Several international round-robin exercises have taken place over the last two decades in this field. The first phase saw the validation of the technique as an accurate defect sizing tool. The second phase helped in confirming the usefulness of the technique as a rapid defect detection tool as well. The third phase involved the validation of TOFD as an alternative inspection tool leading to its widespread application in the industry. This phase saw the validation of TOFD for a wide range of applications which include, high temperature measurements, upto 200°C, duplex steel inspections, thin plate (6-15 mm) inspections and complex geometry inspections. Among other developments during this phase include the validation of TOFD for primary piping inspection confirming to the requirements of ASME XI, appendix 8, the publication of a British Standard for TOFD and the international validation by Lloyds Register to use the AEA Sonomatic TOFD procedures for the inspection of ferritic steel welds upto 300 mm. The fourth phase of trails underway at this moment should lead to the development of international standards for TOFD.

As a direct result of all these four phases, TOFD is widely being used as a solution provider for a wide range of inspection problems. This paper will discuss in detail the specific results of the various trials undertaken and look at the ramifications to the industry, if the conclusions are implemented. The significance of the practical experience gained through the various projects undertaken by AEA Sonomatic, the pioneers of this technique will be highlighted to assess the contribution of TOFD in improving inspection quality. The necessity of personnel qualification, standardisation and the ongoing development of acceptance criteria will also be discussed and analysed to identify future growth potential of this technique in the industry.