Abstract

Pressure vessels such as steam generators are subjected to high temperature, in addition to high pressure during the operating condition. Flanges and bolts are made up of different materials whose coefficient of thermal expansion varies. Usually, thermal expansion in bolts is greater than that of flanges. At elevated temperatures bolts expand more than that of flanges, resulting in decrease of compression in connected members achieved during assembly stage, which in turn decreases the contact stress in gasket. This can lead to leakage of internal fluid. The loss in gasket contact stress due to differential thermal expansion can be nullified by using sleeves of higher thermal expansion between the flange-nut and flange-bolt head interfaces. At higher temperatures sleeves expand more than bolts and flanges, pushing the flanges closer towards each other, thus decreasing gap created due to differential thermal expansion. The behaviour of gasketed blind flange joint with and without sleeves is analysed and the performances are compared under thermal loads. The non-linear behaviour of gaskets is included by specifying the loading and unloading characteristics with hysteresis.

Highlights

  • Flanged joints with gasket play a vital role in sealing the leakage phenomenon, in pressure vessels

  • Sleeves made of material with higher coefficient of thermal expansion are used between the nut-flange and bolt head-flange interface to compensate for the differential thermal expansion between bolts and flanges

  • There is a loss in gasket contact stress due to reduction of loads by applying pressure

Read more

Summary

Introduction

Flanged joints with gasket play a vital role in sealing the leakage phenomenon, in pressure vessels. The significance of gasket material behavior in the sealing performance of the joint is emphasized without including the internal fluid temperature. The effect of thermal loads on flange joint is analysed by considering the nonlinear behaviour of gasket material under loading and unloading condition. It has different responses under loading and unloading conditions. A special material model available in the commercial finite element software ANSYS is used, for characterizing the interface material behavior This model interpolates the required properties of the gasket at the intermediate loading and unloading points. The thermal expansion coefficient of gasket material is taken 11.7x10-6 m/m°C [8]

Joint Configuration
Material properties
Sleeves for compensating the expansion
Finite Element Modelling
Structural and thermal elements
Interface elements
Contact elements
Pretension elements
Thermal
Structure
Analysis Methodology
Temperature distribution
Gasket Stress
Bolt Stress
Conclusions
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.