High temperature In-situ Monitoring of Power Station Steels using Electromagnetic Sensors - POWEREMS

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There are currently no techniques available to monitor the microstructural condition of power station steel components in-service (i.e. at elevated temperatures). This problem will become more acute as coal-fuelled power stations are being developed to operate at higher pressures and temperatures to provide greater efficiency; supercritical power stations could produce output efficiencies of 45 to 50 %, compared to subcritical power stations with efficiencies of 30 to 35 %. Operation at 620 deg C is now possible, with further temperature increases to 700 deg C planned by the year 2014. Supercritical power stations also emit up to 25 % less carbon dioxide into the environment (a one percent increase in efficiency gives a two percent drop in emissions such as carbon dioxide, and nitrogen and sulphur oxides). Currently the condition of power station components is monitored during shut down periods, when insulating lagging layers are removed and replicas from the component surface are made. These replicas are examined to determine the microstructural state (degree of degradation, e.g. through carbide population changes) and whether creep cavitation has initiated. Components are removed from service and replaced when end of predicted service life is reached or significant cavitation is detected. However, as the component condition can only be checked during a scheduled shut down period, sections are often replaced prematurely. If failure of a component occurs the economic impact is severe (an unplanned shutdown is estimated to cost approximately 1.5M per day per power station) and there is potentially significant risk to life and the environment. The proposed project is to investigate the potential of a multi-frequency electromagnetic (EM) sensor system for monitoring microstructural changes in power generation steels (e.g. boiler plate and pipe) due to high temperature exposure and creep for both in-service monitoring and evaluation during maintenance periods. The work will involve development of a sensor system for long term use at elevated temperatures, and analysis and modelling of sensor signals relative to microstructural changes in the steels.