ISO 17640

Applies to: Manual pulse-echo UT of fusion-welded joints ≥8 mm wall thickness in metallic materials; testing levels A (routine monitoring), B (standard fabrication), C (full characterization); optimized for detection of planar defects (lack of fusion, cracks).

Does NOT cover: Phased-array UT (PAUT) — refer to ISO 13588; TOFD — refer to ISO 10863; automated UT; welds thinner than 8 mm; UT for in-service damage assessment (API 579-1 FFS framework applies).

• Calibration block per ISO 2400 (V1) or ISO 7963 (V2)
• Search unit frequency and crystal size selection based on material and weld geometry
• Reference amplitude established from side-drilled hole (SDH) or flat-bottomed hole (FBH)
• Scan plan and 100% coverage documentation
• Indication reporting threshold: echo amplitude 20% DAC or 6 dB below
• Indication sizing and characterization for Level C testing

ISO 17640 defines the manual UT procedure for fabrication weld inspection, complementing radiographic testing where planar defect detection is critical. UT is generally superior to RT for detecting lack-of-fusion and cracks aligned with the X-ray beam, making it the preferred method for thick-wall pipe girth welds and nozzle welds. Testing Level B is the standard reference for ASME B31.3 and EN 13480 piping fabrication.

Engineering note: Manual UT to ISO 17640 is being supplemented by PAUT (ISO 13588) on modern pipeline and pressure vessel projects due to PAUT's superior coverage and sizing capability. However, manual UT remains the most cost-effective method for routine butt weld inspection. For fitness-for-service assessments of in-service welds, supplement ISO 17640 with TOFD (ISO 10863) to obtain defect height measurements for fracture mechanics calculations.