Costerfield produces ore via a single-portal underground mine, with site personnel using a narrow vein method to extract vertical veins of ore. The mine produces up to 80,000 equivalent ounces per annum in gold and antimony in gravity gold and a concentrate compromising approximately 54% antimony and 60g/t gold. The nature of narrow vein mining dictates that ore drives are quite thin to reduce the amount of waste material that is captured.

Costerfield's drilling and blasting programme was designed to maximise ore recovery by throwing the ore towards the draw point; however, historically the site could only recover 75% of the ore. This was due to the remaining ore sitting in the stope void out of reach of the underground loader, as manually operated loaders could not exceed the stope brow.

Mandalay decided to investigate implementing a loader that could be managed remotely to extract additional ore and to safeguard equipment operators from hazardous situations at the mine face.

In 2015, Mandalay Resources engaged RCT to implement its ControlMaster Guidance Automation product on a Sandvik LH203 loader. The automated loader enabled Mandalay Resources to retrieve significant amounts of ore that were previously unreachable.

In recent years, RCT has increased the autonomous fleet at Costerfield by commissioning ControlMaster Guidance Automation on a second Sandvik LH203 as well as a Sandvik LH151D. The machines are managed from fibre optic control stations (FOCS) at secure locations in the underground mine, which are protected by Laser Guard Containment Units as well as stations on the mine's surface.

"Removing operators from the machine is the best outcome as it eliminates their exposure from one of our highest risk jobs which is working at a stope brow," said Jayson Guzzo, major projects and innovation manager - Costerfield at Mandalay Resources. "The small loaders we use are very rigid which has the potential for repetitive strain injuries. They also have open cabs and, in this environment, dust, machine exhaust and debris can be an added safety concern."

In mid-2019, Mandalay made the decision to implement a digital mine communications network to accommodate future technological growth.

"Given that we are a narrow vein operation we may have to access ore a significant distance from the mine access point so we are looking at going to a digital platform so we can run a fibre backbone and autonomously operate machines over a vast distance," said Guzzo.

"In a traditional mine you might spend a whole week bogging a single stope before moving, but at Costerfield we might bog three or four headings in one shift, so the number of sites that we have to have set up at any one time are multiple, hence a digital system will significantly speed up the process of commissioning new drives."

Mandalay has reported that ControlMaster Guidance Automation enabled it to carry out bogging and firing operations simultaneously, saving it substantial time which was previously spent clearing personnel to a safe distance.

Guzzo said ControlMaster Guidance Automation has enabled the company to reduce shift changeover time by two thirds - which is a significant cost saving. He also noted that the site has experienced less unplanned machine downtime.

He explained: "At Costerfield the drives are roughly 2m wide, so Guidance Automation keeps the machines off the walls and stops them bouncing around the tunnels so the damage to the machines is a lot less and results in significantly reduced unplanned maintenance time."

Guzzzo concluded: "Relocating operators from the cab of our loaders to safer environments on the mine's surface is essential, and being able to continue bogging during firing as well as significantly reducing shift changeover time is critical to improving site productivity.

"Plant automation is definitely the way of the future in the mining industry and RCT are the leaders in that area, which is why they are our preferred supplier with this equipment."