Overview
EN ISO 15626:2018 - “Non‑destructive testing of welds - Time‑of‑flight diffraction technique (TOFD) - Acceptance levels” - specifies acceptance criteria for TOFD inspection of full‑penetration welds in ferritic steels with nominal thicknesses from 6 mm to 300 mm. The acceptance levels are aligned with the weld quality levels of ISO 5817 and apply to indications classified in accordance with ISO 10863. This EN version is the CEN adoption of ISO 15626:2018.
Key topics and technical requirements
- Scope and applicability
- TOFD acceptance levels for full‑penetration welds in ferritic steels, t = 6–300 mm.
- Acceptance criteria mapped to ISO 5817 quality levels.
- Relation to other standards
- Acceptance levels are defined relative to ISO 5817 (quality levels B, C, D) and use examination/indication classification from ISO 10863; vocabulary reference ISO 5577 is cited.
- Size definitions
- Length (l) and height (h) of indications are defined by coordinate differences (x- and z-coordinates).
- Length determination
- Techniques for elongated straight and elongated curved indications: fitting hyperbolic (arc‑shaped) cursors and defined cursor-placement procedures to measure indication length.
- Height determination
- Height must be measured from A‑scans with consistent cursor placement; recommended methods include:
- Method 1: transit time between leading edges
- Method 2: transit time between first peaks
- Method 3: transit time between maximum amplitudes
- Method 4: transit time between first zero crossings
- Acceptance levels
- Three acceptance levels are specified and mapped to ISO 5817 quality levels:
- Acceptance level 1 - corresponds to ISO 5817 level B (stringent)
- Acceptance level 2 - corresponds to ISO 5817 level C (intermediate)
- Acceptance level 3 - corresponds to ISO 5817 level D (moderate)
- Additional topics
- Rules for total length, grouping of indications and treatment of point‑like indications.
Applications and users
EN ISO 15626:2018 is intended for professionals performing or specifying TOFD weld inspections and for organizations that need harmonized acceptance criteria for weld quality. Typical users include:
- NDT engineers and technicians (TOFD specialists)
- Welding inspectors and QA/QC personnel in fabrication, pressure vessel, pipeline and structural steel industries
- Engineering firms, inspection bodies and construction contractors specifying weld acceptance criteria
Related standards
Keywords: EN ISO 15626:2018, TOFD, time‑of‑flight diffraction, NDT of welds, acceptance levels, ISO 5817, ISO 10863, weld inspection, ferritic steels.
