A study of airborne wear particles generated from organic railway brake pads and brake discs

Abstract

Brake pads on wheel-mounted disc brakes are often used in rail transport due to their good thermal properties and robustness. During braking, both the disc and the pads are worn. This wear process generates particles that may become airborne and thus affect human health. The long term purpose of ‘Airborne particles in Rail transport’ project is to gain knowledge on the wear mechanisms in order to find means of controlling the number and size distribution of airborne particles. In this regard, a series of full-scale field tests and laboratory tests with a pin-on-disc machine have been conducted. The morphology and the matter of particles, along with their size distribution and concentration, have been studied. The validity of results from the pin-on-disc simulation has been verified by the field test results. Results show an ultra-fine peak for particles with a diameter size around 100 nm in diameter, a dominant fine peak for particles with a size of around 350 nm in diameter, and a coarse peak with a size of 3-7 μm in diameter. Materials such as iron, copper, aluminium, chromium, cobalt, antimony, and zinc have been detected in the nano-sized particles.<p>Selected papers from 14th Nordic Symposium on Tribology, NORDTRIB 2010. Updated from Submitted to Published.</p><p>This is the author’s version of a work that was accepted for publication in Wear. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in WEAR, VOL 273, ISSUE 1, (17 June 2011), DOI: 10.1016/j.wear.2011.04.013.</p><p>QC 20111221</p

Particle Emissions From Rail Traffic: A Literature Review

“…The fine region with the highest particle number frequency was in the 250-650 nm diameter range (Seaton et al, 2005;Gustafsson, 2009;Abbasi et al, 2011;Fridell et al, 2011). All these studies agreed that there was a number peak at approximately 350 nm in diameter.…”

“…A maximum frequency of fine particles at 60-80 nm in diameter was reported by Norman and Johansson (2005), while laboratory tests generating wear particles recorded a peak particle frequency at approximately 70-100 nm (Sundh et al, 2009;Abbasi et al, 2011). However, other researchers reported finer particle sizes.…”

“…However, the laboratory results presented by Sundh et al (2009), Abbasi et al (2011Abbasi et al ( , 2012bAbbasi et al ( , 2013, and Olofsson (2010) indicate that UFPs are also generated by wear processes involving rail, wheel, and braking materials. They reported that the particle concentration in coarse, fine and ultrafine regions are dependent on the contact conditions of mating surfaces (i.e sliding velocity, contact pressure, temperature lubricant and material properties).…”

“…Two report data from laboratory measuremets (Abbasi, 2011 andAbbasi, 2012b) and one discusses emission rates in the Stockholm subway (Johansson, 2005). Other sources address particle concentrations, inherently reflecting emission rates.…”

“…Ultrafine, a few 100 nm and micrometer sized particles are generated at sheer wear processes and the various size modes ought be attributed to various wear modes (Sundh et al, 2009;Abbasi et al, 2011). However no study of the detailed generation mechanisms is known to the authors.…”