Integrity Analysis Of Flange Joints Subjected To External Bending Moment At High Temperatures

The model DN300,PN100and corresponding fasteners, gaskets, sealing surfaces have been chosen from the standard of HG/T20295-2009, its strength and sealing performance under the high temperature and external moments have been analyzed. The details as follow:Firstly, the test of compression rebound performance of the stainless steel flexible graphite gasket has been done at high temperatures, and the stress-strain constitutive relationship has been obtained at the different temperatures.Secondly, the1/16model of flange joints has been analyzed by strength assessment and sealing assessment, withstanding the pre-load, pressure in the steady-state temperature field,the results show that there are more significant temperature gradient at the radial direction of the flange and gasket, the axial direction of the bolt. The greater the temperature gradient is, the greater the displacement produced, the greater the stress generated. The temperatures play a role in reducing the stress concentration.By analyzing the creep of the flanged joints, the results show that, the longer the time is, the more obvious the stress relaxation the bolt performs, the lower the bolt inside becomes but the higher the bolt outside becomes, the lower the stress of gasket becomes; when the creep time is l0000h, the flanged joints system still have the sealing performance.Thirdly,1/2model of flanged joints has been built to analyze the strength and sealing performance of the system which subjected to external bending moment at high temperatures, the results show that the strength assessment can be passed while the sealing assessment can not be passed with loads of pre-load102200N, pressure10.0Mpa, temperature573K and the moment5000N. The flange joints just can withstand moment3000Nm.Finally, the influence of combined loads on tensile stress, bending stress of bolt and the tightness of flange joints has been explored. The results show that, the greater the moment is, the greater the proportion of the bending stress in the tensile stress is, the lower the tightness of pulled side of flange is, the higher the tightness of pressed side of flange is; the higher the temperature is, the higher the tightness of both side of flange is, and the tightness of the pressed side of the flange is more obvious. Since the temperature will affect the creep, elastic modulus of material, so it is recommended that this flange joints can be used at temperature600K or lower. The results of simulation can be used as a reference for the design, production and utility of flange joints.