Question: What is the reason that the tubes extend like that?
Hypothesis: Is it that after material (metal) of the pipes weakens from the heat, it becomes pliable? An explosion will cause outward force which will stretch the weakened pipes?
Hypothesis: Is it that after material (metal) of the pipes weakens from the heat, it becomes pliable? An explosion will cause outward force which will stretch the weakened pipes?
In the photos where the boiler failed in the middle, they just get bowed out from the pressure.
Something the article mentioned was running out of water. As you said, the metal overheats and gets soft because water isn't there to absorb the heat by being turned into steam. So you get either an internal leak or explosion (depending on severity).
The Union Pacific has "Big Boy" 4014 running again. It is traveling with three tenders with water and fuel (but mostly water), because the infrastructure isn't there any more for steam locomotives to refill along the tracks.