It appears that #12 is gutted and undergoing a redesign. Understand the new FRA rules, however this was a "S" stamped boiler.
If they wish to maintain the "S" stamp it will need to be done in accordance with the NBIC and the redesign will need to comply to ASME Sec I. So a "Stamp Holder R/S" and AIA will need to be directly involved. Welding only is not enough.
If this boiler is to be run in FRA Jurisdiction it may or not matter. However, since it was constructed to ASME it may be a problem for a non FRA line. What does the Insurance Carrier say?
Hope someone has looked at this.
Dean D Cockroft