製造時の溶接内部欠陥が管の健全性に及ぼす影響

抄録

In the manufacturing process of piping, radiographic testing (RT) for weld joints is carried out. However, RT is poor in detection of the planar flaws compared with ultrasonic testing (UT) used in in-service inspection, there is a possibility of overlooking of planar flaws in the weld joints. Then, assuming the initial embedded flaw in the weld joints, growth of it during plant operation life was evaluated. Since the cause of growth is limited to fatigue for embedded flaws and the growth rate of them is lower than in water environment, flaws hardly grow during plant operation life, and the reduction of fracture strength of a pipe by embedded flaws is negligible. Therefore, the weld joints whose integrity was confirmed by the weld testing and the pressure test will not break throughout the plant life even if there are initial embedded flaws in the weld joints.