When is an O2 cylinder empty?

Maybe a strange question, but how low can the pressure go in an O2
cylinder and still have the regulator operate properly? My 20 cubic
foot O2 bottle has lasted almost two years with pretty regular jewelry
torch use (Meco midget and Little Torch). The cylinder pressure is
now down to about 475 lbs on the gage -- how low before I should
consider it empty and get it refilled, as I don't want to run out in
Reply to
Bob Edwards
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Bob Edwards wrote in message ...
Don't worry, you can run it down to the torch pressure before it gives you any trouble on those small torches.
Paul K. Dickman
Reply to
Paul K. Dickman
Often the gauge does not read very accurately at the low end, so even if it reads zero on the tank gauge, you might be able to run the torch for quite some time, especially the small torch. I just noticed that at a seminar I went to, the tank gauge was zero, but everything kept working, so we did too. Unless you know the tank gauge, I suggest you just run it out until it quits working.
Bob Edwards wrote:
Reply to
Richard Ferguson
snipped-for-privacy@chromisdesigns.com (Bob Edwards) wrote in news: snipped-for-privacy@posting.google.com:
What is your low-pressure regulator set to?....the bottle should go down to roughly that setting before you have real problems.
Reply to
You sort of stated your own criterion of when the cylinder should be treated as empty: there's not enough left in it to get you through the next work session without worry. You have about 25% of the pressure of a full cylinder, so you have about 25% of the contents left. At the rate you are going, with that small torch, you may be able to go for six months or so without noticing any change in the way your torch runs.
It is good tank ettiquette to close the valve and go for a refill while there is still *some* pressure left, just so the tank definitely does not get any air in it. I have never heard of any conseqences to the customer due to this. When you exchange an empty, they just put it next to the others ready for refill, and don't even keep track of where it came from.
Reply to
Leo Lichtman
Not necessary at all. The first step in refilling is to pull a vacuum on the cylinder- this is to ensure there is nothing (within reason) in the cylinder before filling.
Reply to
Carl Byrns
If it is absolutely critical that you do not run out of gas during midproject, get a second. If it is not that critical, just use it until no more gas comes out, then take it in for refilling or swapout.
When I had a commercial shop, I did not want to run out of gas for any reason. To do so might cost me a couple of days of production if it happened over the weekend. You have to decide based on your own business.
Reply to
Or just get it refilled when there's still plenty of gas left. Even if you fill it now with 475 psi left, you've gotten 2 years on 20 cu ft ($20 worth?) of gas.
Reply to
Bob Engelhardt
directly proportional(?), never thought about it before, but it s/b possible to calculate the fill "level" from your first pressure reading on the hi side.
it would be approximate, depending on temp and guage accuracy. but what about the acet.regulators with markings for gas remaining? seems like they could or you could do the same for other gases. i am surprised i have never seen this typ of regulator/guage. maybe CO2 fire extinguishers? --Loren
Reply to
Loren Coe
Loren Coe wrote: (clip) but what about the acet.regulators with markings for gas remaining? seems like they could or you could do the same for other gases. i am surprised i have never seen this typ of regulator/guage. maybe CO2 fire extinguishers? ^^^^^^^^^^^^ It's proportional for an ideal gas, and for estimating how much is left, that's plenty close. Acetylene works a little differently--the gas is dissolved in a liquid, but I think it is still proportional, which is why the acetylene tank gauge gives you an idea of the contents remaining. However, for carbon dioxide and liquefied fuel gases, it's entirely different. As long as there is liquid in the tank, there is an equillibrium vapor pressure, regardless of how much is remaining. Generally these tanks have to be weighed to determine the contents, although there are some tricks which can be used, such as noticing where the frost-line is on the outside of a propane tank, or having special valves with quarter-point bleeds.
Reply to
Leo Lichtman

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