GM/GN2497. Guidance on Railway Wheelset Tread, Gauging and Damage. Identification. Railway Group Guidance Note. Published by

Transcription

1 GN Published by Rail Safety and Standards Board Evergreen House 160 Euston Road London NW1 2DX Copyright 2007 Rail Safety and Standards Board Limited GM/GN2497 Issue One: December 2007 Railway Group Guidance Note

2 Issue Record Issue Date Comments One December 2007 Original document Derived from draft IB/TT0436, which was derived from MT162 and MT288 Superseded documents Supply This Railway Group Guidance Note does not supersede any other Railway Group documents. Controlled and uncontrolled copies of this Railway Group Guidance Note may be obtained from the Corporate Communications Department, Rail Safety and Standards Board, Evergreen House, 160 Euston Road, London NW1 2DX, telephone or e- mail Railway Group Standards and associated documents can also be viewed at Page 2 of 43 RAIL SAFETY AND STANDARDS BOARD

3 Contents Section Description Page Part 1 Introduction Purpose of this document Copyright Approval and authorisation of this document 5 Part 2 Background Development of the document Rationale Scope 6 Part 3 Guidance on Requirements at Wheelset Re-profiling Application Profile type, tolerance and condition Profile alignment Tread run-out Wheel wobble Wheelset back-to-back Wheel diameter difference Wheel rim / tyre thickness Throat thickness Wheel tread roll-over Tyre security Witness marks 9 Part 4 Guidance on Requirements at Wheelset Tread Profiles In Service Application Profile tread condition Flange height and thickness Toe radius build-up / sharp flanges Wheelset back-to-back dimension Wheel diameter Wheel rim / tyre thickness Throat thickness Wheel tread roll-over Tyre security 11 Part 5 Guidance on Requirements at Wheelset Gauging Principles Gauging following re-profiling Wheelset gauging and inspection of tread condition - in service examination 12 Part 6 Guidance on Requirements at Tread Damage, Examination and Assessment Wheel flats and wheel slide damage Tread run-out Cracking Cavities Flange condition Wheel tread roll-over Other damage 25 Part 7 Guidance on Overheated Wheels Examination of overheated wheels 27 RAIL SAFETY AND STANDARDS BOARD Page 3 of 43

4 Part 8 Guidance on Wheelsets Involved in a Derailment Actions following derailment of wheelsets 28 Appendices 30 Appendix A Wheelset and Tread Profile Gauging Systems 30 Definitions 37 References 43 Tables Table 1 Wheel flat limits and actions applicable to vehicles in traffic 16 Table 2 Speed limits for recovery of vehicles with wheel flats 17 Table 3 Tread run-out limits and actions applicable to vehicles in traffic 18 Table 4 Actions to be taken on discovery of cavities during inspection in traffic 23 Table 5 Actions to be taken on discovery of cavities during routine inspection at maintenance 23 Figures Figure 1 Permissible witness marks on re-profiled wheel treads 9 Figure 2 Photograph of tread roll-over 11 Figure 3 Isolated wheel flat showing measurement of length 14 Figure 4 Multiple wheel flats 15 Figure 5 Thermally induced cracking on wheel tread due to tread brakes 19 Figure 6 Light cracking due to RCF 20 Figure 7 Section through a wheel with RCF 21 Figure 8 Typical damage associated with a wheel slide showing area of cracks in martensite, and spalled material 21 Figure 9 Long cavity 22 Figure 10 Flange toe radius assessment gauge 23 Figure 11 Flange toe radius build-up 24 Figure 12 Display of measured wheel profile with flange toe radius build-up 24 Figure 13 Crack on flange 26 Figure 14 Cracks on wheel tread extending down the chamfer 26 Figure 15 Definition of false flange 37 Figure 16 Definition of profile 38 Figure 17 Diagram of tread roll-over 39 Figure 18 Definition of a sharp flange 40 Figure 19 Definition of cavity 40 Figure 20 Definition of throat thickness 41 Figure 21 Toe radius build-up 41 Page 4 of 43 RAIL SAFETY AND STANDARDS BOARD

5 Part 1 Introduction 1.1 Purpose of this document This document has been published by Rail Safety and Standards Board to give guidance on Wheelset Tread, Gauging and Damage. This guidance is intended to assist duty holders in understanding their responsibilities in relation to Wheelset Tread, Gauging and Damage. It does not constitute a recommended method of meeting any set of mandatory requirements. 1.2 Copyright Copyright in the Railway Group documents is owned by Rail Safety and Standards Board Limited. All rights are hereby reserved. No Railway Group document (in whole or in part) may be reproduced, stored in a retrieval system, or transmitted, in any form or means, without the prior written permission of Rail Safety and Standards Board Limited, or as expressly permitted by law. RSSB Members are granted copyright licence in accordance with the Constitution Agreement relating to Rail Safety and Standards Board Limited. In circumstances where Rail Safety and Standards Board Limited has granted a particular person or organisation permission to copy extracts from Railway Group documents, Rail Safety and Standards Board Limited accepts no responsibility for, and excludes all liability in connection with, the use of such extracts, or any claims arising therefrom. This disclaimer applies to all forms of media in which extracts from Railway Group Standards may be reproduced. 1.3 Approval and authorisation of this document The content of this document was approved by: Rolling Stock Standards Committee on 05 October 2007 This document was authorised by RSSB on 15 October 2007 RAIL SAFETY AND STANDARDS BOARD Page 5 of 43

6 Part 2 Background 2.1 Development of the document This document has been drafted under the auspices of the cross-industry Wheelset Best Practice Group, a technical sub-group of Vehicle Track System Interface Committee, and is designed to supersede MT162 and in part, MT288. It is envisaged that the residual data elements of MT288 will be absorbed into IB/TS0648, or other databases as appropriate This document gives guidance on the practices which should be followed to maintain standards and compliance with GM/RT2466 for wheel and tyre treads of a wheelset whilst it is fitted to a vehicle for operation over Network Rail managed infrastructure, in particular: a) The standards to be applied during wheel profiling b) The standards to be applied whilst in service c) The tread gauges which can be used and their method of use d) Permissible tread damage e) Requirements for dealing with overheated wheels and derailed wheelsets This document sets out arrangements for the recognition of tread damage, including rolling contact fatigue, requiring remedial attention, to be applied in-service and at maintenance. 2.2 Rationale 2.3 Scope To maintain the safe operation of vehicles that run on Network Rail infrastructure, the controls that need to be put in place to manage wheelsets are mandated in GM/RT2466. This document gives guidance on the requirements of GM/RT2466 with regard to the dimensional and physical condition of wheel treads at re-profiling and in-service The identification of wear and tread damage and the subsequent appropriate action to be taken in accordance with this publication, will minimise further damage and reduce maintenance costs for both vehicles and the infrastructure This document supports the requirements of GM/RT The guidance in this document is relevant to organisations engaged in the inspection and maintenance of wheelsets The document identifies the dimensions that should be controlled and in some circumstances, the limits to be applied, either directly or by reference to other sources. Where no data is referenced it is the responsibility of the user to ensure suitable limits are established. It does not mandate the means of measurement. Gauges that have been traditionally used for this purpose have a BR Cat. No. and are identified in Appendix A This document gives guidance for the identification of tread damage requiring remedial attention on all rail-mounted vehicles except possession-only rail vehicles. It is applicable to tread damage on both monobloc and tyred wheels. This document does not cover requirements for resilient wheels. Page 6 of 43 RAIL SAFETY AND STANDARDS BOARD

7 2.3.4 The user should set the examination frequencies in the maintenance plan to ensure that the mandatory safety limits in GM/RT2466 are not exceeded at any time Advice should be sought from a Technically Competent Authority for tread damage that is not covered by this document but is likely to affect the safety of a vehicle. RAIL SAFETY AND STANDARDS BOARD Page 7 of 43

8 Part 3 Guidance on Requirements at Wheelset Re-profiling 3.1 Application When wheels are re-profiled, the wheel profile dimensions should conform with the data contained in the user s maintenance instructions - see During re-profiling, clamps or restraints may be required to prevent the axlebox from rotating and these should be applied in accordance with the relevant lathe manufacturers instructions. 3.2 Profile type, tolerance and condition The tread profile should be that applicable to the vehicle type as defined in the relevant user s maintenance instructions see The profile tolerance should be in accordance with the relevant drawing. However, in general, dimensional tolerances will be ±0.25 mm. Following re-profiling the tread surface including flanges should be free of visible defects such as cracks, cavities, flats or spalling and have a surface roughness no coarser than 12.5 µm (N10). To avoid excessive wheel material removal back flange wear up to a depth of 1mm is allowed to remain following re-profiling Details of the gauges that can be used to confirm that the profile is correct are shown in Figure A.2 of Appendix A. The gauge is held on the profile in contact with the flange back and tread surface. The Go / No-Go gauge should enter with the Go and not enter with the No-Go end between points K to L and M to N. 3.3 Profile alignment The profiles of wheels on the same axle should be aligned relative to each other. There are presently no definitive limits for this, although railway undertakings should be aware that any misalignment of one profile relative to the other will affect wheelset conicity, and hence stability and curving performance: vehicle-specific tolerances may therefore be given on the wheelset assembly drawing or separate local procedure Details of gauges used to assess profile alignment are shown in Figure A.1 of Appendix A. The profile is checked by assessing the gaps between the tread and gauge at positions K to L and M to N. When the gauge is used on a wheelset carrying the weight of a vehicle, it may be necessary to fit the gauge to the profiles at the same height above the rail as the axle (that is 3 o clock or 9 o clock positions) and to release the brakes. This is to avoid errors due to axle deflection under load. 3.4 Tread run-out Following re-profiling the tread run-out should be as detailed in the relevant user s maintenance instructions see Wheel wobble Following re-wheeling and/or re-tyring the permissible wheel wobble should be in accordance with the overhaul limit specified in the relevant user s maintenance instructions. Following re-profiling the permissible wheel wobble should be in accordance with the repair limit specified in the relevant user s maintenance instructions see GCU vehicles are permitted to have up to 0.75 mm wheel wobble at any time. Page 8 of 43 RAIL SAFETY AND STANDARDS BOARD

9 3.6 Wheelset back-to-back This is to be as specified in the relevant user s maintenance instructions see Assessment of the back-to-back dimension can be obtained with Go / No-Go gauges (shown in Figure A.4 of Appendix A) and feeler gauges or a calibrated internal micrometer. 3.7 Wheel diameter difference This is to be as specified in the relevant user s maintenance instructions see Wheel rim / tyre thickness This is to be as specified in the relevant user s maintenance instructions see Throat thickness Where appropriate this information is contained in the relevant user s maintenance instructions see For monobloc wheels, the throat thickness is the dimension between the root of the radius of the tread profile (flange root), and the underside of the flange-side wheel rim, measured at the narrowest point. The gauges used to assess the throat thickness are shown in Figures A.8 and A.9 of Appendix A. Measurements should be taken away from areas that have been machined during balancing of the wheel The minimum or scrapping throat thickness is set by the design strength of the wheel, and cannot therefore be infringed. The general limits are traditionally specified according to the size of the wheel bearings, although in reality they relate to axle loads and wheel forces Wheel tread roll-over Following re-profiling there should be no tread roll-over Tyre security Following re-profiling the tyre and retaining ring security should meet the requirements of IB/TP0001 Tyre Security Maintenance Procedures Witness marks Tread profiles may be machined to remove the minimum amount of metal to restore the profile, leaving a witness mark as shown in Figure 1 is permissible. All visible cracks, cavities and hard spots are to be machined out. Figure 1 Permissible witness marks on re-profiled treads RAIL SAFETY AND STANDARDS BOARD Page 9 of 43

10 Part 4 Guidance on Requirements for Wheelset Tread Profiles in Service 4.1. Application The requirements for the wheel tread profiles to be applied whilst the wheelsets are in service are detailed below Wheelset profiles should not exceed the tolerable criteria defined in GM/RT2466 at any time, including between inspections. To achieve this the limits in the relevant user s maintenance instructions, see 2.3.4, should define the examination intervals, so that normal rates of wear will not result in the mandatory safety limits being exceeded between planned examinations. 4.2 Profile tread condition The profile and tread condition should conform to Part 6 of this document. 4.3 Flange height and thickness These should not exceed the limits defined in the relevant user s maintenance instructions see These limits should ensure that the mandatory limits in GM/RT2466 are not exceeded between wheelset inspections. The gauges used to assess the flange thickness and height are shown in Figures A.3, A.10 and A.11 of Appendix A The gauge shown in Figure A.3 is used by opening out both slides. The gauge is held squarely on the flange back and drawn down onto the profile at right angles to the tread surface. The sliders are then moved to make contact with the tread and measurements taken The user may also choose to set alternative limits to suit their operational requirements, for example restricted flange height for economic tyre re-profiling, or to control vehicle stability as a result of increased conicity. However, the limits should not infringe the mandatory requirements of GM/RT Toe radius build-up / sharp flanges Toe radius build-up and sharp flanges should not exceed the limits in Part 6 of this document. 4.5 Wheelset back-to-back dimension Back-to-back dimension should not exceed the limits defined in the relevant user s maintenance instructions see Wheel diameter Diameter and diameter differentials should not exceed the limits defined in the relevant user s maintenance instructions see Wheel rim / tyre thickness Wheel rim / tyre thickness should not exceed the limits defined in the relevant user s maintenance instructions see Gauges used to assess the wheel rim and tyre thickness are shown in Figures A.7 and A.6 of Appendix A. 4.8 Throat thickness When applicable to a wheel, the throat thickness should not exceed the limits defined in the relevant user s maintenance instructions see Page 10 of 43 RAIL SAFETY AND STANDARDS BOARD

11 4.9 Wheel tread roll-over Wheel tread roll-over (Figures 2 and 17) should not exceed 5 mm from the outer face of the wheel. Any cracks or defects present in the roll-over should not extend into the tread or the rim face. Figure 2 Photograph of tread roll-over 4.10 Tyre security The tyre and retaining ring security should be maintained by the application of the requirements specified in IB/TP0001. RAIL SAFETY AND STANDARDS BOARD Page 11 of 43

12 Part 5 Guidance on Wheelset Gauging Principles 5.1 Gauging following re-profiling Following re-profiling it should be ensured that the requirements of Part 3 of this document are met. As a minimum, compliance with the following should be demonstrated: a) Tread profile b) Profile surface finish c) Tread run out d) Wheel wobble e) Wheelset back-to-back f) Wheel diameter Generally, the machine tools used to re-profile wheels produce highly repeatable results and therefore it is not mandatory to carry out a full inspection of every wheelset. Traditionally the gauges listed in Appendix A have been used at least at the start of each shift and immediately following the change of the master profile. The individual dimensions will control the profile alignment and it is not necessary to carry out a specific check for this. However, it may be convenient to use a profile alignment tool as it allows a number of checks to be carried out simultaneously More modern machines have their own in-built measuring system that prints the result out on the completion of turning and hence no gauging is required, although use of profile alignment tools would again provide a useful back check that the correct profile has been applied. However, it is the user s responsibility to ensure that whatever gauging system is used the requirements of Part 3 are met In addition to the traditional gauges or the integrated measuring system of a machine, there are many alternative systems available such as electronic profile measurement tools for checking tread profiles The user is free to use an alternative system providing it can be demonstrated to provide the required level of repeatability and accuracy and it is subject to a calibration that conforms to the requirements of BS EN ISO Wheelset gauging and inspection of tread condition in service examination The requirements for gauging and measurement are in accordance with GM/RT2466. For the various vehicles they operate, the limits defined in the relevant user s maintenance instructions should be set to ensure that under normal wear conditions the tolerable criteria set in GM/RT2466 will not be exceeded between planned examinations Any gauging procedure used to measure the applicable tolerable criteria should be fit for purpose and capable of demonstrating the required level of accuracy and confidence in compliance (see Part 4). Page 12 of 43 RAIL SAFETY AND STANDARDS BOARD

13 5.2.3 The areas of the tread profile to be assessed should include the following: a) Flange thickness and height b) Toe radius build-up or sharp flange gauging c) Wheel rim / tyre thickness d) Wheel diameter e) Throat thickness f) Profile condition, tread damage, tread roll-over and other abnormal type of damage The user is free to choose their own system of control but all equipment should be subject to a certified calibration system. Potential methods of achieving this are described below: a) Using Go / No Go gauges as described Appendix A, but with revised dimensions to take into account operational environments together with the maintenance regime applied so as not to exceed the limits quoted in GM/RT2466. b) Rather than using gauges, the user can make routine measurements to monitor the wear trends and take appropriate action to ensure that the limits are not exceeded. Suitable gauges for carrying this out are listed in Appendix A. c) Use of suitably calibrated trackside/remote monitoring systems that measure wheel dimensions on a regular basis and allow trends to be established. These systems are to be used as an aid to data capture and analysis but manual inspection should still be carried out to confirm results. Examples of types of system that are currently available are given below: i) Laser and camera, track side based systems that record the tread profile as the vehicle passes over them. The profile data are processed to determine the critical dimensions and carry out analysis to identify wear trends. ii) Wheel out-of-round measurements can be made by use of an instrumented knife rail and bar that makes contact with the flange tip of the wheel. Variations in flange height due to out-of-round will produce measured displacements of the bar Instrumentation of the running rail can record impact loads produced by a wheel. High loads are indicative of wheel defects such as shelling or flats. Generally these systems are used to protect the infrastructure but also provide information that could be used to monitor wheel condition. The results of such systems are speed dependant together with the ramp effect of the surround of the defect. An oval wheel at relatively low speed may not be identified if the measuring equipment was sited on a slow road such as in a depot. RAIL SAFETY AND STANDARDS BOARD Page 13 of 43

14 Part 6 Guidance on Tread Damage, Examination and Assessment 6.1 Wheel flats and wheel slide damage Cause of wheel flats Under braking or traction where there is insufficient adhesion to allow transmission of the braking and traction force between the wheel and rail, the wheel can lock up and slide under braking, or spin under traction. This can result in the formation of isolated or multiple flats on the wheel surface Isolated flats Where an isolated wheel flat is found (Figure 3), the length of the flat around the circumference of the tread should be measured, including any regions of discolouration due to heat conditioning. These usually occur on vehicles that do not have a wheel slide protection (WSP) system fitted, or where the WSP system is faulty or inoperative. Where such flats are observed, corresponding damage would be expected to be found on the opposite wheel of the wheelset The remedial action to be taken is given in Table 1. Figure 3 Isolated wheel flat showing measurement of length Multiple flats Multiple flats (Figure 4) usually occur as a result of the slip/stick type phenomenon seen on early high-speed disc-braked vehicles with a relatively ineffective WSP system. Where multiple flats within a damaged region are found the lengths of individual flats are to be measured, as shown in Figure 3, and remedial action taken in accordance with Table 1. Page 14 of 43 RAIL SAFETY AND STANDARDS BOARD

15 Figure 4 Multiple wheel flats General comments and description of wheel flats On modern vehicles with a more effective WSP, discernible flats tend not to occur. However, discrete slipping or slides can occur of sufficient duration to generate heat, resulting in localised phase change of the material and the formation of martensite. The martensitic material will eventually fall out leaving a series of small cavities generally arranged circumferentially around an arc of the tread. The cavities can be sufficiently close to become linked if they are allowed to remain in service without remedial action, resulting in a large damaged area on the tread Isolated flats are generally as a result of low adhesion and the lack of a WSP system. If the vehicle is fitted with WSP a system check should be carried out to check that it is functioning correctly and other possible causes should be investigated. Additionally, but less frequently, wheel flats may be caused by dragging brakes. The hazards associated with dragging brakes require an effective maintenance and monitoring regime Multiple flats are generally as a result of low adhesion and a relatively slow response from the WSP system. If they occur the WSP system should be checked. RAIL SAFETY AND STANDARDS BOARD Page 15 of 43

16 6.1.5 Actions to be taken on the discovery of wheel flats Vehicle type Any vehicle permitted to operate above 125 mile/h and up to 140 mile/h Passenger or personnel vehicles operating at speeds up to and including 125 mile/h Non-passenger vehicles, locomotives, power cars, driving van trailers Freight vehicles up to 17.5 tonnes axle load Freight vehicles equal to or over 17.5 tonnes axle load Other vehicles Wheel flat length Vehicle to be taken out of service Speed restriction Above 60 mm Immediately See GM/RT2466 Above 40 mm to 60 mm 30 mm to 40 mm On completion of the journey Within 24 hours of the fault being found The speed should be limited to 125 mile/h until the vehicle is taken out of service Discretion of railway undertaking Above 60 mm Immediately See GM/RT mm to 60 mm Within 24 hours of the fault being found Discretion of railway undertaking Above 60 mm Immediately See GM/RT mm to 60 mm On completion of the journey Discretion of railway undertaking Above 80 mm Immediately See GM/RT mm to 80 mm On completion of the journey 60 mile/h Above 70 mm Immediately See GM/RT to 70 mm On completion of the journey 60 mile/h Above 60 mm Immediately See GM/RT to 60 mm On completion of the journey Table 1 Wheel flat limits and actions applicable to vehicles in traffic 60 mile/h Page 16 of 43 RAIL SAFETY AND STANDARDS BOARD

17 Vehicles with wheel flats greater than defined in Table 1 should be recovered from the running line in accordance with Table 2. Damage Flat length longer than 100 mm or tread run-out greater than 8.0 mm Flat length 70 mm to 100 mm long or tread run-out 5.0 mm to 8.0 mm Flat length up to 70 mm long or tread run-out 3.0 mm to 5.0 mm Speed restriction A vehicle shall not be moved except to clear the running line and at a maximum speed of 5 mile/h or with the use of a wheelskate. Further movement shall be with the authorisation of a technically competent authority and the infrastructure manager Speed restriction of 35 mile/h Speed restriction of 60 mile/h Table 2 Speed limits for recovery of vehicles with wheel flats It should be noted that where a vehicle has been stopped in traffic for exceeding any wheel impact load detection threshold limit, the Network Rail requirement for actions supersede any limits contained in this document. In the event that a wheel impact load detection threshold is exceeded, but no visible tread damage is observed, the wheel may be out-of-round and would require further investigation Where damage is less than the lower limit no action is required. However, it is suggested that where smaller defects are found, they are monitored and rectified within two weeks. Consideration should also be given to restoring the tread profile at a convenient point as subsequent damage such as out-of-round or shelling may result. The most common method for the restoration of the wheel tread profile is by machining on a wheel lathe. However, other methods such as grinding (using purpose-built facilities) are acceptable. Hand techniques are not acceptable. 6.2 Tread run out Tread run out occurrence and measurement Tread run out occurs where the wheel tread is no longer circular or concentric with the axle bearing surfaces. A wheel that is no longer circular can take two forms, either out-of-round or oval, although practically all run-out of the wheel tread could be considered to be out-of-round. Generally defects of this type cannot be found by visual inspection and some form of measurement will be required These measurements can be undertaken by manual measurements of the flange height relative to the tread or wheel tread diameters at numerous positions around the wheel. Alternatively, automated systems are available that measure the degree of out-of-round or wheel impact loads in traffic. RAIL SAFETY AND STANDARDS BOARD Page 17 of 43

18 6.2.2 Actions to be taken on the discovery of tread run-out Remedial action to be taken if tread run out is found on a vehicle in traffic is shown in Table 3. These are the mandatory limits specified in GM/RT2466. Vehicle type Tread run-out Vehicle to be taken out of service Any vehicle permitted to operate above 125 mile/h and up to 140 mile/h Above 1.3 mm 0.7 mm to 1.3 mm Immediately Within 24 hours of the fault being found Passenger or personnel vehicles operating at speeds up to and including 125 mile/h Non-passenger vehicles, locomotives, power cars, driving van trailers and on-track plant Above 3.0 mm Immediately 1.3 mm to 3.0 mm Within 24 hours of the fault being found Above 3.0 mm Immediately 1.3 mm to 3.0 mm On completion of the journey Freight vehicles up to 17.5 tonnes axle load Above 5.0 mm 3.0 mm to 5.0 mm Immediately On completion of the journey Freight vehicles equal to or over 17.5 tonnes axle load Other vehicles Above 4.0 mm Immediately 2.0 mm to 4.0 mm On completion of the journey Above 4.0 mm Immediately Speed restriction 60 mile/h 60 mile/h 2.0 mm to 4.0 mm On completion of the journey Table 3 Tread run-out limits and actions applicable to vehicles in traffic 60 mile/h It should be noted that where a vehicle has been stopped in traffic for exceeding any wheel impact load detection threshold limit, the Network Rail requirement for actions supersede any limits contained in this document Where run-out is found during routine examination but which is less than the lower action limit, no action is required. However consideration should be given to restoring the tread profile at a convenient point as subsequent damage such as out-of-round or shelling may result. Page 18 of 43 RAIL SAFETY AND STANDARDS BOARD

19 6.3 Cracking Position and occurrence of wheel tread cracking Cracking can occur at any position on the wheel surface but is most common in the tread area There are three main causes of cracking in the tread: a) Thermal effects due to tread braking b) Rolling contact fatigue c) Thermal effects due to sliding Other types of cracking can occur as a result of specific problems and examples of these are covered in Thermal effects due to tread braking This will normally be found on the tread where the brake block acts on the tread. Initially it is seen as a network of fine cracks or crazing. It is similar in appearance to the cracking shown in Figure 5 and is generally disposed laterally across the tread. Damage of this kind is acceptable providing the cracks have not propagated to the outer chamfered edge of the wheel, or have propagated longer than 40 mm on the tread surface. It is therefore recommended that wheels that exhibit cracks on the chamfer or longer than 40 mm should be removed from traffic immediately. Figure 5 Thermally induced cracking on wheel tread due to tread brakes RAIL SAFETY AND STANDARDS BOARD Page 19 of 43

20 6.3.3 Rolling contact fatigue This occurs due to the repeated loading and unloading of the tread as it both rolls along tangent track and steers around curves. Initially the damage appears as a network of fine cracks similar in appearance to the thermal effects of tread braking. However, rolling contact fatigue (RCF) cracks tend to be positioned at an angle across the tread (Figure 6). Cracking of this type is generally acceptable but it is recommended that regular measurements of the cracks be undertaken to monitor their growth. RCF cracks do not generally result in wheel breakage but will tend to result in the formation of cavities. It is therefore recommended that wheels that exhibit cracks greater than 40 mm long be removed from service for re-profiling. Figure 6 Light cracking due to RCF It should be noted that RCF cracks have a tendency to propagate radially and the surface condition may not reflect the crack depth. A typical section through a wheel with RCF cracking is shown in Figure 7. It can be seen that although the damage at the tread surface is relatively benign, the cracks extend some way into the rim. It may therefore be prudent to re-profile wheels at regular set intervals, irrespective of the visible surface condition, to avoid the formation of cavities and deep cracks that would necessitate large cuts on a wheel lathe to remove all the cracking. Page 20 of 43 RAIL SAFETY AND STANDARDS BOARD

21 Figure 7 Section through a wheel with RCF Thermal effects due to sliding When a wheel slide occurs, the tread can reach elevated temperatures at the contact patch of slide. Once the wheel starts to rotate again the localised temperature will cool to the wheel bulk temperature. This rapid heating and cooling may result in a change in the steel structure and the formation of martensite. Martensite is very brittle and cracks will be able to develop more readily compared to the unaffected parent material. These cracks will be coarser than those discussed previously and there will probably be a group of them disposed laterally across the tread in the area where the wheel slide occurred. An example is shown in Figure 8. Limited damage of this type is acceptable provided none of the crack lengths exceeds 40 mm. It is therefore recommended that wheels that exhibit cracks greater than 40 mm long be removed from service for re-profiling on completion of the journey. Figure 8 Typical damage associated with a wheel slide showing area of cracks in martensite, and spalled material RAIL SAFETY AND STANDARDS BOARD Page 21 of 43

22 6.4 Cavities Although all the above types of cracking are acceptable they should not be allowed to encroach into the area of the chamfer that forms the tread to rim face transition. Of particular concern is any cracking that results in a ragged edge to any roll-over that has occurred in this area. Once damage is seen in this area the profile should be restored to the as-new condition immediately All cracking will eventually lead to the formation of cavities as can be seen in Figures 8 and 9. The acceptance limits for cavities are discussed in 5.4. Whilst it is not necessary to re-profile wheels for coarse cracks, taking remedial action when the damage is relatively benign may reduce the amount of material that has to be removed to restore the wheel profile. In this way it could be possible to extend the overall wheel life. Scheduling the vehicle on to the wheel lathe due to the presence of cracks may also prevent an out of course machining due to unacceptable cavities The above examples of cracking are as a result of normal service degradation, however cracks can occur as a result of specific problems and these are identified in Over a period of time in service, cracks present in the tread will grow and the material around them will become detached, forming a cavity. Generally, cavities do not exceed 3 mm in depth. However the length of the cavity will continue to increase around the tread circumference. Figure 9 illustrates a long cavity. Figure 9 Long cavity Where a cavity, or cavities, is found in the wheel tread, then these should be measured. The actions to be taken are detailed in Tables 4 and 5. Page 22 of 43 RAIL SAFETY AND STANDARDS BOARD

23 Cavities found during an inspection in traffic Any single cavity greater than 15 mm long circumferentially around the wheel Any two cavities, separated by less than 50 mm, having a combined length in excess of 15 mm circumferentially around the wheel Action The wheelset should be withdrawn from service within 24 hours in accordance with the requirements of GM/RT2466 Table 4 Actions to be taken on discovery of cavities during inspection in traffic Cavities found during routine inspection at maintenance Any single cavity greater than 10 mm long circumferentially around the wheel Any two cavities, separated by less than 50 mm, having a combined length in excess of 10 mm circumferentially around the wheel. Action Recommended that the tread profile be restored within 2 weeks Table 5 Actions to be taken on discovery of cavities during routine inspection at maintenance 6.5 Flange Condition Build up, steps or sharp radii on the flange are a potential cause of derailment and are not permissible. A gauge with a 5 mm radius and 7 mm chord length should not rock when placed on any discontinuity or radius on the flange, see Figure 10. Figure 10 Flange toe radius assessment gauge This is usually associated with flange wear and is caused by material plastically flowing into the flange toe area. An example of this damage is shown in Figure 11 and the shape of a wheel profile with flange toe radius build-up in Figure 12. RAIL SAFETY AND STANDARDS BOARD Page 23 of 43

24 6.5.3 In addition, there should be no circumferential step in the flange profile greater than 1.5 mm in depth and no cracks of any kind should be permitted in the flange or within any toe-radius build-up. Figure 11 Flange toe radius build-up Figure 12 Display of measured wheel profile with flange toe radius build-up. Page 24 of 43 RAIL SAFETY AND STANDARDS BOARD

25 6.5.4 This damage usually occurs either: a) When a vehicle is operating over a route where the curve population is such that the flange spends a considerable amount of time in hard contact with the rail side face or b) When the wheel diameters are unequal so that one wheel is constantly making excessive contact with the rail gauge face during steering of the wheelset Wear of the back of the flange (flange back wear) can also occur. To avoid excessive removal of wheel material during re-profiling, flange back wear of up to 1 mm is allowed to remain after re-profiling. 6.6 Wheel tread roll-over An example of tread roll-over in the early stages is shown in Figures 2 and 17. The roll-over should not extend more than 5 mm beyond the face of the wheel rim or have any cracks present. Cracks that have initiated in the rolled over section of material can readily propagate into the wheel rim with the potential for fracture of the wheel. 6.7 Other damage False flange A false flange is not to exceed 2 mm (Figure 15), the mandatory requirement in GMRT Isolated or single cracks Where isolated cracks longer than 30 mm in length are present in the tread area, then the vehicle should be withdrawn from traffic immediately and quarantined pending further investigation by a person or body who is technically competent. Where an isolated crack longer than 20 mm is found in the tread, the wheelset should be withdrawn from service within 24 hours of the fault being found Flange and chamfer cracks Where cracks are found to have occurred on the flange or chamfer (Figures 13 and 14), the vehicle should be immediately withdrawn from traffic. The vehicle should be moved to a repair facility at speeds not exceeding 45 mile/h (72 km/h) and quarantined pending further investigation by a person or body who is technically competent. RAIL SAFETY AND STANDARDS BOARD Page 25 of 43

26 Figure 13 Crack on flange Flange Chamfer Figure 14 Cracks on wheel tread extending down the chamfer Page 26 of 43 RAIL SAFETY AND STANDARDS BOARD

27 Part 7 Guidance on Overheated Wheels 7.1 Examination of overheated wheels When wheels or tyres are found to have overheated or are suspected of having overheated the following checks should be made: a) The wheelset back-to-back dimension is within the limits specified in the user s maintenance instructions b) Evidence of a wheel having moved relative to the axle c) Evidence of a tyre having moved on the wheel centre rim d) Wheel wobble is within the limits specified in the user s maintenance instructions e) There are no dragging brakes f) For vehicles with rheostatic braking, that this is functioning correctly. If it is not, all the wheelsets on that vehicle should be checked Consideration should be given to whether the incident falls within the requirements of GE/RT8250 and if a report on the National Incident Register is required For recovery of vehicles with overheated wheels, the user should consider a suitable restriction on vehicle speed appropriate to the degree of damage. RAIL SAFETY AND STANDARDS BOARD Page 27 of 43

28 Part 8 Guidance on Wheelsets Involved in Derailment 8.1 Actions following derailment of wheelsets Following a derailment the wheelsets that have derailed, or all the wheelsets on a unit that has been involved in a derailment where the wheelsets have re-railed themselves, should be subjected to the following checks as a minimum requirement. Additional checks may be required to take into account the vehicle design and operation The following should be within the limits contained in the user s maintenance instructions or GM/RT2466: a) Damage on the wheel such as scoring, burrs, raised edges, sharp indentations or impact marks b) Evidence of movement at interference fit interfaces c) Back to back dimension, measured at axle height and at three equi-spaced locations around the wheelset d) Wheel diameters e) Wheel diameter differential across the wheelset f) Tread damage such as: i) Flats and cavities ii) iii) iv) Rim thickness Flange height and thickness Flange toe radius and sharp flanges v) Flange angle for GCU vehicles vi) Grooving, false flange, flange step etc. g) Tyred wheels should be examined for: i) Evidence of movement between the tyre and wheel centre ii) iii) iv) Cracks in the tyre Damage to the retaining ring Correct clearance between the tyre snip and wheel centre rim v) Correct clearance between the inside vertical face of the tyre and the retaining ring vi) Ends of retaining ring have correct gap. Page 28 of 43 RAIL SAFETY AND STANDARDS BOARD

29 8.1.3 Prior to moving the vehicle the following should be checked: a) The axle is not fractured. Providing that there are no suspicions of the axle being cracked an ultrasonic axle test is not required until the vehicle reaches the registered maintenance site. b) There is no evidence of wheels having moved on the axle. c) There is no evidence of loose tyres. d) That any damage to wheel profiles is accounted for in the conditions applying to the move. e) There are no parts that may become detached during the move. f) There is nothing to prevent free rotation of the wheelset. g) There is no evidence of axlebox bearing degradation. h) There is no evidence of localised overheating on a wheel to indicate the presence of a wheel flat that is preventing rotation, but is resting on the rail and therefore is not readily obvious. i) For powered axles, that the transmission is free to rotate and has no evidence of degradation. RAIL SAFETY AND STANDARDS BOARD Page 29 of 43

30 Appendix A Wheelset and Tread Profile Gauging Systems A.1 Gauges that have traditionally been used for checking many of the conditions identified in this document and have a Cat. No. allocated are identified in Table A.1. Figures A.1 to A.11 inclusive show typical gauges. A.2 The calibration of gauges used in the examination of wheel treads is outside the scope of this document, but is covered by TM/TT0017. Gauge type Tread profile Drawing No. Cat. No. Profile sliding gauge assembly All /01 39/28048 Profile machining limit gauges P1 B-A1-1324/01 39/29823 P5 F-A /29792 P6 F-A /29786 P8 L-A /29827 P9 L-A /29825 P10 C1-A /27968 P11 C1-C /27972 RD9 B2-C /29846 Plug gauge All F-A3-4909/01 39/29763 Plug gauge (back flange wear) All B-A1-1324/02 39/29826 Flange height and thickness gauge All F-A /29967 Go / No Go back to back gauge All New and overhauled (1360 to 1362) B-A1-1286/01 39/29832 Re-profiled (1360 to ) B-A1-1286/02 39/28114 Tread diameter comparison gauge All F-S /29975 Tyre thickness gauge All F-A /79929 Rim thickness gauge (without magnet) All B2-C /02 39/28032 Rim thickness gauge (with magnet) All B2-C /03 39/28033 Throat thickness gauge 30 mm All F-A2-47/01 39/29968 Throat thickness gauge 36 mm All F-A2-47/02 39/29969 Adjustable throat thickness gauge P1 B2-C /02 39/28038 P5 P6 P8 P10 Surface finish sample profile All Rubert & Co. No /29006 Table A.1 of gauges Page 30 of 43 RAIL SAFETY AND STANDARDS BOARD

31 A.3 It should be noted that many of the Go / No Go gauges are set at the safety limit and so their use at routine examinations will not fulfil the GM/RT2466 requirement that wheels will not exceed these limits at all times. Figure A.1 Profile sliding gauge Figure A.2 Profile limit machining gauge and plug gauge RAIL SAFETY AND STANDARDS BOARD Page 31 of 43

32 Figure A.3 Adjustable flange thickness and height gauge Figure A.4 Go / No Go back-to-back gauge Page 32 of 43 RAIL SAFETY AND STANDARDS BOARD

33 Figure A.5 External tread diameter comparison gauge RAIL SAFETY AND STANDARDS BOARD Page 33 of 43

34 Figure A.6 Tyre thickness gauge Figure A.7 Rim thickness gauge Page 34 of 43 RAIL SAFETY AND STANDARDS BOARD

35 Figure A.8 Go / No-Go throat thickness gauge Figure A.9 Adjustable throat thickness gauge RAIL SAFETY AND STANDARDS BOARD Page 35 of 43

36 Figure A.10 Go / No-Go flange thickness and height gauge Figure A.11 Go / No-Go restricted flange height gauge Page 36 of 43 RAIL SAFETY AND STANDARDS BOARD

37 Definitions Check Determine a particular nominated condition before, during or after repair, for example completeness, security, position, corrosion etc. Crack length The dimension measured end to end on the tread or flange. Defect / defective Any fault or faults in a component or assembly, which may prevent the component or assembly from fulfilling its designed purpose, for example cracking. Diameter differential The difference in diameter (measured at the tread datum) between wheels on an axle, wheelsets in a bogie, or wheels fitted throughout a vehicle. Electronic profile measurement tool A digital means of recording and measuring wheel profiles. Examination The action, using visual methods, to determine the condition of a component or system during or following service operation. False flange False flange (Figure 15) is formed when the outer (field side) of the tread is raised above the nominal tread running band. A false flange may be formed when significant tread wears is concentrated at the running band. A severe flat, such as produced by a prolonged brake drag, can form a localised false flange. This dimension is not to exceed 2.0 mm Figure 15 Definition of false flange Flange angle (qr dimension) The distance in millimetres, parallel to the axis of the axle measured between a point on the flange 10 mm above the tread datum position and a point 2 mm below the flange tip. RAIL SAFETY AND STANDARDS BOARD Page 37 of 43

38 Flange height The height of the flange relative to the tread datum position (Figure 16). Flange toe Flange tip Tread chamfer Flange height Flange root Flange angle Flange back blend Tread datum Tyre/rim width Flange back 70 mm Wheel web Figure 16 Definition of profile Flange thickness The thickness of the flange at a position 13 mm above the tread datum position (Figure 16). Note that European practice as described in the Technical Specifications for Interoperability specifies that the flange thickness is measured 10 mm above the tread datum position. Gauge Determine a nominated dimension by using suitable measuring equipment for example ruler, micrometer, calipers, feeler gauge or Go / No-Go gauge. Gauging is performed over a representative number of points on the surface. GCU vehicle A vehicle registered with the General Conditions of Use Bureau for international operation. Inspection Action to determine the conformance to required standards. Overhaul Overhaul is any attention given to the wheelset when it is removed from a vehicle or bogie and when an interference fit of any item other than a wheelset bearing is broken. Profile tolerance A geometric tolerance for the newly turned wheel profile, defined by a band of the stated width, equally disposed about the defined true form within which the actual profile should lie. Profiles which fall outside the profile tolerance should not be allowed to enter service as they may result in vehicle instability and unpredictable wear patterns. Railway undertaking Any train operator or train operating company responsible for operating the vehicle to which the wheelset is fitted. Page 38 of 43 RAIL SAFETY AND STANDARDS BOARD

39 Record / records Put down in writing/enter in a computer system, the result of any specified examination, test or inspection, in accordance with defined procedures. Re-profiled wheelset A wheelset that has previously run in service and has tread profiles that have been remachined (re-profiled) to regain the design profile. Repair Any attention given to the wheelset when it is removed from a vehicle or bogie which does not require the interference fit of any item other than a wheelset bearing to be broken. Rim thickness The thickness of a monobloc wheel rim measured between the rim inside diameter on the outer (non flange) side of the wheel and the tread datum position. Roll-over A burr of extruded material forming on the edge of the outer rim side of the wheel (Figure 17). This phenomenon develops during service by local plastic deformation of the wheel tread. Figure 17 Diagram of tread roll-over Sharp flange A sharp edge or small radius on the flange tip (Figure 18). RAIL SAFETY AND STANDARDS BOARD Page 39 of 43

40 Rmin=5mm Max step = 1.5 mm Figure 18 Definition of a sharp flange Shelling Cavity (Figure 19) due to local material loss. Figure 19 Definition of cavity Technically competent A company or person having proven competence in a particular process or technology and being independent of the company requiring their services. Page 40 of 43 RAIL SAFETY AND STANDARDS BOARD