When to fill your cylinder.

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I know I read a thread about this a while back, but I could not find it. So here goes. What is the recommended pressure on the gauge to refill your Argon. I have an S cylinder with an Esab flow meter; both are around 1 1/2 months old. The gauge on the Esab reads ~ 250 now.
Reply:I've gone lower than 50 with no problems.
Reply:Well when its out its out....  I have run bottles down to the point that the gauge showed 0, and it still flowed the correct volume.  However I have extra bottles on hand in my shop so its not like I would be out of gas if the bottle did run out.   If you only have one bottle I would start planning on refilling when it hits 100.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Kill it...  It's your $That aint heat lightning in the neighborhood tonight...
Reply:As long as your not running a production shop, run it dry.  And if you have a production shop you should have a spare bottle anyways.
Reply:Unless you are in danger of running out during a critical time when you can't refill it, you can take it to zero.  In fact, since these gauges aren't accurate when they are near zero, mine usually read zero for quite some time before they actually stop flowing gas.
Reply:I did reasearch on this subject for work. The reccomendation I found was to change it at 100 psi. This prevents the cylinder from being contaminated with water vapor and rusting internally. It's also useful to prevent bad welds in a production environment.  Probably it really doesn't matter, but there is a procedure. I'd contact your welding distributer for more info, if needed.
Reply:Originally Posted by Gus_MahnI did reasearch on this subject for work. The reccomendation I found was to change it at 100 psi. This prevents the cylinder from being contaminated with water vapor and rusting internally. It's also useful to prevent bad welds in a production environment.  Probably it really doesn't matter, but there is a procedure. I'd contact your welding distributer for more info, if needed.
Reply:Originally Posted by Gus_Mahn...The reccomendation I found was to change it at 100 psi. ... I'd contact your welding distributer for more info, if needed.
Reply:Run it to 0. Do you really think that water vapor will form? If it does, the contaminate was placed in the tank by your refiller by faulty and un-maintained equipment.Don't run acetylene to 0! It becomes unstable.
Reply:Originally Posted by TSORA distributor also told me I should be running the C25 on my MiG at 25-30cfh! I'm sure they make quite a bit more money giving out advice like that! I'm not saying you're wrong, but I'd like to see proof.  Just how is water vapor going to get into the tank???  Unless it was there already!!
Reply:I found thishttp://www.airproducts.com/products/...bles/32250.aspIt appears that you are leaving just under 4% of the argon in 9" x 51" cylinder changing it at 100 psi. That's about 11.25 cf or a little less than 1/2 hour at 20cfh, assuming you can use all the gas in the cylinder.
Reply:Yeah, it's a direct relationship with pressure.amount left (either unit) / amount full (same unit) = percent left (ANY unit)100 PSI / 2200 PSI = 4.5% left (either in PSI or cubic feet)Then multiply original volume by 4.5% to get exact volume remaining.
Reply:I think leaving some substantial pressure in a tank (100lbs) would be a way for a distributor to easily verify that a tank hasn't been left setting in a open/breathable state. Metal containers with small openings do accumulate moisture quite easily and quickly with temperature changes and humidity. So in that context, it is good advice.On the other hand I've never had, or at least never seen, anybody ever check a tank I took in for pressure let alone whether the valve was even open or not. They just pick it up and wheel it off.   So from this perspective, what would ordinarily be a good idea is wasted on deaf ears.I guess the main thing would be to observe a good work ethic and never leave a valve open on a dead tank then it's not an issue. I fill any of mine when it's the most convenient. I don't want to run out on a Sunday afternoon trying to squeeze the last dimes worth out.
Reply:Here in Kentucky we open the valve and tip the tank upside down.  If no gas runs out we get er filled!
Reply:I usually change my bottle at about 100 - 150 psi........ Sometimes, if I have a long day of welding I may change it even if there is 500 in it just so I won't have to stop and take care of it, or chance my gas running out in the middle of a weld._________________Chris
Reply:Are you buying your own gas or is your employer?
Reply:I disagree with the recommendations above to drain a cylinder to zero pressure.  I guess, like with many of life's admonitions, some of us follow the directions we got at out welding teacher's knee and some of us don't.I think the recommendation to return a bottle with some product pressure is quite valid and the actual volume of gas you are losing is negligible.  Consider the approximate physical volume of the bottle you are using:  A nominal 250 Cu. Ft. size K cylinder is 9.2" O.D. and 54" tall with valve (or, I'd guess about 50" tall without the valve and some of the neck).  That's roughly a gross volume of 1.9 Cu. Ft.  Subtracting about .24 Cu. Ft. for the steel (117 lb. empty cylinder weight/490 lb./Cu. Ft. steel density) leaves a physical volume inside the cylinder of about 1.66 cu ft.So the size K cylinder holds 1.66 cu. ft. of gas at zero psig (let's call it 15 psia (absolute pressure) for simplicity.  At 15 psig (gauge pressure) (30 psia) the bottle will contain 2 * 1.66 = 3.32 Cu. Ft. of gas.  At 60 psia (45 psig) the bottle will contain 6.64 Cu. Ft.  That's 2.6% of the gas you purchased.  So the cash value to you of drawing the bottle down to zero gauge pressure instead of leaving 45 psig in the bottle is about 2.6% of the cost of the gas you purchased - probably about a dollar, depending upon what gas you are buying and where you are.  Now, what is the advantage of leaving 45 psig in the bottle?  For one thing, don't you crack the valve before attaching your regulator to the bottle?  That's for the purpose of ejecting any crap that has accumulated in the valve outlet port, thus keeping your regulator clean and leak-free.  If you left zero pressure in the bottle when you returned it you deprive the gas filling service of the ability to crack the valve and eject any crap that accumulated in the valve port while the bottle sat in your shop or truck awaiting exchange.Gus_Mahn said, "Water vapor could get in an empty tank if it were empty, the valve was open, and there were drastic changes in temperature or atmospheric pressure."  Well, actually a drastic change in pressure or temperature is not required.  The most subtle changes in either will aspirate moist air into the cylinder if the valve is not closed tightly.  A slight amount on each diurnal temperature cycle will be enough to contaminate the cylinder with moisture.  Not much on each cycle, but eventually a significant amount compared to the amount of moisture in the gas you are buying.If the empty, unsealed cylinder is stored in an unheated area in a cold environment the moisture is likely to condense inside the cylinder and not get purged out during the warmer daytime period.  It is a natural pump drawing water into the cylinder, eventually leading to rust, just like in the gas tanks of your garden equipment or motorcycle engines left idle outdoors under tarps for extended periods.  Leaving some product pressure in the cylinder absolutely prevents such a process from occurring, at least until the residual gas leaks out through an imperfectly closed valve.I think it's cheap insurance.awrightLast edited by awright; 05-14-2007 at 04:48 AM.
Reply:So, basically drain it as far as you want, just leave a few pounds in the tank (say, around 40psi, or so)  and close the valve when you're done.   Simple.
Reply:How accurate do you think a $40, 2500 PSI gauge is going to be when you get around 45 PSI?  You probably have anywhere between 20 and 100 PSI anyway.I get several minutes of arc-on time after my gauges read zero anyway.If this were even a deal worth worrying about, there'd be a sign at the gas store asking us to do this.
Reply:Originally Posted by MAC702How accurate do you think a $40, 2500 PSI gauge is going to be when you get around 45 PSI?  You probably have anywhere between 20 and 100 PSI anyway.I get several minutes of arc-on time after my gauges read zero anyway.If this were even a deal worth worrying about, there'd be a sign at the gas store asking us to do this.
Reply:I didn't mean to start a war. Tungsten is cheep enough to grind, so is grinding wheels to remove the contamination. I think I'll try the 50 mark and see what happens after all I'll never know with my flow meter unless I try.Thanks for info.Tom