Offshore wind farms are becoming an increasingly popular source of renewable energy as countries look to reduce their reliance on fossil fuels. These farms rely on sturdy foundations to support the towering turbines that generate power, and the industry has traditionally used submerged arc welding (SAW) to construct these structures.
However, a consortium made up of Sif, SSE Renewables, Cambridge Vacuum Engineering (CVE), and TWI has developed a new technique that could revolutionize the way these foundations are built.
The consortium has successfully incorporated the first-ever electron beam welded section into an offshore wind turbine monopile foundation. This technology, called Ebflow, uses a local vacuum system to create and maintain a vacuum around only the seam being welded.
This eliminates the need for a costly and size-limiting vacuum chamber, making it possible to use EB welding on large structures such as monopiles. The Ebflow technique is significantly quicker, cheaper, cleaner, and more energy-efficient than SAW, producing high-quality welds with excellent fatigue properties.
The project required the installation of an Ebflow system at Sif's Maasvlakte 2 facility in Rotterdam to weld 2750mm length seams on eight-meter diameter rolled cans with a wall thickness of between 67mm to 85mm. The welding machine, weld procedures, and operators were qualified by third-party inspectors and the regulatory body DNV, which subsequently issued a technology qualification for EB welding and non-destructive testing of the longitudinal seams produced with the process.
The resulting can was incorporated into a monopile transition piece in January 2023 and is scheduled to be installed offshore as part of a foundation in the Dogger Bank Wind Farm later this year. The performance testing program demonstrated that Ebflow produces welds with fatigue strength that is at least as good as, if not better than, observed in equivalent arc welded joints.
This UK innovation is a world-leading technology that could realize significant cost savings on future projects. With monopile type foundations accounting for over 90% of foundations used in UK projects, Ebflow RPEB could not only benefit the UK offshore engineering industry but could also be passed on to UK energy consumers.
