ISO 16828:2012 defines 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. It can also be used for 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 sensitivity of the examination.

Although it is applicable, in general terms, to 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 ultrasonic probe positions and directions of scanning.

Unless otherwise specified in the referencing documents, the minimum requirements of ISO 16828:2012 are applicable.

Unless explicitly stated otherwise, ISO 16828:2012 is applicable to the following product classes as defined in ISO 16811: a) class 1, without restrictions; b) classes 2 and 3, restrictions apply as stated in Clause 9.

The inspection of products of classes 4 and 5 requires special procedures. These are also addressed in Clause 9.

Techniques for the use of TOFD for weld inspection are described in ISO 10863.

The related acceptance criteria are given in ISO 15626.