KNUD E HANSEN has designed a “Jack-up on Jack-up” vessel concept for offshore wind farm maintenance.
The four-legged jack-up vessel features a 15m wide working platform that can be jacked-up to the height of a nacelle to provide a safe platform for maintenance work on the blades eliminating the need for rope access.
With a telescopic weather cover fitted on the platform, work on the blades can be done in practically all weather conditions, day or night, resulting in more working hours annually than with conventional maintenance vessels.
A large, air-conditioned workshop is located at the aft end of the work platform, and when the weather cover is deployed, a virtual factory hall is created around the blade, allowing all types of work to be performed on the blade, minimizing the need to remove the blades and transport them to shore for repair.
Additionally, there is the possibility of inserting an X-Y motion compensating system between the work platform and the platform carriers so the “factory hall” can remain geostationary.
A “cherry picker” mounted on a hammer head at the platform’s opposite end provides the access to the nacelle.
The main crane is fitted on the elevating structure, allowing for the use of a conventional pedestal-mounted crane with a boom that is approximately 30% shorter than that of a conventional wind turbine maintenance vessel, which should be able to reach the same height, providing a much better view of the blades and the nacelle from the crane driver’s cabin.
Measuring 154m in length and 64.4 m in breadth, the vessel is designed for all kinds of maintenance work on wind turbines up to 20MW, including replacement and handling of nacelles weighing as much as 1,000t at a hub height of 175m, and managing blades up to 130m long. This can be done while it is jacked up in 80m water depth.
Two crew access vessels are arranged in davits on the aft deck, and with a retractable boat landing that can reach the water when the vessel is jacked up, the vessel can work as a mother vessel for CTVs working in the area.