Automatic Block Signalling Chapter 20 (PDF)
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This document details automatic block signalling, focusing on general principles, and installation procedures for railways.
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Chapter 20: Automatic Block Signalling Section 1: Automatic Signalling - General 20.1.1 Automatic Block System on Double Line/Single Line: General (a) Automatic Block is a system in which the movement of trains is controlled by Stop Signals which are operated automat...
Chapter 20: Automatic Block Signalling Section 1: Automatic Signalling - General 20.1.1 Automatic Block System on Double Line/Single Line: General (a) Automatic Block is a system in which the movement of trains is controlled by Stop Signals which are operated automatically by the passage of trains past the Signals. (b) The automatic Stop Signal which governs entry of Train into an Automatic Signalling section is a multiple aspect colour light signal which is not dependent upon manual operation but is controlled automatically by the passage of a train into, through and out of the Automatic Signalling section which the Signal governs. (c) The line between two adjacent crossing stations shall be divided into a series of Signalling sections and entry into each signalling section shall be controlled by a Manual Stop Signal or an Automatic Stop Signal or a Semi- Automatic Stop Signal which must assume 'ON' position on entry of a train into the section and be maintained in that position until the train has passed clear of the next Automatic Stop Signal in advance and also for an adequate distance beyond it. (d) No automatic signal shall assume 'OFF' position unless the Line is clear not only up to the next Stop Signal in advance but also for an adequate distance beyond it. Except under approved special instructions, this adequate distance shall not be less than; (i) 120 metres, if next Stop signal in advance is an automatic signal. (ii) 180 metres, if *next Stop signal in advance is a Manual stop signal or Semi-automatic signal. (*Note: if such signal is a Home signal or LC gate signal) (e) Signals shall be so spaced as to meet the operational requirements of the section. At the same time the distance between signals shall not be so high as to cause serious repercussions during failures or so small as to provide inadequate braking distance. If the distance between the Caution and Stop Aspects in the case of three aspect signalling or Attention and Stop Aspects in the case of four aspect signalling, is less than the Emergency braking distance of a train, the speed of that train shall be so regulated as to bring the Emergency braking distance within the above mentioned signal spacing. (f) The Signal that governs entry into the Block section shall be Manual or Semi-Automatic Stop Signal, which are explained below. 20.1.2 Manual Stop Signals and Semi-Automatic Stop Signals (a) Manual Stop Signals: Fixed Signals which require manual control each time they are taken 'OFF' are called Manual Stop Signals. Manual stop signals shall be manually operated multiple aspect colour light signals which shall assume ‘ON’ position automatically on the occupation of the section ahead but shall assume ‘OFF’ position only when on clearance of the relevant section and they are operated manually. Chapter 20: Automatic Block Signalling Page 420 of 530 (b) Semi-Automatic Stop Signals: A fixed signal having both manual and track circuit controls and which is capable of being operated either as an Automatic Stop Signal or a Manual Stop Signal, is called a Semi-Automatic Stop Signal i.e they are capable of being operated either as Automatic Stop Signals or as Manual Stop Signals as per need. (i) The Semi-Automatic Stop Signal when working as an Automatic Stop Signal shall conform to an Automatic Stop Signal in all matters relegating to its functioning including its normal aspect. (ii) Similarly, a Semi-Automatic Stop Signal when working as a Manual Stop Signal shall conform to Manual Stop Signals in all matters including its normal aspect. A control may be provided to make a Semi-Automatic Stop Signal to work either as an Automatic Stop Signal or as a Manual Stop Signal as required. 20.1.3 Special Requirements of Automatic Block System on Single Line: In case of single line , Line clear shall be obtained and Direction of Traffic shall be established as per GR 9.03 (Extract given below) GR 9.03. Essentials of the Automatic Block System on single line.–– (1) Where trains on a single line are worked on the Automatic Block System,--- (a) The line shall be provided with continuous track circuiting or axle counters, (b) The direction of traffic shall be established only after Line Clear has been obtained from the block station in advance, (c) A train shall be started from one block station to another only after the direction of traffic has been established, (d) It shall not be possible to obtain Line Clear unless the line is clear, at the block station from which Line Clear is obtained, not only up to the first Stop signal but also for an adequate distance beyond it, (e) The line between two adjacent block stations may, where required, be divided into two or more automatic block signaling sections by provision of Stop signals, (f) After the direction of traffic has been established, movement of trains into, through and out of each automatic block signaling section shall be controlled by the concerned Automatic Stop signal and the said Automatic Stop signal shall not assume ‘off’ position unless the line is clear up to the next Automatic Stop signal: Provided further that where the next Stop signal is a Manual Stop signal, the line is clear for an adequate distance beyond it, and (g) All Stop signals against the direction of traffic shall be at ‘on’. (2) Unless otherwise directed by approved special instructions, the adequate distance referred to in clauses (d) and (f) of sub-rule (1) shall not be less than 180 metres. Chapter 20: Automatic Block Signalling Page 421 of 530 20.1.4 Establishing Direction of Traffic for Automatic Stop Signals on Single Line (a) A Control shall be provided to establish direction of traffic and to ensure that conflicting signals cannot be taken off and a suitable indicator provided to indicate the direction established. It shall not be possible to change the direction unless the entire line between two crossing stations and the overlap in the direction to be established are Clear. The mechanism of the control shall, in addition, be suitably approach locked. (b) Automatic Stop Signals shall operate in the direction of traffic established. Those Automatic Stop Signals which are against the direction of traffic must exhibit 'ON' position. 20.1.5 Train Detection (Track Circuits/Axle Counter) for Automatic Signalling (a) The line shall be provided with track circuits or Axle Counters over its entire length and may be divided into a series of Automatic Signalling Track Sections. The Track Circuit for the overlap must be separated from the Track Circuits for the remaining portion of each signalling section. In case of Axle Counters, track section may be extended from foot of the next signal in advance up to an adequate distance beyond it. (b) DC Track circuits are not to be provided in block section, in future working due to maintenance issues. (c) Track circuits/Axle Counter shall also be provided on all passenger running lines as well as other reception lines between passenger lines including their connections to the main lines at all stations on the Automatic Section including stations at either end of the section. There shall be no dead section between the Track Circuits/Track sections of the station and the Track Circuits/Track sections of the Automatic Section. (d) The design of the Axle Counters between two adjacent stations, shall be such that, individual track sections in each direction shall have resetting facility from dispatching end station master in case of failure of equipment, with co- operation of receiving end station master for verification of last vehicle. (e) Redundancy may be provided in Track circuits/Axle Counters in the Automatic Section to improve availability. (f) Media diversity shall preferably be provided for Axle Counters. (g) Track indicator for Automatic Signalling on Single Line: An indicator shall be provided at each station to indicate whether the block section is occupied or clear. 20.1.6 Markers (a) Each Automatic Stop Signal shall be identified by its number and provided with a Marker consisting of a white disc with letter ‘A’ in black. (b) A Semi-Automatic Stop Signal shall be provided with a Marker which shall show a white illuminated letter ‘A’ against a black background when the signal works as an Automatic Stop Signal. Chapter 20: Automatic Block Signalling Page 422 of 530 (c) Such a Signal interlocked with a level-crossing shall be provided with a yellow disc with letters ‘G’ in black and an ‘A’ marker light. The ‘A’ marker shall be lit only when the gates are closed and locked against road traffic. (d) A Semi-Automatic Stop Signal shall be provided with a Marker which shall show a white illuminated letter 'A' against a black background when the signal works as an Automatic Stop Signal. (i) Such a Signal interlocked with a level-crossing shall be provided with an enamelled yellow disc with letters 'G' in black and an 'A' marker light. The 'A' marker shall be lit only when the gates are closed and locked against road traffic. (ii) When a Semi-Automatic Stop signal is required to protect a level crossing gate as also points, the signal may be provided with an illuminated 'AG' marker in addition to the illuminated 'A' marker. (e) The illuminated markers of a Semi-Automatic Stop Signal shall preferably be repeated at the place of operation of the Signal along with the aspects of the Signal. 20.1.7 Restrictions in Graded Sections (a) Automatic Signalling shall not be provided on sections with heavy and continuous falling gradients steeper than 1 in 80 unless the brake power of trains on the section is adequate to enable the trains being stopped at each of the Automatic Stop Signal. (b) The suitability of Automatic Signalling on heavy and continuous rising gradients shall be decided in consultation with the concerned Departments duly taking into account the ability of a train to start after it has been stopped at an Automatic Stop Signal. (c) Points and Crossings in Automatic Block Sections: Emergency Crossovers and Siding Points shall be secured and approach locked and detected by Signals reading over the Points. Section 2: Installation of Automatic Signalling 20.2.1 The installation and wiring shall be carried out as per approved plan and Circuit Diagrams. The circuits and equipment shall be so installed as to cause minimum failures while ensuring maximum safety. 20.2.2 Circuit Features for Auto Signals (a) The aspects of an automatic signal shall be controlled by the main signal in advance through lamp proving relays/object controller, in addition to the controlling relays. (b) All fail-safe circuits shall work on continuously energized principle such that any open circuit in wiring, relay contacts, etc. or loss of power supplies shall not cause an unsafe condition. Chapter 20: Automatic Block Signalling Page 423 of 530 (c) An automatic signal on a double line/single line shall require all tracks to be clear up to the next signal and an adequate distance beyond, before it can display 'OFF' position as per Para 20.1.1 (d). In case of Single Line, Direction of traffic, shall also be established. (d) LED signals of approved type by RDSO shall be used. (e) All external circuits shall be provided with double cutting arrangements. (f) The circuits shall be so designed that, if the lamp of the aspect displayed fails, the signal shall immediately assume the next restrictive aspect. Also if a signal which must display red aspect does not do so for any reason whatsoever, the signal in rear shall display a red aspect. (g) The circuit for illuminated 'A' marker of a Semi Automatic Signal shall be such that the 'A' marker lights up only when the signal is working as an automatic signal. (h) The circuit for illuminated 'AG' marker where provided shall be such that the 'AG' marker lights up only when the conditions for 'A' Marker to light up are satisfied except for the level crossing gate which may either be open to road traffic or may have failed. (i) The illumination of the 'A' marker shall prove the correct setting and locking of the points as required and ensures the back-locking of the route. Level crossing gates, if any, on the route shall be proved closed and locked to the road traffic. (j) The relevant information of Automatic Signalling gears in section should be available/visible at station like Signals Aspects, track status information, Axle Counter reset information and gate information. 20.2.3 Level Crossings in Auto Section: Please refer to Chapter 14, section 1 of SEM for working of LC gates, approach locking and audible warning to LC gate man. 20.2.4 Installations - Misc (a) Track circuits: Provisions contained in Chapter 17 of SEM shall be adhered to. (b) Power Supply: Provisions contained in Chapter 16 of SEM shall be adhered to. (c) Installation in 25 KV AC electrified areas: Provisions contained in Chapter 22 of SEM shall be adhered to. (d) Installation of Cables: Provisions contained in Chapter 15 of SEM shall be adhered to. (e) Extant guidelines on Installation, Testing & Commissioning shall be adhered to. Note: An example of Automatic signalling scheme using optical fibre cable(OFC), Multi Section Digital Axle Counter (MSDAC) and Object Controllers (of Electronic Interlocking) is given at Annexure: 20-A1 for information. Chapter 20: Automatic Block Signalling Page 424 of 530 Section 3: Maintenance of Automatic Signalling Section 20.3.1 LED signal lamps shall be replaced in case of failure/after completion of codal life. 20.3.2 Marker light shall be replaced on age cum condition basis. 20.3.3 The following shall be tested by the SSE/JE (Signal) at least once in a year: (a) Track Circuit control on signal and aspect control by signals in advance; (b) Automatic Cutting-in of the next restrictive aspect when the LED aspect of the main signal fails; (c) Interlocking equipments and circuits for level crossings and points; (d) The circuits that establish the direction of traffic in Single Line and prevent clearing of conflicting signals on sections provided with Automatic block Signalling on Single Line; (e) Axle Counter resetting circuits, if provided. 20.3.4 All failures reported by the Loco Pilots/Motor man shall be promptly attended. 20.3.5 Track Circuits/Axle Counter Maintenance (a) Adequate precautions should be taken after every track renewal work to ensure proper working of track circuits/Axle counters. (b) Provisions contained in Chapter 17 of SEM shall be adhered to. 20.3.6 Power Supply: Provisions contained in Chapter 16 of SEM shall be adhered to. 20.3.7 Cables: Provisions contained in Chapter 15 of SEM shall be adhered to. Section 4: Modified Semi-Automatic Signalling Working 20.4.1 (a) Under special instructions, one of the automatic stop signals between two stations in the automatic block signalling territory on Double Line may be made as modified semi-automatic stop signal in each direction. During abnormal conditions like fog, bad weather impairing visibility, Modified Semi- Automatic Signal may be worked by extinguishing ‘A’ marker in the manner prescribed under special instructions and this section shall also ensure that the ‘A’ Marker of the Advanced Starter Signal of the station in rear and Home signal of the station in advance shall also be extinguished. (Provisions as per para 9.01 of GR shall be ensured.) (b) Interlocking will be such that during mid-section Modified automatic signal working with ‘A’ marker extinguished, not more than two trains, one on either side of this modified stop signal, will be ensured by the signalling system between two stations in any given direction at any given point of time. The mid-section modified semi-automatic stop signal shall when ‘OFF’ depict the aspect (Green or Double Yellow etc.) based on the aspects and number of Automatic signals (including any other signal) between this signal and the Home signal of the receiving station. Chapter 20: Automatic Block Signalling Page 425 of 530 (c) Such Gate signal, which has been converted as mid-section modified Semi- Automatic Signal, is provided with ‘A’ & ‘AG’ markers. During modified Automatic Signalling working, these markers will be extinguished. (d) During normal conditions, mid-section modified semi-automatic stop signal shall work as normal automatic stop signal. (e) The mid-section Modified automatic signal shall be painted with alternate blue and white strips in between. (f) The relevant indications whether the signal is in normal automatic mode or modified semi-automatic mode shall be available to the station masters at both the ends. Note: This chapter has under mentioned Annexure S.No. Annexure No. Description 1 20-A1 Automatic Signalling Scheme with OFC, MSDAC & OC Note: This chapter has under mentioned Drawings in Appendix II S.No. Drawing No. Description 1 20-D1 Automatic Signalling Scheme with OFC, MSDAC & OC (Sheets-3) Chapter 20: Automatic Block Signalling Page 426 of 530