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Technical Guide about Gas Springs

We like to call gas springs "struts".

Technically they are pneumatic lift assists. The term Gas Springs can imply flammable gas. Actually they are filled with nitrogen which is inert and in the air we breathe. Nitrogen does not mix well with moisture which is an advantage for gas spring use. There is also a measured amount of hydraulic oil to keep the seal from drying out and provide damping at the end of the stroke.

Diagram of a Columbia Strut Gas Spring

The Piston

Gas springs have a piston inside the tube to guide and to control the damping. The piston does not seal the gas since the same pressure is on each side of the piston. The gas just wants to expel the rod. The piston has an orifice in it to regulate the speed of damping. The force we call-out on our part number is at the end of the full extension and then set at 10 mm. This eliminates the breakout force of the seal when the rod is retracted. As the rod is retracted into the tube the force increases since the rod has displaced the area in the tube. From fully extended to fully retracted the force can rise from 30 to 40 percent.

Temperature Sensitive

Gas springs are temperature sensitive. The nitrogen gas molecules speed up when heated and slow down in the cold which affects force. The force we call out in our part number is at room temperature. The standard gas spring is extension type or "push" At its free state it is extended. We also offer retraction gas springs or "pull" which are retracted in there free state. These are also known as close assist gas springs. We can also offer damping in extension or retraction or both in the same gas spring.

Locking Gas Spring

The next type of gas spring is locking. The gas spring is locked until a cable or lever is moved to unlock the gas spring to change position. This is the type used in an office chair where you lower or raise the seat. We also off override locking gas springs which allow the gas spring to be moved in one direction without the locking. This would be used in a seatback where you want to push the seat back up without unlocking it. Only the extension of gas spring is standard. All others are special order. We can also make the gas springs out of 304 or 316 stainless steel for marine or chemical applications.


Most of our gas springs use ball sockets for mounting. Just about any type of connector is available by special order, but a 200 piece order is required. We can stock any special gas spring with a blanket order or forecast. Columbia Struts are maintenance-free and self-contained. They contain high-pressure nitrogen and should not be opened or heated to high temperatures. When you receive your gas springs and try to push the rod in by hand you should know it’s very hard to push in a gas spring over 60 pounds. When replacing gas springs, be sure to prop up the lid or door during the change to be safe.

Columbia Struts Team