As previously noted in ClassNK Technical Information (TEC-1205), ClassNK received several reports of cases of sea water leakage being detected in damaged distance pieces (due to corrosion) of SOx scrubber discharge waterlines fitted to hull structures (see 3 in Figure 1). Since similar incidents are still being reported, ClassNK has decided to publish this Technical Information not only to remind our clients that this remains an ongoing concern, but also to provide the following related information.

According to damage reports received to date, sea water leakage has been observed either on or adjacent to welded parts between distance pieces and their associated flanges (see Picture 1) as well as between distance pieces and bluff bodies (see Picture 2). The reports indicate that the corrosion apparently initiates at the welded parts and then continues to progress until it finally leads to sea water leakage into engine rooms. A peeling of the painted surfaces of the butt-welded parts of distance pieces (see Picture 3) has also been observed.

(To be continued)