Critical turbine components must be evaluated to assure safe operation during their lifetime. Acccurate life assessment procedures, coupled with a knowledge of specific rotor material properties, prevent costly premature retirement of rotors. A high pressure steam turbine rotor in service for more than thirty years was subjected to remaining life assessment evaluation. Such evaluations are essential to determine how far beyond the design life these rotors can safely and reliably be operated. Test specimens, used to obtain critical material properties, are trepanned from aged rotor periphery at plane of balance.
Specimen blanks after trepanning.
Cracking occurs in LP rotor discs in keyways, in the blade attachment areas of the rims, on bore surfaces, and on web surfaces. Under a cooperative industry research project, funded by a consortium of electric utilities, SwRI has developed the technology required to make remaining life predictions for shrunk-on low pressure turbine discs. Heat transfer analysis and stress analysis determine shrink-fit stresses, thermal stresses, and stress due to blade and disc mass. Disc integrity and remaining life assessment are conducted and recommendations are provided to help determine run, replacement, or reinspection intervals. Cracking occurs in LP rotor discs in keyways, in the blade attachment areas of the rims, on bore surfaces, and on web surfaces.