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GlossaryRelubrication intervalPeriod after which the bearings are relubricated. <strong>The</strong>relubrication interval should be shorter than the lubricationinterval.Radial bearingsRadial bearings are those primarily designed to accommodateradial loads; they have a nominal contact angle 0 ≤ 45°. <strong>The</strong> dynamic load rating and the static loadrating <strong>of</strong> radial bearings refer to pure radial loads (seeThrust bearings).Radial clearance<strong>The</strong> radial clearance <strong>of</strong> a bearing is the total distanceby which one bearing ring can be displaced in theradial plane, under zero measuring load. <strong>The</strong>re is a differencebetween the radial clearance <strong>of</strong> the unmountedbearing and the radial operating clearance <strong>of</strong> themounted bearing running at operating temperature.<strong>Rolling</strong> elementsThis term is used collectively for balls, cylindrical rollers,barrel rollers, tapered rollers or needle rollers inrolling contact with the raceways.Seals/SealingOn the one hand the sealing should prevent the lubricant(usually lubricating grease or lubricating oil ) fromescaping from the bearing and, on the other hand, preventcontaminants from entering into the bearing. Ithas a considerable influence on the service life <strong>of</strong> a bearingarrangement (cp. Wear, Contamination factor V ).A distinction is made between non-rubbing seals (e.g.gap-type seals, labyrinth seals, shields) and rubbingseals (e.g. radial shaft seals, V-rings, felt rings, sealingwashers).Radial clearance group<strong>The</strong> radial clearance <strong>of</strong> a rolling bearing must be adaptedto the conditions at the bearing location (fits, temperaturegradient, speed). <strong>The</strong>refore, rolling bearingsare assembled into several radial clearance groups, eachcovering a certain range <strong>of</strong> radial clearance.<strong>The</strong> radial clearance group CN (normal) is such thatthe bearing, under normal fitting and operating conditions,maintains an adequate operating clearance. <strong>The</strong>other clearance groups are:C2 radial clearance less than normalC3 radial clearance larger than normalC4 radial clearance larger than C3.Rated viscosity 1<strong>The</strong> rated viscosity is the kinematic viscosity attributedto a defined lubricating condition. It depends on thespeed and can be determined with diagram 2 (page185) by means <strong>of</strong> the mean bearing diameter and thebearing speed. <strong>The</strong> viscosity ratio (operating viscosity/rated viscosity 1 ) allows the lubricating condition tobe assessed (see also factor a 23 ).Self-aligning bearingsSelf-aligning bearings are all bearing types capable <strong>of</strong>self-alignment during operation to compensate for misalignmentas well as shaft and housing deflection.<strong>The</strong>se bearings have a spherical outer ring raceway.<strong>The</strong>y are self-aligning ball bearings, barrel roller bearings,spherical roller bearings and spherical rollerthrust bearings.Thrust ball bearings with seating rings and S-typebearings are not self-aligning bearings because they cancompensate for misalignment and deflections only duringmounting and not in operation.Separable bearings<strong>The</strong>se are rolling bearings whose rings can be mountedseparately. This is <strong>of</strong> advantage where both bearingrings require a tight fit.Separable bearings include four-point bearings, cylindricalroller bearings, tapered roller bearings, thrustball bearings, cylindrical roller thrust bearings andspherical roller thrust bearings.Non-separable bearings include deep groove ball bearings,single-row angular contact ball bearings, self-191 FAG