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Lip seal, Hydraulic seal, Pneumatic seal, Scraper, Fitting
Text version of the page
| Radial Oil Seal | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ■ Shaft and housing design Shaft Surface finish, hardness and machining methods The shaft design is of vital significance for the performance as well as for the useful life of the seal (see Figure 3). As a basic principle, the hardness of the shaft should be higher for increasing peripheral speeds. The Standard DIN 3760 specifies that the shaft must be hardened at least 45 HRC. As the peripheral speeds increase, the hardness must be increased and at 10 m/s a hardness of 60 HRC is required. The choice of a suitable hardness is dependent not only on the peripheral speed but also on such factors as lubrication and the presence of abrasive particles. Poor lubrication and difficult environmental conditions require a higher hardness of the shaft. DIN 3760 specifies a surface roughness of Rt=1 Limto4 urn. Laboratory tests have however proved that the most suitable roughness is Rt=2 urn (Ra=0.3 urn). Rougher as well as smoother surfaces generate higher friction, resulting in increased temperature and wear. We suggest a surface roughness of Rt=2-3 Lim (Ra=0.3-0.8 Lim). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Measurements of friction and temperature have also shown that grinding of the shaft is the best method of machining. However spiral grinding marks may cause a pumping effect and leakage and plunge grinding should therefore be applied, during which even ratios between grinding wheel speed and work-piece should be avoided. Polishing of the shaft surface with polishing cloth produces a surface which causes higher friction and heat generated as compared with plunge grinding. In certain cases it maybe impossible to provide the necessary hardness, surface finish and corrosion resistance of the shaft. This problem can be solved by fitting a separate sleeve onto the shaft. If wear should occur, only the sleeve need to be replaced (see the chapter Shaft Repair Kit). Shaft run out Shaft run out should as far as possible be avoided or kept within a minimum. At higher speeds there is a risk that the inertia of the sealing lip prevents it from following the shaft movement. The seal must be located next to the bearing and the bearing play be maintained at the minimum value possible. See Figure 13. Eccentricity Eccentricity between shaft and housing bore centers should be avoided in order to eliminate unilateral load of the lip. See Figure 14. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Figure 13 Shaft run out | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Figure 14 Eccentricity | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Latest information available atwww.tss.trelleborg.com Edition April 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| TRELLEBORG SEALING SOLUTIONS | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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