It is essential to identify the critical areas where failures are likely to occur and select suitable techniques for detection of such failures. Based on design criticality, past experience and previous failure information, suitable approach in inspection methodologies is adopted.

Table - 1 gives typical failure mechanisms and the associated inspection methodology for different components of power plant.

COMPONENT DAMAGE MECHANISM INSPECTION TECHNIQUES
Creep Fatigue Erosion Corrosion HTT VT UTG UTF PT MT ET HT REP FOT DT CA SPL
                                   
BOILER & AUXILIARIES
















1. Drums







2. Steam Headers






3. Water Headers






4. Steam Piping






5. Superheater &
Reheater Tubes









a
6. Waterwall tubes








b
7. Ductings











8. Precipitator











9. Structures










TURBINE
















1. Rotor









c
2. Shell








3. Steam Chest







4. Casing








5. Blades







d
6. HT Bolts








1. Rotor












2. Retaining rings











CONDENSER & HEAT EXCHANGER








Table 1: Damage mechanisms and inspection techniques for Boiler Plant components

 

LEGEND : X - APPLICABLE; HTT - High Temperature Tensile Failure; VT - Visual Inspection & Dimensional Check; UTG - Ultrasonic Thickness Gauging; UTF - Ultrasonic Flaw Detection; PT - Penetrant Testing; MT - Magnetic Particle Inspection; ET - Eddy Current Testing; HT - Hardness Measurement; REP - In-situ Replica Metallography; FOT - Fibreoptic Examination; DT - Destructive Tests on Samples; CA - Chemical Analysis In-situ; SPL - Special Test Methods; a - Oxide scale measurement by special Ultrasonic technique; b - Hydrogen damage assessment by special Ultrasonic technique; c - Boresonic Inspection; d - Special Eddy Current Test of Roots