ISO 16827:2012

Overview

ISO 16827:2012 - "Non-destructive testing - Ultrasonic testing - Characterization and sizing of discontinuities" defines general principles and techniques for characterizing and sizing previously detected discontinuities so they can be evaluated against applicable acceptance criteria. The standard applies broadly to materials and applications covered by ISO 16810 and complements other ultrasonic testing (UT) standards. It covers both pulse-echo and transmission approaches and provides normative and informative annexes with practical sizing methods.

Key topics and technical requirements

• Purpose: Determine features required for evaluation - echo height, time-of-flight, shape, orientation, size (dimensions, area/volume), proximity to surfaces or other discontinuities, and probable nature (e.g., crack vs. inclusion).
• Surface condition: Surfaces should permit required sizing accuracy; recommended surface finishes include Ra = 6.3 µm (machined) and Ra = 12.5 µm (shot-blasted) as practical guidance.
• Pulse-echo techniques: Location, orientation, assessment of multiple indications, shape classification (simple and detailed), maximum echo height measurement, and a range of sizing methods:
  • Maximum echo height techniques (e.g., DGS / DAC concepts are discussed in informative annexes)
  • Probe movement sizing techniques (6 dB, 12/20 dB drop, beam-axis tip location, fixed amplitude methods)
  • Focussing probes and use of mathematical algorithms for estimating actual discontinuity size
  • Iterative and special sizing techniques (normative annexes)
• Transmission technique: Principles for locating and sizing discontinuities using through-transmission, including handling multiple discontinuities and amplitude reduction.
• Annexes: Normative and informative annexes provide detailed procedures - analysis of multiple indications, classification techniques, DGS/DAC, probe movement methods, iterative sizing, mathematical algorithms, tip-diffraction and SAFT examples.

Practical applications and users

ISO 16827:2012 is intended for practitioners who must reliably characterize and size flaws found during ultrasonic testing:

• NDT engineers and ultrasonic technicians
• Weld inspectors and quality assurance teams
• Industries: aerospace, oil & gas, power generation, pressure equipment, fabrication and manufacturing Practical uses include assessing whether detected discontinuities meet acceptance criteria for fitness-for-service, planning repairs, and informing fitness-for-purpose decisions.

Related standards

Key associated documents:

• ISO 16810 (UT general principles)
• ISO 16811 (sensitivity and range setting)
• ISO 16823 (transmission technique)
• ISO 16826 (discontinuities perpendicular to the surface)
• ISO 16828 (TOFD method)
• ISO 23279 (characterization in welds)

ISO 16827:2012 is essential reading for anyone performing ultrasonic sizing and characterization as part of a structured NDT program.