Cutting through the fog on pneumatic lubrication

Choosing the right strategy to prolong the life of key equipment will have a major impact for your plant.

By Charles Werdehoff, IMI Precision Engineering June 14, 2017

Click here to view the 2017 Lubrication Guide.

Pneumatic devices that push, pull, lift, position, or convey last longer and perform better when supplied with compressed air that is clean, dry, pressure-regulated, and lubricated. The service life of many air tools, cylinders, valves, air motors, and other air-driven equipment can be extended by consistent aerosol lubrication.

Why lubricate? Environmental factors like extreme temperatures and excessive moisture, along with operational factors such as start-up and operational friction, reduce the life of most working pneumatic devices. Oil aerosol delivered in compressed air reduces the effects of these factors and extends the life of pneumatic components.

How aerosol lubricators work

Aerosol lubricators automatically deliver a metered amount of oil into the air path of operating pneumatic equipment. Lubricators function by creating a pressure drop that causes oil to be siphoned into an adjustable dome. Using the dome adjustment and observing the drip rate allows an operator to set the amount oil to be delivered to downstream equipment.

Operating manuals for pneumatic equipment typically specify the amount of oil required to keep the device operating optimally. Lubricators should be adjusted to deliver the amount of oil specified at defined operating conditions and then validated after the equipment is in operation.

Oil-fog, direct to the tool

The mostly widely used type of lubricator is oil-fog, sometimes called direct feed. These lubricators deliver 100% of the oil drops seen in the dome directly into the air stream. Oil particles traveling downstream are normally 2 microns or larger. Because of gravity, these particles only will remain airborne for a distance up to about 15 feet, and they normally will not travel up or follow intricate flow paths. As a result, oil-fog lubricators should be located in-line and near the tool they are lubricating. They are very efficient at delivering the right amount of oil directly to the cylinder, valve, or tool.

It is not always possible to meet optimal conditions for oil-fog lubricators. When these conditions are not met, the oil will collect in the air line instead of travelling to the equipment. The result is reduced air flow and either inadequate or excessive tool lubrication.

Standard oil-fog lubricators are not efficient for applications where the air line has vertical air paths, multiple tool lines, or bends in the air stream that prevent larger oil particles from reaching a tool. In these situations, a micro-fog lubricator provides better lubrication results.

Micro-fog – multiple paths

With a micro-fog lubricator, the oil drip is atomized into particles smaller than 2 microns. Approximately 10% of the oil drip seen in the dome is transported into the airflow and the rest of the oil is returned to the bowl for future use. Because the particles are small, they can travel long distances, vertically, and through intricate flow paths. Because only 10% of the oil is being delivered downstream, they are good for applications that require better adjustability of small amounts of direct lubrication.


A lubricator is almost always used together with a filter and regulator pre-conditioning the air. These can be stand-alone components or an integrated filter-regulator-lubricator. Air leaving a compressor contains water and contaminants that can cause damage and shorten the life of downstream equipment. Even pre-lubricated components can fail when contaminated air degrades the lubrication or washes it out. Allowing contaminated air into a lubricator can result in reduced oil feed.

Filtering ensures that clean dry air is sent through the lubricator and on to the operating equipment. Regulating air flow to meet conditions specified by the equipment operating manual ensures the equipment performs optimally. Aerosol lubrication is the final step after filtration and regulation. Proper lubrication protects equipment, prolongs tool life, helps control costs, and keeps processes running efficiently and productively.

Charles Werdehoff is a precision engineering and product marketing manager for IMI Norgren Filter/Regulator and Lubricant (FRL) Products.