SIGNALING FUNDAMENTALS IN RAILWAYS
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Deals with type of signals, railway interlocking,block method, metro track circuits
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SIGNALING FUNDAMENTALS IN RAILWAYS
- 2. Elements of a Signaling Yard • Signals • Track Circuits • Points 2
- 3. CLASSIFICATION OF SIGNALS SIGNALS FUNCTION PURPOSELOCATION OPERATION STOP WARNER DISC COLORED OUTER HOME STARTER ADVANCE ROUTING REPEATER CALL ON HAND FIXED DETONATING 3
- 4. STOP SIGNAL The length and width of arm vary from 120-167 cm and 23-35 cm respectively The outer end of the arm is about 2.45 cm Broader than that of the hinged end It is placed on the left hand side of the direction of movement of train The side of the arm facing the driver is painted red with white band near the end The other side is painted white with black bands 7.67 m 4
- 5. WARNER SIGNAL These signals are similar to stop signals with the exception that at their free end V notch is cut to distinguish it from stop signals Signals placed ahead of the stop signals to warn the driver before entering the station Warner signals are placed generally at about 540 m away from the stop signals SIGNAL INDICATIONS Inclined Position: Track is clear and driver can proceed with confidence Horizontal Position: Deriver can take his train upto Stop signal cautiously 5
- 6. SEMAPHORE AND WARNER SIGNAL Semaphore and Warner Signals can be placed on same the pole. Semaphore is placed on top and the Warner at about 2 m below it SIGNAL INDICATIONS Both in Horizontal Position: Neither approaching section nor next block is clear When Semaphore is inclined and Warner Horizontal proceed with precaution i.e. section up to station is clear but not the block beyond. Both in Inclined Position: Track is clear and proceed with confidence SEMAPHORE WARNER 6
- 7. SEMAPHORE Operation Time Position Of Arm Position Of Signal Indication Given Horizontal Arm ON Stop Inclined At 60o or 45o OFF Proceed Red Light ON Stop Green Light OFF Proceed Day Time Night Time STOP SIGNAL
- 8. DISC SIGNAL These are shunting signals which are used for low speed movements during shunting operations. They consist of circular discs with red bands on white background SIGNAL INDICATIONS When Red band is Horizontal: Stop When Red band is Inclined: Proceed 8
- 10. ASS SSHS OS OHS SIGNALS ACCORDING TO LOCATION INTERLOCKING STANDARDS STANDARD-I Applicable for station for train speeds upto 50 kmph STANDARD-II Applicable for station for train speeds upto 75 kmph STANDARD-III Applicable for station for unrestrictedspeeds 10
- 11. ROUTING SIGNAL When many branch lines diverge in different directions from the main line, it is very difficult to provide individual signal for each line at the divergent point. In such situations various signals for main line and branch lines are fixed on the same vertical post. These signals are called routing signal. Generally signal for main line is kept higher than those for branch lines 11
- 12. Track Circuits • Track Circuits are devices that convey the presence of a train on a specified length of a track • There are many types of track Circuits available as follows: 1. DC Track Circuits 2. High Frequency Track Circuits (HFTC) 3. Audio Frequency Track Circuits (AFTC) 4. Axle Counters ( Digital & Analog ) 12
- 13. Device Electronics Tracks Relay Contacts Available for other Higher Level Devices such as SSIs 13
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- 23. Points • Points also referred to as switches are mechanical devices in the railway to change the path that trains may take through a junction. The switch positions are called normal and reverse • These mechanical switches can be manually or Electrically Operated to Change From Normal to Reverse or Vice-Versa 23
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- 26. REFERENCES • Indian Railways Year Book 2002-2003 • http://www.railway-technical.com/sigtxt2.shtml • http://www.eng.ox.ac.uk/InvensysUTC/other%20research/railway- points-machine 26
- 27. THANK YOU 27
Editor's Notes
- HISTORY OF RAILWAY SIGNALLING 1825: FIRST RAILWAY LINE FOR GOODS TRAFFIC WAS OPENED BETWEEN DARLINGTON TO STOCKTON(U.K.) UNIFORMED MEN ON HORSES GUIDED THE TRAIN 1830 : FIRST PASSENGER TRAIN BETWEEN LIVERPOOL AND MANCHESTER POLICEMAN WERE POSTED AT FIXED INTERVALS 1838 : POLICEMEN WERE REPLACED BY FIXED MECHANICAL SIGNALS 1853 : FIRST TRAIN SERVICE INTRODUCED ON INDIAN RAILWAYS, SEMAPHORE SIGNALS WERE USED.
- Signaling: By which the movement of the train is controlled Increasing line capacity Providing systems on safe principles. Preventing conflicting movements of trains.
- INTERLOCKING: An interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. Interlocking system use mechanical devices both to operate the signaling device and ensure their safe operation. Electrical relay interlocking were used. RRI means the station is interlocked and worked with control panel located in RRI office. Control panel has a geometrical layout of the entire yard controlled by route interlocking. Indication Panel is the points setting of the route approach locking and provides in front of the SM(panel).
- A term used for the logical relationships between physical entities in the railway yard such as points, signals, track circuits, and so on. In SSI, this is programmed in the Software; in relay-based interlocking this is hardwired into the relay circuitry, and in ground-frame interlocking it is manifest in the mechanical linkages between physical components RRI Stands for Route Relay Interlocking. An Interlocking System When built completely using Electro mechanical relays is called as Route Relay Interlocking System . SSI Stands for Solid State Interlocking. An Interlocking System When built using Electronics replacing traditional Mechanical Levers and Electro mechanical relays is called as Solid state Interlocking System. SSIs are required to replace the existing RRI and PI Systems Since the traditional systems are very expensive and difficult to maintain because of the huge number of relays and mechanical levers used. SSIs are a better solution to the older systems since they are costing only ¼ the cost of RRI or PI and the maintenance cost is negligible and are easy to maintain.
- Types of Signalling Systems in Railways Time Interval Method Trains are Spaced Over an length of a track in such a way that , if the first train stops, the following train driver should be able to stop the train in sufficient distance without colliding with the first one. This type is used where traffic is less and weight of the trains are less, e.g: Trams This Type of System cannot be used in Passenger rails since weight and traffic is High Space Interval Method In this method of “Control Over Movement”, the length of the track is divided in to sections called Blocks. The Entry of a train in to the ‘Block’ is controlled in such a way that only when it is free, a train can be allowed to enter it. This means that between two consecutive trains , there is definite space interval.
- If the signal is red the trainstop is raised and, if the train attempts to pass it, the arm strikes a "tripcock" on the train, applying the brakes and preventing motoring. The Overlap If a line is equipped with a simple ATP which automatically stops a train if it passes a red signal, it will not prevent a collision with a train in front if this train is standing immediately beyond the signal. If Train 2 was to overrun Signal A2, the raised trainstop (shown here as a "T" at the base of the signal) would trip its emergency brake and bring it to a stand within the overlap of Signal A2.
- Although it is protected by Signal A123 showing red, the driver of Train 2 may see the green signal A121 behind Train 1 and could "read through" or be confused under the "stop and proceed" rule.
- So, where there is a possibility of a green signal being visible behind a train, overlaps are track circuited as shown in Fig. 5. Although there is no train occupying the block protected by Signal A121, the signal is showing a red aspect because the train is occupying the overlap track circuit or "replacing" track circuit, as it is sometimes called. This will give rise to two red signals showing behind a train whilst the train is in the overlap. The block now has two track circuits, the "Berth" track and the "replacing" track.
- Many railways use an "Absolute Block" system, where a vacant block is always maintained behind a train in order to ensure there is enough room for the following train to be stopped if it passes the first stop (red) signal. In Figure 6, in order for Signal A125 to show a proceed aspect (green), the two blocks ahead of it must be clear, with Train 1 completely inside the block protected by Signal A121.
- Types of Signalling Systems in Railways Time Interval Method Trains are Spaced Over an length of a track in such a way that , if the first train stops, the following train driver should be able to stop the train in sufficient distance without colliding with the first one. This type is used where traffic is less and weight of the trains are less, e.g: Trams This Type of System cannot be used in Passenger rails since weight and traffic is High Space Interval Method In this method of “Control Over Movement”, the length of the track is divided in to sections called Blocks. The Entry of a train in to the ‘Block’ is controlled in such a way that only when it is free, a train can be allowed to enter it. This means that between two consecutive trains , there is definite space interval.
- Track circuits work by running a circuit using the rails to connect a power source at one end of the block with a relay at the far end. The relay and power source are connected to each rail by cables. As long as the circuit is complete, low voltage power flows down one rail, through a relay, and returns to the power source via the other rail. If the circuit is complete, the relay will be energized, which keeps signals in the "clear" position. If the circuit is broken, the system fails in a safe manner. A broken rail or a failed power source causes the relay to become de-energized and report the section of track as occupied. An unoccupied track circuit is shown in diagram "A". The power source is located at the number "1", with the relay shown at number "2". The completed circuit is shown in green on the diagram. A train is detected because it shorts the circuit. In railroading, this is called "shunting" the circuit. When a train enters a block, the metal wheels and axle conduct the circuit as a short cut which bypasses the relay. This de-energizes the relay, which causes signals to report the block as occupied. This is reflected in diagram "B": "1" shows the power source, "3" is the wheel/axle of a train, and "4" is the de-energized relay.
- Metro's track circuit system ("C") is a little more advanced. In Metro's case, each block has a relay on each end called a "Wee-Z bond". These bonds are split between blocks. Each one acts as a transmitter for one block and a receiver for the adjacent block. If a given block's transmitter ("5") and receiver ("6"), located on opposite ends of the block, have a complete circuit, the block is considered unoccupied, and therefore safe for trains to enter. If, however, a train is in the block, the transmitter/receiver circuit is broken, stopping subsequent trains from entering the block. Speed commands are sent to the train in the block through the transmitter bond. The commands are sent as high-frequency audio waves through the running rails. The ATC computer uses data from the blocks to determine which blocks are occupied, and therefore how to space trains.