Chapter 18: Block Instruments, BPAC & IBS Working PDF

18.1.6 Non-Co-operative type Instruments The requirements indicated in para 18.1.5 will apply to these instruments. In addition, the following shall be provided in these instruments. (a) Automatic "Train On Line": Means to ensure the instruments are set to "Trai...

18.1.6 Non-Co-operative type Instruments The requirements indicated in para 18.1.5 will apply to these instruments. In addition, the following shall be provided in these instruments. (a) Automatic "Train On Line": Means to ensure the instruments are set to "Train On Line" position automatically by the entry of the train into the block section and maintained in that position until the train has passed the Home Signal at the receiving station and the instrument set to "Line Closed" condition. (b) Audible Indicator: Audible Indicator to warn the receiving station when the train enters the block section at the sending station. (c) Shunting Keys: Two Shunting keys, one for each line, suitably interlocked with the block instruments for use as an authority for shunting in the block section. Train Detection for Proving Block Section to be Clear: On sections where use of track circuits/Axle counters for proving the block section to be clear is to be introduced, the following equipment shall be provided: (a) Track circuits or Axle Counters extending from the Last Stop Signal of the block station at one end of the block section to the other end First Stop Signal of the block section. (b) An indicator in each block station to show whether the block section is occupied or not. (c) A control to ensure that the Last Stop Signal of the block station in rear is automatically replaced to 'ON' by the passage of a train and maintained in that position until the train has cleared the block section. (d) A control to ensure that the First Stop Signal is automatically replaced to 'ON' by the passage of the train. (e) On single line, a control to ensure that the opposing Last Stop Signals of the Block section cannot be taken 'OFF' at one and the same time. Section 2: Special Requirements of Block Working in RE Area 18.2.1 In 25 KV electrified line only following type of block instrument shall be used: (a) Single Line: (i) Single Line Token instrument (Neal's) (ii) Single Line Token less Block Instrument Handle type (Daido) (iii) Block working with Axle Counter (iv) Block Proving by Axle Counter (v) Block working directly from EI Note: (i) Neal's Token instrument shall be progressively phased out. (ii) Push button type block instrument may be used on non-electrified section taking off from electrified section, if length of parallelism does not exceed 1.5 km. Chapter 18: Block Instruments, BPAC & IBS Working Page 360 of 530  (b) Double Line: (i) Double Line Block Instrument (SGE) (ii) Block working with Axle Counter (iii) Block Proving by Axle Counter (iv) Block working directly from EI Note: If any other block instrument is to be used, prior approval of Railway Board shall be obtained. 18.2.2 Media (a) Block instruments may use special PVC insulated quads in the aluminum sheathed cable/4 or 6 quad jelly filled telecommunication cable or other suitable communication means, like OFC and radio, for their working. (b) When quad cable is used for the working of block instruments, Block Telephone and Block Bell circuits shall be worked through a transformer utilizing the two pairs of block quad. The Block circuits shall be worked on the phantom pair or by other suitable means. (c) When OFC, Radio or other communication means are used for block working, Universal Fail Safe Block Interface (UFSBI) of approved design shall be used. UFSBI shall be installed in relay room and the connected block panel shall be provided in ASM room. In case the distance between UFSBI and block instrument is more than 500 meters, block filter and block bell and telephone shall be inserted in cable pairs connecting them. 18.2.3 Others (a) Protective Devices of approved type consisting of two chokes connected in series with a four terminal condenser connected across the junction between two chokes and earth shall be used. A surge arrestor of suitable type shall also be provided across the condenser to absorb surges under faulty conditions. The arrangement is illustrated in Drg. No. 18-D4. (b) The Block Bell shall be worked through Block Bell equipment of approved type. (c) Separate line battery or DC-DC converter shall be used for each block instrument. This battery shall feed only the block instruments and not any other circuit. Note: Two different earths shall be provided separately for SPD and Block. However, the protective earth for SPDs of all Block equipments should be connected to common ring earth of Indoor Signalling system. Chapter 18: Block Instruments, BPAC & IBS Working Page 361 of 530 18.2.4 Single Line Token Block Instrument in RE Area (a) Where earth return is used, the rest contact of the instrument shall be substituted by the contacts of a slow release relay. The arrangement shall be such that the relay is energized during the operation of plunger but is dropped only after the condenser has discharged to a safe limit. The circuit details are illustrated in Drg. No. 18-D5. (b) Whenever stray DC is present in the earth, metallic return is provided for block circuit. Metallic return should be used with a modified filter circuit eliminating the condenser. The chokes and surge arrestors shall be retained and shunt resistors shall be provided across the Galvo (150 ohms) and Polarised Relay (77 ohms). The resistors shall be of substantial rating so that they do not get open circuited. The circuit details are illustrated in Drg. No. 18-D6. In this case, slow to release relay is not required. 18.2.5 Double Line Block Instrument in RE Area (a) IRS type Block Instrument with Block filter shall be used for Double Line section electrified with 25 KV AC. The circuit details are illustrated in Drg. No. 18-D7. (b) The voltage of the Battery shall be sufficient to ensure not less than 18 ma and not more than 25 mA current through the polarized relay. Needle coil resistance shall be modified to obtain this level of current. Section 3: Installation of Block Instruments 18.3.1 General Fixture (a) All block instruments shall be of approved type only. (b) The Table or other fixture on which instruments are placed must be substantial and the Instruments are securely fixed there on. (c) Turn-table arrangement may be provided for fixing the Token and Handle type instruments to enable easier maintenance but the plate on which the instrument turns shall be securely fixed to the table. (d) Block Instruments, Distinction of: Where two or more block instruments are located in the same room, they shall be fitted with bell units/ bell buzzers of distinctive tones. Note: Painting of Block Instruments shall be in accordance with the painting scheme in Annexure: 18-A1. Chapter 18: Block Instruments, BPAC & IBS Working Page 362 of 530 18.3.2 Transmission Media and Wiring (a) Line Wires: The line wires from the point where the lines of two adjacent block sections meet to the terminating point on or near the building shall either be insulated or be so erected as to be not less than 150 mm from any other wire. The provision of insulated wires should be preferred. The insulated line wires must be terminated on pot-head insulators. The line wires must not be easily accessible. Alternatively, a cable, suitably protected, may be used, but a separate cable should be provided for each instrument circuit. The insulated line wires must be led in sloping upward to the building, otherwise a drip loop should be provided. (b) Leading in Wires: The wires leading into the building from the terminating point shall be adequately separated from the wires of other circuits and shall be single, braided or metal sheathed, run in one length from the pot- head insulator to the test panel. Alternatively, a cable, suitably protected, may be used, but a separate cable should be provided for each block instrument circuit. (c) Indoor Wires: Indoor wires must be run in troughing or other suitable form of trunking which provides protection from interference and separation from the wires of any other circuit. (d) Radio/Optical Fibre Cable: Where radio channel or optical fibre cable is used in lieu of line wires, approved type block interface shall be provided. Note: All wires or cables shall be in accordance with the Indian Railway Standard Specification or other approved specification. 18.3.3 Protective Measures against Power Line Parallelism (a) Lightning Dischargers shall not be located in the Block Instrument but installed separately and shall be the demarcating point for test purposes. (b) It shall be ensured that induced voltage due to power line parallelism does not exceed 150 V and the short circuit fault current does not exceed 430 V as prescribed by CCITT. (c) If the induced voltage goes beyond these limits, overhead block circuit shall be transferred to an underground telecom PET quad cable/OFC/Radio, so as to bring the induced voltage within the permissible limits. (d) Since the immunity of PR relay is only up to 10 V, block filters shall be used in all block instruments using this relay where this limit is exceeded. (e) Block filters shall be used with Handle type Block instruments using frequency coded signal. (f) Use of single line push button token less block instruments is permitted in sections where length of parallelism does not exceed 1.5 km, so as to ensure that the DC coding used in these block instruments is not distorted. Chapter 18: Block Instruments, BPAC & IBS Working Page 363 of 530