Eddy current inspection of axial cooling holes in generator rotor teeth
- Tennessee Valley Authority, Chattanooga, TN (United States)
During the rewind of a 43 inch generator rotor, cracks were detected in the axial cooling holes used to vent hydrogen from below the retaining rings. The holes are located in each tooth directly below the shrink fit area of the rings. TVA has a fleet of twelve units and one spare with this rotor design. To understand the root cause of the cracking, finite element stress analysis and fracture mechanics critical flaw size/crack growth models were built. To confirm the structural models and support decisions on run/repair/replace for these rotors. TVA needed to establish the presence of cracks, the crack lengths, and their propagation with time. Crack detection and sizing using non-destructive testing is necessary to ensure safe operation and prevent unnecessary or premature rotor replacement. A semi-automated eddy current technique was developed to meet this requirement. This paper describes the process used to select the NDE technique, develop the equipment to perform the examinations, and the calibration and examination procedure. The detection capabilities and the method of crack sizing are presented. The paper concludes with a summary of findings from the examination of fifteen rotors and the plans for future monitoring of crack growth.
- OSTI ID:
- 549975
- Report Number(s):
- CONF-961006-; ISBN 0-7918-1796-2; TRN: IM9753%%50
- Resource Relation:
- Conference: 1996 international joint power generation conference, Houston, TX (United States), 13-17 Oct 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 international joint power generation conference: Proceedings. Volume 2; PWR-Volume 30; Kielasa, L. [ed.] [Detroit Edison Co., MI (United States)]; Weed, G.E. [ed.] [Eastman Kodak Co., Rochester, NY (United States)]; PB: 936 p.
- Country of Publication:
- United States
- Language:
- English
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