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.

Evaluation of Interfacial and Permeation Leaks in Gaskets and Compression Packing

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Ali Salah Omar Aweimer ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Experimental Testing ◽  
Design Criterion ◽  
Leak Rate ◽  
Theoretical Studies ◽  
Reasonable Accuracy ◽  
Sealing Material ◽  
Order Of Magnitude ◽  
Global Concern ◽  
Bolted Flange ◽  
Experimental And Theoretical Studies

The quantities of leak rate through sealing systems are subjected to strict regulations because of the global concern on radiative materials. The maximum tolerated leak is becoming a design criterion in pressure vessel design codes, 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 conducted to characterize gasket and packing materials to predict leakage. The amount of the total leak is the summation of the permeation leak through the sealing material and the interfacial leak generated between the sealing element and its mating surfaces. Unfortunately, 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 of 0.8 and 6.3 μm (32 and 250 μin) resulting from phonographic grooves in the case of a bolted flange joint. The results indicate that most leakage is interfacial, reaching 99% at the low stress while interfacial leak is of the same order of magnitude of permeation leak at high stresses reaching 10−6 and 10−8 mg/s in both packing and gaskets, respectively. Finally, particular focus is put on the technique of precompression to improve material sealing tightness.

Predicting Leak Rate Through Valve Stem Packing in Nuclear Applications

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Ali Salah Omar Aweimer ◽  
Abdel-Hakim Bouzid ◽  
Mehdi Kazeminia
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Stokes Equations ◽  
Leak Rate ◽  
Flow Models ◽  
Valve Stem ◽  
Wide Range ◽  
Packing Rings ◽  
Bolted Flange ◽  
Flexible Graphite

Leaking valves have forced shutdown in many nuclear power plants. The myth of zero leakage or adequate sealing must give way to more realistic maximum leak rate criterion in design of nuclear bolted flange joints and valve packed stuffing boxes. It is well established that the predicting leakage in these pressure vessel components is a major engineering challenge to designers. This is particularly true in nuclear valves due to different working conditions and material variations. The prediction of the leak rate through packing rings is not a straightforward task to achieve. This work presents a study on the ability of microchannel flow models to predict leak rates through packing rings made of flexible graphite. A methodology based on experimental characterization of packing material porosity parameters is developed to predict leak rates at different compression stress levels. Three different models are compared to predict leakage; the diffusive and second-order flow models are derived from Naiver–Stokes equations and incorporate the boundary conditions of an intermediate flow regime to cover the wide range of leak rate levels and the lattice model is based on porous media of packing rings as packing bed (Dp). The flow porosity parameters (N, R) of the microchannels assumed to simulate the leak paths present in the packing are obtained experimentally. The predicted leak rates from different gases (He, N2, and Ar) are compared to those measured experimentally in which the set of packing rings is mainly subjected to different gland stresses and pressures.

Turbine Blade Life Prediction Using Fluid-Thermal-Structural Interaction Modelling

2015 ◽  
Author(s):  
I. A. Ubulom ◽  
K. Shankar ◽  
A. J. Neely
Keyword(s):  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Experimental Testing ◽  
Fluid Structure Interaction ◽  
High Stress ◽  
Time History ◽  
Life Assessment ◽  
Fluid Structure ◽  
Operational Conditions ◽  
Structure Interaction

The stringent structural requirements posed on aircraft engines, especially the high pressure turbine blades, result from the diversity of the extreme operational conditions they are subjected to. The accurate life assessment of the blades under these conditions therefore demands accurate analytical tools and techniques, and also an elaborate understanding of the operational conditions. Given the drive to reduce cost related to experimental testing, numerical approaches are often adopted to aid in the initial design stages. With recent advancement in numerical modelling, the simultaneous integration of the various numerical codes of fluid flow and structural analysis (otherwise known as fluid-structure interaction) is projected to provide reliable input into fatigue life prediction programs. This study adopts the numerical method of fluid-structure interaction to investigate the fatigue properties of the Aachen turbine test case. A load-time history obtained for the high stress monitor position is superimposed on that from a quasi-static FE solution, and used as input into a fatigue estimation tool. The low cycle fatigue (LCF) is estimated using the Basquin-Coffin-Manson correlation with corrections for mean stress and multi-axial fatigue effects. An FFT analysis of the fluctuating aerodynamic loads show signals with significant high frequency content. There is noticeable increased energy signal at the rotor inlet as compared to stator inlet. The stator inlet signals, however, are characterized by multiple resonances of frequency with lower energy content. By avoiding the resonances, the fatigue analysis predicts a safe design with a safety factor level of 3 for the rotor.

Stabilizing effect of surrounding gas flow on a plane liquid sheet

2011 ◽  
Vol 672 ◽  
pp. 5-32 ◽  
Author(s):  
OUTI TAMMISOLA ◽  
ATSUSHI SASAKI ◽  
FREDRIK LUNDELL ◽  
MASAHARU MATSUBARA ◽  
L. DANIEL SÖDERBERG
Keyword(s):  
Growth Rate ◽  
Gas Flow ◽  
Liquid Velocity ◽  
Air Flow ◽  
Liquid Sheet ◽  
Mean Velocity ◽  
Order Of Magnitude ◽  
The Stability ◽  
The Waves ◽  
Half Thickness

The stability of a plane liquid sheet is studied experimentally and theoretically, with an emphasis on the effect of the surrounding gas. Co-blowing with a gas velocity of the same order of magnitude as the liquid velocity is studied, in order to quantify its effect on the stability of the sheet. Experimental results are obtained for a water sheet in air at Reynolds number Rel = 3000 and Weber number We = 300, based on the half-thickness of the sheet at the inlet, water mean velocity at the inlet, the surface tension between water and air and water density and viscosity. The sheet is excited with different frequencies at the inlet and the growth of the waves in the streamwise direction is measured. The growth rate curves of the disturbances for all air flow velocities under study are found to be within 20% of the values obtained from a local spatial stability analysis, where water and air viscosities are taken into account, while previous results from literature assuming inviscid air overpredict the most unstable wavelength with a factor 3 and the growth rate with a factor 2. The effect of the air flow on the stability of the sheet is scrutinized numerically and it is concluded that the predicted disturbance growth scales with (i) the absolute velocity difference between water and air (inviscid effect) and (ii) the square root of the shear from air on the water surface (viscous effect).

Simplified IGCC With Hot Fuel Gas Combustion

1985 ◽  
Author(s):  
M. W. Horner
Keyword(s):  
Data Analysis ◽  
Alkali Metals ◽  
Experimental Testing ◽  
Fixed Bed ◽  
Coal Ash ◽  
Gas Combustion ◽  
Fuel Gas ◽  
Order Of Magnitude ◽  
Program Description ◽  
Particle Separator

Experimental testing and data analysis performed for simulated simplified IGCC system components have been completed. Earlier papers presented the program description and preliminary testing operations. This paper presents a review of the testing accomplishments and the results of data analysis. An air-blown, fixed-bed coal gasifier, and downstream cyclone particle separator were found to retain or remove coal ash particles and alkali metals very effectively. The low calorific fuel gas delivered to a gas turbine combustor was found to be significantly closer to the current “clean fuel” specification than had been anticipated. These results are very encouraging for the further development of simplified IGCC systems utilizing hot gas cleanup. Observed ash deposition rates imply that turbine cleaning would be less frequent by at least an order of magnitude as compared to operation on treated ash-forming petroleum fuels.

scholarly journals Absolute linear instability in laminar and turbulent gas–liquid two-layer channel flow

2013 ◽  
Vol 714 ◽  
pp. 58-94 ◽  
Author(s):  
Lennon Ó Náraigh ◽  
Peter D. M. Spelt ◽  
Stephen J. Shaw
Keyword(s):  
Gas Flow ◽  
Oil And Gas ◽  
Stability Boundary ◽  
Density Ratio ◽  
Bottom Layer ◽  
Linear Instability ◽  
Absolute Instability ◽  
Two Phase ◽  
Order Of Magnitude ◽  
Temporal Modes

AbstractWe study two-phase stratified flow where the bottom layer is a thin laminar liquid and the upper layer is a fully developed gas flow. The gas flow can be laminar or turbulent. To determine the boundary between convective and absolute instability, we use Orr–Sommerfeld stability theory, and a combination of linear modal analysis and ray analysis. For turbulent gas flow, and for the density ratio $r= 1000$, we find large regions of parameter space that produce absolute instability. These parameter regimes involve viscosity ratios of direct relevance to oil and gas flows. If, instead, the gas layer is laminar, absolute instability persists for the density ratio $r= 1000$, although the convective/absolute stability boundary occurs at a viscosity ratio that is an order of magnitude smaller than in the turbulent case. Two further unstable temporal modes exist in both the laminar and the turbulent cases, one of which can exclude absolute instability. We compare our results with an experimentally determined flow-regime map, and discuss the potential application of the present method to nonlinear analyses.

Two-Temperature Model for the Simulation of Atmospheric-Pressure Helium ICPs

1995 ◽  
Vol 49 (10) ◽  
pp. 1390-1402 ◽  
Author(s):  
Mingxiang Cai ◽  
Akbar Montaser ◽  
Javad Mostaghimi
Keyword(s):  
Electric Fields ◽  
Gas Flow ◽  
Heavy Particle ◽  
Argon Plasma ◽  
Input Power ◽  
Temperature Model ◽  
Inductively Coupled ◽  
Order Of Magnitude ◽  
Coupled Plasmas ◽  
Two Temperature

A two-temperature model (2-T model) was used to predict fundamental properties of pure helium inductively coupled plasmas (He ICPs). Plasma characteristics with the use of the 2-T model were compared to those obtained by the local thermodynamic equilibrum (LTE) model for the He ICP, to those of an Ar ICP, and to the existing experimental data. The distributions of electron and heavy-particle temperatures, electron number density, and electric and magnetic fields were obtained as a function of the internal diameters of the torch, the gas flow rates, the gap between the plasma tube and the MACOR insert, the generator frequency, and the active power. Overall, the He ICP was predicted to have a much higher electron temperature (> 12,000 K) in the load coil region, but its axial heavy-particle and electron temperatures (∼2000 K) at the analytical zone were lower than those of the Ar ICP (4000–6000 K). The high-temperature region in the He ICP was constricted to a smaller region close to the wall of the plasma confinement tube as compared to that in the Ar ICP. Most of the input power in the He ICP was lost through the plasma quartz tube. The magnetic and electric fields inside the induction coil in the helium plasma were approximately one order of magnitude higher than those in the argon plasma.

Numerical Investigations of the Gas Flow Inside the Bassoon

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Andreas Richter
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Musical Instrument ◽  
Mean Flow ◽  
Steady State Flow ◽  
Plane Wave Solution ◽  
Pressure Time ◽  
Flow Features ◽  
Order Of Magnitude ◽  
Three Dimensional Simulations

This work is devoted to the numerical investigation of the gas flow inside a bassoon while it is played. The digitized geometry for the simulations is taken from measurements using laser scan techniques in combination with image processing. Pressure time series measured at the bell and reed were used to define adequate boundaries. Additional pressure measurements inside the musical instrument helped to validate the calculations. With this approach, it was possible to model the characteristics of a bassoon which plays the lowest note. The results of the three-dimensional simulations showed that the acoustic velocities and the underlying mean flow exhibit the same order of magnitude. The calculations indicate that the flow in curved sections such as the crook and the 180 deg bend is considerably different from a steady-state flow. For example, in bends the time-averaged flow features chains of small, alternating vortex pairs, and the pressure distribution differs significantly from a plane wave solution.

Membrane operations

1997 ◽  
Vol 36 (2-3) ◽  
pp. 17-24 ◽  
Author(s):  
Torleiv Bilstad
Keyword(s):  
Municipal Wastewater ◽  
Membrane Separation ◽  
Correct Choice ◽  
Industrial Sector ◽  
Municipal Wastewater Treatment ◽  
Auxiliary Equipment ◽  
Order Of Magnitude ◽  
Pre Treatment ◽  
Hazardous Pollutants ◽  
The Right

The success of any industrial pretreatment program is dependent on correct choice of technology and management. The rapid growth in the industrial sector has increased the mass of toxic and hazardous pollutants to the municipal wastewater treatment works. This may again inhibit the conventional biological treatment processes. Membrane separation is in this context a physical pretreatment process which splits the flow of water in two; a less toxic permeate and a more concentrated retentate. Typically, the volume reduction is one order of magnitude from the feedflow to the retentate. Engineering contractors in general do not possess proper knowledge of membrane technology to convincingly include membranes as a viable process option in design of pre-treatment systems. Attractive features of membranes are low weight and space requirements without use of chemicals. Moreover, the equipment is modular and can be scaled up or operated at partial capacity. The paper documents examples of accumulated field experiences with the intention to prove that membrane separation is a mature technology for the industry to utilize and for the engineering contractor to master. Also, the paper conveys information pertinent to advances in membrane separation to better enable academia to adjust curricula to meet industrial demands for separation engineers. The challenge is to pick the right membrane for a specific wastewater and couple the membrane to compatable auxiliary equipment such as pumps, pipes, valves and meters.

Model Based Simulation of the Active Damping of a Cantilever Plate and Redistribution of Stresses

2000 ◽  
Author(s):  
Sathya V. Hanagud ◽  
Patrick J. Roberts
Keyword(s):  
Control System ◽  
Vibration Control ◽  
Closed Loop ◽  
Active Vibration Control ◽  
High Stress ◽  
Element Simulation ◽  
Control Scheme ◽  
Acceleration Feedback ◽  
Order Of Magnitude ◽  
Active Vibration

Abstract In most structures, fatigue critical areas are associated with regions of high stresses. Sometimes, passive stiffening of structures can displace these high stress regions. Thus, for most applications, active vibration control is preferred. However, the question of whether an active vibration control scheme involving a set of actuators will reduce stresses in the whole structure or create high stress areas in the vicinity of the actuators arises. In previous works, this question has been addressed for cantilever beams which showed that the stresses are reduced by approximately the same order of magnitude as the reduction in vibrations. However, many aerospace structures are constructed of thin walled components whose response to vibration reduction can be very different than that of beams. In this paper, the stresses induced by an active vibration control system, based on the use of an offset piezoceramic stack actuator with acceleration feedback control, are investigated in a plate structure. A 3-D finite element simulation of the closed loop active vibration control system is developed and both the closed loop stresses and vibration amplitude reductions are studied.

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