Thickness range for performance qualification (welder qualification test): ASME BPVC section IX has provided guidelines for the thickness range up to which a welder can weld. This can be found in Table – QW 452.1(b) of ASME BPVC Section IX (2017 edition). A simplified version of that table is given below; According to this table three important points can be drawn: The maximum thickness which a welder can weld is….