Mix of marques for bulker record-breakers
An emergent fleet of ore carriers of record-breaking capacity provides references for electronically-controlled ‘cathedral’ engine designs originating from the two main fountainheads of two-stroke diesel technology in Europe, writes David Tinsley.
Originally dubbed the Chinamax class, but now known as the Valemax type, the new generation of 400,000dwt bulkers is intended to reduce unit transportation costs, and thereby enhance the delivered price competitiveness of Brazilian iron ore in expanding Asian markets. While the economies of scale engendered by such a huge shipment size has the most fundamental bearing on per-ton export costs, the efficiency of the ships’ propulsion systems contributes substantially to the whole, and to the long-term viability of the VLOC (very large ore carrier) shipping solution.
The step-up from a standard Capesize bulker to the 400,000dwt VLOC implies a reduction of between 30-40% in fuel consumption and CO2 emissions per tonne of cargo carried.
A series of 12 such vessels ordered by Brazilian mining group Vale from Jiangsu Rongsheng Heavy Industries has been specified with Wärtsilä RT-flex82T engines, while MAN power in the form of S80ME-C8 machinery has been nominated for seven ships of the same size contracted from Daewoo Shipbuilding & Marine Engineering. Most or all of a further 16 bulkers in the 400,000dwt category, under construction or on order for various owners and destined for employment in the Vale export trade, will also use the MAN design.
Although the 12-ship deal with Jiangsu Rongsheng in China was the first to be transacted, the initial delivery under the entire 35-vessel programme was made this year by Daewoo, with the completion of the Vale Brasil just 17 months after contract-signing.
The MAN main engines for the Vale Brasil series emanate from Korean licensee Hyundai Heavy Industries. Each installation comprises a seven-cylinder model of the S80ME-C type in its Mark 8 version, giving a maximum output of 29,260kW at just 78rpm. This provides direct drive to a single, fixed pitch propeller designed by Mecklenburger Metallguss. At the engine’s normal continuous rating, the ore carrier is expected to be able to make 14.8 knots at the fully-laden, 23m draught in fair conditions.
A pre-swirl stator has been installed at the stern frame in front of the propeller as an energy saving device. It works by introducing a pre-swirl flow ahead of the propeller, to reduce rotational losses and thereby raise propulsion efficiency.
Completion of the lead vessel in the series booked from Jiangsu Rongsheng, the 400,000dwt Vale China, was imminent at the time of writing in September. The Chinese-built series will provide new references for Wärtsilä RT-flex common-rail technology. This affords benefits to owners and operators in a high degree of flexibility in engine settings for lower fuel consumption, lower minimum running speeds, smokeless operation at all engine speeds, and better control of exhaust emissions at large.
A seven-cylinder RT-flex82T engine has been chosen for Vale China and each of her 11 future consorts from the Chinese yard. Manufactured under licence in China by Hefei RongAn Power Machinery Co, part of the Jiangsu Rongsheng group, each VLOC installation entails a seven-cylinder version with a maximum continuous output of 29,400kW at 76rpm.
When the powering contract was awarded in 2008, the RT-flex82T was one of four new types to have been introduced that year by Wärtsilä. All are based on an 820mm bore, and share a common platform. A particular feature is the extended layout diagram, whereby the power/speed combinations encompass higher running speeds at the R1+ and R2+ ratings, while retaining the usual power outputs at those ratings. The extended fields offer greater flexibility in selecting the most efficient propeller speed for the lowest daily fuel consumption.
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