Originally adopted in 1961 by the Manufacturers Standardization Society (MSS) , this standard provides a uniform baseline for identifying and evaluating surface defects in steel pressure castings. Purpose and Scope of MSS SP-55
: The standard is designed for general use on any 4 in. x 5 in. (100mm x 125mm) area of a casting.
: It relies on a set of 60 reference photographs to help inspectors distinguish between acceptable and unacceptable irregularities. The 12 Types of Surface Irregularities
MSS SP-55 categorizes surface defects into 12 distinct types, providing five examples for each—two illustrating acceptable degrees and three illustrating rejectable defects. Description Acceptance General Rule Hot Tears & Cracks Generally not acceptable if visible. II Voids exposed after cutting risers. III Sand Inclusions Sand trapped in the molten metal. IV Gas Porosity Voids caused by gas entrapment. V Ridge-like features from sand movement. VI Depressions from mold surface buckling. VII Wrinkles & Folds Fusing issues like cold shuts. VIII Cutting Marks Marks from mechanical cleaning or burning. IX Slightly raised blemishes of sand/metal. X Evidence of incomplete fusion of chaplets. XI Weld Repair Areas Improper surface prep after welding. XII Surface Roughness General texture from the casting process. Comparison with CTI and SCRATA Standards
The is a critical document for the valve and fitting industry, officially titled the "Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components – Visual Method for Evaluation of Surface Irregularities."
MSS SP-55 includes a comparison table (Table 1) that correlates its acceptance criteria with other industry comparators, such as those from Castings Technology International (CTI) or the SCRATA standard. This helps manufacturers who may use plastic replicas (comparators) instead of photos to ensure they meet the minimum requirements of SP-55. Where to Find the Official PDF
The primary goal of the MSS SP-55 standard is to ensure that steel castings are free from surface irregularities that could compromise their structural integrity or performance. It is intended to supplement ASTM specifications like A216, A217, and A351 by providing a more detailed visual guide for quality control.
Because the printed version published by MSS is the "official" rendering due to variations in digital viewing environments, it is recommended to purchase the most current edition directly from authorized distributors: MSS SP-55-2001 - Peninsula Alloy Inc.
Originally adopted in 1961 by the Manufacturers Standardization Society (MSS) , this standard provides a uniform baseline for identifying and evaluating surface defects in steel pressure castings. Purpose and Scope of MSS SP-55
: The standard is designed for general use on any 4 in. x 5 in. (100mm x 125mm) area of a casting.
: It relies on a set of 60 reference photographs to help inspectors distinguish between acceptable and unacceptable irregularities. The 12 Types of Surface Irregularities mss sp 55 pdf
MSS SP-55 categorizes surface defects into 12 distinct types, providing five examples for each—two illustrating acceptable degrees and three illustrating rejectable defects. Description Acceptance General Rule Hot Tears & Cracks Generally not acceptable if visible. II Voids exposed after cutting risers. III Sand Inclusions Sand trapped in the molten metal. IV Gas Porosity Voids caused by gas entrapment. V Ridge-like features from sand movement. VI Depressions from mold surface buckling. VII Wrinkles & Folds Fusing issues like cold shuts. VIII Cutting Marks Marks from mechanical cleaning or burning. IX Slightly raised blemishes of sand/metal. X Evidence of incomplete fusion of chaplets. XI Weld Repair Areas Improper surface prep after welding. XII Surface Roughness General texture from the casting process. Comparison with CTI and SCRATA Standards
The is a critical document for the valve and fitting industry, officially titled the "Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components – Visual Method for Evaluation of Surface Irregularities." (100mm x 125mm) area of a casting
MSS SP-55 includes a comparison table (Table 1) that correlates its acceptance criteria with other industry comparators, such as those from Castings Technology International (CTI) or the SCRATA standard. This helps manufacturers who may use plastic replicas (comparators) instead of photos to ensure they meet the minimum requirements of SP-55. Where to Find the Official PDF
The primary goal of the MSS SP-55 standard is to ensure that steel castings are free from surface irregularities that could compromise their structural integrity or performance. It is intended to supplement ASTM specifications like A216, A217, and A351 by providing a more detailed visual guide for quality control. Description Acceptance General Rule Hot Tears & Cracks
Because the printed version published by MSS is the "official" rendering due to variations in digital viewing environments, it is recommended to purchase the most current edition directly from authorized distributors: MSS SP-55-2001 - Peninsula Alloy Inc.
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