Wheel dozers help mines increase efficiency of production fleet
Mining companies are always chasing productivity. How quickly can we drill, blast and gain access to the ore? How much rock can we load in a shift? How many tons can we move in a year?
Trucks and loaders are the heroes on the surface mine site, where they are responsible for moving precious material. But sites that remember the importance of support machines like dozers, motor graders and wheel dozers will find their productivity — and profitability — increase as these machines make it possible for the loading and hauling equipment to do their jobs more efficiently.
From constructing and maintaining haul roads to cleaning up the loading and dumping areas, support machines have a direct impact on productivity. There are several types of equipment that do similar jobs, and it’s important to understand their differences to ensure they are being used in the right application to deliver their full value.
Caterpillar’s Kent Clifton, senior marketing professional for surface mining, helps miners understand the best applications for support machines and how to optimize them once they’re on site. He recently shared his insight regarding wheel dozers.
Understanding wheel dozers
Wheel dozers combine the production capabilities of track-type tractors with the mobility and versatility of wheel loaders. Cat® Wheel Dozers are based on Cat Wheel Loaders — designed for mining applications, with structures and a powertrain designed for dozing.
They can be found in a variety of applications, such as:
- Loading area cleanup
- Dump area maintenance
- Haul road construction and maintenance
- Safety berm construction and maintenance
- Blasting area cleanup
- Stock pile
“You’re really looking to take advantage of its versatility,” says Clifton. “They really deliver a lot of value when they’re working with hydraulic mining shovels, backhoes and electric rope shovels. They just make that process more efficient.”
Comparing track and wheeled dozers
Track-type dozers are the traditionally the machine of choice for mine site support. They’re durable and reliable, and have the weight-to-horsepower ratios to push large loads. But when mobility, speed and versatility are the most important aspects of an application, Clifton suggests looking at a wheel dozer.
If properly applied in the right applications, wheel dozers can deliver lower fuel costs, lower undercarriage costs and save mines money by reducing the amount of support equipment required on site.
“A good rule of thumb that I use is, if you’re going to be pushing 70 to 110 percent blade load all the time and you don’t need mobility, you need to be looking at a track-type tractor,” says Clifton. “If you need mobility and are pushing zero to 70 percent blade load, you need to be mobile, and to be quick to get out of the truck’s way, then you want to be looking at the wheel dozer.”
To help its customers understand and compare machines and their applications, Caterpillar produces the Caterpillar Performance Handbook. The handbook offers these considerations when deciding between a track or wheeled dozer for a mining application:
- Speed. Wheel dozers travel at speeds up to three times faster than track dozers.
- Maneuverability. Articulated steering and good visibility give wheel tractors high maneuverability.
- Utility. Mobility, maneuverability and good speed suit wheel dozers for yard and stockpile work and for clean-up around shovels. Lower maintenance costs may be realized in certain soils that can be highly abrasive to track-type undercarriages.
- Coal pile. Wheel dozers are recommended in this application when following conditions are present:
- Long push distances
- Need for good material spread
- High degree of compaction desired
- Production Dozing. A wheel dozer should be considered in the following conditions:
- Long push distances
- Loose soils, little or no rock
- Level or downhill work
- Good underfoot conditions
- Pushloading Scrapers. A wheel dozer should be considered in the following conditions:
- Thin scraper cut
- Good underfoot conditions — no rock
- Higher push speeds
Clifton encourages miners to look carefully at their site-specific conditions to determine the right equipment. For example, if the truck dump is fully burdened and a dozer will be dedicated full time to cleanup at that location, the track-type tractor is ideal. “It’s going to deliver better value in this application because you don’t need to be mobile with that tractor. It’s going to stay on that dedicated dump throughout the day.”
If a site has dumps scattered throughout the site, however, a wheel dozer is a better choice. “If I have two or three dumps and I’m not fully utilizing them, but I need to maintain them, the wheel dozer is going to get from spot to spot much, much quicker,” he says.
Using a wheel dozer on haul roads
There’s no doubt that motor graders are the best tool for haul road repair and maintenance. They help create and maintain constant grade and proper draining, and ensure the floor is smooth in the loading and dumping zones. But there are times when a wheel dozer is an ideal support machine for the grader.
Truck spillage is one example. “I don’t want to be picking the blade up on a motor grader to bring it over to a switchback or a change in the grade on a road to clean up a little bit of spillage that came from the truck,” says Clifton. “So I can get on the radio and call the wheel dozer. It’s going to be extremely quick to get out and clean up that little bit of spillage, push it off to the side of the road, and then go do some of the other activities on the mine site.”
Choosing the right size machine
Clifton stresses the importance of choosing a wheel dozer that is sized appropriately for the production machines. Caterpillar offers several sizes of wheel dozers — the 844 and 854 models — that are designed for ultra-class mines, where trucks range from 227 to 363 tonnes (250 to 400 ton) payload capacity. Mid-sized operations, working with hydraulic shovels like the Cat 6020, 6030 and 6040, should consider an 834 size wheel dozer.
“It really depends on the size of the trucks you’re going to be working with and the size of the loading tools,” says Clifton. “For example, one of the keys when you’re working on a truck dump is that you need to keep up with the trucks. So when you start looking at sizing your machine, you know that within a couple of passes there will be another truck coming in. You want to make sure that you can get that material pushed off in time. A smaller machine may not have the capacity to do that type of cleanup work. It’s the same under a shovel.”
“The truck is what’s really ringing the cash register,” he continues. “You don’t want to get a machine that’s so big that you’re obstructing the trucks running on the haul road. You want to get them back as quickly as you can to the loading tool. So you have to size the wheel dozer accordingly.”
Sizing the blade
Once the right size dozer has been selected, it’s important to select the right blade for the application. Caterpillar offers several different types of blades, from straight blades to u-shaped, semi-u shaped and coal blades.
“The narrower the blade, the more aggressive it’s going to be. You’re going to have more horsepower per inch of cutting edge,” Clifton explains. “The wider the blade, the less aggressive it’s going to be.”
Wide, U-shaped blades are ideal for cleanup work. “Those wings are going to help retain material,” says Clifton. “So if you’re doing a lot of cleanup work, like underneath a shovel, it’s going to take fewer passes with a big wide blade and having the wings on the front. The wings actually help roll that material into the middle of the blade and you’re not going to lose it out around the toes.”
On the other hand, wide, curved blades are not the best choice for harder material. “If you have to get real aggressive, the narrower blade is going to allow better penetration to tear out some of that harder material. But it’s not going to retain as much in front.”
Recognizing the value
In recent years, as mining companies face capital reductions and are continually looking for new ways to control costs, investing in a wheel dozer may seem like an unnecessary expense. Clifton stresses that the exact opposite is true.
“When it comes to a wheel dozer, you may see it as one of those ‘nice-to-have’ things,” he says. “When you look at it from a capital standpoint, it gets to be a fairly pricey machine. But what I encourage people to do is take the cost of that machine and look at the value that it’s adding.”
He uses truck exchange times as an example. “Say the dozer operator’s goal is to come in and make two cleanup passes and get out of the way,” he explains. “You’re not going to be able to do that with a track-type tractor. You’re going to be looking at over a minute to do one cleanup pass. That wheel dozer can do it in about 30 seconds.” Once the area is cleaned, the truck is back on its way to being productive.
“You have to take that credit — the value the wheel dozer is adding in exchanging out the trucks — and give that credit right back to that wheel dozer,” says Clifton. “If I can put the wheel dozer in there and reduce my truck exchange time to 40 seconds, that’s two more trucks an hour … times three or four loading tools. At the end of the year it’s millions of dollars.”
“When you start off-setting it in that way, it’s really easy to justify the value of that wheel dozer,” he says.
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