The 1224 km of the Nord Stream Pipeline have been successfully inspected by the ROSEN Group, achieving a world record for the longest non-stop inspection run world-wide.
The Nord Stream twin pipeline system comprises the longest subsea offshore gas pipelines in the world. Running from Russia to Germany through the Baltic sea, it is a technological challenge to build inspection tools strong enough to withstand subsea conditions for a distance of about 1224 km.
For the ROSEN Group, the project started in 2008 by the development, design and production of an intelligent pipe cap monitoring system. All steps from the first idea to the final certification by Nord Stream were accomplished within 3 months, made possible by focusing ROSEN know-how in a multi-disciplinary team from different ROSEN locations world-wide. Overall, more than 200.000 coated pipes were protected against weathering and corrosion during a storage period of up to 3 years.
All of them were equipped with the ROSEN Pipe Cap Monitoring System. Each cap incorporated a unique electronic box for pipe identification and surveillance, which communicated via a large wireless network with local and global control centers, where the data was managed by a customized ROSEN integrity management software solution.
In 2011 resp. 2012, ROSEN dewatering pigs where sent through the two lines, proofing the extraordinary quality of ROSEN’s products being nearly brand-new after the run. With these pig runs, ROSEN achieved the world record for the longest non-stop pig run. And it would not be the last.
While the Nord Stream pipelines were built and welded together in the Baltic sea, the development of the cleaning and the inspection tools went on. Key challenges were not only the length of the pipelines, but also the high-wall thickness up to 41 mm. The wall thickness varies over the complete distance. Gas pressure drops as it makes its way through the lines and so the pipeline wall is thickest in Portovaya Bay, Russia and thinnest in Lubmin, Germany.
Four different measurement principles were applied to the combined ROSEN inspection tool. Material loss or corrosion that may be enclosed in the steel or occur between the steel and the outside concrete coating will be detected by the magnetic flux leakage sensor. An internal diameter (ID) mapping caliper detects and characterizes any deviations from the original pipe shape. The shallow internal corrosion sensor is a proximity sensor attached to the caliper arm which can map surface metal loss defects. An inertial navigation system or XYZ-unit is installed on the inspection tool to accurately map the pipeline’s geometry. The aim of the geometry measure-
ment is to detect any incremental movement of the pipeline that could result in example in bending strains. Since the tool works best at a speed of 1.5 metres per second, an active speed control system measures the speed of the tool and controls a bypass valve to slow the tool to the required speed.
The 48 inch combined inspection tool was explicitly developed for the Nord Stream project. The tool weighs over 7.3 tonnes – and measures 6.6 metres in length. It is equipped with high-performance batteries to power the sensors during the inspection and a high-density memory device to record the data for later analysis.
The inspection of the second Nord Stream pipeline started September, 16th and the inspection tool arrived only 10 days later in Lubmin, which makes the desired average tool speed of about 1.5 metres per second. This was the longest non-stop inspection run world-wide, achieving another world record for the ROSEN Group. No significant signs of abrasion on the tool after both the inspections show the excellent quality of the inspection tool. During its journey the tool has collected data amounting to over one terabyte that is now analyzed in detail by ROSEN´s data evaluation experts.
“Key to the success of this project was the team effort across nations as well as the technological leadership and the strength of our business approach. We have scheduled and set the schedule two years ago and are very proud of the fact that we have never been one day behind schedule”, explains Stephan Harmsen, Senior Project Manager of the ROSEN Group and responsible for this project. The ROSEN Group again proved their capabilities to ensure the safe and reliable inspection of highly valued industrial assets on the Nord Stream Pipeline System.
For more information about the Nord Stream Pipeline System visit: http://www.nord-stream.com