Frequently Asked Questions About Disc Springs

Frequently Asked Questions

Frequently Asked Questions About Disc Springs

What is the difference between a disc spring and a belleville or pressure washer?
What is the useful life of a disc spring?
Which is better, stainless steel material or anticorrosive coating?
How long can disc spring stacks be?
Do disc springs lose force over time?
Which temperature range can a standard disc spring work?
Do the elastic properties of disc springs vary depending on the material?
Why do some disc springs last longer than others?

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What is the difference between a disc spring and a belleville or pressure washer?

Disc springs are specifically designed for dynamic applications. The type of steel used and the treatments applied during manufacturing are tailored to maintain elastic properties over time. Conversely, pressure washers are intended for static applications, primarily focusing on compression resistance, but they have a limited recovery capacity after compression.

What is the useful life of a disc spring?
The useful life of disc springs depends on various factors and cannot be precisely determined. However, estimates can assist in selecting between different options for the same application. The expected life can be calculated based on the work (force and displacement) the spring will endure. It is ideal to pre-compress the spring by at least 15%, ensuring that the travel does not exceed 75% of its total range. Additional factors, such as friction, temperature, and environmental corrosiveness, can significantly alter these estimates. These considerations apply to springs manufactured in accordance with the DIN standard, as lower-quality steel and incomplete thermal treatments shorten their lifespan. Essential treatments include austenitizing, tempering-hardening, and shot peening to enhance the longevity of disc springs.

Which is better: stainless steel material or anticorrosive coating?
Both options have their benefits and drawbacks. The choice depends on the specific anticorrosive agents involved and the intended use. Generally, stainless steel provides superior protection against most corrosive agents; however, coatings may perform better in specific situations, such as with magnesium chloride. Additionally, in dynamic applications, a well-coated standard material may offer better elastic properties and lifespan compared to stainless steel. Each scenario requires an individual assessment, considering factors like delivery time and cost.

How long can disc spring stacks be?
There is no strict limit on the length of disc spring stacks, but certain factors should be considered. Longer stacks may be prone to buckling, which can increase friction with the guidance system. To mitigate this, it is advisable to insert flat separator washers into the stack. These separators should ensure that the distance between them does not exceed three times the external diameter of the disc springs in the group. It's important to remember that longer stacks can still lead to increased friction, even with separators.

Do disc springs lose force over time?
Disc springs under constant load experience relaxation, resulting in force reduction over time. This loss is most substantial initially and then stabilizes. The specific loss rate cannot be accurately determined as it varies based on multiple factors. Typically, a stack may lose around 15% of its force in the first two weeks, with insignificant further loss afterward. This variation in loss is also influenced by the quality of materials and manufacturing. Proper pre-setting treatment is critical for maintaining performance under relaxation, ensuring the spring is fully flattened and discarding any pieces that cannot revert to their original height.

Which temperature range can a standard disc spring work?
The elastic properties of disc springs are temperature-sensitive. In our calculation program, temperature is a crucial factor that influences stack behavior due to its effect on the elasticity modulus. For standard materials like 50CrV4, the operational temperature range is generally considered to be between -50°C and 100°C, with elasticity varying within this range. For higher or lower temperatures, springs should be manufactured using materials specifically resistant to those conditions, such as 17-7PH, which can withstand temperatures from -200°C to 300°C, or Inconel 718, effective from -260°C to 700°C.

Do the elastic properties of disc springs vary depending on the material?
Yes, they indeed vary. Each material has a different elasticity modulus, which should be considered when conducting calculations on a stack. Additionally, the modulus changes with working temperatures, as explained previously.

Why do some disc springs last longer than others?
The quality of the material and the manufacturing process are critical factors affecting disc springs' fatigue resistance and overall lifespan. The DIN standard specifies suitable steel types, but not all manufacturers implement rigorous quality control for the steel they use. A higher impurity level in the material can lead to increased breakage rates. Moreover, while the standard mandates specific thermal treatments for elasticity, supplementary treatments like austenitizing, following tempering and hardening, can greatly enhance these characteristics. Shot peening, applied after tempering and hardening, also contributes significantly to improving spring quality.

Frequently Asked Questions About Bellevilles

What is the difference between flange washers and a disc spring DIN or Belleville (USA)?
Must you use one or two disc springs for each bolt?
Do you offer flange disc springs in non-magnetic material?
What does presetting mean?
What load should be used?
Which stainless steel should I use?
What does mechanically zinc plated mean?
How can I tell when a spring washer is compressed to 100%?
Why do other spring washers with the same dimensions as our flange washers have different maximum force values?
What types of anti-corrosive protection are available for elastic flange washers?
Why is stainless steel magnetic?
How many times can a flange washer be used?

What is the difference between flange washers and a disc spring DIN or Belleville (USA)?
Flange washers are a type of disc spring, with the main difference being the ratio of external diameter to internal diameter (De / Di), which is approximately 1.75 for flange washers. This design allows flange washers to be used where attachment bolts are closely spaced.

The force in a fully compressed position for a flange washer is typically higher compared to other DIN washers with the same outer diameter and thickness, catering to the demands of many applications.

Must you use one or two disc springs for each bolt?
The answer depends on the specific application. In most cases, a single spring suffices; however, in applications involving expansion, two springs can be utilized, one on each side. Consult our technical team for assistance in determining the appropriate number of springs.

Do you offer flange disc springs in non-magnetic material?
Yes, we provide flange disc springs made from standard materials such as Inconel 718 and 510 Phosphor Bronze.

What does presetting mean?
Presetting is a crucial part of the high-quality disc spring manufacturing process. It involves temporarily flattening the spring to its maximum compression. Springs are manufactured slightly taller than the final height, and through presetting, they adjust to their designed height. This process enhances fatigue life and overall performance, including relaxation and precision regarding displacement forces. Some disc springs might not undergo presetting due to impracticality and cost, especially if they are thin or small.

The flange washer springs typically do not undergo presetting, as fatigue is less of a factor, and they must meet stringent manufacturing tolerances.

What load should be used?
Determining the proper load is essential and varies based on the application. Follow these guidelines for assessing proper load for spring-loaded flange washers:

1) Identify the load or torque needed for effective sealing of the union. For instance, in a flange union, the value will often be decided by the joint manufacturer. In electrical connections, the designer provides the load value.

2) Choose an appropriate material for the spring washer. Generally, it is advisable to use material similar to the bolts used in the assembly.

3) If it is established that the spring can handle a full 100% load, select a spring from the list with maximum load near the joint's design load. Parallel use of multiple springs may be required to achieve the desired load value. Ideally, design load should be within 90% to 100% of the spring's maximum load.

4) Ensure that the selected spring or springs fit the available space for the application.

Which stainless steel should I use?
AISI 301 stainless steel offers the best corrosion resistance at a lower cost. Conversely, 17-7 PH delivers superior mechanical properties and can tolerate high temperatures (up to 300°C). Springs made from AISI 301 are typically manufactured using work-hardened stamped material, which restricts their size range compared to 17-7 PH springs.

What does mechanically zinc plated mean?
This method involves applying zinc to the disc springs to protect them against corrosion. The process entails rotating the spring in a mixture of zinc particles and glass stones, with the stones ensuring the zinc adheres securely. This provides corrosion protection for all our steel components and minimizes the risk of fractures caused by hydrogen, commonly associated with electroplating processes.

How can I tell when a spring washer is compressed to 100%?
Many users find it challenging to determine when complete compression has been achieved, concerned that over-compression may lead to stiffening of the union. Some experts may "feel" when the spring reaches maximum compression, which may work for metric sizes up to one-inch but becomes less reliable with larger measurements.

To accurately control load on the joint, it's essential to monitor the torque applied during assembly. Each washer specification includes torque data. By calculating the appropriate torque and using a standard coefficient of friction (around 0.2 for steel), you can ensure the spring functions without exceeding its maximum load. This operation should be conducted with a torque wrench.

The formula used is:

T = K.Fi.d

Where:
T: Tightening torque
K: Coefficient of friction (approximately 0.2)
Fi (N): Force exerted by the bolt, transmitted to the spring.
D (m): Diameter of the bolt used.

Why do other spring washers with the same dimensions as our flange washers have different maximum force values?
Most manufacturers of DIN spring washers utilize Almen and Laszlo formulas to calculate spring force versus displacement. This equation is reliable if the washer edges remain straight and loads are applied at the outer and inner diameter edges. In practice, as flange washers approach a flat position, the force is applied slightly inward, which increases the strength value. Therefore, the forces stated in our specifications account for this phenomenon.

What types of anti-corrosive protection are available for this type of elastic flange washers?
In addition to zinc plating, we provide alternate protection methods, such as nickel plating, yellow chrome, phosphating (black), and oil coatings.

Why is stainless steel magnetic?
All stainless steels are magnetic except for the austenitic group (300 series). Even among austenitic steels, cold working can induce magnetism. Our springs are manufactured using cold-worked material, which significantly enhances their magnetic properties.

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