Netherlands-headquartered BigLift Shipping has transported the heaviest submerged turret production (STP) buoy ever constructed, from Singapore to Darwin, Australia.
The buoy weighed 1,260 tonnes (1,305 tonnes include grillage). BigLift’s Happy Sky vessel was selected as it could lift the buoy without additional support such as stability pontoons.
To ensure safe handling, the deck strength capacity of the supporting tweendecks was increased.
A special guiding system was also designed and installed on the vessel. This bumper system was designed in-house in order to be able to discharge the buoy damage-free in offshore conditions, as there was only 20 cm to spare between the grillage and the protruding tubes underneath the buoy. With this special guide fitted to the vessel’s coaming and keeping a slight portside heel, it was ensured the cargo leaned against the guide system in the right direction.
The hydrodynamic software tool MOSES, from software development company Bentley, was used to examine potential limiting environmental conditions for the discharge operation.
To unload the buoy in the Beagle Gulf offshore Darwin, it was lifted off the grillage and placed in the water. Then, the buoy remained hanging in the vessel’s cranes for the following 24 hours since it needed to be ballasted to the correct buoyancy. After a further three days, the buoy was towed into its designated location.
