Unit-IV Railway Engineering

8/13/2019 Unit-IV Railway Engineering

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P R E P A R E D B Y

M . S H A N M U G A R A J

L E C T U R E R / C I V I L

V . S . V . N . P O L Y T E C H N I C C O L L E G E

V I R U D H U N A G A R

UNIT-IV RAILWAY

ENGINEERING



Station and Yards

Definition of Station

A railway station or a railroad station and oftenshortened to just station, is a railway facility

where trains regularly stop to load orunload passengers and/or freight

http://en.wikipedia.org/wiki/Railway

http://en.wikipedia.org/wiki/Train

http://en.wikipedia.org/wiki/Passenger_train

http://en.wikipedia.org/wiki/Freight_rail_transport

http://en.wikipedia.org/wiki/Freight_rail_transport

http://en.wikipedia.org/wiki/Passenger_train


http://en.wikipedia.org/wiki/Railway



Station and Yards



Purpose of Railway station

For exchange of passengers and goods. For control of train movements To enable the trains on a single line track to cross from

opposite directions. To enable the following express trains to overtake For taking diesel or coal and water for locomotives For detaching engines and running staff For detaching or attaching of compartments and wagons For sorting of bogies to form new trains, housing of

locomotive in loco sheds. In emergencies in ease of dislocation of track due to rains,

accidents etc... For repairing engines and changing their direction Railway station are having suitable approach roads from

surrounding areas.



Types of Stations

Wayside Stations, Junction Stations, TerminalStations



Wayside Stations

In this type arrangements are made for crossing orfor overtaking trains. Wayside stations are of thefollowing types.

i.Halt stations, ii.Flag Stations, iii.Crossing stations



Halt Stations

A halt, is a small station, usually unstaffed and withfew or no facilities. In some cases, trains stop onlyon request, when passengers on the platformindicate that they wish to board, or passengers onthe train inform the crew that they wish to alight.

http://en.wikipedia.org/wiki/Request_stop

http://en.wikipedia.org/wiki/Request_stop



Halt Stations



Flag Stations

Flag stations describes a stopping point at whichtrains stop only on an as-need or request basis; thatis, only if there are passengers to be picked up ordropped off.

These stations have no overtaking or crossingfacilities and arrangements to control the movementof trains. These stations have buildings, staff and

telegraph facilities. Some of the flag stations have sidings also in the

form of loops.



Flag Stations



Crossing Stations

Provided with facilities for crossing

In this type at least one loop line is provided to allowanother train if one track is already occupied by a

waiting train Generally the train to be stopped is taken on the loop

line and the through train is allowed to pass on themain line



Crossing Stations



Junction stations:

At a junction stations, lines from three or more directionsmeet

The stations where a branch line meets the main line areknown as junctions.

Arrangements in junction stations

Facilities for interchange of traffic between main and branch line

Facilities to clean and repair the compartments of thetrains

Facilities for good sidings, engine sheds, turn table etc.



Junction stations:



Terminal Stations:

It is a station where a railway line or one of its branches terminates

Facilities required in terminal stations

Watering, coaling, cleaning, servicing the engine Turn table for the change of direction of the engine

Facilities for dealing goods traffic. Such asmarshalling yard, engine sheds, sidings etc.

In circulating area, ticket office, restaurant etc areprovided and it is directly connected to the road



Terminal Stations:



Block Stations:

The stations at the end the block sections are called Blockstations

Authority to proceed is given in the shape of token atthese stations.

Class A Station: On these stations the track is cleared up to 400m beyondthe home signal for giving permission to approach a train

Class B Station: In such stations, the other signal is provided at about

580m from the home signalClass C Station: On these stations passengers are not booked. It is simply

a block meant for splitting a long block section and toreduce the interval between the successive trains.



Non Block Stations:

Also known as Class D station or Flag station

Situated between two consecutive block stations

May not be telegraphically connected to the

adjacent stations No equipment or staff is provided for controlling

the movements of the trains.

Trains are stopped by flag signals only



Special class stations:

Stations not coming under block station and non block stations are called special class station



Platforms - Passenger and Goods platforms:

A railway platform is a section of pathway, alongside railtracks at a railway station, metro station or tram stop, at which passengers may board or alight from trains or trams.

Almost all rail stations have some form of platform, withlarger stations having multiple platforms.

Platform types include the bay platform, sideplatform (also called through platform), splitplatform and the island platform.

A bay platform is one at which the track terminates, i.e. adead-end or siding.

A side platform is the more usual type, alongside tracks where the train arrives from one end and leaves towards theother.

An island platform has through platforms on both sides; itmay be indented on one or both ends, with bay platforms.

http://en.wikipedia.org/wiki/Track_(rail_transport)


http://en.wikipedia.org/wiki/Railway_station

http://en.wikipedia.org/wiki/Metro_station

http://en.wikipedia.org/wiki/Tram_stop

http://en.wikipedia.org/wiki/Bay_platform

http://en.wikipedia.org/wiki/Side_platform


http://en.wikipedia.org/wiki/Split_platform


http://en.wikipedia.org/wiki/Island_platform

http://en.wikipedia.org/wiki/Rail_siding

http://en.wikipedia.org/wiki/Rail_siding

http://en.wikipedia.org/wiki/Island_platform





http://en.wikipedia.org/wiki/Bay_platform

http://en.wikipedia.org/wiki/Tram_stop

http://en.wikipedia.org/wiki/Metro_station






Passenger Platform



Goods Platform



Definition of Yard:

An area consisting of a network of railway tracks,sidings, and sheds for storing, maintaining, and

joining engines and carriages.

A yard is defined as a system of tracks laid withindefinite limits for various purposes such as receivingsorting and dispatch of vehicles.



Railway Yard



Types of Yards:

Passenger yards, Goods yards, Marshalling yards,Locomotive yards



Passenger yards:

Function of passenger yard is to provide all the facilitiesfor the safe movement of passengers.

Facilities in passenger yards

Booking office, enquiry office, luggage booking room,

cloak room and waiting room for passengers Parking space for vehicles

Signals for reception and dispatch of trains

Platforms and sidings for shunting facilities

Facilities for changing batteries Facilities for passing a through train

Washing lines, sick lines facilities



Passenger yards



Goods yards:

A goods station (also known as a goods yard, goods depot or freight station) is, inthe widest sense, a railway station which isexclusively or predominantly where goods(or freight) of any description are loaded orunloaded from ships or road vehicles and/or where goods wagons are transferred to localsidings.

These are provided for receiving, loading andunloading of goods


http://en.wikipedia.org/wiki/Freight

http://en.wikipedia.org/wiki/Freight




Requirements of a goods yard

Approach road for movement of goods

Sufficient number of platforms for loading andunloading

Sufficient number of godowns Booking office

Cart weighing machine

Cranes for loading and unloading

Vacuum testing machine



Marshalling yards:

Marshalling yard is a railroad yard found atsome freight train stations, used to separate railroadcars on to one of several tracks

It is the place where goods wagons received fromdifferent centres are sorted out and placed in orderto detached at different stations

The marshalling yards are distribution centres

Empty wagons are also kept in marshalling yards

http://en.wikipedia.org/wiki/Railroad

http://en.wikipedia.org/wiki/Rail_yard

http://en.wikipedia.org/wiki/Goods_station

http://en.wikipedia.org/wiki/Railroad_car




http://en.wikipedia.org/wiki/Goods_station

http://en.wikipedia.org/wiki/Rail_yard

http://en.wikipedia.org/wiki/Railroad



Marshalling yards:



Factors for the efficient functioning ofmarshalling yards

Shunting operations should not disturb the regulartrains

Should be kept parallel to the running trains

Movement of wagons in one direction only Repair facilities should be provided on one or more

sidings

Connected to all important railway stations

Goods yard should be nearer to the marshalling yard



Types of marshalling yards:

(i)Flat yard (ii)Gravity yard (iii)Hump yard



Flat yard:

Flat yards are constructed on flat ground, or on agentle slope. Freight vehicles are pushed by alocomotive and coast to their required location.

A flat yard has no hump, and relies on locomotivesfor all car movements



Gravity yard:

The whole yard is set up on a continuous fallinggradient and there is less use of shunting engines.

Typical locations of gravity yards are places where it

was difficult to build a hump yard due tothe topography

Gravity yards also have a very large capacity but theyneed more staff than hump yards and thus they are

the most uneconomical classification yards.

http://en.wikipedia.org/wiki/Topography

http://en.wikipedia.org/wiki/Topography



Hump-yard:

These are the largest and most effective classification yards, with the largest shunting capacity —often severalthousand cars a day.

The heart of these yards is the hump: a lead track on a

hill (hump) that an engine pushes the cars over.

Single cars, or some coupled cars in a block, areuncoupled just before or at the crest of the hump, androll by gravity onto their destination tracks

A hump yard has a constructed hill, over which freightcars are shoved by yard locomotives, and then gravity isused to propel the cars to various sorting tracks



Hump-yard:



Locomotive yards:

This is the yard which houses the locomotives for various facilities such as watering, fueling, cleaning,repairing, servicing etc.



Locomotive yards:



Requirements of a locomotive yard

Should be located near the passenger and goods yards

Water column

Engine shed, Ash pit, inspection pit, repair shed,turn table

Hydraulic jack for lifting operations

Over head tank and loco well

Sick siding

Place for future expansion



Level crossings

A level crossing (a primarily British term; usuallyknown as a railroad crossing in the United States) isan intersection where a railway line crossesa road or path at the same level

Other names include railway crossing, gradecrossing, road through railroad, and train crossing.

The type of facilities provided at level crossingdepends up on the following

Nature of the road Nature of the traffic on road

Number of trains passing over the level crossing

http://en.wikipedia.org/wiki/Railway_line

http://en.wikipedia.org/wiki/Road

http://en.wikipedia.org/wiki/Trail

http://en.wikipedia.org/wiki/Trail

http://en.wikipedia.org/wiki/Road

http://en.wikipedia.org/wiki/Railway_line



Level crossings



Classification of level crossing:

Special class – Traffic is exceptionally heavy

A class – On grand trunk roads

B class – Metelled roads

C class – unmetelled roads D class – used for cattle‘s as ramps and pedestrians

only



Station Equipments

For efficient running of trains, safety of traffic,repairing, cleaning, examining of locomotives etc.some equipments and machinery is needed. Theseequipments are known as station equipment



Engine sheds:

Railway engine sheds were provided at terminalstations, junctions, and other locations around therailway.

They provided covered accommodation for servicinglocomotives - this could be simple tasks such aschanging brake blocks to more complex task thatinvolved dismantling and repairing the engine.

Types of engine sheds are (i) Rectangular type (ii)Circular type



Rectangular type engine shed:

In this type of engine shed, two parallel tracks arelaid, which meet at one or both the ends.

The engine can come from one end and leave theshed in other end

They need more space; they are widely used in India



Rectangular type engine shed:



Engine sheds:



Circular type engine shed:



Circular type engine shed:

This type of shed consists of radiating tracks and acircular structure known as round house

A turn table is also provided with the help of turntable the incoming locomotive is put up on the unoccupied track of the shed

Needs less place

Skilled labour is needed for the construction



Water Columns:

A water crane is a device used for delivering a large volume of water into the tank or tender of a steamlocomotive. The device is sometimes also called a watercolumn.

As a steam locomotive consumes large quantities of water, water cranes were a vital part of railway station equipment,often situated at the end of a platform, so that water could be refilled during a stop at the station.

They are kept at all main line tracks at a distance of not lessthan 50Km.

It should not any obstruction to traffic Foot valve is provided to regulate the water flow Height of water column is 442cm Projection of pipe is about 225 cms

http://en.wikipedia.org/wiki/Water

http://en.wikipedia.org/wiki/Tank_locomotive

http://en.wikipedia.org/wiki/Tender_locomotive

http://en.wikipedia.org/wiki/Steam_locomotive



http://en.wikipedia.org/wiki/Railway_platform

http://en.wikipedia.org/wiki/Railway_platform




http://en.wikipedia.org/wiki/Tender_locomotive

http://en.wikipedia.org/wiki/Tank_locomotive

http://en.wikipedia.org/wiki/Water



Water Column & Ash Pit



Ash pits: (Ash-pans)

Ash pits are provided to collect the ashes from thelocomotives

They are generally 1.067m deep and length is slightlymore than the length of the locomotive.

They rest on masonry or concrete walls and rails arefixed on longitudinal beams provided at the top ofthe walls



Turn table:

A turntable is a device used to turn railroad rolling stock. Turntables were also used to turn observation cars so that

their windowed lounge ends faced toward the rear of the train.

A turntable is a large circular platform which is used to turnlocomotives and other rolling stock for railways.

A well-engineered turntable is designed in such a way that theefforts of only two or three people are needed to operate theturntable, even when dealing with very large and heavylocomotives

The reason the turntable was developed was because earlysteam locomotives were somewhat difficult to run in reverse

As a result, train companies started building turntables sothat they could quickly turn their locomotives around.



Triangles:

Triangles are used for turning railway equipment By performing the railway equivalent of a three-point

turn, the direction of a locomotive or railway vehiclecan be swapped around, leaving it facing in the

direction from which it came It consists of three short lengths of tracks laid to

form a triangle and connected to each other by threepairs of points and crossings. Two tracks are laid in

curves and third as straight. The engine moves completely round the triangle and

its direction is automatically changed

http://en.wikipedia.org/wiki/Three-point_turn








Triangle



Buffer Stops:

A buffer stop or bumper is a device toprevent railway vehicles from going past the end of aphysical section of track

The design of the buffer stop is dependent in partupon the kind of couplings that the railway uses,since the coupling gear is the first part of the vehiclethat the buffer stop touches

It consists of timber beam 30x13cm section of thelevel of buffer on vehicles, fixed to the two verticalrail parts bolted to the track rails on other ends.

ff



http://en.wikipedia.org/wiki/Coupling_(railway)

http://en.wikipedia.org/wiki/Coupling_(railway)





Buffer Stops:

ff



Buffer Stops:

li k



Fouling Marks:

Purpose is to avoid side collision between two trainson adjacent track.(in between diverging/convergingtracking rear of t/in curve)

It should be fixed at the point where the spacing between the tracks begins to reduce to less than theminimum as specified in schedule of dimension.(i.e.4.27 Meter track centre normally)

They are made up of stone or concrete blocks andpainted in black and white

F li M k



Fouling Marks:

F li M k



Fouling Marks:

E i i i



Examination pits:

Examination pits are similar to ash pits but they areused to examine the engines from underneath.

These pits are generally longer and deeper than theash-pits

Provided in locomotive yards

E i ti it



Examination pits

T



Traversers:

Traversers are used to shift the position of the vehicles or locomotives sideways

They provide an arrangement of transferring enginesand vehicles from one track to a parallel track

Traversers are preferred to turnouts, cross-overs, etc.

It consists of a platform mounted on rollers.

Vehicle to be shifted is placed on the traverser and

then the traverse is moved sideways and adjusted tothe parallel track where the vehicle is to be placed

T



Traversers:

T



Traversers:

D ili it h



Derailing switch:

A derailing switch is an ordinary point switch The switch is open in the normal position and is

generally provided near the dead end of the siding

Any vehicle passing over it shall be derailed becauseof break of continuity of rails



D Pit



Drop Pits:

These are constructed at right angle to the track toexamine and repair or to replace the old wheels bynew ones.

In these pits the wheels of the locomotives arelowered and the wheels and axles are taken out withthe help of different kinds of jacks

Drop Pits:



p

Scotch Block:



Scotch Block:

It consists of a block of wood placed on the rail andsuitably held and locked in position

It forms an obstruction to the passage of vehicles andhence it prevents the escape of vehicle beyond thedead end of the siding

Scotch Block



Scotch Block

Scotch and Sand Hump



Scotch and Sand Hump

Sand hump:



Sand hump:

Method of checking vehicle The rails in the dead end siding after some fixed

distance get embedded in the sand and come to rest

Weigh Bridge:



Weigh Bridge:

These are level platforms with rails and areconnected to the main track

The beam rests on the knife edge and attached to thelever to which loaded wagons come to the siding tothe weigh bridge is fixed

The lever mechanism is activated and weight isindicated

Weigh Bridge



Weigh Bridge



POINTS AND CROSSINGS




Purpose for providing points and crossings: It is the name given to the arrangement which

diverts the train from one track to another, eitherparallel to or diverging from the first track.

Point and Crossings are peculiar arrangement usedin permanent way (railway track) to guide the vehiclefor directional change.




Some definitions:



Some definitions:

1.Angle of crossing: It is the angle between the running faces of point rail and

splice rail

2.Branch Track:

Track to which train is diverted from main track 3.Check rails:

To prevent the tendency of wheel to climb over thecrossing rail lengths are provided on the opposite side of

the crossing4.Heel block: It is the CI block to which tongue rail and

lead rails are both bolted

Branch Track:



Branch Track:

Check rails



Check rails

Heel block



Heel block



Lead Rails



Lead Rails

Nose of crossing



Nose of crossing

Tongue rail



Tongue rail

Switch



Switch

Throw of Switch



Throw of Switch



10.Switch angle: It is the angle formed between thegauge face of the stock rail and the tongue rail

11.Turn outs: A complete set of points and crossingsalong with a lead rail is known as turnout

12. Facing direction: If someone stands at toe ofswitch and looks towards the crossing it is calledfacing direction

13.Trailing directions: If someone stands at thecrossing and looks towards the switches, then thedirection is called Trailing direction

Switch angle



Switch angle

Turn outs



Turn outs



14.Facing points or Facing turn outs: When thetrain pass over the switches first and then they passover the crossing

15.Trailing points or Trailing Turnouts: The

opposite side of facing points in which the trainspass over the crossings first and then over theswitches.

Turnout



o

Right Hand Turn out and Left Hand Turnout:



out:

If a train from main track is diverted to the right ofthe main route in the facing direction, then thisdiversion is known as Right-hand turnouts.

If a train from main track is diverted to the left of the

main route in the facing direction, then thisdiversion is known as Left-hand turnouts.

Right Hand Turn out



g

Left Hand Turn out



Sleeper Laid for Points and crossing:



Two methods of laying sleepers below the points andcrossing

1.Through sleepers

2.Interlaced sleepers

Through sleepers and Interlaced sleepers



g p p

1.Through sleepers:



g p

They are provided in the overall length of points andcrossing

Through sleepers maintain several rails at the samelevel especially in straight and curved tracks.

Difficulties in the procurement and transporting oflong sleepers

Through sleepers



g p

2.Interlaced sleepers:



p

Adopted when longer sleepers are not available Both the tracks are laid on different sleepers, the

curved track often deforms and causes difficulties inmaintenance.

Also possess difficulties in the proper packing of the ballast

Interlaced sleepers



p

Through sleepers and Interlaced sleepers



Types of Switches:



There are two types of switches(i)Stub Switch

(ii)Split Switch

(i)Stub Switch



Earliest type of switch. No separate tongue rails are provided

Some portion of the main tracks is moved from side to side

It is obsolete now and no more in use on Indian Railways



Crossings:



It is a device provided at the intersection of two tailsto allow the trail moving along one of the tracks topass across the other

Types of crossing

(i)Acute crossing or Ordinary crossing

(ii)Double or obtuse crossing

(iii)Square crossing

Crossings:



(i)Acute crossing or Ordinary crossing



Acute angle is formed when a right hand rail of one trackcrosses left hand rail of another track at an acute angle

(ii)Double or obtuse crossing



This crossing is fixed when a track crosses another atan obtuse angle.

(iii)Square crossing:



When one track crosses another track of the same ordifferent gauge at right angle



SIGNALLING:



Objects of Signaling:



To provide facilities for the efficient moving of trains. To ensure safety between two or more trains which

cross or approach each other's path.

To provide facilities for the maximum utility of thetrack.

To provide facilities for safe and efficient shuntingoperations.

To guide the trains movement during maintenanceand the repairs of the track.

To safeguard the trains at converging junctions andgive directional indications of diverging junctions.

Types of Signal:



According to function According to location

Special signals



(a)Stop signals or semaphore type signals



One of the earliest forms of fixed railway signal isthe semaphore.

These signals display their different indicationsto train drivers by changing the angle of inclination

of a pivoted 'arm'

The stop position is the normal position and it issaid to be ON position

The arm can be lowered at an angle of 400 to 600

with horizontal and is said to be OFF position

(a)Stop signals or semaphore type signals

http://en.wikipedia.org/wiki/Railway_signal

http://en.wikipedia.org/wiki/Railroad_engineer

http://en.wikipedia.org/wiki/Railroad_engineer

http://en.wikipedia.org/wiki/Railway_signal



(b)Warner signals:



The warner signal is similar to semaphore signal inshape except a v-notch at free end, ie. The movablearm is fish tailed as shown.

The white band is also of v-shape

The warner signal is placed on the same post of thesemaphore signal 1.8 to 2.1m below the semaphoresignal.

The warner signal is painted yellow and exhibits yellow or amber colour at night instead of redcolour

(b)Warner signals:



Shunting Signals:



These signals are used for shunting operations instation yards They are of the shape of a circular disc with a red

band on a white back ground The disc can revolve in a vertical plane by pulling

the lever by hand. Two holes are provided, one for red lamp and the

other for the green lamp. When the red band is horizontal or shows red light

at night it indicates ―STOP‖ When the red band is inclined at 45 degree or

shown green light at night indicates ―PROCEED‖

Shunting Signals:



Shunting Signals:



Colour light signals:



Semaphore signals are being replaced by highintensity beam colour light signals both during dayand night

In case of colour light signals, the normal position

is to indicate ―PROCEED‖ (ie., shows green light)

When the section is blocked, it automaticallyindicates ―STOP‖ or ―DANGER‖ (ie., shows red

light) In India these signals are used on urban and sub-

urban sections with heavy traffic

Colour light signals:



Colour light signals



Locational characteristics



(i)Reception signals (a)Outer signal

(b)Home signal

(ii) Departure signals

(a)Starter

(b)Advance Starter

Location of signals



(a)Outer signal:



This is the first stop signal which indicates the entry ofthe train from block to the station yard

It should be placed at an adequate distance (0.54km forBG and 0.4 km for MG)

It has one arm but may have a warner signal on the samepost nearly 2m below it.

In the Stop position the driver must bring his train to astop at a distance of about 90m before the outer signaland then proceed to the home signal with caution

If it is in the Proceed position then the driver can takethe train at speed, assuming that home signal is also inthe proceed position.

(b)Home signal:



Due to its location at the door of station, it istermed as Home signal.

The home signal has bracketed arms to indicate which line is to be used.

The function of home signal is to protect thesidings already occupied.

It is located at not more than 180m from the start

of points of switches. Home signals carry as many arms as the number of

diverging lines.

(c)Starter signals:



It marks the limit up to which trains stopping at astation should come to a stand

The starter is the last stop signal at a station

It controls the movements of the trains when theydepart from the stations.

No train can leave the station unless the startersignal shows the ―PROCEED‖ position (ie.,

inclined position)

(d)Advance Starter signals:



Besides the starter signal for each of the stationlines from which trains starts, an advance startermay also be provided.

The advance starter becomes the last stop signal at

the stations where is provided.

It is an indication for the train having left thestation

Special Signals:



(i)Repeater or Co-acting signal:

When a train passes through a station withoutstopping, the driver comes across the five signals inthis sequence WARNER, OUTER, HOME, STARTERand ADVANCE STARTER.

When the drivers vision is obstructed by an over bridge between the signals, a signal is provided witha duplicate arm of smaller size at a suitable position which repeats the indication of signal head. It istherefore termed as Repeater signal.

This signal is linked with the main signal andtherefore, when the lever is pulled both signals arelowered simultaneously. Also called as ―co-actingsignal‖

Repeater or Co-acting Signal



(ii)Routing Signal:



When various signals for main and branch lines arefixed on the same vertical post, they are known asrouting signals.

Generally the signal for the main line is kept at

higher level than that for branch line.

(ii)Routing Signal:



(iii)Calling-on Signal:



These consist of small and short arms fixed on thesame post below main signals

A calling-on signal permits a train to proceedcautiously after the train has been brought to a halt

by the main signal This signals are helpful when repair works are going

on

Calling-on Signal



(iv)Miscellaneous signals:



Various other devices are used for indicating signals.Signals are meant for goods sidings are distinguished by providing rings or writing capital letter S etc.,

Two crossed bars are put up on the signal which is

under repair and it is placed in ON position.



(i)Following trains system:



Used in case of emergencies such as failure oftelegraph and telephone systems.

In this method, a fixed interval of time is maintained between the departure of one train and the departure

of the next train along the same time. This fixed interval is worked out in such a way that

sufficient distance or headway in maintained between the tail of the first train and the head of the

next following train.

(ii)Absolute block system:



The principle of the absolute block system of railwaysignalling is to ensure the safe operation of a railway byallowing only one train to occupy a defined section of track ata time

Instead of a fixed interval of time between successive trains, a varying interval may be kept depending on the time, actually

taken by particular trains. It is a space interval system rather than a fixed interval

system. In the absolute block system the line is assumed to be blocked

until the fact that the line is clear is established by some

suitable information conveyed by block instruments The electric telegraph provided the ability for signalmen to

communicate with each other and provided the basis for theabsolute block system

Absolute Block Diagram

http://en.wikipedia.org/wiki/Railway_signalling








(iii)Automatic signaling:



In order to avoid accidents, automaticsignalling has been found out. In this signalsare operated by trains themselves.

An electric current is conveyed through thetrack when a train occupies that particulartrack and this current puts the signal atdanger position until the train has gone farahead so as to require no further protection

(iv)Pilot guard system:



Used on certain occasions such as breakdown of telephone and telegraphsystem on a single line and one track of a

double line being out of order. In this system, a pilot proceeds by one train

to the station ahead and then he returns by atrain running in the opposite direction.

Centralized Traffic Control:



Centralized traffic control (CTC) is a formof railway signalling that originated in North America

The system consists of a centralized train dispatcher'soffice that controls railroad switches in the CTC

territory and the signals that railroad engineers mustobey in order to keep the traffic moving safely andsmoothly across the railroad.

CTC systems are considered sufficient authority to

run trains based strictly on signal indications. This is because CTC signals default to 'Stop' and require ahuman dispatcher to 'Clear' them.

Centralized Traffic Control






Interlocking:



Definition:

In railway signalling, an interlocking is an arrangement ofsignal apparatus that prevents conflicting movements throughan arrangement of tracks such as junctions or crossings

An arrangement of signals and signal appliances sointerconnected that their movements must succeed each

other in proper sequence". In general terms an interlocking is a location where plain

track ends and trackwork with points and crossingscomplicate train movements. These areas are likely to be:- Junctions where two or more main lines meet.

Complex yards or sidings are encountered. These may be at larger townsor depot facilities.

An interlocking provides for complex train movements andshunting of trains.

It provides for the protection of multiple train movements within a localised area.

Principles of Interlocking:






Not possible to lower the signals for the admissions oftrains from opposite direction or converging directions atthe same time to the same line

Not possible to lower a signal for any approaching trainuntil the correct points

Not possible for loose wagons from any part of the yard toobstruct the line which is set for incoming train afterlowering the signal

When the signal is lowered, it should not be possible to

disconnect any point or reverse unlock the points until thetrain has passed and signals have been raised to its ―ON‖position.

Not possible to lower warner signal unless home andstarting signals have lowered in advance

Methods of Interlocking:



The signals and points are operated by means oflevers.

Levers are located at ground level or platform level orin an elevated structure called signal box or signalcabin

Interlocking is done by grouping levers at one point

The levers are painted for easy identification

There are three methods of interlocking

(i)Tappets and lock system (ii)Key system

(iii)Route relay system.

(i)Tappets and lock system



This method is useful when levers are to beinterlocked so as to prevent conflicting movement

The tappers are of steel sections. 38mmX16mm withsuitable recesses and notches.

They are attached to the levers.

The locks are also of steel with shapes to suit therecesses in the tappers.

The lock move at right angle to the tappers

Working of Tappets and locks system:



The normal setting of the points is for the main line.The signal for the main line should be interlocked with the facing points so that when it is lowered,points cannot be changed. The levers are interlocked

such that pulling one of them prevents the other being pulled. This is known as (1) locks (3)



The loop signal should be interlocked with the facingpoints such that it cannot be lowered unless the points areset for the siding. Also it cannot be lowered when the

joints are set for main line. Levers (2) and (3) areinterlocked so that the lever (2) cannot be pulled unless(3) has already been pulled.

Conversely lever (3) can be restored to its normal positiononly if lever (2) has already been restored to its originalposition. This is known as (3) release (2) or (2) back locks(3)

The outer signal should be so interlocked with the routingsignal that it cannot be lowered until one of them is firstlowered. When levers (1), (2) and (4) are interlocked sothat lever (4) cannot be worked unless lever (1) or (2) hasalready been worked



The working of this system is given in theinterlocking table below

Descriptio

n of levers

Lever

No.

Releas

e

Lock

s

Backloc

ks

Main 1 4 3 -

Loop 2 4 - 3Points 3 2 1 -

Outer 4 - - 1,2

Tappet & Locks System



Tappet & Locks System



Key System:



This is the simplest method of interlocking. The key locks

are manipulated in this systemSingle lock and key system: The principle of this system is to provide two locks which

are worked by a single key. With drawl of the key locksthe signal in the horizontal position and the points in the

normal setting for the main line. And B are two locksoperated by a single key. To lower the signal the key isinserted and turned in the lock B. This releases the signaland when the signal is lowered, it prevents the key from

being withdrawn. Hence when the signal is lowered the

point is correctly set for the main line. For using thesiding, the key withdrawn from the lock B after restoringsignal from normal position and inserted and turned inlock A. This releases the points which may then be set forsiding. Now the main signal cannot be lowered.

Route relay System:



In this system, the points and signals for movementsof trains are electrically operated. This is the modeand sophisticated system of interlocking. Due to thissystem there is a considerable saving of man power

and maintenance expenditure of cabins.

Route relay System



Rapid Transport System:



General

Rapid transport is a type of high-capacity publictransport generally found in urban areas.

Unlike buses and trains, rapid transport systems operateon an exclusive right-of-way which is usually grade

separated in tunnels or elevated railways. Metro is the most common term for underground rapid

transport systems

Rapid transport is used in cities, agglomerations,

and metropolitan areas to transport large numbers ofpeople often short distances at high frequency . The extentof the rapid transport system varies greatly betweencities, with several transport strategies

Elevated railways

http://en.wikipedia.org/wiki/Public_transport


http://en.wikipedia.org/wiki/Urban_area

http://en.wikipedia.org/wiki/Bus

http://en.wikipedia.org/wiki/Tram

http://en.wikipedia.org/wiki/Right-of-way_(transportation)

http://en.wikipedia.org/wiki/Grade_separation


http://en.wikipedia.org/wiki/Tunnel

http://en.wikipedia.org/wiki/Elevated_railways

http://en.wikipedia.org/wiki/City

http://en.wikipedia.org/wiki/Agglomeration

http://en.wikipedia.org/wiki/Metropolitan_area

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Metropolitan_area

http://en.wikipedia.org/wiki/Agglomeration

http://en.wikipedia.org/wiki/City


http://en.wikipedia.org/wiki/Tunnel








http://en.wikipedia.org/wiki/Tram

http://en.wikipedia.org/wiki/Bus

http://en.wikipedia.org/wiki/Urban_area







Mono Rail



Metro Rail in Chennai



Under ground railways:



Advantages :

This system provides rapid and unobstructedtransportation.

This system helps in reducing traffic congestion

problems. This system provides safety during aerial attack in

war.

Suitability :

Underground railways are suitable in the heavilycongested urban areas where the traffic intensity onroads is heavy.

Under ground railways



Tube railways :



The railway provided underground at a greaterdepth of about 18 m or more (up to 52 m) are calledtube railways.

This system of railways is so called as the section of

the underground tunnels, carrying the track, is toavoid the interference of the tracks with water andgas pipes, sewerage systems and oil or drainage

pipes, etc

An electrically powered railroad with tracks runningthrough a tunnel underground; a subway.

Some important features of the tube railways aregiven below :-



The railways stations have to be of cylindrical form.

Escalators or moving stair cases are to be constructedto reach the tube railways.

Only electric traction to be used to avoid the smoke

and ventilation problems. Automatic signaling system is to be used.

Such a mechanism of the train is to be used that itcannot start until all the doors are closed, and it

automatically stops, if the signal is at ‗STOP‘ position. This system of railways is used by the London Post

Office in transporting mails through a small diametertunnel with automatic control without any driver.

Tube railways :

Unit-IV Railway Engineering

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Transcript of Unit-IV Railway Engineering