The ballast system and venting system are designed for the large semi-submersible vessel according to its characteristics. Having decided upon the ballast system of the whole ship, the venting system of the ship is determined as the common venting piping system. Specific measures are proposed to avoid the cumulative water inflow of the relevant tanks caused by the common venting piping system. The safety of the venting system are also analyzed under the worst damage conditions.

The deck-mounted rudder propeller can meet the needs of the vessel with the multiple working conditions and the dynamic positioning (DP) condition due to the simplified system and the convenient layout. It introduces the characteristics and the layout requirements of the deck-mounted rudder propeller, and its application on the submarine cable laying vessel and the semi-submersible vessel. The application flexibility of the deck-mounted rudder propeller can meet the operation requirement very well.