Stopping productivity-sapping deviance

GETTING blast holes to go where they are supposed to is becoming another front in the battle to improve mining productivity.

The Devigyro being used to survey RC holes underground.

The Devigyro being used to survey RC holes underground.

Several companies are developing and deploy technology to help make sure the blast hole goes where it is supposed to.

Blast holes can deviate for any number of reasons. The ground conditions can play a big part. So can the drill operator.

If the blast hole is not in the right place then productivity is impacted.

Deviated holes lead to sub-optimal blasts, which can ripple through to effect the rest of the mining process downstream.

Developing the technology to align drill holes correctly before drilling is started, monitor them while they are drilling to ensure they are going where they should and then surveying them afterwards to confirm the result will only stand the industry in good stead as drilling becomes more automated.

In Victoria, Kirkland Lake Gold has taken a survey approach to improve its blast hole drilling accuracy at its Fosterville operation, deploying a survey tool from Downhole Surveys.

Downhole Surveys founder Mike Ayris said at Fosterville they were typically drilling slot raises with about 10-15 holes to the slot.

The danger is if those holes do not go where they are supposed to and are then blasted the mine can end up with bridging or the blast does not work at all.

"They survey the holes," Ayris said.

"If the holes look to be parting they can take the decision to drill an additional hole or they can adjust how they do blasting."

The tool being used at Fosterville is one of the older survey tools Downhole Surveys has in its armoury.

Ayris said Downhole Surveys was about to introduce the Devigyro to Fosterville.

The Devigyro, developed by Devico, is distributed in Australia by Downhole Surveys.

Compared to the stop-start survey method Fosterville is using at the moment, Ayris said the Devigyro was almost continuous, taking 10 samples per second.

He said the company's surveying tools were also being put to use at Glencore's CSA copper mine near Cobar, New South Wales.

"They wanted to mine an extra 5m deeper between each level," Ayris said.

"They are currently mining 35m and wanted to go to 40m."

That means much more rock is being blasted from each blasthole, making for more bang for the buck.

"But key to the success of that is the holes run straight and the blast works," Ayris said.

"Before it was about production. Now it's about quality. They couldn't afford to make mistakes.

"We've always known blast holes deviated but we didn't know by how much.

"With these super accurate tools we can find out and find out quickly."

Surveying is not the only approach.

Minnovare has developed its Production Optimiser technology - a hardware and software system that can be applied to all underground drill rigs.

At Northern Star Resources' Kalgoorlie Operations, Production Optimiser was able to help the miner get 42,000 additional stoped tonnes, equating to be about another 83,000 ounces a year.

It was run on three long hole production rigs and helped the miner increase the average metres drilled across its Kalgoorlie Operations by up to 33%.

Better yet, those metres were all drilled in the right direction.

The system uses Minnovare's Core software, which digitises drill plans and plods for accurate drill data capture and real time transfer through the mine.

Northern Star Resources principal innovation and technology Jeff Brown said besides the 33% increase in metres drilled, there had been a 54% reduction in bridged tonnes, a cumulative 31% increase in drilling productivity and a 7% reduction in average stope cycle time.

Ayris said the Devigyro could be added to the Minnovare approach to get an even more accurate result.

"Minnovare sets up for the starting collaring of the hole," he said.

"We then use the information from that and survey the hole as drilled.

"You can drill a hole straight but in the wrong direction sometimes.

"Our system records the deviation in the hole.

"We've seen 12% deviation in some holes.

"At [Northern Star Resources gold mine] Jundee there is an area where the deviation is huge, up to more than 10%.

"On the other side of the mine with the same rig and drillers you can have a hole with no deviation."

Both the Devigyro and Minnovare Production Optimiser are designed for underground mining space.

Sandvik has been the latest company to bring out a tool to reduce deviation for blast hole drilling in the surface mining space.

It claims it can help bench drilling top hammer customers reduce hole deviation in challenging conditions by up to 50%.

Called the Guide Adapter the tool is designed to help customers get greater productivity, longer tool service life and improved safety.

Hole deviation of more than 8% can pose problems for bench drillers, particularly those operating in challenging ground conditions such as bad or soft rock, or deep overburden.

This deviation can lead to reduced productivity, safety risks and increased tool wear.

Sandvik product manager top hammer surface tools Fredrik Björk said the Guide Adapter helped drillers increase the service life of their drill strings as well as reducing the number of holes drilled and the amount of blasting needed.

"We have conducted in-depth testing with our customers around the world and the results really do speak for themselves," he said.

"By using the Sandvik Guide Adapter, our customers achieved a hole deviation between 3% to 5% - a reduction by up to 50% - and also increased the service life of their rock tools by up to 40%."

The Guide Adapter is available for T51 and GT60 Top Hammer threads in different diameters.


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