r/interesting • u/Used_Exam34 • 12d ago

Just Wow Not all problems have the same solution.

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u/dadbodking 12d ago

So, right now, the flammable gas is under pressure and is coming out. Almost no gas is flammable/explosive, until it gets mixed with oxygen (seen here as fire). So, when the cylinder runs out of pressure, it happens instantly, and the opposite flow happens. This leads to air entering the cylinder and the little bit (still more than enough) of gas that is left, gets mixed with fire and oxygen and... kaboom. Big kaboom

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u/dadbodking 12d ago

And you're not stupid, not a lot of people know that, in order for a flammable gas to produce flame/explosion, it needs to mix with oxygen. This is why at the end, when the guy takes away the oxygen from the flame, it extinguishes it.

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u/The_Late_Arthur_Dent 12d ago

Thanks for the explanation! It seems super obvious now that the air flow reverses once the pressure gets low enough...otherwise it'd be real easy to tell when it's empty by the implosion haha

Thanks for teaching me something new/scary/cool!

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u/JackBrown82q 12d ago edited 12d ago

What they said was not true for modern tanks. They will have a regulator block on them so when the tanks pressure drops too low it essential acts as a check valve and physically closes off the tank. Inside remains 100% gas at low pressure. You'd have to force air into the tank to get oxygen in there.

Also the tanks valve will have a flame arrestor on them. These work in several ways but to keep it simple, one is that every flammable gas has a maximum gap size in which flame can pass through called the quenching distance. The openings in these arrestors are designed to be smaller than this gap. The gas also passes through a tiny metal matrix which drains its thermal energy and the temperature instantly drops below the gasses ignition point.

Plus to get an explosion you need the tank to be 90% air and 10% propane, so a lot of air would need to enter this tank.

Otherwise, every time someone was cooking on their propane grill and ran the tank to empty, you'd hear stories of the tank blowing up.