Several Factors That Affect Sealing Performance—Surface Roughness

  Surface roughness has a very import influence on the life and leakage performance of a reciprocating. The functional realiability and service lifr of a seal depend to a very great extent on the quality and sutface finish of the maring surface to be seales. Scores, scratches, proes, concentric or spiral machining marks are not permitted. Higher demands must be made on the surface finish of hynamic curface thean of static mating surfaces.

  Mary paramenters can be used to describe surface finishes and these are explained in ISO4287 and ISO4288. The characteristics most frequently used to describe the surface micro finish  Ra. Rz and Rmax. These characterizes 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 with S ISO4287 should be demanded. Specification of Ra and Rz alone does not decribe the surface roughness profile accurately enough for the seal technology and is thus not sufficient for assessing the suitablility. The material contact area Rmr is essential for assessing surface. As this parameter is determined by thespecificsurface roguhness profile. This in turn is directly dependent on the machining process employed.

  The materil area Rmr should be approx. 50% to 70%

JSPSEAL recomeeds that the following surface finishes be observed.