Estimation of efficiency of vibration damage detection in stepped shaft of steam turbine

The vibration based damage detection has practically no alternative as applied to the rotating shafts of steam turbines during operation. However, taking into account the heavy operating conditions of turbines and the complex shape of the turbines shaft, the choice of most effective method of vibration diagnostics is not an easy problem. To solve this problem, there was developed a relatively simple procedure of comparative evaluation of the effectiveness of vibration diagnostics of damage. The procedure is based on the determination of the change of shaft's compliance caused by a crack with the use of linear fracture mechanics. It was demonstrated as applied to the stepped rotors and shafting of steam turbine. The comparative analysis of efficiency of vibration diagnostics was performed based on the change of natural bending, longitudinal or torsional frequency of vibration to detect transverse or longitudinal crack in rotors and shafting of steam turbine K-200-130.