Ball and Roller Bearings

External bearing sealing devicesType Seal construction Name Seal characteristics and selection considerationsNon-contact seals Contact sealsOilsurfaceSlingerSlingerZ grease sealV-ring sealBack up metalLip edgeOil combsleeveOil flowAir flowSpringSeal lipOil comb sleeveSlingerprovided in thehousingSlingerprovidedoutside thehousingZ grease sealV-ring sealOil sealIn this design, lubricating oil thatmakes its way out of the housingalong the shaft is thrown off byprojections on the oil comb sleeveand recirculated.Seal type whereby a slinger isprovided in the housing thatprevents lubricant from leaking bycentrifugal force produced byrotation.By mounting a slinger on the outsideof the housing, centrifugal forcehelps to prevent dust and other solidcontaminants from entering.Cautionary points regarding selectionSeal type whereby a slinger thatutilizes centrifugal force isprovided on the rotating shaft.If mounted on the inside of thehousing, the slinger shouldfunction to seal in lubricant bycentrifugal force produced byrotation.If mounted on the outside of thehousing, the slinger shouldfunction to seal out foreign matterby fan effect produced by rotation.These seal types are commonlyemployed together with othersealing devices.In cross section resembling the letter "Z," this seal's empty spaces are filled withgrease.The seal is commonly used with a plummer block (bearing housing).This design enhances sealing efficiency with a lip that seals from the axial direction.With the aid of centrifugal force, this seal also offers effective protection againstdust, water, and other contaminants entering the bearing. Can be used for both oiland grease lubrication.At seal peripheral speeds in excess of 12 m/s, seal ring fit is lost due to centrifugalforce, and a clamping band is necessary to hold it in place.Oil seals are widely used, and theirshapes and dimensions arestandardized under JIS B 2402.In this design, a ring-shaped springis installed in the lip section. As aresult, optimal contact pressure isexerted between the lip edge andshaft surface, and sealingefficiency is good.When the bearing and oil seal arein close proximity, the internalclearance of the bearing may bereduced by heat produced by theoil seal. In addition to consideringthe heat generated by contactseals at various peripheral speeds,internal bearing clearances mustalso be selected with caution.Cautionary points regarding selectionShaft surface roughness (reference) PeripheralSurface roughness speed m/sRa Rmax 50.8a 3.2s5100.4a 1.6s100.2a 0.8sShaft material (reference) MaterialSurfacehardnessMachine structuralcarbon steel, Low carbonalloy steel, Stainless steelHRC 40 or higher necessaryHRC 55 or higher advisableFor dust proofFor preventinglubricant leakageDepending on its orientation, theseal may function to preventlubricant from leaking out orforeign matter from getting in.ProcessingmethodFinal grinding withoutrepeat (moving), or buffedafter hard chrome platingAllowable speed/temperature according to seal type/material (reference)Oil sealsZ-sealV-ringSeal type/materialNitrile rubberAcrylic rubberFluorinated rubberNitrile rubberNitrile rubberAllowableperipheral speed m/s V(m/s) d(mm)n(r/min)Allowable temp ˚C60,000 16 or less-25 +12026 or less-15 +15032 or less-30 +2006 or less-25 +12040 or less-25 +120A-81