The Oil in Oil-Free Air Compressors

When you think about how oil-less air compressors work, you’ll need to realize that there is oil in the device but that it won’t come into contact with the compressor. There is oil in the gearbox of your oil-less air compressor.

The gearbox of your air compressor is used to drive the two compressor elements via the electromotor. Gearboxes need lubrication to operate properly and can be costly to replace, so maintenance checks should review them on a regular basis. The oil in your gearbox will lubricate the internal gears and bearings, as well as the bearing and timing gear located inside of each compressor element.

Oil will be pumped from an oil sump inside the gearbox, and it’s cooled via an oil cooler and oil filter before it is used to cool compressor or gearbox parts. The filters are used to remove debris during its action.

The main difference is that internal elements and parts of the gearbox will be treated with long-lasting lubrication. This puts more of a strain on the engine over time but requires less day-to-day maintenance.

Different Compression Cooling Elements

Understanding the general pressurization of air compressors is pretty straightforward, as it often operates the same way across oil-injected and oil-free units.

For the oil-free compressors we’re looking at, there are two main methods for cooling the compressor itself: Water and air. Air-cooled compressors, which tend to be rotary screw compressors, use outside air to cool the compressed air and the oil used in the gearbox. Air circulates and moves heat away from internal components as well as from the parts that house the oil, which helps remove heat from your compressor elements.

Water-cooled machines will have a two-part cooling system. Water moves near each element, heats up and flows away from the components, condenses and cools and then moves back toward the equipment (often via gravity). These systems will have a water-cooling circuit used for the oil, intercooler and low-pressure element. The second circuit works to cool the high-pressure element and the aftercooler.

How Long Do Oil-Less Compressors Last?

Generally, an oil-free compressor will not last as long as an oil-lubricated model because its pre-lubrication will gradually wear away and degrade over time. Oil-free compressors also tend to use a universal motor, which won’t last as long as an induction motor.

The Teflon coating often used to lubricate the internal cylinder simply wears off over time, and this wear can increase when an oil-less compressor is used in extreme temperatures or for long durations. If you’re vigilant, you can have an oil-less compressor last for years, but this requires more time and money (typically) than an oil-lubricated air compressor.

If you want to extend how long your oil-less compressor will last, good maintenance is your best friend. Air compressors have a lot of moving parts that can cause significant wear, so ensure that you’re looking inside at least once a month. Check the permanently lubricated elements, such as the cylinder’s Teflon coating and either Teflon or carbon ring seals.

Heat Troubles

Part of how oil-less air compressors work includes a significant generation of heat. The more stress they’re put under or the higher the pressure you’re going for, the more likely it is that your air compressor will grind against itself or generate enough heat to burn out and/or warp components.

Oil-free air compressors tend to have a smaller clearance than their oil-injected counterparts, which means there may be less room for them to intake and move enough air to circulate and cool properly. To avoid this, you need to run the compressor only at its manufactured specifications and ensure that you’re providing plenty of space surrounding the unit to keep its exhaust and intake lines free from heat-causing dust and dirt.