Golden days at Golden Grove: Gerard Anderson, General Manager (left) and Jim Simpson, Mine Superintendent, are delighted with the Simba drill rig and the quality of Atlas Copco's service.

A glittering performer at Golden Grove

Drill rigs make a big difference in Australian zinc and gold mines

The Golden Grove mining venture, owned by Normandy Ltd, comprises two mines with a total zinc ore production of 1.2 million tonnes per year.
Located 375 km north-east of Perth in the Murchison region of Western Australia, its main resources are zinc and copper, with significant amounts of silver, gold and lead. Annual output of zinc concentrate is 200,000-220,000 tonnes.

An Atlas Copco Simba 4356S drill rig is playing a leading role in the operations and has exceeded the budgeted number of 115 mm diameter drillmetres every month since being commissioned in December, 1998. It deals with all the production drilling at both Golden Grove mines - Gossan Hill and Scuddles - and has achieved a record month of 7,165 metres.

Harsh environment

The machine is currently drilling 15.6% above budget and Mine Superintendent Jim Simpson says: "When you take into account the exceptionally hard rock and abrasive ground conditions at Golden Grove, this is extremely good. Usually, for a 30 metre hole, the drill bit would be changed three or four times."

Gerard Anderson, General Manager, adds: "We are very pleased with the performance of the Simba and the service we get from Atlas Copco. We operate within measurable quality control and, based on those parameters, Atlas Copco continues to improve its performance."
Mr Anderson says the reasons for Golden Grove's purchase of the Simba 4356S include:
l Automatic drilling, which enables operations to continue through non-productive time such as meal breaks and end of shift
- The operator has more time to carry out other tasks during the 12-hour shift
- The mine specialises in training unskilled people in all aspects of mining operations, and the high-tech rig offers excellent operator-training opportunities.

Rig operators at the site are enthusiastic about the performance and up-to-the-minute design of the Simba and one of them, Craig Gillies, comments: "The best feature is the automatic drilling, closely followed by the cabin ergonomics and air-conditioning."

Great performance: The Simba 4356S rig that handles all production drilling at both Golden Grove mines - setting a site record of 7,165 metres in one month.

Major contribution

The Atlas Copco full service, cost-per-metre contract has made a major contribution to increased productivity levels. Average availability of the Simba rig is high and Jim Simpson says: "Its great performance reflects the skill of the two technicians in the Atlas Copco team."
The technicians work a rotating roster system so that one is on site 12 hours a day and available for call-outs round the clock. Mr Simpson specially mentioned Justin Wardell, who has been at the mine since the contract started.

Another cost-per-metre contract, with Atlas Copco Rock Tools, covers the supply of all drilling consumables and has a performance-based profit share agreement. It has resulted in significant cost savings for Golden Grove - some 30% over two years.

Jim Simpson concludes: "It has enabled 'best practice' development in terms of drill consumable usage - with the savings providing a good platform for an excellent customer-client relationship."

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Top-class rig in low-cost operation

A confirmed admirer of the Atlas Copco Simba drill rig at the Golden Grove mine: Rig operator Craig Gillies (left) with Fred Dittman, Underground Foreman.

Jolyon Jardine says: "The Atlas Copco Simba is the Number One drill rig for production drilling - and we have the lowest cost-per-metre drilling operation in Australia."

He should know. He is Senior Mining Engineer at Stawell Gold Mines, some 200 km inland from Melbourne, Victoria. And at the site, an impressive drilling performance by a Simba 1354 rig is recording thousands of drill metres per month on a variety of demanding tasks.
Stawell, which took delivery of a second Simba 1354 in March, aims to produce 90,000 ounces of gold per year at a mining cost of AUS 350 per ounce, as well as strengthening safety measures.

But the mine has a very complex and difficult geology, with highly variable grade distribution. Mine head grade is typically 4.7 to 5.5 grams - and all this means that Stawell must be run very efficiently to continue viability at today's gold prices.

Delighted with the Simba rig's performance: Paul Oakley, Atlas Copco Service Technician, Simba Operator Wayne Cox and Jolyon Jardine, Senior Mining Engineer.s per week.

Multitude of tasks

Currently, 50,000 tonnes of ore are produced monthly from the stoping operations. Average yield is four tonnes per metre drilled, requiring the rig to drill some 12,500 blasthole metres of 76 mm diameter a month. The Simba also has other tasks which amount to a further 3,000 metres.

Says Jolyon Jardine: "Thanks to on-site modifications to the machine and a good preventative maintenance programme, which includes the Atlas Copco fitter at the site, the drill rig has coped superbly with this formidable workload."

Stawell is committed to 100% mechanized production, reducing the risk to employees in shrink stopes and airleg raises. But with small stope panels, typically less than 10,000 tonnes, the use of raisebored slots would significantly increase mining costs. So a critical factor has been the development of a cost-effective replacement for previously mined airleg raises.

Today, where stopes have access from above during mining, retreat long-hole raises are used and the Simba drills them from below for the greatest accuracy. The raises, up to 28 m long, are fired in multiple shots from above. But where the stoping sequence is a top-down system, with no access available to the top, the Simba drills a blind Single Shot Raise (SSR).

Implementation of this method hinged on the ability of the Simba to drill accurate, parallel holes up to 20 m long. The slide table allows the critical centre holes in the raise to be drilled without adjusting the angle of the drill between holes. The rig moves along the pattern of measuring tapes on the drive walls, using its lasers to remain parallel, and an Atlas Copco Rock Tools 152 mm reamer creates six holes with adequate voids for blasting the SSRs.

Handling production drilling in two mines: The Simba rig with operator Wayne Cox.

Improved productivity

The mine now uses SSR for all raises up to 16 m long - and sometimes up to 23 m, in favourable ground. The fitting of a 90° feed bracket means that all holes can now be drilled from the safety of the operator platform, and productivity has improved significantly. Automatic drilling has also greatly reduced maintenance costs and further boosted productivity.
Minimising blast vibration is essential as the operation is directly below Stawell town. The accuracy of the Simba ensures that charges are loaded correctly and each blast is carefully monitored.