Mobilisation of a multi purpose pontoon

At the beginning of 2019 we were contracted by Boskalis to assist in the mobilisation of the NP459 for an upcoming cable replacement project for an offshore wind farm. The work consisted of seafastening and deckstrength calculations for various pieces of equipment ranging from small cable handling tools to a 1400t carousel. The seafastening solutions were designed to be easy to install to reduce the mobilisation time.

Saltwater was contracted by Boskalis to assist in the mobilisation of the NP459
Saltwater was contracted by Boskalis to assist in the mobilisation of the NP459
Saltwater was contracted by Boskalis to assist in the mobilisation of the NP459

Loading tower

The replacement cable is loaded into and offloaded from the carousel using a loading tower. loading towers are inherently challenging to fasten to the deck of a vessel due to the loads introduced by the cable and due to vessel motions. Furthermore, spooling towers are usually narrow based structures resulting in high local forces acting on the deck. For this specific case a section of the vessel was modelled to verify the structural integrity of the deck subject to the loads introduced by the loading tower.

NP459

The NP459, is a high standard uniquely versatile multi-purpose accommodation pontoon, of 82,50 x 27,00 x 6,00 meter. The 60 tons CT 8-point mooring system in combination with its spacious and strong 20 tons per m² working deck makes it a versatile and predictable platform. After its first assignment, its station-keeping capability will be further enhanced with the addition of a DP-II system with retractable thrusters for projects that require the maintenance of a dynamic position. The NP459 has departed under tow of the “Dutch Pearl” for its first assignment mid-May 2019.

Project information

Scope of work:

  • Seafastening
  • Deckstrength calculations
  • Design calculations
  • Weld calculations

 

Dimensions NP459:

  • Length 82,5 L x 27 B x 6 D meters
  • Cargo capacity 4000 ton
  • Deck load 20 ton/m2
Saltwater was contracted by Boskalis to assist in the mobilisation of the NP459
Saltwater was contracted by Boskalis to assist in the mobilisation of the NP459
Category
Mobilisation Engineering