ASME VIII div 1 ug-34 (f) Continuation of shell option 1

[colin51]

I am working on a pressure vessel sub-assembly that requires a flat head welded into a nozzle 17.5" dia.
Due to the wall thickness I will have an extended skirt from ASME VIII div 1 ug-34 (f) Continuation of shell option. The shell thickness shall be maintained along a distance inwardly from the inside face of the head. What is the rational for determining the inside face.

 

[GenB]

on some special cases you may have a different wall t shell inwards, so this is a warning, Code allows to calc by this formula but keep the shell t at least ??? inwards,
means you are not allow to thin the shell . not outside skirt. genblr