Numerical Simulation And Analysis Of The Contact Stress Of The Sealing Surface Of A Fixed Ball Valve During The Opening And Closing Process

In recent years,ball valves have been widely used in coal chemical industry,aerospace,nuclear industry,transportation and other fields.The main reason is that ball valves have many advantages.Such as compact structure,easy operation,wide application range,and small flow resistance coefficient.The metal hard seal ball valve as a type of ball valve,because of their valve seats and balls on both sides of the sealing surface are of high hardness metal,so they can withstand high use pressure and temperature.At the same time,they have good sealability and wear resistance.So this type of ball valve can work in harsh conditions such as high temperature,high pressure,medium containing solid particles.In industrial production,there are also many problems with hard-seal ball valves.The main problem is that during the opening and closing process of the ball valve,the local contact stress between the sealing surfaces leads to the wear of the spherical surface and the valve seat sealing surface,which leads to the failure of the seal and causes the ball valve to leak.At present,for this problem,the main research direction at home and abroad is to improve the sealing structure and improve the wear resistance of the sealing surface material.Friction and wear are less studied by analyzing contact surface contact stress and friction mechanism.At the same time,because it is difficult to use the experimental method to measure the contact stress,it is very important to use the software simulation method to analyze the contact stress and friction shear stress between the contact surfaces.In this paper,the finite element analysis software and the nonlinear contact theory are used to simulate the contact stress of the hard seal ball valve in the process of opening and closing.The main research contents are as follows:Taking the CLASS900 three-piece hard-seal ball valve as the research object,the three-dimensional model of the hard-seal ball valve was established through Solidworks software.The mathematical equation was established by combining the three-dimensional model,and the change trend of the contact area between the sealing surfaces of the ball valve during opening and closing of the ball valve was obtained.The ball valve opening angle corresponding to the minimum value of the theoretical contact area was 68.90°.Using the transient dynamics module in the ANSYS Workbench software,contact stress calculations were performed on the opening and closing process of hard-sealedball valves without media.The distribution law of contact stress and the maximum contact stress during the opening and closing of the ball valve when no medium is used are obtained.The ball valve opening angle corresponding to this stress is 75° and the closing angle is 15°.The maximum contact stress values are close to each other in the opening and closing process,and the distribution laws are symmetrical to each other.The dynamic mesh analysis module was used to simulate the change of the fluid pressure in the opening and closing process of the ball valve.The change in fluid pressure at both ends of the high pressure side seat was obtained.By superimposing the media force and the valve seat pretreatment force,the changing trend and magnitude of the total load of the valve seat during the opening and closing process of the ball valve are obtained.The transient dynamics analysis module of ANSYS Workbench software was used to analyze the changing trend of the contact stress between the sealing surfaces of the ball valve during the opening and closing of the ball valve under the normal temperature conditions.The distribution law of contact stress during ball valve opening process under normal temperature and medium conditions is obtained.The law is similar to that without medium.The maximum value corresponds to the opening angle of 78° and the closing angle of 12°.Taking a constant temperature condition of 300°C as an example,the change in the contact stress during the opening and closing process of the ball valve under high temperature load was analyzed.The change law of the contact stress in the open and close process of the hard seal ball valve under high temperature and medium conditions is obtained.The change law is similar to that at room temperature,and the maximum contact stress corresponds to an opening angle of 77° and a closing angle of13°.