RAILWAYS

Railway track(Permanent Way) Combination of rails, fitted on sleepers

and resting on ballast and subgrade Rails are joined in a series using fish bolts Rails are connected to sleepers using

fastenings Rails act as a girder and transfer wheel

load to sleepers Sleepers hold the rails in proper position

and transmit load from rails to ballast Ballast holds the sleepers and distribute

load over the formation

Requirements of ideal permanent way

Gauge should be correct and uniform Rails should in proper level Gradient must be uniform and as gentle as

possible Track must be elastic in order to absorb shock and

vibrations Radii and SE must be properly designed Proper drainage must be provided Joints are to be properly designed All the materials using must have sufficient BC Adequate provision for easy renewals and

replacements Track should be strong, low IC and MC

Gauges Defined as the clear distance between

inner or running faces of two track rails

Selection of gauge Cost of construction

Cost of structures – bridges, tunnels, buildings… Cost of earthwork Land acquisition Rolling stock

Volume and nature of traffic – volume & load

Development of the areas – less populated Physical features of the country Speed of movement

directly proportional to gauge Speed is function of dia. of wheel Wheel dia. Is 0.75 times that of gauge

Uniformity of gauges Delay, cost and hardship in transhipping

passengers and goods Difficulties in loading and unloading of goods Labour charges are saved Possibility of thefts, misplacement while changing

from one train to another train Large sheds to store goods are not req. Labour strikes don't affect service & operation Surplus wagons cannot be used effectively Duplication of resources like platforms,

arrangements, clocks etc. are saved No wastage of time during military operations Quite expensive to convert at later stage as rolling

stock, widening of bridges and tunnels are difficult

Coning of wheels Distance b/w inside edges of wheel

flanges is generally kept lesser than gauge of track

Generally 1cm on either side Wheels are coned at a slope of 1 in 20

Coning of wheels

Advantages of coning To reduce wear and tear of wheel flanges

and rails due to rubbing action To provide possibility of lateral movement

of axle with its wheels To prevent wheels from slipping to some

extent

RAILS

Functions of rails To transmit the load from rolling stock to

sleepers To provide hard, smooth, uniform surface

for the wheels to roll To give minimum wear to rail material To bear the stresses due to vertical loads,

breaking forces and thermal stresses

Requirements of a Good Rail Very stiff i.e. bearing capacity must be high Proper composition of steel (Carbon content) Capable of withstanding lateral forces Tensile strength should not be less than

72kg/cm2 Should withstand “falling weight test or tup

test” without fracture Distribution of material in head, web and foot

of the rail should be balanced Web of rails should be thicker Foot should be wider Wearing surface i.e head must be harder

Types of Rails1) Double headed rails(D.H. Rails)2) Bull headed rails(B.H. Rails)3) Flat footed rails(F.F. Rails)

Double headed(D.H) railLooks like dumb bellIdea is to use another

head when one head is worn out during course of time

But after usage, lower head got dented(eroded)

Smooth running was impossible

So introduced B.H rails

Bull headed(B.H) railMore metal is added at

top compared to lower head to increase the stresses

More solid and smoother track

Chairs and keys are req. so sleepers have longer life

Hence costlier But after usage, they

found that lateral stability is very less

So introduced F.F rails

Chairs and keys

Flat Footed RailsFoot is made thinner and

wider than headDistributes the load to

greater number of sleepersResults in greater stabilityFittings of rails to sleepers

is easierNo chairs and keys req.Invented by CHARLES

VIGNOLESHence called as VIGNOSE

rails90% railway tracks in world

are made of these rails only

Standard rail sections Various types of rails are in use by Indian Railways Every bit of material in the section is to be utilized 90R(44.61kg/m) --- 100kmph for 20 to 25 years 50R, 60R and 75R are also in use To overcome inc. demand for heavier and faster

traffic: 52MR(52kg/m) --- 130kmph for 20-25 years 60MR(60kg/m) --- 160kmph for 20-25 years R- British rail as per Revised British Standards(RBS) MR – Metric rail as per IRS

Selection of rails Rail is designated by its weight per unit

length Various factors to be considered in

deciding: Speed of the train Gauge of the track Axle load and nature of traffic Type of rails Spacing of sleepers Max. permissible wear on top of rails(5% of

weight is allowed) Wt. of rail/locomotive axle= 1/510

Length of rails Longer rail lengths are preferred to shorter one’s Stronger and economy Comfort to passengers increases Length of rails is governed by:

Manufacturing cost is reasonable Transportation facilities Lifting, handling during loading & unloading

Standard length of rails in India are: Length = 12.8m for B.G Length = 11.89m for M.G

Proposed to inc. up-to 25m, USA & UK uses 30m Other alternative is to use welding as it

eliminates difficulty of transportation, lifting & handling

Rail failures

1) Crushed heads:2) Square or angular break:3) Split heads:4) Split web:5) Horizontal fissures:6) Transverse fissures:7) Flowing metal in heads:8) Horizontal cracks:

Wear on rails Prominent defects of rails Heavy axle loads & speed trains have more

impact Classification of wear

On the basis of location On the basis of position of wear

On the basis of location Wear is prominent on the following

locations: On sharp curves On gradients On approaches to stations, brakes are frequently

applied In tunnels

Where sand is used at damp rails to produce more friction but it gives more wear

Gases emitting from engine being confined attack the metal

In coastal area – action of sea breeze, corrosion of metal takes place

On weak foundations – uneven sinking of rails into ground

On the basis of position Following are the positions of wear on

rails:1) Wear on top or head of rail2) Wear at the end of rails3) Wear on the sides of the head

1) Wear on top of rails: occurs on straight and curved tracks

On Straight or tangent tracks: Due to flow of metal: elastic limits exceed and

hence plastic flow of metal takes place and burrs are formed

Heavy axle loads and its recurring impacts Abrasion of rolling wheels Brake application @ skidding Use of sand Corrosion of rails Weak track – loose packing of ballast & fittings to

sleepers On curves

Slipping or skidding of wheels Effect of centrifugal force i.e inner & outer wheels

pressure

Wear at the end of rails Wheel jumps over the gap giving blow to

the end of rail End of rail get battered Due to

Loose fish plates and fish bolts Heavy loads and large joint openings Difference in rail levels at joints Poor maintenance of track

Wear on sides of rail head Prominent at curves Most destructive Inner rails have more thrust Slipping and skidding of wheels at curves

Rail Joints Rail joints are the weakest part in the railway

track It is the joint made between two rails gap of 1.5 to 3mm for expansion Strength of rail joint is 50% of strength of rail Generally we use 2 fish plates and 4 fish bolts

Requirements of Good Rail JointIdeal joint provides same strength & stiffness as a normal rail

2 rails should be in line – vertically and horizontally

Should permit expansion and contraction of rails during temperature changes

Cheap and economical Require less maintenance Should be easily disconnect able without

disturbing whole track Rail ends shouldn’t get battered(worn out) Less wear and tear especially when fittings

become loose

Types of rail joints Supported rail joint: whenrail ends rest on a single sleeper called as “joint sleeper”

Suspended Rail Joint:“Shoulder sleepers”Generally used for timber And steel sleepers

Bridge joint: same as suspended joint but we use a extra plate called as “bridge plate”

Base joint: similar to bridge joint Inner fish plates are of bar type Outer fish plates are of angular type plate is further extended to both bridge plate and

sleeper Welded rail joints: Best rail joint Compromise Joint: when 2 different rail

sections are to be joined

Insulated joint: to stop flow of current beyond track circuit part Square joints: joint of one rail is directly

opposite to other rail track Staggered or Broken joints: joints of one

rail track are not directly opposite to joints of other rail track. Generally @ curves

Welding of rails To increase length of rail by joining 2 or

more rails It reduces no. of joints Req. less no. of fish plates Economy and strength

Repair of worn out or damaged rails

Advantages of welding It is a perfect joint and inc. life of rail Reduction in maintenance cost by 20 to

40% Reduces the creep Expansion effect due to temperature will

decrease Riding quality is increased Wear of the rail decreases Initial cost of the track also decreases

Types of welded rails Short welded rails(SWR): rails of 3, 5 or

10 are welded Standard Indian railways prescribes 3 rails

Long welded rails(LWR): min. length of 300m and max. of 1000m

Continuous welded rails(CWR): longer than 1000m. Sometimes they are in b/w 2 stations

Methods of welding1) Electric arc welding2) Oxy- acetylene welding3) Flash butt welding4) Chemical or thermit welding

Electric arc welding Metal arc welding Current is passed through rails and a thin

rod known as electrode at same time Due to heat, electrode gets melted and

deposits on rail, forming a firm bond Used for building up worn out rails

Oxyacetylene welding Gas pressure welding Heat is produced by combining oxygen &

acetylene gas Due to heat, electrode gets melted and

deposits on rail, forming a firm bond Used for building up worn out rails Best form mobility

point of view

Flash-butt welding Powerful current is passed through rails Rail ends get heated up resulting in a

flash Current is stopped and both the rails are

pressed together under a pressure of 20 tonnes

Heavy machinery req. So not economical for small works

Chemical or thermit welding Use of chemicals like aluminium & iron

oxide Both the chemicals are mixed in powder

form and ignited Exothermic reaction takes place and iron

gets separated & deposits in rail gap Rail ends are also to be heated economical

SleepersFunctions of Sleepers: To transfer the load from rails to ballast Acts as elastic medium & absorbs blows and

vibrations Hold rails in correct gauge and alignment Firm and even support to railsRequirement of Good Sleeper Strong enough to take load Weight must be lesser Bearing area must not be crushed Initial and maintenance cost must be less Should resist vibrations and shocks Fastenings must be min. Should permit track circuiting Should not be damaged by insects easily

Types of Sleepers Wooden Sleepers Metal Sleepers

Steel Cast Iron

Concrete Sleepers R.C.C Pre-stressed

Wooden Sleepers Also called as timber sleepers and its life depends on the

quality of timber used Hard wood(sal & teak) and soft wood(chir & deodar) Advantages:

Good for track circuiting Laying, packing and lifting is easy req. less fastenings Good absorber of shocks and vibrations & give less noisy track Easily available No corrosion

Disadvantages: Scrap value is less Subjected to wear, decay, attack by White ants Less life i.e. 12-15 years High maintenance cost Track is easily disturbed

Metal Sleepers

Made of 6mm thick steel sheets with both ends bent Advantages:

More strength and durability More life (25-30years) Performance of fittings is better, hence less creep occurs Economical No effect of termites Have good scrap value

Disadvantages: Fittings are greater in number, hence difficult to maintain Corrosion More cost compared to wooden Not suitable for track circuiting

Concrete sleepers Advantages:

Maintenance cost is less Free from natural decay Suitable for track circuiting More life- 40 to 60 years No corrosion Can take heavier loads, so fast moving trains

Disadvantages: Scrap value is nil Heavy weight, 2.5 to 3 times heavier Handling is difficult Fittings req are more

Sleeper Density No. of sleepers used per rail length Indicated with M+x or N+x Varies from (M+4) to (M+7) Depends on speed of train, size of rail,

type of joint, strength of sleepers and axle loading

Ballast Material placed and packed below and around

sleepers to distribute the load from sleepers to formation and drainage giving stability to track

Functions of Ballast: Transfer the load Holds the sleepers in position and provides Hard

bed for sleepers to rest on Elasticity to track and thereby improving riding

comfort Prevent growth of vegetation Good drainage

Requirements of Good Ballast Hard without getting crushed Should not make the track dusty or muddy Durable towards abrasion and weathering

action No chemical affect on rails and sleepers Good drainage of water Cheap and economical Near by locality Angular or rough surface Non porous and non absorbent Easily packed in position

Size and section of ballast Size of ballast varies from 1.9 cm to 5.1cm Size of stone ballast should be 5 cm for

wooden sleepers, 4cm for metal & concrete sleepers, 2.5cms at crossings

Section of ballast – Depth and width Depth inc. load bearing capacity and width

implies lateral stability to track Width will be around 38 -43cms America- depth equal to sleeper spacing India – not this recommendation Quantity of ballast req. Per m length is

1.036m3

Sleeper spacing = width of sleeper + 2 * Depth

Sleeper dimensions = 275 * 25*12.5

Types of Ballast Broken stone Gravel or river pebbels Sand Ashes Moorum Kankar Brick ballast Blast furnace slag Selected earth

Renewal of ballast Quantity of ballast is reduced due to:

Blowing away of ballast by movement of trains

Penetration of ballast in the formation Lost due to rain water and wind