The Quantification of Seal-Interface Leakage of an Elastomer Face Seal

2011 ◽  
Author(s):  
Nicholas G. Garafolo ◽  
Christopher C. Daniels
Keyword(s):  
Contact Pressure ◽  
Leak Rate ◽  
Ring Test ◽  
Algebraic Solution ◽  
Definitive Evidence ◽  
Gas Leak ◽  
Face Seals ◽  
Total Leakage ◽  
Ring Seal ◽  
Mating Conditions

Current gas leak rate prediction methods for elastomeric face seals rely heavily on the assumption that all leakage is permeation, rather than leakage across the seal interface [1–3]. To date, there has been no definitive evidence that this is indeed the case. It is essential to investigate the magnitude of interface leakage to facilitate the validation of the current compressible permeation model and to quantify the interfacial leakage for the design of future state-of-the-art face seals. To this end, a series of leak rate experiments is presented on a square-ring seal, manufactured from silicone elastomer S0383-70. The unique experimental design affords the ability to quantify both a metal-elastomer interface, as well as an elastomer-elastomer interface. The experiments utilized two square-ring test specimens, each with a common width but different in height. The test apparatus consisted of stainless steel platens, near-hermetic plumbing, programmable environmental chamber, and the required instrumentation. The initial data reduction was accomplished by the mass point leak rate technique; whereas mass was calculated through measurements of gas pressure, temperature, and volume and a regression analysis yielded the leak rate of the seal. A secondary reduction of the leak rates in the unique experimental configuration further distinguished the total leakage into permeation and interface leak components, accomplished through the algebraic solution of the design of experiments guided matrix. Results showed that, with modest contact pressure, permeation was the largest component of the total leakage. In addition, the interface leakage for the various seal mating conditions (i.e., seal-on-flange, seal-on-seal) was quantified for the contact pressure investigated. Contrary to previous conclusions, the interface leakages were found to be significant. In the application of space docking seals, a common example of elastomeric face seals, the significance of quantifying the interfacial leakages guides the design of the seal for incomplete seal compression conditions as well has for the androgynous docking configuration.

An Empirical Investigation on Seal-Interface Leakage of an Elastomer Face Seal

2012 ◽  
Author(s):  
Nicholas G. Garafolo ◽  
Christopher C. Daniels
Keyword(s):  
Contact Pressure ◽  
Pressure Control ◽  
Leak Rate ◽  
Algebraic Solution ◽  
Gas Flows ◽  
Common Assumption ◽  
Gas Leak ◽  
Total Leakage ◽  
Ring Seal ◽  
Contact Pressures

For the application of seals used in space, a common assumption is that all leakage is attributed to permeation, that is the gas flows through the porous seal material. In this case, leakage across any seal interfaces are assumed negligible. In fact, state-of-the-art gas leak rate prediction methods rely heavily on this assumption. A recent study into the quantification of the seal-interface leakage of elastomer face seals, however, has revealed that this is not the case. As the preliminary study previously presented, with moderate contact pressure the interface leakage components were found to be significant and distinct from zero. The objective of the research presented herein was to further quantify both the elastomer-metal and elastomer-elastomer interface leakages for various contact pressures. To this end, a series of leak rate experiments is presented on a square-ring seal, manufactured from silicone elastomer S0383-70. The unique experimental design affords the ability to quantify both the elastomer-metal interface, as well as an elastomer-elastomer interface. The experiments utilized matched sets of test specimens, each with a common width but different height. The test apparatus contained both a flow fixture capable of quantifying ultra-low leak rates and an electro-mechanical actuated load frame for precision contact pressure control. The leak rate apparatus consisted of stainless steel platens, near-hermetic plumbing, and the required instrumentation. The initial data reduction was accomplished by the mass point leak rate technique; whereas mass was calculated through measurements of gas pressure, temperature, and volume and a regression analysis yielded the leak rate of the seal. A secondary reduction of the leak rates in the unique experimental configuration further distinguished the total leakage into permeation and interface leak components, accomplished through the algebraic solution of the design of experiments guided matrix. Foremost, results confirmed that the interface leakage is non-negligible and distinct from zero, as with previous studies. Furthermore, results suggested that the interface leakage was drastically decreased with modest seal contact pressure.

scholarly journals A Wear Simulation Method for Mechanical Face Seals under Friction Instability Conditions

2020 ◽  
Vol 10 (8) ◽  
pp. 2875
Author(s):  
Wentao He ◽  
Shaoping Wang ◽  
Chao Zhang ◽  
Xi Wang ◽  
Di Liu
Keyword(s):  
Contact Pressure ◽  
Torsional Stiffness ◽  
Frictional Heat ◽  
Axial Stiffness ◽  
Asperity Contact ◽  
Wear Simulation ◽  
Time Rate ◽  
Wear Time ◽  
Face Seals ◽  
Non Gaussian

Mechanical face seals are crucial components of automotive cooling water pumps and affect the safe operation of the pump. This article focuses on the effect of friction instabilities on the wear of the seals. Friction instabilities, such as stick-slip, occur when the axle is decelerated or operated at a low speed. Based on previous studies, a simulation model is proposed of a mechanical face seal that considers the interaction of asperities of non-Gaussian surfaces and the heat transfer between the sealing rings. According to the Archard wear equation, a numerical wear simulation is performed, and the wear distance rate and wear time rate are obtained. A comparison of the contact pressure of the Gaussian and non-Gaussian surfaces indicates that the latter is more likely to generate high contact pressure, thereby producing more significant wear. The viscous shear heat and frictional heat due to asperity contact decrease with an increase in the thickness of the tapered film. As the shaft decelerates, the wear distance rate increases with an increase in the axial stiffness. The axial damping only affects the duration of the oscillations. The wear time rate decreases with an increase in the torsional stiffness and torsional damping. The results of this research provide guidelines for estimating the wear of mechanical seals when friction instabilities occur.

scholarly journals COMPASS – COMparative Particle formation in the Atmosphere using portable Simulation chamber Study techniques

2013 ◽  
Vol 6 (12) ◽  
pp. 3407-3423 ◽  
Author(s):  
B. Bonn ◽  
S. Sun ◽  
W. Haunold ◽  
R. Sitals ◽  
E. van Beesel ◽  
...  
Keyword(s):  
Particle Number ◽  
Comparative Method ◽  
Particle Formation ◽  
Leak Rate ◽  
Atmospheric Conditions ◽  
Elevated Ozone ◽  
Gas Leak ◽  
Negative Effect ◽  
Ambient Particle ◽  
The Impact

Abstract. In this study we report the set-up of a novel twin chamber technique that uses the comparative method and establishes an appropriate connection of atmospheric and laboratory methods to broaden the tools for investigations. It is designed to study the impact of certain parameters and gases on ambient processes, such as particle formation online, and can be applied in a large variety of conditions. The characterisation of both chambers proved that both chambers operate identically, with a residence time xT (COMPASS1) = 26.5 ± 0.3 min and xT (COMPASS2) = 26.6 ± 0.4 min, at a typical flow rate of 15 L min−1 and a gas leak rate of (1.6 ± 0.8) × 10−5 s−1. Particle loss rates were found to be larger (due to the particles' stickiness to the chamber walls), with an extrapolated maximum of 1.8 × 10−3 s−1 at 1 nm, i.e. a hundredfold of the gas leak rate. This latter value is associated with sticky non-volatile gaseous compounds, too. Comparison measurement showed no significant differences. Therefore operation under atmospheric conditions is trustworthy. To indicate the applicability and the benefit of the system, a set of experiments was conducted under different conditions, i.e. urban and remote, enhanced ozone and terpenes as well as reduced sunlight. In order to do so, an ozone lamp was applied to enhance ozone in one of two chambers; the measurement chamber was protected from radiation by a first-aid cover and volatile organic compounds (VOCs) were added using a small additional flow and a temperature-controlled oven. During the elevated ozone period, ambient particle number and volume increased substantially at urban and remote conditions, but by a different intensity. Protection of solar radiation displayed a clear negative effect on particle number, while terpene addition did cause a distinct daily pattern. E.g. adding β pinene particle number concentration rose by 13% maximum at noontime, while no significant effect was observable during darkness. Therefore, the system is a useful tool for investigating local precursors and the details of ambient particle formation at surface locations as well as potential future feedback processes.

Characteristic Analysis of Aircraft Glyd-Ring Seal Based on Mixed Lubrication Model

2020 ◽  
Author(s):  
Wang Wei ◽  
Wenjian Xiao ◽  
Xiaoping Ouyang ◽  
Shengrong Guo ◽  
Huayong Yang
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Frictional Force ◽  
Fluid Pressure ◽  
Mixed Lubrication ◽  
Fluid Film ◽  
Characteristic Analysis ◽  
Piston Seal ◽  
Static Contact ◽  
Ring Seal

Abstract Reciprocating seals are vital components in hydraulic systems. As a kind of reciprocating seal, the glyd-ring is commonly used as a piston seal. For the sealing characteristics of aircraft glyd-ring under severe working conditions, systematic research and experimental verification are not sufficient. The liquid-solid coupling model based on mixed lubrication theory is established in order to analyze the characteristics of the glyd-ring seal in the cylinder piston. The contact stress distribution on the glyd-ring under different fluid pressures or temperatures is discussed through finite element analysis. The mechanical analysis of solids and fluids are carried out separately, and the thickness of the fluid film is continuously updated until the results of the deformation analysis converged. According to the calculation results obtained by this model, three characteristics of the glyd-ring seal (static contact pressure, film thickness, friction force) are discussed. As the fluid pressure rises, the contact pressure in the sealing area increases by a rate which is greater than that of the corresponding fluid pressure, the seal length is shortened, the fluid film thickness is reduced, and the frictional force gradually increases, this force increase is proved by test data. As the temperature rises, the contact pressure in the seal area (near the O-ring) increases by a rate which is greater than that of the corresponding fluid pressure, the seal length increases, the oil film thickness decreases, and the frictional force increases significantly.

SNF Transportation Package Response to MacArthur Maze Fire Scenario: Leak Rate Determination After Seal Failure

2015 ◽  
Author(s):  
H. E. Adkins ◽  
S. R. Suffield ◽  
N. A. Klymyshyn ◽  
J. M. Cuta ◽  
J. Piotter
Keyword(s):  
Spent Nuclear Fuel ◽  
Leak Rate ◽  
Radioactive Material ◽  
Clamping Force ◽  
The Road ◽  
Seal Failure ◽  
Fire Scenario ◽  
Modeling Approach ◽  
Ring Seal ◽  
Accident Conditions

Extensive and detailed modeling of the possible effect of the MacArthur Maze fire scenario on an over-the-road spent nuclear fuel transportation package has shown that the potential consequences could include release of radioactive material due to failure of the package seals. Structural and thermal modeling of the performance of the lid closure and closure bolts show that the lid closure bolts would maintain positive clamping force throughout the fire transient scenario, such that the total release possible, even with conservative and bounding modeling assumptions, is two to three orders of magnitude below the regulatory limit for accident conditions. Typical leak rate models, such as the ANSI standard ANSI N14.5, are based on the expectation of intact seals for the package. Very little analytical work has been done to investigate leak rates from failed seals, since seal failure is, by definition, unacceptable performance in real-world applications. In order to evaluate the potential release from the SNF package subjected to the conditions of this fire scenario, an analytical modeling approach was developed to determine bounding leak rate estimates through the interface of the package closure lid and body flange. This modeling approach postulates complete loss of the O-ring seal material, and assumes only metal-to-metal contact, maintained by the clamping force of the closure bolts, as it varies due to differential thermal expansion and changing internal package pressure during the transient. This paper describes the analytical approach used to perform the leak rate modeling for the SNF package, and presents results for the limiting design basis loading of the package.

Leakage analysis and ground tests of knife edge indium seal to lunar sample return devices

2018 ◽  
Vol 233 (6) ◽  
pp. 2010-2022 ◽  
Author(s):  
Bin Zhang ◽  
Haocen Hong ◽  
Min Yu ◽  
Huayong Yang
Keyword(s):  
Leak Rate ◽  
Knife Edge ◽  
Lunar Sample ◽  
Element Analysis ◽  
Sample Return ◽  
Pressing Force ◽  
Sealing Performance ◽  
Lunar Samples ◽  
Ring Seal ◽  
Key Techniques

This work deals with the lunar sample return project, which requires lunar samples to be returned back to the ground without contamination. In this paper, a knife edge indium seal is proposed as a primary sealing form, where indium–silver alloy is welded into an annular groove of a cylindrical container firstly and then extruded by an annular knife edge of a cylindrical lid. The analysis of the leakage and sealing reliability of knife edge indium seal is the main aim of this paper. Firstly, the pretreatment of knife edge indium seal is discussed. Key techniques on indium welding are studied to evaluate its sealing reliability, with the tensile strength and welding void ratio mainly being discussed. Secondly, by means of “Roth” leakage theory, mathematical models on the leak rate for knife edge seal are established. By means of the finite element analysis, the knife edge geometry is optimized with minimum pressing force required. The results justify that the knife edge seal demands much lower pressing force to achieve a considerable sealing performance, which is suitable for low-powered operation. Finally, the ground tests are carried out to evaluate the feasibility of the indium welding and to measure the leak rate of the knife edge indium seal. Experimental results demonstrate the indium welding onto the stainless steel container is feasible, and the leak rate at room temperature is 3.0 × 10−10 Pa·m3/s, which is much lower than the rubber O-type ring seal. The knife edge indium seal is suitable for lunar sample return devices.

A leakage model of metallic static seals based on micromorphology characteristics of turning flange surface

2015 ◽  
Vol 67 (6) ◽  
pp. 572-581 ◽  
Author(s):  
Chuanjun Liao ◽  
Xibao Xu ◽  
Hongrong Fang ◽  
Hongrui Wang ◽  
Man Man
Keyword(s):  
Contact Pressure ◽  
Leakage Rate ◽  
Content Type ◽  
Leakage Model ◽  
Viscous Compressible Gas ◽  
Leakage Mechanism ◽  
Total Leakage ◽  
Experimental Values ◽  
First Time ◽  
Practical Implications

Purpose – The purpose of this paper is to develop a leakage model of metallic static seals, which can be used to accurately predict the leakage rate and study the corresponding seal characteristics. The metallic static seal is effectively applied to severe rugged environments where conventional seals cannot meet the needs. More research efforts for deepening the understanding of its seal characteristics are important for its effective and safe applications, of which the study about its leak is one key component. Design/methodology/approach – In the microscopic observations of the turning surface that is general in the processing of flange surfaces, it is found that the spiral morphology is dominant, which had been also obtained by other researches. There are two potential leakage paths for the flange surface of spiral morphology, one is the radial direction perpendicular to the spiral ridges and the other is the circumferential direction along the spiral groove. Based on the microgeometry characteristics of spiral morphology, the micromorphology of turning flange surface is simplified for the calculation of leakage rate, and the simplified methods of the radial and circumferential leakage paths are presented separately. The topography of flange surface studied in this paper is actually measured, and the Abbott bearing surface curve is adopted to represent the micro-profiles parameters. The radial and circumferential leakage models are further developed based on the assumption of laminar flow of the viscous compressible gas. Findings – The experiments used to verify the leakage models were carried out, and the experimental values are well agreed with the calculated values. As the contact pressure increases, the change rules of both radial and circumferential leakage rates are obtained and the obvious transition from radial leak to circumferential leak can be found. Using the proposed leakage models, the effects of the key micro-profiles parameters on the leakage rates are studied, and some specific conclusions are given simultaneously, which are favorable for the theoretical study and practical application of the metallic static seal. Practical implications – By the interpretations of the micromorphology characteristics of turning flange surface, the leakage mechanism of the metallic static seal is further made clear. The proposed leakage model reveals the relationships between the key micro-profiles parameters and some sealing performances about the leakage and can predict the leakage rates of the metallic static seal used in various working conditions. Originality/value – For the metallic static seal, the simplification of the radial leakage path and the radial leakage model are put forward for the first time, so the total leakage model can be systematically reported based on the micromorphology characteristics of turning flange surface. The effects of the key micro-profiles parameters on the seal behaviors including of the leak rate, critical contact pressure and transition from radial leak to circumferential leak etc are also clarified firstly.

scholarly journals A tracer gas leak rate measurement method for circular air circuits

2016 ◽  
Vol 47 ◽  
pp. 45-53 ◽  
Author(s):  
Arne Tiddens ◽  
Marc Röger ◽  
Hannes Stadler ◽  
Bernhard Hoffschmidt
Keyword(s):  
Measurement Method ◽  
Leak Rate ◽  
Rate Measurement ◽  
Tracer Gas ◽  
Gas Leak
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