Electromagnetic nondestructive detection for wounded bearings and impellers and correlation of size of defect and signal

A new electromagnetic method for the nondestructive evaluation of electric pumps with ball bearing is proposed. A permanent magnet generates a static magnetic field and a coil of several hundred turns wrapped around it is used to pick up eddy currents induced inside rotating ball bearings and impellers. First, a method that make use of the autocorrelation is applied to the signals of the ball bearings. A relation between the processed signals and the size of the defects in the bearings is obtained. In a second part, the signal of the rotating impeller is measured. The analysis of the measured signal allows evaluating the displacement of the shaft and of the impeller. (author)