ASME.BPVC.VIII.2 - Part 4.4 - Inelastic Buckling Stress

[vonMech]

Hello,

I am doing a minimum wall thickness calculation for a vessel skirt using ASME BPVC Section 8, Division 2 - 4.4 Design of shells under external pressure and allowable compressive stresses. I am confused about Section 4.4.3.2 where you calculate the inelastic buckling stress. I think I understand the procedure in Section 4.4.3.2 but when you calculate the design factor FS, Fic appears to be limited to a maximum of Sy. IF Fic < Sy then you will never have an inelastic buckling stress…

Can someone explain the intent of Section 4.4.3.2?

Thanks