New damage stability device from Japan
MHI's vessel righting moment recovery system
Mitsubishi Heavy Industries says it has developed a system to enhance the damage stability of ships, enabling reduction in capsizing risk, and has received the first order for the new system for a ro-ro cargo vessel.
The order comes from Nippon Shipping, a subsidiary of Nippon Express.
MHI developed the system in response to the strengthening of regulations on ship stability, based on revisions to the SOLAS Convention adopted by IMO in 1974. The new system is targeted in particular at ro-ro ships, PCTCs and ferries. With such ships in mind, MHI developed the system with an emphasis on low cost.
If the ship's hull is damaged at sea, the system transfers flooded seawater into void spaces in the ship's bottom, thereby reducing capsizing risk through enhancement of righting momentum by quickly lowering the ship's centre of gravity. It makes use of void spaces near the ship's bottom by making use of spaces allocated to other functions: e.g. fin stabiliser rooms, duct keels and ballast water tanks. Holes and watertight covers are provided to feed the seawater into the void spaces, and pipes are in place to serve as air vents. The system enables rapid water filling and lowering of the ofCofG to cope with emergencies. The system is claimed to eliminate the need to divide the vehicle deck area into small compartments and not to sacrifice vehicle capacity, and facilitate smoother vehicle manoeuvring within the ship.
The company sees its new righting moment recovery system as another highly promising technology that will sit alongside MHI’s innovations such as the MALS air lubrication system.
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