Maintenance of Rail Surface
The surface of rails is
susceptible to certain defects in the absence of proper care and maintenance.
Each defect should be dealt with carefully at the proper time.
The hogging of a joint is a phenomenon in which the two rail
ends at the joint get depressed on account of the poor maintenance of the rail
joint, loose and faulty fastenings, and other such reasons. The hogging of
joints brings about deterioration in the running quality of the track. The
various techniques for removing this defect are as follows.
measured shovel packing as explained in Chapter 20.
hogging occurs on a small scale, the joint sleepers are overpacked and the
fittings are tightened, which may finally remedy the defect. Use of liners and
shims may also help in removing the defect in case the fittings are loose.
cropping the hogged portions of the rail (preferably 450 cm), reusing the rail
after the necessary drilling of holes, etc.
dehogging the rail, i.e., removing the vertical bends on the reverse side of
the rail with the help of a dehogging machine.
2 High Joints
High joints result in a very uncomfortable ride on the track.
High joints are the outcome of the following.
in track structure, e.g., provision of wooden sleepers in a track that is
normally laid with metal sleepers. Since it is easier to maintain wooden
sleepers as compared to metal sleepers, this discrepancy in the type of
sleepers results in high joints, which in turn produces the effect of camel
of intermediate sleepers
of joint sleepers
defect is removed by lifting and packing the intermediate sleepers.
3 Blowing and Pumping Joints
A joint is called a blowing
joint when it blows out fine dust during the passage of a train. The
surroundings of such a joint are always coated with fine dust. A blowing joint
becomes a pumping joint during the rainy season when it pumps out mud
and water from the mud pockets formed below the joint. This defect is caused
because of poor maintenance of the joint, particularly of the packing of the
joint sleepers, unclean ballast, and bad drainage, and also sometimes due to
surface defects in the rail such as scabbing. As moving loads pass over the
joint, the joint sleepers get depressed and lifted up constantly. As this
happens, the dust or mud gets sucked up and spreads in the vicinity of the
joint. The remedy lies in
screening the ballast below the joint and shoulder sleepers,
the joint sleeper and shoulder sleepers thoroughly,
proper drainage at the joint,
loose fittings, and
the creep, if any.
Lifting of track
Normally, lifting a track becomes
necessary when the track undergoes regrading. This may be due to yard
remodelling, construction of a bridge, etc., or in an effort to eliminate the
sags that develop in the approaches to level crossings and bridges and at other
locations made vulnerable due to defective maintenance or yielding formation.
The points regarding the lifting of tracks that require special mention are as
(a) A maximum
of 75 mm (3") of the track should be lifted at a time. Whenever
heavy lifting is involved, it should be done in different stages, with each
lift being not more than 75 mm.
(b) On single
lines, lifting should commence from the downhill gradient and continue in the
direction of the rising gradient. In the case of double lines, it should
proceed in the direction opposite to that of the traffic, taking care not to
exceed the easement grade.
should be done under the supervision of a PWI after imposing suitable speed
restrictions and setting up the obligatory engineering signals.
Lowering of track
The lowering of a track becomes
necessary when the track is re-graded for various reasons such as yard
remodelling, provision of level crossings, etc. It should be avoided until it
becomes inevitable, as lowering the track makes it unstable and is quite a
difficult, time-consuming, and costly proposal.
4 Longitudinal Sag in the Track
Normally a track between two
rigid structures such as bridges, level crossings, etc., settles due to the
passage of moving loads. The settlement of the track also takes place on
yielding formation owing to the weakness of the formation and the puncturing of
the ballast into the formation. Whereas a longitudinal unevenness in the shape
of a vertical curve may not be noticeable, an irregular longitudinal sag may
make the ride on the track uncomfortable. In such cases, a proper survey of the
track should be carried out, pegs should be fixed at the correct longitudinal
level with the help of a levelling instrument, and the track should then be
lifted. The track should not be lifted more than 75 mm at a time. An adequate
quantity of ballast should be collected in advance so that both packing and
lifting can be done effectively. If excessive lifting is involved, the work
should be done under speed restrictions.
5 Centre-bound Sleeper
This defect is generally noticed
in wooden and steel trough sleeper tracks. This defect occurs when, as a
consequence of plying traffic, the sleeper starts to receive support at the
centre instead of at the ends. If proper care in not taken during through
packing and the middle portion of the sleeper is also packed, the defect can
develop very early. Even under normal circumstances, the ballast under the
sleeper ends, where the sleeper rests, gets more depressed compared to the
ballast at the centre because of the impact of the moving loads and in the
process the sleeper, instead of resting at the ends, stats to rest at the
binding of the sleepers leads to the rocking of the trains and is detrimental
to the quality of the track. The defect can be removed by loosening the ballast
at the centre of the sleeper. It is considered a good practice to make a small
recess or depression in the ballast section at the centre of the sleeper.