NKE Hauptkatalog / General Catalogue 2011

Designof Bearing LocationFig. 7.9b)Double felt seal. For stronger contamination,especially in the presence of heavy dust, doublefelt seal arrangement may be used to increasethe sealing effectiveness.Fig. 7.9c) and Fig. 7.9d)Radial oil seals are standardised machineelements. They are available in a wide variety ofdifferent designs and materials to meet the givenrequirements in an optimum way. In the majorityof designs the radial sealing lip is pressedagainst the sealing surface by a garter belt.Radial oil seals must be arranged dependingon their main purpose. If the radial oil seal isused with the sealing lip facing outwards, asshown in Fig. 7.9c), the entry of contaminationparticles will be avoided. However, whereleaking oil or grease must be avoided theradial oil seal must be mounted with its sealinglip inwards, see fi g. 7.9d).For applications where both are required eithera special radial oil seal having double sealinglips may be used or two single radial oil sealslocated with their sealing lips arranged facingeach other outwards.Radial oil seals are suitable - dependingon their individual design and material - forcircumferential speeds up to 15 metres/second. They are also produced in severalvariations, such as special high temperatureresistant materials, with garter springs instainless steel, multiple sealing lips, etc.For more detailed information please refer tothe individual manufacturer’s data sheets.Fig. 7.9e)V-ring seals are mounted onto the shaft whichrotates whilst the long sealing lip contactsunder light preload on the mating face of thestationary machine part.In cases where the design of the housing as amating face is not possible or uneconomical, aspecial sealing washer may be used.V-ring seals provide good sealing for both oiland grease lubrication even under difficultoperation conditions and feature simplemounting.They also permit, depending on each shaftdiameter, certain misalignments betweenbearing shaft and housing:Shaft diameter[mm]Maximumpermissible> ≤ misalignment-- 50 ≤ 1,5°50 150 ≤ 1°Table 7.13V-ring seals are suitable for circumferentialspeeds up to 12 m/s without special measuresbut they should have an axial location if operatingat speeds of more than 7 m/s. Such axiallocation may be achieved by means of locatingrings etc.Where V-ring seals have to operate at circumferentialspeeds exceeding 12 m/s the liftingof the ring by circumferential forces must beavoided by using supporting rings, such aspressed steel rings etc.For special applications V-rings are alsoavailable in different materials, such as flourfl uoropolymer (FPM) etc.Fig. 7.9f)Split bearing housings are frequently used withtwo-lip seals as shown in fi g. 7.9f).These seals are available in individual size tofit the split housings. Two-lip seals are madefrom polyurea and they are radially split whichmakes their mounting very easy.The space between their sealing lips has to befi lled with grease during mounting.www.nke.at 317