Study On Pivoting Torque Of High-pressure Gas Injection Isolation Valve For Nuclear Power

High-pressure gas injection isolation valve is a control equipment in pressure releasing pipeline of security protection system for some kind of nuclear power plants, which is used to release pipeline pressure in the accident situation and ensure the safe operation of the nuclear power plant. The valve in a domestic nuclear power was in fault that the valve can not open within the prescribed time, after some vulnerable parts such as valve seat were replaced. It was determined that the cause of valve fault is that replacement of spare seat led to excessive pivoting torque. It is understood that the analysis methods of pivoting torque for such valves and the impact of valve seat to pivoting torque are not clear in China's nuclear power business, because such valves and valve seats produced by foreign enterprises. Based on the above background, this thesis has studied the analysis methods of pivoting torque for such valves and the impact of valve seat to pivoting torque. The main research work and the results obtained are as follows:(1) Compression mechanical properties, time effect of compression mechanical performance, friction performance and time effect of friction properties of two types of POM seat material have been tested, and the performance of different types of seat materials has been analyzed comparatively, and the seat material properties have been provided to numerical simulation. It has been found that the mechanical properties between two kinds of seat materials are a little different, and there is time effect of mechanical performance. The friction properties between two kinds of seat materials are almost consistent, and there is time effect of friction performance.(2) The finite element model of contact between the ball and seat has been established, pivoting torque for the valve and the impact of valve seat to pivoting torque have been calculated,and analysis methods of pivoting torque for the valve has been confirmed. The results show that, because of time effect of compression mechanical performance and friction properties, pivoting torque for the valve can increase with the extension of load time. Material properties and structural dimension of the seat affect the pivoting torque for the valve by influencing the force between the seat and ball. In the export side seat tightness condition, the affection to pivoting torque of structural dimension of the seat is main, and the influence to pivoting torque of material performance is limited; In the entrance side seat tightness condition, the influence to pivoting torque of both material performance and structural dimension of the seat are significant.(3) Test equipment and test methods for pivoting torque of the valve have been designed. By using the method of experimental test, pivoting torque and pre-tightening force of the valve have been tested. And the reliability of the numerical simulation has been verified. Test results show that, in the constant load conditions, there is time effect of pivoting torque for the valve, pivoting torque for the valve increasing with the extension of load time. Test results are closed to simulation results highly, which has testifies simulation results are accurate. The test equipment and test methods can be used to assess the reliability of spare seat, which is of great significance.