Mobile-equipment ground-engaging tools, or G.E.T., are those components that typically make initial contact with material being moved and protect base structures—whether bucket, blade, moldboard, ripper, or hauler body—from the worst of abrasion and impact. G.E.T. can have a significant impact on machine productivity, profitability, and job-site safety—and the performance and overall costs of G.E.T. are affected by machine operating techniques, day-to-day maintenance, and the selection of appropriate systems.
G.E.T. ranges from complete lip/tooth/shroud systems for large buckets, to scraper cutting edges, ripper-shank protectors, and weld-on or mechanically attached plates, bars, and buttons that can be placed almost anywhere a basic structure might incur wear. Kevin Stangeland, director of engineering for ESCO, reminds machine users that several factors affect G.E.T. wear rates.
“G.E.T. wear,” says Stangeland, “is dependent on the type of material in which it is used, the machine’s application, and the techniques used by the operator. In well-blasted material, for example, rock is fractured into smaller, easier-to-load fragments that lower G.E.T. wear rates.”
ESCO’s Jared Ames, PE, engineering team leader—construction G.E.T., cites a specific example of the relationship between operating technique and G.E.T. wear in rock-handling applications.
“Curling the bucket primarily wears the teeth from the end and top, while crowding the bucket tends to accelerate wear on the bottom of the system.”
Mark Mohn, director—attachments, Volvo Construction Equipment, agrees that operating technique can affect G.E.T. wear, but says that some applications that accelerate wear can’t be avoided.
“Operating techniques absolutely make a significant impact on G.E.T. wear,” says Mohn. “If an operator engages the ground more than necessary, or drags the bucket, blade, or ripper, that’s going to take years off the life of the attachment. But clean-up jobs are a different story, because even proper operating techniques create wear on the machine and tools. That said, those components should be seen as the investment they are, and observing the best care and maintenance practices are key.”
Ramon Gonzalez, product manager, G.E.T., John Deere Construction and Forestry, has specific advice for keeping G.E.T. wear on wheel loaders and excavators at a minimum.
“Guidelines for operating, of course,” says Gonzalez, “depend on the specific machine and the application. For example, with a four-wheel-drive loader, approaching the load too fast can scratch, dent, or even crack bucket edges and teeth. Also, stay clear of uneven bucket penetration—keeping the approach even will prevent uneven wear along the cutting edges.
“With excavators, be aware of corner loading, which can wear G.E.T. unevenly. Curling the bucket properly when working through material is vital for keeping the G.E.T. as the main point of contact. Let the G.E.T. do the work; any technique that does not use G.E.T. to its full capacity should be re-examined.”
ESCO’s Stangeland says that some mining operations use an excavator-loading technique called “double benching,” in which the machine sits on a bench of material and the bucket is moved downward to scrape the wall, curling the bucket at the bottom of the bench.
“This technique generates issues with heavy loading on the G.E.T.,” says Stangeland. “There’s a lot of raking involved, and if the wall is not blasted consistently to optimize the dig path, it can lead to high loads on the nose geometry [of the tooth adapter]. This technique might lead to higher productivity, but can lead to premature nose fatigue and breakage. If this is common practice at a site, choosing a stronger system and correct point shape can reduce the risk.”
In ripping operations, says Stangeland, the best practice, if the material allows, is to fully engage the shank.
“That’s the ideal,” he says, “because the tip position is lifting material up and out of the cut. If the shank is pulled up and operated at a steeper angle to increase penetration force, wear characteristics and production are less optimal. The operator usually has to adjust the shank position and tooth shape to optimize machine performance.”
Frequent inspections and safety
As trite as it might sound, and as many times as you might have heard it, frequently inspecting G.E.T. is a fundamental practice for extending G.E.T. service life.
“The simple step of visually inspecting work tools before going to work is frequently ignored,” says John Deere’s Gonzalez. “Taking an additional five minutes to assess the condition of G.E.T. can be the difference between a simple tooth swap and replacing an entire bucket. Never ignore signs of even the slightest wear or damage. Also, pay attention to machine performance. If the machine seems to be losing efficiency—requiring excessive work passes or reduced bucket fill, for example—these could be signs that GET components need replacing.”
The consequences of failing to catch worn or damaged G.E.T. such as dull cutting edges and broken teeth, says Volvo’s Mohn, can be extensive and expensive.
“The machine’s production will diminish if the bucket can’t penetrate the material properly,” says Mohn, “leading perhaps to more aggressive machine operation that increases fuel usage and risks damage to the machine itself. A daily routine inspection allows the operator to get a better sense of the difference between normal wear and conditions that could potentially pose safety hazards.”
Those potential safety hazards, says Gonzalez, could include losing a tooth in the crusher or on the haul road, where tire damage and its attendant consequences are a threat. Another safety issue is G.E.T replacement.
“Ensuring that G.E.T. components can be changed out in a safe manner is an important consideration,” says ESCO’s Stangeland, “and there’s been a big push in the industry for hammerless removal and installation of components. If a component is worn thin and hit with a hammer, there is risk of shrapnel causing serious injury. For this reason, ESCO’s policy is to never use steel hammers to remove worn G.E.T.”
That said, Stangeland adds that certain operations and certain job-site conditions might discourage the use of hammerless systems.
“There are certain situations in which it is extremely difficult to remove G.E.T. Handling molten slag in a steel mill, for instance, or if material fines pack into components like concrete. Attempting to clean out this material can be extremely difficult and time consuming. Many customers choose to break out the torch if removal time or difficulty becomes too high.”
Selecting G.E.T. for a particular operation is seldom an exact science, but choices will affect the productivity, safety, and profitability of the operation.
“It’s a trade-off among primarily three factors: material penetration; wear life; and strength,” says ESCO’s Ames. “The priority of these factors is highly dependent on the material in which the machine is working.”
Experience also seems to part of the selection decision.
“Sometimes it’s a matter of personal preference,” says Stangeland. “Finding the right components can be a matter of users trying different options. If the machine is frequently moved to different locations or used by different operators, establishing the best universal G.E.T. can be difficult. We can make recommendations to customers for specific situations, but it ultimately comes down to what works best for them.”
John Deere’s Gonzalez also cautions machine owners about selecting G.E.T. to work in a fairly specific application, then using the machine for a different purpose.
“Some operators may think that they can get away with using the wrong teeth for only a small job or to quickly get something done,” says Gonzalez. “To their credit, their intentions are good—they’re trying to be efficient. In reality, however, they’re causing significant damage to teeth and negatively impacting the bucket, which may lead to increased downtime and maintenance expense.”
Taking the long view of G.E.T. selection, the most-experienced machine owners, says Ames, look beyond just the cost of G.E.T components.
“We encourage our customers to consider the machine’s total cost of ownership,” he says, “which includes such factors as fuel consumption and on-site productivity. The actual cost of G.E.T. components can be dwarfed by costs incurred if a machine is not working as effectively and efficiently as possible.”
Adds Stangeland: “The choice of G.E.T. is tied to machine availability. If components break and the machine must be shut down to prevent damaging structural components, production lost from unplanned downtime can be much more expensive than the components themselves.”
Volvo’s Mohn sums up the wisdom of considering total cost of ownership: “Compromising quality for price will only end up costing the customer more in the long run.”