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With the development of modern industry, rotary lip seal is applied to more complex working conditions. For the lip seal with larger or smaller radial force, and the lip seal with incomplete motion...

The paper presents the results of research into a hybrid seal which is a combination of standard rotary lip seals and a magnetic fluid seal. To maintain the magnetic fluid in the friction zone region, either a specially shaped pole piece was used or the shaft was modified accordingly. The research study concerns the allowable operating pressure and lubrication conditions in short-term and durability tests after which shaft wear was also assessed. Magnetic fluids with different rheological and magnetic properties were considered. The test results showed that the long-term operation of a hybrid seal is possible. The requirements, however, are the appropriate value of the magnetic field and dynamic viscosity of the magnetic fluid.

The pressure between a shaft and a reinforced rubber cuff (a lip seal) is considered. An algorithm is derived for calculating the contact pressure, taking account of the properties of the material, the thickness of the cuff’s active section, its inclination to the shaft, the spring’s tensile force, and the geometric parameters of the cuff’s free section.

A thermomechanical model of a stern tube seal has been developed by paying particular attention to the contact between the seal and the shaft. The finite element method is used to capture the macroscopic behavior of the seal while roughness was evaluated at a microscopic level by applying the boundary element method. The seal material was independently characterized, and the results were used to calibrate the material constitutive model used for the seal. Two specialized setups were built to validate the model in terms of radial force, contact width, and percolation threshold. By combining the two models, the strains, stresses, temperature, and the limits of static tightness can be predicted at high accuracy for a wide range of operating conditions.

The working temperatures of mechanical equipment are continually increasing, leading to rapid deterioration in the service performance of lip seals. Conventional rubber lip seals cannot achieve a b...

This study is devoted to the effect of different coefficients on the calculation results of the rotary lip seal mixed lubrication model. It was proved by experiments that the dry friction coefficient used in the previous models was quite different from the boundary lubrication friction coefficient, which was theoretically more accurate. The pumping rate, friction torque, pressure distribution, and oil film thickness were calculated using both the dry friction coefficient and the boundary lubrication coefficient and the results were quite different. A friction coefficient test method under boundary lubrication condition for numerical simulation of rotary lip seals and an improved method for numerical calculation using the boundary lubrication coefficient instead of the dry friction coefficient were proposed. It was verified that the accuracy of numerical calculation can be improved, and the calculation result was closer to the actual working state.

In some application fields—for example, the automotive industry—lip seals operate over a wide temperature range. Under such conditions, oil temperature plays an important role in determinin...

Typically, film formation in a rotary lip seal is explained by microscopic effects, but here it will be explained from a macroscopic point of view. When the nominal parallelism between the shaft and the seal is lost, the contact area is distorted leading to a skewed sealing profile. The resultant slanted gap between the shaft and the seal presents a macroscopic wedge profile in the direction of rotation, hence constituting a source of hydrodynamics. An elastohydrodynamic model is developed predicting the implications of operating a rotary lip seal under misalignment. It is concluded that the non-concentric operation of rotary lip seals leads to a bidirectional fluid migration from the back to the spring side of the seal and vice versa.

The effect of structural parameters such as contact width, low-angle, high-angle, interference and waist depth on the sealing performance of rotary lip seal was analyzed by finite element method. Based on the macroscopic pumping effect model of the rotary shaft lip seal and the pumping rate equation, the influence of structural parameters on pumping rate was calculated and analyzed. The structural and operational parameters of lip seal were optimized by the response surface method. 32 kinds of the model were made by compounding levels on each factor, and the response surface regression characteristics of each model are analyzed. The results show that low-angle, high-angle and interference are the main factors that influence significantly the seal performance of rotary shaft lip seal, and contact width, low-angle and high-angle are major influential factors for pumping effect. Therefore, these factors are considered as the most important factors for an optimum design of the rotary shaft lip seal. The optimal conditions are obtained, and the results are also verified by analytical methods.

The macroscale simulation methods are commonly used to study wear of rotary lip seals. These methods oftentimes do not address effects of microscopic interfaces, which, according to experimental studies, are important factors in the wear of rotary lip seal. Hence, a multiscale wear simulation method for rotary lip seal under mixed lubricating conditions is proposed, in which the effects of microscopic aspects of interacting surfaces are taken into account. The simulation results indicate that the wear of rotary lip seal can be reduced by reducing axial asperity density while increasing the circumferential asperity density. The results also indicate that wear of the rotary lip seal is susceptible to axial asperity density when it is within a particular range.

Following a research and development project – in collaboration with wind turbine and bearing manufactures – James Walker has launched a new version of its Walkersele® rotary lip seal. The UK-based company, which specialises in sealing technology and materials development, says it is designed to maintain effective sealing against eccentricity of movement and increased offset in applications involving large diameter bearings and shafts – critical components that are found in the latest wind turbines.

Ferrofluid rotary seals are mechanical contact-free magnetic liquid seals that are characterised by their simple structure, low friction and ability to hermetically seal. Although ferrofluid rotary seals for sealing vacuum and gases are part of a well established industry, the sealing of liquids has not been implemented yet. Literature learns that degradation of the ferrofluid seal over time when it dynamically contacts a liquid results into premature seal failure. This paper presents a new type of ferrofluid rotary seal in which a ferrofluid replenishment system is implemented that renews the ferrofluid in the sealing ring while sealing capacity is maintained. By replacing the degraded ferrofluid in the seal at a sufficient rate, service life of the ferrofluid rotary seal can theoretically be unlimited. An analytical model and FEM analysis are used to design the ferrofluid sealing device and to predict its sealing capacity. An experimental test setup has been built on which the sealing capacity and service life of the device has been tested for different sealing conditions. It is demonstrated that the ferrofluid replenishment system successfully extends and controls the service life of the ferrofluid rotary seal that dynamically seals pressurised water.

It is generally agreed that radial lip seals are used in systems with a rotating shaft and a stationary lip. However, according to previous work, it was demonstrated that relative motion between the shaft and the lip has substantial effects on the hydrodynamic lifting load and sealing performances. Nowadays, new generations of textured shafts have emerged in order to reduce friction torque and improve reverse pumping, but no study has confirmed the effect of the relative motion between the rough lip and the shaft grooves on the rotary lip seal performances. In this work, an isothermal hydrodynamic lubrication was performed in transient conditions to investigate the effect of the relative velocity between an oblique grooved shaft and a rough lip. After confirming the validity of the current model with respect to previous works, simulations have underlined the effect of the grooved shaft with relative lip motion on the rotary lip seal performance. Indeed, by keeping the same relative velocity between surfaces, it is shown that moving the shaft with a rate higher than that of the lip surface could produce an important reverse pumping and reduce the friction torque significantly, in comparison with cases where the shaft velocity is weaker.

The sealing system radial lip seal represent a complex tribological system with high requirements to be fulfilled over a long time. The surface texture of shaft counterface has a great influence on the performance of radial lip sealing system. A usability evaluation of shaft counterface with standardized 2D roughness parameters is not possible, because they represent only limited functional properties of the shaft counterface. With optical measurement instruments, shaft counterfaces can be measured in 3D. By using 3D metrology shaft counterface data the circumferential direction can also be evaluated. Together with the 3D surface parameters according to ISO 25178 this provides a fully new approach to evaluate shaft counterface. After the measurement, the data must be preprocessed to obtain meaningful parameters and to get a uniform database regardless of the manufacturing process. Measuring the pumping rate of shaft counterfaces is a common but time-consuming method to describe the quality of radial lip seals. For the evaluation of the 3D surface parameter according to ISO 25178 correlation analyses were performed by using a linear regression analysis. The correlation analyzes have shown, that the 3D parameters have the potential to describe the quality of shaft counterfaces for sealing purpose.

The welded lip seals form part of the torus primary vacuum boundary in between the port plugs and the vacuum vessel, and are classified as Protection Important Component. In order to refurbish the port plugs or the in-vessel components, port plugs have to be removed from the machine. The lip seal design must enable up to ten opening of the vacuum vessel during the life time operation of the ITER machine. Therefore proven, remote reliable cutting and re-welding are essential, as these operations need to be performed in the port cells in a nuclear environment, where human presence will be restricted. Moreover, the combination of size of the components to be welded (∼10 m long vacuum compatible thin welds) and the congested environment close to the core of the machine constraint the type and size of tools to be used. This paper describes the lip seal cutting and welding development programme performed at the VTT Technical Research Centre, Finland. Potential cutting and welding techniques are analyzed and compared. The development of the cutting, TIG and laser welding techniques on samples are presented. Effects of lip seal misalignments and optimization of the 2 welding processes are discussed. Finally, the manufacturing and test of the two 1.2 m × 1 m representative mock-ups are presented. The set-up and use of a robotic arm for the mock-up cutting and welding operations are also described.

A magnetorheological fluid (MRF) is one of many smart materials that can be changed their rheological properties. The stiffness and damping characteristics of MRF can be changed when a magnetic field is applied. This technology has been successfully employed in various low and high volume applications, such as dampers, clutches, and active bearings, which are already in the market or are approaching production. As a result, the sealing performance of MRF has become increasingly important. In this study, the wear properties of seals with MRFs were evaluated by a rotary-type lip seal wear tester. The test was performed with and without a magnetic field. The leakage time was monitored during the tests in typical engine oil conditions. The results showed that the wear resistance of the seal with MRF was decreased under the magnetic field.

This paper is devoted to the theoretical study of rubber-metal friction with particular reference to a lip seal for large high-speed rotor applications. The paper, starting from previously published mathematical models related to friction estimations, presents a semi-analytical mathematical model to estimate friction loss induced by rubber lip seals. The sliding friction model is formulated on the basis of rubber and metal surface properties. Viscoelastic and hysteretic properties of the rubber are considered as function of temperature and excitation frequency. The metal surface profile is modelled as a superimposition of base ideal peak profiles. Finally, the friction coefficient is modelled as a function of temperature, frequency and contact pressure. A preliminary validation of the model is achieved by comparing the estimated friction torque provided by the model with the friction torque measured on an actual rotor-stator system at different operating temperatures.

The effect of aging in oil on the seal performance of a radial lip seal is investigated in the present study by conducting a constant temperature oil bath test to obtain aged rubber samples and seals, and measuring the changes of material properties and seal performance with the aging time. The change of lip surface micro-morphology with the aging time is also measured by using a 3D white light optical interferometer. The leakage and friction torque are computed in a numerical simulation, utilizing a mixed elastohydrodynamic lubrication (EHL) model, to determine how aging in oil affects the lip seal performance. Finally, the simulation results of the EHL model are verified by a bench test on aged lip seals.

The radial force is a critical factor to determine the sealing performance of radial lip seals. The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments. Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used. Radial force, contact width, temperature in the sealing zone, the reverse pumping rate and friction torque are measured. A critical value of interference for a cost-effectively designed radial lip seal is found. Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance. The quantitative results gotten in this study could provide guide for the seal design and improvement.

Pneumatic clutch actuators in trucks transform the force applied on the clutch pedal into the force acting on the clutch. The actuator consists of an anodised aluminium cylinder in which a piston, ...

Radial lip seal leakage is often caused by lead, for example, oriented surface structures deviating from the circumferential direction, on the ground shaft counterface. The shaft must be free of lead and not show any superimposed pumping effect of the counterface itself in order to ensure that good sealing action is achieved. This article describes various ways of measuring lead and shows that a holistic measurement and evaluation approach is required.

A numerical thermoelastohydrodynamic simulation method is proposed in this article with the considerations of the topography of sealing lip and shaft, interference of sealing lip, the elastic deformation of sealing lip and the influence of temperature on the viscosity of lubricant. The proposed method is applied to WR auto water pump bearing seal to study the lubrication and sealing property of lip seal, and the relationships between the lubrication property of lip seal and interference, rotation speed in given working condition are obtained.

In this study, bearings were developed for a high-power propulsion motor operating in inclined operation conditions through a simulation and similitude-experimental methods using commercial rotating machinery dynamics analysis software. The developed journal bearing is electrically insulated and has low thermal conductivity because each part is connected with 2-4 -mm-thick epoxy plates. To realize an appropriate oil thickness, an oil lift system is adopted, and a half separated structure is applied to ensure the feasibility of maintaining very heavy components. This study discusses some of the key design aspects of sleeve bearing design for high-torque and low-speed propulsion motor applications. Furthermore, the conditions of variable slope tests are examined to prevent oil leakage from the bearing lip seal on the test rig.

A combined finite element analysis/computational fluid dynamics scheme is used to investigate the design of a new deflected-helix ribbed lip seal. The deflected-helix design extends the high pressure region in the convergent space between the rib add the lip on the air side and yields higher pumping rate and better sealing performance. A full parametric analysis is performed to identify the optimal parameters of the deflected-helix design. The validity of the optimal design is confirmed by comparing the simulated values of the pumping rate at shaft rotation speeds of 1000–6000 rpm with the experimental results.

A numerical simulation method is proposed to analyse the hydrodynamic lubrication performances of lip seal based on surface topography of sealing lip and shaft, lip interference, lip deformation, etc. The method, which can simulate the lubrication characteristics of lip seal under different interferences, is more reasonable than other existing methods. The proposed method was applied to auto water pump bearing’s seal. The surfaces of sealing lip and shaft are modelled, and the maximum film pressure, the average film pressure, the minimum film thickness, the average film thickness, and the friction on lip surface of stable working stage are calculated. Therelationship between the lubrication characteristics and initial interference are obtained. The results will be very helpful for lip interference determination and optimization of auto water pump bearing’s seal.

The feasibility of using SMA wires to improve the seal effectiveness has been studied experimentally and numerically. In this article, we present only the numerical study of simulating the thermo-mechanical behavior for an SMA enhanced lip seal, leaving the test setup and results in the experimental counterpart. A pseudo 3D SMA model, considering 1D SMA behavior in the major loading direction and elastic response in other directions, was used to capture the thermo-mechanical behavior of SMA wires. The model was then implemented into ABAQUS using the user-defined material subroutine to inherit most features of the commercial finite element package. Two-way shape memory effect was also considered since the SMA material exhibits strong two-way effects. An axisymmetric finite element model was constructed to simulate a seal mounting on a shaft and the sealing pressure was calculated for both the regular seal and the SMA enhanced seal. Finally, the result was qualitatively compared with the experimental observation.

The paper presents the results of experiments on electrostatic and tribological aspects of different ZDDP (zinc dialkyldithiophosphate) contents when ZDDP is added to different mineral and synthetic motor base oils. Experiments were carried out in a rotating shaft–oil–lip seal system which is an experimental facility in whose interior a metal shaft rotated at given angular velocities, and where the level of tribocharging in the interfacial system was measured. The braking torque of a shaft was also measured. The braking torque generally decreased when an external DC electric field was applied to the system.

Radial lip seals are used to retain lubricants and to prevent external contamination. When running against a plain stainless steel shaft, it is generally accepted that the micro-asperities that are developed on the lip seal elastomer by the shaft surface characteristics are responsible for the sealing mechanism in the form of reverse pumping. In this study, lip seals are tested against conventional stainless steel shafts and shafts manufactured with deterministic triangular micro-cavities of different orientations. Comprehensive surface characterization and wear ana-lysis are done using a scanning electron microscope and an optical profilometer to investigate the elastomer micro-asperities and shaft micro-cavities. Surface parameters are computed from the lip seal wear track of both the initial (before testing) and final (after testing) shaft surface. The lip seal elastomer surface wears away depending on the surface characteristics of the shaft. Previous work has concluded that incorporating surface textures on the shaft surface allows for control of the pumping direction through the seal but that the magnitude of that pumping rate has a large variability even for identical shaft surface textures. This study finds that this large variability may be due to the large variability in the elastomer sealing zone surface characteristics that develop due to wear over time. This study also confirms the previous results showing that the deterministic surface textures manufactured on the shaft surface dominate the lip seal pumping direction in spite of the large variation in the elastomer surface. Finally and most interestingly, this study finds a correlation between the axial location of the smoothest portion of the lip seal elastomer and the pumping rate of the lip seals.

A rotating shaft, rotary lip seal, and oil creating a film between the surfaces of a shaft and of a lip of the seal sets up a system, which is relatively simple geometrically, but complex physically and electrochemically. Such a system is characteristic of all machinery, engines, etc. where rotating parts and seals occur. In the experiments and tests performed to date different real commercial motor oils, original base oils, additives to base oils (antiwear and extreme pressure additives), lip seals, and shafts with different roughness have been used for a range of oil temperatures and shaft angular velocities. Tribocharging in the interfacial system: rotating shaft–oil–lip seal (the friction junction) is observed and analysed. Other experiments were performed to compensate for the electric field generated in the system applying an external DC electric field and to find its effect on friction and the braking torque of the shaft. The results show that tribocharging can exert influence on the braking torque of a rotating shaft. The reduction of the braking torque under the action of an external DC electric field is also observed. The similar experiments are repeated with the use of pure base oils and additives including zinc dialkyldithiophosphate (ZDDP). Tribocharging is evident in the case of pure base oils and when these are blended with ZDDP. The external DC electric field also reduces the braking torque while applying the DC voltage to the system. Here the authors try to interpret the former and last research results in their physical aspect and to answer some questions.

An experimental procedure is presented for measuring contact pressure between a pneumatic seal and its counterface. Measurements were performed using pressure-sensitive films, for which a suited calibration procedure was developed, also taking into account humidity influence. Having validated the experimental procedure on a lip seal rectilinear specimen, tests were carried out on commercial piston seals. Results were compared with those coming from numerical simulations performed using a finite-elements analysis.

The numerical simulation of comparative elastohydrodynamic lubrication between axisymmetrical and 3D elastic approaches on the radial lip seals is presented in order to determine the 3D effect of the elastic aspect of the seal lip. Indeed, the consideration of 3D model in other words the circumferential variation of the lip elastic deformation indicated a difference in the deformation distribution of the lip compared to the axisymmetrical approach. Consequently, the results show that the presence of the circumferential variation of the seal lip deformation has a significant effect on the pumping rate values.

Numerical models, proposed to analyse the elastohydrodynamic and thermoelastohydrodynamic (TEHD) behaviour of radial lip seals, have been considered in terms of an axisymmetrical approach to elastic seal deformation. However, the results obtained using a non-axisymmetrical elastic approach to investigating the tip of the lip differed from the axisymmetrical approach results in relation to the deformation distribution of the lip surface. The main objective of the present work is to show through numerical analysis the three-dimensional nonaxisymmetric effect of the lip deformations on the TEHD behaviour of radial lip seals. Hence, a comparison between both elastic approaches is presented in order to analyse the influence of the lip's non-axisymmetric behaviour on all of the operating characteristics of the lip seal. In addition, different forms of the lip surface roughness are investigated.

Although the rotary sealing mechanism of a lip seal with hydrodynamic aids had already been intuitively described, there are two factors to be taken into account. One of which is the existence of many different types, a consequence of experimental development, and the other, the need to standardize design for questions of reliability. Therefore, systematic development of standardized hydrodynamic seals is required. So, a rotary hydrodynamic seal with sine-shaped pumping elements has been designed using the knowledge available on this matter. For theoretical analysis of its reverse pumping capacity, a mathematical model based on the hydrodynamic flow principle was developed.

Improvement of ball-bearing performance requires an optimization of desired properties of rubbery lip seals. Such an application necessitates specific material properties such as thermomechanical and tribological behaviours. These requirements led to investigate relationship between viscoelastic properties and tribological behaviour of filled elastomers. To achieve this objective, an analysis of two nitrile rubbers (NBR), which mainly differed in their glass transition temperature (Tg) values, was performed. This difference was obtained by a modification of the matrix composition. This work is focused on the difference of their tribological behaviour in relation to their viscoelastic, thermomechanic and physicochemical characteristics. It is pointed out that the sample with higher Tg shows the formation of an oxidised protective layer on the surface, which prevents its wear. The lower Tg sample, which shows high wear, does not have such a protective layer.

In this study, a realistic modeling of lip seals and a TEHD analysis are used to show the influence of the mathematical roughness models of the lip surface on such features as power loss, minimum thickness of the lubricant, reverse pumping, temperature, etc. In the three cases examined, the results show that the TEHD characteristics of the lip seal are highly influenced by the roughness model used to represent the irregularities of the lip surface.

PurposeTo present some new designs of magnetic fluid exclusion seals for rolling bearings and possibility to use them in modern industrial sealing applications.Design/methodology/approachIn the paper is given principle of magnetic fluid sealing technology and are presented new designs of magnetic fluid exclusion seals for rolling bearings, such as compact magnetic fluid seals, two‐stages seals being combination of magnetic fluid seal and labyrinth seal or radial lip seal, magnetic fluid seals with “floating” magnetic system. This paper also shows examples of their application in various rotating process equipment.FindingsProvides information about new designs of bearing seals and gives the main advantages of these seals over other types, such as total tightness, low viscous drag, maintenance‐free service and high reliability.Originality/valueThis paper offers some new designs of high‐performance magnetic fluid exclusion seals for rolling bearings and points their practical applications.

In radial lip seals, it is generally accepted that sealing occurs through microasperities that form on the surface of the elastomer. It is most often thought that these asperities form during the first few hours of operation due to the stresses and wear in the seal. Thus, the formation of these asperities is highly dependent upon the specific operating conditions of the seal. This article studies the size, shape, and quantity of the asperities that are present on a specific seal design, when run at a certain set of operating conditions. From this analysis it has been determined that the hydrodynamic pumping aids that are present on the seal significantly affect the formation of microasperities. Radial lip seal samples affected by pumping aids had more distinct microasperities, but these asperities are clustered on the edges of the sealing zone, which is not the case for samples unaffected by pumping aids.

L' etude d'un joint a levre, basee sur une analyse elastohydrodynamique, s'appuie sur un modele original tres proche de la realite. Elle permet de predire la plupart des caracteristiques de fonctionnement d'un joint telles que l'epaisseur du film lubrifiant, le couple de frottement, les zones de contact et de cavitation, la pression hydrodynamique ainsi que le debit de pompage inverse.

In most pervious numerical studies of lip seal behavior, the shaft surface is modeled as perfectly smooth. In the present study, a more realistic shaft surface with asperities is included in a full film lubrication model. An elastohydrodynamic analysis, incorporating both the fluid mechanics of the lubricating film and the elastic behavior of the lip, is performed to predict the hydrodynamic effect of the shaft surface on lip seal operation. Operating characteristics such as load support, reverse pumping rate, cavitation area, average film thickness and liftoff speed are investigated. Scheduled for Presentation at the 58th Annual Meeting in New York City April 28–May 1, 2003

The article considers the factors that directly influence the operation of the lip seals to seal the gap between the piston and the working cylinder in hydraulic props of mechanized supports, this directly affects the tightness of the props and, as a consequence, the safety of work in the production face. A description is given of these factors, which is supported by practical calculations obtained from the results of finite element modeling of lip seals of various designs at different pressures of the working fluid and sealed gaps. The problems of sealing rough surfaces with rubber-like materials are considered. The classification of these factors according to the degree of generalization and the functional interaction between each other is proposed.

It is well known that shaft surface finish can significantly affect the performance of a lip seal, even though the shaft roughness, after run-in, is much smaller than the lip roughness. In the present research, a numerical model demonstrates that small fluctuations on the shaft surface can produce large hydrodynamic effects in the sealing zone due to the non-linearity of the Reynolds equation. The effects of shaft surface profile, roughness height, roughness wavelength, and lead angle on load support, reverse pumping rate and cavitation area are examined. Presented at the 57th Annual Meeting Houston, Texas May 19–23, 2002

Lip seal friction under constant speed sliding is modeled as the sum of three physically based components: (1) viscous shear loss in the lubricant; (2) hysteresis losses due to roughness-imposed deformation of the seal material, and (3) hysteresis losses due to deformation caused by varying intermolecular forces at the sliding interface. Increasingly thick hydrodynamic films progressively reduce contributions of the roughness and intermolecular components. Peaks in friction expected from these two components are smaller, occurring at lower sliding speed, than in “dry” rubber friction. Model simulations capture friction trends with temperature, hydraulic pressure, seal material, lubricant viscosity and shaft roughness.

The performance and basic rating life of rotating contact ball bearings have increased substantially over recent years, but the performance of radial lip seals, designed to protect these bearings against the ingress of contaminants, has not. In particular, the failure of the lip seals used to protect self-lubricating ball bearings has been identified as a major cause of bearing failure. To understand in detail the mechanisms of failure, these bearings and seals have to be assessed by performing carefully controlled experimental tests. As elastomeric lip seals are intrinsically sensitive to test conditions, their performance is often subject to statistical scatter. Therefore, the design of test rigs to carry out this research is vital so as to eliminate as many unwanted variables as possible. Typical test rigs and the usual tests previously carried out by the major bearing manufacturers are detailed, and the performance of both the test rigs and the seals are discussed. A new radial lip seal test rig, designed specifically for assessing seal performance is shown, and improved test methods and data logging are detailed. Typical lip seal test results are presented and analysed. The aim of this work is to characterize empirically lip seal behaviour under both contaminated and uncontaminated conditions, enabling a deeper understanding of lip seal performance to aid future improved lip seal designs to be formulated.

The possibilities increasing the wear resistance of friction pair radial lip seal/shaft were tested using fluoroligomeric materials and selective transfer technologies. Measurements of friction moment, temperature in contact spot and wear of friction surfaces show that fluoroligomeric coat and selective transfer technologies (metallpolymeric oil additives and NABA‐coat on shaft) can considerably decrease the friction losses and increase the wear resistance of friction pair. The microscopic analysis of surfaces shows that using tribotechnical materials in contact spot of friction surfaces forms virtually different structures which can explain the different efficiency mechanisms of the mentioned materials. These tests show that in friction pair radial lip seal/shaft the tribomaterials could be used which create selective transfer effect and have regenerating properties.

Current knowledge of the principles of rotary lip seal operation is assessed through a review of the experimental foundation and the key theoretical models. Studies of the existence of the lubricating film, the load support mechanism, the sealing mechanism, the thermal effects and the followability are described.

Theoretical analysis, combined with experimental verification, is used to study the effect of wear on the performance of a rotary lip seal as characterized by the pumping rate and friction torque. The performance of a rotary lip seal is determined by the sealing lip surface microscopic characteristics and contact characteristics at the sealing zone. The variation of the contact characteristics with wear has been established based on the variation of the sealing lip profiles measured by using a trilinear coordinate measuring instrument. The impression method is used to copy the lip surface microtopography at different wear times and then an optical interferometer is used to measure the impression surface microtopography to obtain the variation of roughness with wear. The variations of the roughness, contact characteristics, and approximate contact temperature with wear are inserted into a mixed lubrication model to obtain the variations of the pumping rate and friction torque. A comparison of the simulated results with those from experimental measurement verifies the validity of the theoretical analysis.

We report on the dynamic behavior of a rotary lip seal by considering the interaction between lip, film and shaft roughness assumed to have a periodic form. The nonlinearities of stiffness and viscosity of the film are taken into account in a mass-spring-dumper model. Using the harmonic balance method, analytical prediction of the lip displacement is obtained, the frequency response is provided and the effect of the shaft undulation on the amplitude jumps of the lip displacement and on the film thickness fluctuations are discussed. The results have direct applications in reducing leakage that may occur between a smooth lip seal and a rough shaft.

Using the Mooney-Rivlin model, the contact force and thermal behaviour of a radial lip seal are studied numerically and experimentally as a function of the interference. The numerical and experimental results on the static contact forces show good correspondence with and without the garter spring. The FEM calculated results indicate that increased interference may increase the eracking of seal material due to the maximum contact stresses close to the contacting area of the seal lip and produce local separation between the seal lip and the shaft. Also a coupled thermal-mechanical analysis method will be a useful tool to predict the contact behaviour of rubber lip seals for small values of the interference.