Overview
ISO 16827:2025 - "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, in general terms, to the materials and applications covered by ISO 16810. It covers pulse‑echo and through‑transmission ultrasonic testing approaches and notes that phased‑array techniques can also be used, although additional verification steps may be required.
Key technical topics and requirements
- Purpose: Determine ultrasonic parameters (echo height, time‑of‑flight), geometry (location, orientation, shape), sizing (dimensions, area/volume or representative parameters) and proximity to surfaces/other discontinuities.
- Surface condition requirements: Recommended surface roughness for accurate sizing - R = 6.3 μm for machined surfaces and R = 12.5 μm for shot‑blasted surfaces. Maximum probe‑to‑surface gap: 0.5 mm. Surface prep must not introduce excessive noise.
- Pulse‑echo techniques: Location, orientation, assessment of multiple indications, echo height, shape classification, and several sizing methods (maximum echo height, probe movement, focusing probes, mathematical algorithms, special and iterative techniques).
- Through‑transmission technique: Location and sizing approaches, treatment of multiple discontinuities and amplitude reduction evaluation.
- Sizing methods and validation: Normative and informative annexes provide detailed procedures - e.g., analysis of multiple indications, classification of discontinuity shape, maximum echo height sizing, probe movement sizing, iterative and algorithmic estimation methods.
- Traceability to acceptance criteria: Characterization techniques must be specified relative to the applicable acceptance criteria; ISO 16810 provisions apply unless otherwise stated.
Practical applications and who uses this standard
ISO 16827:2025 is used by professionals involved in ultrasonic non‑destructive testing (NDT) who need reliable assessment of discontinuities before making fitness‑for‑service or acceptance decisions:
- NDT technicians and inspectors performing sizing and characterization during inspections
- Quality and inspection engineers developing acceptance procedures and inspection plans
- Asset owners and operators requiring consistent evaluation of known defects in components such as forgings and castings (examples illustrated in the standard)
- Standards writers and test laboratories implementing validated ultrasonic sizing methods, including pulse‑echo, through‑transmission and phased‑array workflows
Related standards (for context)
- ISO 16810 - Ultrasonic testing: General principles
- ISO 16811 - Sensitivity and range setting
- ISO 16823 - Through‑transmission technique
- ISO 16828 - Time‑of‑flight diffraction (TOFD) for detection and sizing
Keywords: ISO 16827:2025, ultrasonic testing, non‑destructive testing, characterization, sizing of discontinuities, pulse‑echo, through‑transmission, phased array, echo height, time of flight.