Ultrasonic Testing System and Ultrasonic Testing Technique for Pipe Member

An ultrasonic testing system for a pipe member characterized by comprising:

• a transmitting/receiving unit having a transmitting unit, which transmits an ultrasonic wave to the welded surface of a welded portion in a pipe axis direction of a pipe member and to the inside surface of the pipe member so that the ultrasonic wave is incident at an angle within the range from 33.2° to 56.8°, respectively, and a receiving unit, which partly or entirely receives an echo reflected in a direction within the range from −12° to 16° to the mirror reflecting direction in the welded surface, wherein the transmitting unit and the receiving unit are composed of different groups of transducer elements on one, two, or more array probes disposed in a pipe member peripheral direction;
• and
• a controller for scanning the pipe member in a thickness direction by carrying out a control to change the groups of transducer elements corresponding to the transmitting unit and the receiving unit on the array probe or to change the angle of the array probe as well as controlling the angle of incidence of the ultrasonic wave to the pipe member in the respective transmitting and receiving waves so that the angles of incidence to the welded surface and the inside surface and the angle of the echo on the welded surface are kept within the ranges defined as to the transmitted wave and the received wave, respectively.