Electrify Europe 2018

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Lifetime Monitoring of Boiler Components and Piping Systems at High Temperatures (Room Lehar 3)

Lifetime monitoring of power plant components used in the boiler area as well as in high pressure and high temperature piping to the turbine plays an important role in conventional thermal power plants. The currently new power plants utilize significantly high steam parameters and thus a lower design reserve. At the same time, especially in Germany a higher flexibility due the modulation of the power grid is required so in the future start-up and shut-down processes are expected more frequently associated with the energy turnaround. Accordingly, a continuous online monitoring of the actual piping behavior is an important precondition to maintain the operation reliability, establishing maintenance and inspection intervals and ensure a safe long-term operation. The need for this kind of monitoring arises from the limited lifetime of these components. The limiting factors to components’ life are creep damage and low cycle fatigue. The lifetime calculation is conducted based on the Tresca equivalent stress (maximum shear stress hypothesis) and consider both effects, creep and fatigue, by the degree of exhaustion. It is assumed, that there is no influence by additional system loads. The verification of this boundary condition can be attained through the monitoring of the piping system. Thus, in addition to standard measurements of pressure and temperature, the basis of the monitoring system is the capturing of data on piping movements and hanger loads at selected locations. These additional measurements allow early reactions to eliminate malfunctions in the hanger system and thus contribute to an optimization of the lifetime of the piping. The calculation of the degree of exhaustion and the experience with this kind of monitoring systems and the obtained results are shown by several case studies from recorded operational data.