Overview - ISO 17643:2015 (Eddy current testing of welds by complex‑plane analysis)
ISO 17643:2015 defines standardized eddy current testing (ECT) techniques for detecting surface‑breaking and near‑surface planar discontinuities in welds, primarily in ferritic materials (weld metal, heat‑affected zone, base metal). The standard prescribes use of complex‑plane analysis (vector display of amplitude and phase), applicable to coated and uncoated components during fabrication and in service (onshore and offshore). General principles of ISO 15549 apply unless otherwise stated.
Key technical topics and requirements
- Scope of inspection: Surface and near‑surface planar defects in ferritic materials; possible application to non‑ferritic materials via application standards.
- Personnel & procedures: Personnel should be qualified (ISO 9712 recommended) and follow written procedures (ISO 15549 guidance when required).
- Instrumentation: Instruments must support complex‑plane display, measure amplitude and phase, allow display freeze, and provide phase control with full 360° rotation in steps ≤ 10°. Frequency capability: 1 kHz – 1 MHz (instrument) with probe frequencies specified below.
- Probes:
- Absolute probes for coating thickness/material sorting: operate 1 kHz – 1 MHz.
- Special surface probes for ferritic welds: orthogonal/tangential coil assemblies, differential connection to reduce dependency on conductivity/permeability/lift‑off, operating 100 kHz – 1 MHz. Probe diameter selected to suit weld geometry; covers used during calibration.
- Calibration & accessories: Use a calibration block of the same material with EDM notches 0.5 mm, 1.0 mm, 2.0 mm (±0.1 mm tolerance), recommended notch width ≤ 0.2 mm. Use non‑conductive strips to simulate coatings.
- Procedure highlights:
- Measure coating thickness and material sorting relative to calibration block; ECT can detect cracks through non‑metallic coatings up to 2 mm (thicker coatings require demonstrated sensitivity).
- Optimize frequency (≈100 kHz recommended for ferritic welds), adjust gain so 1 mm notch ≈ 80% full‑screen, and verify 0.5 mm notch ≥ 50% of 1 mm signal.
- Evaluate signals using both phase and amplitude on the complex plane; scanning direction preferably perpendicular to expected crack orientation.
- Maintenance & verification: Equipment must have a valid calibration certificate (ISO 15548 series); perform functional checks at start/end and after condition changes.
Practical applications and users
ISO 17643:2015 is used for routine and special weld inspection, quality control during fabrication, in‑service inspections, and integrity assessments in industries such as oil & gas, petrochemical, power generation, and heavy fabrication. Typical users:
- NDT technicians and inspectors
- Welding engineers and quality managers
- Asset integrity and inspection teams (onshore/offshore)
- Calibration labs and NDT equipment manufacturers
Related standards (normative references)
Keywords: ISO 17643:2015, eddy current testing, weld inspection, non‑destructive testing (NDT), complex‑plane analysis, ferritic materials, calibration block, coating thickness.