The Research On Design Method Of Large Diameter Flange Sealing At High Temperature

Based on theoretical analysis and finite element calculation, the influence of rigidity of flange on sealing characteristic was done in the paper, in which the design method of sealing with tightness as a guideline was modified .Based on structure simplified and deformation assumption, moment equilibrium equation and deformation compatibility equation were obtained. The stress and deformation of sealing system were calculated with finite element method, and the relationship between the residual stress of gasket and the diameter of flange was discussed. The calculating method for rigidity of A-type socket-weld flange, B-type socket-weld flange and welding neck flange were put forward. The influences of nominal pressure, nominal diameter and temperature on rigidity were studied, the functional relationships of them were multiple linear fitted. Sealing characteristic was studied with ROTT test method, the results were contrast verification with theory of seal. The design method of sealing with tightness was introduced, considering the influence of the flange rigidity on seal, the method was modified.The results showed: the flange would deflect and warpage, which caused the inhomogeneity of gasket stress. The radial stress of outer end was much compacter than internal end, while the circumferential stress was relatively uniform. It showed that flanges existed problems of deficient stiffness, while the number of bolts were enough. A-type socket-weld flange could only be used under lower pressure for its rigidity was small; B-type socket-weld flange was fit for large-size situation as its rigidity was relatively larger; the welding neck flange's stiffness was the largest which could endure highest pressure because of the awl-shaped neck. The functional relationships among flange rigidity and the three parameters were fitted with the form of C= f₁ (PN, DN) f₂ (T). During the research on sealing performance of gaskets, the new coefficients were determinate to be Gb=2.92MPa,a=0.362,Gs=0.143MPa. The rigidity concept was introduced to the sealing method with tightness, and the method was modified with a correction coefficient namedΦwhich equaled to (C/[C])^1.92, the design constant Tc was modified to beΦTc.The sealing design of some type of a reactor was done under different levels of tightness .The concept of tightness was introduced into selecting gist of equipment flange . The level of tightness was added as one of standards for flanges selecting. The requirement of gasket's character was put forward from aspects of design coefficient and menufacture.