To throw a little bit more data into the pot about the K-37 boiler design, in the 5 years that 491 has run at the museum (with stays that ran on the grande for god knows how long), only one has needed replacement. It was even suspected that the bolt had not cracked in service at the museum, but rather many years ago and had only begun leaking as a result of better boiler treatment causing old scale to finally let go/erode away.
That said, 491's boiler also has some stays that have a fairly high loading- high enough that a reduction in boiler pressure was required for the engine to meet a safety factor of 4 (no, we don't need to, but we try to anyway- that's another can of worms). Those supporting the knuckle that joins the external firebox side sheets to the backhead are of particular concern. Earl, did the 497 exhibit any "favor" towards these bolts when some broke?
Stating the obvious, 491 doesn't work as hard as the 497 did on either the D&S or the C&TS, however the propensity of 497 to break bolts so much more frequently than other engines seems odd. Is it possible the 97 was just that much more worn out? Coupled with the tales of the engine riding so roughly, and the throttle being such a pig, it's become our impression in the shop at the museum that 497 was, plainly, a trouble case. Would anyone else who worked on 497 like to weigh in?
Edited 1 time(s). Last edit at 07/15/2019 12:02AM by Brett Wiebold.