The container ship Emma Maersk is frequently referred to as ‘the vacuum cleaner’ by leading container ports worldwide as this huge ship comes to a port and ‘sucks up’ a huge load of containers leaving a rather empty port behind.
The capacity is officially 11,000 teu, but figures approaching 13,000 teu has also been seen. “When building a ship this large we had very many parameters we had to get right: For instance we could not just look up the rules in a rulebook as there were none, then we had to sort out the matter of project progression, is our dry dock deep enough, can the vessel get from the dry dock into the open sea, how can we make the construction and design drawings in time and finally – can we get enough steel at the right time?” We are at Odense Steel Ship Yard talking to Kjell M. Harr, Naval Architect and General Manager of the Ship Design Department. He is joined by Henrik Ravnø, Mechanical Engineer from the Machinery Design Department.
With a length overall of 397.1 metres this is among the longest vessels in use, to us it is quite a feat to be able to supply a vessel of this size. “The forces on the hull of a ship this size is tremendous and we had to work hard on design and the work started 2003. For instance the steel thickness of the upper deck can be up to 98 mm. We were a little surprised that the torsion moments and the relative hull movements of the two sides of the ship are larger than anticipated, actually in some places 42 cm in either direction. We also studied the phenomenon of parametric roll by model testing and it was confirmed that in bad weather the ship should not go directly towards the weather. We also secured the largest stabilizers on the market. If Emma Maersk otherwise would roll up to 15 degrees, the stabilizers can reduce this to a mere five degrees, even at low speed” says Harr.
“The need for power on board is also quite large as the ship has a capacity of 1,000 reefers. In total the electrical output on Emma Maersk is 29 MW. When discussing emissions, I think that if we were to build another ship like this, it would probably have less propulsive power. Even so today the ship’s emissions are some 25 per cent less CO2 per tonne kilometre compared to other typical containers ships of today. After all, the more containers you can stack on one keel, the better for the environment. But of course, there is always room for improvement,” says Harr. The waste heat recovery system can capture some ten per of the rated engine output.
Some of the particulars of the ship are quite spectacular – for instance the diameter of the propeller is 9.6 metres and the weight is 130 tonnes. When the propeller, made in a small German town, some 3 to 400 trees had to be cut the get the giant by road to a harbour and a barge here to Odense. All the trees were replaced. The shaft is another giant – 120 metres long. As such, this must be among the longest in the world.
Both Harr and Ravnø agree that this has been a fun project to be a part of with many novel and engineering solutions. There are just so many parameters which can only be tested out in real life.
In spite of the size this is one of the most environmentally friendly vessels ever built. The ship can travel some 71 kilometres using 1 kWh of energy per ton of cargo – more than 100 times less than that of a jumbo jet. The anchor weighs no less than 29 tonnes, and the ship will sail some 170,000 nautical miles every year corresponding to about 7.5 times around the world. If you put all the containers on a train this would be 71 kilometres in length. The silicone paint used saves an estimated 1,200 tonnes of bunker fuel a year.