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    Second Nord Stream pipeline completed

    News // July 4, 2012

    Castoro Dieci lowers the pipe into place.

    Nord Stream has successfully completed the second of the two underwater tie-ins of its second gas pipeline through the Baltic Sea. The tie in was completed on 28 June.

    The 1,224km offshore pipeline is now complete and will be de-watered and dried before being joined to the onshore landfall sections in Russia and Germany in August.

    This second line is on schedule to become operational as part of the twin pipeline system in the last quarter of this year. 


    Nord Stream’s twin pipelines were constructed in three sections with reducing pipe-wall thicknesses as the design pressure of the gas drops from 220 bar to 200 and from 200 bar to 177.5, arriving at the European mainland in Germany at 100 bar.

    
The three sections were joined together underwater inside a hyperbaric welding habitat on the seabed at two locations, off the coast of Finland and off the Swedish island of Gotland in June.

    
“This complex operation was successfully completed a few days ahead of schedule thanks to the excellent international collaboration that has characterized the whole project,” said Nicolas Rivet, Project Coordinator for the hyperbaric tie-in operations at Nord Stream.

    “As with Line 1, our diving contractor Technip completed this challenging task outstandingly well, using equipment from the Pipeline Repair System (PRS) Pool operated by Norway’s oil and gas company Statoil.” 


    The underwater welding operations were remotely controlled from the dive support vessel Skandi Arctic. Specialized divers oversaw the complex operations.

    “New technology has made diving safe and the surveillance of the divers is automated. divers are today used instead of ROVs when precision is required,” said Jahn Erling Nakkestad, Project Manager at Technip.

    “Overseeing the hyperbaric tie-in operations requires experienced and skillful divers and our previous experience from other PRS projects on the Norwegian Continental Shelf has been crucial for the success of the project,” he added.

    
The diameter of the Nord Stream pipelines required the PRS equipment to be specially adapted. “The overall tie-in equipment had to be upgraded: the pipe handling frames and the welding habitat had to be enlarged, because such 48-inch diameter pipelines had not been handled before,” said Jan Olav Berge, Statoil’s Pipeline Repair Pool Manager.

    “The same system as used for the tie-ins will be ready to carry out any repairs to these or other large-diameter pipelines in the future if needed,” he added.

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