ROCK ‘N’ GOLD
Sunrise Dam, Australia. Drilling through hard rock in the harsh, burnt orange environs of the Australian Outback is how Barminco gets to the gold at Sunrise Dam in Western Australia.
A change in the aircraft’s engine tone signals its descent. Below, the terrain’s dark red, the signature colour of the Australian Outback, is slowly changing to brilliant white. Sunrise Dam looms ahead, a tiny oasis in a dry sea of the iridescent salt lakes that are a feature of this remote area.
It’s a gentle hint of things to come – a precursor of the harsh conditions in which mining is carried out in this part of the world, throwing down a stern challenge for both man and machine.
Sunrise dam, 220 kilometres north-east of Kalgoorlie in Western Australia, is owned by AngloGold Ashanti Australia Ltd (AGAA), a wholly owned subsidiary of AngloGold Ashanti Ltd, the world’s third-largest gold producer.
AngloGold Ashanti and Barminco
The Sunrise Dam mine is owned by AngloGold Ashanti Australia Ltd, a wholly owned subsidiary of AngloGold Ashanti Ltd. Since its inception in 1997 the mine has produced almost 6 million ounces of gold.
All underground work at Sunrise Dam is handled by leading Australian mining contractor Barminco, which was awarded the original contract in 2003. The current contract covers all underground development work as well as production. At the time it was signed in 2011, it was one of the largest mining contracts ever awarded in Australia. About 500 people are employed at Sunrise Dam, including the Barminco workforce of 220.
The mine began production as an open cut operation in 1997, and from 2004 until 2014 ore came from both open-cut and underground sources. The open pit was finally completed at a depth of 490 metres in early 2014, and AGAA now sources its ore exclusively from its rapidly expanding underground mine – a veritable rabbit warren of more than 12 kilometres of tunnels extending nearly 800 metres below ground level.
Despite massive fan-driven ventilation systems throughout the underground workings, the air is warm and clammy. This is the environment in which Barminco, the underground mining contractor at Sunrise Dam, operates its load and haul fleet for two 12-hour shifts every day.
A tight fit
To the uninitiated, the massive Sandvik TH663 trucks seem to fit into the narrow tunnels as snugly as pistons. In reality there is a metre of clearance on either side of the truck, which is a testament to the skills of the highly trained driver of a vehicle that weighs over 100 tonnes fully laden, working in absolute darkness relieved only by the headlights.
The loader fills the truck in just three passes with its massive bucket. The truck heads off to the surface and within minutes is replaced by another. The next stage in the load and haul process is at the portals, the entry points to the mine. Trucks emerge from the portal of the mine every five to 10 minutes and dump their ore just a few hundred metres away on a stockpile. From there it is transferred to giant surface trucks and transported to the mine’s crusher. Gold is extracted from the pulverized ore by a conventional carbon-in-leach and gravity process.
Sunrise Dam is recognized as a world-class ore body, but most of the gold is very finely disseminated and only occasionally visible to the human eye. The average grade of ore hauled from the underground mine is 3.5 grams per tonne. A laden truck emerging from the portal carries, on average, 55 to 57 tonnes of ore. This mass of rock, when processed, will yield just under six ounces of gold.
Tech specs – Sandvik TH663 Haul Truck
- Sandvik TH663 weighs in at 43 tonnes, eight tonnes lighter than the model it replaced, with a resultant drop in fuel consumption.
- The truck is powered by a Cummins QSK19 Tier 2 diesel unit rated at 567 kW, which gives a maximum haul speed of 42.5 km/h.
- Operator comfort and safety is enhanced by an ergonomic and noise-suppressed ROPS- and FOPS-certified safety cabin, 35% larger than on earlier models.
- Sandvik TH663 service points are accessible from the ground using an built-in jack system.
- With an overall length of 11.58 metres and a width of 3.48 metres, the truck has an outside turning circle radius of 9.35 metres.
Sunrise Dam’s geology is highly complex, so identifying where the gold is, and then designing the best way to extract it economically, is challenging. Extensive drilling and geological interpretation have determined that bulk mining methods are the most effective. As most of the operating costs are fixed, this means that operational efficiency is vital – the more ore you mine and treat, the more gold you will produce, bringing costs down.
Productivity is paramount
Monthly targets are currently running in the order of 220,000 tonnes of ore. To meet these targets, consistent productivity is demanded, first from the drill and charge-up operators and then from the load and haul teams.
Barminco Chief Operating Officer Victor Rajasooriar explains that the increasing demands on production had prompted the company’s decision to purchase five Sandvik TH663 trucks for use at the mine.
“Barminco is focused on maximizing the value of our projects for our clients,” he says. “Having equipment that enhances the safety and productivity at our operations is key to our success. Sandvik TH663 held high promise of being a cost-effective unit now and in the long term. So far, it’s delivering for us.”
Sandvik TH663 brings to the table outstanding reliability, the biggest tub capacity in the business, low fuel consumption, low diesel particulate emissions and, for a vehicle that weighs well over 100 tonnes fully laden, incredible manoeuvrability and speed across open ground.
But from the perspective of Craig Metzke, Barminco’s Sunrise Dam alternate project manager, possibly the biggest single attribute of the new truck is the attention that Sandvik designers have paid to operator comfort and safety.
“The trucks have a front axle suspension specifically designed to cushion operators from the jarring they experience in every other underground truck in the business,” Metzke says.
“They also have a driver-friendly five-point harness and a level of soundproofing so good that many of our operators feel like they’re driving on a highway,” he says. “These safety attributes together have made a direct and measurable impact on driver productivity. With five Sandvik TH663s we are consistently shifting more ore than we did with our previous fleet of six trucks of a similar load capacity.”
Not only was the fleet moving more ore, he says, but it was using substantially less fuel in the process. Current consumption at Sunrise Dam is 15 percent less compared with earlier vehicles. Sandvik TH663s are also delivering a significant reduction in diesel emissions compared with earlier fleets operated by Barminco. This allows the fleet to operate in sometimes sub-optimal ventilation areas, where the emissions from earlier haul trucks might have posed a hazard.
Metzke has warm praise for the Sandvik technical crew that has helped Barminco to commission its new fleet. This technical backup is still in place, and Sandvik technical staff are regular visitors to the mine.
Barry Martin, Sandvik product support, load and haul, is currently working with Barminco staff on site setting up a wireless data logging system that will ultimately enable data to be remotely accessed from any point in the mine by Barminco and Sandvik personnel at the mine site or even at their respective Perth offices.
Sandvik equipment features prominently in Barminco’s underground fleet at Sunrise Dam, with five Sandvik TH663 underground trucks, all delivered in 2014, two development drills and three production drills. An additional truck is scheduled for delivery early in 2015. Currently each truck hauls more than 800 tonnes per shift, giving a fleet total of more than 8,000 tonnes a day.
Sandvik technical staff members maintain a regular presence at Sunrise Dam, helping to bed down the new fleet and working with Barminco management, mining supervisory staff and operators to further refine its products.
“The system will transmit production information to enable management to track performance against target,” he says. “Operational data will tell training staff whether individual operators can be helped to amend their technique in order to maximize production and minimize unnecessary stress on the equipment, for example by over-revving. But the main benefit is the maintenance data transmitted. This gives early warning to maintenance crews of developing problems, enabling these to be dealt with quickly at an early stage, which minimizes both downtime and the cost of repairs.
“In short,” Martin says, “with the system fully operative, we’ll see further improvement in machine availability, faster and more economical maintenance and optimal performance from our operators.”
A unique safety feature of Sandvik TH663 that has particularly endeared Sunrise Dam is its in-built jack system.
“Because of the very confined space underground, which limits the amount and type of equipment you can bring to bear on the problem, it can take half a shift or more to effect a wheel change,” Metzke says. In the past there has been no easy solution. Manually moving a portable jack into position in such a restricted space is a potentially hazardous operation and has been the cause of many injuries in the industry in the past.