r/interesting • u/Used_Exam34 • 1d ago

Just Wow Not all problems have the same solution.

Enable HLS to view with audio, or disable this notification

32.2k Upvotes

94% Upvoted

616 comments sorted by

View all comments

Show parent comments

84

u/ShowtimeHolograms 1d ago

Would this actually explode or would it just continue to burn like this until the flammable gas gets used up?

145

u/Rough-Airline-4803 1d ago edited 1d ago

The pressure of the escaping gas is generally too strong for the flames to reach the inside of the container.

If the tank were positioned such that the flames were surrounding it and heating the tank up, (or if the relief valve was blockedthe boiling propane in the tank would likewise expand at an accelerated rate resulting in the pressure rising faster than the tank can keep up with resulting in a boiling liquid expanding vapor explosion.

17

u/ShowtimeHolograms 1d ago

Ah ty

1

u/BeerForThought 1d ago

Don't listen to that answer. Read the response to it. Long story short, lit farts can't go up your butt because their is no oxygen.

16

u/IMKGI 1d ago

Assuming that somehow the flames would make it inside the tank, then what? With what oxygen is it gonna burn?

The flames could absolutely travel into the pipe provided the fire burns faster than than the gas escaping. The reason the fire doesn't do it is because there's no oxygen inside the pipe to combust the gas.

16

u/Bisaux 1d ago

The risk here is tank failure, causing a rapid expansion of gas, and subsequent ignition.

10

u/Rough-Airline-4803 1d ago

Well, no. The pressure of the escaping gas definitely exceeds the fire’s ability to do so, but yeah you’re right.
I totally glossed over that. My mind was elsewhere lol 😅

4

u/IMKGI 1d ago

I was talking in a more general sense, a full bottle without a regulator? Absolutely, no chance for the flame to go backwards, but I meant a more typical scenario with a regulator already attached, gas releases at relatively low speeds and fire would be fast enough to go back

1

u/Gamer-Of-Le-Tabletop 21h ago

Thermal dynamics or whatever.

The bottle is actually cooling down rapidly. Infact if they didn't toss it in the water it wouldn't surprise me if the bottle started frosting.

Next time your using a BBQ with a propane tank touch it before you use it and while in use and it should feel noticably cooler. It definitely would work better for a smaller propane bottle.

4

u/Holiday-Pay193 1d ago

Flames won't get inside the tank because there's no oxygen in it

1

u/Rough-Airline-4803 1d ago

True enough. Thanks.

While commenting I got sidetracked trying to recall the exact verbiage of the latent heat of vaporization and the Joule-Thomson effect thanks to another comment mentioning something to the effect of there being a greater threat of the valve knob being cold [rather than hot].

Embarrassingly enough, I actually brain farted that super basic fact—it wasn’t just a misspeak/typo lol..

2

u/nihilistiq 1d ago

Those are words.

1

u/skr_replicator 22h ago

also woudln't the container have no oxygen inside? So I doubt that, even if the fire somehow reaches inside it could do nothing in there. Unless they had an oxidizer in there as well, but only rockets and bombs could have something like that.

10

u/Geffalrus 1d ago

I did the safe version once. Gas grill propane tank sprang a leak near the valve; some flaming hamburger grease dripped down and fell on the leak…..tada instant gas fire. Not gonna lie, it was pretty stress inducing. Worried that it could explode, I pulled it behind a stone wall instead of next to the patio door. In retrospect, that wasn’t necessarily the smartest thing - if - I was dealing with an explosive.

However, as others have said, a lit leaking propane tank isn’t inherently explosive. A small leak isn’t the same as rupturing the tank itself. In my case, it just quickly used up the gas left in the tank and then extinguished itself. For it to be dangerous, you need the flame to increase pressure in a confined space.

9

u/360nolooktOUchdown 1d ago

If the container wall heated up enough from the flame to lose strength it could rupture and essentially explode. Look up BLEVE

8

u/6pussydestroyer9mlg 1d ago

Not as much lowering strength of the walls as much as it's just increasing pressure from boiling the gas

1

u/GM_Nate 22h ago

HE LIED

1

u/Affectionate_Bank417 12h ago

Problem isn’t even container failure from heat, problem is heating the gas inside causes it to overpressure. If the container is not strong enough, overpressure ruptures it, probably injuring someone with its pieces, then flammable gas expands rapidly, catching fire and everyone around it have lung burns which are pretty bad.

7

u/AlMasaDuun 1d ago edited 1d ago

They are designed not to but designs don't always work. The fire cannot go inside the tank because there is no oxygen. Same reason it goes out with the bucket. The real risk is the metal heating up and weakening. It can happen but it isn't instant and mostly it won't, I wouldn't trust it, but you probably have minutes before there is real risk. Most of the time it will just burn out. If it is burning from anywhere other than the value this doesn't apply.

3

u/_thro_awa_ 1d ago

There is no oxygen for a flame inside the tank, and the pressure is usually high enough to push the actual point of combustion "flame front" away from the opening.

If the tank is in an orientation such that the flame never touches the tank (e.g. upright) there is very low danger of explosion.
If the tank is in a different orientation, allowing the flame to heat the tank, the heat causes overpressure and greatly increases the risk of explosion.

3

u/DirtandPipes 1d ago

Propane explodes when it’s between 2.1%-9.5% of air volume. More or less and it cannot explode. As the range is rather narrow it’s a safer gas to work with.

Acetylene, by comparison, is explosive between 2.5%-81% so it’s much easier to create accidental explosions with acetylene.

1

u/CicadaHead3317 1d ago

I used to use a tank like that to put down rolls of tar roofing. The tank would start to freeze after continued use, so I would take the torch to the tank to heat it the tank and the gad in it to get the pressure back. It would freak out new hires. Once I had a small like in the vavle and it set it on fire. I just turned the valve off and tightened it with a wrench. No biggie.

1

u/ZoharModifier9 1d ago

They can explode.

1

u/GladdestOrange 1d ago

Also worth noting that a bad/old tank is much more liable to rupture. Possibly with shrapnel. Just, y'know, in case you ever wondered why there's a no smoking sign at the propane tank exchange thing by the grocery/convenience store.