BS 2 Lift presentation 1

BUILDING SERVICES TWO
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Vertical
Transportation
System

BUILDING | SERVICES | TWO
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Vertical Transportation System
Having completed this lecture, you should be able to:
Type - State the reasons for selecting a particular
type of lift or escalator installation
Location - Appreciate the need for careful
location of lift and escalator installations
Control system - Outline the various methods of
control associated with lifts.
Describe the builders’ work associated with lift
shafts and escalators

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Category of Vertical Transportation
o Vertical Lifts or elevators
o Escalators or moving staircases
o Travelators or moving walkways
Services above mainly associated with
human activity or goods under specific
control.

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Forms of mechanical transportation:
Lifts Escalator Travelato
r

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Primary reasons for the use of this
transportation
1. High rise buildings require rapid vertical
transportation- More offices or residential can
be built.
2. Greater levels of expectation – Life still goes on
without the options but life would be easier
with them.
3. Lift shaft takes up less space than staircase –
lettable or usable space increased.

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Selection of Lift
Selection of location & number of
lifts owes more to natural than
mechanical sciences
Ergonomics (comfort design)
Social behaviour
Psychology

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Location of Lift
Lift should be located centrally
within a building taking into account:
o Proximity of entrances and exits
o Intended ingress and egress routes
o Staircases
o Allowing the use of whole day

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Grouping
o Clustered or group around a nucleus

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Grouping
o Clustered or group around a nucleus
Advantage
o Best standing position.
o Reduce waiting time
o Cost of installation reduced

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Other grouping
 Special purpose:
oGoods lift located close to
production.
oHospitals – Lift for emergency use
oShopping malls – Lift at both ends,
Escalators at
centre

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Number of Lifts
Main considerations
1. Population of building & ingress and
egress times.

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Number of Lifts
2. Quality of service required (waiting
time)

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Number of Lifts
3. Numbers of floors served & height
of building
4. Type of building occupancy
5.Specialist services within building –
transport delicate instrument & equipment
6.Relation of the building with external
public transport services

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Number of Lifts
Which is better?
To have a several small lifts or fewer
large lifts?
(Assuming overall carrying capacity
remains the same)
Answer: Several small lifts

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Round trip time (RTT)
An acceptable method for estimating
and comparing efficiency and
effectiveness of lift installation is
obtained by calculating the round trip
time (RTT)

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• Loading and unloading time
• Opening and closing time
including holding time
• Acceleration & deceleration at
landings
• Operating velocity

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Work example.
A building having five floors at 3m
floor to floor spacing, a car capacity of
six persons and 2m/s speed of travel:

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1. Probable number of stops (S1)
S1 = S – S[(S – 1)/S)]ⁿ
Where S = maximum number of stops
n = number of people or car
capacity
S = 4 – 4 [(4-1)/4]₁ ⁶
= 3.3 stops (3 stops)

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2. Upward journey time (T )ᵤ
T = S [(L/SV) + 2V]₁ᵤ
Where L = lift travel, 4 x 3 m = 12m
V = car speed, 2 m/s
T = 3[(12/4x2] + 2(2)] = 16.5sᵤ

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3. Downward journey time (Td)
Td = L/V + 2V
= 12/2 + 2(2)
= 10s

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4. Passenger transfer time (Tp). Allow
2–3s per person,
At 2s; Tp = 2n
= 2 x 6 = 12s

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5. Door opening time (T ) Assume door speedₒ
(Vd)= 0.5m/s and door width (W) = 1.2m;

Tₒ = 2(S + 1) W/V₁ d
= 2(3 + 1) 1.2/0.5
= 19.2s

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6. Round trip time (RTT)
RTT = T + Tᵤ d+ Tp + Tₒ
= 16.5 + 10 + 12 + 19.2
= 57.7s
Notes:
1. These calculations assume the lift deposits
passengers in one direction only and then
returns.
2. Allowance not made for downward stops,
passengers transfer and door operating times
3. If a group of lifts is being considered, the RTT is
calculated by dividing by the number in the
group.

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Design & Mechanics of Electric Lift

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Electric Lifts
 Components (Traction driven):
 Lift car
 Steel cable
 Driving sheave
 Counterweight
 Load on motor = weight of car + its
load + friction – counterweight
(=about half car load)

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Electric Lifts - Principles of
Operation
 Counterweight reduces load on
electric motor.
 Load on motor = weight of car + its
load + friction – counterweight
(=about half car load)

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Motor set
 Geared type – drive is transmit
through a worm gear.
 Gearless type – direct coupling
from motor to driving sheave.

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Motor set
 Geared type – drive is transmit
through a worm gear.

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Motor set
 Gearless type – direct coupling
from motor to driving sheave.

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 Main requirements of a Lift Motor:
High starting torque
Low kinetic energy
Quietness

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 Powered by direct current (DC)
generator with variable output
due to greater accuracy in use
than Alternating Current (AC)
variations.
 Floor levelling
 Smoother ride

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 DC motor preferred
 More durable in resisting variable
demands
 Frequent stopping and starting.
 Combination of AC & DC
 Traction sheave by AC
 Brakes & reduction gearing by DC

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 Car speed up to .05m/s : 3 phase
AC motors is used.
 Car speed between 0.5m/s to
1.25m/s: a two speed motor
• for quick inter floor travel and
• low landing speeds for comfort.

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 Above 1.5m/s – DC motors is used.
 Advent of modern electronics,
standard AC motors speed is
controlled using static frequency
converters.

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AC induction motor
Induction motor
https://youtu.be/HWrNzUCjbkk
DC Induction motor
https://youtu.be/LAtPHANEfQo

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Roping Arrangements
Two principal methods of drive for
lifts:
1.Drum drive
2.Traction drive

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Drum drive

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Traction Drive (Sheave drive)
a. Single wrap traction
b. Double wrap traction

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Vertical
Transportation
System
Roping
arrangements

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Vertical
Transportation
System
Roping
arrangement
s

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Vertical
Transportation
System
Roping
Arrangement
Compensating cables
(>10 ten sty high
buildings)
-Offset load transfer
from car to
counterweight
-Reduce bounce
-Pit required

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 Pulley system
https://youtu.be/aMx7nIIH9ik
https://youtu.be/LiBcur1aqcg

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 Machine room location
 On top of lift shaft
 Arrangement allows min lengths of
cable
 Allows winding gear to be directly in
line with the load

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 Brakes
 2 types of brake; Operational and
emergency
 Electromagnetic or directly act on
sheave

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 Operational brake
 Electromagnetic or directly act on
sheave
 Mechanically applied but
electromagnetic held off
 Supply failure will apply the brake

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 Emergency brake
 Operates directly on the guide rails
 Consist of a mechanical clamp
controlled by overspeed governor
 Governor fly weights break
electrical contacts in turn applies
mechanical brake
 https://youtu.be/57MID7P3xBc

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Vertical
Transportati
on System
Emergenc
y Brake

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Vertical
Transportati
on System
Emergency
Brake –
overspee
d
governor

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How Lift works
 https://youtu.be/hMdJLXGxynA

(BLD60503/QSB2714)
The End

BS 2 Lift presentation 1

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BS 2 Lift presentation 1