Railway Signalling 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  Signalling Classification of Signalling Permissive Signal Coloured light Signal Outline Stop Signals Signalling Systems Electrical Signalling System Mechanical Signalling System  Have you come across these signs along the road?  What is Signaling Signaling consists of the systems, devices and means by which trains are operated efficiently and tracks are used to maximum extent, maintaining the safety of the passengers, the staff and the rolling stock A fundamental of signal systems is that in the event of an equipment failure, the safety of trains is assured The driver interprets the signal's indication and acts accordingly In simple terms, railway signaling is a system of traffic lights for trains Introduction Objectives of Signalling Classification of Signals Classification of Signals Signals required at stations  Audible Signals Audible signals such as detonators and fog signals are used in cloudy and foggy weather when hand or fixed signals are not visible. Their sound can immediately attract the attention of drivers. Detonators contain explosive material and are fixed to the rail by means of clips. In thick foggy weather, detonators are kept about 90 m ahead of a signal to indicate the presence of the signal to the drivers. Once the train passes over the detonators thereby causing them to explode, the driver becomes alert and keeps a lookout for the signal so that he/she can take the requisite action.  Visible Signals These signals are visible and draw the attention of the drivers because of their strategic positions. Hand signals These signals are in the form of flags (red or green) fixed to wooden handles that are held by railway personnel assigned this particular duty. Fixed signal These are firmly fixed on the ground by the side of the track and can be further subdivided into caution indicators and stop signals. Caution indicators These are fixed signals provided for communicating to the driver that the track ahead is not fit for the running the train at normal speed. These signals are used when engineering works are underway and are shifted from one place to another depending upon requirement. Stop signals These are fixed signals that normally do not change their position. They inform the drivers about the condition of the railway line lying ahead.The stop signals normally used on railways are semaphore signals, coloured light signals, and other such signals. Types of Fixed Signals Semaphore signals The word ‘semaphore’ was first used by a Greek historian. ‘Sema’ means sign and ‘phor’ means to bear. A semaphore signal consists of a movable arm pivoted on a vertical post through a horizontal pin as shown below.  Semaphore signal The arm of the signal on the side facing the driver is painted red with a vertical white stripe. The other side of the signal is painted white with a black vertical stripe. The complete mechanical assembly of the signal consists of an arm, a pivot, a counterweight spring stop, etc., and is housed on top of a tubular or lattice post. In order for the signal to also be visible at night, a kerosene oil or electric lamp, operated through a twilight switch, is fixed to the post. A spectacle is also attached to the moving signal arm, which contains green and red coloured glasses. The red glass is positioned at the upper end and the green glass is positioned at the lower end of the spectacle so that the red light is visible to the driver when the arm is horizontal and the green light is visible when the arm is lowered. The semaphore signal can be used as a stop signal as well as a warner signal. Positions of Semaphore Signals With reference to lower quadrant signalling, the colour aspects of a semaphore signal and their corresponding indications when the arm of the signal is in two distinct positions are shown below in the figure and table Semaphore Signals The signals are designed to These signals are operated Semaphore signals are be fail-safe so that if there by hand levers or buttons normally provided as outer is any failure in the located in a central cabin, signals, home signals, working of the equipment, which is normally provided starter signals, advanced they will always be in the near the station master’s starter signals, and warner stop position. office. signals.  Permissive signal—warner or distant signal In order to ensure that trains speed up safely, it is considered necessary that warning be given to drivers before they approach a stop signal. This advance warning is considered necessary, otherwise the drivers may confront a ‘stop signal’ when they least expect it and take abrupt action, which can lead to perilous situations. A warner or distant signal has, therefore, been developed, which is to be used ahead of a stop signal and is in the form of a permissive signal that can be passed even in most restricted conditions. In the case of a stop signal, the driver has to stop the train when it is in the ‘on’ position, but in the case of a permissive signal, the driver can pass through even when it is in the ‘on’ position. The most restrictive aspect of a permissive or warner signal is that the driver is not supposed to stop at the signal even when it is in the ‘on’ position. The warner signal is similar to a stop signal except that the movable arm is given the shape of fish tail by providing a V-shaped notch at the free end; the white strip is also V-shaped. Position of warner arm or distant signal  These signals use coloured lights to indicate track conditions to the driver both during the day and the night. In order to ensure good visibility of these light Coloured signals, particularly during daytime, the light emission of an electric 12-V, 33-W lamp is passed through a combination of lenses in such a way that a parallel beam of focused light is emitted out. light This light is protected by special lenses and hoods and can be distinctly seen even in the brightest sunlight. signals The lights are fixed on a vertical post in such a way that they are in line with the driver’s eye level. The system of interlocking is so arranged that only one aspect is displayed at a time. Coloured light signals are normally used in suburban sections and sections with a high traffic density.  Coloured light signals Coloured light signals can be of the following types. (a) Two-aspect, namely, green and red (b) Three-aspect, namely, green, yellow, and red (c) Four-aspect, namely, green, yellow (twice), and red. Coloured light signals Calling-on signal This consists of a small arm fixed on a home signal post below the main semaphore arm. When the main home signal is in the horizontal (on) position and the calling-on signal is in on inclined (off) position, it indicates that the train is permitted to proceed cautiously on the line till it comes across the next stop signal. Thus the calling-on signal is meant to ‘call’ the train, which is waiting beyond the home signal. The calling-on signal is useful when the main signal fails, and in order to receive a train, an authority letter has to be sent to the driver of the waiting train to instruct him/her to proceed to the station against what is indicated by the signal. In big stations and yards, the stop signals may be situated far off from the cabin and the calling-on signal expedites the quick reception of the train even the when signal is defective.  Co-acting signal In case a signal is not visible to the driver due to the presence of some obstruction such as an overbridge or a high structure, another signal is used in its place, preferably on the same post. This signal, known as the co-acting signal, is an exact replica of the original signal and works in unison with it.  In cases where a signal is not visible to the driver from an adequate distance due to sharp curvature or any other Repeater reason or where the signal is not visible to the guard of the train from his position at the rear end of a platform, a repeater signal is provided at a suitable position at the rear of the main signal. A repeater signal is provided with an R signal marker and can be of the following types. (a) A square-ended semaphore arm with a yellow background and a black vertical band. (b) A coloured light repeater signal. (c) A rotary or disc banner type signal. The ‘off’ positions of these three types of repeater signals are depicted in Fig. 31.7. Repeater signal  These are miniature signals and are mostly used for regulating the shunting of vehicles in station yards. Unlike Shunt fixed signals, these are small in size and are placed on an independent post of a running signal post. In semaphore signalling areas, the shunt signals are of the disc type. The disc type of shunt signal consists of a circular disc signals with a red band on a white background. The disc revolves a round a pivot and is provided with two holes, one for the red lamp and the other for the green lamp, for the purpose of night indication. At night, the ‘on’ position of the signal is indicated by the horizontal red band and the red light, indicating danger. During the day the red band inclined to the horizontal plane and during the night the green light indicate that the signal is ‘off’ ( Shunt signals Shunt signals in coloured light signalling area Point indicators These are used to indicate whether points have been set for the main line or turnout side. It essentially consists of an open box with two white circular discs forming two opposite sides of the box and green bands on the other two remaining sides. The box rotates automatically about a vertical axis with the movement of the points. The white disc indicates that the points are set for the main line. When the points are set for the turnout side, the green bands are visible. At night white light indicates a main line setting and green light signifies a turnout side setting Point indicators Trap indicator A trap is a device fitted on the track, which in its open position derails the vehicle that passes over it. When the trap is closed, the vehicle passes over it as it would over a normal track. A trap indicator reveals whether the trap is in an ‘open’ or ‘closed’ position. Caution indicators When the track is undergoing repair, trains are required to proceed with caution at restricted speeds and may even have to stop. Caution indicators help the driver of a train to reduce the speed of (or even stop) the train at the affected portion of the track and then return it to the normal speed once that portion has been covered The following indicators are used for this purpose. Caution indicator This cautions the driver to get ready to reduce the speed. Speed indicator The driver has to reduce the speed (or stop) at this location. Stop indicator or stop board The driver has to stop the train at this location. Termination indicator This indicates that the driver can assume normal speed and that the speed restriction zone has ended These indicators are also called temporary fixed engineering signals and are provided in the direction of the approaching train in the case of double lines and in both directions in the case of single lines EVOLVEMENT OF RAILWAY SIGNALLING