elevators (arun.thodupunoori)

8/2/2019 Elevators (Arun.Thodupunoori)

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BUILDING SCIENCES AND SERVICES

(ASSINGNMENT ON ELEVATORS)

BY

T.ARUN

B.ARCH,SEC-A

ROLL-1090100071

SPA-V


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An elevator is a type of verticaltransport equipment thatefficiently moves people orgoods between floors (levels,decks) of a building, vessel orother structures. Elevators aregenerally powered by electricmotors that either drive tractioncables or counterweight systemslike a hoist, or pump hydraulicfluid to raise a cylindricalpiston like a jack. Because ofwheelchair access laws,elevators are often a legalrequirement in new multi-storeybuildings, especially wherewheelchair ramps would beimpractical.

Some people argue that lifts began assimple rope or chain hoists. A lift isessentially a platform that is either

pulled or pushed up by a mechanicalmeans. A modern day lift consists ofa cab (also called a "cage" or "car")

mounted on a platform within anenclosed space called a shaft orsometimes a "hoist way". In the past,

lift drive mechanisms were powered bysteam and water hydraulic pistons orby hand. In a "traction" lift, cars arepulled up by means of rolling steelropes over a deeply grooved pulley,

commonly called a sheave in the industry. The weight of the car isbalanced by a counterweight. Sometimes two lifts always movesynchronously in opposite directions, and they are each other'scounterweight.

The friction between the ropes and thepulley furnishes the traction which gives

this type of lift its name.

Hydraulic lifts use the principles of

hydraulics (in the sense of hydraulic power)to pressurize an above ground or in-groundpiston to raise and lower the car. Roped

hydraulic uses a combination of both ropesand hydraulic power to raise and lowercars. Recent innovations include permanentmagnet motors, machine room-less railmounted gearless machines, andmicroprocessor controls.

The technology used in new installations depends on a variety offactors. Hydraulic lifts are cheaper, but installing cylinders greater
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than a certain length becomes impractical for very high lift hoistways.Hydraulic lifts are usually slower than traction lifts.

ELEVATOR DOORS

Elevator doors protect ridersfrom falling into the shaft. Themost common configuration is tohave two panels that meet in the

middle, and slide open laterally.In a cascading telescopicconfiguration (potentiallyallowing wider entryways withinlimited space), the doors run onindependent tracks so that while

open, they are tucked behind oneanother, and while closed, theyform cascading layers on oneside. This can be configured so

that two sets of such cascading doors operate like the center openingdoors described above, allowing for a very wide elevator cab. In lessexpensive installations the elevator can also use one large "slab" door: asingle panel door the width of the doorway that opens to the left orright laterally. Some buildings have elevators with the single door onthe shaft way, and double cascading doors on the cab.

TYPES OF HOIST MECHANISMSThere are at least four means of moving an elevator:

Traction elevators

Geared and gearless traction elevators

Geared traction machines are driven by AC orDC electric motors. Geared machines use worm

gears to control mechanical movement ofelevator cars by "rolling" steel hoist ropesover a drive sheave which is attached to agearbox driven by a high speed motor. Thesemachines are generally the best option forbasement or overhead traction use for speedsup to 500 ft/min (2.5 m/s). In order to allow

accurate speed control of the motor, to allowaccurate levelling and for passenger comfort,

a DC hoist motor powered by an AC/DC motor-generator (MG) set was the preferred solutionin high-traffic elevator installations for many

decades. The MG set also typically powered the relay controller of theelevator, which has the added advantage of electrically isolating theelevators from the rest of a building's electrical system, thus eliminating

the transient power spikes in the building's electrical supply caused bythe motors starting and stopping (causing lighting to dim every time theelevators are used for example), as well as interference to otherelectrical equipment caused by the arcing of the relay contactors in thecontrol system.
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Gearless traction machines are low speed (low RPM) powered either byAC or DC. In this case, the drive sheave is directly attached to the endof the motor. Gearless traction elevators can reach speeds of up to

2,000 ft/min (10 m/s), or even higher. A brake is mounted between themotor and drive sheave (or gearbox) to hold the elevator stationary at afloor. This brake is usually an external drum type and is actuated by

spring force and held open electrically; a power failure will cause thebrake to engage and prevent the elevator from falling (see inherentsafety and safety engineering).

In each case, cables are attached to a hitch plate on top of the cab ormay be "under-slung" below a cab, and then looped over the drive sheaveto a counterweight attached to the opposite end of the cables whichreduces the amount of power needed to move the cab. The counterweightis located in the hoist-way and rides a separate railway system; as thecar goes up, the counterweight goes down, and vice versa. This action ispowered by the traction machine which is directed by the controller,typically a relay logic or computerized device that directs starting,

acceleration,deceleration and stopping of the elevator cab. The weight

of the counterweight is typically equal to the weight of the elevator cabplus 40-50% of the capacity of the elevator. The grooves in the drive

sheave are specially designed to prevent the cables from slipping."Traction" is provided to the ropes by the grip of the grooves in thesheave, thereby the name. As the ropes age and the traction grooves

wear, some traction is lost and the ropes must be replaced and thesheave repaired or replaced. Sheave and rope wear may be significantlyreduced by ensuring that all ropes have equal tension, thus sharing theload evenly. Rope tension equalisation may be achieved using a ropetension gauge, and is a simple way to extend the lifetime of the sheavesand ropes.

Hydraulic elevators

Conventional hydraulic elevators. They use an undergroundcylinder, are quite common for low level buildings with 25 floors(sometimes but seldom up to 68 floors), and have speeds of up to200 feet/minute (1 meter/second).

Holeless hydraulic elevators were developed in the 1970s, anduse a pair of above ground cylinders, which makes it practical forenvironmentally or cost sensitive buildings with 2, 3, or 4 floors.
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Roped hydraulic elevatorsuse both above ground cylinders and arope system, allowing the elevator to travel further than the

piston has to move.

The low mechanical complexity of hydraulic elevators in comparison to

traction elevators makes them ideal for low rise, low traffic

installations. They are less energy efficient as the pump works againstgravity to push the car and its passengers upwards; this energy is lostwhen the car descends on its own weight. The high current draw of thepump when starting up also places higher demands on a buildings

electrical system. There are also environmental concerns should eitherthe lifting cylinder leak fluid into the ground.

The modern generation of low cost, machine room-less traction elevatorsmade possible by advances in miniaturization of the traction motor and

control systems challenges the supremacy of the hydraulic elevator intheir traditional market niche.

Traction-Hydraulic ElevatorsThe traction-hydraulic elevator has overhead tractioncables and counterweight, but is driven by hydraulicpower instead of an overhead traction motor. The weightof the car and its passengers, plus an advantageous

roping ratio, reduces the demand from the pump to raisethe counterweight, thereby reducing the size of therequired machinery.

Climbing elevator

A climbing elevator is a self-ascending elevator with its own propulsion.The propulsion can be done by an electric or a combustion engine.Climbing elevators are used in guyed masts or towers, in order to make

easy access to parts of these constructions, such as flight safety lampsfor maintenance.

CONTROLLING ELEVATORSGeneral controls

Typical freight elevator control station

A typical modern passenger elevator will have:

Space to stand in, guardrails, seatingcushion (luxury)

Overload sensor prevents theelevator from moving until excess load hasbeen removed. It may trigger a voice prompt orbuzzer alarm. This may also trigger a "full car"

indicator, indicating the car's inability toaccept more passengers until some areunloaded.

Electric fans or air conditioning units toenhance circulation and comfort.

Call buttons to choose a floor. Some ofthese may be key switches (to control access). In some elevators,
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certain floors are inaccessible unless one swipes a security cardor enters a passcode (or both). In the United States and othercountries, call button text and icons are raised to allow blind

users to operate the elevator; many have Braille text besides.

A set of doors kept locked on each floor to prevent unintentionalaccess into the elevator shaft by the unsuspecting individual. The

door is unlocked and opened by a machine sitting on the roof ofthe car, which also drives the doors that travel with the car. Doorcontrols are provided to close immediately or reopen the doors.Objects in the path of the moving doors will either be detected bysensors or physically activate a switch that reopens the doors.Otherwise, the doors will close after a preset time.

A stop switch (not allowed under British regulations) to halt theelevator while in motion and often used to hold an elevator openwhile freight is loaded. Keeping an elevator stopped for too long

may trigger an alarm. Unless local codes require otherwise, thiswill most likely be a key switch.

An alarm button or switch, which passengers can use to signal thatthey have been trapped in the elevator.

Some elevators may have one or more of the following:

An elevator telephone, which can be used (in addition to the alarm)by a trapped passenger to call for help.

Hold button: This button delays the door closing timer, useful forloading freight and hospital beds.

Call cancellation: A destination floor may be deselected by doubleclicking.

Access restriction by key switches, RFID reader, code keypad, hotelroom card, etc..

One or more additional sets of doors that can serve differentfloor plans. For example, in an elevated crosswalk setup, thefront doors may open on the street level, and the rear doors openon the crosswalk level.

Security camera Plain walls or mirrored walls giving the illusion of larger area Glass windowpane providing a view of the building interior or onto

the streets.

Other controls, which are generally inaccessible to the public (eitherbecause they are key switches, or because they are kept behind a lockedpanel), include:

Fireman's service, phase II key switch Switch to enable or disable the elevator. An inspector'sswitch, which places the elevator in inspection mode

(this may be situated on top of the elevator)

Manual up/down controls for elevator technicians, to be used ininspection mode, for example.

An independent service/exclusive mode (also known as "CarPreference"), which will prevent the car from answering to hallcalls and only arrive at floors selected via the panel. The doorshould stay open while parked on a floor. This mode may be usedfor temporarily transporting goods.
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Attendant service mode.

Otis 1920s controller

Large buildings with multipleelevators of this type alsohad an elevator dispatcherstationed in the lobby todirect passengers and tosignal the operator to leavewith the use of a mechanical"cricket" noisemaker.

External controls

An external control panel

Elevators are typically controlled from the

outside by up and down buttons at each stop. Whenpressed at a certain floor, the elevator arrives topick up more passengers. If the particular elevatoris currently serving traffic in a certain direction, it

will only answer hall calls in the same directionunless there are no more calls beyond that floor.

In a group of two or more elevators, the callbuttons may be linked to a central dispatchcomputer, such that they illuminate and cancel

together. This is done to ensure that only one caris called at one time.

In destination control systems, one selects the intended destinationfloor and is then notified which elevator will serve their request.

SPECIAL OPERATING MODESAnti-Crime Protection (ACP)

Anti-Crime Protection will force each car to stop at a pre-defined landingand open its doors. This allows a security guard or a receptionist at thelanding to visually inspect the passengers. The car stops at this landingas it passes to serve further demand.

Up peak (MIT)

During Up Peak mode (also called Moderate Incoming Traffic), elevatorcars in a group are recalled to the lobby to provide expeditious serviceto passengers arriving at the building, most typically in the morning aspeople arrive for work or at the conclusion of a lunch-time period.
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Down peak

During Down Peak mode, elevator cars in a group are sent away from thelobby towards the highest floor served, after which they commencerunning down the floors in response to hall calls placed by passengerswishing to leave the building. This allows the elevator system to provide

maximum passenger handling capacity for people leaving the building.

Independent service (ISC)

Independent service is a special service mode found on most elevators. Itis activated by a key switch either inside the elevator itself or on acentralized control panel in the lobby. When an elevator is placed on

independent service, it will no longer respond to hall calls.

The elevator will remain parked on a floor with its doors open until a

floor is selected and the door close button is held until the elevator

starts to travel. Independent service is useful when transporting large

goods or moving groups of people between certain floors.

Emergency power operation (EPR)

Many elevator installations now feature emergency power systems whichallow elevator use in blackout situations and prevent people frombecoming trapped in elevators.

Traction elevators

When power is lost in a traction elevator system, all elevators will

initially come to a halt. One by one, each car in the group will return tothe lobby floor, open its doors and shut down. People in the remainingelevators may see an indicator light or hear a voice announcementinforming them that the elevator will return to the lobby shortly. Onceall cars have successfully returned, the system will then automaticallyselect one or more cars to be used for normal operations and these cars

will return to service. The car(s) selected to run under emergency powercan be manually overridden by a key or strip switch in the lobby. In orderto help prevent entrapment, when the system detects that it is runninglow on power, it will bring the running cars to the lobby or nearestfloor, open the doors and shut down.

Hydraulic elevators

In hydraulic elevator systems, emergency power will lower the elevatorsto the lowest landing and open the doors to allow passengers to exit.

The doors then close after an adjustable time period and the carremains unusable until reset, usually by cycling the elevator main powerswitch. Typically, due to the high current draw when starting the pumpmotor, hydraulic elevators aren't run using standard emergency powersystems. Buildings like hospitals and nursing homes usually size theiremergency generators to accommodate this draw. However, the increasinguse of current limiting motor starters, commonly known as "Soft-Start"contactors, avoid much of this problem and the current draw of the pumpmotor is less of a limiting concern.

USES OF ELEVATORS


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.

Passenger service

A passenger elevator is designed to move people between a building'sfloors. Passenger elevators capacity is related to the available floorspace. Generally passenger elevators are available in capacities from

1,000 to 6,000 pounds (4502,700 kg) in 500 lb (230 kg) increments.

Types of passenger elevators

Passenger elevators may be specialized for the service they perform,including: hospital emergency (Code blue), front and rear entrances, a

television in high rise buildings, double decker, and other uses. Cars maybe ornate in their interior appearance, may have audio visual advertising,and may be provided with specialized recorded voice announcements.Elevators may also have loudspeakers in them to play calm, easy

listening music. Such music is often referred to as elevator music.

An express elevator does not serve all floors. For example, it movesbetween the ground floor and a skylobby, or it moves from the groundfloor or a skylobby to a range of floors, skipping floors in between.These are especially popular in eastern Asia.

Capacity

Residential elevators may be small enough to only accommodate oneperson while some are large enough for more than a dozen. Wheelchair,or platform lifts, a specialized type of elevator designed to move a

wheelchair 6 ft (1.8 m) or less, can often accommodate just one personin a wheelchair at a time with a load of 1000 lb (450 kg).

Freight elevators

A specialized elevator from 1905 for

lifting narrow gauge railroad cars between

a railroad freight house and the Chicago

Tunnel Company tracks below.

A freight elevator, or goods lift, is an

elevator designed to carry goods,

rather than passengers. Freight

elevators are generally required to display a written notice in the car

that the use by passengers is prohibited (though not necessarily illegal),

though certain freight elevators allow dual use through the use of an

inconspicuous riser. Freight elevators are typically larger and capable

of carrying heavier loads than a passenger elevator, generally from

2,300 to 4,500 kg. Freight elevators may have manually operated doors,

and often has rugged interior finishes to prevent damage while loading

and unloading. Although hydraulic freight elevators exist, electric

elevators are more energy efficient for the work of freight lifting.
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Stage lifts

Stage and orchestra lifts are specialized lifts, typically powered byhydraulics, that are used to lift entire sections of a theatre stage

Pit beneath the orchestra lift at Radio City Music Hall

Orchestra lift at Radio City Music Hall as viewed frombeneath the stage

Vehicle elevators

Vehicular elevators are used within buildings or areas with limited space(in lieu of ramps), typically to move cars into the parking garage ormanufacturer's storage. Geared hydraulic chains (not unlike bicyclechains) generate lift for the platform and there are no counterweights.To accommodate building designs and improve accessibility, the platformmay rotate so that the driver only has to drive forward. Most vehicleelevators have a weight capacity of 2 tons.

Boat elevatorsIn some smaller canals, boats and small ships can pass betweendifferent levels of a canal with a boat lift rather than through a canallock.
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Aircraft elevators

On aircraft carriers, elevators carry aircraft between the flight deck

and the hangar deck for operations or repairs. These elevators are

designed for much greater capacity than other elevators, up to 200,000

pounds (90 tonnes) of aircraft and equipment. Smaller elevators lift

munitions to the flight deck from magazines deep inside the ship.

Residential elevator

The residential elevator is often permitted to be of lower cost andcomplexity than full commercial elevators. They may have unique designcharacteristics suited for home furnishings, such as hinged wooden

shaft-access doors rather than the typical metal sliding doors ofcommercial elevators. Construction may be less robust than incommercial designs with shorter maintenance periods, but safety systemssuch as locks on shaft access doors, fall arrestors, and emergency

phones must still be present in the event of malfunction.

Limited use / limited application

The limited-use, limited-application (LU/LA) elevator is a special purposepassenger elevator used infrequently, and which is exempt from many

commercial regulations and accommodations. For example, a LU/LA isprimarily meant to be handicapped accessible, and there might only beroom for a single wheelchair and a standing passenger.

Dumbwaiter

Dumbwaiters are small freight elevators that are intended to carry foodrather than passengers. They often link kitchens with rooms on otherfloors.

Paternoster

A special type of elevator is the paternoster, aconstantly moving chain of boxes. A similarconcept, called the manlift or humanlift, moves

only a small platform, which the rider mountswhile using a handhold and was once seen in

multi-story industrial plants.
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Scissor lift

The scissor lift is yet another type of lift. As most of these lifts areself-contained, these lifts can be easily moved to where they are needed.

Rack-and-pinion lift

The rack-and-pinion lift is another type of lift. These lifts are powered bya motor driving a pinion gear. Because they can be installed on a buildingor structure's exterior and there is no machine room or hoistwayrequired, they are the most used type of lift for buildings under

construction (to move materials and tools up and down).[26]

ELEVATOR AIR CONDITIONING

Elevator airflow diagram

Concept

Elevator air conditioning is fast becoming a popular concept around theworld. The primary reason for installing an elevator air conditioner isthe comfort that it provides while traveling in the elevator. It stabilizesthe condition of the air inside the lift car. Some elevator airconditioners can be used in countries with cold climates if a thermostatis used to reverse the refrigeration cycle to warm the lift car.

Health

One of the benefits of installing an elevator air conditioner is the cleanair it provides. Air was typically drawn from the elevator shaft or

hoistway into the car using a motorized fan. This air could contain dust

mites, germs and bacteria. With an elevator air conditioner, the air ismuch cleaner because it is re-circulated within the car itself and is
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usually filtered to remove contaminants. A poorly maintained air-conditioning system may promote the growth and spread ofmicroorganisms, but as long as the air conditioner is kept clean, these

health hazards can be avoided.

Drawbacks

Heat generated from the cooling process is dissipated into the hoistway.The elevator cab (or car) is not air-tight, and some of this heat will re-

enter the car and reduce the overall cooling effect, which may be lessthan ideal.

CONCLUSIONElevators have become an essential part of our lives. Every building has

its own set of elevators to function with. This has made going up the

floors so much easier.

elevators (arun.thodupunoori)

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