The world’s greatest dry transportation already done is the floating production unit PETROBRAS 40 from Singapore to Brazil. PETROBRAS 40 is a 42000 tons semi-submersible floating production unit of 150000 b.p.d. which was converted from the derrick barge DB100 hull. All the naval design for this conversion was developed by PROJEMAR S.A. The transportation from the yard at Singapore to the South Marlim field at Campos Basin, Brazil was done in a heavy lift ship to accelerate the delivery of the PETROBRAS 40. This study had several analysis performed to guarantee the feasibility of the operation. Due to the three-pontoon configuration of the hull and its large weight, the loads induced by the hull girder analysis of the heavy lift ship were mandatory to the analysis of the unit. The configuration of the semi-submersible structure did not allow it to be supported only at the side pontoons, leaving the center pontoon free to deflect. This situation would lead to large deflection on the hull and, consequently, high stresses would be installed on the PETROBRAS 40 hull. The separate analysis of the vessel and the PETROBRAS 40 hull generated a very conservative interface load and/or deflection. Therefore, the hull girder analysis of the heavy lift ship had to be detailed for a very specific critical wave conditions that the dry transportation could face in the 45 days trip. In order to minimize the contingency factors in a safe condition, several studies were performed on the weather routing and consequently in the wave height and associated period. Then, this paper presents all the technical aspects used in the dry tow analysis and discuss the possible solutions found to make it feasible.

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