Phased array ultrasonic approach to turbine blade attachment inspection
- AEA Sonomatic, Inc., Charlotte, NC (United States)
- Inst. for Science and Technology, Fort Lauderdale, FL (United States)
- Electric Power Research Inst., Charlotte, NC (United States). Nondestructive Evaluation Center
In situations where particular combinations of material susceptibility, stress, steam conditions and steam chemistry come together, certain steam turbine rotors have exhibited stress corrosion cracking (SCC) on the disk side of the blade attachments, where the blades are held to the disk. Cracking has been most prevalent in multiple-hook, fir-tree attachment designs and normally occurs in the corners of the fir-tree hooks. While attempts have been made to perform ultrasonic inspection of the complex fir-tree attachment geometries, results have been mixed. False calls, poor repeatability, a general lack of resolution and lack of a meaningful sizing capability are standing issues. A unique approach to this inspection features a phased array ultrasonic test system that can both focus the ultrasonic beam and steer it to different points within the complex geometry. The focused beam leads directly to significant improvements in detection performance and resolution, as well as the ability to estimate the size of an indication. The ability to steer the beam to different points within the attachment enables comprehensive examination of all critical locations without repeatedly changing and calibrating numerous transducers. Together these features provide more rapid inspections and improved reliability.
- OSTI ID:
- 72639
- Report Number(s):
- CONF-931061--; ISBN 0-87170-506-0
- Country of Publication:
- United States
- Language:
- English
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