Overview
ISO 19232-3:2025 - "Non-destructive testing - Image quality of radiographs - Part 3: Minimum image quality values" defines the minimum image quality indicator (IQI) values required to ensure uniform radiographic image quality. The standard applies to both wire-type and step/hole-type IQIs (as detailed in ISO 19232-1 and ISO 19232-2) and covers the two radiographic testing classes A and B defined in ISO 5579. Minimum IQI values are specified across thickness ranges and for single-wall and double-wall radiographic techniques.
Key Topics
- Minimum IQI values: Tables 1–12 specify required IQI values (wire numbers W2…W19 and hole numbers H2…H18) versus penetrated thickness for single-image and double-image evaluations, and for testing classes A and B.
- Technique coverage: Single-wall (SWSI) and double-wall (DWSI/DWDI) radiography; IQI placement on the source side is preferred, with defined provisions when placed on the detector side.
- IQI arrangement and marking: IQIs should face the radiation source and be positioned on uniform-thickness areas. If placed on the detector side, the radiograph must show an “F” marking near the IQI.
- Image quality determination: Rules for evaluating wire-type (minimum continuous visible wire length of 10 mm or ≥20% of pipe diameter for small pipes) and step/hole-type IQIs (both holes visible when present). Viewing conditions follow ISO 5580 (film) or ISO 17636-2 (digital).
- Digital image requirements: Use uncompressed images with a zoom between 1:1 and 1:2 for critical analysis.
- Gamma source allowances: Permitted reductions in minimum IQI values when using Ir-192 or Se-75 are specified for certain thickness ranges; such exceptions must be noted in the report.
Applications
ISO 19232-3:2025 is used to:
- Establish acceptance criteria for radiographic inspections in manufacturing, construction, oil & gas, power generation, aerospace and transportation.
- Support weld inspection and pipe/pressure vessel evaluation (in conjunction with ISO 17636).
- Define contractual QA/QC radiography requirements and inspection procedures for NDT service providers and inspection authorities.
Who uses it:
- NDT engineers and radiographers
- Welding inspectors and QA/QC managers
- Certification bodies and regulators
- Fabrication and maintenance teams in heavy industry
Related Standards
- ISO 19232-1 (wire-type IQIs) and ISO 19232-2 (step/hole-type IQIs)
- ISO 5579 (radiographic testing basic rules)
- ISO 17636 (radiographic testing of welds)
- ISO 5580 (radiographic illuminators)
- Compatible alternatives: ASTM E747, JIS Z2306 (where material groups/dimensions fit)
This standard provides a clear, table-driven framework for consistent image-quality verification in radiographic NDT, improving comparability and reproducibility across inspections.