Wind turbine tower collapse - what went wrong.

Two single leg wind turbines were installed to provide electricity to a small size industrial facility. It was alleged that the collapse of the towers occurred as a result of gusting high wind. The investigation, however, revealed that the fall of the aforementioned towers occurred due to the fracture of their poles at the welded mounting flange area.

The analyses of the weldments also divulged that the small radius at the fillet weld toe area, lamellar tear, elevated hardness at the Weld-Metal/Heat Affected Zone in the flange area and the mast (pole, tower) created a stress riser that resulted in crack nucleation and its propagation due to stress induced by the mast lateral movement.

In addition, corrosion that affected these areas, resulted from moisture infiltration through microcracks and delamination of the protective coating.