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dh_lift_op, on 24 December 2009 - 08:43 PM, said:
News says it was a brake failure, but the report explaining why it failed has not been released yet.
from Ski Area Management (SAM) website:
http://www.saminfo.c...le.php?tid=4372
(see original article on SAM website for pictures.
SAM Magazine—Merrimac, Wisc., Dec. 28, 2009—The primary cause of the lift accident at Devil’s Head Resort Dec. 17 was a massive failure of the chairlift’s gearbox, according to the resort. Fourteen people were injured when the lift rolled backward after a stop.
With the gearbox out of commission, the lift’s service brake, the primary braking system on the lift, was inoperable. Two backup brake systems also failed. The first, a “drop dog,” is located at the top terminal of the lift. The drop dog is designed to drop into slots in the top bullwheel, preventing rotation. The drop dog system was properly deployed, but failed to engage completely with the bullwheel.
The second system, a drive-sheave or “e-brake system,” was deployed at the bottom terminal. Again, lift operations personnel followed correct procedures in deploying the system, but the braking was inadequate to prevent the rollback. Further analysis of why this component failed to stop the lift will require additional testing once the lift is repaired this week.
“The accident resulted from a combination of an unforeseen mechanical failure and the failure of the backup braking systems,” concluded Devil’s Head general manager Joe Vittengl. “The entire Devil’s Head family truly regrets that this occurred, and we’re working hard to ensure the safety of all of our guests.”
Interior of gearbox with broken gears
Devil’s Head Resort has re-inspected all of its lifts following the incident, paying special attention to the backup braking systems. Beginning this week, technicians will conduct comprehensive inspections on the gearboxes of other lifts similar to the one that failed. The inspections will include chemical analysis of gearbox lubricants, which can provide clues to mechanical issues.
The resort has also begun to add electronically-controlled, automatic anti-rollback devices to all chairlifts. Newer lifts are required to have these systems; lifts of older design are “grandfathered” under tramway codes. Chairlift 3 will have this system installed prior to re-opening.
Even though the operators of Chairlift 3 followed the correct procedures, the resort is reviewing safety protocols with all lift operations personnel. Further, it is reviewing procedures with its lift maintenance team.
Vittengl said that Devil’s Head has replaced the gearbox Chairlift 3 and has conducted a thorough inspection of all electrical and mechanical systems. It is also inspecting the lift’s wire rope. And the lift will undergo a full load test prior to re-opening.
Vittengl said that he expects the lift to return to service sometime this week.
