Creep is the time-dependent, thermally assisted deformation of a component operating under stress. Metal pressure components such as boiler tubing, headers, and steam piping in fossil-fired power plants operate at thermal conditions (above ~1,000ºF [538ºC]) conducive to causing creep damage over the operating life of the component.
To ensure safe and reliable operation of such components in service, utilities periodically use non-destructive evaluation (NDE) techniques to inspect these components for damage. These inspections are largely targeted at detecting late stage creep damage in which cracking is active in the component and provides qualitative rather than quantitative data.
Recent advances in NDE technology have provided enhanced capabilities for incipient creep failure detection. CreepTest will seek to apply time reversal focusing and full matrix capture techniques that have already shown a capability to identify early stage creep damage. A library of defects will be produced with the aim of providing inspection limits and the probability of detection for the techniques developed in the project and thus enable accurate life cycle prediction for components under inspection.
The objectives of the project will be:
•?To develop new ultrasonic phased NDE testing techniques for the detection of Type IV creep cracking
•?To determine the sensitivity of defect detection and the limits of technique/system/ultrasonic array performance.
•?To produce a field prototype NDE ultrasonic array system, signal processing and software for the examination of power plant steam pipe welds for creep damage.
•?Quantify results to assess the extent of creep detection and categorise into (i) cavitation formation (ii) cavitation coalescence (iii) formation of micro-cracking and (iv) macro-cracking.
•?To demonstrate the NDE systems performance on in-service, in-situ steam pipe welds and to validate the technique results against representative samples containing realistic creep defects