IMPROVING A VALVE PACKING MODEL TO INCREASE PACKING LIFETIME IN MOLTEN SALT

Valves used in molten salt thermal energy storage systems often utilize conventional packing methodology and materials. These packing materials often exhibit relatively short lifetimes because of the reactive interaction of the salt and packing. Past research has indicated that valve packing lifetime is affected by both stress and temperature in the packing. Because of this interaction, it is important to understand the stress in the packing and to find ways to reduce the packing stress. A finite element model of a valve stem/packing system was created and material properties of the packing were determined and validated against previous work. The model was then used to evaluate the stress induced in the packing system through linear axial motion and then extended to include rotational stem motion as well. The analysis confirmed previous results that axial translation created a significant amount of stress in the valve packing. The newly included rotational motion of the valve stem was found to affect the packing stress only minimally. This result suggests that development of better rotary valves would be very useful for utilization in molten salt service, especially as the temperature of the salts are increased in an effort to achieve higher power cycle efficiencies.