Bearing Maintenance Guide - Cat Parts
Contents
1. often under extreme loads Caterpillar offers two fundamental types of bearings plain bushing and antifriction This brochure will focus on antifriction bearings which use balls and rollers as the primary elements between contacting surfaces Antifriction bearings consist of spherical or cylindrical elements held in races that rotate with the adjoining surfaces preventing metal to metal contact and ultimately reducing friction heat and wear Caterpillar offers a variety of different antifriction bearings ball bearings roller bearings and needle bearings All three types of bearings have similar components hardened steel rings called races and optional separators or cages which provide spacing for the rolling elements between the races In some applications the rolling elements are in direct contact with the shaft or other mounting It is evident that bearings play a critical role in safe and reliable equipment operation A bearing failure can cause metal particles to enter the machine s lubrication system wearing gear teeth and ultimately damaging the components Thus maintaining high quality operating conditions for the bearings will minimize repair costs and downtime This Bearing Management Guide is Not a Repair Manual It is not intended to help you diagnose mechanical problems nor is it a substitute for your machine Operation and Maintenance Manual This guide is intended to help you understand2. amount of proper lubricant Use recommended lubricant Adjust to specification Determine what is misaligned housing shaft or bores Shaft may be bent or housing bores not aligned Replace shaft or housing Use less lubricant or use a lower viscosity lubricant Be sure to use recommended lubricant Either inner or outer race is sliding around its seated surface Use proper sized components Grease to proper level Use high temperature grease Replace seal Check shaft for scratches or burrs that may have damaged seal Use recommended lubricant Clean bearing Replace seals and bearing if damaged Replace bearing Use lubricant that resists corrosion Adjust to specification Add proper lubricant Check for damage Use proper size and type of seal If new installation remove bearing and clean all mating surfaces Reinstall bearing if not damaged Replace gasket Frequently Asked Questions 1 What tools do I need to perform proper maintenance of bearings You should always work with clean recommended or approved tools Do not use a wooden mallet Also work in clean surroundings such as on a metal or metal covered bench 2 How should I properly handle a bearing Always handle the bearings with clean dry hands or even clean canvas gloves Never hold a bearing with dirty or moist hands as contamination can easily be transmitted to the bearing When you are finished handling the bearing lay t
3. how bearings work and how they wear With this understanding and by following the machine Operation and Maintenance Manual you can maximize productivity service life and value of your Cat machines Lubrication is an important factor in bearing maintenance Lubrication supplies an oil film for balls and rollers reducing friction between bearing components while providing a protective coating to prevent rust and transports heat away Further using the appropriate quality type and viscosity of lubricant is vital to good bearing performance and life Over lubricating can lead to churning causing friction and heat which eventually initiates premature failure Lack of lubricant can be harmful given that not enough oil will be available to do the job To ensure optimum bearing performance Caterpillar offers a full line of Cat lubricants to meet your everyday needs In splash lubrication systems such as in final drives it 1s imperative to not only retain the right type and quantity of lubricant in the housing but also to change the lubricant and filters at recommended intervals Using lubricant rated for the proper temperature must also be noted When operating at extreme temperatures it can lead to oxidizing the oil and breaking down of additives Regardless of the type of lubrication system you are using be sure to understand and follow the manufacturer s recommendations to establish the right type and
4. Bearing Maintenance Management Guide Sustaining Life Bearings are a critical aspect in sustaining safe and reliable equipment while operating Caterpillar machines Establishing and following a preventative maintenance program is a key factor in guaranteeing long bearing service hours and minimizing equipment downtime Importance of Lubrication Po T Thorough Inspection Hints on Replacement j i T r ry r L e a ie matt Ae E i spit ee iat t f or iets os I i s 7 Detect Then Correct FAQs Ten Factors Causing Premature Failure CATERPILLAR Contents Importance of Lubrication Thorough Inspection Hints on Replacement Detect Then Correct Frequently Asked Questions Ten Factors Causing Premature Failure Caterpillar is known for having products that provide exceptional performance extraordinary durability and long life Caterpillar bearings offer just that and more Bearings are used in every drive train component and virtually every mechanical component of Caterpillar machines But because of the varying speed power and torque and thrust force going through the drive train one type of bearing does not meet all the rigorous demands Several types of bearings are needed with each bearing being highly crafted and precisely matched to the kind of load it carries Bearings serve to allow parts to move together smoothly with minimum friction heat and wear
5. ace a bearing that is in severe applications under heavy load or has high service hours Note that if you are not planning on reinstalling the inspected bearing immediately perform the following steps oil the bearing wrap it in clean oil proof paper place it in a box and store it in a dry dust free place These precautions will help avoid corroding and shortening of the bearing life Any time during inspection you decide to replace a bearing be sure you replace it with a genuine Cat bearing Only then are you assured of the proper performance and long life of your machine Bearings must be compatible with the machine in the areas of lubrication fit surface and load carrying ability Many times a bearing will look like an original yet it might not be a correct replacement Bearings that are not Hints on Replacement compatible in all areas can fail prematurely Cat equipment requires the use of many specialized bearings Some bearings are imprinted with the manufacturer s code that supplies information on the bearing s general dimensions Cat bearings are made specifically for Cat products therefore they have no stamped dimensions In some cases even though a bearing might portray the same identification code as a standard bearing it might be unique and have the ability to provide longer life in certain applications For example a bearing could have a particular surface finish or heat treat o
6. clean bearings in a container that is large enough for the bearings to be splashed around without contacting the bottom where the dirt settles Allow the bearings to soak for an extended period of time to loosen grease and dirt possibly several hours or overnight Use a short bristled brush that will not lose or break off its bristles After visually inspecting the bearing to see that all dirt has been removed rinse the bearing in a container of clean solvent next dip the bearing in oil When drying the bearing notice you should not use compressed air to spin it dry this can cause a non lubricated bearing surface to be damaged To dry the bearing hold both inner and outer races together to avoid spinning and blow air through the bearing After the bearing has gone through the cleaning process examine it thoroughly for cracks in the race dented seals and damaged or broken separators balls or rollers If a brownish blue or bluish black color appears it means the bearing has been overheated At this point replace the bearing If the bearing has a seal or shield inspect it for damage or wear If the seals are damaged or worn you must replace the complete bearing A worn or damaged seal will permit dirt and moisture to enter the bearing minimizing its wear life Check separable bearings for pitted scratched or flaked balls rollers or races If any of these signs are visible replace the bearing Inspect the
7. frequency of lubrication that is needed for your specific bearing design and application Additionally look into setting up a scheduled oil Importance of Lubrication analysis program for your machines if one has not been put in place already This program can easily help identify abnormal wear prior to it becoming a major problem There could possibly be no better way to detect component wear than to utilize a scheduled oil analysis program Detecting defects and deterioration before failure involves periodically removing cleaning and inspecting the bearings Remove bearings carefully as they can easily be damaged during this removal procedure see Frequently Asked Questions It is important to note that you should always use recommended tools and adhere to the outlined procedures in the machine s service manual Avoid harmful removal procedures such as flame cutting inner races or shrinking outer races with weld bead if possible Using these practices can result in uncontrolled heat that can damage housings or shafts When the removal process is complete bearings should always be cleaned before inspection Follow Cat s recommended guidelines to ensure the bearings are not damaged Only use petroleum solvents that are suggested for washing It is important to remember that most solvents are flammable and toxic when inhaled or absorbed into the skin Handle with caution To prevent contamination
8. he bearing out on a clean surface 3 What should I use to clean a bearing To clean a bearing you should use uncontaminated solvents and flushing oils If it is necessary to wipe the bearing only use clean lint free rags It is important to note that you should never use cotton waste or dirty rags to wipe a bearing Further never use the same container for both cleaning and final rinse of used bearings 4 What is the technique I should use to dry a bearing To dry a bearing hold both the inner and outer races together and blow air through the bearing You should never spin any bearing with compressed air 5 How should I store a bearing When storing a bearing remember the most important factor 1s protecting the bearing from dirt and moisture You should be sure to keep the bearing wrapped in oil proof paper Be sure that you do not scratch or nick bearing surfaces while handling and storing the bearing 6 What should I know about installing bearings When installing a new bearing install the bearing as it comes from the package without washing if it was received in a clean container When installing used bearings you should thoroughly clean the inside of housing prior to the installation process 7 What should I know about lubricants Lubricants are a critical aspect of bearing maintenance It is vital that you always keep lubricants clean when applying them and cover the containers when no
9. he races and rollers This may produce a single burn or multiple grooves called fluting A burned bearing allows for excessive noise and will need to be replaced Caterpillar s Solution Be sure to find and repair the root cause of the electrical ground to avoid damage to the new bearing 11 Expect More from the Experts Maximize the Life of Your Bearings For any machine to be safe reliable and productive proper bearing maintenance is an absolute must That s because bearings are used in and affect the performance of virtually all mechanical components You could cross your fingers and hope nothing ever goes wrong Or you could take a proactive approach by eliminating bearing problems before they begin with prevention and scheduled maintenance programs that will ultimately minimize repair costs and downtime And that s what you really want from any machine For more information see us today or visit our Web site at www cat com PEGJ0037 www cat com Printed in USA 2005 Caterpillar All Rights Reserved Caterpillar The difference counts Cat Dealers define world class product support We offer you the right parts and service solutions when and where you need them The Cat Dealer network of highly trained experts keeps your entire fleet up and running to maximize your equipment investment CATERPILLAR
10. ich leads to longer bearing life especially in high load slow speed applications 3 Contamination Contamination is any foreign substance that has the ability to damage a bearing Moisture dirt sand or any type of abrasive material will cause premature bearing breakdown It is important to be able to recognize symptoms of contamination such as scratching scoring brushing pitting grooving bruising matte or satin finish or rust Several causes of contamination involve debris manufactured into the system cracked housings or hoses dirt access through failed seals minute metal particles and contaminated lubricant Caterpillar s Solution When contamination is an issue Caterpillar offers debris resistant bearings These bearings utilize a combination of specialized material and heat treat to produce bearings that are extremely resilient to debris and contaminants in the oil 4 Distortion When the housing or shaft is out of round the bearing roller components are forced together where there is a minimum amount of clearance The heightened pressure can result in the race and other rolling elements to incur surface flaking something that typically happens with normal fatigue Caterpillar s Solution see Improper Fit 5 Misalignment To maximize bearing life the supporting seats and shoulders must meet manufacturer s specific limits If the misalignment is beyond those part
11. icular limits the load on the bearing will be intense on only a segment of the roller and races causing excessive stress and premature failure at that single point Caterpillar s Solution Caterpillar s specialized roller profile provides optimum load distribution across the bearing even when misalignment is present This serves to minimize stress in the bearing and maximize bearing life 6 Improper Fit Having proper bearing fit is essential to capitalizing on bearing performance and life A variety of improper fits can cause significant damage including forcing a bearing onto a shaft that is too large for the inside diameter of the bearing race fitting an outer race insecurely too loose in its housing and having a loose fit between the shaft and the inside bore of the bearing These inadequate fits can cause split races fretting corrosion and creep wear Caterpillar s Solution Caterpillar bearings are made with specialized tolerances for precise fit of the bearing to the shaft or housing and ensures exact positioning of related parts 7 Vibration Damage Anti friction bearings must roll while under a load Subsequently subjecting a bearing to vibration while it remains immobile can cause depressions on the race from fretting Caterpillar s Solution In Caterpillar bearings eliminating vibration is a prime factor in determining the type of bearing cage required Brass cages and nonmeta
12. inner surfaces and rolling components in a non separable bearing by shining a flashlight between the balls and rollers If you notice any pits scratches or surface damage replace the bearings Further scan the outer race for proper wear patterns such as wear tracks that are centered without pits or scratches If you do not visually notice any signs of wear or damage lightly lubricate the bearing and slowly turn the outer race Never spin it If a clicking or sticking is observed clean the bearing again If the condition still exists after cleaning you will need to replace the entire bearing A thrust bearing or tapered roller bearing can be tested the same way but place the bearing on a clean surface lightly apply hand pressure and turn the bearing If no signs of wear or damage are indicated and the bearing has low service hours it can be reused after cleaning However if the bearing has high service hours it is suggested to go with a replacement This is a precaution due to the fact that the bearing might possibly fail and destroy other critical systems Remember that many times it is challenging to determine if a bearing is reusable just by visually inspecting it Rolling contact stress fatigue originates beneath the surface and cannot be seen When choosing whether to replace or reuse a bearing consider the load application and the number of service hours In most situations it is more economical to repl
13. llic bearing cages are two types which minimize vibration and provide maximum life in harsh applications 8 Defects in Material Defects in antifriction bearings are particularly rare especially when it comes to the material forming machining heat treat grinding and assembly difficulties The minimization of defects is a result of the extreme cleanliness of bearing steals and stringent quality control measures used in manufacturing facilities that supply Caterpillar bearings Note that usually only a metallurgist can characterize these types of defects from other causes of premature failures Caterpillar s Solution Caterpillar bearings are manufactured to the highest material quality standards in the industry and will always provide for the optimum performance and component life of our machines 9 Improper Servicing Techniques k It is critical to always follow the manufacturer s recommendations summarized in your service manual Further this means using the proper tools Using inappropriate tools and procedures when removing installing and handling bearings can cause damage and possibly failure Caterpillar s Solution Always refer to your Cat equipment s Operation and Maintenance Manual and other service literature for proper procedures and servicing techniques 10 Electrical Current Bearings pass electrical currents that initiate an arcing and burning at the points of contact between t
14. r possibly include a different roller crown or cage design It is vital that you avoid using a standard bearing when a special bearing is specified Selecting the incorrect bearing will shorten the life and can create further damage If you correctly maintain your bearings they will not incur premature failure however they will eventually fail due to rolling contact stress fatigue A premature failure happens when bearings fail at low hours for causes beyond normal material fatigue If you identify any signs of possible bearing failure such as excessive noise and vibration excessive heat lubricant loss or shaft resistance to turning refer to the Trouble Shooting Antifriction Bearings chart This chart may help you and proper repair options If the recommended maintenance options do not correct the problem disassemble the bearing and try to recognize the cause again Keep in mind determining the cause is usually easier said than done A visual examination may identify the type of damage but it may not aid it recognizing what is causing the problem Take this situation for example if a bearing has scored and heat discoloration on the roller ends you know it is burned up and needs to be replaced Yet the cause could be linked to various factors such as insufficient or improper lubrication improper adjustment or any combination of these factors For this instance you should carefully investiga
15. t in use Further always use the correct type and amount of lubrication as this will play a key role in bearing wear life 1 Overloading Overloading is an especially common factor in premature bearing failure Overloading causes the oil to generate heat which affects the oil viscosity Heat will cause the oil viscosity to decrease and make the lube film thin allowing contact between the rolling components and raceway The contact can cause damage similar to the damage caused by insufficient lubrication Caterpillar s Solution Caterpillar bearings are designed as an integral part of the total machine system By always using genuine Cat parts you will ensure the integrity of those systems and provide high performance and long life especially under high load applications 2 Improper Lubrication As mentioned before proper lubrication is vital to high quality bearing performance and service life Insufficient lubrication allows for metal to metal contact of the major elements and especially of the roller end against the rib producing scoring in these areas Heat has the ability to turn various elements and roller ends dark blue or perhaps in extreme cases black Caterpillar s Solution In applications where inadequate lubrication is a concern Caterpillar uses a proprietary bearing technology called textured bearings Texturing allows for better oil retention on the contact surfaces wh
16. te the mounting installation and parts affecting the bearing operation to decipher the cause of the damage Remember if you merely replace the failed bearing without finding and fixing the root cause the replacement bearing will most likely endure the same wear and damage as the original determine the indicators causes PROBLEM INDICATORS CAUSES Insufficient lubrication Incorrect lubricant Defective bearing Dirt Corrosion Improper Load Misalignment Excessive Noise and Vibration Bearings fit too loose Improper mounting Excessive Insufficient lubrication Heat Incorrect lubricant Improper setting Misalignment Lubricant churning Spinning race Lubricant Too much grease Loss Improper lubricant Leakage through seal Shaft Resistant Incorrect lubricant to Turning Dirt Corrosion Improper setting Lack of lubrication Seal tight Bearing cocked Leakage between bearings caps and housing OPTIONS Fill with correct amount of proper lubricant Use recommended lubricant Replace bearing Replace bearing Replace bearing Use lubricant that resists corrosion Adjust to specification Determine what is misaligned housing shaft or bores Shaft may be bent or housing bores not aligned Replace shaft or housing Chrome plate or metalize shaft or bore and regrind to specification replace bearing if seating surfaces are worn Replace bearing Correct installation mounting problem Fill with correct
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