Life extension strategies of cracked disk attachment for low pressure steam turbines
- Stress Technology Inc., Rochester, NY (United States)
- Public Service of New Hampshire, Manchester, NH (United States)
- Electric Power Research Inst., Palo Alto, CA (United States)
This paper presents a computational approach for the life extension strategy of a cracked disk attachment region for a low pressure steam turbine stage operating in a wet steam environment. The strategy is based on a drop-notch approach to remove the existing stress corrosion cracking. The drop-notch procedure is to remove the top hook of the disk attachment and machine new grooves on the existing rim. The blade root would then be correspondingly dropped. The in-house finite element code BLADE is used for the steady stress, modal analysis and dynamic response studies and a fracture analysis code FRANC is used for the stress intensity factor estimation. Crack growth mechanisms of stress corrosion cracking, low-cycle corrosion fatigue, and high-cycle corrosion fatigue are considered to predict the remaining life of the existing cracked disk as well as the disk after the drop-notch approach are implemented. The life time prediction of the disk attachment is accomplished by using the initial crack size together with the computed crack growth rates and critical crack size. Results are shown for a last stage steeple drop-notch of a low-pressure steam turbine. It was predicted that the drop-notch approach can significantly increase the life of the disk and reduces the need for the rotor replacement.
- OSTI ID:
- 82743
- Report Number(s):
- CONF-941007--; ISBN 0-7918-1382-7
- Country of Publication:
- United States
- Language:
- English
Similar Records
Phased array ultrasonic approach to turbine blade attachment inspection
Blade root attachment evaluation low-cycle fatigue estimates based on probabilistic approach