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Design parameters of hydrodynamic elements had been analyzed and evaluated in respect to pumping and leakage-retaining capacity (SAE J1002). Inconsistencies of previous measurements at medium and high speeds had been resolved. A law of similarity had been discovered, by the use of which an optimized hydrodynamic seal can be calculated already in advance of the design phase. A novel concept of bidirectional seals had been developed which proved superior to unidirectional seals up to circumferential speeds of approx. 12 m/s and gave comparable results at higher speeds up to 25 m/s.

The development of PTFE-seals in lay-down-technology is changing rapidly from an empirical to a more sophisticated engineering approach, due to the use of e.g. Finite Element Analysis (FEA) for optimization of design parameters. FEA is a powerful engineering tool, but its results are only as reliable as the input data for the model and the material. Therefore material tests with a specific PTFE-compound are performed including creep and relaxation. Then an explaination for the ‘bell mouthing’ of the seal lip is given. Further on it is analyzed how some design parameters like seal thickness, length, and grooves influence the contact pressure distribution.

Technology for evaluating and studying the PTFE lay-down sealing element is improving. This paper compares and assesses advanced finite element modeling and measurement techniques for determining the radial load distribution of a PTFE lay-down sealing element and the effective axial contact distance on the mating surface.

The phenomenon of the spring back of radial shaft seals with rubber covered OD, looking for the first glance as a marginal one, should not be ignored during the seal design. From the numerical analysis of the installation process supplemented with experimental data results a considerable influence of the front part of the rubber layer covering the seal case on the run of tangential force and spring back. It will be shown that it is possible by proper design of the rubber layer on OD to counteract the spring back of the seal.

The results of torque measurements as well as discussion of different parameters which affect the measured value of torque are presented. The influence of methodology of experiments carried-out in either high or low temperatures has been accentuated.