Quantification of NDE uncertainty by boresonic evaluation and destructive sectioning of steam turbine rotors
- Southwest Research Inst., San Antonio, TX (United States)
- AEA Sonomatic, Inc., Charlotte, NC (United States)
- Electric Power Research Inst., Charlotte, NC (United States). Nondestructive Evaluation Center
An EPRI project to quantify boresonic inspection uncertainty and to evaluate available boresonic inspection systems by comparing inspection results with natural defect characteristics has been completed. Two high-temperature, 1CrMoV steam turbine rotors retired from service because of unacceptable boresonic indications were selected for the project. Both rotors were thoroughly inspected utilizing non-focused, conventional boresonic systems plus one system utilizing focused, immersion boresonic technology. Additional inspections were conducted on a series of bore blocks with known artificial reflectors to help quantify the size of the indications detected in the rotors. Following boresonic characterization by all participating systems, a number of near-bore indications in the rotors were selected for destructive evaluation. The rotors were sectioned to extract twenty-one ultrasonic indications, and the coupons containing the indications were subjected to progressive sectioning and polishing for detailed metallographic characterization of the indications. Reflectors responsible for ultrasonic indications were evaluated under magnification to determine their axial, radial, and azimuthal dimensions. Metallurgical results from a small but representative sample of the indications analyzed are compared with boresonic data acquired from the selected indications. Results from the focused immersion system and the broad-beam contact systems correlated well with results obtained by destructive sectioning. A sizing factor of 2 is appropriate on the radial dimension of indications. No service-induced cracks were found. These indications were due to nonmetallic inclusion clusters and linear stringers which formed during the initial ingot manufacturing process.
- OSTI ID:
- 82741
- Report Number(s):
- CONF-941007-; ISBN 0-7918-1382-7; TRN: IM9533%%199
- Resource Relation:
- Conference: 1994 international joint power generation conference, Phoenix, AZ (United States), 2-6 Oct 1994; Other Information: PBD: 1994; Related Information: Is Part Of Advances in steam turbine technology for the power generation industry. PWR-Volume 26; Moore, W.G. [ed.]; PB: 337 p.
- Country of Publication:
- United States
- Language:
- English
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