EN ISO 11666:2018 PDF

Overview

EN ISO 11666:2018 - Non-destructive testing of welds - Ultrasonic testing - Acceptance levels (ISO 11666:2018) defines ultrasonic acceptance criteria for full-penetration welded joints in ferritic steels. The standard specifies two acceptance levels, Acceptance Level 2 (AL 2) and Acceptance Level 3 (AL 3), which correspond to ISO 5817:2014 quality levels B and C respectively. It is intended for ultrasonic testing (UT) carried out in accordance with ISO 17640 and applies primarily to welds of thickness 8 mm to 100 mm. Use outside these limits is permitted only when geometry and acoustic properties allow adequate sensitivity.

Key topics and technical requirements

• Acceptance levels: Defines AL 2 and AL 3 for UT; quality level D is not covered (UT is generally not requested for D).
• Scope of application: Full-penetration ferritic steel welds (8–100 mm); may be extended to other weld types/materials with careful consideration of acoustic behavior.
• Probe nominal frequencies: 2 MHz to 5 MHz recommended; other frequencies allowed when attenuation or resolution requirements demand them (use outside range requires justification).
• Sensitivity setting techniques (same technique for setting and testing):
  • Technique 1 - side-drilled holes (3 mm diameter)
  • Technique 2 - DGS curves for flat-bottomed holes (disk reflectors)
  • Technique 3 - DAC curve from rectangular notch (1 mm × 1 mm)
  • Technique 4 - tandem technique referenced to a 6 mm flat-bottomed hole
• Levels used (defined in ISO 17640):
  • Reference level
  • Acceptance levels (AL 2, AL 3)
  • Recording levels (4 dB below acceptance)
  • Evaluation level
• Discontinuity assessment:
  • Length measured using the fixed-amplitude level technique (Annex B)
  • Grouping rules and combined-length evaluation for adjacent indications
  • Requirement for additional beam angles or tandem technique when amplitudes below acceptance but lengths exceed thresholds (e.g., for 8 mm ≤ t