Imperial Belleville Spring Washers
A Belleville spring is a conically shaped disc that will deflect (flatten) at a given rate. This spring rate is usually very high, allowing the spring to produce very large loads in a very small space.
Designed and manufactured by Solon Manufacturing Co., Solon Belleville conical spring washers are used in a variety of applications across many different environments. These springs are used to maintain bolt preload by preventing bolt tension loss due to differential thermal expansion, high-temperature bolt yield, packing and gasket relaxation, and vibration. Solon Manufacturing manufactures a complete line of Belleville springs and washers for use on bolting applications. They are available in several types of materials and finishes to suit the needs of the end-user.
Conical Spring Washers & Bolted Joints
Belleville spring washers are used in many simple as well as highly engineered applications. One of the most common applications for a conical disc spring is a bolted joint. One of the keys to having a sound bolted joint is that some minimum preload must be maintained. If the preload falls below this minimum, then the joint will fail. In some applications, joint failure may cause a minor nuisance to a customer or a cosmetic issue. In other applications, failure may be catastrophic resulting in signiﬁcant property loss, injury, or death.
Bolts lose some of their original load after they are tightened. There are several reasons for loss of preload, most commonly; embedment relaxation, differential thermal expansion, bolt creep, and vibration.
When a bolt is tightened, it is stretched, which produces a load, or force. The bolt is used like a spring, a very stiff spring, but a spring none the less. It is this spring load that keeps the bolt tight and it is the loss of this spring load that allows it to become loose.
A Belleville spring is a conically shaped disc that will ﬂatten or deﬂect at a given rate. Its ability to flex at the appropriate load gives the Belleville spring the ability to maintain the tight joint connections. Most Belleville springs produce very high loads in very small spaces which is why spring washers are so effective on bolted joints.
Typical Belleville Spring Diagram
Washers and disc springs can be stacked in a variety of configurations in order to achieve greater – or more specific load capacity, they include:
Achieving Belleville Washer & Disc Spring Load & Deflection
- Single, one spring
- Parallel, all springs are stacked the same way
- Series, all springs stacked opposing each other
- Parallel-Series, a combination of the two
A single Belleville spring has a specific load and deflection. Belleville springs in stacked arrangements provide increased load and/or deflection. Two springs stacked in parallel doubles the load capacity of a single spring with no increase in deflection. Two springs stacked in series doubles the deflection of a single spring with no increase in load. The parallel -series combination results in the load of two springs and the deflection of two springs.
Solon Disc Springs are also available in standard imperial sizes from 7/64” to 2 ½” ID.
Conical Spring Washer PrestressingMany Solon Belleville Springs are pre-stressed by deflecting them to flat. This flattening procedure produces a pre-stressed deflection as the spring recovers height from the flat position. Belleville springs that are prestressed have the maximum possible load and deflection for any given size of spring. When the spring is loaded through its pre-stressed deflection, the resultant residual stresses build up from the yield strength of the material, instead of from zero stress as with the case of a spring that is not pre-stressed. Pre-stressing is also an excellent inspection method for maintaining the quality of the springs. Because pre-stressing produces consistent free heights, springs not meeting free height tolerances are rejected.
Note: Not all Belleville spring applications require the spring to be pre-stressed. For special applications, consult a Solon application engineer