This project aims to solve the problems experienced at the Thiess-run Curragh North Coal Mine in Central Queensland. Attainment of the solutions was gained through the development of a polymer wear package to be implemented on the ten-truck fleet of Caterpillar 793C Rear Dump Haul Trucks at the Curragh North Project.
The problems experienced are directly related to the overburden material they are mining from above the coal seam. The material consists of sand, clay and rock, and the severe nature of these material types has seen the current steel wear packages perform inadequately in the conditions. The sand is incurring high wear rates in the package; the clay is sticking to the internal tray surface and not fully dumping leading to production limitations; and the rock will introduce impact loading to the tray causing damage.
The excessive weight of the steel package is also acting as a production inhibitor, as it directly decreases the payload capacity of the tray. These problems, when combined, lead to gross inefficiency in the operations, and if solved, the potential for increased production is very high.
It was anticipated at the commencement of the project that a polymeric material would be the best material to resolve the issues experienced, but as proof, the project began with a full investigation into the optimal wear material for the application.
The material found to be the most effective at solving the requirements of the wear package in the conditions was indeed polymer, in particular a plastic called Ultra High Molecular Weight Polyethylene (UHMWPE).
The design of the wear package has been developed from this point, with the components required for the material to be effective in the application being at the forefront of the development. These areas were in the design of a mechanical fastener and pattern suited to the application, and a particle exclusion method aimed at keeping the payload material from beneath the UHMWPE sheets that comprise the wear package. The conceptual solutions derived for these design areas have been evaluated against the requirements devised for them, and the best solution, or the best combination of solutions, has been arrived at. This has then been refined to give a highly effective final solution able to work efficiently in the conditions designed for.
A cost analysis was performed, incorporating maintenance and installation predictions, where the total requirements for the UHMWPE wear package were determined, and compared to those of the current steel wear package at Curragh North. This comparison took the form of a yearly, expected rate of maintenance costs, and the projected increases in profits from extended production calculated to evaluate the overall cost benefits from the project.
The UHMWPE Wear Package solution has been found to be similar to the equivalent Steel Wear Package at Curragh North, in terms of the initial installation costs and the life cycle costs, using a minimum wear life projection. The production increases from the lightened overall tray weight, and the elimination of hang-up is very attractive. The minimum profit increase for Thiess Pty Ltd, is expected to be over $500,000 per truck, per year, indicating over $5million increases in profit over the ten-truck fleet annually.
The potential of the project to increase efficiency at the Curragh North Project will directly benefit the company, but also the possibility of project implementation at other mines increases the significance of the project to the company and wider industry.