I'll be very appriciated for your assistance to comprehend where did I get wrong with understanding of design rules of corner joints type (c) and (d) shown in fig. UW-13.2.
Based on the results of strength analysis the thicknesses of header elements are
tubesheet - 36 mm; top/bottom plates - 36 mm, end plates - 36 mm.
According to notes to type (d)(the corner joint of end plates):
a + b ≥ 2∙ts, whereas a ≥ ts, tp=min(6 mm, ts).
In that case b=ts and tp=6 mm. Besides, the size of the ledge under the end plates rim is 2 mm.
To meet the notes requirement the thicknesses of the tube sheet, top and bottom plates have to be increased:
b + tp + 2 = ts + tp + 2= 36 + 6 + 2 = 44 mm.
And here, I think, I made a mistake, cause if I apply this logic to the type (c) joint, than it appear that we can't weld plates of equal thickness!