Need some tips about plug headers construction

[niz88]

Hi everybody I am new to this forum, I would like to get some usefull tips about a construction of a header using the 'SA516 grad 60 plates'
well, I am trying to determinate the minimal required thickness of the plate to form this header according to the ASME VIII DIV1 2010 rules,Page 34, and I need to know how to choose the joint efficiency and joint type, knowing that I would like to weld the plug header only from the outside and I've chosen skecth 'C' from Fig. UW-13.2.

 

[GenB]

a+b twice the t of the shell , if shell is thinner, "a" can be the
t of the shell
and if shell is >1/4 then use"a" 1/4max

 

[Duwe6]

Thread 794-240454 "Box Headers"

Sect VIII-Div 1 appx 13 for material thicknesses.
Don't forget a corrosion allowance.