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C25 argon small cylinders pros and cons and shelf life question

Hi all, I have been welding with a flux core wire and finally decided to upgrade to C25 (Argon/CO2 mix). I have questions about equipment that I need to buy:

1) I am debating whether to get 40 cu ft or 55 cu ft cylinder These two cylinders differ in design, not just in size. 40 cu ft has a flat bottom, while 55 is spherical. Also, 55 cu ft cylinder is taller, but has smaller diameter than 40 cu ft. Does the fact that 55 cu ft cylinder has a spherical bottom make it less prone to leak? (since there is no seam around the bottom) Or the chance of leaking around the bottom is negligent compared to chance of leaking at the valve or around the valve? On the other hand, a 40 cu ft cylinder can stand upright on its flat bottom. So, what are the pros and cons of each?

2) What is the shelf life of C25 mix? I would rather go for a bigger bottle that would serve me for years, but if it leaks out, than bigger bottle is a waste of money for me. How long can I expect 40 cu ft or 55 cu ft cylinders to hold gas? If they leak relatively fast, I might need to downgrade to a 20 cu ft cylinder.

Thank you.

Reply to
Alex .
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In rec.crafts.metalworking on 2010-12-21 Alex . wrote: ...

[snip Q about 40 vs 55]

As Gunner pointed out, with valve closed there should be no detectable leakage. Note that tanks get pressure and leak tested every few years (10 years to first test, 5 years thereafter).

Ask your welding gas supplier what it will cost to refill the different sizes of tanks. Cost per welding hour is a lot less with larger tanks. Eg, for C25 refills, TSC charges $24 @20CF (= say $24/hr assuming 20 CFH), $40 @80CF (=$10/hr), and $47 @125CF (=$7.52/hr), per

Reply to
James Waldby

I have an 80cf Argon cylinder for my TIG welding and it seems to be a good size for my needs. I pay about $30 for a swap at my local Airgas branch and I usually do one swap a year, two at most.

Reply to
Pete C.

Probably the flat bottom is an extra layer welded on to cover the spherical shape.

What is the relative pressure of the two bottles?

I would think so. And the latter is controllable.

[ ... ]

Does the C25 offer any better welding?

And -- you forgot to mention -- when you open the valve, open it

*hard*. This sets a secondary seal like the one which closes the valve, so you don't get leakage around the valve stem.

Good Luck, DoN.

Reply to
DoN. Nichols

Eau contraire. I once got a bottle, took it home, and it was nearly flat in a week, after one hour's use. I sprayed Windex on the stem, and it was leaking. You can get them leaking from the supplier. Take some Windex with you, and test before you take it home. Even if only slight, you won't get your money's worth. Also test it with the valve open, as it can leak then, too. The supplier happily took the leaker and gave me a full one no charge, which was the right thing to do.

Steve

Reply to
Steve B

More likely it has an inverted dome bottom.

2215-2400 PSI is the norm for most general use gas cylinders. Higher pressure cylinders tend to be limited to special applications, and of course liquefied gas cylinders are a lot lower pressure. Then of course you have the oddball acetylene cylinders with the porous fill and the acetylene dissolved in acetone.
Reply to
Pete C.

I believe you'll find that many MIG users will have entirely positive comments regarding the C25 mix, especially for sheetmetal welding.

Using the Hobart 135 with some Lincoln SuperArc L-56 ER70S-6 .025" wire and C25 mix (75%Argon/25%CO2) with new 20 gauge (.037") mild steel, there were relatively few changes that were required. Connecting the gas regulator, changing polarity and the wire drive roller and with a new contact tip, made for a simple change-over.

The heat/voltage settings for the best results will vary with the operator's skill and experience levels, most likely. For .025" wire and C25 mix (I'm not that skilled at moving fast, so the lower settings of 3 and 2 proved to be completely adequate for lapped joints, and tacking butt-jointed 20 ga. sheetmtal.

A friend and I spent several days replacing rusted sheetmetal in the windshield area of a large RV, and the C25 mix made the job much easier than if we had tried it with flux core wire.

Reply to
Wild_Bill

We were taught to crack the acetylene cylinder only just enough and leave the wrench on, but open the oxygen all the way so the back seat sealed the stem.

jsw

Reply to
Jim Wilkins

I've been welding for 20+ years, but not in every one of them, so before patching a rust hole in the car I took a night class at the high school. I started with their big Miller and C25, then brought in my little Century with straight CO2 since that's what I have to use at home. The instructor liked the Century. I needed an evening to relearn it, then it worked well enough to seal seams in 0.024" steel light- tight without having to build up an unreasonable bead height or melting through (much).

If there was a significant difference between C25 and CO2 it was masked by the different wire sizes, 0.023 on mine and 0.040(?) on the school's. I needed to grind both anyway, thus the bead appearance didn't matter.

A tank of CO2 lasts a whole lot longer. I may have used a quarter of the first one I bought.

jsw

Reply to
Jim Wilkins

By the time you've sprayed Windex on the valve stem with the valve wide open at the dealers, all the gas has run out :-)

Sorry, couldn't resist.

Happy Christmas/solstice/whatever.

Mark Rand RTFM

Reply to
Mark Rand

Yes -- the O2 is a high pressure cylinder, as I suspect the C25 is. (If if is low pressure -- someone correct me.) Acetylene is (*Must* be, for safety) a low pressure gas, so the design of the valve and the rules are different.

Try 6000 PSI N2 some day. :-) (Needed to run tiny cryogenic chillers.)

Enjoy, DoN.

Reply to
DoN. Nichols

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