| Standard | Focus | Relationship to MSS SP 55 | |----------|-------|----------------------------| | | Surface quality of steel castings | Primary document | | MSS SP-25 | Marking systems | Used alongside for traceability | | ASME B16.34 | Valve dimensions & pressure ratings | Requires valves to meet MSS SP 55 surface quality | | ASTM A703 | General requirements for steel castings | References MSS SP 55 as an option | | ISO 4990 | Steel castings general requirements | Similar but not identical to MSS SP 55 | | AWS G1.10M | Casting surface evaluation | Alternative standard using different acceptance levels |
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Non-metallic materials (such as slag, oxides, or molding sand) trapped within the casting wall or on the surface. These can weaken the structure or cause leakage if they bridge the pressure boundary. 4. Type D: Gas Porosity and Blowholes | Standard | Focus | Relationship to MSS
Because the standard relies heavily on high-quality images, the PDF format is particularly valuable—it preserves the resolution and clarity of reference photographs, which printed copies may degrade over time. These can weaken the structure or cause leakage
The ANSI/MSS SP-55-2025 standard provides a visual method for evaluating surface irregularities in iron and steel castings for valves, flanges, and fittings, utilizing 60 reference photographs. Released in April 2025, this updated standard covers 12 types of casting defects, defining acceptable and unacceptable quality levels. Secure the official PDF from the Manufacturers Standardization Society (MSS) . MSS SP-55 - Manufacturers Standardization Society
Shrinkage cavities are voids formed as the molten metal transitions from a liquid to a solid state and contracts. While deep shrinkage requires volumetric testing, surface-accessible shrinkage cavities are evaluated visually. MSS SP-55 establishes limits based on the depth and total area of the cavity. Type 3: Sand Inclusions