An Estimation of the Load Factor and Sealing Performance Evaluation for Bolted Pipe Flange Connections With Gaskets Under Internal Pressure

2017 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Koji Sato
Keyword(s):  
Internal Pressure ◽  
Plate Theory ◽  
Design Method ◽  
Spring Constant ◽  
Leak Rate ◽  
Load Factor ◽  
Real Rate ◽  
Simple Method ◽  
Gas Leakage ◽  
Bolt Preload

In designing bolted pipe flange connections with gaskets, It is necessary to know the actual residual gasket contact stress in the connections under internal pressure. However, the actual reduced gasket stress in the connection has not been sufficiently estimated. In estimating the actual residual contact gasket stress more precisely, it is needed to know the load factor (the ratio of an increment in axial bolt force to the axial force due to the internal pressure per bolt) of the connections with gaskets. The new formula for obtaining the load factor was proposed by one of the authors using the tensile spring constant Ktg and the compressive spring constant Kcg, while the spring constant of bolt-nut system is designated as Kt. In the present paper, for estimating the load factor of the connections with gaskets, the circular plate theory is applied for obtaining the values of Kcg and Ktg and then the load factor is obtained for pipe flanges specified JIS 10K flanges and ASME B 16.5 flanges. The obtained results are in a fairly good agreement with the FEM results. Using the obtained load factor for the connections, a design method is demonstrated taking account of the allowable leak rate. Using the residual contact gasket stress and the fundamental gasket leak rate, an amount of gas leakage is predicted. The predicted amount of gas leakage for 3” and 20” pipe flange connections is fairly coincided with the experimental results and the FEM results. In addition, a design method for determining the bolt preload for a give allowable real rate is demonstrated using the simple method for obtaining the load factor.

A Simple Calculation Method of the Load Factor and a Bolt Preload Determination Satisfying Allowable Leak Late for Bolted Pipe Flange Connections With Gaskets Subjected to Internal Pressure

2018 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Koji Sato ◽  
Toshio Mabuchi
Keyword(s):  
Internal Pressure ◽  
Circular Plate ◽  
Calculation Method ◽  
Plate Theory ◽  
Reaction Force ◽  
Simple Calculation ◽  
Couple Problem ◽  
Load Factor ◽  
Real Rate ◽  
Bolt Preload

In designing bolted pipe flange connections with gaskets under internal pressure, it is important to predict an actual residual contact gasket stress in the connections. For estimating the reduced gasket stress, it is needed how to know the load factor of the connections with gaskets. In the previous paper (2017PVP), for predicting the load factor of the connections with gaskets, a new model was proposed using a circular plate theory. However, the rigidity of the flange hub was assumed and it is necessary to improve the model for calculation. In the present paper, a simple and more accurate calculation method is proposed using a circular plate theory taking into account the reaction force distribution at the gasket interfaces and the effect of flange hub. In addition, the effect of the flange hub is analyzed as a couple problem between a cylindrical shell (hub) and a circular plate. The obtained results of the load factor in the connections are in a fairly good agreement with those obtained from FEM. In the numerical calculations, the values of the load factor for JIS 10K flange connections and ASME flange connections with compressed sheet and spiral wound gaskets (from 2” to 24”) are shown. Using the obtained load factor, the residual contact gasket stress and an amount of gas leakage are predicted. For verification of the simple calculation method for obtaining the load factor and FEM results, experiments to measure the load factor and the amount of the leakage were conducted for 24” connection. The calculated results are compared with the experimental method. In addition, an issue how to determine the bolt preload for satisfying a give allowable real rate is demonstrated.

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.

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.

Effects of Scatter in Bolt Preload of Pipe Flange Connections With Gaskets on Sealing Performance

2003 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Mitsuhiro Matsumoto ◽  
Satoshi Nagata
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Internal Pressure ◽  
Control Method ◽  
Torque Control ◽  
Stress Distributions ◽  
Flange Connection ◽  
Gas Leakage ◽  
Bolt Preload ◽  
Sealing Performance

It has been well known that a scatter in axial bolt forces of pipe flange connections tightened by the torque control method is substantial. It is necessary for evaluating the sealing performance of the pipe flange connections with the gaskets subjected to intemal pressure to know the contact gasket stress distributions due to the scatter of the axial bolt forces in the connections tightened by the torque control method. This paper deals with the leakage of the pipe flange connections with a spiral wound gasket and that with a compressed sheet gasket tightened by the torque control method. The scatter in the axial bolt forces was measured in the experiments. The contact gasket stress distributions at the interfaces of the pipe flange connections with the gaskets were calculated under the measured axial bolt forces by using elasto-plastic finite element method (FEM) taking into account hysteresis and non-linearity in the stress-strain curves of the gaskets. The effects of the scatter in the axial bolt forces tightened by the torque control method on the gas leakage were also examined by using the actual pipe flange connections. As the result, a difference in an amount of gas leakage measured was found to be substantial between our study and PVRC procedure. By using the calculated contact gasket stress distributions under the internal pressure and the results of the leakage tests, the sealing performance was evaluated. It is found that the sealing performance is worse in the actual pipe flange connection than that evaluated by PVRC procedure.

Stress Analysis and the Sealing Performance Evaluation of Pipe Flange Connections With Gaskets Subjected to Internal Pressure and External Bending Moment: Effects of Scatter in Bolt Preload

2004 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Wataru Maezaki ◽  
Satoshi Nagata
Keyword(s):  
Finite Element Method ◽  
Internal Pressure ◽  
Control Method ◽  
Bending Moment ◽  
Torque Control ◽  
Stress Distributions ◽  
Gas Leakage ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Spiral Wound

It has been well known that a scatter in axial bolt forces of pipe flange connections tightened by the torque control method is substantial. It is necessary for evaluating the sealing performance of the pipe flange connections with the gaskets subjected to internal pressure and external bending moment to know the contact gasket stress distributions due to the scatter of the axial bolt forces in the connections tightened by the torque control method. This paper deals with the leakage of the pipe flange connections with a spiral wound gasket subjected to internal pressure and external bending moment tightened by the torque control method. The scattered axial bolt forces were measured in the experiments. The contact gasket stress distributions at the interfaces between pipe flanges and the gasket were calculated under the measured axial bolt force by using elasto-plastic finite element method (FEM) taking into account hysteresis and non-linearity in the stress-strain curves of spiral wound gasket. The effects of the scatter in the axial bolt forces tightened by the torque control method on the gas leakage were also examined by using the actual pipe flange connections under internal pressure and external bending moment. By using the calculated contact stress distributions and the results of the leakage tests, the sealing performance was evaluated. It is found that the sealing performance is worse in the actual pipe flange connection than that evaluated by PVRC procedure.

Stress Analysis and a Design Method for Bolted Pipe Flanged Joints Subjected to Internal Pressure

2009 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Takashi Kobayashi ◽  
Hirokazu Tsuji ◽  
Satoshi Nagata
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Stress Analysis ◽  
Contact Stress ◽  
Rational Design ◽  
Design Method ◽  
Load Factor ◽  
Stress Distributions ◽  
Element Analysis ◽  
Nominal Diameter

This paper deals with the stress analysis of a pipe flange connection with a spiral wound gasket using the elasto-plastic finite element method when an internal pressure is applied to the pipe flange connections with the different nominal diameters from 2″ to 20″. The effects of the nominal diameter of the pipe flange on the contact stress distributions at the interfaces and the hub stress are examined. Leakage tests of the pipe flange connections with 3″ and 20″ nominal diameters were conducted and measurement of the axial bolt force was also performed. The results by the finite element analysis are fairly consistent with the experimental results concerning the variation in the axial bolt force (Load factor). By using the contact stress distributions and the results of the leakage test, the modified gasket constants are proposed and compared with PVRC values. As a result, it is found that the variations in the contact stress distributions are substantial due to the flange rotation in the pipe flange connections with the larger nominal diameter. The hub stress has been overestimated by ASME method. In addition, a method to determine the bolt preload for a given tightness parameter and a rational design method for pipe flange connections are demonstrated.

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