Inspecting HVOF-coated Pelton runners using active thermography

EDF is carrying out an experimental study aimed at protecting Pelton runners with a hard coating made of HVOF (high velocity oxy-fuel), which would provide better abrasion resistance, and thus extend the life of the runners. However, while coating runners may be beneficial for longevity, the in-service inspection of the base metal of these components must be done with equivalent sensitivity as the original magnetic testing (MT) inspection. The need to detect underlying defects and the evolution of standards, which tends to limit the use of high-power MT systems, encouraged EDF to look at what other inspection techniques could be available for this type of non-destructive examination (NDE) inspection.