Home>Products>Gas Spring

Gas spring—also commonly called gas strut or gas shock absorber—works by using compressed nitrogen gas as a springy energy storage material inside a sealed metal cylinder. To make this design work smoothly, the cylinder also holds a mixture of specialized hydraulic oils (like transformer oil or turbine oil). These oils serve three key jobs:

• gas sealed inside

• lubricating moving parts to reduce wear

• making sure mechanical force is transferred evenly.

When you push the piston rod into the cylinder (this is the compression process), the space available for the nitrogen gas gets smaller. Just like squeezing a balloon makes the pressure inside go up, this smaller volume causes the gas pressure inside the cylinder to rise—this follows Boyle’s Law.

The force the gas spring puts out gets stronger as you push the rod in, and it’s strongest when the rod is fully pressed into the cylinder. This more steady, reliable force than coil spring, is why gas springs are used in everyday things like car tailgates (to hold them open gently), industrial machines (to control movement), and ergonomic furniture (like adjustable office chairs).

If you look at the diagram above, you’ll see how the gas spring acts as the piston moves.

With gas springs, force increases exponentially as they are compressed, requiring less initial force to compress them. As the gas spring nears the end of its stroke, the compression force needed rises.

Piston Extended State

When the piston is fully extended, the cylinder has the most space for gas.

Piston Compressed State

As the piston moves to fully compressed, the gas space shrinks—so the pressure goes up (you can see this on the solid line in the diagram). The dashed line shows how the cylinder volume decreases at the same time.

The extension force is calculated by multiplying the filling pressure by the piston rod’s cross-sectional area. Size as well as force can be made according to your requirements.

DK standard gas springs offer extension forces from 10 N to 5000N, with tolerance is ± 5-7%.

The specified force (F₁) is always measured at 20°C ± 2°C, with the piston rod facing downward.

Physically, the actual force of a gas spring depends on the temperature. For each 10°C, the force changes by approx 3,3%.

To define how well a gas spring works, engineers use something called the K-factor (or gas spring progression rate). Put simply, this is the percentage change in force between two states:

Unloaded: When the piston is at P1 (fully extended, the spring’s starting position).

Fully loaded: When the piston is at P2 (fully compressed).

Good quality gas springs have a very low K-factor—usually between 1.05 and 1.8. For comparison, mechanical compression springs (like the coil ones we mentioned earlier) have much higher K-factors. A low K-factor means the spring’s force stays steady as it compresses—this is important for applications where you need consistent lifting or damping (like holding a heavy car tailgate at any angle).

One quick note for calculations: Gas springs are pre-charged to a specific force at P1 (we call this force F1)—so you should always use F1 as your starting point when figuring out the right gas spring for a job.