Braking Systems In Railway Vehicles
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue01,January-2015Braking Systems in Railway VehiclesRakesh Chandmal Sharma1 , Manish Dhingra2,Rajeev Kumar Pathak31Department of Mechanical Engineering, M. M. University, Mullana (Ambala) INDIA,2Department of Mechanical Engineering, T. M. University, Moradabad INDIA3Department of Mechanical Engg, Rakshpal Bahahur College of Engg. and Tech., Bareilly INDIAAbstract— Brake is an essential feature in order to retard andstop the railway vehicle within minimum possible time. Thispaper presents a discussion about the different brakingsystems used in railway vehicles. This paper also considerselectrodynamic and electromagnetic braking of trains, which isof particular importance in high-speed trains. The calculationfor stopping distance for railway vehicle is provided in thisstudy.Keywords— Air brake; Straight air brake system; Automatic air brakesystem; Braking distance; Brake cylinder; Brake pipe; Vacuum brake;Brake delay timeI.INTRODUCTIONThe brakes are used on the coaches of railway trains toenable deceleration, control acceleration (downhill) or tokeep them standing when parked. While the basic principleis similar from road vehicle, the usage and operationalfeatures are more complex because of the need to controlmultiple linked carriages and to be effective on vehicles leftwithout a prime mover. In the control of any braking systemthe important factors that govern braking action in anyvehicle are pressure, surface area in contact, amount of heatgeneration and braking material used. Keeping in view thesafety of human life and physical resources the basicrequirements of brake are: The brake must be strong enough to stop the vehicleduring an emergency with in shortest possible distance. There should be no skidding during brake applicationand driver must have proper control over the vehicleduring emergency. Effectiveness of brakes should remain constant even onprolonged application or during descending on a downgradient Brake must keep the vehicle in a stationary positioneven when the driver is not present.The brake used in railway vehicles can be classifiedaccording to the method of their activation into followingcategories. Pneumatic Brake Electrodynamic Brake Mechanical Brake Electromagnetic BrakePneumatic Brake may be further classified into two types Vacuum Brake Compressed air brakeIJERTV4IS010360Researchers in the past have investigated differentaspects of braking of railway vehicle. Bureika & Mikaliunas[1] provided the calculations for Vehicle Braking ForceFitted with UIC Air Brake for Passenger Trains, WagonBraking Force Fitted with a UIC Air Brake for FreightTrains Wagon, Braking Distance. Liudvinavicius & Lingaitis[2] studied different features and related mathematics ofelectrodynamic braking in high‐speed trains. Vernersson [3]developed a dimensional finite element model of block andwheel, which was coupled through a contact interface for thepurpose of control of heat generation and also the heatpartitioning at block-wheel surface through thermal contactresistances. Influence of temperature in wheels and brakeblock at rail tread braking was analyzed under brake rigconditions in the later part of study by Vernersson [4].Teimourimanesh et al. [5, 6] also investigated the influenceof temperature on railway tread braking in their study.Author in the past evaluated the different performanceindices of railway vehicles [7, 8, 9, 10, 11 and 12], Authoralso carried out a broad study of magnetically levitated [13]and air cushion [14] vehicles in the recent past, presenting asummary of different types of brakes used in railwayvehicles in this paper.II.VACUUM BRAKE & ITS LIMITATIONSThe vacuum brake system derives its brake force from theatmospheric pressure acting on the lower side of the pistonin the vacuum brake cylinder while a vacuum is maintainedabove the piston. The train pipe runs throughout the lengthof the coach and connected with consecutive coaches byhose coupling. The vacuum is created in the train pipe andthe vacuum cylinder by the ejector or exhauster mounted onthe locomotive.Vacuum brake system has following limitations: Brake cylinder piston takes longer time to release aftereach application of brakes because of single train pipe. Ona very long train, a considerable volume of air has to beadmitted to the train pipe to make a full brake application,and a considerable volume has to be exhausted to releasethe brake. Vacuum brakes are not suitable for high speed trains themaximum pressure available for brake application is onlyatmospheric. The brake power is inadequate for higherloads and speed. The practical limit on the degree of vacuum attainablemeans that a very large brake piston and cylinder arerequired to generate the force necessary on the brakeblocks.www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)206
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue01,January-2015The existence of vacuum in the train pipe can cause debristo be sucked in.III.AIR BRAKE SYSTEMSA. Automatic Air Brake SystemAn automatic air brake system is shown in Fig. 1. Aircompressors mounted every two to four coaches supplycompressed air to the air brakes. The air, which iscompressedFig. 2. Principle of straight air brake systemFig. 1. Principle of automatic air brake systemto nearly 8 kg/sq cm, is piped below coach floors to main airreservoirs. The air pressure is lowered to 5 kg/sq cm withpressure regulator and air is fed via the brake valve, brakepipes, and control valves to auxiliary air reservoirs. If thecompressed air in the brake pipes and auxiliary airreservoirs of each coach is at 5 kg/sq cm, brakes are notactivated. The activated brake valve cuts the flow of airfrom the pressure regulator and air pressure in the brakepipes falls. The fall in air pressure is detected by the controlvalves on each coach. The control valves then regulate theflow of compressed air from auxiliary air reservoirs to brakecylinders. The brake cylinders activate the basic brakingmechanisms to slow down and stop the coach. The controlvalves regulate the flow of air from the auxiliary airreservoirs to the brake cylinders at a pressure that isproportional to pressure drop in the brake pipes.B. Straight Air Brake SystemA straight air brake system is shown in Fig. 2. The straightair brake system does not have a control valve or auxiliaryair reservoir in each coach as in automatic air brake system.Activation of brake valve forces compressed air fromstraight air pipe to brake cylinders, activating the basicbraking mechanism. As the straight air pipes do not containcompressed air during normal running conditions, thebrakes would fail if coaches became uncoupled. In order toavoid this, the straight air brake system may be used inconjunction with the automatic air brake system. It can alsobe avoided by using another pipe, called a main air reservoirpipe, from the first to the last coach. The air pressure inmain air reservoir pipe acts like the compressed air in thebrake pipes of the automatic air brake system. If compressedair in this main air reservoir pipe falls, or if it leaks from airpipes or from air hoses between coaches, etc., pressure dropis detected and brakes are applied automatically.IJERTV4IS010360Air brake system may also be classified as follows: Direct release air brake system Graduated release air brake systemDirect release air brake system is most suitable for leveledtrack or constant gradient route. Due to this reason it is notsuitable for Indian Railways. Graduated release air brakesystem is most suitable for Indian Railways. In graduatedrelease air brake system the brake pressure is applied andreleased such that the magnitude of braking force isproportional to reduction in brake pipe pressure.Graduated release air brake system can also be divided intotwo categories. Single pipe graduated release air brake system Twin pipe graduated release air brake systemC. Single Pipe Graduated Release Air Brake SystemSingle Pipe Graduated Release Air Brake System is shownin Fig. 3. The operation is same as that of the twin pipesystem except that the auxiliary reservoir is charged throughthe D.V. instead of feed pipe, since there is no feed pipe insingle pipe system. As compared to single pipe graduatedrelease air brake system, twin pipe graduated release airbrake system is more suitable for passenger coaches.Fig. 3. Single pipe graduated release air brake systemD. Twin Pipe Graduated Release Air Brake SystemIn twin pipe graduated release air brake system (Fig. 4), TheBrake pipe is charged to 5 kg/cm2 by the driver's brakevalve. The auxiliary reservoir is charged by the feed pipe at6 kg/cm2 through check valve and choke. The brakecylinder is connected to the atmosphere through a hole inthe D.V. when brakes are under fully released condition. Toapply brakes, the driver moves automatic brake valve handlewww.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)207
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue01,January-2015either in steps for a graduated application or in one stroke tothe extreme position for emergency application. By thismovement the brake pipe pressure is reduced and thepressure differenced is sensed by the D.V. against thereference pressure locked in the control reservoir. Air fromthe auxiliary reservoir enters the brake cylinder and thebrakes are applied. At the time of release the air in the brakecylinder is vented progressively depending upon theincrease in the brake pipe pressure. When the brake pipepressure reaches 4.8 kg/cm2 the brake cylinder is completelyexhausted and brakes are fully released.IV.ELECTRODYNAMIC BRAKING SYSTEMBraking system used is electric trains is electrodynamicbraking that converts the motor into a braking generatordissipating the kinetic energy in the form of heat.Regenerative braking uses the generated electricity insteadof dissipating it as heat, and is becoming more common dueto its ability to save energy. Principle of the electrodynamictraction, dynamic braking and regenerative braking systemsis shown in Fig. 5, 6 and 7 respectively.Fig. 5. Principle of electrodynamic tractionFig. 4. Twin pipe graduated release air brake systemE. Advantages of Air Brake over Vacuum BrakeThe air brake is preferred in rail vehicles over vacuum brakedue to the reasons listed in Table 1.TABLE I.S.N.1.ADVANTAGE OF AIR BRAKE OVER VACUUM BRAKEParametersEmergency brakingdistance(level track, 65km/hr speed)Air BrakesVacuum Brakes632 m1097 m2.Brake power fadingNo fadingAt least by 20%3.Weight ofEquipments perwagon275 kg (Approx)700 kg (Approx)4.Pressure GradientNoappreciabledifference in airpressure betweenlocomotiveandbrake van upto2000 m.Steep reduction invacuum in trainslonger than 600 m.5.Preparation time inyardsLess thanminutesUpto 4 Hrs6.Safety ongradientsVery safeNeedadditionalprecautions7.Overall reliabilityVery goodSatisfactorydown40Fig. 6. Principle of dynamic brakingFig. 7. Principle of regenerative braking.IJERTV4IS010360www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)208
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue01,January-2015V.MECHANICAL BRAKING SYSTEMThe basic braking devices used by mechanical brakingsystems are: wheel tread brakes (Fig. 10), axle-mounted discbrakes (Fig. 11), and wheel-mounted disc brakes (Fig. 12).These brake mechanisms use a brake shoe that appliesfriction force to the disc. The applied pressure is adjusted tocontrol the braking force. In wheel-tread brake, the brakeshoe applies friction force to the wheel tread, creating asliding effect. High-speed trains cannot use this type ofbrake, because doing so may damage the wheel tread.Therefore, they use axle- or wheel-mounted disc brakes.Axle-mounted disc brakes require sufficient space toaccommodate therefore used in trailer bogies. Wheelmounted disc brakes are used on motor bogies because itrequires accommodating the traction motor only and havinginsufficient space for an axle-mounted brake. In bothsystems, compressed air or oil is applied to a brake cylinderthat pushes the brake lining against the disc. Brake discs aredead weight that is useful only during braking, thereforeoperators can install lighter discs. Carbon/carbon- compositemulti-discs and aluminium composite discs offer lighterweights and are widely used. The carbon/carbon-compositemulti-disc has alternate sections of carbon-fiber rotors andstators. During braking, they rub against each other to createa frictional force that slows down the wheel or axle. Thedisc is lighter in weight than conventional materials and hasgood heat-resistant properties. (Fig. 13) Aluminiumcomposite brake discs may be made much lighter thantoday‟s forged steel and cast-iron brake discs. Moreovertheir structure is common for both axle- or wheel-mounteddiscs, achieving a much lighter disc without design.Fig. 8. Principle of recycled regenerated electric powerFig. 9. Transmission of breaking force from traction motors to wheelsThe traction motor drives and accelerates the train, duringbraking and it acts as an electric generator instead, formingpart of a circuit that consists of a rheostat, armatures and afield system. Electricity is consumed by the main resistor,which converts kinetic energy of the train into heat and actsas a brake. Regenerative braking uses the same type ofcircuit; however the electricity generated by braking is notconsumed by rheostat. It is transmitted to the overheadwire. The flow of this electricity is controlled by a controllerunder the pantograph that opens and closes within fractionof time. Electrodynamic brake systems are economical touse because they do have friction elements, as in mechanicalbrake systems. The regenerative braking system is evenmore economical because the electricity regenerated fromthe train‟s kinetic energy is transmitted to the overheadwire, and becomes available to power other rolling stock(Fig. 8)However electrodynamic brake systems occasionallymalfunction because they have complex circuits. Thereforethey cannot be used as emergency brakes. In anelectrodynamic braking system, the braking force of thetraction motor is transmitted to the wheels via gears (Fig. 9).Fig. 10. Principle of wheel tread brakesFig. 11. Principle of axle-mounted disc brakesIJERTV4IS010360www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)209
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue01,January-2015Fig. 14. Principle of electromagnetic brakeFig. 12. Principle of wheel-mounted disc brakesFig. 13. Carbon/Carbon-composite multi-disc systemVI.Fig. 15. An on field view of electromagnetic brakeELECTROMAGNETIC BRAKING SYSTEMVII. CALCULATION OF TRAIN STOPPING DISTANCEConventional train braking systems depend heavily onadhesion between the wheel tread and the rail. In the casehigh-speed trains, adhesion decreases as speeds increase,making it necessary for the train to reduce braking force toavoid wheel sliding. This result is longer braking distances.To overcome this problem, a electromagnetic brake systemthat does not depend on adhesion was developed. It producea braking force by using magnetic repulsion obtained fromeddy currents generated on the top surface of the rails.Earlier it was not used because of assumption that the eddycurrents would heat small sections of the rail to such adegree that the rail would bend sideways. This is solved bydevelopment of a electromagnetic brake that uses eddycurrents and frictional force. Fig. 14 shows the principle ofelectromagnetic brake. The electromagnetic brake on bogieis connected to batteries that create alternating north andsouth poles forming magnetic fields between the poles. Themagnetic fields generate eddy currents in the top surface ofthe rails, creating a force acting in an opposite direction tothe movement of the train, in other words, a braking force.An on field view of electromagnetic brake is shown in Fig.15.IJERTV4IS010360For trains to safely travel on a railway, trains must beprovided with sufficient distance in which to stop. Allowingtoo long a distance reduces the capacity of the line and hasan impact on rail infrastructure investment. Too short adistance and collisions would occur, because the train wouldnot be able to stop within the available distance and wouldtherefore occupy a section of track that could be allocated toanother train. Consequently it is important that distance beadequate. Train breaking distance is function of followingfactors Train speed when the brakes are applied. The available friction at wheel-rail surface whichinfluences the retardation rate for complete brakeapplication. Time from when the brakes are applied by the traindriver to when they are actually become effective i.e.brake delay time. The magnitude of wear of brake pads and the pressureavailable in brake cylinders. Track gradient when brakes are applied and massdistribution of track.In order to stop the train it requires the work. The requiredwork is the sum of change in the train‟s kinetic energy andthe change in its potential energy due to change in the heightdue to the gradient of the track.www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)210
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue01,January-2015Mathematically it may be expressed as:mV 2ma S m g (h2 h1 ) 02where(1)[4]m mass of train, V Speed at which the retardation beginsS Stopping distance, h1 Height at which the retardation begins,h2 Height at which the train stops (h2 h1 )a Retardation provided by braking system,The above equation suggests that mass has no direct effecton the train stopping distance. However mass distributionhas influence on train stopping distance as train‟s centre ofgravity varies with the mass distribution. In case of freightwagons where the mass varies from no load to full loadthere are two levels of brake force used „empty‟ and„loaded‟. This influences the design of the brake system. Forcalculating the braking distance calculations the lowestdeceleration rate is used to calculate the deceleration rate forthe complete train.Eq. 1 may be written as( V 2 )(2), for a 0S 2(a g tan )[5][6][7][8][9][10] Angle of slope, for small values of , sin tan Assuming constant gradient track and considering brakedelay time the stopping distance can be calculated usingfollowing expression( V b t d ) 2bt 2(3)S V t d2(a b)d[13]VIII. CONCLUSIONS [14]Vacuum brakes have extremely limited applicationsbecause of longer longer to function and unsuitablefor high speed trains.Air brakes are efficient as compared to vacuumbrakes; however they require considerable stoppingdistance therefore cannot be used for emergencybraking.Mechanical brakes should be kept in reserve inparallel with another breaking technique and shouldbe used to completely stop the engine at low speed.The required braking forces can be obtained in awide range, with regeneration braking used in a highspeed range and rheostat braking in low speed ction because they have complex circuits.Therefore they cannot be used as emergency brakes.Electromagnetic braking in high-speed train isefficient method of breaking.REFERENCES[1][2][3]G. Bureika & S. Mikaliunas, “Research on the compatibility of thecalculation methods of rolling‐stock brakes”, Transport, vol. 23, issue4, 2008, pp. 351-355.L. Liudvinavicius & L. P. Lingaitis, “Electrodynamic braking inhigh‐speed rail transport”, Transport, vol. 22, issue 3, 2007, pp. 178186.T. Vernersson, “Temperatures at railway tread braking. Part 1:Modeling”, Proceedings of the Institution of Mechanical Engineers,IJERTV4IS010360[12]2b Retardation provided by gravityt d Brake delay time [11]Part F: Journal of Rail and Rapid Transit, vol. 221, issue 2, 2007, pp.167-182.T. Vernersson, “Temperatures at railway tread braking. Part 2:Calibration and numerical examples”, Proceedings of the Institutionof Mechanical Engineers, Part F: Journal of Rail and Rapid Transit,vol. 221, issue 4, 2007, pp. 429-441.S. Teimourimanesh, T. Vernersson, R. Lunden, F. Blennow, M.Meinel, “Tread braking of railway wheels - temperatures generatedby a metro train”, Proceedings of the Institution of MechanicalEngineers, Part F: Journal of Rail and Rapid Transit, vol. 228, issue 2,2014, pp. 210-221.S. Teimourimanesh, T. Vernersson, R. Lunden, “Modelling oftemperatures during railway tread braking: Influence of contactconditions and rail cooling effect”, Proceedings of the Institution ofMechanical Engineers, Part F: Journal of Rail and Rapid Transit, vol.228, issue 1, 2014, pp. 93-109.R.C. Sharma, “Recent advances in railway vehicle dynamics”, Int. J.Vehicle Structures & Systems, vol. 4, issue 2, 2012, pp. 52-63.R.C. Sharma, “Ride analysis of an Indian railway coach usingLagrangian dynamics”, Int. J. Vehicle Structures & Systems, vol. 3,issue 4, 2011, pp. 219-224.R.C. Sharma, “Modeling and simulations of railway vehicle system”,International Journal of Mechanical Engineering and RoboticsResearch, vol. 1, issue 1, 2014, pp. 55-66.R.C. Sharma, “Sensitivity Analysis of ride behaviour of Indianrailway Rajdhani coach using Lagrangian Dynamics”, Int. J. VehicleStructures & Systems, vol. 5, issue 3-4, 2013, pp. 84-89.R.C. 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release air. brake system, twin pipe graduated release air . brake system is more suitable for passenger coaches. Fig. 3. Single pipe graduated release air brake system. D. Twin Pipe Graduated Release Air Brake System . In twin pipe graduated release air brake system (Fig. 4), The. Brake pipe
Anti-lock brake systems Anti-lock Braking Systems (ABS) is a form of electronic braking which was invented to help a driver control a vehicle under heavy braking by preventing the wheels from locking up. How they work Braking systems take the force applied to the foot pedal by the driver and transfer it via mechanical system to the brakes on .
Abstract—Anti-lock braking systems are one of the most im-portant safety systems for wheeled vehicles. They reduce the braking distance and, most importantly, help the user maintain controllability and steerability of the vehicle. This paper extends and adapts the concept of Anti-lock braking systems to tracked vehicles, in particular to .
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ABS system (Anti-lock Braking System) This device prevents the wheels from locking despite the rider's excessive pressure on the braking system. The risk of skidding and of loss of steering is thus eliminat-ed during intensive braking in a straight line. ABS can be applied to either an inde-pendent or an integrated braking system.
D. Regenerative Anti lock Braking System mechanical brake The mechanical brake in the RABS is a normal mechanical brake which acts on rear wheels only, this mechanical brake has a constant braking torque, which equal to the maximum torque generated by the MG and uses in the second mode of braking (stopping mode). The total torque of braking of the
(a) Railway Board (b) Railway Ministry (c) Both railway Board and Railway Ministry (d) None of these Answer: A 19. The headquarters of South-Central Railways is situated at (a) Mumbai (V.T) (b) Chennai (c) Secundrabad (d) Mumbai (Central) Answer: C 20. The headquarters of Northern Railway is at
by acquiring knowledge of railway infrastructure from various other sources. First and foremost, we consulted one of the state of the art railway engineering textbooks, Modern Railway Track (Esveld, 2001). Additionally, we consulted RailML an existing standard for describing railway infrastructure assets, railway timetables, and railway .
ISO 13849-1 4.2 Braking system 1 4.2 Braking system control - Collision with opsners PL function controls the deceleration function. d 2 4.2 d) Parking braking system control - Unintended motion of the truck: Risk of collision. - Reduction of braking performance if the battery is discon-nect
