1. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
LIFTS AND ESCALATORS
3

2. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
DESIGN OF LIFT SYSTEMS
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. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
1. Population : Population is calculated based on occupancy
type of the building
Type Occupancy area/per person
Residential 12.5
Educational 4
Institutional 15
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
Industrial 10
Storage 30
Hazardous 10

4. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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).
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.

5. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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.

6. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
20 to 25 seconds Excellent
30 to 35 seconds Good
35 to 40 seconds Fair
40 to 45 seconds Poor
Over 45 seconds Unsatisfactory
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:

7. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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 in a car
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 calculation the value of ‘Q’ is taken as 80% of the
maximum carry capacity of the car.

8. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
The waiting interval is calculated by the formula :
T = RTT/N
Where,
T = waiting interval
N = number of lifts, and
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.

9. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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,
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. 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, leveling and
passenger movement.

10. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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.

11. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
Capacity :
Minimum size of car recommended for a single purpose building is one
suitable duty load of 884 Kg. For large building car load of 2040 Kg
according to requirement.
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.
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.

12. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
Recommended Speeds :
The following are general guidelines :
Office Building Passenger Lifts
S. 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
Residential Building Passenger Lifts
S. 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

13. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
Hospital Lifts (Bed cum Passenger Lifts)
S. No. No. of Floors Recommended Speed
1. Up to 4 floors 0.5 MPS
2. 5 to 8 floors 0.75 MPS
3. Above 8 floors 1 MPS
Goods Lifts
S. 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.

14. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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]
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.

15. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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
6 5 5 6 6 7 7

16. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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.
D = ½ ft2
Where,
f = acceleration in m/sec2
t = Time for acceleration
= 2 seconds for lifts upto 2.5 m/s.

17. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
(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.
(c) Loading/ Unloading time: Practically observed loading and unloading
time for lifts of different capacity are given below:
No. of
Passengers
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

18. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
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.

19. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
(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:
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.

20. THIRD YEAR B.ARCH, BUILDING SERVICES SULAKSHANA BHANUSHALI
(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.
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