Rotary Lip Seal Research Articles

Numerical study of the effects of textured shaft on the wear of rotary lip seals

Abstract The effects of the textured shaft on the wear and sealing performance of rotary lip seals have recently attracted considerable attention. This paper presents a numerical method for analyzing the effects of the textured shaft on the seal performance, especially the seal wear. The proposed numerical analysis method has been validated by comparing the simulation results to experimental observations. Based on the simulation results, this study finds that: increasing the textured feature depth and increasing the textured area ratio can increase the seal life and improve the torque of the seal, especially in the axial direction. The reverse pumping rate decreases with the increase of textured area ratio, especially in the axial direction.

The effect of interference on the leakage performance of rotary lip seals

In this study, a test system is developed in order to determine the effect of interference on the lifetime of the sealing element. A set of experiments are carried out with thermoplastic polyurethane radial lip seals with three different inner diameters varied by lip surface tolerance (40, 39.80 and 39.60 mm), and EP gear oil is used as lubricant. In order to determine the lifecycle of the sealing element, mass of the leaking oil is measured. Meanwhile, in order to determine the frictional performance of the sealing element, four load cells are mounted on the cylindrical housing of the system and frictional force values are monitored by a data acquisition terminal and frictional torque values are calculated. As a result, the frictional moment values of the seals increased with the increase in interference. Moreover, the increase in interference leads to a longer service life.

Numerical Investigation of Grooved Shaft Effects on the Rotary Lip Seal Performance with Relative Lip Motion

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.

Study and Optimization of Structural Parameters of Oil Seal by Response Surface Method

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.

Predict the Service Life of Rotary Lip Seals by Machine Learning Methods

This paper aims to use machine learning methods to predict the service life of rotary lip seals to aid manufacturers and users improving the current maintenance procedures. Seals are widely used in most engineering applications. The knowledge of condition of seals throughout their working life is important due to the fact that they are often used on high value engineering products. As the current material properties of the seal and the working environment various, it is difficult to predict useful life of the rotary lip seal. In this paper, the factors relating to life of rotary lip seals are investigated and discussed. The application of machine learning methods using actual testing data in order to estimate the useful life of the seals has been presented. The early results show good agreement between actual and predicted values.

A multiscale wear simulation method for rotary lip seal under mixed lubricating conditions

Abstract 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.

Wear Behavior of Rotary Lip Seal Operating in a Magnetorheological Fluid Under Magnetic Field Conditions

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.

Effect of Relative Velocity Between Rough Surfaces: Hydrodynamic Lubrication of Rotary Lip Seal

Since the sixties, most of numerical studies that model the rotary lip seal lubrication have been restricted by assuming that one of the two opposing surfaces is smooth: either the lip or the shaft. This hypothesis, although it is verified only for a shaft roughness ten times smaller than that of the seal, is the best solution to avoid the transient term “∂h/∂t” in the deterministic approach. Thus, the subject of the present study is twofold. The first part validates the current hydrodynamic model with the international literature by assuming the asperities on the lip and shaft as a two-dimensional cosine function. In the second part the Reynolds equation for rough surfaces with relative motion is solved. The numerical results show that the relative motion between rough surfaces impacts significantly the load support and the leakage rate, but affects slightly the friction torque.

Effect of grooved shaft on the rotary lip seal performance in transient condition: Elasto-hydrodynamic simulations

It is generally accepted that reverse pumping from the air-side to the liquid-side of rotary lip seals is coupled to lip asperities shearing deformation due to hydrodynamic effect. Recently, to enhance this rate, new shaft designs with oblique grooves have been manufactured, but only two computational models were performed up to now: by defining a textured shaft with simple analytical functions, or by using a measured groove geometry from a 3-D micrograph. The weak point of both models is assuming the lip as a smooth surface to make the problem stationary.Therefore, this work aims at performing a numerical parametric study of a grooved shaft in transient conditions and, also, comparing numerical results and experiments between a steady case and the current model.Consequently, simulations show that the oblique grooves on the shaft improve significantly the reverse pumping. In addition, the current model predicts better reverse pumping comparing to a stationary model, and the friction torque is overestimated with a smooth lip surface.

세탁기용 고무 회전 씨일의 밀봉 성능에 관한 연구

RD Revised May 8, 2015; Accepted May 11, 2015)Abstract − In this research, we experimentally investigated the sealing performance of elastomeric rotary lipseals for washing machines. In general, NBR is used as a material for elastomeric rotary lip seals in washingmachines, but the mixing formula of the rubber material can affect the sealing performance. In this study, wemanufactured rotary lip seals using three kinds of NBRs with a different mixing formula, and examined the seal-ing performance using an acceleration test mode. The results of an SEM investigation into the surfaces of threekinds of specimens showed a much smaller wear volume and better sealing performance for the specimens withsmaller particle sizes of mixing composition than for the specimen with the larger. Repeated deformation andrecovery by the shaft-to-seal eccentricity on rotation were shown to cause a phase difference in the rubber mate-rial, and we measured the recovery ratio to find the influence of this phase difference on the sealing performance.As another method for checking the phase difference, we also measured tan a, and a lower tan a was revealedas the recovery ratio increased for each specimen. Specimens with a higher recovery ratio (lower tan a) wereshown to have a better sealing performance. Consequently, specimens with a smaller particle size in the mixingcomposition had a better sealing performance because they show a higher recovery ratio.Keywords − NBR(니트릴 고무), elastomeric rotary lip seal(고무 회전 씨일), abrasive wear(연삭 마모), recoveryratio(탄성 회복율), tan δ(탄젠트 델타)

Shaft roughness effect on elasto-hydrodynamic lubrication of rotary lip seals: Experimentation and numerical simulation

Numerical analyses of the isothermal elasto-hydrodynamic lubrication (EHL) have made considerable advances in order to identify the most important features in the successful operation of rotary lip seal, and the results have shown a good agreement with experiments.Most of the models previously published are capable of predicting the combined effects of thin film through deformed lip and rotating shaft, but they assume a smooth surface of the shaft. Although this assumption is only verified for shaft roughness much smaller than that of the seal lip, it is the best solution to avoid a transient model.First, the present study describes an experimental work that provides a basis upon which a numerical EHL model of rotary lip seal is constructed by taking into account both the shaft and lip roughness. After confirming the validity of the current model by comparing experimental with numerical results, simulations have been performed and have underlined the effect of shaft roughness amplitude and profile on the rotary lip seal performance. It is shown that for shaft roughness beyond half of the lip roughness, the seal may leak.

How do the temperature, angular velocity and electric fields affect mechanical and electrokinetic phenomena in a friction junction?

In the friction junction, that is in a rotating metal shaft–base oil–rotary lip seal system, dynamic phenomena occur which are of mechanical and electrical nature. During the shaft׳s rotation the components of an oil film – a gap between the surfaces of a shaft and a lip of a rotary lip seal – are caused to move about within the film under the action of a centrifugal force. The relative movement of different particles and molecules in turn brings about tribocharging and results in establishing an electric field within the gap. The field and so acting the Coulomb force also affect the distribution of charged species as does the van der Waals attractive force. To analyze the effect of the above factors as well as the temperature of oil in the gap measurements of the shaft׳s braking torque and the voltage between the rotating metal shaft and a stiffening ring of a lip seal for different ranges of the base oil׳s temperatures and of the shaft׳s angular velocities are performed. In the experiments the synthetic PAG (polyalkylene glycol) and PAO (polyalphaolefin) base oils and a fluorocarbon rotary lip seal are used.

The Effect of Wear on the Performance of a Rotary Lip Seal.

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.

A Mixed Lubrication Theoretical Model and Experimental Verification of Rotary Lip Seals

A mixed lubrication model of rotary lip seals using a statistical approach with flow factors based on reverse pumping mechanism has been developed. The model consists of coupled fluid mechanics analysis, asperity contact analysis and deformation analysis. The oil film pressure and shear stress are obtained from solving the Reynolds equation. Using the GREENWOOD- WILLIAMSON surface contact model computes the contact pressure between the lip and shaft. The deformation analysis of lip seals is carried out using the influence coefficient method. Applying the mixed lubrication model to a typical lip seal, the pumping rate and friction torque are the two most important factors of evaluating seal characteristics, which are the output results of theoretical simulation. Most important, the pumping rate and friction torque are measured with bench test designed by the authors. The measurement of these two factors verifies the validity of the mixed lubrication model. For the reverse pumping action of rotary lip seals is resulted from the surface asperities, the influence of roughness on the pumping rate, friction torque and the contact area are carried out by using the verified theoretical mixed lubrication modle.

Dynamic behaviour of rotary lip seal

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.

A mixed lubrication model of a rotary lip seal using flow factors

A mixed lubrication model of a rotary lip seal using flow factors has been developed. The model consists of coupled fluid mechanics, contact mechanics and deformation mechanics analyses. The fluid mechanics analysis is described by a Reynolds equation that takes into account the surface roughness effect using flow factors. The contact mechanics analysis uses the Greenwood and Williamson model to compute contact pressure. The deformation mechanics analysis utilizes the influence coefficient approach to compute deformation of the seal. Results for a typical seal show how the operation parameters and the surface roughness affect seal behavior.

Numerical simulation and experimental study of shaft pumping by plunge ground shafts with rotary lip seals

A computational model that will predict the pumping rate, from the air-side to the liquid-side of rotary lip seals, produced by shafts that are manufactured by various techniques has been developed. Plots of computed pumping rate versus shaft speed, for plain plunge ground shafts and for ground shafts with various laser generated groove patterns, agree well with experimental measurements, providing validation of the model. This validated model is then used to investigate the effects of groove angle, groove density, and groove depth on the pumping rate.

Numerical simulation and experimental study of shaft pumping by laser structured shafts with rotary lip seals

A simulation model to predict pumping by shafts with various surface finishes, in combination with a rotary lip seal, has been developed and validated by experiment. The model consists of a fluid mechanics analysis of the flow in the sealing zone coupled with a deformation analysis of the seal. The experimental validation consists of pumping rate measurements with shafts whose surface structures contain laser generated oblique grooves. Plots of pumping rate vs. various parameters show good agreement between the model and experiment. Plots of torque vs. speed, as well, show good agreement between the model and experiment.

Soft elastohydrodynamic analysis of rotary lip seals

The extensive literature on the elastohydrodynamic analysis of rotary lip seals is reviewed. Models that predict quantities such as film thickness and reverse pumping rate and that elucidate the physical processes governing the behaviour of rotary lip seals are described. Thermal effects, mixed lubrication, capillary effects, transients, viscoelasticity, statistical approaches, and so-called hydrodynamic seals are discussed.

Base Oil and Its Blends with ZDDP and Their Effect on Tribocharging, Braking Torque and Electrical Double Layers in a Friction Junction

The paper presents the results of experiments on tribocharging of a blend of mineral-base oil and different zinc dialkyldithiophosphate (ZDDP) contents in a friction junction. A friction junction is constituted by a rotating shaft, a film of pure base oil, or its blend with the ZDDP, and a rotary lip seal, which is the interfacial system as a whole. Experiments were carried out on the specially built experimental facility to be a simplified model of an engine’s crankcase (or sump) in whose interior an earthed metal shaft rotated at given angular velocities. Electric potential of a stiffening ring of a lip seal, which is a measure of tribocharging, was measured directly with an electrometer. The stiffening ring’s potential is induced by charge in the film of pure base oil or the ZDDP-oil blend and is a function of the oil temperature for different angular shaft velocities and the ZDDP contents. The potential is presented in the form of some characteristics. Also the effects of an external DC electric field on the braking torque of the rotating steel shaft were examined for a range of oil temperatures, angular velocities, and ZDDP contents, and here the torque is presented for one temperature and different DC voltages of both polarities. An analysis of the research results obtained permitted us to show how the ZDDP content in a blend with the base oil tested, angular velocity, and oil temperature could affect tribocharging in the interfacial systems: the rotating shaft-oil and oil-lip seal, as well as the whole oil film in between and both electrical double layers (EDLs) at the surfaces of a shaft and of a lip of a rotary lip seal in the friction junction.