Railway infrastructure managers have to maintain the noise and vibrations generated by the transport activity to the lowest possible level, rail operators have to meet the technical specifications on noise and, given the fact that the number of operators is expected to grow over the coming years, it is mandatory to further reduce the noise and vibrations caused by transport activities. The specialized railway industry is thus seeking to supply solutions and products that help reduce the level of noise and vibrations, being encouraged to develop new and innovating technologies.
The different types of buffers in the railway transport are one of the methods proposed to reduce the level of noise and vibrations. These are adjusted and adapted either to the rail track or to the wheel of the vehicle and manage to efficiently control the noise generated by wheels. Their efficiency in reducing the noise level has determined many operators to try optimising their rolling stock in order to increase the passengers’ comfort.
However, the level of vibrations produced by the source – train – is dependent on the condition of the wheel-track interface, the structural design of the train and of the line, the state of the rolling stock and of the infrastructure and the operating speed of the vehicle. One of the problems in railway transport is the emission of vibrations and noise which are released in the environment and have a negative impact on the infrastructure, increase maintenance costs, both for infrastructure and rolling stock. Therefore, the products and systems for damping vibrations significantly reduce the costs and wear of components.
The railway industry develops technologically advanced economic solutions, such as sleeper fastening systems, solutions for fastening line sections etc. To improve these solutions, the manufacturers perform computer-assisted tests on the materials used, efficiency readings, technical
measurements for noise and vibrations and estimate the efficiency of systems on their entire lifecycles. For example, the mass-spring system provides particularly effective protection against noise and vibrations to people leaving near a railway line. There are possibilities to reduce vibrations in all levels of the superstructure, used both on railway lines and for light rail lines. Physically the two possibilities to increase the effect of a solution are increasing the deflection of the rail which is limited by regulations of the railway companies and increasing the mass above the spring layer. Therefore it is possible to rank the effectiveness of the different solutions from top to the bottom of the superstructure. “Obtainable natural frequencies for the different solutions are elastic fastening systems with baseplate pads, elastic sleeper pads and the mass-spring system”, declared for Railway Pro, Stefan Potocan, Product Manager Railway Applications at Getzner Werkstoffe GmbH. The ballast pads provide vibration protection, preserve the ballast under the tracks and lengthen the service life of the track. They are used on high-speed tracks, on tracks with high axle loads and on existing tracks during refurbishment.
Type of infrastructure influences costs
One vital factor in reducing the level of vibrations and noise is the polyurethane materials that enhance the elasticity of the infrastructure, meeting a wide range of requirements in rail transport implementation. In terms of investments in implementing the solutions that help reduce noise and vibrations, the main cost factor for the different solutions is not the elastic material itself. Construction is the main cost driver for the different systems. “If I need the high performance of a mass spring system I have to build a slap track system which is compared to ballasted track more expensive. Therefore it is very important to investigate the situation and requirements before designing the system. An investigation shows where I really have to build a high performance system to meet the requirements and where I can use a more cost effective solution”, declared Potocan.
Therefore sleeper pads offer the possibility for medium vibration isolation over a lager section of the track. This is necessary if an existing track is upgraded to increase the speed and traffic load and for neighbouring residential areas the vibration levels should at least stay the same. An interesting side effect of the sleeper pad solution is the reduction of maintenance works and costs.
by Pamela Luică
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