Sunday, 28 August 2016

Troll-A Platform – the Largest Structure Moved by Humankind

Troll-A is an offshore natural gas platform in the Troll gas field off the west coast of Norway. Troll-A, with the weight of 1.2 million tons with ballast, the height of 472 meters, and the underwater concrete structure of 369 meters, is an engineering masterpiece. 

Troll-A Platform – the Largest Structure Moved by Humankind

It is not just one of the largest and most complicated technical projects in history, moreover, it is the largest structure ever moved by humankind. The platform was a widely broadcast when it was towed into the North Sea in 1996. Currently it is operated by Statoil. 

Usually platform's legs are transported separately and then, supported by special ships, they are put in place. In the case of Troll-A, the whole platform was assembled at one place and then moved to the sea. The platform was towed over 200 km from Vats, in the northern part of Rogaland, to the Troll field, 80 km north-west of Bergen. The tow took seven days. 

The Troll-A platform stands on the sea floor 303 meters below the surface. One of the concrete cylindrical legs has an elevator that takes workers and engineering staff to the sea floor over nine minutes. The walls of Troll A's legs are over 1 meter thick and are made of steel reinforced concrete formed in one continuous pour. 

The four legs are joined by a reinforced concrete box interconnecting the legs, which has the function of damping out potentially destructive resonances by retuning the leg natural frequencies. Each leg is also sub-divided along its length into independent water-tight compartments. The legs use groups of six 40 meters vacuum-anchors holding it fixed in the sea floor. 

Troll-A Platform – the Largest Structure Moved by Humankind

In 1996, the platform set the Guinness World Record for “largest offshore gas platform”. However today this record belongs to the Petronius platform in the Gulf of Mexico, this platform towers almost 610 meters above the ocean floor. 

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