KCI has been awarded with the installation assistance of tripods series 3, 4, 5 and 6 f or Offshore Wind farm Global Tech I in the German part of the North Sea.
In September 2012, the installation of the first tripods weighing approximately 900 tonnes each started. The tripod installation is still ongoing. As the soil conditions of all 80 tripods to be installed are different, every installation is unique. KCI is assigned with the on bottom stability analyses, the writing of installation procedures and the offshore monitoring of the tripod installation.
The sea bed of the 41`square kilometers wind farm Global Tech I varies from sand to clay. Further, the water depth for the installation of the tripods varies from 38 to 40 metres. Therefore every tripod installation is truly unique and the pile penetration for all three piles per tripod is calculated separately.
KCI performed analyses on bearing & sliding to make sure the tripods will not glide away on the sea bed and a toppling analyses to prevent the tripods from tumbling during installation. As a result of these analyses it was decided to design mudmats which are being installed on the sea bed prior to tripod installation.
In KCI’s on bottom stability analyses, it was calculated during which sea states (gulf heights) installation is still safely possibly.
During the actual operation, in different shifts, KCI engineers Ronald van Dijk and Arash Ramezani are monitoring the complete operation from the control room of the Innovation Jack up barge which transports 3 tripods per tour. They decide which monopile to drive first. The tolerance on the pile driving is determined at only 0.5°. The first 10 metres the piles are vibrated with a vibrohammer. After all three piles per tripod are vibrated, the remaining metres are driven with an impact hammer. A controlled way of pile driving is absolutely necessary to achieve the challenging tolerance of 0.5°!
[mappress]
Press Release, June 11, 2013