______________________________________________________________________________________________________ Case

Study

The wind farm is being developed by SSE, Equinor and Vårgrønn in three phases, Dogger Bank A, B, and C. Mammoet is involved in each phase, providing transportation and weighing of the project’ s three offshore substations.

Fabricated by Aibel, the substations are critical components, collecting and converting the power from the transformers and sending the electricity ashore to power homes. They were constructed in stages at two different locations.

The steel construction of the substations began in Aibel’ s yard in Thailand, before being shipped to a second Aibel yard in Haugesund, Norway, for further steelwork to be carried out, as well as the installation of transformers and other complex components.

With fabrication split between two yards in different parts of the world, and a specialist vessel chartered to move the substations, careful planning and management of personnel and equipment was needed to ensure everything ran to schedule.

Hundreds of axle lines in two places

Mammoet assisted Aibel with the three execution phases of each substation: the loadout in Thailand in Laem Chabang, the load-in in Haugesund, Norway, and the final weighing and load-out for transport to the North Sea.

The biggest challenge was sourcing the large number of Self-Propelled Modular Transporters( SPMTs) required to perform the three phases across two locations.

In Thailand, Mammoet provided 338 axle lines to move the( at that time) approximately 7500-ton structures. In addition, a further 344 lines were needed in Norway – 264 for the load-in, plus a further 80 for the substations’ weighing and second load-outs to accommodate their final weight of 9350 tons. This brought the total number of axle lines used for the project to 682, which were sourced from Mammoet’ s global fleet of over 5000, and delivered on container vessels and via land transport.

Though each structure had the same approximate weight, a variety of tidal, engineering, and logistical challenges needed to be overcome to facilitate their load-out and load-in operations. Following precise configuration, SPMTs lifted the substations using their onboard stroke, following which they were transferred to or from oceangoing vessels.

Jacking was made even smoother through collaboration between Aibel and Mammoet’ s engineering teams, resulting in the fabrication of special grillage beams for the SPMTs. These allowed the loads from the SPMT trailers to be transferred to the strongest points of the topside.

Aibel also fabricated two bespoke loadout frames. These ensured the substations stayed firmly in position when transported on the SPMTs. The first of these travelled with the Dogger Bank A substation from Thailand to Norway, remaining there not only for that load-in but also its load-out, and the load ins and load outs of the Dogger Bank B and C substations.

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