High wear rates on a conventional chute at a large diamond producer in Botswana were costing the mine dearly – in both repairs and downtime. The custom-engineered solution from Weba Chute Systems not only drastically reduced maintenance, but also cut dust levels.
A primary crusher discharge chute had been a diamond producer for many years. The crunch came when, after considerable capital expenditure, the new conventional chute needed maintenance just six weeks after installation.
“The mine needed a long-term solution,” says Hilton Buys, regional manager at the company. “Senior experts from our company visited the site to take a careful look at the conditions the chute needed to deal with, and we took our conclusions back to our design office.”
Among the challenges were large lump sizes in the ore stream, contributing to build-up of material in the chute and regular choking, says Buys. Also, while Botswana’s dry season is long, the rain that does fall causes considerable problems to the flow dynamics. The kimberlite on the mine – depending on which part of the pit it comes from – can become very sticky in wet weather.
“We therefore had to pay particular attention to flow angles, and the design had to effectively accommodate both wet and dry conditions,” he says. The concept design – which included quick-release lips on dead boxes – was approved by the mine and the final design, manufacture and successful installation was conducted.
Adding to the complexity was that the feed end of the primary crusher was some eight metres below ground level, while the crusher itself stood about 10 metres tall. The chute had to be positioned below the rock box which stores the material from the crusher discharge, channelling the stream into the Weba chute at a transfer height of nine metres to the conveyor belt.
“The conventional chute also created excessive dust through uncontrolled rock velocity over this considerable transfer height,” he says. “By contrast, our chute’s controlled-flow meant that the mine did not even have to apply its dust suppression system.”
After installation, the company gave the customer a 12 month guarantee on this chute, which comes with regular inspection reports. Installed in 2017, the chute is still operating with little maintenance.
“Designing a long-lasting chute is not just about creating a box with some reinforcing where you think there will be wear,” he says. “It is an endeavour that must be scientific, based on in-depth analysis of material and flow conditions.”