Rails, Types, Joints, Creep, Failure of Rails and Welding of Rails
- 1. Rails, Creep, Failures, Joints and Welding
- 2. Definition Rails are the members of the track laid in two parallel lines to provide an unchanging, continuous, and level surface for the movement of trains. To be able to withstand high amount of stresses these are made of high carbon steel.
- 3. Functions of Rails Rails are similar to steel girders. These are provided to perform the following functions in a track. Rails provide a continuous and level surface for the movement of trains. Rails provide a pathway which is smooth and has very little friction. Rails serve as a lateral guide for the wheels.
- 4. Functions of Rails 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. Rails carry out the function of transmitting the load to a large area of the formation through sleepers and the ballast.
- 6. Requirements of Ideal rail The section of the rail should be such that the load of each wheels is transferred to the sleepers without exceeding the permissible stresses The section of the rail should be able to withstand the lateral forces caused due to fast moving trains. The bottom of head and top of foot should be given such shapes that fishplates can be easily fitted.
- 7. Requirements of Ideal rail The centre of gravity of the rail section should preferably coincide the centre of the height of the rail so that maximum tensile and compressive stresses are nearly equal. The web of the rail section should be such that it can safely bear the vertical load without buckling. The head of the rail should be sufficiently thick for adequate margin of vertical wear.
- 8. Requirements of Ideal Rail The foot of rail should provide sufficient bearing area on the underlying sleepers so that the compressive stresses on the timber sleeper remain within permissible limits. The section of the rails should be such that the ends of two adjacent rails can be efficiently jointed with a pair of fish plates. The surfaces for rail table and gauge face should be sufficiently hard to resist the wear.
- 9. Requirements of Ideal Rail The contact area between the rail and wheel flange should be as large as possible to reduce the contact stresses. The specimen of rail should be able to withstand the blow of a falling weight in the test specified by the specifications The composition of the steel should conform to the specifications adopted for its manufacture by Open Hearth of Duplex Process
- 10. Requirements of Ideal Rail The overall height of the rail should be adequate to provide sufficient stiffness and strength as a simply supported beam. The foot of the rail should be wide enough so that the rail is stable against overturning. There should be balanced distribution of metal in head, web and foot.
- 11. Track components
- 12. Types of Rails Formerly wooden rails are used with thin plates. Later Cast – iron Malleable iron Wrought iron steel At present, Classified mainly into 3 types Double headed rail Bull headed rail Flat footed rail
- 13. Double headed Rail Consists of 3 parts Upper table Web Lower table Upper and lower tables are identical Idea was to double the life of rails – failed Long contact with chairs made the surface of lower table very rough and smooth running of trains is not possible with them.
- 14. Double headed Rails Now practically out of use Length varies from 610 to 732cm Wrought iron was used to manufacture these rails
- 16. Bull Headed Rails The rails sections having their head of more dimension then that of their foot are known as bull headed rails. These rails consist of Head Web Foot
- 17. Bull Headed Rails The foot is designed only to properly hold the wooden keys with which the rails are secured to chairs. Only to provide necessary strength to the rail 2 cast iron chairs are required for each sleeper.
- 19. Bull headed rails Extensively used in England and in some parts of Europe Weight of standard rail of this type is 47kg per metre on main lines and 42kg for branch lines Length of rail is generally 18.29m.
- 20. Flat footed rails Invented by Charles Vignoles in 1836. Also called as Vignoles rails. In this type of rail, foot is spread out to form a base. Highly popular and most used in railways. 90% of the present railway track consists of flat footed rails.
- 21. Flat footed rails Advantages Chairs: No chairs are required in this form of rails. Foot of rail is directly spiked to sleepers. Economical Stiffness: This form of rail is more stiffer both vertically and laterally than the bull-headed rail of equal weight. Kinks: Less liable to develop kinks and provides a uniform and more regular surface than bull headed rails.
- 22. Flat footed rails The flat footed rails are found to be cheaper than the bull- headed rails. Load Distribution: The flat footed rail distributes the train load over a great number of sleepers. This results in greater track stability. Longer life than bull headed rails
- 23. Flat footed rail
- 24. Standard Rail Section Rail designated by its weight for unit length Ex: 60kg/m or 60lb/yard etc., Weight and section of rail governed by many factors Gauge of track Max. permissible speed Type and spacing of sleepers Depth of ballast cushion Heaviest moving load likely to cross over the rail Spacing of sleepers
- 25. Maximum axle load that can be carried by a rail depends on its weight In India the capacity will be calculated as follows: Max axle load = 560 x sectional weight of rail in lb/yard or kg/m For 52 kg rail, max. axle load = 560 x 52 = 29.12 tonnes
- 26. Standard sections used in Indian railways Standard rails used in Indian railways are 60kg, 52kg, 90R, 75R, 60R, and 50R 60kg and 52 kg are introduced recently Other rails have units in FPS but now their dimensions are talked in SI at present. R stands for revised british specifications IR stands for Indian railwaya
- 29. 5kg/m and 60kg/m standard sections
- 30. Rail sections of type 90R are able to carry only 10GMT of annual traffic Due to increase in traffic heavier sections i.e., 52 kg and 60 kg are introduced. They can withstand annual traffic of 20 to 25GMT and speed of 130kmph. (52kg) 35GMT and 160kmph for 60kg section
- 31. Advantages of heavier rails Economical to have durable track by using heavier rails rather than increasing no of sleepers Cost varies as depth of rail, Strength varies square of depth. Hence heavy rail is economical. Stiffness varies as square of weight, strength as 3/2 power of weight.
- 32. Advantages of heavier rails If wheels move over rails of insufficient capacity, depression and there by additional dragging of locomotive. Causes wastage of power and capacity. Experiment in USA resulted in the following things: 65kg track used over 32km length Saving in initial cost over 55.6kg/m rail Maintenance (13.4%), sleeper renewals (56.9%), ballast renewal (23.3%) Deflection between 2 sleepers is less in case of heavy rails for a given load.
- 33. Criteria for determining length of rails Longer the rail lesser the joints and fittings Longer rails provide smoother and comfortable riding of trains Following factors govern the length of a rail Cost of production Difficulties in handling long rails lack of facilities for transporting longer rails Difficulties in having a bigger expansion joint for long rails Heavy internal thermal stresses Minimum rail length is 3.6m. Standard rail length is different in different countries.
- 34. Wear on Rails Due to the load and movement of wheels on the surface of rails, rail head gets worn out. Main reasons: Impact of moving loads Effect of the forces of acceleration and deceleration braking of wheels Abrasion due to rail wheel interaction Effects of weather conditions Presence of materials such as sand Lack of maintenance
- 35. Wear on Rails Lot of material of rail head worn out, causing a decrease in the weight of rail. Loss of weight should not be excessive Stresses will exceed permissible values otherwise. Rail renewal has to be done in such cases.
- 36. Types of Wear on Rails Wear of Rail on the top or head of the rail (vertical wear) Wear of rails at the end of rails (battering of rail ends) Wear of rails on the sides of the head of rail (lateral wear)
- 37. Wear of rail is more prominent at some special locations of the track. On sharp curves, due to centrifugal forces On steep gradients due to the extra force applied by the engine On approach zones of stations, possibly due to acceleration and deceleration In tunnels and coastal areas, due to humidity and weather effects.
- 38. 1. Wear of Rail on the top of Rail Head The metal from the top of rail flows and forms projections. These projections are known as burrs. Causes of vertical wear Rails worn out on the top due to abrasion of the rolling wheels over them Heavy wheel loads are concentrated on very small areas. High stresses exceeding the elastic limit are developed as a result.
- 39. 1. Wear of Rail on the top of Rail Head • Impact of heavy loads • Grinding action of the sand particles between wheels and rails • Corrosion of metal on the rails • Metal of top rail burns during the starting when wheels slip or when brakes are applied.
- 40. Wear of Rails at Ends of Rails Takes place at end of rails Much greater than the top of rails At expansion gaps, train jumps -> impact load Causes battering i.e., wear of end Other effects seen are as follows: Fish plates become loose Contact surface between sleepers and rails are worn out Sleepers at expansion joints depressed due to settlement of ballast
- 41. 3. Wear of Rail on the Sides of the head of rail Most destructive type of wear Occurs mainly at the curves Causes are as follows: At curvature, due to centrifugal force grinding action of wheel flanges on the inner side of head Vehicles do not bend to the shape of curvature while moving on the curve resulting in the biting of the inner side of curve Slipping action of wheels on the curves. Outer wheel has to cover longer distance compared to inner wheel. But due to rigidity of the wheels they will cover(rotate) same distance. Hence, inner wheel slips over inner rail, resulting a wear on the inner side of the head of inner rail.
- 42. Methods to Reduce Wear 1. Use of Special alloy steel o Special alloy rails are used at places where wear is more o Cost is more o But wear is greatly reduced o Life of rail is increased by 2 to 3 folds on the curves o These type of rails are also used for manufacture of switches and crossings 2. Good maintenance of track o Proper maintenance like ballast checking, using lubricants at places etc., o Tightening of joints and fittings to decrease wear
- 43. 3. Reduction of Expansion Gaps Should be reduced by increasing no of sleepers at joints, by tightening fish bolts Usage of welded rails to get higher length rails also decreases expansion joints 4. Exchange of inner and outer rails Inner rail and outer rail exchanged at curves to increase the life of rails
- 44. 5. Introducing check rails Check rail is kept parallel to inner rail all the way at the curves It holds back the flange of inner wheel to move and prevents damage of outer wheel Gap between inner rail and check rail should be equal to the thickness of the wheel thickness and side clearance 44mm for BG and 41mm for MG Connected to inner rails with suitable fastenings Used when curvature is min 8 degrees in case of BG and 14 degree in case of MG Normally worn rails are used as check rails
- 45. 6. Use of lubricating oil Usage of lubricating oil on curves on the side of head cases decrease in wear Can be done manually or with mechanical equipment attached to the locomotives or rails Allows free expansion of joints and also smooth flowing of traffic Requirements are as follows: Should be in the form of paste of workable consistency at high and low temperatures.
- 46. Efficiency should not be affected by dirt, dust and other atmospheric agencies Should be applied only after cleaning the gauge face Should not be done at extreme temperatures Commonly used lubricants are Lime saponified types of grease on a mineral oil base Mixture of grease and graphite Mixture of plumbago and axle oil in proportion 4:1
- 47. 7. Head hardened rails Used in advanced railway systems Increases life time by 2 to 3 folds Hardening is done at iso thermal treatment plant A depth of 12 to 14mm from top is hardened Heat results in improvement of following characteristics Impact strength 100% Relative elongation 50% Ultimate strength 50% Yield point 75%
- 48. Measuring wear of rails Weighing the worn out rail Rail is removed, weighed and fixed after knowing the wear Max. limit is 5% If lost more than 10%, should not be used anywhere on track Drawing profile of rail Comparison of profile of new rail and old rail to check the wearing
- 49. Renewal of rails After expiry rails are renewed Factors affecting renewal of rails Wear of rails Max 5% Use of heavier locomotives Construction of branch lines New rails for main track, older ones for branch line Bending of rails
- 50. Rail failures - Reasons Sometimes rails fail suddenly without any notice. Factors that influence the failure are as follows. Axle load of locomotive Constant reversal of stresses Defects in manufacture Design of rail joints Fatigue caused by shearing stresses Frequency of rail renewal Maintenance of rail joints
- 51. Rail length Rail quality Rail section Rail welding Speed of trains etc., The above are some of the main reasons of the rail failure
- 52. Rail failures - Types 1. Crushed head 2. Transverse fissure 3. Split head 4. Horizontal fissure 5. Square of angular breaks
- 53. Crushed head Head gets crushed, metal flows on the head of rail Defects in manufacture, flat spots on wheels, slipping of wheels, week support at the rail end etc., Skidding causes flat spots, loose fish bolts cause week support at ends Transverse fissure Fissure or hole in the head In the form of a cross wire crack starts inside head and spreads gradually Poor manufacture, excessive straining Very dangerous, rail breaks with out any sign often
- 54. Split head Head is split into 2 parts If the surface of crack appears smooth and dark, it is called as piped rail Formed due to cavity during manufacture, or shrinkage of metal Horizontal fissure A fissure developed keeps on increasing Outcome of worn fish plates or insufficient ballast Square or angular breaks Rail breaks either in vertical plane or angular plane
- 55. Coning of Wheels Flanges of wheels are never made flat Present in the shape of cone with a slope of 1 in 20. When wheel are moving on track there is a chance of lateral movement Without coning it will cause a sudden impact on the sides of rails Coning of wheels is mainly done to maintain the vehicle in the central position w.r.t to the track
- 56. Coning of Wheels
- 57. Coning of wheels - Disadvantages Smooth riding possible, but the pressure on the inner edge may cause its wearing Gauge widening happens some times If base plates are not provided sleepers under outer rails may damage To minimize these effects, tilting of rails is done by the use of inclined base plates Proper gauge Wear is uniform on head Increased life of sleepers
- 58. Creep of rails Longitudinal movement of rails in a track is termed as creep Common to all railway tracks Value changes from 0 to 130mm per month
- 59. Creep - causes Brakes Due to forces while starting or stopping Starting – rails pushed backward Stopping – rails pushed forward Wave motion of wheels Due to wheel loads rails deflect as continuous beam Crests at supports (i.e., sleepers) Changes in temperature Unequal expansion and contraction Happens more during hot weather
- 60. Creep on rails
- 61. Creep - causes Following are some of the minor causes rails not tightly fixed Bad quality sleepers Bad drainage No proper consolidation of the bed of track Gauge maintained tight Improper super elevation at curves Over capacity of traffic on rails Bad joints due to poor maintenance
- 62. Allowance of rail expansion joints Decaying sleepers Uneven spacing of sleepers Defective packing Insufficient ballast Improper usage of brakes
- 63. Factors determining the magnitude of creep Alignment of track Greater on the curves Gradient of track More on down gradient Direction of motion of trains One way or 2 way, no of lanes, load of trains Embankments Creep more on newly constructed embankments Weight and type of rail Light weight rails creep more than heavy weight rails
- 64. Results of creep Sleepers move out of position Gauge disturbance Gap variation at joints and other parts, results in uneven stresses Points and crossings will be disturbed Difficult to refix rail with creep Interlocking mechanism also gets disturbed
- 65. Measurement of creep Measured using creep indicator On the side of bottom flange of rail on either sides, a mark is made by chisel Two posts of rail are driven in the formation and their tops are in level with top of sleeper String fastened to the post and passed through markings towards rail Distance between string and the marks on the bottom of rails will indicate creep during a course of time
- 67. Methods for correcting creep Pulling back of rails method Rails are pulled back equal to the amount of creep Manually or using jacks Sleeper fittings are made loose, fish bolts are removed at one end while at the other end are made loose At the other end a liner is placed and the rail is pushed or pulled as required Following points should be noted Track should be packed properly after pushing/pulling Facility should be there to avoid restrictions to existing traffic Labour should be procured All fish plates, bolts should be cleaned, oiled and refixed Good to adjust creep before summer
- 68. Usage of Creep anchors Pulling back method is tedious, costly 75% decreased using creep anchor Creep anchor is a cast iron piece which is made to grip the rail The arrangement of anchors prevent the movement of rails there by creep, because the sleepers which are embedded in the ballast should move for movement to take place
- 69. Methods for correcting creep Different types of anchors are available Following points should be kept in mind while using creep anchors Creep anchor should be strong enough to resist stresses No of anchors are determined by the intensity of creep. 4 anchors per rail are provided for a creep of 7.5 to 15cm Creep anchors should be placed at points where the creep originates Should be avoided on railway bridges
- 70. Methods for correcting creep Additional creep anchors should be provided on level crossings, at places where heavy brake applications are made Defective creep anchors should be replaced Anchors fixed to rails by using clamping, wedging and other methods Creep anchors should be fixed to good and sound sleepers
- 71. Methods for correcting creep Use of steel sleepers Use of steel sleepers on a track minimizes creep Sleepers are provided with fittings which do not easily allow the creep to occur They will also have a good grip with ballast to resist their movement in ballast Increase in number of sleepers will also help in prevention of sleep.
- 72. Rail joints Joints are made between 2 rails Forms the weakest part
- 73. Characteristics of Ideal Joint Rail joint should hold the two ends of the rails as nearly as possible. The two ends should be at the same level and in the same straight line. Rail joint should have same strength and stiffness as rails which it joins Joint should provide space for the expansion and contraction of rails Joint should be such that any rail can be taken out easily or disconnected without disconnecting entire track Fishplates, rail contact surfaces wear gradually. Joints should be able to cope up with this adjustment.
- 74. Ideal joint should be cheap and economical for setting up and maintenance. It should be durable Should provide sufficient elasticity so that vibrations and shocks can be absorbed. It should provide resistance to longitudinal forces developed due to acceleration, deceleration to reduce creeping effect. Joints should be universal type so that they can be used for all type of sleepers.
- 75. Avoidance of joints In order to obtain better and smooth running of trains joints are avoided at the following situations. Bridge spans of 6m and below Level crossings Within 3m of approach of the bridge abutment
- 76. Types of Rail Joints Types according to position of joints Square joints Staggered joints Types according to position of sleepers Suspended joints Supported joints Bridge joints
- 77. Square joints When a joint in one rail is exactly opposite to the joint in the parallel rail it is called as square joint. Very common type of joint in straight track. Also most preferred. Staggered joints When a joint in one rail is exactly opposite to the center of the parallel rail length it is called as staggered joint.
- 78. Advantages of staggered joints Centrifugal force has a tendency to push the track out of line. Since the joints are weakest points they are more vulnerable. But staggered joints resist them to a great extent. More uniform vertical continuity of the track is formed Produce more smooth running than square joints Possibility of forming kinks will be decreases
- 79. Decreases the vertical disturbance of wheels Number of impacts at joints are doubled but intensity is halved Number sleepers per rail length will be increased by one. Staggered joints are more adopted on sharp curves and not favoured on straight track. It is not a rigid rule to fix the rail exactly at the center.
- 80. Suspended Joints The rail joint when placed at the center of 2 consecutive sleepers is known as suspended joint. Load is equally distributed on sleepers When the joint is pressed down both the rail ends are pressed down evenly. More commonly adopted Provide greater elasticity to the track Cause less disturbance to the wave motion of track Require more maintenance
- 81. Supported Joints Sleeper is placed exactly below the joint It appears like rails are supported at weakest part. These are not used at present Supported joint did not give sufficient support to the heavy axle loads If the joint is packed too hard it prevents it from settling at times It leads to the battering of rails as wave motion is not carried uniformly.
- 82. Bridge joints It is similar to suspended joint. Difference is here, a sufficient length of metal is used to connect the ends of 2 rails, so that there is no bending stress in the rail. Bridge is placed at bottom of rails and rests on sleepers Sleepers at the end will have to be notched out at the sides or will have to be placed at a lower level than other sleepers to accommodate bridge.
- 83. Bridge joints The end sleepers are supposed to work as unyielding fixed supports. But practically they are not working as fixed unyielding supports. As a compromise between supported and bridge joints Indian railways provide semi-supported joints. Sleepers at rail joints are bought close here in this case.
- 84. Requirements of ideal fastening Good fastening connecting rail and sleeper plays a vital role in improving the efficiency of railway track. Following are some of the requirements of ideal fastenings. Capable of absorbing shocks and vibrations Capable of giving protection to the sleeper against different forces Provide insulation in case of electrified tracks
- 85. Requirements of ideal fastening Capable of resisting the creep Capable of securing the correct gauge Should be economical Consist minimum equipment Should be durable Should be easy to fix and adjust Should be non corrosive Should have sufficient strength to resist damage due to derailment
- 86. Requirements of ideal fastening Should be possible to remove only using special tools Should safe guard the alignment in all aspects Should not adversely affect the rail and sleepers Should not be too rigid Adequate strength to resist lateral forces Should possess high torque resistance
- 87. Fastening for rails Following are the fastenings which are used to keep the rails in their correct position. Fish plates Spikes, fang-bolts and hook-bolts Chairs and keys Bearing plates
- 88. Fish plates Purpose: connecting the rails at the ends Holes are drilled through web and rails and fish bolts, nuts are provided in these holes. When bolts, nuts are tightened it forms a continuous track Design: The pair of fish plates should have the same strength in bending as the original rail. This can be achieved by improving section of fish plate or by using high tension steels. For details, types and failures: refer text book
- 89. Spikes, fang-bolts, hook-bolts Purpose: Spikes are required to hold the rails to the wooden sleepers. Dog spikes Screw spikes Round spikes Elastic spikes
- 90. Chairs and keys For double headed and bull headed rails chairs are required to hold them in position. These are made of cast iron and help in distributing the load from rails to sleepers. Chairs are fixed with sleepers by means of spikes. Keys are required to keep the rail in proper position.
- 91. Welding of rails To join two rails and thus increase the length of rail To repair the worn out or damaged rails and thus increase their life To built up the damaged components of points and crossings
- 92. Advantages of Welding Increases the life of rails due to decrease in wear at ends Decrease in maintenance cost to 25% Smooth functioning of track Decrease in creep Welded rails better for electrified tracks Better for large bridges as rails of length equal to each span give better performance and reduce the effect of impact
- 93. Welding of rails result in decrease in construction cost due to less number of joints Fast and heavy traffic can be permitted on the track Tractive effort is reduced due to elimination of energy losses at joints Risks of sabotages and accidents are reduced More stability in lateral, longitudinal, vertical directions of track
- 94. Welding of Rails Welding methods Gas pressure welding Electric arc welding/Metal arc welding Flash butt welding Thermit welding Looking at the advantages, requirements and facilities available one of the methods is chosen.
- 95. Gas Pressure Welding 2 different types of gases – oxygen, acetylene Kept in 2 different cylinders Burned at 1200C temperature Metal rails butted together and welding done. Metal flows from rails to form a single section Cheaper, good quality but limited outputs
- 96. Electric Arc Welding 2 rails are treated as 2 different terminals. Electric current is passed across the gap of butted rails using different techniques. Insert plate technique Scheron process Enclosed space technique Current produces heat to melt the electrode kept in the gap Electrode will have same metal composition as rail This method can also be used for repair works
- 97. Comparison of flash butt and thermit welding Flash butt welding Chemical/Thermit welding Principle of welding: passing 35000 amp of electric current Quality of weld: excellent Strength of weld: good in fatigue Time required: 3 – 6 mins Exothermic chemical reaction between fe 2O3 and Al at a temp of 2450C Good Weak in fatigue 10 – 12 mins/ 30- 45mins conventional
- 98. Comparison of flash butt and thermit welding Flash butt welding Thermit welding Place of welding: workshop/site Cost of welding: less Tolerances: Very tight Control on quality: controlled using welding recorder At site High Normal No monitoring possible
- 100. Sleepers Functions : in a railway track sleepers add to the stability of the pavement. Following are the functions. Supports the rails firmly Maintains the uniform gauge on track Distributes the weight coming on the rails over a sufficiently large area of ballast Acts as an elastic medium between rails and ballast to absorb vibrations of trains Provides for easy replacement of rail fastenings without disturbing traffic
- 101. Sleepers Functions…contd. Permits insulation of track for electrified sections Maintain the track at proper grade by allowing raising of the rails and tamping the required quantity of ballast To maintain the alignment of track Transfers the load from rails to ballast
- 102. Requirement of sleepers Following are the requirement of good sleepers They should maintain correct gauge Rails should be easily fixed and taken out from the sleepers without moving them Sleepers should provide sufficient bearing area for the rail Sleepers should provide sufficient weight for the stability They should be sufficiently strong to act as a beam under loads They should provide sufficient effective bearing area on the ballast They should not be pushed out easily of their
- 103. Requirement of sleepers…contd.. Design should be such that packing and tamping should not damage them Should be economical in initial as well as in maintenance cost Fittings of the sleepers should be such that rails can be easily adjusted during maintenance operations If track circuiting is required, it should be possible to insulate them from rails They should be able to bear the stresses Should not be too heavy, nor too light Design and spacing should be such that ballast packing can be done easily and effectively in less time.
- 104. Types of Sleepers Depending upon the position in a railway track, the sleepers may be classified as follows Longitudinal sleepers Transverse sleepers Timber or Wooden sleepers Steel sleepers Cast iron sleepers Concrete sleepers
- 105. Longitudinal sleepers Early form of sleepers Consisted of slabs of stones or pieces of timber placed parallel to rails Cross pieces were provided at intervals to maintain the correct gauge of track At present these sleepers are not in use because, Running of train not smooth Cost is more More noise is created Etc.,
- 106. Transverse sleepers Also called as cross-sleepers First introduced in UK in year 1835 Highly popular, and most used in railways at present Most of the disadvantages of longitudinal sleepers are taken care Depending on the type of material used for manufacturing these sleepers, classified into different types: Timber sleepers Steel sleepers Cast iron sleepers Concrete sleepers
- 107. Timber sleepers Also called as wooden sleepers Fulfils most of the requirements of ideal sleeper Used universally Teak wood is considered as best But due to high cost, mainly used as sleepers for girder bridges Salwood, Deodar, fir and chirwood are used as alternatives where those are easily available At present usage and manufacturing decreased because of the advent of new type of sleepers
- 108. Timber Sleepers - Features Utility: Very much useful for heavy loads and high speeds Life: Depends on various factors such as climatic conditions, intensity and nature of traffic, quality of wood, method of packing, type of fastening, protection against mechanical wear etc., Treatment: Liable to be attacked by vermins hence treatment required to have more resistance. Preservatives are used for this purpose. Solutions used for timber sleepers are zinc chloride, creosote solution, salt solution or bi chloride of mercury salt.
- 109. Timber sleepers - Features The methods of zinc chloride solution and mercury salt solutions are known as burnettising and kyanizing respectively. Some times sleepers are just painted. Corrosion: Not corroded Insulation: Ideal for track circuited section as they are good insulators Size: Depends on the load coming and quality of wood. Depending on the treatment i.e., treated or not, size of wooden sleepers are standardized by Indian railways.
- 110. However, longer sleepers upto length 488cm are used for bridges with open flooring, points and crossings. Section of sleepers is also increased by 300x160mm. Rectangular, half round shapes are used often.
- 111. Timber sleepers - Features Driving of spikes: spikes should be driven carefully through the sleeper Else damaged, gauge will be disturbed Name and year: Name of wood used and year of laying the sleepers is normally marked on the top surface of sleeper. Normally nails with letters and markings were used before but not used these days Adzing: Wooden sleepers are adzed or cut at rail seat to get a slope of 1 in 20 when un canted bearing plates are used.
- 112. Timber sleepers - Features Adzed surface will be treated normally with tar or creosote Improper adzing leads to uneven surface for the rails. Further creeping and other types of damage will occur Storage: Large area exposed to air and ventilation is normally used Care will be taken so that sun do not fall directly on the sleepers Stack is some times covered with earth to prevent fire accidents
- 113. Timber Sleepers as Bridge sleepers Thicker than standard sleepers. Minimum depth of sleepers without fastenings should be 150, 125 and 125 mm for BG, MG and NG respectively Length of sleepers is D+30 cm. D is out side distance between edges of parallel girders Should not be adzed Necessary to provide bearing plates Should be placed sufficiently close to prevent the wheels of derailed train falling through the space between the adjacent sleepers. Max space is 50, 30, 25 cm for BG, MG and NG respectively.
- 114. Composite Sleeper Index (CSI) Forest research institute, Dehradun arrived at a formula taking different strength parameters into account for the use of timber for sleepers An index number is worked out using this formula with which we can identify whether a timber can be used or not for sleeper Chir – 54 Deodar – 63 Fir – 58 Sal – 112 Teak - 82
- 115. Composite Sleeper Index (CSI) Minimum CSI values for different sleepers are as follows Bridge sleepers – 1455 Crossing sleepers – 1352 Track sleepers –783 Bearing plates are used in case timber has a CSI value less than 82. CSI = (S+10H)/20 S = strength index of timber at 12% moisture H = Hardness index of timber at 12% moisture
- 116. Timber Sleepers - Advantages Less no of fittings Simplistic design Suitable for all types of ballast Easy to lay, relay, pack, lift and maintain Less noisy track Economical overall Obtained in different sized and lengths for easy adoptability at certain locations viz., bridges, crossings etc
- 117. Permits track circuiting Damage during derailments is less Can be placed on yielding formations because of more bearing area Possible to widen the gauge easily with wooden sleepers
- 118. Timber Sleepers - Disadvantages Difficult to maintain gauge High maintenance cost Less useful period Easily disturbed from their positions Easily subjected to wear and decay due to various forces and causes Require special treatment for protection Possess less scrap value
- 119. Steel Sleepers Extensively used in Indian railways Consist of steel troughs made of 6mm thick steel sheets Both ends bent down to check the running out of ballast 2 types 1. Jaws or lugs pressed out of metal and keys are used for holding the rail. At the time of pressing cant of 1 in 20 is also provided for the rails 2. holes are made in the sleepers and clips, bolts are used for fixing the rail. For fixing the rails, first rails are inserted into the lugs and wedges/keys are fixed on both sides of rails. Gauge can be adjusted with the help of keys.
- 120. Steel Sleepers
- 121. Steel Sleepers - Characteristics Life: Useful life of steel sleepers is taken as 30 to 40 years on a normal route On high density traffic routes it can be taken as about 20 years Track provide with steel sleepers doesn’t require much attention as renewal is not frequent. Corrosion: Steel sleepers not liable to be attacked by vermins But easily corroded due to moisture. Hence, treatment is done to protect against corrosion.
- 122. Steel Sleepers - Characteristics Insulation: Cannot be used in electrification of track. As they are not good insulators. Details: Consist of a trough or channel made of steel plate about 6mm thick. Ends bent down to prevent running of ballast Rails are fixed with steel sleepers by the help of keys to the pressed up lugs.
- 123. Steel Sleepers - Requirements Should be possible to fix the rails easily in sleepers with out disturbing the sleepers Should be possible to insulate them easily incase at place where track circuiting exists. Rail should have enough bearing area Thickness and shape should be such that they will be strong as beams Capable of maintaining correct gauge Should be designed in such a way that tamping or packing should not damage the edges
- 124. Steel Sleepers - Requirements Should be sufficiently heavy for the purpose of stability Should have effective bearing area on the ballast Should not be capable of being easily pushed out of position. Etc.,
- 125. Steel Sleepers - Advantages Less fastenings, simple in nature Maintenance and adjustment of gauge are easy with steel sleepers Manufacturing process of steel sleepers is simple in design and operation Are available in one piece Possess good scrap value Light in weight, easy handling Meets requirement of long welded track in cases Good anti creep sleeper Behaves better in the case of yielding formation.
- 126. Steel Sleepers - Disadvantages Cost of steel sleepers is high Cracks develop at rail seat Rounded ends of sleepers prevent lateral shift Liable to corrosion Are not good insulators Excess damage during derailment Steel sleepers are difficult to pack at the rail joints because of their close spacing. Leads to battering of rails
- 127. Cast-iron sleepers Were adopted on indian railways since 1870 More than 50 % of the sleepers are made of cast iron as of 2000 They are generally of the following types Pot sleepers Plate sleepers Box sleepers C.S.T.- 9 sleepers Duplex sleepers
- 128. Pot sleepers are in the form of two bowls placed under each rail and connected together by a tie- bar Total effective area of the both pot sleepers is kept 0.46sq.m which is equal to effective bearing area of a wooden sleeper. Two holes are provided under each sleeper for inspection and packing ballast And the rail seat is given a slope of 1 in 20. Both the pots are connected together with a tie bar with necessary fittings such as keys, gibs and cotters.
- 129. Plate sleepers consist of a plate of 851x254mm in dimensions, with 254mm side parallel to the rails. Both sleepers provide an effective bearing area of 0.46sq.m under each rail. Plate is provided with projecting rib in the bottom to provide a grip in the ballast to check the lateral movement of sleeper. At the top plate stiffeners are provided to increase the strength. Sleeper plates are connected by means of a tie rod.
- 130. C.S.T. – 9 Sleepers: These are more satisfactory than other type of CI sleepers. It is actually a combination of plate, pot and box sleeper. It essentially consists of a triangular inverted pot on either side of the rail seat. Suitable rail seat or rail chair is provided at the top to hold rails at 1 in 20 cant. Two pieces of sleeper are connected by means of a tie rod.
- 131. Cast-iron sleepers - characteristics Details: C.I sleepers consists of 2 pots or plates with ribs below and connected by a wrought iron tie bar of section of about 51x13mm. Each pot or plate is placed below each rail. Shape of pot or plate is used to be circular prior. But present, oval shape with larger diameter 610mm and smaller diameter 508mm is preferred. Each pot is provided with holes for packing ballast and inspection. Plate sleepers consist of rectangular plates of size about 864x305mm. The projecting ribs are kept below for their lateral stability. Tie bars can be fixed by keys, gibs, cotters and
- 132. Cast-iron sleepers - characteristics Scrap value: Possess considerable scrap value. Broken pots and plates can be melted and reused for preparing new pots and plates. Maintenance of gauge: In case of CI sleepers there is no rigid connection between 2 separate supports. Hence difficult to maintain the correct gauge. Fittings: The cast iron sleepers require a large number of fittings than any other type of sleepers.
- 133. Cast-iron sleepers - characteristics Handling: The C.I. Sleepers are liable to be broken and seriously damaged, if roughly handled. Life: The usual life of C.I. Sleepers may be taken as 35 to 50 years in normal routes. 15 to 20 years in heavy traffic routes. The service life can be increased by proper packing , clean ballast, providing coal tar to tie-bar etc.
- 134. Cast-iron sleepers - Advantages It can be easily dismantled and assembled. Hence, transport is easy even though it is heavy. Can tolerate certain amount of rough handling. Possess high scrap value Good longitudinal and lateral resistance Shape is well suited for ballast packing and skill required for its maintenance is minimum Adjustment in gauge can be done ( about 5mm) with help of cotters in case if it is needed. Sleeper is not affected by the random or irregular dropping of fire by the steam engines.
- 135. Cast-iron sleepers - Disadvantages During derailment damage is excessive and it requires more time for restoration. Not suitable for circuiting of track. Leads to early wear of sleeper because of small bearing area at the rail seat. Not suitable for modern methods of maintenance Possess poor ability to retain the packing due to its rigid fastenings. It takes about 6 months for proper consolidation after complete track renewal and sleeper renewal. When these sleepers are used, rails have longer unsupported length and may therefore lead to battering of rails.
- 136. Concrete Sleepers - characteristics Type: Can be made of R.C.C or pre-stressed concrete. Weight: Weight of concrete sleepers varies from 150 to 300kg which is more than wooden or metal sleepers. This provides more stability to track. Life: Good durability Useful life of about 30 to 25 years on high density routes
- 137. Concrete sleepers - characteristics Suitability: Most suitable for welded tracks Dead weight of entire track assembly including sleepers play an important role in the design of welded rail track. Since, weight is more they perform better under welded rails Fastenings: Should firmly hold the rail to resist creep Should be easily dis-engaged and re-engaged Different types of fastening equipment is available for concrete sleepers. Ideal fastenings for sleepers and rails will differ according to the type of track, type of traffic and the climatic conditions.
- 138. Concrete sleepers - characteristics Special PSC sleepers have been developed to meet with the special requirement of different locations such as sharp curves, level crossings with facilities for providing check rails, guard rails etc., Mass production: Mass production techniques are to be adopted for the design and manufacture of sleepers. Economical production of concrete of high strength, handling of sleepers, good plant design, accelerated hardening of sleepers etc., have to be taken care off. Initial cost of concrete sleepers will be very high, but maintenance and other things will be economical because of long life.
- 139. Concrete sleepers - characteristics Environmental protection: These PSC sleepers are environmental friendly. Conserves forest. Structural advantages: Have lot of structural advantages Center to center distance can be increased by 20% compared to timber sleepers Deflection under loading is much less Improves lateral, longitudinal and vertical stability Reduced bending stresses, reduced wear of rolling track, less chance of derailment, reduction in tractive effort etc.
- 140. Concrete sleepers - Advantages High electrical resistance Good resistance to abrasion Increased bond resulting in shorter transmission length. Increased impermeability Reduction in loss of pre-stress due to reduction in shrinkage, creep and elastic shortening Very high fatigue strength.
- 141. Concrete sleepers - Drawbacks The damage during derailment is excessive Possess no scrap value Require complete machanisation in handling Requires use of superior and costly technology for manufacture.
- 142. Sleeper Density No of sleepers present in a given length of rail Spacing of sleepers is indicated by formula n+x n = length of rail x = no of sleepers more than n. Sleepers density depends on several factors: Lateral thrust of locomotives to which the track is subjected Axle –load which the track is expected to carry Sleepers density cannot be increased indefinitely – minimum spacing is required for packing ballast and maintenance. Wooden sleepers 300mm (for BG), 250mm (for MG) Metal sleepers 380mm (for BG), 330mm (for MG)
- 143. Sleeper density In case of staggered joints an extra sleeper is required Sleepers are placed nearer at rail joints compared to other locations. In n+x expression, x value is fixed by indian railway considering the following: Axle load and speed Type of ballast and ballast cushion Type and section of rails Type of sleeper and its bearing area on the ballast.
- 144. Ballast Material placed between the sleeper and top of the formation is known as ballast. Load from the wheels will be taken up by the ballast through rails and sleepers. Ballast serves as foundation of railway track and is present just below the sleepers.
- 145. Ballast - Functions To provide a hard and smooth surface for the ballast to rest on Hold the sleepers in place during the passage of trains To transmit and distribute the load from sleepers to formation Allow for maintaining correct track levels without disturbing the rail road bed. Protect the surface of formation from direct exposure to sun, frost or rain. To form an elastic bed
- 146. Ballast - Functions To drain the water immediately and keep the sleepers in dry condition To discourage the growth of vegetation To resist lateral, longitudinal and vertical displacement of track.
- 147. Requirements of ideal material for ballast Should be possible to main uniform depth of material for uniformly distributing the load to formation Should provide sufficient grip over the sleepers to prevent their movement Ballast should not be too rigid, it should be elastic in nature. Material of ballast should not be brittle, should possess required compressive strength. Should provide good drainage facility. Should be cheap and easily available. Should not have any chemical action on rail and metal sleepers Should be durable and abrasion resistant
- 148. Ballast Materials Broken stone Gravel Ashes or cinders Sand Kankar Moorum Brickbats Selected earth
- 149. Broken stone One of the best material, but expensive. Many important tracks are having stone ballast Possesses all characteristics of good ballast It has good interlocking characteristics, due to that it holds track in correct alignment and gradient It is resistant to abrasion, provides good drainage. Stones which are non-porous, hard and tough should be used as ballast Granite is best material. But quartize, sandstone, limestone are also used.
- 150. Gravel It is next best material after broken stone. It consists of smooth rounded fragments obtained from river beds and other natural deposits. Washing should be done for the material obtained from pits Uniform and required size of aggregates should be used. Rounded pieces are sometimes broken to improve interlocking properties. Advantages: Cheaper than stone ballast Good drainage property Disadvantages: Easily rolls down due to vibration
- 151. Ashes or Cinders The residue from the coal used in locomotives and other furnaces is known as the ashes or cinders. It is by product of railway systems which are run by coal fuel Advantages Good drainage properties. Used in yards to keep them dry Handling is easy Low cost and easily available. Can be used for repairing formation, and packing during emergency. Disadvantages: Very soft, easily becomes powder hence track becomes
- 152. Sand Coarse sand is preferred to fine sand Not used in main and branch lines. Used only in some unimportant lines, sidings, yards. Advantages: If sand is pure, possesses excellent drainage property Produces a silent track Cheap and easily available Disadvantages: Frequent renewal is required Disturbed easily by vibrations. More maintenance required. Causes more friction, and leads to abrasion and wearing.
- 153. Kankar Found in many places Suitable only if other types of material is not available and if the traffic is less on metre gauge and narrow gauge It becomes powder very easily and hence not prefered More maintenance is required if used
- 154. Moorum Decomposition of laterite results in the formation of moorum Present in red/yellow colour Used for unimportant lines and sidings Advantages: Can be safely used on newly laid track. It serves as soling when the stone ballast is laid afterwards Possesses good drainage properties Disadvantages: Soft and turns into dust very easily Maintenance is very difficult
- 155. Brick bats Over burnt bricks are broken into suitable sizes and used as ballast Advantages: Useful at places where suitable material is not available Good drainage properties Disadvantages: Turns into powder form very easily Track becomes dusty and high maintenance is required. Rails are often corrugated on tracks where brick bats are used as ballast
- 156. Selected earth For sidings and newly constructed tracks, selected earth of suitable quantity is sometimes used as ballast The main purpose of using earth on new formation is to prevent the loss of valuable and expensive ballast sinking into the soft formation.
- 157. Specifications of Stone ballast Quality: Should be durable, hard, resilient to impact and free from adherent coatings. Should not contain more than 10% by weight of quarry dust, rubbish or any other matter which passes through 5mm sieve Faces of ballast should result from crushing, only one smooth surface is allowed Size: 20 to 50mm size with reasonable proportion of intermediate sizes. 50mm – wooden and CI spot sleepers 40mm – CST -9 sleepers
- 158. Specifications of stone ballast grading: Ballast should be well graded Sampling: Sample of ballast is collected at the rate of 1cu.m per 2000cu.m. Over sized ballast: When more than 10% of ballast retains on nominal size sieve it is called over sized ballast Stacking: Ballast should be stacked along the quarry siding. Height of stack should not be less than 120cm.
- 159. Depth of Ballast Section Depth of ballast section can be calculated by using the below formula D = (S-b)/2 Where D – depth of ballast section S – sleeper spacing b – width of sleeper Normally the value ranges in between 20 to 25cm from the above formula.
- 160. Section of Ballast
- 161. Screening of Ballast – Ballast Renewal Ballast used on the railway track is to be renewed from time to time due to following reasons Ballast gets powdered due to hammering of wheels. Fills voids in the ballast layer forming impermeability. Ballast gets pressed into formation. Available ballast quantity gets reduced with time. Elasticity will also gets disturbed. To avoid and remove all these effects ballast is cleaned at regular intervals by means of screening.
- 162. Process of screening Surface will be normally clean. Hence ballast forks are used for cleaning. Dirty ballast is made loose by means of equipment such as picks. Frames of size 150x120cm with expanded metal mesh are put parallel to the track. Dirty ballast thrown on to the mesh to separate the dirt and aggregate ballast. Required quantity of additional ballast is added to screened ballast to make up the deficiency.