Float-Over Analysis for World’s Largest Float-Over Barge

Heerema Marine Contractors has recently converted its launch barge H-851 into a float-over barge able to install ultra heavy topsides with weights up to 38,000 mT. With a length of 260 m, width of 63 m and height of 15 m, the H-851 is the world’s largest float-over barge. By narrowing the bow section to 42 m, the required sub-structure slot to fit the barge is reduced significantly decreasing the size of sub-structure and topsides hence optimizing platform weight and cost. Initially the sheer size of the H-851 was thought to result in high forces on topsides, sub-structure and interface systems during installation. However, engineering analyses show that by choosing the appropriate float-over equipment, loads can be kept below limits which are considered conceivable for the platform design. Special measures are taken to minimize the exposure during load transfer by equipping the barge with a high capacity ballast system. As with all vessels with large displacement, maneuvering before and after float-over requires thorough planning and risk identification during the engineering stage. This paper discusses the critical phases during the float-over operations and demonstrates that the platform design can be optimized by considering float-over equipment and operational limits in an early stage of the project. The approach for extensive hydrodynamic analyses is discussed which have matured over recent times thanks to available software tools and extensive research with respect to comparison with model tests and full scale experience.