Severe operation is the use of an engine that exceeds current published standards for that engine. Caterpillar maintains standards for the following engine parameters:
- Horsepower
- Range of rpm
- Fuel consumption
- Fuel quality
- Altitude
- Maintenance intervals
- Selection of oil
- Selection of coolant
- Environmental qualities
- Installation
Refer to the standards for your engine or consult your Cat dealer to determine if your engine is operating within the defined parameters.
Severe operation can accelerate component wear. Engines that are operating under severe conditions may need more frequent maintenance intervals for the following reasons:
- Maximum reliability
- Retention of full service life
Because of individual applications, identifying all the factors which can contribute to severe operation is not possible. Consult your Cat dealer about the maintenance that is needed for your specific engine.
The following factors can contribute to severe operation: environment, improper operating procedures, and improper maintenance practices.
Extended operation in environments that are cold or hot can damage components. Valve components can be damaged by carbon buildup if the engine is frequently started and stopped in cold temperatures. Hot inlet air reduces the performance capabilities of the engine.
Note: See this Operation and Maintenance Manual, "Cold-Weather Operation" topic (Operation Section), or see Special Publication, SEBU5898, "Cold-Weather Recommendations".
Unless the equipment is cleaned regularly, extended operation in a dirty environment and in a dusty environment can damage components. Built up mud, dirt, and dust can encase components. This condition can make maintenance difficult. The buildup can contain corrosive chemicals. Corrosive chemicals and salt can damage some components.
- Extended operation at low idle
- Minimum cool down periods after high load factor operation
- Operating the engine beyond the guidelines for the engine rating
- Operating the engine at loads that are greater than the rated load
- Operating the engine at speeds that are greater than the rated speed
- Use of the engine for an application that is not approved
Improper Maintenance Practices
- Extension of maintenance intervals
- Not using recommended fuel, lubricants, and coolant/antifreeze
An overhaul is replacing the major worn components of the engine. An overhaul interval is a maintenance interval that is planned. The engine is rebuilt with certain rebuilt parts or new parts that replace the worn parts.
An overhaul also includes the following maintenance:
- Inspection of all the parts that are visible during the disassembly
- Replacement of the seals and gaskets that are removed
- Cleaning of the internal passages of the engine and the engine block
Most owners will save money by overhauling the engine at the intervals that are recommended in this Operation and Maintenance Manual. Consider the graph in Illustration 1.
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| Illustration 1 | g00745964 |
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(Y) Cost
(X) Time (1) Cost of maintenance and repair that is planned (2) Cost of maintenance and repair that is not planned | |
In Illustration 1, line (1) represents the maintenance and repair costs for an owner that followed the recommendations for inspection, maintenance, and repair. The peaks represent overhauls.
Line (2) represents the maintenance and repair costs for an owner that chose to operate beyond the recommended intervals. The initial cost of the “repair-after-failure” philosophy is lower. Also, the first overhaul was delayed. However, the peaks are higher than the peaks for the customer that used the “repair-before-failure” philosophy .
The higher peaks result from two key factors:
- Delaying an overhaul until a breakdown increases the chance of a catastrophic failure. This type of failure requires more parts, labor, and cleanup.
- Excessive wear means that fewer components will be reusable. More labor may be required for salvage or repair of the components.
When all the costs are considered, “repair-before-failure” is the least expensive alternative for most components and engines.
Waiting until the engine exhibits symptoms of excessive wear or failure is not practical. A planned overhaul before failure may be the best value for the following reasons:
- Costly unplanned downtime can be avoided.
- Many original parts can be reused according to the guidelines for reusable parts.
- The service life of the engine can be extended without the risk of a major catastrophe due to engine failure.
- Achieve the best cost/value relationship per hour of extended service life.
Note: For specific overhaul intervals, refer to this Operation and Maintenance Manual, Maintenance Recommendations .
Some factors that are important for determining the overhaul intervals include the following considerations:
- Performance of preventive maintenance
- Use of recommended lubricants
- Use of recommended coolants
- Use of recommended fuels
- Proper installation
- Operating conditions such as: high ambient temperatures, high altitude operation, tunnel operation, and cold-weather operation.
- Operation within acceptable limits
- Engine load
- Engine speed
Generally, engines that are operated at a reduced load and/or speed achieve more service life before an overhaul. However, this service life is for engines that are properly operated and maintained.
Other factors must be considered for determining a major overhaul:
- The total amount of fuel consumption
- The service hours of the engine
- An increase of oil consumption
- An increase of crankcase blowby
- The wear metal analysis of the lube oil
- An increase in the levels of noise and vibration
An increase of wear metals in the lube oil indicates that the bearings and the surfaces that wear may require servicing. An increase in the levels of noise and vibration indicates that rotating parts require service.
Note: Oil analysis can indicate a decrease of wear metals in the lube oil. The cylinder liners may be worn so that polishing of the bore occurs. Also, the increased use of lube oil will dilute the wear metals.
Monitor the engine as the engine accumulates service hours. Consult your Cat dealer about scheduling a major overhaul.
Note: The driven equipment may also require service when the engine is overhauled. Refer to the literature that is provided by the OEM of the driven equipment.
Using Fuel Consumption For Calculating the Overhaul Intervals
| Equation For Calculating Overhaul Intervals |
| F/R = H |
| “F” is the estimated total amount of fuel consumption of the engine. |
| “R” is the rate of fuel consumption in liters per hour or gallons per hour. |
| “H” is the number of estimated hours until the overhaul interval. |
Use the actual records of fuel consumption, when possible. If the actual records are not available, use the following procedure to estimate the fuel consumption.
- Estimate the average percent of the load for the operation of the engine.
- Refer to the fuel consumption data in the Technical Marketing Information (TMI) for your engine. This information will determine the fuel consumption for the percent of the load that was estimated in Step 1. Use this figure as variable "F" for the equation in Table 1. For more information about the Technical Marketing Information (TMI) for your engine, consult your Cat dealer.
Oil Consumption as an Overhaul Indicator
Oil consumption, fuel consumption, and maintenance information can be used to estimate the total operating cost for your Cat engine. Oil consumption can also be used to estimate the required capacity of a makeup oil tank that is suitable for the maintenance intervals.
Oil consumption is in proportion to the percentage of the rated engine load. As the percentage of the engine load is increased, the amount of oil that is consumed per hour also increases.
The oil consumption rate (brake-specific oil consumption) is measured in grams per kW/h (lb per bhp). The brake-specific oil consumption (BSOC) depends on the engine load. Consult your Cat dealer for assistance in determining the typical oil consumption rate for your engine.
When an engine oil consumption has risen to three times the original oil consumption rate due to normal wear, an engine overhaul should be scheduled. There may be a corresponding increase in blowby and a slight increase in fuel consumption.
Refer to the Service Manual for the Disassembly and Assembly procedures that are necessary to perform the required maintenance on the items that are listed. Consult your Cat dealer for assistance.
To determine the reusability publications that are needed to inspect the engine, refer to Guidelines for Reusable Parts and Salvage Operations, SEBF8029, "Index of Publications on Reusability or Salvage of Used Parts".
The Guidelines For Reusable Parts and Salvage Operations is part of an established Cat parts reusability program. These guidelines were developed to assist Cat dealers and customers reduce costs by avoiding unnecessary expenditures for new parts. If the engine parts comply with the established inspection specifications, the parts can be reused.
The use of out-of-spec parts could result in unscheduled downtime and/or costly repairs. The use of out-of-spec parts can also contribute to increased fuel consumption and reduction of engine efficiency. New parts are not necessary if the old parts can be reused, repaired, or salvaged. Otherwise, the old parts can be replaced or exchanged.
Your Cat dealer can provide the parts that are needed to rebuild the engine at the least possible cost.
An economical way to obtain most of the parts that are needed for overhauls is to use Cat remanufactured parts. Cat remanufactured parts are available at a fraction of the cost of new parts. These parts have been rebuilt by Caterpillar and certified for use. The following components are examples of the remanufactured parts:
- Cylinder heads
- High-pressure fuel pumps
- Oil pumps
- Turbochargers
- Water pumps
- Fuel injectors
Consult your Cat dealer for details and for a list of the remanufactured parts that are available.
Your Cat dealer may be offering various overhaul options.
A Flat Rate Overhaul guarantees the maximum price that you will pay for an overhaul. Flat rate prices on preventive maintenance programs or major repair options are available from many servicing dealers for all Cat Engines. Consult your Cat dealer to schedule a before failure overhaul.
Caterpillar recommends a scheduled overhaul to minimize downtime. A scheduled overhaul will provide the lowest cost and the greatest value. Schedule an overhaul with your Cat dealer.
Overhaul programs vary between dealers. To obtain specific information about the types of overhaul programs and services, consult your Cat dealer.