September 1, 2009
A quick review of a few obvious (and not-so-obvious) ways to keep these big machines running productively and your bottom line healthy.
by Kent Pellegrini
At the risk of stating the obvious, few hydraulic excavators are exposed to a working environment more hostile than that of machines employed at a quarry face. The weight and abrasiveness of the rock accelerate wear, and its unyielding nature abuses digging structures and imposes immense twisting forces in the undercarriage when tracks ride up on fallen debris.
So to begin, the first rule of preventive maintenance for these machines is the one we’ve heard so often that the advice often is ignored: visual inspection. In a perfect world, checking fluid levels, looking for leaks, checking for abnormal undercarriage wear, checking track tension, and inspecting for impact damage to the boom, stick, bucket linkage, cylinders, hoses, and steel tubes would be done at least at the beginning of each shift — and any potentially threatening conditions would be resolved immediately.
Leak inspection should include the cooling system, engine oil/fuel, hydraulic system, (cylinders, hose connections, and pumps), swing system, final drives, and track rollers. Some manufacturers also may suggest draining water from the fuel/water separator and fuel tank (in an appropriate manner), cleaning the air-intake pre-cleaner, and inspecting the radiator and coolers for dust accumulation at 10-hour intervals.
GET, welding cautions, and grease
At the top of the visual-inspection list, of course, is the bucket and its ground-engaging tools (GET). Check that retaining hardware for bucket teeth and edge-protector systems is tight and in workable condition. And of utmost importance, keep a close eye on GET wear to avoid jeopardizing the bucket’s structure. In some instances, bucket-tooth positions can be switched to promote even wear.
Although most manufacturers don’t advise the practice, some machine owners “hard-face” GET (add weld beads to wearing surfaces) or add wear plates on buckets to extend life. If this is done, keep three cautions in mind: weight added to the bucket may affect machine balance; bucket base metal may be compromised by welding heat; and improper welding can, potentially, jeopardize electronic controls and bearings. Consult with your manufacturer about minimizing welding hazards.
Given the severity of quarry-face operation, keeping the loading mechanism (boom, stick, and bucket) properly lubricated is essential — at proper intervals and with the proper amount and type of grease. Follow the manufacturer’s recommendations closely, and remember that grease recommendations may change with ambient temperature. Don’t overfill the reservoir of an automatic lubrication system (added pressure could pop the cover) and use care not to introduce debris; blocked lines are disastrous.
Coolant, oils, and predictive repair
The cooling system is likely the least understood and most often ignored system in your excavator. Whether your machine uses “fully formulated” antifreeze (with conventional additives), or an “extended-life” type (with organic-acid additives), check the coolant’s freeze point, clarity, and color at each oil-change. If rust or sediment is present, or if the color is suspect (an indication that antifreeze types have been mixed), ask your dealer’s advice, or that of a fluid-analysis lab, about remedial options.
In general, replenish any cooling system with a 50/50 mix of the correct antifreeze and deionized (mineral-free) water. Remember, too, that fully formulated coolant requires periodic addition of a nitrite-containing supplemental cooling additive (SCA) to protect the engine’s cylinder liners from cavitation.
Like proper coolant care, consistent analysis of the quarry machine’s various oil-filled compartments is essential. Over time, oil-analysis results can help establish optimal drain intervals for various fluids and can provide wear-trend information that allows timely, informed decisions about scheduled component replacement or before-failure repair. Nothing wrecks production schedules and budgets quite as effectively as a good, out-of-the-blue, catastrophic failure.
Also, simple precautions when working with an excavator’s fluid systems can help avoid problems, such as discarding the first small volume of fluid drawn from a sampling tap to clear residual debris, and properly tightening filters. (Caterpillar prints tightening procedures on each filter to ensure its proper performance.)
Among the most potentially useful preventive-maintenance tools available today are wireless information systems that communicate pertinent machine information to the machine owner. Caterpillar’s system, Product Link, for example, is standard equipment on all its new excavators and reports information on three levels: Asset Watch (reporting such data as location and hours); Maintenance Watch (allowing maintenance scheduling and history); and Health Watch (reporting fault codes, event codes, and fuel consumption).
The point is this: If your machine is equipped with such a system (you can also usually retrofit a system to an existing machine), consider subscribing to its reporting capability at the highest level. This level likely will provide immediate alerts (via cell-phone text or e-mail) about machine abnormalities (out-of-range temperatures or pressures, for instance) or machine “events” that could negatively affect the machine’s heath (such as poor operating techniques).
If the machine owner acts on this real-time information, potentially serious problems can be averted — which is the ultimate goal of preventive maintenance.
Kent Pellegrini joined Caterpillar in 2001 and currently is the marketing manager and a product application specialist for hydraulic excavators. He previously held the position of product marketing manager for skid-steer loaders and multi-terrain loaders.
Check items on this checklist once every 10 hours of operation to keep your excavator in peak condition.
· Check coolant level;
· Check engine-oil level;
· Check hydraulic-oil level;
· Drain water from fuel separator/tank;
· Test indicators and gauges;
· Inspect undercarriage and track adjustment;
· Inspect digging structures (boom/stick/bucket);
· Lubricate boom/stick/bucket linkages;
· Inspect seat belt; and
· Test travel alarm.