1 Product information 2 Recommendations 3 Product data Sealed bearings Page ............. 18 Page ............. 32 10 Sealed SKF spherical roller bearings – for demanding environ- ments Sealed SKF spherical roller bearings are designed to fulfil high demands on sealing efficiency and operational reli- ability under difficult environmental con- ditions. The seals were developed using computer simulation, making full usage of the vast expertise within the SKF Group. They have been extens- ively tested both in the laboratory and in the field and have proved their reli- able performance and efficiency. SKF sealed spherical roller bearings include double-lip, sheet steel rein- forced seals made of — nitrile rubber (NBR) — hydrogenated nitrile rubber (HNBR) — fluoro rubber (FPM) and a grease fill which is appropriate to the operating conditions. This forms a ready-to-mount and lubricated-for-life bearing with long service life and normally the same space requirements as a standard open bearing. The advantages include a simplification of the bearing arrange- ment, as well as the option of down- sizing. Facilities for relubrication are normally not required, and there are no more costs for purchasing, applying and disposing of bearing greases. Temperature limits Sealed SKF spherical roller bearings are suitable for normal operating tem- peratures up to 110 °C (230 °F). Bear- ings for higher operating temperatures can be produced upon request. In these cases, the grease and seal material must be chosen accordingly. Other operating conditions such as the speed may need to be considered as well. Please contact the SKF applica- tion engineering service for further advice.
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1 Product information 2 Recommendations 3 Product data
Sealed SKF sphericalroller bearings – fordemanding environ-mentsSealed SKF spherical roller bearingsare designed to fulfil high demands onsealing efficiency and operational reli-ability under difficult environmental con-ditions. The seals were developedusing computer simulation, making fullusage of the vast expertise within theSKF Group. They have been extens-ively tested both in the laboratory andin the field and have proved their reli-able performance and efficiency.
SKF sealed spherical roller bearingsinclude double-lip, sheet steel rein-forced seals made of
and a grease fill which is appropriateto the operating conditions.
This forms a ready-to-mount and lubricated-for-life bearing with long service life and normally the samespace requirements as a standardopen bearing. The advantages includea simplification of the bearing arrange-ment, as well as the option of down-
sizing. Facilities for relubrication arenormally not required, and there are nomore costs for purchasing, applyingand disposing of bearing greases.
Temperature limitsSealed SKF spherical roller bearingsare suitable for normal operating tem-peratures up to 110 °C (230 °F). Bear-ings for higher operating temperaturescan be produced upon request. Inthese cases, the grease and sealmaterial must be chosen accordingly.Other operating conditions such as thespeed may need to be considered aswell. Please contact the SKF applica-tion engineering service for furtheradvice.
1 Product information 2 Recommendations 3 Product data
1Contamination resistanceDue to the efficiency of the integralseals, additional external seals arenormally not required. Generally com-pact bearing arrangements can beproduced in most cases. However, ifthe environmental conditions areharsh, external seals should beemployed (➔ fig ).1
A sealed spherical roller bearing in anSNL plummer block housing
Warning for fluoro rubber (FPM)sealsFPM is very stable and harmlessin normal operating conditions –up to 200 °C (392 °F). However, ifexposed to extreme temperaturesabove 300 °C (572 °F), e.g. fire orthe flame of a cutting torch, fluororubber emits dangerous toxicvapours. Once overheated the fluoro rubber will remain danger-ous to handle even when cooled.Please contact SKF for completesafety instructions. See also SKFcatalog 4006 “CR seals” for furtherinformation.
Rule of thumbSealed bearings do not needrelubrication when the temperat-ures do not exceed 70 °C (158 °F)and speed are not more than 50 %of the speed rating listed in theproduct tables. More precise in-formation is given in the section“Lubrication and maintenance” onpage 28.
Well protectedThe bearings have asheet steel reinforc-ed double-lip sealat each side. Sealscan be made ofnitrile rubber (NBR),hydrogenated nitrilerubber (HNBR) orfluoro rubber (FPM).
Well lubricatedBearings for normaloperating temperat-ures and speeds arelubricated with theSKF lithium basegrease LGEP 2 withexcellent rust inhibit-ing properties.
Always reliableThe bearings are filled with a high-quality grease,which is particularlysuitable for SKFspherical rollerbearings. Integralseals contribute tothe efficient lubrica-tion by keeping thelubricant in positioninside the bearing.
Moisture cannotenterAdequate sealskeep water out ofthe bearing, whichotherwise wouldcause corrosionand considerabledamage to theraceways, leadingto noise and earlyfailure. The im-proved seals areendorsed by therust inhibiting properties of the lubricant.
Solid contamin-ants excludedEliminate dirt in thebearing, which cre-ates indentations inboth raceways androllers and causesearly failure due toflaking. The best andsimplest method todo this is to use SKFsealed spherical roller bearings. Theseals offer protec-tion for the bearinginterior during hand-ling and mounting.
1Fig
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Where maintenance canbe a nightmareTo get to the top is always a challenge,particularly if the goal is the top of ski-liftmasts in mid winter when it is 30 de-grees below zero and the bearings haveto be relubricated. If operational reliabilityis to be achieved, then it has to be done.Regular relubrication is a must if thebearings are to be kept from rustingbecause of condensation. In additionsafety considerations call for regularinspections – a dangerous job high up inmountainous terrain and under difficultweather conditions.
The introduction of SKF sealed spher-ical roller bearings has made all the dif-
Long service life, high reliability, limitedmaintenance and the ability to designcompact arrangements have madeSKF spherical roller bearings indis-pensable in many industries. In addi-tion to the industries listed above SKFspherical roller bearings are also usedin bridges, dam gates, electric motors,generators, plastic calenders, ex-truders, printing machines, robots and many other applications.
Because end users are recognizingthat high quality bearings deliver anexcellent return on investment, SKFspherical roller bearings are becomingthe preferred choice in new applica-tions.
• Long service life • High load carrying capacity• Compact arrangements• Tolerant of misalignment• Minimum maintenance• Reduced operation costs• No unplanned stoppages• Environmental welfare• High availability• Technical support
Solution
ference. It is now only necessary to per-form maintenance once a season –before starting operation. The highly efficient seals reliablyexclude condensa-tion so that corrosion is no longer aproblem. It has also been possible tosimplify the arrangement, saving spaceand costs – as well as making handlingand installation easier.
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1 Product information 2 Recommendations 3 Product data
1Downsizing – more thanjust sizeA typical application for spherical rollerbearings is the winch of a traversingindustrial lift. In this application the load,bending and deformation all call forrugged bearings that can function prop-erly even under misalignment.
Open spherical bearing arrangementsprovided good service, but were toobulky and complicated to be consideredcompletely satisfactory.
As a result, the open bearings werereplaced with SKF sealed sphericalroller bearings eliminating the need forthe external seals and covers.
This obviously saved space and alsomeant that the bearings could be posi-tioned 40 % closer to the drum, thusreducing the stress on the journals. Infact, it was possible to reduce the jour-nal diameter by 20 % and use smallerbearings.
The new compact bearing arrange-ment requires much less maintenanceand there is no loss of load lifting capac-ity. The result has been a 50 % savingsof the total cost of the original bearingarrangement.
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1 Product information 2 Recommendations 3 Product data
Axial location of bearingsAn interference fit alone is generallyinadequate for the axial location of aspherical roller bearing ring. As a rule,some suitable means of axially secur-ing the ring is needed. Both rings of a locating bearing should be axiallysecured at both sides. For non-locatingbearings, on the other hand, it is suffi-cient if the ring having the tighter fit –usually the inner ring – is axiallysecured; the other ring must be free tomove axially with respect to its seating(➔ fig on page 21).
Bearing rings having an interferencefit are generally mounted so that thering abuts a shoulder on the shaft or inthe housing at one side. At the oppos-ite side, inner rings are normallysecured by a snap ring, shaft nut oran end plate attached to the shaft end.Outer rings are usually retained by thehousing end cover (➔ fig on page21).
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The dimensions of the shaft andhousing shoulders adjacent to the bear-ing must provide sufficient support forthe bearing rings, without contactbetween the rotating parts of the bear-ing and a stationary component. Toensure this, appropriate abutmentdimensions are quoted for each indi-vidual bearing listed in the producttables.
When using a shaft nut to locate asealed bearing, insert an intermediatering between the bearing and the lock-ing washer and, probably, to extendthe threaded portion of the shaftaccordingly (➔ fig ).3
Spherical roller bearing of CA design on a cylindrical seating with oil supply ducts and grooves
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Spherical roller bearing of CAK designon a tapered journal with oil supplyducts and grooves
Design of associatedcomponentsFor arrangements with large sphericalroller bearings it is often necessary tomake design provisions to enable thebearings to be mounted or dismountedeasily. For example, withdrawal tools can be applied to dismount bearings,if appropriate slots are machined in theshaft and housing shoulders, or ifthreaded holes are provided in the housing shoulders.
If the oil injection method is to beused to mount and dismount bearingson tapered journals (➔ fig ) or to dis-mount bearings from cylindrical seat-ings (➔ fig ), it is necessary to pro-vide oil supply ducts in the journal andgrooves in the seating. Recommenda-tions are given in the SKF publication4100 “SKF Bearing MaintenanceHandbook” or CD-ROM “SKF Inter-active Engineering Catalogue”.
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An intermediate ring between the bear-ing and lock washer (of the nut) protectsthe seal
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A polymer band in the annular groovecovers the lubrication holes in the outerring of sealed bearings
Retaining rings hold the seals in the outer ring
Grease quantity for periodic relubricationIf the relubrication interval is less than6 months, it is recommended to re-plenish the grease fill in the bearingarrangement at intervals correspond-ing to 0,5 tf. The complete grease fillshould be replaced after three replen-ishments.
Suitable quantities to be added foropen bearings can be obtained from
Gp = 0,005 D B
and for sealed bearings from
Gp = 0,0015 D B
whereGp = grease quantity to be added
when replenishing, gD = bearing outside diameter, mmB = total bearing width, mm
The bearing must rotate during relub-rication to achieve proper distributionof the grease.
Grease quantity for continuous relubricationThe grease quantity to be continuouslysupplied can be obtained from
Gk = (0,3 ... 0,5) D B × 10–4
whereGk = grease quantity to be continuously
supplied, g/hD = bearing outside diameter, mmB = total bearing width, mm
Continuous relubrication can be effi-ciently achieved using the SKF SYS-TEM 24 lubricator.
Relubrication of sealed SKF spherical roller bearingsThe sealed spherical roller bearingsshown in the product tables (page 54onwards) have an annular groove andthree lubrication holes as standard. Toprevent moisture from penetrating andto retain the grease in the bearing apolymer band in the groove covers thelubrication holes (➔ fig ).
If it is anticipated that bearing relub-rication will be necessary during opera-tion, the band should be removedbefore the bearing is mounted. Whenrelubricating, grease should be slowlypressed into the bearing as it rotatesuntil fresh grease emerges from thesealing lips. Excess pressure shouldbe avoided to prevent seal damage.
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Removing a retaining ring Inserting the seal in the outer ring
MaintenanceThe seals of SKF spherical roller bear-ings with a bore diameter of 110 mmand above are secured by retainingrings inserted in the outer ring (➔ fig ).The seals can be removed from thebearing so that the bearing can beinspected, washed and regreased, afterwhich the seals can be reinserted andsecured. To avoid damage to the seals,this work has to be done with care,using suitable, well rounded tools withno sharp edges.
1. Remove the retaining ring by insert-ing a tool under the recessed endof the retaining ring (➔ fig ) andpushing it out of the groove.
2. Remove the second retaining ringas above.
3. Swivel out the inner ring, so thatthe seals are pushed out by therollers.
4. The bearing, seals and retainingrings can now be washed
5. Inspect the parts for further usability.6. Regrease the bearing with inner
ring swivelled out.7. Align the bearing and put it on a
clean surface for remounting theseals.
8. Insert the seal as far as possibleinto its groove in the outer ring.Hold down the already insertedpart of the seal with one hand, andpress in the remainder, stepwisewith the thumb of the other hand (➔ fig ).6
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9. Mount the retaining ring by insert-ing the rectangular end first.Holding this part down, press in theremainder stepwise with a tool,until the whole retaining ring proper-ly contacts the seal as shown in fig .
10. Mount the second seal accordingto steps 7 to 9.
11. If the bearing is not immediately re-used, preserve the bearing sur-faces with oil and make sure thatthe bearing is well packed.
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MisalignmentSpherical roller bearings can accom-modate misalignment between theouter and inner rings without affectingthe bearing. The guideline values ofpermissible misalignment given inTable refer to open bearings andare valid for normal loads (C/P > 10)and operating conditions, and whenthe inner ring rotates under constantmisalignment.
Whether the stated values of mis-alignment between the outer ring andinner ring can be fully exploited or notdepends on the design of the bearingarrangement, the type of seals used etc.
Under the same conditions, sealedSKF spherical roller bearings canaccommodate angular misalignmentsof the shaft with respect to the housingof up to approximately 0,5°.
Influence of operating temperatureon the bearing materialsSKF spherical roller bearings rings androllers are special heat treated so thatthey can be used at temperatures upto +200 °C (390 °F) for up to 2 500hours or for brief periods at even high-er temperatures without any inadmiss-ible dimensional changes occurring. If provision is made to accommodateslight changes of fits and clearance,even higher temperatures or longerperiods can be accommodated.
Sealed SKF spherical roller bearingsshould not be used at operating tem-peratures above +110 °C (230 °F) asthis would be detrimental to the sealsand grease.
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Axial load carrying capacityBecause of their special internal design,SKF spherical roller bearings not onlyhave lower friction than other sphericalroller bearings, they are also able toaccommodate appreciably heavier axialloads. However, if Fa/Fr > e (➔ producttables), a more frequent relubricationthan usual is recommended.
Speed ratingsDue to the friction generated by con-tact seals, the speed ratings for sealedbearings for normal temperatures areapproximately 40 % of those for thecorresponding open bearings.
Guideline values for permissible angularmisalignment
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Supplementary designationsThe designation suffixes used to identi-fy certain features of SKF sphericalroller bearings are explained below.The suffixes used to identify bearing(and cage) design, e.g. CC or E, arenot included here as they are ex-plained under “Designs”.
C2 Radial internal clearancesmaller than Normal
C3 Radial internal clearancegreater than Normal
C4 Radial internal clearancegreater than C3
C08 Increased running accuracyto ISO tolerance class 5
C083 C08 + C3
C084 C08 + C4
2CS Sheet steel reinforced rubbingseals of nitrile rubber (NBR)at both sides of bearing.Grease fill 25 to 35 % withSKF grease LGEP 2. Annulargroove and three lubricationholes in outer ring.
2CSW 2CS + W
2CS2 Sheet steel reinforced rubbingseals of fluoro rubber (FPM)at both sides of bearing.Grease fill 70 to 100 % with a polyurea high temperaturegrease. Annular groove andthree lubrication holes in theouter ring.
2CS2W 2CS2 + W
2CS5 Sheet steel reinforced rubbingseals of hydrogenated nitrilerubber (HNBR) at both sidesof bearing. Grease fill 70 to100 % with a polyurea hightemperature grease. Annulargroove and three lubricationholes in the outer ring.
2CS5W 2CS5 + W
HA3 Case hardened inner ring
K Tapered bore, taper 1:12
K30 Tapered bore, taper 1:30
VA405 Bearing for vibrating applications
VA406 Bearing for vibrating applications with PTFE-coated bore
VE552(E) Outer ring with three equallyspaced threaded holes inone side face to take hoistingtackle; the E indicates thatappropriate eye bolts aresupplied with the bearings
VE553(E) Outer ring with three equallyspaced threaded holes inboth side faces to takehoisting tackle; the E indic-ates that appropriate eyebolts are supplied with thebearings
VG186 Hardened cages
VQ424 Running accuracy betterthan C08
VT143 Grease fill 25 to 35 % withSKF grease LGEP 2
W No relubrication facility inouter ring
W20 Three lubrication holes inouter ring
W26 Six lubrication holes in innerring
W33 Annular groove and threelubrication holes in outerring
W77 Plugged W33 lubricationholes
W509 W26 + W33
235220 Case hardened inner ringwith helical groove in bore
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