RT Railway Signaling and Telecommunication PDF

UNIVERSITY OF MINES AND TECHNOLOGY (UMaT), TARKWA, GHANA SCHOOL OF RAILWAYS AND INFRAUSTRUCTURE DEVELOPMENT (SRID), ESSIKADO -TAKORADI COURSE: Railway Signalling and Telecommunication...

UNIVERSITY OF MINES AND TECHNOLOGY (UMaT), TARKWA, GHANA SCHOOL OF RAILWAYS AND INFRAUSTRUCTURE DEVELOPMENT (SRID), ESSIKADO -TAKORADI COURSE: Railway Signalling and Telecommunication COURSE CODE: RT 132 COURSE INSTRUCTOR: EUNICE E. ATTAFUAH (PE-GhIE) ES 372– Hydrology EMAIL: [email protected] PREPARED BY: 1. ENGR DR EZEKIEL MARTEY 1 2. E. OBU  Outline Sighting Board Stop Signal Outer Signal Home Signal Routing Signal Starter Signal Advanced Starter Signal Signalling System Interlocking System  A sighting board is an indication to the driver that he or she is approaching the first stop signal of a railway station. Sighting The function of a sighting board is to allow the driver to estimate the location of the next stop signal from the current location so that he/she starts applying brakes in case the first stop signal is in an ‘on’ position. Board As the requisite braking distance of goods trains and Rajdhani trains is greater than that of the passenger trains, the sighting boards for goods trains and Rajdhani trains are located farther and their design is different from that of sighting boards meant for passenger trains Sighting Board Distance Stop The various types of signals with reference to their location on a station are discussed in detail below. Signal  This is the first stop signal at a station, which indicates the entry of a train from a block section into the station limits. This signal is provided at an adequate distance beyond the station limits so that the line is not obstructed once the permission to approach has been given. It is provided at a distance of about 580 m from the Outer home signal. The signal has one arm but has a warner signal nearly 2 m below on the same post. When the outer signal is in the ‘on’ (or stop) position, it Signal indicates that the driver must bring the train to a stop at a distance of about 9 m from the signal and then proceed with caution towards the home signal. If the outer signal is in the ‘off’ (or proceed) position, it indicates that the driver does not need to reduce the speed of the train if the home signal is also in the ‘off’ (or proceed) position, which is indicated by the ‘off’ position of the warner. As the outer signal controls the reception of trains, it comes under the category of reception signals.  After the outer signal, the next stop signal towards the station side is a home signal. It is provided right at the entrance of the station for the protection of the station limits. Home The signal is provided about 190 m short of the points and crossings. The arms provided on a home signal are generally as many as the number of reception lines in the station yard. Signal When a home signal is in the ‘on’ (or stop) position it indicates that the train must come to a halt short of the signal. In the ‘off’ (or proceed) position, it indicates that the particular line is free and the train is permitted to enter cautiously. The home signal also comes in the category of reception signals.  The various signals fixed on the same vertical post for both main and branch lines are known as routing signals. These signals indicate the route that has been earmarked for the reception of the train. Generally the signal for the main line is kept at a higher level than that for the loop line. Routing It is necessary for the driver of a train approaching a reception signal to know the line on which his or her train is likely to be received so that he or she can regulate the Signal speed of the train accordingly. In case the train is being received on the loop line, the speed has to be restricted to about 15 km/h, whereas if the reception is on the main line a higher speed is permissible. The various positions of the routing signal for a station with an outer signal, a home signal, and a warner signal are shown below  The starter signal is a stop signal and marks the limit up to which a particular line can be occupied without Starter infringing on other lines. A separate starter signal is provided for each line. The starter signal controls the movement of the train when it departs from the station. Signal The train leaves the station only when the starter signal is in the ‘off’ (or proceed) position. As this signal controls the departure of a train, it comes under the category of departure signals. Advanced This is the last stop signal provided for the departure of trains from a station. The signal is provided about 180 m beyond the Starter outermost points or switches and marks the end of the station limits. A block section lies between the advanced starter signal of one station and the outer signal of the next station. Signal No train can leave the station limits until and unless the advance starter is lowered.  Signalling System The entire signalling system can be classified into two main categories. (a) Mechanical signalling system (b) Electrical signalling system In addition to these two main categories of signalling systems, a solid-state signalling system is also in use. Each system of signalling comprises (a) Operated units such as signals and points (b) A transmission system such as single- or double-wire transmission or electrical transmission (c) Operating units such as levers and press buttons (d) Monitoring units such as detectors, treadle bars, and track circuiting four main components.  Mechanical Signalling System These systems rely on physical mechanisms to convey signals to train drivers, typically through the use of levers, wires, rods, and semaphore arms. The signals used in a mechanical signalling system are semaphore signals. These signals are operated by means of either a lower quadrant or an upper quadrant signalling system. Lower This system of signalling was designed so that the semaphore arm of the signal could be kept either Quadrant horizontal or lowered. The lower left-hand quadrant of a circle is used for displaying a semaphore indication to the driver of a train. Signalling This concept was possibly developed based on the left- hand driving rules applicable on roads in the UK and in India. System  In lower quadrant signalling, the semaphore arm of the signal can only take two positions, namely, horizontal or lower; it is not possible to include a third position for the Upper semaphore arm, such as vertically downward position, due to design as well as visibility problems, since as the semaphore arm would, in that case, be super imposed on Quadrant the signal post. Due to this limitation, the upper quadrant system was developed, which can display more than two aspects. Signalling In this system, it is possible to incorporate three positions of the semaphore arm, namely, (a) horizontal, (b) inclined at an angle of about 45° above the horizontal level, and (c) vertical, i.e., inclined at an angle of 90° System above the horizontal level. See Fig. 31.14. The positions of the arm, the corresponding indications, and their meanings are listed in  Points Points are set mechanically and are kept in locks and stretcher bars. The mechanical arrangement for operating them includes a solid rod with a diameter of 33 mm running from the lever provided in the cabin and connected to the point through cranks. Owing to transmission losses, the operating points with rods is restricted to a specified distance from the cabin. The following devices are used to ensure that the points are held rigidly in the last operated position under a moving train and to ensure absolute integrity of the same. (a) Point locks to hold the point in the required position and to rigidly hold the point in the position of the last operation. (b) Detectors to detect lock and switches. (c) Lock bars to prevent the movement of points when a train is passing over them.  Points Locks A point lock is provided to ensure that each point is set correctly. It is provided between two tongue rails and near the toe of the switch assembly. The point lock consists of a plunger, which moves in a plunger casing. The plunger is worked by means of a plunger rod, which is connected to the signal cabin through a lock bar. Additionally, there are a set of stretcher blades and each blade is connected to one of the tongue rails. Each blade has two notches and they move inside the plunger casing along with the tongue rails. When the points are set correctly for a particular route, the notch in the stretcher blade rests in its proper position and the plunger rod enters the notch, locking the switch in the last operated position.  Detectors Detectors are normally provided for all the points for the following reasons. (a) To detect any defect or failure in the connection between the points and the lever as well as any obstruction between the stock and the tongue rail. (b) To ensure that the correct signal, which corresponds to the point set, is lowered. (c) A detector can be mechanical or electrical. In the case of a mechanical detector, the point is held in the position of the last operation, which is achieved de facto by virtue of its design.  Lock bar A lock bar is provided to make it impossible to change the point when a train is passing over it. The lock bar is made of an angled section and its length is greater than that of the longest wheel base of a vehicle. Short revolving clips are provided to hold the lock bar in place on the inside face of one of the rails. The length of a lock bar is normally 12.8 m for BG and 12.2 m for MG sections  Interlocking Interlocking is a device or a system meant to ensure the safety of trains. With the increase in the number of points and the signals and introduction of high speeds, it has become necessary to eliminate human error, which would otherwise lead to massive losses of life and property. The points and signals are set in such a way that the cabin man cannot lower the signal for the reception of a train unless the corresponding points have been set and locked. The signal is thus interlocked with the points in a way that no conflicting movement is possible and the safety of trains is ensured. Interlocking can, therefore, be defined as an arrangement of signals, points, and other apparatus so interconnected by means of mechanical or electrical locking that they can be operated in a predetermined sequence to ensure that there is no conflicting movement of signals and points and trains run safely. The signal and interlocking system is so designed that the failure of any equipment results in the turning on of the signal, thus ensuring train safety. Methods There are basically two methods of interlocking Key interlocking Key interlocking is the simplest method of interlocking and still exists on branch lines of small stations on Indian Railways. The method involves the manipulation of keys in one form or the other. This type of interlocking is normally provided with standard I interlocking with a speed limit below 50 km/h. Mechanical interlocking Mechanical interlocking or interlocking on lever frames is an improved form of interlocking compared to key locking. It provides greater safety and requires less manpower for its operation. This method of interlocking is done using plungers and tie bars. The plungers are generally made of steel sections measuring 30 cm × 1.6 cm and have notches in them. The tie bars are placed at right angles to the plungers and are provided with suitably shaped and riveted pieces of cast iron or steel that fit exactly in the notches of the tappets.  Summary Signals are used to regulate the movement of trains and interlocking ensures the safe working of signals. There are many different kinds of signals and each one of them gives vital information regarding track conditions. These signals have separate indicators for day and night. There are various methods of interlocking starting with the simple key method to the advanced automatic train control system. With advancement in signalling as well as interlocking systems, it has become possible to run trains at smaller intervals, ensuring optimum use of the track capacity.