May 1, 2013
By Rob Marringa
Over the past decade, the aggregates industry reached the realization that bigger is better when it comes to excavators. In this high-volume, low-margin business, a machine that can handle a bucket capable of digging up tons of raw material brings considerable advantages, with its ability to move aggregate to into the process and eventually to market.
Production and reliability go hand in hand and this is certainly true when it comes to these machines weighing in at 70 tons or more. Yet 10-hour days, high duty-cycles, and unforgiving terrain can threaten the uptime of these massive and invaluable machines. Downtime simply isn’t an option since the rest of the operation typically depends on these excavators to keep production flowing.
Given the important role excavators play at virtually every operation, there is no better time than now to freshen up on basic maintenance for high-volume excavators. Here are eight tips to ensure excavators operate at peak efficiency and achieve maximum uptime.
1. Use high-grade oil.
Maintaining proper oil change intervals per the manufacturer’s recommendation is basic to excavator performance and life. In the demanding aggregates environment, engine oils, particularly those with additives, can break down under high duty-cycle.
The newer Tier 4 engines with exhaust gas recirculation and anti-pollution equipment require higher-grade oils. Engine oil is no place to save money. The high-ash content of these superior oils is formulated to improve wear protection, soot-related viscosity control, and prevent thermal and oxidative breakdown.
Using lesser quality oils or incorrect viscosity can shorten engine life, and cause time-wasting, costly repairs. High duty-cycle boom operation requires proper hydraulic oil type and viscosity because anti-wear and anti-corrosion additives degrade under high heat conditions.
It is also important to be vigilant about changing both engine and hydraulic filters per the manufacturer’s spec. A regular oil sample program uncovers warning signs of potential component failure and enables timely scheduling of repairs to minimize cost and downtime.
2. Frequently lubricate attachments.
Frequent greasing of the attachments is key to long pin and bushing life. Pin/bushing tolerances are tight when the machine is new. But miss just one greasing interval and tolerances won’t stay tight. Adding grease later does not stop the wear.
Avoid cutting corners. A high-quality grease protects components even when heat builds. Lesser grade greases can turn to liquid and run out.
Though many larger machines use an auto-lube system to keep these important pins greased, check often to be sure the grease tub is full and that all fittings are being serviced.
3. Choose high-quality diesel and use caution when fueling.
Fuel supply is important. Most operations will have a fuel truck and a designated fuel/maintenance tech that supplies the #2 diesel fuel and hopefully takes precautions to ensure cleanliness of fuel and delivery.
The increasing trend in bio-diesel of adding generic methyl esters to stretch the volume of diesel through blending, plus additive detergents and stabilizers, affects the quality of fuel and can “wick” and attract water. Most machines now have a primary fuel filter that has a water separator to remove this water-in-suspension within the fuel. However, these water separators are not automatic and require a daily inspection and draining.
When fueling and servicing the machine, pay attention to two points:
• When removing the fuel cap, check for a vacuum. If you feel a vacuum, the fuel tank vent could be clogged. This accumulation is not unusual in dusty aggregate conditions. When clogging happens, the fuel pump must work harder to deliver fuel, and it will fail prematurely.
• Before fueling, drain a small amount of fuel from the bottom of the tank to see how much debris and water are present. If there’s a lot of debris and water, drain the tank until the fuel runs clean.
4. Use OEM filters sized to the excavator.
Filters are the most critical component for trouble-free machine performance. Filters sized to the machine provide a clean fuel supply and prevent water and debris from getting into the engine. Avoid the temptation to use non-OEM filters.
When the fuel tank is not kept clean, the filters are quickly overpowered. Organics entering the fuel tank permit the growth of algae that can foul the filter. The algae sludge must be treated chemically to break it down and drain it. Clogged filters reduce the amount of fuel being delivered to the fuel transfer pump and injection pumps, potentially damaging the fuel transfer pump.
Starving the injection pump can lead to internal failure. As the transfer and injection pumps are pulling hard, loose-fitting O-rings will allow air to be sucked into the injection pump, causing catastrophic failure.
5. Regularly inspect attachments.
At regular intervals, bring the attachment close to the ground to check all welds and joints for cracks. Stress cracks develop over time; if caught early, they can be easily repaired.
Be sure to wipe down the inspection area; grease or debris on the attachment often disguise cracks. At the same time, check grease lines, hydraulic cylinders, and tubing to spot loose bolts.
6. Do a walk-around inspection each day.
• Check the undercarriage for cracks in the frame.
• Make sure all bolts, especially mainframe bolts, are tight.
• Check chain wear and components. Inspect pin wear regularly (pin-to-pin measurement compared to new) to track the percentage of chain wear.
• Inspect pad bolts to be sure all are in place and tight.
• Examine hydraulic components (center swivel, piping, travel motors) for leaks, clamp tightness, and damage. Check the hydraulic piston for scoring, which could indicate hydraulic oil contamination or gland bearing failure.
• Check top and bottom rollers, as well as idler and sprocket for damage and excessive wear. Rollers should move freely.
7. Pay close attention to the bucket.
High-cycle usage in the pit subjects the bucket to considerable wear. In the aggregate environment, it’s essential to inspect the bucket for correct size, design, and wear.
Operators should not run the teeth past 50 percent of their profile, at which point piercing ability and overall performance drops off rapidly. A fresh set of teeth and keepers should be readily available to prevent production interruptions.
Buckets often have cutting edges, side cutters, and hard-faced surfaces that require inspection and upkeep. Inspect the bucket for developing cracks on a daily basis. Discovering these issues early will prevent expensive repairs and downtime.
8. Inspect the cooling system often.
Keep the radiator, oil cooler, and other heat exchangers clean. Oil or coolant leaks can collect dust and debris, which slows air passage and act as an insulator to lessen the heat exchange.
Be sure heat shields and insulation in the radiator and engine compartments are in place and in good condition. Missing components can affect the heat balance and lead to overheating. Replace coolant per the manufacturer’s recommendation.
Coolant additives (especially anti-corrosion additives) stop working over time. A calcium-like build-up can form in the radiator, engine block, and head; causing overheating and eventual engine failure.
Tap into the experts
With the remoteness of many operations, it’s important for personnel to understand the ongoing health of the machines they operate. To acquire the knowledge and skills to carry out these maintenance functions, the manufacturer and the local dealer are always ready to assist in providing the necessary information and training so that when the day starts off, the excavator is ready to do its job.
Rob Marringa is brand-marketing manager for Case Construction Equipment.