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1/14 DUMP TRUCKS: The conveyor belt in open pit production. The most important & normally the biggest cost element in open pit mining - hauling ore & waste. Here is a pic of one of the most widely used & successful OP trucks ever built. The CAT 793. Over 2600HP,
this beast...
2/14 has a capacity of 220t rock each load. Fuel tanks carry 1,150gal/4,350L of diesel which is burned up in 16-20hrs. A mine truck is a highly engineered piece of equipment. Look at the catalogue: bit.ly/2mkjl3K
The 6 tyres are typically pressurized to around
3/14 1 bar, often with nitrogen and carefully managed for optimal life & safety. One 40.00R57 tyre costs anything between $20-40k, so tyre life is really important. A question to ask any OP operator is what is his average tyre life. A good mine will run its tyres
4/14 for 6,000 hours (about a year). Bad floors -> only 1,500 hrs life (pic). Fuel & tyres are by far the biggest cost components. This means the most important aspect to saving costs are OP floor & ramp conditions (smooth), and haul distance optimization. Next to that is the
5/14 actual productivity of your fleet. The impact on total cost based on OP fleet productivity is mind-blowing: The table below shows that for a nominal 50Mt/yr operation-A 1 minute saving on a 20 minute avg. cycle time would save you 4 million dollars per year/ Saving 15s
6/14 saves ~$1 million/yr. The question to be asked is how can productivity be improved? Now, I mention a CAT 793 because it is a MECHANICAL drive truck ie. Diesel engine, running mechanical differential & drive. This has a certain power efficiency. Enter electric-drive trucks.
7/14 Long before clean energy ever became fashionable, mining trucks took a giant leap forward: Electric wheel drives. These trucks, 1st designed because fuel was expensive in the late 70's, have a diesel engine driving a generator driving 2 x GE, electric wheel motors in
8/14 the wheel hubs, & replacing the less efficient mechanical power transfer system to the wheels. Power is transferred along a cable directly to the wheel motor, bypassing mech. torque converters etc. The trolley assist system was the next step, 1st implemented at Palabora
9/14 Trolley assist, is still a very effective cost-saving measure but it is a hassle to manage and can be problematic if ramp life is short (ramps positions change often). Electric drive trucks have now been in operation for about 40 years, so its nothing new.
10/14 Enter the greenies with their lithium battery solutions which are completely impractical, as trucks in OP environments need to run 19-21 hrs/day nonstop, so there is no time for battery charging. Show me a mine running battery trucks & it will be v. high cost. Nuts.
11/14 The thing is there is still room for mechanical drive trucks in places which are very rough and far away. They operate better at altitude. They are tough as nails & last. Electric trucks not so much & are more iffy. Its a case/case decision & spares costs,
12/14 maintenance skills etc. all need to be considered. A take-away for analysts is to look at the pit floor conditions on your visits. If bad, you know the load & haul costs can be reduced materially. If you see trucks parked in a neat row/line or waiting around know they are
13/14 being wildly inefficient. More than two queuing trucks at a shovel is a no-no. Dispatch systems like Wenco & Modular are indispensable in improving the inefficiencies of larger fleets, but they need to be properly managed in conjunction with practical mining considerations.
14/14 Finally, you should be looking at how well the trucks are matched to production loading equipment. Well matched machines = minimum loading times (2-3 shovel/excavator passes to fill a truck) = faster cycle times = lower costs.
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