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 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.

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.

FEM Stress Analysis and Mechanical Characteristics of Bolted Pipe Flange Connections With PTFE Blended Gaskets Subjected to External Bending Moments and Internal Pressure

2017 ◽  
Author(s):  
Koji Sato ◽  
Toshiyuki Sawa ◽  
Riichi Morimoto ◽  
Takashi Kobayashi
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Bending Moment ◽  
Leak Rate ◽  
Bending Moments ◽  
Four Point Bending ◽  
Sealing Performance ◽  
The Difference ◽  
Good Agreement

In designing of pipe flange connections with gaskets, it is important to examine the mechanical characteristics of the connections subjected to external bending moments due to earthquake such as the changes in hub stress, axial bolt forces and the contact gasket stress distribution which governs the sealing performance. One of the authors developed the PTFE blended gaskets and the authors examined the mechanical characteristics of the connections with the PTFE blended gaskets under internal pressure. However, no research was done to examine the mechanical characteristics of the connections with the newly developed PTFE blended gasket subjected to external bending moment due to earthquake. The objectives of the present study are to examine the mechanical characteristics of the connection with PTFE blended gasket subjected to external bending moment and internal pressure and to discuss the difference in the load order to the connections between the internal pressure and the external bending moments. The changes in the hub stress, the axial bolt force and the contact gasket stress distribution of the connection are analyzed using FEM. Using the obtained the gasket stress distribution and the fundamental data between the gasket stress and the leak rate for a smaller test gasket, the leak rate of the connection with the gasket is predicted under external bending moment and internal pressure. In the FEM calculations, the effects of the nominal diameter of pipe flanges on the mechanical characteristics are shown. In the experiments, ASME class 300 4 inch flange connection with 2m pipes at both sides is used and the test gasket is chosen as No.GF300 made by Nippon Valqua Industries, ltd. Four point bending moment is applied to the connection. The FEM results of the hub stress and the axial bolt forces are in a fairly good agreement with the experimental results. In addition, the FEM results of the leak rate are fairly coincided with the measured results.

Effects of Scatter in Bolt Preload on the Sealing Performance of Pipe Flange Connections Under Internal Pressure (Case Where the Nominal Diameter of Pipe Flange Connection is 20″)

2010 ◽  
Author(s):  
Yoshio Takagi ◽  
Toshiyuki Sawa ◽  
Hiroyasu Torii ◽  
Yuya Omiya
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Control Method ◽  
Torque Control ◽  
Stress Distributions ◽  
Flange Connection ◽  
Nominal Diameter ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Contact Stress Distribution

It has been well known that a scatter in axial bolt forces in pipe flange connections tightened by the torque control method is substantial. In practice, pipe flange connections with the large nominal diameter tightened by the torque control method have been used in chemical industry, and so on. In our study, the characteristics of the connections with smaller nominal diameter (less than 8″) have been shown. So, in an optimum design of pipe flange connections with gaskets, it is necessary to understand the characteristics of the pipe flange connections with large nominal diameter under internal pressure and the contact gasket stress distributions due to the scatter in axial bolt forces in the connections tightened by the torque control method. In this paper, the experimental and FE analyses were done to evaluate the effect of scatter in axial bolt force on the gasket stress distribution and the sealing performance of pipe flange connections with 20″ nominal diameter. Two types of torque controlled assembling procedures, that is, ASME PCC-1 and JIS B 2251 procedures, are evaluated as an assembling procedures and an effect of scatter in the axial bolt forces obtained from the above methods is examined. Then, the effect of scatter in the axial bolt forces on the sealing performance of the connection is evaluated. The contact stress distribution in the larger pipe flange connection with 20″ nominal diameter under internal pressure is analyzed using FEM by taking into account a non-linearity and a hysteresis. The measured scatter in the axial bolt forces is applied in the FEM calculations.

A Calculation Method of the Load Factor and Design for Bolted Gasketed Pipe Flange Connections Under Internal Pressure

2019 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Toshio Mabuchi ◽  
Koji Sato
Keyword(s):  
Internal Pressure ◽  
Calculation Method ◽  
Leak Rate ◽  
Load Factor ◽  
Bolted Connections ◽  
Gas Leakage ◽  
Nominal Diameter ◽  
Bolt Preload ◽  
Spring Constants ◽  
Good Agreement

Abstract The contact gasket stress reduces when the bolted gasketed pipe flange connections are subjected to internal pressure. In designing the bolted connections, it is needed to predict the reduced contact gasket stress, so, it is necessary to know the load factor. However, it is difficult to estimate the value of the load factor of the connections under internal pressure. In the previous paper (2018PVP), a more simpler calculation method was proposed. However, a more accuracy for obtaining the values of the load factor is desirable using the spring constants Ktg and Kcg. In the present paper, some calculation models for the spring constants are improved. Then, the values of the load factor for JIS 10K flange connections and ASME B16 flange connections with spiral wound gaskets are shown. The values of the load factor for the above connections are in a fairy good agreement with the FEM results. Using the obtained load factor, the residual contact gasket stress and an amount of gas leakage are predicted. The obtained calculated results of the load factor and the amount of the leakage are in a fairly good agreement with FEM results, and the measured results for 24” connection. As a result, the value of the load factor for the connections with larger nominal diameter is found to be negative and it decreases as the nominal flange diameter increases. In addition, a method how to determine the bolt preload for satisfying a give allowable leak rate is demonstrated.

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.

Stress Analysis and Sealing Performance Evaluation of Bolted Pipe Flange Connections With Smaller and Larger Nominal Diameter Under Repeated Temperature Changes

2014 ◽  
Author(s):  
Yuya Omiya ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Thermal Condition ◽  
Power Plants ◽  
Thermal Exposure ◽  
Flange Connection ◽  
Gas Leakage ◽  
Nominal Diameter ◽  
Other Hand ◽  
Sealing Performance ◽  
Helium Gas

Pipe flange connections with gaskets in chemical plants, electric power plants and other industrial plants are usually exposed to elevated internal pressure with cyclic thermal condition. It is important to investigate the sealing performance of pipe connections under long term severe thermal exposure swings to ensure operational safety. In this study, the effects of cyclic thermal conditions on the sealing performance and mechanical characteristics in larger and smaller nominal diameter of pipe flange connection are examined using FEM calculations. Helium gas leakage is predicted using the contact gasket stress obtained from the FEM results. On other hand, the leakage tests using the smaller nominal diameter of pipe flange connection were conducted to measure the amount of helium gas leakage and to compare with the predicted amount of gas leakage. As the results, the contact gasket stress distributions were changed dramatically under cyclic thermal condition and elevated internal pressure. In the pipe flange connections with smaller nominal diameter, the contact gasket stress was the smallest in the restart condition. On other hand, the minimum contact gasket stress in the pipe flange connection with larger nominal diameter was depending on the materials of connection. In the pipe flange connection with larger nominal diameter, the contact gasket stress distributed and changed in the radial direction due to the flange rotation. A fairly good agreement was found between the experimental leakage result and predicted leakage results.

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.

Effect of External Bending Moment on the Sealing Performance of Pipe Flange Connection

2010 ◽  
Author(s):  
Yoshio Takagi ◽  
Hiroyasu Torii ◽  
Toshiyuki Sawa ◽  
Yuya Omiya
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Deformation Characteristic ◽  
Bending Moment ◽  
Displacement Curve ◽  
Linear Deformation ◽  
Flange Connection ◽  
Sealing Performance ◽  
Non Linear ◽  
The Difference

Since an external bending moment affects the sealing performance of pipe flange connection, it is important to investigate this effect. This paper analyzed the contact gasket stress distribution of pipe flange connections and evaluates the effect of external bending moment on the sealing performance from the viewpoint of changes in contact gasket stress. The study includes the FE analyses and the experimental leakage tests. The FE analyses suggested the large decrease of contact gasket stress at tension side and small increase at compression side. The difference in change in contact gasket stress was caused by the non-linear hysteresis characteristics of stress-displacement curve of gasket. The FE analyses also suggested that the loading order, internal pressure and external bending moment, also affected the sealing performance due to the non-linear deformation characteristic of the gasket. The sealing performance when the external bending moment applied prior to the internal pressure was degraded more than when the internal pressure was applied prior to the external bending moment. The experimental leakage tests using helium (He) gas were analyzed by the finite element method and discussed. This paper also evaluated the stress distribution in the pipe flange under external bending moment. The results suggested that the hub stress dominated the flange structure and the most important factor in designing the flange.

An Analysis of Circular Bolted Flanged Joints on Solid Round Bars Subjected to External Bending Moments

2000 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Tsuneshi Morohoshi ◽  
Akihiro Shimizu
Keyword(s):  
Stress Distribution ◽  
Contact Stress ◽  
Three Dimensional ◽  
Bending Moment ◽  
Theory Of Elasticity ◽  
Load Factor ◽  
Bending Moments ◽  
Sealing Performance ◽  
Contact Stress Distribution ◽  
Good Agreement

Abstract In designing bolted joints, it is important to know the contact stress distribution which governs the clamping effect or the sealing performance and to estimate the load factor (the ratio of an increment in axial bolt force to an external load) from bolt design standpoint. The clamping force by bolts and the external bending moment are axi-asymmetrical loads and not many investigations have seen reported which treat axi-asymmetrical. In this paper, the clamping effect, and the load factor for the case of solid round bars with circular flanges, subjected to external bending moments, are analyzed as an axi-asymmetrical problem using the three-dimensional theory of elasticity. Experiments were carried out concerning the contact stress distribution, and the load factor for the external bending moment (a relationship between an increment in axial bolt force, and external bending moment). The analytical results were in fairly good agreement with the experimental ones.

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