ISO 16828:2025

Overview

ISO 16828:2025 - "Non‑destructive testing - Ultrasonic testing - Time‑of‑flight diffraction technique for detection and sizing of discontinuities" defines the general principles for applying the TOFD (time‑of‑flight diffraction) technique. The standard focuses on detection and accurate sizing of discontinuities in low‑alloy carbon steel components, and it can be applied to other materials when geometry, acoustic properties and test sensitivity are appropriately considered. The document clarifies probe positions and scanning directions (useful for weld testing) and sets minimum requirements unless otherwise stated by referencing documents.

Key topics and requirements

• Principle of the technique: fundamentals of TOFD signal generation (lateral wave, diffracted signals, back‑wall echoes).
• Surface condition and couplant: requirements for acceptable scanning surfaces and fluid coupling.
• Materials and geometry: applicability to low‑alloy carbon steel and guidance for other materials with acoustical considerations.
• Personnel qualification: roles and competence in line with ISO 9712 for ultrasonic NDT certification.
• Test equipment: instrument/display requirements, probe specifications, characterization and verification (referencing ISO 22232).
• TOFD setup procedures: probe selection, probe centre separation (PCS), time‑window and sensitivity settings, scan increment and speed, system performance checks.
• Data interpretation: basic and detailed analysis methods for discontinuity characterization - position, length, depth/height estimation and required additional scans or algorithms.
• Complex geometries & limitations: treatment of obscured zones (lateral and back‑wall obscuration), accuracy and spatial resolution considerations.
• Test procedure and reporting: minimum procedural elements and required test report content; annex with reference blocks.

Practical applications

ISO 16828:2025 is used to implement robust ultrasonic TOFD inspections where accurate detection and sizing of cracks and other discontinuities are required. Typical applications include:

• Weld inspection and fabrication quality control (weld root/heat‑affected zones)
• Inspection of pressure vessels, pipes and structural steel in oil & gas, petrochemical, power generation and shipbuilding
• Condition monitoring and fitness‑for‑service assessments where precise sizing is critical

Primary users:

• NDT technicians and operators (TOFD practitioners)
• Inspection and quality engineers, NDT procedure writers
• Certification bodies and auditors
• Manufacturers of ultrasonic equipment and probes

Related standards

• ISO 16810 (Ultrasonic testing - General principles)
• ISO 16811 (Sensitivity and range setting - test object categories)
• ISO 10863 (TOFD techniques for weld testing)
• ISO 15626 (Acceptance criteria for welds)
• ISO 22232‑1 / ‑2 (Characterization and verification of ultrasonic instruments and probes)

Keywords: ISO 16828:2025, TOFD, time‑of‑flight diffraction, ultrasonic testing, non‑destructive testing, NDT, weld testing, probe centre separation, discontinuity sizing.