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    Electrical & Control System and Moving Walkways

    I indicated in a previous TopicEscalators Basic Components - Part Onethat EscalatorsBasic components are as follows:

    1. Landing Platforms.2. Truss.

    3. Tracks.

    4. Steps.

    5. Handrail.

    6. Escalator Exterior (Balustrade).

    7. Drive system.

    8. Auto-Lubrication System.

    9. Braking system.

    10. Safety devices.

    11. Electrical & Control Systems.

    And I explained the first six items in this previous topic. Also, I explained the items fromseventh to tenth in the previous topicEscalators Basic Components Part Two.

    Today, I will explain the last item; Electrical & Control Systems, also I will explain theMoving walkwaysas it is one of the transportation systems used in buildings.

    Eleventh: Electrical & Control system

    1- Escalator Motor

    The escalator motor is typically an AC direct-on-line flange mounted unit, directly and/orflexibly coupled to the reduction gear. The motor is usually protected by thermal andelectro-magnetic overload devices as well as thermistors in the motor winding. The motoroperation is controlled by the main controller.

    2- Main Controller

    2.1 In Earlier Escalator Systems

    As I mentioned before, in earlier escalator systems it was common to use Conventionalelectromechanical starting systems, which include the following methods:

    1. Full voltage Wye Start/Delta Run connection starting.

    2. Part-winding starting.
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    3. Reduced voltage starting.

    4. Autotransformer starting.

    These Conventional starting methods were used along with relay logic to control thestarting method for the drive motor(s).

    2.2 In Modern Escalators

    But in modern escalators, the main controller will use a soft start controller or a

    variable frequency drive along with a Programmable Logic Controller (PLC) to control and

    monitor the status of the escalator. The PLC may also be capable of communicating via anEthernet to permit remote monitoring of the system. Modern

    escalator controllers incorporate an electronic fault diagnostic system.

    This fault diagnostic system is capable of logging statistical data on the operation

    of the escalator and includes memory to store escalator faults causing shut down. The

    escalator controller and fault diagnostic also includes an English language clear text displayto allow immediate identification of the cause of a shutdown. The display is located withinthe inner decking at the upper end of the escalator.

    The display system normally provides a minimum of 2 lines of 20 characters for

    displaying programmable messages and fault conditions. Operation of the fault diagnosticsystem is possible at the display point via menus and keypads adjacent to or contained aspart of the display system. The escalator controller and fault diagnostic system may include a text display toallow immediate identification of the cause of a shutdown. The controller itself could belocated within the inner decking of the upper end of the escalator as well as the equipmentmachine room. Through the use of a keypad and the display, the technician is provided theability to display programmable messages and fault conditions. Operation of the faultdiagnostic system is possible at the display point by the use of menus and keypads adjacentto or contained as part of the display system.

    2.3 Escalator Controller Components

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    Escalator Controller Componentsa- A Circuit Breakeris a device designed to open and close a circuit by non-automaticmeans and to open the circuit automatically on a predetermined over-current. This isusually mounted near the control cabinet with accessibility of its red color handle or trip

    breaker. When opened, it isolates most electrical controls inside the controller.

    b- Line Fusesare in line with each leg of the three-phase 480 VAC power supply located

    inside the controller or in a separate box. It is used as an over-current protection device,

    which has a similar function as the circuit breaker but normally used as a short circuit

    protection (catastrophic failure).

    Typically, these fuses are of a time-delay category, capable of handling the initial in-rushcurrent when the equipment is energized.

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    c- A Step down Transformeris used to step down voltages normally from 480vac to120vac or other low ac voltages that may be used for controls and demarcation lighting.

    d- A Motor Starter, when energized, its main contacts will provide power to the motor,and its auxiliary contacts may provide power to other control circuits. Typically, a dualcontactor Motor starter is used where one starter controls the motor in the up directionand the other starter is responsible for the down direction. It may also be, one starter foreach motors direction on two motors for dual drive or three for tri-motor drive escalator.Ideally, these contactors will be equipped with a mechanical interlock which would aid in

    preventing a phase-to-phase electrical short. Soft start starters are widely used in the

    modern escalators.

    e- Brake Energizing Relay for the Main Drive Shaft, when energized, its contacts willprovide power to the brake coil thereby disengaging the fail-safe brake for the motor toturn. When de-energized, the tension of the brake spring(s) will mechanically apply thebrake capable of stopping a down running escalator with brake rated load.

    f- Overload Protectionis normally a bi-metal normally closed contact that senses theheaters in line with the 480VAC power supply and the motor leads. When an overcurrentoccurs, the heaters will transfer heat to the bi-metal contacts to open and disconnect themotor contactor coil thereby opening the contactors for the motor. Solid state versions

    use the same detection method but will provide low voltage protection to the control

    circuit thereby shutting down the power circuit as well as the control circuit.

    Overload protection is the result of a device that operates on excessive current, but notnecessarily on a short circuit to cause the interruption of current flow to the electricmotor. Overload protection is not meant to protect the system from direct shorts, but

    rather to provide protection from excessive mechanical overload of the motor or todisable a motor which has overheated due to bearing or winding failure.

    g- A Fault Indicating Deviceis part of the controller that operates to visually indicate theactuation of a safety device causing the escalator to shut down. It has an indication thatremains until manually canceled or reset by the maintenance person or by the StationAgent/Manager. Indicating lamps are of a neon type or LED used to display unitmalfunction or any activated safety devices.

    h- A PLC or programmable logic controller, or programmable controller,is a digitalcomputer used for automation of electromechanical processes, such as control of the

    drive machine, handrail speed, motor speed, motor frequency and voltage input as wellas the monitoring of all safety devices.

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    programmable controlleri- A Soft Start Controlleris a solid state AC drive which controls the speed of AC motorsby controlling the frequency and voltage of the power supplied to the motor.

    An inverter provides the controlled power, and in most cases, the AC drive includes arectifier so that DC power for the inverter can be provided from the main AC power. ACdrives are also called variable-frequency drives, frequency inverters, or inverters. Thespeed of an AC motor is determined by the cycle number of alternating current it receivesat each second and by the number of poles in the motor.

    Since the number of poles of most industrial motors is fixed, the speed is more easilycontrolled by controlling the frequency.

    3- Escalator Control Cabinets

    3.1 Main Electrical & Control Cabinet
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    Usually,The Main Disconnect Switch, motor protection and control devices are typicallyinstalled in an electrical cabinet positioned in the upper machinery well-way of theescalator. The cabinet will typically correspond to NEMA 3, ANSI/ASME standards by theescalator manufacturer comprising a steel enclosure with all required relays, automatic

    circuit breaker, and terminals completely wired for the escalator control. Faultannunciation is generally provided to identify activation of specific escalator safetydevices.

    3.2 Landings Control Station
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    Landings Control Station A control station at both upper and lower landings is provided which includes akey-actuated directional starting safety switch and a key actuated stop switch.

    The control station is located in the newel end skirt deck at the ends of thebalustrades.

    A Code compliant emergency stop station is provided at each end of the escalator.The emergency stop is located in accordance with governing Code requirements and iscovered by a transparent cover and alarm.

    Starting of the escalator in normal continuous operation mode shall only be

    possible using a dedicated key switch at upper and lower ends. (Some units have keyswitches at one end only.)

    3.3 Maintenance Control Station
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    Maintenance Control StationEach escalator is provided with a pendant-style hand station to operate the escalatorduring maintenance or service work. Plug-in connection points for the pendant handsetare provided at both ends of the escalator within the truss enclosure beneath the landing


    The handset includes continuous pressure push buttons to operate the escalator in eitherdirection. A maintenance stop button is included. When plugged into the receptacle,there should be no means of operating or permitting the escalator to run other thanthrough the use of the handset.

    4- Escalator Electrical Lighting

    4.1 Balustrade Lights

    The entire length of the escalator between the interior balustrade panels is illuminatedby continuous fluorescent lighting called the Balustrade Lights. Only the steps and theside sections up to the skirt panels require light so that escalator passengers can seewhere theyre walking without having bright lights shine in their faces.

    An emergency circuit will light every other lamp section on one balustrade in case of apower outage.

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    4.2 Comb Lights

    Comb Lights

    The Comb Lights illuminate the area where the comb-fingers meet the steps. They arelocated in the end skirts above the upper newel and lower newel comb-fingers. Theselights are also on the lighting emergency circuit.

    4.3 Maintenance Lights
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    Maintenance & Step Demarcation Lights Areas inside the upper truss, the lower truss, and the machine rooms areilluminated by Maintenance lights.

    Light switches next to each light turn them off and on.

    These lights are on the emergency circuit and will work if the escalator breaksdown.

    No special procedure should be necessary for changing these lamps.

    4.4 Step Demarcation LightsGaps between steps at the upper and lower newels are lighted by green fluorescent tubes

    below the steps. These Step Demarcation Lights shine between steps to makes it easierand safer for passengers stepping on and off of the escalator. Demarcation Lights are onthe emergency circuit.

    4.5 Direction Indicators

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    Direction IndicatorsA red and a green light mounted on the right side of each newel indicate the escalatordirection of travel when approaching the steps. A rider will usually want to enter thenewel with the lighted green indicator and avoid the lighted red indicator. Each of theselights is made up of LED clusters and can be replaced after taking off the faceplate andthe indicator box cover. By removing the retaining nuts on the back side of the plate,either lens can be replaced. The red light should be replaced in the top position.

    5- Heating Systems and Controls

    5.1 Heater OperationHeating elements are located in the upper, lower, and incline sections of each escalatorinstalled from the entrance to the mezzanine levels. Their design purpose is to preventice from forming on the steps.

    5.2 Heater Elements

    These heaters are 2000 watt, 480 volt, single-phase tubular electrical elementsthat are controlled by a thermostat that is adjustable from 30F to 110F.

    To replace a heating element, it is necessary to first remove four step sections.Move the missing step section over the heater to be removed and disconnect the conduit boxcover.

    Disconnect the heater wiring and conduit.

    It will be a lot easier to replace an element if the wires are tagged before they aredisconnected.
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    5.3 Heater Thermostatic ControlsThe thermostat can be removed after taking out two steps and positioning the missingstep section over the control. Turn the heater disconnect switch off before removing thebox cover. Disconnect the wires and tag them for easy re-connection.

    Moving Walkway

    Moving Walkway

    A moving walkway sometimes called Travelator, Horizontal Escalatoris a slow movingconveyor mechanism that transports people, across a horizontal or inclined plane, over ashort to medium distance. Moving walkways can be used by standing or walking on them.They are often installed in pairs, one for each direction.

    Moving walkways, usually found in airports, are designed to move people over longdistances, usually between different terminals. Moving walkways are similar to anescalator. The only difference is that the steps lay flat, like a conveyor belt. Passengers
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    are able to move from gate to gate or from one baggage area to the next. Movingwalkways, like elevators and escalators, offer a smooth and convenient ride for people

    while providing outstanding energy efficiency for commercial building operators.

    Types of Moving walkways

    1-According To Inclination Angle

    Horizontal and Inclined Moving Walkwaysa- Zero degrees inclination Horizontal Moving Walkways.

    b- Up to 15 degrees inclination Inclined Moving Walkways.

    2- According To the Flat Moving Surface
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    Moving walkways have two basic styles according to the flat moving surface:

    a- Pallet Type

    Pallet Type Moving walkwaysA continuous series of flat metal plates mesh together to form a walkway. Most have ametal surface, though some models have a rubber surface for extra traction.

    b- Moving Belt
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    Moving Belt Moving WalkwayThese are generally built with mesh metal belts or rubber walking surfaces over metalrollers. The walking surface may have a solid feel or a "bouncy" feel.

    Both types of moving walkway have a grooved surface to mesh with comb plates at theends. Also, all moving walkways are built with moving handrails similar to those onescalators.

    3- According To the Speed

    Moving walkways have two basic styles according to the flat moving surface:

    a- Slow- speed Standard type

    The speed of these walkways is determined by the need for safety upon entry and exit,which generally limits it to approximately half normal walking speed, or 3040m/min. The
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    slow speed of the walkway causes impatience, and passengers often walk on the walkwayitself or on the adjacent floor rather use the slower walkway.

    b- High-speed walkways

    High-speed walkwaysUsing the high-speed walkway is like using any other moving walkway, except that forsafety there are special procedures to follow when joining or leaving.

    On entering, there is a 10 m acceleration zone where the "ground" is a series of metalrollers. Riders stand still with both feet on these rollers and use one hand to hold thehandrail and let it pull them so that they glide over the rollers. The idea is to acceleratethe riders so that they will be traveling fast enough to step onto the moving walkwaybelt. Riders who try to walk on these rollers are at significant risk of falling over.

    At the exit, the same technique is used to decelerate the riders. Users step on to a seriesof rollers which decelerate them slowly, rather than the abrupt halt which wouldotherwise take place.

    Moving walkways basic components:
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    Moving walkways basic componentsThe moving walkways are identical to escalators in the basic components of theirconstruction, but they differ in the following:

    Moving walkways may run horizontally or on an incline of up to 15 degrees.

    The flat moving surface of the moving walkways may consist of a continuousrubber belt or a series of jointed treads.
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    Moving walkways basic componentsThe main basic components of the moving walkways will be as follows:

    1. Truss.

    2. Tracks.3. Drive motor.

    4. Gear box.

    5. Service track.

    6. Handrail drive wheels.

    7. Pallet chain sprockets.

    8. Pallets.
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    9. Pallets chain.

    10. Handrail.

    11. Lower reversing station.

    12. Balustrade panels.

    13. Decks.

    14. Newel ends.

    15. Skirts.

    16. Access cover.

    17. Comb plates.

    18. Front plates.

    19. Controller.

    Moving walkways Safety Devices:

    The safety devices that be included in most of the moving walkways are as tabulated inthe below image.

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    In the next Topic, I will explain the Electrical Pumps and Motors. So, please keepfollowing.

    Note:these topics about Escalators in this course EE-1: Beginner's electrical design courseis an introduction only for beginners to know general basic information about Escalatorsas a type of Power loads. But in other levels of our electrical design courses, we will showand explain in detail the Escalators Loads Estimation calculations.

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    Course HVAC-1: An Introduction to Heating, Ventilation andAir Conditioning (HVAC) Systems

    Course Description:

    This course is intended to prepare the target persons with the ability to understand andrecognize different types, components and accessories of HVAC systems.

    The target Persons:

    Design engineers, new graduate engineers, under graduate engineering students, sitefield engineers, maintenance engineers and technicians.

    Skills Development:

    On completion of this course the target person will be able to:
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    Understand the technology, concepts and terminology in the design of HVACsystems.

    Recognize different types, components and accessories of HVAC systems.

    Specify correctly any type of HVAC systems.

    Course Outline

    1-Introduction to Heating, Ventilation and Air Conditioning System Loads (HVAC)HVAC Systems overview.-Units of HVAC systems.-HVAC System Classifications.

    2-Heating Systems Types.

    A-Heat Sources.

    B-Types of heating systems.B.1Central Heating System.-Furnace.-Hot water & steam boiler.-Heat Pump.-In Floor or Under Floor Heating.B.2Local heating Systems.

    3-Air Conditioning System Configurations.A-Decentralized Systems (Individual Room Systems).-Split Cooling Units.-Window Units.-Mini- Heat Pumps.

    B-Semi- centralized systems (packaged systems).B.1One piece systems (Unitary Packaged Systems).-Packaged Air Conditioners with Water Cooled Condenser.-Packaged Air Conditioners with Air Cooled Condensers.B.2Two pieces systems (Ducted Split system).

    C-Centralized systems (Central Hydronic systems).C.1Centralized Ducted All Air Systems.-Types of "All -Air" Systems.-Constant Volume Systems (CAV).-Dual Duct Systems.-Variable Volume Systems.
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    C.2Centralized Fluid Based Hydronic Systems.C.3Combined (Hybrid) Water and Air Systems.

    D-Special types of Air cooling systems.-Evaporative Cooling systems.-Central Air Washer or Central Evaporative Air Cooling Systems.

    4-HVAC Systems Main Equipment.-Heating systems main equipments.-Cooling systems main equipment.-Chillers & Compressors.-Cooling Towers.-Air Handling Units & Fan Coil Units.

    5-HVAC Control systems.-Sensors.-Controllers.-Controlled devices.-Source of energy.-Type of Control Systems.

    6-Supervisory control (building automation) system.

    -Introduction to DDC system design.

    You might also like:

    HVAC Control Systems and Building Automation SystemHVAC Systems Main EquipmentElectrical Rules and Calculations for Air-Conditioning ...Electrical Rules and Calculations for Air-Conditioning ...Electrical Wiring Diagrams for Air Conditioning Systems ...


    Leave a CommentEmail ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest
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    Escalators Basic Components Part Two

    I indicated in the previous TopicEscalators Basic Components - Part One thatEscalators Basic components are as follows:

    1. Landing Platforms.

    2. Truss.3. Tracks.

    4. Steps.

    5. Handrail.

    6. Escalator Exterior (Balustrade).

    7. Drive system.

    8. Auto-Lubrication System.

    9. Braking system.

    10. Safety devices.

    11. Electrical & Control Systems.And I explained the first six items in this previous topic. Today, I will explain otherEscalators Basic Components as follows.

    Seventh: Drive Systems

    Drive Systems
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    An escalator drive system includes the following components:

    1. Drive Machine and Gear Reducer.

    2. The Step Drive System.

    3. The Handrail Drive System.

    The variation on how these two systems are combined is dependent upon the type ofescalator. The Drive Machine used to drive the pinion gear or the main drive chain maydirectly or indirectly drive the Handrail Drive System.

    1- Drive Machine and Gear Reducer

    Drive Machine and Gear ReducerA- Drive Machine

    The Drive machine together with the gear reducer provides the torque to drive the step

    band at a constant speed.

    The drive machine motor is typically a three-phase AC direct-on-line flange mounted unit.It is either directly or flexibly coupled to the reduction gear. The motor is usuallyprotected by thermal and/or electro-magnetic overload devices as well as thermistors inthe motor winding.

    A.1 Types of Drive Machines:

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    There are three types of drive machines:1. External Drive.

    2. Internal Drive.

    3. Modular Drive.

    A.1.1 External Drive

    External DriveMachine is remotely located outside the truss in a different room/space or in the upperpit area. The Drive machine is located outside the truss.

    The main drive machine is located in the upper pit area or in a separate machine roomlocated below the upper section of the escalator. An external drive located in the upperpit area may employ a direct motor to gearbox drive, or a motor to gear reducer with achain drive. An external drive escalator with the drive unit located within a machineroom beneath the upper landing will normally employ a motor/gearbox with a chain driveextending to the upper landing.

    A.1.2 Internal Drive

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    Internal DriveMachine may be located at the upper landing inside the truss between the step bands orat the top pit, and will employ a motor to gearbox drive with a direct drive axleconnection. A separate dual drive machine within the step band is not uncommon withone machine used to directly drive the step chains located a few feet below the upperincline and one above the lower incline. Internal escalator drive machines may be one,two, or three drive. A dual or three-machine may power the same main drive shaft orpinion shaft at the upper incline. Some internal drive escalators are equipped with either

    dual or three drive machines all inside the step band or step-belt.

    A.1.3 Modular Drive

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    Machine is located within the incline of the truss between the step bands. The main driveis located within the incline of the truss within the step band. The motor may be directlyconnected to the gearbox or it may transfer power through a belt drive. The gearbox willhave a direct connection to the drive axle. A modular escalator may have a single drive ora multiple drive depending on the overall length of the escalator.

    A.2 Drive Machine Starting Methods

    There are two common methods for drive machine starting as follows:

    A.2.1 Conventional electromechanical starting systems, which include the followingmethods:

    1. Full voltage Wye Start/Delta Run connection starting.

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    2. Part-winding starting.

    3. Reduced voltage starting.

    4. Auto-transformer starting.

    Disadvantages of conventional electromechanical starting systems are as follows: It requires a higher starting and running amperage.

    It causes some wear and tear on the equipment with startups. The sudden jerk ofthe startup sequence was a shock to all the moving parts.

    A.2.2 Solid-state soft-start controllers,

    Solid-state soft-start controllersThe soft start controller is a solid state AC drive which controls the speed of AC motors bycontrolling the frequency and voltage of the power supplied to the motor.

    It has the following advantages: It can adjust the motor power to the number of riders using the escalator whilemaintaining normal speed.

    It can reduce electricity use by a significant amount.

    It allows for gradual smooth starting of three-phase squirrel cage motors.

    It allow precise adjustment of motor starting torque, eliminating mechanicalshocks which led to premature bearing wear, shaft and belt breakage, increasedmaintenance time, and costly production stoppages.

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    B- The Main Drive Gear (Gear Reducer)

    The Main Drive Gear (Gear Reducer)The Main Drive Gear or gear reducer assembly may be a single-stage type gear reducer.This is an enclosed, mechanical device that takes the drive motor torque and transmitsthis torque to the bull gear through a gearbox shaft (pinion) or the main drive chain. Thegear reducer assembly contains a steel worm gear that is coupled or directly sleeved ontothe motor shaft and it meshes with the pinion (bronze) gear.

    2- The Step Drive System
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    Step Drive SystemThe step motion is achieved by a direct step assembly connection to the step chains.

    Two-step chains; one for each side of the escalator are directly coupled to the Main Drive

    axle, the bull gear shaft, through the step chain sprockets. The step chain form a loop forthe length of the truss, from the step chain sprockets at the upper end down to thetension carriage gear or turnaround (depending on the manufacturer) at the lower end orthe lower reversing station.

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    Step Drive SystemThe Main Drive Axle is driven by the motor and reducer assembly. Sprockets or bull gears(depending on the manufacturer). On both ends of the Main Drive Axle transfer power theStep Drive System. These sprockets or bull gears drive two step chains, one each for theright and left sides of the escalator, which are connected at the lower end of theescalator to the step chain sprockets of the Tension Carriage.

    The Step Chains are endless links connected with link pins to make a complete loop andare attached to an axle on each side of the steps forming a loop which runs for the length

    of the truss from the upper Main Drive Axle to the lower Tension or Turnaround.

    Circle Tracks (Crab Tracks)

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    Circle Tracks (Crab Tracks)

    The Circle Tracks provide smooth step travel at the end of the tracks. The Chain Wheel isused to maintain proper tracking of the step chain. Most of the outer circle tracks haveaccess windows for easy step removal.

    3- Handrail Drive System
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    Handrail Drive System

    The handrail drive moves the handrail along the handrail tracking system through tractionon the V-shaped handrail underside. The handrail drives consists of the following:

    1. The handrail drive and idler sheaves.

    2. Handrail drive sprockets.

    3. Handrail drive chains.

    4. Handrail Take-Up Devices.

    5. The Handrail Support Rollers.

    A- The Handrail Drive and Idler Sheaves

    They are V grooved sheaves located in the upper newel ends of the escalator. Idlersheaves are V grooved sheaves located in the lower newel ends of the escalator. Thehandrail drive sheave drives the handrail in its journey around the escalator while the

    idler sheave reverses the direction of the handrail at the lower end.

    B- The Handrail Drive Chain Sprockets

    They are located on the handrail drive sheave and the outboard end of the bull gearshaft. Handrail drive sprockets are linked by the handrail drive chain and provide a directlink between the bull gear and handrail drive sheave.
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    C- The Handrail Drive Chains

    They are double stranded chains and are the mechanical link between the dual tootheddrive chain sprockets. The drive chain sprockets and handrail drive chain coming totransfer power from the bull gear shaft to the handrail drive sheave. The Handrail drivechain has an adjustable take-up sprocket to keep the drive chain snug. The handrail drivechain receives lubrication from an enclosed bath system.

    D- The Handrail Take-Up Devices

    They are located directly downhill from the handrail drive sheaves. The handrail take-updevices remove slack in the handrail to provide the proper amount of slack in the handrail

    required to drive the handrail. The short handrail take-up device can be adjusted toremove slack from the handrail. The long handrail take-up device can pivot from thecenter and be adjusted at the uphill end to remove slack from the handrail. The longhandrail take-up device is always required.

    E- The Handrail Support Rollers

    They are located at various intervals down the incline. Their function is as follows: They support the handrail and protect it from coming into contact with the trackbrackets or any other truss components which may damage the handrail.

    They help provide the correct loop of slack in the handrail at the lower end whichproves the traction to drive the handrail.

    Eighth: Auto-Lubrication System

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    Auto-Lubrication System

    The escalators have an Automatic Lubrication System that supplies oil to lubricate themain drive chain, step chain, and the handrail drive chains. Oil flow rate is adjustable bysetting the automatic timer control off and on periods to supply more or lesslubrication.

    The Automatic Lubricator has a gage to show oil reservoir level. The Lubrication Timercan be programmed for any time mode but, is pre-set for a 20 hour cycle. The systemdispenses pre-determined amounts of oil to the distribution network which delivers thisoil to the bearing points.

    Note:The Auto Lubrication System does not supply grease to the drive system bearings.Drive bearing lubrication must be done manually. Bearings that need to be manuallylubricated are the Main Drive Bearings, the Tension Carriage Bearings, the Motor Bearing,and the Handrail Drive bearings.

    Additionally, the bearing surface of the Main Drive Shaft Brake, the Step Axle sleeve, theStep Wheel guide-shoe, and the Gear Box are manually lubricated.

    Ninth: Braking Systems
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    Braking SystemsThe braking systems on an escalator utilize three different braking methods as follows:

    1. The Machine Brake.

    2. The drive shaft brake system.

    3. The Main Drive Shaft Brake.

    1- The Machine Brake

    It is an electromagnetically released, spring-applied, disk that is driven by a spline hubmounted to the extended worm input shaft of the gear-reducer. This type of brake isreferred to as a fail-safe brake. When the brake coil is de-energized, springs within theassembly press the armature against the disc, and slowly stop the escalator. If anemergency button is pushed, if any of the safety switches are opened, or if there is a lossof power, the coil will be de-energized and the machine brake will be engaged.

    2- The drive shaft brake system

    It is also known as the Step Chain Locking Device or the broken drive chain device. It isoften referred to by this name when it is used for maintenance purposes to lock the drivesystem. In this case, the guide shoe is removed to allow the pawl to drop and engage theratchet.

    3- The Main Drive Shaft Brake

    It uses a pawl that is welded onto one end of the main drive shaft to engage a ratchet

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    wheel with brake linings on both faces. The brake lining wheel is sandwiched between thehandrail 1st drive sprocket and the step chain sprocket.

    A guide shoe lever is welded onto the opposite end of the main drive shaft. The guideshoe is normally supported by the drive chain and when the chain breaks, the shoe dropsand turns the shaft. The drive shaft brake pawl moves into the ratchet wheel and stopsthe escalator when the guide shoe drops.

    Tenth: Safety devices

    Safety devices

    Escalator systems are provided with many safety devices that will automatically stop theescalator by cutting electrical power to the motor and applying the brake if a problemoccurs. When a safety device stops the escalator, the problem must be corrected and thefault cleared before restarting the system.

    If a safety device is tripped out, a corresponding safety relay (PLC Input/output) will dropout. This applies voltage to the latching circuit of that device. If any safety circuit control

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    is tripped, the escalator will not operate and the tripped devices will do one of thefollowing actions:

    It will automatically reset when the fault is corrected.

    It will require resetting only the main safety reset button inside the controller.

    It will require that the individual controller circuit for that device must also be


    Safety Devices Types:

    there are so many safety devices included in the escalators as follows:

    1- The Broken Drive Chain Device, or Step Chain Locking Device/Pawl Brake, is aratchet- type device that prevents the escalator steps from sliding down from the weightof passengers if the drive chain breaks.

    2- A Broken Step Chain Device (tension carriage) cuts power to the motor and appliesthe brake if the step chain breaks or if the step chain is loose.

    Broken Step Chain Device3- A Skirt Obstruction Devicecuts power to the motor and applies the brake if an object

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    is wedged between the skirt panel and a step. This type of deflection will depress one ofthe plunger limit switches that are located behind the skirt panel at the upper and lowertransitions and at intervals between.

    Skirt Obstruction Device4- A Comb Step Impact Devicecuts power to the motor and applies the brake if a jamoccurs between the comb plate and a step.

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    Comb Step Impact Device5- A Step Level Devicecuts power to the motor and applies the brake if either side ofthe step at the riser end is depressed downward more than 1/8 or, if the step chain axleis depressed downward more than 1/8.

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    Step Level Device6- A Missing Step Devicecuts power to the motor and applies the brake if an opening is

    detected in the step band.

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    Missing Step Device

    7- The Broken Step Deviceis triggered if any of four roller lever limit switches aretripped. Two of the roller switches are located below the main drive and two are locatedbelow the tension carriage. When an out-of-place step trips the switch, power is cut tothe motor and the brake coil will be de-energized.

    Broken Step Device8- A Step Up-Thrust Deviceis located at the transition from the incline to the flatsection of the truss.

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    Step Up-Thrust Device

    9- Handrail Entry Deviceis located at the handrail entry port of each newel section. Thisdevice will cut power to the motor and apply the brake if an object is wedged betweenthe handrail and the rubber entry guard. Any caught object will depress two switchesbehind the handrail guard.

    Handrail Entry Device10- A Broken Handrail Device is located in the escalator incline section. The deviceconsists of a hinged roller that is held up by handrail tension. If a handrail is stretched orbroken, a limit switch is depressed by the roller bracket dropping. When the switch ispressed, it cuts power to the motor and applies the brake. The safety reset button in thecontroller must be pressed to restart the escalator.

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    Broken Handrail Device11- The Handrail Speed Deviceis a 1000 RPM tachometer generator wheel that rolls on

    the handrail. The weight of the tachometer generator and wheel pivots on a bracket tohold the wheel against the handrail. Contact of the tachometer wheel on the movinghandrail turns the generator, which outputs a voltage of 6.72 volts. If the handrail speeddrops below 80% or increases more that 110% over this voltage, then power to theescalator motor is cut and the brake is applied.

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    Handrail Speed Device12- A Reversal Stop Deviceimmediately stops the escalator when the direction of anascending escalator is reversed. This device is located just above the incline section ofthe escalator. It consists of a lever clamped to the middle handrail shaft which rotates inthe direction of travel. If the shaft direction is reversed, the lever will rotate and trip theswitch, cutting power to the motor and brake.

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    Reversal Stop Device13- An Emergency Stop Buttonis provided at both the upper and lower landing of theescalator. This covered button allows anyone to stop the escalator immediately in theevent of an emergency. Lifting the cover of the emergency stop button will cause analarm to sound for five minutes or until the escalator is restarted. Pressing the button willstop the escalator immediately. The escalator can be restarted after releasing the buttonby using the normal start-up procedure.

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    Emergency Stop Button14- A Thermal Overload Relayis installed on the controller panel to protect theelectrical drive motor from burning out due to escalator overload or a current overload.The relay can be reset by pressing the Reset button on the top of the Overload Relay.

    15- MECHANICAL SAFETY DEVICESThere are several mechanical safety devices that areused to stop and prevent movement of the escalator. These include locking bars,emergency brakes, and skirt brushes.

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    In the next Topic, I will continue explaining the Escalators Electrical & Control systemand Moving Walkways.So, please keep following.

    Note: these topics about Escalators in this course EE-1: Beginner's electrical design courseis an introduction only for beginners to know general basic information about Escalatorsas a type of Power loads. But in other levels of our electrical design courses, we will showand explain in detail the Escalators Loads Estimation calculations.

    You might also like:

    Escalators Basic Components - Part OneBasic Elevator Components - Part TwoHydraulic Elevators Basic ComponentsBasic Elevator Components - Part OneEarthing System Components Part Two

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    Leave a CommentEmail ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest

    Escalators Basic Components - Part One

    I explained all the basic components for the traction elevators (Pull elevators) in thefollowing previous Topics:

    Basic Elevator Components - Part One

    Basic Elevator Components - Part Two

    Elevator Machine and Drive System

    Elevator Safety System

    Elevator Control System Part One

    Elevator Control System - Part Two

    And I explained the basic components of the Hydraulic Elevators (Push Elevators) in theprevious topic Hydraulic Elevators Basic Components.

    Today, I will explain the Escalators Basic Componentsas follows.

    You can review the following previous topics for more information and good following. Elevators Types and Classifications Part One

    Elevators Types and Classification - Part Two

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    An escalatoris a moving staircase a conveyor transport device for carrying peoplebetween floors of a building.

    Escalators are powered by constant-speed alternating current motors and move atapproximately 12 feet (0.300.61 m) per second. The maximum angle of inclination of anescalator to the horizontal floor level is 30 degrees with a standard rise up to about 60feet (18 m). Modern escalators have single piece aluminum or steel steps that move on asystem of tracks in a continuous loop.

    Direction of movement (up or down) can be permanently the same, or be controlled bypersonnel according to the time of day, or automatically be controlled by whoever arrivesfirst, whether at the bottom or at the top (the system is programmed so that thedirection is not reversed while a passenger is on the escalator).

    The benefits of escalators are many: They have the capacity to move large numbers of people.

    They can be placed in the same physical space as one might install a staircase.

    They have no waiting interval (except during very heavy traffic).

    They can be used to guide people toward main exits or special exhibits They may be weatherproofed for outdoor use.

    They can help in controlling the traffic flow of people For example, an escalator toan exit effectively discourages most people from using it as an entrance, and may reducesecurity concerns.

    Escalators Configurations:

    Escalators have four typical configuration options:

    1- Parallel

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    Parallel Escalators

    Up and down escalators "side by side or separated by a distance," seen often in metrostations and multilevel motion picture theaters)

    2- Crisscross

    Crisscross Escalators
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    (Minimizes structural space requirements by "stacking" escalators that go in one direction,frequently used in department stores or shopping centers)

    3- Multiple parallel

    Multiple parallel Escalators(two or more escalators together that travel in one direction next to one or twoescalators in the same bank that travel in the other direction).

    4- Up Escalator next to Staircase
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    Up Escalator next to StaircaseIt is preferred that staircases be located adjacent to the escalator if the escalator is theprimary means of transport between floors.

    Note: It may also be necessary to provide an elevator lift adjacent to an escalator forwheelchairs and disabled persons

    Escalators Basic Components
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    Escalators Basic Components

    The Escalator consists of the following components:1. Landing Platforms.

    2. Truss.

    3. Tracks.

    4. Steps.

    5. Handrail.

    6. Escalator Exterior (Balustrade).

    7. Drive system.

    8. Auto-Lubrication System.

    9. Braking system.

    10. Safety devices.

    11. Electrical & Control Systems.

    First: Landing Platforms
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    Landing PlatformsThese two platforms house the curved sections of the tracks, as well as the gears and

    motors that drive the stairs. The top platform contains the motor assembly and the maindrive gear, while the bottom holds the step return idler sprockets. These sections alsoanchor the ends of the escalator truss.

    In addition, the platforms contain a floor plate and a combplate. The floor plate providesa place for the passengers to stand before they step onto the moving stairs.

    This plate is flush with the finished floor and is either hinged or removable to allow easy
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    access to the machinery below. The combplate is the piece between the stationary floorplate and the moving step. It is so named because its edge has a series of cleats thatresemble the teeth of a comb. These teeth mesh with matching cleats on the edges ofthe steps. This design is necessary to minimize the gap between the stair and the landing,which helps prevent objects from getting caught in the gap.

    Major components of Landing Platforms are:

    Combplates also known as walk-on plates are an entrance and exit for thepassengers to the steps. It provides mounting for the comb segments and combplate (combimpact) switch actuator.

    Comb Segments are replaceable sections, usually between 6 to 8 in width ormaybe narrower, with teeth that mesh (comb) into the step treads. Comb segment may alsobe called a combplate by non-standard noun name. A left hand, a right hand, or a middlesection comb segment can be identified by the pattern of the combs on their sides and bythe width or number of combs.

    Access Coversused as an access to the pit area for inspection, maintenance, andrepairs. The lower landing access cover plates provide access to the reversing station andstep removal. The upper access cover plates may provide an access to the driving machine,bull gear, and sometimes the controller.

    Comb Lightsare an optional safety device used to illuminate the area where stepsand comb segments meet, mounted at the upper and lower landing above the combsegments. They are from a different power source that stays on always even if the unit isnot running.

    Second: Truss

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    The escalator trussThe escalator truss is the structural frame of the escalator and consists of three majorareas:

    The lower section,

    Incline section,

    Upper section.

    It is a hollow metal structure that bridges the lower and upper landings. It is composed oftwo side sections joined together with cross braces across the bottom and just below thetop.

    The ends of the truss are attached to the top and bottom landing platforms via steel orconcrete supports. The truss carries all the straight track sections connecting the upperand lower sections. The structural steel truss members are designed to carry the entireload of the escalator equipment and the steel covering without shifting more thanspecified by the contract requirements. The entire structure is rigid enough to maintainclose operating tolerances but will allow for building shift and vibration because of abuilt-in system of shift- plates and Teflon pads.

    Third: Tracks

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    Tracks system

    The track system is built into the truss to guide the step chain, which continuously pullsthe steps from the bottom platform and back to the top in an endless loop. There areactually two tracks:

    One for the front wheels of the steps (called the step wheel track).

    One for the back wheels of the steps (called the trailer-wheel track).

    The relative positions of these tracks cause the steps to form a staircase as they move out

    from under the combplate. Along the straight section of the truss, the tracks are at theirmaximum distance apart. This configuration forces the back of one step to be at a 90-degree angle relative to the step behind it. This right angle bends the steps into a shaperesembling a staircase.

    At the top and bottom of the escalator, the two tracks converge so that the front andback wheels of the steps are almost in a straight line. This causes the stairs to lay in aflat sheet-like arrangement, one after another, so they can easily travel around the bendin the curved section of track.

    The tracks carry the steps down along the underside of the truss until they reach thebottom landing, where they pass through another curved section of track before exiting

    the bottom landing. At this point, the tracks separate and the steps once again assume astaircase configuration. This cycle is repeated continually as the steps are pulled frombottom to top and back to the bottom again.

    Three major assemblies of the tracks are: Upper.


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    The track assembly is bolted but not welded on the truss for easy removal. Sometimesthey are mounted on boilerplate (support plate mounted against the truss) or curve platesat the upper and lower landing sections. The tracks are used to guide steps wheels andstep chains in their travel around the escalator truss. They are curved at the upper andthe lower end of the incline to allow smooth transition of steps from the form of stairs toa horizontal movement, or vice versa. The lower and top end tracks are formed semi-circles to contain the chains and the step rollers going around them.

    Track assembly major components are:

    Track assembly major componentsa.Circle Tracks or Crab tracks (A)are located at the top and bottom pits. Most of theouter circle tracks have access windows for easy step removal. Some are mounted on aremovable or replaceable curve plate. The Montgomery & Montgomery KONE escalatorscircle tracks at the lower reversing station are part of the make-up track that travelswith the carriage. Circle tracks provide smooth step travel at the end of the tracks. Thedistance of the inside circle track from the carriage shaft of Westinghouse escalator isused to measure the wear of the step chain.

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    b. Beveled Track (B)provides smooth transition of chain wheels to and from the carriagesprockets. Beveled track eliminates the bumping effect of the chain wheels to the tracks,thus minimizing premature wear and damage to the wheels.

    c. Chain Wheel, Upper Upthrust (hold down) Track (C)is used to hold down and guidechain wheels to and from the transition.

    d. Chain Wheel, Upper Line Track (D).Used to support the chain wheels to/from thebull gear sprockets' top end through the incline area down to the carriage sprockets' top,or vice versa.

    e. Step Wheel, Lower Upthrust Track (E).A few feet of track used to hold down andguide step wheels to and from the transition area.

    f. Step Wheel, Lower Line Track or Flat Track (F)works in conjunction with the lowerupthrust step wheel track. Flat track supports the step wheels in either ascending ordescending through the incline.

    g. Chain Wheel, Return Track (G) is used to support the chain wheels from the bull gearlower end to the carriage lower end, or vice versa.

    h. Step Wheel, Return Track (H).Slightly above the chain wheel return track at theincline section of the non-passenger side. Step wheel return track is used to position thestep treads to run in parallel with the chain wheel return track.

    Forth: Steps

    The steps are solid, one piece, die-cast aluminum or steel. Yellow demarcation lines maybe added to clearly indicate their edges.

    The steps are linked by a continuous metal