Tata Steel has recently announced an £800 million investment in its plant at Port Talbot, South Wales. While this is not a rail plant, it produces strip for the automotive and white goods industries, it does demonstrate Tata Steel’s commitment to the UK, and prompted the rail engineer to look at some of the work going on in track technology.
When Tata Steel develops new products, a structured stage-gate approach is used to ensure that developments are led by the customer’s needs whilst at the same time taking into account the manufacturing route.
New products first go through a validation and trial phase, followed by the tracking of a commercialised product for a period of five years to continually build on the understanding of new products in service making the innovation process an iterative cycle.
HPrail was developed in response to customer demand for rail better able to withstand the increased traffic and heavier axle loads of today’s railway systems. Based on ten years of research on rail degradation mechanisms combined with world leading metallurgical expertise HPrail provides a high performing solution, which reduces the frequency of rail grinding.
HPrail is a metallurgically engineered rail steel developed to address the three main degradation mechanisms seen on European mixed traffic railways i.e. wear, plastic flow and rolling contact fatigue. The development was underpinned by research work to understand customer needs with respect to reducing the cost of track maintenance.
Additionally, the manufacturing route for HPrail allows flexibility in terms of supplied lengths, profiles and volume as it can be manufactured either in the UK or in Hayange, France.
In the early development of HPrail, the focus was on track monitoring and forensic laboratory examination of the rail microstructure under wheel loading. Rail steel has a pearlitic structure which has two distinct phases, both of which would need to be addressed to make a longer lasting rail.
The result was the creation of a steel using the traditional techniques of refining the harder constituents of the pearlite structure whilst at the same time engineering the softer ferrite phase to contribute to the in-track performance of the rail.
Early trial work included laboratory investigations, which indicated a step change in the resistance to wear and rolling contact fatigue compared to traditional or current pearlitic rail steels found in the European specification EN13674-1. This counters the traditional approach to tackling the degradation mechanisms by increasing the bulk hardness of the rail steel.
This led to the casting and rolling of the first trial HPrail. These were installed in the works track at Scunthorpe under heavy-duty conditions on the torpedo line (used to transport molten steel across the works) to provide the first live trial and give quick results.
Regular monitoring by the Rail Technologies team and the generation of in-service performance data gave the confidence to progress this development into live mainline track trials.
Early customer involvement with Network Rail resulted in a two-year programme of trials. HPrail was installed and monitored at seven very challenging sites in the network to confirm the performance compared to standard grade rail.
One such site was at Hett Mill, Durham, where HPrail was installed in January 2011. The site was chosen as it is a mixed passenger and freight line, with an existing re-rail frequency of around five years. Its curve radius of 1000m and history of developing extensive rolling contact fatigue (RCF) within a short period made this an ideal location for track testing.
Within fifteen months, Network Rail is already making cost savings through reduced track maintenance activities, such as extending the grinding interval due to the rail maintaining profile and increasing the period to initiation of rolling contact fatigue. Network Rail’s projections on life cycle costing indicate that significant savings will be made as a result of HPrail installation.
The early results have led to the installation of 3,000 tonnes of HPrail around the network in 2011 under trial approval certification, in anticipation of full product acceptance by Network Rail in the summer of 2012.
Based on the performance of HPrail in plain line, work is underway on extending its use to switches and crossings for Network Rail, demonstrating how developing new products is often an iterative and evolutionary process.
The introduction of noise legislation via the European Noise Directive has compelled railway authorities to consider how best to limit the exposure of the general pubic to excessive railway noise.
Additionally, the growing public and political awareness of noise as a health and environmental issue has resulted in the search for effective noise control measures that can be applied to the railway infrastructure. Traditional solutions to noise have been the installation of anti-noise screens which are expensive, difficult to install onto an operational railway, and unsightly for the railway’s neighbours.
European funding facilitated a collaborative programme of work to investigate the sources of noise generation and potential solutions to mitigate the problem. Tata Steel participated in partnership with the University of Southampton to develop an understanding of the generation of noise through the wheel-rail interaction. This led to the development of a rail-mounted damper to tackle the rail-wheel interface noise at source.
SilentTrack consists of rail dampers, attached either side of a rail, which are tuned to absorb the vibrations in the rail. The dampers themselves function as a classic mass/spring damping system, with steel masses encased in an elastomeric polymer with a high damping factor.
For each project, site-specific data is used to assess the track characteristics. The damper is then designed to provide the most effective noise reduction and develop a bespoke solution to the specific noise issues encountered on the track.
As a commercial product, SilentTrack has been installed in over 100 kilometres of track in Holland and Germany, providing reductions in noise between three and six decibels.
Approvals are in place for use in the UK and the first installation was at Blackfriars in April 2012.