News reports of elevator free-fall incidents have become increasingly common. In some cases, these incidents result in serious injuries or fatalities. According to accident records from 1 January 2023 to 31 August 2023, approximately 70% of reported elevator accidents were linked to rope slippage or uncontrolled downward movement. This alarming trend demands closer examination of the root causes.
An elevator cabin is typically suspended by 3, 4, 5, or 6 steel ropes, depending on the load and travel height. The likelihood of all ropes breaking simultaneously is extremely low.
Modern elevators are also equipped with multiple safety devices:
If the elevator exceeds its rated speed by approximately 115%, the overspeed governor activates and cuts power to the controller. Simultaneously, the safety gear engages the guide rails and mechanically stops the cabin.
With these safety systems in place, a true free fall is highly unlikely. Most incidents commonly described as "free fall" are actually caused by loss of traction between the ropes and the drive sheave.
Traction is the gripping force generated between the hoist ropes and the pulley grooves of the drive sheave.
In traction elevators, movement is achieved through friction between the ropes and the drive sheave. The ability of the elevator to safely lift and lower passengers depends on maintaining adequate traction.
The traction force is influenced by:
When traction is insufficient, the ropes may slip over the sheave, leading to uncontrolled movement.