Analysis Of The Tightness Of Flange Connection System With Flexible Graphite Covered Wave-serrated Metal Gaskets And Operating Time Forecast

Flange connection structure has been widely used in petroleum,petrochemical,electric power,metallurgy and other industries due to its simple structure and convenient disassembly.With the increase of world energy demand,oil refining and chemical technology are developing rapidly,the process conditions of which became progressively complex.Conditions such as high temperature,ultralow temperature,high pressure and high vacuum generally exist in various refinery equipment.The application of various strong corrosive,rank poisonous,flammable and explosive media is progressively common,thus the requirements for sealing technology are more and more strict.Nevertheless,traditional sealing technology cannot fully meet the requirements of the development of modern technology.The weak sealing of flange connection is a major style of the failure of pressure equipment,which likely leads to disastrous accidents.Bolt flange connection system achieves sealing mainly by increasing the resistance to the leakage of media through the gasket compression deformation.In order to ensure a good initial sealing between the surface of the flange and gasket during prestressing,the gasket needs good compression performance.In order to ensure the tightness of the connection system,the gasket is also required to have excellent rebound performance.This study tests and analyses the compression resilience of graphite wave tooth composite gasket at both room temperature and high temperature,which lays the foundations of the further researches of mechanical behavior of joint system and prediction of leakage rate.This study adopts the finite element simulation method to simulate and analyse the pipe flange connection system under the influence of high temperature and external bending moment,the stress field distribution of each component in which is analysed in detail.Considering the influence of thermal stress and creep on the connection system,the effect of external bending moments on the tightness of the connection system is analysed.The variation pattern of gasket compression force over time is obtained from the analysis,which lays the foundation for the prediction of the safe operating time of the connection system.The sealing performance of bolted flanged connections is studied.the relationship between graphite metal gaskets pressing force and leakage rate is analysed according to the gasket leakage rate,through which the leakage rate formula of the graphite corrugated metal gasket.Based on the US PVRC classification of the tightness degree of the flange connection system as well as the provisions of the domestic gasket standard on the leakage rate index,this study attempts to define the safety level of the flange connection system based on the leakage rate.Combining the gasket compression resilience curve,gasket sealing performance of bolted flanged connection formula and the results of finite element simulating of bolt flange gasket connection system,the connection system safety operating time is concluded as a prediction method based on the tightness analysis,which performs as a powerful tool in order to improve the reliability of bolted flanged connection system as well as its side devices and further ensure its security work.