Belleville springs are used within or adjacent to valves for a variety of purposes—the most common being to maintain load on a seal, gasket or packing. They often are used as machine elements in valve actuators or as a component of the valve mechanism and are designed or arranged to provide useful mechanical properties within small spaces. This means they can be retrofitted into existing valve designs with minimal revisions. Clearly, these mechanisms serve a vital purpose. However, many important factors should be considered in selecting a spring.