The low-pressure stage of a steam turbine rotor has the potential risk of blade scattering caused by stress corrosion cracking in the blade groove where the rotor blade is implanted due to long-term operation. Mitsubishi Heavy Industries (MHI) Group has developed ultrasonic testing technologies for axial entry blade grooves with a complicated processing shape that is used to detect and identify minute stress corrosion cracking occurring in the blade groove that can be used without removing the rotor blade. This report presents an overview and inspection examples of ultrasonic testing techniques that can handle special blade groove processing shapes and disk shapes.
