Determine remaining welding gas in cylinder

[BeezFun]

^^^ Or charge a purge fee.

Yes, good point. They're happy to take it back and charge the extra money.

 

[Rock knocker]

Without any fancy formulas, if you started out at 3000 psi at room temperature, and it now reads 200 psi at room temperature, you now have 1/15th the gas. 1/15th of 330 is 22 cubic feet.

Yup, treat it as an ideal gas. Volume and temp remain the same, so n (mass of gas ) varies.

 

[Todd727]

Thanks for all of your replies! If I remember right, they actually charge the cylinders to 3000/3500 psi but have a limitator of some sort in the cylinder valve which limits the exiting gas to 2400/2500 psi.

The cylinder is stamped for it's max design. Checked my 330 and it's 2400psi. I believe they can do a 10% overfill though. Also, if the tank is returned empty, they are concerned with moisture entering the cylinder and some will charge for an inspection that involves removing the valve.

 

[MoArk Willy]

Let me assume you are using Argon gas. It weighs about 1# per 9.67 cf.
Your tank will have a "tare" weight stamped on it near the top of the tank.
That's the weight of the tank empty, without any valve assembly.
If you weigh your tank and subtract the tare weight that will give you the weight of the gas.
The rest is up to you.
That weight is based on 72 deg. however it won't change enough in the cold or heat to make much difference.
Weighing is the most accurate way to measure what's in the tank.

 

[bigtiller]

Let me assume you are using Argon gas. It weighs about 1# per 9.67 cf.
Your tank will have a "tare" weight stamped on it near the top of the tank.
That's the weight of the tank empty, without any valve assembly.
If you weigh your tank and subtract the tare weight that will give you the weight of the gas.
The rest is up to you.
That weight is based on 72 deg. however it won't change enough in the cold or heat to make much difference.
Weighing is the most accurate way to measure what's in the tank.

I was just going to ask that question. Look for the letters TW followed by a number, that's the weight of the tank. That is how propane tanks are measured.

I have no idea if Argon tanks are the same.

 

[Rock knocker]

That weight is based on 72 deg. however it won't change enough in the cold or heat to make much difference.

How could the mass of a enclosed vessel and its contents change at all with temperature?

 

[Todd727]

How could the mass of a enclosed vessel and its contents change at all with temperature?

It won't in that situation, but pressure will change with temperature.

However, the weight of the gas given above is based on 72 degrees. To keep things constant, you'd have to know the temperature of the gas when it was filled and on subsequent weightings. But, as MoArk said, it is a small difference. I'd guess the temperature during filling was over 120.

 

[MoArk Willy]

"How could the mass of a enclosed vessel and its contents change at all with temperature?"
The mass won't change just it's weight. And it's a small, nearly insignificant change. Just mentioned it to be thorough.
Unfortunately the tare weight isn't always clearly indicated on a cylinder. I believe Baker gas has a diagram as to what means what in the numbering system.

 

[Rock knocker]

"How could the mass of a enclosed vessel and its contents change at all with temperature?"
The mass won't change just it's weight. And it's a small, nearly insignificant change. Just mentioned it to be thorough.

That is contrary to basic physics

 

[MoArk Willy]

That is contrary to basic physics

So when water freezes it doesn't expand? Care to explain that?