Damage Tolerance Approach for Estimation of the Remaining Life of 60 MW Turbine-Generator Shafts of Hydropower Plant - A Case Study

摘要

The structural integrity of the rotor generator and turbine shafts of a 60 MW hydro plant has been carried out through the application of advanced Phased Array Ultrasonic Technique (PAUT) and crack growth rate analysis. The size and orientation of the crack-like defects were evaluated by the PAUT technique. The multi-array ultrasonic sensor was scanned all over the accessible surfaces of the shaft through manual scanning. The scanning was performed in different diameter sections of the shaft. The complete volume of the shaft was evaluated through scanning in different patches made from the top to bottom portion of the shaft. The critical defects identified by this technique with their locations and orientation inside the rotor have been presented. The stress and fatigue life of the shaft under defect-free condition have been carried out by finite element analysis using the commercial code ANSYS Mechanical. The calculation of the remaining life of the rotor shaft was carried out based on the principle of fracture mechanics using the code FRANC3D. The residual life of the shaft was calculated based on the crack growth rate data of critical cracks close to the surface.