Well boys here is my theory..
Scene - Grain silo's next to the shed holding AN.
Any farmer or silo operator knows about 'dust explosions' from grain dust, I learned of this working on a sheep ship as an Electrical Officer 30+ years ago.
Dont believe me, stand back and throw a half handful of flour into the air over a camp fire, dont have anyone standing close, keep them behind you.
The sheep feed pellets produced a lot of dust and were moved around thru pipework with blowers, so keeping the motor switch gear clean and the any panels
was a big priority - a serious fire hazard.
In fact one ship had caught fire and sank in Bass Strait, with loss of a few human lives and a shipload of live stock for this very reason. Some may remember that event.
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I suggest that there was some loading or other work was being done with the grain from the silo's, a dust fire occurred and or dust explosions.
The first fires and bangs. This was largely uncontrolled even with fire fighting attempts.
The AN shed had possibly been damaged by those initial explosions and when mixed with heat and dust or carbon from the fires, it initiated detonation
of the AN stored in the adjacent shed.
Any other table top theories ?
:argh:
Terrifying as these incidents all are.