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Conference programme 

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Poster session

Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Sigurd Hildebrandt NAVCONSULT AWSS GmbH&Co.KG., Germany
Sigurd Hildebrandt (1) F P
(1) NAVCONSULT AWSS GmbH&Co.KG., Brunsbüttel, Germany

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Presenter's biography

Biographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited

Sigurd Hildebrandt has 30 years professional experience in the shipbuilding industry. He started his career as an engineer at shipyard Blohm+Voss, Hamburg, taking over various positions including head of export. Leaving there he became Managing Director of a medium sized shipyard, where he followed projects building monopiles and converting the yard’s production capabilities to the renewable sector.
Afterwards, he worked with Voith Turbo in international sales. With his affinity to the renewables he contributes with his knowledge to interdisciplinary working groups. 2014 he started his own business, supporting companies in the offshore and maritime industry.


New multipurpose service vessel with dp2 at attractive charter rates


A new service vessel design will be presented, not just another CTV but a tailor-made windfarm workboat. Thorough market investigations have shown an over-supply of crew transfer vessels, charter rates fall as the demand decreases, consequently only the most economical ones will survive. On the other side, there is a growing need for multipurpose ships, performing numerous tasks in the O&M phase, DP2 capable, with accommodation for technicians and 2-week offshore endurance. Such vessels are either not available or chartered in from the oil+gas market for day rates which are not appropriate for offshore wind energy.


What capabilities should a new design offer in order to reduce the maintenance costs of the turbines? Looking at the cost drivers we see tasks, such as regular inspection of the foundations by ROVs or divers, oil change in the turbines lasting up to five hours, supply of the OSS with big PSVs, or the daily shuttle between harbour and windpark as endurance is too small.
The new design, called Maintainer, performs all these task at day rates far below the usual ones for comparable DP2 ships. It has been developed by NavConsult AWSS and Voith Turbo Marine Engineering.

Main body of abstract

Main emphasis has been put on offering a stable and save working environment even at significant wave heights of 2,5m. So the ship’s length has been dimensioned to 39m, that’s approx. 50% of the wave length prevailing in the North Sea and thus following a well-known naval architect’s rule for reducing pitch motions. Propulsion will be generated by two Voith Schneider Propellers, offering best manoeuvrability enhanced by roll stabilization. With an endurance of 14 days the vessel will be able to operate independently from onshore supply. Twelve technicians will be accommodated in double cabins. The step-over to the turbines can be facilitated by an offshore access system
The spacious aft deck of 75 m² plus additional space in the bow facilitates material transportation to the wind park, but also allows to ship containerized equipment for service tasks. Additionally, fuel, fresh water and sewage can be shipped. The DP2 systems and the high precision in maneuvering allows the vessel to approach any offshore location and stay for the duration of the task.
The specific maintenance jobs that which will be presented and discussed, have all been developed with partners delivering the suitable equipment. So the design benefits from practical in-filed experience and feed-back from daily operations. Specifically we will look at oil change, fuel transfer, crew transfer, diving support and ROV operations.


Reducing costs in the O&M phase needs tailor-made ships with low daily charter rates. The Maintainer fits perfectly into this market segment, it offers the best features of regular and established supply vessels, tugs and CTV´s. Such a combination of capacities and capabilities does not exist so far. This unique vessel design incorporates years of development, discussions with operators and feed-back from service operations. Well known components as the VSP and DP2 are combined with new systems, e.g. a gangway access-system, to facilitate demanding maintenance jobs even in rough sea conditions.

Learning objectives
Allocating a market need for medium-sized service vessels, which rarely exist presently, have led to a new design. The development of this ship will be presented, discussing the influencing factors and showing the way, how conflicting requirements have been harmonized. Finally, a cost comparison will be elaborated showing the saving potentials versus the charter rates.