Steam Turbine Technology
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.
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Finite element grid is used for disc keywey elastic-plastic analysis.
Remaining Life Assessment
Critical turbine components must be evaluated to assure safe operation during their lifetime. Accurate life assessment procedures, coupled with a knowledge of specific rotor material properties, prevent costly premature retirement of rotors.
A wide range of finite element programs is used at SwRI to perform structural evaluations and remaining life assessment, including:
- ANSYS®: Structural analysis
- NASTRAN®: Structural analysis
- STRAP/SAFER: EPRI rotor integrity and life analysis
- BIGIF: EPRI fracture mechanics
- ADINA/ADINA-T: Structural/thermal analysis
- ABAQUS: Nonlinear structural analysis
- NESSUS®: Probabilistic structural analysis
The SAFER code calculates steady state temperature (oF) contours for a high pressure (HP) rotor (top). Steady state stress contours (psi) for an HP rotor are determined using the SAFER finite element code (bottom).
Low pressure (LP) steam turbine disc cracking caused by stress corrosion is experienced worldwide in rotors used in both nuclear and fossil fuel power plants. 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.