Depending upon the position in a railway track, railway sleepers may be classified as
1- Longitudinal Sleepers
2- Transverse Sleepers
1- Longitudinal Sleepers
These are the early form of sleepers which are not commonly used nowadays. It consists of slabs of stones or pieces of woods placed parallel to and underneath the rails. To maintain correct gauge of the track, cross pieces are provided at regular intervals. At present this type of sleepers are discarded mainly because of the following reasons.
1- Running of the train is not smooth when this type of sleepers is used.
2- Noise created by the track is considerable.
3- Cost is high.
2- Transverse Sleepers
Transverse sleepers introduced in 1835 and since then they are universally used. They remove the drawbacks of longitudinal sleepers i.e. the transverse sleepers are economical, silent in operation and running of the train over these sleepers is smooth. Depending upon the material, the transverse sleepers may be classified as
1- Timber/wooden sleepers
2- Metal Sleepers
3- Concrete Sleepers
1- Wooden Sleepers
The sleepers made of timber are known as wooden sleepers. These sleepers were widely used as the best type of sleepers as they fulfilled all the requirements of an ideal sleeper. But these are now backdated and not used widely.
Advantages Of Wooden Sleepers
1- Timber is easily available.
2- The initial cost of the wooden sleeper is low.
3- They require few fastenings which are also simple to design.
4- These sleepers are easy to handle.
5- Suitable for all types of ballast.
6- They can be used with every section of rails and for any gauge of track.
7- The extent of damage during accidents is less.
8- Best for track circuiting.
9- Easy renewal of the track.
Disadvantages Of Wooden Sleepers
1- The life span of wooden sleepers is minimum (12 to 15 years) compared to other types of sleepers.
2- They are liable to decay, attack of white ants, wear, spike killing, cracking, splitting, rail cutting etc.
3- The lateral and longitudinal rigidity of the track is less as the connections between the rails and the sleepers are not so strong.
4- Difficulty in maintaining gauge of the track.
5- High maintenance cost.
6- Low scrap value.
2- Metal Sleepers
The sleepers usually made of cast iron or steel are known as metal sleepers. Due to the growing shortage of timber to be used for wooden sleepers, their high maintenance, cast and short life, metal sleepers are now being widely used.
Metal sleepers are two types
a- Steel Sleepers
The sleepers made of steel are known as steel sleepers. Steel sleepers are extensively used with excellent results.
Types of steel sleepers
- The key type of steel sleepers
- Clip and bolt type steel sleepers
b- Cast Iron Sleepers
The sleepers made of cast iron are known as cast iron sleepers. These sleepers are extensively used in the world.
Types of cast iron sleepers
- Pot or bowl sleeper
- Plate sleeper
- Box sleeper
- CST-9 sleeper
- Duplex sleeper
Advantages Of Metal Sleepers
1- Longer life span (35 to 50 years).
2- Uniform in strength and durability.
3- The gauge can be easily adjusted and maintained.
4- The lateral and longitudinal stability of the track is more.
5- Renewal is not frequent.
6- High scrap value.
Disadvantages Of Metal Sleepers
1- They require more fittings.
2- Metal is liable to rust.
3- Require more quantity of ballast.
4- These sleepers are not suitable for bridges, level crossing etc.
5- More damage during an accident.
3- Concrete Sleepers
The sleepers made of reinforced or prestressed cement concrete are known as concrete sleepers.
Types of concrete sleepers
a- RCC sleepers
The concrete sleepers constructed of reinforced cement concrete are called RCC sleepers.
RCC sleepers are the following two types
- Mono-black sleeper
- Two back sleeper
b- Prestressed Concrete Sleepers
The concrete sleepers constructed of prestressed cement concrete are known as prestressed concrete sleepers.
Advantages Of Concrete Sleepers
1- Long life span ( 40 to 60 years).
2- Require fewer fittings.
3- Adjustment of the gauge is simple and easy.
4- They provide strong connections between rail and sleeper.
5- The lateral and longitudinal stability of the track is more.
6- Track circuiting is possible.
7- More durable and not liable to decay.
8- Less creep in the track.
9- They can withstand the stresses induced by fast-moving and heavy traffic.
10- Low maintenance cost.
Disadvantages Of Concrete Sleepers
1- Initial cost is high.
2-Liable to break under rough handling or due to improper design.
3- Renewal is a little bit difficult.
4- The scrap value is nil.
Click Here To See Why Crushed Stone ( ballast ) Are Placed In Railway Track?
