The Worlds Biggest Machines

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Engines come in all shapes and sizes and are manufactured for a variety of applications. Modern-day vehicles primarily use petroleum or diesel fed internal-combustion engines as their power plant, with a typical displacement¹ in the range of 1-3 litres. Some modes of transport, however, require more powerful propulsion systems - none more so than ships. The Wärtsilä 14 cylinder RTA-flex96C diesel engine fulfils that requirement for some of the largest ocean-going vessels and proudly holds the title of the worlds' biggest engine with a total displacement of 25,480 litres.

The Development

The RTA-C range of engines were developed in response to 'post-Panamax' container-ship requirements. The term 'Panamax' is used to describe vessels that can successfully navigate the Panama Canal, located in Panama, Central America. Post-Panamax ships have measurements that exceed the capacity of the waterway and the term describes vessels with a length greater than 300m, a beam greater than 43m and a draft greater than 14.5m.

Ship owners and operators continually seek greater efficiency and cost control in their operations. Since 1998, new vessels have been commissioned with a capacity of approximately 10,000 TEU. The abbreviation TEU signifies the number of twenty foot transportation containers (or variations of them) the vessel can hold and stands for Twenty-foot Equivalent Unit. Panamax ships operate in the 2,500-5,000 TEU range while post-Panamax covers 5,000-10,000 TEU vessels. Post-Panamax-plus, or Suezmax are set to become the latest generation of ultra large cargo carriers (ULCC) operating between 10,000-12,000 TEU.

Owners prefer single-engine, single-shaft propulsion at this size to provide them with economy of scale at their preferred service speed of 25 knots. The RTA-flex96C has the capacity to power a 12,000 TEU vessel. Future built ships in excess of 12,000 TEU (post-Suezmax-plus) are predicted to require two engines to maintain this speed. The Suez Canal in Egypt will need to be widened and deepened and ports will require significant restructuring to handle new vessels of this size.

The Range

Wärtsilä produce a number of variants in the range starting at six cylinders and increasing in one cylinder increments to 14. Power outputs range from 34,320kW (46,680bhp) for the six cylinder through to 80,080kW (108,920bhp) for the 14 cylinder version. All engines are two-stroke heavy oil units.

Four 8600 TEU ships are currently being built that will utilise the 14 cylinder engine. Two are under-construction at Hyundai Samho Heavy Industries Co Ltd and two at Hyundai Heavy Industries Co Ltd, both in Korea. The Engines will also be built at Hyundai Heavy Industries Co Ltd, under license from Wärtsilä. The vessels are due to enter service, navigating the East Asia to Europe routes, in the early part of 2008.

Over 100 engines from the RTA96-C range are in service or on order. The first 12 cylinder version entered service in December, 2004.

The internals of the engine are somewhat different to most internal-combustion diesel engines. Instead of the connecting rod being directly attached to the piston it is connected via a huge piston rod to absorb sideways forces traditionally produced by the connecting rod. This design increases the engines service life and reduces the need for major maintenance.

Vital Statistics

Despite the immense size and phenomenal output of this engine it can claim yet another title as it is also the most fuel efficient diesel engine in the world. Fuel consumption at maximum output (or 100% loading) is 171g/kWh (grammes per kilowatt hour) referred to as Brake Specific Fuel Consumption (BSFC). Fuel consumption at maximum economy equates to 163g/kWh. The engine can achieve in excess of 50% thermal efficiency when operated at its maximum economy settings. This means that more than 50% of the inherent energy contained within the fuel-oil can be successfully converted into motion. As a comparison, most small aircraft and automobile engines have quoted BSFC statistics in the region of 300-350g/kWh and only achieve 25-30% thermal efficiency. Engine overhauls for major system components, such as the crank-shaft, are expected to be greater than 3 working years.

• Weight: 2,300,000kg
• Length: 27.31m
• Height: 13.52m
• Number of Cylinders: 14
• Cylinder Bore: 960mm
• Piston Stroke: 2500mm
• Rotational Speed: 92 - 102rpm
• Piston Speed: 8.5m/s
• Maximum Output: 80,080kW at 102rpm
• Fuel Consumption: 171g/kWh (approx 2,540 gallons/hour at 100% load).

Closest Competitors

None. Apart from its brothers and sisters, this engine stands in a class of its own. In theory an increase in the number of cylinders is possible, but allowing for economy of scale and ship owners requirements, this is unlikely. Future generation ships are likely to be significantly larger than the vessels of today and will utilise multiple, smaller engine configurations. The 14-RTA-flex96C is likely to hold its record for some time.