| Tightness of high temperature pipeline flange connection system is the key issue to ensure the long-term safe operation of the high temperature equipment and pipes. However, there is no overall and systematic method on the tightness analysis and evaluation of high temperature flange connection system. The research was launched in the tightness analysis and evaluation method of high temperature bolts and flange connection system.High temperature characteristics of 25Cr2 MoVA and 15 CrMo were investigated by chemical composition analysis, high temperature tensile test, high temperature creep test at 500℃. Analyze the experimental data, the Young’s modulus and creep constitutive equations of 25Cr2 MoVA and 15 CrMo at 500℃ was expressed. The compression resilience characteristic of flexible graphite corrugated metal gasket was studied, and the compression resilience characteristics were detailed analyzed by fitting and summarizing the creep data. The research on the fundamental characteristics of bolt, flange and gasket material provided foundation for the study on tightness.Tightness analysis model of high temperature bolted-flange connection system based on deformation compatibility was proposed. The flange deflection angle was analyzed from three aspects, which are bending moment, internal pressure, creep. Finally the tightness of flange was evaluated through the total deflection angle based on ASME standard. The gasket stress and compression of flexible graphite corrugated metal gasket was calculated. The tightness of flange was evaluated through the gasket stress based on sealing requirements. Integrated the results of total angle and gasket stress tightness assessment, an safety operation time of high-temperature flange connection system was given.The finite element model of bolted flanged connection system was established through ANSYS, and the heat-structure coupling analysis of flange-bolt-gasket connection system was launched. The strength of bolt and flange was evaluated based on JB4732 standard, the sealing of gasket was evaluated through gasket compression force, the stiffness of flange was assessed combined with stiffness requirements given by ASME VIII-1 standard. In a word, the tightness evaluation of bolted flanged connection was given finally.Theoretical analysis model of bolted flange connection with disk spring was built. A disc spring number calculating method based on designed life and the other method based on decreased the relaxation by a certain percentage were given, which provided theoretical basis for the application of disc springs in engineering and make it more normative.A detection device of pipe flange leakage rate and a leakage monitoring device for high-temperature flange connection were proposed. A detection method of surface stress, leakage, deflection angle on flange was given. It provided a control method for the long period safe operation of high-temperature flange connection. |
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