BOLT-12 POINT HEAD 6V8849 - Caterpillar

Electric Power Generation AllGenerator Set AllIntroduction
This Special Instruction provides information about the recommended method to service generator bearings.Generators are equipped with one or two bearings depending on the application. In addition, some configurations include bearing wear sleeves that are located in the bearing bracket. Refer to Illustration 4. Bearing wear sleeves are constructed from a harder material to prevent the brackets from being worn. Some wear sleeves are insulated to prevent shaft currents.Generators are provided with many different bearing configurations. Ball bearings, roller bearings, and sleeve bearings are all common types of bearings used in generators. The type of grease, operational life, temperature limits, and method of grease containment vary throughout the many generator applications.Sleeve bearings are not used in Caterpillar generators, therefore, sleeve bearings will not be covered in this document.Ball bearings and roller bearings are commonly configured with shields to keep grease in, and contaminants out. Testing confirms that grease will pass from bearing bracket cavity through shields when the following occur:
Equilibrium of grease is achieved, that is, excessive grease has purged out of the bearing
Grease in the bearing bracket cavity rises above 50% fillSome SR5 generators are equipped with bearings that never require additional grease for the life of the bearing. Some generators are equipped with bearings that can have grease added to the bearing.Generators that are equipped with bearings that do not require additional grease, do not have threaded holes in the bearing brackets for grease tubes. The grease tubes are used as a means to deliver grease to a bearing. Therefore, if there is no threaded hole for a grease tube in the bearing bracket, then no grease can be added to the bearings. Refer to Table 1, and foot note 4.In applications where the potential for contamination of bearing grease is minimal, some generator ball bearings are configured without shields. Excluding the shields helps to minimize bearing operating temperatures.To determine the type of bearing and generator lubrication requirements, use one of the following:
Engine serial number
Generator arrangement number (that is found on the generator stator)
Generator frame sizeUse the information to look up the bearing part number that is located in the parts replacement publication. Use the information in Table 1 to determine the lubrication guidelines. Many generators that require the addition of grease are labeled with a lubrication plate or decal near the greasing ports.The front of the generator refers to the generator drive end, that is, the end of the generator that is closest to the engine. The rear of the generator refers to the non-drive end.Caterpillar recommends replacement of the generator bearings during a major overhaul unless the bearings have been recently replaced prior to major overhaul. The following conditions may require bearing replacement at other times besides a major overhaul:
High temperature environment
Condensing humidity
Coastal environment
Chemical environment
Abrasive environment
Poor engine room ventilationBearing replacement before major overhaul may also be required when the following common causes or bearing problems are found:
Insufficient amount of grease
Contaminated grease from dirty environment
Grease deterioration
Mixing of incompatible grease
Excessive bearing sleeve