Ore-car coupler performance at BHP-Billiton Iron Ore

The world-class railway operated by BHP-Billiton Iron Ore now runs the highest axle loads globally. Loads have increased an average 16% to 37 tonnes/axle in the past 15 years. A single 330-car train is now being run daily, with a view to eventually increase the number of long trains to further improve productivity; currently 220-car trains form the major traffic. The failure of two couplers in the record-breaking 640-car train run on the BHP-Billiton Newman Mainline in July 2001 indicated the possibility of increased coupler failure rates with longer trains. This study was therefore commissioned by BHP-Billiton Iron Ore in order to (a) characterise coupler failure mode and performance under current service conditions, and (b) identify issues that may influence coupler performance under increased loading. The cast steel couplers were subjected to visual and metallographic examination in order to identify predominant failure mode(s). Materials were characterised in terms of microstructure and mechanical properties (hardness, tensile, impact and fracture toughness). Stress analysis was carried out by measuring the strain response to simulated service loading at locations prone to fatigue cracking. Potential service/performance implications of the observed variability in microstructure and mechanical properties are discussed. (C) 2003 Elsevier Ltd. All rights reserved.