This Article Covers Details About Railway Sleepers Like Function And Types Of Sleepers One By One.
Sleepers are the transverse ties that are laid to support the rails. They have an important role in the track as they transmit the wheel load from the rails to the ballast.
Several types of sleepers are used on Indian Railways.
The characteristics of these sleepers and their suitability with respect to load conditions are,
Functions And Requirements Of Sleepers
The main functions of sleepers are as follows:
- Holding the rails in their correct gauge and alignment
- Giving a firm and even support to the rails
- Transferring the load evenly from the rails to a wider area of the ballast
- Acting as an elastic medium between the rails and the ballast to absorb the blows and vibrations caused by moving loads
- Providing longitudinal and lateral stability to the permanent way
- Providing the means to rectify the track geometry during their service life
Apart from performing these functions the ideal sleeper should normally fulfill the following
- Initial as well as maintenance cost should be minimum
- Weight of the sleeper should be moderate so that it is convenient to handle
- Designs of the sleeper and the fastenings should be such that it is possible to fix and remove the rails easily.
- Sleeper should have sufficient bearing area so that the ballast under it is not crushed
- Sleeper should be such that it is possible to maintain and adjust the gauge properly
- Material of the sleeper and its design should be such that it does not break or get damaged during packing.
- Design of the sleeper should be such that it is possible to have track circuiting.
- Sleeper should be capable of resisting vibrations and shocks caused by the passage of fast moving trains.
- Sleeper should have anti-sabotage and anti-theft features.
Sleeper Density And Spacing Of Sleepers
Sleeper density is the number of sleepers per rail length. It is specified as (M + x) or (N + x), where M or N is the length of the rail in metres and x is a number that varies according to factors such as
- Axle load and speed,
- Type and section of rails,
- Type and strength of the sleepers,
- Type of ballast and depth of ballast cushion, and
- Nature of formation.
If the sleeper density is M+ 7 on a broad gauge route and the length of the rail is 13 m, it implies that 13 + 7 = 20 sleepers will be used per rail length of the track on that route.
The number of sleepers in a track can also be specified by indicating the number of sleepers per kilometre of the track, for example, 1540 sleepers/km.
This specification becomes more relevant particularly in cases where rails are welded and the length of the rail does not have much bearing on the number of sleepers required.
This system of specifying the number of sleepers per kilometre exists in many foreign countries and is now being adopted on Indian Railways as well.
The spacing of sleepers is fixed depending upon the sleeper density. Spacing is not kept uniform throughout the rail length. It is closer near the joints because of the weakness of the joints and impact of moving loads on them.
There is, however, a limitation to the close spacing of the sleepers, as enough space is required for working the beaters that are used to pack the joint sleepers.
Types Of Sleepers
The sleepers mostly used on Indian Railways are
- Wooden sleepers,
- Cast iron (CI) sleepers,
- Steel sleepers, and
- Concrete sleepers.
Wooden sleeper, also called timber sleeper, is one kind of railway sleeper that is made of wood, also known as wooden railway sleeper or wood railroad tie. As a basic railway track components of railway track, wooden sleeper is used for carrying steel rail, it is fastened by common rail fasteners like rail clip, railroad spike, railroad tie plate and etc.
Steel sleepers are different to timber and concrete sleepers, mainly because they are relatively light in comparison to their rigidity. They rely on the ballast in the sleeper “pod” to provide vertical and lateral support.
Concrete sleeper is a kind of railway sleeper made of steel reinforced concrete. With the characteristic of water resistant, sun resistant and corrosion resistant, concrete sleeper has been widely used.
Cast Iron Sleepers
The Sleepers Made Of Cast iron Non As Cast iron Sleepers.
Type Of Cast Iron Sleepers:
- Pot Or Bowl Sleeper
- Plate Sleeper
- Box Sleeper
- CST-9 Sleeper
- Duplex Sleeper
Comparison of different types of sleepers
|Characteristics||Wooden Sleepers||Steel Sleepers||Cast Iron Sleepers||Concrete Sleepers|
|Service life (years)||12-15||40-50||40-50||50-60|
|Weight of sleeper for|
no damage to sleeper while handling
|Manual handling; no damage to sleeper while handling||Manual handling; liable to break by rough handling||No manual handling; gets damaged by rough handling|
|Type of maintenance||Manual or|
|Manual or mechanized||Manual||Mechanized only|
|Cost of maintenance||High||Medium||Medium||Low|
|Gauge adjustment||Difficult||Easy||Easy||No gauge adjustment|
|Track circuiting||Best||Difficult; insulating|
pads are necessary
pads are necessary
|Damage by white|
ants and corrosion
|Can be damaged by white ants||No damage by white|
ants but corrosion is
|Can be damaged by corrosion||No damage by white ants or corrosion|
|Suitable for CF* and EFF||Suitable for CF and EF||Suitable for CF only||Suitable for EF only|
|Scrap value||Low||Higher than wooden||High||None|
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