Most open pit coal mining operations are loath to admit the extent of their rehandle, even to themselves.
Whether it is eight per cent or 20%, excessive rehandle amounts to a staggering waste of resources. So little wonder there is ripple of excitement running through the industry about a new mine terrain mapping system that promises to greatly improve dragline operation accuracy.
Developed by the CSIRO and on the point of commercialisation, DTM (dragline terrain mapping) is an operator assist package that when integrated with mine planning software, visually prompts the dragline operator where to dig and dump overburden.
From the lofty height of the boom tip, the DTM servo scanning system has an unbeatable field of view from which it generates a high-definition dynamic 3D aerial image of the production environment. The system presents this image to operators, mine planning engineers and supervisors – indeed, as the system runs through a web server, anyone, anywhere with permission can dial in and track dragline productivity.
This image is overlaid on the mine dig plan to highlight any variation between the plan and the actual and is presented on screen to operators in their cab.
George Curran CSIRO business development and commercialisation manager Autonomous Systems tells Australian Mining that the industry has really picked up on giving draglines spatial awareness so operators know precisely where they are in relation to the mine dig plan.
“It’s really about not giving dirt frequent flyer points with excessive rehandle,” Curran quips.
“At the moment the supervisor typically comes out once a shift and explains the day’s work to the operator on a 2D image,” Curran says.
“Now, this looks okay when you start but after you’ve been at it for 12 hours there may be no peg lines and a lot of the work is done through the operator’s knowledge and skill of what’s required,” he says.
“It’s very difficult for them to get a ready reckoning of how they are going in relation to what they were asked to do as there are no actual references in the pit.”
When integrated to commercial packages DTM can provide screen prompts that can show operators where they have to dump the overburden and the optimum height for the dig point.
“If you don’t build the spoil in the right way then that’s where the dozers come in and redo the spoil pile,” Curran says.
With DTM operators can work to maximum spoil build as the image eliminates blind spots on top of and behind the spoil piles.
The system can help operators avoid leaving toes covered with overburden as a result of an inaccurate dig depth. Today with the high price of coal, it is important to recover as much of it as possible.
Curran says that while there are already packages that provide estimations, in this day and age this is not really good enough.
“Mines really need to know where they’re at and where they need to get to. This system means the days of sending guys out there with peg lines are well and truly over. We are talking virtual pegging,” he says.
Working closely with operators in the field, the DTM development team was told in no uncertain terms: “no more screens”.
“The first response was ‘not another screen for god’s sake, we’ve got enough as it is’,” Curran says.
“So one of the first design criteria set for the system was it must integrate into the existing screens and into existing commercial software packages,” he says.
The system works like an automated surveying system. A Leica RTK GPS is combined with a laser scanning device mounted at boom tip generates a fan of light on the ground and as the dragline turns it “draws” lines on the surface.
By knowing the precise distance from the scanner to the ground, coupled with detailed information about the actual GPS position of the boom tip, the system generates 3D maps of the surface as accurate as if done by manual surveying.
Importantly, the servo scanning system is resistant to mechanical bounce and visual interference caused by boom motion, ropes, bucket position, rain and dust.
All the operator needs to do is a single 360º rotation to enable the system to build a complete 3D image of the dragline’s operating surrounds. How often this is done depends on how often the mine wants to do a reconciliation. It may be once at the end of each shift to get a complete snapshot of what the crew achieved and benchmark the starting point for the next shift.
On the other hand, at any time during the shift the operator can do a 360º, which takes about a minute, to highlight on screen any variation between planned excavation, spoil build and actual.
Another important advantage of the laser system is it measures true volumetric move and will replace the current system where each bucket is weighed and volumetric move is estimated.
Curran says the DTM is not about taking people out of the seat, but empowering the people in the seat to do the best possible job.
The system can also help improve operator skills because it visually shows the different sequences between the top operator and others, which will allow the supervisor to show all operators the most efficient sequences in a non-confrontational way.
Curran says he expects that fine-tuning underway in collaboration with the dragline operators and mine designers will throw up a whole range of further options for the system. He says DTM will probably hit the market in a next generation version of an existing operator assist package in the near future.
Although DTM is a standalone product, it can also readily plug into a swing assist product the CSIRO team is developing that will allow draglines to consistently dump directly into hoppers.
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