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In the use of radial lip-type oil seals to seal against a rotating shaft, the surface characteristics of the shaft are important to the sealing and to the resultant seal/shaft friction. A plunge ground shaft surface with no lead has long been the recommended mating surface for a radial lip-type oil seal. Recently, however, a peened surface was studied which will reduce frictional torques a maximum of 50%, 60%, and 70% below that of one utilizing a plunge ground shaft surface for silicone, nitrile and polyacrylate seal materials, respectively. Seal performance from a leakage standpoint for standard sharp lip seals exceeds that of the plunge ground surface. However, the preliminary results indicate that the surface is not suitable with hydrodynamic shaft seals. Some insight into elastomeric friction was obtained from the tests.

This paper sets forth the differences between standard sealing systems and elastohydrodynamic sealing systems and reviews a report on the latter prepared by a subcommittee of the SAE Transmission and Drivetrain Committee. An elastohydrodynamic sealing system requires a supplemental sealing device either on the seal itself or on the shaft. The paper describes unirotational and birotational seals for both types of design. It also discusses methods used in evaluating elastohydrodynamic seals, points out the limitations of each, and concludes by narrowing the field of suggested methods to three (visual examination of the seal on a plastic shaft, roll-coined spiral-grooved mandrel testing, and oil drop testing).

A fractional factorial experimental study was conducted to determine the effect of seal size on seal design. The seven factors studied were inside lip diameter (w/o spring), seal size, shaft-to-bore offset, spring position, contact width, flex section thickness, and material modulus. The fractional factorial experiment was designed so all interactions involving seal size were determinable. Leakage was measured as the response or dependent variable. The large seal (nominal 100 mm) differed from the small seal (nominal 50 mm) in three areas: (1) shaft-to-bore offset was not tolerated by the large seal, (2) the spring position was required to be closer to the contact line with the large seal, and (3) a higher material modulus was necessary with the larger seal.

Discussion of research program undertaken to study oil seals. The author is chiefly concerned with seal leakage which covers equipment and procedure for performance tests and its causes. The paper also includes a complete revision of SAB J110 which covers equipment and procedure for performance tests on radial lip type seals for rotating shafts.

The multitude of lip section designs and the continued major automotive warranty problem in the field of radial oil seals indicated that a more thorough knowledge of lip section design was necessary. Seven design factors were investigated by means of fractional factorial experimentation to determine the optimum level for each of the factors. The general effects of trim diameter, radial lip force, seal lip to case eccentricity, spring position, contact width, flex section, and material modulus, plus the interactions between these seven factors, were investigated. Leakage was measured as the response or dependent variable. A detailed drawing of the optimum lip section, derived from the results of tests which optimized on the main effects only, is given.

This treatise addresses the state-of-the-art in dynamic sealing systems for commercial vehicles. A brief review of different seal types is given and a 12 year literature search is included in the references. The scope of the paper, however, is limited to radial lip and mechanical face seals. The lack of understanding of the sealing mechanism is noted. Also discussed are the effects of various design factors; application factors which need specific attention; materials; testing methods; and the need for realistic standardized tests. Field tests are used as the final approval for seal applications, but qualification tests for the same type of application vary widely. Future work should be directed towards understanding the sealing mechanism.

THIS REPORT deals with the major parameters of a seal application which affect its efficiency and life, as determined by controlled laboratory testing in CM Research Laboratories.* A. Shaft 1. Surface Roughness 2. Machining Lead B. Assembly C. Seal 1. Seal Diameter Control Trim Interference Spring Rate 2. Seal Lip Pressure Trim Interference Spring Rate Rubber Hardness Eccentricity 3. Seal Eccentricity Mold Register Assembly Trim

The successful performance of a standard hydrodynamic radial-lip seal requires stringent production controls to maintain the configuration, height, and angle of the hydrodynamic ribs or aids which contact the shaft to create the small hydrodynamic pumps. These minute pumps, if their configuration is maintained, create a pressure differential across the sealing lip which aids in sealing. However, because of production variations, so-called “hydrodynamic” seals are produced which are not hydrodynamic. Therefore, a need exists for a hydrodynamic seal without complicated hydrodynamic aids. To meet this need, a simple hydrodynamic seal was conceived that enhances the viscous shear pump action of a standard sharp lip radial seal by the application of wave sealing theory principles to the seal contact path. A low modulus, easily deformable material was added to the lip contact to enhance and control the deformation of the waves which are inherent in the lip.