The Boiler and Pressure Vessel Code, Section IX The Boiler and Pressure Vessel Code, Section IX covers rules for the qualification and requalification of welders, brazers, and welding, brazing and fusing machine operators so that they may perform welding, brazing, or plastic fusing in the manufacture of components. Welding, brazing, and fusing data cover essential and nonessential variables specific to the joining process used.