The hole truth in blast preparation

Accuracy is everything in drilling. If you are drilling a few centimetres off the mark you can ruin an entire’s day work; put the set grid out or even miss mineralisation completely.

Accuracy is even more important when drilling blast holes.

Drilling in this case is literally a science, where an out of place blast hole is able to completely ruin a well planned blast pattern.

It may also cause shelf collapse, an uneven brim or unexpected fly rock to rain down on the site.

But it is not just accuracy that is needed in drilling blast holes, but speed as well.

If the holes are not drilled within the allotted time, then operations have to be rescheduled to fit in the new blasting period.

Shuffling an entire mine or quarry’s schedule because of poorly drilled holes is a hassle that doesn’t need to occur. At a quarry in Germany, the operator has utilised a drilling control system to ensure accuracy in blast hole drilling.

According to Antonio Polizzi, the quarry/mining foreman at the Schaefer Kalk limestone quarry, they used the MOBA Mobile Automation AG MDS-2000 drilling system to control drilling devices on a Hausherr HSB 2000.

"It really increases the efficiency of our quarrying work processes," Polizzi explained.

When drilling the blast holes, exact parallelism of the holes is essential for creating a smooth brim and preventing any uncontrolled rock fall or unexpected fly rock during blasting.

The MDS-2000 controls the drilling rig with penetration accuracy to a degree that even 15 to 20 metre deep blast holes are all drilled at the exact same angle.

This precise control also allows for drilling in tight spaces.

Where there is limited space and no way to turn the drill rig, the MDS-2000 system still allows drill holes to be bored in the required location as the program can control the drill head exactly even if the machine is diagonal to the drill hole, MOBA Mobile Automation claim.

"With the system, we can drill about five percent more holes than before, in the same amount of time," Polizzi said.

Utilising slope sensors and rotary sensors, the system records all drilling data such as drill hole depth, angle and drilling time.

This information is then displayed to the rig driver on a graphic display and then saved there, or can be sent directly to the office or even to a mobile end device via telemetry.

It also displays the average infeed during drilling.

Originally, MDS-2000 was used as a test version parallel to the Jäger IS-22 drilling system, Polizzi saying that its robustness and operational simplicity had cemented its position as the main drilling system at the limestone quarry.

MOBA stated that the MDS-2000 has been built to withstand the conditions typically found on mine sites and in the quarrying industry, with all electronic parts protected from dust, moisture and vibrations by a completely sealed plastic casing.

Due to its modular design based on CAN-open, the system is also open for other customer requirements, and to allow for future developments to be easily incorporated.

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