The Fundamental Mechanical Characteristics Evaluation for Bolted Pipe Flange Connections With RTJ Gaskets Under Internal Pressure

2019 ◽  
Author(s):  
Kenshiro Nakade ◽  
Koji Sato ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Contact Stress ◽  
Inflection Point ◽  
Mechanical Characteristics ◽  
Design Method ◽  
Leak Rate ◽  
Bolt Preload ◽  
Higher Temperature ◽  
Sealing Mechanism ◽  
Better Than

Abstract Bolted pipe flange connections with metallic flat gaskets or ring type joint (RTJ) gaskets are used under higher pressure and higher temperature. However, a sealing mechanism is not known and a design method is not established how to determine bolt preload for preventing leakage from the connection with metallic gaskets. In addition, the characteristics of the connection are not known when oval and octagonal gaskets are used. In previous paper, when the contact stress of metallic flat gasket reaches the stress at plastic deformation inflection point, the leak rate is decreased rapidly. However, the leak rate could be measured up to 1.0 × 10−5 Pa · m3/s level. The objectives of the paper are to measure the leak rate of the metallic flat gasket of which the contact stress is over the stress at plastic deformation inflection point, and to measure the leak rate of 1.0 × 10−9∼10 Pa · m3/s level in the flat metallic gasket in the platen tests and the connection with RTJ gaskets. In addition, the characteristics of the connection are examined when oval and octagonal gaskets are used. As a result, it is found that the leak rate for the metallic flat gasket can be measured around 1.0 × 10−9∼10 Pa · m3/s in the platen tests when the contact stress of aluminum gasket reaches the stress at plastic deformation inflection point and more while the leak rate of SUS 304 flat gasket is around 1.0 × 10−7∼8 Pa · m3/s even if the contact stress is over 1.3 times of the stress at plastic deformation inflection point. In addition, the sealing characteristics of the connection with oval gasket are shown to be better than that with octagonal gasket. From a laser microscope observation, it is found that the contact area of oval gasket in the connection is smaller than that of octagonal gasket in the connection.

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 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.

Sealing Performance Evaluation in Bolted Flange Connections With Ring Joint Gasket Subjected to Internal Pressure

2013 ◽  
Author(s):  
Koji Kondo ◽  
Koji Sato ◽  
Toshiyuki Sawa ◽  
Shota Tsubaki ◽  
Yuya Omiya
Keyword(s):  
Plastic Deformation ◽  
Performance Evaluation ◽  
Metal Ring ◽  
Stress Distributions ◽  
Ring Type ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Higher Temperature ◽  
Sealing Mechanism ◽  
Bolted Flange

Bolted flange connections with ring type joint gaskets have been used to seal the inner fluid under higher pressure and higher temperature conditions when soft gaskets cannot be used in the connections. However, few researches on the characteristics and the sealing performance evaluation for the bolted flange connections with metal ring gasket have been conducted. Therefore, assembly procedures and tightening methods of the connection with ring type joint gaskets is empirically and not fully elucidated. It is important to know the characteristics such as the contact gasket stress distribution which governs the sealing performance prediction, the sealing performance and the sealing mechanism in the bolted flange connections for determining optimum tightening methods and the bolt preload. In this paper, the differences of the sealing performance for the bolted flange connections (3″) by the re-use octagonal and oval type ring gaskets are examined. In the FEM calculations the contact gasket stress distributions and the range of plastic deformation are examined and the sealing mechanism is discussed. It is found that the basic sealing mechanism is caused by the plastic deformation at the contact area of the gasket. In addition, the leakage tests for the bolted flange connections with the nominal diameter of 20″ with the octagonal ring type joint gaskets being inserted are conducted, where the bolt tightening for the connection is carried out according to both ASME PCC-1 and JIS B2251, respectively. Using these results, the optimum tightening methods for the connection with ring type joint gaskets are discussed.

Physical and Mechanical Properties of Mo5X3+α (X=Si, B, C) Single Crystals

2002 ◽  
Vol 753 ◽  
Author(s):  
Taisuke Hayashi ◽  
Kazuhiro Ito ◽  
Katsushi Tanaka ◽  
Masaharu Yamaguchi
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Single Crystals ◽  
Plastic Anisotropy ◽  
Physical And Mechanical Properties ◽  
Structure Type ◽  
Advanced Materials ◽  
Anisotropy Ratio ◽  
Higher Temperature ◽  
Better Than

ABSTRACTMo5X3+α (X=Si, B, C) intermetallic compounds such as Mo5SiB2 (D8l), Mo5Si3 (D8m) and Mo5Si3C (D88) have a great potential for ultra-high temperature applications. The present study was undertaken putting greater emphasis on clarifying how their physical and mechanical properties are similar or different in terms of a structure type. Some interesting features are summarized in this paper.The resistivity of Mo5SiB2, Mo5Si3 and Mo5Si3C single crystals exhibited a negative curvature (d2ρ(T)/dT2<0), with a tendency towards saturation. In the Mo5Si3C with large ρ0 due to impurity carbon atoms, resistivity saturation is pronounced. In contrast, a much higher temperature is required to reach saturation in the Mo5SiB2. The anisotropy ratio of CTE (αc/αa) for the Mo5SiB2 is about 1.2–1.6 and is significantly reduced from about 2 of the Mo5Si3 and Mo5Si3C. On the other hand, the Young's modulus of the Mo5SiB2 is more anisotropic than those of the Mo5Si3 and Mo5Si3C. Plastic anisotropy was observed in the Mo5SiB2, because only slip on [001] {100} is operative at 1500°C. On the contrary, plastic deformation was observed at temperatures above 1300°C for the Mo5Si3C and Mo5Si3. Anisotropy of their plastic deformation was much less than that of the Mo5SiB2, presumably because more than two slip systems can be activated. Creep resistance of the Mo5SiB2 is much better than that of the Mo5Si3 as well as the most advanced materials such as MoSi2 and Si3N4 based structural ceramics.

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.

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.

Reliability Design Method for Interference Joint in Mechanical Engineering

2008 ◽  
Vol 44-46 ◽  
pp. 773-778
Author(s):  
Shi Chao Xiu ◽  
Q. Feng ◽  
Shi Qiang Gao
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Contact Stress ◽  
Mechanical Engineering ◽  
Design Method ◽  
Reliability Design ◽  
Machining Precision ◽  
Joint Structure ◽  
Main Form ◽  
Practical Design

The plastic deformation as a main form of failure of Interference Joints may happen in engineering works if it is designed unreasonably. In this paper, the contact stress and the strength of Interference Joint parts were analyzed deeply. Based on the theory of the reliability design, the general formulas and the method of the reliability design and computation for Interference Joint were established in consideration of joint structure, machining precision, interference value, mechanical properties of the joint parts and their randomicity. The practical design method, which would promote the reliability of Interference Joint effectively, was proposed for larger size and some other important Interference Joints. Compared to the conventional design method, the working reliability of Interference Joints can be improved obviously by means of the reliability design method.

Stress Analysis and Sealing Performance Evaluation in Bolted Flange Connections With Ring Joint Gasket Subjected to Internal Pressure

2012 ◽  
Author(s):  
Koji Kondo ◽  
Shota Tsubaki ◽  
Toshiyuki Sawa ◽  
Koji Sato ◽  
Yuya Omiya
Keyword(s):  
Performance Evaluation ◽  
Metal Ring ◽  
Stress Distributions ◽  
Pressure Condition ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Metal Metal ◽  
Higher Temperature ◽  
Sealing Mechanism ◽  
Bolted Flange

Bolted flange connections with ring joint gaskets have been used to seal the inner fluid under higher pressure and higher temperature condition when soft gasket cannot be used in the connection. The ring joint gaskets are assumed that they can seal inner fluid by the metal-metal contact between the ring joint gasket and the grooves of flanges under higher pressure condition. However, no research on the characteristics and sealing performance evaluation for the bolted flange connections with metal ring gasket has been conducted. Therefore, assembly procedures and tightening methods of the connection with ring joint gaskets is empirically. It is important to know the characteristics such as the contact gasket stress distribution, the sealing performance and the sealing mechanism in the bolted flange connections for determining optimum tightening methods and the bolt preload. In this paper, the leakage tests for the bolted flange connections (3″) with the octagonal ring joint gaskets are conducted. Measuring the leak rate of inner fluid from the connections using the pressure drop method, the sealing performance of the connections with the ring joint gaskets is evaluated. In addition, using the 3-D FEM stress calculations, the gasket contact stress distributions for the connections with the octagonal ring joint gaskets are examined. Using these results, the optimum bolt preload of the connection with octagonal ring joint gaskets are discussed. Furthermore, the leakage tests for the bolted flange connections (20″) with the octagonal ring joint gaskets are conducted in the case where the bolt tightening is carried out according to both ASME PCC-1 and JIS B 2251, respectively. The optimum tightening methods for the connection with octagonal ring joint gaskets are discussed.

Finite-Element Analysis of Contact Stress at the Bearing Surfaces in Bolted Joints (Effect of Flange Bolt Shape and Dimensions)

2019 ◽  
Author(s):  
Atsushi Shirakawa ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Contact Stress ◽  
Contact Area ◽  
Permanent Deformation ◽  
Bolted Joints ◽  
Bearing Surface ◽  
Element Analysis ◽  
Bolt Preload ◽  
Stress And Deformation ◽  
Critical Contact

Abstract A higher bolt preload is desirable for higher integrity of bolted joints. However, the bearing surface in the joints could be permanently deformed under a higher preload and the bolt preload decreases with an increase of permanent deformation. Various materials are used as clamped parts, so the permanent plastic deformation should be examined for each material clamped parts. In addition, the critical contact stresses should be examined for various clamped materials. In the previous paper, it was found that the relationship between the contact stress when the plastic deformation initiated, and the compressive proof stress of the clamped parts is linear. However, this conclusion was due to the specific bolt shape and dimensions. In the present paper, the effects of shape and dimensions of bolt head on the contact stress and deformation are examined. This applies to normal and undercut type bolts with sloped bearing surfaces. FEM calculations were used and the clamped part materials were steel and aluminum alloy. Also, a new contact area ratio at the bearing surface is defined and investigated because the nominal contact area is different from the actual contact area when the bolt bearing surface is sloped. Finally, discussion is made on an appropriate contact area, and critical contact stress at the bearing surface as well as suitable bolt shape and bolt head dimensions.

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.

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