Locating magnetite on the steam generator tubes with eddy current

The magnetite deposition on the secondary circuit of the steam generator tubing is considered a problem, because is many cases the growing defects are located at the same place as the magnetic deposits. For this reason it is more and more important to locate and size the piles of magnetite on the tubing. The steam generator tubes are generally inspected by eddy current methods. During the in-service inspection the size of the magnetite deposit is not determined, only the notification of its existence is given in the inspection report. In this study experiments were conducted by using eddy current techniques and ordinary bobbin probes to size the thickness of magnetite piles on the test tubes. Tubes were simulating the horizontal steam generator tubes. Results of low frequency tests are shown