Evaluation of Steam Turbine Blades Surface Cracks Detectability by Nondestructive Methods

Abstract

This article describes methods suitable for crack detection on low pressure steam turbine blades, not including the blade root. These cracks, which are initiated in the corrosion pitting, can cause serious damage to the steam turbine blade leading to its breakaway. Therefore, the detection of these cracks on the early stages of blade fracture is very important. Several methods for detecting of surface cracks (ultrasonic Rayleigh waves, eddy current with flexible array probe, etc.) has been tested on artificial flaws, which were manufactured into turbine blades. The comparison of all these methods is described as well as the evaluation of their advantages and disadvantages. Simulations of ultrasonic testing are also presented in this article.