FAQ´s

  • 1. Why is there a warning on the gas spring?

    Gas springs are filled with compressed nitrogen. The warning is intended to prevent unauthorized people from opening the gas spring or making other changes to the gas spring, which negatively impact the strength of the pressure pipe.

  • 2. Can gas springs explode?

    No. The pressure pipes of all SUSPA® pressure pipes have wall thicknesses and materials that are dimensioned so that there is a sufficient level of safety against bursting in all conceivable functional states.

  • 3. What are SUSPA® gas springs filled with?

    Only nitrogen is used as the pressure medium in SUSPA® gas springs. About 75% of the air we breath consists of this gas. Nitrogen is absolutely safe and harmless to health. In addition, nitrogen does not burn. On the contrary, nitrogen is used in the chemical industry to prevent and extinguish fires. In addition, every SUSPA®  pneumatic spring contains flame-retardant oil to lubricate the seals and to achieve certain functions, such as damping or rigid locking.

  • 4. How high is the pressure in a gas spring?

    The filling pressure of SUSPA® gas springs depends on the extension force and the geometry and is between 10 and 230 bar.

  • 5. How does a gas spring work?

    Inside a gas spring, the filling pressure acts on both surfaces of the piston. Once this is firmly bonded with the piston rod, the piston surface on the piston rod side is reduced by the cross-section of the piston rod. This results in a differential pressure on the piston, which acts in the extension direction. The size of the force [F] is equal to the product from the filling pressure [p] and the piston rod cross-section surface [A]. The following formula applies: F = p x A

  • 6. What is "F1 force?"

    The "F1 force" is the designed force of SUSPA® gas springs. This is measured when the piston rod of the gas spring is extended to 5 mm. It should be noted that the measured point of a significantly shorter position is approached with a defined speed and the value of the "F1 force" is read only about 3 seconds after the measurement devices comes to a standstill. The measurement must take place at 20°C gas spring and room temperature

  • 7. Does the force of the gas spring change when displacing the piston rod?

    Yes. The inner volume of the gas spring is closed to the outside. This means that the filled gas volume can only occupy the free space in the pressure pipe that is not needed for components or oil. By pushing the piston rod in, this free space [V] is reduced by the inserted piston rod volume. Because the same gas volume has a smaller volume available, the pressure [p] in the gas spring increases. This formula applies: p2 = (V1 / V2) x p1 The index [1] corresponds to the piston rod position before moving displacement and index [2] after displacement. The force [F] can also be used for the pressure [p] in this formula due to the correlation of the gas spring force with the filling pressure.

  • 8. Does the force of a gas spring differ between retraction and extension?

    Yes. A friction force [FR] is created by the seal contacting the piston rod and the piston contacting the inside of the pressure pipe. This frictional force counteracts the movement direction of the piston rod. This means: During extension, the gas spring force [F = A x p] is reduced by the friction and a force increased by the amount of friction must be applied to push the piston rod in. This results in the following formula correlations: FOut = (A x p) - FOut; FIn = (A x p) + FIn  Since the gas spring friction [FRGF] equals the difference of the insertion and extension force, the following applies: FRGF = FIn + FOut

  • 9. Is it possible to manufacture a gas spring without friction?

    No. So that the gas filling does not escape from the pressure pipe, a hermetic seal of the gas spring interior must be created, even at the moving piston rods. To achieve a hermetic seal, the piston rods and the seal must be in contact with a sufficient surface pressure. The result of the contact of two bodies is always a frictional force. The sealing of SUSPA®  gas springs is designed so that the piston rods slide on the seal when displaced. The resulting friction is reduced to a minimum in SUSPA® gas springs due to a careful selection of the materials and lubricants used.

  • 10. What does the expression "damping" mean with a gas spring?

    Due to the gas spring structure, the interior of the gas spring is divided into two sub-spaces (chambers) by the piston, which is permanently connected with the piston rod. When the piston rod is displaced, the gas flows into a special connection channel through the piston from one chamber to the other. The structural design of this connection chamber has an effect on how big the resistance is that has to be overcome in order to press the gas through the piston. If the resistance is high, this is called a high "damping." The "damping" only occurs when the piston rod is moving and is used in gas springs above all to reduce the extension or insertion speed. In application, a pneumatic spring with a higher damping with all other installation conditions that are the same will insert and extend more slowly than a gas spring with a lower damping.

  • 11. Can the damping of gas springs be changed?

    The damping of SUSPA® gas springs can be preset by using different "damping discs." Furthermore, special "dampings" (e.g. end position damping or insertion damping) can be achieved by filling with larger oil quantities. Here, a larger resistance must be overcome to press the oil through the piston than if gas is flowing through the piston.

  • 12. What is the difference between a gas spring and a damper?

    In general, a gas spring is an energy storage device and a damper is an energy absorber. The most common function of gas springs is to raise, lower and tilt or support doors, flaps or the like and to keep these in their end positions (opened/closed). The force of the gas spring thus acts against the weight force of the application so that the force expenditure of the operator is greatly reduced. Considered from a purely physical perspective, the gas spring stores some of the energy released while lowering a part, which is then released again when raising, which ultimately "helps" the operator. Dampers, on the other hand, are used in applications where the movement or vibration of a weight or body must be braked or reduced. Like a gas spring, a damper also has a piston that divides the interior of the damper pipe into two chambers. These chambers are usually filled with oil. When displacing the piston rod, the oil has to be pressed through the piston via a special connection channel. Depending on the design of the connection channel, the oil can be pushed through more easily or with more difficulty. This resistance "results" in the damping force, which always counteracts the movement direction of the piston rod and increases with an increasing movement speed of the piston rod. Considered from a purely physical perspective, a damper absorbs the movement energy of an application or converts this into heat, thus ensuring for a higher level of comfort in the application. Of course there are many practical applications that require both the force-assisting and damping function in one product. SUSPA® gas springs with various damping properties (damping in retraction or extension direction or in both directions or the end position damping) are designed in such cases.

  • 13. What is a lockable gas spring?

    Like Liftline gas springs, Lockline gas springs have a piston that divides the interior of the pressure pipe into two chambers. Unlike the Liftline gas spring, there is a valve in the connection channel between the two chambers that can be opened and closed from the outside. The valve makes it possible to close the connection channel in any piston rod position. When the valve is closed, the gas can no longer flow between the two chambers. This means: The piston rod is locked in this position. If the two chambers are filled with gas, the locked piston rod can be displaced by high external forces. In this case, the gas is compressed in one of the two chambers and expanded in the other. If the external forces no longer act on the piston rod, then it very quickly moves back to the position in which the valve was previously closed. This is called elastic locking. Special structural designs make it possible to achieve a rigid locking of SUSPA® gas springs.

  • 14. How long is the service life of a gas spring?

    The general service life of SUSPA® gas springs is between 10,000 and 100,000 double strokes (1x retraction and extension) depending on the type of gas spring. At SUSPA®, the service life is tested according to internal test standards. These test standards provide for an optimal installation of gas springs. After the service life tests are completed, only a minimum power loss from escaped gas is tolerated at SUSPA®. However, the actual service life of a pneumatic spring in application depends on many factors. That is why gas springs should be tested in the respective application under the actual conditions to be able to make a reliable statement about the service life of the gas spring.

  • 15. What conditions affect the service life of gas springs?

    The most important criterion is the installation position of the gas spring with the piston rod facing down. This permanently ensures the lubrication of the piston rod seal. The frequency of the actuation also has a very decisive influence on the service life. The attachment of the pneumatic spring may not cause any lateral load on the piston rod. In the case of lateral forces, there is a unilateral, significantly higher wear on the piston rod, guide and seal. In addition, the piston rod may not become dirty or scratched. Extremely high or low temperatures and strong vibrations in the application also lead to a reduction of the service life of a gas spring. Due to these different influences, a careful review of all factors is necessary to achieve an optimal service life of the gas spring and thus the functional suitability of the entire application. 

  • 16. What properties of the gas spring change with its age?

    When a gas spring is optimally installed, the moving parts experience normal wear at the points of contact. This changes the surfaces, which allows the friction to rise slightly between the moving parts. To reduce the friction and wear, the gas springs are filled with a small amount of oil, which lubricates the sealing and sliding surfaces. Like any liquid, oil has the property that it can dissolve a larger amount of gas in it under pressure than under atmospheric pressure without changing its volume. If the pressure in the liquid is reduced, this cannot dissolve as much gas and gas bubbles form in it, which rise to the surface. This effect can be seen particularly well when opening a bottle of mineral water. The oil saturated with gas inside the gas spring wets the surface of the piston rod. When sliding past the seal, a very thin film of saturated oil remains on the piston rod, which then releases the dissolved nitrogen outside of the gas spring into the atmosphere.
    In this way, some nitrogen molecules are "smuggled" out of the gas spring every time it extends and thus the gas volume and the pressure in the gas spring reduce, which ultimately results in a loss of power. If you omit the oil to prevent this effect, the wear on the seal increases so much that this no longer has a sealing effect already after a few load changes and the gas escapes. Even if the piston rod is not moved, gas springs lose pressure over time due to gas molecules that penetrate the seal. This effect is called permeation and can be reduced if the gas spring is installed and/or stored with the piston rod facing down so that the seal is not in direct contact with the gas filling, but rather is covered by the filled oil.

  • 17. What needs to be taken into consideration when using gas springs?

    SUSPA gas springs should always be installed according to our installation instructions:
    1. Install the gas spring with the piston rod facing down wards to ensure the optimal lubrication of the seal.
    2. No lateral forces may act on the piston rod in order to avoid a unilateral and therefore higher wear. When using SUSPA® gas springs of the Liftline model, lateral forces can be excluded by using ball joints to fasten the pneumatic springs. The centric force introduction must be structurally ensured when using other connection parts (e.g. eye or fork head). In the process, the axes of the eye holes and the middle axis of the pneumatic spring must intersect and the fastening bolts must be perpendicular to the middle axis of the gas spring in every position of the application.
    3. The piston rod is to be protected from impacts, dirt and scratches. These factors increase the wear tremendously on the one hand, and on the other hand dirt particles and scratches on the sealing surfaces cause leaks.
    4. The application temperature from -30°C to +80°C should not be exceeded or fallen below, because the sealing materials wear too quickly outside of this range on the one hand, and on the other hand no longer have the necessary elasticity. Within this temperature range, the change in the extension force must be taken into consideration in order to ensure the application function for all occurring temperatures.
    5. Strong vibrations reduce the service life of pneumatic springs. Furthermore, the maximum possible extension force must be chosen during installation, because all pneumatic springs "lose" force during use. This can ensure that the application has a maximum functional duration.

  • 18. Should gas springs be installed with the piston rod facing up or down?

    In general, gas springs should be installed with the piston rod facing down to ensure the piston rod seal is lubricated and to reduce the permeation of nitrogen through the seal. However, the opposite installation may be necessary in some special cases, for example if the gas spring requires a very specific damping characteristic. In such cases, the lubrication of the piston rod seal must be ensured by special measures (space mat). 

  • 19. Does a gas spring have to be maintained?

    No. SUSPA® gas springs are equipped with a lubricant quantity during production that lasts a life time.

  • 20. Can gas springs be repaired?

    No. All SUSPA® gas springs and dampers are by a plastic deformation of the external pipes during production. This makes it impossible to open the gas spring to replace individual components without destroying it. 

  • 21. How do you find the right gas spring for a specific application?

    The function of the entire application is always the focus at SUSPA®. If you know the requirements profile of your application (e.g. opening a flap, holding the flap in both end positions, automatic opening, closing by a defined manual force at a defined handle, weight of the application), it still needs to be clarified in what area it is possible to fasten the gas spring. The exact mounting points must then be determined with this data and a suitable gas spring must be defined. This process, however, proves to be very complex and usually involves a tremendous amount of research and time. That is why we offer you the implementation and selection of a suitable gas spring for you to take over. Simply sketch us the application specifying the rotation point, the weight and the desired opening angle. Furthermore, the sketch should include the location of the center of gravity and the area in which a pneumatic spring attachment is possible. Our experienced employees will use special software to determine an optimal pneumatic spring for your application and make you a sketch with the installation dimensions.

  • 22. How long can the gas springs be stored?

    The storage of SUSPA® gas springs has no negative consequences on their function if it is ensured that the piston rods point down and no dirt accumulates on the piston rod. If gas springs are not actuated for a long time, they only have a slightly increased amount of friction during the first retraction. However, this effect is equalized after the first actuation and the gas spring then again exhibits the usual friction values.

  • 23. Does the temperature affect the function of gas springs?

    Yes. However, three temperatures ranges must be distinguished between. Between -30°C and +80°C (operating range), the temperature only affects the pressure of the gas in the gas spring. The pressure increases / decreases in this range and therefore so too does the extension force of the gas spring by about 3.5% per 10°C of the temperature rise / fall. Below the operating range, the elasticity of the sealing materials used decreases so that the surface pressure distribution in the sealing points is no longer optimally adjusted. If the temperature rises significantly above the operating range, a higher wear results on the dynamically stressed sealing points, such as the piston rod seal, due to the softening of the sealing material. The temperature has an additional effect on the damping behavior of the gas springs. The temperature increase makes the oil be less viscous, which reduces the oil's resistance to the flow of the piston. This results in less damping. Likewise, the damping increases with a lowering temperature.

  • 24. What is a soft-stop gas spring?

    Soft-stop gas springs do not have the same "damping" across the entire stroke like standard pneumatic springs (also see 10). With this gas spring type, the "damping" also continuously increases while the piston rod is being extended, whereby its extension speed reduces consistently. Unlike standard pneumatic springs, the connection channel between the two chambers in soft-stop pneumatic springs is not in the piston, but rather is formed by a groove in the inner surface of the pressure pipe. The gas then flows through this groove past the piston when the piston rod is displaced. The "damping" of the gas spring is determined by the cross-section of the groove at the respective piston position. The groove is designed so that its depth and therefore also the cross-section across the range of movement of the piston is not the same, but rather reduces in the direction of extension. Applications that are equipped with soft-stop gas springs are characterized by a very convenient operation and high sense of value, because the movement is gently braked once the end position is reached.

  • 25. What does Space-Mat mean?

    Space-Mat is a special lubrication system for gas springs developed by SUSPA®. SUSPA® gas springs equipped with Space-Mat can be mounted with the piston rod facing upwards without any problems without causing increased wear of the piston rod seal. in addition, the Space-Mat system greatly reduces the 'breakaway force" of the piston rod during the movement start, whereby the operating comfort and the sense of value of the entire application increases.

SUSPA® Inc.

Phone 616.241.4200

Fax 616.531.3310

sim@us.suspa.com

Kontakt-Formular Kontakt-Formular Contact form

SUSPA® Inc.

Phone 616.241.4200

Fax 616.531.3310

sim@us.suspa.com

Kontakt-Formular Kontakt-Formular Contact form