| 摘要 |
PURPOSE:To detect simply and surely flaws in a welded part of a reaction tube by measuring transmission decibel at a prescribed position of the reaction tube, and by comparing the gage value thereof with a reference gage value determined beforehand corresponding to the result of a breakdown test. CONSTITUTION:A transmitter probe T and a receiver probe R in a pair are set on the outside surface of a tube in the axial direction and at a prescribed interval. An ultrasonic wave S is passed in the axial direction, and the transmission decibel thereof is measured at a proper number of places in the circumferential direction of the tube. A value obtained by subtracting the value of W decibel at a welded part from the sum of the value of T decibel at the top part near a welding line and of the value of B decibel at the bottom part thereof is taken as a gage value, and this value is compared with a reference gage value obtained beforehand by a breakdown test. By this method, the inspection of flaws can be performed without being affected by the attenuation of the ultrasonic wave, if any, caused by the structure of the basic material. Therefore, the presence of the flaws in the welded part of the reaction tube can be detected simply and surely, while this method can be a means for estimating the lifetime of the tube. |
