Heerema Marine Contractors conversion launch barge H-851 into a float-over barge able to install ultra-heavy topsides with weights up to 38,000 mT.
The full engineering service for the largest non-propelled barge in the world. Order for the Dutch company Heerema B.V – our task was to perform all the calculations related to the adaptation of the H-851 barge to transport the drilling platform from the construction yard in South Korea to Australia.
The weight of the large-size structures was 24,000 and 44,000 tons. The calculations concerned both the adaptation of the barge itself to transport with such a heavy load and the behavior of the barge and its cargo at sea (hydrodynamic calculations). The scope of these analyzes also included the preparation of appropriate calculations for the expected course of the process of reloading the platform from land to the barge. The main challenge was the scale and multidisciplinarity of this project. For the needs of this vessel, we have designed the „Rapid ballast System”, i.e. a ballast system that allows the barge to quickly descend and emerge. A similar solution is used on submarines.
Prepared a detailed finite element model of the barge to determine the additional strengthening required for transporting the NRB deck (North Rankin B – project on Australia’s North West Shelf). Loads kept below limits which are considered conceivable for theplatform design.
The scope included the removal of the ballast tanks on either side of the barge for a length of 100m from the bow and reducing the width to 42m.
Sea-keeping analysis and strength, stability and construction calculations had to be made in order to implement the modifications.
The global structural finite element analysis made use of two models: a 3D finite element global model, with a relatively fine mesh in the transition region, covering the full length, depth and breadth of the vessel, to determine the global structure response, and two local models to ensure proper stress evaluation and assessment.
Prepared reinforcements to comply with the strength requirements.
- cutting the first 100m of the H-581 back to the 21m bulkheads, which would then form the new side shell;
- installation of three new internal longitudinal bulkheads over a length of approximately 85m;
- fabrication of a new bow transition piece;
- modifications to the barge piping;
- installation of surge and sway fenders for floatoveroperations;
- modifications to the barge control systems;
- installation of an integrated free flooding ballast system with a control container on deck.