Page 401 - IRSEM_Main Book

17.7.2 The important features of the installation procedure are:

(a) Trolley Suppression: On sections where trolleys are in operation and
existing axle counters do not have inbuilt trolley suppression arrangement,
the arrangement shall be provided to prevent the operation of system by
insulated trolleys. Trolley suppression arrangement shall be closed track
circuit and track devices shall be fixed on rails within the boundaries of track
circuit. It is possible to dispense with the provision of trolley suppression
arrangement for track devices provided on point zone portion by using
approved circuits for this purpose. On sections where non-metallic wheels
are used, trolley suppression arrangement can be dispensed with.

Note: In future, digital axle counters having inbuilt provision of trolley suppression
shall only be provided.

(b) The distance between the two adjacent axle detectors of different axle
counters shall be at least 2 meters or as specified in OEM manuals, so as
to minimise mutual interference.

(c) To protect axle detectors against damage (from hanging parts of moving
trains), deflectors shall be provided, on both sides of the axle detectors on
single line and one side on double line.

(d) The track side electronic equipment shall be housed at a location close to
the axle detectors so that the length of cable between the track side
electronic and the axle detectors is minimum and does not exceed the limit
recommended by the manufacturer. The equipment shall be placed at a
level well above the flooding level of the area.

(e) The incoming cables from axle detectors and evaluator may first be
terminated on a cable distribution board to provide facility for testing.

(f) Wherever applicable, the transmitter and receiver coil cables between axle
detector and associated track side electronics shall be laid in different
pipes as prescribed by OEM.

(g) Ensure minimum of 400 mm Sleeper spacing & packing of sleepers in
between track device (sensor) are fitted & fitting do not vibrate under train
movement & packing of the same shall be done, if required

(h) Track side electronic equipment shall be operated from Central power supply
like DC–DC converter of approved type preferably used for feeding evaluator
with adequate battery backup. At remote locations track side electronic
equipment may be provided with separate power supply. The input power
supply shall have a maximum ripple of 50 mV peak to peak/10 mV rms.

(i) The evaluator shall be installed preferably in a relay room or at a location
which is not accessible to unauthorised persons. Equipment shall be
installed at a high level, well above the flooding level of the area and
protected from rain water. It shall be fixed on a separate shelf away from
signalling relays. As far as possible, it shall be located away from any
source of heavy electromagnetic interference like industrial machinery,
motor/generator or welding plants, etc.

Chapter 17: Train Detection Track Circuits & Axle Counters Page 349 of 535