Select to indicate that the flange material is same as the attached shell material for an integral weld neck or reverse type flange. The larger of the shell allowable and the flange allowable are used to compute the required small end hub thickness for the integral flanges. Otherwise only the flange allowable will be used.
For some materials with relatively low yield strength (e.g. stainless steels), the ASME code has established higher stress values. These higher stress values (indicated by the presence of the note g5) can lead to higher deformation. These material allowables are not used for applications where deformation can cause failure such as flanges.
There could be a case where the flange allowables are lower as compared to the attached shell, for the same material. But, the small end hub thickness is checked as a cylinder so the allowable stresses of the attached shell should be used. Otherwise, the hub required thickness may be more than that of the attached cylinder. If you want the (higher) shell allowables to be used then check this box.