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UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
MEBS 6000 2010 Utilities Services
REFERENCES
1) CIBSE Guide D Transportation systems in buildings. CIBSE, London (1993)
2) BARNEY, Gina. Elevator Traffic Handbook – Theory and Practice. Spon Press,
London (2003)
3) JANOVSKY, Lubomir. Elevator mechanical design, 3rd edition. Elevator World,
Mobile, AL (1999)
4) STRAKOSCH, George R. The Vertical Transportation Handbook, 3rd edition.
Wiley, New York (1998)
5) Building (Planning) Regulations, Chapter 123
6) Lifts and Escalators (Safety) Ordinance, Chapter 327
7) Factories and Industrial Undertakings (Goods Lifts) Regulations Chapter 59
Introduction
There are over 60,000 lifts in Hong Kong and the number is increasing at the rate of
about 1,000 a year. Some old buildings were designed on the basis of 20m2 net
rentable area per person. This figure has come down to 5 to 9m2 per person. Some
designs for industrial buildings and crowded commercial premises go down to as low
as 3m2 per person.
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Types of lifts
There are in general 3 categories of lifts, viz
passenger lifts, designed primarily for passenger use, the following types are also
passenger lifts:
→ Observation lift,
→ Handicap lift;
goods lifts, mainly for cargo but can on occasion carry passengers; and
service lifts for goods only and are of such a size that passengers cannot get into
the car, the following is a typical example of service lift:
→
Dumb waiter
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Besides lifts, escalators and paternosters are also means of vertical transportation,
while travellator is more horizontal than vertical people mover although escalators
and travellators are very similar.
There can also be other classification of lifts, such as
→ hydraulic drive vs
→ electric traction drive
and
→
motor-room-less lift
Handicap lift
(Adopted from The Vertical Transportation Handbook, 3rd edition by George R.
Strakosch)
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Popular types of lift drives
1) Hydraulic drive
(a) Hydraulic lift (contract speed of around 0.63m/s or less); leveling problem
with fluctuation in oil temperature; more flexible in locating lift machine
room; very slow speed; limited height traveling; not recommended for more
than 3 landings and/or travel exceeding 20m (due to strength and length of
the hydraulic jacks)
2) Electric traction drive
(a) DC drives (contract speed of 2m/s or above); reliable and good control,
good comfort, but DC generator needed,
typically motor generator is used; very popular in the past.
Ward Leonard drive
(Adopted from BARNES, M. Variable speed drives and power electronics)
Some DC driven lifts do not use motor generator but static converter to
produce the DC power source. These are called Thyristor Leonard
drives.
(b) AC motor
2-speed (contract speed of around 1m/s or less); economical, poor
comfort, difficult to control; popular in the past.
Variable voltage with single speed motor, less common option.
Variable voltage with 2-speed motor, less common option.
(c) VVVF – variable voltage variable frequency with induction motor (contract
speed of 1.5m/s or above); lower energy cost than DC, faster floor-to-floor
jump time, reasonably good comfort; used to be very expensive but with the
advent of power electronics VVVF has become the prime workhorse
nowadays.
(d) VVVF with permanent magnet synchronous motor (PSTM), compact but
small rating only.
(e) Linear induction motor drives (LIM)
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Hydraulic drives
(a) Low-traffic passenger, goods, vehicle and bullion lifts are all suitable
applications for hydraulic lifts. For applications which involve very large loads,
hydraulic drive often provides the best solution because the floor of the well
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carries the load of the lift. In many older buildings, not originally designed to
include a lift, hydraulic lifts are often the only type suitable due to restricted
building height and building structural strength. For these applications hydraulic
driven lifts have many advantages over electric traction lifts. However,
misapplied, hydraulic lifts can cause major problems for building owners and
users.
(b) Mechanical anti-creep mechanisms may be used where very heavy loads (greater
than 3.2 tons) are carried or forklift trucks are moving in and out of the lift.
Active re-levelling systems may cause problems in these circumstances where
small-wheeled trolleys are used.
(c) Caution must be applied in considering hydraulic lifts for commercial buildings
where continuous heavy traffic is expected since this may require lift speeds of
1m/s or above. Cooling is essential under these cases since 0.63m/s is generally
accepted as the maximum for hydraulic lifts without cooling.
(d) Hydraulic drives are not suitable for intensive use or for groups of lifts. Even
duplex lift groups (i.e. 2 lifts) may exceed the recommended maximum number
of motor starts per hour (i.e. 45) without additional cooling. When hydraulic lift
is the only solution, extra cooling requirement must be considered in the design
of the building itself.
(Adopted from BARNEY, G..C., Elevator & Escalator Micropedia)
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Holeless hydraulic elevator
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Telescoping “holeless” hydraulic
elevator
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Chain driven hydraulic elevator
(Adopted from The Vertical Transportation Handbook, 3rd edition by George R.
Strakosch)
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