General Information on Track Circuits - RGS Online

<strong>General</strong> <strong>Information</strong> on Track Circuits
1 Introduction
2 Routine Examination
3 Drop Shunt Test
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Part H
Maintenance
Railway Group Approved Code of Practice
GK/RC0752
Issue Two
Date December 1998
Page H1 of 2
This Part is a general guide to the principles of track circuit maintenance.
Procedures specific to a particular design of track circuit are given in the relevant
Code of Practice within the Track Circuit Handbook.
Instructions regarding maintenance of track circuits are given in GK/RH0740 and
GK/RC0241.
Track circuit maintenance can be classified into the following activities:
a) Routine Examination.
b) Drop Shunt Test.
c) Full Test.
The objective of the examination is to find/remove potential failures and to
ensure that, as far as possible, the track circuit will function satisfactorily until the
next examination. The examination is mainly visual and can be undertaken
without any need for possession of the track circuit.
Any obstructions or conditions likely to prove detrimental to the reliability of the
track circuit must be dealt with as soon as possible.
The requirements and responsibilities for maintenance and inspection of bonding
are laid down in GM/TT0127 and GM/TT0128. Refer also to GK/RT0252
Specific attention must be given to the examination of the following:
a) Track cables and jumper cables, their connection to the rail and clearance
when passing under other rails.
b) Fishplate type bonding, including traction return bonding where provided.
c) Impedance bonds and connections where provided.
d) Metallic and other conductive debris around insulations and rails.
e) Point rodding, signal wires etc, touching or liable to touch either rail.
f) Insulation deterioration and rail burring over insulations.
g) Rust or other rail contaminants on the surface of the rails.
The relay voltage should be checked and compared with the entries on the
Track Circuit Record Card. If the value is significantly different from previously
recorded values under similar weather conditions, a full test should be
conducted.
The commissioning drop shunt test is always carried out with the shunt box
connected between the rails at the relay end of the track circuit.
However, for routine drop shunt tests on d.c. or a.c. power frequency (50Hz -
831 / 3Hz) track circuits (other than auto–coupled impedance bond types), the
R A I L T R A C K H1