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Electroless nickel phosphor coating is an important technology in the field of industrial coatings which is widely used in many technical applications. The electroless nickel phosphorus layer has high hardness and corrosion resistance, making it ideal for multiple applications for example, automotive, aerospace and electronics industries. Sulfuric acid is an essential agent in many industrial processes. The corrosive and abrasive nature of sulfuric acid results in rapid wear of mechanical parts, resulting in frequent replacement, increased maintenance costs, and may cause environmental and safety issues. The purpose of this work is to investigate the effect of the different conditions such as heat treatment temperature, coating time and coating bath temperature on wear rate and microhardness by employed electroless Ni-P coating, which was effectively assigned to mechanical seal models. The Taguchi design array L9 was used to conduct the experimental work. The coating thickness was measured using an optical microscope. The results showed that the hardness increased reaching peak as 653 HV at 400 °C and coating time 4 hours. As for wear rate, it was recorded the lowest value as 0.00060 g/m under same conditions. Through SEM and XRD, the formation of NiP and Ni3P were found. ANOVA demonstrated that heat treatment temperature was the most effected factor that contributed to enhance both hardness and wear resistance, followed by coating time. [ABSTRACT FROM AUTHOR]

Aiming at the problem of mechanical seal failure due to serious wear and tear in operation, the numerical model of the thermal–solid coupling wear of the seal ring is established by taking the friction sub-material as the research object, and the hardness, wear coefficient, and friction coefficient of different soft-ring materials are obtained by a test to verify the accuracy of the numerical model of wear. Additionally, the temperature field and deformation field of the seal ring of different materials are calculated, and the effects of the material parameters, such as elasticity modulus and thermal conductivity, on the temperature, relative deformation, and axial deformation trend are reported. The wear relation of the mechanical seal was optimized, and the correction coefficients of several materials were calculated. The results show the following: the main wear of the seal ring is due to adhesive wear leading to particle shedding and extrusion, adhesive wear causes material transfer, which alters the composition of the worn surface.in turn leading to cratering, which also causes the wear of the seal ring; the friction performance is better when the soft-ring material is graphite (C); the temperature, as well as the deformation, is smaller when the soft-ring material is silicon carbide (SIC); the correction coefficients for the life of SIC are calculated to be 0.23, for C, to be 0.14, and for stainless steel (Ss), to be 0.31, and the corrected equations can more accurately predict the corresponding material. The corrected equation can more accurately predict the service life of the corresponding material. [ABSTRACT FROM AUTHOR]

The main cause of failure in sealing friction pairs, friction wear, has presented analytical challenges due to rapidly changing and complex friction frequency characteristics. This has led to a focus on surface morphology treatment rather than direct measurement techniques in research. In this context, the present study adopted Acoustic Emission (AE) technology for direct monitoring of friction pairs, aiming to identify friction response signals during their transient contact and abrasion stages. Employing time–frequency analysis, the research delineated the state evolution of AE characteristics during the entire operational cycle of the friction pair, from start to stop. It has established the time–frequency information of AE signals in relation to the surface state of the sealing friction pair and deciphered the correlation between the friction AE signals and the surface state alterations of the friction pair. The study showed that the frequency of friction-induced signals in seals is 270 ± 40 kHz. The transition speeds for the friction pair's state, moving from boundary lubrication to mixed lubrication and then to fluid dynamic lubrication, were identified as 200 rpm and 1000 rpm, respectively. Additionally, an escalation in signal activity was observed in dry friction scenarios and when surface defects were present in the friction pair, markedly exceeding the activity in conditions of no wear. This relationship between the friction signals and the operational state of the seal facilitates precise assessments of wear and operational integrity, underpinning the theoretical aspects of periodic wear in seal tribology. [ABSTRACT FROM AUTHOR]

In view of the problems that the mechanical seal for the water pump is prone to deformation, friction and wear, and loss of sealing performance in the process of use, taking the temperature change of end surface as the research entry point, the temperature distribution, stress and strain diagram of rotating ring, and stationary ring are obtained by thermal-stress coupling simulation. The temperature change of stationary ring is studied by the experiments, and the friction state of end surface of rotating ring and stationary ring are observed. The results indicate that the test temperature of stationary ring is slightly lower than simulation temperature, which is related to the thermocouple fixed on the side of the stationary ring for temperature measurement. In addition, comparing the micro morphology of end surface of rotating ring before and after the experiment, it is found that there is significant plastic deformation on the inner diameter of rotating ring, which is related to the stress generated by the thermal-mechanical coupling of inner diameter of rotating ring exceeding the material limit, consistent with the simulation results. [ABSTRACT FROM AUTHOR]

We proposed a numerical method to investigate the thermo-fluid–structural coupled characteristics of a mechanical seal of a reactor coolant pump (RCP), especially during extended loss of AC power (ELAP) operation. We developed a finite element program for the general Reynolds equation, including the turbulence effect to calculate the pressure, opening force, and leakage rate of fluid lubricant and the two-dimensional energy equation to calculate the temperature distribution of the fluid lubricant. We verified the accuracy of the developed program by comparing the simulated temperature distribution and leakage rate of this study with those of previous research. Heat conduction and elastic deformation due to pressure and temperature changes at the seal structure were analyzed using an ANSYS program. The results showed that temperature more significantly affected the elastic deformation of the seal structure near clearance than pressure both under normal and ELAP operating conditions. High temperature and pressure of the coolant under ELAP operating conditions deform the seal structure, resulting in a much smaller clearance of the fluid film than normal operating condition. However, even with a small clearance under ELAP operation, the leakage rate slightly increases due to the high internal pressure of the coolant. This research will contribute to the development of robust mechanical seals for RCPs by accurately predicting the characteristics of mechanical seals, especially when the RCP is operating under ELAP. [ABSTRACT FROM AUTHOR]

A dry gas seal (DGS) is one of the key basic components of natural gas transmission pipeline compressors, and the sealing performance of a DGS dealing with complex multi-component pipeline natural gas is different from that dealing with conventional nitrogen medium. In this paper, a spiral groove DGS of the compressor in natural gas transmission pipeline systems is taken as the research object. The thermal hydrodynamic lubrication model of the DGS is established considering turbulence effect and choking effect. Based on the finite difference method, the temperature and pressure distributions and the steady-state performance of the DGS are obtained by simulating. The influence of unitary impurity compositions such as light hydrocarbon, heavy hydrocarbon, non-hydrocarbon, and their contents on the steady-state performance of the DGS is analyzed. The steady-state performance of the DGS dealing with multi-impurity natural gas such as in the West-East gas transmission is investigated under different operating conditions. The results show that turbulence had a significant effect on the DGS, while choking had a weak effect. Increasing the content of light hydrocarbon such as C2H6 and heavy hydrocarbon such as C5H10 resulted in an increase in the gas film stiffness, leakage rate, and the temperature difference between the inlet and outlet, while non-hydrocarbon, such as N2, reduced the temperature difference between the inlet and outlet. The greatest impact on seal performance was produced by the heavy hydrocarbon, followed by the light hydrocarbon, and the least was produced by the non-hydrocarbon. [ABSTRACT FROM AUTHOR]

The John Crane 48 V mechanical seal is a long-distance oil transfer pump station shaft end seal; its sealing effect directly affects pipeline production safety. However, it has been found that there is oil leakage at the shaft end of the pump station. In order to explore the oil transfer pump mechanical seal abnormal leakage failure causes, to ensure the safety and stability of production, the end face of the 48 V mechanical seal was analyzed by white light interference and scanning electron microscope technology. The failure mechanism of the 48 V mechanical seal was explored from the perspective of the wear mechanism of moving and stationary rings. Results showed that the wear mechanism of the 48 V mechanical seal stationary ring was mainly abrasive wear, and substantial furrows, bulges, and depressions existed on the wear surface. The material removal mechanism was brittle spalling, and the roughness of the wear surface increased with the increase in wear depth and decreased with the increase in wear average width. Uneven wear occurred on the end face of the stationary ring of the mechanical seal, resulting in the leakage of the sealing medium from the end cover of the mechanical seal. The working condition could be improved by adding a spring compensation device to the stationary ring or increasing the gap between the stationary ring and the shaft sleeve. [ABSTRACT FROM AUTHOR]

The friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester, and the wear of GCr15–graphite seal pairs with the low-temperature time-dependent pretreatment was discussed by comparing the wear morphology. The results show that liquid nitrogen pretreatment can affect the hardness and interlayer spacing of graphite. The range of the friction coefficients of pretreated graphite changes from 0.17 to 0.22. With the increase of liquid nitrogen pretreatment time, the wear mechanism of graphite would change from dominated three-body wear to adhesion wear. The experimental results of the mechanical seal with liquid nitrogen pretreatment show that the wear rate of stator is less than 0.00165 mm3·N−1·m−1, and the graphite shows a good low-temperature compatibility. [ABSTRACT FROM AUTHOR]

Portable hydrolysis reactors for hydrogen storage material reactions are extremely important for the application of hydrogen energy since hydrolysis is a facile path to provide hydrogen. The strain and sealing components are extremely important for a hydrogen reactor. However, most researchers are focusing on the hydrogen storage materials for hydrolysis instead of the hydrolysis reactors. Herein, the structure of a hydrolysis reactor has been designed based on the strain distribution and sealing efficiency. The stress concentration on the threaded connection part and sealing effects have been analyzed using finite element analysis method. The stress concentration has been effectively reduced by increasing thread turns and wall thickness of thread. The stress concentration was also found to be affected by the thread types. Double sealing connection was adopted, where the sealing performance was found to increase with increase pressure in the reactor. This study provides a feasible design of a portable hydrolysis reactor for solid-state hydrogen storage materials. [Display omitted] • The structure of hydrolysis reactor has been designed based on the strain distribution and sealing efficiency. • The stress concentration on the threaded connection part and sealing effects have been analyzed using finite element analysis method. • The sealing performance of the reactor was found to increase with increase pressure in the reactor. • This study provides a feasible structure design scheme for a portable hydrolysis reactor. [ABSTRACT FROM AUTHOR]

Mechanical seals are used in a wide range of industrial applications, including pumps, compressors etc., in order to avoid leakage of the working fluid. The design construction, and the operation of the mechanical seals continue to evolve to meet the demands of new technologies and industries. These developments are the increase of operating parameters, in the condition of strictly respecting the environment protection. A mechanical seal consists of two rings, one being static and the other one dynamic, which are actioned by one or two fluid pressure, and an elastic force (or magnetic) which keeps the two faces of the rings in permanent contact. A direct contact between the frontal face of the rings will increase the surface temperature and the rings wear, so a small fluid film, as a lubricant and coolant, it is kept between the two face sealings. At modern mechanical seal are used also a secondary fluid. The tightening force in the seal, which it is very important, depends on seal construction, materials used, working fluid type, pressure and temperature, rotational speed, secondary fluid type, pressure, and temperature. Paper aims to present the studies made by the authors on a mechanical seal of the AESSEAL, cartridge seal type CDSA of a 1” in order to obtain the correct sealing pressure between seal rings. Calculation was made analytical, with the respect of regulations of the standards, and by FEA method. Was obtained a CFD model, to simulate the pressure inside the chamber of secondary fluid at different inlet/outlet pressures to determine the real value of it. The obtained results by CFD analyses were integrated in FEM analyses by ANSYS Static Structural to calculate the contact pressure on the rings faces and to calculate the minimum spring force for internal and external sealing cartridges for different working and secondary fluid pressure, also considering the seal construction design, materials, and rotational speed of 3000rpm. The results are very important in operation of the mechanical seal because the graphs presented in the paper give the operators the correct value of the spring tightening in the seal depending on the different ranges of fluids pressures.

Aiming at the problem of mechanical seal failure due to serious wear and tear in operation, the numerical model of the thermal–solid coupling wear of the seal ring is established by taking the friction sub-material as the research object, and the hardness, wear coefficient, and friction coefficient of different soft-ring materials are obtained by a test to verify the accuracy of the numerical model of wear. Additionally, the temperature field and deformation field of the seal ring of different materials are calculated, and the effects of the material parameters, such as elasticity modulus and thermal conductivity, on the temperature, relative deformation, and axial deformation trend are reported. The wear relation of the mechanical seal was optimized, and the correction coefficients of several materials were calculated. The results show the following: the main wear of the seal ring is due to adhesive wear leading to particle shedding and extrusion, adhesive wear causes material transfer, which alters the composition of the worn surface.in turn leading to cratering, which also causes the wear of the seal ring; the friction performance is better when the soft-ring material is graphite (C); the temperature, as well as the deformation, is smaller when the soft-ring material is silicon carbide (SIC); the correction coefficients for the life of SIC are calculated to be 0.23, for C, to be 0.14, and for stainless steel (Ss), to be 0.31, and the corrected equations can more accurately predict the corresponding material. The corrected equation can more accurately predict the service life of the corresponding material.

Abstract The friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester, and the wear of GCr15–graphite seal pairs with the low-temperature time-dependent pretreatment was discussed by comparing the wear morphology. The results show that liquid nitrogen pretreatment can affect the hardness and interlayer spacing of graphite. The range of the friction coefficients of pretreated graphite changes from 0.17 to 0.22. With the increase of liquid nitrogen pretreatment time, the wear mechanism of graphite would change from dominated three-body wear to adhesion wear. The experimental results of the mechanical seal with liquid nitrogen pretreatment show that the wear rate of stator is less than 0.00165 mm3·N−1·m−1, and the graphite shows a good low-temperature compatibility.

The paper includes a theoretical approach to the frontal mechanical seals with rubber bellows, used in the conveyance of fluids in centrifugal pumps, in terms of friction coefficients, balancing and possible fluid losses. The study also presents an experimental study for a mechanical seal with rubber bellows and a shaft diameter of 35 mm, operating at different speeds at the pump shaft and different pressures of the transported fluid. At higher pressure the seal is balanced and at lower pressures is discharged. [ABSTRACT FROM AUTHOR]

To improve the reliability of the end faces of high-temperature mechanical seals, a high-performance composite material that introduces carbon nanotubes (CNTs) into the laser-melted Cr coating is proposed. In this study, for high-temperature and high-speed mechanical seals under actual working conditions, friction and wear tests were conducted under different working conditions and using different end face materials. The high-temperature tribological properties of the Cr-CNTs coatings were analyzed, and the strengthening mechanism of the Cr-CNTs coatings on end faces was investigated. The results indicate that the wear resistance of the Cr-CNTs coating at high temperatures is first enhanced and then weakened with the increase in the CNTs content. The composite coating end face performance is optimal when the CNTs content is 10 wt%. The presence of CNTs between the end faces when grinding against the graphite ring favors the generation of a graphite film. The coefficient of friction of the Cr-CNTs coating is reduced by at least 12.46% compared to the Cr coating at a temperature of 483 K. This study provides reference examples for the application of carbon nanotubes in high-performance mechanical seals and new research ideas for improving the performance of mechanical seal end faces. [ABSTRACT FROM AUTHOR]

Mechanical seals are used in a wide range of industrial applications, including pumps, compressors etc., in order to avoid leakage of the working fluid. The design construction, and the operation of the mechanical seals continue to evolve to meet the demands of new technologies and industries. These developments are the increase of operating parameters, in the condition of strictly respecting the environment protection. A mechanical seal consists of two rings, one being static and the other one dynamic, which are actioned by one or two fluid pressure, and an elastic force (or magnetic) which keeps the two faces of the rings in permanent contact. A direct contact between the frontal face of the rings will increase the surface temperature and the rings wear, so a small fluid film, as a lubricant and coolant, it is kept between the two face sealings. At modern mechanical seal are used also a secondary fluid. The tightening force in the seal, which it is very important, depends on seal construction, materials used, working fluid type, pressure and temperature, rotational speed, secondary fluid type, pressure, and temperature. Paper aims to present the studies made by the authors on a mechanical seal of the AESSEAL, cartridge seal type CDSA of a 1" in order to obtain the correct sealing pressure between seal rings. Calculation was made analytical, with the respect of regulations of the standards, and by FEA method. Was obtained a CFD model, to simulate the pressure inside the chamber of secondary fluid at different inlet/outlet pressures to determine the real value of it. The obtained results by CFD analyses were integrated in FEM analyses by ANSYS Static Structural to calculate the contact pressure on the rings faces and to calculate the minimum spring force for internal and external sealing cartridges for different working and secondary fluid pressure, also considering the seal construction design, materials, and rotational speed of 3000rpm. The results are very important in operation of the mechanical seal because the graphs presented in the paper give the operators the correct value of the spring tightening in the seal depending on the different ranges of fluids pressures. [ABSTRACT FROM AUTHOR]

We proposed a numerical method to investigate the thermo-fluid–structural coupled characteristics of a mechanical seal of a reactor coolant pump (RCP), especially during extended loss of AC power (ELAP) operation. We developed a finite element program for the general Reynolds equation, including the turbulence effect to calculate the pressure, opening force, and leakage rate of fluid lubricant and the two-dimensional energy equation to calculate the temperature distribution of the fluid lubricant. We verified the accuracy of the developed program by comparing the simulated temperature distribution and leakage rate of this study with those of previous research. Heat conduction and elastic deformation due to pressure and temperature changes at the seal structure were analyzed using an ANSYS program. The results showed that temperature more significantly affected the elastic deformation of the seal structure near clearance than pressure both under normal and ELAP operating conditions. High temperature and pressure of the coolant under ELAP operating conditions deform the seal structure, resulting in a much smaller clearance of the fluid film than normal operating condition. However, even with a small clearance under ELAP operation, the leakage rate slightly increases due to the high internal pressure of the coolant. This research will contribute to the development of robust mechanical seals for RCPs by accurately predicting the characteristics of mechanical seals, especially when the RCP is operating under ELAP.

A dry gas seal (DGS) is one of the key basic components of natural gas transmission pipeline compressors, and the sealing performance of a DGS dealing with complex multi-component pipeline natural gas is different from that dealing with conventional nitrogen medium. In this paper, a spiral groove DGS of the compressor in natural gas transmission pipeline systems is taken as the research object. The thermal hydrodynamic lubrication model of the DGS is established considering turbulence effect and choking effect. Based on the finite difference method, the temperature and pressure distributions and the steady-state performance of the DGS are obtained by simulating. The influence of unitary impurity compositions such as light hydrocarbon, heavy hydrocarbon, non-hydrocarbon, and their contents on the steady-state performance of the DGS is analyzed. The steady-state performance of the DGS dealing with multi-impurity natural gas such as in the West-East gas transmission is investigated under different operating conditions. The results show that turbulence had a significant effect on the DGS, while choking had a weak effect. Increasing the content of light hydrocarbon such as C2H6 and heavy hydrocarbon such as C5H10 resulted in an increase in the gas film stiffness, leakage rate, and the temperature difference between the inlet and outlet, while non-hydrocarbon, such as N2, reduced the temperature difference between the inlet and outlet. The greatest impact on seal performance was produced by the heavy hydrocarbon, followed by the light hydrocarbon, and the least was produced by the non-hydrocarbon.

Mechanical seals ensure the internal sealing of centrifugal pumps from the surrounding environment. They are one of the most critical components in a centrifugal pump. For this reason, the condition of mechanical seals should be monitored during operation. Mechanical seal friction power is an important component of mechanical losses in centrifugal pumps and is used as an indicator of wear and therefore seal condition. The soft sensor described in this paper is based on temperature measurements at the seal and can be used for determining the frictional power performance. A major factor in determining frictional power performance is the heat transfer between the mechanical seal and the medium inside the pump. For calculating the heat transfer, the stationary temperature fields in the rings of the mechanical seal are described by transmission efficiencies. The root mean squared error was determined for steady-state operating conditions to assess the quality of the soft sensor calculation. The frictional power performance can be determined by recording the temperature at the mechanical seal mating ring and the medium. The algorithm detects when the steady-state operating conditions change but does not map the dynamic changes between the stationary operating conditions.

Taking the mechanical seal of the submersible as the object, a transient coupled heat transfer model was established, and the deformation of the seal face under stable and alternating conditions was investigated by considering the thermal–mechanical coupling effect. The deformation characteristics of the seal face under two different alternative forms of amplitude and period were analyzed. The morphology and wear characteristics of the seal face were measured and discussed based on the pseudo-real test of the mechanical seal under alternating loads. The results showed that the seal face tended to be squeezed near the inner diameter and a tapered convergent gap appeared at the outer diameter of the seal face under alternating loads. The deformation of the seal face presented obvious alternating transient characteristics under alternating loads, and the deformation under alternating rotational speed was greater than that of alternating medium pressure. The deformation of the seal face increased with the amplitude of the alternating loads, while the period of the alternating loads had little influence on it. The wear mechanism of the seal face under alternating conditions was mainly abrasive wear, and the wear caused by alternating rotational speed is more significant. [ABSTRACT FROM AUTHOR]

This research investigated the effect of lubricant's non-Newtonian properties on dynamic characteristics of a herringbone grooved liquid film seal (HG-LFS) considering cavitation. A modified steady-state perturbation Reynolds equation of the non-Newtonian was derived. Visualized experiments were conducted to verify the accuracy of calculations. The non-Newtonian effect on stiffness, cavitation, damping coefficients, and other sealing performance of the liquid film seal at different velocity, pressure and film thickness were discussed and analyzed. The results indicate that the seal has larger stiffness and damping coefficients with the dilatant lubricant, the cavitation can be inhibited by the shearing-thinning lubricant, and the impact of non-Newtonian on the seal stability decreases with the increase of film thickness. This study would contribute to the design and theoretical research of liquid film seals. [ABSTRACT FROM AUTHOR]

The fluid flow in the small pore throat is a nonlinear flow, and the microscopic force between the fluid and the wall cannot be ignored. However, the previously established theories about the leakage between sealing interfaces have not considered the influence of microscopic forces. Based on contact mechanics and percolation theory, the void characteristics of the sealing interface were clarified, and the influence of microscopic force on fluid flow in porous medium was analyzed. Combined with the capillary force, the concept of a critical void radius between the mechanical seal interfaces is proposed. The fluid flow resistance model and leakage rate calculation equation of the sealing interface considering the van der Waals force are established, and the leakage judgment criterion of the sealing interface is provided. Through numerical calculation and experiments, the effect of microscopic force is verified in terms of the fluid flow law and macroscopic leakage rate. The results show that van der Waals forces have an important influence on the fluid flow between the sealing interfaces. As the microchannel size decreases, the van der Waals forces between solid and liquid increase, and the influence of these van der Waals forces on the fluid flow between the sealing interfaces cannot be ignored. The calculation model of the sealing interface leakage rate proposed in this paper shows little difference with the results of the Persson model, and is in good agreement with the experimental results; the maximum relative error is 8.7%, the minimum relative error is only 3.8%. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of the complex relationship among the sealing system, excitation, and response have a considerable impact on the operational reliability of hydrodynamic mechanical seals, which is a critical issue in the field of sealing theory and technology. Scholars at home and abroad have established dynamic models and calculated the displacement responses of dynamic and static rings in the time domain based on the force on these rings so that the response results can be used for system stability analysis. Neither are the excitation characteristics of cavitation load extracted, nor are the distance response and system leakage rate of the dynamic and static rings analyzed under coupled cavitation and random excitation. In this study, under different operating conditions of the hydrodynamic mechanical seal system, the liquid film evaporation load and seismic load are applied to study the frequency domain response of the distance between the dynamic and static rings and the system leakage rate. The following conclusions have been obtained: Assuming that the chamber pressure is 0.5 MPa and the spring specific pressure is 0.055 MPa, during stable operation, the distance between the moving and stationary rings at 1500 rpm~3000 rpm speeds is 1.12 μm~3.05 μm. For a specific spring pressure of 0.055 MPa, medium pressures of 0.2 MPa~1.0 MPa, and spindle speeds of 1500 rpm~3000 rpm, the excitation force is 30 N, and the frequency is 30 Hz, And the seismic load is assumed to be sinusoidal, the excitation force is 6 N, the fundamental frequency is 120 Hz, and the system leak rate is in 0.1 mL/min~1.3 mL/min. Under multi-frequency excitation coupling, the distance between the dynamic and static rings will decrease as the pressure of the medium in the sealing cavity increases, and this will increase with the increase in the rotating speed. The leakage rate of the system will increase with the increase in the rotating speed and the pressure of the medium, and the test value is largely consistent with the theoretical value. [ABSTRACT FROM AUTHOR]

In oil refineries and petrochemical industries, a containment seal (CS) can be applied to a flashing hydrocarbon pump as a sealing device to prevent environmental pollution. It is extremely difficult to design a CS to ensure the contradictory functions of fluid-tight sealing and sealing-surface wear resistance, which are required under both conditions of dry running in gas and wet running in liquid. In this study, a new CS design concept, “CSAM” (Containment Seal by Additive Manufacturing), for the sealing surface and internal structure of a sealing ring was developed by additive manufacturing. A lubrication film formed on the sealing surfaces of mechanical seals is maintained by the opening force (OF) with fluid pressure and the closing force (CF) with fluid pressure and spring load. To obtain the desired OF, the CSAM controls the pressure distribution across the sealing surfaces by introducing outside pressure through slots on the sealing surfaces, and an annular cavity is formed within the sealing ring. Based on a series of numerical analyses and static tests, it has been found that the difference between OF and CF can be properly controlled using slot design parameters. The results suggest the possibility of achieving the contradictory functions of sealing and wear resistance under both the gas and liquid conditions required for CSs.

In this research, a model is proposed using piecewise fractal theory that considers abrasive and adhesive wear. The model demonstrated improved wear computation accuracy of a contact mechanical seal end face. The validity of the model was established by comparing the simulation results with experimental data and the conventional MB and Archard models. The loading effect and surface morphology parameters involved in wear were also investigated. Results show that severe wear occurs with increasing load ratio, large fractal dimensions, and a higher scale coefficient of the surface morphology. The findings offer a novel method for precisely calculating and projecting the amount of wear of a contact mechanical seal and predicting its wear behavior. [ABSTRACT FROM AUTHOR]

The spiral groove seal has a strong hydrodynamic effect, but it has poor pollution resistance at the seal's end and has unfavorable sealing stability. Circumferential waviness seals can use the fluid to clean the surface and have a strong ability to self-rush, protecting the main cover from contamination. This study presents a novel wave-tilt-dam seal design that integrates spiral groove structures to enhance the hydrodynamic performance of circumferential waviness seals. The objective of the research is to evaluate the mechanical effectiveness of this new design through simulation modeling, with a focus on the impact of structural parameters such as rotational speed and seal pressure on the hydrodynamic behavior under various operating conditions. The results of the study indicate that the new structure effectively improves the hydrodynamic performance of the liquid seal, resulting in a significant increase in film rigidity. Additionally, the study identifies optimal values for structural parameters under specific conditions. By addressing the limitations of traditional spiral groove seals and improving their hydrodynamic performance, this research contributes to the advancement of seal technology. [ABSTRACT FROM AUTHOR]

API plan 31 uses a cyclone separator that taps a small portion of discharge line process liquid for mechanical seal cooling process. Despite its simplicity, this piping plan requires comprehensive designing process to ensure its performances (flow rate to mechanical seal and pressure drop) are satisfactory. In this research, API 31 cyclone separator geometrical parameters (length cylinder, conical and vortex finder and radius overflow and underflow) effects onto pressure drop and seal flow rate are investigated using numerical method via ANSYS FLUENT software. It is found that increasing overflow and underflow radius and length of cylinder and conical decrease pressure drop by 15.94%, 24.82%, 20.30% and 11.42% respectively. Increasing vortex finder length meanwhile increases pressure drop by 7.77%. Meanwhile, increasing radius overflow and length of vortex finder increase flow rate to seal by 43.79% and 9.63% respectively. Increasing radius underflow and length of cylinder and conical reduces flow rate to seal by 71.92%, 6.41% and 8.93% respectively. It is also observed that a generalization of a particular cyclone separator geometry is not always applicable as it depends on the cyclone separator base design itself where in this case all geometrical factors are significant to pressure drop and flow to seal.

Taking the mechanical seal of the submersible as the object, a transient coupled heat transfer model was established, and the deformation of the seal face under stable and alternating conditions was investigated by considering the thermal–mechanical coupling effect. The deformation characteristics of the seal face under two different alternative forms of amplitude and period were analyzed. The morphology and wear characteristics of the seal face were measured and discussed based on the pseudo-real test of the mechanical seal under alternating loads. The results showed that the seal face tended to be squeezed near the inner diameter and a tapered convergent gap appeared at the outer diameter of the seal face under alternating loads. The deformation of the seal face presented obvious alternating transient characteristics under alternating loads, and the deformation under alternating rotational speed was greater than that of alternating medium pressure. The deformation of the seal face increased with the amplitude of the alternating loads, while the period of the alternating loads had little influence on it. The wear mechanism of the seal face under alternating conditions was mainly abrasive wear, and the wear caused by alternating rotational speed is more significant.

This paper presents a Rayleigh-steps mechanical seal with reverse steps (RS-MS), and the governing equation was solved by the finite difference method (FDM). The effects of angular misalignment, working condition parameters, and film thickness on sealing performance were discussed, including the opening force, cavitation ratio, leakage rate, frictional torque, stiffness and damping coefficients. The results indicate that the cavitation phenomenon in the reverse step groove can restrain the leakage, while it also affects the stability of the seal. The angular misalignment makes the seal have greater stiffness and damping coefficients. The stiffness and damping coefficients decrease rapidly with the increase of the film thickness, and the dynamic stability of the mechanical seal decreases with the increase of the film thickness, which is not conducive to the stable operation of the seal. The research results can guide the optimization design of mechanical seals. [ABSTRACT FROM AUTHOR]

Requirements such as high opening force, low leakage rate, and design without matching auxiliary flushing systems are expected of the modern fluid machinery shaft seals used in the process industry. A self-pumping hydrodynamic mechanical seal with a conical convergent diffuser groove is proposed and its sealing performance is studied by numerical simulation in this paper. Further, its sealing performance is compared to that of a flat-bottomed equal cross-sectional diffuser groove and the results have shown that the proposed seal has more superior sealing performance. The influence of structural and operating parameters on the sealing performance of the proposed seal is discussed and its working mechanism is explained. The results have shown that when the structural parameters of the spiral groove and the operating parameters are the same, the proposed design has a similar leakage rate and a higher opening force. The conical convergent diffuser groove has better wrapping properties, whereas the fluid energy is utilized more efficiently, improving the sealing interface opening force. The taper degree variation causes a slight change to the pressure at the root of the spiral groove, causing slight fluctuations in the seal leakage rate. The research results broaden the design of non-contact mechanical seals and provide a theoretical basis for the engineering application of the proposed self-pumping hydrodynamic mechanical seal with a conical convergent diffuser groove. [ABSTRACT FROM AUTHOR]

This paper investigates the reliability of welded metal bellows used in mechanical seals under specified working conditions. Firstly, considering the working environment of mechanical seals and the structural characteristics of welded metal bellows, a stress relaxation test bench was developed to obtain projectile loss data of welded metal bellows under different compression loads at elevated temperatures. The creep constants for a stress relaxation simulation were derived from the experimental data, and a stress relaxation finite element analysis (FEA) of the bellows was conducted using Workbench under different compression loads. We found that the stress relaxation simulation of welded metal bellows can accurately simulate the relaxation characteristics of welded metal bellows. The reliability of the welded metal bellows was calculated using Six Sigma response surface reliability by taking the material properties and compression load as variable parameters and the residual elasticity of the bellows as the objective function. We concluded that the reliability calculation method of welded metal bellows promotes reliability research into welded metal bellows for mechanical seals. [ABSTRACT FROM AUTHOR]

This paper presents a computational model to study the lubrication in mechanical seals under multiphase fluid conditions, focusing on immiscible two-phase distribution and cavitation effects on groove-patterned seal faces. Formulated within the framework of the Reynolds equation and adhering to mass conservation principles, this model employs the phase-field method to track the immiscible two-phase interface and incorporates the gas dissolution and release equation to quantify the rate of gas volume variation in the cavitation region, with its accuracy rigorously validated experiments conducted on a mechanical seal test rig. Findings suggest that modifying operating parameters and groove patterns in double-row spiral groove seals can influence the gas-liquid interface and cavitation, improving sealing performance by optimizing the fluid film. [ABSTRACT FROM AUTHOR]

Mechanical seal failure has a great negative impact on the operation of a centrifugal pump system. A method to analyze the stator current characteristics of the motor in a centrifugal pump system is proposed to monitor the internal flow of the centrifugal pump and to identify the failure status of the mechanical seal. Experiments were conducted under different mechanical seal states. Based on sensorless technology, the stator current signal of the motor is collected, processed by windowing function, anti-aliasing filter, singular value decomposition, Hilbert–Huang transform, and the marginal spectrum of correlation quantity is drawn. The results show that according to the external characteristic curve of the centrifugal pump, after the failure of the mechanical seal, the head and efficiency of the centrifugal pump decrease, and the head is greatly affected by the degree of failure, while the degree of mechanical seal failure has little effect on the shaft power of the centrifugal pump; the centrifugal pump has good operation stability under design conditions or near slightly large flow; the stability of centrifugal pump operation decreases with the aggravation of mechanical seal failure; the corresponding maximum amplitude in the marginal spectrum can be used as an index to diagnose the damage degree of the mechanical seal. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the lubrication performance and stability improvement of rocket turbopump mechanical seals by attaching superconducting magnetic force. A comprehensive multiphysics numerical model is presented including microscale clearance flow, magnetic field, as well as three degrees of freedom dynamic motion. The Maxwell equation and modified Reynolds equation considering mass-conserving boundary conditions and turbulence flow were solved simultaneously at each time step to obtain the transient response of sealing parameters. Results indicate that the mechanical seal attaching superconducting magnetic force could dramatically improve carrying capacity and lubrication characteristics under heavy loading conditions, and it also has an appreciable effect on dynamic stability. It is worth exploring the application of superconducting magnetic force in reusable rockets and cryogenic equipment combined with its unique advantages. [ABSTRACT FROM AUTHOR]

Because surface roughness is similar to the size of the sealing gap in terms of scale, the effect of surface roughness on sealing performance must be considered. A calculation model determining the micro-gap flow and surface roughness is used to prove that the existence of surface roughness can effectively improve the sealing performance and that it can especially improve the opening force. The results indicated that the opening force of the lubrication film increases as the surface roughness increases and that the growth rate increases as the rotating speed increases. Due to different roughness sensitivities, the opening force increases differently in different parts of the seal. With regard to leakage, the roughness of the rotating ring's grooved zone only increases the negative leakage when the rotating speed is higher than 8000 rpm. When the non-grooved zone of the rotating ring is rough, it can inhibit the negative leakage flow and cause the negative leakage to become positive when the rotating speed is higher than 1000 rpm. When the end face of the stationary ring is rough, the amount of leakage decreases. Furthermore, the surface roughness increases the friction torque when the rotating speed is higher than 5000 rpm. When the rotating speed is in the range of 1000–10,000 rpm, the roughness of the non-grooved area and the end face of the rotating ring increase the opening force by 2.40~57.94% and 3.55~69.33%, respectively. Meanwhile, by defining SF and SQ, a scheme for providing sealing performance is provided. [ABSTRACT FROM AUTHOR]

The value of face contact pressure has an important influence on the wear life and leakage rate of the mechanical seal. For a long time, people have chosen face contact pressure based on experience and lack of theoretical support, which greatly reduces the effectiveness of the mechanical seal. Based on the percolation theory, the critical porosity of zero-leakage at the wetting and non-wetting sealing interface working in liquid medium is first discussed. The influence of end-face frictional heat on end-face friction and wear is then investigated. The design criteria for the face contact pressure of mechanical seals with zero-leakage and long-life operation are established. Afterwards, the face contact pressure range of the mechanical seal working in conventional different liquid medium is calculated, and the influence of different working conditions on the face contact pressure range change is analyzed. Existing studies have shown that mechanical seals can achieve zero-leakage and long-life operation. Under the rotating and stationary rings' physical parameters and given working conditions, the face contact pressure range of the sealing medium water and propane propylene is 0.477~1.132 MPa. The diesel sealing medium has a larger face contact pressure range than that of water and propane propylene, which can reach 0.477~2.183 MPa. The working condition speed, medium temperature, and medium pressure have an influence on the face contact pressure range, while the influence of the working condition speed is the most significant. [ABSTRACT FROM AUTHOR]

Mechanical seals play an important role in the reliability of a process. Currently, the condition monitoring of mechanical seals is restricted due to the limitations of the traditional monitoring methods, including classical vibration analysis. For this reason, the objective of the present work is the detection and analysis of friction mechanisms inside a mechanical seal that are unfavorable and induce fault conditions using the acoustic emission technique, which allows the measurement of high-frequency vibrations that arise due to material fatigue processes on a microscopic scale. For this purpose, several fault condition modes were induced on a test rig of an agitator vessel system with a double-acting mechanical seal and its buffer fluid system. It was possible to detect the presence of inadequate friction mechanisms due to the absence and limited use of lubrication, as well as the presence of abrasive wear, by measuring a change in the properties of the acoustic emissions. Operation under fault condition modes was analyzed using the acoustic emission technique before an increase in the leakage rate was evaluated using traditional monitoring methods. The high friction due to the deficient lubrication was characterized by a pattern in the high-frequency range that consisted of the harmonics of a fundamental frequency of about 33 kHz. These results demonstrate the feasibility of a condition monitoring system for mechanical seals using the acoustic emission technique.

Unstable flow within a reactor coolant pump (RCP)’s mechanical seal may cause the change of its sealing parameters, possibly threatening RCP’s safe operations. In this study, based on the moving grid technology, a 3D fluid–structure interaction analysis model is established, where the influence of parameters such as the inlet pressure fluctuation, closing force fluctuation, and speed fluctuation on mechanical seal performance characteristics within an RCP is numerically studied. Study results have shown that when pressure and closing force fluctuations are applied, the static ring displacement, the inlet-to-outlet temperature difference, and the leakage difference show similar variational rules. In addition, it is found that the sealing parameters are more sensitive to the step form of fluctuation. When the step change of 4% closing force was applied, the static ring displacement was more than 36.7%, the change of the temperature difference between inlet and outlet zones exceeded 53.5%, and the leakage difference was more than 127.2%. The change of speed has also been found to significantly affect the temperature difference between the RCP mechanical seal’s inlet and outlet, but the effect on the leakage and opening force was negligible.

API plan 31 uses a cyclone separator that taps a small portion of discharge line process liquid for mechanical seal cooling process. Despite its simplicity, this piping plan requires comprehensive designing process to ensure its performances (flow rate to mechanical seal and pressure drop) are satisfactory. In this research, API 31 cyclone separator geometrical parameters (length cylinder, conical and vortex finder and radius overflow and underflow) effects onto pressure drop and seal flow rate are investigated using numerical method via ANSYS FLUENT software. It is found that increasing overflow and underflow radius and length of cylinder and conical decrease pressure drop by 15.94%, 24.82%, 20.30% and 11.42% respectively. Increasing vortex finder length meanwhile increases pressure drop by 7.77%. Meanwhile, increasing radius overflow and length of vortex finder increase flow rate to seal by 43.79% and 9.63% respectively. Increasing radius underflow and length of cylinder and conical reduces flow rate to seal by 71.92%, 6.41% and 8.93% respectively. It is also observed that a generalization of a particular cyclone separator geometry is not always applicable as it depends on the cyclone separator base design itself where in this case all geometrical factors are significant to pressure drop and flow to seal. [ABSTRACT FROM AUTHOR]

Spiral groove liquid film seal is expected to be the prime candidate for application to high-speed liquid-oxygen turbopumps, and the lubricant flow between the sealing faces is turbulent due to the liquid-oxygen properties and the working conditions. Based on the Ng–Pan model and mass-conserving algorithm, the modified dynamic Reynolds equation considering flow regime and cavitation is obtained, which is solved by the finite-difference method. The effects of flow regime and cavitation on the performance of spiral groove liquid film seal are analyzed. The results indicate that the balanced film thickness and opening force increase due to the turbulent flow. The cavitation ratio increases in the laminar–turbulent transition region, which reduces the opening force and liquid film stiffness. [ABSTRACT FROM AUTHOR]

Split mechanical seal has an advantage over non-split type mechanical seal in the area of sealing large rotary equipment, as it takes very less installation time and it can be installed without removing any component of rotary equipment. Many theories regarding the different parameters affecting design of split mechanical seal have been published, however, literatures which discusses the complete design procedure of split mechanical seal is not readily available. An attempt is made in this work to prepare the design guidelines for critical features of split mechanical seal such as balance ratio selection, design against centrifugal leakage and selection of reference plane. Manufacturing method of ring halves is also described which is critical for sealing of gap between ring halves. In split mechanical seal, since leakage across mating faces of split halves is major concern, a testing procedure is presented for checking any leakage before installation. [ABSTRACT FROM AUTHOR]

Mechanical seals are composed of two annular flat rings in contact and relative motion to ensure sealing of a rotating shaft. Because of friction in the sealing interface, a significant temperature rise can be experienced in the contact. Two decades ago, it has been shown that creating a network of shallow dimples on one sealing surface can help to create a lubricant film in the interface and thus reduce friction. Since then, many research works have been carried out on the so-called surface texturing, showing the interest of surface modification for mechanical seals. In the present work, several surface patterns, defined by numerical simulations and machined by plasma etching on stainless steel rings were tested. The rings were mounted on a test bench in which they slide against a sapphire disk counter face. This disk is transparent to infrared radiation and allows interface temperature measurements by infrared thermography. It is shown that all the tested surface texture patterns exhibit a temperature rise at least 2 times lower than with flat smooth surfaces. A slight difference between the different dimple shapes is obtained indicating that the temperature and friction are more controlled by texture area and surface roughness rather than by the texture pattern.

In this research, a model is proposed using piecewise fractal theory that considers abrasive and adhesive wear. The model demonstrated improved wear computation accuracy of a contact mechanical seal end face. The validity of the model was established by comparing the simulation results with experimental data and the conventional MB and Archard models. The loading effect and surface morphology parameters involved in wear were also investigated. Results show that severe wear occurs with increasing load ratio, large fractal dimensions, and a higher scale coefficient of the surface morphology. The findings offer a novel method for precisely calculating and projecting the amount of wear of a contact mechanical seal and predicting its wear behavior.

The spiral groove seal has a strong hydrodynamic effect, but it has poor pollution resistance at the seal’s end and has unfavorable sealing stability. Circumferential waviness seals can use the fluid to clean the surface and have a strong ability to self-rush, protecting the main cover from contamination. This study presents a novel wave-tilt-dam seal design that integrates spiral groove structures to enhance the hydrodynamic performance of circumferential waviness seals. The objective of the research is to evaluate the mechanical effectiveness of this new design through simulation modeling, with a focus on the impact of structural parameters such as rotational speed and seal pressure on the hydrodynamic behavior under various operating conditions. The results of the study indicate that the new structure effectively improves the hydrodynamic performance of the liquid seal, resulting in a significant increase in film rigidity. Additionally, the study identifies optimal values for structural parameters under specific conditions. By addressing the limitations of traditional spiral groove seals and improving their hydrodynamic performance, this research contributes to the advancement of seal technology.

Fluid flow regime has an important influence on the lubrication performance of mechanical seal. A novel method is proposed to analyze the flow regime transition quantitatively based on a cusp catastrophic model with dimensionless analysis. Furthermore, from this method, a turbulence transition factor is derived strictly to describe the turbulent transition process of mechanical seal, which is verified by the published results. Then this factor is applied to hydrodynamic lubrication mechanical seal to analyze the influence of flow regime on sealing performance. The results indicate that the performance parameters of mechanical seal are greatly influenced by the transition of fluid flow regime, and the stability of mechanical seal decreases in the transition to turbulent flow. The novel method of flow regime transition analysis provides a new insight into the turbulence model. [ABSTRACT FROM AUTHOR]