Research On Design Method Of Large-sized Double-cone Seal Structure

Carrying out the scale economy is an effective way to reduce the cost for petrochemical enterprises, so large-sized chemical equipment is inevitable trend of industrial development. The sealing problem of large-sized high pressure equipment has been a key technology need to be solved. Double-cone seal structure has dominant application in the high pressure seal structures due to its good general seal performance. To the double-cone seal structure, the China National Criteria of "GB150-1998" has application scope: the inner diameter of pressure vessel is from 400mm to 2000mm. Therefore, it is very necessary to study the seal mechanism and establish the design method for the large-sized double-cone seal structure (the inner diameter of pressure vessel is larger than 2000mm).Funded by the National Science and Technology Support Project (2006BAK04A02-02), this paper studied the design method for the large-sized double-cone seal structure in theory, numerical simulation and experimentation, discussed the applicability of "GB150-1998" for the design of large-sized double-cone seal structure and put out the modified proposal. The main works were as follows:(1) Research on influence factors of the sealing performance of double-cone seal structure. Influence factors include medium pressure, radial gap, dimension of double-cone ring, width of sealing surface, contact status of sealing surface, pre-tightening force.(2) Established the FEA model and solution algorithm for the double-cone seal structure. Numerical simulation of sealing process was conducted using the nonlinear contact algorithm. Numerical simulation results have good agreement with experimental data, which indicates that FEA model and solution algorithm established by the paper was reliable.(3) Numerical simulation and research on the design method for large-sized double-cone seal structure. Numerical simulation of sealing process for large-sized double-cone seal structure under internal pressure was conducted using the FEA model and solution algorithm established in the work of (2). The stress distribution of double-cone ring and gasket under pre-tightening and working conditions were obtained, respectively. The relation curves of gasket stress vs pre-tightening force, gasket stress vs internal pressure, stain of double-cone ring vs pre-tightening force, stain of double-cone ring vs internal pressure, radial gap vs pre-tightening force and radial gap vs internal pressure were also obtained. If the radial gap was designed by g=(0.1%-0.15%)D₁, the material of double-cone ring would happened the global yielding. Meanwhile, If the radial gap was designed by g=0.05%D₁, the sealing performance in the pressing process could not ensured. After the research above, the paper concluded that the design method of large-sized double-cone seal structure could refer to "GB150-1998" except that the radial gap was advised to designed by g=(0.075%-0.1%)D₁, furthermore, the paper brought forward the propositional value of structure dimension for large-sized double-cone ring. (4) Numerical simulation of steady state thermal-structure coupling. Numerical simulation of sealing process for large-sized double-cone seal structure under internal pressure and thermal load was conducted. The stress distribution of double-cone ring and gasket and the relation curves of gasket stress vs internal pressure under the steady state thermal-structure coupling field were obtained. Compared with the calculation results of (3), the paper concluded that temperature hardly affected the stress distribution of structure and the sealing performance.