Lifts and Escalators 

These are the means of mechanical transportation of goods and people in and around a building. These are energy-using services so this needs designer’s attention at an early stage of building design.

The choice on kind of mechanical transportation used and their installation depends mainly upon following factors.

• Building size and type (type affects peaks to be handled)
• Each car’s capacity
• Car speed
• Maximum acceptable waiting time
• Mode of control/operation

Here we will discuss about the kinds of mechanical transportations popularly used and their choice depending upon the given factors.

# Lifts

These are the system used for vertical movement inside a building and comprises of one or more cars (sheet metal boxes with sliding doors), suspended in a structural ‘sling’ of metals channels, that can be moved up and down the storeys of the building by some driving and controlling mechanism.

in a simple installation, the lift shaft is of concrete or masonry forming the part of service core. Desirably the motor room is directly over the shaft. Safety overruns are kept above the top landing level and in the basement pit. The counterweight balances the car weight and ensures that the hoist rope’s friction grips the driving sheaves, and also this reduces motor power consumption. The motor power is used to overcome friction, acceleration, inertia and the unbalanced load during lifting. The compensating cables are there to offset the weight of the hoist cables, transferring to the counterweight side as the car rises, keeping the load on the sheaves balanced. Slower lifts may be driven by an AC motor but variable voltage DC motors give a better, smoother performance for high speed lifts.

A lift motor room has following features:

• A concrete machine base incorporating a vibration isolating cork slab to separate it’s upper and lower parts.
• Motor and brake equipment bolted to the upper, vibration-isolated, concrete slab.
• Flexible armored electric cable connection to the motor.
• The lift motor main isolator switch close to the plant room door.
• An access hatch into the lift shaft.
• The electric control panel
• A lifting beam built into the structure.
• Adequate artificial illumination
• Natural ventilation
• 13 A power point
• Locked door
• Light colored walls and ceilings

The size, location and number of cars are selected regarding following factors.
a. Building size and type

            Passenger lifts are provided for building of over three storeys, or less if wheelchair movement is required. The minimum standard of service is one lift for each four storeys and with a maximum walking distance of 45m between workstation and lift lobby.

The peak demand of lift service is assessed from the building size, shape, height and population. Up to 25% of the population will require transportation during a 5min peak period. Congestion at peak travel times is minimized by arranging the lift lobbies in a cul-de sac of, say, two lift doors on either side of a walkway, rather than in a line of four doors along one wall.

b. Car’s capacity

            The lift’s carrying capacity is determined by the demand at peak times. Two lifts of 680 kg carrying capacity (10 people) provide a better service than one 1360 kg, 20 person lift. The large single lift would run only partly loaded during the major part of the day with a resulting decrease in efficiency and increased running cost. But additional capital cost for two lifts should be lower than the advantages of using it.

c. Car speed

            it is determined by travel distance and standard of service. Buildings having more than 15 storeys may have high-speed lifts that do not stop at the first 10 storeys.

Car speed for various travel distances can be listed as

Car speed is chosen so that the driving motor can be run at full speed for much of the running time to maximize the efficiency of power consumption.

The overall speed of operation is determined by the acceleration time, braking time; maximum car speed; speed of door opening; degree of advanced door opening; floor-leveling accuracy required; switch timing and variation of car performance with car load.

d. Control mechanism

            The automatic control system should function in an upward collecting and downward collection mode, computer controls are used to optimize the overall performance of the installation by causing the nearest car to stop, and to minimize electricity consumption.

# Special lifts           

Double deck lifts

It is used for increased capacity. There, two cars are mounted one above other in the same shaft so that two floors are served simultaneously.

           Goods lifts

• Are provided for the movement of fragile goods, fluids or patients in hospital. Accurate floor leveling within 5mm is required, to facilitate smooth passage of trolleys.
• The cars have full-width doors, sometimes at each end of the car.
• Goods lifts have slow service at a maximum of 1 m/s.
• Goods lifts complete each journey instruction before accepting another. Door operation can be manual or automatic. Additional structural supports are needed for lifts with high carrying capacity, and well-designed brakes.
• Driving mechanism: Variable voltage electrical or hydraulic power supply. Hydraulically operated lifts have the advantage of very quiet operation and low running costs.

Escalator

Escalators are needed where large numbers of people are to be moved through a limited no of floors. They are used to provide mechanical transportation for large number of passengers from surges at discharge times from offices, railways underground stations, airport terminals and departmental stores.

Specifications

• Capacity is principally governed by the tread width, which are from 0.6 to 1.05m, allowing standing and passing room.
• The angle of inclination is normally 30^o, but 35^o can be used for vertical rise of less than 6m.
• Speed is less significant; since a queue of people can only transfer to an escalator at a given rate of 0.5m/s. Speeds of up to 0.75m/s are permissible as this is the maximum safe entry and exit velocity.

Escalators flights are heavy pieces of equipment, for which the immediate floor structure must allow, and they are preferably, delivered in complete units for which the building’s access must allow.