ISO 20669:2017

Overview

ISO 20669:2017 - "Non-destructive testing - Pulsed eddy current testing of ferromagnetic metallic components" specifies the pulsed eddy current (PEC) testing technique for non-destructive thickness measurement of ferromagnetic metals. It covers in-service carbon steel and low-alloy steel components (including piping ≥ 50 mm diameter) across temperatures from −100 °C to 500 °C, wall thicknesses 3 mm to 65 mm, and coating thicknesses 0 mm to 200 mm. The standard defines principles, equipment, on-site procedures, influence factors and documentation, but does not set acceptance/evaluation criteria (these must be agreed contractually). It also excludes detection of cracks and local pitting.

Key Topics

• Principles of PEC testing: generation of pulsed electromagnetic fields, transmit/receive probe design, and analysis of decay curves (e.g., characteristic time, bending point, decay slope).
• Measurement ranges & limits: applicable metal/coating thickness and temperature ranges; sensitivity to component geometry - applying PEC outside scope may produce unpredictable inaccuracies.
• Equipment & probes: requirements for PEC instruments that generate pulses and separate transmit–receive probes; sensitivity adjustment and verification procedures.
• Influence factors: coating/insulation properties (conductivity, permeability, thickness), component material variability, temperature effects, probe selection, reference zone choice, vibration, and geometry.
• On-site testing procedures: documentation, site investigation, surface preparation, reference selection and recording, test execution, safety and result verification.
• Personnel & quality: qualification of operators, maintenance and verification of equipment, and mandatory documentation (test procedures, records, reports).
• Limitations: not suitable for crack detection or pitting evaluation; geometry knowledge required for reliable setup.

Applications

ISO 20669:2017 is designed for practical use where access or coating removal is difficult:

• Inspection of insulated or coated pipelines and pressure equipment in petrochemical, oil & gas, power generation and industrial plants.
• In-service thickness monitoring during operation (no coupling medium required).
• Situations requiring rapid screening of wall thickness through insulation or weather sheeting. Who uses it: NDT technicians and inspectors, asset owners/operators, integrity engineers, inspection service providers, and PEC equipment manufacturers developing procedures and calibration references.

Related Standards

• ISO 15548-3 (Eddy current equipment characteristics & verification)
• ISO 16809 (Ultrasonic thickness measurement)
• ISO 12718 (Terminology for pulsed eddy currents) These referenced standards support equipment verification, complementary thickness methods, and consistent terminology for PEC-based NDT.