CO2/Argon 5%, 10%, 15% ?? When? Why?

[rwm]

You guys ever, "stir" your tanks?

They tried that on Apollo 13... I would avoid it.
Robert

 

[pontiac428]

Stratification, as I've heard anecdotally, can occur at critical points, but Fick's Law says it won't be an issue. Does the syrup settle out of your Coca Cola? No? Same idea.

 

[General Zod]

All of my mix gas bottles have a valve with "DT" on the stem. Some call that a dip tube, some a siphon and others an inductor tube. As I've read, it draws from two different parts of the tank (Co2 near the bottom) to help draw them out in the correct proportion. Look at a 100% argon bottle and it won't have that "DT" stamped on the stem.

I would love to read that. Nothing that I've read leads me to believe gases will stay separated like that.

 

[G-ManBart]

I would love to read that. Nothing that I've read leads me to believe gases will stay separated like that.

Going off a number of threads, the dip tube/siphon/etc might be more for mixing as the tank is filled, rather than for mixing output. Found this:

Gas cylinders venturi dip tube - The BOC Group plc

A gas cylinder has mounted therein a venturi device through which the constituents of a gas mixture pass when the cylinder is being filled with gas. The venturi device causes rapid and thorough mixing

www.freepatentsonline.com

 

[General Zod]

Yes Matheson TriGas says the same thing - that it has to do with the initial. An improperly mixed mixture is more likely to stay somewhat stratified than one that is properly mixed.

Matheson Article.

 

[graham-xrf]

@General Zod has it exactly right. They mix! Also, the speed of the mixing is really fast - bullet-like!

You can wonder about how we have in the atmosphere the (rare on Earth) gas Helium around, being as it comes from radioactive decay of Thorium, Uranium and Radon, and is in some concentration in natural gas wells in North America. It is a very light element, and supposedly "floats off into space". Does it? Yeah - much more complicated! I won't get into all the mechanisms about mean free path, and collision probability, and achieving escape velocity.

I tried it while diagnosing a leak in a vacuum furnace using a mass spectrometer Helium leak test instrument. I walked around with the leak tester and ended up about 40 metres away at the end of the car park outside, and it was still squealing. We tried again later (after leak fix). There seemed hardly any time lag between the little puff of Helium, and detecting it right across the industrial property. The Helium was everywhere, not quite instantaneously, but damn fast! It takes about 20 minutes to dissipate. It only "floats up" readily if confined in a party balloon. Otherwise, it mixes, no need to shake nor stir.

[Edit: Re: @rwm Robert's Apollo 13 reference to "stirring the gas tank" begs the question - why did NASA bother? I get it they were stirring what was a liquid at the time (Oxygen). ]

 

[General Zod]

by the way graham-xrf, what you need is a Frankenmixer. You can mix any percentages you want. And it works, plain and simple.

 

[G-ManBart]

[Edit: Re: [USER=23938]@rwm Robert's Apollo 13 reference to "stirring the gas tank" begs the question - why did NASA bother? I get it they were stirring what was a liquid at the time (Oxygen). ]

Yes, it was a liquid oxygen tank. They were doing a stir to keep the slush from stratifying.

 

[graham-xrf]

By the way graham-xrf, what you need is a Frankenmixer. You can mix any percentages you want. And it works, plain and simple.

Ohooo - I do like that! Essentially flow meters in the separate gas lines from bottles of Kosher pure.

I ventured out yesterday (carefully, sans vaccine), and picked up a 20 Litre volume bottle at 200bar of 5% CO2/Argon mix.
Converting to US units that's 2900.75psi and the volume is 0.7063 cubic feet.
So at standard pressure 14.503psi, that s close to 141.2 cubic feet. That's enough to do a whole lot of MIG beginner mess-ups!

They had "run out" of pure Argon, and had bottles on order. That's OK. I will play MIG for the time being, but on the way back, I was thinking about a gas mix method. This gadget just bypasses the "stratifying" phenomenon. One thing I did get from this discussion is that you don't get to successfully mix the gases like shaking a Martini ! I guess laying the bottle on it's side for a while now and then might help a bit.

Gas mixing to include 2% Oxygen, and choosing the varied percentage of CO2 is probably a fine nuance optimization for the very advanced welder to add to current control, voltage, electrode diameter, metals involved, etc.

Thin stainless?
I had thought about playing with some TIG is to make up a bigger stainless steel tray by cutting an end off two trays, and welding them together. This would be working with thin stainless, a bit like car body welding. I guess 0.8mm stainless MIG might well do it OK also.

Checking on the value of MIG wire deals.
Duh .. some will sell weld rods and reels by weight. Some by length. Some in inches, feet, yards, metres, cm, whatever.
Some by number of rods in a bunch. This can actually be quite good if the rod happens to be coated with slag cover or gas generation chemicals. It gets more complicated if the stuff is cored. One gets tired of multiplying or dividing by metal density and wire diameters after units conversion. I will find the app/spreadsheet soon.

TIG kit. Selection and costs.
Here I mean the handle, tungstens, pink cups, fittings etc. Everything other than the welder itself. This is a whole other research that we trawl eventually.

 

[G-ManBart]

TIG kit. Selection and costs.
Here I mean the handle, tungstens, pink cups, fittings etc. Everything other than the welder itself. This is a whole other research that we trawl eventually.

I can make the tungsten selection simple for you....get 2% Lanthanated and use it on everything. There are some special cases where another type will work better, but it's nothing you're going to run into for a long, long time. 3/32 will cover most of of what the typical person needs, but having 1/16 and 1/8 on hand will be nice options to have for certain applications.

For cups, #5 to #8 in standard pink alumina cups will get you started. I like #5 for smaller aluminum work, and a #8 gas lens for almost everything else, but there's a lot of wiggle room in between. For stainless you want a bigger cup compared to steel or aluminum. Gas lenses are a nice option, but don't get tricked into thinking they're for saving gas....they're simply for getting better gas coverage for a set amount of flow. You wind up saving a bit of gas, but that's a side benefit.