Unit 1

1.0 Introduction

1.1 Role of Railway in TransportationSince its creation Indian Railways has successfully played the role of the prime carrier

of goods and passengers in the Indian Subcontinent. As the principal constituent of the nation’s transport infrastructure, the railway has important role to play.

1. Cheaper Transport: It is a cheaper mode of transport as compared to other modes of transport. Most of the working expenses of railways are in the nature of fixed costs. Every increase in the railway traffic is followed by a decrease in the average cost. Rail transport is economical in the use of labour also as one driver and one guard are sufficient to carry much more load than the motor transport.

2. Larger Capacity: The carrying capacity of the railways is extremely large. Moreover, its capacity is elastic which can easily be increased by adding more wagons

3. Railways have played a significant role in development and growth of industries. Growth of textile industry in Mumbai, jute industry in areas surrounding Kolkata, coal industry in Jharkhand, etc is largely due to the development of railway network in these areas. Railways help in supplying raw materials and other facilities to the factory sites and finished goods to the market.

4. Agriculture also owes its growth to railways to a great extent. Now farmers can sell their agricultural produce to distant places and even sell them in the world market at remunerative prices.

5. High Speed over Long Distances:Its speed over long distances is more than any other mode of transport, except airways. Thus, it is the best choice for long distance traffic.

6. Suitable for Bulky and Heavy Goods:Railway transport is economical, quicker and best suited for carrying heavy and bulky goods over long distances.

7. Railways play a vital role in mitigating the sufferings of the people in the event of natural calamities like droughts, floods, famines, earthquakes, etc. This is done by carrying relief and rescue teams and essential items to the affected areas and save people from sufferings and starvation.

8. Railways carry the British legacy and connect major ports, thereby lending a helping hand to the overall prosperity of the coastal areas.

9. Introduction of superfast trains and container services in major cities of India have ensured quick movement of men and material.

10. Dependable: The greatest advantage of the railway transport is that it is the most dependable mode of transport as it is the least affected by weather conditions such as rains, fog etc. compared to other modes of transport

11. Better Organised: The rail transport is better organised than any other form of transport. It has fixed routes and schedules. Its service is more certain, uniform and regular as compared to other modes of transport.

12. Safety:Railway is the safest form of transport. The chances of accidents and breakdowns of railways are minimum as compared to other modes of transport. Moreover, the traffic can be protected from the exposure to sun, rains, snow etc.

13. Larger Capacity:The carrying capacity of the railways is extremely large. Moreover, its capacity is elastic which can easily be increased by adding more wagons.

14. Administrative Facilities of Government: Railways provide administrative facilities to the Government. The defense forces and the public servants drive their mobility primarily from the railways.

15. Employment Opportunities: The railways provide greater employment opportunities for both skilled and unskilled labour. Over 16 lakh persons are depending upon railways for their livelihood.

2.0 Indian railwaysIndian Railways is an Indian state-owned enterprise, owned and operated by the Government of India through the Ministry of Railways. Railways were first introduced to India in 1853 from Bombay to Thane. It had 3 locomotive engines, and they were given the name Sindh, sultan and sahib, and there were 400 passengers accompanying them.

In 1951 the systems were nationalised as one unit, the Indian Railways, becoming one of the largest networks in the world. IR operates both long distance and suburban rail systems on a multi-gauge network of broad, metre and narrow gauges. It also owns locomotive and coach production facilities at several places in India and are assigned codes identifying their gauge, kind of power and type of operation. Its operations cover twenty eight states and seven union territories and also provides limited international services to Nepal, Bangladesh and Pakistan.

It is one of the world's largest railway networks comprising 1,15,000 km of track over a route of 65,000 km (40,000 mi) and 7,500 station, with 7800 trains carrying 11 million passengers to their destinations every day. The Indian Railway Network is the largest in Asia and second largest in world. Indian trains also transport about 6 lac tonnes of goods from one place to other every day. IR is one of the wor ld's largest commercial or utility employers, with more than1.6 million employees. As of 2015, 26,269 km (of the total 65,000 km route length was electrified. Since 1960, almost all electrified sections on IR use 25,000 Volt AC traction through overhead catenary delivery.

For administrative convenience Indian railways have been divided into the following seventeen zones:

Sl. No Name Route KMs Headquarters

1 Central Railway 3905 Mumbai

2 East Central Railway 3628 Hajipur

3 East Coast Railway 2572 Bhubaneswar

4 Eastern Railway 2414 Kolkata

5 North Central Railway 3151 Allahabad

6 North Eastern Railway 3667 Gorakhpur

7 North Western Railway 5459 Jaipur

8 Northeast Frontier Railway 3907 Guwahati

9 Northern Railway 6968 Delhi

10 South Central Railway 5803 Secunderabad

11 South East Central Railway 2447 Bilaspur

12 South Eastern Railway 2631 Kolkata

13 South Western Railway 3177 Hubli

14 Southern Railway 5098 Chennai

15 West Central Railway 2965 Jabalpur

16 Western Railway 6182 Mumbai

17 Kolkata Metro Railway Kolkata

4.0 Classification of Railways

4.1 Classification of railway based on gauge

The Indian Railways have three types of railway tracks:

1. Broad Gauge2. Meter Gauge3. Narrow Gauge

Most of the railway tracks are broad gauge. Broad gauge tracks are 1.676 metre wide. The trains running in the plains use broad gauge tracks. In desert areas and other difficult areas where broad gauge tracks are difficult to be laid, metre gauge tracks are laid. These tracks are one metre wide that is why these tracks are known as metre gauge.

The third type is the narrow gauge. This track is 77 cm. wide. Narrow gauge tracks are laid in the hilly and mountainous areas. Kalka to Shimla, Darjeeling to Siliguri and Mettupalayam to Ooty are narrow gauge tracks. These different kinds of tracks are of great inconvenience.

4.2 Classification of Indian Railways Based on Speed

All the B.G routes in India have also been classified based on speed criteria. According to this method, the B.G. railway lines can be divided into the following five groups

1. Group A lines: They consists of those trunk routes on which the train running or are meant for running the trains at a speed of 160 Kmph or more.

2. Group B lines. They consists of those routes on which the trains with a maximum sanctioned speed of 130 kmph are running or are intended to run

3. Group C Lines: they consists of all suburban routes4. Group D lines: all other routes in the country where maximum permissible speed at present is

100kmph5. Group E lines: the routes and branch lines where the permissible speed limits are less t6. han 100 kmph

4.3 Railways have two classes of coaches — First Class and Second Class. First class rail fare is quite high. Second class rail fare is less.

5.0 Basic Requirements of an Ideal AlignmentThe ideal alignment of a railway line should meet the following requirements.

Purpose of the New Railway LineThe alignment of a new railway line should serve the basic purpose for which the railway line is being constructed. The purpose may include strategic considerations, political

considerations, developing of backward areas, connecting new trade centres, and shortening existing rail lines.

Integrated DevelopmentThe new railway line should fit in with the general planning and form a part of the integrated development of the country.

Economic ConsiderationsThe construction of the railway line should be as economical as possible. The following aspects require special attention.

Shortest route It is desirable to have the shortest and most direct route between the connecting points. The shorter the length of the railway line, the lower the cost of its construction, maintenance, and operation. There can, however, be other practical considerations that can lead to deviation from the shortest route.

Construction and maintenance cost The alignment of the line should be so chosen that the construction cost is minimum. This can be achieved by a balanced cut and fill of earthwork, minimizing rock cutting and drainage crossings by locating the alignment on watershed lines, and such other technical considerations. Maintenance costs can be reduced by avoiding steep gradients and sharp curves, which cause heavy wear and tear of rails and rolling stock.

Minimum operational expenses The alignment should be such that the operational or transportation expenses are minimum. This can be done by maximizing the haulage of goods with the given power of the locomotive and traction mix. This can he achieved by providing easy gradients, avoiding sharp curves, and adopting a direct route.

Maximum Safety and ComfortThe alignment should be such that it provides maximum safety and comfort to the travelling public. This can be achieved by designing curves with proper transition lengths, providing vertical curves for gradients, and incorporating other such technical features.

Aesthetic ConsiderationsWhile deciding the alignment, aesthetic aspects should also be given due weightage. A journey by rail should be visually pleasing. This can be done by avoiding views of borrow pits and passing the alignment through natural and beautiful surroundings with scenic beauty.

6.0 Selection of RouteNormally, a direct straight route connecting two points is the shortest and most economical route for a railway line, but there are practical problems and other compulsions which

necessitate deviation from this route. The various factors involved is the selection of a good alignment for a railway line are given below.

1.0 Choice of GaugeThe gauge can be a BG (1676 mm), an MG (1000 mm), or even an NG (762 mm). As per the latest policy of the Government of India, new railway lines are constructed on BG only. 2.0 Obligatory or Controlling PointsThese are the points through which the railway line must pass due to political, strategic, and commercial reasons as well as due to technical considerations. The following are obligatory or controlling points.

Important cities and towns These are mostly intermediate important towns, cities, or places which of commercial, strategic, or political importance.Major bridge sites and river crossings The construction of major bridges for large rivers is very expensive and suitable bridge sites become obligatory points for a good alignment.Existing passes and saddles in hilly terrain Existing passes and saddles should be identified for crossing a hilly terrain in order to avoid deep cuttings and high banks.Sites for tunnels The option of a tunnel in place of a deep cut in a hilly terrain is better from the economical viewpoint. The exact site of such a tunnel becomes an obligatory point.

3.0 Topography of the CountryThe alignment of a new railway line depends upon the topography of the country it traverses. The following few situations may arise.

Plane alignment When the topography is plane and flat, the alignment presents no problems and can pass through obligatory points and yet have very easy gradients.

Valley alignment The alignment of a railway line in valley is simple and does not pose any problem. If two control points lie in the same valley, a straight line is provided between these points with a uniform gradient.

Cross-country alignment The alignment of a railway line in such terrain crosses the watersheds of two or more streams of varied sizes. As the levels vary in cross country, the gradients are steep and varying and there are sags and summits. The controlling or obligatory points for cross-country alignment may be the lowest saddles or tunnels. It may be desirable to align the line for some length along the watersheds so that some of the drainage crossings may be avoided.

Mountain alignment The levels in mountains vary considerably, and if normal alignment is adopted, the grades would become too steep, much more than the ruling gradient (allowable gradient). In order to remain within the ruling gradient, the length of the railway line is increased artificially by the ‘development process’.

The following are the standard methods for the development technique:Zigzag line method In this method, the railway line traverses in a zigzag alignmentand follows a convenient side slope which is at nearly right angles to the general direction of the alignment. The line then turns about 180° in a horseshoe pattern to gain height.

Switch-back method In the case of steep side slopes, a considerable gain in elevation is accomplished the switch-back method (Fig. 3.2). This method involves a reversal of direction achieved by a switch, for which the train has to necessarily stop. The switch point is normally located in a station yard. In Fig, A and B are two switches and A and B are two buffer stops. A train coming from D will stop at B and move in back gear to line BA. It will stop at A again and then follow the line AC.

4.0 Geometrical StandardsGeometrical standards should be so adopted as to economize as much as possible as well as provide safety and comfort to passengers. This can be done by adopting gradients and curves within permissible limits. Transition as well as vertical curves should be used to provide better comfort and safety.

5.0 Geological FormationThe alignment should be so selected that it normally runs on good and stable soil formation as far as possible. Weak soil and marshy land present a number of problems including those of maintenance. Though rocky soil, provides a stable formation, it is a costly proposal.

6.0 Effect of Flood and ClimateThe alignment should normally pass through areas which are not likely to be flooded. The climatic conditions should also be taken into consideration for alignment. In hot climate and sandy areas, the alignment should pass by those sides of sand dunes that face away from the direction of the wind. Similarly, in cold regions, the alignment should pass by those sides of hills that face away from the direction of the wind. A sunny side is more desirable.

7.0 Position of Roads and Road CrossingsA railway line should cross a road at right angles so as to have a perpendicular level crossing and avoid accidents.

8.0 Proximity of Labour and MaterialThe availability and proximity of local labour and good and cheap building material should also be considered when deciding the alignment.

9.0 Location of Railway Stations and YardsRailway stations and yards should be located on level stretches of land, preferably on the outskirts of a town or village so as to have enough area for the free flow of traffic.10.0 Religious and Historical MonumentsThe alignment should avoid religious and historical monuments, as it is normally not possible to dismantle these buildings.

11.0 Cost ConsiderationsThe alignment should be such that the cost of construction of the railway line is as low as possible. Not only the initial cost of construction but also the maintenance cost should be as low as possible. For this purpose, the alignment should be as straight as possible, with least earthwork, and should pass through terrain with good soil.

12.0 Traffic ConsiderationsThe alignment should be so selected that it attracts maximum traffic. In this context, traffic centres should be well planned; so that the railway line is well patronized and the gross revenue arising out of traffic receipts is as high as possible.

13.0 Economic ConsiderationsKeeping in mind the various considerations, it should be ensured that the alignment is overall economical. For this purpose, various alternate alignments are considered and the most economical one, which is cost effective and gives the maximum returns is chosen.

14.0 Political ConsiderationsThe alignment should take into account political considerations. It should not enter foreign soil and should preferably be away from common border areas.

7.0 Permanent way

Fig : Typical Cross section of a permanent way on embankment

The combination of rails, fitted on sleepers and resting on ballast and subgrade is called the railway track or permanent way. Sometimes temporary tracks are also laid for conveyance of earth and materials during construction works. In a permanent way, the rails are joined in series by fish plates and bolts and then they are fixed to sleepers by different types of fastening. The sleepers properly spaced, resting on ballast, are suitably packed and boxed with ballast. The layer of ballast rests on the prepared sub grade called the formation.

The component of permanent way include1. Rails2. Sleepers3. Fasteners4. Ballast 5. Subgrade

The rails act as girders to transmit the wheel load to the sleepers and also it provides level surface for train movement.

The sleepers hold the rails in proper position with respect to the proper position with respect to the proper tilt, gauge and level, and transmit the load from rails to the ballast.

In a permanent way, the rails are joined in series by fish plates and bolts and then they are fixed to sleepers by different types of fastening.

The ballast distributes the load over the formation and holds the sleepers in position.

Subgrade transfers and distributes load to soil layer

On curved tracks, super elevation is maintained by ballast and the formation is levelled. Minimum ballast cushion is maintained at the inner rail, while the outer rail gets more ballast cushion. Additional quantity of ballast is provided on the outer edge of the track for which the base width of the ballast is kept more than for a straight track.

In the early days, a temporary track used to be laid for carrying earth and other building material for the construction of a railway line; this temporary track used to be removed subsequently. The track is also called the permanent way in order to distinguish the final track constructed for the movement of trains from the temporary track constructed to carry building material.Requirements of Ideal permanent wayPermanent track is regarded to be semi elastic in nature. There is possibility of track getting disturbed by the moving wheel loads. The track should, therefore, be constructed and maintained keeping the requirements of the permanent way.

1. The gauge should be correct and uniform2. The rails should be in proper level, in a straight track, two rails must be at the same level. On

curves, the outer rail should have proper superelevation and there should be proper transition at the junction of the straight and a curve

3. The alignment should be correct. i.e it should be free from kinks or irregularities.4. The gradient should be uniform and as gentle as possible. Any change of gradient should be

followed by a smooth vertical curve, to give smooth riding quality5. The track should be resilient and elastic in order to absorb shocks and vibrations of running

track.6. The track should have enough lateral strength, so that alignment is maintained even due to

effects of a. Side thrust on tangent lengths and centrifugal force on curvesb. Lateral forces due to expansion of rails, particularly in case of welded rails

7. The radii and superelevation on curves should be properly designed and maintained8. Drainage system must be perfect for enhancing safety and durability of track9. Joints, including points and crossings which are regarded to be weakest points of railway

track, should be properly designed and maintained10. If there is trouble from the creep, the preventionary measures should be to prevent it11. The various components of track, i.e the rails, fittings, sleepers, ballast and formation must

fully satisfy the requirements for which they have been provided12. There should be adequate provision for easy renewals and replacements.13. The track structure should be strong, low in initial cost as well as maintenance cost.

Selection of gaugeThe following factors givern the choice among the different gauges

1. Cost consideration there is little increase in the initial cost if we select a wider gauge.

2. Volume and nature of traffic. It is evident that with greater traffic volume and greater load carrying capacity, the trains should be run by better traction technique or by better locomotives.

3. Development of areas. Narrow gauges can be used to develop the thinly populated areas by joining the under developed areas with developed or urbanised areas

4. Physical features of the country. Use of narrow gauge is warranted in hilly regions where broad and neter gauges are not possible due to steep gradients and sharp curves. In plains also, where high speed is not required and the traffic is light, N.G is the right choice

5. Speed of movement. The speed of a train is almost proportional to the gauge. Speed is the function of diameter of wheel, which in turn is limited by the gauge. The wheel diameter is generally 0.75 times that of the gauge. Lower speeds discourage the customers, and so for maintaining high speeds, the broad gauge is preferred.

Uniformity of gaugesGauge to be used in a particular country should be uniform throughout as far as possible, because it will avoid many difficulties experienced in a non uniform system. The uniformity of gauges results in the following advantages.

1. The delay, cost and hardship in transhipping passengers and goods from the vehicles of one gauge to another is avoided.

2. As the transhipping is not required there is no breakage of goods.3. Difficulties in loading and unloading are avoided and labour expenses are saved.4. Possibility of thefts and misplacement, while changing from one vehicle to another, is

eliminated5. Large sheds to store goods are not required6. Labour strikes etc. do not affect the service and operation of trains 7. Surplus wagons of one gauge cannot be used on another gauge. This problem with not arise if

gauge is uniform8. Locomotives can be effectively used on all the tracks of a uniform type of gauge is adopted.9. Duplication of equipment such as platforms, sanitary arrangements, clocks etc,. is avoided.

This saves a lot of extra expenditure10. During military movement, no time is wasted in changing personnel and equipment from one

vehicle to another if gauge is uniform11. It is quite expensive to convert one gauge into another at a later stage as it may require new

rolling stock, fresh construction and widening of bridges and tunnels.12. Due to late arrival of trains at the junction, where change of gauge is involved, the missing

links results in number of difficulties. Passengers have to pass time on platforms. In uniform gauge, this problem does not arise

Coning of WheelsThe head of the wheels of railway vehicle are not flat but made sloped, and this sloping of surface along the circumference forms a part of a cone. On straight tracks, the coning of the wheels keep them centrally, thereby reducing the wear of wheel flanges. If at any movement the wheels go out of the central portion, then they have to travel unequal distance due to the change in diameter of inner and outer wheel thus forcing it back to the central position and hence the ride will be smoother.

The problem, however, arises in the case of a curve, when the outer wheel has to negotiate more distance on the curve as compared to the inner wheel. Due to the action of centrifugal force on a curve, the vehicle tends to move out. Hence the conning of wheel helps in outer wheel to travel larger distance since it has larger diameter of the wheel and the inner wheel will travel smaller distance because it has smaller diameter of wheel. The wheels of a railway

vehicle are connected by an axle, which in turn is fixed on a rigid frame. Due to the rigidity of the frame, the rear axle has a tendency to move inward, which does not permit the leading axle to take full advantage of the coning. The rigidity of the frame, however, helps to bring the vehicle back into central alignment and thus works as a balancing factor. On rails laid flat, conning of the wheels will subject the rails to eccentric loading at the inner edge. This would create problem in both rail design and maintenance. To avoid this rails are not laid flat but they are instead tilted inwards at a slope of 1:20. Which is the slope of wheel cone. This is called as canting of rails.

Coning of wheels causes wear and tear due to the slipping action. It is, however, useful as(a) It helps the vehicle to negotiate a curve smoothly,(b) It provides a smooth ride, and(c) It reduces the wear and tear of the wheel flanges.As far as the slip is concerned, it can be mathematically calculated as follows.

Where θ is the angle at the centre of the curve fixed by the rigid wheel box and G is the gauge in metres.

The approximate value of the slip for broad gauge is 0.029 metre per degree of the curve.

Tilting of RailsRails are tilted inward at an angle of 1 in 20 to reduce wear and tear on the rails as well as on the tread of the wheels. As the pressure of the wheel acts near the inner edge of the rail, there is heavy wear and tear of the rail. Lateral bending stresses are also created due to eccentric loading of rails. Uneven loading on the sleepers is also likely to cause them damage. To reduce wear and tear as well as lateral stresses, rails are titled at a slope of 1 in 20, which is also the slope of the wheel cone. The rail is tilted by ‘adzing’ the wooden sleeper or by providing canted bearing plates.

RailsRails are similar to steel girders. These are provided to perform the following functions in a track.

1. Rails provide a continuous and level surface for the movement of trains.2. Rails provide a pathway which is smooth and has very little friction. The friction between the

steel wheel and the steel rail is about one-fifth of the friction between the pneumatic tyre and a metalled road.

3. Rails serve as a lateral guide for the wheels.4. Rails bear the stresses developed due to vertical loads transmitted to them through axles and

wheels of rolling stock as well as due to braking and thermal forces.5. Rails carry out the function of transmitting the load to a large area of the formation through

sleepers and the ballast.

Types of Rails There are mainly three types of rails used

1. Double headed2. Bull headed

3. Flat footed

The first rails used were double headed (DH) and made of an I or dumb-bell section (Fig. 6.1). The idea was that once the head wore out during service, the rail could be inverted and reused. Experience, however, showed that while in service the bottom table of the rail was dented to such an extent because of long and continuous contact with the chairs that it was not possible to reuse it. This led to the development of the bull headed (BH) rail, which had an almost similar shape but with more metal in the head to better withstand wear and tear (Fig. 6.2). This rail section had the major drawback that chairs were required for fixing it to the sleepers.

A flat-footed rail, (Fig. 6.3), with an inverted T-type cross section of inverted T- type was, therefore, developed, which could be fixed directly to the sleepers with the help of spikes. Another advantage of the flat-footed rail is that it is a more economical design, giving greater strength and lateral stability to the track as compared to a BH rail for a given cross-sectional area. The flatfooted (FF) Rail has been standardized for adoption on Indian Railways.Double HeadedThey mainly have 3 components

1. Uppertable2. Wed3. Lower table

Both Upper and lower tables are identical in shape and they were introduced with the hope of doubling the life of the rails. i.e when the upper table is wornout then the rail can be inverted and reused by fixing the upside down. But the idea soon turned out to be wrong as due to continuous contact of the rail with the chair made the surface of the lower table rough and hence the smooth running of the train was impossible

Bull headedIt is similar in shape to double head rail. The only difference between double headed and bull headed rail is that in bullheaded rail more metal is added to the head to allow the greater wear and tear. The lower head or table was kept of just sufficient size to be able to withstand the stresses to be induced by moving loads. This rail also required chair for fixing it to the sleeper. This proved the greatest drawback of this rail

Requirements for an Ideal Rail SectionThe requirements for an ideal rail section are as follows.

1. The rail should have the most economical section consistent with strength, stiffness, and durability.

2. The centre of gravity of the rail section should preferably be very close to the mid-height of the rail so that the maximum tensile and compressive stresses are equal.

3. A rail primarily consists of a head, a web, and a foot, and there should be an economical and balanced distribution of metal in its various components so that each of them can fulfil its requirements properly.

4. They should be of proper composition of steel as given above and should be manufactured by open hearth or duplex process

5. The fillet radii must be larger to reduce the concentration of stresses6. The tensile strength of the rail piece should not be less than 72 kg/m2

7. Foot should be wide enough so that rails are stable against overturning, especially on curves.8. Web of rail should be sufficiently thick to bear the load coming on it and should provide

adequate flexural rigidity in horizontal plane.9. The head must be sufficiently deep to allow for an adequate margin of vertical wear

The requirements, as well as the main considerations, for the design of these rail components are as follows.Head: The head of the rail should have adequate depth to allow for vertical wear. The rail head should also be sufficiently wide so that not only is a wider running surface available, but also the rail has the desired lateral stiffness.Web : The web should be sufficiently thick so as to withstand the stresses arising due to the loads bone by it, after allowing for normal corrosion.

Foot: The foot should be of sufficient thickness to be able to withstand vertical and horizontal forces after allowing for loss due to corrosion. The foot should be wide enough for stability against overturning. The design of the foot should be such that it can be economically and efficiently rolled.Fishing angles: Fishing angles must ensure proper transmission of loads from the rails to the fish plates. The fishing angles should be such that the tightening of the plate does not produce any excessive stress on the web of the rail.Height of the rail: The height of the rail should be adequate so that the rail has sufficient vertical stiffness and strength as a beam.

Merits and demerits of different type of rails

Points of comparison Flat-footed rail Bull-headed rails na double headed rails

Strength and stiffness they have more strength and stiffness for same weight

They have less strength and stiffness for same weight

Laying and relaying Fitting of these rails is simpler and so can be easily laid and re-laid

The fitting of these rail is difficult and time consuming as they are supported on chairs

Arrangement at points, crossings and at sharp curves

The arrangements are simpler and easy

The arrangements are complicated and difficult

Alignment and stability of track

In this impact of rolling wheels affect the fittings

These rails when fitted on chairs, provide a more solid, smooth track

Initial Cost Lesser cost More cost is required because of costly fastening

Rigidity More rigid They are less rigidInspection Daily inspection is not

necessaryDaily inspection of wooden keys is necessary

Maintenance cost Is less MoreSuitability More suitable because of

better stability, economy, strength and stiffness

More suitable at places where lateral loads are more important rather than vertical loads

F.F railsMerits

1. They have more strength and stiffness, both vertically and laterally, than B.H rails2. Fitting of rails with sleepers is simpler, so they can be easily laid and relaid3. No chairs or keys are required as in case of B.H. Rails4. In points and crossings, the arrangements are simpler than B.H. rails

Demerits1. The fitting get loosened more frequently than in case of B.H rails2. The straightening of rails, replacing of rails and dehogginf of battered rails are difficult

B.H railsMerits

1. They keep better alignment and give more solid and smoother connection with the latter2. The heavy chairs with larger bearing on sleepers give longer life to wodden sleepers and

greater stability

Demerits1. They require additional cost of iron chairs2. They have less strength and stiffness3. They require heavy maintenance cost

Section length and weight of rails1.

a) 52 kg rail b) 60 kg rail

The length of rail depends upon the maximum length- size that manufacturers can produce at a reasonable cost. Longer rails lengths require expensive arrangements at the rail mills for their controlled cooling, stacking and handeling. Another limiting factor is the problem of transport. Theoretically, the longer the rail, the lesser the number of joints and fittings required and the lesser the cost of construction and maintenance. Longer rails are economical and provide smooth and comfortable rides. However, the length of rail is governed by the following considerations

1. The length of rail which can be manufactured at the reasonable cost2. The rails should be of such length that they may be carried in the largest wagon

available3. The length of rail is also limited by the facilities available for lifting or handling the

rail4. The length of shortest rail should be larger than largest rigid wheel base of wagon

The length of a rail is, however, restricted due to the following factors.

(a) Lack of facilities for transport of longer rails, particularly on curves.(b) Difficulties in manufacturing very long rails.(c) Difficulties in acquiring bigger expansion joints for long rails.(d) Heavy internal thermal stresses in long rails.

Taking the above factors into consideration, Indian Railways has standardized a rail length of 13 m (previously 42 ft) for broad gauge and 12 m (previously 39 ft) for MG and NG tracks.

But, Rail weld or rail joint is the know zone of weakness in track structure hence should avoided to the extent that is possible. The rolling of rails in longer length is therefore encouraged. The new rail rolling set up by zindal steel and power lmd in india, is rolling rails upto length of 120 m each.

Weight of rail

Though the weights of a rail and its section depend upon various considerations, the heaviest axle load that the rail has to carry plays the most important role. The following is the thumb rule for defining the maximum axle load with relation to the rail section:

Maximum axle load = 560 × sectional weight of rail in lbs per yard or kg per metre

Rail WearDue to the passage of moving loads and friction between the rail and the wheel, the rail head gets worn out in the course of service. The impact of moving loads, the effect of the forces of acceleration, deceleration, and braking of wheels, the abrasion due to rail–wheel interaction, the effects of weather conditions such as changes in temperature, snow, and rains, the presence of materials such as sand, the standard of maintenance of the track, and such allied factors cause considerable wear and tear of the vertical and lateral planes of the rail head. Lateral wear occurs more on curves because of the lateral thrust exerted on the outer rail by centrifugal force. A lot of the metal of the rail head gets worn out, causing the weight of the rail to decrease. This loss of weight of the rail section should not be such that the stresses exceed their permissible values. When such a stage is reached, rail renewal is called for. In addition, the rail head should not wear to such an extent that there is the possibility of a worn flange of the wheel hitting the fish plate.Rail FailuresThe sudden failure of a rail is generally due to defects in its manufacture although the other causes may also exist. Two such other common causes, are

1. Abrupt change of section of rail2. Notches with corners in the foot of the rails

Such failure are rare on Indian railways, but failure may occur in one or more of the following forms

1. Crushed heads: Crushed heads are those which have either sagged or flattened, besides the defect of manufacturer, crushed heads are due to

1. Slipping of wheels2. Flat spots on wheels which are developed due to skidding or wheels3. Weak support at the rail ends

2. Square or angular break: the rails may be completely broken either in a vertical plane or in an inclined plane

3. Split heads: in this, cracks occur in the middle of the head or pieces are split from the side to the end of the head. If the surface of the defective rails is known as piped rail.

4. Split web: this is the through crack in the web, through not necessarily runs through the bolts holes

5. Horizontal fissures: these are developed in the rail head. They are more in the form of a fracture and develop gradually

6. Transverse fissures: this is the most common cause of rail failures. It is a cross wore crack which starts from a point inside the head and spreads like contours shape gradually. The broken surface has smooth oval or round bright spot. This defect is either a manufacturing defect or may occur due to overstraining of metal in service

7. Flowing metal in heads: the metal in the rail head is forced to flow on the sides due to which, the rail head gets widened and depressed

8. Horizontal cracks: these occurs at rail ends between head and web. Such cracks are believed to be due to worn fish plates or insufficient ballast packing under joint sleepers, resulting in pumping of joints and consequent fatigue failure of steel.

Type of Wear on RailsClassification based on location

1. On sharp curves2. On gradient3. On approaches to stations, where brakes are frequently applied4. In tunnels

a. Where sand is used on rails to produce more friction on damp rails but on the contrary it gives more wear

b. In tunnels, the gases emitting from the engine being confined attack the metal and results in wear.

5. In coastal area, due to action of sea breeze, the corrosion of metal takes place6. On weak foundation- sinking of rails due to heavy loads gives uneven surface which results

in wearOn bases of portion of wear

1. Wear on top of head of rail2. Wear at the ends of rails3. Wear on the sides of head

Wear on top or head of rails.This type of wear occurs on straight.i.e tangent tracks and at curves.On tangent tracksThe following are the factors which cause or encourage the wear on top of rails on tangent lengths

1. Due to flow of metal- this is because the heavy loads concentrated on small area produce the stresses which exceed the elastic limit and hence plastic flow of metal takes palce and burrs are formed, which later get chipped off by moving wheel flanges and its recurring impact causes the wear at the top pf rails

2. Due to abrasion of rolling wheels, the rails generally get worn out at the top of rails3. Due to constant brakes application, which results in skidding and burning of the rail head.

This finally results in excessive wear and abression4. Due to use of sand which is spread to produce friction in case of dampness in tunnels. The grinding

action of sand particles with rails gives rise to wear.5. Due to fluctuations in gradients.6. Due to corrosion of rails by the action of sea breeze, which also gives rise to wear on top of rails.7. Due to weak tracks viz., loose packing of ballast or loose fitting of rails and sleepers increase,

war.On curves. The wear on top of rails at curves is due to the following causes

1. Due to slipping or skidding of wheels2. Due to effect of centrifugal force and improper superelevation, load on one rail is greater than

the other. If superelevation is more or less for a given speed, the load will be more on inner or outer rail respectively

3. Due to adzing of sleepers: on curves the sleepers have to be laid at a slope for the purpose of superelevation, but when the rail is laid at a slope of 1 in 20 on sloping sleeper, the resulting slope or tilts s different from the slope of wheel cone, giving lesser a of contact between the wheel and the rail, resulting in more wear due to heavy concentration of stresses

Wear at the end of rails. Wear at the end of rails is due to high static pressure combined with impact bows. This Is prominent on straight tracks only and is much more in magnitude than the wear on top of rails. This type of wear occur, when a wheel jumps over the gap, giving blow to the end of rails. The end of rail get battered. This battered end causes rough riding in the track, loosens the ballast under the joints and even disturbs the sleeper. This further aggravates the intensity of blows and results in battering of ends and metal flow towards the gap and subsequently gets chipped offThis type of wear is encouraged due to following factors:

1. Due to loose fish plates and fish bolts2. Due to heavy loads and larger joint openings3. Difference in rail levels at joints4. Small wheels5. Bad condition of the vehicle springs6. Poor maintenance of the track

Wear on sides of the rail head: This type of wear is only prominent when the rails are laid at curves. This type of wear is more than first two types of wear and is most distructive in nature. This wear occurs due to following causes1. At curves, there is greater thrust on inner rail, when trains run at lesser speed than equilibrium speed2. due to rigidity of the wheel base3. slipping and skidding of wheels at curves.Actually, the thrust of wheel flanges against the inside of the outer rail causes side wear due to grinding actionAllowable limit of wear: the allowable limit of wear depends upon the weight of rails and in turn the weight of rail is proportional to axle load.In India, the prescribed limit of wear is 5% of rail weight because all the wear takes place in the head which contains 35% to 40% of the metal in rail. Allowable wear of 25% of the section of head is also exceptionally adopted.

Rail joints and welding of railsRequirements of an ideal jointAn ideal or perfect rail is one which provides the same strength and stiffness as the other rail section of track. The following requirements should be met by an ideal joint

1. The two rail ends should remain true in line both laterally and vertically when trains move on the track. This is necessary to avoid wheel jumping or changing its correct path of movements.

2. The rail joint should be as strong and stiff as the rail itself and should be elastic both laterally and horizontally

3. The rail joint should provide enough space for free expansion and contraction to account for the effect of temperature variations

4. A good joint should be easily diconnectable so that it can be easily taken out without disturbing the whole track for the purpose of changing rail or a fish plate and lubricating the contact faces

5. It should not..allow the rail ends to get battered in any case.6. The joint should fulfil the above requirements with the minimum of initial and

maintenance cost (i.e., it should be economical).Types of rail jointsSupported rail joints.When the rail ends rest on a single sleeper called a joint sleeper it is termed as supported joint.

Suspended rail jointWhen rail ends are projected beyond sleepers called shoulder sleeper. It is termed as suspended joint. This type of joint is generally used with timber and steel sleepers on Indian and foreign railways

Bridge jointWhen the rail ends are projected beyond sleepers as in case of suspended joint and they are connected by a flat or corrugated plate called a bridge plate, it is termed as a bridge joint

Base jointThis is similar to the bridge joint, with the difference that the inner fish plate are of bar type and outer plates are of special angle type, in which the horizontal leg is further extend over the sleepers to be bolted to both bridge plate and sleepersWelded rail jointsThese are the best joints as they fulfil nearly all the requirements of an ideal or perfect jointStaggered or broken jointIn this, position of joints on railway track is the basis of its nomenclature. In this type of joint, the joint of one rail track are not directly opposite to the joints of the other rail track. These joints are generally provided on curves, where the length of outer curved track is greater than the length of inner curved track

Square or even jointIn this also, the position of rail joint is the basis of its nomenclature, the joints of one rail track are directly opposite to the joints of other rail track.Compromise jointWhere two different rail section are required to be joined together, it is done by means of fishplates which fit both the rails and this joint is called as compromise joint

Insulated jointWhen insulating medium is inserted in a rail joint to stop the flow of current beyond the track circuited part, it is called insulated jointExpansion jointIn bridges, provision for expansion and contraction is kept for girder and rails both. This gap is 2.2cm to 7.2 cms

Welding of railsPurpose of welding

1. To increase the length of rail by joining two or more rails and thus to reduce the number of joints and requirements of fish plates, which lead to economy and strength

2. To repair the worn out or damaged rails and thus increase their life3. To build up worn out points and rails on sharp curves4. To build up the burnt portion of rail head which is caused due to slippage of wheels over the

rails or other defects or spots in rail steel

Advantages of welding rails1. It satisfies the condition of a perfect joint and hence increases the life of the rail, as also the

reduction in maintenance cost of track by about 20 to 40 percent2. It reduces the creep due to increase in length of rail and in turn friction as well3. Expansion effect due to temperature is reduced which in turn also reduces the creep4. Due to discontinuity of joints, a source of track weakness is reduced. The defect, such as

hammering at rail joints, displacement of joints, disturbance in alignment and running surface, which result in bad riding quality, are eliminated

5. Long rail lengths being heavier, dampen the intensity of high frequency vibrations due to moving loads

6. Welding increase the life of rails due to decrease in the wear of rails at joints7. Welding facilitates track circuiting on electrified tracks8. Welding rails provides on large bridge for the span length are helpful as they result in better

perfo9. rmance10. Welded rails provision on curves is under investigation. However, maximum curve length

may be welded depending upon resistance and lateral displacement if track11. The cost of track construction by welding of rails decreases due to less number of rail joints

Types of welded railsShort Welded Rails (SWR). A short welded rail is one which con tracts and

expands throughout its entire length due to temperature variations. These rails are welded into 3, 5 or 10 rail lengths to make Short Welded Rails. The Short Welded Rails of 3 rail length h a ve b e en s t a n de rd i ze d o n In d i a n r a i l w a ys .

Long Welded Rai ls (LWR). Long Welded Rail is one whose-central part does not undergo any longitudinal movement and only end portions are affected due to temperature variations. The minimum length of more than 200 m in ease of B .G. and 300 m for M.G. will function as Long Welded Rail. The maximum length of LWR is prescribed as one kilometre (1000 m) under Indian conditinos.

Continuous Welded Rails (CWR). The Welded Rails longer than one kilometre and extending from one station to other with switch expansion joint are called C.W.R.

Methods of welding of railsThe following are the four methods employed for welding of rails

1. Electric arc method2. Oxy acetylene welding3. Flash butt welding4. Chemical welding

Electrical arc weldingIn this method the current is passed through the rail and at the same time through a thin road known as electrode. As the electrode approaches the rail an electric arc is formed and with its heat the electrode gets melted, and finally the motel metal of the electrode gets deposited on the rails, providing a firm bond. This method of welding is used for building up worn out points and crossings, damaged rails and for small welding operations

Oxyacetylene weldingIn this method, intense heat is produced by combining the oxygen and acetylene gas, which melts the electrode and deposites the molten metal on the rails. This method of welding is used for repairing wornout parts. This is specially used for cutting of steel

Flash butt weldingIn this powerful current is passed through two rails, the end of which are to be joined together. The width of the gap between the two rails is varied till both the ends get heated up to a required temperature . then they are brought in contact with each other resulting in a flash. Finally the current is stopped the rails are pressed together under the pressure of 20 tonnesThis method of welding, being most satisfactory, is used for welding of rails in workshop.Chemical or thermal welding is involves the use also, like aluminium and iron oxide. In this method, aluminium and iron oxide are mixed in power form and ignited. On ignition, the chemical reaction takes place and produces intense head because this reaction is exothermic in nature.

Creep of railsCreep is defined as the longitudinal movement of rails with respect to the sleepers in a trackIndications of creep

1. Closing of successive expansion spaces at rail joints in the direction of creep and opening out of joints at the point from where the creep starts

2. Marks on flanges and webs of rails made by spike heads, by scraping or scratching as the rail slide

Theories of creep

Wave theoryWave action is setup by moving loads of wheels. The vertical reverse curve ABC is formed in the rails ahead of the wheels, resulting from the rail deflection under the load,is the chief cause of creep. The wheels push the wave with a tendency to force the rail in the direction of traffic. On a particular rail, the joint action by several wheels causes creep

Percussion theoryThis theory states that the creep is due to impact of wheels at the rail end a head at joints. The horizontal component P of R tends to cause creep while the vertical component tends to bend down the rail end vertically i.e, to make a battered rail end. Hence as and when the wheels leave the trailing rail and strike the facing rail end at each joint, it pushes the rail forward resulting in creep.

Drag or dragging theory

It states that backward thrust on driving wheels of the locomotive of train has got a tendency to push the rail off the track backwards while the other wheels of the locomotive and the vehicles push the rail in the direction of travel as in case of wave theory. This results in creep of rails in the direction of movement of trains

Starting, accelerating, slowing down or stopping of a trainWhen a train is starting or accelerating , the backward thrust of the engine driving wheels tends to push the rails backwards. When it is slowing down or coming to a stop, the bracking effect tends to push the rails backwards. When it is slowing down or coming to a stop, the braking effect tends to push the rails forward

Expansion or contraction of rails due to temperatureCreep also occurs due to variation in temperature. The creep in this case is influenced by the range in temperature variation, location of track, wheather exposed or shabby surroundings etc.Unbalanced traffic

1. In a single line system if heavy equal traffic runs in both directions, the creep is almost balanced otherwise, heavy traffic is one direction will cause creep, which is partly balanced by light traffic in opposite direction

2. In the double line system, trains on a particular line being unidirectional creep occursThe above mentioned causes are main but by no means the only causes of creep. The following factors also govern the magnitude and direction of creep

1. Alignment of track. Creep is observed greater on curves than on tangent railway track2. Grade of track. Creep is more with steep gradient particularly if the trains move

downward with heavy loads. Though in the opposite direction, it is not impossible for creep to develop

3. Type of rails. Old rails have more creep than new rails4. Direction of heaviest traffic. If the loaded trains run in one direction and empty trains

in opposite direction, creep will usually be found in the direction of loaded trains5. Poor maintenance of track component and ill design of superelevation, curves joints

etc. will also increase creep.