797 Rear Wheel Bearing Full Single Life Reusability Guidelines {4201} Caterpillar

Off-Highway Truck/Tractor

797 (S/N: 5YW1-UP)

797B (S/N: JSM1-UP)

797F (S/N: LAJ1-UP; WSP1-UP)

Introduction

© 2018 Caterpillar All Rights Reserved. This guideline is for the use of Cat dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law.

Information contained in this document is considered Caterpillar: Confidential Yellow.

This Reuse and Salvage Guideline contains the necessary information to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Reuse and Salvage Guideline must be used with the latest technical information that is available from Caterpillar.

For technical questions when using this document, work with your Dealer Technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

Canceled Part Numbers and Replaced Part Numbers

This document may include canceled part numbers and replaced part numbers. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Summary

Illustration 1	g01956052
Section of a 797B rear wheel. (1) Main bearings for the rear wheel

This guideline provides procedures for the evaluation of the main bearings on the rear wheels of 797 Off-Highway Trucks. Due to the continuous oil filtration systems on 797 machines, dealers have often seen main bearings for the rear wheels with high hours, minimal wear, and excellent appearance.

Caterpillar was asked to determine the fatigue life and reusability of the bearings. Multiple bearings with 15,000 to 20,000 hours were tested by using X-ray diffraction technology. The technology was developed by the supplier of the bearings. X-ray diffraction measures the distress on the surface and under the surface. The results indicated that the tested bearings still had 80% plus fatigue life.

To analyze the reusability of wheel bearings, a 2.5 year field test was conducted. The field test involved six machines, two different dealers, and three different mine sites. The machines accumulated between 12,000 and 23,000 hours on the reused bearings without an incident. At the end of the test, all the reused wheel bearings were still in operation.

Note: All wheel bearings that are considered for a full single life must meet all the requirements that are included in Reuse and Salvage Guideline, SEBF8190, "Reusability of Tapered Bearings".

Note: Wheel bearings are not recommended to be used beyond one PCR life. PCR life is typically 20,000 hours, but may vary by application.

Important Safety Information

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly. Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. If a tool, a procedure, a work method, or operating technique that is not recommended by Caterpillar is used, ensure that it is safe for you and for other people to use. Ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance, or the repair procedures that are used.

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Improper operation, lubrication, maintenance or repair of this product can be dangerous and could result in injury or death. Do not operate or perform any lubrication, maintenance or repair on this product, until you have read and understood the operation, lubrication, maintenance and repair information.

Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

The hazards are identified by the safety alert symbol which is followed by a signal word such as danger, warning, or caution. The "WARNING" safety alert symbol is shown below.

Illustration 2	g00008666

This safety alert symbol means:

Pay attention!

Become alert!

Your safety is involved.

The message that appears under the safety alert symbol explains the hazard.

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The safety information in this document and the safety information on the machine are not all inclusive. Determine that the tools, procedures, work methods, and operating techniques are safe. Determine that the operation, lubrication, maintenance, and repair procedures will not damage the machine. Also, determine that the operation, lubrication, maintenance, and repair procedures will not make the machine unsafe.

The information, the specifications, and the illustrations that exist in this guideline are based on information which was available at the time of publication. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete, most current information before you start any job. Caterpillar dealers can supply the most current information.

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When replacement parts are required for this product Caterpillar recommends using Caterpillar replacement parts or parts with equivalent specifications including, but not limited to, physical dimensions, type, strength and material. Failure to heed this warning can lead to premature failures, product damage, personal injury or death.

Tooling and Equipment

References

Reference: Reuse and Salvage Guideline, SEBF8190, "Reusability of Tapered Bearings"

Reference: Reuse and Salvage Guideline, SEBF8187, "Standardized Parts Marking Procedures"

Reference: Reuse and Salvage Guideline, SEBF9118, "Procedure to Remove Large Wheel Bearing Cups"

Considerations for Reusability

Wheel bearings that have not achieved a single PCR life may be reused to achieve one full PCR life if the following guidelines are met. Reusing wheel bearings beyond one full PCR life is not recommended.

Consult Reuse and Salvage Guideline SEBF8190, "Reusability of Tapered Bearings" and instructions contained within this document for guidance on inspecting used bearings. Mark bearings to prevent further reuse using the procedure described in the following section.

Reusable bearing cups and cones should stay matched together. If only one reusable wheel bearing is available, the bearing should be installed in the inner position.

Procedure for Marking Codes on 797 Wheel Bearings

Bearings should be marked in accordance with Reuse and Salvage Guideline, SEBF8187, "Standardized Parts Marking Procedures". The markings should include permanent markings on both the cup and the cone.

Cups and cones should be marked on surfaces that do not wear. Refer to Illustration 3 for the location on the cup. Refer to Illustration 4 for the location on the cone. The cone should be marked on the small end surface. This surface has the least amount of wear against mating components.

For marking the code, use the 9U-7377 Metal Marking Pen or a similar marker such as a paint pen or acid etch. Illustration 3 and Illustration 4 were marked with a suitable marker.

The standardized procedure recommends marking the number of the rebuild and the number of hours at the time of the rebuild. The work order number is marked in the following examples. Specify the location to keep matching cups and cones together. The hours and the serial number should be recorded as a reference back to the work order number that is marked on the part.

Illustration 3	g01955860
Location for marking the cup.

Illustration 4	g01955863
Location for marking the cone.

Removal of the 797 Wheel Bearing

If bearing reusability is determined during the rebuild, it is not necessary to remove the bearing cup from the wheel hub. The cup can be easily inspected in the hub. If the cup is being removed for inspection, use a 301-5725 Bearing Removal Gp or an equivalent to prevent damage to the bearing cup. For more information on removing the cup, refer to Reuse and Salvage Guideline, SEBF9118, "Procedure to Remove Large Wheel Bearing Cups".

Ensure proper handling by using lifting eyes to avoid damage. Refer to Illustration 5.

Illustration 5	g01955871
Bearing handling and inspection.

Inspection of the 797 Wheel Bearing

Separate the cup and the cone for inspection. Keeping the cup and the cone together is required if the bearing is reusable. The corresponding cups and cones should be reused together as a set. Inspect the bearings on a soft surface with good lighting. Use a nonmetallic surface.

A blue-white light emitting diode (LED) light with a 8S-2257 Eye Loupe As provides an effective tool for inspecting dents for cracks. The LED lighting helps to highlight any cracks that may be present.

Inspection Procedure

1. Complete an initial visual inspection of the bearing. Discard any bearing that has the following wear:

   • Corrosion

   • Spalling

   • Pitting

   • Moderate to severe denting

2. Complete a detailed inspection of the bearing. Good lighting and magnification may be necessary.

Examples of Bearing Damage

Corrosion

Rust is not permitted. Even light rust is not permitted. Corrosion can cause surface pitting. Rust and corrosion will weaken the material. Do NOT USE bearings with corrosion.

Illustration 6	g01955904
Damage from corrosion. DO NOT USE THIS PART AGAIN.

Spalling

Spalling is not permitted. Do NOT USE any bearings with spalling.

Illustration 7	g01956194
Heavy spalling on the raceway. DO NOT USE THIS PART AGAIN.

Illustration 8	g01956196
Heavy spalling on the roller. DO NOT USE THIS PART AGAIN.

Illustration 9	g01956197
Spalling has begun at the site of the dents. DO NOT USE THIS PART AGAIN.

Damage from Foreign Objects

Bearings with moderate damage from debris are not considered reusable.

Illustration 10	g01956198
Severe damage from debris. DO NOT USE THIS PART AGAIN.

Surface Denting

Some denting is permitted. Denting should be evaluated according to the following characteristics:

• Size of dents

• Depth of dents

• Quantity of dents

It is important to distinguish between denting and pitting on the surface. An indentation to the surface of the bearing does not penetrate the surface. A pit has a visible penetration of the bearing surface. A bearing race or a roller with surface pitting is not reusable.

Individual dents should be examined under a good light. Magnification of 10X or higher should be used to check for cracks in the surface. In evaluating dents, The following guidelines apply:

• If more than five rollers have denting, the bearing should not be reused.

• Bearings with light denting are reusable.

• Bearings with moderate denting or excessive denting are not reusable.

• Large dents are more likely to have cracks and need examined carefully. Dents over 6.4 mm (0.25 inch) should be inspected.

• Do not use bearings with any sign of cracks or visible ridge around the circumference of the dent.

• Any dent with an irregular shape or a corner that is sharp should not be used.

Note: Every roller must be checked for dents by rotating the roller 360 degrees.Each dent must be examined under magnification for signs of surface cracks. Also inspect the raceway of the cone for denting. This inspection is performed by using a bright flashlight to look between the race and roller cage.

Illustration 11	g01956200
The roller has light denting. Each dent should be inspected for signs of surface cracks.

Illustration 12	g01956274
Roller with a large dent. DO NOT USE THIS PART AGAIN.

Illustration 13	g01956202
The roller has numerous small dents. The dents occur on more than five rollers. DO NOT USE THIS PART AGAIN.

Illustration 14	g01956203
The bearing cup has numerous dents. DO NOT USE THIS PART AGAIN.

Illustration 15	g01956204
The roller has severe denting. Dent (2) has an irregular shape with sharp corners. Dent (3 has surface penetration.) DO NOT USE THIS PART AGAIN.

Illustration 16	g01956205
Moderate denting from debris. DO NOT USE THIS PART AGAIN.

Illustration 17	g01956206
The roller has a pit. There is a visible ridge around the circumference. DO NOT USE THIS PART AGAIN.

Illustration 18	g01956208
The dent has an irregular shape with sharp corners. DO NOT USE THIS PART AGAIN.

Illustration 19	g01956209
The dent has small sharp corners. The dent penetrates the surface. DO NOT USE THIS PART AGAIN.

Examples of Reusable Bearings

Bearings that have light or no damage from debris may be reused. Also, bearings with dents that pass the criteria in "Surface Denting" may be reused.

Illustration 20	g01956217
No significant damage from debris. USE THIS PART AGAIN.

Illustration 21	g01956218
Roller with light wear and no denting. USE THIS PART AGAIN.

Illustration 22	g01956219
Rollers with light denting and light scratches. USE THIS PART AGAIN.

Illustration 23	g01956222
The roller has a small dent (4). The magnification of dent (4) is shown in Illustration 24. USE THIS PART AGAIN.

Illustration 24	g01956224
Dent (4) has no cracks or ridges under magnification. USE THIS PART AGAIN.

Illustration 25	g01956226
Dent (5) has no cracks or raised edges. The magnification of dent (5) is shown in Illustration 26. USE THIS PART AGAIN.

Illustration 26	g01956227
Magnification of dent (5). USE THIS PART AGAIN.

Illustration 27	g01956546
Shallow dents are shown on a single roller. Dent (6) has no cracks. USE THIS PART AGAIN.

Illustration 28	g01956547
The roller has no significant denting or bruising. USE THIS PART AGAIN.

Storage and Handling of 797 Wheel Bearings

1. Bearings should be cleaned in a cold washer for parts to remove any debris.
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   Illustration 29	g01956212
   Tank for coating cups and cones.

   Note: The tanks for dipping should be covered when parts are not being coated.

2. After cleaning, bearings should be coated with a heavy oil. Use SAE 50 oil for protection against corrosion. Refer to the following information for coating the bearings:

   • Bearings with rust or other corrosion should not be reused.

   • TDTO or FDAO oil is recommended. Do not use EP lubricants.

   • Ensure that all surfaces are coated by dipping the parts in oil. Spraying does not always properly coat the surfaces of the inner race and roller. Illustration 29 shows an example of a tank for dipping cups and cones in oil to ensure that the parts are fully coated for storage.

   • Any tank should be covered when parts are not being coated.

   • Grease will not consistently coat all surfaces. Grease is not recommended.

3. Once coated, bearings should be shrinkwrapped in plastic and sealed.
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   Illustration 30	g01956216
   Original box for shipping of a wheel bearing.

4. Store the bearings in a dry place until reusability can be determined. Utilize a storage box to protect the bearings and prevent handling damage. Caterpillar recommends using the same boxes that are used to ship the new bearings.