Shaft Seal Research Articles

Rotary shaft seals at high temperatures

Rotary shaft seals at high temperatures

A study on radial oil seal leakage failure due to viscoelasticity under dynamic eccentricity

Purpose This study aims to investigate the causes of leakage in radial oil seals under dynamic eccentricity, elucidate the influence of operating parameters on leakage failure and develop methods for predicting and preventing such leakage. Design/methodology/approach Based on the principle of cam motion and considering viscoelasticity, develops a motion model of the compression and release of the shaft seal and proposes a method to determine its failure. In addition, this study quantifies the leakage gap and formulates a quantitative calculation model to accurately determine the location and shape parameters of the leakage gap. Findings Leakage gaps predominantly occur during the release phase of the shaft seal. Their presence can be identified by comparing the descending times of the seal and the shaft during this phase. An increase in rotation speed and eccentricity heightens the likelihood of gap formation, with both the dimensions and leakage rate of the gap increasing as these factors escalate. Eccentricity, in particular, has a more pronounced effect on gap formation. Originality/value This study clarifies the failure mechanisms of radial oil seals under dynamic eccentricity and introduces a criterion for identifying leakage gaps, providing valuable theoretical guidance for the design and optimization of radial oil seals. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0192/.

The Abrasive Effect of Moon and Mars Regolith Simulants on Stainless Steel Rotating Shaft and Polytetrafluoroethylene Sealing Material Pairs.

For space missions to either the Moon or Mars, protecting mechanical moving parts from the abrasive effects of prevailing surface dust is crucial. This paper compares the abrasive effects of two lunar and two Martian simulant regoliths using special pin-on-disc tests on a stainless steel/polytetrafluoroethylene (PTFE) sealing material pair. Due to the regolith particles entering the contact zone, a three-body abrasion mechanism took place. We found that friction coefficients stabilised between 0.2 and 0.4 for all simulants. Wear curves, surface roughness measurements, and microscopic images all suggest a significantly lower abrasion effect of the Martian regoliths than that of the lunar ones. It applies not only to steel surfaces but also to the PTFE pins. The dominant abrasive micro-mechanism of the disc surface is micro-ploughing in the case of all tests, while the transformation of the counterface is mixed. The surface of pin material is plastically transformed through micro-ploughing, while the material is removed through micro-cutting due to the slide over hard soil particles.

Implementation of Failure Mode and Effect Analysis (FMEA) for centrifugal pump maintenance in water supply distribution system

A centrifugal pump is an essential mechanical device in the Regional Drinking Water Company (PDAM) to distribute sterile water from the reservoir to local community houses by flowing the fluid through the pipeline. However, improper and inadequate maintenance of centrifugal pumps can result in component damage, including bearings that are broken, ripped, or damaged mechanical seals. Therefore, for the water supply to continue smoothly, proper maintenance needs to be carried out so that the engine's performance will be maintained and last longer. This study aims to conduct a maintenance analysis on centrifugal pumps utilized by the PDAM of Madiun City. The Failure Modes and Effects Analysis (FMEA) method was employed to assess the potential failure of a system, design, process, or service by implementing a systematic approach to analyze damage and devise maintenance strategies. The FMEA analysis revealed that the shaft of the centrifugal pump component had the highest Risk Priority Number (RPN) value, which amounts to 294. The wearing ring had the lowest RPN value among the centrifugal pump components, with a value of 54. The Pareto diagram results classified six components: shaft, clutch, stuffing box, motor, impeller, and mechanical seal to recommend preventative maintenance action. Additionally, three other components suggested for corrective maintenance were the bearing, packing, and wearing rings

ЭЖЕКТОРНОЕ УПЛОТНЕНИЕ ВАЛА РОТОРНОЙ МАШИНЫ

The analysis of designs and the principle of operation of contactless ejector shaft seals of rotary machines, fans, aerodynamic heating furnaces, blowers, turbochargers of gas pumping units and other injection machines is considered. A new type of non-contact ejector seal is shown, which in-creases its efficiency when changing the direction of rotation of the shaft and eliminates friction and sparking between sealing surfaces during operation of a rotary machine

Analytical method for contact characteristics of rubber shaft seals under dynamic eccentricity considering viscous effect

This study introduces a methodology for analyzing the viscous effect on rubber shaft seals under dynamic eccentricity. It models the radial motion of the shaft seal and quantifies the viscous force arising from the viscous effect. A 3-D FEM with a noncircular shaft is established, equating viscous force to the interference distribution equation. Then, simulated mounting yield contact characteristics. Findings indicate increased interference with the viscous effect and heightened sensitivity of contact characteristics to eccentricity and rotational speed variations. This approach enhances precision in calculating rubber shaft seal contact characteristics under dynamic eccentricity.

Replacement of Fault Sensor of Cutter Suction Dredger Mud Pump Based on MCNN Transformer

The mud pump water sealing system (MPWSS) is important in the efficient operation and prolonged service life of the cutter suction dredger’s (CSD) mud pump. Considering that the underwater pump operates underwater and the shaft seal water pressure sensor is prone to failure, a hybrid deep learning model MCNN transformer is proposed to predict the underwater pump shaft seal water pressure in the event of sensor failure. This paper uses big data from the dredging project to deeply excavate the relationship between the shaft end sealing water pressure and other construction data by combining experience and artificial intelligence, and then uses multi-scale convolutional neural network (MCNN) to reconstruct the data, highlighting the time series characteristics of the multi-scale data were then input into the transformer model for prediction, and compared with a single MCNN, transformer model and four other neural networks. Finally, the cutter suction dredger “Hua An Long” was selected as an application research case; experimental comparisons were conducted on seven different models to verify the accuracy and applicability of the MCNN-transformer model.

Enhance the tribological performance of soft AISI 1045 steel through a CrN/W-DLC/DLC multilayer coating

Special equipment vehicles typically operate in complex environments, leading to wear and failure of the chassis's rotary seal shaft predominantly made of soft AISI 1045 steel. An effective approach to prolong the service life is to apply a hard coating on the working surface. Previous research have primarily concentrated on the coating for hard high-speed steel. However, the significant disparity in physical characteristics between soft AISI 1045 steel and the hard coating results in a weak interface adhesion. This study produces a CrN/W-DLC/DLC multilayer coating on the soft AISI 1045 steel with strong interfacial adhesion and superior friction and wear property through modulation of the CrN transition layer thickness. The multilayer coating consists of five layers, a CrN transition layer, a Cr layer, a Cr/WC alternating layer, a W-DLC/DLC alternating layer, and the topmost DLC layer. The thickest CrN interlayer coating achieves the Lc2 and Lc3 value of 13.9 ± 0.2 N and 20.4 ± 0.9 N. The optimized CrN/W-DLC/DLC coating reduces the internal stress of the DLC coating and enhances its adhesion. Importantly, the average friction coefficient and wear cross-sectional area of the CrN/W-DLC/DLC multilayer coatings decrease accordingly. The thickest CrN interlayer coating exhibits superior outstanding wear resistance evidenced by an average friction coefficient of 0.119, a steady-state friction coefficient of 0.097 and a wear volume of 1.508 × 106 μm3. The presence of a high proportion of sp2 bonds in the thickest CrN interlayer coating, which are susceptible to graphitization, along with a thicker transition layer that enhances the coating's support, leads to narrower wear traces. The primary wear mechanisms observed in the friction and wear test of CrN/W-DLC/DLC coatings are oxidative wear and tribo-abrasive wear. The work provides a significant promise for application in vehicle rotary seal components and a theoretical reference for enhancing the wear resistance of the seal surface.

Thermal accumulation effects modelling of investigate radial shaft seal wear and lubrication transition mechanism

A radial shaft seal (RSS) model is established to reveal mixed thermal lubrication (MTL) and wear performance at speeds ranging from 3000 r/min to 7000 r/min. The model takes into account the initial temperatures of the oil medium and the running time of the RSS to investigate the transition limit of lubrication. Then a thermal fluid-solid method was developed to simulate the lubrication performance of RSS, which shows lubrication transition boundaries through rough micro convex bodies for wear deformation. The RSS deforms wedge-shaped during the wear process and a localized fluid pressure is created on the convex bodies. Considering the wear deformation of the convex bodies due to the wedge effect, the micro performance of the RSS can fully describe the mechanism of the leakage rate. As the dynamic pressure decreases and the leakage rate increases with the temperature of the medium, the RSS lubrication gradually transitions from MTL to EHL. Thus, the initial medium temperature should be considered to maintain the RSS under the mixed lubrication regime with low friction.

Merging experiment data and simulation data for parameter identification of shaft seal

A parameter identification method which merges experimentally monitored signals and physics-based simulation data is proposed, targeting the identification tasks in shaft seals which are challenging due to the high-dimensional parameter space. Features were extracted from the monitored acoustic emission signals following a proposed cross-timescale analysis routine, and the simulation data were augmented using Kriging surrogate model to obtain a dataset with stratified fidelity. Then, a transferable architecture of convolutional neural network modified for periodical data was proposed, with which part of the parameters trained by simulation data were reserved when training model using acoustic emission data acquired in experiments. Cross validation shows that transfer learning can effectively improve the performance, provided data augmentation and proper transfer mode. In conclusion, the study provides an effective parameter identification method which merges the simulation data which carry the physical knowledge and the experiment data which carry directly monitored results.

Finite Element Analysis and Optimization of High Speed E-mobility Seal

Background: The use of electric vehicles is expected to increase day by day. The operating conditions of the rotary shaft seals used in the powertrain of electric vehicles are more challenging than those of internal combustion engines. The maximum operating temperature of seal used in electric vehicles is 150℃ and the maximum operating speed is 16,000RPM. It is impossible for a standard seal with a garter spring not to leak under these operating conditions, which has led us to turn to alternative designs. Objective: The objective of starting this study is to develop a new generation rotary shaft seal to be used in electric vehicles with finite element analysis (FEA) and optimization. Methods: During this study, finite elements, optimization and geometry development methods were used. First of all, alternative spiral knurled seal that can operate at high speeds was designed in this study. Secondly, our alternatively designed seal was tested to determine lifetime. Results: When we checked the results coming from test machines, the first design seal had approximately 5g of leakage at the end of 7 days. In the examinations made after the experiment, it was observed that the spirals were deleted at the end of 7 days. A finite element model of the first designed seal was created and radial load control was performed. When the radial load value obtained from the finite element model and the experimental radial load value are compared, it is seen that there is a deviation of around 4.3%. In the light of these data, the accuracy of the FEA model created in the Abaqus has been proven. The created finite element model was optimized within the boundary conditions with the help of Isight. A prototype of the optimized design seal was produced and a life-time test was carried out. The prototype seal of the optimized design had approximately 4g of leakage after 13 days under the same test conditions. Since the lifetime requested by the customer is 10 days, the optimization made on the seal is considered appropriate. The lifetime of the seal was approximately 95% improved. Conclusion: As a result, a new generation rotary shaft seal that can be used in electric vehicles, which is the aim of our study, has been developed. The prototype rotary shaft seal has been validated according to DIN 3761 specification.

Using Fluid Curtains to Improve Sealing Performance in Turbomachinery Applications

Abstract The results from an investigation into the physics of how fluid curtains can be applied to improve the aerodynamic performance of conventional turbomachinery shaft and rotor seals are described in this paper. Computational fluid dynamics and testing on two experimental facilities are used in the study. In the first part of the work, computational fluid dynamics simulations validated against experimental test data demonstrate the fundamental mechanism by which the presence of the curtain can act to reduce leakage flow through conventional seals. These results are consolidated into a single performance carpet map, showing how the leakage reduction performance and the curtain supply pressure needed to achieve it vary with changes in values of key geometrical parameters. In the second part of the work the effect of swirl in the seal inlet flow, as is often encountered in turbomachinery applications, on the performance of the fluid curtain is investigated experimentally. Test results show that if the swirl momentum in the inlet flow is greater than the momentum of the curtain flow, the performance benefit from applying the curtain is greatly diminished. Overall, the results provide some fundamental design rules for applying fluid curtains to enhance turbomachinery sealing performance for the general type of leakage path geometry (cylindrical channel, 45-deg jet angle, curtain upstream of a conventional seal) and working fluid type and conditions (air, ambient temperature, subsonic leakage channel flow) used in the study.

Experimental investigation on large clearance shaft seal for gas-liquid mixtures

In order to find a solution for the oil leakage problem of a large clearance shaft seal on a marine diesel engine, a series of improvement measures were proposed based on the mechanisms of centrifugal separation, reverse pumping, oil groove and staggered labyrinth. A shaft seal test system that can simulate the gas-liquid environment was built, and verification tests were conducted. Test results showed that the oil leakage didn’t decrease after adding radial or inclined ribs on the oil slinger but increased significantly instead. Adding an oil groove on the oil baffle also didn’t reduce any oil leakage. Fortunately, the addition of the staggered labyrinth effectively reduced the oil leakage. By combining with CFD simulation, the test results were explained, and the sealing functions of different structural features were studied. For structural design work of the non-contact shaft seal, the following design suggestions were proposed. First, the centrifugal effect on the liquid medium can be enhanced by adding ribs on the oil slinger, but the obstruction of oil return should be avoided at the same time. Second, the rotational speed should be fully considered when using the reverse pumping effect. Third, the oil guide groove should be adapted to the airflow and rotation state at its location. Finally, the staggered labyrinth has a stronger throttling effect compared with the straight-through labyrinth, which can reduce the outward transportation of oil by airflow.

Design and empirical evaluation of a magneto-rheological fluid-based seal with rectangular and trapezoidal pole head

The focus of this study is on the design and experimental validation of MRF self-sealing (also known as MRF seal) utilizing permanent magnets. The MRF seal has been built to readily replace traditional seal (lip-seal) for rotation shaft sealing. Following a review of studies on MRF seals, two configurations of MRF seal featuring an axial permanent magnet and two distinct pole head forms, rectangular and trapezoidal, are presented. The two MRF seals are then subjected to a magnetic analysis using the finite element method (ANSYS APDL). The Bingham plastic model of MRF and the assumption of linear velocity profile of MRF in the sealing gap are employed to construct mathematical models of crucial seal characteristics such as maximum static working pressure and frictional torque. The seals are optimized employing the optimization toolbox integrated in the ANSYS APDL to obtain the optimal geometric dimensions of the MRF seals. Finally, prototypes of the two MRF seals are fabricated and testing work is conducted to validate and compare them with the simulated results.

Influence of cryogenic turning strategies on the surface morphology and resulting wear behavior of metastable AISI 347 austenitic stainless steel

AbstractCryogenic turning of metastable austenitic stainless steels can improve wear resistance of the resulting surface due to the phase transformation of γ‐austenite into α’‐ and/or ϵ‐martensite in the near surface layer. By using a cryogenic two‐step turning process, the amount of deformation‐induced α’‐martensite in the subsurface regime can be further increased. To determine the influence of the implemented and optimized two‐step turning strategy on the tribological properties of countersurfaces for radial shaft seals, an evaluation of wear behavior of the shaft seal countersurface as well as microstructural analyses in subsurface regime is presented and compared to the cryogenic single step turning process. The results show that not only the integral phase transformation in the overall subsurface region, but also the local phase distribution plays an important role when it comes to the surface performance in tribological applications.

Investigation of the Effect of Underpressure Between Main and Dust Lip on the Performance of Radial Shaft Seals Under Instationary Shaft Movements

Abstract Radial shaft seals (RSS) are increasingly used in applications with highly dynamic rotational shaft movement, high accelerations, and frequent changes in the rotational direction, e.g. positioning robots. For such instationary conditions, the behavior of radial shaft seals has not been adequately understood yet. Therefore, under such conditions, radial shaft seals show leakage much more frequently than under stationary conditions. This is a problem especially in food processing or surface treatment processes where even the smallest amount of oil leakage can cause significant financial and reputational damage. Previous investigations have shown that leakage does mostly occur with shaft seals equipped with a contacting dust lip. Consequently, it is assumed, that the build up of negative pressure between dust and the main lip plays a role in the leakage mechanism. A measuring setup and evaluation strategy for measuring this underpressure during instationary shaft movements have been developed. A measurement regime with variation of different influential parameters has been conducted. Results show build up of a much higher underpressure when compared to stationary shaft rotation with severe impacts on the RSS’s operational behavior.

Measurement and prediction of thermal performance of automotive transmission radial lip seals

The paper reports on the use of a developed novel and specific test-rig for the assessment of performance of radial lip seals of automotive transmissions, with particular emphasis on determination of thermal performance. The test-rig can accommodate original components from a donor vehicle, thus accurately represents vehicular conditions. The specific aim is to experimentally determine the effect of shaft surface roughness parameters on the generated contact temperature. Excessive exposure to high temperatures can accelerate degradation and aging of elastomeric seals, resulting in increased wear. Corundum and CBN (Cubic Boron Nitride) ground shafts are used to ascertain the effect of surface roughness parameters in the shaft seal conjunction. An analytical thermal model is also developed in combination with temperature measurements to determine the exact temperature in the lip seal-shaft contact. It is shown that depending on the type of shaft surface grinding process some potential correlation exists between roughness parameters and generated contact temperatures. It is also shown that the contact temperature can be several degrees Celsius higher than those measured in the proximity of the seal contact.

Study of the Influence of Macrogeometry Parameters on the Tightness of Shaft–Seal Joints

Study of the Influence of Macrogeometry Parameters on the Tightness of Shaft–Seal Joints

Dynamic Characterization of an Adaptive Film-Riding Seal

Abstract Shaft seals control the leakage of fluid between areas of high pressure and low pressure around rotating components inside turbomachinery. Static seals are often subject to damaging rubs with the shaft, caused by assembly misalignments and rotordynamic vibrations during operation. Adaptive seals aim to reduce leakage flows whilst minimizing wear. The film riding pressure actuated leaf seal (FRPALS) is one such design which utilizes a large installation clearance and is blown down toward the shaft under pressure. This paper presents a numerical model which can be used in the design and development of adaptive shaft seals, validated by experimental data from the literature. The model uses a modified version of the Reynolds equation to predict the dynamic, frequency-dependent stiffness and damping coefficients of the fluid film. The dynamic coefficients have been solved for different operational clearances and pressure differences to generate coefficient maps. These maps have been incorporated into a blow down model with compliant mechanical leaves to predict the transient translational and angular displacement paths of the FRPALS when subject to an increasing pressure drop. The blow down model has been compared against experimental measurements collected from a specially designed test facility for the characterization of shaft seal performance. Eddy current probes were used to measure the displacement paths of the FRPALS with the experimental values showing that the model can accurately predict the dynamic movement of the seal when subject to a pressure difference.

Modeling the Pumping Behavior of Macroscopic Lead Structures on Shaft Counterfaces of Rotary Shaft Seals

The leak tightness of the sealing system rotary shaft seal is based on the formation of an active back-pumping effect of the sealing ring. Here, the sealing ring pumps the fluid in the sealing gap back into the housing. However, this active sealing mechanism is disturbed by so-called “lead structures”. Lead structures include all types of directional structures on the sealing counterface which create rotation-dependent axial fluid pumping. Lead-affected sealing counterfaces can thus cause leakage or insufficient lubrication of the sealing contact. To ensure leak tightness, lead must be avoided or tolerated. This article investigates how different structural characteristics of lead affect the amount of fluid pumped by the shaft surface. For this purpose, 26 shafts are subjected to surface analyzing methods and an experimental pumping rate test. The interaction of various geometric features of the lead structures and their combined effect on the pumping capacity is modeled based on the measured data. Appropriated correlation models are discussed and relationships between shaft lead and its pumping effect are shown. The aim is to estimate shaft pumping rates based on surface measurements in future. The results contribute to the derivation of measurable tolerance values for lead and to the prevention of leakage.