Because it is a copyrighted document, you can obtain the official standard from: ANSI (American National Standards Institute) IHS Markit/S&P Global
The foundational standard for valves requires visual examination of casting surfaces to comply with MSS SP-55.
– Rough, thin layers of metal fused to the casting surface, usually caused by mold erosion. mss sp-55 standard pdf
The standard classifies various surface conditions, such as: Surface Porosity (pinholes, gas holes) Inclusions (sand, slag) Cracks and Tears Scabs Surface Discontinuities . Visual Method of Evaluation
– Excess material left behind where molten metal entered the mold cavity. Inspection Methods Under MSS SP-55 The standard utilizes two primary methods for evaluation: 1. Visual Examination (VT) Because it is a copyrighted document, you can
According to the Steel Founders' Society of America (SFSA) , the standard defines two levels of surface quality:
If a defect matches or exceeds the "unacceptable" photo for its type, the part must be rejected or repaired. The 2025 Update: What's New? Visual Method of Evaluation – Excess material left
Inspectors evaluate the casting under adequate lighting with the naked eye.They compare any observed irregularities against the reference images provided in the official MSS SP-55 documentation. Acceptable vs. Unacceptable Ratings
In the piping, valve, and fitting industry, ensuring the integrity of cast components is paramount. Surface imperfections can lead to significant failures under pressure or in corrosive environments. is a critical, widely used industry standard that provides a visual method for evaluating surface irregularities in steel castings.
: Maintain detailed records of inspection results, including which reference photographs were used and the basis for acceptance or rejection decisions. This documentation is critical for traceability and dispute resolution.
The standard provides different degrees of severity for each type of defect. If the casting matches a photograph that is deemed acceptable within the allowed range, it passes inspection. If it exceeds the maximum permitted severity, it is rejected or requires repair. Key Features and Benefits