How to Lubricate a Pneumatic Cylinder

Post By: Ryan King On: 09-11-2023 Read Time: 4 minutes - Guides - Pneumatics

Lubrication is essential to keep your pneumatic cylinders and end-use devices running smoothly. It usually forms part of a filter regulator-lubricator (FRL) unit, which ensures the compressed air system is clean and properly regulated. If a pneumatic cylinder is insufficiently lubricated, its valves and internal mechanisms will dry up and become damaged.

Proper lubrication and assembly of your pneumatic cylinder’s seals or gaskets will also enhance its performance and operational life. These gaskets comprise the static and dynamic seals that separate the cylinder’s pressure chambers. Dynamic sealing rings are usually found between moving parts of the cylinder, such as the pistons and cylinder rods. Applying the appropriate lubricating grease will enhance their operational life and performance.

When you use an appropriate lubricant for your pneumatic cylinder, it helps to reduce the friction between the seals and the lining of the cylinder. This contributes directly to gasket maintenance, limiting lip seal wear and preventing any moisture in the circuit from leaching into the cylinder. Choosing the right lubricant also means it won’t affect the seal’s mechanical properties by swelling or streaking. Nor will a clash of chemical properties lead to structural changes in the seal, which might lead to changes in size, elasticity and sealing power. Properly lubricated and maintained seals ensure a steady air supply with no leakage and an optimal amount of energy available to move the cylinder.

Should You Lubricate Pneumatic Cylinders?

Lubricators were originally designed to introduce oil into a compressed air system as an aerosol vapour. By this means, the lifespan of downstream machinery (e.g. cylinders) was prolonged and its performance enhanced. Lubrication was required because early pneumatic products had seals made from rubber and other natural materials, including leather. Such materials needed lubrication with oil in order to reduce friction and create an effective seal. Lubricators were invented to provide valve and cylinder seals with a consistent supply of oil. But in some instances, additional lubrication isn’t always required. With the advance of sealing technology, lubricators and FRL units are becoming obsolete.

Improvements in the design and material of cylinder seals may now make lubrication unnecessary. A material called Nitrile is the most commonly used material today for making pneumatic seals. This is a synthetic rubber copolymer, which is sometimes blended with other synthetic products like Teflon to provide additional lubrication. Using these materials means that seals can operate effectively without requiring further lubrication. Whether or not to lubricate modern pneumatic cylinders depends on the application requirements and the manufacturer’s recommendations.

During the assembly process, manufacturers may coat the cylinder’s internal surfaces with various greases. This helps them to resist drying out and degrading. A thin film of lubricant on the mating surfaces of moving parts is necessary to ensure they work smoothly and extend their lifespan. When the mating surfaces are insufficiently lubricated, pneumatic cylinders are subject to threats like rubber-metal sliding friction. This could result in a stick-slip jerking motion, especially when changing direction, causing an irregular cylinder stroke pattern.

What Kind of Grease Do You Use on a Pneumatic Cylinder?

Unless your cylinder is already pre-greased, some kind of additional lubricant grease will be necessary. The kind you use depends on several variables, including the design requirements of the cylinder and its application context. The choice of additional lubricants may be tricky. It’s essential to follow manufacturers’ recommendations to get it right.

Industrial greases are generated by dispersing some kind of thickening agent in a lubricating liquid, resulting in a visco-elastic semi-fluid. These speciality lubricants are designed with advanced fluoropolymer additives that offer very high-pressure boundaries. This type of grease can maintain its lubricity and resist separation even under extreme pressure. It also has excellent dispersion properties. Trusted manufacturers like Festo produce their own specialist greases for pneumatic applications, such as silicon-free lubricating grease.

Some factors to consider when choosing an appropriate grease are whether your cylinder is single or double-acting, rodless, guided, compact or magnetically driven. This in turn will influence its choice of construction materials for gaskets, and its operating conditions. You’ll also need to know the length of the cylinder’s implementation strokes, its workload, operating temperature range and actuation speed. Other important considerations are whether the cylinder will come into contact with any process fluids like gases, acids, paints or organic compounds – or have any contact with food or beverages.

How Do You Maintain a Pneumatic Cylinder?

Some best practices you should follow for maintaining a pneumatic cylinder include regular checks of its components for signs of wear. Areas that require special attention are the cylinder seals, piston rod, cushioning and mounting accessories. Some items may need to be replaced if worn and you may need to follow up with a detailed troubleshoot if the wear seems excessive or unusual.

You should also check that the cylinder is being correctly lubricated and with the right type of lubricant. This should be specified in the manufacturer’s product literature. Replace the filter if necessary in the FRL unit to ensure the purity of your air supply, and make sure the unit is operating at the correct pressure and flow rate. You should also check that the environment where your pneumatic cylinder is operating is clean and dry. Eliminate wherever possible all contaminants such as dirt, dust and moisture.

Consult Manufacturer’s Specifications

The first thing to note about lubricating a pneumatic cylinder is whether or not additional lubrication is actually required. You can check this out by consulting the manufacturer’s product specifications and precautions. If you do need to lubricate the cylinder, it’s essential that you apply the correct lubricant according to these specs. The lubrication equipment must be correctly adjusted. If it’s part of an FRL unit, you’ll also need to check the filter and regulator.

To ensure that your pneumatic cylinder is operating correctly and efficiently, you should test it regularly. If you notice any problems, deal with them immediately to prevent further damage. Instituting a programme of preventive maintenance will help to organise these checks and keep your system operating efficiently.