self-aligning bearing systems

Self-aligning bearing systems

Contents

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Summary.......................................................................... 3

The traditional self-aligning bearing arrangement ...... 4

Bearings in rotating equipment .................................... 4Using a self-aligning ball or a spherical roller bearing at both positions...................................... 4Cause of bearing system failures .................................. 5Influence of friction ........................................................ 6Unstable load distribution ............................................ 6A typical example of shaft expansion and its effects .... 7Axial force over time – characteristic examples ............ 8

The new self-aligning bearing system.......................... 9

SKF toroidal roller bearing .......................................... 10Low load performance ................................................ 10Improvement of operating conditions and reliability .. 12Cost reduction through downsizing ............................ 14Low load, high speed .................................................. 14Eliminating risk of poor operating conditions.............. 15The compromise-free solution......................................15Improvements with the new self-aligning bearing system ............................................................16Influences of the self-aligning bearing system for different types of machines ....................................18

The SKF Group – a worldwide organisation .............. 20

Summary

SKF’s new self-aligning bearing sys-tem consists of a CARB® toroidal rollerbearing as the non-locating bearing incombination with a double row spher-ical roller or self-aligning ball bearingas the locating bearing.

The bearing arrangement accomod-ates both misalignment and axial ad-justment internally and without fric-tional resistance, with no possibility ofgenerating internal axial forces in thebearing system. Due to the ideal inter-action between the two bearings, theapplied load is always distributed con-sistently and in the assumed (theoret-ical) manner between all load-carryingelements.

The design characteristics of bothbearings in the new system are fullyexploited; they function as the machinedesigner intends and assumes theyshould. This is often not the case withother bearing systems, which havesome compromise in the arrangementwhich produces non-ideal operatingconditions.

The new compromise-free SKF sys-tem delivers increased reliability andperformance, enabling designers toconfidently optimise the selection ofbearings and the machine construc-tion as a whole.

Both manufacturers and end usersof machines achieve significant costreductions through a leaner designand improved productivity.

Depending on the machine and ap-plication, the benefits seen with SKF’snew self-aligning bearing system are:

• safer, more optimised designs• increased bearing service life• extended maintenance intervals• lower running temperature• lower vibration and noise levels• greater throughput of the machine• same throughput with a lighter, or

simpler machine• improved product quality/less scrap

Traditional arrangement of twoself-aligning bearings with the bearing to the right “axially free”

1Fig

Bearings in rotatingequipmentIn typical industrial equipment, rotat-ing shafts are generally supported bytwo anti-friction (rolling) bearings, oneat each end of the shaft. In addition tosupporting radial loads, one of thebearings must position the shaft axiallywith respect to its supporting structure,as well as carry any axial loads whichare imposed on the shaft. This bearingis referred to as the “locating”, “fixed”or “held” bearing.

The other bearing must also carryradial load, but should accommodateaxial movement in order to compens-ate for:

• thermal elongation and contractionof the shaft or structure with temper-ature variations,

• manufacturing tolerances of thestructure, and

The traditional self-aligning bearing arrangement

• positioning tolerances at assemblyof the machine.

This second bearing is referred to asthe “non-locating”, “floating” or “free”bearing.

Using a self-aligningball or a spherical rollerbearing at both positionsThis bearing combination has longbeen the basis of many industrialbearing arrangements – a simple,robust arrangement capable of with-standing high radial as well as thrustloads whilst easily internally accomod-ating the misalignment typically im-posed through machining and assemblytolerances, thermal distortion or de-flection under load. There are, however,consequences to using self-aligningball bearings or spherical roller bearingsin the non-locating position (➔ fig ).

The non-locating bearing must slideaxially, usually inside the housing, toaccommodate shaft expansion or con-traction. To achieve this movement, oneof the bearing rings must be mountedwith a loose fit and axial space needs

1

to be provided for the intended move-ment. In many cases, the loose fit com-promises the design of the machine,as under certain load conditions, thebearing ring will spin and damage thehousing, accelerate wear and increasevibration, which all adds up to addi-tional maintenace and repair costs. Italso means that the shaft is supportedless rigidly in the radial direction.

Cause of bearing system failuresIf a loose fit is needed for axial move-ment of the non-locating bearing, thenit is necessary that the fit remainsloose during operation. Maintainingthis loose fit is not as simple as itsounds:

• At start-up, machine componentsmust heat up to normal operatingtemperature. The outer ring of thebearing usually expands faster thanthe housing bore. This different rateof expansion can eliminate clearanceand restrict axial movement.

• If the bearing housing seating form isnot within specification (either manu-factured with ovality or taper, or,more commonly, distorted in theapplication due to being mounted ona base which is not sufficiently flatand rigid – either from the beginning

or when the machine is loaded) thenthe bearing ring will be held in placeand be unable to move to accom-modate the required axial movement.

• The wear process from the loosering under unfavourable load con-ditions can also create a conditionknown as fretting corrosion, whichcan effectively “rust” the bearing ringin place.

If the non-locating bearing ring cannotmove for any of the above reasons,then both bearings become axiallypreloaded, meaning that as the shaftor structure changes temperature andtherefore length, very high axial loadsare generated between the two bear-ings (➔ fig ). This is a well-knownconsequence of the compromisebrought about by the need for a loosefit of the non-locating bearing in thistype of arrangement.

2

2Fig

Non-locating bearing restricted from axial motion

Influence of frictionA more general, but less recognised,consequence of a bearing installedwith a loose fit is that there is always acertain amount of friction between theloose bearing ring and the housing (orshaft) seating. In order for the shaft toexpand or contract in the axial direc-tion, it must first overcome the fric-tional resistance at the sliding contact.This resistance has the magnitude Fa = Fr × µ, where Fa is axial force, Fr is the radial load carried by the non-locating end bearing, and µ is the coef-ficient of friction between the loosebearing ring and the housing or shaft(for steel-steel and steel-cast ironinterfaces, values for µ are typicallyaround 0,12–0,16 for surfaces in goodcondition). Therefore, both bearings on the shaft are subjected to an addi-tional thrust load, equivalent to several percent of the radial load (➔ fig ).As a result of these internal thrustforces, the load distribution within thebearings is adversely affected, witheach row of rollers carrying a differentload (➔ fig ). 4

3

Friction between outer ring and housing induces axial load

3Fig

Unstable load distributionIn cases with relatively high speeds,the load distribution is variable andunstable. To visualise how this mech-anism occurs, picture the inner ring ofone bearing being slightly askew onthe shaft relative to the true axis ofrotation – this is a common situation,typically a result of machining inaccur-acy of the shaft, deflection of the shaft,combination of tolerances of shaft,adapter sleeve and bearing ring, andmounting inaccuracy. Then, as theinner ring rotates, it performs a verysmall “wobbling” motion, which im-parts a small axial oscillation to theshaft. This oscillation is then transmit-ted to the inner ring of the secondbearing in the shaft arrangement. Asthe inner rings move back and forthwith a frequency equal to the shaftspeed, the two rows of rollers are al-ternately loaded and unloaded (or atleast change the amount of load theyexperience). In some cases, the axialmotion is transmitted to the outer ringof the non-locating bearing, bringingabout axial ”scuffing” or fretting wear in the housing. The typical results ofthis uneven load distribution can begeneralised as:

• in high load applications – elevatedinternal stresses, elevated temperat-ure, impaired lubrication, acceleratedbearing wear, reduced bearingfatigue life (reduction in fatigue lifecan be calculated)

• in high speed applications – highoperating temperatures, alternatingacceleration and deceleration of theroller sets with fluctuating load distri-bution, high forces on the bearingcages, increased rate of wear, highvibration and noise levels, rapiddeterioration of grease, general reli-ability problems. (It is not possible tocalculate any of these effects – thisis the distinction between fatigue lifeand service life.)

These factors occur to a greater orlesser extent in all such bearing ar-rangements, even when the compon-ents are new and tolerances are withinspecification. If there is somethingother than normal friction which pre-vents movement of the non-locatingbearing ring then the situation isequivalent to having a very high coeffi-cient of friction (µ) at the non-locatingbearing, and the adverse effects dur-ing operation are correspondinglysevere.

Fa = Fr × µ

4Fig

Uneven load distribution due to axial friction forces


A typical example ofshaft expansion and itseffectsDiagram shows measurementstaken at the outer ring of an oil-lubric-ated spherical roller bearing at thenon-locating position on a papermachine roll, during the machine start-up period.

It is apparent that the frictionbetween the bearing and the housingis real and does have a significanteffect on the bearing arrangement. Asthe operating temperature increases,the outer ring axial movement is char-acterised by stationary periods, withoccasional sudden large movements.It is clearly noticed that the move-ments only occur when the axialforces have built to such a level thatthe stick-slip friction is overcome. Witheach movement of the outer ring,there is an immediate and noticeablereduction in the operating temperat-ure, as the internal axial load isreduced.

1

This process is repeated until (orunless) a steady-state operating con-dition is reached, and then will berepeated (in reverse) with any decreasein temperature of the shaft or struc-ture. (Shutdown, idle running, changein process parameters.) During steadystate running conditions, it is likelythat there will be some residual axialloading (uneven load distributionbetween the roller sets)

Note that for SKF “CC” and “E”spherical roller bearings, the ratio ofaxial load to radial load must be quitehigh (15 % or more) before there is asignificant increase in the total rollingfriction inside the bearing (total friction= load-dependent friction + viscousfriction from the lubricant). Therefore,for bearings under nominally pure radial load, there must be a signific-ant axial force resulting from frictionbetween the bearing ring and housingin order for temperature variationssuch as those in the diagram to benoticeable. The fact that a change intemperature is easily measured showsthat the friction factor acting will be > 0,1.

1Diagram

Axial position of outer ring and corresponding bearing temperature during start-up

Time

Temperature

Outer ring axial position

Axial force over time – characteristic examplesThe size of the induced axial forces, in the traditional self-aligning bearingarrangement, and the way in whichthey vary over time (and thereforewhat the average force – averageequivalent friction factor µ – over thelifetime of the bearing system will be)depends on a large number of different,and largely unpredictable parameters,including:

• the initial mounted radial clearancein each bearing

• the amount and direction by whichthe inner and outer rings of eachbearing are axially offset relative toeach other after mounting

• the magnitude of the radial load onthe non-locating bearing

• the nature of the radial load on thenon-locating bearing (steady or fluc-tuating, uni-directional or random)

• level of vibrations from outsidesources

• surface finish of the non-locatingbearing ring and seating

• lubrication conditions between non-locating bearing ring and seating

• looseness of fit (individual diamet-rical tolerances of the non-locatingbearing ring and seating

• form tolerance of the non-locatingbearing seating (ovality and taper)

• distortion of the non-locating bearingseating with load

• distortion of the non-locating bearingseating with thermal changes

• relative rate of thermal axial expan-sion (contraction) of rotating and sta-tionary components (shaft and struc-ture)

• relative rate of thermal radial expan-sion (contraction) of non-locatingbearing ring and seating

• axial stiffness of the supportingstructure

It is obvious that more internal clear-ance is beneficial in reducing thechance of high induced axial forces.However, excessive clearance alsomeans that few rolling elements carrythe load, which also results in reducedbearing fatigue life, and there is ingeneral a higher risk of poor operatingconditions within the bearings.

In the examples below it is assumedthat the shaft expands in relation tothe structure.

Except with very precise tolerancesand painstaking measurements at as-sembly, it is impossible to know whatwill actually occur with any individualmachine.

2

Small initial axial clearance (rings centred at mounting) – start-up period

Diagram

Induced axial load/radial load

Steady state

Time

3Diagram

Induced axial load/radial load

Steady-state operationwith high axial loads

Bearing jammed in housing

Initial axial clearance

Bearing jammed in housing

Time


The new self-aligning bearing system

Until recently, the design compromisesin each case simply had to be accept-ed. Now, however, a completely newdesign of non-locating rolling elementbearing has enabled all the compro-mises to be eliminated from shaft/bearing systems.

The new bearing type is the toroidalroller bearing, so called because of theform of the curvature at the contactsurfaces within the bearing. Thetoroidal roller bearing has a single rowof long rollers with a slightly curvedprofile. The internal design enables thebearing to accommodate axial move-ment internally, like a cylindrical orneedle roller bearing, without any fric-tional resistance. This eliminates theneed for a loose fit for any of the bear-ing rings. There is also no possibilityfor generating additional axial (thrust)forces between the two bearings onthe shaft (➔ fig ).

In addition to eliminating all the axialinteraction between the bearings, theroller and raceway profile in thetoroidal roller bearing is designed toautomatically adjust the roller positioninside the bearing so that the load isdistributed evenly along the roller con-tact length, irrespective of any mis-alignment. This means that there is nopossibility for high edge stresses, sothe bearing always operates at theoptimum stress level, and thereforeachieves its theoretical fatigue lifeunder all conditions (➔ fig ).

The combination of the self-aligningproperties, and the frictionless axialadjustment, ensures that the load isdistributed as evenly and consistentlyas possible along all the rows of rollingelements in both bearings on theshaft. The actual distribution will de-pend on the externally applied radialand axial loads. An optimised load dis-tribution will mean that stresses arelow, temperature is minimised, max-imum fatigue life is always achieved,

2

1

1Fig

2Fig

No internallyinduced axial loadensures even loaddistribution in bothbearings

3Fig

and the chance of vibrations and cagedamage are reduced. In addition,because tight fits can be used for allbearing rings in the system, the risk ofworn out housings due to spinningrings can be eliminated (➔ fig ).3

No axial forceinduced withtoroidal roller bearing

Toroidal rollerbearing contactsurface ensureseven load distri-bution along rollerlength

normal twisted ring misaligned axially displaced

Fa = 0

Please note that when using CARB, the outer ring ofthe non-locating bearing must also be fixed!

4Fig

In a spherical roller bearing which isoperating with pure radial load, bothrows of rollers share the load equally.(necessary radial load factor = 1 fromDiagram ).

However when there is any axialadjustment of one bearing ring relativeto the other, the load distributionchanges, and the effective load on onerow is reduced (➔ fig on page 6).Therefore, in order to be sure that theleast loaded row still has enough loadto keep it rotating properly, the totalradial load on the bearing must beincreased (i.e. multiplied by a radialload factor, ➔ Diagram ) for a givenfriction factor µ between outer ringand housing when shaft axial dis-placement occurs (given ratio of axialto radial load) in order to maintain therequired minimum load level on theleast loaded row.

In Diagram e is the calculationfactor for spherical roller bearingswhich is given in tables of the SKFGeneral Catalogue. The factor e variesbetween 0,15 and 0,40, depending onbearing contact angle.

1

1

4

1

CARB® is available in various ISO Dimension Series

SKF toroidal rollerbearingThe first toroidal roller bearing wasintroduced by SKF in 1995. Known asCARB®, the new bearing is available in a range of ISO Dimension Series,equivalent to self-aligning ball andspherical roller bearings used in stand-ard bearing housings and other com-mon types of assemblies. The rangealso covers wide, low section seriesequivalent to needle roller bearings (➔ fig ).

CARB enables machine manufac-turers and users to optimise bearingarrangements, simply by substitutingthe equivalent size toroidal roller bear-ing at the non-locating bearing posi-tion. The locating bearing remains asbefore, and other standard compo-nents (housings, adapter sleeves etc.)are utlilised. This new standard bear-ing system ensures that the potentialfor unreliable bearing performance andreduced service life is avoided, there-by reducing maintenance requirementsand increasing machine availability.

4

Low load performance One potentially beneficial feature inmany applications of bearing arrange-ments using CARB and a double rowbearing as the fixed bearing, is thatdue to the optimised load distribution,the system is perfectly suited to de-liver maximum fatigue (L10) life underheavy load conditions, but will alsofunction very well at low load levels,compared with the traditional solutionusing two double row bearings. Thereason for the reduced susceptibilityto underloading can be explained asfollows:

– any row of rolling elements must besubjected to a certain minimum radialload, so that the roller set rotatessmoothly at a near-synchronousspeed. This minimum load reducesdamage from skidding of the rollers(raceway smearing damage, cagehammering, noise, vibration, elevatedtemperatures, grease degradation).The amount of load needed dependson the mass of the rolling elements,the rotational speed, and the lubricantviscosity.


In a traditional shaft arrangementwith two spherical roller bearings,where friction between the non-locatingbearing ring and housing means thatthe load distribution is rarely perfect,the radial load required for satisfactoryoperation is drastically increased com-pared with an ideal system, and forequivalent friction factors approaching0,89 it is not possible to adequatelyload the bearings.

If a toroidal roller bearing is used atthe non-locating position then withpurely radial externally applied loadsboth rows of rollers in the locatingspherical roller bearing should alwaysbe equally loaded. Therefore the radialload factor to be used to determinethe applied load required to achievesatisfactory operation is always equalto 1 as described in Diagram .1

Required radial load for smooth operationof two spherical roller bearings, as a function of housing friction

1Diagram

Radial load factor

Traditional bearing

arrangement

New bearing system

2Diagram

3Diagram

Vibration, mm/s

Vibration, mm/s

Hours

Hours

Fan with spherical roller bearing 22244/C3 at both positions

The same fan with toroidal roller bearingC 2244/C3 at non-locating position

Improvement of operating conditions andreliabilityThe following three examples demon-strate the immediate improvements inoperating parameters (temperature,vibration levels) and consequently theincreased reliability/decreased mainten-ance effort which is obtained throughthe better internal load distribution asa result of the frictionless axial free-dom in the toroidal roller bearing. Thefirst case (➔ Diagram and ) is avery large axial flow fan, which wasoriginally equipped with sphericalroller bearings (size 22244/C3) at bothlocating and non-locating positions.During commissioning the overallvibration level fluctuated greatly withintermittent very high peaks and highbearing temperature at approximately60 °C above ambient (➔ Diagram ). The non-locating bearing was thenreplaced by the toroidal roller bearingof the same size (C 2244/C3). Theresult was the elimination of the highvibration peaks and quick stabilisationof bearing temperature at approxim-ately 20 °C above ambient (➔ Diagram

).3

2

32

Temperature

Vibration

Temperature riseabove ambient, °C

Temperature

Vibration

Temperature riseabove ambient, °C


4Diagram

5Diagram

Industrial fan rebuilt with toroidal rollerbearing. Grease lubrication, 3 000 r/min

Industrial fan rebuilt with toroidal rollerbearing. Oil lubrication, 3 000 r/min

Bearing temperature increase above ambient

Bearing temperature increase above ambient

Two other real cases of rebuilds ofindustrial fans are shown in Diagramand . Both examples are convention-al centrifugal fans where the non-locat-ing spherical roller bearings were re-placed by toroidal roller bearings of thesame size.

In both fans, the operating temperat-ure of the non-locating bearing droppeddramatically; the locating bearing tem-perature was also reduced but to a lesser extent. (This is as expected, asthe locating bearings carry some axialload from the fan impellers and there-fore should run somewhat hotter thanthe non-locating bearings.)

54

Low load, high speedIn high speed applications where thereare light loads and the possibility ofmisalignment, self-aligning ball bear-ings have been the standard solution.These applications can also benefitgreatly from using the toroidal rollerbearing at the non-locating position,for all the same reasons as describedpreviously for the spherical roller bear-ing solution. Self-aligning ball bearingsare much more susceptible to damagefrom axial preloading than sphericalroller bearings, so eliminating the poss-ibility of friction-induced axial forceshas even greater significance in avoid-ing premature failure (➔ Diagram ).7

Rel

ativ

e L 1

0lif

e fo

r be

arin

g sy

stem

Friction coefficient µ

The new self-aligning bearing system cangive better life even with smaller bearings

6Diagram

1) As there is no risk of cross-locationof the bearings due to the frictionlessinternal axial movement in CARB,there is less importance placed uponthe form and rigidity of the support-ing structure for the bearings, mean-ing that lighter, more flexible and lessprecise components can be tolerat-ed without a corresponding reduc-tion in bearing performance.

Cost reduction throughdownsizingIn addition to the obvious performanceenhancements, operating cost reduc-tions and productivity improvementsthat the CARB/spherical solution cangive, there are additional benefits thatcan be realised from this new andunique self-aligning bearing system.The bearing system with CARB as thenon-locating bearing has no internallygenerated thrust forces (Fa = 0 for bothbearings) whereas traditional bearingarrangements do have thrust forces(Fa = Fr × µ for both bearings). Fromthis it is a simple matter to calculatethe difference in fatigue life obtained ineach system. In cases where the life ofa conventional arrangement restrictsmachine performance, substituting atoroidal roller bearing at the non-locat-ing position could significantly extendservice life.

Where a conventional arrangementprovides adequate service life, thenusing the new bearing system design,but with smaller bearings in both posi-tions, can also often achieve the re-quired life (➔ Diagram ). Therefore,there can be significant opportunitiesto not only use smaller, less expensivebearing assemblies without the risksof failure associated with axial pre-loading and general lack of axial free-dom, but also to reap the flow-on costbenefits by the consequential size andweight reduction of other structuralcomponents.

For example, if one size smaller bear-ing, housing, seal and adapter sleeveassembly can be utilised at each end ofa shaft, then the potential savings caninclude:

• bearing assembly purchase price• bearing assembly weight• shaft diameter and length reduction

(material cost and weight savings)• support structure size and weight

reduction1) (material cost and weightsavings)

• less stringent machining and assem-bly tolerances1) (production time sav-ings)

• transportation cost reduction as aresult of decreased overall machineweight

6

*) µ = 0,15 for steel against cast iron


Eliminating risk of poor operating conditionsThe diagrams showing comparativebearing system lives (➔ Diagramand ) are simplifications.

The calculations assume that thereis no external axial load on the shaftsystem, and that both bearings carrynominally radial load (such as a beltconveyor pulley, paper machine roll,continuous caster roll, table roll). Theaxial forces used to determine the L10fatigue life are then only those gener-ated within the bearing system itself.

Should there really be external axialforces (which is often the case) thenthe calculated difference between thetwo types of bearing system will bereduced; the slope of the curve for thetraditional arrangement will be less,sometimes appreciably so. Neverthe-less, the same principle applies, in thatthe traditional bearing arrangement

76

7Diagram

Self-aligning ball bearing + CARB

(2222 K + C 2222 K)

Self-aligning ball bearing + CARB (downsized)

(2220 K + C 2220 K)

Self-aligning ball bearing + Self-aligning ball bearing

(2222 K + 2222 K)

Friction coefficient µ

Rel

ativ

e L 1

0lif

e fo

r be

arin

g sy

stem

System life comparison for self-aligning ball bearings

will still experience some variation ofthe internal load distribution due tointernally generated forces, in additionto the nominal externally appliedloads, whereas the new system willnot.

For any specific case, it is almostimpossible to know what the equiva-lent ”average” value of µ will be overthe life of the bearing system (i.e.which position on the x-axis of thegraph is relevant). As seen earlier,there are an infinite number of com-binations involving bearing clearance,initial offset, housing bore toleranceand condition, etc.

Some machines may operate with a low “average” µ, but there is alwaysa significant chance that an individualmachine may have a high average µfor any number of unquantifiable reasons.

Note: Bearing system fatigue life = L10, sys

1 1 1= +(L10, sys )

e (L10, loc )e (L10, non-loc )

e

For roller bearings, e = 9/8For ball bearings, e = 10/9

The compromise-freesolutionWith the new self-aligning bearing sys-tem, utilising a CARB toroidal rollerbearing at the non-locating position,the many excellent design featuresand operating capabilities of SKF double-row spherical roller bearingsand self-aligning ball bearings cannow be fully exploited to provide thebest possible reliability, and to optim-ise the selection of the bearings andthe overall design of machine.

The new self-aligning bearing sys-tem, with a toroidal roller bearing inthe non-locating position, eliminatesany possibility of the high µ factor, asby definition µ is always equal to zero.

Elimination ofaxial forces

Even loaddistribution

Low stresslevels

Downsizedbearings

Increasedfatigue life

Low friction

Lower friction Lowerprice

No risk ofunderloading

Reducedmaintenance

Increasedproductivity

Lower com-ponent costs

Lower powerusage

Reducedmaintenance


Less risk of cagefailure

Increasedfatigue life

Reducedwear

Reducedvibration

Lowernoise

Longergrease life

Less risk ofsmearing

Lower powerusage

Reduced temperature

General machineimprovement

Increased product quality

Reducedmaintenance


Lower re-ject costs

Improved lubefilm thickness

Longergrease life

Lower greasecost

Reducedmaintenance

Lower greasecost

Improved bearingreliability


Lower greasecost

Tight fit possible Even and consistentload distribution

No housingwear

No vibration

Reduced main-tenance costs

Reducedtemperature

Improved prod-uct quality

No axial vibrations

Low cageforces

Less risk of underloading

Reduced cagefailure

Longergrease life

Lower greasecost

Reducedmaintenance


Reducedvibration

Lownoise

Increased grease life

Less risk ofsmearing

Improved bearingreliability

Improved lubefilm thickness


Lower re-ject costs

Reducedmaintenance


General machineimprovement

Improvements with the new self-aligning bearing system(Guaranteed axial freedom)

Improvements with the new self-aligning bearing system

Operating Typical applications Temperature Vibration Housing or Improved reliabilityconditions reduction and noise shaft wear eliminates cata-

reduction reduction strophic failures

WheelContinuous caster

High load Screw conveyor • • • •Low speed Grinding mill

Press rollsGear shaft

Drying cylinderConveyor pulleyRoller table

Medium to Calenderhigh load Crusher • • • • • • • •Medium to Propulsion equipmenthigh speed Flour mills

Gear shaftFelt rollWire roll

Industrial fanLight load BlowerHigh speed Agricultural machinery • • • • • • • • • •

Gear shaftSuction roll

Eccentric motion Vibrating screenCentrifugal Washing machine • • • • • • • •loads Crank press

ShredderChipper

Indeterminate Industrial lawnmowerloads Large electric motorMedium to Crusher • • • • • • • •high speed Blower

MixerHarvesterPump

Paper dryerHeated rotors Heated calenderLarge thermal Cooker • • • •expansion Mixer

Yankee dryerHeat exchanger

no influence: – little influence: • some influence: • • strong influence: • • •


Reduced Increased Decreased Increase Simpler Simplermaintenance throughput stoppage L10 life or cheaper installation

time downsize structure procedure

• • • • • • • • •

• • • • • • • • •

• • • • • • • •

• • • • • • • • •

• • • • • • • • • •

• • • • • • • • • • • • • • •

Influences of the new self-aligning bearing system for different types of machines

The SKF Group – a worldwide corporation

SKF is an international industrial Groupoperating in some 130 countries and isworld leader in bearings.

The company was founded in 1907following the invention of the selfalign-ing ball bearing by Sven Wingquist and,after only a few years, SKF began toexpand all over the world.

Today, SKF has some 40 000 em-ployees and around 80 manufacturingfacilities spread throughout the world.An international sales network includesa large number of sales companies andsome 7 000 distributors and retailers.Worldwide availability of SKF productsis supported by a comprehensive technical advisory service.

The key to success has been a con-sistent emphasis on maintaining thehighest quality of its products and services. Continuous invest-ment in research and

development has also played a vitalrole, resulting in many examples ofepoch-making innovations.

The business of the Group consistsof bearings, seals, special steel and acomprehensive range of other high-tech industrial components. The experi-ence gained in these various fieldsprovides SKF with the essential know-ledge and expertise required in orderto provide the customers with the mostadvanced engineering products andefficient service.

The SKF Engineering & Research Centre is situated just outside Utrecht in TheNetherlands. In an area of 17 000 squaremetres (185 000 sq.ft) some 150 scientists,engineers and support staff are engaged inthe further improvement of bearing perform-ance. They are developing technologiesaimed at achieving better materials, betterdesigns, better lubricants and better seals – together leading to an even better under-standing of the operation of a bearing in itsapplication. This is also where the SKF LifeTheory was evolved, enabling the design of bearings which are even more compact and offer even longer operational life.

SKF has developed the Channel concept infactories all over the world. This drasticallyreduces the lead time from raw material toend product as well as work in progress and finished goods in stock. The conceptenables faster and smoother informationflow, eliminates bottlenecks and bypassesunnecessary steps in production. The Channel team members have the know-ledge and commitment needed to share theresponsibility for fulfilling objectives in areassuch as quality, delivery time, production flow etc.

SKF manufactures ball bearings, roller bearings and plain bearings. The smallestare just a few millimetres (a fraction of aninch) in diameter, the largest several metres.SKF also manufactures bearing and oilseals which prevent dirt from entering and lubricant from leaking out. SKF’s subsidiaries CR and RFT S.p.A. are amongthe world’s largest producers of seals.

The SKF Group is the first major bearingmanufacturer to have been granted approvalaccording to ISO 14001, the internationalstandard for environmental managementsystems. The certificate is the most com-prehensive of its kind and covers more than60 SKF production units in 17 countries.

© Copyright SKF 2000The contents of this publication are thecopyright of the publisher and may notbe reproduced (even extracts) unlesspermission is granted. Every care hasbeen taken to ensure the accuracy ofthe information contained in this pub-lication but no liability can be accepted for any loss or damage whether direct,indirect or consequential arising out ofthe use of the information containedherein.

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self-aligning bearing systems

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