Lip Seal Research Articles

Wear Calculation for a Shaft Lip Seal under Randomly Changing Temperature and Load

A stochastic model of the wear process of a shaft lip seal that takes into account random changes in the temperature and external load was described. The results of a numerical analysis of the process of seal wear in relation to the conditions of operation in open space at near-Earth orbital stations are presented. The importance of taking into account random changes in temperature and external load for predicting the seal durability was evaluated.

Multi-Physical Field, Coupled, Mixed Lubrication Analysis of Hydraulic Reciprocating Vacuum Lip Seal

Engineering practice has demonstrated that seal failure can result in severe leakage and wear, reducing the efficiency of hydraulic systems and even leading to major safety risks. Currently, analyses of the thermal aspect of seal interfaces are relatively limited, with most studies focusing on mechanical analysis. However, in actual applications, temperature has a significant impact on sealing performance. In this paper, nonlinear elastomechanics, viscous fluid mechanics, micro-contact mechanics, micro-deformation theory, and thermodynamics are coupled to establish a mixed lubrication model considering the thermal effect. The reliability of the mixed lubrication model is verified through experiments, and the temperature distribution of the oil film in the sealing area and the temperature distribution of the seal ring are simulated. Finally, the effects of the reciprocating speed, root mean square roughness, fluid medium pressure, and seal pre-compression on seal friction force and leakage are investigated. The results show that the heat generated in the sealing area accumulates at the bottom of the V-ring. Under the same conditions, compared with the instroke, the temperature-rise area of the outstroke is biased to the left and the increase in temperature is greater. In addition, the piston rod speed and the preliminary compression of the seal ring have a greater impact on the overall seal friction force and leakage. Under a lower seal pre-compression, the RMS roughness has a great influence on the leakage and friction in the outstroke, while the impact of the internal stroke is limited.

An approach simulating interacting solid, liquid, and gas domains for dynamic seal applications

AbstractIn seal applications a solid elastic body (the seal) ensures the separation of a liquid (e.g., hydraulic oil in one chamber) from a gas (e.g., air in another chamber). In the case of a dynamic seal, the rod is moving and transports a thin liquid film from the liquid chamber into the air chamber. The seal gap consists of a converging gap, a minimum distance between seal and rod and a diverging gap, where transported liquid detaches from the seal. Between the three states of matter (gas, liquid, gas) appear the following contact conditions: liquid‐to‐solid, gas‐to‐liquid, and gas‐to‐solid. A classical fluid‐structure‐interaction is technically possible with limited effort, but is not sufficient to distinguish between the liquid and the gas. A solution can make use of the fact, that the liquid has significant dimensions only in the liquid chamber and is pressurized only there. There is a thin liquid film on the rod in the air chamber, but it has dimensions clearly lower than the air chamber and has the same pressure as the air. Therefore a simulation is possible with the “variable viscosity approach”: Liquid and gas are modeled in one single fluid domain. Differences between liquid and gas are included by pressure‐dependent fluid parameters, especially viscosity and density. The resulting violation of the mass balance is very small as the low mass flow through the seal lip is low. The presented approach allows to apply a fluid‐structure simulation with special fluid properties to model a system with three states of matter. Advantages are a less complex model with less complex contact conditions and a reduced simulation time.

Behavior of marine thruster lip seals under typical operating conditions

Marine thruster lip seals pose a condition monitoring challenge, yet they are seldom studied tribologically. The present work studies the behavior of a 300 mm diameter NBR marine thruster lip seal (n = 3) under typical operating conditions. Frictional torque and subsurface temperature were measured under 27 combinations of oil temperature, oil pressure, and rotational speed. The frictional torque increased with increasing oil pressure and decreased with increasing oil temperature. The subsurface temperature increased with increasing oil temperature, oil pressure, and rotational speed. There was no clear relation between the frictional torque and subsurface temperature. The frictional torque ranged 9.6–14.4 Nm, and subsurface temperature 57–94 °C. Preliminary wear measurements showed a wear track width of 0.2–0.3 mm and a wear rate of 0.031 ± 0.001 mm3/hour.

Sealing Performance Evaluation and Structural Optimization for Reducing Leakage Failures of Lip Seal Considering High-Speed Rotation Frictional Heat

This article proposes a high-speed rotating thermo-solid coupling finite element model for a lip seal that simulates the lip temperature changes during rotation by cyclically applying thermal loads to achieve lip temperature distribution characteristics. Considering the influence of working condition parameters and structural parameters, the lip temperature and sealing interface contact pressure distribution are obtained, and the lip seal structure is optimized. The results show that ignoring the uneven distribution of lip friction heat will lead to a 25.6% error in the radial force. The optimized lip seal yields an impressive 14.3% reduction in leakage rate compared to the original configuration, showcasing a significant performance enhancement in lip seal.

Surgical Premaxilla Reposition and Secondary Bone Grafting in a Children with Complete Bilateral Trans-Foramen Cleft Lip and Palate: a Case Report

The objective of this study is to report the clinical case of a child with complete bilateral trans-foramen CLP who underwent surgical repositioning of the premaxilla with internal rigid fixation and a secondary bone grafting. The boy was following by different specialists since five days of life, being subjected to the entire surgical protocol to close the lip and palate. At 9 years old it was proposed surgical premaxilla reposition and, in a second surgery, a bone grafting in the alveolar process. After a virtual planning, surgery was performed under general anesthesia. The access was performed maintaining the vestibular pedicle of premaxilla, and after remove the interferences at the vomer and maxilla, premaxilla was fixed with titanium plates and screws. Six months after, fixation material was removed and the remaining gaps were grafted with iliac bone. After 21 months of the first surgery, the patient presents a good anteroposterior positioning of the maxilla and lip seal and, those responsible for the patient, reported an improvement in the patient's quality of life, with improvements mainly in speech, chewing and the patient's social life.

Quantitative Assessment of Lip Morphology in Patients With and Without Cleft Lip and Palate Using 3-Dimensional Stereophotogrammetry.

This study aimed to assess and quantify the morphologic characteristics of the lips and the lower third of the face in cleft and noncleft patients, utilizing three-dimensional (3D) stereophotogrammetry. Sixty patients were included in the study, comprising 30 unilateral cleft lip and palate patients (G1, 24 female, 6 male; aged 20 to 60y, mean age 44.0±12.0y) and 30 noncleft patients (G2, 23 female, 7 male; aged 20 to 59y, mean age 43.5±12.0y). Anthropometric landmarks were identified on the facial surface. Three-dimensional stereophotogrammetry was employed to capture images. Statistical analysis was conducted to compare the groups, with a significance level set at 0.05. The comparative analysis revealed statistically significant differences in 5 linear and 6 angular measurements. Linear measurements such as philtrum width, upper and lower cutaneous lip height, mandibular ramus length, and midfacial depth exhibited significant differences between cleft and noncleft patients. Similarly, angular measurements, including upper lip angle, Cupid's bow angle, lower/medium face convexity, lip seal, nasolabial angle, and left gonial angle, displayed statistically significant disparities. These findings underscore the ongoing surgical challenges in the comprehensive rehabilitation of patients with clefts, highlighting the critical need for continued advancements in treatment strategies.

Effect of rotating shaft vibration on lip seal performance

Rotary lip seals are important components in various rotating machinery and are inevitably affected by vibration. This paper introduces the first simulation model for rotary lip seals under radial sinusoidal vibration conditions based on the mixed lubrication theory. Using the proposed model, the effects of varying vibration amplitudes and frequencies on the tracking performance, leakage rate, and friction torque of lip seals were analyzed. The simulation results indicate that, the leakage rate exhibits an initial increase followed by decrease as the vibration amplitude increases, while the friction torque exhibits a decrease followed by increase. Excessively high vibration frequencies may induce separation between the lip and shaft surface, resulting in severe leakage.

Numerical analysis of lubrication performance of variable cross-section sealing rings

A variable section seal ring is a special type of sealing element that features a regularly changing sealing boundary. This paper proposes a numerical analysis method for calculating the elastohydrodynamic lubrication performance of the sealing surface of a variable section seal, considering factors such as the surface morphology of the seal lip, the initial compression rate of the seal, and the micro-elastic deformation of the rough surface of the seal lip. The three-dimensional distribution of the oil film thickness was obtained. The results show that the oil film thickness on the sealing lip of the variable section seal changes both circumferentially and axially, being thicker in the middle and thinner at the sides when viewed axially, and thicker at the peaks than at the troughs when viewed circumferentially. Higher compression rates of the seal lead to greater friction during operation; different compression rates significantly affect the distribution of the oil film and the oil film pressure on the variable section seal, which directly impacts the lubrication and sealing effectiveness of the seal. Therefore, choosing an appropriate initial compression rate for the seal is very important.

Design and Experiment Verification to Combined Dynamic Seal of Wide-Speed Hydraulic Motor Pump

To reduce the wear of lip seal of wide-speed hydraulic motor pump and prolong the service life, the lip compression is reduced and the non-contacting labyrinth seal is used as the front stage, forming a series combined dynamic seal (CDS). The reliability of CDS in the wide-speed range is verified by model experiment. Initially, the structure form and dimension of labyrinth seal with relatively small leakage and heat production were determined by model experiment. Then, by establishing the model of lip seal and simulating the static structure, the relationship between the compression and maximum contact pressure of the lip was obtained. Finally, using the CDS which is formed by combining the different lip seals with the selected labyrinth seal to carry out experiments, the leakage, temperature distribution and lip wear were obtained. The results show that trapezoidal tooth labyrinth seal (TTLS) has better sealing effect and less heat production. When the sealing clearance is 0.1 mm and 0.3 mm, it accounts for 0.11% and 0.32% of the rotor diameter, respectively. Under the same conditions, the smaller the proportion, the better the sealing effect, but the higher the heat production. With the increase of compression, the maximum sealing pressure first increases and then decreases. When the compression of the lip exceeds 0.1 mm, the CDS will not leak significantly in a wide-speed range, but the greater is the compression, the faster is the temperature rise in the closed cavity. Lip wear is positively correlated with pv and the wear decreases with the decrease of compression.

Effects of two-phase treatment with functional appliances versus one-phase treatment with pre-molar extraction in Class II div 1 monozygotic twins: A case study

The aim of the study was to compare the skeletal, dental, or soft-tissue outcomes of a one-phase camouflage treatment with pre-molar extraction versus a two-phase treatment with combined twin-block high-pull headgear followed by fixed orthodontic treatment in monozygotic twins. 12-year-old male monozygotic twins presented to the dental clinic with complaints about their anterior teeth. Cephalometric analysis of the patients revealed skeletal Class II malocclusion and a long facial type. Extraoral examination of the patients revealed incompetence of lip seal and a convex profile. In Patient 1, the use of a high pull headgear combined with a twin block to correct skeletal anteroposterior and vertical malocclusions with growth modification and then fixed orthodontic treatment was planned. Patient 2 did not comply with the treatment, complaining that the use of the device could cause esthetic problems and difficulties in use. Therefore, camouflage treatment with extraction of four pre-molars was planned as another treatment option for Class II patients in Patient 2. With the camouflage treatment, the patient continued to grow normally. The combined treatment with twin block and a high pull occipital headgear resulted in inhibition of maxillary growth and a reduction in the severity of the skeletal Class II malocclusion, but the mandibular changes were similar in both patients at the end of treatment. Despite the different treatment modalities, both twins achieved a Class I canine-molar relationship and ideal overjet and overbite. Patients can close their lips with improved soft-tissue profiles. The criteria for the choice of treatment depend entirely on the requirements of the patient.

Failure and Damage of Reciprocating Lip Seals for Pneumatic Cylinders in Dry Conditions

Lip seals are components subjected to high mechanical stress and they are responsible for many out-of-service in pneumatic cylinders. The aim of this work is the development of an experimental methodology to evaluate lifetime duration and analyse failures and damages of rod lip seals for pneumatic cylinders. A dedicated test bench was designed and manufactured which reproduces actual working conditions of the seals i.e., compressed air action (seal pressurisation) and relative linear reciprocating motion. Three types of seals made of two elastomers (NBR and polyurethane) were tested; dry condition was considered to speed up the tests. The influence of geometric parameters like seal seat dimension and seal axis misalignment with respect to the rod axis, was analysed by multiple experimental tests. Results in terms of seal life duration and failure modes are presented which allow comparison of seals performance and provide a helpful tool to end-users in a proper selection of seals geometry, material and key working parameters.

Wear Calculation for a Shaft Lip Seal under Randomly Changing Temperature and Load

Wear Calculation for a Shaft Lip Seal under Randomly Changing Temperature and Load

Treatment of Vertical Maxillary Excess in Skeletal Class II Hyperdivergent Face Using Skeletal Anchorage—An IBO Case Report

This case report was presented at the Indian Board of Orthodontics (IBO) examination under category III in September 2022. It describes the case of 13-year-old female with hyperdivergent facial pattern and class II skeletal base, treated using microimplant anchorage. Patient presented with vertical maxillary excess, increased lower facial height, gummy smile, and incompetent lips. All four first premolar extraction treatments were planned with simultaneous retraction and intrusion of maxillary and mandibular dentition. The case was treated using 022 slot MBT prescription appliance. Lip exercises were prescribed to increase the tone of lips, which would aid in attainment of lip seal. Case was completed with class I molars, normal overjet–overbite, and improved smile aesthetics. The patient exhibited competent lips and reduced anterior–posterior gingival show.

Minimisation of Friction Resistance of Elastomeric Lip Seals on Rotating Shafts

This article presents the results of a study of oil lip seals with a modified outer lip layer texture. In the first step, the interaction of flat rubber samples with different surface layer textures with the steel surface was recognised. Measurements of the friction coefficient of flat samples with different surface layer textures were carried out. The next step was an experimental study of rotating shaft lip seals in standard and prototype versions. The contact width of the sealing lip before and after durability tests was examined, and the clamping force of the lip on the shaft before and after durability tests was measured. The final step was to create a FEM model of the interaction of the sealing ring lip with the shaft to determine the lip seal pressure and width. These calculations, in cooperation with the previously determined friction coefficient and porosity of the lip seal, allowed the calculation of the friction torque. The solution proposed in this article was intended to be simple and viable for industrial applications. Satisfactory results were achieved with prototype rings in terms of reduced resistance to movement, tightness, and durability.

Case report – distoclusion treated with Bimler A períod of 12 months

The Bimler type A utilizes forces derived from muscles, particularly the tongue, concomitantly, it acts as a systemic, dynamic and functional treatment, Bimler appliances transmit neural excitation throughout the system. The objective of this study was to present a clinical case and demonstrate the efficacy of the functional orthopedic appliance, specifically the Bimler A elastic modeler, in the treatment of a patient diagnosed with distoclusion (prognathism of the maxilla and retrognathism of the mandible) according to Bimler and McNamara cephalometry. The case involved a 9-year and 11-month-old male patient with atypical swallowing, respiratory issues, and allergic conditions such as asthma. Clinical examination and complementary tests revealed a large overjet, a narrow maxilla and mandible, an open bite, and distoclusion (retrognathism). The proposed intervention included the installation of the Bimler Elastic Modeler (BEM), type A. The treatment duration was 12 months, with ongoing monitoring every 2 or 3 months. The comprehensive approach, combining BEM type A, chewing exercises, and occlusal adjustments, resulted in orthopedic changes improved mandibular, tongue, lip, and head posture, as well as enhanced chewing balance. Importantly, the appliance effectively repositioned the mandible into a more balanced, normoccluded position without the need for elastic or constant forces. Beyond the orthodontic changes, the active engagement of facial expression muscles during these activities contributed to an overall improvement in facial harmony, achieving lip seal and notable enhancements in breathing. These positive changes extended to the patient’s daily activities and sports performance. The observed outcomes not only increased the child’s active participation in the treatment but also positively impacted self-esteem, driven by the aesthetic, functional, and psychological improvements experienced.

Study on the performance of reciprocating seals under the coupling effect of elastohydrodynamic lubrication and rubber wear

Due to the lack of research on the sealing performance of reciprocating combined seals under the coupling of elastohydrodynamic lubrication and rubber wear, this paper uses the UMESHMOTION user subroutine and the improved Archard model to realize the dynamic wear process of the combined seals and the adaptive meshing of the local area to simulate the wear of the seals. At the same time, combined with the elastohydrodynamic lubrication model of the toothed slip ring combined seal ring, the sealing performance of the reciprocating combination under mixed lubrication conditions is studied. Finally, the accuracy of the model is verified by building a two-cylinder reciprocating seal test bench with more accurate measurement. The results show that the influence of the change of fluid pressure on the wear of the seal lip is greater in the fast wear stage than in the stable wear stage. The influence of the change of interference on the wear of the sealing lip is small at different wear stages. The wear of the sealing lip has a significant effect on the sealing performance of the instroke, but has little effect on the sealing performance of the outstroke.

Numerical simulation study of high-speed lip seal considering eccentricity

PurposeThis paper aims to focus on the high-speed rotary lip seal in aircraft engines, combining its service parameters, its own structure and application conditions, to study the influence of different eccentric forms, eccentricity, rotational speed and other factors on the performance of the rotary lip seal.Design/methodology/approachA numerical simulation model for high-speed eccentric rotary lip seals has been developed based on the theory of elastic hydrodynamic lubrication. This model comprehensively considers the coupling of multiple physical fields, including interface hydrodynamics, macroscopic solid mechanics and surface microscopic contact mechanics, under the operating conditions of rotary lip seals. The model takes into account eccentricity and uses the hazardous cross-sectional method to quantitatively predict sealing performance parameters, such as leakage rate and friction force.FindingsEccentricity has a large impact on lip seal performance; lips are more susceptible to wear failure under static eccentricity and to leakage failure under dynamic eccentricity.Originality/valueThis study provides a new idea for the design of rotary lip seal considering eccentricity, which is of guiding significance for the engineering application of rotary lip seal.

Study on the prediction of high-speed rotary lip seal wear in aero-engine based on heat-fluid-solid coupling

PurposeThis paper aims to investigate the effect of frictional heat on the wear of high-speed rotary lip seals in engines.Design/methodology/approachIn this research paper, the authors focus on the high-speed rotating lip seal of aircraft engines. Using the hybrid lubrication theory, a thermal-fluid-solid coupled numerical simulation model is established to investigate the influence of parameters such as contact pressure distribution, temperature rise and leakage rate on the sealing performance under different operating conditions. By incorporating the Rhee wear theory and combining simulation results with experimental data, a method for predicting the wear of the rotating seal lip profile is proposed. Experimental validation is conducted using a high-speed rotating test rig.FindingsThe results indicate that as the speed increases, the rise in frictional heat leads to a decrease in the sealing performance of the lip seal contact region. The experimental results show a similar trend to the numerical simulation results, and considering the effect of frictional heat, the predicted wear of the lip seal profile aligns more closely with the actual wear curve. This highlights the importance of considering the influence of frictional heat in the analysis of rotating seal mechanisms.Originality/valueThis study provides a reference for the prediction of wear profiles of engine high-speed rotary lip seals.

Effects of personalized oral exercises on swallowing function among patients with oral cancer after free flap transplantation: a cluster randomized controlled trial

Dysphagia is a common complication in patients with oral cancer who have undergone free flap transplantation. The aim of this cluster randomized controlled trial was to evaluate the effect of personalized oral exercises on swallowing function in this group of patients. Eligible patients were randomly assigned to the intervention (n = 34) or control (n = 34) group. Intervention group patients received personalized oral exercises starting on day 6 after surgery. Swallowing function was evaluated on days 6 and 15, and at 1 month postoperative using the Mann Assessment of Swallowing Ability–Oral Cancer tool (MASA-OC). On day 15 and at 1 month after surgery, the total MASA-OC score (P = 0.003, P < 0.001) and the mouth opening (P = 0.001, P < 0.001) and lip seal (both P < 0.001) item scores showed a significantly greater improvement in the intervention group than in the control group. Moreover, the changes in salivation (P < 0.001) and tongue movement (P = 0.025) scores at 1 month after surgery were significantly greater in the intervention group than in the control group. There was no significant difference between the groups in the change in tongue strength scores on day 15 or at 1 month postoperative (P = 0.476, P = 0.223). Personalized oral exercises can improve swallowing function in patients with oral cancer after free flap transplantation.