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. 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.
Axial view reveals crack locations in discs with axial-entry fir tree type blade attachment grooves.
Diagram shows typical stress corrosion cracking locations on steeple and rim area of low pressure steam turbine rotor. Finite element grid is used for disc keywey elastic-plastic analysis. Stress corrosion crack propagates in radial directions from the keywey crown of a shrunk-on disc. Nondestructive Evaluation SwRI offers numerous nondestructive evaluation techniques for inspection of turbine rotors, disc steeples, and keyways, including periphery ultrasonic, dye penetrant, magnetic particle, and eddy current inspection services. Focused beam search units provide a reliable means of detecting and sizing flaws without using conventional signal amplitude techniques.