Stable and economical operation of power plants requires an accurate understanding of facility conditions and appropriate maintenance. In recent years, the operating conditions of power plants have been getting difficult, because of the fuel transition toward decarbonization and the need for flexibility in the operating load to balance renewable energy fluctuations. This raises concerns about the progression of any new damage. Although the technology to quantify the height of a discontinuity (a flaw) in a non-destructive manner is pivotal to assessing the strength and remaining life of a structure, it was very demanding in terms of measurement skills and accuracy. This was a bottleneck in maintenance planning. Mitsubishi Heavy Industries, Ltd. has therefore combined Time of Flight Diffraction (TOFD) for robust assessment of flaw height with Total Focusing Method (TFM), which is a multi-channel signal and image processing technology, to create the TOFD-TFM ultrasonic imaging system for flaw height quantification. While currently being used to measure the heights of flaws, the system is also being used to perform a temporal assessment based on the obtained data, thereby helping to make a practical maintenance plan based on the analysis of correlations between flaw progression and boiler operation environment, etc.
