179.100-6 Thickness of plates.

(a) The wall thickness after forming of the tank shell and heads must not be less than that specified in §179.101, nor that calculated by the following formula:

where: d = Inside diameter in inches; E = 1.0 welded joint efficiency; except for heads with seams = 0.9; P = Minimum required bursting pressure in p.s.i.; S = Minimum tensile strength of plate material in p.s.i., as prescribed in §179.100-7; t = Minimum thickness of plate in inches after forming.

(b) If plates are clad with material having tensile strength properties at least equal to the base plate, the cladding may be considered a part of the base plate when determining thickness. If cladding material does not have tensile strength at least equal to the base plate, the base plate alone shall meet the thickness requirement.