Drilling in mining applications has changed drastically over the past 40 years, with one of the most efficient methods being reverse circulation (RC). In this method, a pneumatic hammer drives a drill bit, and the dislodged fragments are then lifted from the hole by a differential pressure caused by forcing air down the drill rods.
Atlas Copco has introduced redesigned versions of the ROC L825 RC and L830 RC models to enable them to meet the requirements of limestone and aggregate quarries, selective and surface mining, and construction sites around the world.
Two engines are available, both Caterpillar Tier III turbocharged diesels, rated at 328 kW (440 hp) in the L825 RC and 402 kW (539 hp) in the L830 RC. The names of the two models come from the maximum working pressure produced: the L825 RC creates 25 bar (363 psi), while the L830 RC produces 30 bar (435 psi), both from Atlas Copco two-stage screw-type compressors.
L8 RC models store 98 ft (30 m) of drill pipe in a revolving magazine, 157 ft (48 m) in a revolving carousel, and an additional 40 ft (12 m); with the insertion of more pipes, depths of up to 328 ft (100 m) are possible. Both long feed and short feed are available, and conversion to traditional down-the-hole drilling is possible.
With the pipes and feeding system located on the boom, holes of 45° forward and 30° to each side enable exploration holes to find the ore body boundaries in a minimum number of holes, rather than purely vertical drilling.
Because the L8 must move as well, the vehicle is tracked for grip and stability around mining sites. A 2.2 mph (3.5 km/h) tramming speed is sufficient since many holes are close to each other. For transporting across sites, the L8 is much like a standard construction excavator in size and weight: 11.7 m (38.4 ft) long and 22,600 kg (49,825 lb) in the larger long-feed version.The cab meets all FOPS (falling-object-protective structure) and ROPS (roll-over-protective structure) requirements and can be outfitted for any environment. L-series models are currently in use in locations as varied as Chile and the Arctic Circle.