A fracture in the welding that connects the tower top flange with the tower had caused the breaking of the turbine Number 7 at the Samsø (Paludans Flak) offshore wind farm, Siemens said in a statement.
With the fracture developing over time, the tower top flange ultimately separated from the rest of the tower.
“The welding at the time of installation was made according to the industry welding standards of the production year 2002. The industry welding standards have subsequently been changed. The specific welding geometry in the Samsø turbine has only been used by a single tower supplier. This specific tower configuration is limited to 14 turbines only and the relevant customers have been informed,” Siemens explained.
The company did not find any cracks at the nine remaining turbines and said there is no evidence that the Samsø incident is related to a generic design or production defect.
The 2.3-MW wind turbine at the Samsø offshore wind farm broke off on 28 November, and the nacelle, hub and blades fell into the sea. No one was injured, and no one was working in or near the turbine at the time of the incident.
The impacted turbine was installed by Bonus Energy in 2002. Siemens acquired Bonus Energy in 2004. The operator of the wind farm is Samsø Havvind A/S.