4.0 Mechanical Transportation System 4.1 Literature Review Vertical transportation is transportation of passengers traveling between floors in a building. There’re four types of lift, which are siting lift, traction lift, hydraulic lift and stair lift. Mechanical transportation systems are of vital importance in high-rise buildings. Escalators are used on lower floors for moving high volumes of people over short distances. A few retail or educational buildings have escalators for up to 10 stories. The principal means of vertical transport in tall buildings is the roped elevator. It moves by a direct current electric motor, which raises and lowers the cab in a shaft with wire ropes running over a series of sheaves at the motor and the cab itself; the ropes terminate in a sliding counterweight that moves up and down the same shaft as the cab, reducing the energy required to move the elevator. Each elevator cab is also engaged by a set of vertical guide tracks and has a flexible electric cable connected to it to power lighting and doors and to transmit control signals. Passenger elevators range in capacity from 910 to 2,275 kilograms (2,000 to 5,000 pounds) and run at speeds from 90 to 510 meters per minute; freight elevators hold up to 4,500 kilograms (10,000 pounds). The speed of elevators is apparently limited to the current value of 510 meters per minute by the acceleration passengers can accept and the rate of change of air pressure with height, which at this speed begins to cause eardrum discomfort. Elevator movements are often controlled by a computer that responds to signals from call buttons on each floor and from floor-request buttons in each cab. The number of elevators in a building is determined by the peak number of people to be moved in a five-minute period, usually in the early morning; for example, in an office building this is often set at 13 percent of occupancy. The average waiting time for an elevator between pressing the call button and arrival must be less than 30 seconds in an office building and less than 60 seconds in an apartment building. The elevators are usually arranged in groups or banks ranging from one to 10 elevators serving a zone of floors, with no more than five elevators in a row to permit quick access by passengers. In a few very tall buildings the sky lobby system is used to save elevator-shaft space. The building is divided vertically into sub-buildings, each with its own sky lobby floor. From the ground floor large express elevators carry passengers to the sky lobby floors, where they transfer to local elevator banks that take them to the individual floors within the sub-buildings. There’s also another mechanical transportation which is escalator, also named as 'moving staircase'. Escalator has the capacity to move large numbers of people with no waiting interval. Escalator is also an important architectural design impact because it can used to guide people towards main exits or special exhibits. Escalators can be constructed in three ways, two of which are parallel arrangements and one crisscross arrangement. Parallel arrangement is up and down escalators are arranged side by side or separated by distance.
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4.2 Introduction Mechanical transportation system is essential in a commercial building like First Subang Mall since it accelerated people's movement, increase efficiency and productivity of the occupants. However, it will create a lot of worries compare to other systems since it's hard to ensure its functionality when electric system shut down or when there's a fire in the building. Hence, First Subang Mall has various types of mechanical transportation like elevator, firefighter elevator and escalator. The system itself will be controlled by the machine room.
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4.3 Case Study 4.3.1 Machine/Control Room
Figure 4.3.1 Lift Control Room
The elevator machine room consists of Frenic lift that functions for elevator machinery and well-established vector control with speed sensor. Control response has been in used of higher speed automatic current regulator(ACR) of 500Hz. Frenic lift is used as the there are features for overload capacity over 200%, as usual ones are over 80% only. The use of Frenic lift in the building shows reduction of torque ripple that caused low vibration(less than 0.10m/s2) and also reduction in rollback during starting up.
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4.3.2 Elevator
Figure 4.3.2 Geared Traction Motor
First Subang uses geared traction elevator with machine room that is driven by AC. Geared traction elevators serves in this mid-rise buildings with speeds between 200 to 500 feet per minute. The motor rotation in speed is reduced by 1/10th using a speed reducer equipped with worm or helical gears, and transmitted to the traction sheave of the traction machine. The geared machine is designed such that the drive sheave is connected to the motor through a gear train. Power from the motor is transmitted to the drive sheave through reduction gears. The geared elevator machine is more prone to wear and tear than the gearless elevators. The machines have a bronze spiral worm gear connected to the hoist motor which drives a bronze ring gear. These machines are generally the best option for basement or overhead traction use for speeds up to 500 feet per minute (3 m/s).
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Figure 4.3.2.1 Axonometric of Geared Traction Lift (Source ElectricKnowhow web 2014)
From the figure 4.2.2.1, it can be seen that there’s an electrically controlled brake between the motor and the reduction unit stops the elevator, holding the car at the desired floor level.
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4.3.3 Fire Control Switch
Figure 4.3.3 Fire Manual Control Switch
In First Subang, there are safety manual lift controls in the motor room. It is to prevent any failure of the motor during the normal working days or emergency. The elevators can be operated by pulling ropes. For belt-driven elevators, there are 3 ropes. Pulling the right rope down once makes the elevator go up, and pulling the left rope down once makes the elevator go down, and pulling the middle rope once stops the elevator. A special made control switch to enable authority to override the fire control of the fireman elevator, in order to control the lift manually by the fire officers under any emergency issue.
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4.3.4 Firefighter’s Elevator
Figure 4.3.4 Firefighter’s Elevator
This elevator is built in order to rescue people who may be trapped on upper floors during an event of fire in a building, therefore this elevator is slightly larger in width compared to the elevator used for public. This type of elevator has the fireman’s service mode activated by a toggle switch. Even though it looks the same as the normal elevator from the exterior, but the performance wise is different from the normal passenger elevator. The features of a fireman elevator are listed as below,
Platform area and contract load should be at least 1.45 m2 and 550 kg.
Its able to reaches the top of the building within one minute.
It has the power-operated doors of not less than 0.80 m clear opening that are arranged to remain open at any floor. Has an overriding ‘Fire Control’ switch at the fire control floor level, to bring the lift under manual control of the fire officer.
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Diagram 4.3.4.1 Basement Plan
The motor room is directly above the lift while machine room is at the bottom. Motor room is to control the lift, with a manual controller, and the lift motors are in the room, whereas the machine room has a buffer for lift emergency landing issue if happens to have accident.
Diagram 4.3.4.2 Section
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4.3.5 Escalator
Figure 4.3.5 Escalator
Diagram 4.3.5 Escalator Section
Escalators are general public access from one floor to the another in First Subang and parallel arrangement of escalator is used. The width between balustrade panels is 800mm where the average power consumption is assumed to be 7.5kW.
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4.3.6 Inclined Moving Walkway
Moving ramp is a moving walk that inclines between 5 degrees and 15 degrees that offers a way for wheeled vehicles(shopping carts) vertically or large and bulky objects to basement parking lots in First Subang. Moving ramp provides an option for people who lack the agility required to use an escalator. Passenger belt conveyor is the self contained powered belt type unit that is capable in operating ascending and descending passenger service. Each unit consists of a support structure, drive machinery, transversely rigid rubber covered belt riding on ball bearing rollers outboard of the tread way, floating combs at entry and exit ends, moving handrails, inside balustrades with stainless steel trim and decks, controls, safety devices and all other parts required to provide a complete passenger conveyor.
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4.4 UBBL According to UBBL 1984,
Section 124 For all non-residential buildings more than 4 storeys above or below the main access level at least one lift shall be provided.
Section 151 - 155 (1) The fire mode of operation shall be initiated by a signal from the fire alarm panel which may be activated automatically by one of the alarm devices in the building or manually. (2) If main power is available all lifts shall return in sequence directly to the designated floor, commencing with the fire lifts, without answering any car or landing calls, overriding the emergency stop button inside the car, but not any other emergency or safety devices, and park with doors open. (3) The fire lifts shall then be available for use by the fire brigade on operation of the fireman’s switch. (4) Under this mode of operation, the fire lifts shall only operate in response to car calls but not to landing calls in a mode of operation in accordance with by-law 154. (5) In the event of mains power failure, all lifts shall return in sequence directly to the designated floor and operate under emergency power as described under paragraphs (2) to (4).
Section 243 (1) In a building where the top occupied floor is over 18.5 meters above the fire appliance access level fire lifts shall be provided. (2) The fire lifts shall be located within a separate protected shaft if it opens into a separate lobby. (3) Fire lifts shall be provided at the rate of one lift in every group of lifts which discharge into the same protected enclosure or smoke lobby containing the rising main, provided that the fire lifts are not located more than 61 meters travel distance from the furthermost point of the floor.
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4.5 Analysis & Conclusion
We noticed there’s an exhaust fan in the life motor room. It is installed at the lift motor room to enhance the air circulation and reduce the heat stored in the room as the the motor releases heat due to the continuous operation for the lift. Mainly is to avoid the motor from over heating as it’s always in operation. Compare to other system, First Subang's lift system is more complete since it fulfill all the UBBL's requirement. The only issue for the system is the fire lift is the normal lift itself. It's not a easy access point and create difficulties to firefighters when there's a fire occurred in the building. Nonetheless, it still considered as a complete system since it functions when there's emergency.
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