Dynamic Characteristic Of Bolted Flanged Sealing System

During petrochemical production, the performance of bolted flange joint sealing is directly related to the long-period operation of mechanical structure. As production cycles are getting longer, process conditions are more and more strict, leakage problem caused by gasket sealing failure is becoming obvious. It is necessary for joint to monitor and test the tightness.Bolted flange connection is the main connection form in the process equipment and piping. If the connection structures are under operating conditions affected by medium pressure, additional load and vibration environment, there dynamic characteristics will change and gasket leakage is the main reason for the failure of structure. When the joint is under operating conditions, there will be the stress relaxation and bolt force is reduced. So the gasket stress will be reduced and sealing performance will become worse. Therefore, theres is a close contact between the structural characteristic and sealing performance of joint, and it is great significant to analyze the relationship between the sealing and dynamic of joint.To ensure the structural integrity and sealability, focusing on the sealing mechanism, experiments and finite element method are carried out on bolted flange joint (BFJ) with metal-to-metal contact type (MMC) in this paper. Determining the qualitative and quantitative relation between the sealing and vibration characteristics, provides feasibility for on-line test of joint.In this paper, the finite element analysis (FEA) of modal analysis, random vibration analysis and the experimental modal analysis (EMA) are made on joint through ANSYS and vibration analyzer. Changes of joint caused by bolt loosening can be reflected be dynamic parameters, which can predict the sealing will be obtained.The results show that with the decrease of the bolt force of BFJ with MMC, first order spectral moment factor takes on the characteristics of the first increase and then decrease, the turning point of which corresponds to the flange joint to metal to metal contact corresponding bolt force, and in the BFJ with MMC, metal to metal contact is the sufficient condition to guarantee the joint sealing. Therefore, the first order spectral moments factor can be used to test and control the sealing performance of BFJ with MMC.