Heerema semi-sub vessel crosses into Baltic Sea in engineering feat

 Heerema Marine Contractors' semi-submersible crane vessel, Thialf, crossed under the Storebaelt Bridge, known as the ‘gate to the Baltic Sea,' marking the first time a Heerema crane vessel has accessed the region.

This crossing is the result of innovative crane alterations to enable passage below the bridge, Heerema said. While ballasted down to Thialf's maximum draught the total air draught was just under 65 meters with the A-frames down.

Unlocking the Baltic Sea

When Thialf was moored in the Port of Rotterdam over the winter of 2021-2022, the team onboard successfully executed modifications to the vessel's A-frames. This action is possible as Thialf's A-frames already have hingable corners that can accommodate the NOV custom-designed semi-permanent adjustment system. The lifting capacity of Thialf is unchanged, with the vessel capable of lifting 14,200 metric tons.

Using this system, Heerema can lower Thialf's cranes and fold the A-frames to create a sufficient air gap when combined with ballasting between the vessel and the Storebaelt Bridge.

The project has been greatly collaborative and was a Heerema Group effort as Heerema Fabrication Group's Opole Yard completed most of the fabrication work. The team fabricated around 150 metric tons of structures required for the modification.