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1. Condition of chamfer Nicks burrs damage Consult the Failure Analysis section of the User s Manual 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 19 20 Helpful hints Do not use chisels impact wrenches and torches Do not use hammers directly on seals or bearings Bearings must be cleaned for inspection and re use Use only clean solvents effectiveness of solvent in removing old lubricant depends on how clean the solvent is Good cleaning requires proper equipment such as Solvent bath A filter system and regular changes of the solvent and the filters The importance of proper lubricants It is important to use the proper amount of lubricant when installing wheel end components If the proper amount of lubricant is not used the working combination of the bearings seals and brakes can create a heat sink ultimately damaging the working condition of the entire wheel end Do not use compressed air After cleaning dry with a clean paper towel or a clean rag Air jets cause small abrasive particles to become jammed in between the bearing surfaces Stay organized a messy shop is dangerous and inefficient Keep loose components together It is important to not mix wheel end components bearings are mates that wear together This includes new bearings 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 20 21 4 Running conditions
2. Poor compatibility with oils that have become oxidized and EP lube additives Tendency to tear and cut during installation Poor abrasion resistance Relatively high cost OPERATING RANGE Silicone seals can withstand a very wide temperature range from 100 to 325 F 73 to 163 C IDENTIFICATION Generally red or orange but sometimes gray or blue Silicone seals feel softer and are more flexible than other materials SUBSTITUTE LIP MATERIALS Fluoroelastomers polyacrylate or nitrile See Seal Substitutions page 53 Fluoroelastomers Viton Fluoroelastomers are recommended for use with special lubricants and chemicals which cannot be handled by nitrile polyacrylate or silicone They are compatible with oils chemicals fuels and lubricants over a broad range of temperatures that are too extreme for other sealing elements 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 47 48 Fluoroelastomers are available in standard line designs as well as large diameter seals One fluoroelastomer Viton is compatible with aliphatic and aromatic hydrocarbons carbon tetrachlorine benzene toluene xylene that are used as solvents for other rubbers Because of its compatibility with many different fluids over a broad temperature range Viton also is effective in aircraft and space equipment applications ADVANTAGES Wide temperature range Low swell characteristics Compatible with lubes additives and ch
3. Bearing Life SKF Lunar Hub TMC endplay 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 33 34 Procedure 1 Hub mating surface must be free of dirt burrs and radial score lines 2 Hub mating surface hubcap flange and gasket should not be greased or oiled 3 Always install and re install a hubcap with a new gasket 4 When using a Tamper Proof system with synthetic grease never fill hubcap with oil Bolt on hubcaps Lockwashers of the split conical or internal toothed design may be used in conjunction with the fastening bolts Do not use flat washers Thread all bolts loosely then tighten down bolts uniformly in a star pattern per the following recommended torque values TF Zytel Hubcap with embedded metal ring 12 16 lbs ft Stamped Steel Hubcaps 10 14 lbs ft Plaastic Hubcap with external metal ring 6 10 lbs ft Threaded hubcaps Lightly lubricate the threads of the hubcap and the O ring with the lubricant that is being retained Install the O ring onto the hubcap Install the hubcap assembly onto the hub Using an 8 point 4 13 16 opening x 4 1 4 high socket torque to the following recommended values Lexan 60 70 lbs ft Hubcap installation procedure 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 34 35 Oil fill Through center fill port Fill wheel end assembly through centerfill port with the specified grade of oil Wheel hub conf
4. Speedi Sleeves offer fleet operators a way to quickly repair worn shaft surfaces right in the garage Downtime is reduced since installation takes only a few minutes often without removing the shaft There is no resizing of the seal Unlike conventional thick sleeves Speedi Sleeves use the original size seal No matter whether the Speedi Sleeve is used on a crankshaft transmission or pinion both labor and hard parts inventory costs are substantially reduced Speedi Sleeves are precision made of ultra thin stainless steel Once installed it provides a new leakproof barrier and a long lasting wear surface for the new seal that can outlast the original shaft finish The Speedi Sleeve repairs damaged shafts efficiently fig 1 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 62 63 7 ADVANTAGES Corrects crankshaft pinion and transmission surfaces Repairs yokes flanges and shafts Can be used without changing the seal size or part number Requires little downtime Each sleeve is built with a removable flange and includes a special tool for installation This tool is placed over the Speedi Sleeve Both the tool and sleeve are tapped into position on the shaft yoke or flange The flange on the Speedi Sleeve allows the sleeve to be pulled on instead of pushed on eliminating sleeve distortion When the Speedi Sleeve is positioned the tool slides off easily The flange can be left intact or cut and peeled
5. b Bumper Lip Wear Pattern a b a b 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 79 80 CHAPTER 8 REVIEW To take this test simply place a card or sheet of paper under the first question After you ve read it and answered it to yourself slide the paper down below the next question The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 01 An alternating pattern of smooth and marked areas on the 0 D indicates that the seal was probably a pressed into an out of round over size bore b cocked during installation c flattened by normal wear d misaligned 1 A 02 If a seal is cocked it should be a replaced b straightened c ignored d lubricated 2 A 03 Improper wear can cause a shaft to leak as a result of a excessive STBM b excessive pressure c a cocked seal d all of the above 3 D 04 Pressure caused seal failures may be corrected by a opening air vents which may be plugged with dirt or paint b straightening the seal c reducing operating temperature d all of the above 4 A 05 If the seal lip is hardened and brittle with many cracks in its surface is probably the cause a pressure b e
6. 2 3 4 Press the seal into the bore evenly by hand Lightly lubricate the OD and ID with the fluid being reetained A rubber mallet may be used to tap into place This seal is hand installable No special tools are required Installation procedures Scotseal PlusXL Caution Do not install the Scotseal PlusXL directly onto the spindle Place the hub wheel assembly flat or at least a 45 angle for seal installation 1 Pre lube the inner bearing cone with the lubricant that is being retained and place it into the hub 2 Lightly lubricate the seal O D and I D evenly with the fluid that is being retained Also apply a thin layer of oil on the hub bore that the seal is being pressed into NEVER INSTALL DRY 3 Press the seal by hand evenly into the bore A rubber mallet or other soft faced tool may be used to gently tap the seal into place Be sure that the seal is evenly seated and bottomed in the bore As in any seal installation apply an even driving force to avoid cocking the seal or damaging the flange surface 4 Allow seal to set for about 5 minutes prior to installing hub assembly onto spindle Caution Install a new seal if the seal is cocked or damaged during or after installation Installation procedures Scotseal Classic Scotseal Longlife 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 28 29 4 The Scotseal Toolboard Keeps tools orderly and lessens chances of tools b
7. Road surface weather terrain speed and load Hardening or destruction of seal lip Lube on the brakes Higher temperatures Lube deterioration Hot running causes physical damage Lube leakage Inspection of lubricant Inspection of grease or oil can provide a clue to other problems Remove a sample from the wheel end and check for the following Presence of contaminants Burnt aroma Presence of water Prior to re installing bearings always check for the proper lubricant Wheel end lubricants are formulated to match the requirements of the truck and bearing manufacturer Always use specified lubricant Do not mix lubricants Chemical interaction between lubricants and seal materials can damage the seal Whenever possible use a grease packer Grease and oil lubricants The truck or trailer manufacturer has pre determined that the wheel end assembly is to be lubricated by grease or oil The importance of following the manufacturer s specifications cannot be over emphasized never change or mix grease and oil in the same assembly Always use lubricants as recommended by the manufacturer Grease lubricated wheel ends For proper lubrication the grease must be packed into the cavities between the rollers and cage of the bearing cone A mechanical grease packer is recommended in order to improve on the common procedure of filling the grease by hand Also apply a light film of grease
8. This book produced for use by SKF distributors and customers should prove of practical value to engineers fleet mechanics maintenance superintendents and anyone who can benefit from a thorough understanding of seals It will explain How to select the best seal for any given application How to improve performance with proper installation How to spot and correct seal problems with the least possible amount of time and money How to Use this Study Guide This self study guide is programmed to increase performance productivity Each chapter consists of a logical organization of material technical diagrams and a short quiz to help you retain what you study Start by carefully reading the text portion of each chapter Make notes or underline if you wish this can help you remember what you ve read It does not matter whether you are a fast or slow learner At the end of the program you will have learned the same information and should retain it as well as any other student The chapter quizzes are an important phase in self study learning since they are intended to reinforce the material covered The quiz questions are straightforward multiple choice and true false There are no trick questions Your answers can easily be checked within the context of the chapter Complete each review in order before going on to the next chapter If you are not sure of an answer to a question check back in
9. True False 8 F 9 Spring loaded seals designed to retain lubricants or keep pressure in the bearing cavity are known as exclusion seals True False 9 F 10 Retention seals stop dirt water and contaminants from entering the bearing cavity True False 10 F 11 Seal components include an outer shell inner shell sealing element primary lip and garter spring True False 11 T 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 10 11 3 CHAPTER 3 SCOTSEALS The Scotseal system In addition to the standard line of grease seals SKF has designed a complete oil bath sealing system Scotseal for trailer wheels tractor front and drive wheels and bus wheels Wheel ends go from grease to oil In the late 1950 s the trucking industry began to bathe wheel bearings in oil instead of packing them in grease But those early designs had a problem the sealing element was pressed into the wheel It turned with the wheel At high speeds centrifugal force would lift the sealing lip off the axle allowing oil to leak The solution was to use extra stiff leather with a heavy tension spring to combat centrifugal force But this added pressure wore grooves in the axle So a special ring was pressed over the axle For years this early design was the only one available Then SKF introduced the Self Contained Oil Type Seal Scotseal now known as Scotseal Classic fig 1 The c
10. to 3 16 Shafts more than 6 3 64 to 7 32 12 If clearance is needed the Speedi Sleeve flange can be removed easily with side cutters and pried away The flange will peel off along a pre cut line fig 5 7 Tap the tool until the sleeve is positioned properly fig 4 Peel off the flange along the pre cut line fig 5 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 65 66 To take this test simply place a card or sheet of paper under the first question After you ve read it and answered it to yourself slide the paper down below the next question The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 01 can cause a seal lip to groove the shaft a Dust heat and dirt b Lack of lubrication c A cocked seal d All of the above 1 D 02 The Speedi Sleeve is an ultra thin wear sleeve made of a bronze b stainless steel c zinc d magnesium 2 B 03 Applying a wear sleeve over a damaged surface can a eliminate shaft leaks b make the shaft usable again c smooth out damaged surfaces d all of the above 3 D 04 Speedi Sleeves can be used on a transmissions b pinions c front and rear crankshafts d all of the above 4 D
11. Self Study Guide_V3 12 1 06 9 50 AM Page 44 45 6 IDENTIFICATION Varies from gray black to shiny jet black SUBSTITUTE LIP MATERIALS Polyacrylate silicone or fluoroelastomer See Seal Substitutions page 53 Duratemp HNBR A special compound based on hydrogenated nitrile HNBR Duratemp offers improved tensile strength and resistance to heat abrasion hardening in hot oil ozone and weathering effects In some cases aerated oils can be a problem for HNBRs OPERATING RANGE Hydrogenated nitrile seals can be used from 40 to 300 F 40 to 149 C ADVANTAGES Tensile strength typically 50 higher than standard nitrile Ozone and UV resistance considerably improved Heat resistance increased 20 with less reduction in hardness and elongation especially in hot oil with additives Better abrasion resistance equal to Duralip LIMITATIONS Decreased elasticity at cold temperatures Lower compression set resistance at cold temperatures but better than Viton Should not be considered a universal replacement for Viton especially considering attack by aerated lubricants and high temperature physical properties such as compression set IDENTIFICATION Visually the same as standard nitrile SUBSTITUTE MATERIALS Polyacrylate Duralip and LongLife elastomers depending on the applications 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 45 46 Duralip Duralip is SKF s special nitrile compound for
12. Surface speed 2000 F P M MAX 5000 F P M MAX Temperature range 40 to 250 F 40 to 300 F 40 to 121 C 40 to 149 C Pressure 2 p s i 2 p s i Spindle finish 100 microinches MAX 100 microinches MAX Spindle hardness Rockwell C28 Rockwell C28 Spindle dia tolerances 0 003 Up to 4 000 0 003 Up to 4 000 0 004 4 001 to 6 000 0 004 4 001 to 6 000 0 005 6 001 to 10 000 0 005 6 001 to 10 000 Bore runout 0 015 TIR MAX 0 015 TIR MAX Spindle to bore 0 020 TIR MAX 0 020 TIR MAX misalignment Seal O D tolerances 0 004 0 004 Bore tolerances 0 015 From 0 015 From 3 001 to 7 000 3 001 to 7 000 0 002 7 001 to 12 000 0 002 7 001 to 12 000 Scotseal Classic fig 7 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 14 15 3 SKF TF Replacement Hubcaps The Scotseal TF Hubcap is fifty times stronger than aluminum Manufactured from DuPont Zytel Scotseal TF Hubcaps have been proven to withstand tough over the road conditions resisting chemicals road salt rocks and bumps The DuPont Zytel construc tion makes the TF Hubcap 1 1 2 pounds per axle lighter Additionally the tamper proof Scotseal TF Hubcap is specifically designed for use with today s synthetic grease packed systems The vented TF Hubcap is easily identifiable in the fleet and protected against accidental contamination
13. This design forms a full 360 seal against the hubcap surface to protect wheel ends from damaging road spray power washers and flooded docks Cloud free window is fusion bonded to body can t loosen or leak Lightweight DuPont Zytel material is 50 times stronger than aluminum Resists chemicals road salt rocks and bumps as well ass UV and ozone Proven vented plug design Elongated bolt holes accommodate multiple bolt circle patterrns Molded pressure ridge bites into sealing gasket to ensure leak proof fit Plated preassembled bbolts included provide positive leak protection at the bolt holes Gasket with slotted bolt holes Embeedded solid aluminum ring distributes lock down pressure evenly ensuring leak proof seal Magnet in fiill plug traps metal particles protecting seal and bearings Oil Bath Type Oil Bath Type Grease Packed Type TP 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 15 16 SKF LUNAR truck hubs Unlike conventional wheel ends with separately installed replaced and adjusted components SKF LUNAR hubs for Longlife Unitized No Assembly Required are fully integrated factory assembled units that are designed for extended trouble free operation Because they require virtually no maintenance for the life of the hub these units have become a popular original equipment choice on new steer drive and trailer axles As with all long life safety cr
14. affecting seal selection is temperature and fluid compatibility Handbook listings are given in 16 continuous ratings the relatively constant ambient temperature next to the seal or the temperature of the lubricant it retains When operating conditions are under 0 F 18 C or above 200 F 93 C the range recommended in the Handbook must be considered in selecting the type of sealing element material As was earlier stated SKF s standard nitrile compound provides good service in most sealing applications from 65 to 250 F 54 to 121 C However silicone polyacrylate or fluoroelastomers provide safer operating limits and are pre ferred with higher or lower temperatures Summary There are many factors involved in selecting seals To avoid confusion the SKF Handbook of Seals contains a Recommended Operating Conditions Selection Chart to assure a correct seal choice All of the selection factors are grouped together along with recommendations about the type of seal to use in almost every application 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 56 57 Oil Seal Installation Instructions 1 Check the bore The leading edge must be deburred A rounded comer or chamfer should be provided 2 Check the shaft Remove surface nicks burrs grooves and spiral machine marks machine lead 3 Check the shaft end Remove burrs or sharp edges The shaft end should be chamfered in application
15. assembly acts as a protective cover for the head of the sealing element and more importantly holds the installed seal in place fig 1 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 6 7 2 2 Inner Shell Case A rigid cup shaped component of a seal assembly which is placed inside the outer seal case It can function as a reinforcing member shield spring retainer or lip clamping device 3 Sealing Element The flexible elastomeric working component of a lip seal assembly which rides against the shaft 4 Primary Lip The flexible spring loaded elastomeric lip component of the sealing element which contacts the rotating surface 5 Secondary Lip Auxiliary Lip A short non spring loaded lip of the sealing element which is located at the outside seal face of a radial lip seal It is used to exclude contaminants 6 Garter Spring A coiled wire spring with its ends connected It is used for maintaining a sealing force between the sealing element and sealing surface How The Seal Works The following is a review of how the seal components work together to retain lubricants confine pressure exclude contaminants and separate liquids Retention Seals Seals designed to retain lubricants or keep normal operating pressure in the bearing cavity are known as retention seals Retention seals normally spring loaded are not recommended for more than light dirt exclusion Because of their specific function they r
16. design and material will consider the application in which it is to be placed including the lubrication media seal location external environment and the operating condition There are three categories of shaft seals used in the truck and bus market 1 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 3 4 Grease Seals Greases have a relatively high viscosity and are thus relatively easy to retain in the bearing arrangement The grease seal design usually includes a fairly lightly loaded spring Grease seals located on a truck or bus would also require the ability to exclude contaminants including dirt and water incorporating radial and or axial dirt lips Oil Seals Lubricating oils particularly relatively low viscosity oils are much more difficult to retain in a bearing arrangement than greases The seal design and material will be critical to oil retention Therefore spring loaded radial shaft seals are used almost exclusively For instance the patented Waveseal lip has a sinusoidally formed lip edge which produces a pumping action to the inside as well as outside irrespective of rotation direction Exclusion is often an important factor for oil seals and radial and axial dirt lips designed to exclude dirt and water are incorporated as well Scotseals SKF introduced Scotseals in the mid 1960 s as truck wheel lubrication moved from grease to oil bath The radial shaft seals used at that time did not adequately reta
17. it seals out a water b salt c dust d all of the above 2 D 3 The Scotseal design utilizes a a heavy duty dirt lip b secondary dirt lip c sealing lip d all of the above 3 D 4 With Scotseal Classic is reduced to zero a the chance of axle damage from the seal b the effect of centrifugal force on the sealing element c both of the above d neither of the above 4 C 5 The Scotseal Classic s O D is coated with which contains no abrasives or thinners a Viton b Bore Tite c engine oil d Lexan 5 B 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 17 18 6 With a Scotseal everything including the sealing element turns True False 6 F 7 The oil leaks suffered by the trucking industry of the late 1950 s occurred because centrifugal force lifted the sealing lip from the axle True False 7 T 8 Scotseal s sealing lip is both elastomeric and spring loaded True False 8 T 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 18 19 CHAPTER 4 SCOTSEAL REPLACEMENT 4 Faulty installation is one of the most common reasons a seal fails No matter how well made a seal is incorrect installation can make even a new seal worthless Good practice tips Our experience has shown that there are many causes of wheel end leakage beyond the oil seal If you look you will find that
18. of clean solvent fig 2 Let the bearings dry naturally in the air 3 Inspect bearing cones and cups Replace them if they are pitted rough or damaged 4 Dip clean bearings in a protective lubricant or coat bear ing surfaces with a light grease Wrap the bearings in waterproof paper and place them in a clean box or carton Keep bearings covered until you are ready to install the new seal fig 3 5 Inspect the spindle bearing and seal surface for burrs or roughness Be careful not to scratch the sealing surfaces when polishing out roughness Even small marks can permit lubricant to seep out under the sealing lip 6 Check where the seal lip makes contact If you can feel a worn groove with your fingernail there will be leakage even with a new seal see Speedi Sleeves Chapter 7 Replace the bearing spacer if it is grooved or worn Rinse the bearing in clean solvent fig 2 Store bearings in protective waterproof paper fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 39 40 Installation checklist 1 Check the bore The leading edge must be deburred A rounded corner or chamfer should be provided 2 Check the shaft Remove surface nicks burrs grooves and spiral machine marks machine lead 3 Check the shaft end Remove burrs or sharp edges The shaft end should be chamfered in applications where the shaft enters the seal against the sealing lip 4 Check splines and keyways Sharp edges should be cover
19. the chapter and review that portion again 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 2 3 CHAPTER 1 GENERAL SEALING Brief History of the Shaft Seal and Scotseals General Sealing Technology Radial shaft seals perform one and only one function an important one They protect bearings serving as a barrier Bearings are necessary to reduce friction between an object and the surface over which it is moved Bearings need to be continuously lubricated and bearing life declines rapidly in the absence of lubrication The seal plays a vital role in the bearing life as Henry Ford discovered with the Model T The greased wheels did not have an adequate system to retain grease and it was flung out as the wheels rotated creating a very dirty environment around the wheel and deprived the bearing of lubrication In 1926 SKF then Chicago Rawhide provided an industry changing product the oil seal coined The Perfect Oil Seal The radial shaft seals are designed to Retain lubricants or fluids Exclude contamination Confine pressure Separate fluids Seals are necessary for sealing in lubricants that are needed to protect the bearings and to seal out dirt water and other contaminants Seal designs and materials are constantly being developed tested and improved The testing is being done to conform with today s increased performance and durability requirements In the Heavy Truck and Bus market seal
20. the inside edge of the seal True False 32 F 6 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 61 62 CHAPTER 7 WEAR SLEEVES Continuous contact between a rotating shaft and a seal always causes shaft polishing friction Under normal operating conditions the friction causes a slight wear track on the shaft But as operating conditions worsen shaft wear can accelerate Heat dirt excessive speed lack of lubrication eccentricity or a cocked seal can produce a deep groove on the surface The ultimate result is a leak If this groove can be felt with a paper clip or with your finger nail it has become too deep to accommodate a replacement seal without leaking There are three solutions 1 Reworking or remetalizing the shaft surface at a machine shop High cost requires hours of fleet downtime 2 Replacing the shaft Also expensive with substantial fleet downtime 3 Installing a wear sleeve Comparatively low in cost with virtually no downtime When it comes to correcting yokes flanges and shafts a wear sleeve requires the least amount of downtime and cost Applied over the damaged shaft it makes the shaft usable again elimi nates shaft leaks and smooths out damaged surfaces all faster and less expensive than re metalizing or replacing the shaft SKF offers one special type of wear sleeve designed for even more efficient shaft repair Speedi Sleeves fig 1 Speedi Sleeves
21. the seal was not properly bottomed out or a centering tool was not used common causes of premature seal failure fig 3 Shiny leading edge Occasionally someone will try to improve seal installation by changing the shape of the seal They ll round off the leading edge of the outer cup on a grinder This distorts the outer diameter and can possibly cause the seal to disassemble fig 4 Outer cup damage If you see dents nicks or a bent casing you can bet that the seal was installed without the proper tool or the tool was damaged Gashes indicate the use of a sharp object like a screwdriver or punch fig 5 fig 1 fig 2 fig 3 fig 4 fig 5 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 72 73 8 External Inspection inner diameter I D wear If the I D of the packing is shiny or has axial scratches the seal has spun on the shaft That can be caused by not bottoming out the seal properly leaving it cocked in the bore or installing the wrong part number fig 6 Installed backwards The only way that the packing can be worn shiny as shown here is by rubbing against the bearing race The only way that can happen is by putting the seal in backwards The Scotseal installation poster makes a convenient guide fig 7 Severely damaged I D Scratches or dents in the I D are signs that the seal has struck the spindle or axle tube during installation Rushing the installation and no
22. 05 If the shaft is deeply scored the groove should be a filled with an epoxy type filler b filed down to a smooth surface c lubricated with oil d all of the above 5 A CHAPTER 7 REVIEW 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 66 67 7 06 The inside diameter of a pipe used to install a 4 Speedi Sleeve should be larger than the shaft a at least 1 2 b less than 1 2 c 1 32 3 16 d 3 4 6 C 07 When a seal groove on a shaft can be felt with a fingernail or paper clip it must be repaired True False 7 T 08 Shaft wear can accelerate as operating conditions worsen True False 8 T 09 Continuous contact between a seal and rotating shaft will always cause shaft polishing friction True False 9 T 10 A deeply scored shaft can only be corrected by remetalizing the surface or replacing the shaft True False 10 F 11 Installing a Speedi Sleeve is expensive and requires substantial downtime True False 11 F 12 The first step to Speedi Sleeve installation is removal of the shaft True False 12 F 13 The surface of the Speedi Sleeve can actually outlast the original shaft surface True False 13 T 14 When installing a Speedi Sleeve over a shaft the original size seal can still be used True False 14 T 15 Each Speedi Sleeve is built with a removable f
23. 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 29 30 Installing hub assembly DO NOT ATTEMPT TO INSTALL THE HUB ASSEMBLY BY HAND Whether the hub is with or without the tire do not install it without mechanical support 1 When installing the hub assembly over the axle spindle be sure to align the hub bore to the center of the spindle Mechanical supports will allow you to do this without scraping or otherwise damaging the spindle the threads and in particular the seal 2 Install the outer bearing cone and adjusting nut Tighten nut only until it is snug against the bearing cone DO NOT USE A PNEUMATIC TOOL during this part of the procedure Be sure to maintain support of the hub assembly until the adjusting nut is secure Failure to do so may cause damage to the seal and subsequent leakage of lubricant 3 Remove tthe hub support so that the hub is resting on the bearings Check for free rotation of the bearings Never allow hub to rest on seal 4 Follow wheel bearing adjustment as instructed on following page Axle spindle shaft 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 30 31 4 Wheel bearing and end play adjustment procedures STEP 1 Lubricate the wheel bearing with clean axle lubricant of the same type used in the axle sump orr hub assembly Note Never use an impact wrench when tightening or loosening lug nuts or bolts during thee procedure INITIAL INITIAL FINAL BACK OFF JAM NUT TO
24. M Page 59 60 13 is the seal s press fit diameter usually 004 to 008 larger than the bore a Shaft diameter b Seal outside diameter c Seal inside diameter d Bore diameter 13 B 14 The most popular and versatile sealing materials in use today are synthetics such as nitrites polyacrylates silicones and fluoroelastomers True False 14 T 15 Nitrite is the most popular material for the majority of sealing applications today True False 15 T 16 One of Vitons disadvantages is its poor resistance to temperature extremes True False 16 F 17 Polyacrylates are elastomers that work well with high operating temperatures and EP lubricants True False 17 T 18 Polyacrylates have high resistance to water True False 18 F 19 The lip of a Waveseal rides the shaft in a straight line pattern True False 19 F 20 The maximum speed at which a seal can operate depends on other operating conditions These conditions include a the design of the seal selected b the lubricant or fluid to be retained c pressure and temperature d all of the above 20 D 21 A thin wall coned assembly sleeve is recommended when a the shaft is not tapered b a keyway is discovered c a spline is present d all of the above 21 D 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 60 61 22 If the se
25. O Self Study Guide_V3 12 1 06 9 51 AM Page 81 NOTES 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 94 SKF is a registered trademark of the SKF Group SKF Group 2006 All rights reserved The contents of this publication are the copyright of the publisher and may not be reproduced even extracts unless permission is granted Every care has been taken to ensure the accuracy of the information contained in this publication but no liability can be accepted for any loss or damage whether direct indirect or consequential arising out of the use of the information contained herein SKF 890 North State Street Suite 200 Elgin Illinois 60123 1 800 882 0008 U S website www vsm skf com 1 866 832 6753 Canada website www skf com Printed in the U S A Form No 457935 Rev 11 06 TFO_Cover06 CVR 12 1 06 9 43 AM Page 1
26. Post installation tips When painting be sure to mask the seal Avoid getting paint on the lip or the shaft where the lip rides Also mask the vents so they will not become clogged If paint is to be baked or the mechanism otherwise subjected to heat the seals should not be heated to temperatures higher than their materials can tolerate In cleaning or testing do not subject seals to any fluids or pressures that could damage them Check the Compound Selection Chart in the SKF Handbook of Seals Catalog 457010 when in doubt Reassemble the wheel 1 Pack the hub cavity between the two bearing cups with an approved wheel bearing grease to the level of the cup s smallest diameter When using a semi fluid grease follow TMC RP631 and vehicle manufacturer s recommendation for proper fill procedure 2 Pack the bearing cones using a pressure packer if possible If not force the grease into the cavities between the rollers and cage by hand from the large end of the cone Coat the ends of the rollers freely with grease 3 Insert the inner bearing cone in the grease filled hub Place the pre lubed seal in the hub with the lip facing the bearing cone Seat it properly 4 Position the spacer on the spindle if present Align the hole and pin Apply a light film of lubricant to the spindle to prevent rusting 5 Use a wheel dolly to center the wheel assembly on the spindle Push the wheel on far enough so the seal is in safe cont
27. RQUE ACCEPTABLE ADJUSTING BACK OFF ADJUSTING END PLAY NUT TTORQUE NUT TORQUE AXLE TYPE THREADS FINAL NUT SIZE TORQUE PER INCH BACK OFF SPECIFICATIONS STEP 2 STEEP 3 STEP 4 STEP 5 STEP 6 STEP 7 STEP 8 12 1 6 TURN 18 1 4 TURN 14 1 2 TURN 18 12 DRIVE 1 4 TURN 16 12 TRRAILER 1 4 TURN 16 200 lb ft 271 N m WHILE ROTATING WHEELS 50 lb ft 68 N m WHILE ROTATING WHEELS STEER FRONT NON DRIIVE INSTALL COTTER PIN TO LOCK AXLE NUT IN POSITION 001 005 025mm 127mm AS MEASURED PER PROCEEDURE WITH DIAL INDICATOR WHEEL BEARING ADJUSTMENT PROCEDURE LESS THAN 2 5 8 66 7mm 2 5 8 66 7mm and over DOWEL TYPE WASHER TANG TYPE WASHER 200 300 lb ft 271 407 N m 300 400 lb ft 407 542 N m 300 400 lb ft 407 542 N m 200 275 lb ft 271 373 N m ONE FULL TURN If dowel pin and washer or washer tang and nut flat are not aligned remove the washer turn it over aand reinstall If required loosen the inner adjusting nut just enough for alignment Bendable type wwasher lock only Secure nuts by bending one wheel nut washer tang over the inner and outer nut Bend the ttangs over the closest flat perpendicular to the hang Printed with permission of the TMC Reference RP618 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 31 32 Wheel bearing end play is the free moveme
28. Shaft Seals A self study guide for improved technician knowledge and fleet efficiency TFO_Cover06 CVR 12 1 06 9 43 AM Page 2 1 TABLE OF CONTENTS Introduction 2 Chapter 1 General sealing 3 Brief history 3 Sealing materials 4 Chapter 2 Shaft seals 6 Seal design components 6 How the seal works 7 Retention Exclusion 8 Review 9 Chapter 3 Scotseals 11 The Scotseal system 11 Scotseal construction 12 SKF TF Replacement Hubcaps 15 SKF Lunar Hubs 16 Review 17 Chapter 4 Scotseal replacement 19 Good practice tips 19 Lubricants 21 Seal replacement 22 Wheel end disassembly assembly 24 Bearing and seal installation 27 Scotseal installation procedures 28 Wheel bearing end play adjustments 31 Wheel
29. a sealing element packing that is assembled between a metal outer and inner case The packing consists of three sealing lips a spring loaded primary sealing lip that is factory pre lubed a dirt exclusion lip and an outer bumper lip that acts as a preliminary dirt excluder The seal is pressfit into the hub bore using Scotseal Installation Tools The Scotseal Classic maintains a metal to metal contact between the seal O D and the hub bore surface as well as a metal to metal contact between the packing I D and the spindle See fig 4 A Scotseal for Every Application With the dated two piece seals fleet operators must buy two parts per wheel and inventory two parts per wheel Installation is more complicated time consuming and costly Scotseal covers more than 300 applications with half as many numbers Scotseal PlusXL The Scotseal PlusXL design fig 5 with extended life capabilities is the premium performance seal from SKF offering maximum sealing life under virtually all driving conditions The new high temperature synthetic lubricant friendly material of the new Scotseal PlusXL Hydrogenated Nitrile Butadiene Rubber HNBR is an excellent choice for frequent braking applications HNBR elastomeric material provides heat resistance up to 300 F and broad compatibility with today s synthetic lubrication fluids The unsurpassed exclusion properties allow the Scotseal PlusXL to perform in very harsh conditions The new Scot
30. act with its riding surface on the bearing spacer or spindle Install the outer bearing cone washer and adjusting nut in reverse order of removal 6 Adjust the bearing according to the TMC RP found in Chapter 4 Secure the locking nut and locking device Position the new gasket on the hub cap and install 7 For oil bath seal replacement see Scotseal Replacement Chapter 4 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 41 42 To take this test simply place a card or sheet of paper under the first question After you ve read it and answered it to yourself slide the paper down below the next question The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 01 An old seal should be replaced whenever a it has been nicked b some of the press fit in the hub is lost c it has been bent d the wheel is pulled from the vehicle 1 D 02 Reusing an old seal can cause failure of the a wheel b brake lining c bearing d any of the above 2 D 03 can damage the bearing cage a Prying out the old seal with a rolling head pry bar b Driving the bearing and seal out with a drift c Removing the inner bearing cone d All of the above 3 B 04 Bearing cones and cups should be
31. al has no identification numbers you should average three measurements of the a seal width b seal bore c lip inside diameter d any of the above 22 C 23 A common reason for seal failure is that it is not the right seal for the application in the first place True False 23 T 24 If there is no seal listed in the exact same width in the SKF Handbook of Seals a narrower width seal may be used True False 24 T 25 Substitutions should be used only when immediate use is more important than the assurance of maximum seal life True False 25 T 26 Using a seal with a premium elastomer lip will always do a better job than a less expensive material True False 26 F 27 Seal bore is the diameter of the hole into which the seal will be fitted True False 27 T 28 Seal width is the width of the inner shell only True False 28 F 29 The outside diameter can be measured by taking one reading around the seal True False 29 F 30 If the actual shaft diameter is unknown you can estimate the shaft diameter by measuring the seal s outside dimensions True False 30 F 31 Use a sleeve type or hollow fitting tool when installing a seal into the housing bore of a pinion with the shaft already inserted True False 31 T 32 Seals are press fitted in transmissions by applying force as close as possible to
32. angle before final setting Oil lubricated wheel ends Coat the bearing cones with a light oil film before inserting them into the bearing cups Always use the specified oil for replacement and do not mix lubricants Installation force Scotseal installation tool Inner bearing cone Hub Seal Seal must bottom in bore Inner bearing cup 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 27 28 Caution Do not install the Scotseal directly onto the spindle Place the hub wheel assembly against a solid surface or bench at a 45 angle for seal installation This aids in centering the bearing and seal in the hub bore Clean bore of any particles rust or grease 1 Pre lube the inner bearing cone with the lubricant that is being retained and place it into the hub 2 Place the Scotseal Classic or Scotseal Longlife into the hub bore and insert the tool assembly with centering plug into the seal Note Be sure to wear proper eye protection 3 Hold the tool handle firmly and straight and drive the seal with firm hammer strokes until the seal is squarely seated Continue driving the seal into the hub until the sound of impact changes 4 After the seal is bottomed in the bore check for freedom of movement by manually moving the packing of the seal up and down Ensure that the inner bearing rotates freely Caution Install a new seal if the seal is cocked or damaged during or after installation 1
33. arely face toward dirt or heavy contaminants Exclusion Seals These seals prevent dirt water and contaminants from entering the bearing assembly There is a wide variety of exclusion seals Some have a single lip and no spring reinforcement With others the lip action is at the outside diameter of the seal Still others were created especially for mud applications Exclusion seals with lips pointing outward can be kept lubricated and clear of dirt by purging forcing grease through them 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 7 8 Retention Exclusion Many applications require the seal to perform both the retention and exclusion functions at the same time For example the seal may need to confine a lubricant as well as exclude road dust mud water or other highway contaminants For applications that require both lube retention and dirt exclusion a special type of protection is needed either a combination of two seals or dual sealing elements within one assembly The kind of seal grease vs oil bath for example depends on the location and function of the seal Wheel or axle seals are either grease seals or oil bath seals Scotseal Self Contained Oil Type Seals 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 8 9 2 To take this test simply place a card or sheet of paper under the first question After you ve read it and answered it to yourself slide the paper down below the next q
34. ature range d all of the above 5 D 6 Seals made of fluoroelastomers a are inexpensive b sometimes require special molds c lack wide temperature range resistance d are compatible with aggressive oil 6 D 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 58 59 7 Felt is a non synthetic material which has long been used as a sealing material Its advantages include a excellent water resistance b good exclusion of dust and dirt c tends to smooth rough shaft surfaces d good oil retention 7 B 08 Using a Waveseal produces significant results which include a less heat produced b less shaft wear c better lip lubrication d all of the above 8 D 9 A replacement seal manufactured by SKF is identified by a an SKF stock number b an SKF drawing number c the original equipment manufacturer s part number d any of the above 9 D 10 Choosing the right seal for an application depends on a seal dimensions b speed and pressure c temperature d all of the above 10 D 11 A substitute material for silicone is a felt b leather c nitrile d none of the above 11 C 12 Nitrile seals will have shortened lifespans if the operating temperature is 250 F a below b above c at d none of the above 12 B 6 2604293 TFO Self Study Guide_V3 12 1 06 9 50 A
35. ause could be excessive end play or a cocked seal Or internal pressure from a blocked vent fig 3 Normal lip flexibility Check the primary sealing lip and dirt lips by pressing downward on them with your thumbs sliding them around the entire circumference The rubber should remain soft and flexible in normal use fig 4 Cracked lips If when you check the primary and dirt lips the lip feels rough and dry it has probably been subjected to excessive heat Loss of lubrication is one of the prime suspects fig 5 Flattened bumper lip Scale or rust on the spindle will prevent the wider Scotseal PlusXL from sealing properly This creates extra pressure on the bumper and axial dirt lips The spindle must be fully cleaned and all wear rings removed before installing a Scotseal PlusXL fig 6 fig 1 fig 2 fig 3 fig 4 fig 5 fig 6 Factory Applied Grease 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 77 78 a Primary Lip Wear Pattern b Radial Dirt Lip Wear Pattern a b a b a b External inspection primary and radial dirt lip wear patterns Good primary lip pattern You should see two parallel lines The primary lip line is slightly wider than the radial lip marking because it s an SKF Waveseal design fig 1 Wide wide If both of the tracks formed by the primary and dirt lips are wide chances are the whole wheel assembly is moving in a
36. bearing end play verification 32 Hubcap installation procedure 34 Review 36 Chapter 5 Wheel end grease seals 38 Seal installation 38 Cleaning and inspection 39 Wheel re assembly 41 Review 42 Chapter 6 Non wheel end seals 44 Synthetics 44 Other synthetics 48 Wave seals 50 Seal selection 51 Oil seal installation 57 Review 58 Chapter 7 Wear Sleeves 62 SKF Speedi Sleeves 62 Speedi Sleeve installation 64 Review 66 Chapter 8 Troubleshooting shaft seals and Scotseals 68 Shaft seals 68 Scotseal failure analysis 71 Review 80 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 1 2 INTRODUCTION
37. bricant absorbency DISADVANTAGES Cannot confine light oils May trap metal particles causing shaft wear Absorbs water which may cause shaft rusting OPERATING RANGE 65 F to 200 F SUBSTITUTE LIP MATERIALS Nitrile polyacrylate or fluoroelastomer See Seal Substitutions page 53 Compound Selection Chart The compatibility of sealing element materials with most fluids currently used can be found in the Compound Selection Chart in the SKF Handbook of Seals Catalog 457010 This chart rates the operation of different sealing materials minor effect moderate effect static only not recommended insufficient data within the range of specified operating temperatures and conditions for most common lubricants fresh or salt water and fluids Sealing Lip Performance Following is a description of the lip itself and how it works In this example the Waveseal will be used The Waveseal SKF s preferred design provides at least 30 more service life than other radial lip seals A number of the toughest fleet applications specify this design to assure top performance and increased service life 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 49 50 Waveseals The SKF Waveseal features a sealing process utilizing hydrodynamics that is completely different from that of conventional seals In technical terms the Waveseal is a smooth lip birotational hydrodynamic radial lip seal More simply it is a sha
38. can suspect high STBM shaft to bore misalignment unless 0 D markings indicated the seal was cocked The lip area with the greatest wear indicates the direction of shaft misalignment Initial leakage will generally occur in the area that shows little or no seal wear This is because of inadequate lip contact But as the worn side is hardened from excess pressure and heat it may crack and cause additional leakage The solution Check the shaft to bore alignment Correct the alignment Operating pressure Excess pressure can crush the lip against the shaft Heavy friction will eventually force the garter spring through the lip Excess pressure can blow the lip completely off fig 3 The solution We recommend two ways to prevent seal failure caused by medium pressure First check all the air vents Dirt or paint may block proper air flow Second if the system is clean try using a high pressure seal such as the CRW5 and CRWA5 Excess pressure can blow the lip off fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 69 70 Excessive temperature The condition of the sealing element can also tell us about temperature conditions If the lip is hardened and brittle with many cracks in its surface overheating is probably the cause fig 4 A seal lip gradually hardens as it ages but it should remain flexible if temperatures do not exceed the recommended maximums for the sealing material Sometimes heat is
39. ccentricity c overheating d a cocked seal 5 C 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 80 81 06 Disulfide additives a give lubricants anti wear properties b can harden the sealing element c both of the above d neither of the above 6 C 07 Many seal failures can be traced back to the condition of the shaft or bore or to poor installation True False 7 T 08 The first surface to check for wear patterns or markings is the inside diameter I D of the seal True False 8 F 09 Improper installation can cause the seal to leak True False 9 T 10 If the lip of the seal wears away during normal operation less lubrication is required by the seal True False 10 F 11 If a leaking seal has a wide wear band on one side and a narrow band on the other high STBM can be suspected True False 11 T 12 Heavy friction caused by excess pressure will eventually force the garter spring through the lip True False 12 T 13 If a sealing lip is hardened and brittle with cracks in the surface the cause is probably excessive temperature True False 13 T 14 Chemicals that are used to improve a lubricant s performance will not spoil a seal True False 14 F 15 A small cut or nick on the sealing lip has no damaging effect on a good seal True False 15 F 8 2604293 TF
40. contacts a wider area of shaft than conventional seals fig 1 Viton is a registered trademark of E I DuPont 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 50 51 6 Seal selection Other than faulty installation the most common reason a seal fails is that it is not the correct seal for the application It is very important to check the old seal and replace it with one that is correct for the application Replacement seals If the old seal being replaced was manufactured by SKF it should have one of four identifying numbers 1 an SKF or Chicago Rawhide stock number 2 an older SKF industrial part number 3 an SKF drawing number 4 the original equipment manufacturer s part number The SKF Master Interchange Catalog 457012 lists the SKF stock numbers that correspond to nearly 150 000 shaft seals in use today The simplest method of replacement is to use the number of the old seal If this number is unreadable or unavailable a replacement can be selected by matching sizes with listings in the SKF Handbook of Seals Catalog 457010 If there is no seal listed in exactly the same width a narrower width is usually the best choice A wider width is perfectly acceptable if space permits however it is often limited Most often replaced seals tractors trucks trailers and buses fig 2 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 51 52 Other applications Installation procedures for transm
41. ed with a lubricated assembly sleeve shim stock or tape to protect the seal lip 5 Check dimenssions Be sure shaft and bore diameters match those specified for the seal selected 6 Check for parts interference Watch out for other machine parts that might rub against the seal and cause friction and damaging heat 7 Check the seal Damage may have occurred prior to installation A sealing lip that is turned back cut or otherwise damaged should be replaced 8 Check seal direction Make sure that the new seal faces in the same direction as the original one Generally the lip faces the lubricant or fluid to be retained 9 Use the correct insstallation tool Press fitting tools should have an outside diameter approximately 010 smaller than the bore size For best results the center of the tool should be open so that pressure is applied only at the outer edge of the seal fig 4 10 Pre lubricate the sealing element Before installation wipe the element with the lubricant being retained 11 Never hammer directly on the surface of the sseal Use proper driving force such as a soft face tool arbor press or soft workpiece wood Apply force evenly around the outer edge to avoid cocking the seal 12 Position the seal properly in the housing and inspect for alignment and installation damage The press fitting tool should be 010 less than the bore I D fig 4 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 40 41 5
42. eel end temperatures and is compatible with synthetic lubricants Scotseal Construction Scotseal PlusXL is a rubber unitized one piece design The Scotseal PlusXL consists of four sealing lips a spring loaded primary sealing lip with patented Waveseal design that is factory pre lubed a radial and axial dirt lip plus an outer bumper lip that acts as a preliminary dirt excluder Scotseal PlusXL requires no special installation tools and maintains a rubber to metal contact between the seal O D and the hub bore surface as well as a rubber to metal contact between the packing I D and spindle See fig 2 Scotseal Longlife is a unitized one piece design consisting of a sealing element packing that is assembled between a metal outer and inner case The Scotseal Longlife s packing consists of four sealing lips a spring loaded primary sealing lip that is factory pre lubed a radial and axial dirt lip plus an outer bumper lip that acts as a preliminary dirt excluder The Scotseal Longlife is pressfit into the hub bore using Scotseal Installation Tools The Scotseal Longlife maintains a metal to metal contact between the seal O D and the hub bore surface as well as a metal to metal contact between the packing I D and the spindle See fig 3 Scotseal PlusXL fig 2 Scotseal Longlife fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 12 Scotseal Classic is a unitized one piece design consisting of
43. eing misplaced or damaged Sturdy metal construction mounts easily on shop wall Fitting chart included Just order Part No TB 1 Installation tooling Scotseal Classic Scotseal Longlife BEARING CONE NO 495AX 497 539 555S 557A 559 560 567 568 575 580 582 593 594 594A 595 596 598 598A 639 641 659 663 663A 664 665 665A 68lA 683 687 CENTERING PLUG NO 708 711 701 702 703 704 706 707 731 708 710 710 712 715 715 710 711 714 714 704 706 708 710 710 732 711 711 714 715 718 BEARING CONE NO 749 749A 749S 756A 758 759 760 776 780 3778 3982 3984 4595 5557 5760 6379 6386 6386A 6389 6461 6461A 6559 6580 28995 33281 33287 33895 39578 39580 39581 CENTERING PLUG NO 719 710 719 709 711 712 717 715 718 730 704 706 701 721 708 705 706 706 706 708 708 710 712 703 716 707 701 701 702 702 BEARING CONE NO 39585 42688 45284 45285 47678 47685 47686 47687 52400 52401 JH217249 JM205149 A JM207049 A JM511946 JM716649 JM718149 JM719149 HM212044 HM212046 HM212047 HM212049 X HM212049 HM215249 HM218248 HM516449 HM518445 H715345 CENTERING PLUG NO 704 708 700 700 708 710 710 710 718 718 719 722 723 724 719 713 733 703 704 704 706 706 707 713 710 712 716 Chart B MATCHUP OF BEARING CONES amp CENTERING PLUGS Tool selection SKF Scotseal Classic and Scot
44. emicals that destroy other synthetic materials Less downtime Extreme abrasion resistance DISADVANTAGES Relatively high cost OPERATING RANGE 40 to 400 F 40 to 204 C IDENTIFICATION Brown to black may also be blue or green SUBSTITUTE LIP MATERIALS See Seal Substitutions page 53 Other Synthetics In addition to these standard materials SKF can supply seals with elements molded of other materials for special conditions ADVANTAGES Excludes dirt and dust well Retains grease efficiently High lubricant absorbency DISADVANTAGES Cannot confine light oils May trap metal particles causing shaft wear Absorbs water which may cause shaft rusting OPERATING RANGE 65 to 200 F 54 to 93 C SUBSTITUTE LIP MATERIALS Nitrile polyacrylate or fluoroelastomer See Seal Substitutions page 53 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 48 49 6 Felt Felt is another non synthetic material which has long been used as a sealing material Made of wool and sometimes laminated with synthetic rubber washers felt is generally limited to light dirt exclusion However it effectively retains heavy lubricants such as wheel bearing grease and performs well in sparsely lubricated applications under some conditions such as small electric motors Felt washers are available only in limited sizes ADVANTAGES Excludes dirt and dust well Retains grease efficiently High lu
45. es Improper installation Wrong or no tool used Cocked installation Lubricant contamination Metal flakes Dirt or water Mixing of lube types Scotseal Longlife Scotseal Classic Scotseal PlusXL Consult the following pages for examples of Failure Analysis Improper bearing adjustment Seal spinning on spindle Damaged spindle Hub imperfections Installed over a wear ring 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 71 72 Scotseal Classic Scotseal Longlife External inspection outer diameter Normal scuffing The surface will show some scraped areas that s normal But signs of nicks scratches metal particles or any foreign material are warning flags that something else is amiss Make sure the hub bore is smooth and free of burrs or nicks fig 1 O D radial grooves If the Bore Tite film has been scored all the way across the width of the seal you should inspect the hub for burrs or damage Before installation the hub should be inspected and cleaned with emery cloth or a fine file fig 2 If you see lines around the seal several things could have happened If the lines are etched to the metal the seal could have spun as a result of being the wrong application or more likely it was installed crooked or cocked As you can see in this example the grooves run from high on the right to low on the left indicating a cocked installation Most likely
46. extreme abrasion resistance It is recommended where scale sand grit dirt or other highly abrasive materials are present ADVANTAGES Extreme abrasion resistance See nitrile DISADVANTAGES See nitrile OPERATING RANGE See nitrile IDENTIFICATION See nitrile SUBSTITUTE LIP MATERIALS See nitrile Polyacrylates Polyacrylates are elastomers that are compatible with higher operating temperatures as well as extreme pressure EP lubricants They are available in most general purpose designs ADVANTAGES Good compatibility with most oils including EP lubricants High resistance to oxidation and ozone Better compatibility with higher operating temperatures than nitrile DISADVANTAGES Low compatibility with water and some industrial fluids Poor compression set characteristics OPERATING RANGE Seals with polyacrylate lips are effective in temperatures ranging from 40 to 300 F 40 to 149 C 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 46 47 6 IDENTIFICATION Generally black with same appearance as nitrile SUBSTITUTE MATERIALS Nitrile silicone or fluoroelastomer See Seal Substitutions page 53 Silicone Silicone s high lubricant absorbency minimizes friction and wear It can be used in a wide range of temperatures Silicone seals are made only in bonded designs ADVANTAGES High lubricant absorbency Very flexible Wide temperature range DISADVANTAGES
47. ft seal that pumps lubricant back into the sump while sealing out contaminants no matter which way the shaft is turning SKF s Scotseal PlusXL utilizes the patented waveseal design This unique design continuously sweeps oil back to the bearings keeping them running longer and stronger In terms of shaft and seal wear the SKF Waveseal is important to truck operators because It offers more dependable performance and up to 30 longer service life than conventional seals It is the first standard line of shaft seals utilizing hydrodynamics Waveseals vs Conventional seals In Chapter 2 the operation of a conventional shaft seal was explained The Waveseal is completely different The lip of a conventional seal rides the shaft in a narrow straight line The Waveseal has a much broader contact fig 1 When the Waveseal s specially molded lip contacts the shaft it forms a sine wave snakelike pattern that moves back and forth on the shaft surface The results are significant Using a Waveseal produces less heat provides better lubrication and reduces shaft wear It also lasts longer Since the Waveseal does not depend on externally molded patterns it does not lose pumping power as it wears Compared to conventional seals Waveseals Generate 25 35 less heat at contact Produce 20 less frictional torque or drag Pump fluids back into the sump and ingest substantially less contaminants The SKF Waveseal
48. hance of axle damage from the seal and the effect of centrifugal force on the sealing element are both reduced to zero Early oil seals had only one leather sealing lip That single lip had to perform the dual function of sealing oil in and sealing dirt out Later designs offered a special axle ring to assist in blocking dirt But still they had just one sealing point Scotseal s design eliminates the problem by incorporating a heavy duty dirt lip and a secondary dirt lip in addition to the sealing lip The design is so efficient it will seal out dust dirt water and salt Scotseal Classic design fig 1 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 11 12 Scotseal Family of Wheel Seals The Scotseal family of seals features three product variations that are suited to your particular preference application and environment The entire Scotseal family offers you the right seal ing solution for every kind of wheel end maintenance The brand recognition along with the outstanding quality and value insures that you are installing the optimum seal for your operation The Scotseal Classic has become the trucking industry standard and best value for more than 30 years The Scotseal Longlife provides you with an extended life seal with superior tolerance to higher wheel end temperatures and is compatible with synthetic lubricants The Scotseal PlusXL provides you with an extended life seal with superior tolerance to higher wh
49. high enough to break down the oil but not hot enough to harden the lip In this case sludge accumulates and is deposited on the seal lip The solution When a sludge deposit cracks or breaks off leakage paths are created A change in seal material or design will do little to improve sealing performance Instead find a lubricant that is more stable at high temperatures Either that or try to reduce the operating temperature Incorrect lubricant A modern lubricant may employ many chemicals to improve its performance Unfortunately additives that improve the lube may adversely affect the seal Disulfide additives for example give lubricants anti wear properties but they also cure or harden the sealing element Many EP extreme pressure lubes have additives that become more active as they heat up They also become more harmful to the seal The solution When the sealing member softens with use or when there is not sufficient overheating to explain the hardening you observe the problem could be that the lubricant and seal are incompatible The remedy is to go back to the SKF Handbook of Seals 457010 and check seal material fluid compatibility specifications Case still unsolved If none of the clues discussed so far are present there still are a few things that you can do Check for foreign particles that may be temporarily trapped under the lip If it s a spring loaded seal check to see if the garter spring is s
50. if they are pitted or damaged a lubricated b replaced c rotated d all of the above 4 B 05 A light film of prevents rusting on the spindle a SKF Bore Tite b lubricant c wax paper d powdered metal epoxy type filler 5 B 06 The press fitting tool used in installation should be the bore I D a 010 less than b 010 more than c 025 less than d equal to 6 A CHAPTER 5 REVIEW 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 42 43 5 07 Edges of the keyway and spline should be covered with a straight mineral oil b lubricated assembly sleeve c ordinary engine oil d SKF Bore Tite 7 B 08 When you pull the wheel change the seal True False 8 T 9 It is unnecessary to check the old seal for damage before dumping it True False 9 F 10 Small scratches on the shaft can allow some lubricant to seep under the sealing lip True False 10 T 11 Replace bearing cups and cones if they are pitted rough or damaged True False 11 T 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 43 44 CHAPTER 6 NON WHEEL END SEALS SKF seals have the lip material bonded to the metal shell case The bonding prevents leakage between the sealing lip and the shell and it provides a longer lasting more effective seal This is different from the process used for assembled seals
51. igurations vary allowing different amounts of oil to be added depending on design Allow for the oil to seep through the outer bearing and fill the hub cavity Continue to add oil until the oil reaches the oil level fill line as indicated on the hubcap Install center fill hubcap plug Through side fill port Fill wheel end assembly through side fill port with the specified grade of oil Wheel hub configurations vary allowing different amounts of oil to be added depending on design Allow for the oil to seep through the outer bearing and fill the hub cavity During this fill operation DO NOT ALLOW THE OIL TO GO ABOVE THE CENTERLINE OR WEEP HOLE This may result in a weeping condition that may be perceived as a leaking hubcap Continue to add oil until the oil reaches the oil level line as indicated on the hubcap Install side fill hubcap plug per the following recommended torque values 3 8 18 NPT Pipe Plug 100 140 lbss in 3 4 16 UNF Zytel Side Fill Plug 15 25 lbs in Clean up any overspills that would give the appearance of a leaky hubcap Grease fill See TMC RP631 Recommendations for Wheel End Lubrication and the vehicle manufacturer s recommendation for proper fill procedure 4 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 35 36 CHAPTER 4 REVIEW To take this test simply place a card or sheet of paper under the first question After you ve read it and answered i
52. in the new oils used to lubricate the bearings Then SKF changed the industry again with the Scotseal Self Contained Oil Type a unitized seal design that retained the oil lubrication in the bearings and excluded water and dirt road contaminants Sealing Materials Seal design is only part of the solution Seals are manufac tured from a wide variety of elastomers determined by the operating conditions The elastomers used by SKF in heavy truck include Nitriles Hydrogenated Nitrile and Viton The temperature and wear capabilities for each are listed below 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 4 5 Operating Temperatures The operating temperature capabilities for each of these materials are listed to the right fig 1A amp 1B Wear Resistance The wear resistance capabilities for each of these are listed to the right fig 2 Chemical Resistance The chemical resistance of the seal material is an important factor to be considered when selecting a seal particularly with today s harsh synthetic fluids used in heavy truck and bus wheel ends The chemical resistance of seals is also influenced by temperature as well as pressure and the amount of media present Because of the complex relationships existing between the individual factors it is not possible to give universally valid data regarding the chemical resistance of a particular material However the Scotseal PlusXL and Scotseal Longlife are designed
53. in which assembly pressure is used to hold the lip in place between the metal parts A wide variety of sealing element lip materials is available Each has its own unique characteristics Selection should be made on the basis of application compatibility with lubricants and fluids being retained operating temperatures and other conditions Synthetics Today the most popular and widely used sealing materials are synthetics These include nitriles polyacrylates silicones and fluoroelastomers Viton Each material has its own advantages and disadvantages Nitrile Nitrile is the most popular material for the major applications today It is actually a mixture of two basic synthetic rubbers Buna and acrylonitrile polymers Different properties are obtained by changing the percentage of each polymer used in the mixture or copolymer Nitrile has generally replaced leather as a sealing lip material ADVANTAGES Good oil grease compatibility Abrasion resistance Good low temperature and swell characteristics Good manufacturing qualities Relatively low in cost DISADVANTAGES Lacks compatibility with synthetic oils such as phosphate ester and Skydrol Not recommended with EP lubes at elevated temperatures OPERATING RANGE Standard SKF seals with nitrile sealing lips are effective in applications involving most mineral oils and greases in temperatures ranging from 40 to 250 F 40 to 121 C 2604293 TFO
54. ing the seal to leak fig 9 Cocked seal inner markings Holding the outer cup just below eye level and flat like a bowl rotate your wrist through 360 If the seal has run cocked the two lines will be parallel to each other but they appear to move closer and then farther from the outer cup flange fig 10 fig 7 fig 8 fig 9 fig 10 a Primary Lip Wear Pattern b Dirt Lip Wear Pattern c Contamination Being Excluded a b a b c a Primary Lip Wear Pattern b Dirt Lip Wear Pattern 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 75 76 Scotseal PlusXL External inspection checking the beads Normal exterior The tough HNBR material covering on the Scotseal PlusXL doesn t supply clues as readily as Bore Tite does But it can still reveal problems and lead to corrective measures There should be lubrication residue in each of the O D I D beads fig 1 Dry exterior If in good illumination you cannot see any residual lubrication between the beads of the outer sleeve the seal may have been installed dry A Scotseal PlusXL does not need special tools but it does need lubrication for proper installation fig 2 Damaged O D beads If the external ridges appear damaged most likely someone has tried to force the seal in place without proper lubrication Burrs or dirt in the bore can also cause problems but they re not as visible with the thick HNBR
55. issions pinions prop shafts timing covers and other fleet seal applications are somewhat similar but with these precautions Seals should be press fitted with a press fitting tool and installation force should be applied as closely as possible to the outside edge of the seal If a seal is installed into the housing bore with the shaft already installed a sleeve type or hollow fitting tool should be used to protect the lip as it is fitted over the shaft Seals have flexible sealing members smaller than the shafts on which they function When the shaft is assembled through the back of the seal no special precautions are necessary other than removing nicks burrs and other rough spots from the shaft The shaft end should be chamfered when it enters the seal against its lip If the shaft is not tapered or if a keyway or spline is present a thin wall coned assembly is recommended Sharp spline and keyway edges should be covered with a lubricated assembly sleeve shim stock or tape to protect the seal lip fig 3 A coned assembly sleeve may be used to protect the seal lip fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 52 53 6 Seal substitutions The SKF Handbook of Seals 457010 lists different seal designs which can be substituted for the old seal within the limits of the operating conditions Seal materials and proper substitutes were discussed throughout this chapter Because of the im
56. itical components these units still require regular inspection Refer to the truck or trailer manufacturer for specific inspection intervals and procedures Greater wheel end stability Under aggressive cornering today s vehicles exert lateral separation forces on the bearings in excess of 6 tons In a conventional hub with its typical bearing clearance these turning forces cause movement in the bearing arrangement In an SKF LUNAR hub designed for a spindle that is straight rather than tapered an 8 ton clamping load is placed across the inner rings This creates a rigid system that keeps the bearings and seal stable during excessive load conditions The result Higher safety reduced maintenance LUNAR steer axle hub LUNAR trailer axle hub 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 16 17 3 CHAPTER 3 REVIEW To take this test simply place a card or sheet of paper under the first question After you ve read it and answered it to yourself slide the paper down below the next question The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 1 SKF designed the Scotseal specifically for wheels a trailer b bus c tractor front d all of the above 1 D 2 Scotseal s design is so efficient that
57. l orders Speedi Sleeves fit seal worn end yokes fig 2 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 63 64 Speedi Sleeve installation Speedi Sleeves are available for shaft diameters ranging from 498 to 8 005 Each sleeve kit contains a disposable installation tool and is marked with the shaft range for proper selection Follow these guidelines for proper Speedi Sleeve installation 1 Clean the surface where the seal contacted the shaft File down and polish any burrs or rough spots 2 Measure the diameter where the sleeve will be positioned on an unworn portion of the shaft Measure in three positions and average the reading in case the shaft is out of round fig 3 If the average diameter is within the range for a given Speedi Sleeve there is sufficient press fit built into the sleeve to keep it from sliding or spinning No cement is necessary 3 If the groove does not require filling apply a light layer of non hardening sealant to the inner surface of the sleeve 4 If the shaft is deeply scored fill the groove with powdered metal epoxy type filler Install Speedi Sleeve before the filler hardens 5 Undersize shafts Shaft diameters a few thousandths under the published minimum may be sleeved if cement is used 6 Oversize shafts Diameters larger than the published maximum can be sleeved if first machined with a finish 125 rms or better Note that the use of Speedi Sleeve eliminates the need for special g
58. l is required use a special tool of the type shown above Remove bearing cone for cleaning and inspection Outer bearing cup remains in hub unless it is damaged and needs replacement Always replace bearings in sets cup and cone Remove and keep locking nuts and washers in a clean container Because most of the components can only be inspected when they are removed from the assembly it is also important to use the proper removal tools to avoid damage or to alter signs of existing damage 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 25 26 WARNING Do not add a handle extension to the tool This tool is to be used for seal removal only The SRT 1 Seal Removal Tool Simple design rugged construction and ergonomic features increase your productivity and eliminate costly bearing damage Saves time no more laborious prying against bearings or driving out seals Saves bearings tool grabs seal only and bearings go undamaged Easy to use wedges and long handle provide exceptional leverage Rubber grip for security in handling Heavy duty construction for long life and dependability Works with steer drive and trailer wheel seals The SKF SRT 1 Seal Removal Tool is recommended for removal of most tractor truck dolly or trailer wheel seals With the wheel hub assembly removed from the axle simply insert the hook tip of the tool between the seal and bearing The uni
59. lange and includes a special tool for installation True False 15 T 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 67 68 CHAPTER 8 TROUBLESHOOTING SHAFT SEALS AND SCOTSEALS You now know the various types of seals available can select the right seal for the right application and are able to install it But before you replace that next seal there are some troubleshooting points that will round out your knowledge of seals Shaft seals Preliminary survey The best way to troubleshoot is to follow a sequence of steps that should lead you to the problem 1 What was the seal supposed to do How well has it done the job in the past If there is a history of failures the problem may not be caused by the seal itself 2 Was it the right seal Check the seal s part number and look up its recommended applications If the correct seal has been installed and there is no history of repeated failures the problem requires further investigation 3 Pinpoint the source of the leak It may be either an I D leak or an 0 D leak Also find out when the leak first occurred and see if this relates to a change in mainte nance or operating procedures fig 1 Investigate clues Seal markings The two areas that should be thoroughly checked are the seal outer diameter 0 D and the seal inner diameter I D Tell tale marks on either of these areas can give you a good idea of why the seal failed The solution The fir
60. lation fig 5 Figure 1 Figure 2 Figure 3 Figure 3a Figure 4 Figure 5 Seal 4 733 ID 6 006 OD 4 625 ID 4 625 ID 6 006 OD Sleeve Scotseals Spindle diameter 4 625 Assembled seal and sleeve Seal Sleeve Hub Bore Bearing Bore Hub Bore Bearing Bore 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 22 23 Inspection of the spindle and hub 1 Inspect the spindle and spindle threads for damage and remove light frett Also check for the following Spalling Corrosion pits Discoloration from overheating Punch marks chisel marks Weld beads Upset metal Note Damaged threads can be repaired using a pitch thread file or die nut 2 Inspect the fastener locknut bearing adjustment nut washer The use of these spindle end components varies by truck or trailer manufacturer Look for chisel marks or other deformation as a sign of improper installation or an attempt to make temporary repairs 3 Inspect the inside and the outside of the hub Look for the following Broken fasteners bolts Cracks in the housing Damage to the hub and bore Note If the bearing cup is loose in the hub this indicates a serious condition and the hub must be replaced WARNING Never work under a unit supported by only a jack Always support the vehicle with stands Block the wheels and make sure the unit will not roll before releasi
61. leaking wheel ends leave clues pointing to which component or components are the culprits Follow the guidelines of the checklist below as you service the wheel end You may find that just changing the seal may not be your permanent solution Inspect for indications of leakage Under vehicle inspection Oil present past the seal Oil contaminated hub brake hardware brake shoes External leakage Oil present around hubcap in wheel cavity Oil present around axle flange drive axle Disassembling the wheel end Caution Block wheels support vehicle on stands Check condition of hubcap Check flange window and centerfill plug Check bolts and axle flange area on drive axle Remove hubcap Axle flange on drive axle Check condition of lube Cloudy or milky indicates water Shiny indicates bearing wear Metal flakes present could indicate loose shavings from an axle component Grit and sand indicates lube contamination Smells burnt indicates overheating Check condition of fastening system Verify end play measurement before removing fastener Examine outer nut washer dowel tang or D type inner nut cotter pin Remove outer bearing Inspect for signs of damage Remove wheel or hub assembly using a wheel dolly Check spindle Threads damaged Chamfer damaged Set bearings aside for inspection Remove seal Check hub
62. mage 6 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 57 58 CHAPTER 6 REVIEW To take this test simply place a card or sheet of paper under the first question After you ve read it and answered it to yourself slide the paper down below the next question The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 01 SKF seals are available in a wide variety of sealing element materials and each has its own unique characteristics Selection should be on the basis of a application b compatibility with lubes and fluids c operating temperature d all of the above 1 D 02 Nitrile has generally replaced as a sealing lip a felt b silicone c leather d Viton 2 C 03 One of nitrile s disadvantages is that it is not compatible with a oil b abrasion c synthetic oils d all of the above 3 C 04 One of polyacrylate s disadvantages is its a low compatibility with water and some industrial fluids b high resistance to oxidation and ozone c relatively high cost d good compression set characteristics 4 A 05 Silicone s advantages include its a high lube absorbency b good flexibility c ability to handle a wide temper
63. n seal selection include Seal bore diameter This is the diameter of the hole into which the seal will be fitted Seal outside diameter O D The O D is the seal s press fit diameter It is usually 004 to 010 larger than the bore so the seal will be held firmly in place Seal width This is the overall width including the inner and outer shells Shaft diameter Because the seal s inside diameter is difficult to measure and varies with seal designs the shaft diameter for which the seal was designed is used as the cataloged inside dimension Measuring the seal O D When measuring the seal s outside diameter measurements should be taken in at least three places equally spaced around the seal The average of these readings can then be used as the diameter How to measure seal I D If you don t know the actual shaft diameter you can estimate it by measuring the seal s inside dimensions It makes no difference if the seal has an inner shell or not Simply average the three measurements of the lip inside diameter fig 4 Estimate shaft size as follows Estimated shaft diameter Add to lip I D Up to 1 031 1 to 2 021 047 2 to 6 047 063 6 to 8 063 094 8 to 12 125 A vernier is used to measure the seal s I D fig 4 fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 54 55 6 Speed The maximum speed at which a seal can operate depe
64. nd out at an excessive rate End play like this causes leaks as well as increased tire wear The solution of course is proper bearing adjustment fig 2 Wide thin If the primary seal lip line bottom is extra wide while the radial dirt lip line top is light there is excessive pressure on the primary lip For steer and trailer axles that can be a plugged vent on drive axles the tube vent may be locked fig 3 fig 1 fig 2 fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 78 79 8 Uneven patterns If the bumper lip path is shiny in one sector but dull in the opposite sector you can be sure the seal was cocked The bumper lip is making hard contact through half the revolution and almost no contact through the rest of it Hard Contact No Contact Internal inspection Good axial and bumper lip patterns When you examine the axial face you have two more wear patterns to learn from About half way up on the face you should see a pencil line track from the axial lip and at the top edge a gently scuffed pattern from the bumper lip fig 4 Wide shiny If both lines are wide or polished clean then you should suspect that the seal has been compressed This will happen if the I D of the seal isn t lubricated before installa tion if the sleeve wasn t sealed fully on the spindle or if the bearing adjustment is too tight fig 5 fig 4 fig 5 a Axial Dirt Lip Pattern
65. nds on other operating conditions These conditions include shaft finish pressure temperature eccentricity the lubricant or fluid to be retained and the particular design of the seal selected For instance as shaft finish is improved to the 10 20 micro inch range shaft speed can be increased As shaft eccentricity run out is reduced shaft speed can be increased Surface speed at the contact point between the seal and the shaft fpm feet per minute is generally a better indicator of seal performance than revolutions per minute rpm To convert rpm to fpm use the following formula or refer to the SKF Handbook of Seals Catalog 457010 262 x rpm x shaft diameter inches fpm Pressure The next aspect important to proper seal selection is pressure Allowable pressure goes down as shaft speed goes up The more pressure applied to a seal the more lip surface contacts the shaft More contact produces more friction and heat Friction and heat rise as shaft speed increases These factors cause faster wear and can shorten seal life Many of the bonded designs in the SKF Handbook of Seals can handle pressures of 15 psi at speeds up to 1 000 fpm These can be found in the Handbook s table of operating condi tions When speeds increase past 1 000 fpm some of these same seals can handle only 5 psi 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 55 56 Temperature fluid compatibility The final consideration
66. ng brakes Always wear eye protection 3 1 2 4 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 23 24 Wheel end disassembly Inner bearing cup remains in hub unless it is damaged and needs replacement Always replace bearings in sets cup and cone Removal of the seal with an SKF SRT 1 is recommended to avoid damaging the bearing or the hub bore Always use a wheel dolly to remove the wheel assembly Drain oil if hub is oil lubricated When the wheel is removed make a visual inspection for signs of damage leaks or wear on undercarriage components Hammers chisels and improper prying tools cause damage to bearings and hubs and can lead to catastrophic results USE ONLY SPECIFIED TOOLS Remove seal and discard Never re use a seal If seal shows damage prior to removal keep it for failure analysis Visually inspect brakes Visually inspect spindle Remove bearing cone for cleaning and inspection RECORD ANYTHING ABNORMAL ON WORK ORDER 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 24 25 4 Wheel end component inspection The bearing cone can usually be removed from the hub by hand When removed place the bearing in the clean containers with the other components If bearing cone is seated too firmly for hand removal use a special removal tool of the type shown above Bearing cups are too tightly fitted in the hub bore to be removed by hand If remova
67. nt of the wheel assembly along the spindle axis It is recommended for verification purposes that wheel bearing end play be measured with a dial indicator Example in photo below Step 1 Make sure the brake drum to hub fasteners are tightened to the manufacturers specifications Step 2 Attach a dial indicator with its magnetic base at the bottom of the hub or brake drum Step 3 Adjust the dial indicator so that its plunger or pointer is against the end of the spindle with its line of action approximately parallel to the axis of the spindle Note For aluminum hubs attach the magnetic base of the indicator to the end of the spindle with the plunger against the hub or brake drum Step 4 Set the dial indicator to zero by rotating the gauge face so the zero mark lines up with the gauge needle For digital indicators push the zero out button Step 5 Grasp the wheel assembly at the 3 o clock and 9 o clock positions while oscillating it to seat the bearings Read bearing end play as the total indicator movement Note If end play is not within specifications refer to the readjustment procedure of SKF technical bulletin No TBF 9301 Wheel bearing end play verification Printed with permission of the TMC Reference RP618 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 32 33 4 The clearance problem solved The biggest obstacle to effective wheel end maintenance is setting the correct bearing clea
68. off along a pre cut line Speedi Sleeves fit seal worn end yokes fig 2 steering gear shafts front and rear crankshafts and almost every part from almost every manufacturer represented in your rigs It takes only a few Speedi Sleeves to meet the needs of even the biggest operators In most cases there s no need to stock more than one size sleeve for each seal application or location Re sleeving can be part of the fleet s regular preventive maintenance schedule It takes little time to tap on a Speedi Sleeve when the rig is already in for replacement of seals and bearings or when a shaft is disassembled for general service Speedi Sleeve Gold is so technologically superior it delivers a surface hardness of 2300 Vickers approximately 80 85 HRc This hardness means abrasive dirt and grit tend to roll off of the surface rather than digging into it Speedi Sleeve Gold has been thoroughly tested for its abrasion resistant qualities in a severe dust environment test using both coarse and fine sand Temperatures were elevated to 225 F and shaft speeds were cranked up to 1 700 fpm Under these conditions shafts without Speedi Sleeve protec tion showed leakage at 450 hours on average Speedi Sleeve Gold protected shafts ran to an average of 2 500 hours Currently Speedi Sleeve Gold is available in 50 sizes that cover the majority of common shaft sizes Other sizes up to eight inches in diameter are available in quantity as specia
69. orrect bearing clearance True False 8 T 9 Always install and re install a hubcap with a new gasket True False 9 T 10 Faulty installation is one of the most common reasons a seal fails True False 10 T 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 37 38 CHAPTER 5 WHEEL END GREASE SEALS In this chapter you will find instructions for installing grease seals on axles Scotseals are needed for oil bath wheel ends First you must replace the seal whenever you pull the wheel The old seal will most likely be nicked or bent when the wheel was removed Some of the seal s press fit in the hub will have been lost during removal of the bearing The seal will not fit as tight as it should which will prevent it from retaining lube and excluding dirt Reusing an old seal can cause costly problems such as failure of the wheel bearing or brake lining Before discarding the old seal check it for damage This will be explained in Chapter 8 Then proceed with the following guidelines for seal installation Seal installation fig 1 Remove the wheel assembly 1 Jack up the wheel off the ground and support the axle with safety stands 2a Remove the hubcap axle nut locking device cotter pin safety wire locking washer tab or bolt 2b Remove the axle flange nuts and lock washers Install pulling screws in axle flange holes if provided If not strike the axle flange in the center sha
70. portance of knowing and understanding these materials they will be reviewed here If a lip material to match the old seal cannot be found in the size listings refer to the Substitute Material Table in the Handbook of Seals Some of the more common seal substitutions are listed below Nitrile instead of felt Nitrile instead of leather Polyacrylate instead of nitrile Fluoroelastomer instead of polyacrylate Fluoroelastomer instead of silicone Remember colors other than black usually mean special materials Materials should generally be substituted only if immediate replacement is more important than the assurance of maximum seal life Because of the great number of factors involved it is not always true that a premium elastomer will do a better sealing job than a less expensive material If the operating temperature is above 250 F 121 C nitrile seals substituted for polyacrylate or silicone may have a shorter life And while silicone has a wider temperature range than polyacrylate it breaks down if it is exposed to oxidized oils Seals for new applications Choosing the right seal for a particular application depends on operating conditions 1 Size 2 Speed 3 Pressure 4 Temperature fluid compatibility Each of these operating conditions should influence your selection of a seal for that application 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 53 54 Size Seal dimensions fig 3 used i
71. que design of the tool allows you to use leverage to easily and safely remove the seal without damaging the spindle U S Patent No 5 617 621 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 26 27 4 General instructions Wheel hub designs differ from one manufacturer to another However the correct procedures for installing bearings and seals remain basically the same Care in handling components and proper tooling are always the critical factors in all procedures which lead to Trouble Free Operation Bearing and seal installation Outer bearing cup mounted in hub Components in a typical hub assembly Installing bearing cup and seal Avoid any direct hammering on the bearing or the Scotseal this will cause deformation or damage which will result in premature failure Use a simple vertical press to push the bearing cup into correct position in the hub Use a recommended Scotseal installation tool to install the Scotseal Classic or Longlife correctly in the hub When hammering on the tool be sure to stop when the seal is bottomed you will hear a definite tone change Do not add extra blows or it will cause immediate damage to the seal Scotseal PlusXL requires no special installation tool Typical hub Scotseal Inner bearing cone Outer bearing cone Inner bearing cup mounted in hub Note if the tire is mounted on the hub place the entire assembly against a solid surface at a 45
72. rance In fact most wheel end bearing failures are the result of incorrect clearance adjustment While in general practice the wheel is rotated only 3 times during adjustment it can take as many as 18 revolutions for bearings to become fully seated How important is clearance to bearing life Immense As this graph illustrates too much or too little pre load even a few thousandths of an inch can dramatically effect fatigue life An experienced technician working with the right tools typically achieves settings ranging from 1 to 5 thousandths of an inch but that doesn t take into account what happens to clearance when the bearings become fully seated So even if a technician sets the bearings as accurately as possible in the shop bearing clearance can be highly inaccurate a mere forty yards down the road The SKF LUNAR Hub solves adjustment problems by precisely match grinding all the components to achieve a 0 001 clearance control Correct clearance adjustments produce increased bearing and seal life ultimately increasing the wheel end s lifetime and a fleet s profitability Bearing adjustments below zero enter preload stage and cannot be measured in the shop Over tightened bearings as you can see lead to bearing failure On the other hand too loose bearing adjustment will also lead to bearing failure Re adjust bearings if an end play cannot be read or if end play is greater than 005 to ensure optimal bearing life
73. rinding or preparation of the surface 7 Speedi Sleeves are wide enough to cover the wear pattern of both standard and wider combination seals Where extra wide combinations are encountered a second sleeve can be installed to butt against the first The flange is then peeled off to provide the clearance necessary for the seal housing to slide into place The Speedi Sleeve installation flange can be left in place as an oil flinger to prevent surges of oil from being pumped into the seal lip by the action of the adjacent bearing Take three measurements to average shaft diameter fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 64 65 8 Determine how far back the sleeve must be positioned to cover the old seal wear tracks Measure to the exact point or mark directly on the surface 9 The sleeve must be placed over the worn area not just bottomed or left flush with the end of the shaft 10 Drop the Speedi Sleeve into the end of the installation tool so only the flange end projects The flange end of the sleeve goes on the shaft first Gently pound the center of the tool until the sleeve reaches the point marked fig 4 11 Speedi Sleeves may be installed to any depth required If the installation tool supplied with sleeve is too short a length of pipe with a squared off burr free end can be substituted Inside pipe diameters should be larger than the shaft by Shafts less than 3 1 32 to 1 8 Shafts 3 to 6 1 32
74. rittle primary seal lip After cleaning the entire seal use your fingers to curl the primary seal lip back Run your finger completely around the circumference The oil lip should be smooth and pliable If not the seal has overheated lack of lubrication could be the cause fig 5 Lack of lubrication may have fried the bearings as well Broken dirt lip Using the same technique check the dirt lip If it s dry and brittle most likely it s been baked It will probably split away from the seal at some point around the circumference fig 6 fig 1 fig 2 fig 4 fig 5 fig 6 fig 3 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 74 75 8 Internal inspection wear tracks Good pattern What you will see in a good Scotseal are the two parallel lines that look like they ve been drawn with a sharp pencil They re approximately the same size and equidistant from the edge all the way around the inside of the outer cup fig 7 Wide wide If both lines are wider than pencil lines it means that the primary lip and dirt lip have been allowed to move in and out on the outer cup The cause of this is excessive endplay indicating that the bearing adjustment is greater than 001 and 005 fig 8 Metal shavings in lip area Before cleaning the seal inspect the seal area for traces of metal particles A magnet can attract metal particles Sharp edges of metal may have cut the seal primary lip caus
75. rply with a heavy hammer It may require several blows to bounce the shaft loose so the tapered washers and axle shaft can be removed A typical front wheel assembly is shown above fig 1 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 38 39 5 3 Remove the locking nut adjusting nut lock washer and outer bearing cone Since the arrangement and design of washers locks and nuts is different with each manufacturer be sure to note the order in which they should be replaced after the seal is installed 4 Slide the wheel and hub assembly off the spindle Be careful not to drag the inner bearing over the spindle thread If possible chain the wheel to the dolly for safety 5 Remove the bearing spacer and pin from the spindle Pry out the old seal with a rolling head pry bar Using a drift to drive the bearing and seal out can damage the bearing cage 6 Remove the inner bearing cone Record the worn seal s part number so you can refer to it when selecting the new seal replacement 7 If pulling more than one wheel be sure to keep all of the parts of each wheel assembly together and separate from the other wheels Cleaning and inspection 1 Clean the hub cavity and cap removing all old lubricant Use a brush to clean the drum and brake mechanism Wipe the spindle clean 2 Use a recommended solvent to remove dirt and grease from the bearing and related wheel axle parts Rinse the bearing in another separate bucket
76. rubber protection fig 3 Worn I D beads A worn I D indicates the seal has been slipping on the spindle Look for three main causes a cocked seal a bent seal section or poor spindle preparation in changing from another seal to the Scotseal PlusXL fig 4 Damaged I D beads Cuts or scarring in the I D is caused by jamming the seal into the spindle or axle tube Misaligning the wheel dolly is usually the result of haste however the work area should be checked to make sure the floor is smooth and free of clutter fig 5 Dented scarred sleeve assembly A dimpled or dented surface indicates damage caused by a problem during installation The use of hard faced tools or seal driver is the most likely culprit fig 6 fig 1 fig 2 fig 3 fig 4 fig 5 fig 6 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 76 77 8 Opening a Scotseal PlusXL Use pliers to straighten the flange on the sleeve section Be sure to wear gloves or use a shop rag to protect your hands The opened flange is extremely sharp fig 1 Pull the two components apart Then set the sleeve assembly aside the top component shown above Place it carefully where it is out of the way but won t be disturbed fig 2 Internal inspection sealing lip condition Check for grease Locate the primary sealing lip and radial dirt lip If the area between them is dry something has allowed oil to wash away the grease The c
77. s where the shaft enters the seal against the sealing lip 4 Check splines and keyways Sharp edges should be covered with a lubricated assembly sleeve shim stock or tape to protect the seal lip 5 Check dimensionss Be sure shaft and bore diameters match those specified for the seal selected 6 Check for parts interference Watch out for other machine parts that might rub against the seal and cause friction and damaging heat 7 Check the seal Damage may have occurred prior to installation A sealing lip that is turned back cut or otherwise damages should be replaced 8 Check seal direction Make sure that the new seal faces in the same direction as the original one Generally the lip faces the lubricant or fluid to be retained 9 Use the correct installatioon tools Press fitting tools should have an outside diameter approximately 010 254 mm smaller than the bore size For best results the center of the tool should be open so that pressure is applied only at the outer edge 10 Pre lubricate the sealing element Before installation wipe the element with the lubricant being retained 11 Never hammer directly on the surface of the seal Use proper driving force such as a softface tool arbor press or soft workplace wood Apply force evenly around the outer edge to avoid cocking the seal 12 Position the seal properly in the housing and inspect for alignment and installation da
78. seal Longlife are to be installed using only SKF Scotseal installation tools See Chart A below Centering the seal Precisely matched centering plugs are engineered to fit within the inside diameter of the inner bearing cone and allow accurate centering of the Scotseal in the bore of the hub as well as preventing cocking of the seal Chart B below provides correct matchup of bearing cone and centering plug Standard tool handle 450237 Seal Drive Plate These components are interchangeable See chart below Standard Plug Bushing Centering Plug Washer Nut Chart A DRIVE PLATES amp SEAL MATCHUPS Drive plates in bold numbers with matching seal numbers 427 34387 36274 36285 36358 36365 428 31175 31244 31264 31266 31281 31307 32470 435 47690 47693 47696 47697 47698 48000 436 34975 35000 35001 35060 35066 35072 35075 35102 35103 441 40086 40090 445 39380 39420 39425 42550 42672 42800 446 43860 43865 43875 46390 47483 48297 48298 48690 48792 48794 48796 48884 50124 448 38709 39988 39990 449 47686 451 46305 46306 46308 452 42623 42624 42630 42631 453 50190 52660 52664 457 40040 40136 40139 40146 40147 461 45152 45160 45162 45163 462 38747 38750 38780 38782 38783 463 27438 28758 28820 28832 465 43752 43764 43765 43800 472 39380 w disc brks 474 52658 484 44922 44964 45010 45099 45100 45103 45108 450737 42625
79. seal helping it to do its job better In simple terms a shaft seal is a barrier Shaft seals are designed to Retain lubricants or liquids Confine pressure Exclude dirt Separate fluids Seals are necessary for sealing in lubricants that are needed to protect the bearings and to seal out dirt water and contaminants To do both jobs effectively all seals demand precise engineering and manufacturing Seal designs and materials are constantly being developed tested and improved This testing is being done to conform with today s increased performance and durability requirements The media being sealed can be anything from light oil to heavy grease or even hot turbine gases Wheel seals are among the most common applications However in the case of wheel seals the shaft remains stationary and the wheel hub rotates The seal retains lube in the bearing and at the same time protects the bearing from contaminants such as water dirt dust and abrasives First it must be decided which is more important retention of lubricant exclusion of foreign matter or in some cases both Seal Design The shaft seal is a small and simple looking product with a big and important job The following describes a typical seal and the function of each of its components fig 1 Scotseals will be covered in the next chapter Page 11 Seal Components 1 Outer Shell Case The outer cup shaped rigid structure of the lip seal
80. seal PlusXL with the unique hand installable design includes a fat footprint ensuring stability on the shaft Worn hubs and spindles are not a problem for the Scotseal PlusXL Scotseal Longlife Building upon the success of the original Scotseal Classic design SKF engineers had a great start in their development of a new extended life seal Computer aided design CAD of lip geometry and the addition of an axial dirt excluder lip was combined with a newly formulated material to produce Scotseal Longlife fig 6 a premium performance seal with the characteristics required by many of today s demanding heavy duty environments 13 3 Scotseal PlusXL fig 5 Scotseal Longlife fig 6 Scotseal Classic fig 4 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 13 14 Scotseal Classic The original Self Contained Oil Type Seal Scotseal Classic fig 7 became the trucking industry standard and the best value for more than 30 years With literally trillions of road miles to its credit Scotseal Classic has proven to be a solid choice for dependable long lasting service Time and time again field studies show that when properly installed using SKF tools and procedures Scotseal Classic is a reliable performer for meeting the sealing requirements between brake maintenance intervals Scotseal family truck wheel seal operating conditions Scotseal Classic Scotseal Longlife amp Scotseal Plus XL
81. st surface to check is the 0 D If the seal has been properly installed the press fit markings will be fairly uniform and straight Cocked seal Markings also can be tell tale signs that the seal was cocked during installation Light scratches on the front of the seal would appear when the seal was first inserted Since the seal was cocked it takes additional force to seat the back half This extra force causes heavier markings on the back of the seal fig 2 Check the seal area for leaks fig 1 This seal was cocked during installation fig 2 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 68 69 8 The solution If the seal is cocked you have only one solution Remove it and put in a new one but be sure it s straight Lip wear patterns Look for clues in the sealing member of the seal A small cut or nick could be the source of the leak But if everything looks intact it s time to look at the wear pattern of the lip A new seal that has never been installed has a sharp edge on its sealing lip at the contact point Following a period of normal operation the lip s sharp edge will be flattened some by normal wear If the lip has been substantially worn away the seal may not be getting enough lubrication the shaft may be corroded or the finish too rough Extreme wear could also be caused by shaft whip If you find a leaking seal with a wide wear band on one side but a narrow band on the other you
82. t lining up the wheel dolly is the usual suspect Or a rough shop floor may be the problem fig 8 Distorted packing One way to damage the packing of a Scotseal is to try to install it over a wear ring The wear ring will deform the inner surface and ruin the seal Any previously installed wear ring must be removed prior to installing a Scotseal fig 9 Foreign matter on I D Occasionally you will come across a seal with a shaft leak that has a mysterious tacky substance on it Most likely someone added a silicone sealant to improve the seal Old habits die hard fig 10 fig 6 fig 7 fig 8 fig 9 fig 10 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 73 74 Factory Applied Grease External inspection outer diameter Opening a Scotseal Use pliers or end cutters and work your way all the way around the seal straightening the outer cup flange fig 1 Remove the inner cup Be sure to wear gloves or use a shop rag to protect your hands as the open flange edges are sharp fig 2 Remove the packing without disturbing the lip surfaces as shown fig 3 Internal inspection The major clues Lip grease Every Scotseal comes with grease between the primary and dirt lip If it s not there it s very likely oil has washed it away Suspects are excessive end play a cocked seal or improper ventilation of the wheel end dirt corrosion or paint plugged vent fig 4 B
83. t to your self slide the paper down below the next question The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 1 The SKF SRT 1 Seal removal tool is recommended for removal of seals in____________ a Tractors b Trucks c Trailers d All of the above 1 D 2 The SKF SRT 1 saves bearings by grabbing the____________ a Bearings b Seals c Bearings and seals d None of the above 2 B 3 The Scotseal PlusXL should not be installed directly on the ____________ a bearing b hub c spindle d none of the above 3 C 4 Over tightened bearings can lead to ____________ a Bearing failure b Increased bearing life c Increased seal life d Non of the above 4 A 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 36 37 4 5 Correct procedures for installing bearings and seals remains basically the same for all hub manufacturers True False 5 T 6 Direct hammering on a bearing or Scotseal will cause premature wheel end failure True False 6 T 7 Changing the seal is always a permanent solution for wheel end leakage True False 7 F 8 The biggest obstacle to effective wheel end maintenance is setting the c
84. till intact Overheating can cause cracks on the seal surface fig 4 2604293 TFO Self Study Guide_V3 12 1 06 9 51 AM Page 70 71 8 A small nick or cut hardly visible to the eye may turn an otherwise good seal into a leaker Look for this type of damage when leakage in slight Compare the fit of a failing seal with a new seal on the same shaft If it feels loose but is unworn the cause may be swelling a reaction to the fluid being sealed Check the compatibility rating in the SKF Handbook of Seals 457010 Scotseals failure analysis Failure analysis of prematurely failed seals is one of the best means to discover the cause of failure and to avoid a similar fate for the replacement seal The cross sectional drawings at right illustrate the critical components of each member of the Scotseal family The captions identify these components as described in the following pages For Scotseal PlusXL failures most likely result from these common errors Improper installation O D and or I D not lubed Lube contamination Spindle not fully prepped Use of a hammer Note replacing a narrow footed seal like the Scotseal Classic and Scotseal Longlife requires cleaning the spindle along the new area where the wider Scotseal PlusXL will sit Below are the key failure modes for Scotseal Classic and Scotseal Longlife These account for the lion s share of premature seal failur
85. to the axle spindle for corrosion protection Typical mechanical grease packer 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 21 22 Two piece seal replacement vs Scotseal replacement Some seal manufacturers utilize a two piece design that includes a wear sleeve and an oil seal fig 1 Be aware that the original seal with the sleeve will have a larger ID dimension compared to the Scotseal unitized design Shown in fig 2 is the two components assembled on the spindle Assuring the correct seal requires specifications that match the spindle sealing surface diameter and the hub seal bore For example fig 3 and 3a the seal component has an ID of 4 733 compared to the spindle diameter of 4 625 The sleeve component has an ID of 4 625 matching the spindle diameter At times in error a comparison is made between the two piece style seal component and a unitized Scotseal replacement The ID dimensions will differ Always check the spindle for any sleeve or axle ring and remove Seals of this nature and Scotseals press into the hub bore therefore outside diameters will match Hub bore vs seal bore In some applications an oil seal will press fit into the bearing bore fig 4 instead of the seal or hub bore Confusion arises when a replacement seal appears too large in the OD dimension when interpretation indicates that the replacement seal is a hub bore installation but in fact it is a bearing bore instal
86. uestion The correct answer to the first problem will appear directly to the right of the new question Be sure not to skip any of the questions This learning technique assures more than four times the normal retention rate for even this technical subject 01 A shaft seal is a barrier designed to a retain lubricants or liquids and exclude dirt b confine pressure c separate fluids d all of the above 1 D 02 A typical vehicle may require a steering seals b transmission rear seals c front crank seals d all of the above 2 D 03 Another name for the outer shell of the seal is the outer a lip b case c cone d spring 3 B 04 Every rotating shaft requires a bearing and a seal for smooth effective operation True False 4 T 05 A shaft seal is a barrier designed only to confine pressure True False 5 F CHAPTER 2 REVIEW 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 9 10 6 Seals are needed to seal in lubricants necessary for the bearings and to seal out dirt water and contaminants True False 6 T 7 If the seal s basic job is to retain lubricants or liquid the seal lip must face toward the lubricant or pressure being retained True False 7 T 8 If the seal s basic job is to exclude contaminants the lip of the seal should face toward the bearing instead of toward the contaminants
87. with a specially formulated HNBR to be compatible with today s harsh wheel end synthetic fluids Heavy Truck Seals Seals are found in many locations on a truck or bus fig 3 The kind of seal depends on the location and function of the seal The diagram below lists the many places seals are located on tractors trucks buses and trailers Today most wheel ends are oil bath lubricated and use SKF s Scotseal 1 Leather Nitrile rubber Duralip X NBR Duratemp H NBR Polyacrylate elastomer Silicone rubber Fluoro rubber Polystrafluoroethylene Temperature C fig 1A Leather Nitrile rubber Duralip X NBR Duratemp H NBR Polyacrylate elastomer Silicone rubber Fluoro rubber Polystrafluoroethylene Temperature F 40 76 112 4 0 122 212 302 392 482 Wear resistance Silicone rubber Polyacrytate elastomer Nitrile rubber Leather Duralip X NBR Duratemp H NBR Fluoro rubber Polytetrafluoroethylene fig 1B This diagram shows the location of seals most often replaced in tractors trucks trailers and busess Wheel or axle seals are most often bath lubrication systems using Scotseals fig 3 fig 2 2604293 TFO Self Study Guide_V3 12 1 06 9 50 AM Page 5 6 CHAPTER 2 SHAFT SEALS In this world of moving parts whenever a shaft rotates it needs a bearing for smooth effective operation In most cases where there s a bearing you ll find a

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