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 for a disc spring?
¿Which is better, stainless steel material or anticorrosive coating?
¿How long can disc springs stacks be?
¿Does disc springs loose force over time?
¿Which temperature range can a standard disc spring work?
¿Do elastic properties of disc springs vary depending on the material?
¿Why some disc springs last longer than other ones?
What is the difference between a disc spring and a belleville or pressure washer?
Disc springs are pieces manufactured for dynamic works. This is why the type of steel used and treatments they are submitted to during the manufacture process are aimed at conferring elastic properties to be maintained over time. On the other hand, pressure washers are pieces for static applications, which must be highly resistant to compression, but whose recovery capacity for new compressions is very low.
What is the useful life for a disc spring?
Useful life of these pieces depends on many factors and cannot be precisely determined. It is possible to carry out an estimate, which will help us decide between two or more possible solutions for the same application. Depending on the work (force and displacement) the piece is submitted to, the number of cycles the piece can withstand can be calculated. In this respect, it is essential at which points of the piece travel the work is going to be made, ideally to be pre-compressed at least 15% and the travel is not over 75% of the total travel. Aspects such as friction, temperature and corrosive environment vary this estimation drastically, therefore they should always be considered. Finally, these aspects are valid for springs which are manufactured in compliance with the standard (DIN 2093), as the use of lower-quality steels as well as incomplete thermal treatments reduce the piece useful life. “Austenising “, combination of ”tempering-hardening” and “shot peening” are the treatments which ensure the longer duration of disc springs.
Which is better, stainless steel material or anticorrosive coating?
Both solutions offer advantages and disadvantaged. The answer depends on the type of anticorrosive agent to withstand and the use. Generally, stainless steels show higher protection to most corrosive agents, however, in some cases such as magnesium chloride, coatings are more efficient. On the other hand, in dynamic applications the different characteristics of the material can make a standard material with better elastic properties and good coating be more lasting than stainless steel. Each situation should be individually analysed and factors such as delivery time or cost of the solution may be decisive.
How long can disc spring stacks be?
There is no limit for the length of stacks, but some aspects should be considered. Buckling of stacks may increase if the length is longer, with the subsequent friction with the guidance system. In order to avoid it, it is recommended to insert separator flat washers in the stack. These washers should be inserted in such a way that sections among them do not exceed three times the external diameter of the disc springs conforming the group. It should also be considered that, even with separator washers, the longer the stack is, the more friction is increased.
Does disc springs loose force over time?
Disc springs as they are under a constant load, suffer relaxation, that produces a decrease in force, over time. The loss is produced at the beginning and afterwards tends to remain stable. This loss cannot be precisely determined as it depends on different factors. In any case, it is possible to estimate that a stack will loose its force by 15% during the first two weeks being the loss of force insignificant from then.
Depending on the spring quality (material and manufacture), this loss may vary. In order to ensure correct performance of the piece in relaxation, pre-setting treatment is of great importance. This treatment is to flatten the spring completely and to discard those pieces which are not able to recover their initial height.
Which temperature range can a standard disc spring work?
Elastic properties of disc springs are affected by temperature. In our calculation program, it is one of the values to be considered when calculating the behaviour of stack because the elasticity module varies depending on the temperature. For standard material (50CrV4), it is considered that the range of temperature to operate under normal conditions ranges from 50ºC to 100ºC, taking into account that elasticity will vary within this range. For higher or lower temperatures, pieces manufactured with materials which are resistant to these temperatures should be used. Materials such as17-7PH (1.4568), which works from -200ºC to 300ºC , or Inconel 718, whose thermal range is between -260ºC and 700ºC, are the most common in these cases.
Do elastic properties of disc springs vary depending on the material?
Yes, they do. Each material has a different elasticity module therefore, when carrying out calculations on stack we should consider what kind of material it is, as the result will be different. Besides, for the same material the elasticity module varies depending on the working temperature as explained in the question above.
Why some disc springs last longer than other ones?
Material quality and manufacture process of disc springs are decisive for their resistance to fatigue and consequently their useful life. DIN 2093 standard establishes which type of steels is suitable for the manufacture. However, not all manufacturers carry out correct quality controls of steels they use. A high level of impurities in the material results in a higher breakage rate in the pieces. With regard to the thermal treatment, which is a decisive factor for the piece elasticity, the standard establishes a tempering and hardening treatment. However, there are complementary treatments which improve this aspect significantly. Austenising is a treatment superior to tempering and hardening , which provides steel with improved characteristics. A similar quality is obtained when carrying out shot peening treatments, after tempering and hardening.
Frequently asked questions about Bellevilles
What is the difference between flange washers and a disc spring DIN 2093 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 Preseting mean?
What load should be used?
Which stainless steel should I use?
What does Mechanically Zinc Plate mean?
How to know when a spring washer is compressed to 100%?
Why other spring washers that have the same dimensions as our flange washers have different values of maximum force?
What types of anti-corrosive protection are available for this type of elastic flange washers?
Why stainless steel is magnetic?
How many times can a washer flange be used?
What is the difference between flange washers and a disc spring DIN 2093 or Belleville (USA)?
Flange washers are a type of disc springs. The main difference is the ratio De / Di. For flange washers this ratio is about 1.75. This allows the flange washers to be used in places where the attachment bolts are very close to each other.
On the other hand, as a general rule, the force in 100% compressed position for a flange washer type is greater when compared with other DIN 2093 same outer diameter and thickness. This is to meet the demand of force required in most applications where they are used.
Must you use one or two disc springs for each bolt?
The answer to this question depends on the application. In most cases it is sufficient to use a single spring. In other applications with dilatation you can put two springs, one on each side.
Consult our technical department for calculating the number of springs.
Do you offer flange disc springs in non-magnetic material?
The answer is yes, using standard materials such as Inconel 718 and 510 Phosphor Bronze.
What does Preseting mean?
The presetting is part of the manufacturing process of high quality disc springs. This process takes the spring to a momentarily flat position (maximum compression). The first piece is manufactured to a slightly higher height than final unit. During presseting, springs yield to its designed height. The objective of this procedure is to improve the fatigue life and the general performances of the springs, such as relaxation or precision values vs displacement forces.
To some disc springs no presetting is applied due to the fact that the procedure is impractical and costly for thin and small disc springs.
The flange washer springs are rarely preset since fatigue usually does not work and must meet very tight manufacturing tolerances.
What load should be used?
This is a very common question. We have to consider the application to determine the proper load. The determination of this spring loaded flange washers can be approximated in terms of:
1) Decide which load or torque must be used for proper sealing of the union. If a union between flanges, the manufacturer of the joint should decide the value. In the case of an electrical connection the connection designer must provide the value.
2) Decide what material we use in the production of spring washer. Generally we recommend a similar bolts used in the binding material.
3) If it is determined that the spring can be used at 100% load then simply choose a spring from the list with a maximum load is similar to the design load of the joint. The use of springs washers in parallel may be needed to achieve the load value sought. Theoretically, the design load should be between 90% and 100% of the maximum load of the spring.
4) Check that the spring or springs selected fit into the space available for the application.
Which stainless steel should I use?
The steel AISI 301 is the least expensive and offers better corrosion resistance. The 17-7 PH has better mechanical properties and can withstand high temperatures (up to 300 ° C). Moreover, since springs in stainless steel AISI 301 are manufactured using stamping material condition: work hardened, the size range of this product line is much more limited, not so for the 17-7 PH -.
What does Mechanically Zinc Plate mean?
This is a method we use apply zinc on the disc springs to protect them against corrosion. The process is to rotate the spring in a mixture of particles of zinc and glass stones. The function of the stones is that zinc is securely attached to the springs. This provides corrosion protection for all our steel parts and eliminates the risk of fracture due to the presence of hydrogen which is very common when this procedure is performed using a deposition method using electricity. (electroplated) -.
How to know when a spring washer is compressed to 100%?
Many users complain that it is difficult to determine when the spring has reached 100% load resisting, fearing for overload would cause the opposite effect. (stiffen the union).
Some experts "feel" when the spring has reached is maximium. This may be true for metric up to an inch but it is difficult for bigger measures besides being a "risky" method.
The most appropriate way to control the load on the joint is controlling the torque applied to the screw during assembly. For this reason one of the data in the list of these washers is the tightening torque. Given the torque for this union and having a coefficient of friction for steel standard 0.2 we will have achieved the spring we deliver without exceeding its maximum load. This operation should be performed with a key held by torque wrench.
The equation used is:
T = K.Fi.d
Where:
T: Tightening torque or constrict
K: Coefficient of friction. (As mentioned above, this value is approx. 0.2)
Fi (N): Force generated by the bolt and thus is transmitted to the spring.
D (mts): Bolt diameter used (M10 = 0.01 mts – mts M12 = 0.012 – M20 = 0.02 mts, etc)
Why other spring washers that have the same dimensions as our flange washers have different values of maximum force?
This is because most manufacturers of DIN 2093 spring washers use Almen and Laszlo formulas for calculating spring force versus displacement. This equation works well as long as the edges of the washers are straight remains true and that the loads are applied at the edges of the outer and inner diameters of the springs. But in reality as we approach the flat position in flange washers (flat washer) and the force is applied a little inward of the points considered by Almen and Lazlo, this makes the strength value increase, therefore the forces specified in our list are taken into account in this phenomenon.
What types of anti-corrosive protection are available for this type of elastic flange washers?
Apart from zinc plating, we offer other methods of protection such as nickel plating, yellow chorme, phosfating (black), oil coating, etc.
Why stainless steel is magnetic?
All stainless steel are magnetic except the group of austenitic (300 series). Even the austenitic group can become magnetic if they are cold worked. Our springs are manufactured using cold worked material thus significantly magnetic.
How many times can a washer flange be used?
Indefinitely, as long as during its use limits are not exceeded and no damage is caused by good or bad use. They can be damaged by excessive fatigue cycles, long exposure to high temperatures or by exposure in highly corrosive environments, etc.