The welder qualification requirements fall into two parts—‘single qualification’ where the test weld is a
butt weld (each position being an essential variable) or ‘multiple qualification’ where a butt weld in pipe of
diameter and wall thickness equal to at least 6 5/8 in (168•3 mm) and 1/4 in (6•35 mm) respectively is
followed by the fitting and welding of a full size branch connection.