Maintenance of immersion ultrasonic testing on the water tube boiler

Ishiyama, Toru ; Kawasaki, Ichio ; Miura, Hirohito*

There are 4-boiler systems in NCL. These boilers have been operated in the long term over 20 years. One of them, the leakage of boiler water was found at one of the generating tubes, and 2 adjoining generating tubes were corroded in Dec, 2011. These generating tubes were investigated by immersion ultrasonic testing (UT) for measure thickness of the tube. As a result, thinner tube was found in a part of a bend and near the water drum. These parts are covered with sulfide deposit, it seems that the generating tubes were corroded by sulfide.