Flange Climb Derailment Criteria and Wheel/Rail Profile Management and Maintenance Guidelines for Transit Operations (2005) / Chapter Skim
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Appendix A - Effect of Wheel/Rail Profiles and Wheel/Rail Interaction on System Performance and Maintenance in Transit Operations
Appendix A - Effect of Wheel/Rail Profiles and Wheel/Rail Interaction on System Performance and Maintenance in Transit Operations
Pages 34-76
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From page 34... ...
A-1 APPENDIX A: Effect of Wheel/Rail Profiles and Wheel/Rail Interaction on System Performance and Maintenance in Transit Operations
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From page 35... ...
Summaries of the information from five of the systems visited are included in the Appendixes A-1 through A-5. The survey identified the following common problems and concerns related to wheel/rail profiles and wheel/rail interaction in transit operation: • Adoption of low wheel flange angles can increase the risk of flange climb derailment.
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From page 36... ...
• Reduction of wheel/rail wear can be achieved by optimization of wheel/rail profiles, properly designed truck primary suspension, improvement of track maintenance, and application of lubrication. • Without a wheel/rail profile measurement and documentation program, transit operators will have difficulty reaching a high level of effectiveness and efficiency in wheel/rail operation and maintenance.
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From page 37... ...
This appendix fulfills the requirement of the first objective. Program Tasks Task 1 Define common problems and concerns related to wheel/rail profiles in transit operation Phase I Task 2 Propose preliminary flange climb criteria for application to transit operation Task 1 Develop general guidelinesfor wheel/rail profile assessment applied to transit operation Phase II Task 2 Propose final flange climb derailment criteria validated by the test data TABLE A-1 Tasks in the program of wheel/rail profile optimization technology and flange climb criteria
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From page 38... ...
The research team visited several of these transit agencies to perform the survey. Due to budget limitations, the team surTransit System Light Rail Cars Bilevel Rapid Transit Commuter Coach Locomotive Total Geographic area 1 San Francisco Bay Area Rapid Transit (BART)
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• Safety concerns related to wheel/rail profiles. • Vehicle curving performance and lateral stability behavior as affected by wheel/rail profiles.
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• Wheel life and wheel re-profiling. • Rail life and rail grinding.
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4.1 WHEEL FLANGE ANGLE The maximum flange angle of the designed wheel profiles applied in transit operation ranges between 63 and 75 degrees. Table A-4 lists the wheel flange angles received for the six visited systems.
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4.1.1 Derailments of Low Floor Light Rail Vehicles Due to Low Flange Angle Figure A-3 compares two examples of designed wheel profiles used by transit systems. First is a wheel profile with a flange angle of 63 degrees that was previously applied to all vehicles on MBTA's Green Line (light rail)
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From page 43... ...
One of MBTA's remedial actions has been to increase the wheel flange angle from 63 degrees to 75 degrees by introducing a new wheel profile. Rail grinding has also been performed to reshape the rail gage corner to help the wheels maintain the 75-degree flange angle.
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From page 44... ...
Again, referring to Figure A-2, reducing the friction coefficient at wheel/rail interface can increase the L/V limit for flange climb. The sharp asperities on the wheel surface after reprofiling may quickly deform or wear off in operation due to very high locally concentrated contact stress.
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From page 45... ...
The wheel profile used on both existing Number 7 cars and new Number 8 cars originally had a flange angle of 63 degrees. To reduce the risk of flange climb derailment on the Number 8 cars, MBTA Green Line implemented an Interim Wheel Profile (IWP)
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From page 46... ...
, higher L/V ratios, and increased wheel and rail wear. Furthermore, without longitudinal force, any L/V values that exceed the Nadal limit will cause wheel flange climb.
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From page 47... ...
Additional control mechanisms, such as linkages or active control systems, can be used to steer wheelsets on curves and through track perturbations. Without such control mechanisms, the wheel/rail profiles and vehicle/track maintenance will need to be much more strictly controlled and monitored to prevent wheel flange climb.
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wider gage. TABLE A-6 Wheel and rail combinations Wheel Profiles Rail Profile Rail Cant CTA (rapid transit, cylindrical)
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Examples of severe two-point contact: (a) MBTA -- light rail (Green Line, 63 degree flange angle)
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WMATA rapid transit, and (c) MBTA light rail -- interim wheel profile with 75-degree flange angle.
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lateral shift range, which indicates a low risk of lateral instability on tangent track from the aspect of wheel and rail profiles. Note that two of these wheels have a cylindrical tread.
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Figure A-24 displays examples of RRD for three nominal diameters of wheels on a standard track gage of 56.5 in. Due to the limit of wheel flange/rail gage clearance (8 to 10 mm)
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. To control wheel slide and wheel flats, several techniques have been applied to migrate the problems, including the following: • Pressurized spray rail cleaners.
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The Newark City Subway (light rail) has installed both wayside flange lubricators and top-of-rail friction modifiers.
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From page 55... ...
Light RailSystem Rapid Transit Commuter MBTA Limited wayside lubricators for back-of-flange and restraining rail. Others have been tested No information was received No information was received NJ TRANSIT Wayside flange lubricators, top-of-rail friction modifiers, and an onboard lubrication system are under testing.
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From page 56... ...
As discussed in the previous sections, poor wheelset steering on curves caused by improper wheel/rail profiles such as two-point contact, low RRD, cylindrical tread wheels, or independently rotating wheels can lead to higher creepages and higher creep forces and, hence, higher levels of wear. In addition to safety concerns, vehicle hunting on tangent track can produce much higher creep forces and creepages during wheelset yaw motion than during normal operation.
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A-25 A 1-day seminar was also provided by the research team to a light rail system on the same topic with more detailed descriptions. Several staff members, including both managers and engineers, stated that they sometimes observed certain scenarios on wheels or rails but did not understand the physics behind them, and sometimes they tried different ways to improve the situation based on experience, such as improving curving or reducing rail wear, but without solid scientific evidence.
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From page 58... ...
Introduction of new wheel and rail profiles needs to be carefully programmed for both wheel re-profiling and rail grinding to achieve a smooth transition. • Without adequate control mechanisms, independently rotating wheels can produce higher lateral forces and higher wheel/rail wear on curves.
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From page 59... ...
Wu, H., and J Elkins, Investigation of Wheel Flange Climb Derailment Criteria, AAR Report R-931, Association of American Railroads, Washington, D.C., July 1999.
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Escalona, "Modeling TwoPoint Wheel/Rail Contacts Using Constraint and ElasticA-28 Force Approaches," Proceedings, IMECE2002 ASME International Mechanical Engineering Congress and Exposition, New Orleans, Louisiana, November 17-22, 2002. Booz Allen & Hamilton, Inc., TCRP Report 2: Applicability of Low-Floor Light Rail Vehicles in North America, TRB, National Research Council, Washington, D.C., 1993.
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From page 61... ...
Combined with the low flange angle, the condition presents a risk of flange climb derailment. Prompted by a series of Number 8 car derailments, MBTA undertook a thorough review of the Green Line infrastructure and reevaluated both track and vehicle maintenance practices.
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From page 62... ...
This limited the shop capacity and further slowed down the transition to a higher and operationally stable wheel flange angle. Finally, the Green Line wheel tread design taper was 1:40, but recent worn-wheel profiles showed that the wheels consistently wore into a 1:20 taper.
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From page 63... ...
Since then, better maintenance of wheel flats has improved the situation. A1.6 LUBRICATION AND WHEEL SLIDE Limited wayside lubricators for back-of-flange and restraining rail lubrication are in use at MBTA.
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A2.1 WHEEL AND RAIL PROFILES A2.1.1 Light Rail Wheel profiles on the Newark City Subway follow an ORE (European Railway Organisation) standard, which is similar to the Pittsburgh LRV profile with a peak flange conFigure A2-2.
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In terms of capacity, four to eight cars can be re-profiled per shift per site. A2.3 RAIL LIFE AND RAIL GRINDING A2.3.1 Light Rail Rail on the Newark City Subway was all replaced in 1984.
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Previously, NJ TRANSIT used hairpin-type fasteners in the curves, but the fasteners did not hold. A2.6 LUBRICATION AND WHEEL SLIDE A2.6.1 Light Rail The Newark City Subway applies a variety of rail lubrication methods in its system.
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From page 67... ...
This is expected, given that commuter systems often operate with greater separation from residential and business areas. A2.8 MAJOR CONCERNS AND ACTIONS A2.8.1 Light Rail As a newly updated system overall, the Newark City Subway is maintaining a high level of operational quality with extensive efforts toward preventative maintenance.
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From page 68... ...
A3.1 WHEEL AND RAIL PROFILES The diameter of all LRV wheels is 27 in. The wheel profile for the LRV cars on the Green Line has a 63-degree flange, a 1:20 tread taper, and a flat top flange that may help to reduce the contact stress as wheels pass special flangebearing trackwork.
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From page 69... ...
This can locally lift the tread contact and cause wheel impacts at an adjacent section. For the wide gage light rail lines, SEPTA owns an 8-stone grinding machine.
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traffic per year and twice a week for sections having traffic more than 5 MGT per year. Various maintenance intervals are used on the light rail and rapid transit lines (including limited cross tie and rail replacement, and surfacing where necessary)
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SEPTA has experienced infrequent derailments that fall into two categories: train handling (traction, braking, excessive speed) and slow-speed flange climb (at more severe curves, yards, climbing switches, and sometimes soon after re-profiling)
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However, a few recent incidents of flange climb derailments have raised concerns related to wheel profiles and track gage. A4.1 WHEEL AND RAIL PROFILES The original WMATA cars were supplied with cylindrical wheel profiles that resulted in excessive wheel and rail wear.
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A4.7 MAJOR CONCERNS AND ACTIONS Major issues for WMATA relative to wheel/rail profiles are the following: • Improving wheel flange angle to reduce flange climb derailment. • Careful planning for a smooth transition to a new wheel profile.
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• Malfunction of the curve lubricator on this section of track. A-42 The combination of these two factors could considerably reduce the L/V limit for flange climb on the tight curve that has a tendency to generate high lateral forces.
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Regarding seasonal wheel slides, the Skokie Swift (Yellow Line) and the Brown Line near the end of the line on ballasted track have received noise complaints due to wheel flats.
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CTA track designers would also like a computer program that allows input of design parameters (e.g., curve radius, operating speed, underbalance, lubrication presence, profile) and produces the expected lateral force ranges generated by the wheels.
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