On the Use of Theory of Rings on Nonlinear Elastic Foundation to Study the Effect of Bolt Spacing in Bolted Flange Joints

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Tan Dan Do ◽  
Abdel-Hakim Bouzid ◽  
Thien-My Dao
Keyword(s):  
Elastic Foundation ◽  
Contact Stress ◽  
Large Diameter ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Linear Elastic ◽  
Circumferential Distribution ◽  
Bolted Flange ◽  
Nonlinear Elastic ◽  
Bolt Spacing

Bolted flange joints are extensively used to connect pressure vessels and piping equipment together. They are simple structures that offer the possibility of disassembly. However, they often experience leakage problems due to a loss of tightness as a result of a nonuniform distribution of gasket contact stresses in the radial and circumferential direction. Many factors contribute to such a failure; the flange and gasket stiffness and bolt spacing design combination being one of them. In our recent paper, the effects of bolt spacing were investigated based on the theory of circular beams resting on a linear elastic foundation (Do, T. D., Bouzid, A. H., and Dao, T.-M., 2011, “Effect of Bolt Spacing on the Circumferential Distribution of Gasket Contact Stress in Bolted Flange Joints,” ASME J. Pressure Vessel Technol., 133 (4), 041205). This paper is an extension of the work in which an analytical solution based on the real nonlinear gasket behavior is developed. This study focuses on the distribution of the gasket contact stress of two large diameter flanges, namely, a 52 in. and a 120 in. heat exchanger (HE) flanges. The nonlinear gasket behavior solution is compared to the Finite Element Analysis (FEA) and the linear gasket behavior solution for evaluation and comparison.

Development of a New Bolt Spacing Formula

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Tan Dan Do ◽  
Abdel-Hakim Bouzid ◽  
Thien-My Dao
Keyword(s):  
Elastic Foundation ◽  
Contact Stress ◽  
Compression Modulus ◽  
Pressure Vessels ◽  
Linear Elastic ◽  
Flange Thickness ◽  
Bolted Flange ◽  
Nonlinear Elastic ◽  
The Relationship ◽  
Bolt Spacing

Bolted flange joints are extensively used to connect pressure vessels and piping equipment together. They are simple structures that offer the possibility of disassembly. However, they often experience leakage problems due to a loss of tightness as a result of a nonuniform distribution of gasket contact stresses in the radial and circumferential directions. Many factors contribute to such a failure; the flange and gasket stiffness, bolt spacing or a combination of them are to name a few. In our recent papers, the effect of bolt spacing was investigated based on the theory of circular beams on linear elastic foundation and on the theory of rings on nonlinear elastic foundation. The variations of the contact stress between bolts were of a concern. This paper is an extension of the work in which an analytical solution, based on the theory of circular beams resting in a linear elastic foundation, has been developed to determine a formulae for flange bolt spacing. The relationship between bolt spacing, gasket compression modulus, and flange thickness is deduced from an analysis that considers a maximum tolerated gasket contact stress difference between any two bolts.

On the Use of Theory of Rings on Non-Linear Elastic Foundation to Study the Effect of Bolt Spacing in Bolted Flange Joints

2010 ◽  
Author(s):  
Tan Dan Do ◽  
Abdel-Hakim Bouzid ◽  
Thien-My Dao
Keyword(s):  
Heat Exchanger ◽  
Analytical Solution ◽  
Elastic Foundation ◽  
Large Diameter ◽  
Pressure Vessels ◽  
Linear Elastic ◽  
Linear Behavior ◽  
Non Linear ◽  
Bolted Flange ◽  
Bolt Spacing

Bolted flange joints are extensively used to connect pressure vessels and piping equipment together. They are simple structures that offer the possibility of disassembly. However, they often experience leakage problems due to a loss of tightness as a result of a non-uniform distribution of gasket contact stresses in the radial and circumferential direction. Many factors contribute to such a failure; the flange and gasket stiffness and bolt spacing design combination being one of them. In our recent paper the effects of bolt spacing was investigated based on the theory of circular beams resting on a linear elastic foundation [1]. This paper is an extension of the work in which an analytical solution based on the true gasket non-linear behavior is developed. The study focuses on the distribution of the gasket contact stress of two large diameter flanges namely a 52 and a 120 in heat exchanger flanges. The non-linear gasket behavior solution is compared to the FEA and the linear gasket behavior solution for evaluation and validation.

On the Development of a New Bolt Spacing Formula

2012 ◽  
Author(s):  
Tan Dan Do ◽  
Abdel-Hakim Bouzid ◽  
Thien-My Dao
Keyword(s):  
Elastic Foundation ◽  
Contact Stress ◽  
Compression Modulus ◽  
Pressure Vessels ◽  
Stress Difference ◽  
Linear Elastic ◽  
Flange Thickness ◽  
Bolted Flange ◽  
The Relationship ◽  
Bolt Spacing

Bolted flange joints are extensively used to connect pressure vessels and piping equipment together. They are simple structures that offer the possibility of disassembly. However, they often experience leakage problems due to a loss of tightness as a result of a non-uniform distribution of gasket contact stresses in the radial and circumferential direction. Many factors contribute to such a failure; the flange and gasket stiffness and bolt spacing design combinations being a couple of them. In our recent papers the effects of bolt spacing was investigated based on the theory of circular beams resting on a linear elastic foundation and based on the theory of ring on non-linear elastic foundation. The variations of the contact stress between bolts were of a concern. This paper is an extension of the work in which an analytical solution based on the theory of circular beams resting on a linear elastic foundation has been developed to determine flange bolt spacing. The relationship between bolt spacing, gasket compression modulus and flange thickness is deduced from an analysis that considers a maximum tolerated gasket contact stress difference between any two bolts.

Effect of Bolt Spacing on the Circumferential Distribution of the Gasket Contact Stress in Bolted Flange Joints

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Tan Dan Do ◽  
Abdel-Hakim Bouzid ◽  
Thien-My Dao
Keyword(s):  
Elastic Foundation ◽  
Contact Stress ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Element Model ◽  
Foundation Model ◽  
Load Increase ◽  
Maintenance Work ◽  
Bolted Flange ◽  
Bolt Spacing

Bolted flange joints are part of pressure vessel and piping components and are extensively used in the chemical, petrochemical, and nuclear power industries. They are simple structures and offer the possibility of disassembly, which makes them attractive to connect pressurized equipment and piping. In addition to being prone to leakage, they often require maintenance while in operation in which case the bolts are either retightened as in hot torquing or untightened to be replaced. Although costly shutdowns are avoided, such maintenance work exposes the operator to a potential risk because the bolt load alteration can produce a gasket load unbalance, which results in the local gasket contact stress to drop below some critical value, causing major leak and hence jeopardizing the life of the worker. This paper addresses the issue of the contact stress level unbalance around the flange when the bolts are subjected to initial tightening. The study compares the contact stress distribution variations, an analytical developed model based on the theory of rings on elastic foundation, to those given by the finite element model and the simple beam on elastic foundation model developed by Koves (2007, “Flange Joint Bolt Spacing Requirements,” Proceedings of PVP2007, ASME Pressure Vessel and Piping Division Conference). This study is developed for the purpose of helping limit the degree of load increase in hot torquing or the maximum number of bolts to be replaced at a time and identify those flanges for which the bolt cannot be replaced in service.

Effect of Bolt Spacing on the Circumferential Distribution of Gasket Contact Stress in Bolted Flange Jonts

2008 ◽  
Author(s):  
Tan Dan Do ◽  
Abdel-Hakim Bouzid ◽  
Thien-My Dao
Keyword(s):  
Contact Stress ◽  
Potential Risk ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Critical Value ◽  
Load Increase ◽  
Circumferential Distribution ◽  
Maintenance Work ◽  
Bolted Flange ◽  
Bolt Spacing

Bolted flange joints are part of pressure vessel and piping components and are used extensively in the chemical, petrochemical and nuclear power industries. They are simple structures and offer the possibility of disassembly which make them attractive to connect pressurized equipments and piping. In addition of being prone to leakage, they often require maintenance while in operation in which case the bolts are either retightened as in hot torquing or untightened to be replaced. Although costly shutdown are avoided, such a maintenance work exposes the operator to a potential risk because the bolt load alteration can produce a gasket load unbalance which results in a local gasket contact stress to drop below some critical value causing major leak and hence jeopardizing the life of the operator. This paper addresses the issue of the contact stress level unbalance around the flange when the bolts are subjected to bolt-up condition. This study is developed for the purpose of helping limit the degree of load increase in hot torquing or the maximum number of bolts to be replaced at a time and identify those flanges the bolt of which cannot be replaced in service.

A Novel Methodology to Optimize the Tightening Sequence in Bolted Flange Joints

2019 ◽  
Author(s):  
Linbo Zhu ◽  
Abdel-Hakim Bouzid ◽  
Jun Hong
Keyword(s):  
Experimental Tests ◽  
Elastic Interaction ◽  
Pressure Vessels ◽  
Successful Operation ◽  
Element Analysis ◽  
Bolt Preload ◽  
Safety And Reliability ◽  
Complex Structural ◽  
Leakage Failure ◽  
Bolted Flange

Abstract Bolted flange joints are the most complex structural components of pressure vessels and piping equipment. Their assembly is a delicate task that determines their successful operation during the service life. During bolt tightening, it is very difficult to achieve uniformity of the target bolt preload due to elastic interaction and criss-cross talk. The risk of leakage failure under service loading is consequently increased because of the scatter of the bolt preload. In previous work, an analytical model based on the theory of circular beams on linear elastic foundation was proposed to predict the bolt tension change due to elastic interaction. Based on this model, this paper presents a novel methodology for the optimization of the tightening sequence. The target preload and the load to be applied to each bolt in each pass can be calculated to achieve uniform final preload and avoid bolt tension reaching yield under a number of specified tightening passes. The validity of the approach is supported by experimental tests conducted on a NPS 4 class 900 welding neck flange joint and by finite element analysis on this bolted joint using the criss-cross tightening and sequential patterns. This study provides guidelines for bolted flange joints assembly and enhances its safety and reliability by minimizing bolt tension scatter due to elastic interaction.

Design-Focused Stress Analysis of Cylindrical Pressure Vessels Intersected by Small-Diameter Nozzles

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Faisal M. Mukhtar ◽  
Husain J. Al-Gahtani
Keyword(s):  
Shell Theory ◽  
Large Diameter ◽  
Small Diameter ◽  
Vessel Diameter ◽  
Theory Of Elasticity ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Overall Design ◽  
Design Charts ◽  
Thin Shell Theory

In a related work previously carried out by the authors, finite element analysis of cylindrical vessel–cylindrical nozzle juncture based on the use of thin shell theory, due to the fact that the intersecting nozzle sizes are moderate to large, have been presented. Such analysis becomes invalid in cases when the nozzles are small in sizes which may result in nozzles whose configuration violates the validity of shell assumption. As a result, use of solid elements (based on theory of elasticity) in modeling the cylindrical vessels with small-diameter nozzles is presented in the present paper. Discussions of the numerical experiments and the results achieved are, first, given. The results are then compared with the prediction by other models reported in the literature. In order to arrive at the overall design charts that cover all the possible ranges of nozzle-to-vessel diameter ratio, the charts for the vessels with moderate-to-large-diameter nozzles are augmented with those of cylindrical vessels intersected by small-diameter nozzles developed in this work.

On the Effect of External Bending Loads in Bolted Flange Joints

2007 ◽  
Author(s):  
Abdel-Hakim Bouzid ◽  
Yves Birembaut ◽  
Hubert Lejeune
Keyword(s):  
Analytical Model ◽  
Contact Stress ◽  
Analytical Approach ◽  
Bolted Joint ◽  
Acceptable Solution ◽  
Sealing Performance ◽  
Circumferential Distribution ◽  
Bending Loads ◽  
Minimum Stress ◽  
Bolted Flange

Most current flange design methods use an equivalent pressure to treat bolted flange connections subjected to external bending loads. This oversimplified approach together with the lack of a proper assessment of the actual affected tightness make these methods inadequate for modern flange design. The substitution of the external applied moment by an equivalent pressure is excessively conservative and not realistic since it assumes that the achieved tightness is that of a gasket unloaded entirely to a minimum stress whereas in reality only a small section of it is, the rest of it is actually at a much higher stress. The successfulness of a valid analytical approach in yielding to an acceptable solution resides in its ability to account for the circumferential distribution of the gasket contact stress and its effect on leakage. This paper presents an analytical model based on the flexibility of the flange to treat flanges subjected to bending loads such as those produced by external moments and misalignments and capable of integrating leakage around the gasket circumference. The bolted joint sealing performance in the presence of such loads is evaluated using the new PVRC gasket constants Gb, a and Gs obtained from ROTT tests. The analytical results including leakage predictions are validated by comparison to those obtained numerically by FEA and experimentally on different size flanges. The over-conservatism of the equivalent pressure is demonstrated.

Numerical and Experimental Study of Elastic Interaction in Bolted Flange Joints

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Linbo Zhu ◽  
Abdel-Hakim Bouzid ◽  
Jun Hong
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Elastic Interaction ◽  
Element Model ◽  
Interaction Coefficient ◽  
Pressure Vessels ◽  
Nonlinear Finite Element ◽  
Element Analysis ◽  
Bolted Flange

Bolted flange joints are widely used to connect pressure vessels and piping equipment together and facilitate their disassembly. Initial tightening of their bolts is a delicate operation because it is extremely difficult to achieve the target load and uniformity due to elastic interaction. The risk of failure due to leakage and fatigue under service loading is consequently increased. This paper presents a study on the effect of elastic interaction that is present during the tightening of bolted flange joints using three-dimensional nonlinear finite-element modeling and experimentation. The nonlinear nonelastic behavior of the gasket is taken into account in the numerical simulation. The scatter in bolt preload produced during the tightening sequence is evaluated. Based on the elastic interaction coefficient method, the initial target tightening load in each bolt for every pass is determined by using the nonlinear finite-element model to obtain a uniform preload after the final tightening pass. The validity of the finite-element analysis (FEA) is supported by experimental tests conducted on a NPS 4 class 900 weld neck bolted flange joints using fiber and flexible graphite gaskets. This study provides guidance and enhances the safety and reliability of bolted flange joints by minimizing bolt load scatter due to elastic interaction.

Leakage analysis of bolted flange joints considering surface roughness: A theoretical model

2017 ◽  
Vol 232 (2) ◽  
pp. 203-233 ◽  
Author(s):  
Benben Ma ◽  
Fan Jin ◽  
Zhi Sun ◽  
Xu Guo
Keyword(s):  
Surface Roughness ◽  
Theoretical Model ◽  
Three Dimensional ◽  
Element Analysis ◽  
Low Leakage ◽  
Theoretical Predictions ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Bolted Flange ◽  
Bolt Spacing

In the present paper, a theoretical model for leakage analysis of bolted flange joints without gaskets, which can take the surface roughness into consideration, is proposed based on percolation theory. In this model, Persson’s rough contact theory is employed to predict the height of the critical constriction along the percolating path. Based on this model, a criterion of maximum allowable bolt spacing is also suggested to guarantee a low leakage rate. The reasonable agreement between the theoretical predictions and detailed three-dimensional finite element analysis results verifies the validity and usefulness of the proposed theoretical model.

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