FEM Stress Analysis of Long-Term Sealing Performance for Bolted Pipe Flange Connections With PTFE Blended Gaskets Under Elevated Temperature

2016 ◽  
Author(s):  
Koji Sato ◽  
Toshiyuki Sawa ◽  
Takashi Kobayashi
Keyword(s):  
Elevated Temperature ◽  
Internal Pressure ◽  
Leak Rate ◽  
Load Factor ◽  
Stress Distributions ◽  
Sealing Performance ◽  
Basic Characteristics ◽  
The Relationship ◽  
Rigid Platen

Mechanical characteristics of bolted pipe flange connections with PTFE blended gaskets under elevated temperature are examined using FEM calculations and experiments. Firstly, the basic characteristics of the PTFE blended gaskets are measured such as the stress-strain curves, the thermal expansion coefficient and the relationship between the contact gasket stress and the leak rate at room temperature and some high temperature. The leak rates of the gasket at the averaged gasket stress are measured using the rigid platen. In addition, the creep characteristics of the gaskets are measured using the rigid platen under elevated temperature. Then, using the gasket basic characteristics measured above, the FEM calculations are carried out to analyze the mechanical characteristics such as 1) changes in axial bolt forces (the load factor), 2) the contact gasket stress distributions, 3) flange hub stress. Then, the sealing performance of bolted pipe flange connections is predicted using the contact gasket stress distributions obtained from the FEM calculations and the relationship between the gasket stress and the leak rate. In the FEM calculations, the value of the load factor due to the internal pressure is obtained as φg = 0.12. Furthermore, the sealing performance in long-term is estimated using the change in the axial bolt forces (creep) and the contact gasket stress distributions under heat cycle and internal pressure. For verification of the FEM calculations, the experiments were performed to measure the load factor (change in axial bolt forces), the leak rate of the connection at each temperature, and the hub stress. The FEM results are in a fairly good agreement with the measured results. In addition, the reduction in the contact gasket stress due to the heat cycle, internal pressure and the creep is demonstrated and the effect of the nominal diameter of pipe flanges on the sealing performance is shown.

FEM Stress Analysis and the Sealing Performance Evaluation of Bolted Pipe Flange Connections With Large Nominal Diameter Subjected to Internal Pressure

2016 ◽  
Author(s):  
Akira Muramatsu ◽  
Koji Sato ◽  
Maksud Uddin Khan ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Measured Data ◽  
Leak Rate ◽  
Load Factor ◽  
Stress Distributions ◽  
Nominal Diameter ◽  
Sealing Performance ◽  
The Relationship ◽  
Good Agreement

The gasket fundamental characteristics such as the stress-strain curves of compressed sheet gaskets (CSG) and the spiral wound gaskets (SWG) and the relationship between the average gasket stress and the leak rate using rigid platens were measured. Then, using the measured data of the gasket properties, the mechanical characteristics of bolted pipe flange connections under internal pressure are examined such as the contact gasket stress distribution, hub stress and changes in axial bolt forces (the load factor) using FEM. FEM code employed is ABAQUS. Using the obtained gasket stress distributions and the fundamental gasket relationship between the gasket stress and the leak rate, the leak rates of bolted pipe flange connections are predicted. In addition, the effect of nominal diameters (from 2” to 24”) on the mechanical characteristics is examined. For verification of the FEM calculations, experiments to measure the load factor, the hub stress and the leak rates were performed using 2” and 24” bolted pipe flange connections. The FEM results of the load factor, the hub stress and the leak rate are in a fairly good agreement with the measured results. The value of the load factor is found to be positive for 2” pipe flanged joints, while it is negative for 24” pipe flanged connection due to the flange rotation. It is noticed that the values of the load factor decreases with an increase of the nominal diameter of pipe flanges. The hub stress is kept constant when the gasket stress is held constant for each connection with each nominal diameter while it increases as the nominal diameter increases according to ASME codes. In addition, the leak rate increases as the nominal diameter increases.

Stress Analysis and Design of Bolted Flange Connections Under Internal Pressure

2014 ◽  
Author(s):  
Yuya Omiya ◽  
Toshiyuki Sawa ◽  
Yoshio Takagi
Keyword(s):  
Internal Pressure ◽  
Contact Stress ◽  
Leak Rate ◽  
Load Factor ◽  
Stress Distributions ◽  
Analysis And Design ◽  
Bolt Preload ◽  
Diameter Pipe ◽  
Bolted Flange ◽  
The Relationship

In the present paper, the gasket stress distributions, hub stress and a variation in axial bolt force in bolted gasketed pipe flange connections under internal pressure are analyzed using elasto-plastic FEM taking into account the nonlinearity of gasket behavior. Non-asbestos spiral wound gaskets were employed. The effect of nominal flange diameter is examined on the gasket contact stress distributions, the hub stress and the variation in axial bolt force (the load factor) is examined. Using the obtained gasket contact stress distribution and the fundamental data of the relationship between gasket compressive stress and gasket leak rate according to JIS B 2490, a method for predicting the leak rate is demonstrated. Experiments to measure the amount of leakage, the hub stress and the variation in axial bolt force when the joint is under internal pressure were carried out. The numerical results of the leak rate, hub stress and the load factor are in a fairly good agreement with the measured results. Then, a method is demonstrated for determining the bolt preload under given conditions, that is, taking into account assembly efficiency, leak rate and internal pressure In addition, bolt preload is determined using the actual gasket contact stress which can be estimated using the value of the load factor. As a design example, the procedure for determining the bolt preload in 3″ and 20″ nominal diameter pipe flange connections is shown for the allowable leak rate of 1.0−3Pa • m3/s. The results are validated by the experiments.

FEM Stress Analysis and Sealing Performance of Bolted Flanged Connections Using PTFE Blended Gaskets Under Internal Pressure

2015 ◽  
Author(s):  
Koji Sato ◽  
Akira Muramatsu ◽  
Takashi Kobayashi ◽  
Toshiyuki Sawa
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Leak Rate ◽  
Load Factor ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Relationship Of ◽  
The Relationship ◽  
Good Agreement

The objective of the paper is to examine mechanical characteristics of bolted flanged connection with newly developed PTFE blended gaskets under internal pressure such as the contact gasket stress distribution, the sealing performance, the load factor, reduction in axial bolt load due to creep and the flange hub stress. The relationship between the leak rate and the contact gasket stress for newly developed PTFE blended gasket were measured according to JIS B 2490 as well as the stress - displacement relationship of the gaskets. Then, the leak rate for bolted flanged connection with the PTFE blended gaskets (2inch nominal flange) was measured under internal pressure while changing the bolt preloads. In addition, the load factor and the hub stress were measured experimentally. The changes in each axial bolt force were measured using the strain gauges taking into account gasket creep. Using FEM, the gasket stress distribution, the load factor and the hub stress are analyzed taking into account the creep phenomenon of the PTFE blended gasket. The optimal maximum bolt preload is determined and the FEM results of the load factor and hub stress are in a fairly good agreement with the measured results. The predicted leak rate is fairly coincided with the measured results.

The Mechanical Characteristics and Sealing Performance Evaluation of Bolted Pipe Flange Connections With Metallic Flat Gaskets Subjected to Internal Pressure

2016 ◽  
Author(s):  
Koji Kondo ◽  
Koji Sato ◽  
Satomi Takahashi ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Mechanical Characteristics ◽  
Experimental Results ◽  
Leak Rate ◽  
Effect Of Temperature ◽  
Load Factor ◽  
Stress Distributions ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Higher Temperature

Bolted pipe flange connections with metallic gaskets have been used under higher pressure as well as higher temperature. However, a few researches on the mechanical characteristics in connections with metallic gaskets have been carried out. It is necessary to examine the mechanical characteristics such as the contact gasket stress distributions which govern the sealing performance, the deformation of the metallic gaskets, changes in axial bolt forces and the hub stress under higher pressure and temperature. In the present paper, the objectives are to examine the changes in axial bolt forces, the hub stress and the contact gasket stress distributions and the sealing performance of the pipe flange connections with metallic flat gaskets. Firstly, the mechanical characteristics of the connections under higher pressure are analyzed using FEA. Then, experiments were carried out to measure the load factor, the hub stress and the leak rate (the sealing performance). The relationship between the average contact gasket stress and the leak rate was measured using platen device at room temperature. The FEA results are fairly coincided with the experimental results. It is shown that the leak rate decreases as the contact gasket stress increases and when the plastic deformation of gaskets occurs, the sealing performance increases. The leak rate was measured in the range of 10−4∼10−7 [Pa·m3/s]. It is found that the sealing performance increases as the gasket width increase in the elastic deformation range while it is independent of the gasket width when the plastic deformation occurs. The effect of temperature on the mechanical characteristics of the connection is also examined. The FEA results are in a fairly good agreement with the experimental results. It is found that the sealing performance increases as the temperature increases. In addition, a method how to determine the bolt preload for increasing the sealing performance is proposed.

FEM Stress Analysis and the Sealing Performance Evaluation in Bolted Flange Connections With Ring Joint Gasket Subjected to Internal Pressure: Effect of Scatter in Bolt Preloads

2012 ◽  
Author(s):  
Koji Kondo ◽  
Shota Tsubaki ◽  
Toshiyuki Sawa ◽  
Tsutomu Kikuchi ◽  
Yuya Omiya
Keyword(s):  
Internal Pressure ◽  
Leak Rate ◽  
Stress Distributions ◽  
Sealing Performance ◽  
Torque Wrench ◽  
Helium Gas ◽  
Higher Temperature ◽  
Bolted Flange ◽  
Better Than ◽  
Good Agreement

Bolted flange connections with ring joint gaskets have been used to seal the inner fluid under higher internal pressure and higher temperature conditions where soft gaskets such as compressed sheet gaskets cannot be applied. Bolted flange connections are frequently tightened using torque wrench, and it is known that the values of bolt preloads are scattered. The effect of the scatter on the sealing performance for bolted flange connections with compressed sheet gasket or semi-metal gasket has been examined. However, no research on the characteristics for the bolted flange connections with ring joint gasket has been found. It is necessary to know the effect of the scattered bolt preloads on the sealing performance and mechanical behavior of the connection with ring joint gasket. In addition, it is important to know an optimum method for determining the bolt preloads taking account of the scatter in bolt preloads. In this paper, leakage tests for bolted flange connections with octagonal ring joint gaskets were conducted for cases where the bolt preloads are uniform and scattered. The sealing performance of these connections with ring joint gaskets was measured and evaluated. In addition, the leak rate was estimated using the contact gasket stress distributions of the connections when the bolt preloads were uniform and scattered using 3-D FEM. Finally, the measured leak rate for the connection using helium gas was compared with the estimated results. The estimated results are in fairly good agreement with the measured values. It is found that the sealing performance of the connections tightened with the uniform bolt methods is better than that with scattered bolt preloads.

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.

FEM Stress Analysis and Mechanical Characteristics of Bolted Pipe Connections With Larger Nominal Diameter Inserting PTFE Blended Gasket Under Internal Pressure

2018 ◽  
Author(s):  
Koji Sato ◽  
Toshiyuki Sawa ◽  
Xing Zheng
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Performance Prediction ◽  
Mechanical Characteristics ◽  
Leak Rate ◽  
Load Factor ◽  
Flange Connection ◽  
Nominal Diameter ◽  
Sealing Performance ◽  
Good Agreement

The sealing performance prediction of bolted pipe flange connections with gaskets is important factor. However, it is known that the sealing performance of the larger nominal diameter connection is worse than that with smaller nominal diameter connection due to the flange rotation. Furthermore, recently PTFE blended gaskets were developed newly and the excellent sealing performance in the bolted pipe flange connection with smaller nominal diameter is found. So, it is necessary to examine the sealing performance and the mechanical characteristics of pipe flange connections with larger nominal diameter under internal pressure. The objectives of present study are to examine the mechanical characteristics of the pipe flange connection with PTFE blended gasket under internal pressure such as the load factor, the contact gasket stress distribution and the sealing performance using FEM and experiments. Using the obtained contact gasket stress distribution and the fundamental leak rate for smaller PTFE gasket, the leak rate of the connection is predicted under internal pressure. In the FEM calculation, the effects of the nominal diameter of pip flange connections on the mechanical characteristics are shown. In the experiments, ASME class 300 24” pipe flange connections is used and the gasket is chosen as No.GF300 in PTFE blended gaskets. The FEM results of the axial bolt forces are in a fairly good agreement with the experimental results. In addition, the leak rate obtained from the FEM calculations are fairly coincided with the measured results. The mechanical characteristics of pipe flange connection with PTFE blended gasket are compared with those with spiral wound gasket.

FEM Stress Analysis and Evaluation of the Sealing Performance in Box-Shape Flange Gasketed Connections Subjected to Internal Pressure

2010 ◽  
Author(s):  
Kentaro Tenma ◽  
Ryou Kurosawa ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Displacement Curve ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Analysis And Evaluation ◽  
Gas Leakage ◽  
Sealing Performance ◽  
Cover Thickness ◽  
The Relationship ◽  
Cover Material

Bolted connections inserting gaskets such as box-shape flange connections have been widely used in mechanical structures, nuclear and chemical industry, and so on. They are usually used under internal pressure. In designing the box-shape flange connections with gaskets under internal pressure, it is important to clarify the gasket stress distribution for evaluating the sealing performance of these connections. However, no research in which the sealing performance of these connections is examined under internal pressure has been carried out. Thus, the design for box-shape connection such as thickness of flange cover, number of bolts, gasket width and so on is not clarified. In this paper, the contact gasket stresses of these connections under internal pressure are analyzed using the finite element method (FEM), taking into account a hysteresis in the stress-displacement curve of the gasket. And then, using the contact gasket stress distributions obtained from FE analysis and the relationship between gasket stress and leak rate obtained from a gasket sealing test (JIS B2490), method for estimating an amount of leakage is examined. The leakage tests were also conducted to measure an amount of gas leakage using an actual box-shape flange connection with a gasket. The estimated results are in a fairly good agreement with the experimental results. In addition, the effect of gasket width, flange cover thickness and flange cover material is examined on the sealing performances of box-shape flange connections under internal pressure. The effects of the above factors are discussed on the sealing performance in designing box-shape flange connections.

FEM Stress Analysis and Sealing Performance Evaluation in Bolted Flange Connections With Metal Flat Gasket Subjected to Bending Moment and Internal Pressure

2014 ◽  
Author(s):  
Koji Kondo ◽  
Yuya Omiya ◽  
Shota Tsubaki ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Bending Moment ◽  
Leak Rate ◽  
Stress Distributions ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Higher Temperature ◽  
Contact Surfaces ◽  
Bolted Flange

Bolted flange connections with metal gasket have been used at higher pressure under higher temperature condition. Assembly procedures and tightening methods the connections including some types of metal gasket is empirically. Generally, it is known that the bolt preload which is required for satisfying an indicated leak rate in the connections including the metal gasket is not higher than that of the connections including sheet gaskets and spiral wound gaskets. However, no research for the evaluating the sealing performance in the bolted flange connections with metal gaskets has been conducted. In this paper, the leakage tests for the bolted flange connections with the metal flat gasket were conducted in the case where the maximum internal pressure of 7MPa and a bending moment are applied, where the leak rate is measured using the pressure drop method. Then, the sealing performance of the connections with the metal flat gasket was evaluated. In addition, using the FEM stress calculations, the flange stress distributions between the flange surface and the gasket were examined as the evaluation. As the result, it is found that the stress distribution at the contact surfaces between the metal flat gasket and the flange surface under the bending moment and the internal pressure. In the leakage tests, it was observed that the amount of the leakage (He gas) depends on the stress distributions and the plastic deformation of the gasket.

The Sealing Performance of a Large Diameter Bolted Joint Under Elevated Temperature

2007 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Naoki Kawasaki ◽  
Yoshio Takagi ◽  
Hiroyasu Torii
Keyword(s):  
Elevated Temperature ◽  
Internal Pressure ◽  
Large Diameter ◽  
Stress Distributions ◽  
Test Results ◽  
Flange Connection ◽  
Gas Leakage ◽  
Nominal Diameter ◽  
Sealing Performance ◽  
Diameter Pipe

Flange rotation with internal pressure affects the sealing performance of pipe flange connections more with increasing the pipe nominal diameter. Therefore, it is hard to estimate the sealing performance of pipe flange connections with larger nominal diameter by using the test results of the sealing performance for pipe flange connections with small nominal diameter. In this study, the 20" diameter pipe flange connection was experimentally used as a large nominal diameter pipe flange connection and analyzed the stress in the connection. In the experiments, the sealing performance of the pipe flange connection was evaluated by measuring the amount of gas leakage at 50 °C and 100 °C under internal pressure. Non-asbestos graphite gaskets were used in the experiments. The bolts and nuts were tightened according to the Japanese method (HPIS Z103 TR). The gasket contact stress distributions of larger nominal diameter pipe flange connection were calculated by FEM under elevated temperature conditions as well as internal pressure application. The estimated results were compared with the experimental results. The results were also compared with the small nominal diameter test result and discussed.

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