Evaluation of Leakage Through Graphite-Based Compression Packing Rings

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Mehdi Kazeminia ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Effective Diffusion ◽  
Practical Interest ◽  
Fugitive Emissions ◽  
Diffusion Term ◽  
Sealing Performance ◽  
Challenging Tasks ◽  
Packing Rings ◽  
Different Gases ◽  
Reliable Correlation

The prediction of leakage is one of the most challenging tasks when designing bolted flanged connections and industrial valves. Failure of these pressure vessel components can cause shutdowns but also accidents, loss of revenue, and environmental damages. With the strict regulations on fugitive emissions and environmental protection laws new tightness-based standards and design methods are being adopted to improve the sealing performance of bolted joints and valves. In addition, there is a practical interest in using a reliable correlation that could predict leak rates of one fluid on the basis of tests carried out with another on compressed packings. The paper presents an innovative approach to accurately predict and correlate leak rates in porous braided packing rings. The approach is based on Darcy–Klinkenberg to which a modified effective diffusion term is added to the equation. Experimentally measured gas flow rates were performed on a set of graphite-based compression packing rings with a large range of leak rates under isothermal steady conditions. Leakage from three different gases namely helium, nitrogen, and argon were used to validate the developed correlation. In the presence of the statistical properties of porous packings, the leak rates for different gases can be predicted with reasonable accuracy.

Prediction of Leak Rates in Porous Braided Packing Rings

2015 ◽  
Author(s):  
Mehdi Kazeminia ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Effective Diffusion ◽  
Practical Interest ◽  
Fugitive Emissions ◽  
Diffusion Term ◽  
Sealing Performance ◽  
Challenging Tasks ◽  
Packing Rings ◽  
Different Gases ◽  
Reliable Correlation

The prediction of leakage is one of the most challenging tasks when designing bolted flanged connections and valves. Failure of these pressure vessel components can cause shutdowns but also accidents, loss of revenue and environmental damages. With the strict regulations on fugitive emissions and environmental protection laws new tightness-based standards and design methods are being adopted to improve the sealing performance of bolted joints and valves. However, there is a practical interest in using a reliable correlation that could predict leak rates of one fluid on the basis of tests carried out with another on compressed packings. The paper presents an innovative approach to accurately predict and correlate leak rates in porous braided packing rings. The approach is based onDarcy-Klinkenberg to which a modified effective diffusion term is added to the equation. Experimental measured gas flow rates were performed on a setof graphite based compression packing rings with a large range of leak rates under isothermal steady conditions. Leakage from three different gases namely Helium, Nitrogen and Argon were used to validate the developed correlation. In the presence of the statistical properties of porous packings, the leak rates for different gases can be predicted with reasonable accuracy.

Patterns of gas flow in the upper bronchial tree

1959 ◽  
Vol 14 (5) ◽  
pp. 753-759 ◽  
Author(s):  
J. B. West ◽  
P. Hugh-Jones
Keyword(s):  
Gas Flow ◽  
Lower Lobe ◽  
Bronchial Tree ◽  
High Flow ◽  
Human Beings ◽  
Lobe Bronchus ◽  
Flow Rates ◽  
Expiratory Flow ◽  
Different Gases ◽  
Expiratory Flow Rates

Patterns of gas flow in the upper bronchial tree have been studied by observing the flow of dye and different gases through a lung cast, and by measurements made on open-chested dogs and on human beings at bronchoscopy. Flow is completely laminar throughout the bronchial tree at low expiratory flow rates (up to 10 l/min.) and completely turbulent, proximal to the segmental bronchi, at high flow rates (80 l/min.). Both at low and high expiratory flow rates, gas from segmental bronchi was not uniformly mixed in the lobar or main bronchi which they supplied. The composition of a catheter sample in these airways would therefore not be representative of the alveolar gas in the corresponding lobe or lung unless the alveolar gas in all areas distal to the sampling tube was homogeneous. Penetration of the left upper lobe bronchus by gas from the lower lobe was demonstrated in the model and a normal subject at bronchoscopy. Submitted on September 3, 1958

scholarly journals Mechanisms Responsible for Arc Cooling in Different Gases in Turbulent Nozzle Flow

2017 ◽  
Vol 4 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Y. Guo ◽  
H. Zhang ◽  
Y. Yao ◽  
Q. Zhang ◽  
J. D. Yan
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Gas Flow ◽  
Ohmic Heating ◽  
Circuit Breaker ◽  
Fault Current ◽  
High Current ◽  
Physical Mechanisms ◽  
Current Zero ◽  
Different Gases

A high voltage gas blast circuit breaker relies on the high speed gas flow in a nozzle to remove the energy due to Ohmic heating at high current and to provide strong arc cooling during the current zero period to interrupt a fault current. The physical mechanisms that are responsible for the hugely different arc cooling capabilities of two gases (SF<sub>6</sub> and air) are studied in the present work and important gas material properties controlling the cooling strength identified.

scholarly journals Experimental and Numerical Study of a Thermal Expansion Gyroscope for Different Gases

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 360 ◽  
Author(s):  
Guillaume Kock ◽  
Philippe Combette ◽  
Marwan Tedjini ◽  
Markus Schneider ◽  
Caroline Gauthier-Blum ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Gas Flow ◽  
Numerical Study ◽  
Rotational Velocity ◽  
Measurement Range ◽  
Gas Temperature ◽  
Hot Air ◽  
Working Principle ◽  
Set Up ◽  
Different Gases

A new single-axis gas thermal gyroscope without proof mass is presented in this paper. The device was designed, manufactured and experimentally characterized. The obtained results were compared to numerical simulation. The working principle of the gyroscope is based on the deflection of a laminar gas flow caused by the Coriolis effect. A bidirectional hot air flow is generated by alternating activation of two suspended resistive micro-heaters. The heated gas is encapsulated in a semi-open cavity and the gas expands primarily inside the cavity. The thermal expansion gyroscope has a simple structure. Indeed, the device is composed of a micromachined cavity on which three bridges are suspended. The central bridge is electrically separated into two segments enabling to set up two heaters which may be supplied independently from each other. The two other bridges, placed symmetrically on each side of the central bridge, are equipped with temperature detectors which measure variations in gas temperature. The differential temperature depends on the rotational velocity applied to the system. Various parameters such as the heating duty cycle, the type of the gas and the power injected into the heaters have been studied to define the optimal working conditions required to obtain the highest level of sensitivity over a measurement range of around 1000°/s. The robustness of the device has also been tested and validated for a shock resistance of 10,000 g for a duration of 400 µs.

scholarly journals Gas flow through a bore-piston ring contact

2020 ◽  
pp. 146808742097112
Author(s):  
Baptiste Hallouin ◽  
Didier Lasseux ◽  
Gerald Senger
Keyword(s):  
Gas Flow ◽  
Piston Ring ◽  
Practical Interest ◽  
Contact Length ◽  
Ideal Gas ◽  
Ideal Gas Law ◽  
Thermodynamic Conditions ◽  
Sinusoidal Shape ◽  
Flow Through ◽  
Ic Engines

This work reports on the derivation of simplified but accurate models to describe gas flow through a bore-piston ring contact in reciprocating machines like compressors or IC engines. On the basis of the aperture field of a contact deduced from real measurements carried out on an expanding ring in a bore, a scale analysis on the complete compressible flow model is performed, assuming ideal gas law. It is shown that the flow can be treated as stationary and three distinct flow regimes can be identified (namely incompressible, compressible creeping, and compressible inertial regimes). Three dimensionless parameters characterizing these regimes are identified. While for the two former regimes, classical analytical Poiseuille type of models are derived, an Oseen approximation is further employed for the latter, yielding a quasi-analytical solution. The models are successfully compared to direct numerical simulations (DNS) of the complete initial set of balance equations in their steady form performed on an aperture field of sinusoidal shape. These simplified models are of particular practical interest since they allow an accurate gas flow-rate estimate through a real contact using the aperture field as the geometrical input datum, together with the thermodynamic conditions (pressure and temperature). This represents an enormous advantage as DNS is still very challenging in practice due to the extremely small value of the contact aperture to contact length ratio.

Reduction of Fugitive Emissions From Bolted Flanged Connections by Using PTFE Blended Gasket

2016 ◽  
Author(s):  
Takashi Kobayashi ◽  
Koji Sato ◽  
Akira Muramatsu ◽  
Toshiyuki Sawa
Keyword(s):  
Heat Resistance ◽  
Pressure Vessel ◽  
Room Temperature ◽  
Research Council ◽  
Estimation Method ◽  
Leak Rate ◽  
Fugitive Emissions ◽  
Flange Connection ◽  
Sealing Performance ◽  
Creep Characteristic

Gasket is the key element which determines the tightness of bolted flanged connection. PTFE blended gaskets which have recently been developed and come onto the market have a superior sealing performance as well as the chemical and temperature resistances and can contribute to reduce fugitive emissions. This paper deals with the sealing behaviors of the PTFE blended gasket and the tightness of a bolted flanged connection in which the gasket is used. The gasket is mainly composed of PTFE and graphite and has a high tightness and heat resistance up to 300 degree C. The creep characteristic is improved by the graphite filler. In this paper, the estimation method of the tightness of bolted flanged connections based on the sealing behavior of gasket is demonstrated. The estimated results are validated by experiments using a flange connection. It is shown that the leak rate below the tightness class 4 defined in the Room Temperature Tightness Test (ROTT, Pressure Vessel Research Council) can be obtained using the PTFE blended gasket.

Experimental Investigation of Interfacial and Permeation Leak Rates in Sheet Gaskets and Valve Stem Packing

2018 ◽  
Author(s):  
Ali Salah Omar Aweimer ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Experimental Testing ◽  
High Stress ◽  
Design Criterion ◽  
Leak Rate ◽  
Environment And Health ◽  
Valve Stem ◽  
Packing Rings ◽  
Order Of Magnitude ◽  
Hazardous Pollutants

The quantities of leak rate through sealing systems are being regulated because of the global concern on the hazardous pollutants being released into the atmosphere and their consequences on the environment and health. The maximum tolerated leak is becoming a design criterion, and the leak rate for an application under specific conditions is required to be estimated with reasonable accuracy. In this respect, experimental and theoretical studies are being conducted to characterize the gas flow through gaskets and packing rings. The amount of the total leak that is present in a gasketed joint or a valve stem packing is the sum of the permeation leak through the sealing material and the interfacial leak at the mating surfaces between the sealing element and mechanical clamp assembly. The existing models used to predict leakage do not separate these two types of leaks. This paper deals with a study based on experimental testing that quantifies the amount of these two types of leaks in bolted gasketed joints and packed stuffing boxes. It shows the contribution of interfacial leak for low and high contact surface stresses and the influence of the surface finish as a result of a 32 and 250 micro-inch RAAH phonographic finish in the case of a bolted flange joint. The results indicate that most of the leak is interfacial reaching 99% at the low stress while the interfacial leak is in the same order of magnitude of the permeation leak at high stress reaching 10−6 and 10−8 mg/s in both packing and gaskets, respectively.

The transients arising from the addition of heat to a gas flow

1952 ◽  
Vol 48 (3) ◽  
pp. 482-498 ◽  
Author(s):  
P. M. Stocker
Keyword(s):  
Gas Flow ◽  
Practical Interest ◽  
Theoretical Interest

Problems involving the addition of heat to a flowing gas have received considerable attention in recent years. The practical interest lies in the application to ram jets and similar engines, and the presence of entropy gradients makes the problem of theoretical interest.

scholarly journals Asymptotic analysis of the Boltzmann–BGK equation for oscillatory flows

2012 ◽  
Vol 708 ◽  
pp. 197-249 ◽  
Author(s):  
Jason Nassios ◽  
John E. Sader
Keyword(s):  
Asymptotic Analysis ◽  
Boundary Conditions ◽  
Steady Flow ◽  
Gas Flow ◽  
Solid Wall ◽  
Practical Interest ◽  
Mean Free Path ◽  
Stokes Number ◽  
Second Order ◽  
Bgk Equation

AbstractKinetic theory provides a rigorous foundation for calculating the dynamics of gas flow at arbitrary degrees of rarefaction, with solutions of the Boltzmann equation requiring numerical methods in many cases of practical interest. Importantly, the near-continuum regime can be examined analytically using asymptotic techniques. These asymptotic analyses often assume steady flow, for which analytical slip models have been derived. Recently, developments in nanoscale fabrication have stimulated research into the study of oscillatory non-equilibrium flows, drawing into question the applicability of the steady flow assumption. In this article, we present a formal asymptotic analysis of the unsteady linearized Boltzmann–BGK equation, generalizing existing theory to the oscillatory (time-varying) case. We consider the near-continuum limit where the mean free path and oscillation frequency are small. The complete set of hydrodynamic equations and associated boundary conditions are derived for arbitrary Stokes number and to second order in the Knudsen number. The first-order steady boundary conditions for the velocity and temperature are found to be unaffected by oscillatory flow. In contrast, the second-order boundary conditions are modified relative to the steady case, except for the velocity component tangential to the solid wall. Application of this general asymptotic theory is explored for the oscillatory thermal creep problem, for which unsteady effects manifest themselves at leading order.

Leakage Predictions for Static Gasket Based on the Porous Media Theory

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Pascal Jolly ◽  
Luc Marchand
Keyword(s):  
Porous Media ◽  
Gas Flow ◽  
Molecular Flow ◽  
Intrinsic Permeability ◽  
Slip Boundary Conditions ◽  
Apparent Permeability ◽  
Slip Boundary ◽  
Porous Media Theory ◽  
Porous Media Model ◽  
Different Gases

In the present work, the annular static gaskets are considered as porous media and Darcy’s law is written for a steady radial flow of a compressible gas with a first order slip boundary conditions. From this, a simple equation is obtained that includes Klinkenberg’s intrinsic permeability factor kv of the gasket and the Knudsen number Kn′o defined with a characteristic length ℓ. The parameters kv and ℓ of the porous gasket are calculated from experimental results obtained with a reference gas at several gasket stress levels. Then, with kv and ℓ, the inverse procedure is performed to predict the leakage rate for three different gases. It is shown that the porous media model predicts leak rates with the same accuracy as the laminar-molecular flow (LMF) model of Marchand et al. However, the new model has the advantage of furnishing phenomenological information on the evolution of the intrinsic permeability and the gas flow regimes with the gasket compressive stress. It also enables quick identification of the part of leakage that occurs at the flange-gasket interface at low gasket stresses. At low gas pressure, the behavior of the apparent permeability diverges from that of Klinkenberg’s, indicating that the rarefaction effect becomes preponderant on the leak.

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