Back to blasthole basics

SOMETHING as simple as good drilling training could make all the difference for blasting productivity. Sarah Belfield writes

COMPUTER animation-based training is helping the De Beers diamond mining company to reduce its blasthole drilling costs.

High-tech software drives the training animations, but basic drilling concepts are behind the sought-after productivity improvements.

“Drill and blast training in my view has the biggest potential and gets the least attention,” De Beers drill and blast engineer Llewellyn Dippenaar told Australian Mining.

He said he thought mining houses in South Africa realised there was a shortage of skilled labour generally but they didn’t know how to attack the problem. Dippenaar described the benefits of the training avenue he has been taking as “exciting stuff”. To help him improve drillers’ blasthole drilling knowledge, Dippenaar has been working with the South African video and multimedia production firm The Boiler Room, which was established in 1999.

Boiler Room managing director Mark Hocker, who at the time of writing employed a staff of eight and had been involved in 3D animation and training for around 12-15 years, spoke to Australian Mining from Johannesburg on Dippenaar’s behalf.

Hocker said mining staff new to blasthole drilling lacked what he called consequential knowledge. They weren’t aware of why good blasting required such high levels of drilling accuracy.

“Whether you’re drilling horizontally or vertically, the ideal thing is you want the same depth every time … because the blasting has been designed in such a way that it will break up the rock and leave a smooth-ish surface afterwards,” he said.

He said if drilling at one blasthole went deeper than neighbouring holes — called overdrilling — the depression created in the resulting rock surface needed to be filled before the next round of drilling and blasting could commence.

Not only did that involve the time and resources needed to bring in a front-end loader to top up the depression, the fill material potentially created headaches of its own as well, Hocker said. The material used, typically a gravel product, involved higher drillbit speeds than when drilling through in situ rock. Reaching true ground at those higher speeds can damage drillbits, bringing with it the time and monetary costs of replacements.

Underdrilling, where blasthole drilling didn’t go deep enough, was the reverse problem. It tended to leave a lump projecting out of the rock surface. One seemingly minor bad habit can lead to systematic underdrilling, according to Hocker.

“You’re supposed to get the drillbit level onto the ground, zero the computer, and then it starts drilling to its required depth,” he said.

“But what a lot of the guys do is just start the drillbit and start down straight away, without zeroing the computer. Basically there’s an extra metre that you’ve now underdrilled.”

Another common problem was drilling off of the intended line. And using too big a drillbit meant not only was the amount of explosive going down the hole greater than need be, but also the size of the drillrig itself was an overkill.

“There are so many permutations to what can actually happen,” Hocker said.

However, it was clear that with suitable training, marked productivity improvements were possible.

According to Hocker, Dippenaar participated in the introduction of a new explosives product at a mine (outside of De Beers) over a period of around six months. In that time he trained a crew of blasthole drillers himself.

“Their drilling and blasting was double that of anybody else in the [mining company’s] group, just by following the correct procedures — drilling on line, drilling to the right depth.

“Because of Llewellyn’s model there, the rest of the group has now picked that up and started using that.”

Hocker said The Boiler Room was currently working on an animation-based training project for Dippenaar to assist with drilling and blasting at De Beers’ Finsch and Cullinan diamond mines. Discussions were also underway for “a lot more” additional future work. This was aside from the work the firm was doing for De Beers about a newly introduced automated mine haulage system.

“What Llewellyn is stressing is the consequence. The big ‘in’ thing over here at the moment is what we call behaviour-based training,” he said.

“If I drive at 120 [kilometres per hour], great, but if the speed limit is only 100, what are the consequences? I have less time to stop in. I run the risk of getting a speeding fine. That’s a consequence of an incorrect action.”

Hocker said the overall rationale was similar for training up blasthole drillers. The aim was to explain the reasons for putting certain practices in place.

“So what we would do is show the person drilling off line. Then we’ll go into the hanging wall and we’ll look down in a birds-eye view and show them drilling off line.”

Llewellyn Dippenaar

De Beers Consolidated Mines

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