Accident: Coal Mine Friction Hoist
December 1977, the personnel hoist cage at Island Creek Coal VP-5 Mine crashed into the headframe at 4734 ft/min. or 53.8 miles/hour. The cage was unoccupied at the time of the accident and no injuries were reported. This semi-automatic hoist had been called to the surface but did not start to move after the brakes were released. The hoist operator noticed this abnormal behavior and depressed the emergency stop button which disconnected the drive motor and should have set the drum brake. However, the brake did not set and the cage began to accelerate at 3 « times its normal rate causing a temporary ventilation reversal in the intake air shaft. The hoist operator began to frantically open circuit breakers to disconnect power to the hoist control in an attempt to stop the hoist. The hoist cage collided into the headframe at about the same time the master circuit breaker was opened which ultimately set the brakes. This hoist had been placed into service approximately 1 year prior to the accident. The accident broke the four suspension ropes and severely damaged the sheave wheel and upper portion of the headframe. The hoist drum was also pulled from its mounting base and a portion of the hoist house roof was torn off. The hoist was out of service for 6 months while repair work was performed.

Accident: Coal Mine Elevator
On February 4, 1987, the automatic elevator car at the Duquesne Light Company's Warwick Mine No. 3 North Portal crashed into the headframe at 2118 ft/min. (24 miles/hour) or 3 times faster than normal. The elevator was unoccupied at the time of the accident. The brake lining failed and was torn away from the brake drum. The car governor tripped, but was unable to set the safety catches in the ascending direction. When the elevator collided into the headframe, the car tilted forward and the car doors sprung open facing directly down the 400 ft. shaft.

Accidents: Commercial and Industrial Elevators
The mining industry accidents were initially believed to be isolated incidents. However, research covering a 5-year period, showed there were at least 17 documented cases of commercial and industrial elevators striking the overhead structure. In fact, survey data indicate that for 90% of the hoisting cycles, the elevator is empty or lightly loaded making the counterweight heavier than the conveyance. Consequently, if the main brake fails there are 9 in 10 chances the conveyance will accelerate and crash in the upward direction.

HOISTING REGULATIONS
Rules and regulations applying to hoist and elevator safety have come under review in response to these accidents. The providence of Ontario in Canada requires all new commercial and industrial geared elevators to be equipped with a device to provide ascending overspeed protection and also guard against uncontrolled movement of the conveyance. The Pennsylvania Bureau of Deep Mine Safety has required ascending car overspeed protection on all new and existing coal mine hoisting systems, effective December 1, 1991.