Integrity And Sealing Influencing Factors Analysis Of Bolted Flanged Joint

Reorming unit high temperature flange was modeled to research the effects of bolt tightening sequence, steady-state and transient thermal coupling, pipeline external load on the strength and sealing performance.In addition, the energy consumption difference was analyzed between insulation structure and noninsulation structure and the importance of insulation structure was confirmed.The model considered material nonlinearity and gasket nonlinear compression-resilience characteristic. Based on spiral wound gasket, the difference under external load between SWG and MMC was analyzed.Sequentially loading and two kinds of cross loading mode was analyzed, the more loading step it needs, the more uniform of stress distribution. Cross loading that needs less loading step have higher efficiency. The larger diameter tend to have more uniform stress distribution. Bolt radial and circumferential bending was happened during loading.Heat loss difference of insulation and noninsulation structure was calculated according to the principle of heat transfer, based on the temperature distribution. Results was got that the insulation layer outer wall temperature was Close to the ambient temperature, illustrate it is reasonable. The insulation structure can save about30tons of standard oil than noninsulation structure, which indicate that rational insulation structure has important significance on enegy saving. The flange structure stress and angle increase after insulation, increasing the possibility of leakage. However,the structure can still meet the sealing requirements.Transient coupled analysis indicated that bolt, gasket and flange have different process of stress variable. Since closing to the inner wall of flange, the temperature of gasket change earlier than bolts.corresponding to the loading process, flange joint components’stress showed four key position of preload-pressure-the largest-stable. Due to the differents of time and change amount, comprehensive effects lead to gasket stress and closure exhibited lower-increase-decrease-stable trend.Pipeline flange stress analysis was calculated using CAESARII and strength and sealing analysis was calculated using ANSYS, which indicated that bolt bending aggravated, gasket inner stress reduced while outer stress increased, as a result, the possibility of leakage increased. The spiral winding gasket flange angle increased while the MMC gasket flange angle deceased, indicating that MMC gasket inner and outside ring limited the rotation of flange.