MHI Vestas has signed up Esvagt to deliver a new service operation vessel for work on the 252MW DeBu offshore wind farm in the German North Sea.
The vessel is expected to be ready for use in August 2019.
Esvagt said the associated 15-year contract is the longest in its history and the largest in terms of value.
DeBu, to be located around 95km west of Borkum, is slated to go live at the end of 2019.
MHI Vestas and Esvagt have worked together since 2010 on the Belwind and Noblewind wind farms off Belgium, for which a replacement SOV will commence a 10-year charter period this autumn.