Routine maintenance for haul trucks

Keeping trucks rolling at an aggregates operation is a largely routine job – a routine maintenance job, that is. Following the inspection guidelines and maintenance intervals detailed in your truck’s operation and maintenance manual is the way to keep operating costs down, and it is the main way to avoid mechanical failures that result in costly unplanned downtime and lost production.

Proper routine maintenance coupled with good operating practices delivers the lowest cost per tonne. It is hard to beat the haulage costs of rigid-frame mining trucks loaded and operated properly on well-designed and maintained haul roads.

Routine maintenance is a shared responsibility of maintenance technicians and truck operators. The pre-shift truck inspection conducted by the operator is both a safety inspection and a maintenance inspection. Ideally, the operator should use a checklist for the walk-around inspection.

The problems that the operator detects and reports during the walk-around 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 manual for your truck provides details that can guide those actions. When you have questions, refer to the operations and maintenance manual first for answers.

Truck systems and components require regular routine maintenance to work optimally and to achieve their design lives.

Perform tyre inspections daily and check tyre inflation every 50 operating hours or at least weekly. Always obtain the proper tyre inflation pressure from your tyre supplier. Low tyre pressure can be hazardous because it affects truck handling and braking. Additionally, low inflation pressure reduces load-carrying capability, allows the tyre to heat up quickly, and increases rolling resistance. The result is accelerated tyre wear and higher haulage costs.

Use dry nitrogen gas for tyre inflation and for tyre pressure adjustments. Nitrogen is an inert gas that will not aid combustion inside the tyre. In addition to reducing the risk of explosion, nitrogen reduces the slow oxidation and deterioration of rubber and reduces corrosion of rim components.

The tyres in a dual-tyre configuration should be the same brand, the same type, and the same construction. The tyres also should be the same designated size and have the same amount of wear to minimise overloading of a single tyre and undue stresses on the drive train.

Conduct regular sampling and analysis of oils in major truck systems, such as the engine crankcase, torque converter and transmission, differential and final drives, steering system and front wheels.

Monitoring the condition of these oils helps to 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 lower operating costs significantly and increase mechanical availability of your trucks.

The recommended oil sampling intervals for the systems noted is 500 service hours for one manufacturer’s trucks. Of course, those oil levels should be checked every operating day as part of the pre-shift inspection, and trucks have a number of bearings that must be lubricated every 50 operating hours or weekly at the least. Recommended oil change intervals for different systems are available in the O&M manual and can be adjusted based on results of oil analyses.

Using clean oil and keeping it clean through proper maintenance procedures is another key to getting long, reliable life from truck 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 around the world has shown that thorough contamination control procedures result in lower costs. It is 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 low investment.

A coolant level check should be performed daily or as part of the walk-around inspection before operation. A sight gauge enables the operator to check coolant levels on most trucks. 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 truck. Mixing different types can reduce effectiveness of the coolant and can shorten the coolant life.

Coolant sampling and analysis every 500 operating hours is recommended 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 resulted in cylinder liner pitting to perforation.

The suspension cylinders, or struts, are charged with oil and nitrogen. Strut pressure should be checked at least every 500 hours or every three months. Improperly charged struts will result in reduced tyre life, uncomfortable ride, and poor handling, and even reduced frame life and accelerated component wear. See the O&M manual for proper checking procedures.

When installing new struts or assembling a new truck, remember that some manufacturers ship suspension cylinders from the factory with a preliminary charge of nitrogen and a preliminary charge of oil. During field assembly, the suspension cylinders must be charged properly.

Frame and body
Thorough frame and body inspections should be performed at least every 1000 hours or six months.

Thoroughly washing the truck is the first step to enabling an inspector to see cracks. If repairs are needed, consult your dealer for repair procedures. Proper weld repairs may be needed to stop further cracking and to avoid high-cost failures.

Regularly washing quarry trucks pays other benefits too. In addition to spotting cracks, inspectors can more easily identify leaks, loose fasteners and other problems. And a clean truck won’t carry the dead weight of dirt and mud that burns more fuel as it is transported around the quarry. Also, accumulations of mud can contribute to overloading, which prematurely wears all components.

Performing truck maintenance is a matter of routine, but the challenge is making good practices part of that routine. Start with the practices recommended in the operation and maintenance manual and build on them. Higher productivity and lower costs will result.

Terry Miller is a Caterpillar product support supervisor.

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