Overview
EN ISO 23279:2017 - "Non‑destructive testing of welds - Ultrasonic testing - Characterization of discontinuities in welds" (ISO 23279:2017) is the CEN-adopted international standard that defines a systematic procedure to classify ultrasonic indications in welds as originating from planar or non‑planar discontinuities. It applies to embedded discontinuities and to indications from discontinuities that become surface‑breaking after weld reinforcement is removed. The document (third edition, 2017) supersedes the 2010 edition and provides a flowchart‑based classification method (Annex A) plus informative guidance on directional reflectivity and echo patterns.
Key topics and technical requirements
- Classification principle: Uses multiple parameters together - welding technique, geometrical position, maximum echo amplitude, directional reflectivity, echo static pattern (A‑scan), and echo dynamic pattern (envelope).
- Flowchart procedure: A staged decision process (five stages) standardizes classification:
- Stage 1 - exclude very low amplitude indications below the evaluation level (reference T, per ISO 11666).
- Stage 2 - high amplitude indications (≥ reference level + 6 dB) are assumed planar.
- Stage 3 - directional reflectivity criteria applied for longer indications (length thresholds defined by plate thickness); requires amplitude comparisons from different beam directions. Key numeric criteria: amplitude difference ≥ 9 dB for transverse‑wave angle‑beam comparisons, or ≥ 15 dB when comparing transverse angle‑beam with longitudinal normal‑beam.
- Stage 4 - echo static pattern (A‑scan) compared with a reference reflector to identify non‑planar reflectors (e.g., inclusions).
- Stage 5 - transverse echo dynamic pattern for crack‑type classification.
- Probe guidance: Recommends using the same probes for detection and characterization; matching wavelengths when comparing longitudinal and transverse probes.
- Applicability & limits: Stage 3 applies only to indications exceeding specific length relative to thickness (e.g., t for 8–15 mm; t/2 or 15 mm whichever larger for >15 mm).
- Normative references: ISO 11666 (acceptance levels) and ISO 17640 (techniques and assessment) are cited.
Applications and users
- Practical for weld inspection in pressure vessels, pipelines, structural steel, heavy fabrication, and maintenance where ultrasonic weld testing is used.
- Primary users: NDT technicians, welding inspectors, quality managers, inspection authorities, engineering firms, and laboratories that assess weld integrity and need to distinguish planar defects (e.g., lack of fusion, cracks) from non‑planar defects (e.g., inclusions, porosity).
Related standards
This standard provides a reproducible, criteria‑based approach to ultrasonic characterization of weld discontinuities, improving consistency and reliability in weld quality assessment.
