Flame Advancing Up A Fuel Supply Line?

My father-in-law said he has a small propane grill. The canister of LP (I assume, or butane?) is sized for like a small blowtorch. Anyhow, he told me how he went to use it during the blackout caused during the hurricane…and flame started to propogate up the small connection line towards the fuel source.

I have heard of this happening, but I forget why. Is it a possibility when there is low pressure in the tank? What are the causes, and how can one prevent it? - Jinx

I have a question: What does “propagate up the small connection line” mean? Isn’t the supply line opaque, probably metal? If so, how could one tell that the flame was advancing, presumably, on the inside of an opaque tube?

Unless you’re saying the flame was advancing on the outside.

Do clarify…

Flames cannot travel “up” fuel lines. Fire requires both fuel and oxygen. Unless you somehow managed to mix air into the fuel, it can’t burn until it leaves the line. Otherwise, use of an Acetylene torch would be a very iffy proposition. And just having low pressure would not allow this to happen until it was down to atmospheric pressure.

(Exception: Anything can happen in the movies.)

  1. It could happen. 2 leaks in the line would be needed. The one nearest the bottle to let in air and the other to vent fuel. Highly unlikely. The fuel nearest the grill would have to ignite first and the fuel in the line would have to be at a low enough pressure to let air into the other line.

  2. Odds are he had a leak at a fitting near the grill and there was a spark or heat to ignite the leak and then the flame traveled ‘up’ the line beacuse thats how the bottle was oriented or there was a drip loop with liquid fuel on it.

Unfortunately, we may never know. I will try and ask him what he observed and what other details he may recall - like how he discovered it, etc. However, he is not one for details, so I do not expect to get much out of him.

I vaguely recall once hearing of some kind of siphon effect that can occur causing such an event. But again, it is just one of those things you hear in passing. Maybe someone else who has heard this can share whatever details are known.

  • Jinx

It still won’t work. Gases and fluids flow from high pressure to low pressure. For air to enter the near leak, it would have to be below atmospheric. Therefore, the tank would have to be very subatmospheric. Can’t be done. The best you could do is have pressure so low you got a flame front at the exit that sputters in and out of the end of the pipe. As soon as the flame front gets inside the line, it smothers and pushes back out.