Rio Tinto Iron Ore engaged Lycopodium to undertake a site assessment of various sections of the Pilbara rail network to review track stability and the interactions between in-train braking forces and track stability.
A large amount of rail creep had been observed at multiple locations on the Pilbara rail network, with remedial works failing at some locations and planned ongoing repairs producing significant and unacceptable network impacts. Lycopodium was engaged to provide an independent assessment of the root cause of failures, assess operating risks, and recommend actions for temporary and permanent repairs together with ongoing condition monitoring and asset management requirements.
Due to the common factors observed at each problem location it was believed that excessive train braking force was the root cause. The current braking practice exerts a high level of longitudinal force which cannot be restrained by the track superstructure or in fact by any contemporary ballasted track or turnout assembly. The rail creep and track damage is well outside existing maintenance standards and the rail creep is reducing the rail Stress Free temperature to between 10°C and 20°C within 1 to 2 months.
For many years the trains on this network used an Automatic Air braking system which uses air to trigger the brakes to activate on each wagon. On long ore trains it could take over 1 minute for the brakes to be fully applied as the air command propagated through the length of the train. Now these trains use Electrically Controlled Pneumatic (ECP) braking commands which delivers the braking activation command electronically throughout the entire train, meaning the brakes on every wagon are basically activated simultaneously. Braking distances are reduced, as are the forces within the train.
However, as the ECP braking is 40-60% more effective than air controlled braking, this in turn produces 40-60% more deceleration from the train mass which is then transmitted as a longitudinal force into the track through the wheel-rail contact. By reducing the current braking effort by 50%, the time lost per train cycle from mine to port is negligible and this reduces the deceleration force to pre ECP levels, where the creep was manageable. This braking effort can be progressively increased until the creep remains at a level still able to be managed.
Lycopodium was referred to Rio Tinto due to many years of quality services delivered across other private heavy haul rail networks.
