Features of vibration-based damage detection in stepped shafts of steam turbines

Abstract

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 turbines shaft, the choice of most effective method of vibration diagnostics is not an easy problem. To solve this problem, a relatively simple method of comparative evaluation of the effectiveness of vibration diagnostics of damage as applied to the stepped rotors and shafting of steam turbine was developed. The method is based on the determination of relative change of shaft's compliance caused by a crack with the use of linear fracture mechanics. As an example there was performed the comparative analysis of efficiency of vibration diagnostics, namely the change of natural bending, longitudinal or torsional frequency of vibration and the nonlinear effects, to detect transverse or longitudinal crack in rotors and shafting of steam turbine K-215-130.