Components of a Turnout (Point & Crossing)

A Turnout Contains the Following Components:

A set of Point or Switch:
• a pair of stock rails,
• a pair of tongue rails,
• a pair of heel blocks,
• a number of chairs,
• two or more stretcher bars,
• a gauge tie plate,
A Crossing:
• a nose consisting of point  rail and splice rails,
• two wing rails,
• two check rails,
Lead Rails:
• four sets of lead rails.

Materials & Required Properties of Ballast

Materials Used for Ballast

1. Broken stone
2. Gravel
3. Coarse sand
4. Brick bats
5. Selected earth

Required Properties

• Aggregate Abrasion Values: Maximum 30%
• Aggregate Impact Test: Maximum 20%
• Soundness: Maximum 10%
• Elongation Index: Maximum 50%
• Flakiness Index: Maximum 50%
• Specific Gravity: Minimum 2.65
• Water Absorption: Maximum 1%

Ballast: Functions & Properties

Functions

• Provide a hard and level bed for sleepers
• Hold sleepers in place during passage of trains
• Transfers and distributes load from sleepers to larger area
• Provides effective drainage and keep sleeper dry
• Prevent vegetation growth
• Prevents water from percolating (capillary rise)
• Provide track stability

Desirable Properties of Ballast

• Good bearing capacity and crushing value
• Tough and wear resistant
• Good drainage property
• Non porous
• Should resist attrition and abrasion
• --Attrition: getting carried/ rubbed away by means of friction
• -- Abrasion: wearing down by means of friction
• Weather resistant
• Low lifecycle cost

Gauge of Railway

Track gauge or rail gauge is the distance between the inner sides of the heads of the two load bearing rails that make up a single railway line. Clear distance measured at a certain vertical distance below the rail table (upper surface) e.g. Europe: 14mm below, Japan 16mm below.

Types of Gauges

Broad gauge:
1.524m- 1.676m (5’ 0’’ -5’ 6”)
Standard gauge:
1.435m-1.451m (4’ 8.5’’ -4’ 9.125”)
Meter gauge:
1m- 1.067m (3’ 3.375’’ -3’ 6”)
Narrow gauge:
0.610m-0.762m (2’ 0’’ -2’ 6”)

Rail Joints

Back-hole Fished

Describes a rail joint in which the fishplates are clamped to the rails by means of bolts through the fishbolt holes furthest from each rail end.

Continuous Welded Rail (CWR)

Rails welded together to form a continuous length greater than a nominal 36m in length.

Emergency Bridging Pieces

Inverted channel sections used to bridge a large gap (up to 165mm (6½″)) between 2 rail ends in an emergency.

Fly-Fished

The joining of two rails by means of a pair of fishplates which are fixed to one rail only.

Insulated Joint

The connection of two rails by means of fishplates which are insulated from the rail steel and bolts by a non-conducting medium.

Ordinary or Expansion Joint

Non-insulated connection of two rails by means of fishplates and bolts, designed to accommodate longitudinal thermal expansion of the rails.

Temporary Rail Clamping System

Specially forged fishplates held together with clamps which can be applied to a rail at a defect (or some breaks) to hold the rails to line and level.

Tight Joint

Non-insulated connection of two rails by means of fishplates and bolts but without an expansion gap between the rail ends.

Welded Joint

• Flash Weld: Weld between abutting rail ends made by the electric Flash Welding process.
• Alumino-thermic Weld: Weld between abutting rail ends made by the Aluminothermic Welding process.

Sleeper Density & Spacing of Sleepers

Sleeper density= Number of sleepers per unit rail length (per unit track length for welded rail)

Factors affecting spacing/density

1. Axle load and speed
2. Type and section of rails
3. Type and strength of sleepers
4. Type of ballast and ballast cushion
5. Nature of formation

Minimum Density
MKS: Minimum sleeper density= M+7 (BG)
FPS: Minimum sleeper density= N+3 (MG)

Spacing is not uniform
Spacing is less at joints. As joints are weak points and more impact of moving loads.

Types of Sleepers

Types of Sleepers

1. Timber Sleepers (Wooden Sleepers)
2. Steel Sleepers
3. Cast Iron Sleepers
4. R.C.C Sleepers
5. Pre-stressed Concrete Sleepers

Requirements of an Ideal Sleeper

A good sleeper should meet the following requirements:

1. The initial cost and the maintenance cost of the sleepers should be low.
2. The fittings required for fixing the rails on to the sleepers, should be simple which can be easily adjusted during the maintenance.
3. The crushing strength of the sleepers should be more with moderate weight.
4. They should be able to maintain a perfect alignment, gauge and levels of the rails and should afford efficient adjustment and maintenance.
5. They should provide sufficient bearing area to hold the rail seats and for the ballast to be supported on, to resist the crushing due to movement of heavy axle loads.
6. The sleeper spacing should be such as to remove and replace the ballast during regular maintenance operation.
7. They should be capable to resist the shocks and vibrations caused due to fast moving vehicles at high speeds.
8. They should provide insulation facilities for track circuiting in the electrified sections.
9. The sleepers should be strong enough to withstand the pressure during packing process.
10. The sleepers should be of such a design that they remain in their positions and do not get disturbed due to movement of trains.
11. The material used for the sleeper be such that it does not attract the sabotage and the theft qualities.

Functions of Sleepers

Wooden, cast iron or R.C.C members which are laid transverse to the track alignment to support the rails and to transfer the load from the rails to the underlying ballast are called sleepers.

Functions of Sleepers:
In a railway track, sleepers perform the following functions:

1. To hold the rails to proper gauge in all situations. i.e. exact gauge along straights and flat curves, slightly loose on sharp curves and slightly tight in diamond crossings.
2. To support the rails firmly and evenly throughout.
3. To distribute the load transmitted through rails over large area of ballast underneath or to the bridge girders.
4. To hold the rails to proper level in turnouts and crossovers, and at 1 in 20 in ward slope along straight tracks.
5. To provide and elastic medium between the rails and ballast and also to absorb the vibrations caused due to moving axle loads.
6. To maintain proper alignment of the track. On curves proper cant is provided by raising the outer rail and tamping the required quantity of ballast bellow the rails.
7. To provide the general stability of the permanent way throughout.
8. To provide the insulation of track for the electrified for signaling.
9. To provide easy replacement of the rail fastenings without any serious traffic disturbances.

Special Rail Sections

Special Rail Sections

• Girder Rail
• Gird Rail
• Grooved Rail
• Crane Rails (175lbs, 135lbs, 105lbs)

Tests Prescribed for Rails

The following tests are prescribed for acceptance of the rails:

1. Tests for Grade 710 rails:
• Falling Weight Test.
• Chemical Analysis Test.
• Tensile Test.
2. Tests for Grade 880 rails:
• Falling Weight Test.
• Chemical Analysis Test.
• Tensile Test.
• Microscopic Examination from Top End/Bottom and Crop.
• Hardness Test for 10% of the Cests.
• Hydrogen Content in Liquid Steel to be Checked for 5% of Costs and shall be Less than 3 PPM.

Wieght of Rail vs Axle Load

Though the weight of the rail and its section depends upon various consideration, yet the heaviest axle load which the rail has to carry plays the most important role. The following is the thumb rule for giving the maximum axle load with relation to rail section:

• Maximum Axle Load = 560 X sectional weight of rail in lbs per yard or Kg per metre.
• Max. Axle load for 90lbs rail = 560 X 90 = 50400lbs = 22.50 Tons
• Max. Axle load for 52Kg rail = 560 X 52 = 29.12 MT.

Requirements for an Ideal Rail Section

1. The section of the rail should be such that the load of each wheels is transferred to the sleepers without exceeding the permissible stresses.
2. The section of the rail should be able to withstand the lateral forces caused due to fast moving trains.
3. The underside of the head and top of the foot of the rail section should be of such aslope that the fishplates fit snugly.
4. The center of gravity of the rail section should preferably coincide the center of the height of the rail so that maximum tensile and compressive stresses are nearly equal.
5. The web of the rail section should be such that it can safely bear the vertical load without buckling.
6. The head of the rail should be sufficiently thick for adequate margin of vertical wear.
7. 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.
8. 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.
9. The surfaces for rail table and gauge face should be sufficiently hard to resist the wear.
10. The contact area between the rail and wheel flange should be as large as possible to reduce the contact stresses.
11. The specimen of rail should be able to withstand the blow of a falling weight in the test specified by the specifications.
12. The composition of the steel should conform to the specifications adopted for its manufacture by Open Hearth of Duplex Process.
13. The overall height of the rail should be adequate to provide sufficient stiffness and strength as a simply supported beam.
14. The stiffness of a rail section depends upon the moment of inertia. The economical design should provide maximum moment of inertia per unit weigh of rail with due regard to other factors.
15. The section moduli of the rail section and that of a pair of fish plates should be adequate so as to keep the rail and fish plates within permissible limits.
16. The foot of the rail should be wide enough so that the rail is stable against overturning.

Functions of the Rails

The main functions of rails in a railway track are as under:

• Rails provide a continuous and level surface for the movement of the trains with minimum friction with steel wheels of the rolling stock.
• Rails provide strength, durability and lateral guidance to the track.
• Rails transmit the axle load to sleepers, which transfer the same load to the underlying ballast and formation.
• Rails bear the stresses developed due to heavy vertical loads, breaking forces and temperature variance.

Components of Permanent Way

Railway Track is also known as Permanent Way.

The Main Components of Permanent Way are as Follows:

• Rails
• Sleepers (or Ties)
• Fasteners
• Ballast (or Slab Track)
• Subgrade