Laboratory investigation of some sanding parameters to improve the adhesion in leaf-contaminated wheel—rail contacts

Abstract

Leaf contamination has been identified as the major cause of low adhesion incidents occurring on some railway networks in the last few decades. In the presence of leaf layers, the trains cannot have the required adhesion at the wheel—rail contact for adequate traction and braking operation. Under these circumstances, not only the punctuality but also the safety of the railway transportation can be threatened. In order to mitigate low adhesion problems, railway organizations have opted for different measures, particularly during the season of Autumn. The most employed measure consists of bringing sand to the wheel—rail interface, which can be performed by means of air-pumped sanders or in the form of sand-based friction modifiers. Although sand has widely been accepted as an effective adhesion improver, the effect of some sanding parameters on the adhesion improvement in leaf-contaminated contacts seems to be unclear. This hinders the possible optimized use of sand on the railway networks. In this paper, the influence of the number of sanding axles, particle size of sand, and wheel slip on the adhesion recovery in leaf-contaminated wheel—rail contacts is presented. Rolling—sliding tests under closely controlled conditions have been performed on a twin-disc roller rig. An electrical circuit has been connected to the rig for monitoring the effect of contamination on the electrical conductivity across the wheel—rail contact. The results show that the application of sand contributes to removing the leaf layers from the disc surfaces, which leads to a higher adhesion coefficient in comparison with the untreated (baseline) situation. Accordingly, the electrical conductivity across the wheel—rail contact is also improved. Furthermore, the adhesion recovery is shown to become larger and faster with the increase in sanding axles and wheel slip. Among the particle sizes tested in this work, medium particles are found to yield the most effective adhesion recovery.

Wheel-rail creep force model for predicting water induced low adhesion phenomena

“…In Great Britain during the autumn period (from October to November) numerous incidents, such as "station overruns" and signals passed at danger (SPADS) occur every year which are related to low adhesion conditions [RSSB T1042]. For about half of the incidents an autumn leaf contamination has been reported [RSSB T1042] which is known to cause low adhesion [Cann 2006, Oloffson 2004, Arias-Cuevas 2010, Li 2009, GallardoHernandez 2008. A proportion of the other half were related to small amounts of water on the rail head caused by prevailing environmental conditions.…”

Wear and damage transitions of wheel and rail materials under various contact conditions

“…strongly influence the adhesion of wheel/rail and cause low adhesion phenomena [17][18][19]. When the adhesion in the wheel/rail interface is poor, traction enhancers (sand, alumina, etc) are often sprayed into the wheel/rail interface for improving the adhesion coefficient.…”

“…However, various traction enhancers can increase wear rate of wheel and rail materials and aggravate surface damage correspondingly. Studies have investigated the influence of sanding particle size, feed rate, and wheel slip on improving adhesion and wear in the wheel-rail contact [17][18][20][21].…”

Monitoring train performance in case of low adhesion : acquiring knowledge for the development of low adhesion measures

“…The layer becomes thicker every time a train passes. According to reference [34] and [24] the layer is more slippery than a dry track, but not so slippery that it causes problems. Not until the black layer becomes moist (rain, dew, fog, etc.)…”

“…Substances on the track might lead to low adhesion. Research (see reference [23] and [24] • Relatively simple measuring tool (inexpensive).…”