April 10 - SAL Heavy Lift is transporting 87 monopiles (MP) from Rostock, Germany to Belfast, Northern Ireland for the Walney Offshore Windfarm, located off the north west coast of England.

The MPs measure up to 8.4 m x 72.6 m and weigh up to 1,100 tons (997.9 tonnes).

In addition to the monopiles, 87 transition pieces (TP) will be carried by SAL's heavy lift vessel, Svenja, from Teesport, UK and Aalborg, Denmark to the project harbour. With a height of up to 30 m, a diameter of up to seven metres and a single weight of up to 579 tons (525 tonnes), SAL claims the TPs are amongst the largest ever built.

According to SAL, the long-term project presents several challenges as the two different types of cargo require their own stowage arrangement on board and need to be shipped separately. Limited space at the Port of Rostock also presented difficulties.

A combination of steel cradles with tailormade wooden linings serve as sea-fastening arrangements for the MPs. They are stowed between steel plates welded as stoppers and additional steel wedges fix them. Thus, when the vessel's crew changes the cargo setting from MPs to TPs, they can easily remove the steel cradles from the hatch covers and the tween deck so the TPs can be secured with grillages on the tank top.

Philip Stackmann, project manager, explained: "We had to design a sea-fastening system that copes with the cargo variety and facilitates quick handling."

SAL Heavy Lift was contracted by Van Oord and DONG energy, and began the transportation in November 2016 with completion expected in August 2017.