A major feature of the ASME PCC-2 guidance is the calculation of required thickness , which must account for bending stresses caused by the eccentricity (the offset between the patch and the original shell). Standard Procedures & Specifications
For thick walls (e.g., >1.5 inches) or P-Number 4 materials (Chrome-Moly), the patch must be stress-relieved per ASME VIII. asme standard patched