Turning down the noise

A minor roughness of the rail or unevenness of the wheel is enough to cause vibrations or the excitation of vibrations. The wheel/rail interface is therefore the key to effective noise abatement. Another focal point is the degree of wear of the rail and the wheel. And exactly this is the starting point of Vossloh’s vibration-reducing product solutions and unique services.

Preventive against noise

As a preventive rail maintenance process, High Speed Grinding (HSG) eliminates the defects in the rail surface that are responsible for the noise and this way extends the rail’s life. Building on its positive experience with acoustic grinding, Vossloh has registered its compact grinder HSG-city for the I-LENA program. The project, initiated by the German Ministry of Transport and Digital Infrastructure (BMVI), provides an opportunity to carry out trials of new noise-reducing developments under real-life conditions on tracks provided by Deutsche Bahn. The program is designed to promote the development of procedures that will significantly contribute to cutting railway noise to half of its current levels (or by about 10 dB(A)), an objective that is to be accomplished by 2020.

As a next step, Vossloh will be seeking approval of the HSG-city from the German Railway Authority specifically for the construction and restoration of track sections conforming to the requirements of the “specially monitoring track” (BüG). This would explicitly allow the deployment of the compact grinding train on BüG sections of the mainline and light rail network when the noise exceeds defined tolerances.

If more metal needs to be removed because the rail defects have already progressed deeper into the rail, milling is the cutting procedure of choice. For finishing, the innovative milling wheel technology of the patented High Performance Milling (HPM) procedure eliminates the residual waviness with particular efficiency. This not only more than satisfies the BüG requirements but also eliminates the need of additional grinding.

Special focus on turnout design and turnout service

Turnouts are exposed to punishing loads. Wear and tear result in defects that may lead to increased noise emissions. In this case, too, regular preventive measures will limit the noise created when the wheels switch track. Ideally, maintenance should start with the removal of the rolling scale immediately after rail installation in order to prevent an early formation of corrugation. Apart from the removal of existing defects, preventive grinding of turnouts is a central component of the Flexis system. Any metal removal is based exactly on the determined need. This way, all components of the turnout that have contact with the wheels of the trains remain in an optimum condition.

Turnout design, material, workmanship, shape of the crossing or frog, the correct angle of inclination during installation and the angle of the diverging track are likewise important aspects for reducing impact and wear and hence avoiding noise.

No vibration—no noise

For a sustainable noise abatement, the efforts should not be limited to an acoustic optimization of the rail head. Just as important is the minimization of the mechanical low-frequency vibrations caused by the passage of trains, and the acoustic, high-frequency noise they produce.

Thanks to the dampening properties of the highly elastic rail pads made of cellentic, Vossloh has already scored substantial success in a number of projects. At Vossloh’s fair stand, industry experts will have an opportunity to see how an impulse hammer test can be used to find the ideal rail fastening solution for their respective requirements, also with a view to the expected structure-borne noise.

For further information about HSG technology, please visit the Vossloh Stand 310 in Hall 26 or www.vossloh.com .

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20.09.2016

Turning down the noise