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

Lead Research Organisation: University of Birmingham
Department Name: Metallurgy and Materials

Abstract

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.

Publications

10 25 50
 
Description 1. Electromagnetic (EM) sensors are sensitive to relatively small microstructural changes in steels during service at high temperatures.

2. Quantitative relationships between individual microstructural parameters e.g. grain size, phase balance and electromagnetic properties of steels have been established, which provides guidance for prediction / evaluation of microstructures from EM sensor signals.

3. Quantitative relationships between EM properties and EM sensor signals of steels through experimental measurements and finite element modelling.

4. Determinant microstructural features to electromagnetic properties of steels of complex microstructures have been identified, which enables interpretation of EM sensor signals into specific microstructural feature changes.

5. Fundamental evidence based on magnetic domain theory and direct observation of interaction between microstructural features and magnetic domain wall movements in applied magnetic fields has been found to support the above findings and provide theoretical basis for further development / improvements of EM sensors.

6. Qualitative correlation between various microstructural features and magnetic properties has been established, which enables selective evaluation of different microstructural features of interests using EM sensors in different applied fields.
Exploitation Route Commercialisation of EM sensor for evaluation of microstructural changes in steels.
Sectors Energy

 
Description The results have been used in interpreting the EM signal from pipeline samples and developing a technique that can distinguish between correctly and incorrectly heat treated material.
First Year Of Impact 2013
Sector Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Title Computation for Relative Permeability Values 
Description A code was developed for fitting experimentally measured EM sensor signals with the finite element modelled data to obtain optimised relative permeability of steels. 
Type Of Material Computer model/algorithm 
Year Produced 2011 
Provided To Others? Yes  
Impact The model has become an established technique for determining relative permeability values from EM sensor measurement and modelling and plays an important role in a number of PhD, EPSRC and industrial funded projects I have been supervising or leading. Many publications out of these projects have used this technique to generate data. 
 
Title Finite Element Models for EM Sensors 
Description 1. 2D finite element (FE) model (on Comsol Multiphyics) for modelling of signal output of cylindrical EM sensors 2. 3D FE models for modelling of signal output of H-shaped EM sensors 
Type Of Material Computer model/algorithm 
Year Produced 2013 
Provided To Others? Yes  
Impact These models have been used and / or modified in a number of PhD projects and industrial funded projects within the group enabling modelling work to be delivered. This has become an established method for the group to look at EM sensor performance and to aid the design of bespoke EM sensors. These models play a major role in the computation tool for determining relative permeability values from experimental measurements and modelling. 
 
Title Electromagnetic sensors 
Description In-house EM sensors were fabricated including cylindrical, H-shaped sensors and ruggedised sensor for high-temperature measurement 
Type Of Technology Physical Model/Kit 
 
Title Modified Optical Microscope and Domain Wall Movement Observation Kit 
Description An optical microscope was modified with high-speed camera attachment to record magnetic domain wall movement in applied magnetic fields. A in-house sample holder and field generator was designed and made for the experiments. 
Type Of Technology New/Improved Technique/Technology