Miners have already extracted the easy deposits. A growing proportion of new discoveries are in highly challenging conditions, in settings where temperatures dip below -50 C, and even short exposure to the elements can cause severe frostbite; or deep below the surface where the air ripples with the Earth’s heat; or high on mountain plateaus where engines and lungs alike must labour much harder to get enough oxygen. If today’s miners are to keep up with the still-growing demand for their products, they must keep getting more efficient and effective in the face of these environments. Many operators and suppliers have already taken up the challenge, and their experience has pushed back the frontiers of mining.
The Arctic front
|Ice roads, carefully groomed and monitored, are a critical winter-
time link to the diamond mines of the Northwest Territories.
Courtesy of Nuna Group
The natural resource rewards reaped in the Far North have been massive – but so have the challenges. Charlie Toeppner, area manager at underground mine contracting and engineering firm Cementation Canada, says these challenges begin before workers ever arrive at the site. At a project above the Arctic Circle in Hope Bay, Nunavut, the only way of getting equipment to the site was by sea lift at a port only clear of ice for six weeks a year. “When the equipment arrives at port, you’re only two weeks away from freezing,” says Toeppner. “Now all your water and hydraulic lines have to have arctic-grade oils and fluids. There are all kinds of little things like that.”
A burst hydraulic line may be a minor repair job in the Sudbury area, but at Hope Bay you had better have remembered to pack replacement lines onto the sea lift. Anything not delivered by sea would need to be flown in with a DHC-5 Buffalo cargo plane at great expense. Toeppner says air freight deliveries to the site cost 10 to 12 times the amount of sea freight.
Grant Pearson, vice-president of business development at Vancouver-based Nuna Logistics, also highlights shipping as the big challenge. Nuna, with the Ekati and Diavik diamond mines among its clients, provides logistics, infrastructure development, transportation, construction and contract mining services to mines in Canada’s Far North.
Pearson says the remoteness of sites and the lack of infrastructure add even greater complexity to cold, high-latitude projects. He describes how Nuna must build roads on top of permafrost – frozen soil that may become dangerously unstable if it is allowed to thaw. To mitigate these risks the company builds its roads using fills – layering material on top of the soil, rather than cutting into the permafrost layer. This provides a protective layer for the permafrost and minimizes the risk of failures in the road embankment.
Equipment must be chosen and operated with care, notes Pearson. For example, Nuna tries to limit crushing work to temperatures above -30 C. “Crushing rock is a high-maintenance activity that is compounded as the weather gets extremely cold. We will see more failures as the temperature approaches -40 C and below on any piece of equipment,” he explains, despite using machinery designed to withstand cold weather conditions. “If we had to shut down all the time when it was cold, we wouldn’t be operating,” Pearson points out.
Toeppner recalls a site visit to Hope Bay when the wind chill brought the temperature down to -67 C. He and his colleagues had gone underground, leaving a scoop tram idling at the surface. Despite their being away for only 40 minutes, they had to drive the tram back and forth for 10 minutes before the arctic-grade steering fluid started flowing properly and the driver was able to turn a corner.
Dave Faber, product line manager for Caterpillar large mining trucks, explains that overcooled engines and cold fluids in hydraulic and powertrain systems lead to early component failure. Engines running cold tend to wear faster, and sooting in the combustion chamber leads to piston ring failures and oil consumption. Cold oil congeals and fails to properly lubricate bearings and gears. Caterpillar uses auxiliary heaters in vehicles destined for cold environments, but Faber also draws attention to recent advances in electronics. To prevent overcooling, Caterpillar used to install mechanical louvers on the radiators, which added another potential point of failure and another component to maintain. Today, Faber says, variable-speed cooling systems that did not exist 10 years ago allow Caterpillar trucks to slow the fans based on the engine temperature – and eliminate the need for louvers.
|Contract mining at the BHP Billiton's Ekati diamond mine
in NWT. Courtesy of Nuna Group
But it is in liquids that Faber says the greatest gains have been made. During the early 2000s, Caterpillar, working with oil companies around the world, developed specifications for improved oils and greases including synthetics, which perform very well in extreme cold climates.
“You want the oil to flow when it’s very, very cold, and as the machine heats up and works you want it to thicken up and provide protection for the component when it’s hot. The trick is to build a fluid that will do both,” he says. Viscosity modifiers are one area in which Faber says Caterpillar has made tremendous breakthroughs.
The reward has been a decrease in early-hour component failures and increased efficiency for the operators, who do not have to spend as long warming up the machines.