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Thursday, 26.11.2015, 21:36
First Nord Stream pipelay vessel enters Baltic Sea
The pipelay vessel Castoro 6 is today passing under the Great Belt Bridge, one of Europe’s greatest bridges, on its way to start construction of one of Europe’s largest infrastructure projects. It is the first time, that a large pipelay vessel has ever entered the Baltic Sea. The vessel is planned to stay there for approximately two years, laying the majority of the Nord Stream natural gas pipeline.
Denmark’s Great Belt Bridge, the gateway to the Baltic Sea, is almost seven kilometres long. With a vertical clearance of 65 metres, even the world’s largest cruise ship could pass under it. No special precautions need to be taken to allow the Castoro Sei to pass.
The Nord Stream pipeline is scheduled to transport natural gas to Europe from 2011. Pipelaying activities will commence in the Swedish Exclusive Economic Zone, about 60 kilometres off the coast of the Swedish island of Gotland. From there, the Castoro Sei will slowly move north toward the Gulf of Finland, laying the pipeline at the rate of up to 2.5 kilometres per day.
Years of Thorough Planning
Before pipelaying could start, Nord Stream spent several years carefully planning the pipeline route, taking account of environmental factors from fish spawning and bird migration to sediment and bedrock geology, as well as social and economic aspects such as ship traffic and fishing activities.
A sophisticated HSE (health, safety and environment) plan and an environmental monitoring system have been developed. All equipment and procedures have been developed and tested to meet internationally-recognised standards.
High productivity offshore
Offshore production requires thorough planning: each of the twin 1,224 kilometre long Nord Stream pipelines will consist of about 100,000 concrete weight coated steel pipes weighing about 25 tons each. To ensure uninterrupted pipe-laying, pipe-carrier vessels will continuously deliver pipes to the pipelay vessel. On board, the 12 metre long pipes will be prepared for welding. Then, each pipe will first be welded to another one to form a 24 metre long double pipe, and then these double pipes will be welded onto the pipeline in the vessel’s central production line. Every millimetre of each weld will undergo thorough testing and the vessel will move ahead, slowly lowering the pipeline on to the seabed.