Friendly FPSO Hull Structure for Robot Inspection

Abstract The Floating Production Storage and Offload system (FPSO) is widely used in offshore oil and gas exploitation. Traditional FPSO hull structures are typically constructed employing stiffened steel panels consisting of steel plates and closely spaced stiffeners. Classification societies require periodic full inspections of the cargo tanks. Nevertheless, the structural impediments created by these stiffeners can pose challenges or even prevent using autonomous equipment for remote inspection of tank structures. Additionally, inspection surveys with people inside the tanks are time-consuming and risky. Hence, a steel-concrete-steel sandwich plate system to address this challenge is proposed as an alternative solution to the conventional stiffened plate composition. Using sandwich panels in the bottom of oil cargo tanks and their longitudinal and transverse bulkheads smooths the surfaces by eliminating the need to use stiffeners, thus facilitating remote inspections with autonomous equipment inside the tanks. Furthermore, this approach can potentially reduce the time needed for periodic inspections of tank structures, following the recommendations set by classification societies to mitigate operational risks. The article presents the results of numerical ultimate strength analyses of sandwich panels and the initial scantlings of an FPSO hull main structure built with the proposed technology. Also, a comparative analysis of the relative total weight is performed.