MSS · MSS SP-25

Classification and Marking of Pipeline Valves According to MSS SP-25 Standard

Technical Regulation for Pipeline Valve Marking

The MSS SP-25 standard defines unified requirements for the marking of valves, fittings, flanges, and flanged assemblies. This identification system covers all types of connections, including welded, threaded, flanged, as well as specialized soldered and bonded joints used in high-load engineering networks.

The primary goal of implementing this specification is to ensure full traceability of metal products throughout their entire life cycle. The marking allows for the unambiguous identification of the manufacturer, pressure class, size range, and chemical composition of the material, which is critical for preventing errors in the design and installation of mission-critical piping systems.

Letter Indices for Metal Alloys

Symbols for Non-Metallic Materials

Standard Designations for Threaded Connection Types