Other Defects in Rails
Rail wear and the battering of
rail ends are the two major defects in rails. However, some other types of
defects may also develop in a rail and necessitate its removal in extreme
cases. These are described below.
Hogging of rails
Rail ends get hogged due to poor
maintenance of the rail joint, yielding formation, loose and faulty fastenings,
and other such reasons. Hogging of rails causes the quality of the track to
deteriorate. This defect can be remedied by measured shovel packing. (For
details, refer to Chapter 20.)
Scabbing of rails
The scabbing of rails occurs due
to the falling of patches or chunks of metal from the rail table. Scabbing is
generally seen in the shape of an elliptical depression, whose surface reveals
a progressive fracture with numerous cracks around it.
burns are caused by the slipping of the driving wheel of locomotives on the
rail surface. As a consequence, extra heat is generated and the surface of the
rail gets affected, resulting in a depression on the rail table. Wheel burns
are generally noticed on steep gradients or where there are heavy incidences of
braking or near water columns.
and black spots
Shelling is the progressive horizontal separation of metal
that occurs on the gauge side, generally at the upper gauge corner. It is
primarily caused by heavy bearing pressure on a small area of contact, which produces
heavy internal shear stresses.
Corrugation consists of minute depressions on the surface of
rails, varying in shape and size and occurring at irregular intervals. The
exact cause of corrugation is not yet known, though many theories have been put
forward. The factors which help in the formation of rail corrugation, however,
are briefly enumerated here.
and age of rails
nitrogen content of the rails
(ii) Effect of
oscillation at the time of rolling and straightening of rails.
and environment conditions of track
speeds and high axle loads
locations of trains
where brakes are applied to stop the train
moisture content in the air particularly in coastal areas
The corrugation of rails is quite an undesirable
feature. When vehicles pass over corrugated rails, a roaring sound is produced,
possibly due to the locking of air in the corrugation. This phenomenon is
sometimes called 'Roaring of rails'. This unpleasant and excessive noise causes
great inconvenience to the passengers. Corrugation also results in the rapid
oscillation of rails, which in turn loosens the keys, causes excessive wear to
fittings, and disturbs the packing.
Corrugation can be removed by grinding the rail
head by a fraction of a millimeter. No method has been standardized on Indian
Railways to grind rail surfaces. The problem of corrugation, however, has been
tackled in great detail on German Railways, where two types of equipment are
normally used for rail grinding.
(i) Hand or
motor-driven trollies that move on the rails at slow speeds and grind the
individual rails one by one.
grinding train, which moves at a speed of 30 kmph and grinds both rails