Railway Engineering

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Prof. Dr. Padma Bahadur Shahi

1. Introduction

• Trains move on the steel tracks laid on the groundresulting in heavy expenditure on basicinfrastructure. Trains can move at much higherspeed than pneumatic type vehicles on modernhighways. Steeltrack cantakethreeto four time

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highways. Steeltrack cantakethreeto four timeheavier axle loads than road. The energy requiredto haul a unit load through a unit distance byrailway is about 16%, in comparison to roadtransport. Thus rail transport is best suited forcarriage of bulk and heavy commodities and largenumber of passengers on long distances.

Historical background

• Firstly the wheel path was strengthen by the stone pavingalong it. And stones are replaced by timber planks.

• By the passing of time period, the timber baulks werereplaced by iron Plates: called as plate ways.

• Iron plate section was improved: I section iron beam.

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• Tractive power was replaced gradually to mechanical.

• Invention of steamengine.

• In 1804 construction of steamlocomotive for railways.

• First public railway in the world: 27th September 1825in UK

• In France:– 1828 railways with horse power

First railways

• First railway operation in some countries:– UK: 1825

– France: 1828

– Germany: 1835

– India: 1853

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– India: 1853

– Japan: 1872

– China: 1875

Advantages

• Trains move on the steel tracks laid on theground. Trains can move at much higher speedsthan pneumatic tyre vehicles on modernhighways. Steel track can take 3-4 times heavieraxel loadthanroad. Theenergyrequiredto haul

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axel loadthanroad. Theenergyrequiredto haula unit load through a unit distance by railways isabout 16 % in comparison to road transport.

Advantages

• Biggest undertaking in the world & employs a sizeablesection of society

• Cheapest mode of transport

• Less traction to movement

• No steeringrequired,controlto themovement

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• No steeringrequired,controlto themovement

• Safe in comparison with road transport

• Political advantages:– Administration,

– National unity

– In wars and emergency situations

– Human Migration and interaction

Advantages

• Social advantages:– Communication

– Religious

• Economical advantages:– Mobility of goods& passengers

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– Mobility of goods& passengers

– During natural calamities

– High employment of the society

– Price stability of goods due to the cheap transportationcost

– Industrial development

Railway Classification

Broad gauge routes:

Based on the speed criteria railways have been classified into fivegroups:

• Group A: speed of 160 kmph or more– New Delhi-Howrah– New Delhi – Bombay– NewDelhi- Madras

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– NewDelhi- Madras– Howrah – Bombay

• Group B: Sactioned speed is 130 kmph• Group C: All sub-urban routes of Calcutta, Bombay and Delhi• Group D: All other routes where sectioned speed is 100 kmph• Group E: Other routes sections, branch lines where the

sanctioned speed is less than 100 kmph.

Railway Classification

Meter gauge routes:

• Q Routes: routes having maximumpermissiblespeed of more than 75 kmph

• R Routes: Routes having maximumpermissiblespeedof 75kmph.

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speedof 75kmph.

• S Routes: The routes having maximumpermissible speed less than 75 kmph

Railway gauges

S/N Type of gauge Gauge, mm Name of countries

1 Standardgauge 1435 England,USA, Canada,China,Turkey

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1 Standardgauge 1435 England,USA, Canada,China,Turkey

2 Broad Gauge 167616701600

India, Pakistan, Sri Lanka, Brazil, ArgentinaSpain, PortugalIreland

3 Broad Gauge 1524 Russia, Finland

4 Cape gauge 1067 Japan, Australia, New Zealand

5 Meter Gauge 1000915

India, France, Argentina,Ireland

6 Narrow gauge 672610

India, BritainSouth Africa, India

Rolling Stock of Railways

Moving part of railways is referred as rolling stock. It includes: Locomotive, Coaches, Wagons and Train Brakes

1. LocomotivesIt is the device which converts the energy of fuels into the

mechanical energy of motion. Fuel may be coal water, or fueloil and the conversion may be brought about by steamorelectricity. Nowelectric locomotives are very popular all overtheworld. Partof Locomotive:

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theworld. Partof Locomotive:• Fire box and Boiler: fuel is burnt in fire box and steamis

generated in boiler.• Proper engine: heat consists of cylinders, pistons and other

various moving parts. It converts heat energy of steamintomechanical energy of motion.

• Frame work: It is mounted on wheels. It has a drawbar whichtransmits the tractive force to the train.

• Tender: To store the fuel, a small bogie is attached with thelocomotive.

Locomotive

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Rolling Stock component

2. Coaches

The compartments which provide accommodationto the passenger in trains are called coaches.

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Rolling Stock component

3. Wagons

• To transport goods wagons are used. Types:– Timber wagons

– Cattle wagons

– Oil wagons: cylindrical

– Petrolwagons:

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– Petrolwagons:

– Hoper wagons: ballast, minerals, coals

– Well wagons: bulky articles of excessive height

– Power wagons: for explosives and chemicals– Refrigerated wagons: milk, fruits, meats and fish

Rolling Stock Component

4. Train Brakes

To stop moving trains brakes are provided inlocomotives. Types:

– Hand brakes– Steambrakes

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– Continuous automatic brakes

• Hand and steambrakes are used to stoplocomotives itself only. They can not be used tostop a train moving with a high speed. For thepurpose of stopping moving train continuousautomatic brakes are used.

Railway Track

• Photos

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Railway track component

Railway track is the permanent way or final track for themovement of trains. The track is the rail road on whichtrains run. It consists of two parallel rails having aspecified distance between them(gauge) and fastened tothe sleepers. These sleepers are embedded in the layer ofballastof specifiedthickness,spreadovertheformation.

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ballastof specifiedthickness,spreadovertheformation.

• Component parts:– Rails

– Fittings & fastenings

– Sleepers

– Ballast

– Formation

Functions of the track component

• Rails: rails are steel girders over which the train moves andtransmit the wheel loads of train to the sleepers below.

• Sleeper: The sleepers hold the rails in proper position andprovide a correct gauge with the help of fittings and fasteningsand transfer the train load to the ballast below.

• Ballast: holds the sleepers in proper positions and provides auniform level surface. They also provide drainageto the track

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uniform level surface. They also provide drainageto the trackand transfer train load to the larger area of the formation below.

• Fittings and fastenings: they provide a grip between rails andsleepers. The rails are fastened with the sleepers by fittings andfastenings.

• Formation: formation is the base of the railway rack. It gives alevel surface where the ballast rests. It takes total loads of thetrack.

Requirements of an ideal railway track

• Correct gauge• Correct alignment• Transition curves should be provided• Rails should have perfect cross level• Gradientshouldbeuniformandasgentleaspossible

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• Gradientshouldbeuniformandasgentleaspossible• Perfect drainage• Minimum friction between rails and wheels.• Joints, points & crossings should be designed• Track should possess and theft and sabotage qualities• Superelevation should be perfectly designed

Railway Track

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Railway Track

Sleeper

3.35 m

Rail Gauge

Sleeper

3.35 m

10.82 m

4.725

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Formation

Ballast

Double Line B. G. Track

Ballast

Rail

Functions:

• Provide level & continuous surface for the trainmovement

• Provide smooth pathway• Serveaslateralguidefor runningwheels

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• Serveaslateralguidefor runningwheels• Rails bear the stresses developed due to vertical

load• Types:

– Double headed– Bull headed rail– Flat footed trail

Rail sections

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Double Headed Rail Bull Headed Rail Flat Footed Rail

Rail cross dimensions and length

• Cross section dimensions of a typical 60 kg railshown in figure. Length og rail depends upon:

– The cost of production

– Difficulties in handlingandtransport

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– Difficulties in handlingandtransport

– Big expansion joints for longer rail

– Heavy internal thermal stresses in long rails

Dimensions

72.33

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16.5

150

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172

60 KG Rail Section

Rail length

Country Rail length, mGermany 30m

France 23m

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USA 12m

UK 18m

IndiaBG track 13m

IndiaMG Track 12m

Sleepers

• Sleepers are transverse support for a railwaytrack to give stiffness to it. Transverse sleeperswere introduced on the railway track for thefirst time in 1853.Functions of sleepers:

– holding rails to correct gauge and alignment– giving firm andevensupportto therails

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– giving firm andevensupportto therails– transfer and distribute the axle load fromrails– acting as an elastic mediumbetween rails and ballast– provide insulation for electrified track– to provide proper grade, longitudinal and lateral

stability

Sleeper density

• Number of sleepers used per rail length is known assleeper density. Generally one sleeper is used for everyone meter length of the rail. It is specified as(N+X)where, N is the length of the rail andX is anmathematical number which depends upon thefollowing factor:

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– Axle load– Type and section of rail– Type and strength of sleepers– Depth of ballast cushion– Nature of the formation

• In India the sleeper density on B.G. track is adopted asN+7 or N+4 or, N+3 for M.G. track.

Sleeper density

Type of sleeper Sleeperdensity

No sleepers perrail length

Rails per Km length

B.G Wooden/Metal N+7 13+7=20 1538

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M.G. Metal/Wooden N+4 13+4=17 1308

Classification of sleepers

• Wooden sleepers

• Cast iron sleepers

• Steel sleepers

• Concretesleepers

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• Concretesleepers

Comparison

Characteristics Wooden sleepers

Steel Sleepers C.I Sleepers

Concrete Sleepers

Service life, yrs. 12-15 40-50 40-50 50-60

Weight, kg for B.G track

83 79 87 267

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Gauge adjustment difficult easy easy Impossible

Scrap value Low scrap value

Higher scrap value than wooden

High scrap value

No scrap value

Ballast

• It is the layer of broken stone or gravel or any othermaterial placed under and around the sleepers todistribute the load fromsleepers to the formation andfor providing drainage as well as lateral andlongitudinal stability to track.

• Functions

– Suitablefoundationfor sleepers

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– Suitablefoundationfor sleepers– Transfer and distribute load fromsleeper to larger area of

formation– Increases elasticity and resilience of the track for getting

good riding comfort– Lateral and longitudinal stability– Provide effective drainage– Protects top surface of the formation

Ballast Types

• Broken stone: it is best to be used as ballast.The size of the ballast is generally is 40 to 50mm. At points and crossing 25 mmsize may beused.

• Gravel ballast: it is cheaper

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• Cinder or coal ash:• Sand ballast: coarse sand is cheap if available

locally.• Moorum ballast: it is the decomposed laterite

rocks.• Brick ballast:

Minimum depth of Ballast cushion

• The dispersion of load can be assumed at 45degree to the vertical. In order to ensure that thelines of dispersionof load do not overlapeach

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lines of dispersionof load do not overlapeachother, the thickness or depth of the ballastshould be enough.

Depth of the ballast Cushion

2

thsleeperwidSpacingD

−=

635

381 254254

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45D

Depth of Ballast Cushion

Minimum width of ballast section:

• To provide lateral stability to the track, thewidth of the ballast section should be sufficient.It should be extended by 30 cmon BGtrack and23 cm on MG track beyond the edge of

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23 cm on MG track beyond the edge ofsleepers. This ballast is known asshoulderballast.The ballast under the sleeper is knownasballast cushion,ballast outside the sleeper isknown asshoulderand in between the sleeper iscalledcrib ballast

Test for ballast

• Abrasion Test: aggregate abrasion value should not bemore than 30%

• Aggregate Impact Test: Aggregate Impact Value shouldnot be more than 20%.

• Flakiness Index: If the least dimension of a aggregate islessthan60% of its meandimension,thenit is known as

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lessthan60% of its meandimension,thenit is known asflaky particle. Flakiness Index is the percentage by weightof particles whose least dimension (i.e. thickness) is lessthan 60 % 0f their mean dimension. It should not be lessthan 50%

Track Fittings & Fastening

• Rail Joints

• It is weakest part of rail. In order to provideprovision for expansion and contraction of railsdue to variation in temperature, certain gap isprovidedat eachjoint. The joint causessevere

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providedat eachjoint. The joint causessevereblows to the passenger due to moving of wheelsover this gap.

Joint Types

a) according to the positionof joints:

– square joints

– staggered joints

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Squared Joint

Staggered Joint

Joint Types

b) According to the positionof sleepers

– Suspended joint

– Supported joint

42Suspended Joint

Supported Jont

Fastening of Rails

• The devices used to connect rails and sleeperstogether to form the track are known asfastenings. Fish plates, bolts, Chairs, keys andbearing plates are the devices for fastening therails.

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rails.• Fish Plates: are used to hold two rails together

in horizontal as well as in vertical planes. Ateach joint a pair of fish plate is used. Holes aredrilled through the plates and the web of rails.Rails are jointed by tightening fish bolts withthe help of nuts.

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Fittings for wooden sleepers

• Spikes: The device used to hold the rails to thewooden sleepers are known as spikes. Types of spikes:

• Dog spikes, Round spikes, screwspikes, elastic spikes.

45Dog Spike Round spikes Screw Spikes Elastic Spike

Slide chair type fitting

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Elastic fitting: Pandrol Clip

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Concrete sleeper Fitting: Pandrol Rail clip

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Materials Requirement per Km of railway track

Quantities of different materials required to lay one Km track can be calculate asfollows:

a) No. of rails per Km length = (1000x2)/rail length =For BG Track 60 kg rail and 13 m length of rail recommended:No. of rails per km length = (2x100)/13=154b) Weight of rail per km length = 154x13x60 = 120120 kg.c)No. of sleepers per km length = (No. of rails per km)/2 x (sleeper density)

On BG track sleeper density = 13 + 7 = 20No. sleepersperkm track= (154/2)x20= 1540nos

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No. sleepersperkm track= (154/2)x20= 1540nosc) No of fish plates per one km of track length = no of rails per km x2 = 154x2 =

308 nosd) No. of fish bolts = 4x no of rails per km = 4x154 = 616 nos.e) No of bearing plates = 2 x No of sleepers per km length = 2x 1540 = 3080 nos.f) No of labours required to lay one km of track (with 8 hour shift) = total tonnage

+ 20%