10.02.16
Standards for best practice in wheel-rail management
Source: RTM Feb/Mar 16
Bridget Eickhoff, RSSB’s professional head of infrastructure, and Ken Timmis, vehicle dynamics engineer, examine the latest developments in wheel-rail management.
The International Organization for Standardization (ISO) definition of a standard is “a document established by consensus and approved by a recognised body that provides for common and repeated use rules, guidelines or characteristics for activities or their results, aimed at the achievement of the optimum degree of order in a given context”.
Some standards are essential for a complex system such as the railway to work. Well thought out standards support the industry in being cost-effective, safe and efficient by ensuring that wheel and rail work together. This avoids repetitive development work and allows us to learn from the experience of others.
There are many different types of standards and the European framework is illustrated by the ‘standardisation pyramid’ (see image). All of these documents contribute to wheel-rail management, one of the key interfaces of the railway.
For the wheel-rail area, some of the key interface requirements are outlined in the Technical Specifications for Interoperability (TSIs) but much of the practical detail is contained in Euro Norms or GB specific standards. Where possible these are performance or output based, in order to allow innovation and application of best practice whilst maintaining compatibility across the network.
A standard will set out the requirements agreed by industry representatives at a point in time. It is usual to review the standards at a predetermined frequency to ensure the requirements remain relevant or when knowledge has progressed and needs to be reflected in relevant standards.
An example of recent development is the ‘track friendly’ P12 wheel tread profile, which was designed to reduce the initiation of rolling contact fatigue (RCF) in rails but has been found to also reduce RCF in wheels and generally improve wheel life. Improved monitoring of wheel profile shape development with mileage, and the identification of emerging defects, also allow maintenance to be planned rather than reactive whilst maximising economic wheelset life. This tread profile was introduced into the Railway Group Standard, GM/RT2466 Railway Wheelsets, and is now being used on many vehicles.
Learning from experience
Research can be another incentive for the review of standards. Experience from European Research projects, with a wide range of partners each bringing their own expertise, has also improved cost-effective management of the wheel-rail interface.
DynoTRAIN, which studied a range of issues around vehicle approval testing, included a huge amount of data collection and analysis of wheel and rail profiles across the networks and demonstrated that the in-service wheel-rail interface was not fundamentally different, depending on the design rail inclination but much more influenced by the pattern of wheel profiles and vehicle types.
This fundamental change in understanding is now incorporated in the TSIs and ENs and will have a major influence on the amount of approval testing needed for new vehicles, as it is no longer required to test on both ‘1in20’ and ‘1in40’ networks.
Euraxle had a wide scope to investigate all aspects of the axle from design, manufacture, use, maintenance and disposal. Part of the remit was to inform standards of best practice and available technologies. The axle Euro Norms are now being revised to include the latest knowledge originating from the project such as protective coatings, surface blasting processes and transition geometries.
The GB wheelset Railway Group Standard GMRT2466 is being revised to address the specific cases in the TSIs and will become the national rule for how GB manages the compatibility with our existing infrastructure. Other industry documents will provide more details on wheelset design, manufacture, maintenance and defect monitoring/detection.
Looking forward
Looking into the future, where might the next development come from?
Will future wheelsets have sensors attached that can be used to monitor signs of fatigue fractures initiating in the axle surface or the stress regime an axle is experiencing in order to predict its life? Similarly could wheels be instrumented to monitor wear and deterioration and plan maintenance intervention even more intelligently?
Sometimes it is tempting to settle for the ‘status quo’, knowing that the current process works even though it may be inefficient and costly. Challenging these assumptions and looking for improved approaches may appear to add risk in the short term but is essential if the railway is to continue to develop.
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