Crack depth measurements in stainless steel pipes - methods and reliability

It still is a challenging development goal to improve sizing of discontinuities by using NDT, since essential characteristics, as for instance crack depth extension, in many cases only can be evaluated within the scope of a large scale measurement: New NDT-techniques such as specially designed UT-probes to suit the test problem, and also a substantially extended theoretical background contribute to reliable statements concerning crack depth. The development of imaging UT-reconstruction methods will help to improve this situation. Practical experience with genuine testing problems are needed to judge the evidence of these methods. Experience with manual crack depth measurements is quite useful to create a practicable and reliable instrument based on reconstruction methods. (orig.)