An ultrasonic non-destructive testing system for detection and quantification of early-stage subsurface creep damage in the thermal power generation industry
Creep is the time-dependent, thermally assisted deformation of a component operating under stress. It is often a key factor not only in the design of components used in the power generation industry, particularly in fossil fuel and nuclear plant, but also in the assessment of their remaining life. Pressurised components such as boiler tubing, headers, and steam piping in fossil-fuel power plants operate at temperatures of 538ºC up to about 570ºC and this is conducive to causing creep damage over the operating life of the component. Although creep in this material has been known about for some time it has only become a pressing issue over the past few years because of two reasons:
- Failure is occurring at a much earlier stage than previously anticipated, i.e. in some cases about half to three quarters the number of years that where first anticipated, and
- Large fossil fuelled power plants are now being expected to work beyond their original design life (plant life extension programmes) and therefore creep damage is becoming more likely during the extension period.
Hence the early detection of creep damage in components which are in-service stands to aid in the better management of the power plant and to prevent often catastrophic failures which can lead to severely adverse human, environmental and economic consequences to society.