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Text version of the page
| Material Overview | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ■ Surface roughness DIN EN ISO 4287 The functional reliability and service life of a seal depend to a very great extent on the quality and surface finish of the mating surface to be sealed. Scores, scratches, pores, concentric or spiral machining marks are not permitted. Higher demands must be made on the surface finish of dynamic surfaces than of static mating surfaces. The characteristics most frequently used to describe the surface microfinishRa,Rz and Rmax are defined in DIN EN ISO 4287. These characterics alone, however, are not sufficient for assessing the suitability in seal technology. In addition the material contact area of the surface roughness profile Rmr in accordance withDIN EN ISO 4287 should be demanded. The significance of this surface specification is illustrated in Fig. 1. It shows clearly that specification of Ra and Rz alone does not describe the surface roughness profile accurately enough for the seal technology and is thus not sufficient for assessing the suitability. The material contact area Rmr is essential for assessing surfaces, as this parameter is determined by the specific surface roughness profile. This in turn is directly dependent on the machining process employed. Trelleborg Sealing Solutions recommends that the following surface finishes be observed: | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Figure 1 Profile forms of surfaces | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Figure 1 shows two surface profiles, both of which exhibit nearly the same value for Rz in the test procedure. The difference becomes obvious only when the material contact area of the survace roughness profiles are compared. These show that the upper roughness profile withRmr = 70% has the better seal/mating surface ratio. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Table VI Surface roughness | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| The material contact area Rmr should be approx. 50 to 70%, determined at a cut depthc = 0.25 x Rz,relativeto a reference line of Cref 5%. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| w TRELLEBORG il mua iRurm.'k | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Latest information available at www.tss.trelleborg.com Edition April 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 7 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||