TANK wagons carrying hazardous cargoes will need to be fitted with crash buffers by 2010, the next step in a European process which began with the introduction of UIC standards mandating the use of the energy-absorbing buffers on tank wagons built after January 1 2005.
To meet the need to retrofit existing wagons as simply as possible, Durel GmbHhas been established to supply buffers and drawgear incorporating Arnitel TPE-E elastomers produced by DSM Engineering Plastics. Offering a range of products formerly supplied by ELH in Halle, Durel holds rights to elastomer springs patented by Belgian firm Bureau Mertens SPRL. Distribution and application engineering is handled by John Staub and ETQ in Quedlinburg, Germany.
Installed in buffers in place of rubber or steel springs, Arnitel TPE-E absorbs predictable amounts of energy to smooth coupling, starting and stopping. Unlike metal spring systems, the Arnitel TPE-E parts will not corrode or exhibit catastrophic failure due to metal fatigue, and efficiency is not reduced through wear. The elastomer offers a longer life than rubber, and to minimise the effects of compression set, toroidal elements are strung like large beads along a central guiding rod and separated by circular steel discs with outer diameters matching the expansion of the elastomer at maximum pressure.
EST Eisenbahn-Systemtechnik has used the high load-bearing capability of Arnitel TPE-E to produce a crash buffer which has similar dimensions to conventional side buffers, allowing simple retrofitting to older rolling stock. The springs work in tandem with controlled plastic deformation of the buffer’s steel housing, and if forces in a collision exceed a pre-set threshold, the outer shell will peel back to dissipate energy, giving the appearance of a banana. The shell remains intact during bumps and nudges in routine operation, with the elastomer providing damping at the rated energy absorption level of the buffer.
Durel says its elastomers will have consistent perfomance throughout a maintenance-free life of at least 20 years.
. The springs also can be combined with traditional metal dry friction systems and with hydraulic systems to achieve the very high capacity levels required for the heaviest freight trains.