Study On Dynamic Sealing Components Of Butterfly Valve And Its Sealing Performance

Nowadays,Chinese valve industry is developing rapidly and has a bright future,especially butterfly valves,which have unique advantages in pipeline control and are widely used in various fields such as national production and life.However some valves often fail because of their complex structure,complex working conditions and frequent opening.Therefore,it is necessary to study and analyze the components with frequent butterfly valve faults,improve the reliability of butterfly valves,reduce the cost of manufacturing and using butterfly valves,promote Chinese economic development,improve the quality and performance of our valve products and realizing valve technology innovation.In this thesis,the butterfly valve is taken as the research object.And specifically conducts finite element static stress analysis on the main seal and stem seal of its dynamic seal components,and conducts the following work on the failure and sealing of the butterfly valve in the service process:(1)Aiming at the problem of hard seal valve sealing failure due to the wear of the sealing surface,the Archard theory is used,and the contact of the sealing surface is simulated with the help of finite element software.Taking the O-shaped hard seal with the initial extrusion amount of 0.08mm as an example,the contact pressure of sealing surface under different wear depths is simulated and solved step by step by using the discrete calculation method,calculate the contact pressure and penetration of the sealing surface under different wear depth,and analyze the wear trend and wear life of the sealing surface.It is calculated that the total service life of the valve can reach 5855 times of opening and closing.By comparing the service life of seal pairs under different initial interference,it is found that the design of seal structure is more reasonable when the initial interference is 0.08 mm.(2)In order to explore the sealing performance of the main seal structure of butterfly valve more truly and accurately,according to the wear model in Chapter 3,the finite element model of the main seal structure with different wear states is established and simulated in ANSYS.The research shows that the wear of sealing surface is severe before the wear depth reaches 0.04mm,and leakage will occur after the wear depth reaches 0.07mm.By analyzing the sealing pressure on the sealing surface,it is found that the sealing pressure on the downstream side is larger than that on the upstream side,and the setting of the valve plate truss is beneficial to improve the sealing pressure on the sealing surface.When the wear depth is 0.08mm,the leakage will be about 1.47×10-3 m3/s.(3)In order to study the influence of different packing assembly conditions on the sealing performance of valve stem packing seal structure,the stress of the seal structure was analyzed by ANSYS finite element analysis software,and verified by mechanical theory.The results showed that when the clearance was set on the inner and outer sides of packing seal,the pressure at the bottom of packing with clearance will decrease sharply,which was not conducive to valve stem sealing.When the inner and outer sides of packing seal are designed with interference,the overall reduction trend of the seal contact pressure changes smoothly.By comparison,it is found that the whole contact stress distribution of packing is the most uniform when the same interference is set on the inner and outer sides,which is beneficial to improve the sealing performance of valve stem packing seal structure.