Belleville Springs in Valves

Dec. 23, 2024

Belleville Springs in Valves

But even before exploring the design and selection considerations, it is important to understand the Belleville spring itself, which is also known as a Belleville washer, conical washer, disc spring, coned-disc spring and other terms. It is a washer with a conical shape that produces spring characteristics when loaded axially. The term Belleville is derived from its inventor, Julian Belleville. The original application was for a valve.

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TODAY&#;S APPLICATIONS

Among the uses for this mechanism today are:

Live Loading of Packing

One common application for Bellevilles in valves is live loading of packing. The term &#;live loading&#; means using a spring to maintain load on a seal. Most of these valves use studs or bolts to exert load onto the gland follower, which loads the packing (Figure 1). As the valve is operated, some of the seal material is lost during each operation. High temperature and thermal cycling can accelerate this loss. As this occurs, preload is lost on the seal. Once the preload falls below a certain threshold, a leak will occur. Since the stretch in the stud is small, loss of preload can occur rapidly.

Bellevilles are used to maintain load on the gland follower. The springs are typically arranged in a stack on the stud to increase the elasticity of the system. Seal materials are lost over time; however, the live-loaded stud will lose less load because the deflection of the spring stack is significantly greater than the stretch of the stud alone. If load is maintained on the seal, a leak is much less likely to occur.

Flange/Bonnet Gasket Live Loading

Live Loading Ball Seats

These springs are also used with ball seats. Ball seats provide a seal between the ball and the valve&#;s body. An entire article could be devoted to seat design because there are so many materials and styles to consider. The load on the seat must be within a certain range for the seat to be effective. If the load is too low, leakage is possible. If the load is too high, excessive wear will occur or the valve will not operate. Often, the seat will have little elasticity (especially when made of metal). Since the valve components are generally machined to a set of tolerances, it is difficult to guarantee the seat is properly loaded.

The ball seat can be live loaded with a Belleville to ensure that the load is within the proper range. Since these loads are usually much lower than those used to seal packing stems or gaskets, the spring stresses can be lower. Some Bellevilles with very low stresses can produce a load curve with a rate of nearly zero. This means that as the spring deflects, there is little change in load, a desirable quality for a spring used in this application since a specific load can be maintained through a wide range of tolerances.

Actuators or Mechanisms

Some low-stress Bellevilles can be designed to &#;snap over.&#; This is similar to an oil can effect. Relief valves can be designed with snap-acting Bellevilles to open the valve quickly at a desired load. Stacked Bellevilles also may be used anywhere a spring rate is required because they can produce a variety of load characteristics. This is especially true in cases where the maximum load for a coil compression spring is too low.

DESIGN CONSIDERATIONS

Some of the factors to consider when selecting Belleville springs are:

Loading/Stacking

Materials

Bellevilles are often highly stressed; thus, the material selection is an important factor. Valves are often subjected to corrosive and/or extreme temperature environments; therefore, the Belleville material chosen should not only be high strength, but able to withstand the environment without significant property changes. Also, the material needs to be commercially available in a form conducive to manufacturing the spring. Finally, potential materials costs are always an important consideration.

Engineers commonly attempt to select a material that matches the body or hardware material used to construct the valve. However, this is not always a suitable spring material. For instance, a valve that employs 316 stainless steel for the body material does not mean that same material would be a good selection for the Bellevilles because 316 stainless steel has a low yield strength unless it is cold worked. This limits the available material thickness. Also, the material may be difficult to source in this form, which can drive up cost and manufacturing lead times. Another issue is that the material may be more susceptible to stress corrosion cracking in its strengthened condition. In that case, it might be necessary to employ more exotic alloys in corrosive applications.

THE GEOMETRY

Bellevilles are commonly described by their inside diameter (ID), outside diameter (OD), thickness (T) and deflection (h). Once these dimensions and material are known, the load versus deflection may be modeled. As the spring is loaded axially, it often will deflect linearly until it is extremely close to flat. The load will then increase exponentially until it reaches flat.

CONCLUSION

Belleville springs are used in various valve applications. The most common purpose is to maintain load on packing, gaskets, ball seats or any other seal, a practice referred to as &#;live loading.&#; Although it is important to consider the limitations of any Belleville design, live loading itself can be very effective when the right choices are made.

George Davet, BSME, MBA, is vice president/chief engineer for the Belleville Springs and Pressure Switch Divisions for Solon Manufacturing Company (www.solonmfg.com), located in Chardon, OH. Reach him at .

Belleville spring characteristics on clutch actuation

Thread starter

k.udhay
Start date
Jun 7,
Tags

Clutch Spring

In summary, the conversation discusses the use of a belleville spring in a clutch mechanism. The graph attached shows the displacement and force of the mechanism, with different patterns for new and old clutches. The behavior of the belleville spring is described as potentially strange but can be understood through testing and analysis. It is also mentioned that the number and orientation of the springs in the system can affect its behavior. The speaker has not yet seen the arrangement of the springs and only has the graph as reference. They request further explanation for the observed behavior.

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Jun 7,

k.udhay

: 170

: 13

Hi,

I have been working on designing something for a clutch. The clutch plate is pressed against the pressure plate using a belleville spring. The belleville spring is connected to the clutch pedal using a linkage with leverage. I came across a graph that describes the displacement of the linkage (this value divided by leverage will give the clutch plate movement) and the force at the linkage at that point. The graph is attached.

As you can see, the mechanism needs totally a different pattern of forces to displace the clutch between new and old. Especially when the clutch is new, the curve is flat at some place and climbs up again. For an old clutch condition there is no flat portion as such and there is a drop of force after a displacement of 12 mm.

Can someone pl explain why this happens? Thanks.

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Research team develops metamaterial to enable real-time shape and property control
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Jun 7,

kazx9r

: 49

: 4

Man this is confusing, are you saying your using a belleville spring against the belleville spring already on the pressure plate?

Jun 7,

Pkruse

: 466

: 2

I've done a lot of work with Belleville spring washers, but never in a clutch. I'm at a loss to explain this behavior, but it does not surprise me. Belleville springs are prone to doing things that seem strange at first, but can eventually be understood after testing and analyzing the system as a whole. One spring can behave much differently from another. Some have maximum force at full deflection, whereas others switch to zero force at full deflection.

I would also like to know how many springs you have in the system and how they are orientated with respect to each other. It is common to use more than one, and it matters how you stack them.

Jun 7,

k.udhay

: 170

: 13

kazx9r said:

Man this is confusing, are you saying your using a belleville spring against the belleville spring already on the pressure plate?

No... The pressure plate is operated by a belleville spring. A mechanism with some leverage actuates the pressure plate. The graph shows the force and displacement on the mechanism to operate the belleville spring...

Thanks.

Jun 7,

k.udhay

: 170

: 13

Pkruse said:

I've done a lot of work with Belleville spring washers, but never in a clutch. I'm at a loss to explain this behavior, but it does not surprise me. Belleville springs are prone to doing things that seem strange at first, but can eventually be understood after testing and analyzing the system as a whole. One spring can behave much differently from another. Some have maximum force at full deflection, whereas others switch to zero force at full deflection.

I would also like to know how many springs you have in the system and how they are orientated with respect to each other. It is common to use more than one, and it matters how you stack them.

Hi. Thanks for the answer. It has only one spring I think. I actually haven't seen the arrangement yet. The graph was handed-over to me and nothing else...

FAQ: Belleville spring characteristics on clutch actuation

What is a Belleville spring?

A Belleville spring, also known as a conical spring or disc spring, is a type of spring that is shaped like a cone or disc. It is commonly used in mechanical assemblies to provide tension or compression force.

How does a Belleville spring work in clutch actuation?

In clutch actuation, the Belleville spring is used to provide the necessary force to engage and disengage the clutch. When the clutch pedal is pressed, the Belleville spring is compressed, creating tension that allows the clutch to be engaged. When the pedal is released, the tension is released, disengaging the clutch.

What are the main characteristics of Belleville springs?

The main characteristics of Belleville springs include their high load capacity, excellent fatigue resistance, and high spring force relative to their size. They also have a low profile and are easy to install, making them popular in various applications.

Can Belleville springs be customized for specific clutch actuation needs?

Yes, Belleville springs can be customized for specific clutch actuation needs. The dimensions, material, and force requirements can be tailored to suit the specific application. This allows for optimal performance and durability in the clutch actuation system.

Are there any limitations or drawbacks to using Belleville springs in clutch actuation?

One potential limitation of using Belleville springs in clutch actuation is their relatively short travel distance. This means they may not be suitable for applications that require a longer distance between the engaged and disengaged positions. Additionally, they may require frequent replacement due to fatigue, depending on the load and frequency of use in the clutch system.

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