The thing is, you’re weakening the cylinder as you heat it. So instead of the torch just cutting through, the cylinder is likely to fail suddenly where you are heating it. So yeah removing the valve, or CAREFULLY drilling into it are a good idea.
yikes
ok well what was your objective?
like over here we use tanks to smuggle weed
yeah so I’m pisseed you give away our techniques?!
1 Like
Welcome to BoingBoing, Stranger and Strange Person!
6 Likes
Yeah, but again, if you have a basically empty tank (same air pressure as surrounding air) heating up and weakening the metal I think would still result in pretty much nothing happening. The added pressure from the heat has got to be minimal. Now I want to mythbuster this.
Still, if I were doing it, I’d take the valve off.
“Sh*t! I better kick it…” 
1 Like
It depends on what has been in the cylinder. Inert gases like argon will be harmless, but I’d be cautious about flames anywhere near flammable gases, especially ones that have tendency to detonate. Few years ago a scrap metal worker in my town was gravely injured, when acetylene from the cutting torch accumulated and detonated in home furnace that was being cut for scrap. The acetylene was at atmospheric pressure, and still explosion was so powerful, that pressure wave could be felt in my workshop, nearly a kilometer form the place of accident. The worker survived, but has lost his limbs.
There’s also a lot of fatal accidents during cutting or welding steel drums, mostly to detonation of vapors inside, here are some examples (tragic, but SFW links):
https://www.public-health.uiowa.edu/face/Reports/REPORT-033.html
Flammable powders and dust can also ignite and detonate (even common flour or fine metal powders used in 3d printers).
1 Like
OK, fair point. I was thinking like propane, which I would think would be different. Granted its a gas, not liquid.
1 Like
You’re right, propane would probably deflagrate, especially with very rich mixture when air not yet entered the cylinder, but when air to fuel ratio is near stochiometric, all the bets are off 
Depends on the gas and the tank, actually.
Empty gasoline tanks are very very dangerous, and acetylene tanks are filled with cementitious foam, which is in turn saturated with acetone, which is in turn saturated with acetylene… which makes the tank behave differently depending on whether you’ve stored it right-side-up or not… and hydrogen gas penetrates some metals, of course, and sits inside the metallic molecular structure waiting for temperature changes… there’s a great many variables.
This is the ONLY reliably safe way I know of.
If you have a buried propane tank, you can run water into the fill, and burn off the gas as it is driven out by the water.
4 Likes
On the other hand, things like liquid nitrogen can be quite dangerous if mishandled, and not just from quick-freezing body parts. In particular, sealing up a liquid nitrogen tank is an extremely bad idea.
3 Likes
I’ve heard of people chucking in some dry ice, to let the CO2 drive out anything else that was there. Not sure I’d trust it, though. The one time I cut into a propane tank (to turn it into a forge) I used the water technique. And it was new from the store. And it was still unnerving.
2 Likes
Nice video. Yup, that’s what happens when the heads come off of unsecured gas cylinders, assuming they don’t hit other cylinders, tear up wiring and cause a fire, or take out a classroom of students.
I always get kinda wiggy around gas cylinders that aren’t tied down–and you see that all the time if you look for it–because one day my father, who worked in a university engineering lab, said “Get in the car, there’s a fire at the lab.” When we got to lab where my father worked, a fairly large four-story cinderblock and brick building, there was a five foot hole in the outside brick wall, a banged up gas cylinder maybe a 100 feet away, and a smoldering fire in the building being put out by the fire department. Apparently, one of dad’s students left a torch pilot light on, the pilot burned through canvas straps holding the cylinder up, the cylinder fell, lost its valve, went airborne in the main lab space, bounced off a few walls, and then tore threw a electrical box on the way out of the building. It made an impression on me at the time, in part because instead of seeing my dad as the nerd he is, I got to think “Cool, he works around dozens of bomb-rockets that might go off at any minute.”
9 Likes
Um, propane is a liquid- it’s formal name is Liquified Petroleum Gas (LPG).
Based on the video of that imgur gif (there was a youtube video of it that I saw some years ago) and the way it went up, I’m guessing that was a propane cylinder that some chucklehead thought was junk, and didn’t bother following normal protocols to ensure it was safe before using a torch to cut it open (which is why it burst into flames). when he kicked it, he sloshed around the liquid that was in the tank and rolled it around for the liquid to better escape, which is why it turned into a conflagration and destroyed a (probably expensive) excavator.
The idiot is extremely lucky he wasn’t killed. Hopefully he learned from the experience.
2 Likes
While in the pressurized container most of it is in liquid state, but once you depressurize it, propane rapidly boils and turns into gas. This continues until temperature is low enough that it stops boiling, or all of it changes into gas phase. At atmospheric pressure and room temperature propane is a gas.
Another bad idea is transporting liquid nitrogen tank in elevator. I see this all the time at university where I work.
2 Likes
That’s a great non-obvious hazard. It’s fine…unless the elevator gets stuck, then the nitrogen fills the elevator.
2 Likes
Inflammable means flammable? what a country
2 Likes
They did do that at my uni, but no one was allowed in the lift at the same time as the dewar.
Ah, the days of having free access to large amounts of liquid nitrogen, those were the days
3 Likes
Yes, right. Same as how C02 can be liquid, but will evaporate quickly into gas. Unlike say acetone I wouldn’t think there would be anything left if the valve was removed. Flush with water to make sure.
Granted my main experience with compressed air is CO2 and N2 and regular compressed air. (which I concede are non flammable.)
1 Like
It’s one of those Ye Olde English artifacts that the language is (in)famous for:
The in- of incombustible is a common prefix meaning “not,” but the in- of inflammable is a different prefix. Inflammable, which dates back to 1605, descends from Latin inflammare (“to inflame”), itself from in- (here meaning “in” or “into”) plus flammare (“to flame”). Flammable also comes from flammare but didn’t enter English until 1813. In the early 20th century, firefighters worried that people might think inflammable meant “not able to catch fire,” so they adopted flammable and nonflammable as official safety labels and encouraged their use to prevent confusion.
_from Inflammable Definition & Meaning - Merriam-Webster
Personally, if I see the word ‘inflammable’ I parse that as “tends to catch on fire at the drop of a hat; use extra caution.”
4 Likes
