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The successful demonstration of Sudbury-based Rail-Veyor Technologies’ innovative material handling system at Vale’s 114 Orebody could lead to a significant change in mine design, enabling smaller openings, improved safety and faster advance rates.
A surface demonstration of the rail-veyor at Vale’s Stobie Mine proved that the technology worked, but it had to be put to the test in an actual mining operation before the company could specify it for future mine developments.
“We proved the ore-handling capability of the rail-veyor at Stobie,” said Alex Henderson, Vale’s general manager of underground technology for base metals. “This demonstration is more about how we integrate it into our development and production processes.”
Assuming the final verdict is positive – and all indications suggest it will be – the rail-veyor can be classified as proven technology and considered as an option in feasibility studies for new mine developments in Sudbury and elsewhere across Vale’s global footprint.
A cross between a railroad and a conveyor system, the rail-veyor is a 53-car moving trough propelled by foam-filled tires at drive stations located at intervals of 140 feet along the track. The tires provide the forward thrust by turning against the cars’ side plates. At any one time, the rail-veyor is in contact with three drive stations, which engage automatically as the rail-veyor approaches and provide both acceleration as well as braking.
The track, which is extended to keep pace with development, runs through a 12-foot by 10-foot restricted-access ramp to a planned distance of 2,500 feet. A 700-foot dumping loop outside the portal deposits the muck on surface.
A parallel “fresh air” ramp is reserved for rubber-tire equipment and personnel.
The 114 Orebody, a marginal, near-surface deposit adjacent to Vale’s Copper Cliff North Mine, was partially developed in 2008 using conventional mining methods, but shut down as a result of the financial crisis and plunging commodity prices.
When Vale decided to put the rail-veyor to the test, the 114 Orebody was selected as an ideal location to demonstrate the technology.
The part of the fresh air ramp that was excavated in 2008 was 17 feet wide and 16 feet high, but “if we had started this project without any (prior construction), it would have been driven 12 feet by 10 feet,” the same dimensions as the rail-veyor ramp, said Dan McIntyre, project manager for the 114 Orebody.
Smaller drifts
“It’s extremely important for deep mines to have small drifts because the bigger the drifts get, the more seismically active they could be,” said Henderson. “If we keep applying our existing thinking to mining, we won’t be able to mine any deeper.”
Smaller drifts mean less excavation and less excavation translates into both faster development and considerable cost savings. At the same time, replacing haul trucks with an electrically powered rail-veyor system reduces diesel emissions and ventilation requirements, resulting once again in a safer, more cost-effective operation.
“Diesel is classified as a carcinogen, so the more diesel equipment we can get rid of in the underground environment, the better the working conditions are for our employees,” said Henderson.
A 12-foot by 10-foot drift also allow for the use of smaller equipment – in this case, a 3.5-yard “scoop,” which is less expensive and safer to operate than an 8, 10 or 12-yard load-haul-dump machine that would typically be used in mines with a conventionally-sized openings.
The rail-veyor at the 114 Orebody consists of 53 eight-foot by 30-inch cars, each of which holds one tonne of material. A series of crosscuts at intervals along the two parallel ramps serve as loading areas. A load-haul-dump (LHD) machine deposits muck in the crosscuts and another piece of equipment transfers it into the railveyor. A total of 12 or 13 crosscuts will eventually be constructed as ramp development progresses.
The twin ramp system allows for the segregation of fresh air and exhaust. The restricted access rail-veyor ramp exhausts air from the blasts and from fumes,” explained McIntyre. “That makes for a better workplace for our operators and makes for a more productive operation because our blasting fumes go right to the return air system and our people are always on the fresh air side.”
The rail-veyor proceeds at a speed of 0.3 metres per second during the loading operation, speeds up to 3 metres per second once loading is complete and slows down again to 1.5 metres per second in the dumping loop on surface.
“It takes eight minutes to load the 53-car train and the total cycle time from the point of loading it, tramming up to surface, dumping and returning underground is between 17 and 20 minutes,” said McIntyre.
The dumping loop can be equipped with a bin for loading trucks. Alternatively, the rail-veyor could be extended directly to the mill, depending on the distance.
The maximum muck size of 18 inches is primarily achieved through blasting design, but occasional oversize material can be separated out of the muck stream through other means.
The rail-veyor is controlled by an operator in a control room located on surface between the portal and the dumping loop. The operator starts and stops the train, adjusts the speed and co-ordinates with the operator in the crosscut where the loading takes place.
The technology has several advantages over conveyors and conventional rail systems. It’s easier to extend as development progresses, it handles corners much better than conveyors, it’s lighter and easier to install than a rail system, it’s energy efficient, and easy to disassemble and move somewhere else.
“Typically, with a rail system, you have timber ties,” said Henderson. “We don’t have any of that. The rails are just sitting on ballast with pieces of steel that link them together so they can’t separate.”
Advance rate
Vale is targeting an advance rate of 400 feet per week and came within 70 feet of the target six weeks into the project/
Since 1965, advance rates in Canada have declined and now average 150 feet per week, said Henderson. “A lot of that is because drifts got bigger and bigger and the amount of ground support required increased, so development became slower and slower. Going to smaller drifts reverses that trend.”
The rail-veyor is the centerpiece of the 114 Orebody demonstration project, but several other innovative practices are also being trialed.
“One thing we’re doing, for example, is altering our ground support process,” said McIntyre. “We’re putting in the minimum support necessary for the short term so no one will be exposed to unsupported ground. Then, a few days later, we install secondary support. This is because in any typical mine development process, the bolting activity is what takes the longest, so if we can take some of that off the critical path, then we gain on our advance.”
Another innovation involves the use of emulsion instead of anfo and a loading unit that allows for the loading of emulsion in a controlled manner.
“Typically, with anfo, you completely fill the hole, so the only chance you have of controlling your blast is with the spacing of the holes,” explained McIntyre.
Better control of the blast helps with fragmentation, and affects the perimeter of the blast area, resulting in a cleaner cut.
The demonstration project is costing Vale $49 over two years and concludes in December.
Vale isn’t the only mining company interested in the technology. Delegations from Barrick, Goldcorp, Australian iron ore miner Fortescue Metals Group Ltd. and several other mining companies have made the trip to Sudbury to see the rail-veyor in action, said Pat Fantin, Rail-Veyor Technolgies’ vice-president, technical.
“We met all of our deadlines and targets and, when you meet all your targets, you make believers out of people,” said Fantin. “Vale came to us with a problem and we’ve been able to come up with a solution for them. We executed the project on schedule and on budget, so we’re basically where we want to be.”
The next step is to showcase the rail-veyor at MINExpo in Las Vegas September 24 to 26 and introduce the technology to the global mining market.
A video of the rail-veyor in action is available for viewing on the Rail-Veyor Technologies’ website.
www.railveyor.com