Duct Keel

Some bulk carriers and in some container ships, a duct keel is fitted along the centreline of th ship between  port and starboard double bottom tanks. It extends from the collision bulkhead till the forward of engine room bulkhead. It is used as a passage for the fuel oil, steam and ballast piping to the double bottom tanks.

Where a duct is arranged, the centre girder is replaced  by two girders spaced not more 1.83 metres apart. Additional strengthening of the tank top of the keel plate maintains the strength of the transverse floor. The image below illustrates a duct keel.