Experience refilling argon or 75/25 cylinders yourself?

[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?