Metal Bellows Expansion Joints Research Articles

The Effects of Convolution Geometry and Boundary Condition on the Failure of Bellows

Bellows have wide applications in automobile, aerospace, piping systems and industrial systems. An optimised shape for the bellows is expected to give good guidelines for practical design. Metallic bellows expansion joints are subject to displacement loading, this frequently results in cyclic strains. The effects of convolution geometry and boundary conditions on the failure of bellows are analysed in this study. Lateral deflection is considered as a boundary condition and a FEM solution for bellows is obtained. The stress distribution and the number of cycles to failure in the conditions of lateral deflection are obtained. Comparing results, the relation between the number of load cycles to failure and the flexible tube radius is obtained. In addition, the relation between stress and boundary conditions for the model in this study is also obtained.

Analysis of Expansion Joints Movement Test in FCC Unit

The turboexpander is an equipment that works under very critical conditions requiring very low allowable nozzle forces and moments. A solution to minimize the piping loads transmitted to the equipment is the use of expansion joints (EJ). A usual piping stress analysis normally is not enough to guarantee the turboexpander reliability. This paper shows the results obtained in a movement test realized on metallic bellows EJ used in a turboexpander piping system. The EJ were designed according to the expansion joints manufacturer association code (EJMA), the diameters range from 0.457 to 2,898 m, the material of the bellows is Inconel 625 LCF and the shell materials are “killed” carbon steel, for refractory lined EJ or stainless steel 304H. A special test device was developed to apply the design movements on the EJ at the factory. A digital dynamometer was used for data acquisition and the tests were performed on 16 EJ of two distinct types: hinged and gimbal. The EJ were pressurized with water during the test. The reactions and corresponding displacements for each step of the test were recorded during loading and unloading.

Development of a CAD/CAPP Integrated System for Metal Bellows Expansion Joints

To meet the requirements of improving design efficiency and decreasing technique mistakes in the enterprise whose productions are customized by users, a method is introduced to develop CAD/CAPP integrated system. The functions of the integrated CAD/CAPP system developed according to this method include 3D modeling automatically assembled, 2D engineering drawing automatically drawn, process planning sheets automatically filled and parameters of key parts checked and optimized. This method is based on adding special features to the 3D modeling. An example CAD/CAPP integrated system of Metal Bellows Expansion Joints (MBEJ) is developed by using VisualBasic6.0 based on SolidWorks platform. This system can design MBEJ part parameters per GB/T12777 standard. These parameters have been used to generate MBEJ 3D models, engineering drawings and processing planning sheets automatically. All the functions have been integrated in SolidWorks software environment. The drawing paper and processing planning sheets can be modified manually to satisfy special demand.

Determination of Gimbal and Hinged Expansion Joints Reaction Moments

This paper proposes a method to estimate the actual reaction loads in gimbal and hinged metal bellows expansion joints. Friction and some media pressure forces, which are not considered in current Expansion Joint Manufactures Association (EJMA) standard calculations, are added to bellows spring rate to estimate the expansion joint movement reaction moment. The proposed calculation method is based upon pressure and movement tests of large size expansion joints.

THE EFFECT OF GEOMETRY ON FATIGUE LIFE FOR BELLOWS

A bellows is a component installed in the automobile exhaust system to reduce or prevent the impact from engine. Generally, the specifications on the bellows are determined in the system design process of exhaust system and the component design is carried out to meet the specifications such as stiffness. Consideration of fatigue is generally an important aspect of design on metallic bellows expansion joints. These components are subject to displacement loading which frequently results in cyclic strains. This study has been investigated to analyze the effect of geometry on fatigue life for automotive bellows. 8 node shell element and non-linear method is employed for the analysis. The optimized shapes of the bellows are expected to give good guidelines to the practical designs.

Fatigue of bellows, a new design approach

Consideration of fatigue is generally an important aspect of the design of metallic bellows expansion joints. These components are subject to displacement loading which frequently results in cyclic strains well beyond the proportional limit for the material. At these high-strain levels, plastic strain concentration occurs. Current design practice relies on use of empirical fatigue curves based on bellows testing. Prediction of fatigue behavior based on the combination of analysis and polished bar fatigue data is not considered to be reliable. One of the reasons for the unreliability is plastic strain concentration. It is shown that the difference between bellows and polished bar fatigue behavior, as well as the difference between reinforced and unreinforced bellows, can be largely attributed to this strain concentration. Further, it is shown that fatigue life of bellows can be better predicted by partitioning the bellows fatigue data based on a geometry parameter.

B31.3 Appendix X Rules for Expansion Joints

Abstract In 1988, ASME B31.3 added Appendix X containing requirements for Metallic Bellows Expansion Joints into the Chemical Plant and Petroleum Refinery Piping Code. These have been revised and improved in subsequent addenda to the Code. This paper describes some of the salient features of this Appendix, as well as the revisions and the background behind them.

Simplified Dynamic Analysis Methods for Metallic Bellows Expansion Joints

An investigation into dynamic characteristics and seismic response of bellows expansion joints is described. For axial and lateral vibrations of the bellows, simplified methods are developed to evaluate their natural frequencies and seismic response, based on analogies with those of a uniform rod and a Timoshenko beam, respectively. For the lateral vibration modes, effect of fluid-structure interaction between the convolutions and flow-sleeve is taken into account. The validity and applicability of the simplified methods are shown, by comparing with the results of vibration experiments using a simple bellows model and a piping model with bellows, along with corresponding detailed FEM analyses’ results.