Bilder

Pipe-laying process

1) The pipes are unloaded from the pipe-carrier vessels and stacked on the storage areas on each side of the laybarge. Pipes are delivered regularly to ensure that there are always enough supplies on board to maintain the 24-hour construction schedule.

2) To prepare the pipes for welding, the ends are bevelled to make them exactly the right shape to be fitted together. The inside of the pipe is then cleaned using compressed air before it is conveyed to the double-joint welding station.

3) At the double-joint welding station, two bevelled, 12-metre pipe joints are aligned and welded together to create a double-joint segment measuring 24 metres. These double-joint sections will later be connected to the main pipe string.

4) The double-joint is moved to the non-destructive testing station where every millimetre of the weld undergoes ultrasonic testing to detect any unacceptable flaws. If required, the defect will be repaired and the weld rescanned to meet international quality standards.

5) Following non-destructive testing, the double-joint is moved in a pipe elevator to the central assembly line, or "firing line". There, the insides are checked for debris. The ends of the double-joint are then pre-heated in preparation for welding onto the main pipe string.

6) The prepared double-joints are now joined to the end of the pipeline in a semi-automatic welding process. Qualified welders oversee each of the steps to ensure that welding procedures meet Nord Stream's and authority approved quality standards.

7) The weld of the double-joint that has been welded onto the main pipeline also undergoes ultrasonic testing at another non-destructive testing station. Any unacceptable
flaws will be repaired, and the weld rescanned so that it meets international quality standards.

8) Once the weld is confirmed acceptable, a corrosionresistant, heat-shrink sleeve is applied around its entire circumference. Then, polyurethane foam is poured into a mould surrounding the weld area. This foam hardens, providing further protection.

Kategorien

Pipelinebau › Grafiken / Karten
Grafiken / Karten › Bau und Verlegung der Pipeline

Quelle

Nord Stream AG

Datum

8. April 2010

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