Wartsila powers Emma Maersk

The largest container ship built to date, the 11,000 TEU ?Emma Maersk?, is propelled by a Wartsila developed 14-cylinder RT-flex96C engine, the worlds most powerful engine in service with an output of 80,080 kW at 102 rpm.

Traditionally low-speed marine engines have been built with a maximum of 12 cylinders. However, when it was recognised some years ago that envisaged container ships would need more than was available from existing RTA96C and RT-flex96C low-speed engines, a solution was found to extend the engine power range to 80,080 kW by offering also 13- and 14-cylinder engines.

The 14-cylinder RT-flex96C is thus based on an already well-established 12-cylinder RT-flex96C design, which itself was developed from the RTA96C engine type widely applied in container ships since 1998. It thus benefits from the wealth of service experience with engines of the same type. To date there are more than 300 RT-flex96C and RTA96C engines in service or on order worldwide.

Extensive consideration was nevertheless given to the practicality of the increased numbers of cylinders and to ensure that the engines match everyone?s expectations in terms of safety, reliability and durability.

With regard to the engine structure, the opportunity had already been taken when adapting the RTA96C engine type to accommodate the RT-flex common-rail system to introduce certain modifications in all cylinder numbers for better manufacture. These changes also resulted in greater stiffness and reduced stresses in the structure. The revision also took into account the 14-cylinder engines to ensure that they had adequate structural strength and rigidity without further modification.

The crankshaft of the RT-flex96C has sufficient torque capacity for 14 cylinders, the material having been upgraded to enable an increased shrink fit for a greater design margin. The thrust bearing structure in RT-flex96C engines with a mid-gear drive has been revised to reduce deformations and stresses even with the increased thrust in the 14-cylinder engine when the vessel is equipped with a shaft motor.

To achieve the designed service speed of 24.5 knots, the propeller drive shaft is fitted with two electric motors powered by five diesel generators with a combined power of 20,700 kW and one combined gas/steam turbine generator of 8,500 kW driven by the main engine exhaust are installed. A waste heat recovery system is installed to optimise the use of the energy produced.