The Nordergrunde offshore wind project needed an electrical cable to connect their offshore substation to the onshore power grid, so they contracted VBMS to install this 28km-long cable.
VBMS planned on using their BSSII burial sledge system to put the cable into the seabed. The BSSII is a tool that creates a trench into the seabed by fluidizing the soil and simultaneously lay the cable.
During the project, VBMS would occasionally have to launch and recover the BSSII , something that would normally require a floating sheerleg.
“However, using a floating sheerleg would put severe restraints on the project. Letting a floating sheerleg can be quite costly and floating sheerlegs often have to be reserved well in advance,” Mammoet said.
VBMS therefore involved Mammoet in the early stages of the project. “What we basically did is apply our land-based expertise to an offshore situation,” commercial manager at Mammoet Richard van Looij said.
By combining two of the beams that were used for the lifting of the Kursk with three winches, Mammoet was able to equip a standard barge with a custom-designed system that could hoist the BSSII without the need for a floating sheerleg.
The hoisting system was also specifically designed to keep the installation time on the barge to a minimum.
“After a 12-day quayside assembly period the system was installed on the barge and fully operational within 2 days, allowing the client to minimize barge rental time and get the job done more efficiently,” said Mammoet.
The Kursk submarine was lifted from Barents sea floor by Mammoet in 2001. The operation took 15 hours, with the Dutch company using 26 steel cables that had been attached to holes made in the hull. The Giant 4 recovery barge, owned by Smit, Mammoet's partner in the project, pulled the submarine to the surface using massive hydraulic strand jacks.
