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:
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
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
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
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. Sapwood is 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)
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 12 mm thickness
Pressed to a suitable trough shape.
Ends of rolled sections are flattened in the shape of a
spade to retain the ballast
12 mm
25.
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
29.
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
31.
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
33.
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
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.
38.
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.
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.