Effects of adjusting ring and spring stiffness on fluid dynamics of steam spring-loaded safety valve

As the most typical direct-loaded safety valves, spring-loaded safety valves are automatically opened by fluid pressure. Their stable and reliable dynamic characteristics are vital for overpressure protection in nuclear power plants. Notably, the adjusting ring structure and the spring, as important components affecting the dynamic characteristics of the valve, are among the easiest way to adjust and replace. Dynamic numerical simulation method is employed to analyze the effect of adjusting ring height and spring stiffness on the valve dynamic characteristics. This study investigates the effect of the upper and lower adjusting rings heights on dynamic characteristics and highlights the unbalanced moment created by the angular structure of valve during opening and closing processes. The superiority of graphical method is revealed by comparing three spring stiffness calculation methods for steam spring-loaded safety valve - the lift formula method, the structural parameter method, and the graphical method. When the graphical method is combined with the lift formula method, a more accurate range of spring stiffness can be determined for a particular spring-loaded safety valve.