Gas Springs FAQ

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 (315)-668-2172, or email us.

 

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.

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 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.

Ameritool gas springs, also often referred to as “struts” or “gas stays”, 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.

The body of our gas springs are engraved with the following:

  • Manufacture Date
  • Company Information
  • Part Number
  • Do Not Open High Pressure/Made in USA

If the part number marked on your gas spring does not follow the Ameritool part numbering system, it may be marked with the OEM part number. 

Please email us or call us at (315) 668-2172 and we will provide you with all the information you will need to procure your replacement!

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.

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  -10°F to 180°F (-23°C to 82°C). (High temp or Low temp seal packages are also available.)

The force changes approximately 3% for every 50°F change in temperature. Gas springs are filled at around 72°F and the force is determined at these conditions.

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 -10°F to 180°F (-23°C to 82°C). (High temp or Low temp seal packages are also available.)

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.

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.

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 test lab environment.

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.

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.

Yes, Ameritool gas springs are ROHS-compliant.

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.

Carbon steel gas springs offer a range of benefits, making them an excellent choice for a number of applications across industries. Here are some key advantages:

  1. Strength and Durability:
    • Carbon steel is renowned for its high strength, providing robust support in applications requiring significant force and load-bearing capabilities.
    • The durability of carbon steel gas springs ensures a long service life, even in demanding environments.
  2. Cost-Effective:
    • Carbon steel gas springs are generally more affordable than their stainless steel counterparts, offering a cost-effective solution without compromising on performance.
    • The cost savings make them an attractive option for large-scale projects or applications with budget constraints.
  3. Versatility:
    • These gas springs are available in various sizes, force ratings, and configurations, making them suitable for a wide range of applications, from automotive and industrial machinery to furniture and medical equipment.
    • The versatility allows for customization to meet specific requirements, ensuring optimal functionality.
  4. Ease of Maintenance:
    • Carbon steel gas springs are easy to maintain, with straightforward procedures for inspection and replacement if necessary.
    • The availability of spare parts and ease of repair reduce downtime and maintenance costs.
  5. Corrosion Resistance:
    • With corrosion resistance coating, carbon steel gas springs offer enhanced resistance to corrosion and wear, extending their lifespan even in various environments.
  6. Performance Consistency:
    • Carbon steel gas springs provide consistent performance, ensuring reliable operation in applications requiring precise control and movement.
    • The stability of carbon steel ensures that the gas springs maintain their force and functionality over time.