Evacuation System for Lifts in event of Power Failure
In event of power failure in a building that traps passengers in a lift there are a range of systems in use that can take the lift car to a landing, open the doors and release entrapped passengers without requiring a lift mechanic to release the passengers.
It is important to note that the lift safety circuit that checks that all the doors are correctly closed must be proven before any automatic release systems can operate. This is a fundamental feature that all lifts must abide by to ensure passengers are not injured by the lift moving with open doors. It also prevents open lift doors with no lift at the landing and allowing the public to fall down lift shafts. If the lift can’t prove the doors are all closed correctly the emergency release system must not operate, in this case the passengers will need to be released by a qualified lift mechanic. The passengers will be trapped in the cabin but safe!
- Hydraulic commercial and residential lifts. Auto evacuation in hydraulic lifts is a relatively simple system. In event of a power failure the lift will travel down at slow speed to the designated main entrance, the lift doors will open and the passengers can exit the lift. The battery back-up system (UPS) required for this is relatively small as it is only opening valves to allow the flow oil, the lift is descending under gravity.
- The most common auto release system in event of power failure for Traction lifts is different to hydraulic lifts. Commercial and residential traction lifts have a cabin connected with steel ropes going up over a sheave and down to a counterweight to create an energy efficient system to move passengers quickly. These lifts require energy to release brakes in a pulsing manner to allow the cabin with passengers to travel. This type of system travels slowly and may feel a bit disconcerting to passengers as it pulses to release and re apply the brake in a controlled manner. If the cabin and passengers weigh less than the counter weight the lift will travel up to the nearest floor and open the doors. If the passengers and lift weigh more than the counter weight the lift will travel down and open the doors. An expensive system using a large battery power supply is available to drive the lift to a designated floor in event of power failure but this system is not in common use due to cost.
- Some commercial and residential lifts in Melbourne are being supplied with an in-cabin auto release button. This system must be avoided as it exposes passengers to serious injury. This system over rides the lifts primary safety circuit that proves doors are closed. Severe injury to passengers or falling down shafts is a possibility with this system. Lifts with this system should either be turned off and reported to Worksafe or engage a reputable company to disconnect the self-rescue button in the cabin. For further advice on this you may wish to contact a lift consultant.
If you have any further queries relating to this article please contact Melbourne Elevators.
Published: August 16, 2019
