Foreword

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This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee SC 3, Ultrasonic testing, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 138, Non-destructive testing, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition ( ISO 16828:2012 ), which has been technically revised.

The main changes are as follows:

title revised by removing “as a method”;
clarifications of abbreviations and symbols;
figures have been updated;
formulae have been corrected;
term "dead zone" replaced by "obscured zone".

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html .

Introduction

The following standards on ultrasonic testing developed by ISO/TC 135 are related.

ISO 16810 , Non-destructive testing — Ultrasonic testing — General principles

ISO 16811 , Non-destructive testing — Ultrasonic testing — Sensitivity and range setting

ISO 16823 , Non-destructive testing — Ultrasonic testing — Through-transmission technique

ISO 16826 , Non-destructive testing — Ultrasonic testing — Testing for discontinuities perpendicular to the surface

ISO 16827 , Non-destructive testing — Ultrasonic testing — Characterization and sizing of discontinuities

1 Scope

This document specifies the general principles for the application of the time-of-flight diffraction (TOFD) technique for both detection and sizing of discontinuities in low-alloyed carbon steel components.

This document also applies to other types of materials, provided the application of the TOFD technique is performed with necessary consideration of geometry, acoustical properties of the materials, and the test sensitivity.

Although this document is applicable, in general terms, for discontinuities in materials and applications covered by ISO 16810 , it contains references to the application on welds. This approach has been chosen for reasons of clarity as to the probe positions and directions of scanning.

Unless otherwise specified in the referencing documents, the minimum requirements specified in this document apply.

Unless explicitly stated otherwise, this document is applicable to the following categories of test objects as specified in ISO 16811 :

category 1, without restrictions;
categories 2 and 3, specified restrictions apply (see Clause 10);
categories 4 and 5 require special procedures, which are also addressed (see Clause 10).

NOTE Techniques for the use of TOFD for weld testing are described in ISO 10863 and the related acceptance criteria are given in ISO 15626 .

2 Normative references

3 Terms and definitions

4 Symbols and units

5 General

5.1 Principle of the technique

5.2 Requirements for surface condition and couplant

5.3 Materials and process type

6 Qualification of test personnel

7 Requirements for test equipment

7.1 General

7.2 Instrument and display

7.3 Probes

7.4 Scanning

8 TOFD setup procedures

8.1 General

8.2 Probe selection and probe separation

8.3 Time window setting

8.4 Sensitivity setting

8.5 Scan increment setting

8.6 Setting of scanning speed

8.7 Checking of system performance

9 Interpretation and analysis of data

9.1 Basic analysis of discontinuities

9.2 Detailed analysis of discontinuities

10 Detection and sizing in complex geometries

11 Limitations of the TOFD technique

11.1 General

11.2 Accuracy and resolution

11.3 Obscured zones

12 TOFD testing without data recording

13 Test procedure

14 Test report

Bibliography

ISO 16828:2025

Non-destructive testing. Ultrasonic testing. Time-of-flight diffraction technique for detection and sizing of discontinuities

Current

Published:

10 Jul 2025