Analysis of Crack in Kaplan Turbine Blade

Abstract

The paper deals with the analysis of the crack detected in the Kaplan turbine blade. In order to keep the blade integrity the sample was removed by using small sample method. Fractographic and metallographic analyses were used to determine the cause of a detected crack appearance and propagation. The material of the turbine blade was made in 1937 and its structure containing numerous eutectic sulphide inclusions corresponded to the steelmaking technology of that time. Numerous occurrences of sulphide inclusions and sulphide eutectics were identified as the main cause of material failure. Regardless of these non-metallic inclusions the blade was repaired by welding and nowadays the repaired blade has been under safe operation for more than 9 years.