The aim in the development of the Sevan technology was to provide a unit that would provide ample cargo storage in tanks within the hull, be able to carry a significant topside load and at the same time give favorable motions and accelerations when  exposed to harsh wave environments such as the North Sea wave climate. The cylindrical Sevan unit with its characteristic bilge box offers these capabilities.

The development of the hull and tank configuration is a joined effort requiring competencies on hydrodynamics and stability as well as on structural design. The design is made with focus on safety and robustness, operability and efficiency in construction.

Advanced tools such as the CATIA V5 and the DNV SESAM pack-age including GeniE, WADAM, SESTRA, PULS and XRACT are applied in an iterative process to end up with a design that puts the steel “in the right place”. In addition to the yield and buckling check used as the basis for determining the main scantlings such as plate thickness and stiffener cross section, extensive fatigue analysis is also included in the design process to explicitly control the fatigue life of critical details such as stringers/girder terminations and side structure subject to dynamic sea pressures.

Once completed, the basic design (main scantling level) is forwar-ded to Class for approval and passed on to the shipyard for development of fabrication drawings. As a part of the verification process, the Sevan Structure Section reviews both the fabrication drawings and closely follows the yard during the construction phase to ensure that the unit is built in accordance with the design specifications.