Standard Safety devices in an elevator
Updated: May 31, 2020
LIFT DOOR PROTECTION Multiple-Infra red door protection and mechanical shoes shall be provided for all lift to control door movement which shall cover the entire door opening effectively.
OTHER SAFETY DEVICES Safety devices shall be capable of operating only in the downward direction and stopping fully loaded car, at the tripping speed of the over speed governor, even if the suspension devices break, by gripping the guides, and holding the car there. Governor sheave in elevator pit shall be enclosed in a wire cage to a height of 2.40 mtr. All safety devises statutorily required by Lift Inspector, including but not restricted to the following shall be provided:
• Terminal slow down switches These shall be provided and installed to slow down the lift car when approaching the top and bottom landings. The slow down switches shall act independently from the normal car operating device.
• Over travel limit switches These shall be provided and installed to stop the car within the top and bottom clearance, independent of the normal car operating device. The bottom over travel limit switch shall become operative when the bottom of the car touches the buffer. When the over travel limit switches are operative, it shall be impossible to operate the car until the car has been hand would to a position within the normal travel limits.
• Pit Switch An emergency stop switch shall be located in the pit which when operated shall stop the car regardless of the position of hoist way.
• Terminal Buffers Suitable spring buffers mounted on RCC foundation blocks shall be provided in the pit in compliance with ANSI/ASME/ CENEN-81 /JIS codes for stopping the car in case of maloperation. Dowels for the purpose shall be left while casting the pit floor alternatively floor reinforcement could be exposed by chipping for welding additional reinforcement for Dowels. However clearance from underside of the car resting on a fully compressed buffer shall not be less than 1.20 mtr. Buffers shall be designed for a design speed + 15%. Oil buffers shall be provided for the passenger elevators for speed of more than 1.75 mps and spring buffers for lower speed.
• Interlocking Adequate interlocking is to be provided so that the car shall not move if the landing doors are even partially open and also the lift is overloaded.
• Over speed governor Over speed governor shall be of centrifugal type and shall operate the safety gear at a speed at least equal to 115% of the rate speed and less than the over speed governors shall be driven by flexible wire ropes with the following requirements: – The breaking load of ropes shall be related to the force required to operate the safety gear by the safety factor of at least 8
– The nominal rope diameter shall be at least 7 mm- The radio between the pitch diameter of the over speed governor pulley and the nominal rope diameter shall be at least 30 The over speed governors shall be sealed after setting the tripping speed. – The breaking or slackening of the governor rope shall cause the motor to stop by an electric safety device.
• Alarm bells A Concealed 200 mm diameter alarm bell shall be installed in the main security area. The alarm bell shall sound when the alarm bell button in the car operating panel is pressed. The bell shall mute when the pressure on the alarm bell button is released.
• Emergency Stop Switches An emergency stop for use by maintenance personal shall be provided in each lift car.
FIREMAN SWITCH Each Lift shall have a Fireman switch with glass front for access by the Firemen. The operation of this switch shall cancel all calls to this lift and shall stop at the next nearest landing if traveling upwards. The doors shall not open at this landing and the lift shall return to the ground floor. In case the lift is traveling downwards when the fireman’s switch is operated it shall go straight to the ground floor bypassing all calls enroute. The emergency stop button inside the car shall be rendered inoperative.
The fireman’s switch shall be located adjacent to the lift opening at the terminal floor and shall be at a height of approximately 2 m above the floor level. For easy identification of firemen’s lift which confirm to the local authorities requirements, a red and white diagonal striped backing shall be provided behind the glass of the firemen’s switch.
A permanent notice of prominent size indicating the floors served shall be provided and displayed adjacent to the firemen’s lift at the terminal floor. The notice shall be made of laminated plastic sheet or other approved materials with red letters on white background. Details of the notice shall be submitted to the Engineer-in-Charge for approval prior to fabrication.
• Automatic By-pass Load weighing devices located either on car top or under the car cage shall be provided for all lifts. Whenever the load exceed 60-70% of the capacity load of the lifts, the lifts shall ignore all landing calls and only respond to car calls.
• Over load device A load weighing devices shall operate when the load in the car exceeds the rated capacity. The operation of the device shall activate buzzer sound and flashing ‘overload’ signals. At the same time the car doors shall be prevented from closing. When the excess load has been removed form the car, the buzzer alarm shall be muted automatically and the car shall function normally. The sensitivity shall be 30 kg for Passenger lifts and 5% of the contract load for service lifts.
• Automatic self-leveling All lifts shall be provided with automatic self-leveling feature that shall bring the lift car level to within ± 3 mm for passenger/service elevators and + 5mm for freight elevators of the landing floor regardless of load or direction of travel. The automatic self leveling feature shall correct for over travel and rope stretch.
Automatic Rescue Device The ARD shall have the following specifications: a) ARD should move the elevator to the nearest landing in case of power failure during normal operation of elevator. b) ARD should monitor the normal power supply in the main controller and shall activate rescue operation within 10 seconds of normal power supply failure. It should bring the elevator to the nearest floor at a slower speed than the normal run. While proceeding to the nearest floor the elevator will detect the zone and stop. After the elevator has stopped, it automatically opens the doors and parks with door open. After the operation is completed by the ARD the elevator is automatically switched over to normal operation as soon as normal power supply resumes. c) In case the normal supply resumes during ARD in operation the elevator will continue to run in ARD mode until it reaches the nearest landing and the doors are fully opened. If normal power supply resumes when the elevator is at the landing, it will automatically be switched to normal power operation. d) All the lift safeties shall remain active during the ARD mode of operation e) The battery capacity should be adequate so as to operate the ARD at least seven times a day provided the duration between usage is at least 30 minute. In addition, all the car and landing doors shall meet the following general requirements. a) Car door locking devices Every car door shall be provided with an electrical switch to prevent the lift car from being started or kept in motion unless the car door is closed. A mechanical locking device shall also be provided to prevent door opening from inside the car whilst the car is in motion. b) Landing door locking devices Every landing door shall be provided with a mechanical locking device to prevent opening of the door from the landing side in normal cases unless the lift car is in that particular landing zone. c) Projections and recesses Sliding car and landing doors shall be guided on door tracks and sills for the full travel of the doors. The distance between the cars and the landing sills shall not exceed 35 mm. d) Door locking devices All doors locking devices, door switches and associated actuating rods, levers or contracts, shall be inaccessible from the landing or the car. e) Protective devices Protective devices shall be fitted to the leading edges of both car door panels. It shall automatically initiate reopening of the door in the event of a passenger being struck (or about to be struck) by the door in crossing the entrance during the closing movement. The obstruction of either leading edge when closing shall actuate the protective device to function. f) “Door open” alarm “Door open” alarm shall be provided in the car to initiate alarm and a continuous buzzer if a car or landing door has been mechanically kept open for a present period. The period shall be adjustable from 0-10 minute.