French tidal turbine pilot proves maintenance-free BUMAX fastener solution


The BUMAX fastener solution has been verified by a two-year pilot project that has contributed to the development of the next generation tidal turbine, capable of providing Europe with reliable renewable energy.

Excellent corrosion resistance and durability

BUMAX® 88 fasteners were used on the 1 MW HydroQuest tidal turbine installed off the coast of Brittany in Northwest France that began operation in April 2019. After over two years of operation at the Paimpol-Bréhat site at 30 m depth, the turbine fasteners showed no traces of corrosion or galling. Tests of the mechanical properties (both strength and ductility) of the bolts conducted by BUMAX after the pilot project showed that they had maintained their properties.

“No issues were found related to bolting during this project, and our team didn’t have any issues with galling during disassembly,” says Raphaël Coquet, Project Director at Hydroquest. “These lessons give us positive learnings for the long-term deployments, and we are confident to manufacture our future turbines with BUMAX bolts.”

The BUMAX® 88 grade was selected for its high molybdenum content and high Pitting resistance equivalent number (PREN) that indicates a high resistance to localized pitting corrosion. This particular grade of 316L stainless steel has an excellent track record when used for BUMAX fasteners in demanding marine applications, to provide durable and maintenance-free fastener solutions.

“Working with BUMAX followed a constructive process where they helped us to find the right bolt for our particular application,” explains Coquet. “The meetings we had with their team helped to develop our design.”

The tidal turbine prototype was designed by HydroQuest, which is a French turbine technology developer of vertical axis turbines. The Paimpol Bréhat site is owned and operated by the energy company EDF.

A maintenance-free fastener solution

The project partners wanted a maintenance-free fastener solution for tidal turbines to minimize operation costs over a lifespan of 20 years. Besides durability, the fasteners also had to be easy to install.

The corrosion resistance, high pitting resistance and high strength provided by BUMAX® 88 bolts are essential for maintenance-free fasteners in corrosive saltwater marine environments. By avoiding the need to maintain or replace the bolts during the operation of the turbine, costs and potentially dangerous procedures can be avoided.

Next generation tidal turbines

Following the pilot project at Paimpol Bréhat, HydroQuest is integrating the learnings from the pilot to design the next generation of tidal turbine, which will also use BUMAX® 88 bolts. Seven of these 2.5 MW tidal turbines will be deployed at the FLOWATT project at the Raz Blanchard site off the coast of Normandy with a design lifespan of 20 years.

The commissioning of FLOWATT is planned for 2025 with the construction of the tidal turbines starting in 2023.

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