On-line creep-fatigue monitoring system for components at elevated temperature

A system has been developed for on-line monitoring of various aging effects e.g. creep, fatigue and creep fatigue interaction. The earlier developed fatigue monitoring system has been modified to account for creep damage and creep-fatigue interaction. The present system is based on the finite element method. The system can take care of the fluctuations of the process fluid temperature, pressure and flow rate. This can also account for the system induced loads such as axial forces and bending moments. The system converts the plant transients to temperature/ stress responses using the finite element method. This computes the fatigue usage factor using rainflow cycle counting algorithm. The creep damage index is evaluated from the computed temperature and stress histories and the material creep curve. To account for the combined damage mechanism, the damage accumulation approach is adapted. This system is capable of analysing several components of a plant using a P.C. This system will be helpful in life estimation and life extension program of thermal power plants, nuclear power plants, chemical process industries, etc.