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
- Operation within acceptable limits
- Engine load cycles
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
- The total number of engine starts
An increase of wear metals in the lube oil indicates that the bearings and the surfaces that wear may need servicing. An increase in the levels of noise and vibration indicates that rotating parts require service.
Note: Oil analysis may 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.
Service Hours and Fuel Consumption
Experience has shown that maintenance intervals are most accurately based on fuel consumption. Fuel consumption corresponds more accurately to the engine load.
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.
Use gallons, hours, or load cycles, WHICHEVER OCCURS FIRST, to determine Overhaul.
Operating at greater than
| Overhaul Schedule | ||||
| Fuel Consumption | |
|
|
|
| Load Factor | < 25 Per Cent | 25 - 30 Per Cent | 30 - 50 Per Cent | > 40 Per Cent |
| Service Hours | 24000 | 21000 | 18500 | 16000 |
| Load Cycles(1)(2) | 192000 | 192000 | 192000 | 192000 |
| (1) | To illustrate engine capability, a load cycle has been defined as an increase of at least an 80 per cent rated power followed by a decrease of at least 80 per cent rated power. Load cycles of less than 80 per cent rated power may also impact the engine overhaul interval, requiring your specific operating profile to determine your appropriate interval. |
| (2) | Determining the appropriate overhaul interval will require understanding of the locomotive operating profile including total operating hours, amount of fuel burned, load factor, load cycles, and total number of engine starts. Caterpillar requires the use of data recorders to help determine the operating profile and to set appropriate intervals for a fleet on a given route. Changes in operating profiles (a different deployment or change in the operating profile for the existing route) may require adjustment of overhaul intervals to ensure reliable performance. Failure to follow the overhaul intervals may result in unplanned repairs. For assistance with calculating load cycles, installing data recording equipment and/or confirming overhaul intervals, contact your Cat dealer. |
- 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. Use this figure as variable "F" for the equation in Table 2. For more information about the Technical Marketing Information (TMI) for your engine, consult your Cat dealer.
| 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. |
Engine Starts as an Overhaul Indicator
Engines that experience a high number of engine starts may be susceptible to accelerated component wear. This wear may include, but not limited to, the main bearings and camshaft lobes.
For applications that exceed 6500 engine starts before the fuel burn, operating hours, or load cycles to overhaul limits are met, consult your Cat dealer for guidance. Your Cat dealer will identify a course of action including an appropriate inspection and repair plan.
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.
Severe operation is the use of an engine that exceeds current published standards for that engine. Caterpillar maintains standards for the following engine parameters:
- Altitude
- Environmental qualities
- Fuel consumption
- Fuel quality
- Horsepower
- Installation
- Maintenance intervals
- Range of rpm
- Selection of coolant
- Selection of oil
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 may not be 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. These conditions can make maintenance difficult. The buildup can contain corrosive chemicals. Corrosive chemicals and salt can damage some components.
The high-pressure fuel system is sensitive to debris. The debris can lead to early erosion and replacement for many of the high-pressure fuel system components and lack of performance. Caution should be taken by covering any fuel system opening during maintenance with a CLEAN cover. Refer to Special Instruction, SEBF9107, "CR1100 Fuel System Flushing Procedure" and Special Instruction, SEBF9109, "CR1100 Fuel System Assembly and Handling Guidelines" for information on handling and assembling fuel system 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
- Operating the engine in a manner that causes an excessive number of engine load cycles.
- 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