Question about the actual pressure rating on some older ASME plates

I was looking at a 1970s boiler in an old mill building last week and the stamped MAWP was way higher than I expected for the shell thickness. Did some digging in an old code book and found out the allowable stress for some grades of steel was nearly 20% higher back then. Anyone run into this and had to explain it to an inspector?

2 comments

2 Comments

simonl8621h ago

Old codes are old for a reason. That higher stress rating was a mistake they fixed. Inspectors should just use the current book.

perez.barbara15h ago

Hold up, are we sure it was a "mistake" and not just them being extra careful back then? I've seen old houses built to those specs still standing solid after storms that wrecked newer places. Maybe the old number had a bigger safety cushion for stuff we don't even test for now, like decades of wear. Just slapping the new code on everything feels like we might be cutting it too close sometimes.