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How a Pneumatic Cylinder Works: Pneumatic cylinders & Linear Motion
06/12/2022

How a Pneumatic Cylinder Works: Pneumatic cylinders & Linear Motion

Matara stocks a vast range of pneumatic cylinders and pneumatic components. If you want to discover why pneumatic cylinders are perfect for all of your linear motion needs, we explore exactly how they operate and how you can find the perfect pneumatic cylinder for your applications. 

How a Pneumatic cylinder Works

Pneumatic cylinders use compressed air as the input source to move a load. There are various pneumatic cylinder types, including single-acting, double-acting, and rodless. Most contain a piston inside the pneumatic cylinder, and the compressed air is pushed in at one end of the pneumatic cylinder and acts upon the piston within the contained environment to translate the energy into movement, using a rod to move the external load. In the case of rodless pneumatic cylinders, these are engineered to perform as a self-contained linear actuator with the piston moving within a pneumatic cylinder bore for improved flexibility.

Unlike a hydraulic cylinder, which uses fluid and is, therefore, prone to leakage or cross-contamination, a pneumatic cylinder relies solely on air. This makes them suitable for use in a wide array of mechanical applications (although generally in fixed installations, as moving large air compressors around is not ideal or easy!).

Pneumatic cylinders at the heart of a linear motion system

Pneumatic cylinders are often the most crucial component of a linear motion system. If the pneumatic cylinder fails, the linear motion system cannot function, and, in most instances, the machine it is part of and even the entire production line is out of action until the pneumatic cylinder can be replaced.

This downtime is undesirable in any setting, but in a harsh environment where contaminants are heavily present, standard pneumatic cylinders will fail all the more frequently, resulting in more significant downtime. Pneumatic cylinders can be contaminated internally by the air supply or externally by the operating environment. In the latter case, seals become damaged from particles and corrosive elements in the immediate atmosphere, which can then enter the main workings of the pneumatic cylinder, reducing its effectiveness and life.

What environmental factors impact a pneumatic cylinder’s longevity?

Airborne particles in the form of dust and grit are the most apparent threat to pneumatic cylinders. If this penetrates a nose seal, it builds up and sits in seals and bearings with a similar effect to sandpaper. In a normal environment, with regular preventative maintenance, standard cylinders can cope well with basic levels of dust, but where these contaminants are prevalent, such as in flour mills, mines, and quarries, a more robust pneumatic cylinder must be considered.

Water may not be deemed a contaminant in the usual sense, but when it comes to pneumatic cylinders, it is very much a problem, as where there is compressed air, there is water vapour. Furthermore, several industries, including food and pharmaceuticals, conduct washdowns regularly and thoroughly. In these situations, water collects within system components, where it can block air flow through orifices, dilute or adulterate lubricants, corrode the barrel or rod finish, and, of course, freeze in cold weather.

Contamination from synthetic oils used to lubricate the air compressor can have a similar impact on pneumatic cylinders as water: it can block orifices and cause seals to swell. In harsh environments, greater quantities of lubricant are often used, making the contamination situation worse.

The piston rod and rod seal are prone to damage in applications where extreme heat is used and/or chemicals, paint, or weld splatter are present.

So, these are the problems, but what are the solutions?

Selecting a pneumatic cylinder for harsh applications

First and foremost, invest in pneumatic cylinders manufactured and sealed to a high quality from a well-established, recognised manufacturer. However, for really harsh environments, you will need to look to a more customised cylinder. The good news is that most of these customisations are relatively straightforward and represent a good ROI.

Let’s start with some pneumatic accessories, such as cylinder seals, one of the most important means of preventing dirt and water ingress. Standard seals can be replaced with specialist versions to meet the needs of your specific application. Viton—a fluoropolymer elastomer—and synthetic rubber compound seals have been designed for use in some of the harshest environments, where temperature extremes and chemical interactions are common. These can readily be used in Matara’s standard rod-type pneumatic cylinders and rodless pneumatic cylinders.

Moving further into the cylinder construction, with rod-type pneumatic cylinders, a rod seal/wiper can be incorporated to stop contaminants from entering the inner body of the cylinder and remove larger particulates from the rod. For added protection, the rod can be fitted with a rod bellow/gaiter, which keeps contaminants away from piston rods.

When it comes to corrosion prevention, then you may need to consider going further than just swapping out seals for tougher versions. For corrosive environments, including those where regular washdowns are conducted, the choice of rod material may need to be reconsidered. Standard rods are primarily manufactured from chrome, but swapping to stainless-exercised steel rods, fasteners, or even a stainless steel rod will provide extra protection against corrosion. This will impact the cost, usually by an additional 10% of the overall cost of the cylinder. Matara offers a range of 100% stainless steel pneumatic cylinders for complete corrosive protection.

The other option is to stick with existing materials but use specialist coatings or epoxy paints. There is a good range of options here, including Armoloy TDC® coating, which we use on our linear rail and ballscrews for maximum longevity in demanding applications and locations. Armoloy TDC® is a hard (78Rc), thin, dense chromium coating with a micro-nodular surface texture that provides corrosion protection equal to that of 440 series stainless steel.

Maintanence matters

Having selected the right cylinder type for your environment, it’s essential to conduct basic preventative maintenance regularly. This should include the regular cleaning of external parts of the system so that visual inspection of seals and other parts are straightforward; inspection for wear and tear; draining of air line filters and checking that the water traps are operating as they should; lubrication of the cylinder, rod seal, piston seals, and surfaces; checking for air leaks and resealing where required; and last, but not least, replacement of air filters.

Harsh environments make for difficult operating conditions, but by selecting quality pneumatic cylinders customised to your specific site, you can cost-effectively prolong a cylinder’s service life and reduce costly downtime.

Find all the pneumatic cylinder you need at Matara

Find the perfect pneumatic cylinder for your linear motion needs here at Matara. We design and manufacture a wide selection of pneumatic and linear automation products, which are available in stock or can be custom-built to order.

Be sure to check out our entire range. If you want to learn more about what Matara can do for you, check out our case studies and technical articles. If you have any questions, be sure to contact us, and a member of our team will be happy to help. 

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