I have a bottle of argon for TIG welding. They fill it to ~2000 psi, but of course the pressure will vary with ambient temp.
How warm an environment can I safely store this in before the safety relief valve blows and vents the pressure?
If it’s a relief valve, you don’t need to worry, it’ll just vent a little bit of gas until the internal pressure goes down to safe level. But most bottles have rupture discs, which I think is what you are talking about.
Let’s say they filled it to 2000 psi at 70F temperature, and the bottle warms up to 130F. That’s 294K to 328K; a 12% increase in absolute temperature. Approximating as an ideal gas, it will go up to 2240 psi.
I looked at the first data sheet for rupture discs (PDF) I came across on Google, and it seems to be saying a gas cylinder rated for 2015 psi will have a rupture disc with minimum rupture pressure of 3025 psi. Which implies you’re OK unless you put the cylinder in a 340F oven.
Also, your bottle is probably NOT rated for 2015 psi. I think most are rated for 3500 psi.
I’d imagine it would say right on the bottle what the max psi is.
I don’t know where the OP is, but I’m in Wisconsin. We regularly get temps above 100 and which time my garage probably hovers 10 degrees on one side or the other of it. I have a bottle of straight Argon and a bottle of 80/20 and, so far as I know, never had an issue with either of them.
If I’d thought about it, it may have been interesting to check the gauges and see how much they move over the course of a day or so (when not being used, of course).
I have to assume that if a full bottle, when exposed to temps that they would reasonably see, could be an issue, they wouldn’t fill them as much.
They’re designed to be kept outside, even in areas where they’ll regularly see 50 or 60 degree swings in 24 hours as well as having extended times below zero or over 100, there doesn’t seem to be an issue with it.
I can’t imagine how loud it would be if a rupture disc blew. Venting a little bit before putting on the regulator is damn near deafening.
On the dome of the cylinder, you should see a string of characters that starts with the letters “DOT” stamped into the bottle. Following that will be a code that signifies the cylinder type. Since this is argon, it is probably a steel cylinder, so that code will probably be something like “3A” or “3AA”. Finally, after the cylinder type, will be a 3 - 4 digit number that is the maximum service pressure (in psia) for that gas bottle.
Gas cylinders are pressure tested at least every five years at 5/3 of that marked service pressure, so if yours is marked, say, “2250”, then the bottle will have been tested to at least 3750 psia before it could be put into service. Most gas companies will fill to about 90% of that service rating, depending on the dew point of the gas.
Your gas bottle will be fine even if you’re welding outside in the hot sun.
OK, mine says “DOT-3AA2015”.
I’m asking because I was curious about picking up an argon bottle from the welding shop at lunch, and leaving it in my trunk all afternoon at work on a warm summer day. If you’re right about the bottle test pressure, and if scr4 is right about the burst disc pressure rating, then there shouldn’t be any issue - especially if I lay the rear seats down and open the windows and crack the trunk lid open a bit. Under those conditions, the bottle shouldn’t get warmer than 100F.
Thanks.
I know our gas cylinders are delivered on open trucks. Also, I know at least one rocket launch facility in New Mexico where they store their nitrogen and argon cylinders outdoors, strapped to the south wall of the building in full sunlight - and the safety officer there is about as strict/anal as they get.