Real-Time Monitoring of High Temperature Components

The remaining life assessment of components in a thermal power plant operating in the creep regime has drawn considerable attention. The structural integrity of such critical components is essential for operational safety, reliability and economic plant operation. Boiler headers and high energy pipings operating at high temperatures and pressure are subjected to different degradation mechanisms synergistically. A finite-element analysis based real-time monitoring system for four 210 MW units of a power station of NTPC Ltd. is evaluating creep and fatigue usage factors being accrued in the components. The candidate components under 24 x 7 assessments are super-heater-outlet-header, re-heater outlet and inlet headers, and the piping bends before the control valves of intermediate pressure turbine of each unit. The cyclic stresses with a mean stress at an elevated temperature lead to a damage mechanism due to creep, fatigue and creep fatigue interaction. The process data i.e., steam pressure, steam temperature and steam flows of the components are made available through a local plant information server on a real-time basis. The system evaluates the material temperature, stress and usage factors due to creep, fatigue and creep-fatigue interaction and computes the remaining life fraction in all the components. The application of a real-time monitoring system thus enables the on-line damage assessments followed by surveillance inspection of critical components of a station comprehensively.