CARB Bearing

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  • CARB toroidal roller bearingsA revolutionary concept

  • The SKF brand now stands for more than ever before, and means more to you as a valued customer.

    While SKF maintains its leadership as the hallmark of quality bearings throughout the world, new dimensions in technical advances, product support and services have evolved SKF into a truly solutions-oriented supplier, creating greater value for customers.

    These solutions encompass ways to bring greater productivity to customers, not only with breakthrough application-specific products, but also through leading-edge design simulation tools and consultancy services, plant asset efficiency maintenance programmes,and the industrys most advanced supply management techniques.

    The SKF brand still stands for the very best in rolling bearings, but it now stands for much more.

    SKF the knowledge engineering company

    A Productinformation3 Thewinningcombination

    4 CARBtoroidalrollerbearingswithrevolutionarydesigncharacteristics

    5 SKF Explorer class bearings

    6 Arangeforallrequirements7 Availability7 Bearing benefits

    8 TheCARBtoroidalrollerbearingthecornerstoneoftheSKFself-aligningbearingsystem

    8 The conventional solution9 The SKF solution

    10 Successfulinservice

    BRecommendations12 Selectionofbearingsize12 Longer life or downsizing

    14 Designofbearingarrangements14 Radial location16 Axial location18 Design of adjacent components20 Sealing the bearing arrangement

    22 Lubrication22 Grease lubrication24 Deviating conditions25 Oil lubrication

    26 Mounting26 Mounting on a cylindrical seating26 Mounting on a tapered seating

    34 Dismounting34 Dismounting from a cylindrical seating35 Dismounting from a tapered seating

    36 TheSKFconceptforcostsavings

    Contents

    C Productdata37 Bearingdatageneral

    44 Producttables44 CARB toroidal roller bearings56 Sealed CARB toroidal roller bearings58 CARB toroidal roller bearings on an

    adapter sleeve68 CARB toroidal roller bearings on a

    withdrawal sleeve

    78 OtherassociatedSKFproducts

    82 SKFtheknowledgeengineeringcompany

    2

  • The winning combination

    Self-alignment ...

    Self-aligning bearings are the hallmark of SKF not surprising since SKF was founded in 1907, based on the invention of the self-aligning ball bearing by Sven Wingquist. But the development did not stop there, other SKF inventions followed: the spherical roller bear-ing in 1919 and the spherical roller thrust bearing in 1939.

    Self-alignment is called for

    when misalignment exists as a result of inaccurate manufacturing or mounting errors

    when shaft deflections occur under load

    and these have to be accommodated in the bearing arrangement without negative effects on performance or any reduction in bearing service life.

    ... and axial displacement ...SKF was also heavily involved in the develop-ment of bearings having rings that can be axially displaced relative to each other. In 1908, for example, the cylindrical roller bear-ing in its modern version was developed to a large extent by Dr.-Ing. Josef Kirner of the Nor-ma Compagnie in Stuttgart-Bad Cannstatt, which became a subsidiary of SKF.

    Cylindrical roller bearings are applied when

    heavy radial loads and relatively high speeds prevail

    thermal changes in shaft length must be accommodated within the bearing with as little friction as possible provided, of course, that there is no significant misalignment.

    ... combined for success

    In the past, almost every bearing arrange-ment was a compromise due to misalignment and shaft deflections. In most cases, depend-ing on the load and speed requirements, design engineers were limited to self-aligning ball bearings or spherical roller bearings.

    Though these bearings could accommodate misalignment, they could not accommodate axial displacement within the bearing like a cylindrical roller bearing. Therefore, it was necessary for one of the bearings to move axially on its seating in the housing. This movement, which generated a considerable amount of friction, produced additional axial forces in the bearing arrangement. The result was a shortened bearing service life and rela-tively high maintenance and repair costs.

    Today, this scenario is a thing of the past because Magnus Kellstrm, a product design-er at SKF, had the brilliant idea to create a bearing that could compensate for misalign-ment without friction like a spherical roller bearing, and accommodate changes in shaft length internally, like a cylindrical roller bearing.

    This completely new type of bearing, called a toroidal roller bearing gives engineers an opportunity to design bearing arrangements without compromise. Additional benefits include much longer service life for the com-plete bearing arrangement and minimized maintenance and repair costs

    Self-alignment

    and axial displacement

    combined in a toroidal roller bearing

    A

    3

  • CARB toroidal roller bearings with revolutionary design characteristics

    The CARB toroidal roller bearing represents one of the most important breakthroughs in rolling bearing technology over the past sixty years. The bearing was introduced to the market in 1995 under the SKF trademark CARB.

    The CARB toroidal roller bearing is a com-pletely new type of roller bearing, which offers benefits that were previously unthinkable. Irrespective of whether a new machine is to be designed or an older machine maintained, there are benefits to be gained by using a toroidal roller bearing. Which of these benefits is realized depends on the machine design and its operating parameters.

    A CARB bearing is a single row roller bear-ing with relatively long, slightly crowned roll-ers. The inner and outer ring raceways are correspondingly concave and symmetrical (fig.1). The outer ring raceway geometry is based on a torus (fig.2), hence the term toroidal roller bearing.

    The CARB toroidal roller bearing is designed as a non-locating bearing that combines the self-aligning ability of a spherical roller bear-ing with the ability to accommodate axial dis-placement like a cylindrical or needle roller bearing. Additionally, if required, the toroidal roller bearing can be made as compact as a needle roller bearing.

    An application incorporating a CARB toroidal roller bearing provides benefits outlined in the following.

    Self-aligning capabilityThe self-aligning capability of a CARB bearing is particularly important in applications where there is misalignment as a result of inaccurate manufacturing, mounting errors or shaft de- flections. To compensate for these conditions, a CARB bearing can accommodate misalign-ment up to 0,5 degrees between the bearing rings without any detrimental effects on the bearing or bearing service life (fig.3).

    Axial displacementPreviously, only cylindrical and needle roller bearings could accommodate thermal expan-sion of the shaft within the bearing. Today, however, the CARB bearing has been added to that list (fig.4). The inner and outer rings of a CARB bearing can be displaced, rela-tive to each other, up to 10 % of the bearing width. By installing the bearing so that one ring is initially displaced relative to the other one, it is possible to extend the permissible axial displacement in one direction.

    In contrast to cylindrical and needle roller bearings that require accurate shaft align-ment, this is not needed for toroidal roller bearings, which can also cope with shaft deflection under load. This provides a solution to many problem cases.

    Long system lifeThe ability to accommodate misalignment plus the ability to accommodate axial dis-placement within the bearing with virtually no friction enables a CARB bearing to provide benefits to the bearing system and its associ-ated components (fig.5):

    Internal axial displacement is virtually with-out friction; there are no internally induced axial forces, thus operating conditions are considerably improved.

    The non-locating bearing as well as the locating bearing only need to support external loads.

    The bearings run cooler, the lubricant lasts longer and maintenance intervals can be appreciably extended.

    Taken together, these benefits contribute to longer system life.

    The CARB toroidal bearing

    Fig.1

    The torus Fig.2

    Angular misalignmentThe most frequently occurring misalignments in operation are not a problem for a CARB toroidal roller bearing

    Fig.3

    Axial displacementChanges in shaft length are accommodated within the bearing, virtually without friction

    Fig.4

    Freedom of movementPermissible angular misalignment + axial displacement within the bearing

    Fig.5

    4

  • Deviations from cylindrical form are less problematicDemands on accuracy of form of the bearing seatings are less stringent, making simpler and less costly bearing arrangements possible

    Fig.6

    time

    conventional bearing system bearing system with a CARB bearing

    in the non-locating position

    axial vibration

    Diagram1

    Axial vibrationWith a CARB bearing axial vibrations are considerably reduced, meaning longer service life and quieter operation

    Full dimensional interchangeabilityThe advantages of CARB bearing can be fully exploited when refurbishing nonlocating bearing arrangements designed for selfaligning as well as rigid bearings

    Fig.7

    High load carrying capacityCARB toroidal roller bearings can accommo-date very heavy radial loads. This is due to the optimized design of the rings combined with the design and number of rollers. The large number of long rollers makes CARB bearings the strongest of all aligning roller bearings. Due to their robust design, CARB bearings can cope with sm