Visco-Elastic FEM Stress Analysis of Bolted Flange Connections With PTFE-Blended Gaskets Under Elevated Temperature

2012 ◽  
Author(s):  
Koji Sato ◽  
Shinya Kurokawa ◽  
Toshiyuki Sawa
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Fluid Temperature ◽  
Long Term Conditions ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Strain Relationship ◽  
Bolted Flange ◽  
Relationship Of

Bolted flange connections with gaskets have been used under high temperature and long-term conditions. Sometimes leakage accidents occur from the gasket interfaces due to the creep and relaxation phenomena. In the present paper, the changes of the gasket stress in bolted flange connections under high temperature conditions for a long-term are analyzed using FEM calculations taking into account the gasket temperature dependency. The gaskets used are PTFE-blended (V#GF300). It’s shown that the effect of the temperature on the stress-strain relationship of the gasket is substantial. The changes in the gasket stress of the connections for 12 months are analyzed using the FEM. The effects of nominal diameter of flanges, retightening and the fluid temperature (20 to 300 °C) on the change of gasket stress in the connections under elevated temperature are examined using the FEM calculations. It is found that the reduction in the gasket stress is over 40%. In addition, experiments to measure the axial bolt force were carried out. The calculated results are in a fairly good agreement with the experimental results. The results reveal that the long-term behavior of the bolted flange connections can be estimated in our study. Discussion is made on the effects of the bolt preload and retightening on the reduction of the gasket stress and the sealing performance.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Evaluation of Leakage Probability of Non-Asbestos Fiber Sheet Gasket at Elevated Temperature Based on Percolation Theory

2010 ◽  
Author(s):  
Masahiro Hagihara ◽  
Hirokazu Tsuji ◽  
Atsushi Yamaguchi
Keyword(s):  
High Temperature ◽  
Percolation Theory ◽  
Life Prediction ◽  
Prediction Method ◽  
Acoustic Tomography ◽  
Leakage Path ◽  
Temperature Environment ◽  
Fiber Sheet ◽  
Bolted Flange

A long-term life prediction method for a compressed fiber sheet gasket under a high-temperature environment is studied. Non-asbestos compressed fiber sheet gaskets are now being used as a substitute for asbestos in the bolted flange joint, for instance petrochemical factories. Consequently, there is a real need for a technology to predict the lifetime of non-asbestos compressed fiber sheet gaskets quantitatively. In this report, the facing surface of the gasket and flange is visualized with scanning acoustic tomography (SAT). Voids were observed on the facing surface of the gasket and increased with the increase in exposure time at high temperature. If a leakage path for inner fluids is created by the increasing number of voids, the leak occurs on the facing surface of the gasket. The probability of a leak due to voids and the lifetime of this gasket are predicted by applying the percolation theory, which describes the connectedness of clusters.

Three-Dimensional Numerical Analysis for Bolted Flange Joints Considering Effect of Creep

2018 ◽  
Author(s):  
Lewen Bi ◽  
Lanzhu Zhang
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Numerical Analysis ◽  
Yield Strength ◽  
Room Temperature ◽  
Three Dimensional ◽  
Short Term ◽  
Flange Connection ◽  
Petroleum Chemical ◽  
Bolted Flange

Bolted flange joints are widely used in petroleum, chemical, nuclear and power industries, etc. With more and more devices are used at high temperature, the performance of flange connections becomes more complex, especially with creep of different components in flange connection. At elevated temperature, with the loss of bolt force and gasket force due to creep, the joints are prone to leak. Based on this, this paper analyzed the relaxation of bolt force at elevated temperature due to creep of bolt, flange and gasket separately and simultaneously. Besides, the influence of different initial installation stress of bolts was also studied. The results showed bolted flange joints relaxed due to gasket creep during early short term service. However, contribution of bolt and flange creep became more and more significant with the extension of time. With considering the creep of bolt, flange and gasket simultaneously, 50% to 60% of the bolt material yield strength at room temperature was recommended as the bolt initial installation stress for the joint case studied in this paper.

scholarly journals The relationship of the perceived impact of the current Greek recession with increased suicide risk is moderated by mental illness in patients with long-term conditions

2017 ◽  
Vol 96 ◽  
pp. 98-105 ◽  
Author(s):  
Elisavet Ntountoulaki ◽  
Vassiliki Paika ◽  
Dimitra Papaioannou ◽  
Elspeth Guthrie ◽  
Konstantinos Kotsis ◽  
...  
Keyword(s):  
Mental Illness ◽  
Suicide Risk ◽  
Long Term Conditions ◽  
Perceived Impact ◽  
Relationship Of ◽  
The Relationship

An Estimation of Long-Term Sealing Performance for Bolted Pipe Flange Connections With Spiral Wound Gaskets Under Elevated Temperature

2020 ◽  
Author(s):  
Koji Sato ◽  
Toshiyuki Sawa
Keyword(s):  
Elevated Temperature ◽  
Heat Conduction Problem ◽  
Estimation Method ◽  
Transient State ◽  
Sealing Performance ◽  
Nominal Size ◽  
Calculation Results ◽  
Flexible Graphite ◽  
Spiral Wound

Abstract SWGs (Spiral Wound Gaskets) are well known as a most used gasket type in bolted pipe flange connections all over the world. Recently, the connections with SWGs have been used under more severe conditions such as higher temperature and pressure, and in addition, the connections have been used in the more long-term application. Thus, it is necessary for plant owners (gasket users) to know the long-term characteristics of the connections with SWGs from a standpoint of integrity in the connections. In this study, the objective is to establish a long-term estimation method of sealing performance for bolted pipe flange connections with SWGs under elevated temperature. The long-term characteristics of pipe flange connections with SWGs are estimated using FEM calculations in which the fundamental mechanical characteristics of SWGs such as compression property under changed temperature is considered, thermal expansion behavior, creep relaxation and sealing performance are taken into considerations. For verification of FEM calculations, the experiments are carried out for the pipe flange connections with SWGs of which the nominal size is ASME class 300 2inch under elevated temperature and internal pressure. The gasket used is chosen as SWG with flexible graphite filler. The change in axial bolt forces and an amount of leakage are measured and the measured results are fairly coincided with the FEM calculation results. In addition, the contact gasket stress in the connection with SWG is shown in 72 months. The FEM calculations are performed as heat conduction problem in transient state.

FEM Stress Analysis and Sealing Performance in Bolted Flange Connections With Cover of Pressure Vessel Subjected to Internal Pressure

2003 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Rie Higuchi
Keyword(s):  
Internal Pressure ◽  
Contact Stress ◽  
Pressure Vessel ◽  
The Finite Element Method ◽  
Flange Connection ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Bolted Flange ◽  
Contact Stress Distribution ◽  
Spiral Wound

The stresses of a bolted flange connection with a cover of pressure vessel (CPV) in which a spiral wound gasket is inserted, under internal pressure are analyzed taking account a hysteresis of the gasket by using the finite element method (FEM). The leakage tests were also conducted using an actual bolted flange connection with a CPV with a spiral wound gasket. Using the contact stress distribution of the bolted flange connection with a CPV under internal pressure and the tightness parameter, the values of the new gasket constants were obtained by taking into account the changes in the contact stress. A difference in the new gasket constants between the estimated values obtained from the actual bolted flange connection with a CPV and the values obtained by the PVRC procedure was small. In addition, a method to determine the bolt preload for a given tightness parameter was demonstrated. The obtained results of the bolt preload for the bolted flange connection with a CPV were in a fairly good agreement with those obtained by the PVRC procedure under a lower pressure application. However, a difference in the bolt preload was about 7% when the internal pressure was increased.

Practical Evaluation of PTFE Thermal Behavior Using the Hot Blowout Thermal Cycling Test

2012 ◽  
Author(s):  
Anita R. Bausman ◽  
A. Fitzgerald (Jerry) Waterland
Keyword(s):  
Thermal Cycling ◽  
Compressive Load ◽  
Temperature Limit ◽  
Cycling Performance ◽  
Current Status ◽  
Test Results ◽  
Sealing Performance ◽  
Practical Evaluation ◽  
Bolted Flange

Differential thermal expansion between polytetrafluoroethylene (PTFE) gasket materials and metallic flange/bolt systems, combined with thermally influenced creep relaxation characteristics of all PTFEs, creates limitations in the ability of some PTFE gasket materials to provide long term, reliable sealing performance in process or thermal cycling applications. ASTM F-36 gasket recovery data is sometimes used to assess a gasket’s thermal cycling capabilities; however, it is a poor means of establishing suitability for cycling performance as it is a short duration, ambient temperature test that measures recovery, or springback, of the gasket after the compressive load has been completely released. In order to provide a direct qualification of thermal cycling performance and capabilities, the Hot Blowout Thermal Cycling (HOBTC) test was developed under the guidance of the PVRC (Pressure Vessel Research Council)Bolted Flange Connection Committee as part of the 1995 PTFE Gasket Protocol. The HOBTC test results provide a practically applicable temperature limit under which the tested material, typically a PTFE, can operate safely. In addition, test data reported graphically provide additional insight about the long term behavior of the PTFE material. This paper reviews the current status of the HOBTC test, in the process of being made into an ASTM standard, and practical application of test results to achieve reliable gasket performance.

Effect of Internal Pressure on Gasket Stress and Leakage Rate of Bolted Flanged Joint During the Long Term Service at High Temperature

2019 ◽  
Author(s):  
Jilin Xue ◽  
Xuedong Chen ◽  
Zhichao Fan ◽  
Lu Wang
Keyword(s):  
High Temperature ◽  
Internal Pressure ◽  
Leakage Rate ◽  
Time Dependent ◽  
The Finite Element Method ◽  
Process Industries ◽  
Bolted Flange ◽  
Internal Pressures

Abstract Bolted flange joints (BFJs) are very common in the process industries, and they play an important role in equipment connection. A lot of BFJs are working at high temperature. The temperature and internal pressure will lead to gasket stress redistribution, and then affect time-dependent leakage rate of BFJs. In this paper, the effect of internal pressure on gasket stress and leakage rate of BFJ during the long term service at high temperature was discussed. The time-dependent gasket stresses of BFJ during the long term service at high temperature under two tightness levels and three internal pressures were calculated by using the finite element method. And then, based on the leakage rate prediction model of BFJ during the long term service at high temperature proposed, the corresponding time-dependent leakage rates of BFJ during the long term service at high temperature were acquired. The results showed that the internal pressure had a significant impact on the time-dependent gasket stresses and time-dependent leakage rates of BFJ during the long term service at high temperature. This research will help the engineers and technicians to understand the role of the internal pressure on the time-dependent gasket stresses and time-dependent leakage rates of BFJ during the long term service at high temperature.

The Sealing Performance Evaluation of Bolted Flexible Box-Shaped Flange Joints Under Thermal Conduction Conditions

2009 ◽  
Author(s):  
Ryou Kurosawa ◽  
Toshiyuki Sawa ◽  
Yuya Omiya ◽  
Kentaro Tenma
Keyword(s):  
Elevated Temperature ◽  
Internal Pressure ◽  
Thermal Conduction ◽  
Stress Distributions ◽  
Flange Joint ◽  
The Finite Element Method ◽  
Gas Leakage ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Helium Gas

Bolted joints with gaskets such as flexible box-shaped flange joints have been used in mechanical structures. The joints are usually used under internal pressure as well as other loadings such as thermal, impact loadings and so on. In designing the bolted flexible box-shaped flange joint with gaskets, it is important to evaluate the sealing performance of the joints under internal pressure and thermal conduction conditions. In this paper, the contact gasket stress distributions and changes in bolt load in the bolted flexible box-shaped flange joint with joint sheet gaskets subjected to internal pressure and thermal conduction condition are analyzed using the finite element method (FEM). The leakage tests were conducted using an actual box-shaped flange connection with a joint sheet gasket. Using the contact gasket stress distributions under internal pressure at an elevated temperature (Helium gas) obtained from the FEM calculations and the amount of the gas leakage measured in the experiment, the sealing performances are evaluated experimentally and numerically. In addition, the effect of the thermal conduction condition on the sealing performance is examined. Furthermore, a method how to determine the bolt preload of the flexible box-shaped flange joint at an elevated temperature for a given tightness parameter is demonstrated. Discussion is made on the sealing performance.

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