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Saturday, October 5, 2013

Elevators for Buildings


Elevators are one of the critical machinery in a highrise Apartment Building. It is important that the maintenance staff as well as Management Committee Members are aware of some of the important aspects of their Elevators.

Types of Elevators in Apartment Complexes

Generally there are two types of Elevators in Residential Complexes:
1. Geared-traction elevators. These are moved by hoist cables driven by a geared reduction unit, and are
generally used in midrise, mid-speed applications, such as commercial buildings of nine floors or less and
residential buildings of 18 floors or less.  Speed of these Elevators:
Five floors or less: 200 feet per minute
Nine floors or less: 350 feet per minute
Eighteen floors or less: 450 feet per minute
2. Gearless-traction elevators. These are moved by hoist cables driven directly by a large-frame motor, and are
generally used for high-rise, high-speed applications, such as commercial buildings over nine floors and
residential buildings over 18 floors. Speed of these Elevators:
Fifteen floors or less: 500 feet per minute
Fifteen to 25 floors: 700 feet per minute
Above 25 floors: 1,000 plus feet per minute
There should be 1 Elevator for every 60-90 Apartments. Also, it is useful to have one over-sized elevator to carry Furnitures.
Most elevator related Emergencies are due to either Power Failure or Fire. Residents face horrific moments when trapped inside an Elevator during any of these emergency situations. While safety devices need to be in place to safely evacuate the Residents, the Residents also need to be instructed so they are prepared for such emergencies.

Power Failure

Frequent Elevator related issues are related to safe exit of Residents when the ELevator stops midway when Power Failure happens. When Power fails, as a safety mechanism, all brakes are applied in the Elevator, so it stops where it is – this could be between two floors. Hence, the doors do not open. This causes panic for the Resident, especially if the inside lights and fans also switch off.  Most modern Elevators have battery backup for the light and fan inside the Elevator and also come with the mechanism of Automatic lowering of the Elevator to the Ground Floor when Power Failure Happens.
However, such fixtures can be provided in existing Elevators as well. A Battery Lowering Device is a device intended to automatically lower an elevator in a pre-determined manner in the event of a main power supply failure. When the power goes off, the Battery Lowering Device comes on while all elevator safety features remain operative. Immediately the functions of control and door operation are given their proper voltage by the use of a battery operated transistorized power supply. The elevator then descends to the lowest landing and opens its doors to discharge passengers who might otherwise have been trapped.
In the absence of an Emergency Lowering Device, the Elevator needs to be manually lowered to a floor for exit. The Machine Room of the Elevator can be accessed and the Hoisting Machine and Controller can be used to manually lower the Elevator. All Maintenance staff must be trained in doing so, the training can be imparted by the AMC personnel of the Elevator.
Typical Traction Elevator

Fire

In case of Elevators with integration with Fire Alarms, when the Fire Alarm is activated in any elevator lobby of any floor of a building, the elevator cars that report to that location get disabled and will automatically return to the ground level floor, where the doors will open. The recalled elevators will remain inoperative in that position with the doors open until the alarm is cleared and reset or until an emergency responder overrides the automatic shutdown systems and takes manual control of the car, a sequence called Phase 1 or Phase 2 override.
An “Alternate recall” should happen when a fire alarm originates in the ground floor elevator lobby itself. In that case, the elevator system will still go into recall mode, but the cars will return to a floor other than the Ground Floor, called an Alternate Floor. It should be a floor that would be the quickest and easiest to evacuate from after the ground floor.
“Phase 1 Override”: All elevators have built in systems to manually activate the recall functions and/or to override them.
Phase 1 override is activated by a key switch on the wall outside the elevators. Similarly functioning key switches may additionally be located in elevator control panels in fire control rooms or other emergency control locations. By inserting the right key, this switch enables an operator to manually initiate an elevator recall of the adjacent bank of elevators, or to bypass a recall that may have already happened. An emergency responder may want to manually activate an elevator recall because of an emergency situation that has not been detected by an automatically alarm system. Conversely, an emergency responder or maintenance person may want to override an automatically initiated recall because an alarm area has been found to be safe and the automatic system has not yet been reset or has malfunctioned.
“Phase 2 Override”:
Phase 2 is an emergency service that is initiated with a key in a switch inside each elevator car. Each individual car works separately in phase 2 and the condition can only be initiated when the car is actively in recall. Phase 2 gives the emergency responder the option of accessing an active alarm area by elevator, but alters the functions of the elevator car in ways that increase the margin for safety of the responder. When Phase 2 is activated, the responder assumes manual control of an individual elevator car. The car works almost normally, with important exceptions. The firefighter can instruct the car to go to any floor it serves. When the car arrives at the floor, the doors do not open automatically. The doors will open only with continuous pressure on the door open button. If the button is released during opening, the doors will stop opening and reclose. This feature is meant to protect firefighters from opening the doors into a fire situation. Once the doors have been fully opened the elevator will stay in place with the doors open and they will remain open until a command is given to close them by continuously holding the door close button. The elevator will then remain in place with the doors closed until a floor button is pressed, when it will then start the same process on the selected floor.
Safety Instructions to Passengers: Please also see the Post “Elevator Safety for Residents“, that has instructions for Safe Usage of Elevators by Apartment Residents.

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