Currently a large number of converter stations are placed on the North Sea to connect the built and planned offshore wind farms to the onshore power grid. Wind farms are part of a cluster with each a converter station since not every wind farm has its own cable to land. The DolWin cluster, with i.a. the Alpha Ventus, Borkum West II and Riffgrund wind farms, will be extended with a third connection: DolWin 3. DolWin 3 will have a capacity of 900 MW and shall be connected to the onshore substation in Dörpen (Germany) by a DC cable. The entire project is currently scheduled to be completed in 2017.

Illustration by TenneT
Illustration by TenneT

A careful and safe approach

Recently a leading company in the energy and telecom cable industry asked Wagenborg to ship 34 km of DC cable, destined for this DolWin 3 project, from the manufacturing plant in Finland, to the German port of Emden. The plant is located near Helsinki and has no port facilities. However, the plant has constructed a new jetty, measuring 400 meters in length, fitted with a cable line which leads into the bay located south of the plant. This bay has only a draught of approx. 5 meters. 

A careful approach, in which safety came first, was absolutely necessary to ensure safe mooring and loading operations because of this challenging circumstances. The cable manufacturer and the supercargo of Wagenborg invented the general idea to pick up the cable at the end of the jetty, bring it on board and lead it over the deck into a special purpose constructed cable tank in the cargo holds. Mooring the stern of the vessel to the jetty, while loading the cable through the stern, was considered to be the safest and most practical loading method, as it guaranteed a unobstructed and straight route to the hold. Based on local information, such as maps, sounding cards, jetty position and other practical information, a thorough cargo mooring and loading plan was created. In close consultation with the Projects & Newbuilding department of Wagenborg and other technical departments special deck loading equipment was engineered for leading the precious cargo into the holds. This proposal was shared, discussed and modified with our customer and finally got approved for execution. Wagenborg designated one of their successful A-class vessels to do the job: m.v. Albanyborg.

Preparing the vessel for her special cargo

Before the plan could be executed, the the m.v. Albanyborg had to be prepared for the cargo as described in the cargo and loading plan. The preparation involved the assembly and installation of a cable tank measuring 16 meters in diameter in the vessels cargo hold, which was constructed at a shipyard in Tallinn, Estonia. Also the load installation for the cable line had to be assembled and installed on deck. A great cooperation between the vessels crew, the shipyard, the customer and local agents ensured all preparations were completed in a short time frame. Six days later the m.v. Albanyborg left Tallinn and set sail to Finland. 

Arrival at the Finnish plant

Upon arrival at Finland the m.v. Albanyborg had to wait until winds were reduced to 4-5 Bft. This was the maximum allowed wind speed to perform safe maneuvering activities at the bay located near the plants jetty. Tugs were fastened, the vessel was turned around 180 degrees, spanned bow anchors were placed and 2 x 600 meters of mooring lines were fixed ashore to position the vessel perfectly to place. Four pieces x 7 tons anchors were placed with the deck cranes, which would  be used as extra mooring points for this project. When these extensive mooring operations were completed, the m.v. Albanyborg was official the largest vessel ever at the Finnish plant location.

Loading and leaving

The loading of the cables, measuring 200mm in diameter and weighing 45 kg/m, could start and was completed exactly 3 days later, as initially was planned according the time schedule. The complete operations were surveyed and approved by the customer and insurance surveyors. After completion the loading equipment was stowed and secured, upon which the m.v. Albanyborg set sail to Emden. After a smooth trip of three days the the m.v. Albanyborg was welcomed at the German port, where she is waiting to be discharged....

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