: It establishes a standard "visual method" for inspection, meaning it does not require complex non-destructive testing (NDT) like X-rays, though it can be supplemented by other MSS standards like SP-54 (Radiographic) or SP-93 (Liquid Penetrant).
The standard is most known for its collection of illustrating various surface irregularities. These photos allow inspectors to perform a side-by-side visual comparison with actual castings to determine if a surface condition is acceptable or rejectable. Key Features and Scope
– General texture based on the casting method. Where to Find the MSS SP-55 PDF mss sp-55 standard pdf
: Twelve types of irregularities are categorized, with five examples for each—two showing acceptable levels and three showing rejectable ones. Categories of Surface Irregularities
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. : It establishes a standard "visual method" for
– Linear fractures; generally never acceptable.
– Improper surface prep after a weld repair. Key Features and Scope – General texture based
– Blemishes from the cleaning or riser removal process.
– Ridges on the surface from mold sand cracking.
While the standard is widely used, it is a copyrighted document that must be purchased for official inspection use.