Sizing of IGSCCs by crack-tip diffraction technique

The Electric Power Research Institute, through its Non-Destructive Evaluation Center, conducted a round-robin sizing exercise to test the accuracy of the size estimates of inter-granular stress corrosion cracks (IGSCCs) made by inspectors using manual ultrasonic techniques. The results show the following: the number of teams doing an adequate job is much lower than anticipated; the range of performance from best to worst is very large; the advanced techniques provide verification that the crack-tip diffraction sizing approach is the most viable method; the influence of the ultrasonic measurement uncertainty to the flaw evaluation results must be assessed on case-by-case basis; and corrective actions are needed. The recommended corrective actions are: develop and implement a training program for people who size IGSCC; implement a qualification program that requires all people who perform sizing operations to demonstrate their capability prior to making field measurements; and accelerate completion, evaluation, and deployment of advanced systems. The present program is the result of the accelerated development of the crack-tip diffraction sizing technique. The immediate objectives of this program were: 1) to develop computerized techniques that result in being able to make reliable and reproducible estimates of crack depth using the crack-tip diffraction technique, and 2) to prepare an off-line service capability for sizing IGSCCs for the utilities