Technical information in this article was provided by MISUMI product engineer Kris Szewczyk.
Gas springs, also known as nitrogen gas springs, operate on fundamentally different principles than well-known metallic wire helical coil springs, which rely on elastic deformation to absorb displacements and store energy.
Gas springs are energy storage elements that use compressed nitrogen gas mixed with a small amount of lubricating oil. In this way, gas springs can be considered pneumatic devices that operate like springs.
Gas springs consist of an enclosed cylinder filled with the working gas and sealed at the working end by the rod and piston components. Gas springs are increasingly replacing traditional helical coil die springs in industrial die molding and casting equipment.
4 Reasons Why Choosing the Right Gas Spring is Critical
A properly specified gas spring offers numerous benefits for large production equipment compared to traditional helical coil mechanical die springs.
1. Improved Productivity
Replacing helical coil die springs with gas springs reduces equipment downtime because gas springs are not vulnerable to metallic fatigue failure. Fewer spring mechanical failures mean reduced production downtime and lower equipment repair costs, leading to more productive manufacturing equipment.
2. Enhanced Safety
Because gas springs operate with an inert gas as the compressible medium, they have a far more favorable personnel safety profile than helical coil springs. If a helical coil spring fractures under loading, the uncontrolled release of stored energy may result in debris becoming liberated, endangering personnel in the production area.
If a gas spring experiences a failure during operation, the result is a controlled release of inert gas. Furthermore, gas springs also possess additional active safety systems designed to protect against over-pressurization and overstroke conditions.
3. Increased Durability
As mentioned above, gas springs are durable because gas is the working fluid. Compared to helical coil die springs, which are metallic components stressed repeatedly through their elastic range during operation, gas springs are durable, reliable, and quiet.
4. Improved Precision
Gas springs can be adjusted to provide the exact force needed for each application. This adjustment is achieved by relieving the initial gas pressure in the cylinder via the release valves present on the gas spring. In this way, gas springs offer functionality that traditional die springs cannot.
Key Considerations in Choosing the Right Gas Spring
When specifying the proper gas spring for your application, consider the following design parameters for your gas spring.
Force
The most apparent design parameter you need to know is the required force that your gas spring must provide. This force is necessary to lift or support the die spring and associated equipment.
While there are other variables related to the ideal gas law, in general, the force that the gas spring is required to provide is related to the charge pressure (p) and the dynamic seal diameter (D_seal) of the gas spring as follows:
Stroke
The stroke represents the linear distance the gas spring travels from fully compressed to fully extended. The stroke length is the range of motion of the spring and determines the maximum movement the spring can offer in the intended application.
Mounting
Mounting brackets and equipment depend on the gas spring orientation, which is critical for proper operation. Most gas springs are mounted vertically, but horizontal or angular orientations are achievable depending on the rated orientation angle of the spring.
The allowable orientation of a gas spring is specified as a degree from the vertical axis. For example, a 60-degree orientation gas spring is designed to be oriented, mounted, and installed no more than 60 degrees from vertical. Many gas springs are rated for a complete 360-degree orientation angle, meaning they may be installed horizontally with no performance impact.
In all cases, always orient and mount gas springs according to their rated orientation specifications. This ensures that the friction components are adequately lubricated by the rod seal oil, and it operates reliably over the life of the spring.
Environment
You should also consider your intended operational environment, considering design parameters, such as temperature and humidity. For example, the internal gas pressure increases with temperature, impacting the spring’s force output at high temperatures. High operating temperatures also reduce the oil’s effectiveness at lubricating the surfaces.
Additionally, high humidity negatively impacts the seal integrity of the piston rod assembly, which may lead to gas leakage. Furthermore, high humidity may also lead to increased corrosion of metallic components.
However, you can mitigate design concerns by selecting certain gas spring materials and geometry so the entire assembly performs reliability in the chosen operational environment. For example, a stainless steel rod and cylinder will significantly enhance a gas spring’s corrosion resistance.
Durability
Progressive dies and industrial stamping equipment employ large loads to plastically shape high-strength metal into complex geometries, representing thousands of daily impacts in high-production environments.
To this end, helical coil production die springs bear the brunt of these impacts and experience notable degradation in load-carrying capability over time. Gas springs offer more durability than helical coil mechanical die springs for industrial applications.
4 Types of Gas Springs
There are a few different types of gas springs designed for different use cases, applications, and environments.
1. Standard Gas Springs
Standard gas springs are used for medium-load applications and typical factory production environments.
2. Compact Gas Springs
Compact gas springs are smaller and economically sized for smaller applications such as compact equipment and low-load applications.
3. Heavy-Duty Gas Springs
Heavy-duty gas springs are rated for higher loads and adverse operating conditions. They are fabricated from high-strength materials to accommodate high loads and temperatures during operation reliably.
4. Custom Gas Spring
Custom gas springs can be designed to specific design requirements, such as stroke distance and rated load.
For example, MISUMI’s configurable model makes it possible to choose a standard gas spring and choose out diameter, stroke, length, initial load, and maximum load.
Gas Springs Safety Features
Numerous notable, cleverly designed passive safety features are available on various gas spring models to increase operational safety.
Over Stroke Active Safety (OSAS)
OSAS is a common gas spring safety feature that protects the spring from catastrophic failure when the gas spring is extended beyond the maximum allowable stroke length during normal operating loads.
The active safety mechanism is self-activated via a release channel, which serves as a vent path when the piston is over-extended in the cylinder, allowing for controlled depressurization during an overstroke.
Uncontrolled Speed Active Safety (USAS)
USAS protects against damage to the spring or personnel when the gas spring experiences an uncontrolled or abnormal mechanical shock load that acts on a gas spring during a return stroke.
The active safety mechanism is self-activated by an interaction of engineered features in the valve cylinder, bushing, and cylinder sealing elements, which open a vent path when the piston is over-compressed.
USAS is a reliable system that allows for safe, controlled depressurization during an uncontrolled return stroke, preventing catastrophic failure during a sudden large impact load in the stroke direction.
Over Pressure Active Safety (OPAS)
OPAS prevents damage to personnel and equipment during a system over-pressurization. OPAS is a passive system involving a rupture plug that works and an integrated exhaust groove feature on the valve body.
OPAS allows for the controlled release of gas if the pressure exceeds the maximum rated pressure of the system, ensuring that the gas spring pressure remains at a safe operational level.
MISUMI Offers a Wide Range of Gas Springs
MISUMI offers industrial high-quality, configurable gas springs. Explore a wide range of gas springs, from compact to heavy duty.
