1
Safeties in Escalator
Sachin Chauhan (Airport Systems)

2
What is an Escalator ?
An escalator is a moving staircase which
carries people between floors of a building or
structure. It consists of a motor-driven chain of
individually linked steps on a track which cycle
on a pair of tracks which keep them horizontal.
Applications:
Escalators are commonly used in buildings
where the movement of a large number of
people is required, such as shopping centers,
airports, railway stations, exhibition halls,
hotels etc.

3
How an Escalator works ?

4
Parts of an Escalator

5
Escalators safety device

6
Safety devices in an Escalator
1. Comb Plate
2. Skirt deflector brushes
3. Missing step safety sensor
4. Step Sagging safety switch
5. Emergency Stop push button
6. Comb plate switch
7. Handrail inlet safety switch
8. Handrail break switch
9. Handrail speed monitoring sensor
10. Main drive chain break sensor
11. Handrail drive chain break sensor
12. Motor speed monitoring sensor
13. Step Chain tension switch
14. Skirt micro switch
15. Fire activation alarm
16. Cover plate switch

7
Safety devices
• Comb Plates
The main purpose of the comb plates at the two ends of
the escalator step travel is to prevent injury to persons
riding on the escalator or damage to their clothing or
belongings caused by movement of the step tread
surface beneath the floor plate at the end of the
escalator.
• Skirt deflector brushes:
The escalator brushes are actually a safety feature.
These brushes keep shoes, feet, loose clothing away from
the gap. These are a warning sign or a buffer. The escalator
brushes or ‘skirt deflector’ is designed to minimize the risk of
trapping objects between the steps and the side of the
escalator.

8
Safety devices
• Missing step safety device:
4 sensors are used for checking the steps in escalator.
2 on entry side and 2 on exit side. If any missing step is
detected then these sensors will stop the escalator.
• Step Sagging safety switch:
In case of step sagging, to avoid collision between
Step and comb plate this switch will stop the escalator.

9
Safety devices
• Emergency stop push button:
Usually 2 or 3 emergency stop push buttons are used
in escalators. These emergency stop push buttons are
installed in entry and exit side. If the length of escalator is
large then one emergency stop is installed in mid of the
escalator.
• Comb plate switch:
The comb plate safety switches protect the escalator in
case there is a collision between the steps and the comb
plate. Gap between fix comb plate and movable comb
plate is 5 mm. This movable comb plate is further
connected with a push rod which activates the comb
plate switch and escalator will stop immediately.

10
Safety devices
• Handrail Inlet safety switch:
This switch is used to prevent entering any object or
passenger body part inside the handrail inlet. This
switch will stop the escalator immediately when
activated. 4 Handrail inlet safety switches are used
in an escalator.
• Handrail break switch:
This switch is installed under both handrails and will
be activated if handrail is broken or loose. This switch will
stop the escalator immediately.

11
Safety devices
• Handrail speed monitoring sensor :
A proximity sensor counts the rotation of a roller
which rotates when handrail rotates. Speed of
handrail and this roller is same. This roller is mounted
under the handrail and is having direct contact with
the handrail. If the speed of handrail exceeds more
than the desired speed then escalator will stop
immediately.
• Main drive chain break sensor:
A proximity sensor is used to ensure that the main
drive chain is not broken. This is an inductive type
proximity sensor and give continue signal if the
chain is normally working. if chain is broken then
this sensor will stop the escalator.

12
Safety devices
• Handrail drive chain break sensor :
This sensor is used to ensure the secondary
Or handrail drive chain is not break. This is
also an inductive proximity sensor and will
stop the escalator immediately if chain is broken.
• Motor speed monitoring sensor:
Here, two sensors are used to calculate the speed of
motor. If the speed of motor is more or less than the
desired speed then escalator will be stopped by the
controller and fault will be shown on DDU (Diagnostic
Display Unit). Both breaking units (main brake and
auxiliary brake) will be activated at this time.

13
Safety devices
• Chain tension safety switch:
These switches are used to ensure the step chain
is revolving with proper tension. These switches
will be activated if step chain is loose and
escalator will be stopped by these switches.
• Skirt micro-switch:
Skirt micro-switches shut down the escalator as soon
as an object enters the gap between the steps and
the skirt. 4 micro switches are usually used in
escalators. Depending on requirements, they can be
located in the transition curve areas.

14
Safety devices
• Fire alarm activation switch:
Escalators are also linked with fire alarm
system. If any fire alarm activation command
is received by the escalator then it will be shut down
immediately. Only those escalators will be shut down
which are linked to that particular fire alarm signal. Others
will run normally.
• Cover plate switch:
A limit switch is installed under the cover plate to
prevent any injury at the time of inspection/maintenance.
It also ensure that escalator will not work if cover plate
is open or not closed properly.

15
Safeties in Elevator

16
What is an Elevator ?
Definition:
An elevator is a platform or compartment housed in a shaft for raising and lowering people
or things to different floors or levels.
Applications:
Elevators are highly used in shopping
Malls, railway stations, airports,
Industries etc.

17
Safeties in Elevators
1. Overspeed Governor
2. ARD (Automatic Rescue Device)
3. Door IR sensor
4. Car door contact switch
5. Landing door contact switch
6. Buffers
7. Door Level sensor
8. Floor level sensor
9. Over weight sensor
10. Seismic sensor
11. Fireman switch
12. Up maximum limit switch
13. Down maximum limit switch
14. Emergency door open switch
15. Emergency call / alarm button
16. Buffer limit switch
17. Pit Emergency switch
18. Brake coil switch

18
Safety Devices in Elevator

19
OSG ( Over Speed Governor)
– OSG : OVER SPEED GOVERNOR
This is most important safety of elevators . When elevator
speed cross its Specified speed Limit (additional 20% speed of
rated speed) then OSG is activated. A rod is directly
connected with rope which activates a limit switch which cuts
the power supply of motor.

20
Safety Gear Device
• Safety Gear Device is directly
connected to the Overspeed
Governor.
• It allows the breaking of Elevator in
case of Intervention of Governor
which is activated if there is
deviation in Elevator speed.
• In TKE lifts progressive type
safety gear is used. It decreases
the impact of emergency brakes inside the car.

21
ARD ( Automatic Rescue Device)

22
 ARD (Automatic Rescue Device) is a special
device installed in an Elevator which is Only
used in event of power failure or Balckout in
building.
 ARD act as An Emergency landing Device which
prevent passenger from becoming trapped inside an
Elevator during power failure.
 ARD gives power supply to brake coil to release brake
until the lift reaches to nearest landing floor. ARD can
not rotate the motor.
ARD ( Automatic Rescue Device)

23
• Door IR sensor:
This sensor keeps the door open if senses any
object in between transmitter and receiver end.
• Landing door contact switch:
This switch ensures that landing door is
properly closed before the lift is ready to move.

24
• Door level sensor:
A metallic strip is mounted on the shaft and a
magnetic sensor is mounted on car top. This
sensor will activate when reaches to door level
and it slows down the speed of lift.
• Floor level sensor:
This sensor is also a magnetic sensor and
activates when reaches to floor level. It will
stop the lift at floor level.

25
• Car door contact switch:
This switch ensures that Car door is properly
closed before the lift is ready to move.
• Buffers:
A device located at the bottom of an
elevator hoist way, designed to stop a
car and counter-weight from descending
beyond Its normal limit of travel.

26
SENSORS
• Seismic Sensor:
Detect the tremors of an earthquake
and safely stop the elevator at closest
floor.
• OWS (Over Weight Sensor):
This sensor is mounted under the car
and sense the over weight in Car. This
is an analog PNP type proximity sensor
which gives 0 to 10 V output to
controller which further shows the
weight in percentage.

27
SENSORS
• Fireman Switch:
When fireman switch is activated then lift
will only move to its pre defined floors
and will open its door and stop for
further operation.
• Up maximum limit switch:
When this switch activates lift will not
move up further.

28
SENSORS
• Down maximum limit Switch:
When this switch activates the car will
not move down further.
• Emergency or trap door open switch :
A trap door is available for emergency
rescue of passenger. This switch
activates if trap door is open and lift will
not move till this switch is activated.

29
SENSORS
• Emergency call /Alarm button:
A call button is available inside the car
for inter communication in case of
emergency.
• Pit stop Switch:
In case of maintenance work in pit, an
emergency switch is available in pit. It
will stop the movement of car.

30
SENSORS
• Brake coil switch:
Two switches are used for sensing of
proper working of break coil. When
command is given by controller to break
coil these both switches activates at the
same time. If one or both switches are
not closed at the same time then lift will
not operate.

Thank you