...Both lines of the Nord Stream Pipeline system were laid in three sections. The three sections have different wall thicknesses following the direction of the gas flow. Gas pressure reduces as it makes its way through the pipelines. Therefore, the walls are thickest at the start of the pipelines at Portovaya Bay, Russia, and thinnest at the landing point at Greifswald, Germany.
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In preparation for pipe laying, the seabed was surveyed with a remotely operated vehicle (ROV) to ensure pipelay safety and to confirm the seabed data gathered during the lengthy route planning phase. Additionally, in some locations along the route, the strategic placement of coarse gravel was necessary to create a stable base on which the pipeline can rest. Gravel was transported and placed by dedicated rock placement vessels to the specific locations where support was required prior to pipe laying. On board the pipelay vessels, the construction cycle is made up of several steps including bevelling, welding, testing and the lowering of the pipeline onto the seabed. There are exact procedures defined for each process to ensure quality and compliance with health and safety regulations. Following the laying process, the pipelines were again monitored underwater by ROV to ensure correct positioning...