May 19, 2009
Production loaders, which set the pace for putting rocks in the box, need to be maintained properly to ensure lowest cost per ton.
Routine maintenance of your production loaders helps ensure high productivity, keeps operating costs down, and promotes long machine life.
by Todd Tuntland
Production loaders set the pace for putting rock in the box. Keeping them digging and loading efficiently is largely a function of routine maintenance. Proper routine maintenance, coupled with good operating practices, delivers the lowest cost per ton.
Following the inspection guidelines and maintenance intervals detailed in your wheel loader operation and maintenance manual is the best way to keep operating costs down, and it’s the main way to avoid mechanical failures that result in costly unplanned downtime and lost production. Additionally, routine inspection and maintenance — with emphasis on repair before failure — enable components to achieve their full design lives. Worn components taken out of service before they fail also have a greater likelihood of providing valuable cores for remanufacturing.
Routine maintenance is a shared responsibility of maintenance technicians and wheel loader operators. The pre-shift truck inspection conducted by the operator is both a safety inspection and a maintenance inspection. Ideally, the operator will use a checklist for the walk around inspection. Figure 1 is an example checklist for wheel loaders. Additional information about conducting a wheel loader walkaround inspection can be viewed on the Caterpillar Web site: safety.cat.com.
The problems that the operator detects and reports during the walkaround inspection and during the operating shift often can avert costly mechanical failures. Regardless of who is conducting inspections, monitoring machine health, or performing routine maintenance, the operation and maintenance (O&M) manual for your wheel loader provides details that can guide those actions. When you have questions, refer to the O&M manual first for answers.
Here’s an overview of maintenance recommendations for key systems.
Perform tire inspections daily and check tire inflation every 50 operating hours or at least weekly. Always obtain the proper tire inflation pressure from your tire supplier. Low tire pressure can be hazardous, especially in load-and-carry applications. Additionally, low inflation pressure reduces load-carrying capability, makes the tire more susceptible to cutting, and increases rolling resistance. The result is accelerated tire wear and higher costs.
Use dry nitrogen gas for tire inflation and for tire pressure adjustments. Nitrogen is an inert gas that will not aid combustion inside the tire. In addition to reducing the risk of explosion, nitrogen reduces the slow oxidation and deterioration of rubber and reduces corrosion of rim components.
Oils and scheduled sampling
Perform regular sampling and analysis of oils in wheel loader systems, such as the engine crankcase, transmission, final drives, and hydraulics. Monitoring the condition of these oils helps establish appropriate change intervals and helps identify problems before they lead to mechanical failures. Fluids analysis is an integral part of machine health monitoring and machine management. Such a program can significantly lower operating costs and increase mechanical availability of your loaders.
Recommended oil sampling intervals for the systems noted, except for engines, is 500 service hours or three months for some large wheel loaders. Engine oil should be sampled every 250 hours. Recommended oil change intervals are available in the O&M manual and can be adjusted based on results of oil analyses.
Of course, those oil levels should be checked every operating day as part of the pre-shift inspection. Ground-level access service points and grouped service points facilitate safe and accurate inspections and maintenance.
Using clean oil and keeping it clean through proper maintenance procedures is another key to getting long, reliable life from loader components. Similarly, clean fuel improves the life and efficiency of engine fuel systems, and clean hydraulic oil adds life and helps maintain efficiency of hydraulic components. Data from mines around the world have shown that thorough contamination control procedures result in lower costs. It’s worth taking a look at the way your maintenance department handles oils, fuel, and maintenance procedures. Cleaning up the shop and the lube and fuel trucks, and adding appropriate filters and tank breathers may provide a big return on a relatively small investment.
A coolant level check should be performed daily or as part of the walkaround inspection before operation. A sight gauge enables the operator to check coolant levels on most loaders. If the coolant level is low, follow the directions for adding coolant in the O&M manual. Always add the same coolant type that is in the loader. Mixing different types can reduce effectiveness of the coolant and can shorten the coolant life.
Conduct coolant sampling and analysis every 500 operating hours to help maintain appropriate levels of coolant additives. In addition to freeze protection, the antifreeze additives protect against corrosion and effectively raise the boiling point of the coolant, which reduces cylinder liner pitting. Extended operation of diesel engines without antifreeze has shown cylinder liner pitting to perforation.
Bucket and front linkage
The business end of a large wheel loader operating in a quarry requires inspection each shift. To maintain high productivity and reduce wear on related components, prompt action is in order if any repairs are needed.
Look for damage to the bucket cutting edge and for loose, broken, or missing tips. Ensure that bucket wear plates are solidly in place. Examine loader boom pins and lift-cylinder boom pins to determine if they are worn or loose. Look for leaks from hoses and cylinders. Lubricate the loader pins and bearings as necessary. Maintenance-free sleeve bearing linkage pins eliminate greasing on some Cat large loaders.
Caterpillar recommends periodic washing to allow thorough inspections of loader structures, including the rollover protective structure. Washing the loader is the first step to enable an inspector to see cracks. Regular washing pays other benefits, too. Inspectors can more easily identify leaks, loose fasteners, and other problems, and a clean loader lends itself to good contamination control when performing preventive maintenance.
Performing loader maintenance is a matter of routine. Follow the routine, and look for lower costs and higher productivity to result.
Todd Tuntland has been with Caterpillar for more than five years in a number of engineering functions. Currently, he is in the Caterpillar Quarry and Specialty Industries Division as Product Application Specialist for wheel loaders in the aggregates industry.