TWI Industrial Member Report Summary 646/1998
M R Kirby and B W Kenzie
This report from the Core Research Programme (CRP) contains a compilation of TWI staff knowledge and experience of the interpretation of ultrasonic time-of-flight diffraction (TOFD) data.
Background
The ultrasonic TOFD technique was developed for the UK nuclear industry during the 1970s to provide a more accurate ultrasonic method for measuring the through-wall height of planar flaws. Over the last decade a general increase in the understanding of the technique has resulted in its use for weld inspection in a wider range of industries, especially oil, gas and petrochemical. Further, the use of TOFD for initial flaw detection as well as accurate flaw sizing has become more commonplace due to the rapidity of data acquisition. This has resulted in the publishing of UK and provisional European standards for the application of the TOFD technique.
TWI has extensive experience of the TOFD technique for inspection of a wide range of materials and applications. However, the majority of the work has concerned examination of welds in ferritic steels including critical flaw sizing to provide data for fitness-for-purpose assessments. This report is intended for inspection personnel who have a basic understanding of the technique and provides guidance on the interpretation of TOFD data acquired primarily from plane geometry welds in ferritic steels. The report contains many useful hints and tips learned through TWI's experience of interpretation of TOFD data.
Objective
- To develop guidelines for accurate interpretation of images obtained from the ultrasonic TOFD technique.