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This document is the property ofRailtrack PLC. It shall not bereproduced in whole or in part withoutthe written permission of the Controller,Railway Group Standards,Railtrack PLC.

Published by

Safety & Standards Directorate

Railtrack PLC

Floor DP01, Railtrack House

Euston Square

London NW1 2EE

Copyright 2000 Railtrack PLC

Railway Group Standard

GM/RT2045Issue Two

DateApril 2000

Braking

Principlesfor Rail

Vehicles

SynopsisThis document defines the principlesof operation and performancerequirements for the brakingsystems

of rail vehicles for operation onRailtrack controlled infrastructure, inorder to ensure safety of operationand safe interworking.

Signatures removed from electronic version

Submitted by

Martin FargherStandards Project Manager

Authorised by

Brian AlstonController, Railway Group Standards

Uncontrolled When Printed

Document to be withdrawn as of 03/12/2011

To be superseded by GMRT2045 Iss 3 published on 03/09/2011

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Braking Principles for Rail Vehicles

R A I L T R A C K 1


GM/RT2045IssueTwoDate April 2000

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ContentsSection Description Page

Part A

Issue Record 2

Responsibilities 2

Compliance 2

Health and Safety Responsibilities 2

Supply 2

Part B

1 Purpose 32 Scope 3

3 Definitions 3

4 BrakeSystem - general 55 Performance 6

6 BrakeSystem energy 7

7 Control system 7

8 BrakeForce application system 119 BrakeSystem Coupling between vehicles 12

10 Parking Brake 12

11 Acceptance requirements 12

Appendices

A Assessment of stopping distance test results 15

B Dynamometer tests of friction materials 16

C Principlesof operation of current friction BrakeSystems in use on 17

Railtrack controlled infrastructureD Guidance on the BrakeSystem energy requirements to take account of 20

WSP activityE Factors to be taken into account when considering the protection of drivers 21

brakevalve exhaust outlets

References 22




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GM/RT2045Issue TwoDate April 2000

Page 2 of 22

Part AIssue Record

This document will be updated when necessary by distribution of a completereplacement. Amended or additional parts of revised pages will be marked by avertical black line in the adjacent margin.

Issue Date CommentsOne October 1998 Supersedes GM/TT0168Two April 2000 Supersedes Issue One

ResponsibilitiesRailway Group Standards are mandatory on all members of the Railway Group *and apply to all relevant activities that fall into the scope of each individualsRailway Safety Case. If any of those activities are performed by a contractor, the

contractors obligation in respect of Railway Group Standards is determined bythe terms of the contract between the respective parties. Where a contractor isa duty holder of a Railway Safety Case then Railway Group Standards applydirectly to the activities described in the Safety Case.

* The Railway Group comprises Railtrack and the duty holders of the RailwaySafety Cases accepted by Railtrack

ComplianceThe provisions in this document are to be complied with for new vehicles and formodification to existing vehicles where the contract date between the RailwayGroup Member and their supplier for procurement or modification is after 3 June2000. The requirements do not apply to modifications where the requirements

are specified as applying to new vehicles.

Health and Safety

ResponsibilitiesIn issuing this document, Railtrack PLC makes no warranties, express orimplied, that compliance with all or any documents published by the Safety &Standards Directorate is sufficient on its own to ensure safe systems of work oroperation. Each user is reminded of its own responsibilities to ensure health andsafety at work and its individual duties under health and safety legislation.

SupplyControlled and uncontrolled copies of this document may be obtained from theIndustry Safety Liaison Dept, Safety and Standards Directorate, Railtrack PLC,Railtrack House DP01, Euston Square, London, NW1 2EE.




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Part B1 Purpose

The purpose of this document is to define the principlesof operation andperformance requirements of rail vehicle brakesystems to enable safety ofoperation and safe interworking to take place.

2 ScopeThe overall scope of Railway Group Standards is as specified in Appendix A ofGA/RT6001.

Specifically the contents of this document apply to any rail vehicle operating onRailtrack controlled infrastructure, except vehicles registered for and working ininternational traffic under RIV or RIC regulations, which are deemed, by virtue oftheir International registration, to have met the necessary requirements.

3 DefinitionsAutomatic Brake

A brakingsystem where any interruption of the continuity of the brakecontrolsystem causes an emergency application of the power braketo be madeautomatically (see also definition of continuous brake).

BrakeApplicationWhere an application of the brakeresults in a brakeforce being applied to thevehicle.

BrakeControllerThe device operated by the driver at the driving position by which means thedemand for a brakeapplication or release is relayed to the brakesystem.

BrakeForceThe force applied to the brakeblock / pad / brakingsurface interface.

BrakeForce Build Up TimeThe elapsed time from when the brakecontroller handle is moved to signal therequirement for a brakeapplication until the brakeforce has reached a specifiedvalue.

BrakeForce Release TimeThe elapsed time from when the brakecontroller handle is moved to signal therelease of a brakeapplication until the brakeforce has fallen to the level at whichit is effectively released.

BrakeRetarding Force

The resultant force on the vehicle, generated by the brakesystem, that producesa retardation of the vehicle.

BrakeSystemAll the components and sub-assemblies that provide the means by which brakeapplications on rail vehicles are made and controlled, including the means bywhich the energy is provided and / or stored to generate the brakeretardingforce and the equipment which provides the retarding force.

BrakeSystem CouplingsThe inter-vehicle couplings that connect the brakesystems on adjacent railvehicles and transmit the brakecontrol signals that provide the system continuityand, where appropriate, also transmit the energy.

Compatible BrakeSystems

Those systems which have the same brakecontrol signals and produce a similarretardation rate on a vehicle for a given position of the brakecontroller handle.




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ContinuousAn unbroken series of connections through all individual vehicles in any trainformation and where the power brakecontrol system relies on the integrity ofthese connections for its operation.

Continuous BrakeA power brakethat operates on all parts of the train, such that any interruption ofthe Continuous element of the inter-vehicle connections of the brakecontrolsystem, results in an emergency application of the power brakebeingautomatically made on all parts of the train, that will bring all parts of the train toa standstill.

Drag BrakingA partial brakeapplication that is sustained for a period of time to hold the speedof a train constant, down a falling gradient for example.

Driving PositionThe designated position from which a driver controls the brakingof a vehicle ortrain.

Dynamic BrakingA method of brakingwhere retardation of a vehicle is produced by a method thatdoes not involve friction as the principal means by which the kinetic energy isdissipated.

Emergency BrakeApplicationA brakeapplication that uses a more direct and separate part of the controlsystem, that as a result may be quicker, to signal the requirement for a brakeapplication, than that used for the full service application. On certain vehicles,the retardation rate may be specified to be higher than that of the full service

application and is described as enhanced emergency braking(see GM/RT2044).

Friction BrakingSystemA system in which friction is used to convert the kinetic energy of the vehicle intoheat energy.

Full Service BrakeApplicationThe brakeapplication that gives the minimum retardation rate that meets theperformance requirements.

Graduated BrakeApplicationAn application of the brakethat results in the value of brakeforce beingcontrolled incrementally to a particular value that may be less than the maximumvalue that the system can generate.

Graduated BrakeReleaseA brakerelease in which the value of the brakeforce can be reducedincrementally to a particular value without completely releasing the brake.

Maximum Loaded ConditionA defined condition in excess of the normal fully laden condition that may ariseduring exceptional operating circumstances. Also commonly known as crushladen.

Multiple UnitFor the purposes of this document a Multiple Unit is a fixed formation of fivevehicles or less having a driving position at both outer ends of the formation.

This definition excludes traction units (see GM/RT2042), on-track machines (see

GM/RT2400) and freight vehicles (see GM/RT2043).

Note: Fixed formations of more than five vehicles that incorporate tractionequipment distributed within the train do not therefore comply with the definitionof either a trailer coach (because some vehicles have traction equipment) or a




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Multiple Unit (more than 5 vehicles). For the purposes of brakingperformance,these fixed formations may either meet the requirements of GM/RT2044or therequirements of GM/RT2041. At operating speeds in excess of 125 mile/h, therequirements of GM/RT2046apply.

New VehicleA vehicle introduced to Railtrack controlled infrastructure whose procurementcontract date between the Railway Group Member and their supplier is after therelevant compliance date of this document or the documents listed in section 5.Such vehicles shall comply with the requirements for new vehicles defined in thisdocument and the relevant document listed in section 5.

On-Track MachineAny rail mounted machine meeting the requirements of this Standard andpermitted by the Master Rule Book GO/RT3000to be moved, either self-propelled or in train formation, outside a possession.

Parking BrakeA brakesystem designed to hold a rail vehicle stationary for an indefinite periodwithout the addition of further energy to maintain the brakeforce, provided noadditional external force is applied to the vehicle.

Power BrakeA means by which the retardation of a rail vehicle or a train can be achieved bythe application of a brakeforce that is generated by energy stored on thevehicle.

Stored EnergyEnergy that is stored on the rail vehicle and is used to generate the brakeforce.

Traction UnitA vehicle with its own source of traction, that is designed to haul otherrailway vehicles, that has one or more driving positions and is able to controlthe brakingof the vehicles coupled to it.

Wheelslide Prevention Equipment (WSP)A system designed to make the best use of available adhesion by a controlledreduction of the brakeforce to prevent wheelsets from locking and sliding.

4 BrakeSystem -

general4.1Brakesystems in use shall be those that have proved to be safe and reliable inoperation on either Railtrack controlled infrastructure or another major railway

network having equivalent operating conditions and speeds to Railtrackcontrolled infrastructure. For information the principlesof operation of thecurrent friction brakingsystems in use on Railtrack controlled infrastructure arelisted in Appendix C.

4.2If a brakesystem not covered by section 4.1 is proposed, it may be introduced,providing that the system and / or any novel component part thereof complieswith the requirements of this document and has been proved to be satisfactoryby the processes defined in section 11.

4.3All vehicles shall be equipped with a power brake, except existing vehicles thatare not so fitted.

4.4Continuous and automatic operation of the power brakeand its control shallresult where vehicles are required to run coupled to others in a train formation toprovide a system of emergency brakingthat defaults to brakesapplied (see alsosection 9).




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4.5Any type of brakingsystem may be combined with any other type of brakingsystem but where more than one system of brakingis used there shall be asmooth transition between the systems of braking, without any degradation ofbrakingperformance.

4.6The brakesystem of new vehicles shall be designed to operate correctly withinthe temperature range -20C to 35C, and the following weather conditions:

relative humidity of 100% up to temperatures of 19C;

any reasonably foreseeable meteorological conditions.

4.7For all vehicles the train operator shall be satisfied that the brakesystems of thetrains it operates function safely in all the ambient weather conditions in which

the vehicles operate. In the case of existing vehicles at least in the temperaturerange -15C to 35C.

4.8Where full compliance with the requirements of sections 4.6 and 4.7 cannot beachieved, or the train is subjected to ambient conditions beyond those specified,the train operator shall introduce suitable control measures, such as operatingrestrictions or special maintenance, that will ensure safety. See alsosection 7.4.5.

4.9An existing vehicle that has a modification to the brakesystem shall comply withthe requirements defined for new vehicles in this document and thosedocuments defined in section 5 when it is reasonably practicable to do so.

5 Performance5.1The key performance parameter is characterised by the stopping distance / initialspeed relationship, which is defined in the following documents for specificgroups of vehicles:

GM/RT2041- BrakingSystem Requirements and Performance for TrailerCoaching Stock

GM/RT2042- BrakingSystem Requirements and Performance for Traction UnitsGM/RT2043- BrakingSystem and Performance for Freight TrainsGM/RT2044- BrakingSystem Requirements and Performance for Multiple UnitsGM/RT2046- BrakingSystem Requirements and Performance for Trains which

operate above 125 mile/hGM/RT2400- Design of On-Track Machines

5.2The brakingperformance defined in these documents relies on the normal levelof adhesion being available that is necessary to sustain the brakeretarding forcedemanded. It is accepted that in conditions of low wheel / rail adhesion thefriction force that can be maintained at the wheel / rail interface is reduced andother measures to achieve the required stopping distance are necessary, suchas a reduction in speed, railhead surface conditioning or a means of brakingthatdoes not rely on the wheel / rail adhesion.

5.3Compliance with the performance requirements defined in the documents listedin section 5.1, will ensure that trains whose brakingsystems are functioningcorrectly, are able to stop within the appropriate signal spacing distance or within

the appropriate in cab train control system requirements, when normal levels ofadhesion are available.




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6 BrakeSystem energy

6.1The energy used directly to provide the brakeforce for the emergency brakeshall be stored on the vehicle and there shall be:

a) safe methods that do not endanger the staff or public for the following:

storing the energy;

discharging the energy during any operation to apply or release the brakeor vent the system;

b) as a minimum, sufficient energy dedicated for use by the brakesystem,stored on a vehicle to make at least one full service brakeapplicationcapable of stopping the vehicle from its maximum speed and maximumloaded condition, without the addition of any further energy;

c) on new vehicles in normal operating conditions, sufficient energy dedicatedfor use by the brakesystem, stored on the vehicle to enable an emergencybrakeapplication (enhanced emergency where fitted) to be made that shallbe capable of stopping the vehicle from its maximum speed and maximumloaded condition without the addition of any further energy. In a pneumaticsystem normal operating conditions shall represent the minimum pressureto which the brakesupply reservoir can fall as permitted by the tolerances inthe system components, whilst all the system is operating normally. See alsosection 7.2.6.

6.2If the energy used to provide the brakeforce is generated on the train, thereshall be sufficient capacity to supply all the train formations and all combinationsof brakeapplications, including the effect of WSP operation, (where fitted). In

some train formations the effect of WSP activity will significantly influence theamount of energy required on the train.

See section 11.7 and Appendix D for guidance on the amount of energy requiredto be available.

6.3If the same medium that is used for providing the brakeforce, is also used totransmit the signal that a brakeapplication is required (either normal orautomatic) there shall be a means of preventing the signal brakeapplicationrequired being suppressed. If for example, there is a division of a train with anautomatic air brake, it shall be impossible for sufficient air to be supplied to thebrakepipe to overcome the drop in brakepipe pressure caused by the open pipeat the division.

6.4If a vehicle has its own source of brakeenergy for use when operatingindependently, it shall be impossible for this to interfere with the operation of theautomatic power brakewhen the vehicle is in a train.

6.5The brakesystem shall be protected from the effects of any auxiliary systemsthat derive their energy from that used for braking, so that these auxiliarysystems cannot in any circumstance impair the efficiency of the brakesystem.

7 Control system7.1 General7.1.1The control system shall enable the graduated application of the brakesand the

release of the brakeson a vehicle to be made from the operative driving positionon that vehicle or another vehicle with a compatible brakesystem coupled to it ina train formation. On new vehicles the control system shall enable a graduatedrelease of the brakesto be made.




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7.1.2There shall be sufficient devices and redundancy incorporated into the brakingcontrol and energy storage systems, to reduce the effect that a failure of one partof the system has on the brakingof the minimum train formation. This isparticularly important where a stored energy system is used to produce the brakeforce.

There shall be no single point failure which can result in a lower than demandedbrakeforce being achieved on more than one vehicle in the train simultaneously.A particular example of this is that the brakeretardation rate change required,where the brakeforce is reduced when operating at speeds exceeding125 mile/h, is to be initiated individually on each vehicle and not solely through atrain wire.

7.1.3If several types of brakesystem are to work in conjunction with one another,

there shall be provision for all types to be controlled by the same brakecontroller. On all new vehicles, there shall be an automatic return to the type ofbrakethat provides the emergency braking, in the event of a failure of any othertype of braking.

7.1.4Where the control system permits tolerances in the level of energy to apply andrelease the brakethat could result in it being impossible to fully release thepower brakeafter changing the source of the control, a control system shall beprovided that will enable the brakesto be fully released on the train. Theovercharge facility on automatic air brakesystems is an example of this.

7.1.5Driving Positions shall be provided with devices to enable the driver to:

monitor the brakecontrol system, where continuity is not self-proving asdefined in section 7.2.4;

monitor the energy supply used for the automatic brakingsystem;

monitor the level of the brakeapplication being achieved on the vehicle withthe operative driving position as follows:

the emergency brakesystem;

on new vehicles each brakingsystem or the overall brakingperformance (retardation).

7.1.6It shall be possible for a train to be parked with a full brakeapplication that eitherresults automatically from the action of the driver shutting down the operativecab or under manual control of the driver.

7.1.7Except in the case of hydraulic type parking brakes, a means shall be providedby which any type of brakeapplication can be released manually if there is afailure of the normal method of release. These devices shall comply with therequirements of sections 6.1a) and 7.5.1.

7.2 Continuous and Automatic Features

7.2.1The control system shall be designed so that an emergency brakeapplication,which shall bring the train to a stand, shall result if:

a) there is a failure of the medium providing the method of control for theautomatic brakesystem;

b) on new vehicles there is a failure of the primary source of the energy that isthen supplied to the train to provide the brakeforce. It shall be impossible tooverride this part of the system using the normal operating controls, excepton trains that also operate through the Channel Tunnel;




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c) there is a loss of the continuity in the control system caused by an accidentaldivision of the train;

d) either:

the stored energy on the vehicle falls below that defined in section 6.1b;or

there is a failure of the method of replenishing the stored energy on thevehicle, if the method is not the same as that which provides thecontinuity as required by section (c) above.

Neither of the requirements of section (d) apply to existing locomotives whenbeing hauled dead.

7.2.2It shall be impossible for the control system (excluding WSP) to release the

brakesif the system is in such a condition that there would be insufficient energyremaining to make a brakeapplication, as required by section 6.1.

7.2.3The control system shall be capable of initialising a brakeapplication with aretardation equivalent at least to a full service brakeapplication as a result of aninput from safety and emergency systems such as passenger communicationalarm, AWS,TPWS, DSD, Vigilance. In the case of new vehicles it shall bepossible for the driver to override the signal from the passenger communicationalarm so that the train can be braked to a stop at a suitable location. In theabsence of a positive acknowledgement by the driver, the passengercommunication alarm shall result in the initiation of a full service brakeapplication.

7.2.4

Where continuity is not self-proving as part of the control system design,vehicles shall be provided with a means by which a brakecontinuity test can beundertaken in order to prove the continuity of the automatic brakewhen in a trainformation.

7.2.5Either a full service or emergency brakeapplication shall automatically inhibit orinterrupt traction power. It shall however be possible to apply traction power witha partial brakeapplication in order to assist the starting of trains on gradients.

7.2.6Except on existing vehicles not so fitted and trains that also operate through theChannel Tunnel, there shall be a system of interlocks between the tractioncontrol system and the brakecontrol system that prevents traction power being

applied:

until sufficient energy for the automatic brakesystem has been proved to beavailable to provide at least an emergency brakeapplication;

until, on new vehicles, sufficient energy for the automatic brakesystem hasbeen proved to be available to provide an enhanced emergency brakeapplication if this facility is fitted.

In the case of trains that also operate through the Channel Tunnel, there shall bea system to monitor the brakesystem energy as an alternative to the tractioninterlock.

7.3 Service BrakeControl

7.3.1Drivers brakecontrollers shall be provided at driving positions in accordancewith GM/RT2161and have the following features:




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a) They shall enable graduated brakeapplications to be made between the fullyreleased and fully applied conditions, with intermediate levels of brakingavailable as are appropriate to the operating duty of the vehicle.

b) The normal convention adopted for vehicles operating on Railtrack controlledinfrastructure is that the brakecontroller shall be arranged to apply the brakewhen the handle is moved forwards / away from the driver and release thebrakewhen the handle is moved backwards / towards the driver.

c) Where it is preferred that the brakecontroller apply and release directionscomply with the UIC standard directions (apply when moved backwards /towards the driver and release when moved forwards / away from the driver),the train operator shall undertake a study to identify the implications forsafety of train operation which could result from the introduction of vehicleswith such brakecontrollers. The study shall consider factors such as:

whether drivers will be required to work totally on vehicles of oneparticular type or are required to interwork with other fleets;

the ability to retrain existing drivers from the standard direction of control;

the proposed duty of the train.

7.3.2Where there is no additional safety risk, it shall be permissible to adopt the UICstandard directions. However, where the adoption of the UIC standard directionsposes an increased risk to train operation, additional safeguards shall beadopted to counteract the risk.

7.3.3Service brakeapplications and releases shall only be possible from that drivingposition which the driver has designated as the operative driving position.

7.4 Emergency BrakeControl

7.4.1The method of control shall have a separate arrangement for demanding anemergency brakeapplication from that for demanding a full service application.The system for the emergency application shall be as direct as possible, toeliminate as far as practicable any possible failure of this arrangement.

The stopping distance given by the emergency brakingshall be equal to or lessthan that produced by the full service braking.

7.4.2Normally the emergency brakecontrol arrangement shall be operable at all timesfrom any of the positions at which it is provided, unless there is a specialarrangement by which it can be by-passed from all except that at the driving

position.

7.4.3The drivers brakecontroller shall be provided with an emergency brakeapplication position beyond the full service position, where the control systemenables this to be incorporated. A separate control shall be provided:

on existing vehicles where it is not possible to incorporate an emergencybrakeapplication position as part of the service brakecontrol;

on new vehicles, in addition to the provision of any emergency brakeapplication position on the brakecontroller.

Except for on-track machines on new vehicles the separate emergency brakecontrol shall take the form of a plunger type control(s) as follows:

a) An emergency brakeapplication shall be initiated by depressing the control,which shall be coloured red and remain latched in the application positionuntil manuallyreleased.




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b) It shall be possible to visually determine when the control is in the applied orreleased position.

In the case of on-track machines an alternative type of separate emergencybrakecontrol is permitted.

7.4.4Where the emergency and full service brakeapplications rely on the venting ofenergy, consideration shall be given to protection from blockage of the exhaustoutlets, particularly by ice or frozen snow (see Appendix E). On new vehicles theemergency and full service exhaust outlets shall be kept separate.

7.4.5On existing vehicles with driving positions, consideration shall be given to thefitting of a separate device to enable an emergency brakeapplication to bemade. This device shall not be adversely affected by freezing weather

conditions.

7.5 Isolation Devices and Drain Cocks

7.5.1Devices incorporated into the brakesystem to enable particular parts to beisolated or drained shall:

a) be accessible and visible to authorised users and, in the case of isolationdevices, clearly and indelibly labelled to indicate their function;

b) be located and protected to prevent, as far as is reasonably practicable,inadvertent or malicious operation;

c) in the case of pneumatic or hydraulic systems, be arranged to be open whenthe operating handle is in line with the pipe in which they are connected. Ifthis is not possible there shall be a label to indicate the functional state.(Except for those drain cocks where the handle is in line with the pipe whenclosed);

d) where drain cocks that are in an exposed position, either be protected asrequired by section b) above, or have the axis of the handle arranged to be inline with the direction travel of the vehicle, so that when operated the handleis moved across the vehicle. This will reduce the risk of the handle beingmoved by debris during vehicle operation. In the case of new vehicles, thosedrain cocks on reservoirs that provide energy for the brakesystem shall beprotected to prevent them being damaged.

7.5.2If a dynamic brakeis provided it shall be possible for this to be isolated, in a

manner that does not in any way impede the operation of the emergency brake.

8 BrakeForce

application system8.1The brakeforce application system shall be designed to:

a) have sufficient thermal capacity and / or cooling to prevent the occurrenceofunacceptably high temperatures that could adversely affect brakingor thestructural integrity of the brakingcomponents, taking into account anyplanned brakingduty cycle, including drag braking;

b) accept the loads that will arise from the brakingforces and from the dynamicenvironment associated with its particular location on the vehicle;

c) use materials that prevent the generation and emission of any products thatare hazardous to health;




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d) in the case of disc brakes, minimise the build up of ice by incorporating anautomatic slack adjuster mechanism that maintains an appropriate clearancebetween the brakingsurface on the disc and the friction material.

8.2For information, specifications previously used for disc brakepads and brakeblocks are shown in the related documents section of this document.

9 BrakeSystem

Coupling between

vehicles9.1Brakesystem couplings to provide the required continuity can be automaticallyor manually connected. They shall be designed to prevent inadvertentdisconnection while vehicles remain connected by the normal drawgear but shall

disconnect easily if vehicles separate due to the failure of the drawgear andthereby ensure that an emergency brakeapplication results.

9.2If the brakesystem couplings contain stored energy and can be manuallydisconnected, except on vehicles that are coupled by semi-permanent couplings,there shall be a method adjacent to the coupling of isolating the coupling fromthe stored energy supply. On new vehicles there shall be a means of dissipatingany energy trapped in the coupling, before disconnecting.

9.3If it is the intention to connect the end of a new vehicle directly to existingvehicles during their normal operation, and the brakesystem has been designedand proven to be compatible with the characteristics of the existing vehicle brakesystem, the inter-vehicle brakesystem coupling at that end shall be compatiblewith that of the existing vehicle.

9.4It shall not be possible to connect the brakesystem couplings of vehicles whosebrakesystems are not compatible. It is acceptable for these vehicles to bemechanically coupled together via auto-couplers but if the brakecontrol systemsare incompatible there shall be measures to prevent their connection via theauto-coupler.

10 Parking BrakeParking brakerequirements are defined in thedocuments listed in section 5.1.

11 Acceptance

requirements 11.1Static and stopping distance tests, designed to prove that the vehicle or trainmeets the stopping distance requirementsspecified in the appropriate RailwayGroup Standard for that particular group of vehicles, shall be undertaken on thefollowing:

all new vehicle designs;

existing vehicle designs that are modified such that the brakingperformancecould be affected.

11.2Stopping distance tests are not required in the following circumstances:

a) Each individual vehicle of a particular design does not have to be tested butthere shall be sufficient tests to establish that the new design of vehicle ormodified vehicle design meets the specified requirements.




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b) If the brakesystem and brakeforces of a new vehicle are very similar to anexisting design and the vehicle operating weight is similar and records existof satisfactory stopping distance tests.

c) If for modified vehicles with friction brakingthere is sufficient data availablefrom stopping distance tests with other vehicles that meet the conditionslisted below, to enable a calculation to be made to verify that the modifiedvehicle will meet the required stopping distances:

the same brakeforces and friction materials (friction couple) were used;

the specific pressure at the friction couple is similar to that used on theprevious vehicles;

the vehicle weights are similar;

the maximum vehicle speeds are the same.

If the maximum speed or weight of the modified vehicle is greater than the value

of the existing test data, limited testing at the speeds and or weight for whichthere is no data shall be undertaken.

11.3Before any operation on Railtrack controlled infrastructure, there shall beappropriate scrutiny of the design of new systems and components. In additionappropriate integrity and reliability tests shall be undertaken to ensure that anynew major components, sub-assemblies or friction materials that affect brakingperformance will operate reliably and safely. These tests shall be undertaken onthose components, sub-assemblies and friction materials (see Appendix B) thathave not previously demonstrated satisfactory service experience in brakesystems. The tests can be undertaken on a test rig, provided that all the forcesand conditions, including climatic, that could reasonably be expected to be metin service are covered.

11.4Before they are put into fleet-wide service all new major components or sub-assemblies that employ new principlesof operation, new friction materials orcomplete brakesystems that do not comply with section 4.1 shall be subject toand satisfactorily complete, a service trial. The trial shall normally be of12 months duration, and shall cover representative climatic conditions and dutycycles on a sufficient number of vehicles.

11.5If a service trial of 12 months is not considered necessary, a risk analysis shallbe undertaken to determine the minimum length of the trial. A risk analysis shallalso be undertaken to determine whether a component should be the subject ofthe procedures defined in sections 11.3 and 11.4.

11.6The results of the stopping distance tests shall be assessed on the basis of amean stopping distance curve derived from the individual stopping distances.The following requirements shall be met:

a) There shall be sufficient test speeds to generate a stopping distance curve,unless limited testing is being carried out as permitted by section 11.2.

b) There shall be at least two stopping distance tests at each nominal testspeed.

c) The mean stopping distance curve shall normally be derived from a suitablemathematical process.

d) The mean stopping distance curve shall be less than or equal to the targetstopping distance.




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e) Except for test results from freight trains, it is permissible for a certain amountof the scatter in the stopping distances to exceed the maximum brakingdistance by a maximum of 5% of the target brakingdistance.

f) The total amount of scatter in the stopping distances at any speed shall notexceed 15% of the mean stopping distance curve.

g) Stopping distances are based on the signal spacings defined in GK/RT0034.Note that in the case of GK/RT0034Appendices 2 and 3 signal spacings forspeeds below 40 mile/h are the same as those for 40 mile/h. However, whenassessing trains against these two Appendices, tests shall be conducted atspeeds of 30, 20 and 10 mile/h to check the brakingperformance. For newfriction couples, these low speed tests shall be used to confirm that theretardation has not significantly degraded.

See Appendix A for an illustration of test results.

11.7On new trains that have WSP equipment and use compressed air for the brakesystem energy, a test shall be undertaken to simulate WSP activity by creating alarge air flow rate in the brakesystem. Appendix D gives guidance on the airflow rate to be achieved and the duration of the test. At the end of the test thepressure in the brakesupply reservoir shall be sufficient to provide a full servicebrakeapplication. Consideration of requirements for sufficient brakesystemenergy shall also be undertaken when alternative energy systems are usedwithin the brakesystem.




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Appendix A

This Appendix is for information only

Assessment of stopping dis tance test resul ts

yb

xa

0

50

100

150

0 500 1000 1500 2000 2500Stopping Distance

InitialSpeed

Target stopping distance curve

from Railway Group Standard

Mean stopping distance from

tests

xis acceptable if x 1.15 b

y is not acceptable if y< 0.9 b

See Paragraph 11.5

Note: acceptability of a, b, x and y comparisons are to be performed usingdistance and not speed measurements.




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Appendix B


Dynamometer test ing of fr ict ion m aterials

B.1

To meet the requirements of section 11.2, dynamometer tests should be carriedout using a full scale dynamometer and a friction face equivalent to that whichthe friction material will act upon. The following minimum requirements shouldbe included:

B.2

The dynamometer should simulate the axleload to be used in service up to andincluding the maximum. The axleload shall be proportioned to that shared by

the friction material position subject to test.

B.3

The brakingforce on the friction material should be equivalent to that obtained infull service brakingand within 10% of the calculated value for the appropriateaxleload. The area of the friction material should be the same as that used theapplication on the vehicle.

B.4

Dynamometer tests should be carried out simulating brakestops from a range ofspeeds up to and including the maximum vehicle speed. The tests shouldsimulate the tare and fully laden conditions of the vehicle or brakingduties.

B.5

The following measurements should be recorded:

Initial speed;

Force on friction material;

Stopping distance;

Stopping time;

Initial friction face temperature;

Maximum friction face temperature achieved during braking;

Average friction coefficient;

Instantaneous friction coefficient as a function of speed.

B.6

A brakefade sequence should be carried out which will include 4 stops from themaximum speed axleload and full service brakingforce.

B.7A drag brakesequence should be carried out at 47 mile/h for 20 minutes against20kW for friction materials to be used for passenger applications or 40kW forfreight applications. If the brakingcycle is predicted to be worse than thesevalues an alternative figure appropriate to the new cycle should be used.

B.8

A wet test should be carried out simulating the minimum and maximum brakingforces at the equivalent axleloads. This should use a water spray delivering atleast 25 litres / hour on to the friction surface for disc pad tests and 14 litres /hour for tests of brakeblocks.

B.9

The designation of the friction material tested should be recorded and thedesign, method of manufacture and principal constituents should not be changedwithout changing the designation of the material. In this case the new materialshould be subject to retesting.

B.10

The result of the dynamometer tests should be assessed to ensure the frictionmaterial meets the requirements of section 8.1 of the document.




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Appendix C


Principlesof o perat ion of current f r ic t ion brake

systems in use on Rail t rack co ntro l led inf rast ructure1 Automatic air-brake

(single or two pipe)C.1.1

Each vehicle has a distributor or triple valve (existing fleets only), air operatedbrakecylinders and an auxiliary reservoir (AR) and is connected by an automaticair-brakepipe (ABP) charged to 5 bar, which is continuous throughout the train.The distributor is connected to the ABP and responds to variations in brakepipe

pressure to pass compressed air from the AR to the brakecylinders or vent theair from the brakecylinders. A second pipe, the main reservoir pipe (MRP),normally charged to 7 bar, can be used to charge the AR directly but not when atriple valve is used, to form the two pipe system. Failure of the MRP does notaffect the automatic air-brakepipe and the system reverts to single pipeoperation.

C.1.2

An initial reduction of the pressure in the ABP sensed by the distributor isnecessary to generate an application of the brakeon each vehicle. The amountof application is proportional to the reduction in the ABP pressure and the brakeis released by recharging the ABP pressure. A reduction of 1.5 bar in the ABPpressure is required to produce a full service brakeapplication and the ABPpressure reduction occurs in 5-8 seconds. In an emergency brakeapplicationthe ABP pressure falls to zero.

C.1.3

The reduction or increase in the ABP pressure can be achieved by means of anair-brakevalve at the driving position or by a control at the driving position whichis connected electrically or pneumatically to devices remote from the drivingposition which regulate ABP pressure in response to the electrical signals.

C.1.4

The continuous and automatic element is given by the inter-vehicle connectionsof the automatic air-brakepipe. If these are broken, the loss of air pressureresults in an automatic brakeApplication on both parts of the train. The couplingheads comply with the following:

Pipe Colour Bore Specification

ABP Red 25.4 mm BS 3710 Fig 5 Type b not fitted with valve orUIC Leaflet 541-1 Appendix 4.

MRP Yellow 19 mm BS 3710 Fig 4 Type a, 19 mm fitted withvalve to suit 28.5 mm hose.




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C.1.5

BrakeForce Bui ld Up and Release Times Current ly in Use

To take account of the different coupling characteristics and operating speeds offreight and passenger trains, different brakeforce application and release timesare used. For the automatic air-brakesystem, the following times have beenadopted for an individual vehicle. These times are related to an emergencybrakeapplication, with its very rapid reduction in ABP pressure in order that theyare not influenced by the rate of fall of the air-brakepipe pressure in a fullservice brakeapplication:

BrakeTiming Type Application Time for BrakeCylinder Pressureto Reach 95% of Maximum (Seconds)

Release Time for BrakeCylinder Pressure toFall from Maximum to 0.4 bar (Seconds)

Single Pipe System Two Pipe System Single Pipe System Two Pipe System

PASSENGER

GOODS

3 5

18 30 *

2 3

9 - 15 *

15 - 20 **

30 - 45

15 - 20 **

30 - 45

Note that for traction units:* these times are 20 - 28 seconds, ** these times are 9 - 12 seconds.

2 Automatic air-brake

with electro-pneumatic

(EP) assis tC.2.1

The arrangement is as for section 1.1 but in addition to the continuous ABP,there are train wires connecting EP valves on each vehicle. When the driveroperates the air-brakecontroller, the train wires are arranged to carry anelectrical signal to the EP valves which locally vary the brakepipe pressure

simultaneously on each vehicle, on the basis of either an energise to apply orrelease principle.

C.2.2

The continuous and automatic element is given by the inter-vehicle connectionsof the automatic air-brakepipe.

The brakeforce build up time is 4 - 5 secs and release time is 5 - 6 secs.

3 Automatic air-brake

and electro-pneumatic

(EP) con trolC.3.1

As for section 1.1 with regard to the vehicle mounted compressed air-brakeequipment but there is an additional EP system with train wires that carry anelectrical signal to EP valves on each vehicle, which control the application ofthe brakesby admitting air from the main reservoir pipe to the brakecylinders,on the basis of energise to apply. The release of the brakesis obtained byventing the brakecylinders. Under normal operation, the brakepipe is not usedto control the brakebut can be used if the EP control fails.

C3.2

As the EP system in 3.1 is not fail-safe, the continuous and automatic element isgiven by the inter-vehicle connections of the air-brakepipe.

The brakeforce build up time is 4 - 6 secs.




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4 Air-brakew i th elect ro-

pneum atic (EP) contr olC.4.1

Each vehicle has air operated brakecylinders, together with a reservoir for thestorage of compressed air and is connected by a main reservoir pipe (MRP) thatsupplies compressed air to each vehicle. A train wire is arranged to carry theelectrical supply to the drivers brakecontroller from the rear of the train, therebyensuring electrical continuity throughout the train is proven. Electrical signalsfrom the drivers brakecontroller are then carried down train wires to the EPvalves on each vehicle that control the release and application of the brakes, onthe basis of the energise to release principle.

C.4.2

The continuous and automatic element is given by the inter-vehicle connectionsof the train wires. If the continuity in the train wires is interrupted and thereforethe electrical supply to the brakecontroller and thus to the EP valves is lost, the

brakesautomatically apply.

The brakeforce build up time is 2 - 3 secs and release time is 3 - 6 secs.

5 Direct air-brakeC.5.1

Provides an additional brake, independent of the automatic train brakeontraction units, using compressed air controlled separately from the automaticbrakesystem, that is fed directly to the air-brakecylinders on the vehicle.

C.5.2

This brakeis not fail-safe (because when running as a single vehicle there is norequirement for a continuous or automatic element) but the control system shallbe as direct as possible.

C.5.3

Direct Air-Brake, brakeforce Bui ld Up and Release Times Current ly in Us e

Application Time for BrakeCylinderPressure to Reach 95% of Maximum

(Seconds)

Release Time for BrakeCylinderPressure to Fall from Maximum to

0.4 bar (Seconds)

2.5 4 7

6 Autom at ic vacuum

brake(for exist ing

f leets only)C.6.1

A vacuum brakepipe, continuous throughout the train, connects all the vehiclesthat have vacuum brakecylinders. The vacuum regime releases the brakeandalso creates vacuum on both sides of the piston in the cylinder, one side actingas a reservoir and providing brakepower when vacuum is reduced in the brakepipe. A brakevalve is provided to control the admission of atmospheric air to thevacuum brakepipe and the underside of the piston in the vacuum cylinder. Theextent to which the level of the vacuum is reduced determines the level of thebrakeapplication.

C.6.2

The transmission of the signal down the vacuum train pipe can be improved bymeans of a direct admission (DA) valve or accelerated freight inshot valve (AFI)at each brakecylinder.

C.6.3

The continuous and automatic element is provided by the vacuum brakepipe asadmission of atmospheric air automatically results in a brakeapplication.




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Appendix D


Guidance on the BrakeSystem energy requirements to take

accoun t of WSP act iv i ty

D.1

WSP activity will increase the energy used by the brakesystem although theamount of additional energy will depend on the value and extent of the lowadhesion and the effectiveness of the WSP system.

D.2

In the case of a compressed air system, the ability of the system to provide

sufficient air will depend on:

the compressor delivery capacity and reservoir volume;

the ability of the system pipework and valves to deliver the required flowrates to all the vehicles;

the effectiveness of the WSP system.

D.3

Experience indicates that a flow rate of approximately 600 litres / min / vehicle isrequired. This air consumption needs to be sustained for the length of time thatwould be required to stop the vehicle in low adhesion conditions. This willdepend on the vehicle maximum speed and adhesion available.

D.4

Based on adhesion surveys, a reasonable value likely to be present over theentire duration of a stop would be one that gave a mean retardation of 4.5%g.Using the vehicle maximum speed and this retardation, it is possible to calculatethe time taken for the stop and therefore the time over which the air should bedelivered. For vehicles with a maximum speed of 100 mile/h this equates to100 secs.

D.5

Air delivery less than 600 litres/min can be accepted if it can be demonstratedthat the WSP system on the train is such that the air consumption requirementsof the WSP under low adhesion conditions is less than this value.

D.6

The following test will enable a check to be made on the ability of the brakesystem to provide sufficient energy. To create the air flow defined in section D5,

the air pipes to sufficient brakecylinders should be disconnected on eachvehicle and a full service brakeapplication made which will then result in high airconsumption. By monitoring the time that the compressor runs and its rateddelivery capacity the air consumption can be established. The air pressure onwhich the delivery rate of the compressor is established should be the mid pointbetween the governor settings.

D.7

At the end of the period of time calculated by the method described in sectionD4, the pressure in the reservoir on each vehicle should be sufficient to providea full service brakeapplication.




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Appendix EThis Appendix is for information only

Factors to be taken into account w hen cons ider ing the

protect ion of d r iver s brakevalve exhaust o ut lets

E1

If there has been an incident on a vehicle when ice and / or snow blocked thevent pipes that exhaust compressed air from the drivers brakevalve andprevented a brakeapplication being made.

E2

For particular vehicles the following should also be considered:

a) Is the current location of the vent pipe vulnerable to the build up of ice andsnow?

b) Is the vehicle likely to be involved in snowploughing which could increase thepossibility of ice and snow build up round the vent pipe orifice?

c) Does the vehicle operate in areas where there is experience of heavysnowfalls combined with periods of low temperatures (less than -15C)?

d) Has there been any experience of vent pipes being blocked on the vehicleconcerned in the current area of operation of the vehicle?

E3

If the result of the above analysis reveals that there is an unacceptable risk of

the vent pipe being blocked by the build up of ice or snow, arrangements shouldbe made to protect the vent pipes from being blocked.




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References

Railway Group Standards

GA/RT6001 Railway Group Standards Change Procedures

GK/RT0034 Lineside Signal Spacing

GM/RT2041 BrakingSystem Requirements and Performance for Trailer Coaching Stock

GM/RT2042 BrakingSystem Requirements and Performance for Traction Units

GM/RT2043 BrakingSystem and Performance for Freight Trains

GM/RT2044 BrakingSystem Requirements and Performance for Multiple Units

GM/RT2046 BrakingSystem Requirements and Performance for Trains Which OperateAbove125 mile/h

GM/RT2161 Requirements for Driving Cabs of Railway Vehicles

GM/RT2400 Design of On-Track Machines

GO/RT3000 Master Rule Book

The Catalogue of Railway Group Standards and the Railway Group StandardsCD-ROM give the current issue number and status of documents published by

the Safety & Standards Directorate.

Related DocumentsBR Specification 569

and UIC Leaflet 541-3 define acceptance requirements for disc brakecomposition brakepads.

For tread brakes, the following specifications define the requirements for brakeblocks

TL/TS0150 Cast iron brakeblocks (supersedes BR 142);BR 567 High friction composition K blocks;BR 574 Low friction L composition blocks;

UIC 541-1 Regulations concerning the construction of various brakecomponents.Railway Safety (Miscellaneous Provisions) Regulations 1997 (see Regulation 6)




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