Transcript WEAR OF RAILS

WEAR OF RAILS
Engr. Muhammad Hussain
TYPES
1.
Wear on head of rail
2.
Wear on ends of rail
3.
Wear of rail on curve
WEAR ON HEAD OF RAIL

Wear on head of rail is due to abrasion on
moving rails.

Due to grinding action of sand or dust
between the rails and wheels of the train.
Cont…

When train starts or applies brakes, the
wheel just slides on the rails causing wear on
the head.

Load coming on to a track may exceed the
carrying capacity of the section. Thus causing
the wear in the head of rail.
WEAR AT THE ENDS OF THE RAIL




It is much greater than the wear on the head
of the rail.
This type of the wear is resulted due to the
blows which the rail receive when the wheel
jumps the space between the rail ends.
The ends are battered by such blows.
The contact surface between the sleepers
and the rail is worn as the as the effect of
these blows increased.
CONT…

The ballast under the sleepers will loosen due to
increase in the intensity of vibrations, also he
sleeper will depressed due the displacement of
ballast, also the fish plates will get loose under the
constant impact of increasing vibrations
WEAR OF RAIL ON CURVE

On the curve the wear of the
rail takes place in both inner
and outer rails.

On the curve, the outer
wheel has to move through
greater distance than the
inner wheel. And the inner
wheel has to slide over the
inner rail.
Curved Crossing
CONT…


As a result of this sliding
wear of the inner rail
occur because the metal
in the rail head is burnt.
At the curve, flange of
outer wheel will strike the
inner surface of the outer
wheel due to centrifugal
force. Thus side of the
head of rail wears out.
Wheel
Slope 1:20
Flange of Wheel
TYPES OF CROSSING
TYPES OF CROSSING
1.
Square Crossing
2.
Diamond Crossing
3.
Cross Over
4.
Scissor Crossing
5.
Symmetrical Split
SQUARE CROSSING

When two railway lines cross each other at 90o
it is called Square Crossing
DIAMOND CROSSING

Angle of intersection (crossing angle) of two tracks is
when not 900 , then crossing is called diamond
crossing
CROSS OVER

A
cross
over
is
introduced to transfer a
train from one track to
another track which
may or may not be
parallel to each other
SCISSOR CROSSING

If two cross overs are
required between two
parallel
tracks
and
there is no sufficient
space for crossing to be
kept separate, then
they are made to overlap each other and
result is a scissor
crossing.
SYMMETRICAL SPLIT

If radius of main track is equal to the radius of
turn out curve, then the turn out is known as
symmetrical split.
CREEP OF RAILS
CREEP OF RAILS
Definition:
It is a horizontal movement of rails in a track.
It can be minimized but cannot be stopped.
Causes Of Creep
There are three main causes of Creep
1.
Wave motion of trains.
2.
Expansion and contraction of rails due to
variation in temperature.
3.
Due to starting, accelerating, slowing down
(decelerating) and stopping of trains.
Wave Motion

When train passes on a track, the portion of
rail length under the wheel of train will under
more stresses and little depression will exist.

As a result, this depression will cause (set) a
wave motion in the rail or track
Direction Of Creep
Alignment Of Track:
Creep is more on curve track than on a tangent portion (straight
track).
Grades:
In upgrades tracks, creep will be less and in down grades track
creep will be more.
Direction of movement of trains:
Creep will be more in the direction to which the loaded train
moves more.
Extent Of Creep

Creep does not vary at some constant rate.
(it is not constant)

Creep does not continue in one direction
only.

Creep for two rails of the track will not be in
equal amount.
Result Of Creep

Expansion gap is reduced, buckling of track
take place.

Sleepers are moved out of a square.

Crossing points get disturbed.
Square Position of Sleeper
Sleeper out of square
SOME IMPORTANT
TERMS
SUPER ELEVATION
The outer edge is raised with respect to the
inner edge on curve rail section called super
elevation.
2
GV
SUPER ELEVATION =
gR
Where,

G = Gauge of track (ft)
V = Design speed of train (ft/Sec)
R = Radius of curvature (ft)
g = Acceleration due to gravity (ft/sec2)
Problem
Fine the Design speed of railroad on a curve
if Super elevation is 0.5ft, Gauge is 5’-6” and
Radius of Curve is 3500 ft
Sol:
101 Km/h