David Benton, Product Marketing Manager Rail Sector – Tata Steel
Targeted noise reduction using rail dampers
Tata Steel’s Rail Sector has being supplying SilentTrack ® rail dampers to the global railway industry for a number of years. Third party acoustic measurements, either by railway authorities or independent testing companies, have shown that reductions in overall train pass-by noise of between 3dB(A) and 6dB(A) are readily achievable for an optimised damper.
As a response, Tata Steel has investigated the options for supplying dampers with varying compositions in order to better target those frequencies where noise is generated, whilst also producing an economic solution to gives Clients a tailored solution which enables them to comply with appropriate legislation.
The rail damper test rails at Tata Steel’s R&D facility at Swindon Technology Centre comprise of 6m lengths of 54E1 and 60E1 rail supported on ‘soft’ supports to isolate them from the ground. The soft mounts used are placed at either end of the rail, in accordance with the test protocol established in the recent STARDAMP project. Rail dampers are then attached to the rail, at the same spacing as will be used on track.
The first series of tests examined the effect of reducing the damper length, and of using an alternative clip design. Two damper lengths were examined – the standard damper at 360mm length (the maximum length allowed by most European networks for track with a 600mm sleeper spacing), and a reduced length damper of the same cross section and internal mass arrangement at 300mm length. These dampers were fastened onto the rail with three types of clip – the standard 40mm spring steel clip currently used, and two alternative clips of narrower width manufactured from stainless steel.
Decay rate measurements, in both vertical and lateral directions, were then undertaken to quantify the performance of the dampers relative to each other. The STARDAMP software was then also used to make a noise prediction for an installation on a known track. The second series of tests compared alternative polymer materials used in the damper blocks. For these tests, the damper lengths and steel configuration were kept constant, and the polymer was changed. Decay rates were measured, and a comparison between the dampers’ likely performance was taken.
Rail dampers can be designed to target specific noise issues, and can be tested off site in the laboratory to produce an optimised solution. Decisions regarding the configuration of the damping system can therefore more readily be made, and the most economic solutions provided to a client.