Face Seal Research Articles

A Method for Calculating the Reliability of Welded Metal Bellows for Mechanical Seals

Welded metal bellows are an elastic element widely used in the field of mechanical seals. The main objective of the present study was to investigate the reliability of welded metal bellows in mechanical seals under specified working conditions. To this end, a stress relaxation test bench was built to obtain the residual elastic force data of welded metal bellows under different compression loads in high-temperature environments. Then, the elastic force loss equation of the bellows was fitted. Moreover, a failure judgment form of welded metal bellows in the mechanical seal is proposed. According to the calculation relationship between the seal face pressure and the welded metal bellows’ elastic force, the elasticity force loss range of the bellows was 556–708 N. Finally, according to the elastic force loss equation, elastic force loss was determined. The maintenance time of the welded metal bellows, and the bellow’s failure limit state equation were determined, and the limit state equation was substituted into the center point method. The reliability of the welded metal bellows was 0.9958. The results show that the new failure criterion and the center point reliability calculation method proposed in this paper have certain practical value for the rapid reliability prediction of welded metal bellows.

Experimental and theoretical investigations on dry gas seal transient performance and its disparity with steady performance

Through high-speed dry gas seal test rig, the real-time film thickness and leakage rate of spiral grooved dry gas seal have been monitored under different closing forces which are changed by adjusting spring compression. Under the conditions of different spring pressures and seal face deflection rates, the change rules of transient opening force and leakage rate are obtained by solving the transient-state Reynolds equation based on the measured real-time film thickness. Meanwhile, the steady opening force and leakage rate are figured out by solving the steady-state Reynolds equation using the average value of the real-time film thickness. Results show that the variation trends of calculated results based on steady-state or transient-state theory coincide well with experimental results. But with the influence of nonlinear effect, the average value of transient opening force and leakage rate are larger than steady opening force and leakage rate calculated with the average value of real-time film thickness, and compared with the value of steady leakage rate, the average value of transient leakage rate considered seal face deflection is closer to the experimental monitoring results.

Utilization of a mask fitter or micropore tape to improve the fit of a surgical mask.

This study aimed to test the face seal of a surgical mask modified using a custom-made mask fitter or by sealing all borders with micropore tape, in comparison to the N95 mask as a gold standard. Fifteen participants were assigned to wear an N95 mask, a surgical mask sealed with a mask fitter, and a surgical mask sealed with micropore tape. A quantitative fit test was performed using a Portacount respirator fit tester in 4 different actions: bending over, talking, moving the head from side to side, and moving the head up and down. The N95 showed the highest overall fit factor score (134.67 ± 66.62), passing Occupational Safety and Health Administration (OSHA) standards. The surgical mask alone had the lowest overall fit factor score of 4.73 ± 3.30. Modification of the surgical mask using a mask fitter or micropore tape significantly increased the overall fit factor to 35.33 ± 14.58 and 29.33 ± 9.73, respectively. This pattern was similar for all exercises. The N95 was the only mask type that passed the OSHA standard for protection. Use of a mask fitter or micropore tape significantly increased the face seal of a surgical mask. This could offer useful levels of protection during a non-aerosol dental procedure.

THE IMPACT OF SELECTED PARAMETERS ON PRESSURE DISTRIBUTION IN THE FACE THROTTLE OF A CENTRIFUGAL PUMP AUTOMATIC BALANCING DEVICE

Face throttles are a necessary functional element of non-contact face seals and automatic balancing devices of centrifugal pumps of different constructions. To calculate the hydrodynamic forces and moments acting on the rotor and fluid flow through the automatic balancing device, it is necessary to know the pressure distribution in the cylindrical and face throttle when considering all important factors which predetermine fluid flow. The face throttle surfaces are moving, which leads to unsteady fluid flow. The movement of the walls of the face throttle causes an additional circumferential and radial flow, which subsequently leads to the additional hydrodynamic pressure components. The paper analyses viscous incompressible fluid flow in the face throttle of an automatic balancing device taking into account the axial and angular displacements of throttle’s surfaces and the inertia component of the fluid. The effect of local hydraulic losses as well as random changes in the coefficients of local hydraulic resistance at the inlet and outlet of the throttle is analysed.

Model validation of mechanical face seals in two-phase flow conditions

A steady-state one-dimensional axisymmetric numerical model of a mechanical seal in two-phase flow is presented. In this work a non-linear thermal model is implemented using a coupled (monolithic) approach, linking the fluid film and sealing rings. It is solved for the temperature fields of the fluid and solids, heat fluxes between fluids and solids, enthalpy of the fluid, and the vapor mass fraction, using Newtons method. The novelty of this approach lies in 1) the thermal coupling between fluid and solids, and 2) the implementation of saturation curves to couple temperature, enthalpy, and vapor mass fraction. The temperature across the seal gap is described by an analytical parabolic temperature profile by assuming a plane Couette flow in the radial direction. From this assumption, an equation for the wall heat fluxes is derived, which couples the temperature fields of the fluid and solids. The IAPWS-IF97 standard for the thermodynamic properties of water is used to obtain non-linear equations that couples the fluid temperature, enthalpy and the vapor mass fraction. The model and its implementation is described in detail. Several cases of seal behavior and two-phase flow are studied and show good agreement with other results from literature, validating the coupled approach for modelling phase-change in mechanical seals.

Dynamic failure analysis of static seals under pressure fluctuation in an ultrahigh-pressure water piston pump

For ultrahigh-pressure piston pumps, in the reciprocating action of the piston, the fretting between the static face seal and the mating surface occurs with the change of the pressure in the piston chamber. This phenomenon will seriously affect the service life of the seal ring and lead to the failure of the pump. However, the failure of static seals used to seal ultrahigh-pressures is usually studied from the directions of shear, stress, or rubber material. These studies cannot explain the failure phenomenon of the sealing ring found in our experiment. This paper analyzed the failure of the face seal ring in a piston pump with a maximum pressure of 120 MPa. A two-dimensional axisymmetric finite element model was established based on the Mooney-Rivlin constitutive relation of the rubber material, and the fretting conditions of the sealing ring were analyzed. Combined with the wear scars observed by the scanning electron microscope the face seal ring’s dynamic failure mechanism on the ultrahigh-pressure piston pump was determined. A better sealing scheme was proposed and verified by the duration test of the pump, which provided a basis for the design of the sealing of the ultrahigh-pressure fluid with high-frequency fluctuations.

A Unique 14th Century Seal Matrix from Giebło, Zawiercie District

A unique lead seal-matrix with majuscule legend: LUCIANI PRESBITERI belonging to a priest was found by the Romanesque castle church in Giebło. The name of its owner is mentioned in written sources from the years 1325–1327 as plebanus ecclesie de Kebel. As PRESBITER he probably didn’t enjoy all privileges that the collator usually bestows on a parish priest on his property. Possibly for that reason he had his matrix made in an easy-to-process material, infrequently used for such objects in this part of Europe. The use of this raw material suggests someone who tried avoid the high costs of making the item. Special attention is merited by the composition of a fleur-de-lis crowned with the cross engraved on the seal face that resembles a heraldic device. The repetition of a schematic lily flower on the reverse of the matrix shows the special importance of this sign (identified in medieval time with the Blessed Virgin Mary); this symbol was treated in this way by, for example, Cistercians. By presenting his name in the company of these symbols, Lucianus gave his seal strength and credibility.

Semi Salix Leaf Textured Gas Mechanical Face Seal with Enhanced Opening Performance.

Seal performance of a novel gas mechanical face seal with semi salix leaf textures was introduced and theoretically investigated with the purpose of enhancing hydrostatic and hydrodynamic opening performance. First, a theoretical model of a laser surface textured gas mechanical face seal with semi salix leaf textures was developed. Second, the impact of operating and texturing parameters on open force, leakage, and friction torque was numerically investigated and has been discussed based on gas lubrication theory. Numerical results demonstrate that the semi salix leaf textured gas face seal has larger hydrostatic and hydrodynamic effects than the semi ellipse textured seal because of the effect of the inlet groove. All semi salix leaf textured surfaces had better open performance than the semi ellipse textured surface, which means that the inlet groove plays an important role in improving open performance and consequently decreasing contact friction during the start-up stage. Texturing parameters also influenced the seal performance of thee semi salix leaf textured gas face seal. When the inclination angle was 50°, the radial proportion of the inlet groove was 0.8, the dimple number was 9, and the open force resulted in the maximum value. This research has demonstrated the positive effects of the applications of a semi salix leaf textured gas mechanical face seal that combines the excellent hydrostatic and hydrodynamic effects of groove texture and the excellent wear resistance of microporous textures.

The protective performance of reusable cloth face masks, disposable procedure masks, KN95 masks and N95 respirators: Filtration and total inward leakage.

Face coverings are a key component of preventive health measure strategies to mitigate the spread of respiratory illnesses. In this study five groups of masks were investigated that are of particular relevance to the SARS-CoV-2 pandemic: re-usable, fabric two-layer and multi-layer masks, disposable procedure/surgical masks, KN95 and N95 filtering facepiece respirators. Experimental work focussed on the particle penetration through mask materials as a function of particle diameter, and the total inward leakage protection performance of the mask system. Geometric mean fabric protection factors varied from 1.78 to 144.5 for the fabric two-layer and KN95 materials, corresponding to overall filtration efficiencies of 43.8% and 99.3% using a flow rate of 17 L/min, equivalent to a breathing expiration rate for a person in a sedentary or standing position conversing with another individual. Geometric mean total inward leakage protection factors for the 2-layer, multi-layer and procedure masks were <2.3, while 6.2 was achieved for the KN95 masks. The highest values were measured for the N95 group at 165.7. Mask performance is dominated by face seal leakage. Despite the additional filtering layers added to cloth masks, and the higher filtration efficiency of the materials used in disposable procedure and KN95 masks, the total inward leakage protection factor was only marginally improved. N95 FFRs were the only mask group investigated that provided not only high filtration efficiency but high total inward leakage protection, and remain the best option to protect individuals from exposure to aerosol in high risk settings. The Mask Quality Factor and total inward leakage performance are very useful to determine the best options for masking. However, it is highly recommended that testing is undertaken on prospective products, or guidance is sought from impartial authorities, to confirm they meet any implied standards.

Heat Transfer Analysis for Non-Contacting Mechanical Face Seals Using the Variable-Order Derivative Approach

This article presents a variable-order derivative (VOD) time fractional model for describing heat transfer in the rotor or stator in non-contacting mechanical face seals. Most theoretical studies so far have been based on the classical equation of heat transfer. Recently, constant-order derivative (COD) time fractional models have also been used. The VOD time fractional model considered here is able to provide adequate information on the heat transfer phenomena occurring in non-contacting face seals, especially during the startup. The model was solved analytically, but the characteristic features of the model were determined through numerical simulations. The equation of heat transfer in this model was analyzed as a function of time. The phenomena observed in the seal include the conduction of heat from the fluid film in the gap to the rotor and the stator, followed by convection to the fluid surrounding them. In the calculations, it is assumed that the working medium is water. The major objective of the study was to compare the results of the classical equation of heat transfer with the results of the equations involving the use of the fractional-order derivative. The order of the derivative was assumed to be a function of time. The mathematical analysis based on the fractional differential equation is suitable to develop more detailed mathematical models describing physical phenomena.

Modified Two-Rescuer CPR With a Two-Handed Mask-Face Seal Technique Is Superior To Conventional Two-Rescuer CPR With a One-Handed Mask-Face Seal Technique

Bag-valve-mask (BVM) ventilation using a two-handed mask-face seal has been shown to be superior to a one-handed mask-face seal during cardiopulmonary resuscitation (CPR). We aimed to compare CPR quality metrics during simulation-based two-rescuer CPR with a modified two-handed mask-face seal technique and two-rescuer CPR with the conventional one-handed mask-face seal technique. Participants performed two-rescuer CPR on a simulation manakin and alternated between the modified and conventional CPR methods. For the modified method, the first rescuer performed chest compressions and thereafter squeezed the BVM resuscitator bag during the ventilatory pause, while the second rescuer created a two-handed mask-face seal. For the conventional method, the first rescuer performed chest compressions and the second rescuer thereafter delivered rescue breaths by creating a mask-face seal with one hand and squeezing the BVM resuscitator bag with the other hand. Among the 40 participants that were enrolled, the mean ± standard deviation (SD) delivered respiratory volume was significantly higher for the modified two-rescuer method (319.4 ± 71.4 mL vs. 190.2 ± 50.5 mL; p < 0.0001). There were no statistically significant differences between the two methods with regard to mean ± SD compression rate (117.05 ± 9.67 compressions/min vs. 118.08 ± 10.99 compressions/min; p = 0.477), compression depth (52.80 ± 5.57 mm vs. 52.77 ± 6.77 mm; p = 0.980), chest compression fraction (75.92% ± 2.14% vs. 76.57% ± 2.57%; p = 0.186), and ventilatory pause time (4.62 ± 0.64 s vs. 4.56 ± 0.43 s; p = 0.288). With minor modifications to the conventional method of simulated two-rescuer CPR, rescuers can deliver significantly higher volumes of rescue breaths without compromising the quality of chest compressions.

A special oropharyngeal oxygenation device to facilitate apneic oxygenation in comparison to high flow oxygenation devices.

Oxygen application and apneic oxygenation may reduce the risk of hypoxemia due to apnea during awake fiberoptic intubation or failed endotracheal intubation. High flow devices are recommended, but their effect compared to moderate deep oropharyngeal oxygen application is unknown. Designed as an experimental manikin trial, we made a comparison between oxygen application via nasal prongs at 10 L/min (control group), applying oxygen via oropharyngeal oxygenation device (at 10 L/min), oxygen application via high flow nasal oxygen with 20 L/min and 90% oxygen (20 L/90% group), oxygen application via high flow nasal oxygen with 60 L/min and 45% oxygen (60 L/45% group), and oxygen application via sealed face mask with a special adapter to allow for fiberoptic entering of the airway. We preoxygenated the lung of a manikin and measured the decrease in oxygen level during the following 20 minutes for each way of oxygen application. Oxygen levels fell from 97 ± 1% at baseline to 75 ± 1% in control group, and to 86 ± 1% in oropharyngeal oxygenation device group. In the high flow nasal oxygen group, oxygen level dropped to 72 ± 1% in the 20 L/90% group and to 44 ± 1% in the 60 L/45% group. Oxygen level remained at 98 ± 0% in the face mask group. In conclusion, in this manikin simulation study of apneic oxygenation, oxygen insufflation using a sealed face mask kept oxygen levels in the test lung at 98% over 20 minutes, oral oxygenation device led to oxygen levels at 86%, whereas all other methods resulted in the decrease of oxygen levels below 75%.

Cross-Scale Flow Field Analysis of Sealing Chamber and End Face Considering the CO2 Real Gas Effect

The dry gas seal (DGS) is a non-contacting, gas-lubricated mechanical face seal commonly used in rotating machinery. Traditional analyses of DGSs treat the end face as an independent factor by setting the end-face inlet as boundary conditions, but limited attention is focused on the sealing chamber of the DGS. Using the finite volume method and the shear stress transport (SST) k-ω model, the coupling between the millimeter-scale sealing chamber and the micrometer-scale end face are simulated with regard to the real gas effect of CO2. The three-dimensional distributions of velocity, pressure and temperature in the cross-scale flow field are investigated under different working conditions. Moreover, the boundary parameters of the end-face inlet are modified by response surface methodology with a central composite rotatable design. The results demonstrate that the real gas effect of CO2 leads to an increased total inlet flow. When the pressure reaches 10.3 MPa, the relative difference is 51.90% compared to ideal gas. Minor temperature and pressure changes occur in the sealing chamber when the dry gas seal is in operation. However, the inlet temperature of the end face Tf increases and the inlet pressure of the end face pf decreases. These research results provide a reliable reference for engineering practice.

Simulation of the Operation of Contact Face Seals for Multimode Turbomachinery

Simulation of the Operation of Contact Face Seals for Multimode Turbomachinery

Cavitation and film formation in hydrodynamically lubricated parallel sliders

Cavitation influences the pressure distribution in hydrodynamically lubricated contacts and therefore also the load carrying capacity. Film formation in parallel sliders is investigated experimentally and numerically by focusing on its relationship with cavitation. Cavitation is observed and film thickness measurements are conducted on a structured rectangular face seal by using the laser induced fluorescence method. Hydrodynamic film formation is modeled based on cavitation by implementing a JFO cavitation model with a mass conservative Fischer-Burmeister-Newton algorithm. The numerical results are validated via the experiments. Influences of structuring, macro surface irregularities, and cavitation pressure are investigated.

Thermoelastohydrodynamic Characteristics of Low-Temperature Helium Gas T-Groove Face Seals.

Thermoelastohydrodynamic lubrication behaviors of helium gas T-groove face seals are numerically simulated under conditions of low temperature and high pressure, with the consideration of real-gas properties including compressibility coefficient, viscosity, and heat capacity. It is found that helium gas T-groove face seal presents a sharp divergent deformation at low temperature and high pressure, which makes the opening performance weaken and the leakage rate increase. This result is obviously different from the case of high-temperature gas face seals. As the sealing temperature drops from 300 K to 150 K, the leakage rate increases about 17% and the opening force decreases about 15%. Moreover, with the growth of rotational speed, both the outlet film pressure and the sealing performance present a non-monotonic trend. Specifically, while the rotating speed of moving ring raises from 3000 to 30,000 r·min−1, the leakage rate changes more than 30%, and the opening force is reduced about 10%.

Efficacy of face coverings in reducing transmission of COVID-19: Calculations based on models of droplet capture.

In the COVID-19 pandemic, among the more controversial issues is the use of masks and face coverings. Much of the concern boils down to the question—just how effective are face coverings? One means to address this question is to review our understanding of the physical mechanisms by which masks and coverings operate—steric interception, inertial impaction, diffusion, and electrostatic capture. We enquire as to what extent these can be used to predict the efficacy of coverings. We combine the predictions of the models of these mechanisms which exist in the filtration literature and compare the predictions with recent experiments and lattice Boltzmann simulations, and find reasonable agreement with the former and good agreement with the latter. Building on these results, we explore the parameter space for woven cotton fabrics to show that three-layered cloth masks can be constructed with comparable filtration performance to surgical masks under ideal conditions. Reusable cloth masks thus present an environmentally friendly alternative to surgical masks so long as the face seal is adequate enough to minimize leakage.

3D-gedrucktes Siliciumcarbid als Gleitringwerkstoff

Reaction bonded silicon carbide is well known for use as axial seal faces. The properties have been optimized in order to improve the performance of dynamic seals. 3D-printed silicon carbide will be introduced. The new material allows forming much more complicated shapes and seal ring designs. The new material shows a different structure compared to compression molded reaction bonded silicon carbide due to the special manufacturing process. Therefore, first comparative tests of seal-rings under marginal lubricated conditions have been performed. The results are presented and the possible use of 3D-printed silicon carbide in the sealing technology is discussed. A first fundamental design study implies the potential of producing seal rings with an additional functionality. A simplified model of a seal ring with internal structures is shown and some ideas will be shared whether additional benefit could be achieved.

Ultra-high-speed TEHL characteristics of T-groove face seal under supercritical CO2 condition

Purpose The purpose of this paper is to acquire sealing properties of supercritical CO2 (S-CO2) T-groove seal under ultra-high-speed conditions by thermo-elastohydrodynamic lubrication (TEHL) analysis. Design/methodology/approach Considering the choked flow effect, the finite difference method is applied to solve the gas state equation, Reynolds equation and energy equation. The temperature, pressure and viscosity distributions of the lubricating film are analyzed, and sealing characteristics is also obtained. Findings The face distortions induced by increasing rotational speed leads to the convergent face seal gap. When the linear velocity of rotation exceeds 400 m/s, the maximum temperature difference of the sealing film is approximately 140 K, and the viscosity of CO2 is altered by 17.80%. Near the critical temperature point of CO2, while the seal temperature increases by 50 K, the opening force of the T-groove non-contact seal enhances by 20% and the leakage rate declines by 80%. Originality/value The TEHL characteristics of the T-groove non-contact seal are numerically analyzed under ultra-high-speed, considering the real gas effect and choked flow effect. In the supercritical conditions, the influence of rotational speed, seal temperature, seal pressure and film thickness on sealing performance and face distortions is analyzed.

Effect of taper parameters on mechanical seal performance of taper/pores composite mechanical seal

a new combination fluid seal with the cone/pores is given, and the 3D fluid/solid coupling theory model is constructed, considering the interaction between the liquid pressure field and the stress deformation of the seal rings, led to seal clearance unceasingly change. Through the corresponding numerical calculation, film pressure distribution and end face deformation situation are obtained between the seal end faces, the influence rule of taper on sealing performance under the high and low pressure conditions is analyzed. The results show that the dynamic pressure effect caused by rhomboid pores can produce circumferential and radial wavy deformation of the seal end faces, while the static pressure effect also changes with the taper change of the end faces. For the low pressure and medium speed equipment, the conical end face which the taper is 0-2.4 should be chosen priority. For higher pressure and rotational speed device, the convergence end face seal which the taper is 0-2.4 should first be chosen.