49 C.F.R. § 179.202-4
Thickness of plates
The wall thickness after the forming of the tank shell and heads must be, at a minimum, 9/16 of an inch AAR TC-128 Grade B, normalized steel, in accordance with § 179.200-7(b).
The wall thickness after the forming of the tank shell and heads must be, at a minimum, 9/16 of an inch AAR TC-128 Grade B, normalized steel, in accordance with § 179.200-7(b).