As America’s largest gas spring manufacturer, we get a lot of questions. If you don’t find the technical information or answer to the question you’re looking for below, please call one of our technical assistance professionals at (888)-870-4884, or email us.

How a spring works?

A gas spring consists of a piston attached to a shaft moving within a sealed cylinder charged with nitrogen. The output forces are the result of the differential between the pressure in the cylinder and the atmospheric pressure outside the cylinder acting on the cross section of the piston/shaft. As the piston/shaft is compressed into the cylinder the internal pressure increases according to the volume of gas displaced by the rod. This increase in force is called the K-Factor. Because they operate on simple pressure differentials, gas springs will perform as well in the vacuum of space as they do on land.

Force

Gas spring force is often designated as P1 which is the force measured 1 inch from full extension. Force is a function of the charge pressure in the cylinder acting on the cross section of the rod. The smaller the diameter of the piston/rod the lower the force at the same pressure. For example, a gas spring with a 9/16 (14mm) rod charged to 1000 psi will have a P1 force of 200 pounds while a spring with a 5/16 (8mm) rod charged to the same pressure will have a P1 force of 65 pounds.Compressed force is referred to as P2. This force is measured .2” (5mm) from full compression. The P2 force will always be greater than the P1 force.

K-Factor

K-factor is the ratio of the compressed force (P2) and the extended force (P1). As governed by Boyle’s Law, P2 force is always greater than the P1 force. During compression, the volume of the piston/shaft introduced in the cylinder displaces an equal volume of gas, increasing the pressure in the cylinder which increase the force of the spring.

What is a Gas Spring?

Ameritool gas springs are self-contained, pneumatic devices capable of producing very large forces (5-1,200 lbs.) from a compacted piece. A gas spring consists of a piston attached to a shaft moving within a sealed cylinder charged with nitrogen. The piston has an orifice which allows gas pressure to pass through and act equally on both sides. It is the pressure acting on the shaft cross-sectional area which provides the springs its force.

The output forces are the result of the differential between the pressure in the cylinder and the atmospheric pressure outside the cylinder acting on the cross section of the piston/shaft. As the piston/shaft is compressed into the cylinder the internal pressure increases according to the volume of gas displaced by the rod. This increase in force is called K-Factor.

Because they operate on simple pressure differentials, gas springs will perform as well in the vacuum of space as they do on land.

What is K-Factor?

K-factor is the ratio of the compressed force (P2) and the extended force (P1). As governed by Boyle’s Law, P2 force is always greater than P1 force. During compression, the volume of the piston/shaft introduced in the cylinder displaces an equal volume of gas, increasing the pressure in the cylinder which increases the force of the spring.

What is gas spring force?

Gas spring force is often designated as P1 which is the force measured 1 inch from full extension. Force is a function of the charge pressure in the cylinder acting on the cross section of the rod. The smaller the diameter of the piston/rod the lower the force at the same pressure. For example, a gas spring with a 9/16 (14mm) rod charged to 1000 psi will have a P1 force of 200 pounds while a gas spring with a 5/16 (8mm) rod charged to the same pressure with have a P1 force of 65 pounds.

How does temperature affect the life and performance of gas springs?

Temperature affects gas springs in two ways. As the pressure of the gas spring changes, the internal pressure also changes. As internal pressure changes, so does the output force.

Very high or very low temperatures can adversely affect the gas springs ability to retain its gas charge. At very high temperatures, the permeability of the seal increases and the gas molecules may diffuse through the seal more quickly. Ameritool gas springs can support and perform reliably at temperatures ranging from -40°F to 300°F (-40°C to 148°C).

How does Temperature affect gas spring force?

The force produced by a gas spring varies linearly by .19% for each degree F change from Ambient Temperature of 70 degrees F. For example, a 30 degree change in temperature results in a 5.7% change in springs force (30 x .19% =5.7%).

Very high or very low temperatures can adversely affect the gas springs ability to retain its gas charge. At very high temperatures, the permeability of the seal increases and the gas molecules may diffuse through the seal more quickly. Ameritool gas springs can support and perform reliably at temperatures ranging from -40°F to 300°F (-40°C to 148°C).

What is a damper?

A damper unlike gas springs provides no push or pull force, but instead controls the rate of movement throughout the stroke. Dampers look identical to gas springs, so careful consideration must be taken when specifying a gas spring versus a damper. There are three types of dampers: extension, compression and dual direction. Extension dampers provide controlled speed while the rod is being extended out of the tube. Compression dampers provide a controlled speed while the rod is being compressed back into the tube. Dual rate dampers have equal amount of damping in both directions.

What is a tension spring?

Tension gas springs also known as traction gas springs work by keeping the piston rod in the closed position, operating in the opposite direction of other gas springs. Since a tension gas spring is compressed in its relaxed state, it always returns to it relaxed state once extension is stopped.

What is the expected life of a gas spring?

When calculating the approximate life of a gas spring, one must first determine how much force the gas spring can lose before the user considers the gas spring too weak in the application. The time it takes to lose this amount of force is considered to be the life of the gas spring.

All gas springs lose output force over time. The rate at which force loss occurs varies greatly by application. Factors which affect the rate of loss include size of the gas spring, orientation, number of cycles, ambient temperature, vibration and the geometry of the application. Considering all of the variables, it is very difficult to estimate life expectancy accurately without actual testing of the application. Gas springs manufactured at Ameritool have surpassed 125,000 strokes in a certified test lab environment.

What is the preferred mounting orientation of a gas spring?

In general, gas springs should be installed with the rod facing down to ensure the seals are lubricated and to reduce the permeation of nitrogen through the seal. However, the opposite installation may sometimes be necessary in special cases, for example if the gas spring requires a very specific damping characteristic. In such cases, the keeping the seals lubricated much be achieved by other means internally.

How does Ameritool prevent dirt and debris from entering gas springs?

Ameritool gas springs come with a rod wiper which prevents foreign matter from entering into the gas springs by wiping away any material that has settled on the rod surface. This is a key component that gives Ameritool the leading edge on the durability and life of a gas spring.

Are Ameritool gas springs ROHS compliant?

Yes, Ameritool gas springs are ROHS-compliant.

Can gas springs be used in the food industry?

Our high-quality 316 stainless steel gas springs and dampers meet the highest requirements of the food industry. If required, food grade oil is available upon request.