Noise Reduction in Railway Traffic Noise Abatement at Source

Transcription

1 Noise Reduction in Railway Traffic Noise Abatement at Source Dipl.-Ing. Harald Willrich, FUCHS LUBRITECH GmbH, D Weilerbach 1 The Problem Many railway companies throughout the world are increasingly facing difficulties being accepted by the residential population near railway networks, because the different types of noise produced by a travelling train are more and more felt as disturbance or annoyance. This is caused by the fact, that people tend to be more sensitive against all kinds of environmental influences including noise in general, which is very often felt to be inconvenient and disturbing. The mentioned aspects are becoming more and more part of the respective legislation, so that railway companies nowadays have to fulfil much stricter requirements regarding noise preventing measurements than they had in the past. 2 The Reasons In railway vehicles, there are a lot of sources of noise, but only the curve- or friction-caused noises can be influenced by lubricants or other suitable media. The main source of noise are surely the curveinduced noises. They come up from longitudinal and transversal slip effects in the contact zone between the wheel and the rail surface when travelling through narrow curves. Different travelling distances between outer and inner rail induce a difference in circumferential speeds of the wheel set, which distorts the axle. As soon as the resulting forces exceed the adhesive friction between wheel and rail this gives rise to a so-called differential slip equalising the difference in velocity. This effect can take place several times in a very quick sequence, which generate high-frequent and very inconvenient noises. When travelling through curves, transversal slip is generated additionally. The wheel moves crosswise to the travelling direction, because the wheel set respectively the bogie cannot give optimum position to all single wheels. This effect causes noises, too. Therefore, neither conventional bogie designs, nor the low-floor-concepts which are getting more and more popular, are free from these disturbing effects. Bogie design, principle

2 3 The Remedy The most intensive noises are generated in the contact zone between wheel and rail. For this reason, noise preventing measurements have to be taken at exactly this region, too. The problem is, that in the very same area the traction forces (Acceleration, Braking) have to be transmitted. In consequence the interactive medium must not reduce the friction coefficient between rail and wheel in an undefined manner. Braking distances and deceleration properties are precisely described in the manuals of the railway operators, e.g. in Germany these values are given in the so-called BOStrab for tramway cars. For this reason we don t talk about lubricants in a conventional sense but about intermediate agents in this context. Numerous tests and practical experience with the use of rail head treatment products have shown that noise can be drastically reduced by means of such intermediate agents without influencing the friction coefficients in an unacceptable manner. 4 The Products The rail head treatment products of the TRAM-SILENCE-series are based on biodegradable base oils and special thickeners. Furthermore, they con tain a special package of solid lubricants, which is responsible for the extraordinary performance of the product. The solid content generates a kind of tribo-coating on the surfaces, which equalises the existing surface roughness and produces a well-defined state of friction between wheel and rail. These products are not made for reducing friction coefficients to a minimum, but for creating a stable friction level, which is responsible for predictable tribological circumstances. This property, together with the excellent adhesion, guarantees, that even smallest quantities have a remarkable noise reducing effect, without affecting the operational safety. Operational safety in this context means, that there is no detrimental effect on the braking behaviour of the train and furthermore no danger for the individual traffic of bikes or motorbikes crossing the railway tracks. 5 The Application Rail head treatment products of the TRAM-SILENCE-series can be applied with respect to the local requirements manually as well as by means of automatic lubricating systems. The automatic lubricators can be divided into On-Board-Systems (OBS) and Track-Side-Systems (TSS). The large variety of application methods helps the user to apply the product in a way, which fits best to the local conditions and for all application methods FUCHS LUBRITECH can supply the appropriate products.

3 On-Board-Lubricator, type VOGEL SP-9 Track-Side-Lubricator, type RTE

4 TRAM-SILENCE, application pattern 6 The Quantities Needed Generally speaking, the quantity needed for a special part of the track follows from the above mentioned basic statement: as much as necessary, as few as possible. Re-lubrication quantities and intervals depend very much on the local conditions. Influencing parameters are the weather conditions, the condition of the rail material and the undercarriage, the train frequency as well as the average velocities and wheel loads, the design of the wheel sets and bogies, the rail and wheel materials and, of course, the degree of the desired noise reduction. With On-Board-Systems it makes some sense to calculate the consumption with regard to the distance which has to be treated. From practical experiences we recommend quantities up to 0.1 g/m. Track- Side-Systems normally dispense constant volumes per cycle and the consumption control is being done by counting the number of trains passing the lubricator between two cycles. Typical consumption quantities vary between 0.1 and 1g per train, depending from the above mentioned parameters as well as from the number of wheel sets of the trains. 7 The Results In the meantime we have a lot of practical test results, which are all showing the excellent performance of TRAM-SILENCE-products in reducing curve noises. In order to guarantee well defined starting conditions, the rails should be cleaned thoroughly prior to the tests, because dust, dirt and wear particles will of course influence the test results. Additionally, it makes some sense to compare the friction values of a rail treated with TRAM-SILENCE to those of a wet rail, because generally the friction

5 coefficients achieved with such products should not be lower than those of wet rails. This fact has been proved by all test results being available yet. 8 Summary Practical experience shows that there are very effective methods for reducing railway noises. Noise reduction by means of railhead treatment products is highly effective and at the same time these products are easy to apply with different kinds of automatic lubricators which are available from the leading manufacturers. If these products are used properly, only small amounts of lubricant are needed. These neither influence our environment due to the high biodegradability and the low consumption, nor affect the operational safety of railway traffic or individual traffic crossing the rails. Test results showing the excellent noise reduction effect without influencing braking distances are available. In the future the focus for these products will be more and more the application by means of automatic lubricators, which demands a very close co-operation between railway operator, supplier of the lubricator and the supplier of the railhead treatment product. FUCHS LUBRITECH is ready to provide any assistance in this matter to our world-wide customers.