Shorter Takes Longer
For orebody definition, Major Drilling uses the U6 exclusively. It’s a powerful drill that has earned a reputation as one of the most competent drills in the underground exploration market, capa-ble of drilling beyond 900 m. However, shallower definition drilling as speci-fied by their client may involve holes only 20 to 200 m deep.

Major Drilling Area Manager D.J. Wilson explained that moving the U6 and its ancillary equipment, and then resetting it to make a series of these shallower holes, entails disproportion-ately long accumulations of downtime. “If our targets are 400 to 500 m, then we would have our crews con-tinue to use the skid-mounted U6s,” Wilson said.

Consider how shallower holes cost more. Making two 500-m holes pro-vides 1,000 m of coring in two moves. Total downtime on skid-mounted equip-ment is six to eight hours. By compari-son, drilling 10 50-m holes achieves the same drill-feet but requires 10 moves totaling 30 to 40 hours of down-time. It’s 500% more time and labor cost for the same amount of coring.

After trying various solutions, Major Drilling put the Diamec U6 MCR (Mobile Carrier Rig) to the test. They are the first North American company to try the combination of the U6 and Simba 1257 multipurpose carrier after successful trials in Australia.

Costly Transport
Underground exploration rigs in general are specialty drill rigs used in confined areas. The drill rig and its ancillary equipment are not integrated in one bulky vehicle but kept separate.

Matthew Bullee, who has been with Major for seven years, detailed the steps of a move: Crews have to call for a tractor or lift to move not only the rig but the steel sloop, stage scaffolding, helper’s equipment and safety stations. The crew must disassemble the drill rig from its power plant and water supply and move each one separately. Setting up at the next pillar could take half a shift. Setting up at another mine level could take more than one shift. Each move exposes disassembled part con-nections, such as the rig’s hydraulics, to contamination.

In recent years, Major has been exploring ways to make the U6 more mobile. Mounting the U6 to a carrier as is done for almost all surface rigs was an obvious solution, but each attempt brought a mix of advantages and disadvantages.

When Major mounted the U6 to a crawler frame, it cut transportation and setup to just a couple hours. It allowed the driller good flexibility for drilling descending angles. It didn’t have much range above, though. The driller and helper had to build up cribbing to drill upward, and there were certain approaches to the wall it just couldn’t reach. But its mobility meant the drilling crew didn’t have to wait for another piece of equipment to move the drill—it moved itself.

The crawler-U6 combination was a successful concept, at least on level terrain. Wilson said it didn’t provide much advantage when they moved from level to level and was awkward up and down the ramps in general mine traffic. One of Major’s clients challenged the company to investigate wheeled mounts to cut transportation and reset time even further. The first attempt was a six-wheeled carrier.

A wheeled carrier enabled the U6 to travel much quicker up and down the ramps and take less of a beating than a crawler during the move. The drawback of this first wheeled design was its height. The carrier was so tall that the helper had to build and work from stag-ing. Though it could certainly drill down, the drill itself couldn’t be positioned lower than the carrier deck. During each move, this staging was an additional item to disassemble, transport and re-erect.

“I’ve drilled plus 90 and minus 90 holes in the same place,” Bullee said.

Quick on its Feet
“It is quick,” Wilson said of the U6 MCR rig. “Move time is down to 40% to 50%.” Bullee reported similar gains, saying they are making moves in an hour to hour and a half now, while moving skid-mounted U6s requires three to four hours. “You can make a level-to-level move and still get 40 to 60 m yet on a single shift, depending on rock condi-tions, of course.”

The wheeled carrier they had tried before, said Bullee, had allowed them 20 to 40 m after a level-to-level move.

“It might not seem like much differ-ence, just 10 m or so more a move over another carrier system,” Bullee said. “But if you get even that 10 m a shift or a little more in a year of shifts, that can be as much 1,000 m more drilled.”

Bullee also commented on ramp speed. The wheel-mounted Simba 1257 carrier was actually determined to be too fast, so they keep it in first gear.

Safer Moves
Bullee made sure to point out Major Drilling is a safety-conscious com-pany, taking measures beyond federal requirements and even the require-ments of their hosts. For instance, part of the time they spend in a move involves transferring and re-setting safety equipment—fire extin-guisher, eyewash station, descalers, lighting—which Major requires to be highly visible and accessible at every drill site.

“But safety is better in a move now. The most serious injuries happen usual-ly when people are moving things. Less time spent moving, and having less stuff to move, all equals less risk of serious injury.”

Brief Learning Curve
Darian Woods has been drilling with Bullee for years, but this is his first shift on the U6. “Basically, drilling is no different than any other U6, but what’s new is learning knuckle points and the boom, and driving it,” Woods said.

Easy to learn, spending more time spent drilling and less moving, and all this with increased safety—it’s no stretch to conclude that Canada’s first U6 MCR is a major improvement.

Joe Bradfield is senior writer for Ellenbecker Communications, an inter-national communications firm special-izing in the drilling, mining and con-struction industries.