Cummins Success At Stawell Gold Mine

QSK19 engines are good as gold

Like any other mine, Stawell Gold Mine in Victoria s constantly looking for productivity improvements.

A fleet of five Cummins-powered Atlas Copco haul trucks, each able to carry 60 tonnes of gold-bearing ore, is the latest step in Stawell’s efficiency drive.

In 2009, these trucks will haul around 750,000 tonnes of ore to the surface from which 120,000 ounces of gold will be extracted.

It costs Stawell $650 to produce every ounce of gold.

“We’re a low cost producer…we wouldn’t be here if we weren’t,” says underground mine manager Craig Walker.

“We have to keep on pushing technology to remain viable,” he stresses. “Our equipment suppliers can’t sit back. If they want to keep our business they have to keep working with us.”

Over the years, the mine has quickly embraced advances in haulage technology. And for good reason – Stawell is now going deeper to access gold reserves than any other ramp-accessed mine.

Gold-bearing ore is currently being mined at a vertical depth of 1,400 metres and planned exploitation of further ore bodies will eventually extend to 1,900 metres.

Back in the 1970s, 400 metres was considered the practical and economical limit for truck haulage to the surface in metalliferous mines.

The advances in truck development have certainly been crucial to Stawell’s cost competitiveness.

The latest trucks at the mine, the 60-tonne payload Atlas Copco MT6020s, are powered by the 19-litre Cummins QSK19 rated at 760 hp.

“Ten years ago, we just wouldn’t have thought it possible that a truck could haul 60 tonnes at 12 km/h on a 1-in-7 grade,” says Craig Walker. “But that’s what is exactly happening now with our MT6020 trucks.”

The MT6020 units, which gross over 100 tonnes fully loaded, have replaced the 50-tonne payload MT5010 at Stawell. The 50-tonner was also powered by the Cummins QSK19, but rated at the lower 650 hp.

Stawell was a key driver in the development of the MT6020 when it became clear the mine would need an even bigger truck as mine depths increased.

Before being launched globally, the MT6020 was trialed at the Stawell mine and the results were overwhelmingly positive.

The trial proved that the MT6020 could achieve the same speed on the ramps as the smaller MT5010 but with an extra 10 tonnes in the box.

Stawell’s 60 tonners are averaging 165,000 tonnes/km per month – a 29% improvement in productivity over the 50 tonners.

“The next step will be to carry another 10 tonnes of payload at the same ramp speed,” Craig Walker asserts.

Stawell’s requirement is for its trucks to achieve 12 to 14 km/h up a 1:7 gradient.

The trucks are currently hauling ore to the surface from a depth of 1,400 metres. The distance is 13 km on an average gradient of 1:7 and a steepest gradient of 1:6 – a punishing task in anyone’s language. A 1:6 is difficult to even walk up, while Stawell’s diesel Landcruisers are back in 2^nd gear on such a gradient.

Stawell is aiming for an 15,000-hour life from its 760 hp QSK19 engines.

“We run our engines right to the end of their life and then replace them,” explains maintenance supervisor Mal McCombe.

“Our experience with the QSK19 is extremely good. It’s definitely at the front end of technology for this application.

“We’ve already proved with the QSK19 in the MT5010 truck that it is capable of a 17,000 to 18,000-hour life.

“Cummins’ service and technical support capability is also very important to us and will continue to be into the future as we look at engine options for even higher payloads.”

When the QSK19 was approved for underground mining in 2000, it didn’t take long for the engine to start making its mark as a high availability hauler.

Atlas Copco, which initially offered a competitor engine in the MT5010,  soon switched to the QSK19 for significantly improved reliability, durability and performance.

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