Experts offer tips on dozer maintenance:
undercarriage, hydraulics, blades, and
cooling systems.
Over the life of a dozer, approximately 50% of repair and maintenance costs are related to the undercarriage—the ground zero of much “dozer abuse.” With that said, manufacturers agree that it is the undercarriage particularly, which should be meticulously monitored and managed. Beyond that, today’s tips concern crawler dozer hydraulics, blades and cooling systems. It’s a lot to consider. And, the standard of maintenance indeed varies from contractor to contractor depending upon the locations and types of job sites, the availability of experienced mechanics, and the skill of machine operators. As such, manufacturers stress that contractors should augment daily in-the-field maintenance strategies by relying upon the product support representative from one’s local dealer as each is a trained advisor whose recommendations will ultimately preserve the integrity of the fleet and maximize the return on crawler dozer investments.
Undercarriage Maintenance
Good undercarriage maintenance involves daily inspections, daily cleaning, proper track tensioning and alignment, the monitoring and turning of pins and bushings, and much more.
“You give your engine and transmission a major portion of your time. Because of the dollar value of your undercarriage, it deserves at least an equal measure of attention. The bad news is that the working components of the undercarriage are open to soil, sand, rock, water, chemicals, and the elements. The good news is that, unlike engine and transmission components, which provide only indirect indications of wear before teardown (for instance, through oil analysis), undercarriage components are visible and available for inspection and evaluation without disassembly,” says Mike Murphy, global product manager for crawler dozers for Case Construction Equipment.
“Track frames are designed to shed material; however, areas around the sprocket, final drive housing, carrier roller, and front idler should be cleaned at the end of the work day, especially in muddy and freezing conditions. If material packs in around rolling parts and freezes overnight, those parts may be restricted from moving properly and can lead to seal failures and lower component life,” says Dan Drescher, product manager, crawler dozers, for John Deere Construction & Forestry.
Bruce Boebel, product manager, crawler dozers, for Komatsu, agrees that daily cleaning and daily inspections are imperative to minimize undercarriage repair costs. “Crawler dozers operate in harsh environments and take many impact loads and twists. For example, if a loose track shoe is noticed before it comes off, it could eliminate the possibility of any secondary damage to the machine. A leaky carrier roller replaced early could reduce the possibility of the track jumping off, which maximizes the contractor’s uptime,” he says.
As to track tension, Murphy says that tight tracks put undue stress on all components. “Check track tension at least once a shift—more often if the materials change or get wet or begin packing,” he says.
Drescher says that a track chain that is too tight can increase track wear by 50% to 70% over a properly adjusted track; and a track chain that is too loose increases the risk of derailments and track kinking.
“Over-tightening the track can drastically reduce bushing life by up to three times, and can also wear other undercarriage components by creating extra loads and stresses in the system,” says Boebel. As to alignment, he says that typically alignment does not change unless there is a wear issue. “Manufacturers have improved tolerances over the years, so alignment is not a common issue. But if a replacement undercarriage is installed, it must be checked after installation to ensure components are running straight and are properly aligned,” he adds.
Murphy takes a bit different stance on alignment and encourages owners to refer to the operator and service manuals for proper alignment procedures. “Track frames, idlers, sprockets, and carrier roller alignment need to be checked periodically, as unusual and unnecessary wear will occur when components are misaligned,” he says.
“Many contractors choose to turn pins and bushings as a way to maximize the life of their sealed and lubricated track chains. This is particularly common where the link wear is much slower than the bushing wear. If links are around 50% to 60% worn at the turn, a contractor can usually perform the pin and bushing turn and then run to destruction on the back side of the bushing, utilizing the entire link and bushing life,” says Drescher.
Boebel points to new undercarriage designs that eliminate the need to turn pins and bushings. “Komatsu’s Parallel Undercarriage System, known as PLUS, has a rotating bushing that is sealed and lubricated. It offers up to twice the life of a conventional undercarriage and is standard on various crawler dozer models,” he says.
Murphy stresses that, if possible, do not mix old and new components, as the new components will quickly wear to match the warn profile of the older components. As an example, one track roller (bottom) is replaced with a new one. The new roller, with its new diameter, will touch the track chain before the worn rollers touch. The new roller will take most of the machine weight for that side of the machine until it wears to match the profile of the other track rollers.
Drescher says that ultrasonic measuring devices are becoming more prevalent as they reduce the time required to complete an undercarriage inspection.
Boebel explains that the ultrasonic wear indicator measures part thickness by sending high-frequency sound waves through the material to be measured rather than using conventional undercarriage measuring tools. The elapsed time between sending and receiving the sound waves determines the thickness. Boebel says that the ultrasonic devices are becoming more popular for several reasons. They greatly reduce the time spent in cleaning parts to get accurate measurements, while eliminating measurement errors due to dirt packing around the parts. They will also minimize errors due to measurement technique differences among inspectors. Plus, some ultrasonic devices are capable of storing multiple measurements and downloading directly to a personal computer.
“Collect data. Measuring your undercarriage on a periodic basis gives you the information you need to help manage this asset,” says Murphy. “Use the information generated by undercarriage measurement to help decide on configuration, operational and maintenance changes. You can know what is really happening and take specific, corrective actions. Also, you can better decide between repair options and choose the optimum timing of needed repairs,”
Hydraulic System Contamination Control
Contaminants within hydraulic systems accelerate wear and shorten component life. Caterpillar reports that a three-year independent study of hydraulic systems found that some hydraulic components lasted up to 10 times longer with proper contamination control. Preventing fluid system contamination is a big priority for Caterpillar, which has instituted effective and extensive contamination control programs within its factories and dealer locations.
Contaminants can be introduced during assembly, when being serviced, or while on the job—and they can impair machine performance and reduce component life. Microscopic particles suspended in the fuel can be particularly damaging to injectors and control valves, causing premature wear. Subsequently, engine power drops off, fuel consumption rises, emissions increase, and so too, the odds of a costly breakdown.
“As particulates build up on metal surfaces and impede hydraulic flow, system efficiency erodes. Even a skilled operator may not notice a drop in responsiveness until the system has lost nearly 20% of its power,” says Carmen Rose, senior consultant with the Caterpillar Product Support Division in Peoria, IL. “With a reduction of that magnitude, you’d be getting just four days worth of production for every five days on the job,” she adds.
Rose explains that most manufacturers assess the cleanliness of their fluid systems by counting and measuring the particles present in the oil and comparing those results to an International Standards Organization (ISO) code. An ISO contaminant code contains three numbers, but Caterpillar only uses the last two—the first number refers to the number of 6-micron and larger particles in a one-millimeter oil sample. The second indicates the quantity of 14-micron and larger particles in that same sample. A rating of 21/17, for example, means that one millimeter of oil contains up to 221 (about two million) particles that are 6 microns and larger, as well as 217 (130,000) particles 14 microns and larger. A one-millimeter oil sample that earns a 21/17 rating is equivalent to a 55-gallon drum of oil contaminated with a half-teaspoon of very fine dust. “Although that’s considered ‘clean’ by ISO standards, it’s not acceptable for our new machines,” says Rose. “In fact, if your machine meets the 21/17 standard—and the hydraulic pumps operate at 32 gallons per minute, 8 hours a day, 200 days per year—you’re actually running more than 625 pounds of dirt through the hydraulic system annually. By improving cleanliness to ISO 18/15, you can reduce the amount of dirt in your system to about 80 pounds per year. Achieve a 16/13 rating, and the number drops to 20 pounds,” she says.
Equipment owners should do their part in controlling contamination during operation and maintenance. Rose recommends the following maintenance practices:
- Control operating temperatures to reduce internal wear.
- Fix leaks immediately. If oil is leaking out, particles are getting in.
- Replace worn seals without delay, as a bad seal makes a perfect entry point for dirt.
- Remove old filters carefully: They hold sludge that can fall back into the system.
- Keep new filters packaged until they are ready for
installation.
- Drain oil when it’s warm and agitated and make sure to drain the dirty fluid as thoroughly as possible.
- Use a filtered fluid transfer cart to add new oil.
- Enroll in an oil-analysis program. When collecting samples, use proper procedures and clean materials, and follow the recommendations you receive after your samples have been analyzed.
Boebel says that Komatsu has also seen examples of how oil analysis can prevent a major failure. He says to think of oil sampling as a proactive monitoring of a machine’s health. “For example, if you see an engine oil sample trending higher and higher in silica content—that should be a red flag to do a thorough machine inspection. Why is the trend increasing? Is it contamination from the maintenance crew? Is there a loose hose clamp at the air-filter base? Did the operator install the air filter correctly? If you can catch an issue like this early, it could save you from ‘dusting’ an engine,” he says.
Maximizing Blade Life
“Check blades daily for damage to guards, hoses, and cylinders—and inspect for any hydraulic leaks. Ensure that ground engaging parts such as end bits and cutting edges are not loose or excessively worn. These small steps will save you money. If you do not let a cutting edge go beyond its maximum wear point, you will prevent excessive wear to the blade bottom. Repairing this part of the blade requires a welder and can be prevented by conducting good inspections,” says Boebel.
As you walk around the blade, Drescher says, check the condition of the hydraulic hoses, or wire harnesses if you have a grade-control system on the machine. “Make sure that all of the grease zerks will take grease for each joint,” he says. “Check to see that each side of the blade or end bits is wearing evenly. If there is a lot of side cutting with only one side of the blade, the wear will not only decrease the life of the blade, but it can also decrease the life of the undercarriage and linkage joints.”
Regarding rotating, reversing, or replacing tips, Boebel says that many of the Komatsu ground engaging parts have reversing in mind to maximize wear life and reduce owning and operating costs. “Refer to the shop manual specific to the crawler dozer model. Often there are published wear-limit specifications as well as pictorial examples of when to replace tips. Some cutting edges are meant to be reversed, and others are not. Consult with your product support representative if you are unsure. Tip wear is usually gradual and care must be given to replace before damage is done to the mounting structure. Remember, trying to save a little by going beyond wear limits could cause other damage,” he says.
Operational skills also contribute greatly to blade life. “Back dragging can make a job look good, but it can decrease the life of the blade. Knowing where to adjust the blade pitch for each application can also increase blade life,” says Drescher.
Cooling System Care
“Again, daily checks are very important for cooling systems, as you never want to run low on coolant due to a leak or normal machine consumption. Systems that require corrosion resistors should be replaced per the instructions in the O&M Manual. Some systems do not require corrosion resistors and use a ‘super coolant’ that protects the system via the use of special additive packages. The condition of the fluid should be checked every month or two to be sure the concentration is correct. This becomes more critical in colder climates,” says Boebel. “Also, contact your dealer’s service manager for periodic tune-ups. Many of the dozers on the market today have calibrations that can be done to check pressures and maximize performance by optimizing machine settings.”
Onsite Service
Drescher stresses that trained field service technicians are extremely valuable and will perform tasks onsite that used to require the machine to be hauled to the dealer’s maintenance facility. Trucks fully equipped with hoists can perform major component exchange and can service most units in the field.
Boebel says that a contractor should always have a full set of common OEM filters available in the service truck. “This should include oil filters, air filters, and fuel filters. In addition, a contractor should always have fluids onsite for top-offs and replacement if necessary. Damage to machines will inevitably happen, and everyone should be prepared to deal with it. For example, if a blade hose fitting comes loose and starts leaking, do you have the proper fluid to refill the reservoir? Is it the correct type? Using the wrong fluids or running a component low on fluid can cause costly repairs. Manufacturers do extensive testing with the fluids they recommend to maximize a machine’s life. Having a little bit extra of everything onsite is cheap insurance,”
he says.