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EB welding sparks transformation in offshore turbine foundations

4C Offshore | Chloe Emanuel
By: Chloe Emanuel 11/05/2023 CVE

A collaboration between Cambridge Vacuum Engineering (CVE), SSE Renewables, Sif Group and TWI has successfully incorporated the first ever electron beam welded section into an offshore wind turbine monopile foundation, also known as a transition piece. The monopile, which will be installed in the second phase of the Dogger Bank wind farm located off the Northeast coast of England, marks a significant advancement in fabrication techniques for monopiles.

Conventionally, monopiles are fabricated using submerged arc welding (SAW), but the consortium's collaboration has demonstrated that electron beam (EB) welding offers several advantages. EB welding is considerably faster, cheaper, cleaner, and more energy-efficient than SAW, states CVE, while producing high quality welds with excellent fatigue properties.

The specific EB welding technology utilized, known as EbflowTM, represents a development in the electron beam welding industry. Unlike traditional methods that require welding within a costly and size limiting vacuum chamber, Ebflow employs a local vacuum system that creates and maintains a vacuum only around the welded seam. This breakthrough enables the use of EB welding on large structures like monopiles, which aims to significantly reduce costs and increase productivity. Developed by CVE, the technology has demonstrated welding speeds at least 25 times faster than current methods, while utilizing 90% less energy, costing 88% less, and resulting in 97% fewer CO2 emissions compared to SAW techniques.

To implement the Ebflow system, an installation was carried out at Sif's Maasvlakte 2 facility in Rotterdam. The system performed longitudinal welds on 2750 millimetre length seams of eight metre diameter rolled cans with wall thickness ranging from 67 to 85 millimetres. The welding machine, weld procedures, and operators underwent qualification witnessed by third party inspectors and regulatory body DNV, which subsequently issued a technology qualification for EB welding and non destructive testing (NDT) of the longitudinal seams produced with the process.

A comprehensive performance testing program demonstrated that Ebflow produces welds with fatigue strength equal to, if not better than, those observed in equivalent arc welded joints.

In January 2023, the resulting can was incorporated into a monopile transition piece, and its installation as part of a foundation in the Dogger Bank Wind Farm is scheduled for late 2023.

Olly Cass, SSE Renewables Project Director for Dogger Bank Wind Farm, expressed his excitement about this pioneering project and its potential impact on the UK offshore engineering industry. With monopile foundations accounting for over 90% of foundations used in UK projects, the Ebflow RPEB technique has the potential to deliver significant cost savings for future projects. These savings can ultimately benefit UK energy consumers. Cass further emphasized the collaborative efforts between CVE, Sif Group, and TWI that made this project possible, and the potential for scaling up this technique to accelerate progress towards net-zero targets.

Dogger Bank Wind Farm, a joint venture between SSE Renewables, Equinor, and Vårgrønn, will consist of three 1.2GW phases and is expected to begin generating power this summer.

For more information on offshore wind farms worldwide, click here.


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