Design and Engineering Approaches for Hull and Topsides Interface Integration in Heavy Floater Production Units: Addressing Challenges, Best Practices, and Installation Techniques

Abstract The integration of offshore topside with the hull floating production unit (FPU) requires high precision to ensure smooth float-over and installation of 32,000 MT topsides into the 30,000 MT hull structure. The main leg interface must withstand installation loads and guide the process to minimize misalignment and smooth load transfer as per the intended design. It also facilitates towing the unit to a safe zone before welding the main legs which typically performed at the integration yard. This paper presents the design and engineering approach for topside and hull interface system discussion comprising the topside stabbing cone, mating post casting, elastomer bearing, and sand can arrangement which was implemented in the actual project. The float-over operation covers the arrival of the structure on site, pre-entry preparations, Topside Transport Vessel (TTV) entry between the hulls, mating between the stabbing cone and Leg Mating Unit (LMU) receptacles, TTV exit, and the post float-over activities. The elastomer compression performance was tested to achieve the target deformation during integration. In addition, the strength of the stabbing cone was checked based on finite element analysis to ensure the adequacy of the stabbing cone against the vertical and horizontal loads during mating operation. Furthermore, the stability of the stabbing cone was checked to ensure there are no uplifts during wet-tow operation. The predicted elastomer stack deformation stiffness is consistent with the behavior observed in compressive load testing. This is important to ensure there is no gap during compression load transfer during float-over conditions. The design of the stabbing cone used in this project is made of steel with concrete grout filling which gives advantages by increasing fabrication efficiency, reducing weight, and improving the cost and schedule performance. In addition, the validated interface system ensured balanced load transfer through the LMU elastomer stack, precise mating alignment, and effective post‑mating access through the sand can lowering arrangement. Collectively, these approaches provide a robust, field‑proven approach for heavy FPU float‑over operations and provide best practice insights for future offshore installations.