M/V Margrethe Fighter is a 35m long dredger equipped with a Liebherr P964 Litronic backhoe excavator which can work to a dredging depth of 10m.

A J-tube is the duct/pipe work that is used to transport the cable up from the seabed into the monopile and up to the base of the windmill. At Kentish Flats, the external J-tubes are 10m long, weigh 1 ton each and are bolted onto a connection flange coming out of the monopile at seabed level. They are positioned on the seabed with the help of M/V Margrethe Fighter 's excavator, then winched into position and bolted into place with diver assistance.

Because of the very strong tidal conditions in the area, diving is generally limited to about two hours around high and low water. Just to make matters worse, there is zero visibility in the working area for the divers.

As a result, what would under normal conditions be a relatively simply task requires careful planning and coordination to ensure that the connection can be made in the short working period, with safety for the divers being of the almost importance.

Weather permitting, the contract for a total of 57 J-tubes should be complete at the end of this month or in early February.

The contract is a continuation of both Peter Madsen Rederi and PM Diving's deep involvement with offshore wind farms. Both companies have carried out extensive works on Horns Rev, Nysted, and Middelgrunden offshore wind farms in Denmark.

This is the their first contract in the UK.

MJ Information No: 20201