Buying Advice – Service: Disassembly of a Gas Spring

WHAT CAN GO WRONG WITH A GAS SPRING?

Two problems with a gas spring are conceivable: First, the set height remains locked and can no longer be changed, even with a lot of wiggling on the seat. Second: The spring loses tension and, as soon as weight is put on the seat, it moves to its lowest position. In addition, the seat is no longer dampened. Assuming it is not a manufacturing defect – and thus a warranty case that occurs shortly after purchase – such failures usually only appear after many years of use. How long a gas spring lasts under normal operation is difficult to say – the lifespan varies from model to model. However, the reason it stops working is almost always that fine particles combine with lubricant to form a mixture that clogs or blocks the gas spring's valve. It is therefore, in the broadest sense, a sign of wear and tear. Due to daily use in the large dust hotspot "office," where clouds of toner mist combine with stirred-up dust from PC coolers and flying carpet fibers, it is practically unavoidable that over the years, fine particles accumulate at the gas spring's valve. As a result, they get inside and glue or block it.

Either way: The broken part must be repaired – or removed entirely.

DEFECTIVE SPRING – WHAT TO DO?

Before calling the caretaker, the toolbox, or prematurely a new chair, it is advisable to check the accounting: How old is the chair? If there is still a warranty, then off it goes, back to the manufacturer. If this option is out, there are two ways. The first is to repair the gas spring, which can be done yourself with a little skill. The second is to replace the defective part, which can be ordered as a spare part from the manufacturer or the office chair shop.

Note that this is only if the chair was bought from a specialist dealer. Cheap chairs from the supermarket, hardware store, or furniture discounter rarely have interchangeable components. In these cases: Hands off! A gas spring can be dangerous. Anyone who forcibly removes plastic parts that hold the spring under tension risks the piston shooting uncontrollably out of the cylinder and, in extreme cases, even breaking through the casing. Serious injuries are a threat; in some cases, reckless tinkerers have already lost their eyesight. In the best-case scenario, a huge mess is threatened if lubricant leaks from the cylinder.

As with all repairs: caution is the mother of the porcelain box. Health comes first, and if a procedure cannot be carried out according to the manufacturer's description, it is better to leave it to a specialist.

HOW DOES A GAS SPRING WORK?

Even those who haven't yet gotten under an office chair in a mechanic's pose and removed plastic covers are most likely familiar with the principle of a gas spring from its other applications: for example, on the trunk of a car. When you open it, you can observe how two pistons on the right and left of the tailgate slowly extend and eventually hold the trunk lid open. This is made possible by a gas inside the piston that is compressed when closed and slowly expands when opened. This system is also increasingly used for car hoods. Where older car models required a support rod to be folded out and locked to keep the hood open, today a gas spring extends and then independently supports the engine cover. But how does such a pneumatic spring work?

Simply put, it essentially consists of a piston and a cylinder. Inside this cylinder is gas under high pressure. In most cases, this compressed gas is nitrogen. It is responsible for the spring force and also serves for damping.

The amount of gas determines the spring force, which is why the piston is precisely matched to the fill volume. Complex designs feature a separating piston, which allows the damping piston to run in oil and thus be exposed to less friction.

It should be explicitly pointed out again that a gas spring must not be opened. Since the nitrogen inside the cylinder is under high pressure, the pneumatic component cannot be opened in a controlled manner or the nitrogen released in portions. The metallic piston will literally fly off into the tinkerer's face.

SIMPLE REPAIR

At the closed end of the cylinder is the valve, usually in the form of a ball or pin, which is operated by the lever. This is exactly where the component's weakness lies: If dust particles accumulate at the edges of the fitting, they will eventually block the smooth closing of the valve. The result: It remains permanently open and allows the piston to compress the gas inside the spring under weight load. The other possibility is that a combination of dirt and lubricant gums up the valve. The result: The valve can no longer be opened – the gas spring remains closed.

It can help to treat this valve with common universal sprays that are used as lubricants and cleaners. The lever should be operated repeatedly to mobilize the valve closure. The cleaning substances and nourishing properties of these sprays, which are available at any hardware store and are good for hinges, bicycle cleaning, or rusted screws, can loosen baked-on dirt and make the gas spring smooth again.

DISMANTLING THE GAS SPRING

If this repair attempt is unsuccessful, only replacing the broken gas spring will help. All you need for this is a standard rubber mallet. The tool is usually used to drive wooden dowels into furniture, lay tiles, or drive tent pegs into the ground – but it also serves well for the task at hand.

Basically, you should know that the gas spring is only screwed to the base in rare cases. Most modern office chairs are literally assembled by plugging components together, which means that the conically tapered cylinder of the gas spring is inserted into the base so that it sits firmly. There are two ways to get it out. If you want to spare your back, lay the office chair on its side so that it is stable. Now, hold the base with one hand and gently but vehemently tap the protruding end of the gas spring cylinder with the other hand. Feel free to shake the base vigorously back and forth and tap the defective part out of its socket as carefully as possible. Next, grip the hard plastic sleeve of the gas spring firmly and tap around the opening where the spring sits in the seat of your swivel chair or executive chair, in order to indirectly act on the gas spring and loosen it.

The second option is just as effective but requires a bit of back muscle: Lift your office chair by the seat and literally shake the gas spring, along with the base, out of its socket. This uses the weight of the chair's base, which should come out of its socket after a bit of shaking and rattling. Be careful of your feet so that the heavy metal or hard plastic component doesn't fall on your toes! Now hold the base vertically and knock the gas spring out of its socket from the side.

INSTALLING A NEW GAS SPRING

Before you replace the defective component with a new one, take the opportunity to thoroughly clean your office chair. You won't get such easy access to the individual parts of your office furniture again soon. Especially the hard plastic parts can be maintained with the same spray you used earlier to make the old gas spring run smoothly again. First, clean the individual parts with paper towels and window cleaner or a soft cloth and a mild all-purpose cleaner. Let the parts dry thoroughly and then take a spray oil and a soft cloth and carefully rub all hard plastic parts.

The oil not only protects the surface, but also gives it new shine. For chrome, you can either use a chrome cleaner from a hardware store – or you can resort to an old home remedy: citric acid. Halve a lemon and carefully rub off any oxidized or tarnished chrome components. Alternatively, you can mix a lye from a handful of cold ash and a splash of water, mixed in a rinsed-out yogurt cup. Carefully rub the affected parts, rinse with plenty of water and let the clean chrome part dry thoroughly. Afterwards, to prevent further corrosion, you can rub the whole thing with a thin layer of petroleum jelly.

Now take the new gas spring and carefully insert it – if necessary, according to the manufacturer's instructions – into the recess in the spider base. There is no need to hit the spring with a hammer – especially since you could damage the new valve. Simply press it firmly into the opening, put the seat on top and sit on the chair. Make sure that the lever that operates the valve of the gas spring can move freely.