Major shipowner orders 34 slow steaming kits

12 Jul 2010
Axel Maersk, one of the 34 ships to receive a Wärtsilä slow steaming kit

'Axel Maersk', one of the vessels to which the Wärtsilä slow steaming upgrade kit will be fitted. (picture: A.P. Moller-Maersk Group)

Wärtsilä reports the signing of a major contract with the AP Moeller-Maersk group covering the installation of Wärtsilä slow steaming upgrade kits to 34 more of the company's large container vessels.

The kit was trialled on a sister ship in late 2009, and this had led to more ships, all powered by Wärtsilä RT-flex96C and RTA96C low speed main engines with 10, 11 and 12 cylinders, being fitted with slow steaming upgrades. Wärtsilä says that the kits will produce major savings in fuel consumption while also cutting CO2 emissions. The upgrade kits will be fitted by Wärtsilä, with the company supplying materials, labour, ship-specific engineering and full project management.

It is anticipated that as a result of installing the upgrade kits, these vessels will achieve fuel savings of between 3% and 7% with the engine running at low load. These savings are in addition to those attained through reducing speed to slow steaming operation.

"During recent years we have been continuously looking into solutions that improve the overall fuel efficiency and emissions of our vessels. As operators and charterers of the world's largest container ships fleet, we soon recognised the savings potential of optimising ship speed, and we have been a forerunner in the wide implementation of slow and super slow steaming as a means for substantial fuel consumption and emissions reduction. The Wärtsilä slow steaming upgrade kit provides us with a solution for further fuel savings, while maintaining the necessary full operational flexibility of the ships. The contract for the upgrade kits is an important decision for us," says Palle Laursen, vice president, Maersk Line.

The fuel savings are achieved by cutting out one of the engine's turbochargers at engine loads of less than about 60% (this figure is valid for engines with three turbochargers), thereby providing greater scavenge air pressure for better combustion and optimal engine component temperatures. This cut out is controlled and fully automated.

In addition to the fuel savings, this solution provides full flexibility - with unrestricted operation from 10% to 100% load. The engine is not permanently derated, and can be operated at any time up to its full installed power for full sea speed. It also decreases the risk of engine fouling and excessive component temperatures.

The Upgrade Kit involves fitting shut-off valves in the engine's exhaust duct before the turbocharger turbine, and in the scavenge air duct after the compressor. The valves are remotely operated by a control system included in the kit.

The upgrade is available for most Wärtsilä RTA and RT-flex engines with multiple turbochargers. The achievable BSFC figures are strongly dependent on the final NOx emission balances over the whole load range.

The kits have already been installed in numerous vessels. A typical example is that of a large container vessel, powered by a 12-cylinder Wärtsilä RTA96C with a 60,000 kW continuous rating output. On a round trip from Northern Europe to China and back, which takes eight weeks at a ship speed of 24 knots, the total main engine fuel savings for the roundtrip are in excess of 2900 tons sailing at 20 knots. With the upgrade kit installed, the additional savings amount to 210 tons, which corresponds to about $95,000 in additional savings on one roundtrip. At the same time, the CO2 emissions will be reduced by more than 9,000 tons thanks to the reduced speed, and by an additional 650 tons using the slow steaming upgrade kit.

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