Refilled tank pressures

[Chain Bender]

I get my air and acetyline from AirGas. Supposedly a reputable company.

I've got it in my head that oxygen and Argon/mix in medium/bigger bottles is supposed to be either 2500 or 3000 psi. My last bottle of oxygen and argon/mix were barely 2000. Is that right or do I need to start taking my guages with me when I swap out tanks.

thanks in advance,
CB

 

[CurlyDave]

45 years ago I was taught how to read the tanks.

Near the top of the tank there are a bunch of numbers stamped in the steel. You are looking for one that says 1950+ or 2250+ or something like that. This is the psi rating the tank had when it was last tested hydrostatically. The + means that the tank is good for 10% more pressure than the number stamped in it. The date of the last hydrostatic test should also be stamped in the metal.

The tanks should never be filled more than 10% above the number stamped on them. Frequently the fill level will be less than the tank rating, and yes you should bring your gauge and check the fill level.

Things may have changed over the years.

 

[Scotty Dive]

Curlydave is correct - all tanks that are CTC/DOT approved will have the working pressure stamped on it. In the old days it might have had a + to it and it was generally accepted that you coud overfill it by 10%. However that is up to fill station. What you might be experiencing is when a tank is filled and the gas is compressed it becomes hot and increases the pressure in the cylinder. when you get it home it has cooled significantly and you recieve low pressures. Most fill stations overfill so that when it cools you get a good fill but since these are considered explosive devices, as a fill operator I would not take the chance. To remedy this is to wait for the tank to cool and have them top it off or leave the tank and come back for it. Then bring a set of gauges out and before you leave check your pressures compared to theirs....it could be your gauges are off. There shoud not be a problem telling them you received a short fill - 2000 psi on a 3000 psi rated tank is too much change. You also might want to have them check the valve and the neck for leaks.... it happens and could be the cause of what seems to be a short fill.

 

[yomax4]

Co2 and O2 are not filled with the same pressure as Argon. Like post above said, It's stamped on the shoulder of the tank. Most overfill to stay legal. Ok to gauge your investment. These days it is an investment. Funny thing is and I probably shouldn't mention it. There is only .40 cents worth of O2 in a large tank. The rest is supposedly overhead. Argon and Argon Mixes are worth 1/2 of that.

 

[5030]

Co2 and O2 are not filled with the same pressure as Argon. Like post above said, It's stamped on the shoulder of the tank. Most overfill to stay legal. Don't to gauge your investment. These days it is an investment. Funny thing is and I probably shouldn't mention it. There is only .40 cents worth of O2 in a large tank. The rest is supposedly overhead. Argon and Argon Mixes are worth 1/2 of that.

...and the air (atmosphere) that those gases come from is free. It's all around you (with the exception of acetylene). It's the cost of the equipment to compress it and seperate it that makes the cost of a fill....

Don't believe you could charge up your O2 tank with your shop compressor......

 

[Jim in ICT]

The size of the tank may dictate the pressure limits also. You didn't say what size the tank was that you exchanged. A 300 size Oxygen holds 337cu. ft. of Oxygen @ 2,640 PSI max while a 200 size Oxygen holds 282 cu. ft. @ 2,200 PSI max. It's doubtful that you would have been shorted much in volume. If you were, it would have been an oversight. It's not as if there's a shortage of it.

 

[Haywire]

What you might be experiencing is when a tank is filled and the gas is compressed it becomes hot and increases the pressure in the cylinder. when you get it home it has cooled significantly and you receive low pressures.

Different world, but when the station would fill my scuba tanks, they would submerge them in a water tank to keep the bottle cool during filling.

Ian

 

[Scotty Dive]

yeah ...they put them in water to keep them cool and to absorb some of the energy in case it exploded. Many dive shops have stopped doing this as water sometimes got into the tanks and caused damage in the enriched O2 environment

 

[Mark @ Everlast]

Seasonally you'll find PSI differences as well, whether it was filled on a hot day or a cool day. I've noticed that as well.

 

[rcowan]

In a related thought, which generally runs out first Oxygen or Acetylene?

RC