HUB 9S2837 - Caterpillar

Corrective Measures for Bond Separation
The corrective measures for a bond failure will vary depending on the severity of the damage. If one bearing has a bond failure that allows a small amount of aluminum or copper-based material in the system, the problem is not as severe. Replacement of that damaged bearing is probably sufficient.If a bond failure occurs on more than one bearing, or if the bond failure causes failure of other bearings, more corrective measures are needed. When the damage is severe, do the following:
Determine if other damage caused the bond separation (lack of lubrication, debris). Take corrective action as necessary.
Clean all oil passages in the block, crankshaft, and auxiliary equipment
Make certain that a new oil filter is installed. Also, install a new auxiliary filter if the engine is so equipped
Install a new oil cooler. Oil coolers cannot be cleaned to remove debris or bearing material
Illustration 70 g03479600
Bond separation between the lead-tin overlay and aluminum.
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Bond separation between aluminum and steel.
Electrical Discharge Damage
Note: This type of damaged is unusual, and is most often limited to engines in generator sets but also has occurred on engines with large alternators.Electrical Discharge Damage is when electrical current goes through the crankshaft, bearings, and into the block due to poor grounding. When the electrical current goes through the engine, an arc occurs between the bearing and the crankshaft and block. This arcing causes damage on only the main bearing. Electrical Discharge damage makes the main bearings shiny and causes significant damage. Electrical Discharge also creates a frosted appearance on the crankshaft journals from pitting from arcing current.
Illustration 72 g03480144
Main bearings that have been damaged by electrical discharge. Note the "chrome like" bearing surface
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A crankshaft journal that has been damaged by electrical discharge. Note the "frosted" appearance on the journal.
Illustration 74 g03480160
A bearing back damaged by electrical discharge. Note the unusual wear pattern caused by arcing current.
Bearing Failure Analysis
Bearing failure analysis is not always simple. Many times the cause of a failure cannot be determined by looking at the bearings alone. More information, such as engine repair history or information from the operator may be needed. Also, mating parts must sometimes be inspected to determine involvement in the failure. Frequently, a bearing set will show evidence of more than one failure cause. Bearings may be destroyed during a failure, thus removing the evidence shown by the present attributes.Procedure for Analyzing Bearing Failures
If a bearing failure is suspected in an engine, it is important to perform the correct failure analysis steps in the correct sequence. The following recommendations will help you to be more successful in analyzing failures.
Get operating information from the operator: How was the engine being operated at the time of failure? What was the engine coolant temperature before and during the failure? Did oil pressure change before or during failure? What were the symptoms during the failure?
Get maintenance information: What were the oil change intervals? When was the oil last changed? What oil was used? What was the classification and viscosity? If