Wind turbines, like helicopters, are fatigue machines-always vibrating and working to loosen their fasteners. More vibration will come as engineers develop longer blades to capture more wind energy and towers reach higher to accommodate them. These increased vibration levels may loosen some tower fasteners. To prevent this, engineers are looking for better ways to measure tension (rather than torque) and prevent corrosion. Finally, fastening companies are becoming more wary of costs especially as they count toward total cost of ownership (TCO). Torque control is a risky way to achieve consistent pretension in structural bolts. It all comes down to the k-factor, the relationship between the torque applied to a fastener assembly and the actual tension reached in the bolt. K-factors range from 0.10 to 0.20.
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