BS 2 Lift presentation 1

BUILDING SERVICES TWO (BLD60503)

Vertical Transportation System

BUILDING | SERVICES | TWO (BLD60503)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 installationsControl system - Outline the various methods of

control associated with lifts.Describe the builders’ work associated with lift

shafts and escalators

Category of Vertical Transportationo Vertical Lifts or elevatorso Escalators or moving staircaseso Travelators or moving walkways

Services above mainly associated with human activity or goods under specific control.

BUILDING | SERVICES | TWO (BLD60503)

Forms of mechanical transportation:

Lifts Escalator Travelator

Vertical Transportation SystemPrimary 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.

Selection of LiftSelection of location & number of lifts owes more to natural than mechanical sciences

Ergonomics (comfort design)Social behaviourPsychology

Location of LiftLift should be located centrally within a

building taking into account:o Proximity of entrances and exitso Intended ingress and egress routeso Staircaseso Allowing the use of whole day

Groupingo Clustered or group around a nucleus

Advantageo Best standing position.o Reduce waiting timeo Cost of installation reduced

Other grouping Special purpose:

oGoods lift located close to production.oHospitals – Lift for emergency useoShopping malls – Lift at both ends,

Escalators at centre

Number of Lifts Main considerations

1. Population of building & ingress and egress times.

Number of Lifts2. Quality of service required (waiting time)

Number of Lifts3. Numbers of floors served & height of

building 4. Type of building occupancy5.Specialist services within building – transport delicate instrument & equipment 6.Relation of the building with external public transport services

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

Vertical Transportation SystemRound 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)

• Loading and unloading time• Opening and closing time including

holding time• Acceleration & deceleration at

landings• Operating velocity

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:

1. Probable number of stops (S1)S1 = S – S[(S – 1)/S)]ⁿWhere S = maximum number of stops n = number of people or car capacity

S₁ = 4 – 4 [(4-1)/4]⁶

= 3.3 stops (3 stops)

2. Upward journey time (Tᵤ)Tᵤ = S₁ [(L/SV) + 2V]

Where L = lift travel, 4 x 3 m = 12m V = car speed, 2 m/s

Tᵤ = 3[(12/4x2] + 2(2)] = 16.5s

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

= 12/2 + 2(2)= 10s

4. Passenger transfer time (Tp). Allow 2–3s per person,

At 2s; Tp = 2n= 2 x 6 = 12s

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

Tₒ = 2(S₁ + 1) W/Vd

= 2(3 + 1) 1.2/0.5 = 19.2s

Vertical Transportation System6. Round trip time (RTT)

RTT = Tᵤ+ Td+ 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 times3. If a group of lifts is being considered, the RTT is

calculated by dividing by the number in the group.

Design & Mechanics of Electric Lift

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)

Vertical Transportation SystemElectric Lifts - Principles of Operation

Counterweight reduces load on electric motor.

Load on motor = weight of car + its load + friction – counterweight (=about half car load)

Vertical Transportation SystemMotor set

Geared type – drive is transmit through a worm gear.

Gearless type – direct coupling from motor to driving sheave.

Geared type – drive is transmit through a worm gear.

Gearless type – direct coupling from motor to driving sheave.

Main requirements of a Lift Motor:

High starting torqueLow kinetic energyQuietness

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

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

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.

Above 1.5m/s – DC motors is used.

Advent of modern electronics, standard AC motors speed is controlled using static frequency converters.

Vertical Transportation SystemAC induction motor

Induction motorhttps://youtu.be/HWrNzUCjbkk

DC Induction motorhttps://youtu.be/LAtPHANEfQo

Roping Arrangements

Two principal methods of drive for lifts:1.Drum drive2.Traction drive

Vertical Transportation SystemDrum drive

Vertical Transportation SystemTraction Drive (Sheave drive)

a. Single wrap tractionb. Double wrap traction

Vertical Transportation

System

Roping arrangements

System

Roping arrangements

System

Roping arrangements

BUILDING | SERVICES | TWO (BLD60503)Vertical

Transportation System

Roping arrangements

SystemRoping arrangements

Roping ArrangementCompensating cables (>10 ten sty high buildings)-Offset load transfer from car to counterweight-Reduce bounce-Pit required-High tensile steel wire (9 to 19mm dia

BUILDING | SERVICES | TWO (BLD60503/QSB2714)

Vertical Transportation System Pulley system

https://youtu.be/aMx7nIIH9ik

https://youtu.be/LiBcur1aqcg

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

Brakes 2 types of brake; Operational and

emergency Electromagnetic or directly act on

sheave

Operational brake Electromagnetic or directly act on

sheave Mechanically applied but

electromagnetic held off Supply failure will apply the brake

Vertical Transportation System 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

Vertical Transportatio

n System

Emergency Brake

n System

Emergency Brake

n System

Emergency Brake

System

Emergency Brake –overspeed governor

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

The End

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