'Forgotten washer' heard in hub before wind turbine collapsed in Cape Breton

Just hours before a massive wind turbine collapsed last year in Cape Breton, a technician performing routine maintenance heard what was believed to be a washer lost in the structure's hub. 

The incident — believed to be the first catastrophic failure of its kind in the country — is described in internal emails between turbine manufacturer Enercon Canada Inc. and the provincial Labour Department. CBC News obtained the documents through a freedom of information request.

The 80-metre turbine at the Point Tupper Wind Farm buckled around its midpoint and crashed to the ground on Aug. 17, 2016. 

No workers were injured, no personal property was damaged and the power grid was not affected by the failure.

Brake not applied

The heavily redacted documents said the turbine's blades and damaged hub were removed the day before the collapse. The hub was replaced while the blades were reattached. 

"Some technical challenges were encountered, but were overcome upon consulting technical support," Enercon's managing director said in an email dated Dec. 16, 2016. The director's name has been blacked out. 

Enercon's email did not elaborate on the hub's damage. However, documents from the Labour Department regarding a subsequent stop-work order said a hub assembly was damaged in a "bearing failure" in March 2016.

On Aug. 17, workers tested the turbine's lightning-protection system, which required positioning the blades so they pitched into the wind.

That's when something went wrong, according to Enercon's email.

"When the rotor is unlocked, a noise is heard (suspected to be a forgotten washer in the hub)," it said. 

"The Enercon technician opens the hatch to look for the washer. He notices the blades are pitched in (approx. 2 [degrees]) instead of pitched out at 90 [degrees].

"The electromechanical brake was not applied ... At this moment, the Enercon technician informs the workers to climb down the WEC [wind energy converter] and proceed to the next site."

Tower evacuated

The email said the tower was evacuated and the site cleared "as soon as the situation became dangerous." Personnel were moved to a safe distance away from the turbine before the structure toppled.

"Four hours after the evacuation of the turbine, the tower collapsed without harming anyone, no explosion nor fire was witnessed so no reporting of this property damage incident needed to be reported according to the Nova Scotia Health and Safety Act and regulations," the email said.

Some residents in nearby Port Hawkesbury said at the time they saw the turbine spinning unusually fast before it fell.

The 10 other turbines at the site, built in 2010, were not affected by the collapse, according to Renewable Energy Services Ltd., which owns and operates the wind farm.

'Bending it like a straw'

CBC News also obtained a separate email sent from provincial staff members to the deputy energy minister.

"There was an incident that occurred resulting in the blades of the turbine hitting the tower and 'bending it like a straw,'" the deputy minister was told.

A stop-work order was issued by the Labour Department, which remained in place while Enercon explained what led to the collapse.

The stop-work order was lifted four months after the collapse, when the company showed it had complied with each of the department's requests for information.

Enercon is a major player in the Nova Scotia wind power community, with its turbines generating 2.6 MW of electricity — enough to power thousands of homes.

The same turbine that collapsed in Point Tupper, called the E82, is also installed elsewhere in the province. 

Second collapse

Less than five months after the collapse, a 50-metre turbine in Grand Étang, N.S., snapped in half during winds reaching 160 km/h. The turbine was made by Denmark-based Vestas.

Nova Scotia Power said no one was at the site at the time and no one was injured.