Markings on "owner" gas cylinders

I think they overfilled the oxygen. I was startled by a POP and brief hiss, but didn't smell MAPP gas. I just opened the windows and kept going.

I vaguely recall the pressure as around 2400 or 2500 PSI after I put the regulator on the basement-temperature cylinder, and was disappointed when the next tank was only 1800. The hose they filled cylinders with didn't have a fragile gauge on the ends, they just left it connected while they serviced customers, then disconnected it after 'a while'.

"Tanks are normally filled and sold by volume not pressure." PV = nRT

I mentioned this so you will be prepared when you go to buy them.

-jsw

I hope you have a good excuse for that, like heavy drinking, rather than senility.

On 3/17/2015 7:25 AM, Jim Wilkins wrote: ...

...

I wonder how they measure volume, if not by pressure! Especially since cylinders are often/usually filled from a manifold & many cylinders in parallel. Unless there is a flow gauge on each tank. Doesn't sound right to me.

Bob

Cylinder gas is sold by the volume when expanded at atmospheric pressure.

You can calculate the amount you actually received if you know the pressure, temperature and 'water' volume of the cylinder, or like packaged food you can just trust them.

-jsw

Probably both. 24 hours too, I bet.

Right, I know. That's why I wondered when your quote from the practicalmachinist said: "Tanks are normally filled and sold by volume not pressure." I'll repeat: how do they measure it if NOT by pressure?

Bob

I'm pretty sure they measure temperature and pressure to arrive at the volume of gas in the cylinder. But since the temperature may be different when you pick up the cylinder the pressure will vary. So on a cold day there is less pressure, a hot day more pressure, but the same volume of gas in all cylinders. Acetylene cylinders show a very wide pressure swing with changing temperature. That's why it is hard to know how much gas is really left in the acetylene cylinder unless you know both temp and pressure. Eric

Bob Engelhardt fired this volley in news: snipped-for-privacy@news6.newsguy.com:

Bob... pressure AND temperature.

A bit of simple algebra does it for the one-timer, but they have tables of the pressure they need to make at a given ambient temperature and filling time (and thus, the presumed heating of the contents during pump-up) to make the STP volume.

Lloyd

I put the Ideal Gas Law equation, without comment, under that quote to see if anyone caught on that I disagree with it.

Yeah, it was Sheldon/Amy humor.

-jsw

The little I've seen suggests they hook the cylinder to a hose from the manifold and just leave it for a while, hopefully long enough for it to fill and cool to loading dock temperature. It's hard enough to get a good answer on welding from them, I won't even try physics or chemistry.

-jsw

Loved 'em.

Kinda like this guy with a tanker truck?

I don't drink, so it can only be attributed to a creative streak.

Wow. So many people with good sense unemployed. And that guy's got a job. Well....maybe not now.

What about by weight -- if there is a tare weight stamped on the cylinder. Not sure how that would work with acetylene howeer, with all that liquid acetone in there.

Enjoy, DoN.