The Barrick Porgera gold mine in Papua New Guinea has become the first mine in the world to use an Atlas Copco DM 45 blasthole rig for in-pit grade control with reverse circulation drilling.
A reverse circulation (RC) kit that enables mines to use their DM45/50 blasthole drill rigs for in-pit grade control is now being successfully operated in the field.
The first mine to take advantage of this technology is the Barrick Porgera gold mine in Papua New Guinea, located high in the mountains about 600 km northwest of Port Moresby.
To accommodate the RC kit, the mine’s DM45 was upgraded with a number of modifications. Craig Rintoul, who was Open Pit Manager at the time, says: “This drill rig is world class with multiple onsite engineered improvements to the original second hand drill. The upgrade means huge savings on a new rig and RC system.”
Safety, functionality, ease of maintenance and cost were all improved with the installation of the kit. Previously, the mine used its standard blasthole drills to take core samples from the drill cuttings, but this often contaminated the holes making it difficult, if not possible, to analyze the ore.
Good business sense
The new reverse circulation package helps the geologists to better locate and analyze the ore, which, in turn, increases productivity as more time can be spent drilling in mineralrich ground, compared to waste material. “It will also improve our mine planning, budgeting and reconciliations,” adds Rintoul, “and that makes good business sense.”
However, why spend time modifying an existing drill rig, when there are rigs specifically made for reverse circulation drilling?
According to Rintoul, the main reasons include uniformity with the existing drilling fleet, ease of sourcing parts, and easy transition for drillers who are familiar with the DM operating system.
In addition, a number of components are included with the optional kit, which can also be retrofitted on drills in the field. The cyclone arm allows for sampling from the ground or platform level, with a vertical raise and lowering function. A cyclone rotation of 160 degrees provides safe access for cleaning, maintenance, and attaching new sample hoses from ground level.
The cyclone assembly includes a hydraulic upper knife valve and pneumatic lower knife valve for collecting and isolating the sample; a hydraulic hinge between the dump box and cone splitter that allows for easy cleaning; and a fixed cone splitter with primary and duplicate sample chutes. All cyclone and sample functions are easily controlled from the operator’s cab. Along with the DM45, the RC kit is also available on the DML, offering hole diameters in the 114–146 mm (4½ – 5¾ in) range with maximum hole depths of 44 m (145 ft).