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Unpredictable and uncertain failure of the bellows needs the attention of the designer toward maximum meridional deflection stresses generated on the U-shaped convolutions. Evaluation of these maximum stress points on the flexible convolutions is multifaceted. This paper deals with the identification of these stresses induced on the bellows convolutions by analytical and experimental methods. Further, the influence of the pivotal design parameters on meridional deflection stresses is studied mainly in two aspects: (1) effect of number of convolutions (N) and pitch diameter (d p) on the meridional deflection stresses and (2) the determination of the optimized design parameters to reduce the stress levels using effective multi-response gray relational grade (GRG) optimization technique. Three bellows of stainless steel material (Grade SS321) are used for the experimentation with a different number of convolutions (N) and pitch diameters (d p). The optimal design parameter setting is found by using GRG analysis through ANOVA and regression mathematical model. The effect of design factors on GRG is analyzed. Besides, using GRG, the regression model enhances to give alternative optimal solutions; in turn, it increases the designer's choice for the selection of the parametric levels. In the confirmation test, it is seen that the average improvement in GRG for all selected Taguchi orthogonal runs is 23%.

Metal expansion bellows are a mechanical device for absorbing energy or displacement in structures. It is widely used to deal with vibrations, thermal expansion, and the angular, radial, and axial displacements of components. The main objective of this paper is to perform numerical analysis to find various characteristics of stresses in U-shaped metal expansion bellows as per the requirement of vendor and ASME standards. In this paper, extensive analytical and numerical study is carried out to calculate the different characteristics of stresses due to internal pressure varying from 1 MPa to 2 MPa in U-shaped bellows. Finite element analysis by using Ansys14 is performed to find the characteristics of U-shaped metal expansion bellows. Finally, the results of analytical analysis and finite element method (FEM) show a very good agreement. The results of this research work could be used as a basis for designing a new type of the metal bellows.

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Bellows Expansion joints are mostly linked with the piping connections of turbines, heat exchangers, process equipment’s etc. Its primary function is to absorb expansion and contraction in pipelines on which it is fixed and fulfill its functioning through peculiar springy shaped convolutions. At design stage, it is very difficult to guess fatigue life cycles due to evolved stresses in convolutions. When it is subjected to purely axial load, stress generation per convolution acting along longitudinal line is same; however the behavior is different under very small angular rotation and axial shift due to misalignments in structural mountings. To understand it, preliminary investigations on axial case is necessary and also to identify the location of various stresses in convoluted section. This work aims to determine the meridional and circumferential stresses on the convoluted shape when it is subjected to an axi-symmetric internal pressure loading. Experimentation is carried out to determine the maximum stresses and verified it with the help of numerical simulation and analytically. 10 convolution bellows is used for the experiments. It is observed that the meridional stresses are highly dominating the circumferential stresses along the same longitudinal line. Meridional membrane stresses and meridional bending stresses due to pressure are evaluated on two different locations, one on perfectly meridional line and another at the top surface of convolution along the same longitudinal line. The stresses found higher on the top surface of convolutions. Meridional membrane and bending stresses due to deflection are higher than the meridional membrane and bending stresses due to pressure. Evaluation of the maximum stresses is very helpful for the designers to develop the fatigue analysis model and exact prediction of the cycle life of the bellows.

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Process industries typically utilize bellows expansion joints (compensators), which offer both axial flexibility and circumferential strength on convolutions. These components are utilized in pipe structures as well as their connections to vital process equipment’s, such as boilers, fixed tube heat exchangers, pressure vessels, pressure relief equipment, pulsation dampeners, etc. The expansion-contraction operation of the compensators attached to the pipes produces different thrusts and stresses, rendering process equipment vulnerable to catastrophic failure if there is an axial misalignment or lateral offset in connection. For the purpose of maintaining structural integrity, it is essential to determine the meridian stresses generated on bellows compensator under various operating conditions. This study examines the quantitative effects of combined lateral shift and angular rotational misalignment on meridional stress levels for the heat exchanger shell bellows. Mainly the generation of the stresses on the U-shaped convolution profile is multifaceted and difficult to evaluate. An experimental setup has been designed to make it easier to see the combined angular rotation and offset at various levels and to improve evaluating the stress levels for analysis purposes. The paper presents the results pertaining to meridional deflection-based stresses. The analysis process signifies the assessment of structural integrity to enable designers to implement mitigating measures regarding the installation of bellows compensators and adequate support conditions.