Pipe Flange Research Articles

805 NiTi合金製ガスケットを用いたフランジ締結体の密封性能に及ぼす温度の影響(フランジガスケット締結体の力学と密封性能評価I)

805 NiTi合金製ガスケットを用いたフランジ締結体の密封性能に及ぼす温度の影響(フランジガスケット締結体の力学と密封性能評価I)

Numerical simulation of mechanical stress relieving in a multi-pass GTA girth welded pipe–flange joint to reduce IGSCC

Welding of piping components produces highly non-uniform residual stresses in the weldment which consequently affect material structural response under loading and also expedite origination/propagation of defects such as stress corrosion cracking and brittle fracture. For welding-induced residual stresses, mechanical stress relieving (MSR) is one of the mitigation techniques to improve the service life of pressure vessel components. However, its application to piping systems is rarely reported in the literature. This paper presents a two-dimensional axisymmetric finite element model of a pipe–flange joint subjected to a multi-pass girth welding followed by an MSR process. Sequentially coupled non-linear transient thermo-mechanical analysis for multi-pass gas tungsten arc welding is first performed to calculate welding residual stresses. Subsequently separate parametric studies for three different types of MSR load including internal pressure, external pressure and axial pull are performed on the pre-stressed model, and stress relieving behaviour is studied. It is concluded that both the internal pressure and axial pull have a significant effect on residual stresses on the inner surface of the joint.

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.

Structural strength: Gasketed vs non-gasketed flange joint under bolt up and operating condition

This paper presents results of an experimental study of the behaviour of the stress variation at the flange of a gasketed and non-gasketed flanged pipe joints during both the bolt up (pre-loading) and operating (internal pressure loading) conditions. Stress variations showing flange yielding, flange rotation, effects of joint tightening sequence, identification of the mode of response to loading (static or dynamic) is discussed. In addition the effects of re-tightening, importance of high quality bolting with proper surface treatment and use of proper tooling are also discussed.

Numerical simulation of the effect of constraints on welding deformations and residual stresses in a pipe–flange joint

This paper presents a detailed three-dimensional finite element (FE) study to investigate the effect of mechanical constraints on welding distortions and residual stresses in a pipe–flange joint. The FE model of a pipe–flange joint is subjected to sequentially couple nonlinear transient thermo-mechanical analysis to simulate complex welding phenomena. Single-pass gas metal arc welding for single ‘V’ butt-weld joint geometry of a 100 mm diameter pipe with compatible weld-neck ANSI flange class #300 of low carbon steel is simulated. Two tack-welds at 90° and 270° from the weld start position are modelled. Four different constraint conditions representing the welding of unassembled joints, welding of assembled joints, welding of assembled joints with reflective symmetry and welding of perfectly constrained joints are analysed. To model the constraints and boundary conditions more realistically contact pairs are used between the matching surfaces of different structural components. Basic FE models are validated with experimental data for temperature distribution and deformations. Predicted welding distortions and residual stresses are compared and discussed in detail. From the results, axial displacement and tilt of the flange face are found to be strongly dependant on the constraint conditions. Minimum axial distortion on the flange face is found for rigidly clamped flanges. However, residual stresses have a weak dependence on the constraints set.

Prediction of welding distortions and residual stresses in a pipe–flange joint using the finite element technique

This paper presents a comparative study of three- and two-dimensional axisymmetric finite element (FE) analyses of a welded pipe–flange joint for residual stresses and deformations in order to identify their merits or demerits. Sequentially coupled thermal stress analysis is performed to simulate single pass metal inert gas welding. Butt weld geometry with a single ‘V’ for a 100 mm nominal diameter pipe and same sized weld neck type ANSI class #300 flange is used. The heat input is modelled by using the Goldak double ellipsoidal heat source model. Temperature dependent material properties are used and deposition of filler metal is obtained by element birth and death feature. Both thermal and structural FE models are validated with experimental measurements. Residual stresses predicted by two-dimensional model are generally on the higher side and hence more conservative. However, we conclude that the three-dimensional FE model is preferable for the prediction of flange face distortion since it is a vital parameter for flange joint performance.

Determination of Gasketed and Non-gasketed Flanged Pipe Joint’s Capacity Subjected to Combined Loading: An Experimental Approach

This paper presents details of an experimental set up for the determination of a flanged pipe joint’s capacity subjected to singly and combined loading. Most international codes and design standards have rules based on internal pressure loading only and a little or no consideration is given to the loads acting in combination. The main aim of this experimental setup is the performance testing of both gasketed and non-gasketed flange pipe joints subjected to singly and combined loading i.e. internal pressure plus axial plus bending in different combinations. A test rig is designed and manufactured and details of design, strain gauging, instrumentation, calibration and assembly of different parts used in test rig are presented and discussed. Results for strains on bolts and test rig under application of combined loading observed are also presented.

FEM Stress Analysis and Sealing Performance Evaluation in Pipe Flange Connections with Spiral Wound Gaskets Subjected to External Bending Moments (Case where Internal Fluid is Liquid)

The leakage evaluation when gas is used is more severe than that when liquid is used in pipe flange connections. In a practical design, it is also necessary to examine the leakage in the connections under liquid internal pressure application. The contact gasket stress distributions in the connection with a spiral wound gasket subjected to internal pressure and bending moment were analyzed by using elasto-plastic finite element method (FEM) taking account hysteresis and nonlinearity in the stress-strain curve of the gasket. The effects of the initial clamping bolt force (bolt preload), the nominal pressure and the nominal diameter of the pipe flange and the equivalent pressure on the contact gasket stress distributions were examined. The leakage tests for the connections under the bending moment and the internal pressure were also conducted by using liquid (water). By using the results of the leakage tests and the calculated contact gasket stress distributions, the sealing performance of the connections was evaluated. It was found that the sealing performance of the connection can be estimated when liquid (water) was used. In addition, a method for determining the bolt preload in the connections under the bending moments was proposed for the reliable design.

120 ボルト締付け荷重と内圧を受ける配管フランジ構造部の漏れ特性(材料力学IV)

120 ボルト締付け荷重と内圧を受ける配管フランジ構造部の漏れ特性(材料力学IV)

615 内圧を受けるフランジ締結体におけるNiTi合金製ガスケットの密封性能評価(OS2-3 フランジガスケット締結体の力学と密封性能評価,OS2 フランジガスケット締結体の力学と密封性能評価3)

615 内圧を受けるフランジ締結体におけるNiTi合金製ガスケットの密封性能評価(OS2-3 フランジガスケット締結体の力学と密封性能評価,OS2 フランジガスケット締結体の力学と密封性能評価3)

618 接着併用管フランジ締結体に内圧と曲げモーメントが作用する場合の密封特性(OS2-3 フランジガスケット締結体の力学と密封性能評価,OS2 フランジガスケット締結体の力学と密封性能評価3)

618 接着併用管フランジ締結体に内圧と曲げモーメントが作用する場合の密封特性(OS2-3 フランジガスケット締結体の力学と密封性能評価,OS2 フランジガスケット締結体の力学と密封性能評価3)

Sealing Performance of Pipe Flange Connections

In these environmentally sensitive times, it is very important to reduce the amount of gasses released into the environment from pipe flange connections. The design procedure in which the tightness of the joint is used as a design parameter, therefore, must be established for the pipe flange connection. In this study, sealing performance of the pipe flange connection is examined by conducting both the finite element simulation taking account of nonlinear stress-strain relationship of the gasket and the leakage test using nitrogen gas. The analytical objects are the pipe flange connections with the compressed asbestos sheet gasket, in which the gasket width and flange thickness are varied for the purpose of changing the amount of flange rotation. It is concluded that the leak rate of the pipe flange connection largely depends on the maximum gasket contact stress remained when the internal fluid is pressurized. The validity of the axisymmetric finite element model of the pipe flange connection is also demonstrated by comparing numerical and experimental results of the flange rotation angle.

620 管フランジ締結体の応力緩和特性と有限要素解析(OS2-4 フランジガスケット締結体の力学と密封性能評価,OS2 フランジガスケット締結体の力学と密封性能評価3)

620 管フランジ締結体の応力緩和特性と有限要素解析(OS2-4 フランジガスケット締結体の力学と密封性能評価,OS2 フランジガスケット締結体の力学と密封性能評価3)

Surface sensitivity study of non-gasketed flange joint

From analytical contact pressure studies of gasketed and non-gasketed flanged pipe joints, it is known that good contact maintained over consistently large areas occurs in a no-gasketed flange joint compared with a gasketed joint, where contact is only on the seal ring portion of the gasket. However, the presence of contact pressure and a good flange surface finish does not in itself eliminate the problem of leakage. Rather, it is the surface flatness in combination with contact pressure and surface finish that is necessary to generate effective contact at the inside diameter of the flange. This occurs providing there are no gaps due to deformation arising from the welding process to the mating pipe as flow is proportional to gap height. However, the question remains as how to ensure adequate surface flatness as non-gasketed flange surfaces are sensitive to damage, which may be present in the form of surface deformation, scratches and dents or bulges. A detailed experimental study is therefore carried out to measure the surface finish and surface flatness post manufacture and welding of such flanges. Results of actual flanges were compared with solid circular plates of the same dimension with inserted shims to provide gaps in order that flow rate/gap height ratio be studied. Manufacturing issues with respect to monitoring and controlling deformations are discussed and recommendations are suggested for flange redesign, appropriate welding approaches and manual handling of non-gasketed flanges.

Bolt-Up Guideline for Pipe Flange Connections

Numerical simulations are systematically executed for pipe flanges with wide variety of nominal size by using finite element analysis, which can simulate the bolt-up process of a pipe flange connection. Effects of the gasket modeling method on the bolt-up simulation and the bolu-up procedure which can prevent open up deformation are evaluated. It is indicated that the simplified linear modeling of gasket, in which two different Young's moduli are used in loading and unloading, is valid for estimating the variations, of mean bolt preloads during bolting up operations. The bolt-up procedure, in which four bolts located 90 degrees apart each other are tightened uniformly with the target bolt preload at the installation process, is effective to prevent the open up deformation. Finally, the methodical guideline for bolt-up operation of pipe flange connections with joint sheet gasket or spiral wound gasket is proposed.

501 管フランジの応力および変形解析ソフトウェアの開発(フランジガスケット締結体の力学と密封性能評価)

501 管フランジの応力および変形解析ソフトウェアの開発(フランジガスケット締結体の力学と密封性能評価)

Stress Analysis and Sealing Performance Evaluation of Pipe Flange Connections under Internal Pressure (Effects of Scatter in Bolt Preloads)

The effects of scatter in bolt preloads of pipe flange connections with gaskets subjected to internal pressure are examined. The scatter in the bolt preloads tightened by a torque wrench 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 bolt preloads using elastoplastic 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 bolt preloads on the gas leakage were also exmained using actual pipe flange connections. As the result a difference in an amount of measured gas leakage was found to be substantial between our study and PVRC (ASME) procedure. By using the calculated contact gasket stress distributions in the connections under the internal pressure and the results of the leakage tests, the sealing performance was evaluated. The effect of the scatter in the bolt preloads is found to be substantial on the leakage. It is found that the sealing performance is worse in the actual pipe flange connection than that evaluated by PVRC procedure. The tightening efficiency was proposed taking account the leakage due to the scatter in bolt preloads.

551 接着-ガスケット併用管フランジ締結体の密封性能 : ガスケット幅およびハブが密封性能に及ぼす影響(接着接合の力学)

551 接着-ガスケット併用管フランジ締結体の密封性能 : ガスケット幅およびハブが密封性能に及ぼす影響(接着接合の力学)

Effects of The Clamping Force Scatter on The Bolting-Up Performance of Pipe Flange Connections

Effects of The Clamping Force Scatter on The Bolting-Up Performance of Pipe Flange Connections

503 温度変動下での管フランジ締結体の熱応力解析と密封性能評価(フランジガスケット締結体の力学と密封性能評価)

503 温度変動下での管フランジ締結体の熱応力解析と密封性能評価(フランジガスケット締結体の力学と密封性能評価)