Nord stream has concluded a unique and comprehensive inspection of the internal condition of its two pipelines carrying natural gas from Russia to Germany across the Baltic Sea, as part of its long-term safety and pipeline integrity management strategy.

A measurement tool about 7 m long and weighing more than 7 tonnes was sent through the pipeline from Portovaya Bay in Russia to Lubmin, Germany, travelling at 1.5 m a second propelled by the gas pressure.

The pipeline inspection gauge (PIG) collected high-resolution data on material integrity along the 1,224 km route. The journey from Russia to Germany took 10 days. This was the first time that a pipeline of this length and a wall thickness of up to 41 mm has been analysed in this way. For the inspection run, a device with one of the strongest magnetic fields was developed by Rosen Group in Lingen, Germany. The “intelligent PIG” has an array of electronic sensors, which screen the material integrity and the geometry of the pipeline.

The PIG has collected over one terabyte of data on its journey from Russia and the data was recorded at a rate equivalent to 12 megabits per second, 30 times faster than cellular data networks.

The high-resolution measurement technology can detect the smallest changes in the condition of the pipelines. The exact geographical position of the pipelines is also being documented. The first evaluation of the results confirms that the pipelines have moved only minimally while being operated under full pressure and that there has been no corrosion or deformation.

(From left) Andrey Voronov, offshore manager, operations and maintenance, Nord Stream AG, and Rosen Group officials Sergej Weingandt, survey engineer, and Stephan Harmsen, senior project manager

In 2012 and early summer of 2013, Nord Stream had already examined the external condition of both pipelines. This external visual and instrumental inspection of the pipeline was conducted via remotely operated vehicles (ROVs) followed by support vessels.

The results of the internal and external inspections form the baseline data for regular inspection cycles in the coming years. This will allow any potential changes in the position of the pipes, minimal corrosion and even the smallest mechanical defects to be detected at an early stage.

Nord Stream AG is an international joint venture established for the planning, construction and subsequent operation of the twin offshore gas pipelines through the Baltic Sea.

Russian OAO Gazprom holds a 51 per cent stake in the joint venture. The German companies BASF SE/Wintershall Holding GmbH and E.ON Ruhrgas AG hold 15.5 per cent each, and the Dutch gas infrastructure company NV Nederlandse Gasunie and the French energy company GDF Suez SA each hold a 9 per cent stake. Nord Stream’s head office and operations centre are both in Zug, Switzerland. Nord Stream’s natural gas pipelines through the Baltic Sea have the capacity to transport 55 billion cu m of Russian gas a year to the EU, for at least 50 years. Both lines run in parallel for 1,224 km from Portovaya Bay, near Vyborg, on the Russian Baltic Sea coast to Lubmin, Germany. Each pipeline comprises some 100,000 24-tonne concrete-weight-coated steel pipes laid on the seabed along the precise route approved by the authorities of the five countries through whose waters the pipelines now pass.

The first Nord Stream Pipeline started operation in November 2011, and the second line came on-stream in October 2012, on schedule and on budget.