Rotor and blades fall from turbine at Rugby wind farm, North Dakota

What happened

On 14 March 2011, the rotor and three large blades detached from one turbine tower at the Rugby wind farm, near Rugby, North Dakota, and fell to the ground. The site, operated by Iberdrola Renewables Inc., has 71 turbines and a capacity of up to 149 megawatts. No one was injured. Iberdrola described the failure as a rotor assembly failure in a letter to North Dakota's Public Service Commission. The wind farm was inspected following the incident and judged safe, resuming operation about a week later, on 21 March 2011.

An investigation into the cause had not been completed at the time the farm resumed generating. The turbine manufacturer, Suzlon Wind Energy Corp., called the event an isolated incident and stated confidence in the safe operation of its global turbine fleet.

Contributing factors

Iberdrola stated the cause was a rotor assembly failure, though the full investigation had not concluded by the time reporting occurred.

Lessons learned

1. Rotor assembly failure on a wind turbine can cause the full rotor and blades to detach without warning, so operators should add detailed checks of hub and bearing bolts to routine inspections.
2. After a rotor assembly failure at one turbine, the operator must inspect all turbines of the same design before resuming output.
3. A nacelle or hub fault that drops blades requires early detection systems and exclusion zones, as ground crews cannot prevent the fall.

More lessons on structural integrity and turbines, from every incident on the register.

Not yet known

• Full results of the cause investigation
• Turbine model and age
• Cost of repairs and lost revenue

This entry is updated when these are reported. Get an alert for the next one like it.

Source

deseret.com