ASME has been defining piping safety since 1922.



This standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60. Included are flanges with rating class designations 75, 150, 300, 400, 600, and 900 with requriements given in both SI (Metric) and U. S. Customary units, with diameter of bolts and flange bolt hole expressed in inch units.