An introduction to blade root failures
The wind energy sector is grappling with a surging challenge: blade gap failures — once considered rare — are now a tangible threat to operational efficiency. Recent incidents, like the blade “liberations” (or detachments) at wind farms in Biglow Canyon (Oregon), Findlay Whirlpool (Ohio), and Lundgren (Iowa), starkly illustrate this troubling trend.
A single incident of blade liberation carries significant reputational risk, severely damaging the trust between wind projects and local communities, beyond the serious safety implications.
In the last decade, wind turbine blades have generally been configured with one of two different types of bolted joint architectures to connect the turbine blade to the pitch bearing.
Of these two types, the root insert style derives its name from having an embedded metallic bushing in the blade composite with internal threads to engage the bolt stud. This bolted joint configuration is popular with modern designs because it allows a higher bolt count and smaller root diameters on blades, namely due to lower overall system cost.
Despite the higher bolt count, the root insert architecture is not immune to failures. In recent years, blade losses have occurred due to the failure of this jointed connection and in some cases have led to the collapse of the entire wind turbine.
Modern wind turbines have not only grown to enormous scales but have also evolved to stay cost-competitive; a consequence of this mixture is the higher imbalance loads created when large blades are detached from the rotor in an instant, high enough to buckle towers. A growing sense of urgency for solutions among owners and operators has spurred root cause investigations in OEMs, recommendations for inspections, and monitoring solutions to provide effective containment and advanced warning of progressive failures.
