In regards to the steam tractor explosion, I read the boiler
inspector's report in "Live Steam" magazine.  I think the operator
error was in running it at all.

There were pictures in the magazine of the firebox stay bolts and they
showed very little distortion, which meant that the firebox crown sheet
simply pulled off of the staybolts.  Where there was supposed to be so
many threads of the bolts holding the sheets there were very
little.  (Fire erosion?)

It was also stated that the safety valve would not have operated even
if the boiler could have ever gotten to that pressure without blowing
up.  It is unbelievable that the guy ever thought it would be safe and
equally unbelievable that he was willing to take the chance with his
own life and those of others.  I don't remember all the details and the
magazine is in the shop.

Tony Marsico