The MSS SP-55 standard, titled "Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components - Visual Method for Evaluation of Surface Irregularities", is the industry benchmark for the visual inspection of steel castings.
Casting defects are inevitable. Even with perfect gating and metallurgy, surface irregularities like cracks, scabs, laps, and cold shuts can appear. The critical question is: "Which defects are acceptable, and which require rejection?" mss sp-55 standard pdf