STEAM TURBINE INTERNAL BLADES/DIAPHRAGM CORROSION AND FATIGUE FAILURES

摘要

The failure damage modes of mechanical steam turbines are classified in terms of main components of the steam flow path in either the rotating components such as rotor, groove, disk, and blade or in the stationary parts such as control valves, or bearings.This paper discusses case studies of turbine internal parts damage where the mechanism of failure / damage has been caused by one of the following: solid particles, water droplet erosion, thrust bearing heavy rubbing, corrosion fatigue blade failure, diaphragm and blade and rotor disk failure. For urgent plant recovery and/or to minimize the duration without a spare rotor, a damaged turbine has to be repaired as quickly as possible. In order to repair the catastrophically damaged turbine rotor as an emergency spare, a new welding technique has been developed based on risk analysis of repair and laboratory element tests. The author introduces methodologies for repairing rotors by special welding procedures to find the optimized welding condition. They use detailed strength calculations to confirm the integrity, and perform a heat transfer analysis to assure proper heat treatment process conditions. These basic procedures are discussed to show the usefulness of such data. Finally, the typical repair cases of the revived rotor are introduced for large steam turbines and high speed steam turbines.