Sweden-based BUMAX has announced that its premium stainless steel fastener solution has been verified by a pilot tidal power project in France, with the fasteners suffering no corrosion, wear or galling after two years of operation in extreme conditions.

BUMAX 88 fasteners were used on the 1MW HydroQuest tidal turbine installed off the coast of Brittany in Northwest France that began operation in April 2019. After two years of operation at the Paimpol-Bréhat site at 30m depth, tests of the mechanical properties (both strength and ductility) of the bolts conducted by BUMAX 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,” said 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. The 316L grade stainless steel has an excellent track record in demanding marine applications to provide durable and maintenance-free fastener solutions.

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.

Following the pilot project, HydroQuest is integrating the learnings 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.