I ran across this photo of a C&O explosion near Chillicothe, Ohio in 1948. Some further research shows that most locomotive explosions looked very similar, with the front half of the boiler being torn off.

What causes this particular pattern of damage? The classic failure mode is when the crown sheet above the firebox is exposed to dry steam, overheats, and fails. But how does that blow off the front of the boiler? I figured a crown sheet failure would blow out the firebox, and launch the boiler forward off the engine frame.

(boiler (full).jpg)

boiler (full).jpg (67KB - 71 downloads)