Electromagnetic acoustic transducer (EMAT) inspection of cracks in boiler tubes

An EMAT device for non-destructive inspection of the surface of a tube for cracks using acoustic surface waves, the device comprising:

• a pulsed magnet having an active surface for facing the surface of a tube being inspected;
• a receive EMAT coil on the active surface, the receive EMAT coil having a second surface opposite the active surface;
• a transmit EMAT coil on the second surface of the receive EMAT coil, the transmit EMAT coil having a scan surface opposite the second surface, the scan surface for scanning over the tube surface, the pulsed magnet and the EMAT coils being mounted on a common probe head having a handle connected to the probe head for holding and scanning the active surface along the surface of the tube;
• a transmitter for generating and transmitting an RF signal to the transmit EMAT coil for generating a transmitted acoustic wave signal along the tube, the transmitted wave creating a reflected acoustic wave if a crack in the tube is encountered, the reflected wave generating a reflection signal in the receive EMAT coil;
• a receiver connected to the receive EMAT coil for receiving the reflection signal;
• digital computing means connected to the receiver for receiving and for processing the reflected signal;
• and
• display means for displaying real-time information about the presence, size and position of a crack in the tube which has created the reflected acoustic wave and resulting reflected wave.