First adopted in 1961, MSS SP-55 was developed by the Manufacturers Standardization Society (MSS) to supplement ASTM casting specifications. It bridges the gap between general casting requirements and the specific visual quality needed for pressure-containing parts in industries such as oil and gas, power generation, and chemical processing.
: You can buy the official hard copy or PDF from the MSS Store or authorized distributors like the ANSI Webstore .
– Surface folds from incomplete metal fusing. mss sp-55 standard pdf
The standard classifies defects into to ensure inspectors use consistent terminology:
: The standard is intended for use on any 4 in. x 5 in. (100mm x 125mm) area of a casting surface. First adopted in 1961, MSS SP-55 was developed
The edition recently replaced the 2011 version. A major update in this version is the inclusion of iron and ductile iron castings , expanding the standard's scope beyond just steel. It also aims to align surface quality expectations more closely between manufacturers and purchasers in the broader piping industry. MSS SP-55 - Manufacturers Standardization Society
: Specifically covers steel and (in the 2025 edition) iron castings for valves, flanges, and fittings. – Surface folds from incomplete metal fusing
– Ridges on the surface from mold sand cracking.