[Steam-engine] lap seam calculations

[steamman at ptdprolog.net]

Engine friends,

I just came from a show in Maryland. Spent 2 hours with the Chief Inspector 
and his inspectors going over the interpretation of their antique boiler 
code. I was limited to 100 lbs. operating pressure because of my lap seam 
boiler. In PA I'm allowed 125 lbs.  They refer back to the 1971 code for new 
construction of lap seam boilers. They will not even do any calculations for 
a lap seam boiler, they flat out say 100 lbs.

I'd like to know if anyone can calculate the difference from 125 lbs to 100 
lbs for a double riveted lap seam, What I'm really after is just how safe is 
100 lbs vs 125 lbs.  My last ultra sound on my crown sheet last year was .365 
around the fusible plug and found the lowest to be .310 in the rear left 
corner of the crown sheet. My stays are 4 15/16"x 5". It's a 1909 Frick 8 x 
10 and I very rarely work the engine. I ran a sawmill, thresher and a rock 
crusher once. I run a baker fan every so often for 15 minutes or so. Other 
than that I pull a sled just for show.

Lets here everyone's thoughts and comments