ANCC M.14.1-1973 Supplementary regulations on the use of materials for the construction of pressure equipment operating under low temperature conditions
These provisions apply to materials to be used in the construction of pressure vessels whose members are subject to minimum temperatures declared in the design lower than - 10 °C, with the exceptions referred to in the following points a) and b), in which cases, specific provisions are not prescribed for the acceptance of materials and for the control of welding, without prejudice to the provisions in force for the acceptance of materials and for welding of equipment intended to operate at room temperature: a) materials to be used in construction of equipment intended to operate at temperatures between - 10 °C and - 30 °C provided that the materials are permitted for uses up to - 10 "C; the minimum calculation thickness, limited to sheet metal only, is not greater than 20 mm and the actual thickness is in any case not greater than 35 mm; the stability check under pressure conditions at the minimum operating temperature is satisfied by introducing in the calculation formulas, in place of the maximum allowable unit stress of the material, a value not exceeding 25% of this stress and, in any case, not exceeding 6 kgf/mm2; (b) materials to be used in the construction of equipment intended to operate at temperatures between — 10 "C and — 20 °C or between — 20 °C and — 30 "C or between — 30 "C and — 50 °C, provided that materials are allowed for uses up to - 10 °C; the minimum calculation thickness, limited to sheets only, is not greater than 20 mm, the stability check in pressure conditions at the minimum operating temperature is satisfied by introducing in the calculation formulas , in place of the maximum allowable unit stress of the material, a value not exceeding, respectively in the above temperature ranges, 75%, 50% and 25% of this stress and, in this last case, not exceeding 6 kgf/ mm2, the welded members of the appliance have in any case undergone a distension heat treatment.