installation vessels Standardised, optimised layout has many benefits
In the turbine installation business, few things are as important as deck layout
AN optimal deck layout makes life easier. Loading becomes more efficient, transportation more stable and lifting positions and procedures function like clockwork – and ideally, the same basic layout can be used from project to project and with as many different types of components as possible. As Glen Andersen, senior manager, project engineering at
A2SEA explained, the company’s project management team has been hard at work designing an optimised, standardised layout for the latest addition to its fleet, Sea Installer, working in close co-operation with a client and the wind turbine manufacturer. The focus was on creating a highly efficient set-up that worked not just for Siemens 3.6 megawatt (MW) turbines but also for their larger 6MW units. As Mr Andersen explained in a recent issue of A2SEA’s house magazine, the crane on Sea Installer is located in such a way that maximises the free deck area. With a deck built to withstand massive loads, a leg centre-installed crane that can slew 360 degrees without encountering another leg, extended crane reach and many other advantages, Sea Installer is prepared for a future lift capability upgrade to 900 tonnes, but there is always room for improvement.
“Achieving an optimal deck layout demands an in-depth understanding of everything from the principles of vessel architecture to hands-on experience with lifting operations,” he explained. “The end goal is to determine exactly where blades, towers and nacelles are best positioned in relation to the vessel and to each other, in order to smoothly facilitate loading, transport and lifting, keeping a watchful eye on safety aspects for the vessel’s crew and contractors.” The layout adopted on Sea Installer is characterised by the
grouping of towers, blades and nacelles in distinct areas. This is in contrast to the usual practice of trying to make maximum use of the space on deck by placing different types of components
A2SEA believes the optimised deck layout it has adopted on Sea
Installer has a number of benefits, is safer and reduces costs
together throughout the deck space. Another obvious difference is in the way the blade rack is centred such that the blades protrude both to port and starboard. Normally, blades protrude on one side of the vessel. A2SEA believes that the layout it has adopted has benefits during the installation phase and during loading too. One of these is the ability not only to perform simultaneous lifts but to be able to prepare for the next lift (such as hooking a crane up to the next component) before the preceding lift is completed. What makes this possible is the distance between dedicated component areas on the deck. “This means that is possible to reduce loading time to some degree,” he explained. “Another advantage is seafastenings. Thanks to specific, dedicated areas for each component on deck, we have been able to standardise the design of seafastenings rather than requiring a different fastening (such as a specially constructed bracket) for the same component at varying deck locations. “Stability of the vessel is also enhanced. Typically, with a full complement of components on board, there’s a lot of load at the aft end of an installation vessel, requiring vast amounts of ballast water as a counter weight. With the new deck layout, however, the load is distributed optimally around the vessel’s centre of gravity, requiring less ballast water and reducing structural stress. Related to the issue of stability but also to the vessel’s ability to sail in a variety of sea conditions is the way in which the new layout calls for the blade rack to be centred such that blades protrude both port and starboard. Doing so reduces the likelihood of blade tip immersion (waves touching the blades) in higher sea states, enabling the vessel to confidently sail in adverse conditions. Mr Andersen said A2SEA believes that sticking with the same basic deck layout makes mobilisation easier too. With, for example, towers and their foundations concentrated in one deck area and nacelles in another, multiple teams can work simultaneously, each focusing on their particular component type. With such clear delineation, each operation is safer, despite the fact that there may be more than one lift being performed at the same time. Perhaps the best aspect of the standardised arrangement,
Mr Andersen believes, is the way in which it enables on-site installation. An important part of that puzzle involves the positioning of the gangway in relation to the transition piece. Towers, for example, placed far from the nacelles on the starboard side don’t present the usual conflicts that can make lifting nacelles a delicate task. Moreover, with the blades positioned forward, there’s more free space at the aft end where the transition piece is located, approximately 20m from the vessel. The blade rack is high and wide, which means that, if it were placed aft, it would be likely to come too close to the transition piece. As a result, lifts seldom take place above the gangway except, of course, for final tower lifts onto the transition piece. The Siemens installation team on board the vessel also benefits
from the optimised deck layout. Their office is located adjacent to the gangway – and with fewer lifts over the gangway area, they have greater access to the turbine being installed as well as a better overview of operations from the office. OWJ
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