Steam Turbine Components NDE
Steam turbines depending on the operating conditions are subject to damage by creep, thermal fatigue, stress corrosion cracking, steam erosion-corrosion, and foreign object damage. All of these damage mechanisms occur on the external and peripheral areas of the rotors and components at stress concentration locations such as steam balance holes, changes of section, blade roots, shrouds, tenons, tie wires, etc. High pressure (HP) rotors, Intermediate pressure (IP) rotors, and their components are exposed to creep damage, thermal fatigue, steam erosion damage, and foreign object damage. Low pressure (LP) rotors and their components are exposed to thermal fatigue, stress corrosion cracking, steam erosion damage, and foreign object damage. The amount of damage induced in the rotors by these mechanisms is dependent upon the type of duty service, operating temperatures, local stress level; steam quality, and material susceptibility to damage among other factors. Therefore, the detection, classification, and sizing of damage in the form of flaws are critical to the structural integrity of steam turbine. The NDE examinations performed on steam turbine rotor and components for service induced damage detection include visual testing (VT), eddy current testing (ET), wet fluorescent magnetic particle testing (WFMT), ultrasonic testing (UT), and liquid penetrant (PT) examinations.