Linear fractures caused by internal or external stresses. Usually never acceptable Voids caused by metal contracting during solidification. Sand Inclusions
It is referenced extensively in valve and piping specifications (such as API 600 and ASME B16.34) to define what a "commercially smooth" casting looks like.
| Standard | When to use instead of or with SP-55 | |----------|--------------------------------------| | | Quality standard for steel castings – magnetic particle & liquid penetrant | | ASTM A802 | Visual acceptance of steel castings (similar but different photo reference) | | ISO 11971 | Visual examination of steel castings (international equivalent) | mss sp55 standard pdf work
💡 The PDF includes a “Surface Discontinuity Acceptance Chart” – bookmark this page for quick field reference.
MSS SP-55, titled "Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components - Visual Method for Evaluation of Surface Irregularities," provides a standardized system for identifying and classifying surface defects. It is primarily used during the manufacturing and procurement process to ensure that castings meet acceptable quality levels before they are put into service. How the Standard Works Linear fractures caused by internal or external stresses
View the reference photos closely to compare micro-surface textures with the physical casting.
Disclaimer: This article is for informational purposes. Always refer to the official MSS SP-55 document for binding criteria. Standards are subject to revision; ensure you have the current version. | Standard | When to use instead of
Many inspectors only look at the surface footprint of a pit. The standard also implies depth relative to the casting wall thickness. A shallow pit 1/4" wide might be acceptable, but a deep pit of the same width could be a reject.