ISO 19232-3:2013

Overview - ISO 19232-3:2013 (Image quality classes)

ISO 19232-3:2013 defines minimum image quality values for radiographic non-destructive testing (NDT) to ensure uniform and reproducible radiographic image quality. It applies to both wire-type and step/hole-type image quality indicators (IQI) (as referenced in ISO 19232‑1 and ISO 19232‑2) and to the radiographic techniques described in ISO 5579. The standard specifies required image quality for two radiographic technique classes (Class A - basic; Class B - improved) and provides tabulated IQI values for single‑wall and double‑wall radiography with IQIs placed on the source or detector side.

Key topics and technical requirements

• Image quality classes: Defines Class A and Class B minimums for single‑wall and double‑wall techniques. Tables list IQI values (wire and step/hole) versus penetrated or nominal thickness.
• IQI types and placement: Applies to wire‑type IQIs and step/hole IQIs. Preferred arrangement is IQI on the source side; if placed on the detector (film) side the radiograph must show an “F” mark near the IQI.
• Determination rules:
  • Wire IQI: the thinnest wire visibly continuous for at least 10 mm is the achieved image quality value.
  • Step/hole IQI: the smallest hole (or both holes in a two‑hole step) clearly visible determines the value.
  • Viewing and illuminator conditions shall comply with ISO 5580.
• Gamma radiography exceptions: Clause 7 provides agreed allowances (reduced IQI requirements) for Ir‑192 and Se sources under specified thickness ranges; these require contracting‑party agreement.
• Scope limits: Applies to film and digital detectors (detector term replaces film in this edition).

Practical applications and users

• Typical use: radiographic examination of metallic materials and welds to verify image quality for defect detection.
• Who uses it:
  • NDT technicians and radiographers performing X‑ray/gamma inspections
  • Welding inspectors and quality assurance (QA) engineers specifying acceptance criteria
  • Technical writers, procurement specialists and regulators referencing consistent image quality limits
• Benefits: Enables consistent acceptance criteria, reproducible IQI selection, clear pass/fail image quality evaluation for industrial radiography programs.

Related standards

• ISO 19232-1 - wire‑type IQI determination
• ISO 19232-2 - step/hole IQI determination
• ISO 19232-4, -5 - experimental evaluation and unsharpness methods
• ISO 5579 - radiographic examination basic rules (techniques A/B)
• ISO 5580 - industrial radiographic illuminators requirements
• ISO 17636 - radiographic testing of welds

Keywords: ISO 19232-3, image quality of radiographs, IQI, wire IQI, step/hole IQI, non‑destructive testing, radiographic technique, ISO 5579, gamma radiography.