Page 417 - IRSEM_Main Book
P. 417
Section 5: Installation of Single Line Tokenless Block Instrument
18.5.1 (a) The instruments shall be mounted level. The instruments shall be so placed
as to have an easy access and space for their maintenance.
(b) Before installation, the instrument shall be checked for the following:
(i) Free from mechanical damage, corrosion. All nuts and bolts shall be
secure and complete.
(ii) The Front Panel shall be free from splitting, twisting or warping in case
of Push Button type instruments.
(iii) The seal of all the relays and counters shall be intact.
(iv) Sealing.
(c) All the external connections to the block instrument shall be removed and
insulation resistance measured between individual insulated circuits and
Earth. The minimum value between each individual insulated circuit and
Earth shall not be less than 10 mega ohms.
(d) Block release shall be by operation of two track circuits sequentially.
18.5.2 Testing of Single Line Tokenless Block Instruments
(a) Check that the Last Stop Signal at the sending station can not be taken
'OFF' until the receiving station instrument is set to "Train Coming From"
condition and the sending station instrument is set to "Train Going To"
condition.
(b) Check that the Line Clear can be granted only when reception signals and
the Last Stop Signal are proved at 'ON'.
(c) Check that the Last Stop Signal is replaced to 'ON' by the entry of a train
into the block section and the same is maintained in the 'ON' position until
the train has cleared the block section and the instruments are brought
back to the 'Line Closed' condition and fresh "Line Clear" is obtained.
(d) Check that the opposing Last Stop Signals of the block section can not be
taken "OFF" at one and the same time.
(e) Check that the circuit for proving the arrival of a train is directional.
(f) Check that the shunting key can be taken out only when the instruments
are in "Line Closed" condition or "Train Going To" condition.
Chapter 18: Block Instruments, BPAC & IBS Working Page 365 of 535
