Figure this out...

[SignWave]

Another head scratcher...

We all know that oil and water will not mix. If you can get it to mix it wont stay mixed for long. Right? Right.

So what happens when you mix Argon and Helium inside the bottle?
Would logic not dictate that Argon sink to the bottom and Helium float to the top of the bottle even though they are under pressure. For the same matter what about CO2 and Argon or any other gas mix out there.

[6010]

I believe you stumped everybody with this question. I guess I will have to get out my old chemistry book to try and figure this one out.

[Engloid]

No, they will not separate while under pressure.

[Archaic]

Engloid:

I disagree with you on this, but not because I am any kind of an expert. Let me explain.

A couple of years ago when I first got my MM251 I got a 300CF tank of 75/25 with it. I had the same question as SignWave, and questioned my Airgas rep as to how with the tank sitting still on my welder for a long time the gases would not separate. I reasoned that CO2 is heavier than Argon, and that would happen. Airgas rep said that yes, it would, but their 75/25 tanks contained a "mixing tube" which caused the gas to be drawn out correctly mixed. I never did fully understand this, and could find no one with Airgas that could show, or explain the mixing tube to me.

Fast forward. I welded the entire tank of gas and the arc characteristics did not change from start to finish. Emptied tank. Went over to Airgas to exchange and they have no 300 CF tanks of 75/25, but they gave me an 80 CF tank of 75/25 to use until the big tanks came in. Hooked it up and the arc was completely different. Different color arc, much hotter and more penetration. I figured I had forgotten how to weld. Two days of this I call my Airgas guy and explain to him what I am seeing. Go outside, he says, and see if there is a round green sticker on the tank that says "dip tube." I did and there was. He says that they have mistakenly filled tanks with 75/25 with a dip tube, I am pulling off the bottom of the cylinder, and am getting pure CO2. Take it back to AirGas, get a 300 CF with mixing tube, and it is back to welding as normal.

So, first I disagree that pressure will prevent different weight gasses from separating. Second, my experience as stated above would seem to indicate that they do. Now I am not trying to be rude or pick a fight here, but to say that there is a lot that I do not know. And hopefully someone will come along that can clarify if there is actually a mixing tube that draws gas out of a mixed gas cylinder or not, and whether two different weight gasses in a cylinder under pressure will separate according to weight. As usual, I may be very wrong.

Adios----

[SkidSteerSteve]

http://www.freepatentsonline.com/5232017.html

maybe this will help a little...

SSS

[SignWave]

I figured that there had to be some sort of way to mix the gases together.

Im sure Boyles laws come into play somewhere too.

[FusionKing]

So with all that being said I suppose then the only way to insure results is have separate cylinders and adjust your mix to suit your particular requirements as you go.
That way as the the part in question got hotter you could back off the helium a bit and save a buck or two as in the case of a welder lacking enuff amps.
I sorta feel like the guys working in welding supply places sorta lack the passion for their jobs that us the welders who use their products seem to display. The recent giant disasters at gas plants sorta shows this. I don't remember to many recent articles about professional welders blowing up entire facilities. What I'm driving at is I seriosly doubt the % of mix being exact in the first place let alone with the idiots and attitude I encounter daily. It is much like the auto supply industry only about a decade behind in technology mixed in with an ''old money attitude'' stating at the top.

[HMW]

It also seems to me sometimes a new, full bottle works better than an almost empty one. And it does seem some new bottles don't work very well, so I agree I think it depends some on the competence of the one filling it

[SignWave]

It also seems to me sometimes a new, full bottle works better than an almost empty one. And it does seem some new bottles don't work very well, so I agree I think it depends some on the competence of the one filling it

I concur.

Thats why I like to take my bottles 4x4'n that shakes 'em up real good!! Then once back at the farm, I weld stuff!

The last fill I got, was a short fill I only got 1700 pounds.. Those Bstrds!!!!
the nextitme I went in to get another bottle, I told the guy who had filled it previously that he had shorted me, and he just sorta stood there with a dumb look on his face. His body language said: " so? what do you want me to do about it?"

[TS-Off-Road]

I concur.

Thats why I like to take my bottles 4x4'n that shakes 'em up real good!! Then once back at the farm, I weld stuff!

The last fill I got, was a short fill I only got 1700 pounds.. Those Bstrds!!!!
the nextitme I went in to get another bottle, I told the guy who had filled it previously that he had shorted me, and he just sorta stood there with a dumb look on his face. His body language said: " so? what do you want me to do about it?"

I've had the pressure in my tanks vary by + or - 200lbs from day to day, just due to the temperature.