Research and development on an Electro-Magnetic Acoustic Transducer for testing heat exchanger tubes

In-service inspection (ISI) of heat exchanger tubes is usually carried out using an eddy current testing method, and is useful for evaluating the safety of plants. However, a new method providing higher flaw detectability and completion time is required. Therefore, we developed an ultrasonic testing method using an Electro-Magnetic Acoustic Transducer (EMAT). This transducer generates ultrasonic waves through the interaction of an eddy current and a static magnetic field in the surface of the material, so that ultrasonic testing can be carried out without a couplant yet high speeds can be expected. But it has been difficult to produce small EMATs with sufficient flaw detectability because of their inherent low electric-acoustic energy transformation efficiency. The authors have investigated testing methods and EMAT structures to develop an EMAT for heat exchanger tubes and examine flaw detectability