Larger Nominal Diameter Research Articles

内圧作用下における大口径管フランジ締結体のFEM応力解析及び密封性の評価

内圧作用下における大口径管フランジ締結体のFEM応力解析及び密封性の評価

内圧を受ける大口径 (20B) リングジョイントガスケット付き管フランジ締結体の有限要素法応力解析と密封性能評価

内圧を受ける大口径 (20B) リングジョイントガスケット付き管フランジ締結体の有限要素法応力解析と密封性能評価

Elasto-Plastic FEM Stress Analysis and Mechanical Characteristics of Pipe Flange Connections with Non-Asbestos Gaskets under Internal Pressure

The effects of the nominal diameter of pipe flange connections with non-asbestos spiral wound gaskets(SWG) under internal pressure on the mechanical characteristics such as the contact gasket stress distribution which governs the sealing performance, the load factor and the hub stress of the connections were evaluated. The stresses in the connections with the nominal diameters from 3” to 24” under internal pressure are analyzed using the elasto-plastic(EP) FEM analysis taking account the hysteresis and non-linearity of deformation behavior of the non-asbestos SWG. As a result, it is found that the variations in the contact gasket stress distributions are substantial due to the flange rotation in the connections with the larger nominal diameter. Leakage tests were conducted to measure the axial bolt forces (the load factor) and the hub stress. The results obtained from the EP-FEM analyses are fairly consistent with the experimental results concerning the variation in the axial bolt forces (the load factor) and the hub stress. Using the obtained contact gasket stress distributions and the fundamental relationship between the amount of leakage and the contact gasket stress, the amount of the leakage of the connections is estimated. It is observed that the sealing performance of the connections with larger nominal diameter is worse than that of the connection with smaller nominal diameter because of the flange rotation. The estimated results are in a fairly good agreement with the measured results. The difference in the hub stress between the EP-FEM and ASME code is demonstrated and the differences in the load factor and the sealing performance of the connections are shown between the asbestos and non-asbestos gaskets.

S112034 軸直角振動による小ねじのゆるみについて : ゆるみ実験装置([S11203]機械要素の設計・製造・応用技術(3))

There are many causes that the bolted joints be loosed in use. A lot of researches have been carried out on the self-loosening of bolt under transverse vibration. The cause of loosening due to nut rotation in bolted joints is the spiral shape of screw thread. For a machine screw of JIS, the proportion of screw thread is larger than the minor diameter of the external thread. Thus, the self-loosening of machine screw is thought to be different from the screw with large nominal diameter. And form of use of machine screw is different from the screw with large nominal diameter. However, only few researches have been reported on the loosening of machine screw under transverse vibration. In this paper, fabrication of experimental apparatus examining the self-loosening of machine screw under transverse vibration and experimental results showed, and loosening load discussed according to the behaviors of the bolted joints using FEM calculations.

604 ボルト軸力のばらつきがガスケット付き大口径フランジ締結体の密封性能に及ぼす影響(フランジガスケット締結体の力学と密封性能評価I)

604 ボルト軸力のばらつきがガスケット付き大口径フランジ締結体の密封性能に及ぼす影響(フランジガスケット締結体の力学と密封性能評価I)

808 内圧を受ける大口径管フランジ締結のFEM応力解析と密封性能評価 : ボルト初期締付け力のばらつきの影響(OS8-2 フランジガスケット締結体の力学と密封性能評価)

808 内圧を受ける大口径管フランジ締結のFEM応力解析と密封性能評価 : ボルト初期締付け力のばらつきの影響(OS8-2 フランジガスケット締結体の力学と密封性能評価)

OS0511 内圧を受ける大口径フランジ締結体のFEM解析および漏洩評価 : ボルトのばらつきの影響(OS05-03 フランジ締結体の密封性能評価,OS05 フランジガスケット締結体の力学と密封性能評価)

本研究では,内圧を受ける20インチフランジ締結体のボルト初期締め付け力のばらつきの影響について調べた.ガスケットの応力-ひずみ曲線のヒステリシスおよび非線形性を考慮した有限要素解析法によりガスケット接触応力分布を算出し,実際に実験を行うことでトルク管理法におけるボルト初期締め付け力のばらつきとその影響による漏洩量を測定し,両者の結果を比較検討した.その結果,ボルト軸力管理法に比べてトルク管理法(ASME法,HPIS法)ではいずれもボルト軸力がばらつき,目標ボルト締め付け力に達しないことが示された.

New solution for the discharge of a plunger gate for development of stop and balanced fittings

A principally new design for the discharge of a plunger gate is developed. The discharge gate makes it possible to lower the force of the drive, reduce weight and clearance characteristics, and increase the speed of response, and at the same time, enhance the smoothness and accuracy of the regulation of stop and balanced valves in pipeline systems, especially those of large nominal diameter and high nominal pressure.

New Development in Studies on the Characteristics of Bolted Pipe Flange Connections in JPVRC

This paper deals with some studies carried out in the bolted flanged connection committee (BFC) in Japan Pressure Vessel Council (JPVRC) on the stress analysis of a pipe flange connection using the elastoplastic finite element method. The characteristics of the connections with the different nominal diameters from 2in. to 20in. such as the contact gasket stress distribution, the hub stress, and the load factors were examined. The results from the finite element analyses were fairly consistent with the experimental results concerning the variation in the axial bolt force. By using the contact stress distributions and the results of the leakage test, the new gasket constants were evaluated. As a result, it was found that the variations in the contact stress distributions were substantial due to the flange rotation in the pipe flange connections with the larger nominal diameter. A method to determine the bolt preload for a given tightness parameter was demonstrated and the difference in the bolt preload between our research and PVRC was shown. In addition, the characteristics of pipe flange connection under a bending moment and internal pressure were also discussed and a newly developed bolt tightening method was demonstrated.

Potential of using Hydrocyclone and Hydrocyclone equipped with Grit pot as a pre-treatment in run-off water treatment

The large nominal diameter Hydrocyclone process and the new process, Hydrocyclone equipped with Grit pot, were tested as a pre-treatment for run-off water. Many operational parameters such as inlet pressure, feed concentration and type of suspension solid were varied to study their performances. Both processes showed high efficiency in terms of solid separation and cutting diameter while the Hydrocyclone equipped with Grit pot has a very high concentration and low volume sludge compared to the classical Hydrocyclone process. Moreover, the advantage of the Hydrocyclone equipped with Grit pot was clearly demonstrated by comparing with the classical sedimentation tank.

Evaluation of the Method for Lowering Stress Concentration at the Thread Root of Bolted Joints With Modifications of Nut Shape

Many studies have been devoted to investigate how the maximum stress occurred in the bolted joint could be reduced. Patterson and Kenny suggest that a modified nut with a straight bevel at the bearing surface is effective. However, they only dealt with M30, and estimations on the nut geometry had not been necessarily sufficient. In this study, an extensive finite element approach for solving general multi-body contact problem is proposed by incorporating a “regularization method” into stiffness matrices with singularity involved; thus, numerical analyses are executed to accurately determine the optimal shape of the modified nut for various design factors. A modified nut with a curved bevel is also treated, and it is concluded that the modified nuts are significantly effective for bolts with larger nominal diameter and fine pitch, and are practically useful compared to pitch modification and tapered thread methods.

Evaluation of the Method for Lowering Stress Concentration at the Thread Root with Modifications of Nut Shape.

In a bolted connection, failures usually initiate at the root of the first bolt thread where the maximum stress occurs. Patterson and Kenney have conducted a comprehensive study for reducing the maximum stress using a 3-dimensional photo-elastic method, and they suggested that a modified nut with straight bevel at the bearing surface was very effective. However, they only dealt with M30 and estimations on the geometry of the modified nut had not been necessarily sufficient. Consequently, it is considered that numerical analyses are needed to determine the optimal shape of the modified nut and to accurately estimate how much the modified nut could reduce the maximum stress for various design factors. In this paper, a numerical approach for multibody contact problem with FEM is proposed by incorporating a regularization method into stiffness matrices to avoid the singularities involved and the validity of the modified nut is investigated as elastic contact problems using the FEM. It is concluded that modified nuts are significantly effective for bolts with large nominal diameter and fine pitch and are practically useful compared with pitch modification and tapered thread methods.