There are various types of sleepers used in railways, according to their suitability, availability, economy, and design.
Based on the material used in the construction, the sleepers can be classified into the following three categories:
1. Wooden sleepers.
2. Metal sleepers.
Cast iron sleepers.
3. Concrete sleepers.
Reinforced concrete sleepers.
Prestressed 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 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 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:
Key type 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 India than any other country in the world.
Types of cast iron sleepers:
Pot or bowl sleeper.
Advantages Of Metal Sleepers:
1. Longer life span (35 to 50 years).
2. Uniform in strength and durability.
3. 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 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:
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 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.