Nord Stream will utilise high-performance steel pipes coated to underwater specifications. The pipes’ reliability when exposed to high pressure and mechanical force will be thoroughly tested. A sophisticated logistics concept ensures timely and safe delivery of the pipes. The seabed will be surveyed and prepared before any pipes are laid.

The pipes will be manufactured from high-tensile steel in accordance with DNV Offshore Standard OS-F 101. The pipewall thickness will vary from 27 millimetres to 41 millimetres, depending on pressure along the route.

The pipes’ interiors will be treated with an anti-friction coating in order to increase performance. They will be coated with an external anti-corrosion layer and with concrete that is between 60 and 110 millimetres thick to give them extra weight and ensure their stability on the seabed. Approximately one ton of concrete is needed per metre of pipe to counteract buoyancy. Each pipe joint is 12 metres long.

Pipe Testing

Experts from pipe mills and Nord Stream AG, as well as independent experts from renowned certification companies, will conduct inspections and quality control to ensure that the pipeline can withstand internal pressure up to 220 bar. During manufacturing, the pipes will be thoroughly inspected to detect possible material defects not visible to the naked eye.

During pipe manufacturing, the mechanical properties of the pipe steel will also be continuously tested. This ensures that only pipes with the specified strength and durability are used. Finally, each of the finished pipes will undergo a number of rigorous quality checks before being released from the pipe mill. As part of this process, each pipe will be filled with water to a pressure substantially higher than the maximum operational pressure.

Pipes used to construct the Nord Stream pipelines are subject to a three-level quality system with the highest inspection standards. Each offshore weld will be 100% tested in accordance with Det Norske Veritas (DNV) Standard for Offshore Pipelines (DNV-OS-F101, Appendix E). On the pipelay vessel, each pipe weld will be 100% tested by Saipem, the contractor with which Nord Stream has signed a contract to construct the pipeline system. Additionally, the welds will then be checked by Nord Stream inspectors. DNV will monitor all of these procedures.