The Numerical Simulation Of Large-scale High-pressure Container Bipyramid Sealing System

To improve the benefit of device, large-sized development of petrochemical equipment is an inevitable trend, but also has brought new challenges on the pressure vessel industry. In order to facilitate the installation, maintenance and transportation, pressure vessels are equipped with a certain number of static sealing detachable connection structures, the bolt-flange-gasket static sealing connection structure are used most widely. Double-cone seal structure is used commonly in high temperature and pressure, large-sized pressure vessel due to simple structure, easy manufacturing and good sealing performance. As for a double-cone seal structure, the Chinese criteria of "GB150-1998" applies only in the 400～2000mm diameter cylinder, but the double-cone seal structure of large-sized (cylinder diameter greater than 2000mm) high pressure vessel appeared leakage and seal failure due to the cylinder end expansion during the process of design and manufacture. Therefore, the double-cone seal structure of large-sized and high-pressure vessels, the research in seal performance and structural strength has a practical significance.As the rapid development of computer technology, the linear or nonlinear finite element analysis method is commonly used in bolt-flange-gasket static sealing connection structure. The sealing process of the double-cone seal structure under the conditions of pre-tightening and operation (internal pressure) was simulated by using the finite element analysis software, and the influence factors of double-cone sealing performance and the failure reasons of structural strength were also researched. The main researches and achievements are as follows:(1) Design of large-sized double-cone seal structure. The design method of inner diameter 2000mm double-cone seal structure was analyzed. The program of large-sized double-cone seal structure was designed according to the Chinese criteria of "GB150-1998". The double-cone seal structure with parameters of 1800～3000mm diameter was designed by the program. The model for research on the sealing performance and structural strength of the large-sized double-cone seal structure was provided.(2) Research on the sealing performance and structure strength of the double-cone seal structure. The sealing mechanism of double-cone seal structure was analyzed. The influence factors of the sealing performance of double-cone seal structure were researched including medium pressure, radial gap, self-compactness factor of double-cone ring, pre-tightening force. The load distribution of the cylinder end under pre-tightening load and operation load conditions was analyzed, and the load relationships were obtained. The stress check method of the cylinder end was researched, and the relation curves of outer edge length were obtained.(3) Numerical simulation of sealing process for double-cone seal structure. The 3D FEA model was established, and the numerical simulation of sealing process under pre-tightening load and operation load conditions for the double-cone seal structure for 1800～3000mm diameter. The stress distribution of double-cone ring and gasket under pre-tightening load and operation load conditions were obtained. The relation curves of double-cone ring stress VS radial gap were also obtained. When the double-cone ring material is 20MnMo, if the radial gap was designed by g≥0.088%D1, the double-cone ring would happened global yielding. Therefore the radial gap was advised to be designed by (0.05%～0.088%)D1. Under the pre-tightening condition, the designed pre-tightening force could meet the demand of pre-tightening sealing pressure, and the lower gasket stress was greater than the upper. Under the working condition, the gasket stress with the rise of pressure to a minimum value then began to rise, and the upper gasket stress was greater than the lower. The radial gap was designed by (0.05%～0.088%)D1, the gasket stress were greater than the operation of sealing pressure in the whole working process, the sealing performance was good. The double-cone ring self-compactness factor 2 was appropriate to take together, and the increase of the self-compactness factor could add the gasket stress.(4) The numerical simulation of cylinder end of the double-cone seal. The three-dimensional finite element model of the cylinder end was established, the numerical simulation of the load response of cylinder end under pre-tightening load and operation load conditions was made, and the relation curves of cylinder end stress VS outer edge length and bolt load were also obtained.