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I’m looking around trying to find something to back the current thinking about pure acetylene’s propensity to spontaneously explode over 30 psig. Clearly, we have some limits on use/storage/movement/and so forth, but the curious part of me really wants to know “how did we learn that?”. I mean, a scientific paper describing how exactly that was determined would be great. But I stumbled across the above.

It’s not the result of a high-pressure explosion of acetylene, but instead of one high pressure cylinder that outgassed (secondary to the collision), then combusted either against a vehicle’s hot exhaust or was ignited by a rich-burning engine.

Then all hell breaks loose.

You’d want an acetylene cylinder to outgas when it’s being boiled. Much more preferable. Outgassing with a dangerous but impressive flaming spire is significantly more agreeable (they have plugs that will melt to release the gas) than having the 250 psi steel bottle burst and release its high-pressure acetylene+acetone mix into a flames.

Rapid decomposition ensues.

Fine… explodiness ensues.

Those bottles weigh perhaps 60 kg. Empty, they’re perhaps 55 kg. If you knock the valve off of it, it’s a rocket.

Those rockets are not at all predictable in their paths. While you -do- see those impressive flame plumes behind them, it’s not the fire accelerating them. Any acceleration is entirely from the gas pressure inside the cylinder.

Scary stuff.

So what about oxygen bottles? Typically oxygen bottles are at slightly higher pressure than acetylene. About 2000 psi compared to acetylene cylinder’s 250 psig. Industrial, medical, aviation — with a few uncommon exceptions (low-pressure O2 tanks for example), oxygen bottles are typically charged to about 2000 psig.

It’s a bit scary to see what even a small medical-grade O2 cylinder can do when its valve is expeditiously detached from a 2000 psi tank… inside of an old-style ambulance. That little rocket very quickly added an extra window to truck’s metal box.

Fortunately, while oxygen isn’t flammable, it does tend to aide in combustion. Think Fire Triangle. Fire would have been horrifying.

Speaking of oxygen and fires, many years after I observed the result of what an unsecured O2 cylinder could do to an ambulance, there was a guy who once used LOX to rapidly (instantly?) create a ready to use BBQ grill by using a single match. Ah… here’s it is:

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