Inspection of the welded pipes with automatic ultrasonic equipment
The Nord Stream pipeline will be made up of high-quality steel pipes with walls ranging in thickness from 41 mm to 27 mm as the pressure drops along the route. They will be sent to specialised coating yards to be coated internally with anti-friction coating and externally with an anti-corrosive and weight coating. From inland storage, the pipes will be taken by pipe carrier to a large pipe-laying vessel, where they will be inspected for possible transport damage.
In a "double-joint welding station", two 12 m pipes will be welded together to a 24 m "double joint", with a welding pass from both inside and outside. Upon completion, the joint will be inspected by ultrasonic testing to identify possible welding defects. Good welds will be covered with an anti-corrosion coating and the double joint lowered to the seabed in a continuous line by pulling the pipe-laying vessel 24 m forward while the pipeline sections are kept under tension over the stinger.
Source for the image and text, is owned by Nord Stream AG