Residual Life Assessment (RLA)
Assessing the condition and remaining life of power plant components operating at high temperatures and at high stresses is necessary to optimize inspection and maintenance schedules, to make RUN, REPAIR, REPLACE decisions and to avoid unplanned outages. While two different approaches are available for Residual Life Assessment of Power Plant components, one using data analysis based on operational history and the other based on periodic examination of critical components, the latter method is widely adopted as it is more accurate since it does not rely on standard material data with their associated uncertainties and does not necessarily require knowledge of the operational stress-temperature data.
Methods based on periodic examination involve:
- Various NDT techniques for detection of cracks, effects of corrosion / erosion etc. in addition to commonly adopted techniques such as Ultrasonic thickness gauging, Ultrasonic flaw detection, Penetrant testing, Flourescent magnetic particle testing, Specialised techniques such as assessment of hydrogen damage by Ultrasonics, measurement of steam side oxide scale by in-situ ultrasonics, boresonic inspection of rotors, eddy current examination of rotor blades and root, video probe examination of critical components are employed.
- Metallurgical tests such as in-situ metallography using replica method, in-situ chemical analysis by metal spectroscope / X-ray flourescence method, in-situ hardness measurement etc.
- Sampling of component specimens for detailed laboratory analysis.This paper deals with the periodic inspection approach adopted by Industrial Quality Concepts for Residual Life Assessment of power plant components.
