Constructing the Pipeline

Nord Stream 2 will be one of the world’s longest offshore natural gas pipelines and a major international infrastructure project.

Route

Measuring over 1,200 km in length, Nord Stream 2 will travel from the coast of Russia, through the Baltic Sea, reaching landfall near Greifswald in Germany.

From there, the natural gas enters the European internal energy market and will connect to other pipelines for onward transportation.

Nord Stream 2 will largely follow the route of the existing Nord Stream pipeline. This route has been selected based on years of research and public consultations, optimising for safety, environmental, social, economic and technical considerations.

Industry-leading partners

Safety and environmental protection are foremost considerations throughout the planning, construction and operation of the pipeline. Nord Stream 2 will work with some of the world’s leading suppliers to plan the pipeline, assess environmental impacts, develop the pipes, and lay them in the Baltic Sea. Independent certification body DNV GL will examine key steps in the process, as well as the completed pipeline, to ensure its technical integrity and to oversee Nord Stream 2’s commitments to the highest standards for safety and sustainability.

Pipe design

The Nord Stream 2 twin pipeline will comprise about 200,000 individual pipe sections, each 12 metres long.

The pipes will have a constant internal diameter of 1,153 millimetres and a wall thickness of up to 41 millimetres.

The insides will receive a high-gloss coating to reduce friction as the gas flows through the system. An external coating is applied to prevent corrosion, followed by a concrete weight coating to provide added protection and weigh down the pipeline so that it remains stable on the seabed.

Pipe laying

Once the pipes are produced, coated and tested onshore, they are shipped to the pipelay vessel in the Baltic Sea. There, the individual pipe sections are welded together, scanned to ensure that there are no areas of weakness, and then gradually lowered into the sea in a continuous string. In this way, up to 3 kilometres of pipe can be laid each day.

Pipelaying

The completed pipeline undergoes further testing before being independently verified and certified.

The new pipeline will be connected to the existing gas transportation grid and gas can begin to flow. The system will be continually monitored and regularly maintained to ensure that it operates safely, every day.

The industry behind the pipes

Germany-based pipe manufacturer Europipe is supplying 90,000, or almost half, of the large-diameter pipes that Nord Stream 2 needs to build its twin pipeline across the Baltic Sea. Take an exclusive look inside the pipe mill and find out what goes into making over a thousand kilometres of high-quality offshore pipes on a tight schedule.

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It all begins with steel plates. Huge stacks of them can be found at the start of the production line, ready to be fed in. Plates are delivered to the pipe mill in Mülheim an der Ruhr each day, and one to two production weeks’ worth are stored here as buffers.

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Baret Topikyan (left) and Stefan Klasen (right) are there to assist with the unloading process. “We have to be careful to prevent accidents with the crane moving around above our heads: A plate could come loose and fall,” says Topikyan. “The production for Nord Stream 2 is intensive and things do move quite fast, but safety is still our top priority here,” Klasen adds.

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The first step on the production line is the welding of so-called “run-on” and “run-off” tabs on each end of the plates. These will be removed once the pipes are welded – they only serve to ensure a good and continuous weld all the way to the extremities of each pipe.

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On the so-called forming line, the steel plates first pass through the edge beveller, which machines the longitudinal plate edges. This is important not just for the forming procedure, but also for the subsequent welding process. They then enter the crimping press, which crimps the plate edges to the desired pipe radius. This ensures that the pipes will be almost perfectly round, even in the seam area.

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A couple of years ago, Europipe invested in a new, more powerful crimping press that can apply 11,000 tonnes of pressure and handle wall thicknesses of up to 50 millimetres. The 12-metre long pipes being produced for Nord Stream 2 here have wall thicknesses of 26.8 and 34.6 millimetres: The thickness varies according to which section of the pipeline they will be used for, and the relevant pressure level there.

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The so-called “U-ing” and “O-ing” presses form the plates into round pipes with great precision: The pipes for Nord Stream 2 must all have an internal diameter of exactly 1,153 millimetres. Several thousand tons of steel plates are formed into pipes this way over the course of a single day.

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Carsten Dobbert (middle) and his colleagues are responsible for entering the specific parameters of the Nord Stream 2 pipes into the PLC system that controls the machinery. They then monitor the automated forming process along the entire forming line and fix any problems that occur.

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A fully formed, slit pipe comes out of the “O-ing” press. This machine applies 60,000 tonnes of pressure to the steel plates, making it possible to cold-form them into pipes.

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“Continuous monitoring on our part is necessary because the plates can vary slightly in texture. This has an impact on the pressing process, so we have to make sure that each and every plate is formed into the proper shape,” Carsten Dobbert explains. “We have measurements to check this, and there are specific times when we perform visual inspections.”

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Once the pipes have been formed, they are high-pressure washed with water, and then dried, inside and out. The weld edges in particular must be perfectly clean and dry for the welding process.

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“At this stage, we have a procedure to lift a certain number of pipes up for inspection,” says Walter Tamedl, the machine operator for the washing unit. “I have to check every fifth pipe for imperfections, making sure there are no bumps or dents on it – I use a torch for this, because minuscule irregularities are easier to see by the shadows they create.”

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The imperfections Walter Tamedl looks for can be just a fraction of a millimetre in size, so although he has a well-trained eye after 25 years working for Europipe, he still needs to stay highly concentrated throughout the day.

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The edges of the slit pipes are fixed by tack welding before the pipes receive their final weld on one of seven machines for the inside and outside welds respectively.

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Mustafa Yavuz operates the machine that welds the pipes’ inside seam: “I was specifically trained for this machine when I joined Europipe,” he says. “We do have to produce a lot of pipes per shift for Nord Stream 2, but we’re not constantly under pressure to work faster – the important thing is that we do our job well, and in safe conditions.”

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“When a pipe arrives at my station, I start by making sure it is properly positioned and aligned with the welding machine,” says Mustafa Yavuz. “Then, I configure the position of the welding wires, which have to be directly in front of the joint. Once everything is properly set up, I launch the ignition.”

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“The weld seam has to be continuous – if the process is interrupted halfway through for some reason, it would have to be reversed and the pipe would have to be brought back into its original state to be welded again properly,” Mustafa Yavuz explains.

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Once the machine has run all the way through, Mustafa Yavuz checks the quality of the weld seam on either side. “The specifications tell me how wide and how high the seam has to be on the Nord Stream 2 pipes,” he explains. “Looking at the data on the PC, I can tell whether everything is all right, but I also measure these characteristics manually.”

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The next step, out of a total 23 along the production line, is to weld the pipes from the outside: This is the so-called external welding pass.

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Minor imperfections on the seam can always be corrected by hand in the repairs area.

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After they leave the welding area, the pipes are inspected internally and externally. Ultrasonic and X-ray inspections are also carried out to detect possible material and welding defects. In fact, more than half of the production steps at the pipe mill are about quality control.

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Nord Stream 2 has extremely high requirements when it comes to quality. Even the tiniest irregularities have to be ground down to ensure the pipes’ surfaces are perfectly smooth.

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Once the run-on and run-off tabs have been removed, the pipe ends also have to be ground until they are smooth.

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The so-called “mechanical expander” expands the pipes until they reach exactly the right diameter and a minimal out-of-roundness. The consistency of these parameters is important for the girth welding on the lay vessel, and hence for the productivity and quality of future offshore pipe-laying operations.

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X-raying is just one of the numerous technologies that Europipe uses to test and control the quality of its pipes. The company uses filmless radiography, which improves the reliability of X-ray inspections thanks to automatic image evaluation software.

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The weld reinforcement at the ends of each pipe have to be ground until they blend seamlessly into the surface of the pipes. This is necessary to allow a proper ultrasonic inspection of the girth weld on the offshore installation vessel. A machine performs most of the work…

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… but the finishing touches have to be done by hand. Louis Duarte and his colleagues at the grinding station make sure that the seams don’t stick out or dent the pipe’s surface – not even by a few tenths of a millimetre. “When you have experience, this is easy enough,” says Duarte, who has been working at Europipe for four years. “The main challenge is just the sheer scale of the Nord Stream 2 project – the number of pipes we have to get through during each shift.”

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Finally, the fully formed, welded and ground pipes have to pass one last inspection and quality control before leaving the pipe mill. The production plant puts out several kilometres’ worth of pipes every single day.

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The geometry of all pipe ends is measured comprehensively with automated pipe-end measuring equipment based on optical laser sensors. At this station, Enes Avci additionally measures all of the pipes’ geometrical properties and determines whether they are fit to be delivered to Nord Stream 2. “Among other things,” he says, “I control the seam offset…”

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Enes Avci: “I check the weld bead height…”

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Enes Avci: “I check the bevel angles…”

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“Even at this late stage, pipes that I report as non-compliant with the Nord Stream 2 specifications can still be returned and repaired,” says Enes Avci.

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It takes about three hours to produce one kilometre of pipes here: In total, Europipe will need to deliver the equivalent of 1,134 kilometres to Nord Stream 2.

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Once the pipes have received the final stamp of approval, they are transported out of the plant…

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… and to the coating facility of Mülheim Pipecoatings, the Europipe subsidiary that handles the coating and transport of the steel pipes. Here, they receive an internal epoxy coat to optimise the flow of gas, and an external coating – including the so-called “rough coat” – that both protects them from corrosion and prepares them for the concrete weight coating.

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The coated pipes are either loaded directly onto trains to be delivered, or held at the storage yard to serve as buffers. If on a certain day, production should slow down for some reason, this stock of finished pipes allows Europipe to maintain the agreed daily delivery rate nonetheless. At the moment, 296 pipes are being sent out every single day.

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Alexander Jähring is the head of the logistics department at Mülheim Pipecoatings. He and his team are responsible for transporting the pipes on the premises of the coating plant, and for loading them onto the trains that will deliver them to the Nord Stream 2 logistics hub in Mukran, on the German island of Rügen.

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“Because of the coating, we have to be very careful when lifting and loading the pipes,” says Alexander Jähring. “At the same time, we also have to work fast to keep to Nord Stream 2’s delivery schedule.”

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Pipes are delivered to Mukran at the rate of two trainloads per day, each carrying 148 pipes. “Starting in March, we will even have a third train departing every second day,” says Alexander Jähring.

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Between the pipe mill and the coating plant, 650 employees come to work here each day to ensure that the next trainload goes out as planned. At the end of February 2017, Europipe has already delivered about 10 percent of the total order to Nord Stream 2.