Calculation methodU.K.
16.—(1) The minimum thickness of pressurised parts must be calculated having regard to the intensity of the stresses and to the following provisions—
(a)the calculation pressure to be taken into account must not be less than the maximum working pressure PS selected;
(b)the permissible general membrane stress must not exceed the lower of the values 0.6 ReT or 0.3 Rm and the manufacturer must use the ReT and Rm minimum values guaranteed by the producer of the material in order to determine the permissible stress.
(2) Where the cylindrical portion of the vessel has one or more longitudinal welds made using a non-automatic welding process, the thickness calculated as referred to in sub-paragraph (1) must be multiplied by the coefficient 1.15.
(3) In this paragraph—
(a)“ReT” means the yield strength in N/mm2, which is the value at the maximum working temperature Tmax of any of the following—
(i)the upper yield point ReH in N/mm2, for a material with both a lower and an upper yield point;
(ii)the 0.2% proof strength Rp0.2 in N/mm2;
(iii)the 1.0% proof strength Rp1.0 in N/mm2, in the case of non-alloy aluminium;
(b)“Rm” means tensile strength in N/mm2.