After seeing the pictures, I too am amazed nobody was killed by that, or even seriously injured.
Reading that account is fascinating from a technical perspective. I've always been interested in the forensics of engineering failures.
What always amazes me is the audacity of the people involved in these problems:
"We know that the boiler is operating improperly and going into fail-safe. Instead of addressing these problems with proper maintenance, we'll bypass safety systems that allow the boiler to fail-safe. Then, knowing that the boiler is operating in an un-safe condition, we'll allow the alarm system to remain inoperative, and additionally, we'll let the boiler run unattended for considerably longer than would be allowed even if it were operating safely."
It's incredible the number of things that had to go wrong for that boiler to explode, and equally incredible that the people operating the boiler had absolutely no problem letting all those things go wrong. Honestly, while reading that it reminded me of the accounts of the series of technical and personal failures that lead up to the Chernobyl explosion.