Oil Sands Mining Equipment Built Tough
Big, tough and powerful are the best words to describe the enormous mining equipment that roams the Canadian oil sands like prehistoric beasts. Here in the wilds of northern Alberta, the oil-rich Canadian province that fuels the country’s economy, the boreal forest lies overtop vast stores of hydrocarbons comparable to the deserts of Iraq or Saudi Arabia.
But unlike Middle Eastern oil, or the undersea oil found in the Gulf of Mexico, this oil is trapped in sand, and must be mined in huge open pits using some of the largest earthmoving equipment on the planet.
To get to the ore bodies, which are between 30 and 70 metres thick and buried at depths of 15 to 35 metres, mineable areas are cleared of trees or marsh. Most of the terrain is muskeg or forest and, underneath, an overburden layer containing silt, clay and shale must be stripped off before the work of digging and hauling the oil sands can begin.
The overburden is used to build haul roads and tailings dikes, while the oil sands, thick and heavy with tarry bitumen, are piled high in long benches using hydraulic or electric rope shovels, then hauled away for refining in gargantuan mining trucks capable of carrying up to 400 tons of material.
The environment is harsh, both for people and equipment. In winter the temperature plunges to -30C, meaning that the equipment must break through a layer of permafrost to get to the sand; in spring and summer, thawing temperatures turn the pits to mud, presenting other challenges to the equipment, which must be built to withstand sinking into the soft and sticky ground.
Haul Truck Behemoths
“It’s one of the toughest applications in the world for a mining truck,” says Tim Denehy, Canadian mining sales manager for Liebherr, one of a handful of heavy equipment companies that manufacture the largest class of haul trucks used in the oil sands.
The German company has a fleet of 26 trucks operating at Syncrude’s Mildred Lake oil sands mine. Liebherr’s T282C mining truck moves 400 tons of material with a 4,023-hp diesel engine and an AC drive.
Denehy says that the T282C has a very light empty vehicle weight compared to competing trucks, meaning that the truck uses less horsepower and fuel to get up the loading ramp, resulting in reduced cycle times. “It’s like a sports car compared to a semi,” he says.
The harsh conditions found in the oil sands put a lot of stress on a mining truck’s drive system and frame, which must be designed for both strength and flexibility. “It’s almost like plasticine or play dough; it allows things to sink into it, so you have very high rolling resistance,” says Denehy. “It causes a lot of racking so you’re tortionally twisting the frame.”
Liebherr’s answer to the problem is a Double A Frame front suspension that provides for longer vertical wheel travel and less strut travel, which also increases tire life. According to Denehy, the truck’s electric drive system has advantages over competing mechanical drive vehicles.
“You don’t lose power through your drive train and there are fewer components to maintain, less oil to replace, and fewer ancillary components, such as gear pumps, resulting in lower maintenance.”
Another important factor with haul trucks is having a reliable supply of components on hand, especially because the trucks are running 24/7 due to the cold weather. Companies such as Liebherr and Caterpillar are “vertically integrated,” meaning that all the parts come from the same factory rather than being outsourced. “For the mine operator it’s more of a one-stop shop, and for us at the retail end we’re only dealing with one supplier: ourselves,” Denehy says. “The idea is to have parts quicker and at a better price because we’re making them.”
Steve Brosseau, general manager for mining at SMS Equipment, Canada’s largest Komatsu dealer, says that when oil sands operations were running full-out in 2008, getting replacement tires used to be a problem, but now, most of the “big three” tire manufacturers — Bridgestone, Goodyear and Michelin — have caught up to demand. The massive tires, which are twice the height of an average man and cost close to $50,000 each, often get rock cuts from shale, with tread wear less of a problem due to the soft pit conditions.
Brosseau points to the weld design and frame castings allowing for a “flexible” frame good for 100,000 hours, and a wider dump at the back end of the truck box that allows the material to slide, as two of the truck’s key features.
“When you’re going down the haul road the oilsand packs in there, so when you dump the truck box it comes out in one lump, like a loaf of bread,” he describes.Komatsu’s 930E-4SE electric drive truck competes with Liebherr, Cat and Bucyrus haul trucks, at 320 short-ton capacity, powered with a Cummins 2,700-hp engine.
Brosseau points to the weld design in the truck box, which gives a flexible frame good for 100,000 hours, and a wider dump body that allows the material to slide, as two of the truck’s key features.
“When you’re going down the haul road it packs in there, so when you lift it comes out in one lump, like a loaf of bread,” he describes.
Before the haul trucks roll, they are loaded with one of two shovel types used in the oil sands — hydraulic or electric rope shovels. Bucyrus and P&H are the two main players in the rope shovel market, with Bucyrus’ 495HR2 featuring a LatchFree Dipper System that the company says increases shovel productivity, and the AC-drive 4100C BOSS by P&H Mining Equipment.
Built on tracks and designed for stationary loading, the 4100C BOSS has a shovel payload of 100 short tons, meaning that it can fill a 300-ton haul truck in three passes every 80 seconds.
“The electric rope shovel is used in situations where you need to move an incredible amount of material very consistently and do it as inexpensively as possible,” says Steve Droste, electric rope shovel product manager with P&H. Operated with an electric rope and pulley system, these oil sands workhorses are immune to hydraulic fluid freeze up, making them more weather-resistant than hydraulic shovels.
“There are fewer components and it’s just in essence a simpler machine,” says Droste.
Noting the “mushy” conditions in the pit during spring and summer, Droste says that the 4100C BOSS features 144-inch-wide crawler shoes designed to accommodate the low ground-bearing pressure needed to prevent the machine sinking into the ground. At the same time, the machine is powerful enough to cut into the frozen banks in winter.
“Breaking through the ice shelf requires a heck of a lot of force,” he says.
The main advantage that hydraulic shovels have over rope shovels is their mobility. Hydraulic machines are more flexible to move around the pit, and can also dig at different levels of the bench, moving the waste material and leaving the oil sands to be loaded onto trucks.
Hitachi’s EX8000-6 front-loading shovel is mostly used for removing overburden or backing up electric rope shovels, says Brian Mace, manager of mining product marketing and applications, noting six machines are currently operating in the oil sands.
The bucket holds 40 cubic metres of material, with a maximum cutting height of 20 metres and a breakout force of 501,000 pounds. The cab on the machine is so large, there is room for a microwave and lockers, and for the operator to stand up and walk around.
Komatsu’s competing hydraulic shovel, the PC8000-6, has a 42-cubic-metre capacity and will load the Komatsu 930E-4SE haul truck in three passes. The PC8000-6 features chromium carbide liners on the shovel and wide tracks for better ground-bearing pressure.
These machines use a lot of fuel. The PC8000-6 will burn through 6,000 to 8,000 litres of diesel in a single 12-hour shift; and its hydraulic fuel tank holds 800 litres.
The cab-forward design allows the operator good visibility from the upper left side, with three cameras mounted on the blind side.
“The operators are able to look down between their feet and see the bottom of the pit and the front of their tracks,” says SMS Equipment’s Steve Brosseau, noting that the shovel can cut up to 17-metre-high benches.
Not all machines used in the oil sands are behemoths. Smaller dozers are used for working in overburden, flattening out the pile after the truck dumps its load onto the berm. Dozers can also be seen pushing material down the bench for the shovel to grab, cleaning up around the shovel, or ripping material in winter using long shanks on the backs of the machines.
Most dozers are equipped with joystick controls, “so if you’re trying to level a road out, for example, you can shift your speeds with one controller and control your blade height and tilt with the other one,” says Brosseau, referring to Komatsu’s D475A-5 dozer.
Some dozers are designed to withstand the harshest and potentially most dangerous applications. Air conditioners and radiators are built on top of the machines instead of underneath, and in the case of tailings dozers, an escape hatch is built into the cab in case the dozer is submerged in a tailings pond and the operator needs to exit quickly.
Dozers also have problems with abrasion. The life of an oil sands dozer undercarriage is typically half that of other mining applications, because the sand gets into the track links and rollers and wears on them like sandpaper.
“It clogs in there and it’s almost like a grinding compound,” says Brosseau. “It’s sticky, it’s abrasive and it just wears out an undercarriage.”
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