3516C Marine Engine Caterpillar

Overhaul Intervals

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

• Engine speed

Generally, engines that are operated at a reduced load and/or speed achieve more service life before an overhaul. However, the engines must be operated and maintained properly.

Other factors must also 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 need serviced. 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.

Using Fuel Consumption For Calculating the Overhaul Intervals

Experience has shown that maintenance intervals are most accurately based on fuel consumption. Fuel consumption corresponds more accurately to the engine load. Table 1 lists average ranges of fuel consumption and service hours for standard displacement engines. These tables are based on a load factor of approximately 60 percent.

• Overhaul intervals are guidelines and are dependent on the maintenance and usage factors described in this Operation and Maintenance Manual.

• Maintenance intervals must be reduced for engines that operate in a severe service application. Maintenance intervals must also be reduced for engines that operate in excess of the engine rating definition.

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 the oil consumption of an engine has risen to three times the original oil consumption rate, an engine overhaul should be scheduled. There may be a corresponding increase in blowby and a slight increase in fuel consumption.

Severe Operation

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 in order 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, all of the factors which can contribute to severe operation cannot be identified. 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.

Environmental Factors

Extreme Ambient Temperatures

Extended operation in environments that are too cold or too hot can damage components. Valve components can be damaged by carbon buildup if the engine is frequently started and stopped in temperatures that are too cold. Inlet air that is too hot 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".

Cleanliness

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 and make maintenance difficult. The buildup can contain corrosive chemicals. Corrosive chemicals and salt can damage some components.

Improper Operating Procedures

• 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