The Danish-based company, Knud E. Hansen, has revealed a “next-generation” maintenance vessel for offshore wind turbines, capable of handling repairs on-site, minimising the need to remove the components and transport them to shore for servicing.
The “Jack-up on Jack-up” concept includes a four-legged vessel with a 15-metre wide working platform, which can be elevated to the height of the nacelle.
Measuring 154 metres in length and 64.4 metres in breadth, the vessel is designed for all kinds of maintenance work on wind turbines up to 20 MW, including the replacement and handling of nacelles weighing as much as 1,000 tonnes at a hub height of 175 metres, and managing blades up to 130 metres long.
This can be done while the vessel is jacked up in 80-metre water depth, Knud E. Hansen said.
When raised, the working platform provides a safe environment for maintenance work on the blades, eliminating the need for hazardous rope access.
Equipped with a telescopic weather cover, the platform allows blade maintenance to be carried out in practically all weather conditions, both day and night, said Knud E. Hansen. According to the company, this results in far more working hours annually than with conventional maintenance vessels and rope access, making it possible to set up a dependable schedule for planned maintenance.
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, the company said, allowing all types of work to be performed on the blade, minimising the need to remove the blades and transport them to shore for repair.
In addition, with the possibility of inserting an X-Y motion compensating system between the work platform and the platform carriers, the “factory hall” can remain geostationary.
A “cherry picker” mounted on a hammer head at the platform’s opposite end provides access to the nacelle.
The main crane is installed on the elevating structure, allowing for the use of a conventional pedestal-mounted crane with a boom around 30 per cent shorter than that of a typical wind turbine maintenance vessel. This configuration should allow the crane to reach the same height while offering the operator an improved view of the blades and the nacelle from the cabin.
Two crew transfer vessels (CTVs) 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 ship can work as a mother vessel for CTVs operating in the area.
The design is currently patent pending for the “Jack-up on Jack-up” concept, according to Knud E. Hansen.
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