fill your gas tank by cu. ft. because it's liquid. If you had a 100 cu. ft. cylinder it would have 75 cu. ft. of argon and 25 cu.ft of Co2. When you buy straight argon and pretty much every other high pressure cylinder, it is sold by cu. ft. Straight Co2 is sold by pounds because it is pumped in as a liquid. Try to pick up the same size high pressure and Co2 cylinders. You will know right away. Co2 can be pumped in as liquid prior to adding the argon but will turn to a gas once the argon is pumped in under high pressure. Larger filling plants pump the co2 in as gas and have monitors to tell them the mix ratio's of the gasses they're mixing. I saw a small filling station pump liquid C02 into the cylinder before adding the argon quite a few years ago but I don't think this is as accurate as measuring both as gasses when filling the cylinders.

 

[jwmorris]

The ends that I used for my tube were hanging on the wall in my local welding supply. They are 1/4" NPT opposite the end that fits the tank and are for repairing regulators.

If you can't find them there, you can get them here.
CGA 580 Nut and 2 1 2" Nipple Regulator Inlet Fitting for Argon Nitrogen Helium | eBay

 

[ishiboo]

My .02 is that saving a few bucks on gas is not worth the risks of your DIY high pressure gas transfer. Being the 20cf bottle with you. Explain to them what your doing and maybe a good gas supplier will give you the discount rate on the 20.

 

[Sodo]

?good gas supplier will give you the discount rate on the 20.

They won't discount. That method will simply cost too much and there will be one more person saying that a 20CF is useless waste of money (me). The only way to make use of a small 'travel' bottle is the ability to refill it yourself, which is the subject of this thread.

Sodo is not afraid of high pressure gas transfer, Sodo is only afraid of getting wrong information, or not enough information, missing important safety aspects, and that is lessening as more and more experienced folks chime in. If Sodo was afraid he would not own devices that made molten steel and would not drive tractors (maybe limited to mowing the lawn).:laughing:

These are very real problems of using a forum, as opposed to getting info directly from an experienced professional. I prefer to talk to a compressed gas professional and get the straight scoop (very well understood, Arc!) but I can't wait a whole lot longer for this professional to appear. Sifting thru forum responses will have to do. I already know the response from my gas supplier, which will be self-serving in a very safety-oriented manner, I would expect nothing else.

Thx all for the CGA 580 info that is an important part!

 

[dfkrug]

They won't discount. That method will simply cost too much and there will be one more
person saying that a 20CF is useless waste of money (me). The only way to make use of a small 'travel' bottle is
the ability to refill it yourself, which is the subject of this thread.

Sorry to hear they are charging so much for the 20cf C25 bottle. Here in the land of semiconductors, I pay nearly
50% less for a 20. About $23 at a smaller family-run gas supplier in San Jose. Their 80cf bottle is a bit less than
4x that, and I have been going there for more than 25y. Maybe the big chain gas suppliers would punish me for
the small bottles; I don't know.

I guess I will be the sole defender of the much-maligned 20. I love mine. Sure, I get only a bit more than an hour
MIG welding with it, but that is good enough. I can throw it in the car and swap it out easily. Can't really do that
with a big 80. I was offered one free, but turned it down. The 20 rides on my Hobart 210 welder, which I roll
around pretty often, in and out of my workshop. An 80 on the cart would be much more unwieldy.

Clearly pro welders are going to use the big bottles in the shop, but there is a place for 20s. I hope you get
a good DIY refill system worked out.

 

[CNC Dan]

Sodo:
One thing you will need to deal with is getting rid of the air that is in the line. You might have to leave one of the fittings loose, while you crack the tank valves to expell the air. Then tighten the fittings, and open both valves to transfer gas.
A small valve in the line would be easyer.

 

[Sodo]

Need to purge oxygen for sure. Do you think cracking one fitting could be simpler than a valve cuz it's one-way?