ISO 17635

Applies to: Metallic fusion-welded joints subject to NDT; governs method selection and performance levels for RT, UT, PT, MT, and ET; used whenever a piping or pressure vessel code references the ISO weld NDT family.

Does NOT cover: Method-specific technique parameters (refer to individual standards ISO 17636, ISO 17640, ISO 17637, etc.); acceptance criteria specific to construction codes (refer to applicable code); resistance welds or electron beam welds.

• NDT method selection table by weld type, material, and joint geometry
• Testing level assignment (B, C, D for RT/UT; 1, 2 for PT/MT)
• Linkage of testing levels to construction code acceptance levels
• Personnel qualification requirement: ISO 9712 Level 2 minimum
• Coordination with welding procedure qualification records

ISO 17635 is the master reference that ties together the ISO family of weld NDT standards. Its method selection matrices and testing-level concept provide a systematic framework for constructing a weld NDT inspection plan, replacing the ad-hoc method selection that construction codes historically left undefined. The standard coordinates RT, UT, PT, MT, and ET into a unified inspection planning approach.

Engineering note: When building an inspection test plan (ITP) for an ISO-referenced piping fabrication contract, ISO 17635 is the starting document. Specify the testing level explicitly on the ITP — defaulting to "Level B" for butt welds in ASME B31.3 Normal Fluid Service is common practice. Ensure NDT contractor personnel hold valid ISO 9712 certifications for each applicable method.