Research And Optimization On Sealing Performance Of Hard Seal Fixed Ball Valve

With the continuous development of global industrialization,the demand and use of valves are increasing.Ball valve is widely used in petroleum,coal chemical industry and other industries with the advantages of simple operation,quick opening and closing,small flow resistance and high sealing performance.Therefore,the sealing performance of ball valve is an important factor to ensure production safety.High temperature,high pressure and wear are the common characteristics of hard seal fixed ball valve,which puts forward higher requirements for sealing performance.At present,domestic high-performance,large-size hard seal fixed ball valve is in the research and development stage,mainly relying on imports.Therefore,improving its sealing performance has become an important research direction.The NPS16 CLASS600 hard seal ball valve in the ball valve research and development project of an enterprise in Wenzhou is taken as the research object.According to the valve design criteria,the overall structure and size are determined,and the design specific pressure on the sealing surface and the necessary specific pressure on the sealing surface are calculated.The model of ball valve is established by SolidWorks,and the finite element software ANSYS Workbench is used to analyze the strength and sealing condition of valve body,sealing pair and ball valve under pressure and sealing test and normal working condition.The variation trend of contact stress during the opening and closing process of seal pair under various working conditions was studied.The influence of structure size and manufacturing process on the sealing performance is analyzed,and the structure optimization is carried out on the premise of meeting the sealing requirements.Finally,the pressure and seal tests of the ball valve prototype are carried out and compared with the simulation results.Through the combination of simulation and experimental test,the strength and sealing performance of the ball valve are verified.The simulation results show that the valve body and cover meet the strength requirements of each design condition,but there is a risk of leakage in the high temperature condition.The results show that the contact stress of the sealing surface in the process of opening and closing can meet the use requirements,and the change trend of the contact stress in the process of opening and closing is opposite.The research shows that the manufacturing process has a significant effect on the improvement of sealing performance.The smaller the roughness of the sealing surface is,the better the sealing performance is;the spraying coating has a significant improvement on the sealing performance,and the sealing effect is the best when the coating thickness of this structure is 0.22 mm.A total of 10 structural parameters,such as the diameter of the ball,the radial thickness and the axial length of the valve seat,are analyzed,and the structural optimization of the valve seat size parameters is carried out by using the response surface optimization method and the multi-objective genetic algorithm.The results show that increasing the radial thickness and decreasing the axial length of the valve seat are beneficial to improve the sealing performance;after optimization,the mass of the valve seat is reduced by 1.89%,the deformation is reduced by 23.07%,and the opening degree of the sealing surface is reduced by 71.34%.Finally,the shell test and sealing test of the designed ball valve prototype are carried out,and the results show that the strength and sealing performance of the ball valve meet the requirements of relevant standards.