Chapter 17: Train Detection - Track Circuits & Axle Counters PDF

Chapter 17: Train Detection - Track Circuits & Axle Counters Section 1: Track Circuits 17.1.1 Track Circuits General (a) A closed type track circuit shall be provided to prove the clearance of rail track. (b) Double rail track circuits shall be...

Chapter 17: Train Detection - Track Circuits & Axle Counters Section 1: Track Circuits 17.1.1 Track Circuits General (a) A closed type track circuit shall be provided to prove the clearance of rail track. (b) Double rail track circuits shall be provided on non-RE areas. In RE areas, Single Rail track circuit for D.C track circuit and Double Rail track circuit for AFTC shall be used. (c) Minimum Length: The length of a track circuit shall not be less than the maximum wheel base of any vehicle. The Track circuits shall cover at least two rail lengths (26 meters). (d) Series Connection of Tracks: The various portions of tracks in a line shall, as far as possible, be connected in series. (e) Track relays shall be of an approved design. 17.1.2 Permanent Way Requirements of Track Circuits (a) Glued Joints or Insulation Joints of approved type shall be provided for defining boundary of track circuit. In all future works of track circuiting, glued insulated joints should be provided. Glued joint should be tested before insertion. Note: Where ever Insulation Joint is mentioned, it also applies to glued insulated joint. (b) Where staggering cannot be avoided the distance between staggered joints shall not exceed the minimum wheel base of the vehicles. (c) Rail ends of glued/insulated joints shall be square and true. All rough edges and burrs shall be removed from bolt holes. Battered ends shall be put right and the gap between the rails should be equal to the thickness of the end post. (d) Fish bolts at the joints must be kept tight and the sleepers well packed in the vicinity of the joints. (e) Proper drainage should be ensured so as to avoid flooding of tracks during rains, particularly in yards where watering of coaches is done and in water columns. It would be desirable to provide washable concrete aprons on platform lines at originating stations, in track circuited areas. (f) Ballast shall be kept clean throughout the track-circuited section and care should be taken to see that the ballast is kept clear off the rails and rail fastenings. The clearance from the foot of the rail should not be less than 50 mm. Well screened ballast right up to the formation level shall be provided. Chapter 17: Train Detection Track Circuits & Axle Counters Page 331 of 530  (g) Rail ends shall be kept free from brake-dust, dirt, sand, rust, other foreign materials etc. All rough edges and burrs at rail ends must be removed. (h) To avoid crushing of end posts of insulated rail joints due to creep, at least one rail length on either side of insulated joint should be provided with anti creep devices. (i) Rail screws should preferably be used in place of dog spikes at insulated joints. Note: The requirements mentioned in the para no. 17.1.2(a) to (i) are covered in the chapter II, Part "H" of Permanent Way Manual. (j) Wooden sleepers, concrete sleepers or any other approved type of insulated sleepers shall be provided for track circuiting. Concrete sleepers where used, shall have a minimum resistance of 500 ohms between insert to insert. (k) Where short welded rail panels are used, SWR shall not butt against insulated joint. Two rail lengths of 13 meters/12 meters shall be interposed to isolate short welded rail from insulated joint. This standard length of rails shall be anchored effectively to arrest movement in either direction. (l) In case of turnouts and crossings, insulated stretchers, insulated gauge tie plates and insulated crossing plates shall be provided as per approved drawings. (m) GFN liners shall be provided in the track circuited area using concrete sleepers. (n) Track circuited area shall be free of vegetation. Only insulated trolleys shall be used. Section 2: Installation of DC Track Circuits 17.2.1 Location of Track Relays (a) Track relays shall be located at the entry end of the track circuits wherever possible. (b) Where track relays cannot be located in the cabin/Relay Room, they shall be housed in locations of an approved type. (c) Where relays are likely to be subjected to vibration, suitable anti-vibration measures may be provided. They shall be mounted on shock absorbers such as rubber pad, foam etc. (d) Connections between the track relays and track repeating relays shall be made in accordance with the approved wiring diagram and must invariably incorporate both cross protection and double cutting arrangements. (e) The feed and relay ends shall be connected by separate and individual cables. Chapter 17: Train Detection Track Circuits & Axle Counters Page 332 of 530  (f) Relay End and Feed End of the track circuit should be located at the boundaries of the track circuit. (g) Loading of Track Relay Contacts: All the contacts of the track relay shall be loaded as far as possible. Where spare contacts are available, they shall be connected in parallel to the loaded contacts. 17.2.2 Jumper Connections (a) Jumper connections shall normally be so made that the whole of track circuit is in series excluding traction return rail. When the rails of a track circuit are in parallel, care shall be taken that the jumper connections are effective. (b) Jumper connections, preferably duplicated, shall be so arranged that they are as far as possible protected from damage. (c) All connections to the track shall be of sufficient length and allow for rail creep. Connections shall be firmly fitted to the web of the rail. (d) For short jumpers, galvanized iron wires and for long jumpers cables, may be used. Where galvanized iron jumper is used, duplicate jumpers shall be run. The cross section of galvanised iron wire shall not be less than 8 SWG. Where cables are used, the size shall not be smaller than 7/0.750 mm. (e) The lead wires used for connecting the feed set to the feed end boot leg/track lead Junction Box (JB) and the track relay to the relay end boot leg/track lead JB shall preferably be of copper conductor having a minimum cross section of 2.5 sq.mm. Lead wires crossing the track should be protected through suitable means. (f) Track lead JB shall be clear of ballast. (g) The Feed as well as Relay Ends +ve & -ve leads shall be connected by using individual 2 x 2.5 sq.mm cable, duly paralleled at each end. 17.2.3 Bond Wires and Rope Wires (a) Bond wires/Rope wires shall be of an approved type. Duplicate wires shall be installed close to the fish plate, it is desirable to use bond wire clips for securing the bond wire. (b) Bond holes shall be drilled with a twist drill and the bonds driven-in immediately. The wires may be fixed by using channel pins in the holes or by brazing/welding. (c) The resistance of rail and bonding per 1000 meters of track shall not exceed 0.5 ohm for track circuits longer than 700 meters. A rail and bond resistance up to 1.5 ohm per 1000 meters of track may be allowed for length of track circuit less than 700 meters. (d) The rail bonding and connections to the relay and feed set shall be made according to approved drawings. (e) The lugs of impedance bond connections shall be firmly fixed by pressing rivets into the web of the rail with a bond press. Chapter 17: Train Detection Track Circuits & Axle Counters Page 333 of 530 17.2.4 Track Circuit Terminations (a) For track circuited points or lines in a station, track circuit termination shall be provided sufficiently before the Fouling Mark* so as to avoid infringement to the standard dimension by any portion of the vehicle. The distance between track circuit termination and Fouling Mark shall not be less than 3 meters. (b) Cut Section (Fed Over) Arrangement of Track Circuits: Where cut section track circuits are installed, the track relays concerned, when de- energized, shall open the track feed and shunt the track circuit. *Note: Fouling marks should be fixed at the point at which the spacing between the tracks, begin to reduce to less than the minimum as laid down in the schedule of dimensions, i.e. not less than 4.265 m for existing yards and 5.3 m for new yard lines. (Para No. 650 of IRPWM) 17.2.5 Insulated Rail Joints (a) All components of insulated joint shall be of approved type and shall conform to RDSO drawings. The components shall be installed using correct sizes and combinations. (b) Insulated Rail Joints shall, as far as possible, not be provided on the outer rail in curves. Insulated rail joints shall be so placed to minimise dead zone (where a standing vehicle is not detected). (c) Before an insulated joint is installed, it shall be ensured that permanent way requirements stipulated in Para no. 17.1.2 are complied with. The installation of glued rail joints shall be done by Civil Engineering Department. The installation of Nylon insulated rail joints shall be done in accordance with RDSO's booklet No.STS/E/IRJ/lMI - Installation and Maintenance Instructions for Nylon insulated rail joint. Particular attention shall be paid to the following: (i) Hammer driving offish-bolt shall be avoided, as this will damage nylon bushes, If the rail hole and the fishplate holes are in their proper position and alignment, the fish bolt can be easily inserted by hand pressure. (ii) If an end-post, projects above the rail at the ends, it shall be trimmed and brought to the level of the rail table, especially when inserted between the worn-out rails, before first wheel of a train passes over it. (iii) The distance of 13 meters between the insulated Block Joint or Detection Point and the starter Signal can be reduced from 13 meters to 3 meters for Signaled movements. The insulated Rail Block Joint or Device of Axle Counter or Joint Less Track Circuit shall be so fixed that their boundary shall be within zero to 3 meters in advance of the starter signal. (iv) In the case of point track circuits, the insulation joint shall not be in the stock rail joint but in the rail joint ahead of it wherever feasible. (d) Only 'J' type clip shall be used in glued joint portion of track. Chapter 17: Train Detection Track Circuits & Axle Counters Page 334 of 530 17.2.6 Track Indicators: At Track circuited stations where track indicators are provided, the following arrangements shall be made: (a) At Panel Interlocked/Route Relay Interlocked Stations (i) Normally, the track indicators would show no light when the line is unoccupied. When action is initiated to set the route for taking off a signal and the concerned route is set, the track indicator light for the route shows Yellow/White, if unoccupied. However, if any portion of the track circuited area is occupied, a "RED" indication is shown on the panel diagram, irrespective of the route being set or not. (ii) The track indicators would show white/yellow light when the track is cleared after the intended movement is completed till the route signal button or switch is restored to normal unless the panel interlocking/route relay interlocking is provided with Automatic Route Release facility in which case the indication would be lit until the sub route/sectional route/ route is released. (iii) In case of berthing track having multiple track circuit sections, it is desirable to show individual indications of each track circuit on the panel. (b) At Other Stations: The indicator shall show yellow/white Light when the line is unoccupied and RED when line is occupied. 17.2.7 Limiting resistance of DC track circuits shall be adjustable and of an approved type. 17.2.8 Track Relays (a) DC track relays of approved design shall be used. In future installations, only plug in type track relays (9 ohm) shall be used, both in Non-RE & RE areas. (b) Q series track relay must be used in conjunction with Q series slow to pick up relay as a repeater relay. (c) Excitation of DC Track Relay: The relay shall be excited at minimum 125% of its rated pick up voltage under minimum ballast resistance condition and normal working voltage of the supply. The maximum excitation shall not exceed 235% for QBAT Relays and 300% for other plug- in type relays. 17.2.9 Maximum Length of Track Circuits: Maximum length of track circuit under different track parameter conditions shall not exceed the limits as given in the following table. Maximum length of track circuit under different track parameter conditions shall not exceed the limits as given in the table below. Chapter 17: Train Detection Track Circuits & Axle Counters Page 335 of 530  Min. Max. Section Ballast TSR Length of Sl. RE/ Type of Track Relay to Sleeper (Yard/ Resistance in Track No. Non-RE be used Block) in Ohm per Ohms Circuit in Km meters 1 Non-RE *Wooden/PSC Block 4 0.5 1000 QT type 9 ohm 2 Non-RE *Wooden/PSC Yard 2 0.5 670 -do- 3 RE *Wooden Block 4 0.5 450 QT 9 ohms AC immune 4 RE *Wooden Yard 2 0.5 450 -do- 5 RE PSC Block 4 0.5 450 -do- 6 RE PSC Yard 2 0.5 350 -do- 7 RE PSC Yard 2 0.5 750 QBAT in conjunction with QSPA1 with B type choke at relay end (* where existing) 17.2.10 Track Feed (a) Approved type of secondary cells shall be used for feeding track circuits. (b) Secondary cell(s) shall be used along with battery charger/solar panel of adequate capacity. (c) Separate feed shall be provided for each track circuit. Section 3: Maintenance of DC Track Circuits 17.3.1 General: Track circuits shall be so maintained that: (a) There is always a good connection between power feed and track, Relay and track and also between adjoining rails, through jumpers and rail bonds. (b) The ballast resistance always remains high and does not fall below prescribed minimum values. (c) The limiting resistance shall be as high as possible. (d) The insulating joints are of high resistance. (e) The surface of rail is clean and is free of dust, sand and foreign materials. (f) The circuit is properly energised during wet weather on minimum ballast resistance conditions and during dry weather on maximum ballast resistance conditions. The track circuit shall not be over-energised to such an extent that the shunting value drops below 0.5 ohms for all types of track circuits. These values shall be obtained irrespective of whether the track is provided with concrete sleepers or wooden sleepers. (g) The connection of DC track relay shall be quarterly interchanged to prevent permanent magnetisation. Chapter 17: Train Detection Track Circuits & Axle Counters Page 336 of 530