EXPLORATION I
mproved technology over recent years
has tended to reduce rig size for the same duties, also tending to improve mobility. It is an important method study calculation to make in deciding on rig drilling capacity compared to mobility.
Te choice of design and supplier of bit can have important effects on blasting economy, especially with regards to durability. Any need for unscheduled bit replacement or failure in the hole is disruptive of drilling schedules and costs. Te cone elements run on bearing surface or roller bearings that may be air-cooled or grease-filled to prevent overheating and failure. Many rigs have the capability of being switched to down-hole drilling (DHD/DTH/ITH) for harder strata and very long hole. In this case the main breaking force comes form the drill hammer and rotary action is for repositioning for the next impact.
blastholes. With the realisation of practical means of devising automatic control systems for accurate drill- string location and alignment, full automation without drilling errors and their consequent problems, is becoming practical. Te advantages of automated
rotary drilling rigs include improved safety (chiefly by less fly rock), more predictable fragmentation, more level benches, better control of rig operation for predictable wear and maintenance requirements, and more economical explosives use. All these, plus better adherence to agreed blast designs, should result in improved rock excavation economy and crushing productivity.
Te major drill-rig manufacturers
have all been tackling the practical means of achieving automation, some with more success than others and some with the assistance of independent control specialists Following an automation co- operation agreement with Sandvik in 2011, in 2013 Flanders of Evansville, Indiana, USA developed its own rig, the Ardvarc 4.0. It is claimed to be the world’s first fully automated multi- pass drill rig, and it also incorporates the world’s first autonomous angle drill implementation.
Monitoring station for the Flanders Ardvarc 4.0 automatic multipass rotary drill rig.
Photo: Flanders.
Another importance choice when designing the open-pit mine drill- and-blast system is bench height and how to achieve it. Single-pass drill-rig bench heights are obviously limited but serve most requirements except for the largest mines. Te time taken to add and remove drill steel in multipass drilling is non-productive and has to be minimised, but may allow more productive bench heights depending on other mine conditions. As with many other types of mining plant and equipment, rotary drilling rigs are becoming ripe for automation, and this is perhaps the major technical development in rotary drilling for
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Big names Te recent history of rotary drill- rig manufacturing has been one of takeovers, consolidation and subsequent innovation. Atlas Copco, which bought out
the Ingersoll-Rand rotary drill-rig range and manufacturing facilities in Garland, Texas in 2004, claims the most comprehensive line of rotary blasthole drills for hole diameters of 4 to 16in (102-406mm), many models of which can be adapted to DTH drilling for harder rocks. Atlas Copco Drilling Solutions developed the Pit Viper rigs, which incorporate the
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