found it........ Here's a quote from a British report...
"The occurrence of a decomposition is highly stochastic and unpredictable. It may be
initiated internally by a spark or small flame or externally by a mechanical shock or as a
result of external heating. In general it requires that a critical volume of the gas must be
raised to a temperature above 400°C. It may also occur spontaneously as a result of ingress
of a small amount of oxygen into the cylinder."
So I guess it's the heat of the flashback that gets to the cylinder that initiates the decomposition...The full report can be found here
What to do with Acetylene cylinders that are involved in a fire Interestingly, some European agencies recommend shooting holes in the cylinders to reduce explosion risk. Fun!!!
I've read the same reports. They're in lots of safety literature, not always with attribution.
I'm just going to assume that the anecdotes are true, and at that point, I have to think about what caused it.
I see two possibilities.
First, that oxygen had been forced all the way back into the acetylene cylinder. This is pretty unlikely, as it would have to get past the regulator, and in any case, the oxygen regulator pressure will be lower than the acetylene tank pressure (unless the oxygen regulator failed, and even then, I think that the burst of high pressure oxygen would burst a hose before it was able to force its way past the regulator). I don't think this is it, but it certainly could accelerate a flashback, back along the hoses, up to the acetylene regulator.
Second, that the acetylene has been driven to decompose by the energy of the flashback. My guess is that the pressure wave of the flashback starts off this reaction. The solvent and packing of the acetylene cylinder are there to prevent this, but give enough energy, decomposition can start, and since it is an exothermic reaction, once started, it will want to run away to the point of explosion. This happens all without oxygen present. Yeah, acetylene is capable of some bad things (and this is the tip of the iceberg; acetylene in copper pipes can be much worse).
I have slept since the last bottle change but I seem to remember a full 125 bottle coming in around 160-170psi. It was not hot either, in the shade in the low eighties. Whereabouts is the danger point with acetylene getting unstable under pressure (even with acetone)....I read something about that somewhere.
