SP-25-2013

Standard Marking System for Valves, Fittings, Flanges, and Unions (ANSI-approved American National Standard)

This marking system applies to valves, fittings, flanges, and unions used in piping connections which include (but are not limited to) flanged, soldered, brazed, threaded, or welded joints.
The markings specified within this Standard Practice serve to identify the manufacturer, the rating designation, materials of construction, and special service limitations imposed by the manufacturer. They are used for product identification and to assist in proper application.