| 摘要 |
PURPOSE:To detect a flaw of a tube with high precision by a flaw detecting method which transmits an ultrasonic wave through a flaw-detected part in a tube axis direction at right angles by calculating deviation from measured value in a tube axis direction of a specific phase and in tube axis direction of both sides. CONSTITUTION:Ultrasonic waves from a transmitting probe 3a and a receiving probe 3b are transmitted through the flaw-detected part 1a of the tube 1 in the direction of an axis P. A weld zone Wn is detected by a detection sensor 2. A measurement is taken while the probes 3a and 3b and sensor 2 are elevated, and the flaw-detected part 1b of the tube 1 on the opposite side is lowered to take a measurement, thus obtaining decivel value Dn. When, the measurement is taken at near both sides in a specified phase in the same manner, thus obtaining decibel values Dn-1 and Dn+1. The deviation Xn is calculated from Xn=Dn-[(Dn-1+Dn+1)/2] and compared with a set value to decide on the defect. Thus, an ultrasonic measurement is taken at numbers of points of the flaw-detected part and the deviation of a measured decibel value is compared with the set value to improve the measurement precision without any evil influence of the macrostructure and surface roughness of the tube. |
