This document discusses factors to consider when designing lifts, including population, handling capacity, and quality of service. It provides guidelines for calculating population based on building occupancy type and floor area. Handling capacity is calculated using a formula considering average passengers carried per trip, waiting interval, and total peak population. Quality of service is measured by passenger waiting time, with intervals classified as excellent, good, or fair. Round trip time is also calculated, considering time for passenger entry/exit, door operation, acceleration/deceleration, and travel speeds. Recommended lift speeds are provided for different building types.

1. 1
DESIGN OF LIFT

2. 2
For design of lifts factors to be
considered are –
1. Population or no. of people who
require lift service.
2. Handling capacity or maximum flow
rate required by the people.
3. Interval or quality of service required.

3. 3
1. Population : Population is calculated
based on occupancy type of the
building
Type Occupancy
area/per person
Residential 12.5
Educational 4
Institutional 15

4. 4
Assembly hall with
(a)Dance floor
(b)Dinning
0.6
1.5
Business 10
Mercantile
(a)With basement
(b)With shops on
uppers
3
6

5. 5
Industrial 10
Storage 30
Hazardous 10
Above area per person is gross
area of the floor in square meters. In
case of office building 75% of the
inherent occupancy is expected to
arrive in time (period of ½ hr. before
opening time which peak traffic period
also).

6. 6
Floating population may also be
there to counterfeit the effect of late
coming persons. 100% population as
calculated from floor occupancy basis to
be adopted as total population to be
served, during peak hours.

7. 7
2. Quantity of Service :
The quantity of service is a measure
of the passenger handling capacity of
a vertical transport system. It is
measured in terms of the total number
of passengers handled during each
five minutes peak period of the day.

8. 8
3. Quality of Service :
The quality of service on the other
hand is generally measured by the
passenger waiting time of the various
floors. Quality of service or Acceptable
interval:
20 to 25
seconds
Excellent
30 to 35
seconds
Good
35 to 40
seconds
Fair

9. 9
Handling Capacity & RTT :
The handling capacity is calculated by
the formula:
H = (300 x Q x 100)/T x P
Where
H = Handling capacity as the percentage of
the peak population handled during 5
min.
Q = Average number of passengers carried

10. 10
T = waiting interval, and
P = Total population to be handled during
peak morning period. (It is related to
the area by a particular bank of lifts)
The value of ‘Q’ depends on the
dimensions of the car. It may be noted that
the capacity loaded always to its maximum
capacity during each trip and, therefore,
for calculate the value of ‘Q’ is taken as
80% of the maximum carry capacity of the
car.

11. 11
The waiting interval is calculated by
the formula :
T = RTT/N
Where,
T = waiting interval
N = number of lifts, and

12. 12
RTT = round trip time, that is, the
average time required by each lift in
taking one full load of passengers from
ground floor, discharging them in
various upper floors and coming back
to ground floor for taking fresh
passengers for the next trip.

13. 13
RTT is the sum of the time required in the
following process :
a) Entry of the passengers on the ground
floor,
b) Exit of the passengers on each floor of
discharge,
c) Door closing time before each floor of
discharge,
d) Door opening time on each discharging
operation,

14. 14
e) Acceleration periods,
f) Stopping and leveling periods,
g) Period of full rated speeds between
stops going up, and
h) Period of full rated speeds between
stops going down.
It is observed that the handling capacity is
inversely proportional to the waiting
time which in turn is proportional to
RTT.

15. 15
The round trip time can be decreased
not only by increasing the speed of the
lift but also by improving the design of
the equipment related to opening and
closing of the landing and car doors,
acceleration, deceleration, levelling and
passenger movement.

16. 16
a) The most important factor in shortening
the time consumed between the entry
and the exit of the passengers to the lift
car is the correct design of the door and
the proper car width, for comfortable
entry and exit for passengers, it has
been found that most suitable door
width is 1000 mm and that of car width
is 2000.
b) The utilization of centre opening doors
also favors the door opening and
closing time periods.

17. 17
Capacity :
Minimum size of car recommended
for a single purpose building is one
suitable duty load of 884 Kg. For large
building car 2040 Kg. according to
requirement.

18. 18
Layout :
The width of car is determined by
the width of entrance, and the depth of
car is regulated by loading per sq.mtr.
Permissible. Centre opening door are
the most practicable and most
efficiency entrance with for passenger
lifts.

19. 19
Speed :
It is dependent upon quality of
service required and the quality of service
desired. Therefore, no set formulae for
indicating the speed can be given.
Recommended Speeds :
The following are general guidelines :

20. 20
Office Building Passenger Lifts
Sl.
No.
No. of Floors Recommended
Speed
1. 4 to 5 floors 1 MPS
2. 6 to 12 floors 1.5 MPS
3. Above 12 floors Above 1.5 MPS

21. 21
Residential Building Passenger Lifts
Sl.
No.
No. of Floors Recommended
Speed
1. 4 to 8 floors 1 MPS
2. 8 to 12 floors 1.5 MPS
3. Above 12 floors Above 1.5 MPS

22. 22
Hospital Lifts (Bed cum Passenger Lifts)
Sl.
No.
No. of Floors Recommended
Speed
1. Upto 4 floors 0.5 MPS
2. 5 to 8 floors 0.75 MPS
3. Above 8 floors 1 MPS

23. 23
Goods Lifts
Sl.
No.
No. of Floors Recommended
Speed
1. Upto 6 floors 0.5 MPS
2. Above 6 floors 0.75 MPS
Note:
(1) For passenger cum gods lifts speed shall be
followed as that of passenger lifts.
(2) Actual speed shall be worked out on the
basis of traffic analysis.

24. 24
Calculation of R.T.T.
The most probable number of floors on
which lift may have to be stopped is given
by statistical formula:
Sn = n [ 1-(n-1)/n)Np
]

25. 25
Where
Np= Total number of passengers entering
the car at ground floor (Entrance Lobby)
during peak period which is equal to car
capacity.
n = Total number of floors served
above ground floor.
Sn = Most probable number of stops.

26. 26
No. of upper
floors served
Number of
Passenger/Trip
(Car Capacity)
10 12 14 16 18 20
18 8 9 10 11 12 13
16 8 9 10 10 11 12
14 7 8 9 9 10 11
12 7 8 9 9 10 10
10 6 7 8 8 9 9
8 6 6 7 7 8 8

27. 27
Now,
R.T.T. = Entrance lobby time + Sn x floor
serving time + Return trip time (D-2d)/Vc.
Where, Sn = Probable number of stops
D = Total Lift travel in one direction (m)
d = Distance travelled during acceleration
or deceleration (m)
Vc = Contract speed of elevator in m/s
also.

28. 28
D = ½ ft2
Where,
f = acceleration in m/sec2
t = Time for acceleration
= 2 seconds for lifts upto 2.5 m/s.

29. 29
(a)Entrance Lobby Time : This consists of
door opening, car loading, door closing
time and acceleration at entrance lobby
generally ground floor plus retardation
time (while returning from top).
(b)Floor serving time: This consists of
door opening time, transfer (loading or
unloading time), door closing time,
acceleration and de-acceleration
(retardation) time.

30. 30
(c)Loading/ Unloading time: Practically
observed loading and unloading time
for lifts of different capacity are given
below:
No. of
Passenger
s
Entrance lobby
Loading time in
second
Transfer time i.e.
loading and
unloading time at
upper floors
8 7 1
13 12 1.25
16 14 1.5
20 17 1.6

31. 31
Actually average time required for
entrance of each passenger in car
depends upon total number of persons
entering the car and already available in
car. It may be one second per person
when car is partially loaded and 0.75
second when it is completely empty.
Time for emptying car is less and equal
to 0.75 second for single person but
there is a tendency that all persons
vacate the car simultaneously after
opening if the doors.

32. 32
(d)Door Opening and closing time: Door
closing time is more as compared to
door opening time. This is due to fact
that when all persons have entered in
the car, it takes time for people to
select and press the push button for
summoning the lift to various
destinations.
Total time for door opening and closing
operation can be taken as given below:

33. 33
Type of Door operation Capacity
8 13 16 20
(a) Power operated single slide
(b) Power operated double slide
(c) Power operated centre
Opening
(d) Collapsible with attendant
(e) Collapsible without attendant
3.8 3.8 - -
3.2 3.2 - -
2.8 2.8 3.2 3.2
2.5 2.5 3 3
4 4 - -
Door closing and opening time, at
entrance floor shall be one second more than
all above.

34. 34
(e)Distance travelled by lift during
acceleration or retardation is assumed
to be equal. This can be calculated by
using formula.
d = ut + ½ ft2
Where U is initial speed = 0, f is
acceleration or retardation rate and t is
the time elapsed. It is assumed that
during each cycle, lifts acceleration and
retardation time is about 2 second.

35. 35
Rate of acceleration will vary with type of
as given below:
Lifts speed m/s Rate of
acceleration m/sec2
1 0.50
1.5 0.75
2.5 1.00
More than 2.4 to 8 2.50
More than 8 and
floors more than 50
4.00