INTRO: Attention to vehicle and track component life at high axleloads has enabled BHP Billiton Iron Ore to boost the capacity of its Mount Newman rail operations
BYLINE: Mike Darby, Peter Mutton and Graham Tew *
* Mike Darby is Vice-President, Railroad, at BHP Billiton Iron Ore Pty Ltd. Peter Mutton is Associate Director of the Institute of Railway Technology at Monash University, and Graham Tew is Director of the Institute.
GROWTH in the international iron ore market has spurred BHP Billiton Iron Ore (originally Mount Newman Mining) to expand the capacity of its heavy haul rail network in Western Australia. The A$77m PACE (Port And Capacity Expansion) programme due for completion by the end of this year is intended to boost annual carryings from around 70 million to over 100 million tonnes (RG 9.03 p531).
The expansion programme has already seen the opening of the recently-completed 38 km branch from the Yandi line south to Mining Area C, increasing the total network to 734 route-km. Other developments include increasing the number and length of passing loops to accommodate more and longer trains.
Expansion of the wagon fleet will come from the addition of 250 wide-bodied gondola cars. The bodies for all new vehicles are being assembled from corrosion-resistant steel to minimise long-term structural degradation (top). The latest cars are fitted with an upgraded design of three-piece bogie which will permit operation with 40 tonne axleloads in the future.
For many years, BHP Billiton Iron Ore has increased capacity on its predominantly single-track railway by raising axleloads. In doing so it has achieved rolling stock productivity levels that are the best in the world1. This strategy has been supported by an ongoing research and development programme that has focused on the effects of heavier axleloads on component performance2.
Today’s maximum axleload is one of the highest in the world. The wide-bodied cars used on trains serving the Yandi mining operations have enabled average loadings of 37·5 tonnes to be achieved (Fig 1). This figure was achieved by the introduction of more consistent and even loading procedures.
Unlike some other railways which serve a single mine, BHP Billiton draws its ore from several different locations. Differences in the design of loading facilities between mine sites resulted in a greater variability in axleloads. This necessitated tight limits on peak loads, to avoid any risk of the wagon suspensions bottoming when running at speed on the main line.
Longer not heavier
Although a further increase in the axleload is being considered, at present the scope is limited by the increased risk of component deterioration and failure, particularly the aluminothermic rail welds. The current increase in capacity is therefore being implemented through increased use of three-rake (300-car) train formations.
As the name suggests, three-rake trains are formed by coupling three 100-car sets together and controlling the intermediate locomotives remotely from the front unit. Three-rake operation began in July 2000, and has steadily increased (Fig 2). Today the line carries four or five such trains each day, out of a total of nine; the others are predominantly two-rake (200-car) trains, with the occasional single-rake train.
All ore trains are worked using driver-only operation. Coupled with the use of longer trains has been the introduction of automatic train protection to improve safety. However, the increased use of longer trains has brought additional challenges in the management of in-train (longitudinal) forces. The railway has been working to identify optimum driving strategies for long trains, to avoid delays due to broken trains and damage to couplers and drawgear components.
Building on previous research and development programmes, a three-pronged strategy is being applied to the management of track and rolling stock to enable the higher haulage rates required: