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potential of the system which Becker cited as delivering power savings of between three and eight per cent. During their investigations, it was found that


a 118,000dwt vessel operating at design speed of 14.6knots and with a fixed pitch propeller could attain a 0.27 speed increase with a 6.9% power reduction by using the Mewis Duct arrangement. A 12,000dwt vessel with a design speed of 15.2knots and operating a controllable pitch propeller could benefit from a 0.22 speed increase using 7.7% less power, and consequently fuel. The system consists of two strong fixed


elements mounted on the vessel: a duct positioned ahead of the propeller together with an integrated fin system within. Te duct straightens and accelerates the hull wake into the propeller and also produces a net ahead thrust. Te fin system provides a pre-swirl to the ship wake which reduces losses in propeller slipstream, resulting in an increase in propeller thrust at given propulsive power. Both effects contribute to each other. The achievable power savings from the


Mewis Duct are dependent on the propeller thrust loading, but virtually independent of ship draught and speed, says Becker. Launched during last year’s SMM


exhibition, in Hamburg, the manufacturer has already taken orders for system. Te first retrofit units were installed in July to the first of three 46,600dwt, Grieg Shipping-owned vessel; the second order came from Sweden’s Laurin Maritime who will retrofit the 182m tanker Tambourin with a system during a scheduled docking this September. According to Becker, first calculations promise 7.5% of power reduction. Sweden’s Berg Propulsion has also been


swiſt to take orders for a relatively new and untried thruster product. The company announced during Nor- Shipping that it has taken orders for the first two BAT 626 (Berg Azimuth Truster) production units. Tese will be delivered in 2010 to Dubai Shipbuilding and Engineering for installation in an Offshore Supply Vessel. Suitable for either electric or diesel drive


up to 2500kW, BATs are designed for high performance and heavy duty operation and will be available in both the controllable pitch propeller and fixed pitch propeller versions. Te first two production units are designed with controllable pitch propellers and will be diesel engine driven. Each unit


The Naval Architect July/August 2009 2 x SCD 2020 · 2 x STT 4CP Innovators in propulsion technology


SCHOTTEL GmbH Mainzer Str. 99 · D-56322 Spay/Germany Tel.: + 49 (0) 26 28 / 6 10 · Fax: + 49 (0) 26 28 / 6 13 00 info@schottel.de · www.schottel.de


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is designed for 1839kW. Te order follows the June delivery of a full


scale prototype for installation to a Swedish Survey Vessel in Sweden, operational data from which Berg will evaluate so as to optimise the design, manufacturing and installation process. But successful delivery of the first production units, to be built in Singapore at its newly built factory, is strategically important since the order marks the company’s entry into the workboat, tugboat and specialised vessel sectors. Compared with more established thrusters


NavalArchitect_SCD_115x175_0609:NavalArchitect_SCD_115x175_0609 01.07.200 marketed towards these sectors, Berg believes


its BAT units will offer a competitive technical edge. The development of the azimuth thrusters is based on Berg’s controllable pitch hub (BCP), which has been on the market for eight years. Te gearbox and lower part of the thruster is based on its tunnel thruster products. “So it is not a completely new design for us. We know the bits and pieces and we can put them all together to develop a reliable product. Customers will recognise our previous designs in the new product. We have focused on reliability without compromising performance,” explained product manager Emil Cerdier. NA


SCD SCHOTTEL Combi Drive


A highly efficient azimuth drive system


• Combination of electric drive system with proven mechanical components


• Utmost manoeuvrability due to 360° steering


• No shaftline required • Extremely compact design • Easy to install by the shipyard


2 x SCD 2020


Our product range comprises azimuth propulsion systems, manoeuvring and take-home devices, and also complete conventional propulsion packages rated at up to 30 MW.


Through our worldwide sales and service network we offer economical and reliable solu- tions for vessels of a wide range of different sizes and types. So we can provide the right thrust.


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