Frequently Asked Questions

A Belleville spring can be used indefinitely as long as it is not damaged. It is perfectly acceptable to reuse the springs many times in bolted applications. However, it is important to note that as highly stressed parts, Belleville springs can be prone to failures if they have been compromised in some way. Parts can be damaged by excessive cycling, corrosion, exposure to temperatures beyond the material ratings, and mechanical damage such as galling.

Load on a Belleville spring changes (or cycles) to some extent in all applications. We consider an application to be cyclical when these changes in load will eventually result in the failure of the part. If this is the case, we must then determine if the number of calculated cycles provides adequate life of the product. Cycle life is calculated by considering the maximum load (and resultant stress) for each cycle and the change in load. Generally, the calculated cycle life in a bolting application will be nearly infinite.

Depending on the application, about 90% of the time, the most common bolting arrangement is to have one Solon Belleville Spring on each side of the joint. On the other hand, there are many applications where a single spring adds enough elasticity to the system. Conversely, there are other situations where three or more springs may be needed for a sound design. Your Solon application engineer can suggest how many Belleville springs should be used for a specific application.

In general, Solon Belleville Springs are designed to be loaded to flat without damaging them. However, this does not mean they should be bolted to flat in every case. There are some applications where a spring should be employed at a load considerably lower than the flat load. For instance, when elevated temperatures may damage the springs, it may be necessary to use a heavier spring in order to keep the stresses below a certain threshold. Additionally, in some elevated temperature applications it may be desirable to allow the spring to partially "absorb" the differential expansion to prevent excessive loading.

In general, Solon Manufacturing Co. suggests that torque be used to determine the bolt load. If lubricant is used on the joint, then the torque should be reduced. If the nuts and bolts are stainless, then torque may need to be increased. Use the following torque calculation to determine torque values, or a Solon application engineer can help determine the appropriate torque value for your requirement.

Imperial: (ft. - lbs.) = .2 x Bolt Diameter (in.) x Load (lbs.) / 12
Metric: (N-m) = .2 x Bolt Diameter (mm) X Load (N) / 1000

The application will determine proper load. The following factors are important for live loading a bolted joint:

• Decide what load or torque should be used for a sound joint design. If the joint is a flange, the gasket manufacturer should provide this value. If the joint is a bus (electrical) connection, the designer of the system should provide this value.
• Decide which material the Belleville spring should be. We generally suggest a material that is similar to the bolt material.
• If the Belleville spring may be used at its flat load, use a spring whose flat load is close to the design preload. It may be necessary to use multiple Belleville springs in parallel in order to acheive the requisite flat load. Ideally, the design preload will be 90%-100% of the flat load.
• Confrim the spring arrangement fits into the space contraints of the application.

Actually, thickness plus deflection is not equal to overall height (H). This is because thickness is measured on an angle with respect to the deflection. However, since this angle is typically very small, the thickness plus deflection is approximately equal to overall height. In addition, if a spring is not prestressed the overall height will usually be greater than the thickness plus deflection.