Sleepers and Their types

Notes for Sleepers and their types in Railways Engineering

1. Sleepers, their Types

2. Sleepers / Ties

3. Sleepers
Wooden, cast iron, steel or RCC members which
are laid transverse to the track alignment to
Support the rails and to transfer the load from the
rails to the under line blast are called sleepers
Rails have to withstand the heavy load from the
locomotive ,wagons & coaches
in the absence of sleepers the
track would just settle down

4. Purpose and Functions of Sleepers
Two lines of rails are transversely connected & held
to correct gauge
Load Transmitted to Rail is borne (carry/to turn)
Load is then transmitted with diminished &
distributed unit load along the sleeper length to
ballast beneath

5. Functions of sleepers
Hold rails to correct gauge & alignment
Holding gauge in proper gauge & level
Act as elastic medium
Support the rails firmly & evenly
Distribute the load transmitted from the rolling stock
over large of ballast
Provides stability to permanent way
To provide the general stability of permanent way
To provide the insulation of track for the electric field
tracks of signaling
To provide easy replacement of rails fastening

6. Action of Sleepers under load
In freshly tamped ballast, a loaded sleeper is like a
beam with reactions concentrated under the rails
and with equal end lengths overhanging the
supports.
Shape assumed by tie under these conditions is:

8. Centre
Bound
End Bound

9. Requirements of ideal sleeper
Proper maintenance of gauge
Should have fitting that can be fitted ,remove it ,lifted
,packed & replaced
Long life
Economical
In respect of initial cost & subsequent maintenance
strong enough to withstand bending stress
Should provide resistance against slide
Should resist being pushed forward due to passage of
train

10. Types of Sleepers

11. Wooden Sleepers
Regarded as best sleepers as they fulfil all the
requirements of an ideal sleeper
Universally used since the invention of sleepers
Sal, deodar and chir are mostly used as they are
cheaper
Teak is not used due to high cost
Life in indo-Pak is 12 years whereas in UK 20 years

12. Railway Track Having Wooden Sleepers
Connection Of Wooden Sleeper With Rail

13. Advantages
Low initial cost
Few & simple fastening
Easy to handle
Suitable for all types of ballast
Can be used with every type of rail
Less damage during accident
Easy renewal of track
Timber used is available in all parts of Asia
Absorb shocks & dampen vibrations
More useful for yielding formations

14. Disadvantages
Short life
Liability of decaying
Easily attacked by vermins (white ants) & weather
Connections b/w a rail and sleepers are not strong
Maintenance of gauge is difficult
Higher maintenance cost
Susceptible to fire
Low scrap value

15. Sleeper Dimension
The wide dimension on a crosstie (sleeper) is
referred to as a tie face, and the narrow dimension is
called the side.
Side
Tie Face

16. How Wooden Sleepers are classified?

17. Why wooden sleepers require Treatment?
To enhance their SERVICE LIFE, timber sleepers are
treated by forcing the preservatives into them
(sleepers) under pressure
Ideally ties should be cut with the heartwood
centered in the tie. Sapwoodis more readily treatable
than heartwood, and by putting the heartwood in the
center of the tie a protective envelope of treated
sapwood surrounds the heartwood, contributing to
longer service life.
But before that, they are seasoned so as to bring their
moisture content to allowable limits (e.g. 25%)

18. SEASONING OF WOODEN SLEEPERS
Proper seasoning of sleeper is resorted to for reducing
there moisture. A well seasoned sleeper should not
contain>25%
Methods of seasoning
Air seasoning
One and nine method
Open crib method
Treatment of sleepers
The life of timber sleepers may be increased 30% to 50%
by treating them before they are actually put to use in
the track
Creosote oil
Salt solution (zncl2)
Mercury bi-chloride (Hgcl2)

19. Air Seasoning Of Timber

20. To make something
appear to be
Liquid containing
wood

21. Air Drying

22. Dimensions of Wooden Sleepers

23. Steel Sleeper
Steel sleepers having long useful period steel
sleepers are in the form of inverted channels with
folded ends & having thickness 12 mm.
•Maintain perfect gauge.
•Should not get pushed easily out of position.
•Contain high strength.
•Provide sufficient bearing area of rail.
Requirements

24. Steel sleepers
Rolled steel plate about 12mm thickness
Pressed to a suitable troughshape.
Ends of rolled sections are flattened in the shape of a
spade to retain the ballast
12 mm

26. Steel Sleepers
Advantages
Very durable
Easy to maintain gauge & lesser maintenance probs.
Better lateral rigidity
Lesser damage during handling & transport
Easy to manufacture
Not susceptible to vermin attack
Not susceptible to fire attack
Good scrap value.

27. Steel Sleepers
Disadvantages
Liable to corrosion
Unsuitable for track circuiting areas
Liable to become centre bound due to slopes at two
ends
More fittings are required in number
More ballast is required as compared to other types.

28. Cast Iron Sleepers
Advantages
Easy to manufacture
Lesser liable to crack at rail seats
Useful life 50 to 60 years.
Provide high lateral & longitudinal stability to track
Lesser liable to corrosion
Scrap value is high
Low maint cost

30. Cast Iron Sleepers
Disadvantages
High initial cost
Gauge maintenance is difficult as tie bars get bent up
Broken easily if not handled carefully
Need large number of fittings
No elastic bed, so great damage in accidents

32. Concrete / RCC Sleepers
Advantages
Concrete sleepers being heavy give more elastic modulus,
strength & stability to track
Great resistance to buckling of track
Best suited for modern maintenance methods for track as
they are flat at bottom
They are neither susceptible to be attacked by vermin,
corrosion nor are they inflammable
Due to longer life, rail and sleeper renewals can be matched
They could be easily manufactured locally with local
available materials
More life

34. Concrete Sleepers
Disadvantages
Manufacturing process, transportation, handling &
laying is difficult & costly because they are heavy
Excessive damage can be caused in derailment
No scrap value

36. Twin-Block Sleepers

37. Twin-block sleepers
Lighter by 30% compared to a regular concrete
sleeper thus allowing it to be manually moved and
the four faces of the two blocks resist movement
better.
Excellent for some lighter track forms like those used
for tramway systems.

39. Plastic sleepers
Made of old tires and recycled plastic
Cost about 50% less and save on trees
Practically impervious to the seasons, but otherwise
exhibit the same properties as their wooden
counterparts with respect to damping of impact
loads, lateral stability, and sound absorption.

40. Sleeper less Track

41. Pre-stressed sleepers
Advantages
The P.S.S result in reduced rail pending stresses
The P.S.S reduce the wear of rolling stocks.
The P.S.S produce less vertical motion.
Life 50 years.

42. Disadvantages
Economical –high cost.
Derailments –heavy damages caused.
Maintenance –high cost.
Rigidity –more.
Scraped no value.