Track training 03082013

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Track training 03082013

  1. 1. MBTA Standardized Track Training
  2. 2. CHAPTER ONETRACK STRUCTUREATTENTION VIEWERS
  3. 3. Chapter 1: Track StructureThe track structure for railroads consists basically of:Subgrade Ballast Ties Rail Plates Spikes Splice BarsBoltsTrack Structure
  4. 4. The two primary functions of the track structureSupport the Train Guide the Train• The weight of the train istransferred from the steelwheels to the steel rail• It is then distributed by thebeam action of the rail to severalcross-ties.• The crossties furtherredistribute the load, passing inon to the ballast.• Finally the ballast redistributesthe load again and passes it onto the subballast and groundTrack StructureChapter 1: Track Structure
  5. 5. HEADBASERUNNING SURFACESIDEFILLETWEBThe T-rail is the standardfor railroads in theUnited States today.T-rails vary in shape(section) and weightChapter 1: Track StructureRAIL
  6. 6. RAILChapter 1: Track Structure
  7. 7. RAILChapter 1: Track Structure
  8. 8. Chapter 1: Track StructureRAIL
  9. 9. Almost all rail of standard 39’ length used to befastened together at joints by the use of joint barsToday, (39’), the joints have been considerablyreduced by welding standard length rails togetherinto continuous stringsJoints and Continuous Welded RailChapter 1: Track Structure
  10. 10. With bolted rail, the joint bars are attached to the rail byeither 4 or 6 bolts. The rail is eventually battered down by thisrepeated actionFour-hole joint bars are 24 inches long and six-hole bars are36 inches long. Spacing of bolt holes in the rail and joint barsoften differ for each rail weight and sectionProper maintenance of joints is essential to prevent endbatter of rail, to provide support, and to give a smooth ride.End batter is caused by the slight pounding action of carwheels as they leave one rail and ride onto the next. The railsare normally drilled at the mill.Joints and Continuous Welded RailChapter 1: Track Structure
  11. 11. Holds the rail inproper gage andline.Transmits thetrain weight fromrail to ballast.Distributes the trainweight over a largerareaProvides a base towhich the rail canbe anchored.Provides supportwhich distributesthe load & acrossthe roadbed andunder both rails .CrosstiesCrossties serve several important functions including the following:Most wood crossties are treated with a preservative toinhibit decay and insect attack. Average life of a tie isabout thirty years, but tie life expectancy varies due toclimatic conditions, damage and amount and type oftraffic.Standard size crossties range from 6” x 8” to 7” x 9”in cross section and 8’ to 8’6” in length. Longertimbers 9’ to 22’ in length are used under switches.Chapter 1: Track Structure
  12. 12. GAGEGage of the track is the distance between the rails.Standard gage today is 4’ 8 ½” measured from the insideedge of one rail to the inside edge of another rail.Gage widths have varied over the years ranging from 3feet for narrow gage and up to six (6) feet for broad gage.The origins of the 4’ 8 ½” gage width have been lost inantiquity. Some people claim it was based on the RomanChariot.Perhaps the most logical explanation is that sincerailroads were a natural progression from the tramways,and since the tramways had a gage of 4’ 8 ½” then, as amatter of convenience, the railroads adopted thetramway gage.Chapter 1: Track Structure
  13. 13. CHAPTER TWORAIL
  14. 14. Chapter 2: RailIdentificationRail is described as steel rolled into a shape referred to as a“Tee” configuration usually in thirty-nine (39) or seventy-eight(78) foot lengths.Some section names:RE American Railroad Engineering &Maintenance of Way AssociationASCE America Society of Civil EngineersRail is rolled into different sizes (dimension) and shapes or ofdifferent weight and section
  15. 15. IdentificationChapter 2: Rail
  16. 16. Rail is identified by the upset letter and numbers hot stamped on the web ofthe rail. The hot stamping shows the weight and section of the rail, coolingand end hardening process, name of the manufacturer, mill location, and theyear and month the rail was rolled.(Example: 132, RE, CC (or CII), BSCO, STEELTON, 1961, ////////)Meaning:132 - Weight of the rail per yardRE - Rail Section (area in this case)CC - Rail is control cooledCH - Rail is control cooled and endhardenedBSCO - Manufactured at Bethlehem SteelCorporationSTEELTON - At Steelton Mill (in Steelton, PA)1961 - Year Rolled//////// - Month rolled (August)OH - When shown means Open Hearth(process of making steel)IdentificationChapter 2: Rail
  17. 17. On the opposite side of the rail web cold stamped inset lettersand numerals are shown. This is commonly called the heatnumber.(Example: CH 2900065 B 6)Meaning:CH - Control Cooled and End Hardened290 - Heat Number (can also identify the type offurnace)065 - Heat Number, the number representing afurnace loading(charge) of metal. Eachloading consecutively numbered.B -The second rail produced (rolled) downfrom the top of an ingot. Either the secondrail is rolled from the first bloom or first railfrom the second bloom. (See Figure 2-2)6 -This rail was rolled out of the sixth ingot ofthe heat.IdentificationChapter 2: Rail
  18. 18. Manufacture of RailThere are three (3) basic types of heating used for steelmade today in the United States:Open HearthBasic OxygenElectricSteel mills generally manufacture rail metal by theOpen Hearth (OH) process.Chapter 2: Rail
  19. 19. Furnaces are charged withscrap metal, lime stone,and or molten pig iron toproduce rail steelThe molten metal istapped (poured) from thefurnace into the hugeladleThe molten steel is thenpoured into ingot moldsThis cavity (pipe) end ofthe rail is visuallyinspectedManufacture of RailChapter 2: Rail
  20. 20. ProcedureDuring the rolling processthis cavity, or most of it, isrolled (pressed) togetherresulting in usable steelAs the metal cools in theingot mold, there is ashrinkage cavity formed inthe center of the ingot fromthe top downwardThe rail bloom is furthercut back until the defectdisappearsAs the ingot cools, themetal shrinks (contracts)and the ingot mold isremovedManufacture of RailChapter 2: Rail
  21. 21. Once mold is stripped from ingot,mills move the red hot ingot directlyto rail mill for immediate rolling.After the rolling process the hotrolled rail moves to the hot saw andis sawed into 39’ lengthsThe rail then goes to the hot bedand cools to about 800 FThe rail is then moved to thecontrol cooling boxes (cars),covered and further cooled forabout 10 hoursRail is processed through thefinishing mills for straightening,end milling, and final inspectionto acceptance.Manufacture of RailChapter 2: Rail
  22. 22. CHAPTER THREECROSSTIES
  23. 23. Hold rail inproper gageand lineTransmit thetrain weightfrom rail toballastDistribute thetrain weightover a largerareaProvidesbase to whichthe rail can beanchored toprevent the railfrom movingProvide supportto distributesthe load acrossthe roadbed andunder the railsallowsadjustments tobe made intrack line andsurfaceChapter 3: CrosstiesUseCrossties serve several important functions:1. The Crosstie mustbe strong enoughto support thisweight2. Hold the rail inproper gage3. Withstand outwardforces and;4. Transmit the loadto the ballast.
  24. 24. Wood Ties• Provide elasticity of support to thetrack structure, are easily workedand have relatively long life• Decay, fire, derailments and wearfrom heavier loads cansignificantly reduce the life of a tieor destroy it entirely• Exposure to wet conditions reducestie life• Many varieties of wood can be usedfor ties, including both hardwoods andsoftwoods. **The MBTA uses mostlyoak timber ties• Regardless of the type of wood used,the tie should be free from large splits,numerous knots, and obvious decayChapter 3: Crossties
  25. 25. Wood TiesTies are graded by size to allow the larger ones to be sorted foruse in tracks carrying heavier and faster traffic. Practically allrailroads use the same grading system shown as follows:**The MBTA uses ties that are 7” x 9” in section, and 8’-6” long, forstandard track. Longer ties are used in turnouts.Grade of Crosstie1 6” thick x 6” wide (top)2 6” 6” thick x 7” wide (top)3 6” thick x 8” wide (top)3a 7” thick x 7” wide top (8” wide through body)4 7” 7” thick x 8” wide (top)5 7” thick x 9” wide (top)Chapter 3: Crossties
  26. 26. Anti-Splitting DevicesDue to the natural tendency of wood to split, the practice ofapplying anti-splitting devices into the ends of the tie has beenused for many yearsChapter 3: Crossties
  27. 27. Treatment (wood)Wood, unless it is protected, will bedestroyed by insects, ice, and decay. Toextend the life of wood ties, ties are treatedwith a preservativeCreosote is a primary ingredient in most ofthe preservatives used to treat ties andtimberSpecies that are hard to treat or have verylittle sapwood are run through a machinewhere the surfaces receive hundreds ofknife cuts. This is called incising.Chapter 3: Crossties
  28. 28. It is important to remember that the preservative does not penetratecompletely through the tie or timber, only about ¼”Thus, rough handling, reshaping or old spike holes can exposethe untreated wood to decay fungus, wood destroying insectsand moisture which will cause early failure of the timberAll holes should he plugged and all exposed areas treated withpreservativeSome railroads, including the MBTA order their ties with spikeholes pre-bored prior to treatmentChapter 3: CrosstiesTreatment (wood)
  29. 29. Concrete Ties• Concrete then installed on the AshmontLine are still in service though• Concrete ties are pre-cut and madewith 7000 psi concrete• The typical railroad concrete tie is 780lbs while the transit version is 680 lbs• MBTA has had some bad experienceswith concrete on the commuter railsystem due to chemical reactionbetween the concrete and aggregate• There are two types, monoblock anddual block. Dual block are made ofseparate cement blocks, one undereach rail, connected by a steel bar.Monoblock concrete ties are onecontinuous beamChapter 3: Crossties
  30. 30. Tie SpacingTimber ties on MBTACommuter Railstandard track, arespaced at 191/2”.Transit timber ties arespaced at 24”Concrete ties arespaced at 24” forcommuter railsand 30” fortransit.Switch ties willhave variedspacing due to thenature of the switchhardware theysupport.Chapter 3: Crossties
  31. 31. Chapter 3: CrosstiesDirect Fixation
  32. 32. CHAPTER FOUROTHER TRACK MATERIAL
  33. 33. There are 3 types of jointbars in useInsulatingJointCompromiseJoint (stepbars)StandardTrack Joint(splice bars)Chapter 4: Other Track MaterialJoint Bars, Bolts, and Nut Locks
  34. 34. Tie PlatesTie PlatesFunctionsForm a seat for the railEnable the weight to bedistributed over a larger areato reduce tie cutting &abrasive effects of the loadsProvide better holding powerfor the spikes and help holdthe track gageThe size of tie plates ranges from 7” x 10 ¼” to 7¾” x 15 ½”depending on the width of the base of the railChapter 4: Other Track Material
  35. 35. The MBTA uses so called “double shoulder” tie plates. Theseplates have two shoulders, one on each side of the rail seat• The double shoulder plates must be designed for eachspecific weight of rail• All double shoulder plates are punched with square or roundholes to hold a maximum of 8 spikes or screw spikesrespectively• When a rail is properly seated in a plate, lateral movement isrestrained which helps hold the track in gageTie PlatesChapter 4: Other Track Material
  36. 36. Track SpikesThe track spike stands alone as the one item of track fasteningthat hasn’t changed a great deal over many years of railroadconstructions and maintenance in the United StatesThey are generally 6 incheslong, ¾ inch square and 1 ¼inches wide across the headSpikes are made of soft (ductile)metal because if they were brittlethey would break when driven orfracture when stressed undertraffic conditionsThey weigh about 10 ounceseach and are shipped in metalcontainers with approximately240 spikes per containerChapter 4: Other Track Material
  37. 37. All spikes are driven straight down with the extended head endfacing the rail. Spikes driven against or at the base of the rail arecalled rail holding spikes. Other spikes driven in the plate holes arecalled plate holding spikes or anchor spikesTrack SpikesLEGENDIndicates Rail holding Spikes In all Cases• 1st Plate Holding Spike (Where Only One is Required).• 2nd Plate Holding Spike (Where Two Are Required).• Use Additional Spike Holed, if specs require itSPIKE APPLICATION WITHINJOINT BAR LIMITSSPIKE APPLICATION OF RAIL ANDPLATE HOLDING SPIKES(TANGENT AND CURVED TRACK)Rail holding spikes shall haveapproximately ¼” clearance betweenunderside of head and top of base of railSpiking on bridges and trenchesshall be the same as forStandard Ballasted TrackChapter 4: Other Track Material
  38. 38. Chapter 4: Other Track MaterialPandrol Clip Fasteners
  39. 39. Concrete Tie FasteningStandard track spikes or screws cannot be usedfor fastening rail to concrete tiersThe type of rail fastening utilized for concrete ties isa shoulder inserted into the tie concrete when wetat the pre cast plantChapter 4: Other Track Material
  40. 40. Rail Anchors• Rail anchors are devices that retard expansion andcontraction of rail, on any movement or slippage ofthe rail through the ties plate• They are used on either side of the tie, which iscalled box anchoring• Contact with banded clips, the anchoring isaccomplished by the vertical face of the clips on thetop of the rail base providing about 2000lbs oflongitudinal resistanceChapter 4: Other Track Material
  41. 41. Chapter 4: Other Track MaterialRail Anchors
  42. 42. Chapter 4: Other Track MaterialRail Anchors
  43. 43. Derails• Derails are used as a last resort to prevent a run-away car from causing great damage, by movinginto the path of an incoming train• Derails actually derail the car under theassumption that the cost of re-railing one car isless than clearing a massive wreck the loose carcould cause if it ran into another train• There are three main types, the hinges on slidingderails used in freight sidings, and the switch pointderails commonly associated with moveable bridgeand track crossings at interlockingChapter 4: Other Track Material
  44. 44. Bumping Posts• Bumping Posts are placed at the ends of tracks toprevent cars from rolling off the end of the track• They cannot stop a speeding train, only very slowlymoving cars• Other end-track devices involve wheel stops,concrete blocks, or a pile of fill which reducesdamage to the car if hit• Piston bumpers are used at North and SouthStations to absorb a slow speed strike, presumablyup to 15 mphChapter 4: Other Track Material
  45. 45. CHAPTER FIVEGRADE CROSSINGS
  46. 46. Chapter 5: Grade CrossingsGrade Crossings are used toallow automobile traffic to crossover tracksCrossings must be designed for gooddrainage. If the track is in a grade, theuphill side becomes a dam that holdswater and causes deterioration. Trackdrains on the uphill side freely alleviatethis problem.This pattern is most seen on the GreenLine surface road medians where thetracks are on a grade.General Information
  47. 47. CHAPTER SIXTURNOUTS
  48. 48. Chapter 6: TurnoutsTurnouts or switches are track structures thatallow trains to move from one track to anotherThey consist of various rails, plates, braces,rods and other fixtures to allow for themechanical transfer of a train from one trackto anotherGeneral Information
  49. 49. General InformationChapter 6: TurnoutsGuard RailGuard Rail
  50. 50. Turnouts are designatedas left or right, equilateral,or curvedIf a person stands at theswitch end of a turnoutand looks toward the frog,the turnout is right if thediverging route turns to theperson’s right, and left if itturns to the person’s leftGeneral InformationChapter 6: Turnouts
  51. 51. • Turnouts can be thrown manually or by use of aswitch machine• A terminology commonly used for powered switches isto designate the two routes as either “normal” or“reverse.”• It is important to know how to “read” a switch• Reading a switch is determining what route it is set forjust by looking at the mechanical setting of the switchpointsGeneral InformationChapter 6: Turnouts
  52. 52. With respect to terminology, movingover the turnout in the direction fromthe switch points to the frog is called a“facing point” moveMoving in a direction over the turnoutfrom the frog toward the switch pointsis called a “trailing point” moveGeneral InformationChapter 6: Turnouts
  53. 53. Size DesignationTurnout sizes are designated by either the curved radius ofthe curved route, or the frog numberTransit turnouts can be: 50’75’100’150’200’250’Turnouts on the Red, Orange, and Blue lines are as smallas 150’ radius and the smallest on the Green line are 50’Chapter 6: Turnouts
  54. 54. • Beyond 250’, the designation of a turnout changes to anumber system related to the frog angle, the smallest being aNo. 5, which is close to a 250’ CR turnoutSize Designation• The smallest turnouts on railroads are eitherNo. 7’s or 8”s• The smallest prescribed on the MBTA commuter railsystem is the No.8• The terminal tracks outside of South Station arefilled with No. 8’s• However in new MBTA work, No 10’s are the smallest anare used for industrial sidings coming off the main track,while No. 15’s and 20’s are common for use in the mainline track for crossovers and sidingsChapter 6: Turnouts
  55. 55. Size DesignationNo. 6No. 8No. 20Chapter 6: Turnouts
  56. 56. Size DesignationThe number of the turnout refers to the frog numberthat designates a characteristic of the geometry ofthe frog angleThe frog number is defined by AREMA as ½COT (1/2(frog angle))This system makes it easy to determine the frognumber in the fieldChapter 6: Turnouts
  57. 57. The ½” Point of Frog (PF)In plans and drawings of frogs, a dimension called the ½” point of frog isoften shown, rather than the theoretical point of frogChapter 6: Turnouts
  58. 58. Point of Intersection (PI) and Point of Switch (PS)A critical construction point of a turnout is the point of intersection, from whichthe point of switch, and the ½” point of frog are measuredThe point of intersection, or the PI, is the point where the tangent extension of thecenterline of the diverging route intersects the track centerline of the main routeThe point of switch, or PS, is the physical end of the switch point rails, andthe ½” point of frog, or PF, is as discussed in the previous paragraphChapter 6: Turnouts
  59. 59. Point of Intersection (PI) and Point of Switch (PS)The equivalent radii of turnouts with number designations, actual lead,length of tie bed, and speeds are as follows, based on AREMA standards:Notice that the higher the turnoutnumber, the greater the lengthand speed*Speed depends on whetherstraight or curved switch pointsare used. It is higher for curvedpointsChapter 6: TurnoutsTurnout No. Curved Radius Actual Lead Length of Tie Bed Speed*No.5 177.80’ 42’-6 1/2” 60’-11” 2 mphNo. 6 258.57’ 47’-6” 69’-8” 13-15 mphNo. 8 487.28’ 68’-0” 97’-8” 19-20 mphNo. 10 779.39’ 78’-9” 115-11” 20-25 mphNo. 12 1104.63’ 96’-8” 141’-4” 27-29 mphNo. 15 1720.77’ 126’-4 ½” 182’-3” 36-38 mphNo. 20 3289.29’ 151’-11 ½” 226’-7” 36-50 mph1
  60. 60. Turnout ComponentsTurnoutComponentsIncludeSwitchPoints StockRailsClosureRailsFrogsSwitchTiePlatesBracesHeelBlocksSwitchRodsRailRestraintGuardRailsSwitchTiesChapter 6: Turnouts
  61. 61. CHAPTER SEVENTRACK ALIGNMENT & CURVATURE
  62. 62. Simple CurvesThe primary purpose of any curve is to provide the required change indirection in a form best suited to the operating conditions• A simple curve is a segment ofa circle having a constantradius and length• The tangent touches thecircumference (on the circle)at only one point, the point oftangency• At this point the radius ofthe circle and the tangentare at right angles (90 )Chapter 7: Track Alignment and Curvature
  63. 63. If two or more simple curves of different degree of sharpness are joinedtogether without a tangent section between them, it is a compound curvePCPCCPCPC = Point of CurvaturePCC= Pointof CompoundCurvatureCompound CurvesChapter 7: Track Alignment and Curvature
  64. 64. Spiral curves having constantly changing radii are used to provide a gradualtransition between a curve and its tangents, or between two or more simplecurves to form a compound curveTS0 + 00SC1 + 00CS3 + 00ST4 + 00Direction of increasingStationingTC - Tangent of SpiralSC – Spiral to CurveCS – Curveto SpiralST – Spiral to TangentSpiral CurvesChapter 7: Track Alignment and Curvature
  65. 65. 1. A curve or is defined by its radius2. For most railroad curves, the radius is so large that thecenter of the curve is inaccessible in the field, andalthough it is necessary for computation purposes, it is notused in field work3. Instead, the degree of curvature is used to definerailroad curvatureThere are two definitions of degree of curveChord definition Arc definitionSpiral CurvesChapter 7: Track Alignment and Curvature
  66. 66. Chord definition – Thedegree of curve is equal tothe central angle subtendedby a 100 foot chordArc definition – The degree ofcurve is equal to the centralangle subtended by a 100foot arcCurve DefinitionChapter 7: Track Alignment and Curvature
  67. 67. Vertical Curves• Where different grade lines meet, the change from onegrade to another must be gradual• To accomplish this gradual change in elevation requiresthe use of some type of curve• For horizontal alignment, a simple curve of constantradius, supplemented with spirals, is generally used• In the vertical plane (profile), the constant radius curve doesnot provide the gradual transition required for smoothoperation• Consequently, parabolic curves are used toaccomplish a gradual change in gradesChapter 7: Track Alignment and Curvature
  68. 68. Parabolic curves as compared to a simple curve of constant radiusdeviate from grade line gradually, providing a smooth transitionA parabolic curve plotted on a coordinate axis would appear asshown below:Vertical CurvesChapter 7: Track Alignment and Curvature
  69. 69. The following basic equation is used for calculating vertical parabolic curves:G1 = - Grade No. 1 in %.G2 = - Grade No. 2 in %L = - Length of Curve = No. of 100ft. stations measured horizontally.2a = - Rate of change of adjacent chords, and is a constant that hasbeen established through usage. The maximum value of “2a” ingeneral practice has been established at 0.05 ft. per 100ft. forsag curves, and 0.10 ft. per 100ft. for crest (summit) curves onhigh speed main tracks. These values of “2a” are frequentlydoubled for main and secondary tracks of lesser speeds therebypermitting shorter and sharper vertical curves.2a = 100 (G2 – G1)LVertical CurvesChapter 7: Track Alignment and Curvature
  70. 70. CHAPTER EIGHTTRACK SURFACE AND SUPERELEVATION
  71. 71. Chapter 8: Track Surface and SuperelevationTrack SurfaceCommonly used to describe the smoothness of trackTechnically, it is the height relation of opposite rails to eachother in profile and cross levelCross level is the difference in elevation at the top of the railmeasured at right angles to the trackProper track surface is attained when the rails are at thesame height throughout their length or when the elevationchanges uniformlyGeneral Information
  72. 72. Chapter 8: Track Surface and SuperelevationGeneral Information
  73. 73. High RailLow RailSuperelevationSUPERELEVATED TRACKTANGENT TRACKChapter 8: Track Surface and SuperelevationGeneral Information
  74. 74. The following table shows the maximum allowable variations in profile,elevations, and cross level for safe passage of trainsTrack Surface ConditionClass of Track – Maximum Speeds1F- 10P- 152F- 25P- 303F- 40P- 604F- 60P- 805F- 70P- 906F- 70P- 100The runoff in any 31 feet of track at theend of a raise may not be morethan………………….The deviation from the uniform profile oneither rail at the mid-ordinate of a 62- footchord may not be morethan……………..........Deviation from designated elevation onspirals may not be morethan…………………Variation in cross level on spirals in any31 feet may not be morethan…………………….Uniform deviation from zero cross level atany point on tangent or from designatedelevation on curves between spirals maynot be morethan……………………………………………….The difference in cross level between anytwo points less than 62- feet apart ontangents and curves between spirals maynot be morethan…………………….....................................3-1/2”3”1-3/4”2”3”3”3”2-3/4”1- 1/2”1-3/4”2”2”2”2-1/4”1-1/4”1-1/4”1-3/4”1-3/4”1-1/2”2”1”1”1-1/4”1-1/4”1”1-1/4”3/4”3/4”1”1”1/2”1/2”1/2”1/2”1/2”5/8”Chapter 8: Track Surface and SuperelevationGeneral Information
  75. 75. A curved section of track is superelevated when the verticaldistance or height of the outer rail is above the inner railOn curved sections of track, superelevations counteract thecentrifugal force which tends to keep cars going in a straight lineaway from the curveFor perfect equilibrium, the amount of superelevation will exactlybalance the centrifugal forceIt has been found that by introducing less elevation in a curve thanthat which produces equilibrium increases the weight on the highrail, improves ride comfort, and reduces rocking of equipmentChapter 8: Track Surface and SuperelevationSuperelevation
  76. 76. R = 5730. E can be shown to be equal to:DE = 0.0007 V²D or V² = E .0.0007 DChapter 8: Track Surface and SuperelevationSuperelevationWhere: E = amount of superelevation to achieve equilibrium in inchesV = Velocity (speed) in MPEE, D = degree of curve in degrees
  77. 77. CHAPTER NINEBALLAST
  78. 78. To provide structural support forthe track, holding it in good lineand surfaceTo distribute the load evenly to thesubballast and subgrade and thushelp to provide stabilityProvide for drainageChapter 9: BALLASTPurposeBallast in railroad terminology is durable granular material placed betweenthe crosstie and the sub ballast to hold the track in line and gradeThe primary purposes of ballast are:
  79. 79. BALLASTSUBBALLAST SUBGRADEBALLAST SECTIONChapter 9: BALLASTPurpose
  80. 80. Types of BallastMBTA uses crushed granite for ballast in its track.It is quarried locally. MBTA normally uses AREMANo. 4 ballastStone ballast (particularly trap rock) is most suited toheavy service. Railroads attempt to buy the beststone ballast available for use in heavy service tracksChapter 9: BALLAST
  81. 81. Functions of BallastIn discussing the functions of ballast, the first three items, support,distribution of load, and stability should be handled as one subject. Astandard ballast section for a double track system is shown below:Chapter 9: BALLAST
  82. 82. Ballast FailurePumping ties is a condition where the roadbed has becomeunstable and when a train passes over the section, the ties arepushed down forcing water out from under themA pumping situation may also indicate an unstable subgradebrought about by too much water in itThe excess water may be a result of dirty (fouled) ballast,inadequate surface drainage, high ground water table orcapillary actionThe ballast and sub ballast material is then forced down in-to thesubgrade and the subgrade material works its way up through theballastPumping begins when water accumulates under the tie and isforced out by the train pushing the tie down, carrying with it thesmallest particles of soilChapter 9: BALLAST
  83. 83. Ballast TestingIn general, ballast shall be composed of angular fragments, reasonablyuniform in quality and having specified durability and wear-resistantqualitiesThese tests for compliance are made by special inspectors andlaboratory technicians; however, some knowledge of these procedures isnecessary for quality field workRemember, the basic objective is to obtain a material which will supportthe loads, provide stability, and be free drainingChapter 9: BALLASTSieve AnalysisAbsorptionSoundnessAbrasionCementing ValueTypical laboratory tests for determining the quality of ballasts include:
  84. 84. Field InspectionIn-transit shaking of a car of ballast may cause some separation of varioussizes of aggregateBallast should be inspected for conformance to specifications as it isunloadedSize No.(SeeNote 1)NominalSizeSquareOpeningPercent Passing3” 2 ½” 2” 1 ½” 1” ¾” ½” 3/8’ No. 4 No. 824 2 ½” – ¾” 100 80-100 25-60 0-10 0-5 - -- -25 2 ½” – 3/8” 100 80-100 60-85 50-70 25-50 - 5-20 0-10 0-3 -3 2” – 1” - 100 95-100 35-70 0-15 - 0-5 - - -4A 2” – ¾” - 100 90-100 60-90 10-35 0-10 - 0-3 - -4 1 ½” – ¾” - - 100 90-100 20-55 0-15 - 0-5 - -5 1” – 3/8” - - - 100 90-100 40-75 15-35 0-15 0-5 -57 1” – No. 4 - - - 100 90-100 - 25-60 - 0-10 0-5Note 1: Gradation Numbers 24, 25, 3, 4A and 4 are main line ballast materials. Gradation Numbers 5and 57 are yard ballast materials.Table of Recommended Ballast GradationsChapter 9: BALLAST
  85. 85. SubballastSubballast is defined as any material of a superior character, whichcan be spread on top of the finished subgrade, between the subgradeand the topballast, to provide better drainage, prevent upheaval byfrost, and better distribute the load over the roadbedThe Subballast is:• Six (6) inches or more thick• helps to spread the load over the subgradeSubballast material should be placed entirely over the roadbed crosssectionSome typical subballast materials are Compacted gravel at 100%compactionChapter 9: BALLAST
  86. 86. CHAPTER TENRAIL WELDING
  87. 87. Chapter 10: RAIL WELDINGWelded Rail JointsThermite ProcessRail endpreparationSetting theweld gapUniversalclampapplicationApplying andluting themoldsPlacingThermit®portion intothe cruciblePreheatingthe rail endsIgnition andpouring ofThermit®steelDemoldingShearing ofexcess headmetalRoughgrindingFinalGrinding
  88. 88. Electrifying the two opposing rails and then pushing themtogether to create a huge short circuit that producesenough heat to melt the rails so they fuse into one anotherAfter being fused, they are sheared, grounded andsubsequently testedThe strings roll from the welder right into anawaiting welded rail train comprised of flat cars withracks of rollersThe train of rails then delivers the rails to the sitewhere individual rails are rolled off the train andonto the trackElectric Flash Butt WeldsElectric flash butt welding is mostly used in a rail shopwhere long strings are being fabricatedThe Flash Butt Weld works by:Chapter 10: RAIL WELDING
  89. 89. • The flash butt weld, or shop weld, is desirable because it iscomprised of the parent rail steel material• Rails of different sections can be welded together in ashop and brought to the field as a 19’ plug to connect railsof different sections without the need for compromise joints• Portable flash butt weld plants can be erected in the field.This allows for smaller strings to be made in areas for whicha rail train is impractical and the transportation of longstrings over roadways by truck is impossible• Oxyacetylene welding is another method of welding railstrings. In this case, the rail ends are flame heated to themelting point and then pushed together in the samemanner as described above for electric flash butt weldingElectric Flash Butt WeldsChapter 10: RAIL WELDING
  90. 90. Laying Welded RailIn laying the rail, it is heated to thedesired temperature using a railheater. Rail thermometers are usedto monitor the rail temperatureOnce it reaches the desiredtemperature, also known as theneutral temperature, it is clippedinto placeThe rail will then be fieldwelded to the next rail andthe process continuesSometimes, after the track has been resurfaced, it will be unclippedand re-stressed because the surfacing process may have disturbedthe track enough to require re-stressing and re-anchoringChapter 10: RAIL WELDING
  91. 91. Expansion of Welded Rail on BridgesOn bridges where the rail is fastened to ties directly attached to thebridge, or on direct fixation deck bridges, welded rail is anchoreddifferentlyThis is accomplished in a few waysAnchoring the rail in the middle of the bridge only for about 100feet, and then use so-called zero toe load fasteners on the railson either side of it over the remaining length of the bridgeAnchoring the rail on the outside of one end of the bridge, usezero toe load fasteners over the entire length of the bridge, andthen employ Conley joints on the opposite end of the bridgeORChapter 10: RAIL WELDING
  92. 92. QUESTIONS???

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