Patent ID: 6164137
Filing Date: 2000-12-26
Classification: G01N

Abstract:
An EMAT testing device for nondestructively detecting defects in the surface of a tube using acoustic surface waves, the device comprising:transmitter means for generating and transmitting a pair of acoustic surface wave signals in opposite directions around a circumference of the tube;first receiving means for receiving each of the pair of acoustic surface waves signals at first and second times and converting the received acoustic surface waves signals to a pair of electronic signals having amplitudes proportionate to the acoustic surface wave signal amplitudes received at the first and second times;second receiving means for receiving each of the pair of acoustic surface wave signals at third and fourth times and converting the received acoustic surface wave signals to a second pair of electronic signals having amplitudes proportionate to the acoustic surface wave signal amplitudes received at the third and fourth times, andcomputing means for comparing the amplitudes of the first pair of electronic signals to the amplitudes of the second pair of electronic signals and for determining the presence of defects in the surface of the tube from the comparison of the amplitudes of the two pair of electronic signals, whereby when no defects are present in the tube, the amplitudes of the two pairs of electronic signals are substantially the same, and when a defect is present adjacent one of the first receiving means and second receiving means, the corresponding amplitude of the electronic signal from the receiving means adjacent the defect is lower than the amplitude of the corresponding electronic signal from the other receiving means.