Truck Size and Speed
Sustainability is achieved when the least amount of energy exerted results in the greatest productivity outcome.
At least that’s the philosophy HudBay Minerals Inc.’s management used at its Chisel North Mine near Snow Lake, Manitoba when it decided to reduce its fleet of haul trucks and go with a larger machine to save energy and increase productivity.
Until recently, the mine had been operating with multiple 50-tonne (55-ton) haul trucks, but by going to a single, larger-capacity Atlas Copco MT6020, 60-tonne (66-ton) vehicle, the company’s production goal is now achieved with fewer trips per day which, as expected, equates to reduced fuel and manpower costs, plus less wear on equipment.
The truck is one of the newer additions to the mining market and Atlas Copco says there is no underground mine truck that can match its hauling speed at capacity.
At Chisel North, for instance, the MT6020 has been successfully used mostly for ore excavation. With its heavier specific gravity, zinc ore results in less than a full volume load, but the truck’s deeper bed compensates by allowing a greater load capacity for hauling waste.
The goal of the mine is to haul 950 tonnes (720 tons) a day.
Randy Cockle, who is responsible for mine operations, likes the boost in productivity he gets from the new truck: “I gain two loads at the end of the day- that’s more material with less expense.”
The mine’s current ramp is 5.2 km (3.2 miles) long with a vertical depth of 670 m (2,200 feet) and has grades up to 15 per cent. On the steepest grades, the truck can reach climbing speeds of 14 km/h (8 ½ mph) in fourth gear. The average speed, though, is 11 to 12 km/h (7 mph). The average cycle time is 47 to 50 minutes.
Mine Manager Bob Libby reiterates the importance of these savings by saying, “Fewer loads means less manpower, fuel, and maintenance-it all adds up.”
The zinc ore has a specific gravity of 3 to 3.2 insitu, which is 45 to 50 per cent more dense than the waste material. Operator Ron Spruyt says a zinc rock the size of a soccer ball is more than an average man can lift. So it’s important to know when the load reaches capacity during loading.
The mine rear-loads the truck with an Atlas Copco ST14, which is made easier by the onboard weight readout. This helps to prevent accidental overloading, which could not only damage the truck but makes for quicker, more decisive cycle times, eliminating any second-guessing.
But the truck’s features don’t end with its on-board scaling capability. The operators all agree that the comfort of the truck is greater due to features like the suspension system and automatic transmission. If the operator chooses, he can shift the transmission manually when conditions require it.
Truck operators Ron Spruyt, Darwin Spenser and Ryan Erickson, who have been trained on the MT 6020, find it’s a very comfortable truck to run. These men are also cross-trained to run loaders and other mining equipment, which makes the mine even more efficient by utilizing manpower wherever necessary.
Having an expert trainer like Atlas Copco’s Joe Benoit on site helps too. By working with experienced operators, Benoit has the opportunity to highlight features that can help with efficiencies. For example, the transmission’s manual override feature allows for down-shifting to keep the speed even. “Most of the time the automatic transmission will take care of shifting, but it’s the steeper section of the ramp where a manual shift is a handy option,” said Benoit.
Again, Bob Libby talked about the efficiency and reduced costs that come with the MT6020, but he said it’s the service that really stands out. “From the support onsite right through to the warehouse people, Atlas Copco’s service is top-notch. As for Joe, he’s always there when we need him, day or night. He’s a great guy to get the job done and he doesn’t stop until it’s finished.”
According to Randy Cockle, the plan at the mine is to use the MT6020 to take care of the bulk of the ore. Using one ore truck has made operations run smoother for the mine while cutting down on expenses.
As long as the equipment keeps running as it has been, Libby believes they can achieve their haul goals by running 18 loads a day. “Day-in and day-out, just keep doing what you say you can do,” said Libby. And isn’t that the definition of sustainability?